Aldehyde Dehydrogenase 2 Activator Augments the Beneficial Effects of Empagliflozin in Mice with Diabetes-Associated HFpEF.

To ameliorate diabetes mellitus-associated heart failure with preserved ejection fraction (HFpEF), we plan to lower diabetes-mediated oxidative stress-induced 4-hydroxy-2-nonenal (4HNE) accumulation by pharmacological agents that either decrease 4HNE generation or increase its detoxification.A cellular reactive carbonyl species (RCS), 4HNE, was significantly increased in diabetic hearts due to a diabetes-induced decrease in 4HNE detoxification by aldehyde dehydrogenase (ALDH) 2, a cardiac mitochondrial enzyme that metabolizes 4HNE. Therefore, hyperglycemia-induced 4HNE is critical for diabetes-mediated cardiotoxicity and we hypothesize that lowering 4HNE ameliorates diabetes-associated HFpEF. We fed a high-fat diet to ALDH2*2 mice, which have intrinsically low ALDH2 activity, to induce type-2 diabetes. After 4 months of diabetes, the mice exhibited features of HFpEF along with increased 4HNE adducts, and we treated them with vehicle, empagliflozin (EMP) (3 mg/kg/d) to reduce 4HNE and Alda-1 (10 mg/kg/d), and ALDH2 activator to enhance ALDH2 activity as well as a combination of EMP + Alda-1 (E + A), via subcutaneous osmotic pumps. After 2 months of treatments, cardiac function was assessed by conscious echocardiography before and after exercise stress. EMP + Alda-1 improved exercise tolerance, diastolic and systolic function, 4HNE detoxification and cardiac liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) pathways in ALDH2*2 mice with diabetes-associated HFpEF. This combination was even more effective than EMP alone. Our data indicate that ALDH2 activation along with the treatment of hypoglycemic agents may be a salient strategy to alleviate diabetes-associated HFpEF.

E-cigarette aerosol exacerbates cardiovascular oxidative stress in mice with an inactive aldehyde dehydrogenase 2 enzyme.

BACKGROUND: E-cigarette aerosol containing aldehydes, including acetaldehyde, are metabolized by the enzyme aldehyde dehydrogenase 2 (ALDH2). However, little is known how aldehyde exposure from e-cigarettes, when coupled with an inactivating ALDH2 genetic variant, ALDH2*2 (present in 8% of the world population), affects cardiovascular oxidative stress. OBJECTIVES: The study was to determine how e-cigarette aerosol exposure, coupled with genetics, impacts cardiovascular oxidative stress in wild type ALDH2 and ALDH2*2 knock-in mice. METHODS: Using selective ion flow mass spectrometry, we determined e-cigarette aerosol contains acetaldehyde levels 10-fold higher than formaldehyde or acrolein. Based on this finding, we tested how isolated ALDH2*2 primary cardiomyocytes respond to acetaldehyde and how intact ALDH2*2 knock-in rodents instrumented with telemeters respond physiologically and at the molecular level to 10 days of e-cigarette aerosol exposure relative to wild type ALDH2 rodents. RESULTS: For ALDH2*2 isolated cardiomyocytes, acetaldehyde (1 µM) caused a 4-fold greater peak calcium influx, 2-fold increase in ROS production and 2-fold increase in 4-HNE-induced protein adducts relative to wild-type ALDH2 cardiomyocytes. The heart rate in ALDH2*2 mice increased ∼200 beats/min, while, heart rate in ALDH2 mice increased ∼150 beats/min after 10 days of e-cigarette exposure, relative to air-exposed mice. E-cigarette aerosol exposure triggered ∼1.3 to 2-fold higher level of protein carbonylation, lipid peroxidation, and phosphorylation of NF-κB for both strains of mice, with this response exacerbated for ALDH2*2 mice. CONCLUSIONS: Our findings indicate people carrying an ALDH2*2 genetic variant may be more susceptible to increases in cardiovascular oxidative stress from e-cigarette aerosol exposure.

East Asian variant aldehyde dehydrogenase type 2 genotype exacerbates ischemia/reperfusion injury with ST-elevation myocardial infarction in men: possible sex differences.

