title: The individual and combined effects of obesity- and ageing-induced systemic inflammation on human skeletal muscle properties.
abstract: The purpose of this study was to determine whether circulating pro-inflammatory cytokines, elevated with increased fat mass and ageing, were associated with muscle properties in young and older people with variable adiposity.
  
  
  
  Seventy-five young (18-49 yrs) and 67 older (50-80 yrs) healthy, untrained men and women (BMI: 17-49 kg/m2) performed isometric and isokinetic plantar flexor maximum voluntary contractions (MVCs). Volume (Vm), fascicle pennation angle (FPA), and physiological cross-sectional area (PCSA) of the gastrocnemius medialis (GM) muscle were measured using ultrasonography. Voluntary muscle activation (VA) was assessed using electrical stimulation. GM specific force was calculated as GM fascicle force/PCSA. Percentage body fat (BF%), body fat mass (BFM), and lean mass (BLM) were assessed using dual-energy X-ray absorptiometry. Serum concentration of 12 cytokines was measured using multiplex luminometry.
  
  
  
  Despite greater Vm, FPA, and PCSA (P<0.05), young individuals with BF% ⩾40 exhibited 37% less GM specific force compared to young BF%<40 (P<0.05). Older adults with BF% ⩾40 showed greater isokinetic MVC compared to older BF%<40 (P=0.019) but this was reversed when normalised to body mass (P<0.001). IL-6 correlated inversely with VA in young (r=-0.376; P=0.022) but not older adults (p>0.05), while IL-8 correlated with VA in older but not young adults (r⩾0.378, P⩽0.027). TNF-alpha correlated with MVC, lean mass, GM FPA and maximum force in older adults (r⩾0.458; P⩽0.048).
  
  
  
  The age- and adiposity-dependent relationships found here provide evidence that circulating pro-inflammatory cytokines may play different roles in muscle remodelling according to the age and adiposity of the individual.
authors: Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Liverpool, UK.|Institute of Sport, Exercise & Health, University College London, London, UK.
authors: R M
authors: RM
authors: Erskine
authors: Centre for Health, Exercise and Active Living, Manchester Metropolitan University, Crewe, UK.
authors: D J
authors: DJ
authors: Tomlinson
authors: Centre for Health, Exercise and Active Living, Manchester Metropolitan University, Crewe, UK.
authors: C I
authors: CI
authors: Morse
authors: Centre for Health, Exercise and Active Living, Manchester Metropolitan University, Crewe, UK.
authors: K
authors: K
authors: Winwood
authors: Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK.
authors: P
authors: P
authors: Hampson
authors: Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK.
authors: J M
authors: JM
authors: Lord
authors: Centre for Health, Exercise and Active Living, Manchester Metropolitan University, Crewe, UK.
authors: G L
authors: GL
authors: Onambélé
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism / Q000502:physiology*; D001696:Biomechanical Phenomena; D016207:Cytokines / Q000378:metabolism; D005260:Female; D006801:Humans; D007249:Inflammation / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000473:pathology* / Q000503:physiopathology*; D009765:Obesity / Q000150:complications / Q000378:metabolism / Q000503:physiopathology*; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D016207:Cytokines