Genome-wide association and transcriptome analysis suggests total serum ghrelin to be linked with GFRAL

in European Journal of Endocrinology
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  • 1 Department of Psychiatry and Psychotherapy, Clinical Chemistry and Molecular Diagnostics
  • | 2 Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics
  • | 3 Institute for Medical Informatics, Statistics, and Epidemiology (IMISE)
  • | 4 LIFE Research Center for Civilization Diseases, University of Leipzig, Leipzig, Germany
  • | 5 Department of Neurology, Max Planck Institute for Cognitive and Brain Sciences, Leipzig, Germany

Correspondence should be addressed to D A Wittekind or M Kluge; Email: dirkalexander.wittekind@medizin.uni-leipzig.de or michael.kluge@medizin.uni-leipzig.de
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Objective

Ghrelin is an orexigenic peptide hormone involved in the regulation of energy homeostasis, food intake and glucose metabolism. Serum levels increase anticipating a meal and fall afterwards. Underlying genetic mechanisms of the ghrelin secretion are unknown.

Methods

Total serum ghrelin was measured in 1501 subjects selected from the population-based LIFE-ADULT-sample after an overnight fast. A genome-wide association study (GWAS) was performed. Gene-based expression association analyses (transcriptome-wide association study (TWAS)) are statistical tests associating genetically predicted expression to a certain trait and were done using MetaXcan.

Results

In the GWAS, three loci reached genome-wide significance: the WW-domain containing the oxidoreductase-gene (WWOX; P = 1.80E-10) on chromosome 16q23.3-24.1 (SNP: rs76823993); the contactin-associated protein-like 2 gene (CNTNAP2; P = 9.0E-9) on chromosome 7q35-q36 (SNP: rs192092592) and the ghrelin And obestatin prepropeptide gene (GHRL; P = 2.72E-8) on chromosome 3p25.3 (SNP: rs143729751). In the TWAS, the three genes where the expression was strongest associated with serum ghrelin levels was the ribosomal protein L36 (RPL36; P = 1.3E-06, FDR = 0.011, positively correlated), AP1B1 (P = 1.1E-5, FDR = 0.048, negatively correlated) and the GDNF family receptor alpha like (GFRAL), receptor of the anorexigenic growth differentiation factor-15 (GDF15), (P = 1.8E-05, FDR = 0.15, also negatively correlated).

Conclusions

The three genome-wide significant genetic loci from the GWA and the genes identified in the TWA are functionally plausible and should initiate further research.

Abstract

Objective

Ghrelin is an orexigenic peptide hormone involved in the regulation of energy homeostasis, food intake and glucose metabolism. Serum levels increase anticipating a meal and fall afterwards. Underlying genetic mechanisms of the ghrelin secretion are unknown.

Methods

Total serum ghrelin was measured in 1501 subjects selected from the population-based LIFE-ADULT-sample after an overnight fast. A genome-wide association study (GWAS) was performed. Gene-based expression association analyses (transcriptome-wide association study (TWAS)) are statistical tests associating genetically predicted expression to a certain trait and were done using MetaXcan.

Results

In the GWAS, three loci reached genome-wide significance: the WW-domain containing the oxidoreductase-gene (WWOX; P = 1.80E-10) on chromosome 16q23.3-24.1 (SNP: rs76823993); the contactin-associated protein-like 2 gene (CNTNAP2; P = 9.0E-9) on chromosome 7q35-q36 (SNP: rs192092592) and the ghrelin And obestatin prepropeptide gene (GHRL; P = 2.72E-8) on chromosome 3p25.3 (SNP: rs143729751). In the TWAS, the three genes where the expression was strongest associated with serum ghrelin levels was the ribosomal protein L36 (RPL36; P = 1.3E-06, FDR = 0.011, positively correlated), AP1B1 (P = 1.1E-5, FDR = 0.048, negatively correlated) and the GDNF family receptor alpha like (GFRAL), receptor of the anorexigenic growth differentiation factor-15 (GDF15), (P = 1.8E-05, FDR = 0.15, also negatively correlated).

Conclusions

The three genome-wide significant genetic loci from the GWA and the genes identified in the TWA are functionally plausible and should initiate further research.

Introduction

Ghrelin is a 28-amino-acid peptide hormone predominantly synthesized in the stomach (1). Ghrelin binds to its receptor, the growth hormone secretagogue receptor 1a (GHSR1a), after being acylated by ghrelin-O-acyl-transferase (GOAT) (2, 3). Ghrelin is secreted in a pulsatile manner and factors regulating ghrelin serum levels are circadian rhythm, sex, feeding status, body fat and stress (4, 5). However, underlying genetic mechanisms of ghrelin secretion are unknown. Ghrelin receptors and GOAT are broadly expressed, including in the intestine, pituitary, kidney, lung, heart, pancreatic islets, endocrine tissue and the CNS (6). Accordingly, ghrelin has been shown to be involved in various biological functions. It stimulates the hypothalamic pituitary (HP)-adrenal and the growth hormone axes (1) but inhibits the HP-gonadal and the HP-thyroid axes (TSH) (7, 8). In the CNS, ghrelin was shown to activate the reward system (9, 10) increasing food, drug and alcohol consumption, being considered a relevant factor for the development of addiction (10, 11). Published evidence consistently points to anxiolytic and antidepressant effects and a prominent role in learning, memory and neuroprotection (11, 12). It increases blood glucose by suppressing pancreatic insulin secretion, increases hepatic gluconeogenesis and stimulates gastric motility and emptying as well as lipogenesis (5, 13). While ghrelin has been implicated in various cancers, its precise role in cancer development and progression is unclear (14).

Ghrelin increases weight by reducing energy expenditure and increasing appetite and thereby food intake (15). The orexigenic (appetite increasing) effect is mediated at hypothalamic level by stimulating neurons containing orexigenic neuropeptide Y (NPY) and agouti-related protein (AgRP) and by inhibiting neurons containing anorexigenic a-melanocyte-stimulating hormone (a-MSH) and cocaine- and amphetamine-regulated transcript (CART) (5, 16, 17). Leptin, an important adipocyte-derived anorexigenic hormone, exerts opposite effects on these neurons (18). GDF15 is another anorexigenic peptide with a different mode of action (19, 20). GDF15 binds to GFRAL located in the area postrema (21, 22, 23, 24). The clinical relevance of the GDF15/GFRAL-pathway, for example, in mediating metformin’s metabolic effects, is just being recognized (20). There has been almost no information on the association between GDF15/GFRAL-pathway and the ghrelin system so far.

Due to its involvement in various auto-regulatory systems, the ghrelin system has been identified as a potential drug target for several conditions including tumor cachexia (25) and addiction with promising results in recent years (26).

In order to elucidate genetic mechanisms underlying the ghrelin secretion, a first GWAS of total ghrelin in serum and a TWAS were performed, integrating the expression quantitative trait loci (eQTL) information across various tissues with GWAS results using MetaXcan (27).

Methods

Study design and subjects

Subjects were recruited in the framework of the LIFE-Adult study, a population-based cohort with 10 000 adults (age range mainly 40–79 years, 400 subject with an age range of 18–39 years). Participants were age- and sex-stratified randomly recruited in the city of Leipzig, Germany (for details of the study design see) (28). Total ghrelin was measured in 1666 subjects. From these, 165 subjects were excluded due to an incomplete data set, that is, when any of the parameters required for data analyses were missing such as BMI or genetic data of sufficiently high quality. Thus, the resulting study population comprised 1501 subjects (807 men and 694 women). All participants gave written informed consent to take part in the study. The procedures were conducted according to the Declaration of Helsinki and approved by the ethics committee of the University of Leipzig (registration-number: 263-2009-14122009).

Ghrelin measurements

Blood samples were collected after an overnight fast between 07:30 and 10:30 h, serum was separated by centrifugation and then frozen and stored at −80°C. Samples were not pre-treated with enzyme inhibitors or acidification. Due to this, only total ghrelin was measured, as it is much more stable than acyl-ghrelin. Ghrelin in serum was measured using a RIA for total ghrelin (Mediagnost, Reutlingen Germany). Sensitivity of the assay was 0.04 ng/mL, mean intra-assay coefficients of variation were 2.7–4.3%; inter-assay coefficients of variation were between 6.9 and 9.2% for the mean expected range of clinical data around 0.88 and 0.97 ng/mL.

Genotyping, preprocessing and imputation

Subjects were genotyped with the genome-wide SNP array Axiom Genome-Wide CEU 1 Array Plate (Affymetrix). Details of genotyping and primary quality control of samples and SNPs can be found elsewhere (29). In brief, sample quality control included analysis of dishQC, call rate, heterozygosity, sex mismatches, cryptic relatedness and for X-chromosomal analysis irregularities of X-Y intensity plots. SNP quality control included call rate (≤97%), parameters of cluster plot irregularities as suggested by Affymetrix best practice, violation of Hardy–Weinberg equilibrium (P ≥ 10–6 in exact test) and plate associations (P ≥ 10–7). In total, 4985 (4978) samples and 532 875 (13554) SNPs fulfilled all quality criteria for autosomal (X-chromosomal, respectively) analysis.

Genotypes of the 1000 genomes reference phase 3, version 5 were (30) imputed using IMPUTE2 (version v2.3.2) (31) after pre-phasing with SHAPEIT (version v2.r837) (32). SNPs with low imputation quality (IMPUTE info score < 0.5) and bad power (minor allele frequency < 2%) were filtered. A total of 9 868 623 SNPs were considered for analysis.

GWAS analyses

Ghrelin, covariables and genotype data are available for a total of 1501 samples. Association analysis was performed with SNPTEST (version 2.5.2). Logarithmized ghrelin levels were adjusted for age, sex, alcohol intake, smoking status, and logarithmized BMI and an additive model of inheritance was assumed. X-chromosomal variants were analyzed assuming total X-inactivation. A-value cut-off of 5 × 10-8 was considered genome-wide significant. Independent SNPs were determined by priority pruning applying a linkage disequilibrium cut-off of r2 ≥ 0.1.

