Effect of Weight Loss by Gastric Bypass Surgery Versus Hypocaloric Diet on Glucose and Incretin Levels in Patients with Type 2 Diabetes

Abstract

Context: Gastric bypass surgery (GBP) results in rapid weight loss, improvement of type 2 diabetes (T2DM), and increase in incretins levels. Diet-induced weight loss also improves T2DM and may increase incretin levels.Objective: Our objective was to determine whether the magnitude of the change of the incretin levels and effect is greater after GBP compared with a low caloric diet, after equivalent weight loss. Design and Methods:Obese women with T2DM studied before and 1 month after GBP (n ϭ 9), or after a diet-induced equivalent weight loss (n ϭ 10), were included in the study. Patients from both groups were matched for age, body weight, body mass index, diabetes duration and control, and amount of weight loss. Setting: This outpatient study was conducted at the General Clinical Research Center.Main Outcome Measures: Glucose, insulin, proinsulin, glucagon, gastric inhibitory peptide (GIP), and glucagon-like peptide (GLP)-1 levels were measured after 50-g oral glucose. The incretin effect was measured as the difference in insulin levels in response to oral and to an isoglycemic iv glucose load.Results: At baseline, none of the outcome variables (fasting and stimulated values) were different between the GBP and diet groups. Total GLP-1 levels after oral glucose markedly increased six times (peak:17 Ϯ 6 to 112 Ϯ 54 pmol/liter; P Ͻ 0.001), and the incretin effect increased five times (9.4 Ϯ 27.5 to 44.8 Ϯ 12.7%; P Ͻ 0.001) after GBP, but not after diet. Postprandial glucose levels (P ϭ 0.001) decreased more after GBP. Conclusions:These data suggest that early after GBP, the greater GLP-1 and GIP release and improvement of incretin effect are related not to weight loss but rather to the surgical procedure. This could be responsible for better diabetes outcome after GBP. T ogether with the epidemic of obesity (1), the number of weight loss surgeries has surged in the last decade (2). Roux-en-Y gastric bypass surgery (GBP) results in significant and prolonged weight loss with resolution of type 2 diabetes (T2DM) in 80% of cases (3). The mechanism by which T2DM improves rapidly after GBP, often before significant weight loss, has not yet been elucidated. The hormonal changes described after GBP suggest a possible endocrine effect of this surgery. We (4) and others (5-10) have shown that the mealor glucose-stimulated incretin levels, which are blunted in T2DM, increase after GBP. In parallel with the increased levels of glucagon-like peptide (GLP)-1 and gastric inhibitory

Circadian rhythms of GIP and GLP1 in glucose-tolerant and in type 2 diabetic patients after biliopancreatic diversion

“…In contrast, the effect of RYGB on GLP1 is quite different from that of BPD. After RYGB, an increase in the GLP1 level after OGTT or a meal was observed in people with NGT [14] and in diabetic patients [12,13], and was associated with increased circulating levels of insulin.…”

“…Relatively few data are available concerning the effect of bariatric surgery on incretin secretion [10][11][12][13][14][15] and, at least to our knowledge, no data exist regarding the response of incretin to multiple meals.…”

Endocrine mechanisms mediating remission of diabetes after gastric bypass surgery

“…Careful glucose-homeostasis phenotyping was carried out shortly before surgery and again postoperatively at an equivalent amount of weight loss (B9.5 kg in both groups). 25 The groups were exquisitely matched for preoperative severity and duration of diabetes, homeostatic model assessment values, oral glucose tolerance, magnitude of incretin effect, BMI, age and gender. After the weight-loss interventions, however, post-RYGB patients displayed substantially better glucose tolerance and incretin effect than did patients who had lost the same amount of weight with dieting.…”

“…27,28,40,41 Consistent with elevated postprandial GLP-1 secretion, post-RYGB patients display an increased incretin effect. 25,40 As GLP-1 not only enhances insulin secretion but can also increase proliferation and decrease apoptosis of b cells, 39 it is a candidate mediator of the increase in b-cell mass that is claimed by some investigators to accompany post-RYGB hyperinsulinemic hypoglycemia. 30,31 Further support for the lower intestinal hypothesis comes from experiments involving ileal interposition.…”

A Morbid Obese Japanese Woman with a Body Mass Index of 83.2 kg/m²: Before and after Sleeve Gastrectomy

“…GIP and GLP-1, a hormone synthesized by the intestinal mucosa in response to food and rapidly inactivated by serine protease dipeptidyl-peptidase (31), has been reported to increase after bariatric surgery (11,32,33). In the present case, though the GLP-1 level measured before the operation is for reference only, the GLP-1 level showed a small elevation, and the GIP levels decreased.…”