The relationship between lifestyle and obesity is a major focus of research. Personalized nutrition, which utilizes evidence from nutrigenomics, such as gene-environment interactions, has been attracting attention in recent years. However, evidence for gene-environment interactions that can inform treatment strategies is lacking, despite some reported interactions involving dietary intake or physical activity. Utilizing gene-lifestyle interactions in practice could aid in optimizing interventions according to genetic risk.

Obesity is a reported risk factor for various health problems. Genome-wide association studies (GWASs) have identified numerous independent loci associated with body mass index (BMI). However, most of these have been focused on Europeans, and little evidence is available on the genetic effects across the life course of other ethnicities.

Environmental and genetic factors are suggested to exhibit factor-based association with HDL-cholesterol (HDL-C) levels. However, the population-based effects of environmental and genetic factors have not been compared clearly. We conducted a cross-sectional study using data from the Japan Multi-Institutional Collaborative Cohort (J-MICC) Study to evaluate the population-based impact of smoking, drinking, and genetic factors on low HDL-C.

Stress coping strategies are related to health outcomes. However, there is no clear evidence for sex differences between stress-coping strategies and mortality. We investigated the relationship between all-cause mortality and stress-coping strategies, focusing on sex differences among Japanese adults.

Prostate cancer is emerging as a significant global public health burden. The incidence and prevalence of prostate cancer has increased in Japan, as westernized lifestyles become more popular. Recent advances in genetic epidemiology, including genome-wide association studies (GWASs), have identified considerable numbers of human genetic factors associated with diseases. Several GWASs have reported significant loci associated with serum prostate-specific antigen (PSA) levels. One GWAS, which was based on classic GWAS microarray measurements, has been reported for Japanese so far. In the present study, we conducted a GWAS of serum PSA using 1000Genomes imputed GWAS data (n =1,216) from the Japan Multi-Institutional Collaborative Cohort (J-MICC) Study, to detect candidate novel genetic loci that influence serum PSA levels in Japanese. The association of SNPs/genetic variants with serum PSA as a continuous variable was tested using the linear Wald test. SNP rs10000006 in SGMS2 (sphingomyelin synthase 2) on chromosome 4 had genome-wide significance (P <5×10-8), and eight variants on three chromosomes (chromosomes 12, 14, 15) had genome-wide suggestive levels of significance (P <1×10-6). With an independent data set from the J-MICC Shizuoka Study (n = 2,447), the association of the SGMS2 SNP with blood PSA levels was not replicated. Although our GWAS failed to detect novel loci associated with serum PSA levels in the Japanese cohort, it confirmed the significant effects of previously reported genetic loci on PSA levels in Japanese. Importantly, our results confirmed the significance of KLK3 SNPs also in Japanese, implying that consideration of individual genetic information in prostate cancer diagnosis may be possible in the future.

Mitochondrial DNA (mtDNA) mutator mice are proposed to express premature aging phenotypes including kyphosis and hair loss (alopecia) due to their carrying a nuclear-encoded mtDNA polymerase with a defective proofreading function, which causes accelerated accumulation of random mutations in mtDNA, resulting in expression of respiration defects. On the contrary, transmitochondrial mito-miceΔ carrying mtDNA with a large-scale deletion mutation (ΔmtDNA) also express respiration defects, but not express premature aging phenotypes. Here, we resolved this discrepancy by generating mtDNA mutator mice sharing the same C57BL/6J (B6J) nuclear background with that of mito-miceΔ. Expression patterns of premature aging phenotypes are very close, when we compared between homozygous mtDNA mutator mice carrying a B6J nuclear background and selected mito-miceΔ only carrying predominant amounts of ΔmtDNA, in their expression of significant respiration defects, kyphosis, and a short lifespan, but not the alopecia. Therefore, the apparent discrepancy in the presence and absence of premature aging phenotypes in mtDNA mutator mice and mito-miceΔ, respectively, is partly the result of differences in the nuclear background of mtDNA mutator mice and of the broad range of ΔmtDNA proportions of mito-miceΔ used in previous studies. We also provided direct evidence that mtDNA abnormalities in homozygous mtDNA mutator mice are responsible for respiration defects by demonstrating the co-transfer of mtDNA and respiration defects from mtDNA mutator mice into mtDNA-less (ρ(0)) mouse cells. Moreover, heterozygous mtDNA mutator mice had a normal lifespan, but frequently developed B-cell lymphoma, suggesting that the mtDNA abnormalities in heterozygous mutator mice are not sufficient to induce a short lifespan and aging phenotypes, but are able to contribute to the B-cell lymphoma development during their prolonged lifespan.

Mitochondria have their own DNA (mtDNA), which encodes essential respiratory subunits. Under live imaging, mitochondrial nucleoids, composed of several copies of mtDNA and DNA-binding proteins, such as mitochondrial transcription factor A (TFAM), actively move inside mitochondria and change the morphology, in concert with mitochondrial membrane fission. Here we found the mitochondrial inner membrane-anchored AAA-ATPase protein ATAD3A mediates the nucleoid dynamics. Its ATPase domain exposed to the matrix binds directly to TFAM and mediates nucleoid trafficking along mitochondria by ATP hydrolysis. Nucleoid trafficking also required ATAD3A oligomerization via an interaction between the coiled-coil domains in intermembrane space. In ATAD3A deficiency, impaired nucleoid trafficking repressed the clustered and enlarged nucleoids observed in mitochondrial fission-deficient cells resulted in dispersed distribution of small nucleoids observed throughout the mitochondrial network, and this enhanced respiratory complex formation. Thus, mitochondrial fission and nucleoid trafficking cooperatively determine the size, number, and distribution of nucleoids in mitochondrial network, which should modulate respiratory complex formation.