April 28, 2011

Diabetics: Gastric Bypass Better than Diet?

(Ivanhoe Newswire) -- As the risks and diseases associated with morbid obesity are becoming more known, people are constantly looking for ways to slim down and improve their health. Though eating healthy and getting plenty of exercise are always recommended, many people need something more to help them. Researchers at Duke University Medical Center and St. Luke's and Roosevelt Hospital Center, Columbia University, have discovered a novel clue for why bariatric surgery is more effective than dietary remedies alone at controlling glucose levels.

Physicians have examined and concluded that bariatric surgery results in improved blood sugar levels in up to 80 percent of cases; however, the explanation has not been unreservedly apparent to them thus far. Even though substantial weight loss is essential to the individual and study's success, gastric bypass surgery (GBP) improves glycemic control in type 2 diabetes even before considerable weight loss occurs, which implies alternate mechanisms interrelated to biochemical and/or hormonal changes.

The existing study illustrated that exceptionally overweight individuals with type 2 diabetes undergoing GBP surgery have much lower levels of circulating branched-chain amino acids (BCAA) and the aromatic amino acids phenylalanine (Phe) and tyrosine (Tyr), in comparison to a corresponding group of obese patients with diabetes who lost an equivalent amount of weight by following a particular diet.

This superior decrease in BCAA and aromatic amino acids Phe and Tyr was linked to improvement in glycemic (blood sugar) control in the GBP group. Lead author Blandine Laferrre, M.D., of the New York Obesity Nutrition Research Center at St. Luke's and Roosevelt Hospital Center, provided one cohort of patients for comparison, and Duke University provided a cohort of obese patients without diabetes, matched also into GBP and diet groups for evaluation. Both sets of results showed the preferential reduction in amino acids in the GBP subjects, correlating with better glucose control.

"The most intriguing finding from the current study is that amino acids, particularly the branched-chain amino acids, decreased more significantly after gastric bypass surgery than after the same weight loss through a diet intervention," Dr. Laferrre was quoted as saying. "The next step will be to characterize the pathways involved in these metabolic changes, so we can understand how the specific metabolic signature of gastric bypass surgery is related to changes in hormones and hormone action, including gut hormones, that occur after surgery."

Christopher B. Newgard, Ph.D., senior author of the study, as well as colleagues at the Sarah W. Stedman Nutrition and Metabolism Center at Duke University, assessed samples at the Center's metabolic profiling ("metabolomics") laboratory. The Center's laboratory uses mass spectrometry to calculate hundreds of metabolic intermediates concurrently in blood samples.

In previous studies conducted by the Duke group with the aid of collaborators, bunches of branched-chain amino acids, Phe, Tyr in addition to the breakdown products of the BCAAs were ultimately revealed to be connected with insulin resistance and with coronary artery disease.

"The evidence is mounting that BCAA and related metabolites are linked with insulin resistance and diabetes, and that they can cause metabolic dysfunction," Newgard added. "The current study shows that these metabolites are also highly-responsive to a very efficacious diabetes intervention, gastric bypass surgery."

"Moving forward, we will need to design studies in the general population to completely demonstrate the value of the amino acid signature in models of risk and to come up with clinically valuable algorithms," Newgard concludes. "We also need to understand how BCAA and related metabolites become elevated in patients at risk for diabetes-- is this genetics, diet, gut bacteria, or some combination of these factors?"

SOURCE: Science Translational Medicine, April 27, 2011