Acetaldehyde dehydrogenase 2 deficiency increases mitochondrial reactive oxygen species emission and induces mitochondrial protease Omi/HtrA2 in skeletal muscle

Coculture with Colon-26 cancer cells decreases the protein synthesis rate and shifts energy metabolism toward glycolysis dominance in C2C12 myotubes

Cancer cachexia is the result of complex interorgan interactions initiated by cancer cells and changes in patient behavior such as decreased physical activity and energy intake. Therefore, it is crucial to distinguish between the direct and indirect effects of cancer cells on muscle mass regulation and bioenergetics to identify novel therapeutic targets. In this study, we investigated the direct effects of Colon-26 cancer cells on the molecular regulating machinery of muscle mass and its bioenergetics using a coculture system with C2C12 myotubes. Our results demonstrated that coculture with Colon-26 cells induced myotube atrophy and reduced skeletal muscle protein synthesis and its regulating mechanistic target of rapamycin complex 1 signal transduction. However, we did not observe any activating effects on protein degradation pathways including ubiquitin-proteasome and autophagy-lysosome systems. From a bioenergetic perspective, coculture with Colon-26 cells decreased the complex I-driven, but not complex II-driven, mitochondrial ATP production capacity, while increasing glycolytic enzyme activity and glycolytic metabolites, suggesting a shift in energy metabolism toward glycolysis dominance. Gene expression profiling by RNA sequencing showed that the increased activity of glycolytic enzymes was consistent with changes in gene expression. However, the decreased ATP production capacity of mitochondria was not in line with the gene expression. The potential direct interaction between cancer cells and skeletal muscle cells revealed in this study may contribute to a better fundamental understanding of the complex pathophysiology of cancer cachexia.NEW & NOTEWORTHY We explored the potential direct interplay between colon cancer cells (Colon-26) and skeletal muscle cells (C2C12 myotubes) employing a noncontact coculture experimental model. Our findings reveal that coculturing with Colon-26 cells substantially impairs the protein synthesis rate, concurrently instigating a metabolic shift toward glycolytic dominance in C2C12 myotubes. This research unveils critical insights into the intricate cellular cross talk underpinning the complex pathophysiology of cancer cachexia.

Monocarboxylate transporter 4 deficiency enhances high-intensity interval training-induced metabolic adaptations in skeletal muscle

High-intensity exercise stimulates glycolysis, subsequently leading to elevated lactate production within skeletal muscle. While lactate produced within the muscle is predominantly released into the circulation via the monocarboxylate transporter 4 (MCT4), recent research underscores lactate's function as an intercellular and intertissue signalling molecule. However, its specific intracellular roles within muscle cells remains less defined. In this study, our objective was to elucidate the effects of increased intramuscular lactate accumulation on skeletal muscle adaptation to training. To achieve this, we developed MCT4 knockout mice and confirmed that a lack of MCT4 indeed results in pronounced lactate accumulation in skeletal muscle during high-intensity exercise. A key finding was the significant enhancement in endurance exercise capacity at high intensities when MCT4 deficiency was paired with high-intensity interval training (HIIT). Furthermore, metabolic adaptations supportive of this enhanced exercise capacity were evident with the combination of MCT4 deficiency and HIIT. Specifically, we observed a substantial uptick in the activity of glycolytic enzymes, notably hexokinase, glycogen phosphorylase and pyruvate kinase. The mitochondria also exhibited heightened pyruvate oxidation capabilities, as evidenced by an increase in oxygen consumption when pyruvate served as the substrate. This mitochondrial adaptation was further substantiated by elevated pyruvate dehydrogenase activity, increased activity of isocitrate dehydrogenase - the rate-limiting enzyme in the TCA cycle - and enhanced function of cytochrome c oxidase, pivotal to the electron transport chain. Our findings provide new insights into the physiological consequences of lactate accumulation in skeletal muscle during high-intensity exercises, deepening our grasp of the molecular intricacies underpinning exercise adaptation. KEY POINTS: We pioneered a unique line of monocarboxylate transporter 4 (MCT4) knockout mice specifically tailored to the ICR strain, an optimal background for high-intensity exercise studies. A deficiency in MCT4 exacerbates the accumulation of lactate in skeletal muscle during high-intensity exercise. Pairing MCT4 deficiency with high-intensity interval training (HIIT) results in a synergistic boost in high-intensity exercise capacity, observable both at the organismal level (via a treadmill running test) and at the muscle tissue level (through an ex vivo muscle contractile function test). Coordinating MCT4 deficiency with HIIT enhances both the glycolytic enzyme activities and mitochondrial capacity to oxidize pyruvate.

