Glucose Metabolism and Insulin Action in Sheep Exposed to Cold

[U-^&lt；13&gt；C]葡萄糖同位素稀释法与后肢动静脉差和血流量测定相结合，研究冷暴露对绵羊全身和净后肢糖代谢的影响。测定是在中温环境下和轻度寒冷暴露的第5天进行的。全身血糖转换率在中温环境下为1.56 mg·kg~(-1)，冷暴露时为1.91 mg·kg~(-1)·min~(-1)。臀部净葡萄糖摄入量分别为0.79和1.19 mg·kg~(-1)·min~(-1)，分别占全身周转率的50%和61%。这些结果表明，在冷暴露期间，绵羊后肢对葡萄糖摄取的贡献有增加的趋势，尽管全身血糖转换率没有显著增加。冷暴露和采食量对血糖动力学、血浆胰岛素和高血糖素对饲料的反应以及组织反应性和敏感性…的影响绵羊对胰岛素的敏感性更高。用同位素稀释法测定血糖转换率，用高胰岛素正血糖钳夹法测定胰岛素作用和敏感性。血浆胰岛素和胰升糖素对摄食的反应分别主要受饲料水平和环境温度的影响。冷暴露期间的血糖周转率高于热中和环境中的血糖周转率，对于随意饲喂的绵羊来说，血糖周转率往往更高。在摄食的同时，这些比率变化不大。高胰岛素正血糖钳夹技术在中温环境下和冷暴露第8天进行。冷暴露下的葡萄糖输注速率(GIR)大于热中和环境，限制喂养的葡萄糖输注速率(GIR)大于自由喂养的葡萄糖输注速率(GIR)。冷暴露期间的最大GIR也较大，但不受饮食水平的影响。在冷暴露期间，半上颌骨GIR处的血浆胰岛素浓度往往低于热中频环境中的血浆胰岛素浓度，并且不同饮食之间没有差异。因此，冷暴露对胰岛素作用的敏感性有影响，但不能证明冷暴露对胰岛素作用的影响与粗饲料采食量有关。较少

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