Treating Type 2 Diabetes Mellitus With Sleeve Gastrectomy in Obese Patients

Globally, there are over 1.7 billion adults classified as overweight and 300 million considered clinically obese (1). Major comorbid disease related to obesity include type 2 diabetes mellitus (T2DM), hypertension, and hyperlipidemia, which all contribute to increased risk of cardiac events. Bariatric surgeries, including roux-en-Y gastric bypass (RYGB) and bilio-pancreatic diversion with duodenal switch (BPDDS) have been shown to improve long-term control of obesity and T2DM (2,3). In a recent systematic review, which included RYGB and BPDDS, 76% of obese patients had resolution of T2DM following bariatric surgery (4). Both RYGB and BPDDS remain complex surgical procedures with significant postoperative morbidity. Based on early data, laparoscopic sleeve gastrectomy (LSG), a less technically complex procedure, is being considered as a surgical option for obese patients (5). LSG was initially proposed as the first stage of a staged approach to BPDDS in high risk, severely obese individuals (6). LSG involves creating a gastric “tube” (60–100 ml capacity) by removing a majority of the fundus of the stomach. Weight loss after LSG is believed to due to restriction of food intake by the small gastric reservoir. The mechanisms through which LSG improves glycemic control are not fully understood, but both hormonal changes (7) and hindgut mechanisms (8,9) may be involved. The evidence to support LSG as a surgical option for bariatric patients to produce long-term sustainable weight loss, with improvement of T2DM, is increasing. Silecchia and colleagues assessed LSG in 17 obese (BMI >50) patients with T2DM, and demonstrated an 80% resolution rate for T2DM (5). Cottam and colleagues preformed LSG on 75 high-risk morbidly obese (BMI >60) patients with T2DM as first stage procedure prior to RYGB. These patients had a percentage excess weight loss of 46% and had 81% T2DM resolution following LSG at 12 months follow-up (10). Vidal and colleagues also performed a prospective study, which included 39 patients with T2DM (11). These patients had a T2DM resolution rate of 81%, with a reduction of HbA1c levels from 7.4 to 6.9. Shah and colleagues evaluated LSG in 58 obese (mean BMI 45) T2DM and found an impressive 96% resolution rate for T2DM (12). HbA1c levels in these patients dropped on average from 8.4% to 6.1%. Based on early evidence from these studies, it appears that LSG for morbid obesity, results in remarkable resolution rates for T2DM (5,10,11,12). A systematic review by Buchwald and colleagues assessed T2DM resolution rates by other bariatric surgical procedures (4). In this review, gastric banding, gastric bypass, and BPDDS resolved T2DM in 48%, 84%, and 98% of patients, respectively (4). LSG appears to resolve T2DM, ranging from 80% to 96%, of morbidly obese patients (5,10,11,12). The Swedish Obesity Subjects study also demonstrated that recovery rates from T2DM in the group treated with bariatric surgery was significantly higher than the control group (13). Furthermore they demonstrated that there was an 80% reduction in annual mortality in the surgically treated group compared to control group (13). LSG is considered to be technically comparable to gastric banding by bariatric surgeons. However, compared to the review by Buchwald and colleagues, it appears that LSG may have a higher degree of T2DM resolution (4). Abbatini and colleagues reached a similar conclusion in comparing LSG and gastric banding in 60 morbidly obese patients (14). They reported a T2DM resolution rate of 80.9% for LSG compared to 60.8% for gastric banding, along with greater improvements in insulin resistance in the LSG-treated group. Additional benefits for the patients undergoing LSG include both lack of need for adjustments to a gastric band and avoidance of needles. LSG restricts the size of the stomach by removing the gastric fundus. Furthermore, the pylorus functions as a natural band facilitating further restriction. The removal of the gastric fundus reduces ghrelin levels (7), a stimulator of food intake in humans (15). Karamanakos and colleagues found significantly decreased levels of ghrelin in 16 patients following LSG surgery, which may be associated with greater appetite suppression levels (7). A hormonal mechanism is also suggested by Abbatini et al., who found a similar T2DM resolution rate with LSG and laparoscopic gastric bypass surgery (14). In superobese patients, LSG was initially proposed as a first-stage procedure (6). LSG, unlike other restrictive procedures, was found to increase transit time of stomach contents (16). This may explain benefits of LSG that are similar to RYGB and BPDDS according to the hindgut theory, which postulates that with rapid transit of undigested nutrients, the distal bowel upregulates the production of GLP-1 and Peptide YY. Both derivatives of L-cells, GLP-1 stimulate insulin secretion and have an antiapoptotic effect on β cells in the pancreas (17). Peptide YY may ameliorate insulin resistance in mice (18). If the hindgut theory holds true, it may explain the apparent additive improvement of T2DM following LSG compared to other restrictive procedures. In conclusion, LSG appears to have a considerable beneficial effect on T2DM, producing resolution in a majority of individuals. Further research, including randomized controlled trials are needed to delineate the role of this promising surgical intervention for the management of individuals with T2DM. The authors declared no conflict of interest.

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