Association Study of Alcohol Dehydrogenase and Aldehyde Dehydrogenase Polymorphism With Alzheimer Disease in the Taiwanese Population

The aldehyde dehydrogenase 2 rs671 variant enhances amyloid β pathology

In the ALDH2 rs671 variant, a guanine changes to an adenine, resulting in a dramatic decrease in the catalytic activity of the enzyme. Population-based data are contradictory about whether this variant increases the risk of Alzheimer's disease. In East Asian populations, the prevalence of the ALDH2 rs671 variant is 30-50%, making the National Human Brain Bank for Development and Function (the largest brain bank in East Asia) an important resource to explore the link between the ALDH2 rs671 polymorphism and Alzheimer's disease pathology. Here, using 469 postmortem brains, we find that while the ALDH2 rs671 variant is associated with increased plaque deposits and a higher Aβ40/42 ratio, it is not an independent risk factor for Alzheimer's disease. Mechanistically, we show that lower ALDH2 activity leads to 4-HNE accumulation in the brain. The (R)-4-HNE enantiomer adducts to residue Lys53 of C99, favoring Aβ40 generation in the Golgi apparatus. Decreased ALDH2 activity also lowers inflammatory factor secretion, as well as amyloid β phagocytosis and spread in brains of patients with Alzheimer's disease. We thus define the relationship between the ALDH2 rs671 polymorphism and amyloid β pathology, and find that ALDH2 rs671 is a key regulator of Aβ40 or Aβ42 generation.

Impact of common ALDH2 inactivating mutation and alcohol consumption on Alzheimer's disease

Aldehyde dehydrogenase 2 (ALDH2) is an enzyme found in the mitochondrial matrix that plays a central role in alcohol and aldehyde metabolism. A common ALDH2 polymorphism in East Asians descent (called ALDH2*2 or E504K missense variant, SNP ID: rs671), present in approximately 8% of the world's population, has been associated with a variety of diseases. Recent meta-analyses support the relationship between this ALDH2 polymorphism and Alzheimer's disease (AD). And AD-like pathology observed in ALDH2-/- null mice and ALDH2*2 overexpressing transgenic mice indicate that ALDH2 deficiency plays an important role in the pathogenesis of AD. Recently, the worldwide increase in alcohol consumption has drawn attention to the relationship between heavy alcohol consumption and AD. Of potential clinical significance, chronic administration of alcohol in ALDH2*2/*2 knock-in mice exacerbates the pathogenesis of AD-like symptoms. Therefore, ALDH2 polymorphism and alcohol consumption likely play an important role in the onset and progression of AD. Here, we review the data on the relationship between ALDH2 polymorphism, alcohol, and AD, and summarize what is currently known about the role of the common ALDH2 inactivating mutation, ALDH2*2, and alcohol in the onset and progression of AD.

Brain-wide transcriptome-based metabolic alterations in Parkinson's disease: human inter-region and human-experimental model correlations

Alterations in brain metabolism are closely associated with the molecular hallmarks of Parkinson's disease (PD). A clear understanding of the main metabolic perturbations in PD is therefore important. Here, we retrospectively analysed the expression of metabolic genes from 34 PD-control post-mortem human brain transcriptome data comparisons from literature, spanning multiple brain regions. We found high metabolic correlations between the Substantia nigra (SN)- and cerebral cortex-derived tissues. Moreover, three clusters of PD patient cohorts were identified based on perturbed metabolic processes in the SN - each characterised by perturbations in (a) bile acid metabolism (b) omega-3 fatty acid metabolism, and (c) lipoic acid and androgen metabolism - metabolic themes not comprehensively addressed in PD. These perturbations were supported by concurrence between transcriptome and proteome changes in the expression patterns for CBR1, ECI2, BDH2, CYP27A1, ALDH1B1, ALDH9A1, ADH5, ALDH7A1, L1CAM, and PLXNB3 genes, providing a valuable resource for drug targeting and diagnosis. Also, we analysed 58 PD-control transcriptome data comparisons from in vivo/in vitro disease models and identified experimental PD models with significant correlations to matched human brain regions. Collectively, our findings suggest metabolic alterations in several brain regions, heterogeneity in metabolic alterations between study cohorts for the SN tissues and the need to optimize current experimental models to advance research on metabolic aspects of PD.

Aldehyde dehydrogenase 2 polymorphism is associated with chemotherapy-related cognitive impairment in patients with breast cancer who receive chemotherapy

BACKGROUND

Chemotherapy-related cognitive impairment (CRCI) is a common but easily overlooked condition that markedly affects the quality of life (QOL) of patients with breast cancer. The rs671 is a common gene polymorphism of aldehyde dehydrogenase 2 (ALDH2) in Asia that is involved in aldehyde metabolism and may be closely related to CRCI. However, no study has yet summarised the association between ALDH2 and CRCI.

