BATON ROUGE, La., Feb 06, 2006 /PRNewswire via COMTEX/ -- A new study published in February's Journal of Nutrition reports chromium prompts muscles to become more efficient. Researchers found that daily use of chromium picolinate enhanced muscle sensitivity to insulin in obese, insulin-resistant rats. Specifically, chromium improved the ability of insulin, after attaching to muscle cells, to enhance chemical signals in the cell that promoted blood sugar uptake. The study, funded in part by the National Institutes of Health (NIH) and conducted by researchers at Pennington Biomedical Research Center (PBRC), is the first published study using this animal model to demonstrate chromium's action in this way.
"Insulin resistance is a condition in which tissues such as fat and muscle in the body respond poorly to insulin, the major hormone required for glucose metabolism. This condition is present in pre-diabetic states and continues when a person develops diabetes. Previous research suggested that supplementation with chromium picolinate may help improve this condition," said Dr. William Cefalu, investigator and chief of the division of nutrition and chronic diseases at PBRC. "This animal study is significant because it suggests a more detailed mechanism of action for chromium on improving insulin sensitivity in muscle, a major insulin-sensitive tissue."
Chromium is one of the few essential trace minerals for which a specific mechanism of action had not been completely identified. This study demonstrated that chromium picolinate helps insulin receptor sites on muscle cells work more efficiently. Insulin receptors on the outer part of a cell allow the cell to bind with insulin in the blood. When the cell and insulin bind, signals within the cell activate "glucose transporters" so that the cell can then take up glucose from the blood and use it for energy. The result was a significantly improved rate at which muscles absorbed glucose from the blood and metabolized it. Impaired insulin action, in the obese rats used in this study, was partially restored with chromium supplementation. In a control group of lean, healthy rats with no abnormalities, chromium supplementation exhibited no observable additional effect on insulin receptor activity.
The study also found that obese, insulin resistant rats treated with chromium picolinate had improved triglyceride and total high-density lipoprotein (HDL) cholesterol ratios. These findings support previous research demonstrating chromium picolinate's potential benefits in reducing cardiovascular risk factors in subjects exhibiting insulin resistance.
"These results add to a growing body of evidence, but more importantly provide a cellular mechanism to explain the effects of chromium picolinate on carbohydrate metabolism," added Dr. Cefalu.
Ongoing research at PBRC is now focusing on the effect of chromium picolinate on cellular proteins associated with insulin function.
About the Study
The 16-week randomized study (four-week baseline phase and 12-week treatment phase) evaluated 21 rats using a unique animal model for obesity, insulin resistance and cardiovascular disease, known as the JCR: LA-cp rat. Obesity and insulin resistance are major conditions associated with pre-diabetes. Male JCR: LA-cp rats were randomly assigned to receive either Chromax(R) chromium picolinate or placebo for three months. The chromium picolinate was provided in the rats' water. The overall impacts of chromium on factors that influence insulin sensitivity were examined by measuring insulin-stimulated phosphorylation of insulin receptor subtrate IRS-1 and phosphatidylinostol (PI)-3 kinase. Researchers also assessed the effect of chromium on enzymes and/or proteins that inhibit insulin function by turning off the chemical signals resulting from insulin binding, including tyrosine phosphatase 1B (PTP1B).
Chromium is an essential mineral that is needed for insulin activity in carbohydrate, fat and protein metabolism. In August 2005, the U.S. Food and Drug Administration (FDA) allowed a qualified health claim for chromium picolinate, and confirmed its' safety. The FDA's ruling was based on the findings of an earlier randomized, double-blind, placebo-controlled trial conducted by Dr. Cefalu that showed chromium picolinate helps to significantly increase insulin sensitivity in those at high risk for diabetes.
The chromium form used in this study was provided by Nutrition 21, the makers of Chromax(R) chromium picolinate, the most studied form of chromium and more bioavailable.
About Pennington Biomedical Research Center
The Pennington Biomedical Research Center is a campus of the Louisiana State University System and conducts both clinical and basic research. It is the largest academically based nutrition research center in the world, with the greatest number of obesity researchers on faculty. The Center's nearly 600 employees occupy several buildings on the 234-acre campus.