Identification of rs671, a common variant of ALDH2, as a gout susceptibility locus

The pathogenesis of gout: molecular insights from genetic, epigenomic and transcriptomic studies

The pathogenesis of gout involves a series of steps beginning with hyperuricaemia, followed by the deposition of monosodium urate crystal in articular structures and culminating in an innate immune response, mediated by the NLRP3 inflammasome, to the deposited crystals. Large genome-wide association studies (GWAS) of serum urate levels initially identified the genetic variants with the strongest effects, mapping mainly to genes that encode urate transporters in the kidney and gut. Other GWAS highlighted the importance of uncommon genetic variants. More recently, genetic and epigenetic genome-wide studies have revealed new pathways in the inflammatory process of gout, including genetic associations with epigenomic modifiers. Epigenome-wide association studies are also implicating epigenomic remodelling in gout, which perhaps regulates the responsiveness of the innate immune system to monosodium urate crystals. Notably, genes implicated in gout GWAS do not include those encoding components of the NLRP3 inflammasome itself, but instead include genes encoding molecules involved in its regulation. Knowledge of the molecular mechanisms underlying gout has advanced through the translation of genetic associations into specific molecular mechanisms. Notable examples include ABCG2, HNF4A, PDZK1, MAF and IL37. Current genetic studies are dominated by participants of European ancestry; however, studies focusing on other population groups are discovering informative population-specific variants associated with gout.

Hyperuricemia Subtypes Classified According to Renal Uric Acid Handling Manifesting Distinct Phenotypic and Genetic Profiles in People With Gout

OBJECTIVE

Hyperuricemia can be stratified into four subtypes according to renal uric acid handling. The aim of this study was to comprehensively describe the biologic characteristics (including genetic background) of clinically defined hyperuricemia subtypes in two large geographically independent gout cohorts.

METHODS

Hyperuricemia subtype was defined as renal uric acid overload (ROL), renal uric acid underexcretion (RUE), combined, or renal normal. Twenty single nucleotide polymorphisms (SNPs) previously identified as gout risk loci or associated with serum urate (SU) concentration in the East Asian population were genotyped. Weighted polygenic risk scores were calculated to assess the cumulative effect of genetic risks on the subtypes.

RESULTS

Of the 4,873 participants, 8.8% had an ROL subtype, 60.9% RUE subtype, 23.1% combined subtype, and 7.2% normal subtype. The ROL subtype was independently associated with older age at onset, lower SU, tophi, and diabetes mellitus; RUE was associated with lower body mass index (BMI) and non-diabetes mellitus; the combined subtype was associated with younger age at onset, higher BMI, SU, estimated glomerular filtration rate (eGFR), and smoking; and the normal subtype was independently associated with older age at onset, lower SU, and eGFR. Thirteen SNPs were associated with gout with 6 shared loci and subtype-dependent risk loci patterns. High polygenic risk scores were associated with ROL subtype (odds ratio [OR] = 9.63, 95% confidence interval [95% CI] 4.53-15.12), RUE subtype (OR = 2.18, 95% CI 1.57-3.03), and combined subtype (OR = 6.32, 95% CI 4.22-9.48) compared with low polygenic risk scores.

CONCLUSION

Hyperuricemia subtypes classified according to renal uric acid handling have subtype-specific clinical and genetic features, suggesting subtype-unique pathophysiologic mechanisms.

Mitochondrial functioning in Rheumatoid arthritis modulated by estrogen: Evidence-based insight into the sex-based influence on mitochondria and disease

Alteration of immune response and synovium microvasculature in Rheumatoid arthritis (RA) progression has been suggested to be associated with mitochondrial functioning. Mitochondria, with maternally inherited DNA, exhibit differential response to the female hormone estrogen. Various epidemiological evidence has also shown the prominence of RA in the female population, depicting the role of estrogen in modulating the pathogenesis of RA. As estrogen regulates the expression of differential proteins and associated signaling pathways of RA, its influence on mitochondrial functioning seems evident. Thus, in this review, the studies related to mitochondria and their relation with estrogen and Rheumatoid arthritis were retrieved. We analyzed the different mitochondrial activities that are altered in RA and the possibility of their estrogenic control. The study expands to in silico analysis, revealing the differential mitochondrial proteins expressed in RA and examining these proteins as potential estrogenic targets. It was found that ALDH2, CASP3, and SOD2 are the major mitochondrial proteins involved in RA progression and are also potent estradiol targets. The analysis establishes the role of mitochondrial proteins in RA progression, which were found to be direct or indirect targets of estrogen, depicting its potential for regulating mitochondrial functions in RA.