Deficiency of aldehyde dehydrogenase 2 aggravates ethanol-induced cytotoxicity in N2a cells via CaMKII/Drp1-mediated mitophagy

Chronic alcohol abuse causes brain damage and has been associated with an increased risk of Alzheimer's disease. The toxic metabolite of alcohol, acetaldehyde, which is converted to acetate by aldehyde dehydrogenase 2 (ALDH2), has been shown to induce excessive mitochondrial fragmentation and dysfunction leading to neurotoxicity. However, it is still unclear how alcohol affects mitochondrial function in ALDH2-deficient cells. The present study investigated the association between abnormal mitochondrial dynamics, mitophagy and cytotoxicity in ALDH2-deficient N2a cells treated with ethanol. It was found that ethanol induced dynamin-related protein 1 (Drp1)-mediated mitochondrial fragmentation and impaired mitochondrial function, causing excessive mitophagy and cytotoxicity in ALDH2-deficient N2a cells while inducing Ca2+ influx and activating Ca2+/calmodulin-dependent protein kinase II (CaMKII). Inhibition of Ca2+ overload or CaMKII activation prevented Drp1 phosphorylation and ameliorated ethanol-induced mitophagy and cytotoxicity, indicating that Ca2+-dependent CaMKII activation was critical for mediating Drp1-dependent excessive mitochondrial fission and mitophagy in ALDH2-deficient N2a cells. The results of the present study suggested that prevention of intracellular Ca2+ overload might be beneficial for preventing neurotoxicity associated with alcohol abuse in individuals with defective ALDH2.

Dietary apple polyphenols enhance mitochondrial turnover and respiratory chain enzymes

Previous studies have demonstrated the beneficial effects of apple polyphenol (AP) intake on muscle endurance. Since mitochondria are critical for muscle endurance, we investigated mitochondrial enzyme activity, biogenesis, degradation and protein quality control. Twenty-four Wistar rats were randomly fed a 5% AP diet (5% AP group, n = 8), a 0.5% AP diet (0.5% AP group, n = 8), or a control diet (control group, n = 8). After a 4-week feeding period, the expression level of peroxisome proliferator-activated receptor γ coactivator-1α, a mitochondrial biosynthetic factor, did not increase, whereas that of transcription factor EB, another regulator of mitochondrial synthesis, significantly increased. Moreover, the mitochondrial count did not differ significantly between the groups. In contrast, mitophagy-related protein levels were significantly increased. The enzymatic activities of mitochondrial respiratory chain complexes II, III and IV were significantly higher in the AP intake group than in the control group. We conclude that AP feeding increases the activity of respiratory chain complex enzymes in rat skeletal muscles. Moreover, mitochondrial biosynthesis and degradation may have increased in AP-treated rats. NEW FINDINGS: What is the central question of this study? Does the administration of apple polyphenols (AP) affect mitochondrial respiratory chain complex enzyme activity, biogenesis, degradation and protein quality control in rat skeletal muscles? What is the main finding and its importance? AP feeding increases respiratory chain complex enzyme activity in rat skeletal muscle. Moreover, AP administration increases transcription factor EB activation, and mitophagy may be enhanced to promote degradation of dysfunctional mitochondria, but mitochondrial protein quality control was not affected.

