Bariatric Times - August 2008 - (Page 8) 8 Surgical Perspective Bariatric Times • August 2008 An In-Depth Look at Metabolic Surgery: What Is It and Where Is It Going? by Natan Zundel MD, FACS; Majed Maalouf, MD; Soni Chousleb, MD orbid obesity has risen to epidemic levels in western countries. It is now a grave public health burden in terms of the related medical illnesses and the cost of treatments. Bariatric surgery is the most effective treatment to accomplish sustained weight loss and address medical comorbidities. Candidates for bariatric surgery must fulfill the National Institute of Health (NIH) criteria for obesity, which includes a body mass index (BMI) greater than 40kg/m2 without associated comorbid conditions or a BMI greater than 35kg/m2 with medical problems.1 Type 2 diabetes and obesity will likely become the two greatest health problems in the next decade, with an estimated 333 million people expected to be affected worldwide by the year 2025.2 In the United States, from 1980 to 2005 the number of Americans with diabetes increased from 5.6 million to 15.8 million. These conditions are strongly linked to each other, with the increased prevalence of type 2 diabetes mellitus (T2DM) correlating with the increased prevalence in obesity. The adjusted relative risk of developing T2DM in participants with a BMI greater than 35 is 93% for women and 42% for men.3 (AUT:OK as edited?) Weight loss surgery has dramatically gained acceptance in the last decade. Its role and the metabolic outcomes are being described with positive results all over the world. Observational evidence suggests that bariatric surgery results in resolution of obesity in 60 to M 80 percent of patients.3 Multiple surgical procedures have been developed to help with weight loss: restrictive, malabsorptive, and a combination of both. Most comorbidities can be prevented or cured by bariatric surgery in severely obese patients.4,5 Resolution of diabetes is procedure-dependent with 47- to 70-percent cure after restrictive procedures, 80- to 98-percent cure after Roux-en-Y gastric bypass (RYGB), and 92- to 100-percent cure after biliopancreatic diversion (BPD).6,7 The mechanism by which bariatric surgery results in resolution of comorbidities is not fully understood. Multiple theories have been proposed. The most beneficial effect of bariatric surgery is the resolution of diabetes. Most of these patients are medication-free shortly after surgery. Antidiabetic agents, oral or injectable, have multiple limitations and side effects.8 Furthermore, glycemic control tends to deteriorate over time even after treatment.9 Surgical management of T2DM might have several advantages over conventional therapies. First, long-term glycemic control would not be impaired by a patient’s lack of compliance, as happens with diets, exercise, or complex medical regimens.10 These results lead to the development of “metabolic surgery.” Metabolic surgery is performed to treat metabolic diseases, especially diabetes and dyslipidemia. These procedures are performed in patients that do not fit the criteria for obesity surgery. In this review, we will discuss the different mechanisms that contribute to the resolution of comorbidities, especially diabetes, and the different procedures performed for this purpose. PATHOPHYSIOLOGY Diabetes control is closely related to multiple enzymes. These include insulin, glucagon, glucagon-like peptide 1 (GLP1), gastric inhibitory peptide (GIP), leptin, and incretin effect. Glucagon-like peptide 1(GLP-1). GLP-1 is a peptide stored in the L-cells of the ileum and colon, and is released in response to the presence of food in contact with distal small bowel mucosa.11,12 GLP-1 stimulates insulin secretion by promoting pancreatic β-cell proliferation, suppresses postprandial glucagon, and slows gastric emptying.13-15 GLP-1 acts as a satiety hormone by suppressing appetite at the brain level during a meal.13-15 In the human pancreas, GLP-1 promotes the secretion of somatostatin and inhibits that of glucagon.16,17 GLP-1 promotes glycogenogenesis and lipogenesis.18-21 Patients with type 2 diabetes as well as obese patients have low GLP-1 concentrations at base and in response to a meal.22,23 In experimental settings, perfusion of nutrients into the distal gut or ileal transposition in experimental animals increases the release of GLP-1.24,25 Multiple studies have shown that administration of GLP-1, either subcutaneous or intravenous, was effective in
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