Superoxide Dismutase 2 Genetic Variation as a Susceptibility Risk Factor for Alcoholic Cirrhosis

The intersection between alcohol-related liver disease and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) and alcohol-related liver disease (ALD) are the leading causes of chronic liver disease worldwide. NAFLD and ALD share pathophysiological, histological and genetic features and both alcohol and metabolic dysfunction coexist as aetiological factors in many patients with hepatic steatosis. A diagnosis of NAFLD requires the exclusion of significant alcohol consumption and other causes of liver disease. However, data suggest that significant alcohol consumption is often under-reported in patients classified as having NAFLD and that alcohol and metabolic factors interact to exacerbate the progression of liver disease. In this Review, we analyse existing data on the interaction between alcohol consumption and metabolic syndrome as well as the overlapping features and differences in the pathogenesis of ALD and NAFLD. We also discuss the clinical implications of the coexistence of alcohol consumption, of any degree, in patients with evidence of metabolic derangement as well as the use of alcohol biomarkers to detect alcohol intake. Finally, we summarize the evolving nomenclature of fatty liver disease and describe a recent proposal to classify patients at the intersection of NAFLD and ALD. We propose that, regardless of the presumed aetiology, patients with fatty liver disease should be evaluated for both metabolic syndrome and alcohol consumption to enable better prognostication and a personalized medicine approach.

Global prevalence, incidence, and outcomes of alcohol related liver diseases: a systematic review and meta-analysis

BACKGROUND

Alcohol related liver disease (ARLD) is one of the major chronic liver diseases worldwide. This review aimed to describe the global prevalence, incidence, and outcomes of ARLD.

METHODS

Medline, Embase, The Cochrane Library, and China National Knowledge Infrastructure (CNKI) were searched from inception to May 31, 2022. The language was restricted to English or Chinese. According to the criteria, articles describing the basic characteristics of the population were selected. Two reviewers extracted the data independently.

RESULTS

A total of 372 studies were identified: 353 were used for prevalence analysis, 7 were used for incidence analysis, and 114 were used to for outcome analysis. The prevalence of ARLD worldwide was 4.8%. The prevalence in males was 2.9%, which was higher than female (0.5%). Among the ethnic groups, the percentage was highest in Caucasians (68.9%). Alcoholic liver cirrhosis comprised the highest proportion in the disease spectrum of ARLD at 32.9%. The prevalence of ascites in ARLD population was highest (25.1%). The ARLD population who drinking for > 20 years accounted for 54.8%, and the average daily alcohol intake was 146.6 g/d. About 59.5% of ARLD patients were current or former smokers, and 18.7% were complicated with hepatitis virus infection. The incidence was 0.208/1000 person-years. The overall mortality was 23.9%, and the liver-related mortality was 21.6%.

CONCLUSION

The global prevalence of ARLD was 4.8% and was affected by sex, region, drinking years, and other factors. Therefore, removing the factors causing a high disease prevalence is an urgent requisite.

TRIAL REGISTRATION

PROSPERO Nr: CRD42021286192.

Exercise Affects the Formation and Recovery of Alcoholic Liver Disease through the IL-6-p47phox Oxidative-Stress Axis