ALDH2 Inhibition by Lead and Ethanol Elicits Redox Imbalance and Mitochondrial Dysfunction in SH-SY5Y Human Neuroblastoma Cell Line: Reversion by Alda-1

Lead (Pb), a common environmental contaminant, and ethanol (EtOH), a widely available drug of abuse, are well-known neurotoxicants. In vivo, experimental evidence indicates that Pb exposure affects oxidative EtOH metabolism with a high impact on living organisms. On these bases, we evaluated the consequences of combined Pb and EtOH exposure on aldehyde dehydrogenase 2 (ALDH2) functionality. In vitro exposure to 10µM Pb, 200mM EtOH, or their combination for 24h reduced ALDH2 activity and content in SH-SY5Y human neuroblastoma cells. In this scenario, we observed mitochondrial dysfunction characterized by reduced mass and membrane potential, decreased maximal respiration, and spare capacity. We also evaluated the oxidative balance in these cells finding a significant increase in reactive oxygen species (ROS) production and lipid peroxidation products under all treatments accompanied by an increase in catalase (CAT) activity and content. These data suggest that ALDH2 inhibition induces the activation of converging cytotoxic mechanisms resulting in an interplay between mitochondrial dysfunction and oxidative stress. Notably, NAD⁺ (1mM for 24h) restored ALDH2 activity in all groups, while an ALDH2 enhancer (Alda-1, 20µM for 24h) also reversed some of the deleterious effects resulting from impaired ALDH2 function. Overall, these results reveal the crucial role of this enzyme on the Pb and EtOH interaction and the potential of activators such as Alda-1 as therapeutic approaches against several conditions involving aldehydes accumulation.

Branched-chain amino acid supplementation suppresses the detraining-induced reduction of mitochondrial content in mouse skeletal muscle

Exercise training enhances oxidative capacity whereas detraining reduces mitochondrial content in skeletal muscle. The strategy to suppress the detraining-induced reduction of mitochondrial content has not been fully elucidated. As previous studies reported that branched-chain amino acid (BCAA) ingestion increased mitochondrial content in skeletal muscle, we evaluated whether BCAA supplementation could suppress the detraining-induced reduction of mitochondrial content. Six-week-old male Institute of Cancer Research (ICR) mice were randomly divided into four groups as follows: control (Con), endurance training (Tr), detraining (DeTr), and detraining with BCAA supplementation (DeTr + BCAA). Mice in Tr, DeTr, and DeTr + BCAA performed treadmill running exercises [20-30 m/min, 60 min, 5 times/week, 4 weeks]. Then, mice in DeTr and DeTr + BCAA were administered with water or BCAA [0.6 mg/g of body weight, twice daily] for 2 weeks of detraining. In whole skeletal muscle, mitochondrial enzyme activities and protein content were decreased after 2 weeks of detraining, but the reduction was suppressed by BCAA supplementation. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) protein content, a master regulator of mitochondrial biogenesis, was decreased by detraining irrespective of BCAA ingestion. Regarding mitochondrial degradation, BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3), a mitophagy-related protein, was significantly higher in the Tr group than in the DeTr + BCAA group, but not different from in the DeTr group. With respect to mitochondrial quality, BCAA ingestion did not affect oxygen consumption rate (OCR) and reactive oxygen species (ROS) production in isolated mitochondria. Our findings suggest that BCAA ingestion suppresses the detraining-induced reduction of mitochondrial content partly through inhibiting mitophagy.

ALDH2 gene polymorphism is associated with fitness in the elderly Japanese population

PURPOSE

The aldehyde dehydrogenase 2 (ALDH2) rs671 polymorphism, which is exclusive to the Asian population, is related to many diseases. A high reactive oxygen species production in mitochondria, and low muscle strength in athletes and non-athletes, has been observed, as our previous study demonstrated. The purpose of this research was to investigate the influence of ALDH2 rs671 on the loss of muscle strength with aging and replicate our previous study in non-athletes.

