Genetic Risk, Healthy Lifestyle Adherence, and Risk of Developing Diabetes in the Japanese Population.

AIM: This study examined the relationship between genetic risk, healthy lifestyle, and risk of developing diabetes. METHODS: This prospective cohort study included 11,014 diabetes-free individuals ≥ 20 years old from the Tohoku Medical Megabank Community-based cohort study. Lifestyle scores, including the body mass index, smoking, physical activity, and gamma-glutamyl transferase (marker of alcohol consumption), were assigned, and participants were categorized into ideal, intermediate, and poor lifestyles. A polygenic risk score (PRS) was constructed based on the type 2 diabetes loci from the BioBank Japan study. A multiple logistic regression model was used to estimate the association between genetic risk, healthy lifestyle, and diabetes incidence and to calculate the area under the receiver operating characteristic curve (AUROC). RESULT: Of the 11,014 adults included (67.8% women; mean age [standard deviation], 59.1 [11.3] years old), 297 (2.7%) developed diabetes during a mean 4.3 (0.8) years of follow-up. Genetic and lifestyle score is independently associated with the development of diabetes. Compared with the low genetic risk and ideal lifestyle groups, the odds ratio was 3.31 for the low genetic risk and poor lifestyle group. When the PRS was integrated into a model including the lifestyle and family history, the AUROC significantly improved to 0.719 (95% confidence interval [95% CI]: 0.692-0.747) compared to a model including only the lifestyle and family history (0.703 [95% CI, 0.674-0.732]). CONCLUSION: Our findings indicate that adherence to a healthy lifestyle is important for preventing diabetes, regardless of genetic risk. In addition, genetic risk might provide information beyond lifestyle and family history to stratify individuals at high risk of developing diabetes.

Body mass index stratification optimizes polygenic prediction of type 2 diabetes in cross-biobank analyses.

Type 2 diabetes (T2D) shows heterogeneous body mass index (BMI) sensitivity. Here, we performed stratification based on BMI to optimize predictions for BMI-related diseases. We obtained BMI-stratified datasets using data from more than 195,000 individuals (nT2D = 55,284) from BioBank Japan (BBJ) and UK Biobank. T2D heritability in the low-BMI group was greater than that in the high-BMI group. Polygenic predictions of T2D toward low-BMI targets had pseudo-R2 values that were more than 22% higher than BMI-unstratified targets. Polygenic risk scores (PRSs) from low-BMI discovery outperformed PRSs from high BMI, while PRSs from BMI-unstratified discovery performed best. Pathway-specific PRSs demonstrated the biological contributions of pathogenic pathways. Low-BMI T2D cases showed higher rates of neuropathy and retinopathy. Combining BMI stratification and a method integrating cross-population effects, T2D predictions showed greater than 37% improvements over unstratified-matched-population prediction. We replicated findings in the Tohoku Medical Megabank (n = 26,000) and the second BBJ cohort (n = 33,096). Our findings suggest that target stratification based on existing traits can improve the polygenic prediction of heterogeneous diseases.

Activation of NOTCH signaling impedes cell proliferation and survival in acute megakaryoblastic leukemia.

The genetic lesions that drive acute megakaryoblastic leukemia (AMKL) have not been fully elucidated. To search for genetic alterations in AMKL, we performed targeted deep sequencing in 34 AMKL patient samples and 8 AMKL cell lines and detected frequent genetic mutations in the NOTCH pathway in addition to previously reported alterations in GATA-1 and the JAK-STAT pathway. Pharmacological and genetic NOTCH activation, but not inhibition, significantly suppressed AMKL cell proliferation in both in vitro and in vivo assays employing a patient-derived xenograft model. These results suggest that NOTCH inactivation underlies AMKL leukemogenesis. and NOTCH activation holds the potential for therapeutic application in AMKL.

Associations of combined genetic and lifestyle risks with hypertension and home hypertension.

