Hoppel C L, Genuth S M
Am J Physiol. 1980 May;238(5):E409-15. doi: 10.1152/ajpendo.1980.238.5.E409.
Carnitine metabolism was studied in normal-weight and obese subjects by measurement of carnitine and its acyl derivatives in plasma and urine. When first fed an isocaloric, low-carnitine diet, both groups showed a decrease in plasma total carnitine, primarily due to a decrease in the free carnitine fraction. Urinary free carnitine excretion also fell significantly. When fasting was instituted, plasma total carnitine concentration increased. This was the net result of a rapid increase in short-chain and long-chain acylcarnitine and a delayed decrease in free carnitine. Urinary excretion of short-chain acylcarnitines increased parallel to rising plasma concentrations, whereas free carnitine excretion first decreased and then tended to increase slightly. Both plasma and urinary short-chain acylcarnitine correlated with beta-hydroxybutyrate. All of these changes were reversed by refeeding, in the obese even with a low-carnitine hypocaloric intake. Obese subjects also developed hyperketonemia significantly more slowly than did normal-weight subjects, yet demonstrated substantially the same changes in magnitude and direction in carnitine and its metabolites.
通过测量血浆和尿液中的肉碱及其酰基衍生物，对正常体重和肥胖受试者的肉碱代谢进行了研究。当首次给予等热量、低肉碱饮食时，两组受试者的血浆总肉碱均下降，主要是由于游离肉碱部分减少。尿中游离肉碱排泄也显著下降。开始禁食时，血浆总肉碱浓度升高。这是短链和长链酰基肉碱快速增加以及游离肉碱延迟减少的综合结果。短链酰基肉碱的尿排泄量与血浆浓度升高平行增加，而游离肉碱排泄量先减少，然后略有增加趋势。血浆和尿液中的短链酰基肉碱均与β-羟基丁酸相关。重新进食后，所有这些变化均被逆转，在肥胖受试者中，即使摄入低肉碱低热量饮食也是如此。肥胖受试者发生高酮血症的速度也明显比正常体重受试者慢，但在肉碱及其代谢产物的变化幅度和方向上基本相同。
