van Loon Luc J C, Goodpaster Bret H
Department of Movement Sciences, Nutrition Research Institute Maastricht, Maastricht University, 616, 6200, Maastricht, MD, The Netherlands,
Pflugers Arch. 2006 Feb;451(5):606-16. doi: 10.1007/s00424-005-1509-0. Epub 2005 Sep 10.
Numerous studies have reported a strong correlation between intramuscular triacylglycerol (IMTG) content and insulin resistance. However, the proposed relationship between IMTG accumulation and skeletal muscle insulin resistance is not unambiguous, as trained athletes have been shown to be markedly insulin sensitive despite an elevated IMTG storage. Though the latter has often been attributed to differences in muscle fibre type composition and/or structural characteristics of the intramyocellular lipid deposits, recent studies have failed to provide such evidence. The greater insulin sensitivity despite an elevated IMTG deposition in the endurance-trained state has often been described as a metabolic paradox. However, divergent metabolic events are responsible for the greater IMTG content in the endurance-trained versus insulin-resistant states. The greater IMTG storage in the trained athlete represents an adaptive response to endurance training, allowing a greater contribution of the IMTG pool as a substrate source during exercise. In contrast, elevated IMTG stores in the obese and/or type 2 diabetes patient seem to be secondary to a structural imbalance between plasma free fatty acid availability, fatty acid (FA) storage and oxidation. Therefore, the reported correlation between IMTG content and insulin resistance does not represent a functional relationship, as it is strongly influenced by training status and/or habitual physical activity. It can be argued that the ratio between IMTG content and muscle oxidative capacity represents a more accurate marker of insulin resistance. Interventions to augment mitochondrial density and/or function are likely to improve the balance between FA uptake and oxidation and should be applied to prevent and/or treat insulin resistance.
众多研究报告称，肌肉内三酰甘油（IMTG）含量与胰岛素抵抗之间存在密切关联。然而，IMTG积累与骨骼肌胰岛素抵抗之间的假定关系并不明确，因为尽管IMTG储存量升高，但训练有素的运动员已被证明具有显著的胰岛素敏感性。尽管后者通常归因于肌纤维类型组成和/或肌细胞内脂质沉积物的结构特征存在差异，但最近的研究未能提供此类证据。在耐力训练状态下，尽管IMTG沉积增加，但胰岛素敏感性更高，这一现象常被描述为一种代谢悖论。然而，耐力训练状态与胰岛素抵抗状态下，导致IMTG含量更高的代谢事件有所不同。训练有素的运动员中更高的IMTG储存量代表了对耐力训练的适应性反应，使得IMTG库在运动期间作为底物来源能做出更大贡献。相比之下，肥胖和/或2型糖尿病患者中升高的IMTG储存量似乎继发于血浆游离脂肪酸可用性、脂肪酸（FA）储存和氧化之间的结构失衡。因此，所报道的IMTG含量与胰岛素抵抗之间的相关性并不代表一种功能关系，因为它受到训练状态和/或习惯性身体活动的强烈影响。可以认为，IMTG含量与肌肉氧化能力之间的比率是胰岛素抵抗更准确的标志物。增加线粒体密度和/或功能的干预措施可能会改善FA摄取与氧化之间的平衡，应将其应用于预防和/或治疗胰岛素抵抗。
