Odland L M, Howlett R A, Heigenhauser G J, Hultman E, Spriet L L
Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
Am J Physiol. 1998 Jun;274(6):E1080-5. doi: 10.1152/ajpendo.1998.274.6.E1080.
To investigate the regulation of intramuscular fuel selection, we measured the malonyl-CoA (M-CoA) content in human skeletal muscle at three exercise power outputs [35, 65, and 90% maximal rate of O2 consumption (VO2 max)]. Four males and four females cycled for 10 min at one power output on three separate occasions with muscle biopsies sampled at rest and at 1 and 10 min. The respiratory exchange ratio was 0.84 +/- 0.03, 0.92 +/- 0.02, and >1.0 at 35, 65 and 90% VO2 max, respectively. Muscle lactate content increased and phosphocreatine content decreased as a function of power output. Pyruvate dehydrogenase a activity increased from 0.40-0.64 mmol . kg wet muscle-1 . min-1 at rest to 1.57 +/- 0.28, 2.80 +/- 0.41, and 3. 28 +/- 0.27 mmol . kg wet muscle-1 . min-1 after 1 min of cycling at the three power outputs, respectively. Mean resting M-CoA contents were similar at all power outputs (1.85-1.98 micromol/kg dry muscle). During exercise at 35% VO2 max, M-CoA decreased from rest at 1 min (1.85 +/- 0.29 to 1.20 +/- 0.12 micromol/kg dry muscle) but returned to rest level by 10 min (1.86 +/- 0.25 micromol/kg dry muscle). M-CoA content did not decrease during cycling at 65% VO2 max. At 90% VO2 max, M-CoA did not increase despite significant acetyl-CoA accumulation (the substrate for M-CoA synthesis). The data suggest that a decrease in M-CoA content is not required for the increase in free fatty acid uptake and oxidation that occurs during exercise at 35 and 65% VO2 max. Furthermore, M-CoA content does not increase during exercise at 90% VO2 max and does not contribute to the lower rate of fat oxidation at this power output.
为研究肌肉内燃料选择的调节机制，我们在三种运动功率输出水平[35%、65%和90%最大耗氧量（VO₂max）]下测量了人体骨骼肌中丙二酰辅酶A（M-CoA）的含量。4名男性和4名女性在三种不同情况下，分别以一种功率输出进行10分钟的骑行运动，并在静息状态、运动1分钟和10分钟时采集肌肉活检样本。在35%、65%和90%VO₂max时，呼吸交换率分别为0.84±0.03、0.92±0.02和>1.0。肌肉乳酸含量随功率输出增加而升高，磷酸肌酸含量则随功率输出增加而降低。丙酮酸脱氢酶a活性从静息时的0.40 - 0.64 mmol·kg湿肌肉⁻¹·min⁻¹分别增加到在三种功率输出下骑行1分钟后的1.57±0.28、2.80±0.41和3.28±0.27 mmol·kg湿肌肉⁻¹·min⁻¹。在所有功率输出水平下，静息时的平均M-CoA含量相似（1.85 - 1.98 μmol/kg干肌肉）。在35%VO₂max运动时，M-CoA在运动1分钟时从静息水平（1.85±0.29降至1.20±0.12 μmol/kg干肌肉）下降，但在10分钟时恢复到静息水平（1.86±0.25 μmol/kg干肌肉）。在65%VO₂max骑行过程中，M-CoA含量未下降。在90%VO₂max时，尽管乙酰辅酶A（M-CoA合成的底物）大量积累，但M-CoA并未增加。数据表明，在35%和65%VO₂max运动期间，游离脂肪酸摄取和氧化增加并不需要M-CoA含量降低。此外，在90%VO₂max运动期间，M-CoA含量并未增加，且在该功率输出下对脂肪氧化率降低没有影响。
