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Aims. Visceral obesity is associated with an increased risk of cardiometabolic diseases and it is important to identify the underlying mechanisms. There is growing evidence that mitochondrial dysfunction is associated with metabolic disturbances related to visceral obesity. In addition, maintaining mitochondrial DNA (mtDNA) copy number is important for preserving mitochondrial function. Therefore, we investigated the relationship between mtDNA copy number and visceral fat in healthy young adults. Methods. A total of 94 healthy young subjects were studied. Biomarkers of metabolic risk factors were assessed along with body composition by computed tomography. mtDNA copy number was measured in peripheral leukocytes using real-time polymerase chain reaction (PCR) methods. Results. The mtDNA copy number correlated with BMI (r = −0.22, P = 0.04), waist circumference (r = −0.23, P = 0.03), visceral fat area (r = −0.28, P = -0.01), HDL-cholesterol levels (r = 0.25, P = 0.02), and hs-CRP (r = 0.32, P = 0.02) after adjusting for age and sex. Both stepwise and nonstepwise multiple regression analyses confirmed that visceral fat area was independently associated with mtDNA copy number (β = -0.33, P < 0.01, β = 0.32, and P = 0.03, resp.). Conclusions. An independent association between mtDNA content and visceral adiposity was identified. These data suggest that mtDNA copy number is a potential predictive marker for metabolic disturbances. Further studies are required to understand the causality and clinical significance of our findings.

[1] Changes in the Earth's climate caused by global warming are a looming problem that poses serious challenges not only for our generation but for future generations. An accurate determination of CO 2 gas plays a critical role in this field of research. The measurement of greenhouse gases is pivotal to understanding the changes in Earth's climate and needs to be carried out with a high degree of accuracy. Precision measurements on a 0.1 mmol/mol scale may provide research data for precisely monitoring the continuing changes that the planet is undergoing. The World Meteorological Organization (WMO) has recommended that carbon dioxide concentrations in air can be measured by comparing these with national reference gases using a nondispersive infrared (NDIR) analyzer to standardize international data. The CO 2 molecules absorb the distinctive resonant frequencies in IR spectrometers. The NDIR analyzers usually use narrow band path filter to determine 12 CO 2 in all carbon dioxide molecules, which can possibly ignore the measurement of 13 CO 2 partially or totally. However, if the carbon isotopic abundances of CO 2 samples deviate from those in standard CO 2 gas, the NDIR measurement will not be exact. For accurate measurements, producers of reference gas mixtures either must use gas with natural isotopic abundances, or report the isotopic abundances of CO 2 . In order to document shifts based on isotopic variability, we prepared artificial air as CO 2 reference gas mixtures gravimetrically with CO 2 having different carbon isotopic signatures to study the resulting isotopic variations. We used different d13 C values of two CO 2 source gases, A and B, corresponding to À41.97% and À14.88%, respectively, which were measured using an isotope ratio mass spectrometer. One set of reference gas mixtures (A1 to A5) was prepared from the CO 2 source of d 13 C = À41.97%, and the other set of reference gas mixtures (B1, B2) was prepared from that of d 13 C = À14.88%. The CO 2 abundances of the two sets of mixtures were compared by using NDIR. The reproducibility test for the set A showed that the data are consistent within uncertainty (calibration line was obtained by the best secondary polynomial least squares fit). The uncertainty of CO 2 concentration in the reference gas mixtures are 0.06 mmol/mol with a 95% confidence level. The reproducibility of the NDIR measurement is 0.012 mmol/mol (standard deviation). The difference between the set A (A1 to A5) and set B (B1, B2) was found to be 0.17 ± 0.01 mmol/mol, which is in excellent agreement with the theoretically predicted value of 0.17 mmol/mol.

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Our study shows an inverse association between urine melatonin and sarcopenia, suggesting that melatonin may have a protective role in the pathophysiology of sarcopenia. Further studies are required to better understand the clinical significance of our findings.