(1) Background: To explore the effect of exercise on the formation and recovery of alcoholic liver disease (ALD) and whether the IL-6−p47phox oxidative−stress axis is involved in that process. (2) Methods: Firstly, 23 six-week-old male C57BL/6J mice were randomly divided into the Con group, ALD group, ALD + NOXI group, ALD + Ex group, and ALD + Ex + NOXI group. The Liber−DeCarli alcoholic liquid diet was used for 6 weeks to establish the ALD mice model, and the Con group was given the TP4030C control diet. The remaining groups were fed with the TP4030B alcoholic diet, and exercise intervention was started after the ALD model establishment and lasted for another 6 weeks, with or without administration of the NOX inhibitor apocynin by intraperitoneal injection on every exercise training day. Secondly, 28 mice were randomly divided into the Sed group, Eth group, Eth + Ex group and Eth + Ex + NOXI group. The Sed group was given the TP4030C control diet. The remaining groups were fed with the TP4030B alcoholic diet and exercise intervention was started synchronously combined with or without administration of intraperitoneal apocynin injections on every exercise training day for 5 weeks. After each individual experiment was accomplished, physiological assessment and biochemical analysis of blood and tissue samples were examined. (3) Results: The levels of TG in serum and IL-6 protein content in liver tissue in the ALD group were significantly increased compared to the Con group (p < 0.05); compared with ALD, p47phox expression in muscle was increased significantly in the ALD + NOXI group (p < 0.05), and TG in serum decreased in the ALD + Ex group (p < 0.05). TG in serum, AST/ALT ratio, and IL-6 content in both liver and muscle decreased (p < 0.05) in the ALD + Ex + NOXI group with MDA in muscle significantly increased (p < 0.01). The AST/ALT ratio, TG in serum, SOD in liver, and p47phox in both liver and muscle in the ALD + Ex + NOXI group were significantly decreased compared with the ALD + NOXI group (p < 0.01). Compared with the ALD + Ex group, the liver index and HDL-C levels in serum were decreased (p < 0.05) in the ALD + Ex + NOXI group. The degree of hepatocyte steatosis and inflammatory infiltration were ameliorated after exercise intervention. In the Eth group, the relative epididymal fat content, HDL-C level, and AST/ALT ratio were significantly decreased, and TG and gp91phox in liver were significantly higher than in the Sed group (p < 0.05, p < 0.01). Compared with the Eth group, the AST/ALT ratio, MDA in the liver, and NOX4 and p47phox protein expression in the liver were significantly increased, and body weight decreased significantly in the Eth + Ex group (p < 0.05, p < 0.01), as did TG in the liver and MDA in muscle. In the th + Ex + NOXI group, gp91phox expression in the liver and body weight were significantly decreased (p < 0.05, p < 0.01). In the Eth + Ex + NOXI group, the ratio of AST/ALT and MDA in muscle were increased when compared with the Eth + Ex group, and the protein expression of gp91phox and p47phox were much lower (p < 0.01). (4) Conclusions: 6 weeks of exercise intervention during the recovery phase of ALD ameliorates hepatocyte damage and dyslipidemia through the IL-6−p47phox oxidative−stress axis, and applying a NOX inhibitor in combination could optimize this. However, drinking alcohol during exercise exacerbates dyslipidemia and oxidative stress, with hepatocyte IL-6−p47phox downregulated.

Superoxide Dismutase Administration: A Review of Proposed Human Uses

Superoxide dismutases (SODs) are metalloenzymes that play a major role in antioxidant defense against oxidative stress in the body. SOD supplementation may therefore trigger the endogenous antioxidant machinery for the neutralization of free-radical excess and be used in a variety of pathological settings. This paper aimed to provide an extensive review of the possible uses of SODs in a range of pathological settings, as well as describe the current pitfalls and the delivery strategies that are in development to solve bioavailability issues. We carried out a PubMed query, using the keywords "SOD", "SOD mimetics", "SOD supplementation", which included papers published in the English language, between 2012 and 2020, on the potential therapeutic applications of SODs, including detoxification strategies. As highlighted in this paper, it can be argued that the generic antioxidant effects of SODs are beneficial under all tested conditions, from ocular and cardiovascular diseases to neurodegenerative disorders and metabolic diseases, including diabetes and its complications and obesity. However, it must be underlined that clinical evidence for its efficacy is limited and consequently, this efficacy is currently far from being demonstrated.

Genetic variations of three important antioxidative enzymes SOD2, CAT, and GPX1 in nonalcoholic steatohepatitis

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is closely related to reactive oxygen species (ROS). Superoxide anion radicals, the main product of ROS, can be reduced by manganese superoxide dismutase (SOD2) to hydrogen peroxide, which is further reduced by catalase (CAT) and glutathione peroxidase (GPX) to water. We aimed to investigate the association between the most important genetic variants of SOD2, CAT, and GPX1 and susceptibility to NASH.

