Genetic Polymorphisms of the Mitochondrial Aldehyde Dehydrogenase ALDH2 Gene in a Large Ethnic Hakka Population in Southern China

Aldehyde Dehydrogenase 2 rs671 G/A and a/A Genotypes are Associated with the Risk of Acute Myocardial Infarction

Background

Aldehyde dehydrogenase 2 (ALDH2) is a key catalytic enzyme involved in the aldehyde metabolism that plays an important role in the occurrence and development of acute myocardial infarction (AMI). However, the relationship of ALDH2 polymorphism and susceptibility to AMI may differ among different regions and populations, and it has not yet been reported in Hakka population. The purpose of the present study was to investigate it in this population.

Methods

Four hundred and nineteen AMI patients and 636 individuals without AMI were included in the present study. The ALDH2 rs671 polymorphism was genotyped using polymerase chain reaction (PCR)-microarray. Differences in ALDH2 rs671 genotypes and alleles between patients and controls were compared, and the relationship between ALDH2 rs671 genotypes and AMI risk was analyzed.

Results

Patients with AMI had a lower frequency of ALDH2 rs671 G/G genotype (43.2% vs 52.7%, p=0.003), and a higher G/A genotype (45.6% vs 38.5%, p=0.025) than controls. And AMI patients had a lower frequency of ALDH2 rs671 G allele (66.0% vs 71.9%), and a higher A allele (34.0% vs 28.1%) (p=0.004) than controls. Logistic regression analysis showed that overweight (body mass index (BMI)≥24.0 kg/m2 vs BMI 18.5-23.9 kg/m2: odds ratio (OR) 2.046, 95% confidence interval (CI): 1.520-2.754, p<0.001), history of hypertension (yes vs no: OR 3.464, 95% CI: 2.515-4.770, p<0.001), ALDH2 rs671 G/A genotype (G/A vs G/G: OR 1.476, 95% CI: 1.102-1.976, p=0.009), and A/A genotype (A/A vs G/G: OR 1.656, 95% CI: 1.027-2.668, p=0.038) maybe the independent risk factors for AMI.

Conclusion

Overweight (BMI≥24.0 kg/m2), a history of hypertension, and ALDH2 rs671 G/A or A/A genotypes increased the risk of developing AMI in Hakka population.

The role of circulating cell-free DNA as an inflammatory mediator after stroke

Stroke is the second leading cause of death worldwide and a leading cause of disability. Clinical and experimental studies highlighted the complex role of the immune system in the pathophysiology of stroke. Ischemic brain injury leads to the release of cell-free DNA, a damage-associated molecular pattern, which binds to pattern recognition receptors on immune cells such as toll-like receptors and cytosolic inflammasome sensors. The downstream signaling cascade then induces a rapid inflammatory response. In this review, we are highlighting the characteristics of cell-free DNA and how these can affect a local as well as a systemic response after stroke. For this purpose, we screened literature on clinical studies investigating cell-free DNA concentration and properties after brain ischemia. We report the current understanding for mechanisms of DNA uptake and sensing in the context of post-stroke inflammation. Moreover, we compare possible treatment options targeting cell-free DNA, DNA-sensing pathways, and the downstream mediators. Finally, we describe clinical implications of this inflammatory pathway for stroke patients, open questions, and potential future research directions.

Effects of intracardiac delivery of aldehyde dehydrogenase 2 gene in myocardial salvage

Intrinsic activity of aldehyde dehydrogenase (ALDH)2, a cardiac mitochondrial enzyme, is vital in detoxifying 4-hydroxy-2-nonenal (4HNE) like cellular reactive carbonyl species (RCS) and thereby conferring cardiac protection against pathological stress. It was also known that a single point mutation (E487K) in ALDH2 (prevalent in East Asians) known as ALDH2*2 reduces its activity intrinsically and was associated with increased cardiovascular diseases. We and others have shown that ALDH2 activity is reduced in several pathologies in WT animals as well. Thus, exogenous augmentation of ALDH2 activity is a good strategy to protect the myocardium from pathologies. In this study, we will test the efficacy of intracardiac injections of the ALDH2 gene in mice. We injected both wild type (WT) and ALDH2*2 knock-in mutant mice with ALDH2 constructs, AAv9-cTNT-hALDH2-HA tag-P2A-eGFP or their control constructs, AAv9-cTNT-eGFP. We found that intracardiac ALDH2 gene transfer increased myocardial levels of ALDH2 compared to GFP alone after 1 and 3 weeks. When we subjected the hearts of these mice to 30 min global ischemia and 90 min reperfusion (I-R) using the Langendorff perfusion system, we found reduced infarct size in the hearts of mice with ALDH2 gene vs GFP alone. A single time injection has shown increased myocardial ALDH2 activity for at least 3 weeks and reduced myocardial 4HNE adducts and infarct size along with increased contractile function of the hearts while subjected to I-R. Thus, ALDH2 overexpression protected the myocardium from I-R injury by reducing 4HNE protein adducts implicating increased 4HNE detoxification by ALDH2. In conclusion, intracardiac ALDH2 gene transfer is an effective strategy to protect the myocardium from pathological insults.