SNPs were comprehensively annotated by an in house pipeline as explained elsewhere (33). In brief, annotation comprised nearby genes using Ensemble, LD based look-up of other GWAS traits presented in the GWAS Catalog (34), and of expression quantitative trait loci (eQTLs) as reported by GTex and own blood data (35).

TWAS analysis

For gene-based expression association analyses, we utilized MetaXcan (27). We applied the GTEXv7 models, MESA (36), and DGN-model as it was trained by the authors. For this analysis, we used the same SNP filter criteria regarding MAF and info-score as in our main GWAS. We calculated the false discovery rate according to Benjamini and Hochberg accounting for the number of tested genes. Thereby, we considered a FDR ≤ 0.05 as significant association in our dataset.

Results

GWAs analysis

GWAS was performed in the population-based ‘LIFE-Adult study’. Sample description is provided in Table 1. GWA analysis revealed no signs of general inflation of test statistics (Lambda=1.00). Independent SNPs reached genome-wide significance and could be attributed to three distinct genetic loci.

Table 1

Description of the study sample. Data are presented as mean±S.D. or as n (%).

Total sampleMalesFemalesP-value
Total, n1501807 (53.8%)694 (46.2%)
Age, years57.9 ± 15.257.5 ± 15.558.3 ± 14.70.78a
BMI, kg/m2)27.1 ± 4.527.4 ± 4.026.7 ± 4.9<0.001***a
Non-smokers*1235 (84.8%)651 (82.4%)584 (87.6%)0.006**b
Ghrelin serum, pg/ml927.6 ± 450.6812.9 ± 306.71061.0 ± 545.0<0.001***a

*The total number of non-smokers=1457 (males=790; females=667); aA Kolmogorov-Smirnov-Test was performed in order to assess normal distribution. Because of non-normal distribution of the dependent variables according to these results, a Mann-Whitney-U-test was applied to compare ghrelin serum levels (Z=-11.13), age (Z=-0.29) and BMI values (Z=-4.19) between sexes. bA chi2 test for two-by-two tables was used.

The strongest hit was an intronic variant of the WW-domain containing the oxidoreductase-gene (WWOX) located on chromosome 16q23.3-24.1 (SNP: rs76823993; MAF=1.7%, explained variance 2.4%, P =1.8E-10.) Carriers of the minor allele had lower ghrelin serum levels (Fig. 1 and Table 2). Six further SNPs in the WWOX gene support the signal (P <E-6) (Fig. 2).

Figure 1
Figure 1

Manhattan plot showing the SNP associations for total ghrelin serum levels. The limit for genome-wide significance (P =5.0x10-8) is displayed as line.

Citation: European Journal of Endocrinology 184, 6; 10.1530/EJE-20-1220

Figure 2
Figure 2

Regional association (RA) plots of three GWAS hits. The lead SNP is colored blue, and the other SNPs are colored according to their LD with the lead SNP (using 1000 Genomes Phase 3, Europeans only). (A) RA plot for rs143729751 and GHRL at cytoband 3p25.3. (B) RA plot for rs192092592 and CNTNAP2 at 7q35. (C) RA plot for rs76823993 and WWOX at 16q23.1.

Citation: European Journal of Endocrinology 184, 6; 10.1530/EJE-20-1220

Table 2

Loci showing genome-wide significance (P ≤5E-8) and loci with independently associating SNPs showing trend significance (P ≤1E-6) for total ghrelin serum levels. Independent association was defined as R2<0.1 with any other shown SNP.

SNPCytobandChrPositionCandidate genesII scoreEffect alleleOther alleleMAFBeta (CI)Pη2
Loci showing genome-wide significance
 rs7682399316q23.11678740996WWOX0.927AC0.017-0.382 (-0.5 to -0.27)1.80E-100.024
 rs1920925927q357147356108CNTNAP20.859GA0.012-0.439 (-0.59 to -0.29)9.00E-90.019
 rs1437297513p25.3310330266GHRL0.952TG0.021-0.299 (-0.4 to -0.19)2.72E-80.018
Loci showing trend significance
 rs1393592419q33.19121992761BRINP10.834AG0.015-0.36 (-0.5 to -0.24)6.82E-80.017
 rs744832187p14.1738031039SFRP40.902AG0.015-0.35 (-0.48 to -0.22)1.37E-70.016
 rs1996533205q12.3565124780NLN0.997ACA0.010-0.40 (-0.55 to -0.25)1.59E-70.016
 rs1124264081q441244052447AKT30.87GA0.029-0.23 (-0.33 to -0.15)2.68E-70.016
 rs775637045q14.3591845530RP11-1330.936AC0.050-0.17 (-0.24 to -0.11)3.92E-70.015
 rs18786096020p12.3205920093TRMT60.84TC0.025-0.25 (-0.35 to -0.15)6.58E-70.015
 rs1382961285q12.3936885124PAX50.827AC0.012-0.38 (-0.53 to -0.23)7.60E-70.015
 rs802407061q441243997795AKT30.901TC0.027-0.23 (-0.32 to -0.14)8.87E-70.014
 rs14365357211p11.21144370951ALX40.818TC0.011-0.39 (-0.54 to -0.23)9.21E-70.014
 rs1422247184q244102643916BANK10.900CT0.011-0.37 (-0.53 to -0.23)9.64E-70.014

AKT3, AKT Serine/Threonine Kinase 3; ALX4, ALX Homeobox 4; BANK1, B Cell Scaffold Protein With Ankyrin Repeat; Beta (CI), Beta coefficient (CI); BRINP1, BMP/retinoic acid inducible neural specific 1; Chr, Chromosome; CNTNAP 2, Contactin Associated Protein Like 2; GHRL, Ghrelin And Obestatin Prepropeptide; II score, information quality of imputed SNPs according to IMPUTE 2; MAF, Minor allele frequency; NLN, Neurolysin; PAX 5, Paired Box 5; RP11-133, long ncRNA, manual annotation from Havana project; SFRP4, Secreted frizzled related protein 4; SNP, SNP; TRMT6, TRNA Methyltransferase 6; WWOX, WW-domain containing oxiduoreductase-gene; η2, explained variance.

The second strongest genetic variant reaching genome-wide significance is located on chromosome 7q35-q36.1 in the Contactin-Associated Protein-Like 2 gene (CNTNAP2; SNP: rs192092592; MAF=1.2%, explained variance 2.0%, P =9.0E-9) (Fig. 1 and Table 2). However, this SNP is not supported by other variants, requiring future validation. Carriers of the minor allele showed lower ghrelin serum levels.

The third genetic variant reaching genome-wide significance was on the Ghrelin And Obestatin Prepropeptide (GHRL) gene in the position 3p25.3 itself which is biologically highly plausible (SNP: rs143729751; MAF=2.1%, explained variance 1.8%, P =2.72E-8). The SNP is in some linkage disequilibrium (LD) with an eQTL of GHRL in blood (r2=0.64). Carriers of the minor allele showed lower ghrelin serum levels (Fig. 1 and Table 2). 10 independent hits in nine different genes reached trend significance (Table 2).

TWAs analysis

TWA analyses are statistical tests associating genetically predicted expression to a certain trait (36). In a MetaXcan-analysis, ghrelin serum levels were strongest associated with mRNA (mRNA) expression of the RPL36 gene (Ribosomal protein L36, z- score=4.8; P =1.3E-06, False-discovery-rate (FDR)=0.011, number of SNPs used=20) in a variety of tissues including whole blood, skin and lung, and at a nominal level, also in cerebellum, s.c. fat, esophagus mucosa, skeletal muscles and transverse colon. We also found significant association of the AP1B1 gene (adaptor related protein complex 1 subunit beta 1, zscore = 4.4, P =1.1E-5, FDR = 0.048, 26 SNPs used), observed strongest in spleen, and at nominal level, in adipose tissue, skin and blood. Although missing our significance cutoff, interestingly, the third-strongest associated gene was GFRAL in adipose tissue (GDNF family receptor alpha-like, z-score= -4.3; P =1.8E-05, FDR=0.15, number of SNPs used=109). Thus, a higher expression of RPL36 and a lower expression of AP1B1, and possibly, also a lower expression of GFRAL were associated with higher levels of serum ghrelin. Regional association plots summarizing the evidence of all eQTLs of RPL36, AP1B1 and GFRAL used to identify the gene-expression association with serum ghrelin are shown in Fig. 3.

Figure 3
Figure 3

Regional association plots of RPL36 (A), AP1B1 (B) and GFRAL (C) showing all eQTL-included in the top three gene expression models. It illustrates that many only nominal association of SNPs with ghrelin contribute jointly to the significant gene-level association of RPL36 (A) and AP1B1 (B), and to the gene level association of GFRAL (C), respectively.

Citation: European Journal of Endocrinology 184, 6; 10.1530/EJE-20-1220

Discussion

In this GWAS total ghrelin serum levels as trait were investigated. We were able to identify three genetic loci reaching genome-wide significance and 10 loci in nine genes that showed an association with ghrelin serum levels at a trend level, i.e. reaching a significance level between p≤1E-6 and p≥5E-8. The strongest and best supported hit was an intronic variant in the WWOX-gene (P =1.80E-10). WWOX spans the second most common fragile site FRA16D and encodes for a 414-amino acid protein that contains two WW domains. WW structures are known to be involved in protein-protein interactions. WWOX is highly expressed in hormonally regulated tissues (testis, prostate, and ovary) (37).

The second strongest hit was an intronic variant in the CNTNAP2-gene (P =9.0E-9). It is the longest gene in the human genome, encompassing almost 1.5% of chromosome 7. It encodes for the protein Contactin-Associated Protein-Like 2 (CASPR2). CASPR2 is part of the neurexin superfamily and functions as cell adhesion molecules and receptors in the CNS of vertebrae. It is mainly localized at the juxtaparanodes of myelinated axons and mediates interactions between neurons and glia during nervous system development. It is also involved in localization of potassium channels within differentiating axons (38).

