Gastroenterology

Gastroenterology

Volume 143, Issue 4, October 2012, Pages 897-912
Gastroenterology

Reviews and Perspectives
Reviews in Basic and Clinical Gastroenterology and Hepatology
Effects of Bariatric Surgery on Glucose Homeostasis and Type 2 Diabetes

https://doi.org/10.1053/j.gastro.2012.07.114Get rights and content

Obesity is an important risk factor for type 2 diabetes mellitus (T2DM). Weight loss improves the major factors involved in the pathogenesis of T2DM, namely insulin action and beta cell function, and is considered a primary therapy for obese patients who have T2DM. Unfortunately, most patients with T2DM fail to achieve successful weight loss and adequate glycemic control from medical therapy. In contrast, bariatric surgery causes marked weight loss and complete remission of T2DM in most patients. Moreover, bariatric surgical procedures that divert nutrients away from the upper gastrointestinal tract are more successful in producing weight loss and remission of T2DM than those that simply restrict stomach capacity. Although upper gastrointestinal tract bypass procedures alter the metabolic response to meal ingestion, by increasing early postprandial plasma concentrations of glucagon-like peptide 1 and insulin, it is not clear whether these effects make an important contribution to long-term control of glycemia and T2DM once substantial surgery-induced weight loss has occurred. Nonetheless, the effects of surgery on body weight and metabolic function indicate that bariatric surgery should be part of the standard therapy for T2DM. More research is needed to advance our understanding of the physiological effects of different bariatric surgical procedures and possible weight loss–independent factors that improve metabolic function and contribute to the resolution of T2DM.

Section snippets

Common Bariatric Surgical Procedures and Effects on Body Weight

Five bariatric surgical procedures are considered acceptable therapy for appropriate patients: (1) roux-en-Y gastric bypass (RYGB), (2) laparoscopic adjustable gastric banding (LAGB), (3) laparoscopic sleeve gastrectomy (LSG), (4) biliopancreatic diversion (BPD), and (5) BPD with duodenal switch (Figure 1). Bariatric surgery causes weight loss by inducing a negative balance between energy intake (or absorption) and energy expenditure. The composite of data from a series of studies found that

Effect of Bariatric Surgery on T2DM

The therapeutic superiority of bariatric surgery over medical therapy has been shown in three 1-year or 2-year prospective randomized controlled trials.21, 22, 23 In one study, 73% of patients who underwent LAGB surgery but only 13% in the medical and lifestyle therapy group achieved remission of T2DM (defined as fasting plasma glucose concentration <126 mg/dL and HbA1c <6.2% without diabetes medications).21 In the second study, 42% of subjects who underwent RYGB surgery and 37% who underwent

Assessment of Insulin Action

Insulin regulates a large number of metabolic functions across various organ systems. Therefore, reduced sensitivity to the action of insulin (ie, insulin resistance) represents a suboptimal biological response of different metabolic pathways to normal circulating insulin concentrations.43 However, it has become common to define insulin sensitivity by its effects on glucose metabolism alone, particularly the ability of insulin to stimulate glucose disposal, which occurs primarily in skeletal

Normal Beta Cell Function

The ability of pancreatic beta cells to secrete insulin in response to circulating glucose is critical for normal glucose homeostasis. This process involves a complex series of events that integrates nutritional, hormonal, and neural factors. Insulin is first synthesized as preproinsulin, which is cleaved to proinsulin and then packaged in secretory granules where it is cleaved into equimolar amounts of insulin and C-peptide. These secretory granules fuse with the cell membrane, thereby

Conclusions and Future Research Directions

Bariatric surgery is the most effective available therapy for patients with T2DM. Most patients with T2DM who are treated with RYGB surgery achieve remission of their diabetes, defined as maintaining normal or near-normal blood glucose concentrations and HbA1c without the use of diabetes medications. Remission rates as high as 95% have been reported after the BPD with duodenal switch procedure, but this operation is not widely used because of a high rate of postoperative nutritional

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    Conflicts of interest The authors disclose the following: S.K. serves on a Scientific Advisory Board for Ethicon Endo-Surgery. The remaining authors disclose no conflicts.

    Funding Supported by National Institutes of Health grants DK37948, DK56341 (Nutrition Obesity Research Center), and UL1 RR024992 (Clinical and Translational Science Award).

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