No study, to our knowledge, has constructed a polygenic risk score based on clinical blood pressure and investigated the association of genetic and lifestyle risks with home hypertension. We examined the associations of combined genetic and lifestyle risks with hypertension and home hypertension. In a cross-sectional study of 7027 Japanese individuals aged ≥20 years, we developed a lifestyle score based on body mass index, alcohol consumption, physical activity, and sodium-to-potassium ratio, categorized into ideal, intermediate, and poor lifestyles. A polygenic risk score was constructed with the target data (n = 1405) using publicly available genome-wide association study summary statistics from BioBank Japan. Using the test data (n = 5622), we evaluated polygenic risk score performance and examined the associations of combined genetic and lifestyle risks with hypertension and home hypertension. Hypertension and home hypertension were defined as blood pressure measured at a community-support center ≥140/90 mmHg or at home ≥135/85 mmHg, respectively, or self-reported treatment for hypertension. In the test data, 2294 and 2322 participants had hypertension and home hypertension, respectively. Both polygenic risk and lifestyle scores were independently associated with hypertension and home hypertension. Compared with those of participants with low genetic risk and an ideal lifestyle, the odds ratios for hypertension and home hypertension in the low genetic risk and poor lifestyle group were 1.94 (95% confidence interval, 1.34-2.80) and 2.15 (1.60-2.90), respectively. In summary, lifestyle is important to prevent hypertension; nevertheless, participants with high genetic risk should carefully monitor their blood pressure despite a healthy lifestyle.

PNPO-PLP axis senses prolonged hypoxia in macrophages by regulating lysosomal activity.

Oxygen is critical for all metazoan organisms on the earth and impacts various biological processes in physiological and pathological conditions. While oxygen-sensing systems inducing acute hypoxic responses, including the hypoxia-inducible factor pathway, have been identified, those operating in prolonged hypoxia remain to be elucidated. Here we show that pyridoxine 5'-phosphate oxidase (PNPO), which catalyses bioactivation of vitamin B6, serves as an oxygen sensor and regulates lysosomal activity in macrophages. Decreased PNPO activity under prolonged hypoxia reduced an active form of vitamin B6, pyridoxal 5'-phosphate (PLP), and inhibited lysosomal acidification, which in macrophages led to iron dysregulation, TET2 protein loss and delayed resolution of the inflammatory response. Among PLP-dependent metabolism, supersulfide synthesis was suppressed in prolonged hypoxia, resulting in the lysosomal inhibition and consequent proinflammatory phenotypes of macrophages. The PNPO-PLP axis creates a distinct layer of oxygen sensing that gradually shuts down PLP-dependent metabolism in response to prolonged oxygen deprivation.

Bag1 protein loss sensitizes mouse embryonic fibroblasts to glutathione depletion.

Bcl2-associated athanogene-1 protein (Bag1) acts as a co-chaperone of heat shock protein 70 and heat shock cognate 70 and regulates multiple cellular processes, including cell proliferation, apoptosis, environmental stress response, and drug resistance. Since Bag1 knockout mice exhibited fetal lethality, the in vivo function of Bag1 remains unclear. In this study, we established a mouse line expressing Bag1 gene missing exon 5, which corresponds to an encoding region for the interface of heat shock protein 70/heat shock cognate 70. Despite mice carrying homoalleles of the Bag1 mutant (Bag1Δex5) expressing undetectable levels of Bag1, Bag1Δex5 homozygous mice developed without abnormalities. Bag1Δex5 protein was found to be highly unstable in cells and in vitro. We found that the growth of mouse embryonic fibroblasts derived from Bag1Δex5-homo mice was attenuated by doxorubicin and a glutathione (GSH) synthesis inhibitor, buthionine sulfoximine. In response to buthionine sulfoximine, Bag1Δex5-mouse embryonic fibroblasts exhibited a higher dropping rate of GSH relative to the oxidized glutathione level. In addition, Bag1 might mitigate cellular hydrogen peroxide levels. Taken together, our results demonstrate that the loss of Bag1 did not affect mouse development and that Bag1 is involved in intracellular GSH homeostasis, namely redox homeostasis.

A fine-scale genetic map of the Japanese population.

Genetic maps are fundamental resources for linkage and association studies. A fine-scale genetic map can be constructed by inferring historical recombination events from the genome-wide structure of linkage disequilibrium-a non-random association of alleles among loci-by using population-scale sequencing data. We constructed a fine-scale genetic map and identified recombination hotspots from 10 092 551 bi-allelic high-quality autosomal markers segregating among 150 unrelated Japanese individuals whose genotypes were determined by high-coverage (30×) whole-genome sequencing, and the genotype quality was carefully controlled by using their parents' and offspring's genotypes. The pedigree information was also utilized for haplotype phasing. The resulting genome-wide recombination rate profiles were concordant with those of the worldwide population on a broad scale, and the resolution was much improved. We identified 9487 recombination hotspots and confirmed the enrichment of previously known motifs in the hotspots. Moreover, we demonstrated that the Japanese genetic map improved the haplotype phasing and genotype imputation accuracy for the Japanese population. The construction of a population-specific genetic map will help make genetics research more accurate.