The third hit was in the GHRL-gene itself (P =2.72E-8). GHRL encodes for a 117-amino acid preprohormone called preproghrelin. From this, the 28-amino acid des-acyl ghrelin is spliced, as well as obestatin and the C-terminal ending of the preproghrelin, called C-ghrelin. Obestatin was originally believed to be a ghrelin-antagonist, but more recent evidence has questioned this and both its exact function and the function of C-ghrelin remain unclear (5).

All candidate genes are functionally plausible:

When looking at the biological functions coded by WWOX and CNTNAP2, there is an overlap with functions of ghrelin, mainly concerning processes in the CNS. Both WWOX and CNTNAP2 seem to be involved in neuronal development, branching and maturation (39, 40). CNTNAP2 is involved in language processing and development in both animals and humans and a multitude of studies shows mental retardation and speech impairment in children with genetic aberrations in both genes as well as strong associations with epilepsy (41). This is of relevance, as ghrelin has been consistently shown to exert neuroprotective and anticonvulsant effects and promote neurogenesis, mainly in the hippocampus (11). WWOX and CNTNAP2 are associated with Alzheimer’s disease. SNPs of these genes (CNTNAP2 rs802571 and WWOX rs62039712) were previously reported to be associated with late ons, et alzheimer disease (LOAD) in GWAS and GWA-meta-analyses, respectively (42, 43). These previously reported SNPs are not in LD with SNPs identified in this study (R2<0.1).

Like ghrelin, WWOX seems to be involved in energy metabolism. WWOX SNPs again independent of those reported here showed genome wide significant association with obesity (44) and type 2 diabetes (45, 46). Another study reanalyzing 27 GWA datasets found several SNPs in the WWOX-gene to be associated with high fasting glucose, abnormal waist circumference, high BMI and dysregulated triglyceride levels. Notably, some of these SNPs were in the gene’s coding sequence (47). Underlining the significance of WWOX involvement in energy metabolism, WWOX-double-knockout mice die by an age of 3 weeks due to severe hypoglycaemia (47, 48). A loss of function of WWOX has been documented in many tumor entities (49) and WWOX has been shown to be a tumor-suppressor gene (50). Ghrelin is expressed in many cancers like renal cell carcinoma, pancreatic cancer, thyroid cancer, lung cancer, breast cancer, prostate cancer, gastric cancer and colorectal carcinoma. However, its role in cancer growth and progression seems to be complex and is being controversially discussed (14).

CNTNAP2 has been repeatedly linked to psychiatric diseases. Especially for autism, there is broad evidence suggesting an involvement of CNTNAP2 in the pathogenesis of this disease (51, 52). CNTNAP2 has also been shown to be associated with schizophrenia, bipolar disorder and major depression (38, 53). Also the fact that auto-antibodies against CASPR2, CNTNAP2’s gene product, can cause autoimmune-encephalitis often presenting with schizophrenia-like symptomatology is in line with CNTNAP2’s involvement in psychiatric illnesses (54). Ghrelin has been consistently shown to exert antidepressant and anxiolytic properties in animals models and the ghrelin system has been repeatedly shown to be altered in patients suffering from major depression (11).

In a TWAS using MetaXcan (27), exploiting tissue-specific expression quantitative trait loci (eQTLs), a positive association between ghrelin serum levels was found for mRNA expression levels of the RPL36 gene in various tissues including cerebellum, whole blood, s.c. fat, esophagus mucosa, skeletal muscles and transverse colon. Additionally, a negative association of ghrelin serum levels was found with mRNA expression levels of AP1B1 in spleen, adipose tissue, skin and blood.

RPL36 is a subunit of the 60S ribosomal protein and as such involved in protein synthesis and cell proliferation (55). This finding is also biologically plausible as ghrelin functions as an anabolic hormone. Furthermore, RPL36 has been implicated like ghrelin in carcinogenesis with a so far unclear role (55).

AP1B1 is an epithelium-specific variant of one of at least seven subtypes of adaptor proteins on vesical protein coats involved in intracellular vesicular transport of proteins (56, 57) and was found to be responsive to fasting in an animal model in that it was down-regulated in a fasting state (58). This is in line with its inverse relationship to ghrelin levels observed here.

The third-strongest associated gene in our TWAS was the GFRAL gene where mRNA in s.c. adipose tissue was negatively correlated with ghrelin serum levels. This association missed our stringent FDR-significance criterion of FDR=0.05 with a q-value of 0.15. We nonetheless deem it an interesting, biologically plausible finding worth being reported, particularly considering, that another common FDR-significance cut-off is 0.2 (59, 60). The GDF15/GFRAL-system has only been identified recently. In 2017, four groups reported that brain-stem located GFRAL, detected in 2005 as an orphan receptor (61), is the receptor for GDF15, requiring receptor tyrosine kinase (RET) as a co-receptor (21, 22, 23, 24). GDF15, also known as Macrophage Inhibitory Cytokine-1 (MIC-1), had been identified in 2007 as a peptide mediating anorectic/cachectic and aversive effects (19). Its relevance is just being recognized: For example, weight loss associated with metformin, the worldwide most prescribed antidiabetic, was shown to correlate with increase of GDF15 and to depend on the integrity of the GDF15/GFRAL system (20).

Our findings suggest that increased expression of GFRAL in s.c. adipose tissue has a directional effect on reducing ghrelin serum levels. It is unclear at this point, by which mechanism this might be facilitated and even if there is a direct effect of GDF-15/GFRAL on ghrelin serum levels. Furthermore, our association was not robust and requires independent validation. Functionally, however, this link is very plausible, as the GDF15/GFRAL-system and the ghrelin system have opposing effects in the organism, not only in energy metabolism and appetite control. A further parallel between ghrelin and GDF15, is that both are produced in times of stress (5, 62, 63). Here, too, they have opposite effects on appetite and food intake, being in line with a metabolic interaction also in stress. In addition, very recently, GDF-15 was shown to have pro-emetic effects (64). while ghrelin is known to be a strong anti-emetic agent and promoter of gastric motility (65). This further points to an antagonistic relationship between ghrelin and GDF-15/GFRAL. Finally, for ghrelin and GDF15 both tumor-growth promoting and -inhibiting effects are being discussed (14, 66). Yet, while the presence of GFRAL-mRNA in s.c. adipose tissue is a robust and replicated finding (23, 27; Supplementary figure, see section on supplementary materials given at the end of this article) with s.c. adipose tissue showing the strongest expression of GFRAL in humans (GTEx Portal accessible at https://www.gtexportal.org/home/gene/GFRAL) its biological relevance in s.c. tissue remains to be elucidated, since its protein product, the GFRAL-receptor, has been detected so far only in the brain stem (22, 23).

So far, no data exists linking GFRAL and ghrelin and only very scarce data studying GDF15 and ghrelin. Here, a non-peptidergic ghrelin receptor agonist did not affect GDF15 in mice (67).

Limitations of this study are the relatively small case sample for a GWAS and that no replication cohort was available. Larger samples sizes, replication samples and meta-analyses are required to validate our findings and to further unravel genetics of ghrelin serum levels. Furthermore, only total ghrelin but not acylated ghrelin was measured, due to methodological reasons. Since acylated ghrelin is the biologically active form, measuring it directly would allow for more direct conclusions. Thus, the goal for future GWA studies should be to determine both acylated- and total ghrelin.

In conclusion, we identified three functionally plausible genetic loci reaching genome-wide significance in the GWAS of ghrelin serum levels. Furthermore, performing a TWAS, we could link total ghrelin serum levels with RPL-36 and AP1B1, genes involved in basic cell metabolism and protein synthesis, as well as the GDF15/GFRAL-system. The exact nature and mechanism of interaction at this point remains elusive and should be subject of further research. This might lead to a better understanding of and innovative treatment approaches for metabolic, oncological and neuropsychiatric diseases.

Supplementary materials

This is linked to the online version of the paper at https://doi.org/10.1530/EJE-20-1220.

Declaration of interest

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of this study.

Funding

This work was supported by LIFE − Leipzig Research Center for Civilization Diseases, University of Leipzig. LIFE is funded by means of the European Union, by means of the European Social Fund (ESF), by the European Regional Development Fund (ERDF), and by means of the Free State of Saxony within the framework of the excellence initiative.

References

  • 1

    Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H & Kangawa K Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature 1999 402 656660. (https://doi.org/10.1038/45230)

    • Search Google Scholar
    • Export Citation
  • 2

    Gutierrez JA, Solenberg PJ, Perkins DR, Willency JA, Knierman MD, Jin Z, Witcher DR, Luo S, Onyia JE & Hale JE Ghrelin octanoylation mediated by an orphan lipid transferase. PNAS 2008 105 63206325. (https://doi.org/10.1073/pnas.0800708105)

    • Search Google Scholar
    • Export Citation
  • 3

    Yang J, Brown MS, Liang G, Grishin NV & Goldstein JL Identification of the acyltransferase that octanoylates ghrelin, an appetite-stimulating peptide hormone. Cell 2008 132 387396. (https://doi.org/10.1016/j.cell.2008.01.017)

    • Search Google Scholar
    • Export Citation
  • 4

    Cummings DE, Purnell JQ, Frayo RS, Schmidova K, Wisse BE & Weigle DS A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans. Diabetes 2001 50 17141719. (https://doi.org/10.2337/diabetes.50.8.1714)

    • Search Google Scholar
    • Export Citation
  • 5

    Müller TD, Nogueiras R, Andermann ML, Andrews ZB, Anker SD, Argente J, Batterham RL, Benoit SC, Bowers CY & Broglio F et al.Ghrelin. Molecular Metabolism 2015 4 437460. (https://doi.org/10.1016/j.molmet.2015.03.005)

    • Search Google Scholar
    • Export Citation
  • 6

    Gnanapavan S, Kola B, Bustin SA, Morris DG, McGee P, Fairclough P, Bhattacharya S, Carpenter R, Grossman AB & Korbonits M The tissue distribution of the mRNA of ghrelin and subtypes of its receptor, GHS-R, in humans. Journal of Clinical Endocrinology and Metabolism 2002 87 2988. (https://doi.org/10.1210/jcem.87.6.8739)

