Christensen E, Hagve T A, Grønn M, Christophersen B O
Institute of Clinical Biochemistry, University of Oslo, Rikshospitalet, Norway.
Biochim Biophys Acta. 1989 Aug 8;1004(2):187-95. doi: 10.1016/0005-2760(89)90267-1.
The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.
在禁食、喂食和果糖再喂养大鼠的肝细胞中研究了中链脂肪酸的β-氧化和酯化作用。与油酸的氧化相比，果糖再喂养和（+）-癸酰肉碱对月桂酸（12:0）的β-氧化抑制作用较小，这表明月桂酸存在过氧化物酶体β-氧化。除了在高底物浓度或果糖再喂养状态下，月桂酸很少酯化到三酰甘油部分。以[1-14C]肉豆蔻酸（14:0）、[1-14C]月桂酸（12:0）、[1-14C]辛酸（8:0）和[2-14C]肾上腺酸（22:4（n-6）]作为碳水化合物喂养大鼠肝细胞的底物时，大部分14C标记的酯化脂肪酸由新合成的棕榈酸（16:0）、硬脂酸（18:0）和油酸（18:1）组成，而完整的[1-14C]油酸底物则直接酯化。以[9,10-3H]肉豆蔻酸为底物时，发现了少量缩短的3H标记的β-氧化中间体。以[U-14C]棕榈酸为底物时，未检测到缩短的脂肪酸。得出的结论是，当线粒体脂肪酸氧化如在碳水化合物喂养状态下被下调时，中链脂肪酸可通过过氧化物酶体β-氧化部分重新调整为长链脂肪酸，随后合成C16和C18脂肪酸，然后可作为三酰甘油储存。
