A Certain Weight-Loss Surgery Shows Type 2 Benefits
Sangeeta Kashyap, MD
|ADA Research Funding
Bariatric surgery, which reduces the size of patients' stomachs to help them lose weight, became a more common weight-loss option in the mid-1990s. Ever since, researchers have been eyeing the various surgical procedures to see if they might be an effective tool in the fight against type 2 diabetes as well.
Early research on bariatric surgery patients suggested that the procedure's benefits went further than weight loss, somehow changing the way the body responded to food.
With the help of a grant from the American Diabetes Association, Sangeeta Kashyap, MD, a researcher at the Cleveland Clinic, is conducting a study to determine whether surgery indeed beats medication when it comes to achieving blood glucose control in people with type 2 diabetes. For the purposes of the study, the goal is an A1C of less than 6 percent—with or without medication—after the first and second years of treatment. An A1C that low amounts to putting type 2 diabetes in remission.
The study involves 150 people, assigned at random to three groups representing different approaches to treating diabetes: Two groups were given operations to reduce the size of their stomachs, through Roux-en-Y gastric bypass (which involves removing part of the stomach and a chunk of the upper intestine) or sleeve gastrectomy (a surgery that reduces the size of the stomach without touching the intestine). The third group was put on cutting-edge diabetes medications designed to increase their sensitivity to insulin. "We wanted to look at how these interventions affected insulin sensitivity and insulin secretion," Kashyap says. "The goal was to tease out the mechanisms by which surgery produces beneficial effects in people with diabetes."
Other researchers have looked at the effects of gastric bypass and other stomach surgeries, but Kashyap says this is the first to follow so many people for so long after their surgeries. It's also the first randomized controlled trial looking at bariatric surgery: People who signed up for the experiment, all of whom had lived with type 2 diabetes for seven to 10 years, didn't know if they would be given medications or go under the knife.
Kashyap's study also had another key difference. She selected people who were overweight but not unusually so. Typically, candidates for bariatric surgery are extremely obese, with a body mass index (BMI) of 47 to 50. "The people in our study are far more representative of a diabetic group than any study in the past. Most of our patients had a BMI of 36, very close to the people with type 2 we regularly see in medical clinics," she says. "We wanted to see the effects on people who are … not morbidly obese."
All three groups got nutritional advice and a psychological evaluation to make sure that they were ready for the dramatic changes stomach surgery involves (including the dangers of surgery, reduced stomach size, and potential problems with absorbing nutrients). Everyone who signed up for the study had to be willing to undergo surgery.
Kashyap's preliminary results suggest that surgery is a potent weapon in the fight against diabetes—and that not all surgery is created equal. Roux-en-Y gastric bypass, the most dramatic type of bariatric surgery, had the best results, with more than a third of patients meeting their A1C goal by the end of the study's second year—nearly six times the success rate of medication alone.
Sleeve gastrectomy helped patients lose weight at nearly the same rate as gastric bypass. But just 10 percent of the sleeve gastrectomy patients met their A1C goals after a year. Medicine alone helped only 6 percent of those patients meet the target.
For Kashyap, the study's most exciting finding is that gastric bypass may actually help beta cells—the cells in the pancreas responsible for producing insulin—bounce back. Study participants in the gastric bypass group had a nearly sixfold increase in beta cell function after two years. An unrelated study by University of Washington endocrinologist David Cummings supports Kashyap's findings: Cummings recently reported that 88 percent of people with type 2 diabetes were producing insulin on their own six years after Roux-en-Y gastric bypass surgery.
What researchers still don't know for sure is why the surgery has such an impact. Kashyap suggests that because the surgery makes food bypass the upper intestine, it enters a part of the gut responsible for activating the pancreas almost immediately. "It goes right to the area, stimulates good hormones, and gets the pancreas producing insulin," she says.
Thus far, surgeons have been reluctant to offer gastric bypass to people with lesser degrees of obesity. Kashyap's findings suggest that such people with type 2 diabetes should be considered for the surgery as well. "We want to capture people when the pancreas is still working and they can still harness the benefits," she says.
And as Kashyap and others continue to research the reasons gastric bypass is so effective—why it stimulates digestive hormones in a different way, for example—they may discover ways to mimic the effects of the procedure without the surgery itself.
For now, though, the surgery offers remarkable promise for people struggling with type 2 diabetes. "We've never had a treatment for diabetes that can reverse beta cell failure—but that's what gastric bypass is doing," Kashyap says. "It truly is a breakthrough."
The ADA wishes to express gratitude for the estate gift made In Memory of Dorothy Schaffer.
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