ALDH2 Polymorphism rs671 *1/*2 Genotype is a Risk Factor for the Development of Alcoholic Liver Cirrhosis in Hakka Alcoholics

Background

Alcoholics are prone to alcoholic cirrhosis (ALC). Aldehyde dehydrogenase 2 (ALDH2) is involved in alcohol metabolism. Herein, the relationship between ALDH2 genotypes and ALC was analyzed among Hakka alcoholics in southern China.

Methods

A total of 213 alcoholics and 214 non-alcoholics were included in the study. The ALDH2 gene rs671 polymorphism was analyzed, life history, disease history, and auxiliary examination results of these participants were collected.

Results

The alcoholics had higher level of total serum protein, and serum globulin, lower level of serum albumin, serum albumin/globulin ratio, serum prealbumin, neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), and platelet-to-lymphocyte ratio (PLR) than non-alcoholics. In the 213 alcoholics, 180 developed ALC. There were 206 non-ALC persons in the 214 non-alcoholics. The proportion of the ALDH2 rs671 G/G homozygous (*1/*1) was significantly lower in ALC patients (83.3%) than that of other groups (100.0% in non-ALC in alcoholics, 95.6% in non-ALC in non-alcoholics), while the proportion of the G/A heterozygous (*1/*2) was significantly higher in ALC patients (16.7%) than that of other groups (0% in non-ALC in alcoholics, 4.4% in non-ALC in non-alcoholics). Logistic regression analysis indicated that participants with low level of NLR (adjusted OR 5.543, 95% CI 2.964–10.368, P<0.001), LMR (adjusted OR 9.256, 95% CI 4.740–18.076, P<0.001), and PLR (adjusted OR 6.047, 95% CI 3.372–10.845, P<0.001), and ALDH2 G/A genotype (adjusted OR 6.323, 95% CI 2.477–16.140, P<0.001) had a significantly higher risk of ALC.

Conclusion

ALDH2 polymorphism rs671 *1/*2 genotype is a potential risk factor for the development of ALC among Hakka alcoholics.

ALDH2/SIRT1 Contributes to Type 1 and Type 2 Diabetes-Induced Retinopathy through Depressing Oxidative Stress

Clinical observations found vision-threatening diabetic retinopathy (DR) occurs in both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) patients, but T1DM may perform more progressive retinal abnormalities at the same diabetic duration with or without clinical retinopathy. In the present study, T1DM and T2DM patients without manifestations of DR were included in our preliminary clinical retrospective observation study to investigate the differentiated retinal function at the preclinical stage. Then, T1DM and T2DM rat models with 12-week diabetic duration were constructed to explore the potential mechanism of the discrepancy in retinal disorders. Our data demonstrated T1DM patients presented a poor retinal function, a higher allele frequency for ALDH2GA/AA, and a depressed aldehyde dehydrogenase 2 (ALDH2) activity and silent information regulator 1 (SIRT1) level, compared to T2DM individuals. In line with this, higher amplitudes of neurovascular function-related waves of electroretinograms were found in T2DM rats. Furthermore, the retinal outer nuclear layers were reduced in T1DM rats. The levels of retinal oxidative stress biomarkers including total reactive oxygen species, NADPH oxidase 4 and mitochondrial DNA damage, and inflammatory indicators covering inducible/endothelial nitric acid synthase ratio, interleukin-1, and interleukin-6 were obviously elevated. Notably, the level of retinal ALDH2 and SIRT1 in T1DM rats was significantly diminished, while the expression of neovascularization factors was dramatically enhanced compared to T2DM. Together, our data indicated that the ALDH2/SIRT1 deficiency resulted in prominent oxidative stress and was in association with DR progression. Moreover, a differentiating ALDH2/SIRT1 expression may be responsible for the dissimilar severity of DR pathological processes in chronic inflammatory-related T1DM and T2DM.

