Dietary Supplement Helps Obese With Prediabetes

For obese persons who are at risk for diabetes mellitus, dietary supplementation with resveratrol may improve their insulin resistance, according to the results of a new study.

“Our meta-analysis shows that people with abnormal glucose metabolism may benefit from taking resveratrol as a dietary supplement. Those with normal glucose tolerance, however, do not improve their insulin resistance with resveratrol,” Meredith Hawkins, MD, Professor of Medicine at Albert Einstein College of Medicine, Bronx, New York, told ConsultantLive.

Resveratrol, found in red wine, is a plant-derived polyphenol whose beneficial metabolic effects include improved insulin sensitivity, reduced inflammation, and increased muscle mitochondrial biogenesis. “We set out to examine the effects of resveratrol on insulin sensitivity, muscle mitochondria, and adipose inflammation,” said Roger Maginley, MD, Postdoctoral Research Fellow in the Division of Endocrinology & Diabetes at Albert Einstein College of Medicine, at the American Diabetes Association 74^th Scientific Sessions in San Francisco.

In a randomized, double-blind trial, Dr Maginley and colleagues administered resveratrol, 2 gm/d, or placebo for 28 days to 21 nondiabetic subjects, median age 52 years, with an average body mass index of 31.9 kg/m² and homeostasis model assessment-estimated insulin resistance of 3.9 (Abstract 144-OR). All subjects underwent 6-hour, 2-step euglycemic hyperinsulinemic pancreatic clamp studies that assessed their hepatic and peripheral insulin sensitivity. The researchers also took biopsies of vastus lateralis muscle and subcutaneous abdominal adipose tissue before and after administering the resveratrol or placebo. Muscle mitochondria were analyzed for quantity, size, and percentage area covered.

Resveratrol induced a 22% increase in glucose uptake but did not affect endogenous glucose production. There were no changes in quantity or average size of muscle mitochondria or percentage area covered.

“There were no changes in basal or resting energy expenditure or respiratory quotient, as assessed by indirect calorimetry, or in muscle strength in these healthy middle-aged subjects,” Dr Maginley said. “However, resveratrol reduced adipose tissue inflammation, with significantly decreased expression of the pro-inflammatory cytokines tumor necrosis factor alpha and interleukin 6 in whole fat and of IL-6 and PAI-1 in adipose macrophages.”

Adiponectin expression in whole fat was increased by 53% with resveratrol. “While improved insulin sensitivity was not accompanied by changes in number or size of muscle mitochondria in these insulin resistant humans, the anti-inflammatory effects in adipose tissue could contribute to resveratrol’s favorable effects on glucose disposal,” Dr Maginley said.

Dr Hawkins noted, “If we delve in more, mitochondrial activity might be changed, so we haven’t ruled out a benefit to mitochondria.”

She continued: “It seems the profile of fat changes with resveratrol supplementation and becomes less inflammatory. The amount of adiponectin, which is a favorable hormone for metabolism, is doubled. This may be why we see a favorable effect on insulin action.” The fat also becomes more brown, which she said is more favorable metabolically.

Dr Hawkins noted that the amount of resveratrol in red wine is small compared to the 2-g capsules administered in the study. “This may explain why recent red wine studies did not show health benefits. We are using resveratrol as a dietary supplement,” she said.