Glucose Metabolism and Insulin Action in Sheep Exposed to Cold

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Isotope dilution using [U-^<13>C] glucose was combined with measurement of hindquarters arteriovenous difference and blood flow to examine the effect of cold exposure on whole-body and net hindquarters glucose metabolism in sheep. Determinations were carried out in a thermoneutral environment and on day 5 of mild cold exposure. Whole-body blood glucose turnover rate was 1.56 and 1.91 mg kg^<-1> min^<-1> in the thermoneutral environment and during cold exposure, respectively. Net hindquarters glucose uptake was 0.79 and 1.19 mg kg^<-1> min^<-1>, corresponding to 50 and 61% of whole-body turnover rate, respectively. These results suggest that in sheep the contribution of glucose uptake by the hindquarters tended to increase during cold exposure, even though whole-body blood glucose turnover rate did not increase significantly.Effects of cold exposure and level of feed intake on blood glucose kinetics, plasma insulin and glucagon responses to feeding and tissue responsiveness and sensitiv … More ity to insulin were measured in sheep. The isotope dilution technique was used for determination of blood glucose turnover rates, and the hyperinsulinemic euglycemic clamp technique was applied for determination of insulin action and sensitivity. Plasma insulin and glucagon responses to feeding were mainly influenced by dietary level and environmental temperature, respectively. Blood glucose turnover rates were greater during cold exposure than in the thermoneutral environment, and tended to be greater for the sheep fed the diet ad libitum. The rates changed little accompanied by feeding. The hyperinsulinemic euglycemic clamp technique was carried out in the thermoneutral environment and on day 8 of cold exposure. The glucose infusion rate (GIR) was greater during cold exposure than in the thermoneutral environment, and were greater for restricted feeding than for ad libitum feeding. The maxmal GIR was also greater during cold exposure, whereas was not influenced by dietary level. Plasma insulin concentrations at the half maxmal GIR tended to be lower during cold exposure than in the thermoneutral environment, and did not differ between diets. Therefore, insulin action sensitivity were influenced by cold exposure, whereas it could not be obtained the evidence that they were influenced by level of feed intake in sheep fed roughage diet. Less