The gut lactic acid bacteria metabolite, 10-oxo-cis-6,trans-11-octadecadienoic acid, suppresses inflammatory bowel disease in mice by modulating the NRF2 pathway and GPCR-signaling.

Various gut bacteria, including Lactobacillus plantarum, possess several enzymes that produce hydroxy fatty acids (FAs), oxo FAs, conjugated FAs, and partially saturated FAs from polyunsaturated FAs as secondary metabolites. Among these derivatives, we identified 10-oxo-cis-6,trans-11-octadecadienoic acid (γKetoC), a γ-linolenic acid (GLA)-derived enon FA, as the most effective immunomodulator, which inhibited the antigen-induced immunoactivation and LPS-induced production of inflammatory cytokines. The treatment with γKetoC significantly suppressed proliferation of CD4+ T cells, LPS-induced activation of bone marrow-derived dendritic cells (BMDCs), and LPS-induced IL-6 release from peritoneal cells, splenocytes, and CD11c+ cells isolated from the spleen. γKetoC also inhibited the release of inflammatory cytokines from BMDCs stimulated with poly-I:C, R-848, or CpG. Further in vitro experiments using an agonist of GPR40/120 suggested the involvement of these GPCRs in the effects of γKetoC on DCs. We also found that γKetoC stimulated the NRF2 pathway in DCs, and the suppressive effects of γKetoC and agonist of GPR40/120 on the release of IL-6 and IL-12 were reduced in Nrf2-/- BMDCs. We evaluated the role of NRF2 in the anti-inflammatory effects of γKetoC in a dextran sodium sulfate-induced colitis model. The oral administration of γKetoC significantly reduced body weight loss, improved stool scores, and attenuated atrophy of the colon, in wild-type C57BL/6 and Nrf2+/- mice with colitis. In contrast, the pathology of colitis was deteriorated in Nrf2-/- mice even with the administration of γKetoC. Collectively, the present results demonstrated the involvement of the NRF2 pathway and GPCRs in γKetoC-mediated anti-inflammatory responses.

GWAS meta-analysis of kidney function traits in Japanese populations.

BACKGROUND: Genetic epidemiological evidence for the kidney function traits in East Asian population including Japanese remain still relatively unclarified. Especially, the number of GWASs for kidney traits reported still remains limited, and the sample size of each independent study is relatively small. Given the genetic variability between ancestries/ethnicities, implementation of GWAS with sufficiently large sample sizes in specific population of Japanese is considered meaningful. METHODS: We conducted the GWAS meta-analyses of kidney traits by leveraging the GWAS summary data of the representative large genome cohort studies with about 200,000 Japanese participants (n = 202,406 for estimated glomerular filtration rate [eGFR] and n = 200,845 for serum creatinine [SCr]). RESULTS: In the present GWAS meta-analysis, we identified 110 loci with 169 variants significantly associated with eGFR (on chromosomes 1-13 and 15-22; p < 5×10-8), whereas we also identified 112 loci with 176 variants significantly associated with SCr (on chromosomes 1-22; p < 5×10-8), of which one locus (more than 1Mb distant from known loci) with one variant (CD36 rs146148222 on chromosome 7) for SCr was considered as the truly novel finding. CONCLUSIONS: The present GWAS meta-analysis of largest genome cohort studies in Japanese provided some original genomic loci associated with kidney function in Japanese, which may contribute to the possible development of personalized prevention of kidney diseases based on genomic information in the near future.

Differential squamous cell fates elicited by NRF2 gain of function versus KEAP1 loss of function.

Clinical evidence has revealed that high-level activation of NRF2 caused by somatic mutations in NRF2 (NFE2L2) is frequently detected in esophageal squamous cell carcinoma (ESCC), whereas that caused by somatic mutations in KEAP1, a negative regulator of NRF2, is not. Here, we aspire to generate a mouse model of NRF2-activated ESCC using the cancer-derived NRF2L30F mutation and cancer driver mutant TRP53R172H. Concomitant expression of NRF2L30F and TRP53R172H results in formation of NRF2-activated ESCC-like lesions. In contrast, while squamous-cell-specific deletion of KEAP1 induces similar NRF2 hyperactivation, the loss of KEAP1 combined with expression of TRP53R172H does not elicit the formation of ESCC-like lesions. Instead, KEAP1-deleted cells disappear from the esophageal epithelium over time. These findings demonstrate that, while cellular NRF2 levels are similarly induced, NRF2 gain of function and KEAP1 loss of function elicits distinct fates of squamous cells. The NRF2L30F mutant mouse model developed here will be instrumental in elucidating the mechanistic basis leading to NRF2-activated ESCC.

