The Association between Gut Microbiota and Depression in the Japanese Population.

Depression is a leading cause of disease worldwide. The association between gut microbiota and depression has barely been investigated in the Japanese population. We analyzed Iwaki health check-up data collected from 2017 to 2019 and constructed generalized linear mixed models. The independent variable was the relative abundance of each of the 37 gut microbiota genera that were reported to be associated with depression. The dependent variable was the presence of depression assessed by the Center for Epidemiologic Studies Depression Scale. Potential confounders, including grip strength, gender, height, weight, smoking, and drinking habits, were adjusted in the regression models. Nine genera's regression coefficients (Alistipes, Blautia, Coprococcus, Dorea, Faecalibacterium, Holdemania, Lactobacillus, Mitsuokella, and Oscillibacter) showed statistical significance after multiple comparisons adjustment. Among these nine gut bacteria genera, Alistipes, Blautia, Coprococcus, Dorea, Faecalibacterium, and Oscillibacter were reported to be associated with butyrate production in the intestine. Our results indicate that gut microbiotas may influence the depression condition of the host via the butyrate-producing process.

Low Level of Serum Cadmium in Relation to Blood Pressures Among Japanese General Population.

Hypertension (HT) is an important risk factor for mortality and morbidity. Previous studies showed that cadmium (Cd) was associated with increased blood pressures and the prevalence of HT. This study hypothesized that Cd, regardless of its level, may increase blood pressures/HT. The objective of this study was to examine the associations between a low level of serum Cd concentration and blood pressures/HT among a general population in the Iwaki area, Japan. This was a cross-sectional study, conducted in the Aomori prefecture with 1144 volunteers aged over 19 years old, who were participants of the Iwaki health check-up in 2014. The study assessed questionnaire survey, body composition, and serum Cd concentrations. Median serum Cd concentration was 0.06 ng/mL (interquartile range 0.05-0.08 ng/mL) among our study population. Compared to the lowest quintile of serum Cd concentration group, the highest quintile of serum Cd concentration group had 4.9 mmHg higher systolic blood pressure (SBP) (95% confidence interval [CI] 1.53-8.31, p < 0.01) and 2.4 mmHg higher diastolic blood pressure (DBP) (95% CI 0.36-4.34, p < 0.05), compared to the lowest quintile group. Similarly, the highest quintile of serum Cd concentration group had 1.7 times higher prevalence of HT (95% CI 1.10-2.51, p < 0.05) than the lowest quintile group. This study identified that higher serum Cd concentration was significantly, positively, associated with SBP and DBP and HT prevalence. This study provided evidence for the associations between environmental exposure to Cd and blood pressures/HT which should be considered for future preventive measures.

The relationship between cigarette smoking and the tongue microbiome in an East Asian population.

Background: The oral microbiome, which consists of various habitats, has been shown to be influenced by smoking. However, differences in the tongue microbiomes of current and former smokers, as well as their resultant functional consequences, have rarely been investigated in East Asian populations. Methods: We used 16S rRNA amplicon sequencing of tongue-coating samples obtained from East Asian subjects who were current, former, or never smokers to identify differences in their tongue microbiomes and related metagenomic functions. Two sets of participants from 2016 to 2017 (n = 657 and n = 187, respectively) were analyzed separately. Results: We found significant differences between the overall microbiome compositions of current versus never smokers (p = 0.0015), but not between former versus never smokers (p = 0.43) based on the weighted UniFrac distance. Twenty-nine of 43 investigated genera showed significantly different expression levels in current versus never smokers. Neisseria and Capnocytophaga were less abundant, and Streptococcus and Megasphaera were more abundant in current smokers. Moreover, the abundances of metagenomic pathways, including those related to nitrate reduction and the tricarboxylic acid cycle, were significantly different between current and never smokers. Conclusions: The tongue microbiomes and related metagenomic pathways of current smokers differ from those of never smokers among East Asians.

Metagenomic analysis of bacterial species in tongue microbiome of current and never smokers.

Cigarette smoking affects the oral microbiome, which is related to various systemic diseases. While studies that investigated the relationship between smoking and the oral microbiome by 16S rRNA amplicon sequencing have been performed, investigations involving metagenomic sequences are rare. We investigated the bacterial species composition in the tongue microbiome, as well as single-nucleotide variant (SNV) profiles and gene content of these species, in never and current smokers by utilizing metagenomic sequences. Among 234 never smokers and 52 current smokers, beta diversity, as assessed by weighted UniFrac measure, differed between never and current smokers (pseudo-F = 8.44, R2 = 0.028, p = 0.001). Among the 26 species that had sufficient coverage, the SNV profiles of Actinomyces graevenitzii, Megasphaera micronuciformis, Rothia mucilaginosa, Veillonella dispar, and one Veillonella sp. were significantly different between never and current smokers. Analysis of gene and pathway content revealed that genes related to the lipopolysaccharide biosynthesis pathway in Veillonella dispar were present more frequently in current smokers. We found that species-level tongue microbiome differed between never and current smokers, and 5 species from never and current smokers likely harbor different strains, as suggested by the difference in SNV frequency.