Genetic Variations of ALDH (rs671) Are Associated With the Persistence of HBV Infection Among the Chinese Han Population

Alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2), members of the alcohol dehydrogenase family, have important roles in liver diseases. The roles of the polymorphisms of ADH1B rs1229984 and ALDH2 rs671 in hepatitis B virus (HBV) susceptibility and persistent infection were investigated in the present study. Total 1,034 patients with hepatitis B [99 acute hepatitis B (AHB), 521 chronic hepatitis B (CHB), 158 acute-on-chronic liver failure (ACLF), 159 liver cirrhosis (LC), and 97 hepatocellular carcinoma (HCC)] and 1,262 healthy controls (HCs) of the Chinese Han population were recruited, and single nucleotide polymorphisms (SNPs) of rs671 and rs1229984 were genotyped. Independent and joint roles of rs671 and rs1229984 in HBV infection were analyzed. The results showed that rs671 genotypes had a significantly different distribution among different subgroups. Compared with HCs, the frequency of rs671-AA genotype was higher in hepatitis B individuals, especially in the CHB group [adjusted OR (95%CI) = 1.899 (1.232–2.928), p = 0.003, in the co-dominant model], which showed a significant positive association. It was further confirmed that CHB individuals who carried ALDH2 rs671-AA genotype had a higher risk of persistent HBV infection and higher HBV-DNA quantitation compared with those with GG/GA genotype. In addition, the rs671-AA genotype might predict HCC incidence in patients with CHB. There were no different distributions of alleles or genotypes in rs671 mutant among AHB, ACLF, LC, or HCC groups compared with HCs. These data suggested the possible hazardous role of rs671-AA variant in HBV infection and persistence.

The genetic basis of urate control and gout: Insights into molecular pathogenesis from follow-up study of genome-wide association study loci

This review focuses on the post-genome-wide association study (GWAS) era in gout, i.e., the translation of GWAS genetic association signals into biologically informative knowledge. Analytical and experimental follow-up of individual loci, based on the identification of causal genetic variants, reveals molecular pathogenic pathways. We summarize in detail the largest GWAS in urate to date, then we review follow-up studies and molecular insights from ABCG2, HNF4A, PDZK1, MAF, GCKR, ALDH2, ALDH16A1, SLC22A12, SLC2A9, ABCC4, and SLC22A13, including the role of insulin signaling. One common factor in these pathways is the importance of transcriptional control, including the HNF4α transcription factor. The new molecular knowledge reveals new targets for intervention to manage urate levels and prevent gout.

The Aldehyde Dehydrogenase ALDH2*2 Allele, Associated with Alcohol Drinking Behavior, Dates Back to Prehistoric Times

Human alcohol-consumption behavior is partly genetically encoded. The alcohol consumption of 987 residents in Keelung, Taiwan, was evaluated by using the Alcohol Use Disorder Identification Test (AUDIT). We assessed ~750,000 genomic variants of 71 residents who drank hazardously (AUDIT score ≥ 8) and 126 residents who did not drink in their daily lives (AUDIT score = 0), using high-density single nucleotide polymorphism (SNP) arrays. The rs671 G > A manifests the highest significance of the association with drinking behavior (Fisher’s exact P = 8.75 × 10⁻⁹). It is a pleiotropic, non-synonymous variant in the aldehyde dehydrogenase 2 (ALDH2) gene. The minor allele “A”, commonly known as ALDH2*2, is associated with non-drinkers. Intriguingly, identity-by-descent haplotypes encompassing genomic regions with a median length of 1.6 (0.6–2.0) million nucleotide bases were found in all study participants with either heterozygous or homozygous ALDH2*2 (n = 81 and 13, respectively). We also analyzed a public-domain dataset with genome-wide genotypes of 2000 participants in Guangzhou, a coastal city in Southern China. Among them, 175 participants have homozygous ALDH2*2 genotype, and again, long ALDH2*2-carrying haplotypes were found in all 175 participants without exceptions. The median length of the ALDH2*2-carrying haplotype is 1.7 (0.5–2.8) million nucleotide bases. The haplotype lengths in the Keelung and Guangzhou cohorts combined indicate that the origin of the ALDH2*2 allele dates back to 7935 (7014–9381) years ago. In conclusion, the rs671 G > A is the leading genomic variant associated with the long-term drinking behavior among residents of Keelung, Taiwan. The ALDH2*2 allele has been in Asian populations since prehistoric times.

Analysis of gender-specific associations between aldehyde dehydrogenase 2 (ALDH2) rs671 genetic polymorphisms and serum uric acid levels in Han Chinese

Background

Serum uric acid (SUA) is influenced by lifestyle and genetics, and unbalanced SUA levels are linked to various common disorders. While the aldehyde dehydrogenase 2 (ALDH2) rs671 polymorphism appears to be associated with SUA levels, the evidence remains inconclusive. The aim of this study was to examine the distribution of the ALDH2 rs671 polymorphism among Han Chinese in Beijing and determine the association between this polymorphism and SUA.

Methods

A total of 6,461 randomized healthy individuals were included in the study. Biochemical indicators were tested and ALDH2 rs671 polymorphism testing was conducted for subjects enrolled in the study. The distribution of the ALDH2 rs671 polymorphism and the relationship between genotype and the levels of serum lipids and uric acid (UA) were analyzed.

Results

The ALDH2 rs671 genotype frequencies were 68.1% (G/G), 29.3% (G/A), and 2.6% (A/A). There was no significant difference in allele distribution between males and females. In males, different ALDH2 genotypes exhibited significant differences in several biochemical analytes, including body mass index (BMI), blood glucose (Glu), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), UA, glutamyl transpeptidase (GGT), and creatinine (Cr) (P<0.05). No such differences were found in females. SUA levels in G/A and A/A-carrying males were significantly lower than those of G/G-carrying males. The effect of the ALDH2 polymorphism on UA was still significant after further adjustment for factors including BMI, Glu, TC, HDL-C, Cr, and GGT.

Conclusions

The ALDH2 polymorphism is related to SUA in Beijing males, and A allele-carrying males have lower SUA levels.

