Smith S B, Lin K C, Wilson J J, Lunt D K, Cross H R
Department of Animal Science, Texas Agricultural Experiment Station, Texas A&M University, College Station 77843-2471, USA.
Comp Biochem Physiol B Biochem Mol Biol. 1998 May;120(1):165-74. doi: 10.1016/s0305-0491(98)10005-6.
The primary objective of this study was to document the effects of starvation on acylglycerol biosynthesis in homogenates of intramuscular and subcutaneous adipose tissues. Adipose tissue samples were obtained from 8th-13th thoracic rib sections from 12 Angus cattle (six steers plus six heifers). Three steers and three heifers were starved for 72 h prior to slaughter while the remainder were slaughtered 4 h after food was withheld. Fat-free 700 x g centrifugal fractions were used to measure the esterification of radiolabeled sn-glycerol 3-phosphate (G-3-P) into acylglycerols at 1.0 mM palmitic or stearic acid, or 0.2 mM oleic, linoleic, or alpha-linolenic acid. There were significant tissue x fatty acid interactions for rates of incorporation into diacylglycerols and triacylglycerols; in subcutaneous, but not intramuscular homogenates, palmitic > stearic = oleic = linoleic = alpha-linolenic acid. Subcutaneous homogenates incorporated a greater percentage of G-3-P into triacylglycerols, and a lesser percentage into phospholipid, than intramuscular homogenates (P < 0.05). In intramuscular homogenates, the primary product of G-3-P esterification to saturated fatty acids was phospholipids. When unsaturated fatty acid served as substrates, triacylglycerols and phospholipids were produced in equal proportions in intramuscular homogenates, and triacylglycerols were the predominant product in subcutaneous homogenates. Intramuscular adipose tissue homogenates exhibited no response to starvation, whereas triacylglycerol and diacylglycerol synthesis was depressed by approximately 50% in subcutaneous adipose tissue homogenates. Similarly, phosphatidic phosphohydrolase activity, initially greater in subcutaneous than in intramuscular adipose tissue, was decreased by approximately 50% by starvation in subcutaneous adipose tissue, but not in intramuscular adipose tissue. We conclude that differences in rates of diacylglycerol and triacylglycerol biosynthesis, and response to starvation, between intramuscular and subcutaneous adipose tissues were due to dissimilarities in the activity of phosphatidic phosphohydrolase.
本研究的主要目的是记录饥饿对肌肉内和皮下脂肪组织匀浆中酰基甘油生物合成的影响。脂肪组织样本取自12头安格斯牛（6头公牛和6头母牛）第8至13胸肋段。3头公牛和3头母牛在屠宰前饥饿72小时，其余的在禁食4小时后屠宰。使用无脂700×g离心级分来测量在1.0 mM棕榈酸或硬脂酸，或0.2 mM油酸、亚油酸或α-亚麻酸存在下，放射性标记的sn-甘油3-磷酸（G-3-P）酯化生成酰基甘油的情况。在二酰基甘油和三酰基甘油的掺入率方面存在显著的组织×脂肪酸相互作用；在皮下而非肌肉内匀浆中，棕榈酸＞硬脂酸=油酸=亚油酸=α-亚麻酸。与肌肉内匀浆相比，皮下匀浆将更高百分比的G-3-P掺入三酰基甘油，而掺入磷脂的百分比更低（P＜0.05）。在肌肉内匀浆中，G-3-P与饱和脂肪酸酯化的主要产物是磷脂。当不饱和脂肪酸作为底物时，肌肉内匀浆中三酰基甘油和磷脂以相等比例产生，而皮下匀浆中三酰基甘油是主要产物。肌肉内脂肪组织匀浆对饥饿无反应，而皮下脂肪组织匀浆中三酰基甘油和二酰基甘油合成降低约50%。同样，磷脂酸磷酸水解酶活性最初在皮下脂肪组织中高于肌肉内脂肪组织，饥饿使皮下脂肪组织中的该活性降低约50%，但肌肉内脂肪组织不受影响。我们得出结论，肌肉内和皮下脂肪组织中二酰基甘油和三酰基甘油生物合成速率以及对饥饿反应的差异是由于磷脂酸磷酸水解酶活性不同所致。