    • Search Google Scholar
    • Export Citation
  • 7

    Kluge M, Schüssler P, Uhr M, Yassouridis A & Steiger A Ghrelin suppresses secretion of luteinizing hormone in humans. Journal of Clinical Endocrinology and Metabolism 2007 92 32023205. (https://doi.org/10.1210/jc.2007-0593)

    • Search Google Scholar
    • Export Citation
  • 8

    Kluge M, Riedl S, Uhr M, Schmidt D, Zhang X, Yassouridis A & Steiger A Ghrelin affects the hypothalamus-pituitary-thyroid axis in humans by increasing free thyroxine and decreasing TSH in plasma. European Journal of Endocrinology/European Federation of Endocrine Societies 2010 162 10591065. (https://doi.org/10.1530/EJE-10-0094)

    • Search Google Scholar
    • Export Citation
  • 9

    Damian M, Marie J, Leyris JP, Fehrentz JA, Verdié P, Martinez J, Banères JL & Mary S High constitutive activity is an intrinsic feature of ghrelin receptor protein: a study with a functional monomeric GHS-R1a receptor reconstituted in lipid discs. Journal of Biological Chemistry 2012 287 36303641. (https://doi.org/10.1074/jbc.M111.288324)

    • Search Google Scholar
    • Export Citation
  • 10

    Jerlhag E, Egecioglu E, Landgren S, Salomé N, Heilig M, Moechars D, Datta R, Perrissoud D, Dickson SL & Engel JA Requirement of central ghrelin signaling for alcohol reward. PNAS 2009 106 1131811323. (https://doi.org/10.1073/pnas.0812809106)

    • Search Google Scholar
    • Export Citation
  • 11

    Wittekind DA & Kluge M Ghrelin in psychiatric disorders – a review. Psychoneuroendocrinology 2015 52 176194. (https://doi.org/10.1016/j.psyneuen.2014.11.013)

    • Search Google Scholar
    • Export Citation
  • 12

    Spencer SJ, Xu L, Clarke MA, Lemus M, Reichenbach A, Geenen B, Kozicz T & Andrews ZB Ghrelin regulates the hypothalamic-pituitary-adrenal axis and restricts anxiety after acute stress. Biological Psychiatry 2012 72 457465. (https://doi.org/10.1016/j.biopsych.2012.03.010)

    • Search Google Scholar
    • Export Citation
  • 13

    Li Z, Xu G, Qin Y, Zhang C, Tang H, Yin Y, Xiang X, Li Y, Zhao J & Mulholland M et al.Ghrelin promotes hepatic lipogenesis by activation of mTOR-PPAR signaling pathway. PNAS 2014 111 1316313168. (https://doi.org/10.1073/pnas.1411571111)

    • Search Google Scholar
    • Export Citation
  • 14

    Soleyman-Jahi S, Sadeghi F, Pastaki Khoshbin A, Khani L, Roosta V & Zendehdel K Attribution of ghrelin to cancer; attempts to unravel an apparent controversy. Frontiers in Oncology 2019 9 1014. (https://doi.org/10.3389/fonc.2019.01014)

    • Search Google Scholar
    • Export Citation
  • 15

    Tschöp M, Smiley DL & Heiman ML Ghrelin induces adiposity in rodents. Nature 2000 407 908913. (https://doi.org/10.1038/35038090)

  • 16

    Schaeffer M, Langlet F, Lafont C, Molino F, Hodson DJ, Roux T, Lamarque L, Verdié P, Bourrier E & Dehouck B et al.Rapid sensing of circulating ghrelin by hypothalamic appetite-modifying neurons. PNAS 2013 110 15121517. (https://doi.org/10.1073/pnas.1212137110)

    • Search Google Scholar
    • Export Citation
  • 17

    Yanagi S, Sato T, Kangawa K & Nakazato M The homeostatic force of ghrelin. Cell Metabolism 2018 27 786804. (https://doi.org/10.1016/j.cmet.2018.02.008)

    • Search Google Scholar
    • Export Citation
  • 18

    Zanchi D, Depoorter A, Egloff L, Haller S, Mählmann L, Lang UE, Drewe J, Beglinger C, Schmidt A & Borgwardt S The impact of gut hormones on the neural circuit of appetite and satiety: a systematic review. Neuroscience and Biobehavioral Reviews 2017 80 457475. (https://doi.org/10.1016/j.neubiorev.2017.06.013)

    • Search Google Scholar
    • Export Citation
  • 19

    Johnen H, Lin S, Kuffner T, Brown DA, Tsai VWW, Bauskin AR, Wu L, Pankhurst G, Jiang L & Junankar S et al.Tumor-induced anorexia and weight loss are mediated by the TGF-β superfamily cytokine MIC-1. Nature Medicine 2007 13 13331340. (https://doi.org/10.1038/nm1677)

    • Search Google Scholar
    • Export Citation
  • 20

    Coll AP, Chen M, Taskar P, Rimmington D, Patel S, Tadross JA, Cimino I, Yang M, Welsh P & Virtue S et al.GDF15 mediates the effects of metformin on body weight and energy balance. Nature 2020 578 444448. (https://doi.org/10.1038/s41586-019-1911-y)

    • Search Google Scholar
    • Export Citation
  • 21

    Emmerson PJ, Wang F, Du Y, Liu Q, Pickard RT, Gonciarz MD, Coskun T, Hamang MJ, Sindelar DK & Ballman KK et al.The metabolic effects of GDF15 are mediated by the orphan receptor GFRAL. Nature Medicine 2017 23 12151219. (https://doi.org/10.1038/nm.4393)

    • Search Google Scholar
    • Export Citation
  • 22

    Hsu JY, Crawley S, Chen M, Ayupova DA, Lindhout DA, Higbee J, Kutach A, Joo W, Gao Z & Fu D et al.Non-homeostatic body weight regulation through a brainstem-restricted receptor for GDF15. Nature 2017 550 255259. (https://doi.org/10.1038/nature24042)

    • Search Google Scholar
    • Export Citation
  • 23

    Mullican SE, Lin-Schmidt X, Chin CN, Chavez JA, Furman JL, Armstrong AA, Beck SC, South VJ, Dinh TQ & Cash-Mason TD et al.GFRAL is the receptor for GDF15 and the ligand promotes weight loss in mice and nonhuman primates. Nature Medicine 2017 23 11501157. (https://doi.org/10.1038/nm.4392)

    • Search Google Scholar
    • Export Citation
  • 24

    Yang L, Chang CC, Sun Z, Madsen D, Zhu H, Padkjær SB, Wu X, Huang T, Hultman K & Paulsen SJ et al.GFRAL is the receptor for GDF15 and is required for the anti-obesity effects of the ligand. Nature Medicine 2017 23 11581166. (https://doi.org/10.1038/nm.4394)

    • Search Google Scholar
    • Export Citation
  • 25

    Khatib MN, Gaidhane A, Gaidhane S & Quazi ZS Ghrelin as a promising therapeutic option for cancer cachexia. Cellular Physiology and Biochemistry 2018 48 21722188. (https://doi.org/10.1159/000492559)

    • Search Google Scholar
    • Export Citation
  • 26

    Lee MR, Tapocik JD, Ghareeb M, Schwandt ML, Dias AA, Le AN, Cobbina E, Farinelli LA, Bouhlal S & Farokhnia M et al.The novel ghrelin receptor inverse agonist PF-5190457 administered with alcohol: preclinical safety experiments and a phase 1b human laboratory study. Molecular Psychiatry 2020 25 461475. (https://doi.org/10.1038/s41380-018-0064-y)

    • Search Google Scholar
    • Export Citation
  • 27

    Barbeira AN, Dickinson SP, Bonazzola R, Zheng J, Wheeler HE, Torres JM, Torstenson ES, Shah KP, Garcia T & Edwards TL et al.Exploring the phenotypic consequences of tissue specific gene expression variation inferred from GWAS summary statistics. Nature Communications 2018 9 1825. (https://doi.org/10.1038/s41467-018-03621-1)

    • Search Google Scholar
    • Export Citation
  • 28

    Loeffler M, Engel C, Ahnert P, Alfermann D, Arelin K, Baber R, Beutner F, Binder H, Brähler E & Burkhardt R et al.The LIFE-Adult-Study: objectives and design of a population-based cohort study with 10 000 deeply phenotyped adults in Germany. BMC Public Health 2015 15 691. (https://doi.org/10.1186/s12889-015-1983-z)

    • Search Google Scholar
    • Export Citation
  • 29

    Pott J, Burkhardt R, Beutner F, Horn K, Teren A, Kirsten H, Holdt LM, Schuler G, Teupser D & Loeffler M et al.Genome-wide meta-analysis identifies novel loci of plaque burden in carotid artery. Atherosclerosis 2017 259 3240. (https://doi.org/10.1016/j.atherosclerosis.2017.02.018)

    • Search Google Scholar
    • Export Citation
  • 30

    1000 Genomes Project Consortium, Auton A, Brooks LD, Durbin RM, Garrison EP, Kang HM, Korbel JO, Marchini JL, McCarthy S & McVean GA et al.A global reference for human genetic variation. Nature 2015 526 6874. (https://doi.org/10.1038/nature15393)

    • Search Google Scholar
    • Export Citation
  • 31

    Howie BN, Donnelly P & Marchini J A flexible and accurate genotype imputation method for the next generation of genome-wide association studies. PLoS Genetics 2009 5 e1000529. (https://doi.org/10.1371/journal.pgen.1000529)

    • Search Google Scholar
    • Export Citation
  • 32

    Delaneau O, Howie B, Cox AJ, Zagury JF & Marchini J Haplotype estimation using sequencing reads. American Journal of Human Genetics 2013 93 687696. (https://doi.org/10.1016/j.ajhg.2013.09.002)

    • Search Google Scholar
    • Export Citation
  • 33

    Pott J, Schlegel V, Teren A, Horn K, Kirsten H, Bluecher C, Kratzsch J, Loeffler M, Thiery J & Burkhardt R et al.Genetic regulation of PCSK9 (proprotein convertase subtilisin/kexin type 9) plasma levels and its impact on atherosclerotic vascular disease phenotypes. Circulation: Genomic and Precision Medicine 2018 11 e001992. (https://doi.org/10.1161/CIRCGEN.117.001992)