METHODS

Healthy Japanese individuals (n = 1804) aged 23-94 years were genotyped using DNA extracted from saliva. Muscle strength was assessed using grip strength and chair stand test (CST). The interaction between age and genotypes was analyzed by two-way analysis of covariance (ANCOVA) adjusted for sex, body mass index (BMI), and exercise habit.

RESULTS

Individuals aged ≧55 with the AA genotype had a lower performance than those with the GG + GA genotype in the grip strength test (28.1 ± 9.1 kg vs. 29.1 ± 8.3 kg, p = 0.021). There was an interaction between age and genotype, where individuals with ≧55 years old AA genotype had a higher loss of strength compared to GG + GA genotypes in the CST (0.025). No interaction in other models and no sex differences were found.

CONCLUSION

This study replicated previous results of the relationship between the AA genotype with lower muscle strength and as a novelty showed that this genotype is associated with a higher age-related loss of strength.

The Association between the ALDH2 rs671 Polymorphism and Athletic Performance in Japanese Power and Strength Athletes

The rs671 polymorphism is associated with the enzymatic activity of aldehyde dehydrogenase 2 (ALDH2), which is weakened by the A allele in East Asians. We recently reported the association of this polymorphism with the athletic status in athletic cohorts and the muscle strength of non-athletic cohorts. Therefore, we hypothesized the association of ALDH2 rs671 polymorphism with the performance in power/strength athletes. We aimed to clarify the relationship between the ALDH2 rs671 polymorphism and performance in power/strength athletes. Participants comprising 253 power/strength athletes (167 men and 86 women) and 721 healthy controls (303 men and 418 women) were investigated. The power/strength athletes were divided into classic powerlifting (n = 84) and weightlifting (n = 169). No differences in the genotypes and allele frequencies of the ALDH2 rs671 polymorphism and an association between performance and the ALDH2 rs671 genotype were observed in weightlifters. However, the relative values per body weight of the total record were lower in powerlifters with the GA + AA genotype than those with the GG genotype (7.1 ± 1.2 vs. 7.8 ± 1.0; p = 0.010, partial η2 = 0.08). Our results collectively indicate a role of the ALDH2 rs671 polymorphism in strength performance in powerlifters.

Effects of Lactate Administration on Mitochondrial Respiratory Function in Mouse Skeletal Muscle

Recent evidence has shown that mitochondrial respiratory function contributes to exercise performance and metabolic health. Given that lactate is considered a potential signaling molecule that induces mitochondrial adaptations, we tested the hypothesis that lactate would change mitochondrial respiratory function in skeletal muscle. Male ICR mice (8 weeks old) received intraperitoneal injection of PBS or sodium lactate (1 g/kg BW) 5 days a week for 4 weeks. Mitochondria were isolated from freshly excised gastrocnemius muscle using differential centrifugation and were used for all analyses. Lactate administration significantly enhanced pyruvate + malate- and glutamate + malate-induced (complex I-driven) state 3 (maximal/ATP synthesis-coupled) respiration, but not state 2 (basal/proton conductance) respiration. In contrast, lactate administration significantly decreased succinate + rotenone-induced (complex II-driven) state 3 and 2 respiration. No significant differences were observed in malate + octanoyl-l-carnitine-induced state 3 or 2 respiration. The enzymatic activity of complex I was tended to increase and those of complexes I + III and IV were significantly increased after lactate administration. No differences were observed in the activities of complexes II or II + III. Moreover, lactate administration increased the protein content of NDUFS4, a subunit of complex I, but not those of the other components. The present findings suggest that lactate alters mitochondrial respiratory function in skeletal muscle.

