Smith S B, Prior R L
J Nutr. 1986 Jul;116(7):1279-86. doi: 10.1093/jn/116.7.1279.
Studies were initiated to compare glucose and lipid metabolism in vitro in subcutaneous adipose tissue of mature sheep and cattle. Mean adipocyte volume was significantly less in subcutaneous adipose tissue of sheep than in adipose tissue from cattle. The presence of acetate and lactate in the incubation medium increased total glucose utilization two- to three-fold in ovine adipose tissue, but had no effect on total glucose utilization in adipose tissue from cattle. Acetate provided 72-82% of the acetyl units to lipogenesis, depending on species and substrate concentration. There were no significant (P greater than 0.05) differences in the contribution of the pentose cycle to the provision of reducing equivalents to fatty acid biosynthesis, based on the incorporation of label from [3-3H]glucose into fatty acids. In ovine adipose tissue, acetyl-CoA carboxylase appeared to be rate-limiting to lipogenesis, while in bovine subcutaneous adipose tissue, the activity of fatty acid synthetase may have been the limiting step in lipogenesis. In addition, the low activity of ATP-citrate lyase, especially relative to aconitate hydratase, probably limited the conversion of lactate to fatty acids in ovine adipose tissue. It is unlikely that ATP-citrate lyase activity was rate-limiting to lipogenesis from lactate in bovine adipose tissue. The data indicate that extending the results obtained from adipose tissue from one species to lipid metabolism in ruminants in general may not be valid.
开展了多项研究，以比较成熟绵羊和牛皮下脂肪组织在体外的葡萄糖和脂质代谢情况。绵羊皮下脂肪组织中的平均脂肪细胞体积显著小于牛的脂肪组织。孵育培养基中乙酸盐和乳酸盐的存在使绵羊脂肪组织中的总葡萄糖利用率提高了两到三倍，但对牛脂肪组织中的总葡萄糖利用率没有影响。根据物种和底物浓度，乙酸盐为脂肪生成提供了72%至82%的乙酰基单位。基于[3-³H]葡萄糖中的标记物掺入脂肪酸的情况，戊糖循环对脂肪酸生物合成提供还原当量的贡献没有显著（P大于0.05）差异。在绵羊脂肪组织中，乙酰辅酶A羧化酶似乎是脂肪生成的限速酶，而在牛皮下脂肪组织中，脂肪酸合成酶的活性可能是脂肪生成的限速步骤。此外，ATP-柠檬酸裂解酶的低活性，尤其是相对于乌头酸水合酶而言，可能限制了绵羊脂肪组织中乳酸向脂肪酸的转化。ATP-柠檬酸裂解酶的活性不太可能是牛脂肪组织中乳酸生成脂肪的限速因素。数据表明，将从一个物种的脂肪组织获得的结果推广到反刍动物的一般脂质代谢可能并不有效。
