title: The effect of a single 2 h bout of aerobic exercise on ectopic lipids in skeletal muscle, liver and the myocardium.
abstract: OBJECTIVE
  Ectopic lipids are fuel stores in non-adipose tissues (skeletal muscle [intramyocellular lipids; IMCL], liver [intrahepatocellular lipids; IHCL] and heart [intracardiomyocellular lipids; ICCL]). IMCL can be depleted by physical activity. Preliminary data suggest that aerobic exercise increases IHCL. Data on exercise-induced changes on ICCL is scarce. Increased IMCL and IHCL have been related to insulin resistance in skeletal muscles and liver, whereas this has not been documented in the heart. The aim of this study was to assess the acute effect of aerobic exercise on the flexibility of IMCL, IHCL and ICCL in insulin-sensitive participants in relation to fat availability, insulin sensitivity and exercise capacity.
  
  
  METHODS
  Healthy physically active men were included. VO(2max) was assessed by spiroergometry and insulin sensitivity was calculated using the HOMA index. Visceral and subcutaneous fat were separately quantified by MRI. Following a standardised dietary fat load over 3 days, IMCL, IHCL and ICCL were measured using MR spectroscopy before and after a 2 h exercise session at 50-60% of VO(2max). Metabolites were measured during exercise.
  
  
  RESULTS
  Ten men (age 28.9 ± 6.4 years, mean ± SD; VO(2max) 56.3 ± 6.4 ml kg(-1) min(-1); BMI 22.75 ± 1.4 kg/m(2)) were recruited. A 2 h exercise session resulted in a significant decrease in IMCL (-17 ± 22%, p = 0.008) and ICCL (-17 ± 14%, p = 0.002) and increase in IHCL (42 ± 29%, p = 0.004). No significant correlations were found between the relative changes in ectopic lipids, fat availability, insulin sensitivity, exercise capacity or changes of metabolites during exercise.
  
  
  CONCLUSIONS
  In this group, physical exercise decreased ICCL and IMCL but increased IHCL. Fat availability, insulin sensitivity, exercise capacity and metabolites during exercise are not the only factors affecting ectopic lipids during exercise.
authors.affiliation: Department of Endocrinology, Diabetology and Clinical Nutrition, Inselspital, University Hospital of Bern, Freiburgstrasse, 3010, Bern, Switzerland.
authors.forename: Julie
authors.initials: J
authors.lastname: Bucher
authors.forename: Marion
authors.initials: M
authors.lastname: Krüsi
authors.forename: Thomas
authors.initials: T
authors.lastname: Zueger
authors.forename: Michael
authors.initials: M
authors.lastname: Ith
authors.forename: Christoph
authors.initials: C
authors.lastname: Stettler
authors.forename: Peter
authors.initials: P
authors.lastname: Diem
authors.forename: Chris
authors.initials: C
authors.lastname: Boesch
authors.forename: Roland
authors.initials: R
authors.lastname: Kreis
authors.forename: Emanuel
authors.initials: E
authors.lastname: Christ
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism; D007333:Insulin Resistance; D008055:Lipids / Q000032:analysis*; D008099:Liver / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D019518:Postprandial Period; D012146:Rest; D013997:Time Factors; D055815:Young Adult
chemical_list: D007328:Insulin; D008055:Lipids