Prior R L, Scott R A
J Nutr. 1980 Oct;110(10):2011-9. doi: 10.1093/jn/110.10.2011.
Crossbred steers (seven to nine per treatment) fed a pelleted alfalfa hay diet were biopsied (preinfusion) to obtain subcutaneous adipose tissue (SAT). Five days later a continuous intravenous infusion was begun of either 0.9% NaCl, glucose (2.75 moles/day), DL-lactate (5.5 moles/day of L-lactate), propionate (5.5 moles/day) or acetate (8.25 moles/day); after infusion for 14 days, a second biopsy sample of SAT was obtained. Glucose and DL-lactate infusion increased acetyl-CoA carboxylase activity about 12-fold compared to preinfusion activity of 5.3 +/- 4.2 nmoles/minute/g of wet weight. Glucose infusion induced activities of fatty acid synthetase (2.6 fold) and NADP+-malate dehydrogenase (7-fold) relative to preinfusion activities of 26.8 +/- 5.2 and 30.3 +/- 15.5 nmoles/minute/g of wet weight, respectively. Glucose, DL-lactate and propionate infusion increased NADP-isocitrate dehydrogenase activity 20-30% compared to preinfusion activity. Activity of NAD-malate dehydrogenase was not altered by any infusion treatment (P > 0.05). Activity of ATP-citrate lyase was decreased 48% by lactate infusion. Glucose, lactate and propionate infusion increased the rates of lactate and glucose incorporation into fatty acids in SAT incubated in vitro three to fourfold over preinfusion incorporation rates. Increased availability of glucose or gluconeogenic precursors may be responsible for induction of lipogenesis in steers fed high concentrate diets.
给每组（每组7至9头）饲喂颗粒状苜蓿干草日粮的杂交阉牛进行活检（输液前），以获取皮下脂肪组织（SAT）。五天后，开始持续静脉输注0.9%氯化钠、葡萄糖（2.75摩尔/天）、DL-乳酸（5.5摩尔/天的L-乳酸）、丙酸（5.5摩尔/天）或乙酸（8.25摩尔/天）；输液14天后，获取SAT的第二个活检样本。与输液前5.3±4.2纳摩尔/分钟/克湿重的活性相比，葡萄糖和DL-乳酸输液使乙酰辅酶A羧化酶活性增加了约12倍。相对于输液前分别为26.8±5.2和30.3±15.5纳摩尔/分钟/克湿重的活性，葡萄糖输液诱导了脂肪酸合成酶（2.6倍）和NADP⁺-苹果酸脱氢酶（7倍）的活性。与输液前活性相比，葡萄糖、DL-乳酸和丙酸输液使NADP-异柠檬酸脱氢酶活性增加了20%至30%。任何输液处理均未改变NAD-苹果酸脱氢酶的活性（P>0.05）。乳酸输液使ATP-柠檬酸裂解酶的活性降低了48%。葡萄糖、乳酸和丙酸输液使体外培养的SAT中乳酸和葡萄糖掺入脂肪酸的速率比输液前掺入速率提高了三到四倍。葡萄糖或糖异生前体可用性的增加可能是导致饲喂高浓缩日粮阉牛脂肪生成增加的原因。