Risk of gout among Taiwanese adults with ALDH-2 rs671 polymorphism according to BMI and alcohol intake

BACKGROUND

Gout stems from both modifiable and genetic sources. We evaluated the risk of gout among Taiwanese adults with aldehyde dehydrogenase-2 (ALDH2) rs671 single nucleotide polymorphism (SNP) according to body mass index (BMI) and alcohol drinking.

METHODS

We obtained information of 9253 individuals having no personal history of cancer from the Taiwan Biobank (2008-2016) and estimated the association between gout and independent variables (e.g., rs671, BMI, and alcohol drinking) using multiple logistic regression.

RESULTS

Alcohol drinking and abnormal BMI were associated with a higher risk of gout whereas the rs671 GA+AA genotype was associated with a lower risk. The odds ratios (ORs) and 95% confidence intervals (CIs) were 1.297 and 1.098-1.532 for alcohol drinking, 1.550 and 1.368-1.755 for abnormal BMI, and 0.887 and 0.800-0.984 for GA+AA. The interaction between BMI and alcohol on gout was significant for GG (p-value = 0.0102) and GA+AA (p-value = 0.0175). When we stratified genotypes by BMI, alcohol drinking was significantly associated with gout only among individuals with a normal BMI (OR; 95% CI = 1.533; 1.036-2.269 for GG and 2.109; 1.202-3.699 for GA+AA). Concerning the combination of BMI and alcohol drinking among participants stratified by genotypes (reference, GG genotype, normal BMI, and no alcohol drinking), the risk of gout was significantly higher in the following categories: GG, normal BMI, and alcohol drinking (OR, 95% CI = 1.929, 1.385-2.688); GG, abnormal BMI, and no alcohol drinking (OR, 95% CI, = 1.721, 1.442-2.052); GG, abnormal BMI, and alcohol drinking (OR, 95% CI = 1.941, 1.501-2.511); GA+AA, normal BMI, and alcohol drinking (OR, 95% CI = 1.971, 1.167-3.327); GA+AA, abnormal BMI, and no alcohol drinking (OR, 95% CI = 1.498, 1.256-1.586); and GA+AA, abnormal BMI, and alcohol drinking (OR, 95% CI = 1.545, 1.088-2.194).

CONCLUSIONS

Alcohol and abnormal BMI were associated with a higher risk of gout, whereas the rs671 GA+AA genotype was associated with a lower risk. Noteworthy, BMI and alcohol had a significant interaction on gout risk. Stratified analyses revealed that alcohol drinking especially among normal-weight individuals might elevate the risk of gout irrespective of the genotype.

Genetics of hyperuricemia and gout: Insights from recent genome-wide association studies and Mendelian randomization studies

Gout is the most common form of inflammatory arthritis in adults. Elevation serum uric acid (SUA) concentration is known to be the key to gout pathogenesis. Since the first genome-wide association study (GWAS) for SUA was performed in 2007, the number of gene loci known to be associated with hyperuricemia and gout has grown rapidly. GWASs and Mendelian randomization studies have also reported numerous novel results regarding the genetics of hyperuricemia and gout since 2018. We concisely review recent advances in scholarship on the effects of genetics on hyperuricemia and gout risk. We also review data from genetic association studies in Taiwan and perform GWASs of SUA levels among Taiwan Biobank participants.

Strong association between the 12q24 locus and sweet taste preference in the Japanese population revealed by genome-wide meta-analysis

The sweet taste preference of humans is an important adaptation to ensure the acquisition of carbohydrate nutrition; however, overconsumption of sweet foods can potentially lead to diseases such as obesity and diabetes. Although previous studies have suggested that interindividual variation of human sweet taste preference is heritable, genetic loci associated with the trait have yet to be fully elucidated. Here, we genotyped 12,312 Japanese participants using the HumanCore-12+ Custom BeadChip or the HumanCore-24 Custom BeadChip microarrays. The sweet taste preference of the participants was surveyed via an internet-based questionnaire, resulting in a five-point scale of sweet taste preference. The genome-wide meta-analysis of the Japanese participants revealed a strong association between the 12q24 locus and sweet taste preference scale (P = 2.8 × 10^-70). The lead variant rs671 is monoallelic in non-East Asian populations and is located in the aldehyde dehydrogenase (ALDH2) gene, encoding an enzyme involved in alcohol metabolism. The association between the minor allele of rs671 and sweet taste preference was attenuated by adjusting for alcohol drinking. The subgroup analysis showed that the effect of rs671 on sweet taste preference was greater in males than in females. In conclusion, we found an association between the 12q24 locus and sweet taste preference in the Japanese population, and showed that the adjustment for drinking habits attenuated the association. This novel genetic association may provide new clues to elucidate mechanisms determining sweet taste preferences.

Subtype-specific gout susceptibility loci and enrichment of selection pressure on ABCG2 and ALDH2 identified by subtype genome-wide meta-analyses of clinically defined gout patients

OBJECTIVES

Genome-wide meta-analyses of clinically defined gout were performed to identify subtype-specific susceptibility loci. Evaluation using selection pressure analysis with these loci was also conducted to investigate genetic risks characteristic of the Japanese population over the last 2000-3000 years.

METHODS

Two genome-wide association studies (GWASs) of 3053 clinically defined gout cases and 4554 controls from Japanese males were performed using the Japonica Array and Illumina Array platforms. About 7.2 million single-nucleotide polymorphisms were meta-analysed after imputation. Patients were then divided into four clinical subtypes (the renal underexcretion type, renal overload type, combined type and normal type), and meta-analyses were conducted in the same manner. Selection pressure analyses using singleton density score were also performed on each subtype.