    • Search Google Scholar
    • Export Citation
  • 34

    MacArthur J, Bowler E, Cerezo M, Gil L, Hall P, Hastings E, Junkins H, McMahon A, Milano A & Morales J et al.The new NHGRI-EBI Catalog of published genome-wide association studies (GWAS Catalog). Nucleic Acids Research 2017 45 D896–D901. (https://doi.org/10.1093/nar/gkw1133)

    • Search Google Scholar
    • Export Citation
  • 35

    Kirsten H, Al-Hasani H, Holdt L, Gross A, Beutner F, Krohn K, Horn K, Ahnert P, Burkhardt R & Reiche K et al.Dissecting the genetics of the human transcriptome identifies novel trait-related trans-eQTLs and corroborates the regulatory relevance of non-protein coding loci†. Human Molecular Genetics 2015 24 4746–4763. (https://doi.org/10.1093/hmg/ddv194)

    • Search Google Scholar
    • Export Citation
  • 36

    Wainberg M, Sinnott-Armstrong N, Mancuso N, Barbeira AN, Knowles DA, Golan D, Ermel R, Ruusalepp A, Quertermous T & Hao K et al.Opportunities and challenges for transcriptome-wide association studies. Nature Genetics 2019 51 592599. (https://doi.org/10.1038/s41588-019-0385-z)

    • Search Google Scholar
    • Export Citation
  • 37

    Bednarek AK, Keck-Waggoner CL, Daniel RL, Laflin KJ, Bergsagel PL, Kiguchi K, Brenner AJ & Aldaz CM WWOX, the FRA16D gene, behaves as a suppressor of tumor growth. Cancer Research 2001 61 80688073.

    • Search Google Scholar
    • Export Citation
  • 38

    Gao R, Piguel NH, Melendez-Zaidi AE, Martin-de-Saavedra MD, Yoon S, Forrest MP, Myczek K, Zhang G, Russell TA & Csernansky JG et al.. CNTNAP2 stabilizes interneuron dendritic arbors through CASK. Molecular Psychiatry 2018 23 18321850. (https://doi.org/10.1038/s41380-018-0027-3)

    • Search Google Scholar
    • Export Citation
  • 39

    Dennis EL, Jahanshad N, Rudie JD, Brown JA, Johnson K, McMahon KL, Zubicaray de GI, Montgomery G, Martin NG & Wright MJ et al.Altered structural brain connectivity in healthy carriers of the autism risk gene, CNTNAP2. Brain Connectivity 2011 1 447459. (https://doi.org/10.1089/brain.2011.0064)

    • Search Google Scholar
    • Export Citation
  • 40

    Liska A, Bertero A, Gomolka R, Sabbioni M, Galbusera A, Barsotti N, Panzeri S, Scattoni ML, Pasqualetti M & Gozzi A Homozygous loss of autism-risk gene CNTNAP2 results in reduced local and long-range prefrontal functional connectivity. Cerebral Cortex 2018 28 11411153. (https://doi.org/10.1093/cercor/bhx022)

    • Search Google Scholar
    • Export Citation
  • 41

    Davids M, Markello T, Wolfe LA, Chepa-Lotrea X, Tifft CJ, Gahl WA & Malicdan MCV Early infantile-onset epileptic encephalopathy 28 due to a homozygous microdeletion involving the WWOX gene in a region of uniparental disomy. Human Mutation 2019 40 4247. (https://doi.org/10.1002/humu.23675)

    • Search Google Scholar
    • Export Citation
  • 42

    Hirano A, Ohara T, Takahashi A, Aoki M, Fuyuno Y, Ashikawa K, Morihara T, Takeda M, Kamino K & Oshima E et al.A genome-wide association study of late-onset Alzheimer’s disease in a Japanese population. Psychiatric Genetics 2015 25 139146. (https://doi.org/10.1097/YPG.0000000000000090)

    • Search Google Scholar
    • Export Citation
  • 43

    Kunkle BW, Grenier-Boley B, Sims R, Bis JC, Damotte V, Naj AC, Boland A, Vronskaya M, Lee van der SJ & Amlie-Wolf A et al.Genetic meta-analysis of diagnosed Alzheimer’s disease identifies new risk loci and implicates Aβ, tau, immunity and lipid processing. Nature Genetics 2019 51 414430. (https://doi.org/10.1038/s41588-019-0358-2)

    • Search Google Scholar
    • Export Citation
  • 44

    Wang K, Li WD, Zhang CK, Wang Z, Glessner JT, Grant SFA, Zhao H, Hakonarson H & Price RA A genome-wide association study on obesity and obesity-related traits. PLoS ONE 2011 6 e18939. (https://doi.org/10.1371/journal.pone.0018939)

    • Search Google Scholar
    • Export Citation
  • 45

    Tsai FJ, Yang CF, Chen CC, Chuang LM, Lu CH, Chang CT, Wang TY, Chen RH, Shiu CF & Liu YM et al.A genome-wide association study identifies susceptibility variants for type 2 diabetes in Han Chinese. PLoS Genetics 2010 6 e1000847. (https://doi.org/10.1371/journal.pgen.1000847)

    • Search Google Scholar
    • Export Citation
  • 46

    Cho YS, Chen CH, Hu C, Long J, Hee Ong RT, Sim X, Takeuchi F, Wu Y, Go MJ & Yamauchi T et al.Meta-analysis of genome-wide association studies identifies eight new loci for type 2 diabetes in east Asians. Nature Genetics 2012 44 6772. (https://doi.org/10.1038/ng.1019)

    • Search Google Scholar
    • Export Citation
  • 47

    Abu-Remaileh M, Abu-Remaileh M, Akkawi R, Knani I, Udi S, Pacold ME, Tam J & Aqeilan RI WWOX somatic ablation in skeletal muscles alters glucose metabolism. Molecular Metabolism 2019 22 132140. (https://doi.org/10.1016/j.molmet.2019.01.010)

    • Search Google Scholar
    • Export Citation
  • 48

    Aqeilan RI, Hassan MQ, Bruin De A, Hagan JP, Volinia S, Palumbo T, Hussain S, Lee SH, Gaur T & Stein GS et al.The WWOX tumor suppressor is essential for postnatal survival and normal bone metabolism. Journal of Biological Chemistry 2008 283 2162921639. (https://doi.org/10.1074/jbc.M800855200)

    • Search Google Scholar
    • Export Citation
  • 49

    Hussain T, Liu B, Shrock MS, Williams T & Aldaz CM WWOX, the FRA16D gene: a target of and a contributor to genomic instability. Genes, Chromosomes and Cancer 2019 58 324338. (https://doi.org/10.1002/gcc.22693)

    • Search Google Scholar
    • Export Citation
  • 50

    Fabbri M, Iliopoulos D, Trapasso F, Aqeilan RI, Cimmino A, Zanesi N, Yendamuri S, Han SY, Amadori D & Huebner K et al.WWOX gene restoration prevents lung cancer growth in vitro and in vivo. PNAS 2005 102 1561115616. (https://doi.org/10.1073/pnas.0505485102)

    • Search Google Scholar
    • Export Citation
  • 51

    Anderson GR, Galfin T, Xu W, Aoto J, Malenka RC & Südhof TC Candidate autism gene screen identifies critical role for cell-adhesion molecule CASPR2 in dendritic arborization and spine development. PNAS 2012 109 1812018125. (https://doi.org/10.1073/pnas.1216398109)

    • Search Google Scholar
    • Export Citation
  • 52

    Yoo HJ, Kim BN, Kim JW, Shin MS, Park TW, Son JW, Chung US, Park M & Kim SA Family-based genetic association study of CNTNAP2 polymorphisms and sociality endophenotypes in Korean patients with autism spectrum disorders. Psychiatric Genetics 2017 27 3839. (https://doi.org/10.1097/YPG.0000000000000150)

    • Search Google Scholar
    • Export Citation
  • 53

    Friedman JI, Vrijenhoek T, Markx S, Janssen IM, Vliet van der WA, Faas BHW, Knoers NV, Cahn W, Kahn RS & Edelmann L et al.CNTNAP2 gene dosage variation is associated with schizophrenia and epilepsy. Molecular Psychiatry 2008 13 261266. (https://doi.org/10.1038/sj.mp.4002049)

    • Search Google Scholar
    • Export Citation
  • 54

    Sonderen van A, Ariño H, Petit-Pedrol M, Leypoldt F, Körtvélyessy P, Wandinger KP, Lancaster E, Wirtz PW, Schreurs MWJ & Sillevis Smitt PAE et al.The clinical spectrum of Caspr2 antibody-associated disease. Neurology 2016 87 521528. (https://doi.org/10.1212/WNL.0000000000002917)

    • Search Google Scholar
    • Export Citation
  • 55

    Hu YW, Kang CM, Zhao JJ, Nie Y, Zheng L, Li HX, Li X, Wang Q & Qiu YR LncRNA PLAC2 down-regulates RPL36 expression and blocks cell cycle progression in glioma through a mechanism involving STAT1. Journal of Cellular and Molecular Medicine 2018 22 497510. (https://doi.org/10.1111/jcmm.13338)

    • Search Google Scholar
    • Export Citation
  • 56

    Alsaif HS, Al-Owain M, Barrios-Llerena ME, Gosadi G, Binamer Y, Devadason D, Ravenscroft J, Suri M & Alkuraya FS Homozygous loss-of-function mutations in AP1B1, encoding beta-1 subunit of adaptor-related protein complex 1, cause MEDNIK-like syndrome. American Journal of Human Genetics 2019 105 10161022. (https://doi.org/10.1016/j.ajhg.2019.09.020)

    • Search Google Scholar
    • Export Citation
  • 57

    Boyden LM, Atzmony L, Hamilton C, Zhou J, Lim YH, Hu R, Pappas J, Rabin R, Ekstien J & Hirsch Y et al.Recessive mutations in AP1B1 cause ichthyosis, deafness, and photophobia. American Journal of Human Genetics 2019 105 10231029. (https://doi.org/10.1016/j.ajhg.2019.09.021)

