One-carbon genetic variants and the role of MTHFD1 1958G>A in liver and colon cancer risk according to global DNA methylation

Low-Penetrance Susceptibility Variants in Colorectal Cancer-Current Outlook in the Field

Colorectal cancer (CRC) is one of the most frequent and mortality-causing neoplasia, with various distributions between populations. Strong hereditary predispositions are the causatives of a small percentage of CRC, and most cases have no transparent genetic background. This is a vast arena for exploring cancer low-susceptibility genetic variants. Nonetheless, the research that has been conducted to date has failed to deliver consistent conclusions and often features conflicting messages, causing chaos in this field. Therefore, we decided to organize the existing knowledge on this topic. We screened the PubMed and Google Scholar databases. We drew up markers by gene locus gathered by hallmark: oncogenes, tumor suppressor genes, genes involved in DNA damage repair, genes involved in metabolic pathways, genes involved in methylation, genes that modify the colonic microenvironment, and genes involved in the immune response. Low-penetration genetic variants increasing the risk of cancer are often population-specific, hence the urgent need for large-scale testing. Such endeavors can be successful only when financial decision-makers are united with social educators, medical specialists, genetic consultants, and the scientific community. Countries' policies should prioritize research on this subject regardless of cost because it is the best investment. In this review, we listed potential low-penetrance CRC susceptibility alleles whose role remains to be established.

Assessment of circulating proteins in thyroid cancer: Proteome-wide Mendelian randomization and colocalization analysis

The causality between circulating proteins and thyroid cancer (TC) remains unclear. We employed five large-scale circulating proteomic genome-wide association studies (GWASs) with up to 100,000 participants and a TC meta-GWAS (nCase = 3,418, nControl = 292,703) to conduct proteome-wide Mendelian randomization (MR) and Bayesian colocalization analysis. Protein and gene expressions were validated in thyroid tissue. Through MR analysis, we identified 26 circulating proteins with a putative causal relationship with TCs, among which NANS protein passed multiple corrections (P BH = 3.28e-5, 0.05/1,525). These proteins were involved in amino acids and organic acid synthesis pathways. Colocalization analysis further identified six proteins associated with TCs (VCAM1, LGMN, NPTX1, PLEKHA7, TNFAIP3, and BMP1). Tissue validation confirmed BMP1, LGMN, and PLEKHA7's differential expression between normal and TC tissues. We found limited evidence for linking circulating proteins and the risk of TCs. Our study highlighted the contribution of proteins, particularly those involved in amino acid metabolism, to TCs.

Association Between Multiple Single Nucleotide Polymorphisms in Folate Metabolism Pathway and Breast Cancer Risk in Georgian Women: A Case-Control Study

Background

The folate metabolism pathway plays an integral part in DNA synthesis, methylation, and repair. Methylenetetrahydrofolate reductase (MTHFR) and methylenetetrahydrofolate dehydrogenase (MTHFD1) are both enzymes that are involved in this pathway, and the single nucleotide polymorphisms (SNPs) in genes coding for them have modulatory effects on DNA expression. This study aimed to investigate the relationship between MTHFR C677T (rs1801133) and MTHFD1 G1958A (rs2236225) polymorphisms and the risk of developing breast cancer in Georgian women.

Methods

A case-control study was performed examining the MTHFR C677T and MTHFD1 G1958A SNP in breast cancer-confirmed cases and healthy matched controls. Real time-polymerase chain reaction (PCR) was used to genotype SNPs. The case individuals' pathology reports were obtained following surgeries for cancer characteristic data. Statistical analysis was performed to investigate the significance of the acquired data.

Results

Statistical analysis of MTHFR C677T SNP revealed that the CT genotype increased the risk of breast cancer by 2.17 folds in the over-dominant model. Statistical analysis of MTHFD1 G1958A SNP showed that the GA genotype increased the risk of breast cancer by 4.12 folds in the codominant model and 2.41 folds in the over-dominant model. No statistically significant link was found between genotypes and lymph node status, however, patients with the CT genotype had higher percentages of proliferative activity.

Conclusions

Breast cancer seems to have a statistically significant association with the CT genotype in MTHFR C677T and the GA genotype in MTHFD1 G1958A in Georgian women.