RESULTS

In addition to the eight loci we reported previously, two novel loci, PIBF1 and ACSM2B, were identified at a genome-wide significance level (p<5.0×10-8) from a GWAS meta-analysis of all gout patients, and other two novel intergenic loci, CD2-PTGFRN and SLC28A3-NTRK2, from normal type gout patients. Subtype-dependent patterns of Manhattan plots were observed with subtype GWASs of gout patients, indicating that these subtype-specific loci suggest differences in pathophysiology along patients' gout subtypes. Selection pressure analysis revealed significant enrichment of selection pressure on ABCG2 in addition to ALDH2 loci for all subtypes except for normal type gout.

CONCLUSIONS

Our findings on subtype GWAS meta-analyses and selection pressure analysis of gout will assist elucidation of the subtype-dependent molecular targets and evolutionary involvement among genotype, phenotype and subtype-specific tailor-made medicine/prevention of gout and hyperuricaemia.

Genetic advances in gout: potential applications in clinical practice

PURPOSE OF REVIEW

Many novel genetic associations in the field of hyperuricaemia and gout have been described recently. This review discusses advances in gout genetics and their potential clinical applications.

RECENT FINDINGS

Genome-wide association studies have identified approximately 30 serum urate-associated loci, some of which represent targets for drug development in gout. Some genes implicated in initiating the inflammatory response to deposited crystals in gout flares have also been described. In addition, genetic studies have been used to understand the link between hyperuricaemia and other comorbidities, particularly cardiometabolic diseases. ABCG2 has been established as a key genetic determinant in the onset of gout, and plays a role in the progression and severity of disease. Recent pharmacogenetic studies have also demonstrated the association between ABCG2 and poor response to allopurinol, and the link between HLA-B58:01 genotype and adverse drug reactions to allopurinol.

SUMMARY

Advances in gout genetics have provided important molecular insights into disease pathogenesis, better characterized the pharmacogenetics of allopurinol, and raised the possibility of using genetic testing to provide personalized treatment for patients. Prospective studies are now needed to clarify whether genetic testing in gout provides further benefit when added to established clinical management.

Genome-wide association study revealed novel loci which aggravate asymptomatic hyperuricaemia into gout

OBJECTIVE

The first ever genome-wide association study (GWAS) of clinically defined gout cases and asymptomatic hyperuricaemia (AHUA) controls was performed to identify novel gout loci that aggravate AHUA into gout.

METHODS

We carried out a GWAS of 945 clinically defined gout cases and 1003 AHUA controls followed by 2 replication studies. In total, 2860 gout cases and 3149 AHUA controls (all Japanese men) were analysed. We also compared the ORs for each locus in the present GWAS (gout vs AHUA) with those in the previous GWAS (gout vs normouricaemia).

RESULTS

This new approach enabled us to identify two novel gout loci (rs7927466 of CNTN5 and rs9952962 of MIR302F) and one suggestive locus (rs12980365 of ZNF724) at the genome-wide significance level (p<5.0×10-8). The present study also identified the loci of ABCG2, ALDH2 and SLC2A9. One of them, rs671 of ALDH2, was identified as a gout locus by GWAS for the first time. Comparing ORs for each locus in the present versus the previous GWAS revealed three 'gout vs AHUA GWAS'-specific loci (CNTN5, MIR302F and ZNF724) to be clearly associated with mechanisms of gout development which distinctly differ from the known gout risk loci that basically elevate serum uric acid level.

CONCLUSIONS

This meta-analysis is the first to reveal the loci associated with crystal-induced inflammation, the last step in gout development that aggravates AHUA into gout. Our findings should help to elucidate the molecular mechanisms of gout development and assist the prevention of gout attacks in high-risk AHUA individuals.

An update on the genetics of hyperuricaemia and gout

A central aspect of the pathogenesis of gout is elevated urate concentrations, which lead to the formation of monosodium urate crystals. The clinical features of gout result from an individual's immune response to these deposited crystals. Genome-wide association studies (GWAS) have confirmed the importance of urate excretion in the control of serum urate levels and the risk of gout and have identified the kidneys, the gut and the liver as sites of urate regulation. The genetic contribution to the progression from hyperuricaemia to gout remains relatively poorly understood, although genes encoding proteins that are involved in the NLRP3 (NOD-, LRR- and pyrin domain-containing 3) inflammasome pathway play a part. Genome-wide and targeted sequencing is beginning to identify uncommon population-specific variants that are associated with urate levels and gout. Mendelian randomization studies using urate-associated genetic variants as unconfounded surrogates for lifelong urate exposure have not supported claims that urate is causal for metabolic conditions that are comorbidities of hyperuricaemia and gout. Genetic studies have also identified genetic variants that predict responsiveness to therapies (for example, urate-lowering drugs) for treatment of hyperuricaemia. Future research should focus on large GWAS (that include asymptomatic hyperuricaemic individuals) and on increasing the use of whole-genome sequencing data to identify uncommon genetic variants with increased penetrance that might provide opportunities for clinical translation.

Causal effect of alcohol consumption on hyperuricemia using a Mendelian randomization design

AIM

We used a Mendelian randomization analysis to assess the causal effect of alcohol consumption on hyperuricemia in Koreans.

