title: Intramyocellular lipids: anthropometric determinants and relationships with maximal aerobic capacity and insulin sensitivity.
abstract: The existence of metabolically relevant intramyocellular lipids (IMCL) as assessed by the noninvasive (1)H-magnetic resonance spectroscopy (MRS) has been established. In the present studies, we analyzed the relationships between IMCL in two muscle types [the predominantly nonoxidative tibialis muscle (tib) and the predominantly oxidative soleus muscle (sol)] and anthropometric data, aerobic capacity (VO(2)max, bicycle ergometry, n = 77) and insulin sensitivity (hyperinsulinemic euglycemic clamp, n = 105) using regression analysis. In univariate regression, IMCL (tib) was weakly but significantly correlated with percentage of body fat (r = 0.28, P = 0.01), whereas IMCL (sol) was better correlated with waist-to-hip ratio (r = 0.41, P < 0.0001). No significant univariate correlation with age or maximal aerobic power was observed. After adjusting for adiposity, IMCL (tib) was positively correlated with measures of aerobic fitness. A significant interaction term between VO(2)max and percentage of body fat on IMCL (tib) (P = 0.04) existed (whole model r(2) = 0.26, P = 0.001). In contrast, aerobic fitness did not influence IMCL (sol). No correlation between insulin sensitivity as such and IMCL (tib) (r = -0.13, P = 0.2) or IMCL (sol) (r = 0.03, P = 0.72) was observed. Nethertheless, a significant interaction term between VO(2)max and IMCL on insulin sensitivity existed [P = 0.04 (tib) and P = 0.02 (sol)]; [whole model (sol) r(2) = 0.61, P < 0.0001, (tib) r(2) = 0.60, P < 0.0001]. In conclusion, obesity and aerobic fitness are important determinants of IMCL. IMCL and insulin sensitivity are negatively correlated in untrained subjects. The correlation between the two parameters is modified by the extent of aerobic fitness and cannot be found in endurance trained subjects. Thus, measurements of aerobic fitness and body fat are indispensable for the interpretation of IMCL and its relationship with insulin sensitivity.
authors.affiliation: Department of Endocrinology and Metabolism, Eberhard-Karls-University, D-72076 Tübingen, Germany.
authors.forename: Claus
authors.initials: C
authors.lastname: Thamer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Machann
authors.forename: Oliver
authors.initials: O
authors.lastname: Bachmann
authors.forename: Michael
authors.initials: M
authors.lastname: Haap
authors.forename: Dominik
authors.initials: D
authors.lastname: Dahl
authors.forename: Beate
authors.initials: B
authors.lastname: Wietek
authors.forename: Otto
authors.initials: O
authors.lastname: Tschritter
authors.forename: Andreas
authors.initials: A
authors.lastname: Niess
authors.forename: Klaus
authors.initials: K
authors.lastname: Brechtel
authors.forename: Andreas
authors.initials: A
authors.lastname: Fritsche
authors.forename: Claus
authors.initials: C
authors.lastname: Claussen
authors.forename: Stephan
authors.initials: S
authors.lastname: Jacob
authors.forename: Fritz
authors.initials: F
authors.lastname: Schick
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Häring
authors.forename: Michael
authors.initials: M
authors.lastname: Stumvoll
mesh_terms: D000273:Adipose Tissue; D000328:Adult; D000886:Anthropometry; D001786:Blood Glucose / Q000032:analysis; D001823:Body Composition; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008055:Lipids / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000648:ultrastructure; D009765:Obesity / Q000503:physiopathology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010807:Physical Endurance; D010809:Physical Fitness
chemical_list: D001786:Blood Glucose; D007328:Insulin; D008055:Lipids