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) detoxifies toxic aldehydes generated during ischemia/reperfusion (I/R) injury in ST-elevation myocardial infarction (STEMI). The deficient variant ALDH2 genotype (ALDH2*2) is prevalent among East Asians. Whether ALDH2*2 exacerbates I/R injury of in patients with STEMI is not known. The study subjects comprised 218 Japanese patients with STEMI (158 men and 60 women, mean age 67.9 ± 11.9) who underwent successful percutaneous coronary intervention. Of these, 120 (55.0%) were the carriers of variant ALDH2*2 and 98 (45.0%) those of wild ALDH2*1/*1 on genotyping. There were no differences in clinical characteristics between the ALDH2*2 and ALDH2*1/*1 group except lower alcohol habit (14.2% vs 46.3%, P < 0.001) in the ALDH2*2 group. The peak plasma levels of creatine phosphokinase myocardial binding (CKMB), a marker of myocardial injury, however, were significantly higher in the patients with ALDH2*2 than in those with ALDH2*1/*1 [a median 275.0 (175.8-407.5) vs 177.5 (126.9-344.3) U/L, P = 0.001] among men but not among women (P = 0.811). There was a significant interaction between men (male sex) and ALDH2*2 for I/R injury (χ2 = 4.425, P = 0.040). The variant ALDH2*2 was associated with more severe I/R injury than the wild ALDH2*1/*1 in STEMI patients in men with possible sex differences.

Acetaldehyde Enhances Alcohol Sensitivity and Protects against Alcoholism: Evidence from Alcohol Metabolism in Subjects with Variant ALDH2*2 Gene Allele.

Alcoholism is a complex behavior trait influenced by multiple genes as well as by sociocultural factors. Alcohol metabolism is one of the biological determinants that can significantly influence drinking behaviors. Alcohol sensitivity is thought to be a behavioral trait marker for susceptibility to develop alcoholism. The subjective perceptions would be an indicator for the alcohol preference. To investigate alcohol sensitivity for the variants ADH1B*2 and ALDH2*2, sixty healthy young males with different combinatory ADH1B and ALDH2 genotypes, ADH1B*2/*2-ALDH2*1/*1 (n = 23), ADH1B*2/*2-ALDH2*1/*2 (n = 27), and ADH1B*1/*1-ALDH2*1/*1 (n = 10), participated in the study. The subjective perceptions were assessed by a structured scale, and blood ethanol and acetaldehyde were determined by GC and HPLC after an alcohol challenge in two dose sessions (0.3 g/kg or 0.5 g/kg ethanol). The principal findings are (1) dose-dependent increase of blood ethanol concentration, unaffected by ADH1B or ALDH2; (2) significant build-up of blood acetaldehyde, strikingly influenced by the ALDH2*2 gene allele and correlated with the dose of ingested alcohol; (3) the increased heart rate and subjective sensations caused by acetaldehyde accumulation in the ALDH2*2 heterozygotes; (4) no significant effect of ADH1B polymorphism in alcohol metabolism or producing the psychological responses. The study findings provide the evidence of acetaldehyde potentiating the alcohol sensitivity and feedback to self-control the drinking amount. The results indicate that ALDH2*2 plays a major role for acetaldehyde-related physiological negative responses and prove the genetic protection against development of alcoholism in East Asians.

ALDH2 deficiency induces atrial fibrillation through dysregulated cardiac sodium channel and mitochondrial bioenergetics: A multi-omics analysis.

Point mutation in alcohol dehydrogenase 2 (ALDH2), ALDH2*2 results in decreased catalytic enzyme activity and has been found to be associated with different human pathologies. Whether ALDH2*2 would induce cardiac remodeling and increase the attack of atrial fibrillation (AF) remains poorly understood. The present study evaluated the effect of ALDH2*2 mutation on AF susceptibility and unravelled the underlying mechanisms using a multi-omics approach including whole-genome gene expression and proteomics analysis. The in-vivo electrophysiological study showed an increase in the incidence and reduction in the threshold of AF for the mutant mice heterozygous for ALDH2*2 as compared to the wild type littermates. The microarray analysis revealed a reduction in the retinoic acid signals which was accompanied by a downstream reduction in the expression of voltage-gated Na+ channels (SCN5A). The treatment of an antagonist for retinoic acid receptor resulted in a decrease in SCN5A transcript levels. The integrated analysis of the transcriptome and proteome data showed a dysregulation of fatty acid ß-oxidation, adenosine triphosphate synthesis via electron transport chain, and activated oxidative responses in the mitochondria. Oral administration of Coenzyme Q10, an essential co-factor known to meliorate mitochondrial oxidative stress and preserve bioenergetics, conferred a protection against AF attack in the mutant ALDH2*2 mice. The multi-omics approach showed the unique pathophysiology mechanisms of concurrent dysregulated SCN5A channel and mitochondrial bioenergetics in AF. This inspired the development of a personalized therapeutic agent, Coenzyme Q10, to protect against AF attack in humans characterized by ALDH2*2 genotype.

