Gut microbiota plays an important role in the harvesting, storage, and expenditure of energy obtained from one’s diet. Our cross-sectional study aimed to identify differences in gut microbiota according to body mass index (BMI) in a Korean population. 16S rRNA gene sequence data from 1463 subjects were categorized by BMI into normal, overweight, and obese groups. Fecal microbiotas were compared to determine differences in diversity and functional inference analysis related with BMI. The correlation between genus-level microbiota and BMI was tested using zero-inflated Gaussian mixture models, with or without covariate adjustment of nutrient intake. We confirmed differences between 16Sr RNA gene sequencing data of each BMI group, with decreasing diversity in the obese compared with the normal group. According to analysis of inferred metagenomic functional content using PICRUSt algorithm, a highly significant discrepancy in metabolism and immune functions (P < 0.0001) was predicted in the obese group. Differential taxonomic components in each BMI group were greatly affected by nutrient adjustment, whereas signature bacteria were not influenced by nutrients in the obese compared with the overweight group. We found highly significant statistical differences between normal, overweight and obese groups using a large sample size with or without diet confounding factors. Our informative dataset sheds light on the epidemiological study on population microbiome.

The presence of an association between chronic hepatitis B virus (HBV) infection and fatty liver is controversial. We examined the association between HBV infection and the development of nonalcoholic fatty liver disease (NAFLD). We conducted a cohort study of 83,339 participants without NAFLD at baseline who underwent serologic testing for hepatitis B surface antigen (HBsAg) between 2002 and 2006 and were followed annually or biennially until December 2014. NAFLD was defined as the presence of ultrasonographic fatty liver in the absence of excessive alcohol use or other identifiable causes. We used a parametric Cox model to estimate adjusted hazard ratios with 95% confidence intervals of incident NAFLD. During 484,736.1 person‐years of follow‐up, 20,200 incident NAFLD cases were identified. In models adjusted for age, sex, year of visit, smoking status, alcohol intake, regular exercise, education level, and body mass index, the adjusted hazard ratio (95% confidence interval) for incident NAFLD comparing HBsAg‐positive to HBsAg‐negative participants was 0.83 (0.73‐0.94). After introducing HBV infection and confounders (including homeostasis model assessment of insulin resistance and metabolic factors) as time‐dependent exposures, the association between HBV infection and decreased risk of incident NAFLD was attenuated but persisted. These associations were consistently observed across clinically relevant, prespecified subgroups. Conclusion: In this large cohort of apparently healthy Korean adults, HBsAg seropositivity was associated with lower risk of developing NAFLD, indicating a possible effect of HBV infection on the pathogenesis of NAFLD development. (Hepatology 2017;65:828‐835).

The association between relative muscle mass (RMM) and incidence of type 2 diabetes (T2DM) is largely unknown. We examined whether RMM predicted development of T2DM in an apparently young healthy population. This cohort study was comprised of 113,913 men and 89,854 women, free of T2DM at baseline, who underwent a health checkup examination and were followed-up annually or biennially for an average of 2.9 years. We used skeletal muscle mass index (SMI) as an indicator of RMM. SMI (%) [total skeletal muscle mass (kg)/body weight (kg)×100] was estimated using a bioelectrical impedance analyzer. The study outcome was incident T2DM, defined as fasting serum glucose ≥126 mg/dL, HbA1C ≥6.5%, or use of medication for T2DM. During 589,098.8 person-years of follow-up, 4,264 individuals developed T2DM (incidence rate, 7.2 per 1000 person-years). Median age (range) at baseline was 39.1 years (18.1–87.1). RMM was negatively associated with incidence of T2DM in a dose-response manner. The multivariate-adjusted hazard ratios (95% CIs) for incident T2DM comparing quartiles 3, 2 and 1 of RMM to the highest quartile were 1.32 (1.14–1.52), 1.63 (1.42–1.86), and 2.21 (1.94–2.51), respectively, for males and 1.18 (0.88–1.58), 1.46 (1.11–1.91), and 1.96 (01.51–2.53) for females (P for trend <0.001; 0.011). This association was stronger in younger or premenopausal subjects. RMM was negatively associated with development of T2DM in a large sample of young and middle-aged Korean adults. Further research is required to determine whether preservation of muscle mass through intervention affects the risk of T2DM.

Objective—: Sarcopenia or low muscle mass is related to cardiovascular risk factors; however, the association between low muscle mass and subclinical atherosclerosis has been largely unexplored. We investigated whether muscle mass is related to coronary artery calcification (CAC) in a large sample of middle-aged asymptomatic adults. Approach and Results—: We performed a cross-sectional study of 31 108 asymptomatic adults without cancer, diabetes mellitus, or known cardiovascular disease who underwent a health checkup examination including cardiac tomography estimation of CAC scores between 2012 and 2013. Skeletal muscle mass index (SMI) [SMI (%)=total skeletal muscle mass (kg)/body weight (kg)×100] was estimated using a bioelectrical impedance analyzer. We assessed the relationship between SMI and CAC scores using both multivariate-adjusted Tobit models and multinomial logistic regression models. Of the 31 108 subjects, 3374 subjects (10.9%) had a CAC score 1 to 100, and 628 subjects (2.0%) had a CAC score >100. SMI was inversely associated with CAC score ratios. Specifically, in a multivariable-adjusted model adjusting for potential confounders, CAC score ratios (95% confidence intervals) of SMI for quartiles 1, 2, and 3 compared with quartile 4 were 2.27 (1.70–3.05), 1.46 (1.15–1.85), and 1.24 (0.98–1.55), respectively ( P for trend <0.001). Adjusting for insulin resistance reduced the magnitude of the associations, but they remained statistically significant. Conclusions—: Relative muscle mass was negatively associated with the prevalence of coronary calcification, supporting low muscle mass as an independent risk factor of coronary heart disease.