METHODS

The Korean Cancer Prevention Study-II (KCPS-II) Biobank cohort consisted of 156 701 healthy Korean aged 20 years or older. Clinical data including serum uric acid, alcohol consumption, and other related confounding variables were collected at baseline. The 27 single nucleotide polymorphisms (SNP) including rs671 in aldehyde dehydrogenase 2 (ALDH2) were obtained from a genome-wide association study of alcohol consumption in the KCPS-II Biobank among 11 678 men and women in 2017. Both unweighted and weighted genetic risk score (wGRS) were calculated using 10 SNPs selected based on linkage disequilibrium.

RESULTS

As strong instrumental variables, both rs671 and wGRS were associated with an increased amount of alcohol drinking in men and women. Alcohol consumption was also positively associated with hyperuricemia risk in men (P < .001) and women (P = .014). Both rs671 major G allele and wGRS were not associated with hyperuricemia. In Mendelian randomization analysis, the causal relationship between any alcohol consumption and hyperuricemia was found only in men, albeit non-significant after correction for multiple testing. The associations did not change after excluding heavy drinkers or the elderly.

CONCLUSIONS

These results provide evidence that alcohol consumption is causally associated with risk of hyperuricemia in Korean men and support its role as a risk determinant.

Identification of the 12q24 locus associated with fish intake frequency by genome-wide meta-analysis in Japanese populations

Background

Japan is traditionally a country with one of the highest levels of fish consumption worldwide, although the westernization of the Japanese diet has resulted in the reduction of fish consumption. A recent meta-analysis of genome-wide association studies (GWASs) on Western populations has identified a single nucleotide polymorphism (SNP) associated with fish intake frequency. Here, we examined the genetic basis for fish intake frequency among Japanese individuals.

Results

We conducted a meta-analysis of a GWAS including 12,603 Japanese individuals and identified a susceptibility locus for fish intake frequency at 12q24 (lead variant was rs11066015, P = 5.4 × 10^-11). rs11066015 was in a strong linkage disequilibrium with rs671, a well-known SNP related to alcohol metabolism. When adjusted for alcohol drinking, the association between rs11066015 and fish intake frequency was substantially attenuated. Subgroup analysis revealed that the effect of the 12q24 variant on fish intake frequency was stronger in males than in females (P for interaction = 0.007) and stronger in the older subgroup than in the younger subgroup (P for interaction = 0.006).

Conclusions

Our findings suggest that the 12q24 locus is associated with fish intake frequency via alcohol drinking. This study can help contribute to personalized nutrition information, suggesting that fish intake should be promoted to consumers who have the rs11066015 minor allele, which is genetically linked to low fish intake frequency, especially in male and older individuals.

Association between rs2188380 and the risk of breast cancer in southwest Chinese population

Background

Previous studies have revealed that the single nucleotide polymorphism (SNP) rs2188380 was identified as a novel locus of gout. Interestingly, gout resulting from high serum uric acid (SUA) was also identified to be associated with the risk of breast cancer (BC). We hypothesized that maybe there was a relationship between rs2188380 and the risk of BC. Therefore, our study was conducted to investigate whether this novel gout‐related SNP (rs2188380) was associated with BC risk as well as the clinical and pathological characteristics in the southwest Chinese population.

Materials and methods

We performed a case‐control study including 104 breast cancer patients and 112 healthy controls to investigate whether rs2188380 is associated with BC risk in the southwest Chinese population. The genotyping was performed by the SNP scan method. General characteristics and clinicopathological characteristics of tumors were also included in the analysis. The statistical evaluations were performed using the Student t test, the chi‐square test or Fisher's exact test, and unconditional logistic regression analysis.

Results

The C/C genotype of rs2188380 might be related to BC risk to some extent compared with G/G genotype (OR = 9.241, 95% CI = 1.122‐76.101, P = 0.039). Furthermore, after adjusting the age, the association still existed (OR = 8.788, 95% CI = 1.063‐72.636, P = 0.044). However, no significant association was observed between rs2188380 and the clinicopathological characteristics of BC.

Conclusions

Our study primarily indicated that rs2188380 might have a potential association with BC risk to some extent. With a limited sample size and statistical power, further studies based on larger populations are needed to confirm the association.

Association Between Aldehyde dehydrogenase-2 Polymorphisms and Risk of Alzheimer's Disease and Parkinson's Disease: A Meta-Analysis Based on 5,315 Individuals

Objective: A number of studies have reported that aldehyde dehydrogenase-2 (ALDH2) polymorphisms maybe associated with the risk of Alzheimer's disease (AD) and Parkinson's disease (PD). However, the results of such studies are inconsistent. We therefore conducted a meta-analysis to clarify the association between ALDH2 polymorphisms and the risk of AD and PD.

Methods: Five online databases were searched and the relevant studies were reviewed from inception through May 10, 2018. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated in each genetic model of the general population and various subgroups. Furthermore, we simultaneously performed heterogeneity, cumulative, sensitivity, and publication bias analyses.

Results: Overall, nine case-control studies involving 5,315 subjects were included in this meta-analysis. Potential associations were found between the ALDH2 rs671 G>A polymorphism and the risk of AD (A vs. G: OR = 1.46, 95%CI = 1.01–2.11, P = 0.05, I² = 84.2%; AA vs. GG: OR = 2.22, 95%CI = 1.03–4.77, P = 0.04, I² = 79.2%; AA vs. GG+GA: OR = 1.94, 95%CI = 1.03–3.64, P =0.04, I² = 71.1%). In addition, some similar results were observed in other subgroups. Moreover, no significant association between ALDH2 polymorphisms and PD risk.

