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Background: The association between obesity and albuminuria in the general population remains unclear. We aimed to identify the association between obesity and albuminuria as well as sex differences regarding the associations using several obesity indices, including waist circumference (WC), body mass index (BMI), and waist-to-height ratio (WHR). Methods: This study included 3841 subjects (1730 males and 2111 females; age 20-80 years) who participated in the Fifth Korea National Health and Nutrition Examination Survey conducted in 2011. Subjects with hypertension, diabetes, renal failure, or a malignant tumor and those who were pregnant or menstruating were excluded. Albuminuria was defined as a urinary albumin-to-creatinine ratio ≥30 mg/g. Anthropometric parameters were categorized into sex-specific quartiles. Logistic regression models were used to assess the associations between each anthropometric parameter and albuminuria. Results: All of the obesity indices of the fourth quartile group of females showed a twofold higher risk for albuminuria than the second quartile group, and it was persistently significant after adjusting for age, smoking, and physical activity. After further adjustment for high blood pressure and impaired fasting glucose and triglyceride levels, WC and BMI of the fourth quartile group of females still showed a significantly higher risk for albuminuria than the second quartile group (odds ratios 1.96 and 2.24; 95 % confidence intervals 1.03-3.74 and 1.15-4.37). None of the associations between albuminuria and the obesity indices were significant in males. Conclusion: Higher WC and BMI were significantly associated with the risk of albuminuria among females, but not males. [ABSTRACT FROM AUTHOR]

Abstract: Objective: This cross-sectional study analyzed the association of serum irisin concentrations with cardiorespiratory fitness levels and common single nucleotide polymorphisms (SNPs) in the FNDC5 gene and examined the relationships between cardiorespiratory fitness levels, common SNPs in FNDC5, and glucose metabolism. Materials/Methods: Cardiorespiratory fitness was assessed by measuring peak oxygen uptake (VO2peak) and serum irisin levels by ELISA in 163 Japanese men (age, 21–79years). Subjects were divided into low- and high-fitness groups within each age group according to the median VO2peak value. Common SNPs (rs3480 and rs16835198) of the FNDC5 gene were genotyped with the TaqMan assay. Glucose metabolism was evaluated by measuring HbA1c, fasting plasma glucose (FPG), insulin levels, and HOMA-IR. Results: Serum irisin levels were negatively correlated with age (p <0.001) and not associated with the VO2peak or HOMA-IR. In the low-fitness group, SNP analysis revealed that subjects with the rs3480 AG and GG genotypes had higher levels of insulin and HOMA-IR than those with the AA genotype (p <0.01; no significant difference was observed in the high-fitness group). The GG genotypes of rs16835198 were associated with increased HbA1c and FPG in the low-fitness group only (p <0.05). SNPs and both fitness groups were not associated with serum irisin levels. Conclusions: In Japanese men, cardiorespiratory fitness levels and common SNPs in FNDC5 are not associated with circulating irisin levels, whereas high cardiorespiratory fitness abolishes the association between the rs3480 and rs16835198 SNPs and glucose metabolism independent of serum irisin levels. [Copyright &y& Elsevier]