Diabetic Aldehyde Dehydrogenase 2 Mutant (ALDH2*2) Mice Are More Susceptible to Cardiac Ischemic-Reperfusion Injury Due to 4-Hydroxy-2-Nonenal Induced Coronary Endothelial Cell Damage

Background

Aldehyde dehydrogenase‐2 (ALDH2), a mitochondrial enzyme, detoxifies reactive aldehydes such as 4‐hydroxy‐2‐nonenal (4HNE). A highly prevalent E487K mutation in ALDH2 (ALDH2*2) in East Asian people with intrinsic low ALDH2 activity is implicated in diabetic complications. 4HNE‐induced cardiomyocyte dysfunction was studied in diabetic cardiac damage; however, coronary endothelial cell (CEC) injury in myocardial ischemia‐reperfusion injury (IRI) in diabetic mice has not been studied. Therefore, we hypothesize that the lack of ALDH2 activity exacerbates 4HNE‐induced CEC dysfunction which leads to cardiac damage in ALDH2*2 mutant diabetic mice subjected to myocardial IRI.

Methods and Results

Three weeks after diabetes mellitus (DM) induction, hearts were subjected to IRI either in vivo via left anterior descending artery occlusion and release or ex vivo IRI by using the Langendorff system. The cardiac performance was assessed by conscious echocardiography in mice or by inserting a balloon catheter in the left ventricle in the ex vivo model. Just 3 weeks of DM led to an increase in cardiac 4HNE protein adducts and, cardiac dysfunction, and a decrease in the number of CECs along with reduced myocardial ALDH2 activity in ALDH2*2 mutant diabetic mice compared with their wild‐type counterparts. Systemic pretreatment with Alda‐1 (10 mg/kg per day), an activator of both ALDH2 and ALDH2*2, led to a reduction in myocardial infarct size and dysfunction, and coronary perfusion pressure upon cardiac IRI by increasing CEC population and coronary arteriole opening.

Conclusions

Low ALDH2 activity exacerbates 4HNE‐mediated CEC injury and thereby cardiac dysfunction in diabetic mouse hearts subjected to IRI, which can be reversed by ALDH2 activation.

Association between ALDH2 polymorphism and esophageal cancer risk in South Koreans: a case-control study

Background

Alcohol consumption is a major risk factor for esophageal cancer; however, a high incidence of esophageal cancer is observed particularly among Eastern Asians, although they consume relatively less alcohol, presumably due to the high frequency of aldehyde dehydrogenase 2 (ALDH2) rs671 polymorphisms. Nevertheless, the association between ALDH2 polymorphisms and esophageal cancer remains under debate. In the present study, we evaluated the association between ALDH2 rs671 polymorphisms and the risk of esophageal cancer in the South Korean population.

Methods

This study included 783 hospital based-cases and 8732 population-based controls. Information on smoking history and alcohol consumption was obtained from the medical records or interview questionnaires. Age-adjusted logistic regression analysis was performed to assess the association between ALDH2 rs671 polymorphisms and esophageal cancer.

Results

Odds ratios (ORs) for esophageal cancer in men with GA and AA genotypes were 2.75 (95% confidence interval [CI]: 2.34–3.23) and 0.08 (95% CI: 0.00–0.35), respectively; whereas, in women, these ratios were 2.99 (95% CI: 1.43–6.34) and 6.18 (95% CI: 1.40–19.62), respectively, taking subjects with the ALDH2 GG genotype as a reference. In men, the association between ALDH2 polymorphisms and esophageal cancer was modified by alcohol consumption.

Conclusion

In Eastern Asians, ALDH2 rs671 polymorphisms are associated with esophageal cancer, which may be linked to acetaldehyde accumulation.

Transformed ALDH2-/- hepatocytes by ethanol could serve as a useful tool for studying alcoholic hepatocarcinogenesis

Alcohol is a well-recognized hepatic carcinogen. Alcohol is metabolized into genotoxic acetaldehyde in hepatocytes, which is catalyzed by aldehyde dehydrogenase 2 (ALDH2). The detailed underlying mechanisms of alcohol-related hepatocellular carcinoma (HCC) remains unclear, at least partially, due to the absence of appropriate experimental models. Current studies suggest that rodents are not good models of the most common liver diseases that trigger HCC including alcoholic liver injury. We hypothesize that ethanol could induce transformation of immortalized normal liver cells, which may serve as a versatile tool for studying alcoholic HCC. Besides, we believe that knockout of ALDH2 will help to shorten the time course of transformation, as ALDH2 deficiency will significantly increase the accumulation of acetaldehyde in hepatocytes. Using this model, the dynamic changes of carcinogenesis-related molecular events could be easily examined. Furthermore, the transformed cells isolated from soft agar could be inoculated to mice for studying invasion, metastasis, and also for screening prophylactics.

