Tove Lekva, Thor Ueland, Hege Bøyum, Johan Arild Evang, Kristin Godang and Jens Bollerslev
Patients with endogenous Cushing's Syndrome (CS), as long-time treated patients with exogenous glucocorticoids (GCs), have severe systemic manifestations including secondary osteoporosis and low-energy fractures. The aim of the present study was to investigate the functional role of TXNIP in bone with focus on osteoblast (OB) differentiation and OB-mediated osteoclast activity and function in vitro.
Design and methods
Nine bone biopsies from CS before and after surgical treatment were screened for expressional candidate genes. Microarray analyses revealed that the gene encoding TXNIP ranked among the most upregulated genes. Subsequent in vitro and in vivo studies were performed.
We found that TXNIP gene in bone is downregulated in CS following surgical treatment. Furthermore, our in vivo data indicate novel associations between thioredoxin and TXNIP. Our in vitro studies showed that silencing TXNIP in OBs was followed by increased differentiation and expression and secretion of osteocalcin as well as enhanced activity of alkaline phosphatase. Moreover, treating osteoclasts with silenced TXNIP OB media showed an increased osteoclast activity.
TXNIP expression in bone is highly regulated during the treatment of active CS, and by GC in bone cells in vitro. Our data indicate that TXNIP may mediate some of the detrimental effects of GC on OB function as well as modulate OB-mediated osteoclastogenesis by regulating the OPG/RANKL ratio.
Kristin Godang, Kathrine Frey Frøslie, Tore Henriksen, Gunhild A Isaksen, Nanna Voldner, Tove Lekva, Thor Ueland and Jens Bollerslev
During pregnancy, changes occur in the maternal calcium homeostasis to fulfill fetal demand. We hypothesized that the fibroblast growth factor 23 (FGF23) system and Wnt signaling pathway are important for normal skeletal development in the offspring.
Circulating α-klotho, FGF23, sclerostin, and 25-hydroxyvitamin D (25(OH)D) at the fetal and maternal sides of the placenta were measured to investigate associations with newborn bone mass independent of maternal BMI, calcium and phosphate levels, placental weight, and birth weight.
In a prospective cohort of healthy pregnant women, the total body bone mineral content (BMC) in 202 newborns was measured by dual-energy X-ray absorptiometry. Maternal circulating levels of the biomarkers were measured at gestational weeks 30–32 and in umbilical cord plasma (UCP) at birth.
Mean α-klotho and sclerostin concentrations in the UCP were significantly higher than maternal levels (3004 vs 1077 pg/ml; P<0.001 and 629 vs 346 pg/ml; P<0.001 respectively), and mean 25(OH)D was lower (31 vs 45 nmol/l; P<0.001). The UCP and maternal FGF23 levels were similar. No significant effects of maternal biomarkers on BMC were found in regression analyses. Among UCP biomarkers, only UCP sclerostin was significantly associated with BMC in univariate analyses, and the effect remained significant after adjustment for birth weight and other confounders.
We found that UCP sclerostin levels, birth weight, and placental weight were significant predictors of neonatal BMC but found no evidence for a main role of maternal levels of α-klotho, FGF23, sclerostin, or 25(OH)D nor of UCP levels of α-klotho, FGF23, or 25(OH)D.
Tove Lekva, Jens Bollerslev, Kristin Godang, Marie Cecilie Paasche Roland, Camilla Margrethe Friis, Nanna Voldner, Tore Henriksen and Thor Ueland
Glucose intolerance in pregnancy predicts an increased risk of future type 2 diabetes.
The aim of the study was to evaluate glucose metabolism in women with and without gestational diabetes mellitus (GDM) at 5 years follow-up and identify risk factors associated with disturbed glucose metabolism post-partum.
This follow-up study included 300 consecutively enrolled women from a previous population-based cohort study. The participants underwent oral glucose tolerance test under pregnancy and in the follow-up study, in addition to dual-energy X-ray absorptiometry in the follow-up study.
Fifty-two women (17.7%) were found to have GDM in pregnancy with an odds ratio of 4.8 developing prediabetes 5 years later. β-cell function, but not insulin resistance or sensitivity, was reduced in the follow-up study after adjusting for known risk factors. Furthermore, visceral fat content at follow-up was increased in GDM women compared to non-GDM women, and the β-cell function declined with increasing visceral fat in both groups but was more pronounced in the women with previous GDM.
Women with GDM are at increased risk of developing prediabetes and have a decreased β-cell function 5 years post-partum that is associated with increased visceral fat mass.
Camilla Maria Falch, Arvind Y M Sundaram, Kristin Astrid Øystese, Kjersti Ringvoll Normann, Tove Lekva, Ivars Silamikelis, Alexander Kirkeby Eieland, Marianne Andersen, Jens Bollerslev and Nicoleta Cristina Olarescu
Reliable biomarkers associated with aggressiveness of non-functioning gonadotroph adenomas (GAs) are lacking. As the growth of tumor remnants is highly variable, molecular markers for growth potential prediction are necessary. We hypothesized that fast- and slow-growing GAs present different gene expression profiles and reliable biomarkers for tumor growth potential could be identified, focusing on the specific role of epithelial-mesenchymal transition (EMT).
