title: Aerobic exercise + weight loss decreases skeletal muscle myostatin expression and improves insulin sensitivity in older adults.
abstract: OBJECTIVE
  To determine whether aerobic exercise training + weight loss (AEX + WL) would affect the expression of myostatin and its relationship with insulin sensitivity in a longitudinal, clinical intervention study.
  
  
  METHODS
  Thirty-three obese sedentary postmenopausal women and men (n = 17 and 16, age: 61 ± 1 years, body mass index: 31 ± 1 kg/m(2) , VO2 max: 21.9 ± 1.0 mL/kg/min, X ± Standard error of the mean (SEM)) completed 6 months of 3 days/week AEX + WL. During an 80 mU m(-2) min(-1) hyperinsulinemic-euglycemic clamp, we measured glucose utilization (M), myostatin, myogenin, and MyoD gene expression by real-time RT-PCR in vastus lateralis muscle at baseline and 2 h.
  
  
  RESULTS
  Body weight (-8%) and fat mass (-17%) decreased after AEX + WL (P < 0.001). Fat-free mass (FFM) and mid-thigh muscle area by computed tomography did not change but muscle attenuation increased (P < 0.05). VO2 max increased 14% (P < 0.001). AEX + WL increased M by 18% (P < 0.01). Myostatin gene expression decreased 19% after AEX + WL (P < 0.05). Basal mRNA myostatin levels were negatively associated with M before the intervention (r = -0.43, P < 0.05). Insulin infusion increased myoD and myogenin expression before and after AEX + WL (both P < 0.001) but basal levels did not change. The insulin effect on myostatin expression was associated with the change in M after AEX + WL (r = 0.56, P < 0.005).
  
  
  CONCLUSIONS
  Exercise and weight loss results in a downregulation of myostatin mRNA and an improvement in insulin sensitivity in obese older men and women.
authors.affiliation: Baltimore VAMC, Division of Gerontology and Geriatric Medicine, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA. aryan@grecc.umaryland.edu
authors.forename: A S
authors.initials: AS
authors.lastname: Ryan
authors.forename: G
authors.initials: G
authors.lastname: Li
authors.forename: J B
authors.initials: JB
authors.lastname: Blumenthal
authors.forename: H K
authors.initials: HK
authors.lastname: Ortmeyer
mesh_terms: D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D001835:Body Weight; D015536:Down-Regulation; D015444:Exercise / Q000502:physiology*; D005215:Fasting; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D008019:Life Style; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D055435:Myostatin / Q000235:genetics / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism / Q000628:therapy; D017698:Postmenopause; D012044:Regression Analysis; D057185:Sedentary Behavior; D013848:Thigh / Q000502:physiology; D015431:Weight Loss
chemical_list: D001786:Blood Glucose; D007328:Insulin; C525911:MSTN protein, human; D055435:Myostatin