Mette Faurholdt Gude, Rikke Hjortebjerg, Claus Oxvig, Anne Anker Thyø, Nils Erik Magnusson, Mette Bjerre, Steen Bønløkke Pedersen and Jan Frystyk
Adipose tissue secretes pregnancy-associated plasma protein-A (PAPP-A), which may increase local IGF action through cleavage of IGF-binding protein-4 (IGFBP-4). We tested whether this mechanism was operational in human visceral and subcutaneous adipose tissue (i.e. VAT and SAT).
Explants of VAT and SAT from 26 obese subjects (hereof 17 women, BMI 39.5 (37.2; 42.8) kg/m2 (median (25%; 75% confidence interval) and SAT from eight lean, age-matched women (BMI 23.6 (22.4; 24.9) kg/m2) were incubated with or without GH (100 µg/L) and the media were harvested.
Media were assessed for concentrations of PAPP-A, intact and PAPP-A-cleaved IGFBP-4, IGF-I and IGF-II, and IGF-I receptor (IGF-IR) activation by bioassay.
In obese subjects, VAT media contained higher concentrations than SAT of PAPP-A (4.4-fold) and both PAPP-A-generated IGFBP-4 fragments (C-terminal: 3.3-fold, N-terminal: 1.5-fold) (all P < 0.0005). Intact IGFBP-4 levels were similar in SAT and VAT. VAT media contained elevated IGF-II (1.4-fold; P < 0.005), but similar IGF-I concentrations compared with SAT. Still, VAT media contained a 1.8-fold increased ability to stimulate the IGF-IR (P < 0.005). IGF-I protein concentration and IGF-IR activation increased more in VAT media than SAT media following GH stimulation (both P < 0.05). At baseline, SAT media protein levels from lean and obese women were similar, with the exception of PAPP-A being 1.8-fold elevated in VAT media (P < 0.05). GH induced a similar increase in IGF-I media levels in SAT from obese and lean women.
Human adipose tissue cultures secrete enzymatically active PAPP-A, IGFBP-4 and IGF-II in a depot-specific manner, suggesting differential regulation of IGF activity. Further, IGF-II appears to be more prominent than IGF-I. Finally, VAT appears more GH responsive than SAT.
Rikke Hjortebjerg, Esben Laugesen, Pernille Høyem, Claus Oxvig, Brian Stausbøl-Grøn, Søren T Knudsen, Won Y Kim, Per L Poulsen, Troels K Hansen, Mette Bjerre and Jan Frystyk
Perturbations in the insulin-like growth factor (IGF) system may contribute to the accelerated cardiovascular disease (CVD) that occurs in patients with type 2 diabetes (T2D). However, it remains unknown whether the IGF system is also involved in the development of early, subclinical CVD. We characterised the IGF system in T2D patients and matched controls and examined the associations with markers of subclinical target organ damage.
The study included 99 patients with recently diagnosed T2D and 99 age- and sex-matched controls. IGF-1 and IGFBP-1 to -4 were measured by immunoassays, as were pregnancy-associated plasma protein-A (PAPP-A) and the PAPP-A-generated N-terminal (NT) and C-terminal (CT) IGFBP-4 fragments, which are novel CVD risk markers. Arterial stiffness was evaluated by carotid-femoral pulse wave velocity (PWV). Cerebral white matter lesions (WMLs) and carotid artery remodelling were determined by MRI.
After multivariate adjustments, patients with T2D had lower concentrations of IGFBP-2, IGFBP-4, NT- and CT-IGFBP-4, when compared with controls. IGFBP-2 was inversely correlated to PWV in all subjects in multivariate analysis (P < 0.05), and IGFBP-3 was inversely associated with severity of WMLs (P < 0.05). The NT-IGFBP-4 fragment was associated with the degree of carotid artery remodelling among all subjects (regression coefficient (95% CI): 2.95 (0.70, 5.16), P = 0.011). Levels of NT- and CT-IGFBP-4 were reduced in T2D patients receiving metformin compared to those in controls and patients not receiving metformin.
Even in recently diagnosed and well-controlled T2D patients, IGF protein levels are altered and associated with CVD risk factors.
Freja B Kampmann, Anne Cathrine B Thuesen, Line Hjort, Anne A Bjerregaard, Jorge E Chavarro, Jan Frystyk, Mette Bjerre, Inge Tetens, Sjurdur F Olsen, Allan A Vaag, Peter Damm and Louise G Grunnet
Fetal exposure to gestational diabetes mellitus (GDM) increases the risk of metabolic diseases in the offspring. Leptin, adiponectin, and fibroblast growth factor 21 (FGF21) may play potential roles in the underlying disease mechanisms. We investigated the impact of fetal exposure to GDM on leptin, adiponectin, and FGF21 concentrations and their associations with measures of adiposity and metabolic traits during childhood/adolescence.
Design and methods
The follow-up study included 504 GDM and 540 control offspring aged 9–16 from the Danish National Birth Cohort. Anthropometric measurements, fasting blood samples, puberty status and fat percentages by dual-energy X-ray absorptiometry were examined. Serum concentrations of leptin, adiponectin, and FGF21 were measured by validated immune assays.
GDM offspring had 38% (95% CI: 22–55%) higher leptin, 0.6 mg/L (95% CI: −1.2, −0.04 mg/L) lower adiponectin, and 32% (95% CI: −47%, −12%) lower FGF21 concentrations than control offspring (P < 0.05). After adjustment for confounders including maternal pre-pregnancy BMI, GDM offspring had borderline higher leptin (P = 0.06) and significantly lower FGF21 concentrations (P = 0.006). When accounting for offspring BMI z-score, GDM exposure had no significant independent effect on leptin or adiponectin concentrations, whereas FGF21 was still significant. In univariate analyses, leptin and adiponectin were associated with fasting insulin, HOMA-IR, and adiposity, and FGF21 with total fat percentage.
GDM offspring had higher leptin, lower adiponectin and FGF21 concentrations than control offspring. Elevated leptin and decreased adiponectin concentrations associated with adverse metabolic traits and were most likely driven by higher obesity prevalence among GDM offspring. The functional implications of decreased FGF21 concentrations among GDM offspring need to be further explored.