Conclusions: In conclusion, our meta-analysis indicated that the ALDH2 rs671 G>A polymorphism plays an important role in AD development.

Genome-wide association and gene-environment interaction study identifies variants in ALDH2 associated with serum ferritin in a Chinese population

Ferritin is not only a biomarker of total iron status and systemic inflammation but is also associated with metabolic disorders. A number of genetic variations have been identified to affect serum ferritin, but there is limited understanding of the genetic variations in serum ferritin. To evaluate the relationships among genetic variations, metabolism and ferritin, we performed a secondary analysis of our previous genome-wide association study of ferritin. After adjusting for population stratification and age, the rs671 in ALDH2 was significantly associated with ferritin concentrations (P-combined = 2.98 × 10-8). Men carrying the mutated genotype of rs671 had lower serum ferritin levels. BMI was the mediation between rs671 and ferritin (P = 0.003). Moreover, a significant interaction between rs671 and alcohol consumption on ferritin levels was observed (P = 3.02 × 10-4). rs671 genotypes were significantly relevant to serum ferritin in drinkers (P = 2.39 × 10-7). We reported that rs671 was associated with ferritin in a manner of BMI mediation. These findings will provide new insights into the impacts of genetic variations and metabolisms on serum ferritin levels.

The Bidirectional Effect of Defective ALDH2 Polymorphism and Disease Prevention

Despite the role of aldehyde dehydrogenase 2 (ALDH2) in the detoxification of endogenous aldehydes, the defective polymorphism (rs671), which is highly prevalent among East Asians, does not show a serious phenotype, such as congenital abnormality. However, unfavorable and favorable impacts of the variant allele, ALDH2*2, on various disease risks have been reported. The underlying mechanisms are often complicated due to the compensatory aldehyde detoxification systems. As the phenotypes emerge due to overlapping environmental factors (e.g., alcohol intake and tobacco smoke) or individual vulnerabilities (e.g., aging and apolipoprotein E ε4 allele), polymorphism is therefore considered to be important in the field of preventative medicine. For example, it is important to recognize that ALDH2*2 carriers are at a high risk of alcohol drinking-related cancers; however, their drinking habit has less adverse effects on physiological indices, such as blood pressure, body mass index, levels of lipids, and hepatic deviation enzymes in the blood, than in non-ALDH2*2 carriers. Therefore, opportunities to reconsider their excessive drinking habit before adverse events occur can be missed. To perform effective disease prevention, the effects of ALDH2*2 on various diseases and the biological mechanisms should be clarified.

Multiple Membrane Transporters and Some Immune Regulatory Genes are Major Genetic Factors to Gout

Gout is a common form of inflammatory arthritis caused by hyperuricemia and the deposition of Monosodium Urate (MSU) crystals. It is also considered as a complex disorder in which multiple genetic factors have been identified in association with its susceptibility and/or clinical outcomes. Major genes that were associated with gout include URAT1, GLUT9, OAT4, NPT1 (SLC17A1), NPT4 (SLC17A3), NPT5 (SLC17A4), MCT9, ABCG2, ABCC4, KCNQ1, PDZK1, NIPAL1, IL1β, IL-8, IL-12B, IL-23R, TNFA, MCP-1/CCL2, NLRP3, PPARGC1B, TLR4, CD14, CARD8, P2X7R, EGF, A1CF, HNF4G and TRIM46, LRP2, GKRP, ADRB3, ADH1B, ALDH2, COMT, MAOA, PRKG2, WDR1, ALPK1, CARMIL (LRRC16A), RFX3, BCAS3, CNIH-2, FAM35A and MYL2-CUX2. The proteins encoded by these genes mainly function in urate transport, inflammation, innate immunity and metabolism. Understanding the functions of gout-associated genes will provide important insights into future studies to explore the pathogenesis of gout, as well as to develop targeted therapies for gout.

Identification of three novel loci of ALDH2 Gene for Serum Folate levels in a Male Chinese Population by Genome-Wide Association Study

BACKGROUND

Serum folate is important in clinical researches and DNA synthesis and methylation. Some loci and genes that are associated with folate levels had been detected by genome-wide association studies (GWAS), such as rs1801133 in MTHFR and rs1979277 in SHMT1. Nevertheless, only a small part of variants has been clearly identified for serum folate. Hence, we conducted a GWAS to discover new inherited susceptibility and gene-environment interactions on serum folate concentration.

MATERIALS AND METHODS

In a healthy Chinese population of 1999 men, genotyping was performed using Illumina HumanOmni1-Quad BeadChip. Serum folate levels were measured by enzyme-linked immunosorbent assay (ELISA), pathway enrichment analysis and statistical analysis were performed by Database for Annotation, Visualization and Integrated Discovery (DAVID) and Statistic Package for Social Science (SPSS).

RESULTS

We validated that rs1801133 in MTHFR was significantly involved in serum folate (P = 4.21 × 10^-19). Surprisingly, we discovered three novel loci rs3782886, rs671, and rs4646776 of ALDH2 gene were suggestively significantly associated with folate serum folate levels in the male population studied (P = 2.17 × 10^-7, P = 3.60 × 10^-7, P = 3.99 × 10^-7, respectively) after adjusting for population stratification, BMI and age. Men with the AA genotype had significantly higher serum folate levels compared with men with the GG/AG genotype. But we found ALDH2 gene mutation no relation to part of environmental factors on serum folate levels.

