Bariatric surgeries can produce virtually instantaneous improvements in metabolic parameters, such that patients with type 2 diabetes before surgery can have complete remissions of diabetes afterwards.
But as Brigham and Women’s Hospital (BWH) surgeon Eric G. Sheu, MD, and colleagues in the Center for Metabolic and Bariatric Surgery have found, not all bariatric surgery procedures are alike in their ability to improve metabolic parameters, and they are working to find out why.
“We have compared gastric bypass with a Roux-en-Y procedure to sleeve gastrectomy, they are both great for weight loss, but the sleeve does not seem to have the same diabetes remission effects that bypass does,” Dr. Sheu said. “We have pinpointed a few changes in intestinal immune signatures between these two procedures that could explain the difference.”
Their investigations have shown that different bariatric procedures induce changes in intestinal immunity that is specific to the type of surgery and specific segments of the intestinal tract. The changes may be related, at least in part, to changes in the routing of nutrients and intestinal microbiome, but at present that is only a hypothesis, Dr. Sheu said.
“The goal of the research is to identify the differences in outcomes that contribute to the metabolic changes seen following gastric bypass, and, ideally, to modify the safer and simpler sleeve gastrectomy procedure so that it is a more effective metabolic surgery for diabetes,” he said.
Dr. Sheu and colleagues have recently initiated a follow-up study of patients who have undergone sleeve gastrectomy at BWH, looking at changes over time in both intestinal and peripheral immunity from baseline before and after surgery.
“There is growing evidence that after bariatric surgery, the chronic inflammation of obesity resolves. We have indications that this dysregulation is more specific – for example, several autoimmune diseases seem to get better after bariatric surgeries, but the specifics of how bariatric surgery impacts innate and adaptive immune responses has not been well-studied to date,” Dr. Sheu explained.
Early evidence suggests that bariatric surgery can improve inflammatory conditions such as rheumatoid arthritis and psoriatic arthritis. Dr. Sheu cited a 2015 study by a BWH team of investigators led by Jeffrey A Sparks, MD, MMSC, from the Division of Rheumatology, Immunology and Allergy. (Arthritis Care Res 2015. Dec;67(12):1619-26). They conducted a retrospective cohort study of patients who underwent either Rouxen-Y gastric bypass, laparoscopic adjustable gastric banding, or sleeve gastrectomy and looked at rheumatoid arthritis (RA) disease activity at baseline and at six and 12 months after surgery and at the most recent follow-up visits.
The researchers found that after substantial weight loss from bariatric surgery, RA patients had lower disease activity, decreased serum inflammatory markers, and less RA-related medication use.
With this in mind, Dr. Sheu and colleagues are using mass cytometry, a novel technique that allows detailed immune profiling with small specimens, in their patients undergoing bariatric surgery.
“We think that changes in the immunology in the intestine may be a key initiating factor in the systemic metabolic and inflammatory changes of the obese and diabetics. Studying these changes after our best treatment for obesity and diabetes – bariatric surgery – may help us find less invasive treatments in the future,” he said. Results are expected in one to two years. For more information on the study, contact Dr. Sheu at esheu@partners.org or 617-732-6337.
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