Association between ALDH2 Polymorphism and Gastric Cancer Risk in a Korean Population

The association between alcohol and gastric cancer is stronger in East Asians than in other ethnic groups, presumably due to an aldehyde dehydrogenase 2 (ALDH2) polymorphism. Therefore, we investigated the relationship between the ALDH2 rs671 polymorphism and gastric cancer in a Korean population. This case-control study included 3,245 hospital patients newly diagnosed with gastric cancer and 8,732 population controls. The ALDH2 rs671 genotype was classified as inactive ALDH2 (GG) or active ALDH2 (GA/AA). The risk of gastric cancer was higher in men with the inactive ALDH2 than in those with active ALDH2 (odds ratio [OR], 1.25; 95% confidence interval [CI], 1.09-1.39), whereas no significant association was found between ALDH2 genotype and gastric cancer in women (OR, 1.00; 95% CI, 0.99-1.02). In men, the association between ALDH2 genotype and gastric cancer was stronger in current drinkers. Our findings support the previously reported association between inactive ALDH2 and high risk of gastric cancer.

The role of MTHFR C677T and ALDH2 Glu504Lys polymorphism in acute coronary syndrome in a Hakka population in southern China

Background

Acute coronary syndrome (ACS) is the most serious type of coronary heart disease and is a global medical burden. The pathogenesis of ACS is very complex and still poorly understood. Epidemiologic studies have revealed that the manifestation of ACS are the results of the interactions between multiple environmental and genetic factors. The present study aimed to investigate the role of polymorphisms of MTHFR C677T and ALDH2 Glu504Lys as risk factors for ACS in a Hakka population in southern China.

Methods

Between September 1, 2015 and October 31, 2017, a total of 1957 individuals, including 860 ACS patients and 1097 controls were recruited. Blood samples were collected and genotypes were determined by DNA microarray chip method and direct sequencing method.

Results

For the MTHFR C677T polymorphism, frequencies of CC, CT, and TT genotypes were 53.60% versus 55.33, 39.53% versus 38.65 and 6.86% versus 6.02% in patients with ACS versus controls, respectively(p > 0.05). The differences in genotype frequencies between the ACS patients and controls in the three genetic model were not statistically significant. For the ALDH2 Glu504Lys polymorphism, the frequencies of ALDH2*1*1, ALDH2*1*2, and ALDH2*2*2 genotypes were 48.72, 42.67 and 8.6% in the ACS patients, respectively, while these were 53.33, 39.11 and 7.57% in the controls, respectively, showing no significant difference in the distribution of the ALDH2 genotype between the groups. Using the wild genotype ALDH2*1*1 as reference, relative risk analysis revealed a slightly increased risk for ACS in individuals with the ALDH2*1*2 plus ALDH2*2*2 genotypes (odds ratio (OR) = 1.203, 95% confidence interval (CI) = 1.006–1.438, p = 0.043). In a multivariate logistic regression model, even after adjusting for potential covariates, the association between ALDH2 *2 allele and ACS remained significant (OR = 1.242, 95% CI = 1.045–1.561, p = 0.038).

Conclusions

We present findings regarding the possible clinical impact of the ALDH2*2 variant on ACS patients in a Hakka population in southern China and our findings might help to stratify the high-risk ACS patients and implement appropriate strategies for this genetic subpopulation to ultimately guide the precision preventive procedures in the future.

Association Between the Polymorphism of Aldehyde Dehydrogenase 2 Gene and Cerebral Infarction in a Hakka Population in Southern China

