Bariatric Surgery, Exercise, and Inpatient Glycemia Treatment

Bariatric surgery in diabetes Lee Kaplan (Boston, MA) discussed new information based on studies of bariatric surgery in diabetes. Surgery is performed in 0.25% of Americans with obesity, so it is unlikely that it in itself can address the U.S. diabetes or obesity issues, but lessons from its use may shed light on the approach to obesity and diabetes for the overall population. The biology of obesity suggests that it is caused by inactivity and overnutriton and likely stress as well. There is a huge burden of obesityassociated illness, including malignancy, and obesity has a devastating effect on quality of life and also on what is termed societal “efficacy” and socioeconomic status. The physiology of obesity involves central regulation of food intake, nutrient handling, and energy expenditure, with adipose tissue energy stores regulating levels of signals such as leptin, and information from liver, muscle, and bone on metabolic needs coupled with information from the gastrointestinal tract and sensory organs regarding the quantity and quality of nutrient intake. A unifying theme is the body’s defense of fat (rather than of total body weight). Surgery includes the Roux-en-Y combination gastric restriction and bypass (RYGB) of distal stomach, duodenum, and proximal jejunum, which is the most effective, and may be the most appropriate, for diabetes treatment. Adjustable gastric banding is a gastric restriction procedure, while vertical sleeve gastrectomy removes the greater curvature of the stomach, acting in a fashion very different from gastric banding, causing more rapid gastric emptying. In the Swedish Obesity Study, lifestyle was compared with bariatric procedures. Gastric banding led to 20% weight loss initially, which decreased to 14% after a decade. RYGB led to 38% weight loss initially, decreasing to 28% at 10 years. Lifestyle modification led to an initial weight loss of 7%, dropping to 2% at 10 years. Gastric bypass improved all and cured 18% of diabetes (1). In a retrospective cohort study of 9,949 patients who had undergone gastric bypass surgery and 9,628 severely obese individuals who applied for driver’s licenses in Utah, a 7.1-year follow-up of 7,925 age-, sex-, and BMI-matched pairs showed mortality reduction of 40%, with 56% less coronary disease–related mortality (2). There are, of course, adverse outcomes, and neither study was a randomized controlled trial. Currently accepted indications for surgery in individuals for whom other approaches to weight loss have failed are 1) BMI 40 kg/m or 2) BMI 35 kg/m with major medical complications of obesity. A total of 250,000 such operations are performed annually in the U.S.—far fewer than the 10 million people who fill these criteria. Contraindications include severe cirrhosis, unstable coronary disease, psychiatric illness, noncompliance, and substance abuse. It is not clear, Kaplan pointed out, why gastric bypass is so effective. It appears to alter both endocrine and neuronal gastrointestinal signals to the brain, pancreas, and liver rather than just exerting a mechanical effect in decreasing food intake. Dramatic effects on hunger and satiety are seen, but few patients become underweight and then usually only in association with major surgical complications. Because the improvement in metabolism often reestablishes ovulation, it is noteworthy that there is weight gain in women who have had the procedures and then become pregnant. When the procedures are carried out in thin people or in animals, weight loss does not occur. Changes are variously reported in endocrine markers such as ghrelin, peptide YY, glucagon-like peptide-1, and glucosedependent insulinotropic polypeptide, and bariatric surgery causes increased energy expenditure. It may, then, increase the effectiveness of gastrointestinal signals and, hence, physiologically create an overfed state that leads to weight loss to attain a new set point. In contrast to the improvements seen after surgery, with diet, appetite increases, energy expenditure decreases, and stress responses increase. RYGB reduces food intake and changes food preference, central dopamine signaling, energy expenditure, insulin sensitivity, pancreatic -cell biology, lipid metabolism, and gastrointestinal mucosal remodeling. Its effects on diabetes are profound, with the condition resolving in 45% of patients after gastric banding, 85% after sleeve gastrectomy or gastric bypass, and 98% after the more radical bilio-pancreatic diversion, correlating with weight loss after gastric band procedures but exceeding the degree of weight loss with the latter three approaches, perhaps because of changes in gastrointestinal hormone signaling independent of weight loss. In an animal model, RYGB induces weight loss from reduction in fat mass and fasting glucose improves, as does glucose tolerance. In a relatively lean animal model of insulin resistance and diabetes, comparing diet-induced and RYGB weight loss, both reduce development of fasting hyperglycemia, but patients un● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●