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Intramyocellular lipid content in human skeletal muscle
Vera B Schrauwen-Hinderling1, Matthijs K C Hesselink, Patrick Schrauwen
1Department of Radiology, University Hospital Maastricht, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands. vhi@rdia.azm.nl
Obesity (Silver Spring, Md.)
|May 2, 2006
Summary
Intramyocellular lipids (IMCLs) in skeletal muscle are quantified by various methods. IMCLs serve as fuel during exercise but can negatively impact insulin sensitivity when fat availability is high without regular physical activity.
Area of Science:
- Exercise Physiology
- Metabolic Biochemistry
- Cellular Biology
Background:
- Skeletal muscle stores fat as intramyocellular lipids (IMCLs) in addition to adipose tissue.
- IMCLs play a role in energy metabolism, particularly during prolonged exercise.
- Quantification methods for IMCLs vary, each with limitations.
Purpose of the Study:
- To review methods for quantifying IMCLs in skeletal muscle.
- To discuss the physiological role of IMCLs in energy provision and storage.
- To explore the implications of IMCL accumulation on insulin sensitivity.
Main Methods:
- Biopsy-based methods: biochemical quantification, electron microscopy, histochemistry.
- Non-invasive methods: magnetic resonance spectroscopy (MRS), magnetic resonance imaging (MRI), computed tomography (CT).
- Review of existing literature on IMCL quantification and physiology.
Main Results:
- IMCL content decreases during prolonged submaximal exercise.
- Trained individuals exhibit higher IMCL content, particularly in oxidative type 1 muscle fibers.
- Elevated plasma fatty acid or dietary fat intake increases IMCLs, potentially impairing insulin sensitivity.
Conclusions:
- IMCLs are a readily available fuel source during exercise, with content increasing in trained states to match fat oxidation capacity.
- High IMCL accumulation due to excessive fat availability, without sufficient physical activity, can be detrimental to muscle insulin sensitivity.