METHODS

This study enrolled one hundred and twenty-four patients diagnosed with breast cancer according to the pathology results, genotyped for ALDH2 single-nucleotide polymorphisms (SNP) to explore these. The mini-mental state exam (MMSE), verbal fluency test (VFT), and digit span test (DST) results were compared in these patients before and after chemotherapy (CT).

RESULTS

We found that patients with ALDH2 gene genotypes of rs671_GG, rs886205_GG, rs4648328_CC, and rs4767944_TT polymorphisms were more likely to suffer from cognitive impairment during chemotherapy. A trend toward statistical significance was observed for rs671_GG of DST (z = 2.769, p = 0.006), VFT (t = 4.624, P<0.001); rs886205_GG of DST (z = 3.663, P<0.001); rs4648328_CC of DST (z = 2.850, p = 0.004), VFT (t = 3.477, p = 0.001); and rs4767944_TT of DST (z = 2.967, p = 0.003), VFT (t = 2.776, p = 0.008). The cognitive indicators of these patients significantly decreased after chemotherapy (p < 0.05). The difference in ALDH2 rs671 was most obvious.

CONCLUSION

Our results showed what kinds of ALDH2 genotyped patients that are more likely to develop CRCI. In the future, it may be possible to infer the risk of CRCI by detecting the single-nucleotide locus of ALDH2 that is conducive to strengthening clinical interventions for these patients and improving their QOL. More importantly, this study has important implications for Asian women with breast cancer as ALDH2 rs671 is a common polymorphism in Asians.

Association Study and Meta-Analysis of Polymorphisms and Blood mRNA Expression of the ALDH2 Gene in Patients with Alzheimer’s Disease

Background:

Late-onset Alzheimer’s disease (LOAD) is a complex disease in which neuroinflammation plays an important pathophysiological role, and exposure to neurotoxic substrates such as aldehydes may contribute. Blood mRNA expression levels of neuroinflammation-related genes appear to be potential biological markers of LOAD. A relationship between ALDH2 and LOAD has been suggested.

Objective:

Our objective was to examine blood ALDH2 expression in Japanese LOAD patients, conduct a genetic association study, and add new studies to an extended meta-analysis of the Asian population.

Methods:

A blood expression study (45 AD subjects, 54 controls) in which total RNA was isolated from whole peripheral blood samples and ALDH2 expression measured was conducted. In addition, a genetic association study (271 AD subjects, 492 controls) using genomic DNA from whole peripheral blood samples was conducted. Finally, a meta-analysis examined the relationship between ALDH2^*2 frequency and the risk of LOAD.

Results:

ALDH2 mRNA expression was significantly higher in LOAD than in controls, and also higher in men with LOAD than in women with LOAD (p = 0.043). The genotypes in the two classified groups and the allele frequency were significantly different between AD and control subjects. The meta-analysis showed a significant difference in the ALDH2^*2 allele, with an increased AD risk (OR = 1.38; 95% CI = 1.02–1.85; p = 0.0348, I² = 81.1%).

Conclusion:

There was a significant increase in blood ALDH2 expression, and a genetic association with ALDH2^*2 in LOAD. ALDH2 may have significant roles in the pathogenesis of LOAD in the Asian population.

Associations of Alcohol Dehydrogenase and Aldehyde Dehydrogenase Polymorphism With Cognitive Impairment Among the Oldest-Old in China

Recent literature suggested that ALDH2 mutation is associated with alcohol metabolism, and ethanol intake might jointly increase the risk of Alzheimer’s disease (AD) in mice. However, it is unclear whether this synergistic effect exists among humans. We examined the associations of four single nucleotide polymorphisms (SNPs) on aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH) genes (i.e., ALDH2 rs671, ADH1B rs1229984, ADH1B rs1042026, and ADH1C rs1693482) and cognitive impairment among the oldest-old. We also investigated whether this association was modified by ethanol intake from alcohol consumption. Data were from the Chinese Longitudinal Healthy Longevity Survey genetic sub-study, including 1,949 participants aged over 90 years. Participants with a Mini-Mental State Examination (MMSE) score of < 18 were considered cognitively impaired. Alcohol consumption was categorized as heavy, moderate, or never drinkers. With the dominant model, carrying A allele on rs671, C allele on rs1229984, and T allele on rs1042026 was associated with 33% (95% confidence interval [CI]: 5%, 69%), 33% (95% CI: 2%, 75%), and 29% (95% CI: 3%, 62%) higher odds of cognitive impairment in the multivariable-adjusted logistic model, respectively. We did not observe a significant interaction between those SNPs and alcohol consumption. Among the oldest-old, carrying ALDH2 rs671 mutation was associated with higher odds of cognitive impairment independent of alcohol consumption.