The Mediating Effect of the Choline-to-Betaine Ratio on the Association Between PEMT rs7946 and Digestive System Cancer: A Nested Case-Control Study in a Chinese Population

Background

The enzyme phosphatidylethanolamine N-methyltransferase (PEMT) is responsible for synthesizing phosphatidylcholine by methylating phosphatidylethanolamine. We hypothesized that a polymorphism of the PEMT gene, rs7946, is involved in carcinogenesis.

Objectives

We aimed to investigate the relationship between PEMT rs7946 and digestive system cancer and examine possible effect modifiers and mediators.

Methods

We conducted a nested, case-control study within the China H-type Hypertension Registry Study, including 751 cases and 1:1 matched controls. To assess the association of PEMT rs7946 and digestive system cancer, we estimated odds ratios with 95% confidence intervals (CIs) using conditional logistic regression. We used the bootstrap test to examine the potential mediating effects of related metabolites.

Results

Our results revealed that wild-type homozygous CC genotype carriers of PEMT rs7946 had a significantly increased risk [odds ratio (OR): 1.31; 95% CI: 1.04, 1.66; P = 0.023] compared with the TT/CT combined genotypes. The effect was found to be more pronounced in individuals with a lower choline-to-betaine ratio (<0.412, P-interaction = 0.021). Furthermore, the mediation analysis indicated that the choline-to-betaine ratio played a significant role in mediating 13.55% of the association between PEMT rs7946 and digestive system cancer (P = 0.018).

Conclusions

Our study suggested that PEMT rs7946 may affect risk of digestive system cancer through direct and indirect pathways, and the choline-to-betaine ratio may partially mediate the indirect effect.This trial was registered at Chinese Clinical Trial Registry as ChiCTR1800017274.

Common Variants in One-Carbon Metabolism Genes (MTHFR, MTR, MTHFD1) and Depression in Gynecologic Cancers

We investigated the association between methylenetetrahydrofolate reductase (gene MTHFR 677C>T, rs1801133), 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR 2756A>G, rs1805087), and methylenetetrahydrofolate dehydrogenase, cyclohydrolase and formyltetrahydrofolate synthetase 1 (gene MTHFD1 1958G>A, rs2236225)-well-studied functional variants involved in one-carbon metabolism-and gynecologic cancer risk, and the interaction between these polymorphisms and depression. A total of 200 gynecologic cancer cases and 240 healthy controls were recruited to participate in this study. Three single-nucleotide variants (SNVs) (rs1801133, rs1805087, rs2236225) were genotyped using the PCR-restriction fragment length polymorphism method. Depression was assessed in all patients using the Hamilton Depression Scale. Depression was statistically significantly more frequent in women with gynecologic cancers (69.5% vs. 34.2% in controls, p < 0.001). MTHFD1 rs2236225 was associated with an increased risk of gynecologic cancers (in dominant OR = 1.53, p = 0.033, and in log-additive models OR = 1.37, p = 0.024). Moreover, an association was found between depression risk and MTHFR rs1801133 genotypes in the controls but not in women with gynecologic cancers (in codominant model CC vs. TT: OR = 3.39, 95%: 1.49-7.74, p = 0.011). Cancers of the female reproductive system are associated with the occurrence of depression, and ovarian cancer may be associated with the rs2236225 variant of the MTHFD1 gene. In addition, in healthy aging women in the Polish population, the rs1801133 variant of the MTHFR gene is associated with depression.

The negative effect of G1958A polymorphism on MTHFD1 protein stability and HCC growth

PURPOSE

Methylenetetrahydrofolate dehydrogenase (MTHFD1), a key enzyme on the folate pathway, has been implicated in the tumor development of distinct types of cancers. The single nucleotide polymorphism (SNP) of 1958G > A mutation in the coding region of MTHFD1 (arginine 653 is mutated into glutamine) has been detected in a significant proportion of clinical samples of hepatocellular carcinoma (HCC). METHODS : Hepatoma cell lines, 97H and Hep3B were used. The expression of MTHFD1 and SNP mutation protein was determined by immunoblotting analysis. The protein ubiquitination of MTHFD1 was detected by immunoprecipitation analysis. The post-translational modification sites and interacting proteins of MTHFD1 in the presence of G1958A SNP were identified by mass spectrometry. Metabolic flux analysis was used to detect the synthesis of relevant metabolites sourced from serine isotope.