CONCLUSION

In a male Chinese population, genome-wide association study discovered that three novel SNPs rs3782886, rs671 and rs4646776 of ALDH2 gene were suggestively significantly associated with serum folate levels.

Common variant of BCAS3 is associated with gout risk in Japanese population: the first replication study after gout GWAS in Han Chinese

Background

Gout is a common disease resulting from hyperuricemia which causes acute arthritis. A recent genome-wide association study (GWAS) of gout identified three new loci for gout in Han Chinese: regulatory factor X3 (RFX3), potassium voltage-gated channel subfamily Q member 1 (KCNQ1), and breast carcinoma amplified sequence 3 (BCAS3). The lack of any replication studies of these three loci using other population groups prompted us to perform a replication study with Japanese clinically defined gout cases and controls.

Methods

We genotyped the variants of RFX3 (rs12236871), KCNQ1 (rs179785) and BCAS3 (rs11653176) in 723 Japanese clinically defined gout cases and 913 controls by TaqMan method. rs179785 of KCNQ1 is also evaluated by direct sequencing because of difficulties of its genotyping by TaqMan method.

Results

Although the variants of RFX3 and BCAS3 were clearly genotyped by TaqMan method, rs179785 of KCNQ1 was not, because rs179785 (A/G) of KCNQ1 is located at the last nucleotide (“A”) of the 12-bp deletion variant (rs200562977) of KCNQ1. Therefore, rs179785 and rs200562977 of KCNQ1 were genotyped by direct sequencing in all samples. Moreover, by direct sequencing with the same primers, we were able to evaluate the genotypes of rs179784 of KCNQ1 which shows strong linkage disequilibrium with rs179785 (D’ = 1.0 and r² = 0.99). rs11653176, a common variant of BCAS3, showed a significant association with gout (P = 1.66 × 10^− 3; odds ratio [OR] = 0.80); the direction of effect was the same as that seen in the previous Han Chinese GWAS. Two variants of KCNQ1 (rs179785 and rs179784) had a nominally significant association (P = 0.043 and 0.044; OR = 0.85 and 0.86, respectively), but did not pass the significance threshold for multiple hypothesis testing using the Bonferroni correction. On the other hand, rs200562977 of KCNQ1 and rs12236871 of RFX3 did not show any significant association with gout.

Conclusion

BCAS3 is a coactivator of estrogen receptor alpha, and the influence of estrogen to serum uric acid level is well known. Our present replication study, as did the previous gout GWAS, demonstrated the common variant of BCAS3 to be associated with gout susceptibility.

[Importance of an Aldehyde Dehydrogenase 2 Polymorphism in Preventive Medicine]

Unlike genetic alterations in other aldehyde dehydrogenase (ALDH) isozymes, a defective ALDH2 polymorphism (rs671), which is carried by almost half of East Asians, does not show a clear phenotype such as a shortened life span. However, impacts of a defective ALDH2 allele, ALDH2*2, on various disease risks have been reported. As ALDH2 is responsible for the detoxification of endogenous aldehydes, a negative effect of this polymorphism is predicted, but bidirectional effects have been actually observed and the mechanisms underlying such influences are often complex. One reason for this complexity may be the existence of compensatory aldehyde detoxification systems and the secondary effects of these systems. There are many issues to be addressed with regard to the ALDH2 polymorphism in the field of preventive medicine, including the following concerns. First, ALDH2 in the fetal stage plays a role in aldehyde detoxification; therefore, prenatal health effects of environmental aldehyde exposure are of concern for ALDH2*2-carrying fetuses. Second, ALDH2*2 carriers are at high risk of drinking-related cancers. However, their drinking habits result in less worsening of physiological findings, such as energy metabolism index and liver functions, compared with non-ALDH2*2 carriers, and therefore opportunities to detect excessive drinking can be lost. Third, personalized medicine such as personalized prescriptions for ALDH2*2 carriers will be required in the clinical setting, and accumulation of evidence is awaited. Lastly, since the ALDH2 polymorphism is not considered in workers' limits of exposure to aldehydes and their precursors, efforts to lower exposure levels beyond legal standards are required.

The polymorphism rs671 at ALDH2 associated with serum uric acid levels in Chinese Han males: A genome-wide association study

Serum uric acid (SUA) levels are highly heritable and an increased SUA level is one of important risk factors for gout, diabetes, metabolic syndrome, and cardiovascular diseases. The genetic variants underlying SUA remains largely unexplored. The aim was to explore new genetic variants underlying SUA in Chinese Han. We performed a genome-wide association study of SUA levels in Han Chinese. The discovery set contained 1634 samples and subsequent replication was comprised of 1649 females and 1169 males. 2620 subjects were recruited in the detailed analysis of rs671, alcohol drinking and SUA. We found a genome-wide significant association between SUA level and the SNP rs671 at ALDH2 (P = 1.2 × 10^-10) in the merged data. In addition, we also replicated the signal from rs3733590 at SLC2A9 (P = 1.0 × 10^-10). In males, about 0.21% to 1.95% of the total variance for SUA can be explained by rs671 using linear regression models in four independent cohorts. Of those, 56.75% to 93.51% might be explained by altering alcohol consumption due to rs671. No statistical association of rs671 and SUA was observed in females (P = 0.409). Furthermore, we observed a causal relationship between alcohol consumption and SUA in males using rs671 as an instrumental variable (P = 5.1 × 10^-4). We replicated the previous findings in SLC2A9. Our evidence supported that rs671 was associated with SUA by affecting alcohol consumption in males. This finding strongly suggests a role for alcohol consumption in the development of hyperuricaemia and uric acid related traits.