Effect of different types of muscle activity on the gene and protein expression of ALDH family members in C57BL/6J mouse skeletal muscle

Aldehyde dehydrogenase (ALDH) is an enzyme that detoxifies aldehydes and is primarily involved in alcohol metabolism. Recently, we have shown that ALDH also plays an important role in skeletal muscle homeostasis. To better understand the role of ALDH in skeletal muscle, it is necessary to clarify the adaptability of ALDH. In this study, we examined the effects of endurance training, compensatory hypertrophy by synergist ablation (SA), and denervation-induced atrophy on gene expression and protein levels of selected ALDH isoforms in skeletal muscle. Ten-week-old C57BL/6J mice were subjected to each intervention, and the plantaris muscle was collected. Gene expression levels of Aldh1a1 were decreased by SA and denervation, but ALDH1A1 protein levels were not affected. Protein levels of ALDH1B1 increased after chronic endurance training, SA, and denervation interventions. However, the increase in Aldh1b1 gene expression was observed only after SA. The gene expression of Aldh2 was decreased after SA, but ALDH2 protein levels remained unchanged. Denervation increased both the Aldh2 gene and ALDH2 protein levels. Taken together, each isoform of ALDH undergoes unique quantitative adaptations in skeletal muscle under different conditions.

Aldehyde dehydrogenase 2 deficiency promotes skeletal muscle atrophy in aged mice

Aldehyde dehydrogenase 2 (ALDH2) detoxifies acetaldehyde produced from ethanol. A missense single nucleotide polymorphism (SNP) rs671 in ALDH2 exhibits a dominant-negative form of the ALDH2 protein. Nearly 40% of people in East Asia carry an inactive ALDH2*2 mutation. Previous studies reported that ALDH2*2 is associated with increased risk of several diseases. In this study, we examined the effect of ALDH2 deficiency on age-related muscle atrophy and its underlying mechanisms. We found that ALDH2 deficiency promotes age-related loss of muscle fiber cross-sectional areas, especially in oxidative fibers. Furthermore, ALDH2 deficiency exacerbated age-related accumulation of 4-hydroxy-2-nonenal (4-HNE), a marker of oxidative stress in the gastrocnemius muscle. Similarly, mitochondrial reactive oxygen species (ROS) production increased in aged ALDH2-knockout mice, indicating that ALDH2 deficiency induced mitochondrial dysfunction. In summary, ALDH2 deficiency promotes age-related muscle loss, especially in oxidative fibers, which may be associated with an increased accumulation of oxidative stress via mitochondrial dysfunction.

The ALDH2 rs671 polymorphism is associated with athletic status and muscle strength in a Japanese population

Aldehyde dehydrogenase 2 (ALDH2) catalyses aldehyde species, including alcohol metabolites, mainly in the liver. We recently observed that ALDH2 is also expressed in skeletal muscle mitochondria; thus, we hypothesize that rs671 polymorphism-promoted functional loss of ALDH2 may induce deleterious effects in human skeletal muscle. We aimed to clarify the association of the ALDH2 rs671 polymorphism with muscle phenotypes and athletic capacity in a large Japanese cohort. A total of 3,055 subjects, comprising 1,714 athletes and 1,341 healthy control subjects (non-athletes), participated in this study. Non-athletes completed a questionnaire regarding their exercise habits, and were subjected to grip strength, 30-s chair stand, and 8-ft walking tests to assess muscle function. The ALDH2 GG, GA, and AA genotypes were detected at a frequency of 56%, 37%, and 7% among athletes, and of 54%, 37%, and 9% among non-athletes, respectively. The minor allele frequency was 25% in athletes and 28% in controls. Notably, ALDH2 genotype frequencies differed significantly between athletes and non-athletes (genotype: p = 0.048, allele: p = 0.021), with the AA genotype occurring at a significantly lower frequency among mixed-event athletes compared to non-athletes (p = 0.010). Furthermore, non-athletes who harboured GG and GA genotypes exhibited better muscle strength than those who carried the AA genotype (after adjustments for age, sex, body mass index, and exercise habits). The AA genotype and A allele of the ALDH2 rs671 polymorphism were associated with a reduced athletic capacity and poorer muscle phenotypes in the analysed Japanese cohort; thus, impaired ALDH2 activity may attenuate muscle function.

