title: Influence of gender, obesity, and muscle lipase activity on intramyocellular lipids in sedentary individuals.
abstract: BACKGROUND
  Obesity and type 2 diabetes are associated with elevated intramyocellular lipids (IMCLs) and insulin resistance.
  
  
  OBJECTIVE
  We tested the hypothesis that skeletal muscle lipases activity could influence IMCL content (including diacylglycerol and ceramides).
  
  
  METHODS
  The present study included 48 subjects with a wide range of age (19-68 yr) and body mass index (20-45 kg/m(2)) who underwent skeletal muscle biopsy, dual-energy x-ray absorptiometry and a hyperinsulinemic euglycemic clamp.
  
  
  METHODS
  Insulin sensitivity by hyperinsulinemic clamp, and intramyocellular triacylglycerol (IMTG), diacylglycerol (DAG), and ceramides content, and triacylglycerol and diacylglycerol hydrolase activities were measured in biopsies of vastus lateralis. IMCL was measured by (1)H-magnetic resonance spectroscopy in a subgroup of 25 subjects. Multivariate regression analyses were performed to identify the main predictors of IMCL.
  
  
  RESULTS
  Body fat was the main predictor of IMTG independently of the method and the type of muscle; IMTG concentration was higher in females vs. males and obese vs. nonobese subjects. Muscle DAG and ceramides concentrations were elevated in obese and type 2 diabetic subjects and were not related to body fat and fasting free fatty acids, whereas a direct association with the ratio of diacylglycerol hydrolase to triacylglycerol hydrolase activity (an index of incomplete triacylglycerol hydrolysis) was observed, which explained 54 and 38% of the variance in DAG and ceramides (P < 0.001), respectively. DAG content was the main determinant of insulin resistance.
  
  
  CONCLUSIONS
  These data suggest that intramyocellular DAG is an independent predictor of insulin resistance in humans and that its levels correlate with lipolytic enzymes activity in skeletal muscle but not with markers of adiposity.
authors.affiliation: Department of Molecular and Experimental Endocrinology, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, Louisiana 70808, USA. cedric.moro@pbrc.edu
authors.forename: Cedric
authors.initials: C
authors.lastname: Moro
authors.forename: Jose E
authors.initials: JE
authors.lastname: Galgani
authors.forename: LanChi
authors.initials: L
authors.lastname: Luu
authors.forename: Magdalena
authors.initials: M
authors.lastname: Pasarica
authors.forename: Aline
authors.initials: A
authors.lastname: Mairal
authors.forename: Sudip
authors.initials: S
authors.lastname: Bajpeyi
authors.forename: Gerd
authors.initials: G
authors.lastname: Schmitz
authors.forename: Dominique
authors.initials: D
authors.lastname: Langin
authors.forename: Gerhard
authors.initials: G
authors.lastname: Liebisch
authors.forename: Steven R
authors.initials: SR
authors.lastname: Smith
mesh_terms: D000328:Adult; D000368:Aged; D002518:Ceramides / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism*; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008049:Lipase / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism*; D012737:Sex Factors; D014280:Triglycerides / Q000378:metabolism
chemical_list: D002518:Ceramides; D004075:Diglycerides; D014280:Triglycerides; D008049:Lipase