How Weight Loss Surgery Helps Diabetes
Study Explains Why Surgery Improves Blood Sugar Levels Even Before Patients Lose Weight
By Salynn Boyles
WebMD Health News
Reviewed By Louise Chang, MD
Sept. 2, 2008 — Obese diabetes patients who have gastric bypass weight loss surgery often show dramatic improvement in blood sugar controlwithin days, long before significant weight loss occurs.
The reversal of type 2 diabetes tends to occur much more rapidly than with gastric banding, and a new study may help explain why.
The findings could also advance the search for better diabetestreatments that target the small intestine and not the pancreas,researchers say.
“It is increasingly clear that the intestine is not just a conduit forfood transit,” gastric bypass surgeon Francesco Rubino, MD, tells WebMD.”We now know that it is also a very important organ for the regulation of glucose.”
Intestine Produces Glucose
Several recent studies have suggested that weight loss surgery is a moreeffective treatment for type 2 diabetes in obese people than standardtreatments for the disease.
Because weight loss alone cannot explain the rapid remission of disease inmany gastric bypass patients, researchers have looked for other causes.
One theory has been that surgery alters the expression of hormones that helpcontrol appetite, blood sugar, and weight.
But studies designed to test this hypothesis have proven contradictory,diabetes researcher Gilles Mithieux tells WebMD.
In their newly published study, reported in the September issue of thejournal Cell Metabolism, Mithieux and colleagues looked elsewhere foranswers.
“We know from earlier work that the small intestine can produceglucose,” he says. “We showed that with gastric bypass surgery youessentially double the capacity of the intestine to do this.”
By studying mice treated with either gastric bypass or banding, researchersconfirmed that the bypass operation was associated with increased production ofglucose, or blood sugar, in the small intestine, while gastric banding wasnot.
Gastric bypass surgery essentially produces a “double intestine,”Mithieux says. The portion of the small intestine that is closest to the stomach is bypassed so that it no longer received nutrients. The lower smallintestine is then attached to the stomach where it becomes the main nutrientreceiver.
By surgically repositioning the lower small intestine, which usually doesnot produce much glucose, it ramps up intestinal glucose production andimproves insulin sensitivity, he says.
Treating Diabetes With Surgery
Rubino tells WebMD that the findings offer important insights into the roleof the small intestine in blood sugar regulation.
“This doesn’t tell the whole story, but it appears to be an importantpiece of the puzzle,” he says.
The gastric bypass surgeon is a strong advocate of using the surgery as afirst-line treatment for type 2 diabetes — a position that remainscontroversial.
He directs the diabetes surgery center at the New York-PresbyterianHospital/Weill Cornell Medical Center.
“Surgery promises to be one of the most powerful resources we have tofight this disease,” he says. “I don’t think it will be the answer foreveryone. But for patients with the right profile, the results can beremarkable.”
Rubino believes that the surgery can help not just diabetic patients who aremorbidly obese, but also people who are overweight but don’t weigh enough undercurrent guidelines to be considered for the gastric bypass procedure.
“We hope to study this to see if surgery is better than conventionaltreatment in patients who are moderately obese or just overweight,” hesays.
SOURCES: Troy, S. Cell Metabolism, September 2008; vol 8: pp 201-211. Gilles Mithieux, Institut National de la Sante et de la Recherche Medicale, Paris. Francesco Rubino, MD, director, metabolic surgery program, New York-Presbyterian/Weill Cornell Medical Center, New York City.
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