DNA methylation of genes regulating appetite and prediction of weight loss after bariatric surgery in obese individuals.

PURPOSE: Epigenetic traits are influenced by clinical variables; interaction between DNA methylation (DNAmeth) and bariatric surgery-induced weight loss has been scarcely explored. We investigated whether DNAmeth of genes encoding for molecules/hormones regulating appetite, food intake or obesity could predict successful weight outcome following Roux-en-Y gastric bypass (RYGB). METHODS: Forty-five obese individuals with no known comorbidities were stratified accordingly to weight decrease one-year after RYGB (excess weight loss, EWL ≥ 50%: good responders, GR; EWL < 50%: worse responders, WR). DNAmeth of leptin (LEP), ghrelin (GHRL), ghrelin receptor (GHSR) and insulin-growth factor-2 (IGF2) was assessed before intervention. Single nucleotide polymorphisms of genes affecting DNAmeth, DNMT3A and DNMT3B, were also determined. RESULTS: At baseline, type 2 diabetes was diagnosed by OGTT in 13 patients. Post-operatively, GR (n = 23) and WR (n = 22) achieved an EWL of 67.7 ± 9.6 vs 38.2 ± 9.0%, respectively. Baseline DNAmeth did not differ between GR and WR for any tested genes, even when the analysis was restricted to subjects with no diabetes. A relationship between GHRL and LEP methylation profiles emerged (r = 0.47, p = 0.001). Searching for correlation between DNAmeth of the studied genes with demographic characteristics and baseline biochemical parameters of the studied population, we observed a correlation between IGF2 methylation and folate (r = 0.44, p = 0.003). Rs11683424 for DNMT3A and rs2424913 for DNMT3B did not correlate with DNAmeth of the studied genes. CONCLUSIONS: In severely obese subjects, the degree of DNAmeth of some genes affecting obesity and related conditions does not work as predictor of successful response to RYGB.

The impact of triglycerides on glucose tolerance: Lipotoxicity revisited.

Elevated plasma triglycerides (TGs) are early key features of conditions associated with a dysregulation in glucose metabolism and may predict the development of type 2 diabetes (T2D) over time. Although the acute ingestion of lipid, either mixed with or shortly before the meal, is neutral or slightly beneficial on glucose tolerance, a short-term increase in plasma TGs induced by either an i.v. lipid infusion or a high-fat diet produces a deterioration of glucose control. Accordingly, chronic lowering of plasma TGs by fibrates improves glucose homeostasis and may also prevent T2D. The chronic effects of the elevation of dietary lipid intake are less clear, particularly in humans, being the quality of fat probably more important than total fat intake. Although on the bases of the available experimental and clinical evidence it cannot be easily disentangled, with respect to elevated non-esterified fatty acids (NEFA) the relative contribution of elevated TGs to glucose homeostasis disregulation seems to be greater and also more plausible. In conclusion, although the association between elevated plasma TGs and impaired glucose tolerance is commonly considered not causative or merely a consequence of NEFA-mediated lipotoxicity, the available data suggest that TGs per se may directly contribute to disorders of glucose metabolism.

Direct effect of GLP-1 infusion on endogenous glucose production in humans.

AIMS/HYPOTHESIS: Glucagon-like peptide-1 (GLP-1) lowers glucose levels by potentiating glucose-induced insulin secretion and inhibiting glucagon release. The question of whether GLP-1 exerts direct effects on the liver, independently of the hormonal changes, is controversial. We tested whether an exogenous GLP-1 infusion, designed to achieve physiological postprandial levels, directly affects endogenous glucose production (EGP) under conditions mimicking the fasting state in diabetes. METHODS: In 14 healthy volunteers, we applied the pancreatic clamp technique, whereby plasma insulin and glucagon levels are clamped using somatostatin and hormone replacement. The clamp was applied in paired, 4 h experiments, during which saline (control) or GLP-1(7-37)amide (0.4 pmol min⁻¹ kg⁻¹) was infused. RESULTS: During the control study, plasma insulin and glucagon were maintained at basal levels and plasma C-peptide was suppressed, such that plasma glucose rose to a plateau of ~10.5 mmol/l and tracer-determined EGP increased by ~60%. During GLP-1 infusion at matched plasma glucose levels, the rise of EGP from baseline was fully prevented. Lipolysis (as indexed by NEFA concentrations and tracer-determined glycerol rate of appearance) and substrate utilisation (by indirect calorimetry) were similar between control and GLP-1 infusion. CONCLUSIONS/INTERPRETATION: GLP-1 inhibits EGP under conditions where plasma insulin and glucagon are not allowed to change and glucose concentrations are matched, indicating either a direct effect on hepatocytes or neurally mediated inhibition.

Long term predictors of post-partum glucose metabolism in women with gestational diabetes mellitus.

AIMS: The question asked by this study was whether ß-cell function expressed by insulin secretion/sensitivity measured during pregnancy in women with gestational diabetes (GDM) predicts post-partum long-term derangement in glucose metabolism. METHODS: Seventy-four Caucasian women with previous GDM were retested through a 75 g-2-h-OGTT after 8 [6] years (median[interquartile range]) from index pregnancy, measuring at pregnancy and follow-up insulin sensitivity, insulin secretion (1-h-incremental-insulin-area/incremental-glucose-area: ΔAUC60 (I)/ΔAUC60 (G)) as well as the product of Stumvoll-first-phase - secretion x insulin sensitivity (insulin-secretion-sensitivity index (ISSI). RESULTS: At follow-up 47 women were normotelerant to glucose and 27 had altered glucose metabolism (AGM:10 with type 2 diabetes and 17 with IGT). Women progressed to AGM had at their index pregnancy higher mean 2-h-OGTT-glucose area (1.15±0.09 VS. 1.09±0.09 mol l 2-h (-1);p=0.014), and lower ΔAUC60 (I)/ΔAUC60 (median [interquantile range]) (54.4 [51.7] vs. 73.4 [60] pmol mmol (-1)) and ISSI (2 977 [766] vs. 3 708 [1 141]; p<0.05 for both), but similar insulin sensitivity index 2.9 [2.5] VS. 3.2 [2.2] ml min (-1) m (-2);p=NS). Two-h-OGTT-glucose area, or decrease in ΔAUC60 (I)/ΔAUC60 (G) and ISSI were significantly associated with glucose tolerance impairment and with raised adjusted risk for AGM while insulin sensitivity at pregnancy did no predict AGM development. CONCLUSIONS: In this group of women increased post-load plasma glucose and impaired ß-cell function assessed during GDM pregnancy predict long-term post-partum AGM, while insulin sensitivity measured at the same time does not.