The drug-specific properties of hypoxia-inducible factor-prolyl hydroxylase inhibitors in mice reveal a significant contribution of the kidney compared to the liver to erythropoietin induction.

AIMS: Kidney disease often leads to anemia due to a defect in the renal production of the erythroid growth factor erythropoietin (EPO), which is produced under the positive regulation of hypoxia-inducible transcription factors (HIFs). Chemical compounds that inhibit HIF-prolyl hydroxylases (HIF-PHs), which suppress HIFs, have been developed to reactivate renal EPO production in renal anemia patients. Currently, multiple HIF-PH inhibitors, in addition to conventional recombinant EPO reagents, are used for renal anemia treatment. This study aimed to elucidate the therapeutic mechanisms and drug-specific properties of HIF-PH inhibitors. METHODS AND KEY FINDINGS: Gene expression analyses and mass spectrometry revealed that HIF-PH inhibitors (daprodustat, enarodustat, molidustat, and vadadustat) alter Epo gene expression levels in the kidney and liver in a drug-specific manner, with different pharmacokinetics in the plasma and urine after oral administration to mice. The drug specificity revealed the dominant contribution of EPO induction in the kidneys rather than in the liver to plasma EPO levels after HIF-PH inhibitor administration. We also found that several HIF-PH inhibitors directly induce duodenal gene expression related to iron intake, while these drugs indirectly suppress hepatic hepcidin expression to mobilize stored iron for hemoglobin synthesis through induction of the EPO-erythroferrone axis. SIGNIFICANCE: Renal EPO induction is the major target of HIF-PH inhibitors for their therapeutic effects on erythropoiesis. Additionally, the drug-specific properties of HIF-PH inhibitors in EPO induction and iron metabolism have been shown in mice, providing useful information for selecting the proper HIF-PH inhibitor for each renal anemia patient.

Enhancing Wear Resistance in Functionally Graded Metallic Components: Insights from Nanoindentation and Mechanical Analysis.

To manufacture metallic components with high wear resistance, treatments such as nitriding and carburising followed by quenching and tempering (NQT and CQT, respectively) are applied to various types of steel to increase the hardness (H) of the friction surface. However, the wear mechanism of the resulting functionally graded materials has not been fully understood. In this study, specimens of industrial 99.82% pure iron treated with NQT at 913 and 1033 K, and CQT at 1203 K, as well as hot-rolled sheets without heat treatment were examined by performing nanoindentation tests to measure changes in their H, reduced Young's moduli (Er), elastic deformation energies (We), and plastic deformation energies (Wp) along the depth direction. The relationship between Wp/We and the elastic strain resistance (H/Er) can be expressed for all specimens via the equation Wp/We = -1.0 + 0.16 (H/Er)-1. Furthermore, the obtained H/Er av measured at 5 µm intervals based on the specimen profile and wear volume has a good correlation depending to the sliding distance, as confirmed by the results of the ring-on-plate sliding tests conducted for the carbon-treated, nitrogen-treated, and hot-rolled specimens. This study provides a new approach, using H/Er parameters to identify the dominant factors affecting wear resistance at the initial stage of wear that may contribute to the development of wear-resistant materials.

The Health History of First-Degree Relatives' Dyslipidemia Can Affect Preferences and Intentions following the Return of Genomic Results for Monogenic Familial Hypercholesterolemia.

Genetic testing is key in modern healthcare, particularly for monogenic disorders such as familial hypercholesterolemia. This Tohoku Medical Megabank Project study explored the impact of first-degree relatives' dyslipidemia history on individual responses to familial hypercholesterolemia genomic results. Involving 214 participants and using Japan's 3.5KJPN genome reference panel, the study assessed preferences and intentions regarding familial hypercholesterolemia genetic testing results. The data revealed a significant inclination among participants with a family history of dyslipidemia to share their genetic test results, with more than 80% of participants intending to share positive results with their partners and children and 98.1% acknowledging the usefulness of positive results for personal health management. The study underscores the importance of family health history in genetic-testing perceptions, highlighting the need for family-centered approaches in genetic counseling and healthcare. Notable study limitations include the regional scope and reliance on questionnaire data. The study results emphasize the association between family health history and genetic-testing attitudes and decisions.

