Abstract
To date, weight loss surgeries are the most effective treatment for obesity and glycemic control in patients with type 2 diabetes. Roux-en-Y gastric bypass surgery (RYGB) and sleeve gastrectomy (SG), two widely used bariatric procedures for the treatment of obesity, induce diabetes remission independent of weight loss while glucose improvement after adjustable gastric banding (AGB) is proportional to the amount of weight loss. The immediate, weight-loss independent glycemic effect of gastric bypass has been attributed to postprandial hyperinsulinemia and an enhanced incretin effect. The rapid passage of nutrients into the intestine likely accounts for significantly enhanced glucagon like-peptide 1 (GLP-1) secretion, and postprandial hyperinsulinemia after GB is typically attributed to the combined effects of elevated glucose and GLP-1. For this review we focus on the beneficial effects of the three most commonly performed bariatric procedures, RYGB, SG, and AGB, on glucose metabolism and diabetes remission. Central to this discussion will be the extent to which the effects of surgery are mediated by GLP-1. Better understanding of these mechanisms could provide insight to development of novel therapeutic strategies for treatment of diabetes as well as refinement of surgical techniques.
Highlights
To date, weight loss surgeries are the most effective treatment for obesity and glycemic control in patients with type 2 diabetes
Longitudinal study based on bariatric-specific data from 28,616 obese diabetic patients, rate of remission or improvement in diabetes at 1 year after Roux-en-Y gastric bypass surgery (RYGB) was 83 % compared to 55 % and 44 % after sleeve gastrectomy (SG) and adjustable gastric banding (AGB), with BMI reductions of ~15 kg/m2 compared to 12 and 7 kg/m2, respectively [7]
The substantial impact of gastric bypass on glucose metabolism is exemplified by the syndrome of postprandial hyperinsulinemic hypoglycemia, which occurs in a small subset of subjects, but has not been reported after restrictive
Summary
Bariatric surgeries were originally categorized based on what was commonly believed to be their mechanisms of action, volume restriction, malabsorption or both. Roux-en-Y gastric bypass (RYGB), including components of restriction (a small gastric pouch) and malabsorption (bypass of the stomach and proximal portion of small intestine), was endorsed by National Institutes of Health Consensus Development Panel as the ‘gold standard’ procedure in 1991 because of its predictable high weight-loss efficacy and low post-operative complication rates [1]. Longitudinal study based on bariatric-specific data from 28,616 obese diabetic patients, rate of remission or improvement in diabetes at 1 year after RYGB was 83 % compared to 55 % and 44 % after SG and AGB, with BMI reductions of ~15 kg/m2 compared to 12 and 7 kg/m2, respectively [7] In keeping with these observational studies, three randomized clinical trials have recently demonstrated that a greater portion of patients with uncontrolled diabetes achieve target A1C levels at 1–2 years after RYGB compared to those receiving lifestyle and/or medical interventions alone [9,10,11]. Preliminary evidence suggests that RYGB may be more effective for treating diabetes than SG [13] with longerlasting effects even when weight reduction is comparable [14]
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