title: Reduction in midthigh low-density muscle with aerobic exercise training and weight loss impacts glucose tolerance in older men.
abstract: BACKGROUND
  Intramuscular lipid content increases with aging and obesity and is directly related to impaired glucose tolerance and insulin resistance.
  
  
  OBJECTIVE
  Our purpose was to determine the effects of aerobic exercise training (AEX) with and without weight loss (WL) on midthigh low-density muscle (LDM; a measure of im lipid) and whether changes in LDM impact glucose tolerance in sedentary older men.
  
  
  METHODS
  Forty-six men (60.4 +/- 1.1 yr) completed 6 months of AEX (n = 34) or AEX + WL (n = 12) and had oral glucose tolerance tests (OGTTs) and computed tomography measures of LDM and regional abdominal and thigh fat depot areas.
  
  
  RESULTS
  At baseline, LDM area directly correlated with fasting plasma glucose (FPG), 120-min glucose (G(120)), and glucose area under the curve (G(AUC)) during an OGTT (r = 0.44, r = 0.51, and r = 0.54, respectively, P < 0.01). After the interventions, the AEX + WL group had greater decreases in LDM (-13.5 vs. +1.3%, respectively), FPG (-8.3 vs. +2.1%, respectively), G(120) (-22.5 vs. -3.6%, respectively), and G(AUC) (-17.3 vs. - 3.1%, respectively) than the AEX group. In the entire sample, the decreases in LDM correlated with reductions in FPG, G(120), and G(AUC) during an OGTT (r = 0.31, r = 0.34, and r = 0.41, P < 0.05). Changes in other regional fat depots did not independently correlate with glucose tolerance or insulin responses.
  
  
  CONCLUSIONS
  AEX + WL is more efficacious than AEX for reducing LDM and glucose tolerance. The improvement in glucose tolerance may be partially mediated by decreases in LDM in older men.
authors.affiliation: Division of Gerontology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA. sprior@grecc.umaryland.edu
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Prior
authors.forename: Lyndon J
authors.initials: LJ
authors.lastname: Joseph
authors.forename: Josef
authors.initials: J
authors.lastname: Brandauer
authors.forename: Leslie I
authors.initials: LI
authors.lastname: Katzel
authors.forename: James M
authors.initials: JM
authors.lastname: Hagberg
authors.forename: Alice S
authors.initials: AS
authors.lastname: Ryan
mesh_terms: D001786:Blood Glucose / Q000032:analysis*; D001823:Body Composition; D050218:Body Fat Distribution; D015444:Exercise / Q000502:physiology*; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D013848:Thigh / Q000033:anatomy & histology*; D015431:Weight Loss / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D007328:Insulin