title: Functional and histological characteristics of skeletal muscle and the effects of leptin in the genetically obese (ob/ob) mouse.
abstract: BACKGROUND
  Skeletal muscle mass in genetically obese (ob/ob) mice displays a reduced mass compared with their normal lean counterpart mice. However, the functional capacity of the available skeletal muscle mass in these animals has not yet been determined.
  
  
  OBJECTIVE
  To investigate the properties of skeletal muscle in ob/ob mice and determine the effects of leptin administration on skeletal muscle in these mice.
  
  
  METHODS
  Following 4 weeks of i.p. leptin administration (or control treatment) anaesthetized ob/ob and lean mice had their extensor digitorum longus and soleus muscles removed, and standard measures of isometric contractile properties and fatigability were performed. Histochemistry was used to determine fibre type proportions and individual fibre areas of all muscles.
  
  
  RESULTS
  Leptin had no effect on the morphology or function of ob/ob skeletal muscle despite reducing body mass in ob/ob mice. Force production was unaltered in obese mice. However, a significant prolongation of contraction and relaxation times were evident. Obese skeletal muscle was also more fatigue resistant. Fibre proportions displayed a more slow type profile in ob/ob skeletal muscle, and in conjunction with previous work a reduced ability to hypertrophy.
  
  
  CONCLUSIONS
  Skeletal muscle from obese mice is morphologically and functionally different from lean mouse skeletal muscle. Obese muscle is very similar to skeletal muscle from aged mice, and the specific contractile properties examined appear to be determined by the fibre make-up of these muscles.
authors.affiliation: Department of Physiology, University of Dublin, Trinity College, Dublin 2, Ireland. warmings@tcd.ie
authors.forename: S A
authors.initials: SA
authors.lastname: Warmington
authors.forename: R
authors.initials: R
authors.lastname: Tolan
authors.forename: S
authors.initials: S
authors.lastname: McBennett
mesh_terms: D000818:Animals; D020738:Leptin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008820:Mice, Obese; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018763:Muscle Fatigue / Q000187:drug effects / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000187:drug effects / Q000502:physiology*; D009765:Obesity / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*
chemical_list: D020738:Leptin