RESULTS

The present study showed G1958A SNP of MTHFD1, encoding MTHFD1 R653Q, was associated with the attenuated protein stability caused by ubiquitination-mediated protein degradation. Mechanistically, MTHFD1 R653Q displayed an enhanced binding to the E3 ligase TRIM21, which was responsible for the augmented ubiquitination, and MTHFD1 K504 was identified to be the primary ubiquitination site. The subsequent metabolite analysis revealed MTHFD1 R653Q resulted in the repressed flux of serine-derived methyl group into metabolite precursors for purine synthesis, and the compromised purine synthesis was demonstrated to be responsible for the impeded growth capability in MTHFD1 R653Q-expressing cells. Moreover, the suppressive effect of MTHFD1 R653Q expression in tumorigenesis was verified by xenograft analysis, and the relationship between MTHFD1 G1958A SNP and its protein levels was revealed in clinical human liver cancer specimens.

CONCLUSION

Our results uncovered an unidentified mechanism underlying of the impact of G1958A SNP on MTHFD1 protein stability and tumor metabolism in HCC. which provides a molecular basis for the according clinical management when considering MTHFD1 as a therapeutic target.

DNA methylation in cell plasticity and malignant transformation in liver diseases

The liver possesses extraordinary regenerative capacity mainly attributable to the ability of hepatocytes (HCs) and biliary epithelial cells (BECs) to self-replicate. This ability is left over from their bipotent parent cell, the hepatoblast, during development. When this innate regeneration is compromised due to the absence of proliferative parenchymal cells, such as during cirrhosis, HCs and BEC can transdifferentiate; thus, adding another layer of complexity to the process of liver repair. In addition, dysregulated lineage maintenance in these two cell populations has been shown to promote malignant growth in experimental conditions. Here, malignant transformation, driven in part by insufficient maintenance of lineage reprogramming, contributes to end-stage liver disease. Epigenetic changes are key drivers for cell fate decisions as well as transformation by finetuning overall transcription and gene expression. In this review, we address how altered DNA methylation contributes to the initiation and progression of hepatic cell fate conversion and cancer formation. We also discussed the diagnostic and therapeutic potential of targeting DNA methylation in liver cancer, its current limitations, and what future research is necessary to facilitate its contribution to clinical translation.

Host pharmacogenetic factors that may affect liver neoplasm incidence upon using direct-acting antivirals for treating hepatitis C infection

Introduction

Direct-acting antivirals (DAAs) represent a breakthrough in hepatitis C virus (HCV) treatment as they directly inhibit HCV nonstructural (NS) proteins (NS3/4A, NS5A, and NS5B). However, ongoing debates exist regarding their relationship with hepatocellular carcinoma (HCC) whose incidence is widely debated among investigators. This study was conducted to identify host pharmacogenetic factors that may influence HCC incidence upon using HCV DAAs.

Materials and methods

Details regarding 16 HCV DAAs were collected from literature and DrugBank database. Digital structures of these drugs were fed into the pharmacogenomics/pharmacovigilance in-silico pipeline (PHARMIP) to predict the genetic factors that may underpin HCC development.

Results

We identified 184 unique genes and 40 unique variants that may have key answers for the DAA/HCC paradox. These findings could be used in different methods to aid in the precise application of HCV DAAs and minimize the proposed risk for HCC. All results could be accessed at: https://doi.org/10.17632/8ws8258hn3.2.

Discussion

All the identified factors are evidence related to HCC and significantly predicted by PHARMIP as DAA targets. We discuss some examples of the methods of using these results to address the DAA/HCC controversy based on the following three primary levels: 1 - individual DAA drug, 2 - DAA subclass, and 3 - the entire DAA class. Further wet laboratory investigation is required to evaluate these results.

Genetic variants in the folate metabolic pathway genes predict cutaneous melanoma-specific survival

BACKGROUND

Folate metabolism plays an important role in DNA methylation and nucleic acid synthesis and thus may function as a regulatory factor in cancer development. Genome-wide association studies (GWASs) have identified some single-nucleotide polymorphisms (SNPs) associated with cutaneous melanoma-specific survival (CMSS), but no SNPs were found in genes involved in the folate metabolic pathway.

OBJECTIVES

To examine associations between SNPs in folate metabolic pathway genes and CMSS.

