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Increased intramuscular lipid storage in the insulin-resistant and endurance-trained state. Pflugers Arch

Department of Movement Sciences, Nutrition Research Institute Maastricht, Maastricht University, 616, 6200, Maastricht, MD, The Netherlands,
Pflügers Archiv - European Journal of Physiology (Impact Factor: 4.1). 03/2006; 451(5):606-16. DOI: 10.1007/s00424-005-1509-0
Source: PubMed

ABSTRACT

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.

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    • "After moderate exercise training, the latter could improve their IMCL content by 21%[68]. The lipid droplets are usually aggregated in the vicinity of mitochondria and are regarded as energy source during prolonged exercise[13]. It is also well known that human skeletal muscle responds to endurance training by the formation of new capillaries[69,64,61]. "
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    Full-text · Article · Apr 2015 · PLoS ONE
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    • "A methionine-choline-deficient high-fat diet (MCD) induced histological changes similar to those of human NASH in a murine model [12]. IMCL of soleus muscle is reportedly higher than that of the other skeletal muscles [2] [13], and IMCL of type I is higher than type II fiber types [8], while soleus muscle is mainly composed of type I fibers [14]. The objective of this study was to examine the effect of exercise training on glycogen and IMCL content of soleus muscle in NASH model rats. "

    Full-text · Article · Jan 2015 · Open Journal of Endocrine and Metabolic Diseases
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    • "Skeletal muscle is the major organ for fatty acid consumption, barely for lipid synthesis or storage. The increase of the lipid content in skeletal muscle which mainly results from increased fatty acid uptake and decreased β-oxidation can directly affect glucose and lipid metabolism and insulin sensitivity [39]. Several studies have indicated that inflammation may regulate fatty acid oxidation in skeletal muscles. "
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