Design and methods
Eight GAs selected for RNA sequencing were equally divided into fast- and slow-growing group by the tumor volume doubling time (TVDT) median (27.75 months). Data were analyzed by tophat2, cufflinks and cummeRbund pipeline. 40 genes were selected for RT-qPCR validation in 20 GAs based on significance, fold-change and pathway analyses. The effect of silencing MTDH (metadherin) and EMCN (endomucin) on in vitro migration of human adenoma cells was evaluated.
350 genes were significantly differentially expressed (282 genes upregulated and 68 downregulated in the fast group, P-adjusted <0.05). Among 40 selected genes, 11 showed associations with TVDT (−0.669<R<−0.46, P < 0.05). These were PCDH18, UNC5D, EMCN, MYO1B, GPM6A and six EMT-related genes (SPAG9, SKIL, MTDH, HOOK1, CNOT6L and PRKACB). MTDH, but not EMCN, demonstrated involvement in cell migration and association with EMT markers.
Fast- and slow-growing GAs present different gene expression profiles, and genes related to EMT have higher expression in fast-growing tumors. In addition to MTDH, identified as an important contributor to aggressiveness, the other genes might represent markers for tumor growth potential and possible targets for drug therapy.
Thor Ueland, Tove Lekva, Kari Otterdal, Tuva B Dahl, Nicoleta Cristina Olarescu, Anders P Jørgensen, Kristian J Fougner, Kim Brixen, Pål Aukrust and J Bollerslev
Patients with adult onset GH deficiency (aoGHD) have secondary osteoporosis, which is reversed by long-term GH substitution. Transforming growth factor β1 (TGFβ1 or TGFB1) is abundant in bone tissue and could mediate some effects of GH/IGFs on bone. We investigated its regulation by GH/IGF1 in vivo and in vitro.
Design and methods
The effects of GH substitution (9–12 months, placebo controlled) on circulating and cortical bone matrix contents of TGFβ1 were investigated in patients with aoGHD. The effects of GH/IGF1 on TGFβ1 secretion in osteoblasts (hFOB), adipocytes, and THP-1 macrophages as well as the effects on release from platelets were investigated in vitro.
In vivo GH substitution increased TGFβ1 protein levels in cortical bone and serum. In vitro, GH/IGF1 stimulation induced a significant increase in TGFβ1 secretion in hFOB. In contrast, no major effect of GH/IGF1 on TGFβ1 was found in adipocytes and THP-1 macrophages. Finally, a minor modifying effect on SFLLRN-stimulated platelet release of TGFβ1 was observed in the presence of IGF1.
GH substitution increases TGFβ1 in vivo and in vitro, and this effect could contribute to improved bone metabolism during such therapy, potentially reflecting direct effect of GH/IGF1 on bone cells.
Gunn-Helen Moen, Marissa LeBlanc, Christine Sommer, Rashmi B Prasad, Tove Lekva, Kjersti R Normann, Elisabeth Qvigstad, Leif Groop, Kåre I Birkeland, David M Evans and Kathrine F Frøslie
Hyperglycaemia during pregnancy increases the risk of adverse health outcomes in mother and child, but the genetic aetiology is scarcely studied. Our aims were to (1) assess the overlapping genetic aetiology between the pregnant and non-pregnant population and (2) assess the importance of genome-wide polygenic contributions to glucose traits during pregnancy, by exploring whether genetic risk scores (GRSs) for fasting glucose (FG), 2-h glucose (2hG), type 2 diabetes (T2D) and BMI in non-pregnant individuals were associated with glucose measures in pregnant women.
We genotyped 529 Norwegian pregnant women and constructed GRS from known genome-wide significant variants and SNPs weakly associated (p > 5 × 10−8) with FG, 2hG, BMI and T2D from external genome-wide association studies (GWAS) and examined the association between these scores and glucose measures at gestational weeks 14–16 and 30–32. We also performed GWAS of FG, 2hG and shape information from the glucose curve during an oral glucose tolerance test (OGTT).
GRSFG explained similar variance during pregnancy as in the non-pregnant population (~5%). GRSBMI and GRST2D explained up to 1.3% of the variation in the glucose traits in pregnancy. If we included variants more weakly associated with these traits, GRS2hG and GRST2D explained up to 2.4% of the variation in the glucose traits in pregnancy, highlighting the importance of polygenic contributions.
Our results suggest overlap in the genetic aetiology of FG in pregnant and non-pregnant individuals. This was less apparent with 2hG, suggesting potential differences in postprandial glucose metabolism inside and outside of pregnancy.