title: Blood-cell bioenergetics are associated with physical function and inflammation in overweight/obese older adults.
abstract: BACKGROUND
  Physical function and strength decline with age and lead to limited mobility and independence in older adults. Alterations in mitochondrial function are thought to underlie numerous age-related changes, including declining physical ability. Recent studies suggest that systemic changes in bioenergetic capacity may be reported by analyzing mitochondrial function in circulating cells. The objective of this study was to determine whether the bioenergetic capacity of peripheral blood mononuclear cells (PBMCs) is related to differences in physical function among older, overweight/obese, adults. To address this, we tested the hypothesis that greater PBMC respirometric capacity would be associated with better physical function, muscular strength, leg lean mass, and muscle quality. Furthermore, we tested whether the respirometric capacity of PBMCs is related to cellular composition and inflammatory status reported by interleukin-6 (IL-6).
  
  
  METHODS
  Fasted PBMC respiration (pmol/min/500,000 cells), expanded short physical performance battery (Ex-SPPB), peak knee extensor (KE) strength (Nm), grip strength (kg), leg lean mass (kg, via dual energy X-ray absorptiometry [DXA]), muscle quality (Nm/kg), and plasma IL-6 (pg/mL) were analyzed in 15 well-functioning, community-dwelling, sedentary overweight/obese older men (n=9) and women (n=6) aged 65 to 78 (mean 68.3 ± 3.5 years). Pearson and partial correlations were calculated to determine associations between PBMC respiration and these variables.
  
  
  RESULTS
  Higher maximal respiration of PBMCs was associated with better Ex-SPPB (r=0.58, p=0.02), greater KE strength (r=0.60, p=0.02), greater grip strength (r=0.52, p=0.05) and lower IL-6 (r=-0.58, p=0.04). Higher spare respiratory capacity was associated with better Ex-SPPB (r=0.59, p=0.02), greater KE strength (r=0.60, p=0.02), greater grip strength (r=0.54, p=0.04), greater leg muscle quality (r=0.56, p=0.04), and lower IL-6 (r=-0.55, p=0.05). Monocyte and lymphocyte counts were not related to PBMC respiratory capacity.
  
  
  CONCLUSIONS
  Our results indicate that respirometric profiles of readily obtainable blood cells are associated with physical function and strength. Future studies should be undertaken in order to determine whether blood-based bioenergetic profiling can provide an objective index of systemic mitochondrial health.
authors.affiliation: Sticht Center on Aging and Department of Internal Medicine, Section on Gerontology and Geriatrics, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Tyrrell
authors.affiliation: Sticht Center on Aging and Department of Internal Medicine, Section on Gerontology and Geriatrics, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States.
authors.forename: Manish S
authors.initials: MS
authors.lastname: Bharadwaj
authors.affiliation: Sticht Center on Aging and Department of Internal Medicine, Section on Gerontology and Geriatrics, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States.
authors.forename: Cynthia G
authors.initials: CG
authors.lastname: Van Horn
authors.affiliation: Department of Health and Exercise Science, Wake Forest University, Winston-Salem, NC 27109, United States.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Marsh
authors.affiliation: Sticht Center on Aging and Department of Internal Medicine, Section on Gerontology and Geriatrics, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States.
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Nicklas
authors.affiliation: Sticht Center on Aging and Department of Internal Medicine, Section on Gerontology and Geriatrics, Wake Forest School of Medicine, Winston-Salem, NC 27157, United States. Electronic address: amolina@wakehealth.edu.
authors.forename: Anthony J A
authors.initials: AJ
authors.lastname: Molina
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D019069:Cell Respiration / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D005080:Exercise Test / Q000379:methods; D005260:Female; D006801:Humans; D007249:Inflammation / Q000097:blood* / Q000503:physiopathology; D015850:Interleukin-6 / Q000097:blood; D007958:Leukocyte Count; D007963:Leukocytes, Mononuclear / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology; D009765:Obesity / Q000097:blood / Q000503:physiopathology; D050177:Overweight / Q000097:blood* / Q000503:physiopathology; D010809:Physical Fitness / Q000502:physiology*
chemical_list: D015415:Biomarkers; D015850:Interleukin-6
keywords: Bioenergetics; Blood; Inflammation; Mitochondria; Physical function