    • Search Google Scholar
    • Export Citation
  • 58

    Liu L, Yi J, Ray WK, Vu LT, Helm RF, Siegel PB, Cline MA & Gilbert ER Fasting differentially alters the hypothalamic proteome of chickens from lines with the propensity to be anorexic or obese. Nutrition and Diabetes 2019 9 13. (https://doi.org/10.1038/s41387-019-0081-1)

    • Search Google Scholar
    • Export Citation
  • 59

    Barber RF & Candés EJ Controlling the false discovery rate via knockoffs. Annals of Statistics 2015 43 20552085. (https://doi.org/10.1214/15-AOS1337)

    • Search Google Scholar
    • Export Citation
  • 60

    Shen A, Fu H, He K & Jiang H False discovery rate control in cancer biomarker selection using knockoffs. Cancers 2019 11 744. (https://doi.org/10.3390/cancers11060744)

    • Search Google Scholar
    • Export Citation
  • 61

    Li Z, Wang B, Wu X, Cheng SY, Paraoan L & Zhou J Identification, expression and functional characterization of the GRAL gene. Journal of Neurochemistry 2005 95 361376. (https://doi.org/10.1111/j.1471-4159.2005.03372.x)

    • Search Google Scholar
    • Export Citation
  • 62

    Patel S, Alvarez-Guaita A, Melvin A, Rimmington D, Dattilo A, Miedzybrodzka EL, Cimino I, Maurin AC, Roberts GP & Meek CL et al.GDF15 provides an endocrine signal of nutritional stress in mice and humans. Cell Metabolism 2019 29 707 .e8718.e8. (https://doi.org/10.1016/j.cmet.2018.12.016)

    • Search Google Scholar
    • Export Citation
  • 63

    Tsai VWW, Husaini Y, Sainsbury A, Brown DA & Breit SN The MIC-1/GDF15-GFRAL pathway in energy homeostasis: implications for obesity, cachexia, and other associated diseases. Cell Metabolism 2018 28 353368. (https://doi.org/10.1016/j.cmet.2018.07.018)

    • Search Google Scholar
    • Export Citation
  • 64

    Borner T, Shaulson ED, Ghidewon MY, Barnett AB, Horn CC, Doyle RP, Grill HJ, Hayes MR & de Jonghe BC GDF15 induces anorexia through nausea and emesis. Cell Metabolism 2020 31 351 .e5362.e5. (https://doi.org/10.1016/j.cmet.2019.12.004)

    • Search Google Scholar
    • Export Citation
  • 65

    Sanger GJ & Furness JB Ghrelin and motilin receptors as drug targets for gastrointestinal disorders. Nature Reviews: Gastroenterology and Hepatology 2016 13 3848. (https://doi.org/10.1038/nrgastro.2015.163)

    • Search Google Scholar
    • Export Citation
  • 66

    Fang L, Li F & Gu C GDF-15: a multifunctional modulator and potential therapeutic target in cancer. Current Pharmaceutical Design 2019 25 654662. (https://doi.org/10.2174/1381612825666190402101143)

    • Search Google Scholar
    • Export Citation
  • 67

    Villars FO, Pietra C, Giuliano C, Lutz TA & Riediger T Oral treatment with the ghrelin receptor agonist HM01 attenuates cachexia in mice bearing colon-26 (C26) tumors. International Journal of Molecular Sciences 2017 18 986. (https://doi.org/10.3390/ijms18050986)

    • Search Google Scholar
    • Export Citation

 

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  • View in gallery

    Manhattan plot showing the SNP associations for total ghrelin serum levels. The limit for genome-wide significance (P =5.0x10-8) is displayed as line.

  • View in gallery

    Regional association (RA) plots of three GWAS hits. The lead SNP is colored blue, and the other SNPs are colored according to their LD with the lead SNP (using 1000 Genomes Phase 3, Europeans only). (A) RA plot for rs143729751 and GHRL at cytoband 3p25.3. (B) RA plot for rs192092592 and CNTNAP2 at 7q35. (C) RA plot for rs76823993 and WWOX at 16q23.1.

  • View in gallery

    Regional association plots of RPL36 (A), AP1B1 (B) and GFRAL (C) showing all eQTL-included in the top three gene expression models. It illustrates that many only nominal association of SNPs with ghrelin contribute jointly to the significant gene-level association of RPL36 (A) and AP1B1 (B), and to the gene level association of GFRAL (C), respectively.

  • 1

    Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H & Kangawa K Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature 1999 402 656660. (https://doi.org/10.1038/45230)

    • Search Google Scholar
    • Export Citation
  • 2

    Gutierrez JA, Solenberg PJ, Perkins DR, Willency JA, Knierman MD, Jin Z, Witcher DR, Luo S, Onyia JE & Hale JE Ghrelin octanoylation mediated by an orphan lipid transferase. PNAS 2008 105 63206325. (https://doi.org/10.1073/pnas.0800708105)

    • Search Google Scholar
    • Export Citation
  • 3

    Yang J, Brown MS, Liang G, Grishin NV & Goldstein JL Identification of the acyltransferase that octanoylates ghrelin, an appetite-stimulating peptide hormone. Cell 2008 132 387396. (https://doi.org/10.1016/j.cell.2008.01.017)

    • Search Google Scholar
    • Export Citation
  • 4

    Cummings DE, Purnell JQ, Frayo RS, Schmidova K, Wisse BE & Weigle DS A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans. Diabetes 2001 50 17141719. (https://doi.org/10.2337/diabetes.50.8.1714)

    • Search Google Scholar
    • Export Citation
  • 5

    Müller TD, Nogueiras R, Andermann ML, Andrews ZB, Anker SD, Argente J, Batterham RL, Benoit SC, Bowers CY & Broglio F et al.Ghrelin. Molecular Metabolism 2015 4 437460. (https://doi.org/10.1016/j.molmet.2015.03.005)

    • Search Google Scholar
    • Export Citation
  • 6

    Gnanapavan S, Kola B, Bustin SA, Morris DG, McGee P, Fairclough P, Bhattacharya S, Carpenter R, Grossman AB & Korbonits M The tissue distribution of the mRNA of ghrelin and subtypes of its receptor, GHS-R, in humans. Journal of Clinical Endocrinology and Metabolism 2002 87 2988. (https://doi.org/10.1210/jcem.87.6.8739)

    • Search Google Scholar
    • Export Citation
  • 7

    Kluge M, Schüssler P, Uhr M, Yassouridis A & Steiger A Ghrelin suppresses secretion of luteinizing hormone in humans. Journal of Clinical Endocrinology and Metabolism 2007 92 32023205. (https://doi.org/10.1210/jc.2007-0593)

    • Search Google Scholar
    • Export Citation
  • 8

    Kluge M, Riedl S, Uhr M, Schmidt D, Zhang X, Yassouridis A & Steiger A Ghrelin affects the hypothalamus-pituitary-thyroid axis in humans by increasing free thyroxine and decreasing TSH in plasma. European Journal of Endocrinology/European Federation of Endocrine Societies 2010 162 10591065. (https://doi.org/10.1530/EJE-10-0094)

    • Search Google Scholar
    • Export Citation
  • 9

    Damian M, Marie J, Leyris JP, Fehrentz JA, Verdié P, Martinez J, Banères JL & Mary S High constitutive activity is an intrinsic feature of ghrelin receptor protein: a study with a functional monomeric GHS-R1a receptor reconstituted in lipid discs. Journal of Biological Chemistry 2012 287 36303641. (https://doi.org/10.1074/jbc.M111.288324)

    • Search Google Scholar
    • Export Citation
  • 10

    Jerlhag E, Egecioglu E, Landgren S, Salomé N, Heilig M, Moechars D, Datta R, Perrissoud D, Dickson SL & Engel JA Requirement of central ghrelin signaling for alcohol reward. PNAS 2009 106 1131811323. (https://doi.org/10.1073/pnas.0812809106)

    • Search Google Scholar
    • Export Citation
  • 11

    Wittekind DA & Kluge M Ghrelin in psychiatric disorders – a review. Psychoneuroendocrinology 2015 52 176194. (https://doi.org/10.1016/j.psyneuen.2014.11.013)

    • Search Google Scholar
    • Export Citation
  • 12

    Spencer SJ, Xu L, Clarke MA, Lemus M, Reichenbach A, Geenen B, Kozicz T & Andrews ZB Ghrelin regulates the hypothalamic-pituitary-adrenal axis and restricts anxiety after acute stress. Biological Psychiatry 2012 72 457465. (https://doi.org/10.1016/j.biopsych.2012.03.010)

    • Search Google Scholar
    • Export Citation
  • 13

    Li Z, Xu G, Qin Y, Zhang C, Tang H, Yin Y, Xiang X, Li Y, Zhao J & Mulholland M et al.Ghrelin promotes hepatic lipogenesis by activation of mTOR-PPAR signaling pathway. PNAS 2014 111 1316313168. (https://doi.org/10.1073/pnas.1411571111)

    • Search Google Scholar
    • Export Citation
  • 14

    Soleyman-Jahi S, Sadeghi F, Pastaki Khoshbin A, Khani L, Roosta V & Zendehdel K Attribution of ghrelin to cancer; attempts to unravel an apparent controversy. Frontiers in Oncology 2019 9 1014. (https://doi.org/10.3389/fonc.2019.01014)

    • Search Google Scholar
    • Export Citation
  • 15

    Tschöp M, Smiley DL & Heiman ML Ghrelin induces adiposity in rodents. Nature 2000 407 908913. (https://doi.org/10.1038/35038090)

  • 16

    Schaeffer M, Langlet F, Lafont C, Molino F, Hodson DJ, Roux T, Lamarque L, Verdié P, Bourrier E & Dehouck B et al.Rapid sensing of circulating ghrelin by hypothalamic appetite-modifying neurons. PNAS 2013 110 15121517. (https://doi.org/10.1073/pnas.1212137110)