Development of phenotyping algorithms for hypertensive disorders of pregnancy (HDP) and their application in more than 22,000 pregnant women.

Recently, many phenotyping algorithms for high-throughput cohort identification have been developed. Prospective genome cohort studies are critical resources for precision medicine, but there are many hurdles in the precise cohort identification. Consequently, it is important to develop phenotyping algorithms for cohort data collection. Hypertensive disorders of pregnancy (HDP) is a leading cause of maternal morbidity and mortality. In this study, we developed, applied, and validated rule-based phenotyping algorithms of HDP. Two phenotyping algorithms, algorithms 1 and 2, were developed according to American and Japanese guidelines, and applied into 22,452 pregnant women in the Birth and Three-Generation Cohort Study of the Tohoku Medical Megabank project. To precise cohort identification, we analyzed both structured data (e.g., laboratory and physiological tests) and unstructured clinical notes. The identified subtypes of HDP were validated against reference standards. Algorithms 1 and 2 identified 7.93% and 8.08% of the subjects as having HDP, respectively, along with their HDP subtypes. Our algorithms were high performing with high positive predictive values (0.96 and 0.90 for algorithms 1 and 2, respectively). Overcoming the hurdle of precise cohort identification from large-scale cohort data collection, we achieved both developed and implemented phenotyping algorithms, and precisely identified HDP patients and their subtypes from large-scale cohort data collection.

Dietary habits and plasma lipid concentrations in a general Japanese population.

INTRODUCTION: Accumulating data on the associations between food consumption and lipid composition in the body is essential for understanding the effects of dietary habits on health. OBJECTIVES: As part of omics research in the Tohoku Medical Megabank Community-Based Cohort Study, this study sought to reveal the dietary impact on plasma lipid concentration in a Japanese population. METHODS: We conducted a correlation analysis of food consumption and plasma lipid concentrations measured using mass spectrometry, for 4032 participants in Miyagi Prefecture, Japan. RESULTS: Our analysis revealed 83 marked correlations between six food categories and the concentrations of plasma lipids in nine subclasses. Previously reported associations, including those between seafood consumption and omega-3 fatty acids, were validated, while those between dairy product consumption and odd-carbon-number fatty acids (odd-FAs) were validated for the first time in an Asian population. Further analysis suggested that dairy product consumption is associated with odd-FAs via sphingomyelin (SM), which suggests that SM is a carrier of odd-FAs. These results are important for understanding odd-FA metabolism with regards to dairy product consumption. CONCLUSION: This study provides insight into the dietary impact on plasma lipid concentration in a Japanese population.

Strain-dependent modifiers exacerbate familial leukemia caused by GATA1-deficiency.

GATA1 plays a critical role in differentiation, proliferation, and apoptosis during erythropoiesis. We developed a Gata1 knock-down allele (Gata1.05) that results in GATA1 expression at 5% of endogenous level. In female mice heterozygous for both the Gata1.05 and wild-type alleles, we observed a predisposition to erythroblastic leukemia three to six months after birth. Since no male Gata1.05 progeny survive gestation, we originally maintained heterozygous females in a mixed genetic background of C57BL/6J and DBA/2 strains. Around 30% of these mice reproducibly develop leukemia, but the other subset did not develop leukemia, even though they harbor a high number of preleukemic erythroblasts. These observations prompted us to hypothesize that there may be potential influence of genetic determinants on the progression of Gata1.05-driven hematopoietic precursors to full-blown leukemia. In an initial examination of Gata1.05/X mice backcrossed into C3H/He, BALB/c, DBA/2, C57BL/6J and 129X1/SvJ strains, we discerned that the backgrounds of C57BL/6J and 129X1/SvJ significantly expedited leukemia onset in Gata1.05/X mice. Conversely, backgrounds of C3H/He, BALB/c and DBA/2 did not substantially modify the effect of the Gata1 mutation. This indicates the existence of genetic modifiers that accentuate Gata1.05 leukemogenesis. Subsequent cohort studies evaluated Gata1.05/X mice within mix backgrounds of BALB/c:129X1/SvJ and BALB/c:C57BL/6J. In these settings, Gata1.05-driven leukemia manifested in autosomal dominant patterns within the 129X1/SvJ background and in autosomal recessive patterns within C57BL/6J background. To the best of our knowledge, this study provides the inaugural evidence of genetic modifiers that can reshape the outcome based on leukemia-associated gene signatures.

