- Intramuscular fat
Intramuscular fat or Intramuscular triglycerides (IMTG) is located throughout
skeletal muscle and is responsible for the marbling seen in certain cuts ofbeef . In humans, excess accumulation of intramuscular fat is associated withinsulin resistance andtype 2 diabetes . The human immunodeficiency virus (HIV)-lipodystrophy syndrome is associated with over-accumulation of intramuscular fat which may contribute toAIDS wasting syndrome .Diabetes
IMTG is known to contribute to the increase of lipid metabolites within seditary individuals, which is speculated to be a key cause of insulin resistance, leading to
type 2 diabetes . Athletes also have a high level of IMTG which is favorable for energy uptake viamitochondria . [cite journal |author= |title=The Influence of Endurance Exercise Training and Sex on Intramyocellular Lipid and Mitochondrial Ultrastructure, Substrate Use, and Mitochondrial Enzyme Activity |journal=Am J Physiol Regul Integr Comp Physiol |volume= |issue= |pages= |year= |pmid=17095651]Insulin Resistance
Increased supply of
adipose tissue correlates with the increased accumulation of IMTG which both can lead toinsulin resistance in the muscles. Athletes often do not exhibit this correlation as they are typically insulin sensitive while having high levels of IMTG. It is thought that the improved efficiency of trained skeletal muscles prevents the development of insulin resistance. [cite journal |author=Timmermans R, Saris W, van Loon L |title= [Insulin resistance: the role of intramuscular triglyceride and the importance of physical activity] |journal=Ned Tijdschr Geneeskd |volume=150 |issue=3 |pages=122–7 |year=2006 |pmid=16463611]Exercise
"Intramuscular triacylglycerol (IMTG) represents an energy store that can be used during exercise, when it may contribute up to 20% of total energy turnover depending on diet, gender, and exercise type." [cite journal |author=Roepstorff C, Vistisen B, Kiens B |title=Intramuscular triacylglycerol in energy metabolism during exercise in humans |journal=Exerc Sport Sci Rev |volume=33 |issue=4 |pages=182–8 |year=2005 |pmid=16239835 |doi=10.1097/00003677-200510000-00006]
It is thought that a low calorie diet and exercise induced proteins (
Sterol regulatory element-binding proteins) are what cause high levels of IMTG in the skeletal muscle of trained athletes. This is in contrast to the build-up of IMTG in the obese which correlates to high levels of adipose tissue. [cite journal |author=Nadeau K, Ehlers L, Aguirre L, Moore R, Jew K, Ortmeyer H, Hansen B, Reusch J, Draznin B |title=Exercise training and calorie restriction increase SREBP-1 expression and intramuscular triglyceride in skeletal muscle |journal=Am J Physiol Endocrinol Metab |volume=291 |issue=1 |pages=E90–8 |year=2006 |pmid=16449296 |doi=10.1152/ajpendo.00543.2005]Women have been shown to use more IMTG during exercise than men which directly correlates to the higher IMTG content in women over men. [cite journal |author=Roepstorff C, Donsmark M, Thiele M, Vistisen B, Stewart G, Vissing K, Schjerling P, Hardie D, Galbo H, Kiens B |title=Sex differences in hormone-sensitive lipase expression, activity, and phosphorylation in skeletal muscle at rest and during exercise |journal=Am J Physiol Endocrinol Metab |volume=291 |issue=5 |pages=E1106–14 |year=2006 |pmid=16822962 |doi=10.1152/ajpendo.00097.2006]
References
Wikimedia Foundation. 2010.