Alcohol Consumption, Cardiovascular-Related Conditions, and ALDH2*2 Ethnic Group Prevalence in Asian Americans.

BACKGROUND: Little is known about the relationships between alcohol consumption and cardiovascular disease (CVD) and related chronic conditions in Asian Americans and how such risk relationships vary among their subgroups. We examine these relationships in Asian Americans and their moderation by ethnic prevalence of a variant the aldehyde dehydrogenase gene: ALDH2*2. METHODS: Multiple logistic regression modeling was performed using a nationally representative sample of Asian-American adults aged 30 to 70 (n = 1,720) from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) Waves 2 (2004 to 2005) and 3 (2012 to 2013). Outcomes considered were diabetes, hypertension, high cholesterol, CVD, any of the 3 conditions (i.e., diabetes, high cholesterol, and CVD) documented to have a J-shaped relationship with drinking (CVDRC3), and any of the CVD-related conditions (ANYCVD). Demographic and socioeconomic characteristics, health insurance coverage, and other lifestyle risk factors (smoking and obesity/overweight) were adjusted. Analyses were stratified by gender. RESULTS: Alcohol consumption level was positively associated only with hypertension in Asian males, with consuming 7 to 14 drinks per week associated with more than double the risk of lifetime abstinence. For females, alcohol consumption had a dose-response relationship with high cholesterol and CVDRC3. Membership in the higher ALDH2*2 ethnic group overall was associated with lower risk of CVD-related conditions. However, compared to abstainers in lower ALDH2*2 group, females in the higher ALDH2*2 group who consumed more than 7 drinks per week had a higher risk of diabetes, hypertension, CVDRC3, and ANYCVD. CONCLUSIONS: Asian Americans may have increased risk of CVD-related conditions at relatively low alcohol consumption levels. Among Asian-American females, in particular, any amount of drinking may increase risk for high cholesterol or any of the CVD-related conditions previously documented to have a curvilinear relationship with drinking. These risks may be particularly elevated for those in ethnic groups with a high prevalence of ALDH2*2.

Aldehyde dehydrogenase 2 activity and aldehydic load contribute to neuroinflammation and Alzheimer's disease related pathology.

Aldehyde dehydrogenase 2 deficiency (ALDH2*2) causes facial flushing in response to alcohol consumption in approximately 560 million East Asians. Recent meta-analysis demonstrated the potential link between ALDH2*2 mutation and Alzheimer's Disease (AD). Other studies have linked chronic alcohol consumption as a risk factor for AD. In the present study, we show that fibroblasts of an AD patient that also has an ALDH2*2 mutation or overexpression of ALDH2*2 in fibroblasts derived from AD patients harboring ApoE ε4 allele exhibited increased aldehydic load, oxidative stress, and increased mitochondrial dysfunction relative to healthy subjects and exposure to ethanol exacerbated these dysfunctions. In an in vivo model, daily exposure of WT mice to ethanol for 11 weeks resulted in mitochondrial dysfunction, oxidative stress and increased aldehyde levels in their brains and these pathologies were greater in ALDH2*2/*2 (homozygous) mice. Following chronic ethanol exposure, the levels of the AD-associated protein, amyloid-ß, and neuroinflammation were higher in the brains of the ALDH2*2/*2 mice relative to WT. Cultured primary cortical neurons of ALDH2*2/*2 mice showed increased sensitivity to ethanol and there was a greater activation of their primary astrocytes relative to the responses of neurons or astrocytes from the WT mice. Importantly, an activator of ALDH2 and ALDH2*2, Alda-1, blunted the ethanol-induced increases in Aß, and the neuroinflammation in vitro and in vivo. These data indicate that impairment in the metabolism of aldehydes, and specifically ethanol-derived acetaldehyde, is a contributor to AD associated pathology and highlights the likely risk of alcohol consumption in the general population and especially in East Asians that carry ALDH2*2 mutation.

