Interrelations Between Mitochondrial DNA Copy Number and Inflammation in Older Adults.
BACKGROUND
Interplays between inflammation and mitochondrial biology are reported. Here, we examined the cross-sectional interrelationships of mitochondrial DNA copy number (mtDNACN) and inflammation and their interaction with physical functioning.


METHODS
A total of 1990 community-dwelling adults aged 65 years and older who were participating in the Healthy Aging Longitudinal Study in Taiwan underwent measurements of peripheral-blood leukocytes MtDNACN, multiple inflammatory markers, grip strength, and gait speed.


RESULTS
Principal components analysis revealed two inflammatory factors: factor 1 (high-sensitivity C-reactive protein [hs-CRP], white blood cell count, fibrinogen and interleukin-6 [IL-6]); factor 2 (tumor necrosis factor receptor 1, D-dimer and soluble interleukin-6 receptor). Participants with severe physical functioning impairment (low grip strength and gait speed) had higher (p < .05) levels of factor 1 and 2, but not mtDNACN, than did those with moderately impaired (low grip strength or gait speed) and normal physical functioning. MtDNACN was negatively related to factor 1 (r = -.221, p < .001) but not factor 2 (r = -.002, p = .938). Increased factor 1 was strongly associated with higher odds of physical functioning impairment in those with a low mtDNACN (adjusted odds ratios [OR] of moderate physical function impairment 1.21, 95% CI 1.01-1.44; adjusted OR of severe physical function impairment 1.52, 95% CI 1.25-1.85) but not in those with a high mtDNACN (p for interaction = .016).


CONCLUSIONS
A low mtDNACN was associated with an inflammation exhibiting elevated hs-CRP, IL-6, fibrinogen, and white blood cell count, and strengthened the association of this inflammation with physical functioning impairment.
Institute of Population Health Sciences, National Health Research Institutes, Miaoli County, Taiwan.
I-Chien
IC
Wu
Department of Family Medicine, China Medical University Hospital, Taichung, Taiwan.
Cheng-Chieh
CC
Lin
Department of Neurology and Vascular and Genomic Research Center, Changhua Christian Hospital, Taiwan.
Chin-San
CS
Liu
Institute of Population Health Sciences, National Health Research Institutes, Miaoli County, Taiwan.
Chih-Cheng
CC
Hsu
Institute of Population Health Sciences, National Health Research Institutes, Miaoli County, Taiwan.|Department of Family Medicine, College of Medicine and Hospital, National Taiwan University, Taipei, Taiwan.
Ching-Yu
CY
Chen
Institute of Population Health Sciences, National Health Research Institutes, Miaoli County, Taiwan.
Chao A
CA
Hsiung
D000368:Aged; D000375:Aging / Q000502:physiology*; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis; D056915:DNA Copy Number Variations; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D007249:Inflammation / Q000097:blood / Q000473:pathology / Q000503:physiopathology; D015850:Interleukin-6 / Q000097:blood; D007958:Leukocyte Count / Q000379:methods; D007962:Leukocytes / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000235:genetics*; D010809:Physical Fitness / Q000502:physiology*; D013223:Statistics as Topic; D013624:Taiwan; D000072797:Walking Speed / Q000502:physiology
D015415:Biomarkers; D004272:DNA, Mitochondrial; D015850:Interleukin-6; D002097:C-Reactive Protein
Aging; Biological markers/blood; Gait; Geriatric assessment; Muscle strength