    • Search Google Scholar
    • Export Citation
  • 17

    Yanagi S, Sato T, Kangawa K & Nakazato M The homeostatic force of ghrelin. Cell Metabolism 2018 27 786804. (https://doi.org/10.1016/j.cmet.2018.02.008)

    • Search Google Scholar
    • Export Citation
  • 18

    Zanchi D, Depoorter A, Egloff L, Haller S, Mählmann L, Lang UE, Drewe J, Beglinger C, Schmidt A & Borgwardt S The impact of gut hormones on the neural circuit of appetite and satiety: a systematic review. Neuroscience and Biobehavioral Reviews 2017 80 457475. (https://doi.org/10.1016/j.neubiorev.2017.06.013)

    • Search Google Scholar
    • Export Citation
  • 19

    Johnen H, Lin S, Kuffner T, Brown DA, Tsai VWW, Bauskin AR, Wu L, Pankhurst G, Jiang L & Junankar S et al.Tumor-induced anorexia and weight loss are mediated by the TGF-β superfamily cytokine MIC-1. Nature Medicine 2007 13 13331340. (https://doi.org/10.1038/nm1677)

    • Search Google Scholar
    • Export Citation
  • 20

    Coll AP, Chen M, Taskar P, Rimmington D, Patel S, Tadross JA, Cimino I, Yang M, Welsh P & Virtue S et al.GDF15 mediates the effects of metformin on body weight and energy balance. Nature 2020 578 444448. (https://doi.org/10.1038/s41586-019-1911-y)

    • Search Google Scholar
    • Export Citation
  • 21

    Emmerson PJ, Wang F, Du Y, Liu Q, Pickard RT, Gonciarz MD, Coskun T, Hamang MJ, Sindelar DK & Ballman KK et al.The metabolic effects of GDF15 are mediated by the orphan receptor GFRAL. Nature Medicine 2017 23 12151219. (https://doi.org/10.1038/nm.4393)

    • Search Google Scholar
    • Export Citation
  • 22

    Hsu JY, Crawley S, Chen M, Ayupova DA, Lindhout DA, Higbee J, Kutach A, Joo W, Gao Z & Fu D et al.Non-homeostatic body weight regulation through a brainstem-restricted receptor for GDF15. Nature 2017 550 255259. (https://doi.org/10.1038/nature24042)

    • Search Google Scholar
    • Export Citation
  • 23

    Mullican SE, Lin-Schmidt X, Chin CN, Chavez JA, Furman JL, Armstrong AA, Beck SC, South VJ, Dinh TQ & Cash-Mason TD et al.GFRAL is the receptor for GDF15 and the ligand promotes weight loss in mice and nonhuman primates. Nature Medicine 2017 23 11501157. (https://doi.org/10.1038/nm.4392)

    • Search Google Scholar
    • Export Citation
  • 24

    Yang L, Chang CC, Sun Z, Madsen D, Zhu H, Padkjær SB, Wu X, Huang T, Hultman K & Paulsen SJ et al.GFRAL is the receptor for GDF15 and is required for the anti-obesity effects of the ligand. Nature Medicine 2017 23 11581166. (https://doi.org/10.1038/nm.4394)

    • Search Google Scholar
    • Export Citation
  • 25

    Khatib MN, Gaidhane A, Gaidhane S & Quazi ZS Ghrelin as a promising therapeutic option for cancer cachexia. Cellular Physiology and Biochemistry 2018 48 21722188. (https://doi.org/10.1159/000492559)

    • Search Google Scholar
    • Export Citation
  • 26

    Lee MR, Tapocik JD, Ghareeb M, Schwandt ML, Dias AA, Le AN, Cobbina E, Farinelli LA, Bouhlal S & Farokhnia M et al.The novel ghrelin receptor inverse agonist PF-5190457 administered with alcohol: preclinical safety experiments and a phase 1b human laboratory study. Molecular Psychiatry 2020 25 461475. (https://doi.org/10.1038/s41380-018-0064-y)

    • Search Google Scholar
    • Export Citation
  • 27

    Barbeira AN, Dickinson SP, Bonazzola R, Zheng J, Wheeler HE, Torres JM, Torstenson ES, Shah KP, Garcia T & Edwards TL et al.Exploring the phenotypic consequences of tissue specific gene expression variation inferred from GWAS summary statistics. Nature Communications 2018 9 1825. (https://doi.org/10.1038/s41467-018-03621-1)

    • Search Google Scholar
    • Export Citation
  • 28

    Loeffler M, Engel C, Ahnert P, Alfermann D, Arelin K, Baber R, Beutner F, Binder H, Brähler E & Burkhardt R et al.The LIFE-Adult-Study: objectives and design of a population-based cohort study with 10 000 deeply phenotyped adults in Germany. BMC Public Health 2015 15 691. (https://doi.org/10.1186/s12889-015-1983-z)

    • Search Google Scholar
    • Export Citation
  • 29

    Pott J, Burkhardt R, Beutner F, Horn K, Teren A, Kirsten H, Holdt LM, Schuler G, Teupser D & Loeffler M et al.Genome-wide meta-analysis identifies novel loci of plaque burden in carotid artery. Atherosclerosis 2017 259 3240. (https://doi.org/10.1016/j.atherosclerosis.2017.02.018)

    • Search Google Scholar
    • Export Citation
  • 30

    1000 Genomes Project Consortium, Auton A, Brooks LD, Durbin RM, Garrison EP, Kang HM, Korbel JO, Marchini JL, McCarthy S & McVean GA et al.A global reference for human genetic variation. Nature 2015 526 6874. (https://doi.org/10.1038/nature15393)

    • Search Google Scholar
    • Export Citation
  • 31

    Howie BN, Donnelly P & Marchini J A flexible and accurate genotype imputation method for the next generation of genome-wide association studies. PLoS Genetics 2009 5 e1000529. (https://doi.org/10.1371/journal.pgen.1000529)

    • Search Google Scholar
    • Export Citation
  • 32

    Delaneau O, Howie B, Cox AJ, Zagury JF & Marchini J Haplotype estimation using sequencing reads. American Journal of Human Genetics 2013 93 687696. (https://doi.org/10.1016/j.ajhg.2013.09.002)

    • Search Google Scholar
    • Export Citation
  • 33

    Pott J, Schlegel V, Teren A, Horn K, Kirsten H, Bluecher C, Kratzsch J, Loeffler M, Thiery J & Burkhardt R et al.Genetic regulation of PCSK9 (proprotein convertase subtilisin/kexin type 9) plasma levels and its impact on atherosclerotic vascular disease phenotypes. Circulation: Genomic and Precision Medicine 2018 11 e001992. (https://doi.org/10.1161/CIRCGEN.117.001992)

    • Search Google Scholar
    • Export Citation
  • 34

    MacArthur J, Bowler E, Cerezo M, Gil L, Hall P, Hastings E, Junkins H, McMahon A, Milano A & Morales J et al.The new NHGRI-EBI Catalog of published genome-wide association studies (GWAS Catalog). Nucleic Acids Research 2017 45 D896–D901. (https://doi.org/10.1093/nar/gkw1133)

    • Search Google Scholar
    • Export Citation
  • 35

    Kirsten H, Al-Hasani H, Holdt L, Gross A, Beutner F, Krohn K, Horn K, Ahnert P, Burkhardt R & Reiche K et al.Dissecting the genetics of the human transcriptome identifies novel trait-related trans-eQTLs and corroborates the regulatory relevance of non-protein coding loci†. Human Molecular Genetics 2015 24 4746–4763. (https://doi.org/10.1093/hmg/ddv194)

    • Search Google Scholar
    • Export Citation
  • 36

    Wainberg M, Sinnott-Armstrong N, Mancuso N, Barbeira AN, Knowles DA, Golan D, Ermel R, Ruusalepp A, Quertermous T & Hao K et al.Opportunities and challenges for transcriptome-wide association studies. Nature Genetics 2019 51 592599. (https://doi.org/10.1038/s41588-019-0385-z)

    • Search Google Scholar
    • Export Citation
  • 37

    Bednarek AK, Keck-Waggoner CL, Daniel RL, Laflin KJ, Bergsagel PL, Kiguchi K, Brenner AJ & Aldaz CM WWOX, the FRA16D gene, behaves as a suppressor of tumor growth. Cancer Research 2001 61 80688073.

    • Search Google Scholar
    • Export Citation
  • 38

    Gao R, Piguel NH, Melendez-Zaidi AE, Martin-de-Saavedra MD, Yoon S, Forrest MP, Myczek K, Zhang G, Russell TA & Csernansky JG et al.. CNTNAP2 stabilizes interneuron dendritic arbors through CASK. Molecular Psychiatry 2018 23 18321850. (https://doi.org/10.1038/s41380-018-0027-3)

    • Search Google Scholar
    • Export Citation
  • 39

    Dennis EL, Jahanshad N, Rudie JD, Brown JA, Johnson K, McMahon KL, Zubicaray de GI, Montgomery G, Martin NG & Wright MJ et al.Altered structural brain connectivity in healthy carriers of the autism risk gene, CNTNAP2. Brain Connectivity 2011 1 447459. (https://doi.org/10.1089/brain.2011.0064)

    • Search Google Scholar
    • Export Citation
  • 40

    Liska A, Bertero A, Gomolka R, Sabbioni M, Galbusera A, Barsotti N, Panzeri S, Scattoni ML, Pasqualetti M & Gozzi A Homozygous loss of autism-risk gene CNTNAP2 results in reduced local and long-range prefrontal functional connectivity. Cerebral Cortex 2018 28 11411153. (https://doi.org/10.1093/cercor/bhx022)

    • Search Google Scholar
    • Export Citation
  • 41

    Davids M, Markello T, Wolfe LA, Chepa-Lotrea X, Tifft CJ, Gahl WA & Malicdan MCV Early infantile-onset epileptic encephalopathy 28 due to a homozygous microdeletion involving the WWOX gene in a region of uniparental disomy. Human Mutation 2019 40 4247. (https://doi.org/10.1002/humu.23675)