Identification of CDC42BPG as a novel susceptibility locus for hyperuricemia in a Japanese population

Chronic kidney disease and hyperuricemia are serious global health problems. Recent genome-wide association studies have identified various genetic variants related to these disorders. However, most studies have been conducted in a cross-sectional manner. To identify novel susceptibility loci for chronic kidney disease or hyperuricemia, we performed longitudinal exome-wide association studies (EWASs), using ~ 244,000 genetic variants and clinical data of Japanese individuals who had undergone annual health checkups for several years. After establishing quality controls, the association of renal function-related traits in 5648 subjects (excluding patients with dialysis and population outliers) with 24,579 single nucleotide variants (SNVs) for three genetic models (P < 3.39 × 10^− 7) was tested using generalized estimating equation models. The longitudinal EWASs revealed novel relations of five SNVs to renal function-related traits. Cross-sectional data for renal function-related traits in 7699 Japanese subjects were examined in a replication study. Among the five SNVs, rs55975541 in CDC42BPG was significantly (P < 4.90 × 10^− 4) related to the serum concentration of uric acid in the replication cohort. We also examined the SNVs detected in our longitudinal EWASs with the information on P values in GKDGEN meta-analysis data. Four SNVs in SLC15A2 were significantly associated with the estimated glomerular filtration rate in European ancestry populations, although these SNVs were related to the serum concentration of uric acid with borderline significance in our longitudinal EWASs. Our findings indicate that CDC42BPG may be a novel susceptibility locus for hyperuricemia.

Replication of Gout/Urate Concentrations GWAS Susceptibility Loci Associated with Gout in a Han Chinese Population

Gout is a chronic disease resulting from elevated serum urate (SU). Previous genome-wide association studies (GWAS) have identified dozens of susceptibility loci for SU/gout, but few have been conducted for Chinese descent. Here, we try to extensively investigate whether these loci contribute to gout risk in Han Chinese. A total of 2255 variants in linkage disequilibrium (LD) with GWAS identified SU/gout associated variants were analyzed in a Han Chinese cohort of 1255 gout patients and 1848 controls. Cumulative genetic risk score analysis was performed to assess the cumulative effect of multiple “risk” variants on gout incidence. 23 variants (41%) of LD pruned variants set (n = 56) showed nominal association with gout in our sample (p < 0.05). Some of the previously reported gout associated loci (except ALDH16A1), including ABCG2, SLC2A9, GCKR, ALDH2 and CNIH2, were replicated. Cumulative genetic risk score analyses showed that the risk of gout increased for individuals with the growing number (≥8) of the risk alleles on gout associated loci. Most of the gout associated loci identified in previous GWAS were confirmed in an independent Chinese cohort, and the SU associated loci also confer susceptibility to gout. These findings provide important information of the genetic association of gout.

Independent effects of ADH1B and ALDH2 common dysfunctional variants on gout risk

Gout is caused by hyperuricemia, with alcohol consumption being an established risk factor. Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are crucial enzymes for alcohol metabolism. We recently performed a genome-wide association study of gout and a subsequent fine-mapping study which identified rs671 of ALDH2 as a gout locus. However, the association between gout and common variants of ADH1B has hitherto remained unreported, prompting us to investigate the association between gout and common dysfunctional variants of ADH1B (rs1229984) and ALDH2 (rs671). We used 1,048 clinically defined gout cases and 1,334 controls of Japanese male. The "His carrier" (His/His or His/Arg) of rs1229984 (His48Arg) of ADH1B significantly increased gout risk (P = 4.3 × 10^-4, odds ratio = 1.76), as did the "non-Lys carrier (Glu/Glu)" of rs671 (Glu504Lys) of ALDH2. Furthermore, common variants of ADH1B and ALDH2 are independently associated with gout. Our findings likewise suggest that genotyping these variants can be useful for the evaluation of gout risk.

A missense single nucleotide polymorphism in the ALDH2 gene, rs671, is associated with hip fracture

Hip fracture is the most severe bone fragility fracture among osteoporotic injuries. Family history is a known risk factor for fracture and now included among criteria for osteoporosis diagnosis and treatment; however, genetic factors underlying family history favoring fracture remain to be elucidated. Here we demonstrate that a missense SNP in the ALDH2 gene, rs671 (ALDH2*2), is significantly associated with hip fracture (odds ratio = 2.48, 95% confidence interval: 1.20–5.10, p = 0.021). The rs671 SNP was also significantly associated with osteoporosis development (odds ratio = 2.04, 95% confidence interval: 1.07–3.88, p = 0.040). For analysis we enrolled 92 hip fracture patients plus 48 control subjects without bone fragility fractures with higher than −2.5 SD bone mineral density. We also recruited 156 osteoporosis patients diagnosed as below −2.5 SD in terms of bone mineral density but without hip fracture. Association of rs671 with hip fracture and osteoporosis was significant even after adjustment for age and body mass index. Our results provide new insight into the pathogenesis of hip fracture.