METHODS

We comprehensively evaluated 2645 (422 genotyped and 2223 imputed) common SNPs in folate metabolic pathway genes from a published GWAS of 858 patients from The University of Texas MD Anderson Cancer Center and performed the validation in another GWAS of 409 patients from the Nurses' Health Study and Health Professionals Follow-up Study, in which 95/858 (11·1%) and 48/409 (11·7%) patients died of cutaneous melanoma, respectively.

RESULTS

We identified two independent SNPs (MTHFD1 rs1950902 G>A and ALPL rs10917006 C>T) to be associated with CMSS in both datasets, and their meta-analysis yielded an allelic hazards ratio of 1·75 (95% confidence interval 1·32-2·32, P = 9·96 × 10-5 ) and 2·05 (1·39-3·01, P = 2·84 × 10-4 ), respectively. The genotype-phenotype correlation analyses provided additional support for the biological plausibility of these two variants' roles in tumour progression, suggesting that variation in SNP-related mRNA expression levels is likely to be the mechanism underlying the observed associations with CMSS.

CONCLUSIONS

Two possibly functional genetic variants, MTHFD1 rs1950902 and ALPL rs10917006, were likely to be independently or jointly associated with CMSS, which may add to personalized treatment in the future, once further validated. What is already known about this topic? Existing data show that survival rates vary among patients with melanoma with similar clinical characteristics; therefore, it is necessary to identify additional complementary biomarkers for melanoma-specific prognosis. A hypothesis-driven approach, by pooling the effects of single-nucleotide polymorphisms (SNPs) in a specific biological pathway as genetic risk scores, may provide a prognostic utility, and genetic variants of genes in folate metabolism have been reported to be associated with cancer risk. What does this study add? Two genetic variants in the folate metabolic pathway genes, MTHFD1 rs1950902 and ALPL rs10917006, are significantly associated with cutaneous melanoma-specific survival (CMSS). What is the translational message? The identification of genetic variants will make a risk-prediction model possible for CMSS. The SNPs in the folate metabolic pathway genes, once validated in larger studies, may be useful in the personalized management and treatment of patients with cutaneous melanoma.

The influence of polymorphisms of xenobiotic-metabolizing and DNA repair genes in DNA damage, telomere length and global DNA methylation evaluated in open-cast coal mining workers

Coal plants represent one of the main sources of environmental pollution due to the combustion process of this mineral and the consequent release of gases and particles which, in significant quantities, can lead to a potential risk to health and the environment. The susceptibility of individuals to the genotoxic effects of coal mining can be modulated by genetic variations in the xenobiotic detoxification and DNA repair processes. The aim of this study was to evaluate if xenobiotic metabolism polymorphism, base excision repair polymorphisms and non-homologous end joining repair polymorphism, could modify individual susceptibility to genomic instability and epigenetic alterations induced in workers by occupational exposure to coal. In this study, polymerase chain reaction was used to examine the polymorphic sites. The sample population comprising 70 coal mine workers and 71 workers non-exposed to coal. Our results demonstrated the effect of individual genotypes on different biomarkers evaluated. Significant decrease in % of global DNA methylation were observed in CYP1A1 Val/- exposed individuals compared to CYP1A1 Ile/Ile individuals. Coal workers who carried the XRCC4 Ile/Ile genotype showed decrease NBUD frequencies, while the XRCC4 Thr/- genotype was associated with decrease in Buccal micronucleus cells for the group not exposed. No influence of GSTM1 null, GSTT1 null, GSTP1 Ile105Val, hOGG1 Ser326Cys, XRCC1 Arg194Trp polymorphisms was observed. Thus, the current study reinforces the importance of considering the effect of metabolizing and repair variant genotypes on the individual susceptibility to incorporate DNA damage, as these processes act in a coordinated manner to determine the final response to coal exposure.