Environmental Aldehyde Sources and the Health Implications of Exposure.

Aldehydes, which are present within the air as well as food and beverage sources, are highly reactive molecules that can be cytotoxic, mutagenic, and carcinogenic. To prevent harm from reactive aldehyde exposure, the enzyme aldehyde dehydrogenase 2 (ALDH2) metabolizes reactive aldehydes to a less toxic form. However, the genetic variant of ALDH2, ALDH2*2, significantly reduces the ability to metabolize reactive aldehydes in humans. Therefore, frequent environmental aldehyde exposure, coupled with inefficient aldehyde metabolism, could potentially lead to an increased health risk for diseases such as cancer or cardiovascular disease.Here, we discuss the environmental sources of reactive aldehydes and the potential health implications particularly for those with an ALDH2*2 genetic variant. We also suggest when considering the ALDH2*2 genetic variant the safety limits of reactive aldehyde exposure may have to be reevaluated. Moreover, the ALDH2*2 genetic variant can also be used as an example for how to implement precision medicine in the field of environmental health sciences.

An integrative bioinformatics pipeline to demonstrate the alteration of the interaction between the ALDH2*2 allele with NAD+ and Disulfiram.

Alcohol use disorder (AUD) is a multifactorial psychiatric behavior disorder. Disulfiram is the first approved drug by the Food and Drug Administration for alcohol-dependent patients, which targets the ALDH2 enzyme. Several genes are known to be involved in alcohol metabolism; mutations in any of these genes are known to be associated with AUD. The E504K mutation in the ALDH2 of the precursor protein or the E487K of the mature protein (E504K/E487K; ALDH2*2 allele) is carried by approximately 8% of the world population. In this study, we aimed to test the known inactive allele ALDH2*2, to validate the use of our extensive computational pipeline (in silico tools, molecular modeling, and molecular docking) for testing the interaction between the ALDH2*2 allele, NAD+, and Disulfiram. In silico predictions showed that the E504K variant of ALDH2 to be pathogenic and destabilizing with the maximum number of prediction in silico tools. Consequently, we studied the effect of this mutation mainly on the interaction between NAD+ -E504K and Disulfiram-E504K complexes using molecular docking technique, and molecular dynamics (MD) analysis. From the molecular docking analysis with NAD+ , we observed that the interaction affinity of the NAD+ decreases with the impact of E504K variant. On the other hand, the drug Disulfiram showed similar interaction in both the native and mutant ALDH2 proteins. Further, the comprehensive MD analysis predicted that the E504K destabilizes the protein and influences the NAD+ and Disulfiram interactions. Our findings reveal that the interaction of NAD+ to the protein is disturbed by the E504K/E487K variant whereas the drug Disulfiram has a similar effect as both native ALDH2 and ALDH2 bearing E504K/E487K variant. This study provides a platform to understand the effect of E504K/E487K on the molecular interaction with NAD+ and Disulfiram.

Could ALDH2*2 be the reason for low incidence and mortality of ovarian cancer for East Asia women?

It is curious that East Asian women have a low incidence and mortality of ovarian cancer in various epidemiological studies. Although different explanations were given, they appear unsubstantial. We notice that East Asian population usually are inactive aldehyde dehydrogenase 2 mutation (ALDH2 * 2) carriers, and ALDH plays an important role in the resistance of ovarian cancer to chemotherapeutics, especially in ovarian cancer stem cells. Therefore, we hypothesize whether ALDH2 mutation is the major reason for low incidence and mortality of ovarian cancer in East Asian women, and use the evidence from literature, transcriptomic data with average 5-year overall survival to confirm our hypothesis.

Aldehyde-Induced DNA and Protein Adducts as Biomarker Tools for Alcohol Use Disorder.

