Bariatric surgery is better at controlling glucose levels than dieting

A study has found a new clue as to why bariatric surgery is more effective than dietary remedies alone at controlling glucose levels.

Researchers at Duke University Medical Center and St Luke's and Roosevelt Hospital Center, Columbia University, made the discovery.

The current study showed that obese people 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), compared to a matched group of obese patients with diabetes who lost an equal amount of weight by following a diet.

This enhanced reduction in BCAA and aromatic amino acids Phe and Tyr was linked to better improvement in glycemic (blood sugar) control in the GBP group.

Lead author Blandine Laferrere, MD, of the New York Obesity Nutrition Research Center (NYONRC) at St Luke's and Roosevelt Hospital Center, provided one group of patients for comparison and Duke University provided a group 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, correlated 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," Laferrere said.

"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," Laferrere explained.

Senior author Christopher B Newgard, PhD, and colleagues at the Sarah W Stedman Nutrition and Metabolism Center at Duke University, evaluated specimens at the Center's metabolic profiling ("metabolomics") laboratory.

The Center's laboratory uses mass spectrometry to measure hundreds of metabolic intermediates simultaneously in simple blood samples.

"The evidence is mounting that BCAA and related metabolites are linked with insulin resistance and diabetes, and that they can cause metabolic dysfunction," Newgard said.

"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.

"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?" he added.

The results were published in Science Translational Medicine on April 27.