MTHFD1L, A Folate Cycle Enzyme, Is Involved in Progression of Colorectal Cancer

Identification of new molecular targets is needed for the treatment of colorectal cancer (CRC). Methylenetetrahydrofolate dehydrogenase 1 like (MTHFD1L), an enzyme in the folate cycle, is involved in formate generation and therefore in one-carbon metabolism. Here, we examined the expression and the role of MTHFD1L in CRC progression. Bioinformatics analysis of several public databases showed overexpression of MTHFD1L in CRC tissues as compared to normal tissues. Quantitative real-time PCR and Western blotting revealed that expressions of MTHFD1L RNA and protein were higher in CRC tissues compared to their corresponding normal tissues of CRC patients. Immunohistochemical staining demonstrated higher cytoplasmic MTHFD1L reactivity in tumor tissues compared to paired normal tissues. Further, to determine the functional relevance of MTHFD1L, it was knocked down by an siRNA in CRC cells. Silencing of MTHFD1L inhibited CRC cell proliferation, colony formation, invasion, and migration. Thus, to our knowledge for the first time in the literature, we show that MTHFD1L is involved in CRC progression and that blocking of MTHFD1L decreases the growth of colon cancer cells, thus providing an avenue to target this enzyme with small molecule inhibitors.

Overexpression of MTHFD1 in hepatocellular carcinoma predicts poorer survival and recurrence

Aim: MTHFD1 was the enzyme providing one-carbon derivatives of tetrahydrofolate. We sought to investigate the impact of MTHFD1 on hepatocellular carcinoma (HCC). Methods: Bioinformatic analysis, western blot and immunohistochemistry were conducted to detect MTHFD1 expression in HCC. The relationships between MTHFD1 and prognosis of 172 HCCs were analyzed by Kaplan-Meier method and Cox proportional hazards model. Results: High MTHFD1 expression in HCC represented poor prognosis (overall survival p = 0.025; time to recurrence p = 0.044). Combining MTHFD1 with serum AFP, survival analysis demonstrated the prognosis of the MTHFD1 low expression and AFP ≤20 ng/ml group was better than that of the MTHFD1 high expression or AFP >20 ng/ml group and the MTHFD1 high expression and AFP >20 ng/ml group (overall survival p < 0.0001; time to recurrence p < 0.0001). Conclusion: High MTHFD1 expression in HCC indicated poorer prognosis. Combining MTHFD1 with serum AFP improved the accuracy of prognostic prediction.

Methylenetetrahydrofolate Dehydrogenase 1 (MTHFD1) is Underexpressed in Clear Cell Renal Cell Carcinoma Tissue and Transfection and Overexpression in Caki-1 Cells Inhibits Cell Proliferation and Increases Apoptosis

Background

The aims of this study were to investigate the expression of methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) in human tissue containing clear cell renal cell carcinoma (CCRCC) compared with normal renal tissue, and the effects of upregulating the expression of MTHFD1 in the human CCRCC cell line, Caki-1.

Material/Methods

Tumor and adjacent normal renal tissue were obtained from 44 patients who underwent radical nephrectomy for CCRCC. Caki-1 human CCRCC cells were divided into the control group, the empty vector (EV) group, and the plasmid-treated group that overexpressed MTHFD1. MTHFD1 mRNA and protein levels were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot, respectively. The cell counting kit-8 (CCK-8) assay measured cell viability. Flow cytometry evaluated apoptosis and the cell cycle. Western blot measured the protein levels of MTHFD1, Bax, Bcl-2, Akt, p53, and cyclin D1, and qRT-PCR determined the gene expression profiles.

Results

MTHFD1 mRNA and protein levels in CCRCC tumor tissues were significantly lower compared with adjacent normal renal tissue. MTHFD1 over-expression in Caki-1 cells inhibited cell proliferation, arrested cells in the G1 phase, increased cell apoptosis, and upregulated gene and protein expression of Bax/Bcl-2 and p53, and inhibited p-Akt, and cyclin D1.

Conclusions

MTHFD1 was underexpressed in CCRCC tissue when compared with normal renal tissue. MTHFD1 transfection of human CCRCC Caki-1 cells in vitro inhibited cell proliferation and promoted apoptosis, associated with reduced expression of cyclin D1, reduced Akt phosphorylation, and increased expression of Bax/Bcl-2 and p53.

