Effects of aerobic exercise training on C1q tumor necrosis factor α-related protein isoform 5 (myonectin): association with insulin resistance and mitochondrial DNA density in women.
BACKGROUND
The C1q TNFα-related protein (C1QTNF) families exhibit a C-terminal complement factor C1q globular domain similar to that of TNF. However, their clinical implications are largely unknown. We recently found that the C1q TNFα-related protein isoform 5 (C1QTNF5 or myonectin) level was increased in insulin-resistant rodents and mitochondrial DNA (mtDNA)-depleted myocytes.


OBJECTIVE
We aimed to determine the effects of aerobic exercise training on C1QTNF5 level and its association with insulin resistance and mtDNA density in young and old healthy women.


METHODS
Fourteen healthy young women aged 22.5 ± 2.7 yr and 14 healthy older women aged 60.3 ± 5.2 yr performed aerobic exercise at 60-80% of maximal oxygen consumption (VO(2)max) over three 1-h sessions per week for 10 wk. Insulin resistance was assessed by homeostasis model assessment of insulin resistance and adiponectin concentration. Serum C1QTNF5 level was estimated by immunoblotting. The mtDNA/28S rRNA ratio was used to determine mtDNA density.


RESULTS
VO(2)max increased significantly after the exercise training from 33.1 ± 6.2 to 35.3 ± 5.3 ml/kg · min in younger women and from 23.2 ± 3.1 to 27.2 ± 4.8 ml/kg · min in older women (P < 0.05). The C1QTNF5 level and homeostasis model assessment of insulin resistance decreased significantly after exercise training and were correlated positively (r = 0.462; P < 0.01). There were negative correlations between the changes in C1QTNF5 level and the changes in VO(2)max, mtDNA density, and adiponectin level (r = -0.495, -0.672, and -0.569, respectively; all P < 0.01).


CONCLUSIONS
These findings suggest a physiological function for C1QTNF5 (myonectin) in linking insulin resistance with quantitative changes in mtDNA. Further research exploring the role of C1QTNF5 in the development of insulin resistance is warranted.
Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
Soo
S
Lim
Sung Hee
SH
Choi
Bo Kyung
BK
Koo
Seon Mee
SM
Kang
Ji Won
JW
Yoon
Hak Chul
HC
Jang
Soon Mi
SM
Choi
Man Gyoon
MG
Lee
Wan
W
Lee
Hayley
H
Shin
Young-Bum
YB
Kim
Hong Kyu
HK
Lee
Kyong Soo
KS
Park
D000293:Adolescent; D000328:Adult; D000368:Aged; D003094:Collagen / Q000235:genetics* / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007333:Insulin Resistance / Q000235:genetics* / Q000502:physiology; D008875:Middle Aged; D009994:Osmolar Concentration; D010806:Physical Education and Training; D005082:Physical Exertion / Q000235:genetics / Q000502:physiology; D055815:Young Adult
C487851:C1QTNF5 protein, human; D004272:DNA, Mitochondrial; D003094:Collagen