Tighten Your Belt! Banded Roux-en-Y Gastric Bypass for Diabetes Remission?

In this issue of Diabetes Care, Murphy et al. (1) report on the use of silastic ring laparoscopic Roux-en-Y gastric bypass (SR-LRYGB) compared with laparoscopic sleeve gastrectomy (LSG) to achieve remission of type 2 diabetes at 5 years postoperatively. Figure 1 illustrates the relative impact on diabetes remission and overall surgical risk of the more commonly performed bariatric surgeries in the context of their primary weight loss mechanisms. With SR-LRYGB, practitioners attempt to leverage the benefits of both a standard Roux-en-Y gastric bypass (RYGB) and adjustable gastric band to achieve increased restriction and potentially reduce long-term weight regain. Although this is a single-center study, 114 subjects were randomized in double-blind fashion to either procedure—a remarkable achievement, especially considering how randomization was stratified. This is important because several factors other than the type of procedure and quantity of weight loss determine the likelihood of diabetes remission after bariatric surgery (2). The authors report that diabetes remission 5 years postprocedure was significantly higher after SR-LRYGB (47 vs. 33%, P < 0.01) due to greater weight loss with this procedure compared with LSG (1). Perhaps more surprisingly, early and late complications did not differ between groups.

While previous studies comparing SR-LRYGB with either LSG or standard RYGB have not adequately addressed the long-term outcome of diabetes remission (3,4), prior work has shown that LSG has effects equivalent to those of laparoscopic Roux-en-Y gastric bypass (LRYGB) at 1 year on weight loss, fasting glucose, and HbA_1c (5). However, these effects are not sustained, so diabetes remission rates and weight loss are superior within 3 years of surgery among patients undergoing RYGB (6). Of course, although diabetes remission after bariatric surgery is an important consideration and treatment outcome, it should be considered as part of the clinical indications for the treatment of medically complicated obesity. In fact, it is our opinion that a desire to achieve diabetes remission alone should never be the sole indication for bariatric surgery.

How does bariatric surgery cause diabetes remission? Many have reported rapid improvement in fasting glucose concentrations after surgery prior to appreciable weight loss (7–9). Whatever mechanisms are invoked to explain this improvement need to account for the effect (both in terms of magnitude and in terms of rapidity) of caloric restriction alone on carbohydrate metabolism (10). This is independent of weight loss and is accompanied by improved β-cell function (11) and insulin action (to be expected given the negative effects of high insulin concentrations per se on insulin signaling) (12). In fact, RYGB has little effect on β-cell secretion in response to submaximal stimuli (13) or on insulin secretion in response to an oral glucose tolerance test (14).

Therefore, a corollary of these observations is that once baseline β-cell health is accounted for using surrogates such as insulin use before surgery and duration of diabetes (2), between-procedure differences in diabetes remission are likely accounted for by differences in weight loss after surgery. In a meta-analysis by Buchwald et al. (15), 1,417 of 1,846 (76%) patients experienced complete resolution of type 2 diabetes after bariatric surgery. There were clear differences in the efficacy of procedures; for example, there was a 99% remission rate after biliopancreatic diversion or duodenal switch. In contrast, the rate was only 48% after adjustable gastric banding (15), reflecting the degree of weight loss associated with these procedures.

It is important to remember that although diabetes is a disease defined by glucose concentrations, normalization of glucose concentrations does not imply a reversal of the underlying pathophysiology and abnormalities of islet dysfunction—as discussed above. Unsurprisingly, weight regain after bariatric surgery is strongly associated with relapse of type 2 diabetes in many case series or longitudinal studies (16,17). Multiple factors govern satiety including stomach capacitance (18). Bariatric surgery typically introduces some restriction on stomach capacity (Fig. 1). In LSG a functioning pylorus is retained, and gastric volume is usually larger than the pouch created after LRYGB, but in both, dysfunctional eating can increase reservoir volume over time, leading to loss of efficacy of the procedure (19).

Various procedures have been developed to address weight regain (or lack of sufficient weight loss) after bariatric surgery. These include open or endoscopic revision of the gastrojejunal anastomosis after RYGB. In fact, sleeve gastrectomy emerged as a stand-alone procedure when the duodenal switch operation was performed as a staged procedure, following the SG part of the operation if initial weight loss was unsatisfactory (20). Adjustable gastric banding was also devised as a procedure that would enable enhanced mechanical restriction of the stomach over time if weight loss plateaued or was insufficient. However, adjustable gastric banding has fallen out of favor because of its relative lack of long-term efficacy and, more germane to the current discussion, association with significant complications such as pouch dilation and band slippage, erosion, or perforation (21). These complications are similar to prior experience with prosthetic devices encircling portions of the upper gastrointestinal tract (22).

Therefore, the concern arising out of the current study is that the silastic ring intended to produce durable gastric restriction in SR-LRYGB will be the cause of long-term morbidity and, perhaps, mortality associated with the procedure (Fig. 1). In the current study, early minor and major complications did not differ significantly between the groups and none of those reported are clearly attributable to the surgery performed (1). On the other hand, although the difference in late major complications between groups did not reach statistical significance, there were more events in the SR-LRYGB group, with an estimated number needed to cause an additional late major complication (SR-LRYGB vs. LSG) of 11. These events included dysphagia requiring change of the silastic ring and anastomotic ulcer perforation. Overall, it is quite possible that the study was underpowered to detect such relatively uncommon, but serious, complications.

It is also important to remember that the design of the current study does not allow quantification of the contribution of the SR in achieving diabetes remission beyond that of a standard LRYGB. This will need to be addressed in future work to enable better quantification of the risks versus the benefits of placing an SR around the gastric pouch in comparison with those of standard RYGB. Finally, although LSG continues to be the most frequently performed bariatric procedure in clinical practice (23), the observed effects are certainly supportive of prior data demonstrating the inferiority of LSG in maintaining diabetes remission compared with a bypass procedure (24,25).

In summary, this study demonstrates that SR-LRYGB may prove to be an effective option for patients with obesity and type 2 diabetes who are suitable surgical candidates. However, long-term efficacy and safety, compared with conventional RYGB, still need to be established prior to widespread adoption of this procedure.