Methylenetetrahydrofolate Dehydrogenase 1 Silencing Expedites the Apoptosis of Non-Small Cell Lung Cancer Cells via Modulating DNA Methylation

BACKGROUND Non-small cell lung cancer (NSCLC) accounts for about 85% of all types of lung cancer. Methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) is involved in DNA methylation, and DNA methylation is related to tumorigenesis. The role of MTHFD1 in NSCLC was examined in our study. MATERIAL AND METHODS The correlation between the expression of MTHFD1 and the clinicopathological features of patients diagnosed with lung cancer was investigated using the chi-square test. The viability and apoptosis of NCI-H1299 cells was respectively detected using cell counting kit-8 and flow cytometry assays. The expression levels of MTHFD1, apoptosis-related factors and DNA methyltransferase-related factors were assessed by quantitative real-time PCR (qRT-PCR) and western blot assays. RESULTS We found that MTHFD1 expression in the tumor tissues and cells was higher than that of adjacent normal tissues and cells. The survival time of patients with high MTHFD1 expression was shorter than those with low MTHFD1 expression. The expression level of MTHFD1 was related to tumor size, TNM stage, histologic grade, and metastasis, but not linked to gender and age. Besides, si-MTHFD1 significantly decreased the viability of cells in a time-dependent manner, and increased cell apoptosis. When cells were transfected with MTHFD1-siRNA, the levels of surviving and B-cell lymphoma-2 (Bcl-2) were attenuated, while p53 and Bcl-2 associated X protein (Bax) levels were enhanced. Moreover, si-MTHFD1 markedly downregulated the expression levels of DNA methyltransferase 1 (DNMT1), DNMT3a, and DNMT3b. CONCLUSIONS Collectively, our results proved that MTHFD1 silencing obviously reduced the proliferation and enhanced the apoptosis of NSCLC via suppressing DNA methylation.

Sex Differences in Genetic Associations With Longevity

IMPORTANCE

Sex differences in genetic associations with human longevity remain largely unknown; investigations on this topic are important for individualized health care.

OBJECTIVE

To explore sex differences in genetic associations with longevity.

DESIGN SETTING AND PARTICIPANTS

This population-based case-control study used sex-specific genome-wide association study and polygenic risk score (PRS) analyses to examine sex differences in genetic associations with longevity. Five hundred sixty-four male and 1614 female participants older than 100 years were compared with a control group of 773 male and 1526 female individuals aged 40 to 64 years. All were Chinese Longitudinal Healthy Longevity Study participants with Han ethnicity who were recruited in 1998 and 2008 to 2014.

MAIN OUTCOMES AND MEASURES

Sex-specific loci and pathways associated with longevity and PRS measures of joint effects of sex-specific loci.

RESULTS

Eleven male-specific and 11 female-specific longevity loci (P < 10-5) and 35 male-specific and 25 female-specific longevity loci (10-5 ≤ P < 10-4) were identified. Each of these loci's associations with longevity were replicated in north and south regions of China in one sex but were not significant in the other sex (P = .13-.97), and loci-sex interaction effects were significant (P < .05). The associations of loci rs60210535 of the LINC00871 gene with longevity were replicated in Chinese women (P = 9.0 × 10-5) and US women (P = 4.6 × 10-5) but not significant in Chinese and US men. The associations of the loci rs2622624 of the ABCG2 gene were replicated in Chinese women (P = 6.8 × 10-5) and European women (P = .003) but not significant in both Chinese and European men. Eleven male-specific pathways (inflammation and immunity genes) and 34 female-specific pathways (tryptophan metabolism and PGC-1α induced) were significantly associated with longevity (P < .005; false discovery rate < 0.05). The PRS analyses demonstrated that sex-specific associations with longevity of the 4 exclusive groups of 11 male-specific and 11 female-specific loci (P < 10-5) and 35 male-specific and 25 female-specific loci (10-5 ≤P < 10-4) were jointly replicated across north and south discovery and target samples. Analyses using the combined data set of north and south showed that these 4 groups of sex-specific loci were jointly and significantly associated with longevity in one sex (P = 2.9 × 10-70 to 1.3 × 10-39) but not jointly significant in the other sex (P = .11 to .70), while interaction effects between PRS and sex were significant (P = 4.8 × 10-50 to 1.2 × 10-16).

CONCLUSION AND RELEVANCE

The sex differences in genetic associations with longevity are remarkable, but have been overlooked by previously published genome-wide association studies on longevity. This study contributes to filling this research gap and provides a scientific basis for further investigating effects of sex-specific genetic variants and their interactions with environment on healthy aging, which may substantially contribute to more effective and targeted individualized health care for male and female elderly individuals.