Which Form of Bariatric Surgery Is The Most Effective for Obese Diabetic Patients?

"Familiarity with these effects can help physicians decide among the different surgical procedures [for patients with type 2 diabetes] and avoid postoperative hypoglycemia," write Marion L. Vetter, MD, from the Hospital of the University of Pennsylvania in Philadelphia, and colleagues.

The review article was based on a literature search of 4 decades' worth of studies on bariatric surgery and diabetes. Most of the studies had serious methodological weaknesses, the authors state. Few were randomized controlled trials, and important data were missing in a number of the studies. A total of 10 studies met minimum criteria for quality and had follow-up rates of at least 80%.

Bariatric surgery was found to reduce the patients' body mass index by 10 to 15 kg/m2 and their weight by 30 to 50 kg in these studies. In 1 study, Roux-en-Y gastric bypass (RYGB) — the procedure considered the current gold standard — was associated with a 25% reduction in total body weight at 10 years, whereas restrictive procedures such as laparoscopic adjustable gastric banding and vertical banded gastroplasty were associated with 16% and 14% weight loss, respectively. Diabetes resolution was reported in 60% to 80% of patients treated surgically.

Bariatric surgery procedures achieve resolution of type 2 diabetes in 49% to 98% of patients. These procedures have different effects on the enteroinsular axis (connection between the gut and pancreatic islet cells), including effects on hormones called incretins (glucagons-like peptide 1 [GLP-1] and glucose-dependent insulinotropic peptide) and nonincretin gut peptides (peptide YY [PYY] and gherelin). Intestinal bypass procedures that expedite nutrient delivery to the distal ileum, such as biliopancreatic diversion and RYGB, increase GLP-1 and PYY levels; in contrast, restrictive procedures do not increase incretin or PYY levels. After surgery, gherelin levels are determined by the remaining amount of gherelin-producing tissue and by whether vagal innervation is intact.

The authors postulate that augmented levels of GLP-1 probably account for the antidiabetic effect of procedures that bypass the small bowel. It is also thought that altered secretion of anorexigenic peptides (ie, GLP-1 and PYY) may mediate a reduction in appetite and sustained weight loss that occurs more often after intestinal bypass procedures.

"Collectively, caloric restriction and alterations in the enteroinsular axis probably affect both insulin secretion and sensitivity. Physicians must anticipate the rapid improvements in insulin action after bariatric surgery and adjust diabetic regimens accordingly to avoid hypoglycemia. In addition to identifying the antidiabetic mechanisms of bariatric surgery, future research should focus on making medical management safer, particularly if the patient takes GLP-1 analogues or DPP-IV inhibitors," the authors write.

Arch Intern Med. Jan, 20, 2009;150:94–103.