Bariatric Surgery Erases Type 2 Diabetes in Obese Patients

By John Gever
MELBOURNE, Australia, Jan. 22 -- Type 2 diabetes was virtually eliminated in three-quarters of obese patients two years after gastric banding surgery, researchers here said. Disease remission was seen in 22 of 30 patients (73%) who underwent the procedure, but in only four of 30 control patients (13%, P<0.001) receiving conventional diabetes treatment, reported John B. Dixon, M.B.B.S., Ph.D., of Monash University, and colleagues in the January 23 issue of the Journal of the American Medical Association. Remission was defined as fasting plasma glucose levels less than 126 mg/dL, glycated hemoglobin values less than 6.2%, and no use of oral hypoglycemic drugs or insulin.
This is the first randomized trial to study bariatric surgery as a treatment for type 2 diabetes in obese patients, the researchers said.
"This study presents strong evidence to support the early consideration of surgically induced loss of weight in the treatment of obese patients with type 2 diabetes," they concluded.
The researchers believe the antidiabetic effect follows from weight loss rather than by altering insulin resistance or beta-cell activity directly.
"Degree of weight loss, not the method, appears to be the major driver of glycemic improvement and diabetes remission in obese participants," they said.
In an interview, Dr. Dixon added, "The greater the weight loss, the more likely they were to remit."
After two years of follow-up, surgery patients weighed 19.6 kg less on average than those treated conventionally (95% CI: 15.2 to 23.8, P<0.001). Mean loss from baseline was 21.1 kg in the surgery patients and 1.5 kg in the control group.
Glycated hemoglobin values were 1.43 points lower in the surgery patients than in controls at the two-year evaluation (95% CI: 0.80 to 2.1, P<0.001). They decreased 1.81 points from baseline after surgery compared with a 0.38-point decrease with standard treatment.
Plasma insulin and glucose levels were also significantly decreased following surgery, with respect to both control therapy and baseline.
Other aspects of metabolic syndrome also improved more with surgery than conventional treatment. These included triglyceride levels and the ratio of high-density lipoprotein cholesterol to total cholesterol.
Entering the study, patients had body mass indices of 30 to 40 kg/m2 and had received a diagnosis of type 2 diabetes within the preceding two years. Evidence of renal impairment or diabetic retinopathy, history of substance addiction or mental illness, type 1 diabetes, diabetes secondary to another disease, recent major vascular event, portal hypertension, or internal malignancy were exclusion criteria.
Nearly all patients had hypertension and metabolic syndrome at enrollment. Mean age was about 47 and mean levels of glycated hemoglobin were 7.6% in the control group and 7.8% in those assigned to surgery.
The surgery involved laparoscopic placement of an adjustable gastric band by the pars flaccida technique.
Conventional treatment was better than ordinary, Dr. Dixon said. Patients were seen by a research team member every six weeks through the two-year study period. They received medications as individually determined by a diabetologist. Lifestyle modification programs focusing on diet and exercise were designed for each participant.
Adverse effects related to the surgery included one case of superficial wound infection at the access site, successfully treated with antibiotics. Two patients developed gastric pouch enlargement 10 months after placement. They underwent a second laparoscopic surgery to correct the problem. One patient was unable to tolerate the band and it was removed after two weeks.
An accompanying editorial by David E. Cummings, M.D., and David R. Flum, M.D., M.P.H., of the University of Washington in Seattle, highlighted the relatively mild degree of diabetes and its short duration in the patient sample.
"It is unclear whether secondary effects from weight loss alone after [gastric banding], without apparent direct antidiabetes surgical mechanisms, would suffice to reverse more severe, longstanding disease with greater beta-cell deterioration," they wrote.
Dr. Dixon agreed, but he added that the question should be tested in a future clinical trial.
Drs. Cummings and Flum also said that other studies have suggested much stronger antidiabetic effects for Roux-en-Y gastric bypass surgery. In those studies, diabetic remission has been observed within days or weeks of surgery, "long before substantial weight loss has occurred," they wrote.
That is true as well, Dr. Dixon said. But he emphasized the differences in risk between the two procedures. He said the literature suggests a mortality rate of about one in 200 for bypass surgery versus about one in 2,000 for the banding procedure. Bypass surgery also creates more problems with nutrient absorption, he said.
Nevertheless, Dr. Dixon said, bypass surgery could be considered for patients at the highest risk for diabetic complications.
"Surgery on the gastrointestinal tract and its effect on type 2 diabetes is a very exciting research area," he said.
The study was funded by Monash University through an unrestricted grant from Allergan Health.
Dr. Dixon reported financial relationships with the National Health and Medical Research Council, Allergan Health, and Novartis Australia. Other co-authors reported relationships with Eli Lilly, Novo Nordisc, sanofi-aventis, Alphapharm, and Abbott Australia.
Dr. Cummings and Dr. Flum reported receiving travel grants to attend a meeting sponsored by Johnson & Johnson, Autosuture, Allergan, Roche, Storz, GI Dynamics, Amylin, and Power Medical Interventions.
Primary source: JAMASource reference:Dixon J, et al "Adjustable gastric banding and conventional therapy for type 2 diabetes: a randomized controlled trial" JAMA 2008; 299: 316-23. Additional source: JAMASource reference: Cummings D, Flum D, "Gastrointestinal surgery as a treatment for diabetes" JAMA 2008; 299: 341-43.