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Acute effects of gastric bypass versus gastric restrictive surgery on β-cell function and insulinotropic hormones in severely obese patients with type 2 diabetes

Kashyap, S.R., Daud, S., Kelly, K.R., Gastaldelli, A., Win, H., Brethauer, S., Kirwan, J.P., Schauer, P.R.
International journal of obesity 2010 v.34 no.3 pp. 462-471
human diseases, carbohydrate metabolism, islets of Langerhans, men, women, glucose, kinetics, models, surgery, noninsulin-dependent diabetes mellitus, insulin secretion, obesity, insulin resistance, c-peptide, obesity-related diseases, weight loss, glucagon-like peptides
Context: Hyperglycemia resolves quickly after bariatric surgery, but the underlying mechanism and the most effective type of surgery remains unclear. Objective: To examine glucose metabolism and β-cell function in patients with type 2 diabetes mellitus (T2DM) after two types of bariatric intervention; Roux-en-Y gastric bypass (RYGB) and gastric restrictive (GR) surgery. Design: Prospective, nonrandomized, repeated-measures, 4-week, longitudinal clinical trial. Patients: In all, 16 T2DM patients (9 males and 7 females, 52±14 years, 47±9 kg m−2, HbA1c 7.2±1.1%) undergoing either RYGB (N=9) or GR (N=7) surgery. Outcome measures: Glucose, insulin secretion, insulin sensitivity at baseline, and 1 and 4 weeks post-surgery, using hyperglycemic clamps and C-peptide modeling kinetics; glucose, insulin secretion and gut-peptide responses to mixed meal tolerance test (MMTT) at baseline and 4 weeks post-surgery. Results: At 1 week post-surgery, both groups experienced a similar weight loss and reduction in fasting glucose (P<0.01). However, insulin sensitivity increased only after RYGB, (P<0.05). At 4 weeks post-surgery, weight loss remained similar for both groups, but fasting glucose was normalized only after RYGB (95±3 mg 100 ml−1). Insulin sensitivity improved after RYGB (P<0.01) and did not change with GR, whereas the disposition index remained unchanged after RYGB and increased 30% after GR (P=0.10). The MMTT elicited a robust increase in insulin secretion, glucagon-like peptide-1 (GLP-1) levels and β-cell sensitivity to glucose only after RYGB (P<0.05). Conclusion: RYGB provides a more rapid improvement in glucose regulation compared with GR. This improvement is accompanied by enhanced insulin sensitivity and β-cell responsiveness to glucose, in part because of an incretin effect.