Effects of high-intensity interval training on mitochondrial supercomplex assembly and biogenesis, mitophagy, and the AMP-activated protein kinase pathway in the soleus muscle of aged female rats

PURPOSE

Exercise helps improve mitochondrial function to combat sarcopenia. Certain parts of the mitochondrial respiratory chain complex can form a higher-order structure called "supercomplex" to reduce the production of reactive oxygen species and improve muscle mass. The effect of exercise on the assembly of the mitochondrial supercomplex is still unclear. The aim of this study was to investigate the effects of long-term high-intensity interval training (HIIT) on mitochondrial biogenesis, mitophagy, and mitochondrial supercomplexes (mitoSCs) assembly in aging soleus muscle.

METHODS

Female Sprague-Dawley rats (n = 36) were randomly divided into four groups: young sedentary (Y-SED, 8 months old, n = 12), old sedentary (O-SED, 26 months old, n = 12), moderate-intensity continuous training (MICT, from 18 to 26 months old, n = 12), and HIIT (from 18 to 26 months old, n = 12). Rats in the MICT and HIIT groups were subjected to an 8-month training program. Real-time fluorescent quantitative polymerase chain reaction was used to measure the expression of the antioxidative factors, inflammatory factors, and mitochondrial fusion- and division-related genes. Western blotting was used to detect the expression of mitochondrial biogenesis and mitophagy markers and AMP-activated protein kinase (AMPK) pathway proteins. Enzyme-linked immunosorbent assays were used to determine serum irisin contents. Blue native polyacrylamide gel electrophoresis was used to assess the formation of mitochondrial supercomplexes.

RESULTS

Compared with the Y-SED group, the soleus muscle and mitochondria in the O-SED group showed reduced expression of mitophagy- and mitochondrial biogenesis-related proteins. In the HIIT group, the expression of autophagy-related proteins in the soleus muscle and mitochondria was significantly increased compared with that in the MICT group. Serum irisin and mitochondrial fusion protein levels significantly decreased with age. Superoxide dismutase 2 protein levels and AMPK pathway protein expression were significantly increased in the HIIT group compared with those in the other groups. Additionally, the expression levels of mitoSCs and the mRNA levels of interleukin-15 and optical atrophy 1 increased in the HIIT group compared with that in the MICT group.

CONCLUSION

Compared with MICT, HIIT activated the AMPK pathway to upregulate mitochondrial biogenesis- and mitophagy-related proteins, and promote the assembly and formation of mitoSCs to improve the mitochondrial function of aging soleus muscles.

Effects of endurance training on the expression of host proteins involved in SARS-CoV-2 cell entry in C57BL/6J mouse

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is threatening people's lives and impacting their health. It is still unclear whether people engaged in physical activity are at an increased risk of SARS-CoV-2 infection and severe forms of COVID-19. In order to provide data to help answer this question, we, therefore, investigated the effects of endurance training on the levels of host proteins involved in SARS-CoV-2 infection in mice. Eight-week-old C57BL/6J mice were subjected to treadmill running (17-25 m/min, 60-90 min, 5 sessions/week, 8 weeks). After the intervention, the levels of angiotensin-converting enzyme 2 (ACE2; host receptor for SARS-CoV-2), transmembrane protease serine 2 (TMPRSS2; host protease priming fusion of SARS-CoV-2 to host cell membranes), FURIN (host protease that promotes binding of SARS-CoV-2 to host receptors), and Neuropilin-1 (host coreceptor for SARS-CoV-2) were measured in 10 organs that SARS-CoV-2 can infect (larynx, trachea, lung, heart, jejunum, ileum, colon, liver, kidney, and testis). Six organs (heart, lung, jejunum, liver, trachea, and ileum) showed changes in the levels of at least one of the proteins. Endurance training increased ACE2 levels in heart (+66.4%), lung (+37.1%), jejunum (+24.7%) and liver (+27.4%), and FURIN in liver (+17.9%) tissue. In contrast, endurance training decreased Neuropilin-1 levels in liver (-39.7%), trachea (-41.2%), and ileum (-39.7%), and TMPRSS2 in lung (-11.3%). Taken together, endurance training altered the levels of host proteins involved in SARS-CoV-2 cell entry in an organ-dependent manner.

