Ha T Y, Otsuka M, Arakawa N
Rice Utilization Research Center, Korea Food Research Institute, Japan.
J Nutr. 1994 May;124(5):732-7. doi: 10.1093/jn/124.5.732.
L-Ascorbic acid is required for the synthesis of L-carnitine, which is essential for the oxidation of long-chain fatty acids. The purpose of this study was to investigate the role of ascorbate on the oxidation of long-chain fatty acids in primary cultured guinea pig hepatocytes. The hepatocytes were incubated in medium containing carnitine in the presence or absence of fatty acids. Exogenous fatty acids had no influence on the uptake of total carnitine into cells, but they lowered the free carnitine and consequently raised the concentration of short-chain acyl carnitine. Furthermore, carnitine supplementation of the medium in the presence of fatty acids led to a decrease of triglycerides in cells and an increase in the secretion of beta-hydroxybutyrate. These changes were also induced by the supplementation of the medium with both ascorbate and the precursor of carnitine (gamma-butyrobetaine) in the presence of fatty acids, although either ascorbate of gamma-butyrobetaine alone had no effect. In addition, increasing the concentration of supplemental ascorbate resulted in an enhancement of ketogenesis and a decrease of triglyceride accumulation. These results suggest that ascorbate enhances carnitine synthesis, which in turn stimulates beta-oxidation of fatty acids.
左旋肉碱的合成需要L-抗坏血酸，而左旋肉碱对于长链脂肪酸的氧化至关重要。本研究的目的是探讨抗坏血酸盐在原代培养的豚鼠肝细胞中对长链脂肪酸氧化的作用。将肝细胞在含有肉碱的培养基中培养，同时存在或不存在脂肪酸。外源性脂肪酸对细胞摄取总肉碱没有影响，但它们降低了游离肉碱的含量，从而提高了短链酰基肉碱的浓度。此外，在存在脂肪酸的情况下向培养基中补充肉碱会导致细胞内甘油三酯减少，β-羟基丁酸分泌增加。在存在脂肪酸的情况下，向培养基中同时补充抗坏血酸盐和肉碱前体（γ-丁基甜菜碱）也会引起这些变化，尽管单独使用抗坏血酸盐或γ-丁基甜菜碱均无效果。此外，增加补充抗坏血酸盐的浓度会导致生酮作用增强和甘油三酯积累减少。这些结果表明，抗坏血酸盐增强了肉碱的合成，进而刺激了脂肪酸的β-氧化。