Genetic factors play an important role in determining the susceptibility to ischemic stroke. Herein, we examined the association of an aldehyde dehydrogenase 2 (ALDH2) gene polymorphism with cerebral infarction. Patients with cerebral infarction (n = 963) and healthy controls (n = 921) were included. Genotyping was performed using gene chip platform analysis, and Sanger sequencing was used to confirm ALDH2 genotypes. The risk prediction of ALDH2 polymorphisms for cerebral infarction was examined under three genetic modes of inheritance. For males, ALDH2*2/*2 genotype was a significant risk factor for cerebral infarction in the co-dominant model (age-, smoking-, and drinking-adjusted OR 1.514, 95% CI 1.005-2.282, p = 0.047) and the recessive model (age-, smoking-, and drinking-adjusted OR 1.601, 95% CI 1.078-2.379, p = 0.020). However, for females, ALDH2*2/*2 genotype was a protective factor for cerebral infarction in the co-dominant model (age-, smoking-, and drinking-adjusted OR 0.450 95% CI 0.215-0.941, p = 0.034) and the recessive model (age-, smoking-, and drinking-adjusted OR 0.440, 95% CI 0.214-0.903, p = 0.025). Further, logistic regression analysis revealed that age, smoking, hypertension, hyperlipidemia, and hypercholesterolemia were significant risks for the presence of cerebral infarction. In conclusion, these findings support an association of ALDH2 gene polymorphisms with ischemic stroke in a Chinese Hakka population. In particular, homozygote ALDH2*2/*2 may be a risk factor for cerebral infarction in males, but contribute to reduced risk for cerebral infarction in females.

Aldehyde dehydrogenase 2 rs671G>A polymorphism and ischemic stroke risk in Chinese population: a meta-analysis

Introduction: Recently, molecular epidemiological studies have suggested that aldehyde dehydrogenase 2 (ALDH2) rs671 G>A polymorphism may be a risk factor for ischemic stroke (IS). However, the results reported have not been consistent. Methods: We conducted the meta-analysis to explore the precise association between ALDH2 rs671 G>A polymorphism and IS risk. Five online databases were searched and the relative studies were reviewed from inception to October 1, 2018. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated in each genetic model of the general and subgroup. Furthermore, the heterogeneity, accumulative analyses, sensitivity analyses and publication bias were calculated simultaneously. Results: Overall, nine case-control studies involving 6,129 subjects were included in this meta-analysis. All studies were focused on the Chinese population and some significant associations were found between ALDH2 rs671 G>A polymorphism and IS risk (A vs G: OR=1.29, 95% CI=1.01-1.65, P=0.04, I²=78.2%; AA vs GG: OR=1.86, 95% CI=1.27-2.21, P<0.01, I²=11.3%; AA vs GG + GA: OR=1.67, 95% CI=1.27-2.19, P<0.01, I²=0%). Some significant and similar results were also observed in the subgroup analysis. Conclusion: Our meta-analysis indicates that the ALDH2 rs671 G>A polymorphism may play an important role in the occurrence of IS by reducing the activity of ALDH2 and interfering with the metabolic processes involving acetaldehyde.

Genetic polymorphisms of methylenetetrahydrofolate reductase C677T and risk of ischemic stroke in a southern Chinese Hakka population

Previous studies have shown that methylenetetrahydrofolate reductase (MTHFR) gene to be a genetic risk factor for the susceptibility to ischemic stroke. The aim of this case-control study was to investigate whether the polymorphisms of MTHFR C677T were associated with the susceptibility to ischemic stroke in a southern Chinese Hakka population. In this study, a total of 1967 ischemic stroke patients and 2565 controls of Chinese Hakka ethnicity were recruited. The MTHFR C677T polymorphisms were genotyped by polymerase chain reaction (PCR) amplification and microarray method. The risk of ischemic stroke was estimated by logistic regression analysis. The frequencies of CC, CT, and TT genotypes were 52.67% versus 55.63%, 40.31% versus 38.52%, and 7.02% versus 5.85% in patients with ischemic stroke versus controls, respectively. The frequency of T allele was significantly higher in ischemic stroke patients (27.17%) than in controls (25.11%) (P = .026, odds ratio [OR] 1.113, 95% confidence interval [CI] 1.013-1.223). The homozygous TT genotype in the ischemic stroke patients was associated with increased risk (P = .049, OR 1.132, 95% CI 1.001-1.281) when compared with the controls after adjustment for age and sex. The positive association was only found in dominant model without adjustment for age and sex (P = .047, OR 1.127, 95% CI 1.002-1.268). Also, the carrier status of the MTHFR T allele was identified as an independent risk factor for the development ischemic stroke even after the adjustment for conventional risk factors (P = 0.047, OR 1.109, 95% CI 0.964-1.225). Our results provide evidence that variants of MTHFR C677T gene may influence the risk of developing ischemic stroke in a southern Chinese Hakka population. Further studies are needed to confirm this association, which will promote the development of strategies for prevention and treatment of ischemic stroke in our study population.