Alcohol use disorder (AUD) screening frequently involves questionnaires complemented by laboratory work to monitor alcohol use and/or evaluate AUD-associated complications. Here we suggest that measuring aldehyde-induced DNA and protein adducts produced during alcohol metabolism may lead to earlier detection of AUD and AUD-associated complications compared with existing biomarkers. Use of aldehyde-induced adducts to monitor AUD may also be important when considering that approximately 540 million people bear a genetic variant of aldehyde dehydrogenase 2 (ALDH2) predisposing this population to aldehyde-induced toxicity with alcohol use. We posit that measuring aldehyde-induced adducts may provide a means to improve precision medicine approaches, taking into account lifestyle choices and genetics to evaluate AUD and AUD-associated complications.

ALDH2*2 and peer drinking in East Asian college students.

BACKGROUND: The ALDH2*2 allele (A-allele) at rs671 is more commonly carried by Asians and is associated with alcohol-related flushing, a strong adverse reaction to alcohol that is protective against drinking. Social factors, such as having friends who binge drink, also contribute to drinking in Asian youth. OBJECTIVES: This study examined the interplay between ALDH2*2, peer drinking, and alcohol consumption in college students. We hypothesized that the relationship between ALDH2*2 and standard grams of ethanol per month would vary based on the level of peer drinking. METHODS: Subjects (N = 318, 63.25% female) were East Asian college students in the United States who reported drinking alcohol. Data were from the freshman year of a university survey that included a saliva DNA sample. ALDH2*2 status was coded ALDH2*2(+) (A/G and A/A genotypes) and ALDH2*2(-) (G/G genotype). Peer drinking was students' perception of how many of their friends "got drunk". RESULTS: Main effects of ALDH2*2(-) and having more friends who got drunk were associated with greater alcohol consumption. The ALDH2*2 × peer drunkenness interaction showed a stronger positive association with alcohol consumption for ALDH2*2(-) versus ALDH2*2(+) at increasing levels of peer drunkenness. Follow-up comparisons within each peer drunkenness level identified significantly higher alcohol consumption for ALDH2*2(-) compared to ALDH2*2(+) at the all friends got drunk level. CONCLUSION: There was evidence of a stronger effect for ALDH2*2(-) compared to ALDH2*2(+) with greater alcohol use when students were more exposed to peer drinking. Findings contribute to a growing literature on the interrelationships between genetic influences and more permissive environments for alcohol consumption.

Reactive aldehydes: an initial path to develop precision medicine for pain control.

With the risks of opioid addiction, abuse, and overdose, there is a need to identify new molecular targets contributing to pain sensation in order to develop directed treatments for pain. One mechanism to treat pain is to target reactive aldehydes either by limiting production or by increasing metabolism. In response to a recent editorial in the Annals of Translational Medicine (ATM), we discuss how reactive aldehyde production can trigger pain and how the enzyme mitochondrial aldehyde dehydrogenase 2 (ALDH2) regulates inflammatory pain by reactive aldehyde metabolism. We also comment about the possible clinical impact caused by the inefficiency of reactive aldehyde metabolism for the ~540 million people with an ALDH2*2 variant. Further, we discuss how developing therapeutics specifically targeting ALDH2 may lead to the development of a pathway to potentially create precision medicine for pain control.

ALDH2(E487K) mutation increases protein turnover and promotes murine hepatocarcinogenesis.

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) in the liver removes toxic aldehydes including acetaldehyde, an intermediate of ethanol metabolism. Nearly 40% of East Asians inherit an inactive ALDH2*2 variant, which has a lysine-for-glutamate substitution at position 487 (E487K), and show a characteristic alcohol flush reaction after drinking and a higher risk for gastrointestinal cancers. Here we report the characterization of knockin mice in which the ALDH2(E487K) mutation is inserted into the endogenous murine Aldh2 locus. These mutants recapitulate essentially all human phenotypes including impaired clearance of acetaldehyde, increased sensitivity to acute or chronic alcohol-induced toxicity, and reduced ALDH2 expression due to a dominant-negative effect of the mutation. When treated with a chemical carcinogen, these mutants exhibit increased DNA damage response in hepatocytes, pronounced liver injury, and accelerated development of hepatocellular carcinoma (HCC). Importantly, ALDH2 protein levels are also significantly lower in patient HCC than in peritumor or normal liver tissues. Our results reveal that ALDH2 functions as a tumor suppressor by maintaining genomic stability in the liver, and the common human ALDH2 variant would present a significant risk factor for hepatocarcinogenesis. Our study suggests that the ALDH2*2 allele-alcohol interaction may be an even greater human public health hazard than previously appreciated.