van Kempen T A, Odle J
Division of Nutritional Sciences, University of Illinois, Urbana 61801.
J Nutr. 1993 Sep;123(9):1531-7. doi: 10.1093/jn/123.9.1531.
To investigate the role of L-carnitine in medium-chain fatty acid (MCFA, fatty acids with 6-12 carbons) metabolism, 16 newborn pigs were fitted with umbilical arterial catheters. Pigs were placed in respiration chambers, and [1-14C]MCFA were infused for 9-12 h providing energy equivalent to 50-175% of the animals' metabolic rate. After 5-7 h (carnitine-free infusion period) of MCFA infusion, a primed (12.5, 25 or 50 mumol) co-infusion of L-carnitine [5, 10 or 20 mumol/(h.kg0.75), respectively] was started and maintained for 4-5 h (carnitine infusion period). The fatty acid oxidation rate (MCFA-derived CO2/total CO2 x 100) was calculated based on the specific radioactivity of expired CO2 (measured per 20-min interval) and the specific radioactivity of the MCFA infused. A single-pool exponential curve was fitted to the fatty acid oxidation rate of the carnitine-free infusion period and was extrapolated to the carnitine infusion period. For each piglet, the average difference between fatty acid oxidation rate during the carnitine infusion period and the extrapolated curve was calculated and tested for significance using a t test. Under steady state conditions, MCFA oxidation accounted for 40% of MCFA infused. Carnitine, independent of the level, increased the fatty acid oxidation rate by as much as 20% if the energy provided as MCFA exceeded 50% of the metabolic needs of the pig (P < 0.01), and the response above 50% was proportional to the relative rate of fatty acid infusion (increase in fatty acid oxidation rate = -3.9 + 0.07 x infusion rate, r0.76).(ABSTRACT TRUNCATED AT 250 WORDS)
为研究左旋肉碱在中链脂肪酸（MCFA，含6 - 12个碳原子的脂肪酸）代谢中的作用，给16头新生仔猪安装脐动脉导管。将仔猪置于呼吸舱中，输注[1 - ¹⁴C]MCFA 9 - 12小时，提供的能量相当于动物代谢率的50% - 175%。在输注MCFA 5 - 7小时（无肉碱输注期）后，开始并维持左旋肉碱的预充量（12.5、25或50 μmol）共输注[分别为5、10或20 μmol/(h·kg⁰.⁷⁵)]4 - 5小时（肉碱输注期）。根据呼出二氧化碳的比放射性（每20分钟间隔测量）和输注的MCFA的比放射性计算脂肪酸氧化率（MCFA衍生的CO₂/总CO₂×100）。对无肉碱输注期的脂肪酸氧化率拟合单池指数曲线，并外推至肉碱输注期。对于每头仔猪，计算肉碱输注期脂肪酸氧化率与外推曲线之间的平均差异，并使用t检验进行显著性检验。在稳态条件下，MCFA氧化占输注MCFA的40%。如果作为MCFA提供的能量超过仔猪代谢需求的50%，肉碱无论水平如何，均可使脂肪酸氧化率提高多达20%（P < 0.01），且超过50%时的反应与脂肪酸输注的相对速率成正比（脂肪酸氧化率增加 = -3.9 + 0.07×输注速率，r = 0.76）。（摘要截断于250字）
