Chromium supplementation does not influence glucose metabolism or insulin action in response to cold exposure in mature sheep

An isotope dilution method using [U-(13)C] glucose infusion and a glucose clamp approach were applied to determine the effects of supplemental Cr and cold exposure on blood glucose turnover rate and tissue responsiveness and sensitivity to insulin in eight sheep. The daily profiles of blood metabolites and hormones were also determined. The sheep consumed diets containing either 0 or 1 mg of Cr/kg from a high-Cr yeast and were exposed from a thermoneutral environment (20 degrees C) to a cold environment (0 to 4 degrees C) for 9 d. The experiment used a crossover design. Body weight was lost (P = 0.02) during cold exposure, regardless of Cr supplementation. Blood glucose turnover rate and the maximal glucose infusion rate did not differ between diets, but both were higher (P = 0.0004 and P = 0.0001, respectively) during cold exposure than in the thermoneutral environment. The plasma insulin concentration at half-maximal glucose infusion rate changed with neither diet nor environment. Plasma concentrations of glucose and NEFA increased (P < 0.05) during cold exposure for both diets. In sheep, Cr supplementation, 1 mg/kg of diet as high-Cr yeast, has little influence on blood glucose metabolism and insulin action, whereas cold exposure enhances both without further modification by Cr supplementation.