Bariatric Times - August 2008 - (Page 9) Bariatric Times • August 2008 Surgical Perspective controling blood sugar in diabetic patients.26-29 In animal models with ileojejunal transposition, the early arrival of food to the interposed isoperistaltic ileal L-cells produces an increase in GLP-1.30,31 Increased levels are also seen after gastric bypass surgery.32 Gastric inhibitory peptide (GIP). Gastric inhibitory peptide (GIP) or glucose-dependent insulinotropic peptide is a peptide stored in the K cells of the proximal jejunum that is released in response to direct contact with a meal rich in carbohydrates or fat.33,34 GIP helps to maintain blood glucose homeostasis; however, its mechanism of action is not well defined.35,36 It may increase insulin secretions by β cells of the pancreas. It also stimulates lipoprotein lipase activity. Patients with T2DM have decreased sensitivity to GIP with either normal or increased concentrations.22 High theories have been proposed. Pories proposed that excessive stimulation of incretins by food in the foregut of vulnerable individuals was the cause of T2DM, and cure by bypass operations was due to removal of the excessive stimulation and exclusion of the site responsible for the production of the incretin.42,43 Mason proposed the hindgut hypothesis: Early arrival of undigested food to the terminal ileum is responsible for the improvement of glucose tolerance.44 The hindgut hypothesis holds that diabetes control results from the expedited delivery of nutrient chyme to the distal intestine, enhancing a physiologic signal that improves glucose metabolism.45 The mediator of this effect can potentially be GLP-1 secreted by the L cells of the terminal ileum and the peptide tyrosine-tyrosine PYY336, which share an anorectic effect. GLP-1 stimulates the production of insulin. Jejunoileal bypass supports the enteric nervous system. The main advantages of restrictive procedures are the simplicity of the operation and the low mortality rates. Malabsorptive procedures confer better results in weight loss and resolution of comorbidities. Jejunoileal bypass. Jejunoileal bypass was first described in the early 1950s to promote weight loss.48 This procedure consists of dividing the proximal jejunum and performing a jejunoileal anastomosis just proximal to the ileocecal valve. Different segment length has been described, but satisfactory weight loss was reported in patients in whom 30 to 35cm of jejunum was anastomosed to 10 to 15cm of terminal ileum.49 Weigth loss was successfully achieved as well as resolution of diabetes.50,51 However, multiple complications have been reported including malnutrition, diarrhea, and cirrhosis. The extent of these complications led to a public months postoperatively. No weight loss was noted after nine months.2 Pacheco randomized 12 nonobese diabetic rats to gastrojejunal bypass or no intervention. No weight loss was obtained in the two groups. There was an improvement in glycemic control and in basal glucose level in the gastrojejunal bypass group.41 Ileal transposition. The concept of “ileal brake” was first introduced in 1983.54 Mason suggested that the combination of a restrictive procedure with ileal interposition could be appropriate in mildly obese diabetic patients.44 Early arrival of nutriments to distal small bowel results in increased levels of GLP-1, which is responsible for diabetes control.30,44 In a series of 19 patients with a mean BMI of 40kg/m2, de Paula from Brazil performed laparoscopic ileal interposition with sleeve gastrectomy. The biliopancreatic limb is divided 50cm distal to the Bariatric surgery is also effective in curing diabetes in normal-weight subjects.59 concentrations are also seen after bariatric surgery.37,38 Leptin. Leptin is an adipocytederived hormone and is the hormone of satiety. It reflects the total amount of fat present in the body. Low leptin levels are usually seen among weight loss patients39 and after bypass surgery.40 In a series of nonobese diabetic rats who underwent gastrojejunal bypass, leptin levels decreased one week after surgery and remained low at one month. However, in this series, GIP and GLP-1 levels remained unchanged. This suggests that leptin may be regulated by the proximal bowel and enhancement of leptin sensitivity results in improvement of glycemic control.41 Incretin effect. The incretin effect is defined by a greater insulin response of the pancreas to oral than intravenous glucose load. This is thought to be due to glucose-dependent insulinotropic peptide (GIP) and GLP-1.35 The improvement in glycemic control occurs during the first week after bypass surgery,40 suggesting that weight loss is not the only mechanism responsible for the resolution of diabetes. Multiple this hypothesis. An alternate hypothesis is the foregut hypothesis. Bariatric operations that exclude the duodenum and the jejunum from the transit of nutrients improve glucose tolerance. This hypothesis was tested on nonobese diabetic rats.45 Bypass of the duodenum and proximal jejunum is responsible for the glycemic control by alternating the enteroinsulinic axis and incretin production of GLP-1 and GIP.45 BPD and gastric bypass are two examples. In a series of 10 morbidly obese women with T2DM undergoing BPD, insulin sensitivity increased as early as one week after surgery with decreased GIP levels and inceased GLP-1.46 These changes occurred before any modification in body weight. A reduction in GIP secretion was obtained after both RYGBP and BPD as a result of bypassing the duodenum and the proximal jejunum, the areas with the highest K-cell content.47 repudiation of JIB in 1979 and favored gastric bypass as a surgical treatment for morbid obesity.52 Duodenojejunal bypass (DJB). DJB consists of excluding the duodenum and proximal jejunum without restriction of the gastric volume. It was first described by Rubino and Marescaux in 2004 on an animal model.53 They performed a stomach-preserving gastrojejunal bypass on nonobese type 2 diabetic rats and proved that bypassing the duodenum and jejunum reduces fasting glycemia and improves both glucose tolerance and insulin action without any changes in weight. In addition, lower levels of FFA and cholesterol were obtained in the feeding state. Cohen perfomed this procedure laparoscopically on two nonobese patients with T2DM and BMIs of 22 and 34.2 The duodenum is transected 1 to 2cm distal to the pylorus. The biliopancreatic limb is divided 30cm distal to the ligament of Treitz and a 50cm Roux limb is constructed. A pylorojejunostomy is performed. Complete resolution of diabetes was obtained by the fifth postoperative week. The hemoglobin A1c levels were 6g/dL at the last follow-up visit nine ligament of Treitz and a 100-cm Roux-en-Y ileal limb is created 50cm proximal to the ileocecal valve. After one month, all the diabetic patients were normoglycemic and with a percentage of mean weight loss from perioperative weight less than 10 percent.55 Biliopancreatic diversion. BPD combines an antrectomy, a Rouxen-Y limb of 2.5m, and a common channel of 50cm. The residual volume of the stomach is 400mL. The small bowel is transected at 2.5m from the ileocecal valve and is anastomosed to the remaining stomach. The biliopancreatic limb is anastomosed in an end-to-side fashion to the bowel 50cm proximal to the ileocecal valve.46 Pories and Albrecht56 suggested that the improvement in glycemic control is the result of the exclusion of food from the proximal intestinal tract and an alteration of incretin secretions. BPD cures diabetes by altering the enteroinsular axis by diverting nutrients away from the proximal gastrointestinal tract down, regulating GIP secretion, and by delivering incompletely digested nutrients to the ileum, enhancing the secretion of GLP-1.57 SURGICAL PROCEDURES Common surgical methods are restrictive, malabsorptive, or a combination of these two. These operations exert appetite regulation at the level of both the central and
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