Remission of type 2 diabetes in severely obese people after bariatric surgery hinges on baseline beta cell function, not weight loss….
The study by Richard Perugini, MD, and colleagues from the University of Massachusetts Medical Center in Worcester, involved 137 people with diabetes who were severely obese (body mass index ranged from 33 to 75 kg/m²).
All patients required medication for glycemic control and had achieved HbA1c levels under 7.5% prior to undergoing Roux-en-Y gastric bypass surgery.
In 46% of patients, diabetes had remitted at 40 days (remission was defined by the researchers as the withdrawal of diabetic medications). That rose to 57% at 180 days and 70% at 1 year.
For all subjects (those who were no longer on medication and those who were), mean HbA1c level was 5.9% at 40 days, 6.0% at 180 days, and 6.1% at 1 year, Dr. Perugini reported. At 1 year, subjects no longer taking medication had a better mean HbA1c level than those taking medication (5.7% vs 6.3%).
Weight loss was similar in those who experienced remission and those who did not (23% to 27% at 6 weeks and 58% to 60% at 1 year), suggesting that the remission of diabetes is independent of weight loss, said Dr. Perugini.
Dr. Perugini noted that, "The majority of patients who went off their medications were off by 6 weeks." At that point, the only phenomena at play were independent of weight loss, such as the incretin response, he explained.
The researchers compared the remission and nonremission groups and found that the 2 strongest predictors of postsurgical remission were baseline insulin use and baseline homeostasis model assessment disposition index (HOMA-DI), a measure of residual beta cell function. Patients with a HOMA-DI greater than 30% of normal at baseline had a 4-fold increased chance of remission, and patients who achieved adequate baseline glycemic control without using insulin had an 8-fold chance of remission, he said.
"Patients who did not require insulin and who had a HOMA disposition index greater than 30% had a 98% chance of remission, whereas patients…who required insulin and who had a HOMA disposition index below 30% only had an 18% chance of remission," he said.
Dr. Perugini said in a statement that, "The study shows that beta cell function…and insulin dependence, not initial weight or subsequent weight loss, are the greatest predictors of potential diabetes remission after gastric bypass."
John Dixon, PhD, senior researcher at the Baker IDI Heart and Diabetes Institute in Melbourne, Australia, mentioned that the decision by bariatric surgeons to withdraw diabetes medications might not be advisable in the long term and pointed to emerging evidence indicating that up to 50% of obese diabetic patients who are able to stop medications after bariatric surgery resume them within 5 years.
"I don’t know how you can stop medications within 6 weeks when you haven’t got a hemoglobin A1c [measurement]…. And why would you stop metformin, which prevents diabetes in an obese group of high-risk people?" Dr. Dixon expressed concern that many diabetic patients are also stopping other medications after bariatric surgery.
"Sometimes people have their antihypertensives stopped and their statins stopped…. Metformin, blood-pressure-lowering drugs, and statins have all been shown to save lives in diabetics, so we’ve got to be very careful…. I don’t think they should ever be stopped."
Dr. Perugini noted that there is no evidence to support keeping patients on metformin. "The onus should be on Dr. Dixon to provide data indicating that in formerly diabetic patients with good glycemic control off medications following gastric bypass, the benefits of continued therapy with metformin outweigh the risks and costs. I am not aware of such data."
American Society for Metabolic and Bariatric Surgery (ASMBS) 29th Annual Meeting: Abstract PL110. Presented June 20, 2012.