Voluntary exercise prevents abnormal muscle mitochondrial morphology in cancer cachexia mice

This study aimed to examine the effects of voluntary wheel running on cancer cachexia-induced mitochondrial alterations in mouse skeletal muscle. Mice bearing colon 26 adenocarcinoma (C26) were used as a model of cancer cachexia. C26 mice showed a lower gastrocnemius and plantaris muscle weight, but 4 weeks of voluntary exercise rescued these changes. Further, voluntary exercise attenuated observed declines in the levels of oxidative phosphorylation proteins and activities of citrate synthase and cytochrome c oxidase in the skeletal muscle of C26 mice. Among mitochondrial morphology regulatory proteins, mitofusin 2 (Mfn2) and dynamin-related protein 1 (Drp1) were decreased in the skeletal muscle of C26 mice, but exercise resulted in similar improvements as seen in markers of mitochondrial content. In isolated mitochondria, 4-hydroxynonenal and protein carbonyls were elevated in C26 mice, but exercise blunted the increases in these markers of oxidative stress. In addition, electron microscopy revealed that exercise alleviated the observed increase in the percentage of damaged mitochondria in C26 mice. These results suggest that voluntary exercise effectively counteracts mitochondrial dysfunction to mitigate muscle loss in cachexia.

Ethanol, neurosteroids and cellular stress responses: Impact on central nervous system toxicity, inflammation and autophagy

Alcohol intake can impair brain function, in addition to other organs such as the liver and kidney. In the brain ethanol can be detrimental to memory formation, through inducing the integrated stress response/endoplasmic reticulum stress/unfolded protein response and the molecular mechanisms linking stress to other events such as NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammation and autophagy. This literature review aims to provide an overview of our current understanding of the molecular mechanisms involved in ethanol-induced damage with endoplasmic reticulum stress, integrated stress response, NLRP3 inflammation and autophagy, while discussing the impact of neurosteroids and oxysterols, including allopregnanolone, 25-hydroxycholesterol and 24S-hydroxycholesterol, on the central nervous system.

The Association and Interaction of Aldehyde Dehydrogenase 2 Polymorphisms with Food Group Intake and Probability of Having Non-Alcoholic Fatty Liver Disease

PURPOSE

This study investigated the association between the aldehyde dehydrogenase 2 (ALDH2) rs671 polymorphism, food group intake, and the probability of having non-alcoholic fatty liver disease (NAFLD) in a Chinese population.

PATIENTS AND METHODS

A total of 3506 adults were enrolled in this study, and all underwent physical examinations and genotyping of polymorphisms with polymerase chain reaction. Participants filled out a dietary questionnaire that was used to assess the frequency and quantity of food consumption.

RESULTS

We found that milk groups were associated with a lower probability of developing NAFLD. On the contrary, meat and salted and smoked foods were associated with a higher probability of NAFLD. However, the influences of salted and smoked foods and fresh fruit and vegetables on NAFLD were obviously different in the two genotype groups. Salted and smoked foods intake was a factor associated with a higher probability of having NAFLD or nonalcoholic steatohepatitis (NASH) in the A genotype group, but there was no effect in the G genotype group. Moreover, eating salted and smoked foods several times per week was associated with a higher probability of having NAFLD than seldom consuming them. Consumption of fresh fruit and vegetables was not a factor influencing the probability of having NAFLD in the A genotype group, and there was no effect in the G genotype group. Further analysis of the interaction indicated that the GA +AA genotype showed an interaction with fresh fruit and vegetables and salted and smoked foods. Moreover, it was not obvious that meat intake increased the probability of having NAFLD or NASH among different genotypes.

CONCLUSION

Our results indicate that ALDH2 rs671 GA and AA genotypes are factors associated with increased probability of NAFLD among Chinese subjects. This could stimulate the development of novel approaches for preventing NAFLD.