    • Search Google Scholar
    • Export Citation
  • 42

    Hirano A, Ohara T, Takahashi A, Aoki M, Fuyuno Y, Ashikawa K, Morihara T, Takeda M, Kamino K & Oshima E et al.A genome-wide association study of late-onset Alzheimer’s disease in a Japanese population. Psychiatric Genetics 2015 25 139146. (https://doi.org/10.1097/YPG.0000000000000090)

    • Search Google Scholar
    • Export Citation
  • 43

    Kunkle BW, Grenier-Boley B, Sims R, Bis JC, Damotte V, Naj AC, Boland A, Vronskaya M, Lee van der SJ & Amlie-Wolf A et al.Genetic meta-analysis of diagnosed Alzheimer’s disease identifies new risk loci and implicates Aβ, tau, immunity and lipid processing. Nature Genetics 2019 51 414430. (https://doi.org/10.1038/s41588-019-0358-2)

    • Search Google Scholar
    • Export Citation
  • 44

    Wang K, Li WD, Zhang CK, Wang Z, Glessner JT, Grant SFA, Zhao H, Hakonarson H & Price RA A genome-wide association study on obesity and obesity-related traits. PLoS ONE 2011 6 e18939. (https://doi.org/10.1371/journal.pone.0018939)

    • Search Google Scholar
    • Export Citation
  • 45

    Tsai FJ, Yang CF, Chen CC, Chuang LM, Lu CH, Chang CT, Wang TY, Chen RH, Shiu CF & Liu YM et al.A genome-wide association study identifies susceptibility variants for type 2 diabetes in Han Chinese. PLoS Genetics 2010 6 e1000847. (https://doi.org/10.1371/journal.pgen.1000847)

    • Search Google Scholar
    • Export Citation
  • 46

    Cho YS, Chen CH, Hu C, Long J, Hee Ong RT, Sim X, Takeuchi F, Wu Y, Go MJ & Yamauchi T et al.Meta-analysis of genome-wide association studies identifies eight new loci for type 2 diabetes in east Asians. Nature Genetics 2012 44 6772. (https://doi.org/10.1038/ng.1019)

    • Search Google Scholar
    • Export Citation
  • 47

    Abu-Remaileh M, Abu-Remaileh M, Akkawi R, Knani I, Udi S, Pacold ME, Tam J & Aqeilan RI WWOX somatic ablation in skeletal muscles alters glucose metabolism. Molecular Metabolism 2019 22 132140. (https://doi.org/10.1016/j.molmet.2019.01.010)

    • Search Google Scholar
    • Export Citation
  • 48

    Aqeilan RI, Hassan MQ, Bruin De A, Hagan JP, Volinia S, Palumbo T, Hussain S, Lee SH, Gaur T & Stein GS et al.The WWOX tumor suppressor is essential for postnatal survival and normal bone metabolism. Journal of Biological Chemistry 2008 283 2162921639. (https://doi.org/10.1074/jbc.M800855200)

    • Search Google Scholar
    • Export Citation
  • 49

    Hussain T, Liu B, Shrock MS, Williams T & Aldaz CM WWOX, the FRA16D gene: a target of and a contributor to genomic instability. Genes, Chromosomes and Cancer 2019 58 324338. (https://doi.org/10.1002/gcc.22693)

    • Search Google Scholar
    • Export Citation
  • 50

    Fabbri M, Iliopoulos D, Trapasso F, Aqeilan RI, Cimmino A, Zanesi N, Yendamuri S, Han SY, Amadori D & Huebner K et al.WWOX gene restoration prevents lung cancer growth in vitro and in vivo. PNAS 2005 102 1561115616. (https://doi.org/10.1073/pnas.0505485102)

    • Search Google Scholar
    • Export Citation
  • 51

    Anderson GR, Galfin T, Xu W, Aoto J, Malenka RC & Südhof TC Candidate autism gene screen identifies critical role for cell-adhesion molecule CASPR2 in dendritic arborization and spine development. PNAS 2012 109 1812018125. (https://doi.org/10.1073/pnas.1216398109)

    • Search Google Scholar
    • Export Citation
  • 52

    Yoo HJ, Kim BN, Kim JW, Shin MS, Park TW, Son JW, Chung US, Park M & Kim SA Family-based genetic association study of CNTNAP2 polymorphisms and sociality endophenotypes in Korean patients with autism spectrum disorders. Psychiatric Genetics 2017 27 3839. (https://doi.org/10.1097/YPG.0000000000000150)

    • Search Google Scholar
    • Export Citation
  • 53

    Friedman JI, Vrijenhoek T, Markx S, Janssen IM, Vliet van der WA, Faas BHW, Knoers NV, Cahn W, Kahn RS & Edelmann L et al.CNTNAP2 gene dosage variation is associated with schizophrenia and epilepsy. Molecular Psychiatry 2008 13 261266. (https://doi.org/10.1038/sj.mp.4002049)

    • Search Google Scholar
    • Export Citation
  • 54

    Sonderen van A, Ariño H, Petit-Pedrol M, Leypoldt F, Körtvélyessy P, Wandinger KP, Lancaster E, Wirtz PW, Schreurs MWJ & Sillevis Smitt PAE et al.The clinical spectrum of Caspr2 antibody-associated disease. Neurology 2016 87 521528. (https://doi.org/10.1212/WNL.0000000000002917)

    • Search Google Scholar
    • Export Citation
  • 55

    Hu YW, Kang CM, Zhao JJ, Nie Y, Zheng L, Li HX, Li X, Wang Q & Qiu YR LncRNA PLAC2 down-regulates RPL36 expression and blocks cell cycle progression in glioma through a mechanism involving STAT1. Journal of Cellular and Molecular Medicine 2018 22 497510. (https://doi.org/10.1111/jcmm.13338)

    • Search Google Scholar
    • Export Citation
  • 56

    Alsaif HS, Al-Owain M, Barrios-Llerena ME, Gosadi G, Binamer Y, Devadason D, Ravenscroft J, Suri M & Alkuraya FS Homozygous loss-of-function mutations in AP1B1, encoding beta-1 subunit of adaptor-related protein complex 1, cause MEDNIK-like syndrome. American Journal of Human Genetics 2019 105 10161022. (https://doi.org/10.1016/j.ajhg.2019.09.020)

    • Search Google Scholar
    • Export Citation
  • 57

    Boyden LM, Atzmony L, Hamilton C, Zhou J, Lim YH, Hu R, Pappas J, Rabin R, Ekstien J & Hirsch Y et al.Recessive mutations in AP1B1 cause ichthyosis, deafness, and photophobia. American Journal of Human Genetics 2019 105 10231029. (https://doi.org/10.1016/j.ajhg.2019.09.021)

    • Search Google Scholar
    • Export Citation
  • 58

    Liu L, Yi J, Ray WK, Vu LT, Helm RF, Siegel PB, Cline MA & Gilbert ER Fasting differentially alters the hypothalamic proteome of chickens from lines with the propensity to be anorexic or obese. Nutrition and Diabetes 2019 9 13. (https://doi.org/10.1038/s41387-019-0081-1)

    • Search Google Scholar
    • Export Citation
  • 59

    Barber RF & Candés EJ Controlling the false discovery rate via knockoffs. Annals of Statistics 2015 43 20552085. (https://doi.org/10.1214/15-AOS1337)

    • Search Google Scholar
    • Export Citation
  • 60

    Shen A, Fu H, He K & Jiang H False discovery rate control in cancer biomarker selection using knockoffs. Cancers 2019 11 744. (https://doi.org/10.3390/cancers11060744)

    • Search Google Scholar
    • Export Citation
  • 61

    Li Z, Wang B, Wu X, Cheng SY, Paraoan L & Zhou J Identification, expression and functional characterization of the GRAL gene. Journal of Neurochemistry 2005 95 361376. (https://doi.org/10.1111/j.1471-4159.2005.03372.x)

    • Search Google Scholar
    • Export Citation
  • 62

    Patel S, Alvarez-Guaita A, Melvin A, Rimmington D, Dattilo A, Miedzybrodzka EL, Cimino I, Maurin AC, Roberts GP & Meek CL et al.GDF15 provides an endocrine signal of nutritional stress in mice and humans. Cell Metabolism 2019 29 707 .e8718.e8. (https://doi.org/10.1016/j.cmet.2018.12.016)

    • Search Google Scholar
    • Export Citation
  • 63

    Tsai VWW, Husaini Y, Sainsbury A, Brown DA & Breit SN The MIC-1/GDF15-GFRAL pathway in energy homeostasis: implications for obesity, cachexia, and other associated diseases. Cell Metabolism 2018 28 353368. (https://doi.org/10.1016/j.cmet.2018.07.018)

    • Search Google Scholar
    • Export Citation
  • 64

    Borner T, Shaulson ED, Ghidewon MY, Barnett AB, Horn CC, Doyle RP, Grill HJ, Hayes MR & de Jonghe BC GDF15 induces anorexia through nausea and emesis. Cell Metabolism 2020 31 351 .e5362.e5. (https://doi.org/10.1016/j.cmet.2019.12.004)

    • Search Google Scholar
    • Export Citation
  • 65

    Sanger GJ & Furness JB Ghrelin and motilin receptors as drug targets for gastrointestinal disorders. Nature Reviews: Gastroenterology and Hepatology 2016 13 3848. (https://doi.org/10.1038/nrgastro.2015.163)

    • Search Google Scholar
    • Export Citation
  • 66

    Fang L, Li F & Gu C GDF-15: a multifunctional modulator and potential therapeutic target in cancer. Current Pharmaceutical Design 2019 25 654662. (https://doi.org/10.2174/1381612825666190402101143)

    • Search Google Scholar
    • Export Citation
  • 67

    Villars FO, Pietra C, Giuliano C, Lutz TA & Riediger T Oral treatment with the ghrelin receptor agonist HM01 attenuates cachexia in mice bearing colon-26 (C26) tumors. International Journal of Molecular Sciences 2017 18 986. (https://doi.org/10.3390/ijms18050986)

    • Search Google Scholar
    • Export Citation