The abundance of the short GATA1 isoform affects megakaryocyte differentiation and leukemic predisposition in mice.

Transcription factor GATA1 controls the delicate balance between proliferation, differentiation and apoptosis in both the erythroid and megakaryocytic lineages. In addition to full-length GATA1, there is an GATA1 isoform, GATA1s, that lacks the amino-terminal transactivation domain. Somatic GATA1 mutations that lead to the exclusive production of GATA1s appear to be necessary and sufficient for the development of a preleukemic condition called transient myeloproliferative disorder (TMD) in Down syndrome newborns. Subsequent clonal evolution among latent TMD blasts leads to the development of acute megakaryoblastic leukemia (AMKL). We originally established transgenic mice that express only GATA1s, which exhibit hyperproliferation of immature megakaryocytes, thus mimicking human TMD; however, these mice never developed AMKL. Here, we report that transgenic mice expressing moderate levels of GATA1s, i.e., roughly comparable levels to endogenous GATA1, were prone to develop AMKL in young adults. However, when GATA1s is expressed at levels significantly exceeding that of endogenous GATA1, the development of leukemia was restrained in a dose dependent manner. If the transgenic increase of GATA1s in progenitors remains small, GATA1s supports the terminal maturation of megakaryocyte progenitors insufficiently, and consequently the progenitors persisted, leading to an increased probability for acquisition of additional genetic modifications. In contrast, more abundant GATA1s expression compensates for this maturation block, enabling megakaryocytic progenitors to fully differentiate. This study provides evidence for the clinical observation that the abundance of GATA1s correlates well with the progression to AMKL in Down syndrome.

Progress report of the Tohoku Medical Megabank Community-Based Cohort Study: Study profile of the repeated center-based survey during second period in Miyagi Prefecture.

BACKGROUND: The purpose of this study was to report the basic profile of the Miyagi Prefecture part of a repeated center-based survey during the second period (2nd period survey) of the Tohoku Medical Megabank Community-Based Cohort Study (TMM CommCohort Study), as well as the participants' characteristics based on their participation type in the baseline survey. METHODS: The 2nd period survey, conducted from June 2017 to March 2021, included participants of the TMM CommCohort Study (May 2013 to March 2016). In addition to the questionnaire, blood, urine, and physiological function tests were performed during the 2nd period survey. There were three main ways of participation in the baseline survey: Type 1, Type 1 additional, or Type 2 survey. The 2nd period survey was conducted in the same manner as the Type 2 survey, which was based on the community support center (CSC). RESULTS: In Miyagi Prefecture, 29,383 (57.7%) of 50,967 participants participated in the 2nd period survey. The participation rate among individuals who had visited the CSC was approximately 80%. Although some factors differed depending on the participation type in the baseline survey, the 2nd period survey respondents in the Type 1 and Type 2 survey groups at baseline had similar traits. CONCLUSIONS: The 2nd period survey of the TMM CommCohort Study provided detailed follow-up information. Following up on the health conditions of the participants will clarify the long-term effects of disasters and contribute to personalized prevention.

Dietary melatonin and liver cancer incidence in Japan: From the Takayama study.

There is some biological plausibility that exogenous melatonin plays a role in preventing liver carcinogenesis. There has been little research on the association between melatonin intake in a normal diet and health outcomes. We evaluated the association between dietary melatonin intake and the incidence of liver cancer in a population-based prospective study in Japan. This study included 30,824 residents of Takayama city who were 35 years of age or older in 1992 and had participated in the Takayama study, Japan. Dietary intake was assessed using a validated food frequency questionnaire at the baseline. Melatonin content in foods was measured by liquid chromatography-tandem mass spectrometry. Cancer incidence was confirmed through regional population-based cancer registries in Gifu. Liver cancer was defined as code C22 according to the International Classification of Diseases and Related Health Problems, 10th Revision. Hazard ratios for liver cancer were estimated for the tertile groups of melatonin intake using a Cox proportional hazards model. During the mean follow-up period of 13.6 years, 189 individuals developed liver cancer. Compared with subjects in the lowest tertile of melatonin intake, those in the middle and highest tertiles had decreased risks of liver cancer, with a significant linear trend after multivariate adjustments (hazard ratios: 0.64 and 0.65, respectively, trend p = 0.023). There was no significant interaction by sex (interaction p = 0.54). This initial finding, which needs to be confirmed by further studies, suggests that consuming melatonin-containing foods might play a role in the prevention of liver cancer.