METHODS

A total of 126 adults with liver tissue-verified NASH, 56 patients with liver tissue-verified nonalcoholic fatty liver (NAFL), and 153 healthy controls were enrolled. Their DNA profiles were retrieved for genotype assessment of SOD2 47T>C (rs4880), CAT -262C>T (rs1001179), and GPX1 593C>T (rs1050450) variation.

RESULTS

There were statistical differences between the SOD2 and CAT genotypes across the NASH, NAFL, and control groups, but not GPX1. The NASH group had a significantly higher frequency of subjects with SOD2 C allele (38.8%) compared with the NASL group (25.0%) and the controls (22.9%, p = 0.010). Similarly, the NASH group had a significantly higher percentage of subjects with CAT T allele (23.0%) compared with the NAFL group (10.7%) and the controls (7.2%, p = 0.001). For subjects with both the SOD2 C allele and CAT T allele, 88.2% were in the NASH group. After adjusting for confounders, the CAT mutant T allele and SOD2 mutant C allele were still the highest independent risk factors for NASH (odds ratio [OR] 3.10 and 2.36, respectively). In addition, there was a synergistic effect for those two alleles and the occurrence of NASH with an adjusted OR of 8.57 (p = 0.030).

CONCLUSION

The genetic variations of CAT and SOD2 may increase the risk of NASH, which may aid in the screening of patients who are at high risk of NASH, and offer a potential anti-oxidant targeting route for the treatment of NASH.

Oxidative Stress-Related Gene Polymorphisms Are Associated With Hepatitis B Virus-Induced Liver Disease in the Northern Chinese Han Population

Oxidative stress is closely related to the occurrence and development of various diseases such as cancer, diabetes, and cardiovascular and infectious diseases. We identified six critical genetic variants related to oxidative stress, and evaluated their main effects and their interaction effects on hepatitis B virus (HBV)-induced liver diseases. We enrolled 3,128 Han Chinese subjects into five groups: healthy controls, chronic hepatitis B (CHB), liver cirrhosis (LC), hepatocellular carcinoma (HCC), and natural clearance. We then determined the genotypes in each group for CYBA-rs4673, NCF4-rs1883112, NOX4-rs1836882, rs3017887, SOD2-rs4880, and GCLM-rs41303970, and evaluated the association between these variants and HBV-induced liver diseases. Gene-gene interactions were evaluated using generalized multifactor dimensionality reduction, logistic regression, and four-by-two tables. Significant associations were observed between healthy controls and the CIB group (CHB+LC+HCC). The CYBA-rs4673AG genotype was associated with a 1.356 rate of susceptibility of HBV-induced liver disease compared to the wild type GG genotype. The NCF4-rs1883112G allele occurred more frequently in healthy controls than in the CIB group in all three models (dominant, codominant, and recessive). Nox4-rs1836882 TC showed a protective association, being more frequent in healthy controls compared to the wild type TT genotype. GCLM-rs41303970A was associated with HBV-induced liver disease. The overall best model by multifactor dimensionality reduction was a five factor interaction model that had the highest cross validation consistency (10/10) and test accuracy (0.5669), P= 0.001. Oxidative stress-related gene polymorphisms are likely to be associated with HBV-induced liver disease, suggesting that information on these variations is useful for risk assessment of HBV-induced liver disease.

Oxidative Stress and First-Line Antituberculosis Drug-Induced Hepatotoxicity

Hepatotoxicity induced by antituberculosis drugs is a serious adverse reaction with significant morbidity and even, rarely, mortality. This form of toxicity potentially impacts the treatment outcome of tuberculosis in some patients. Covering only first-line antituberculosis drugs, this review addresses whether and how oxidative stress and, more broadly, disturbance in redox homeostasis alongside mitochondrial dysfunction may contribute to the hepatotoxicity induced by them. Risk factors for such toxicity that have been identified, in addition to genetic factors, principally include old age, malnutrition, alcoholism, chronic hepatitis C and chronic hepatitis B infection, HIV infection, and preexisting liver disease. Importantly, these comorbid conditions are associated with oxidative stress. Thus, the shared pathogenetic mechanism(s) for liver injury might be in operation due to disease-drug interaction. Our current ability to predict, prevent, or treat hepatotoxicity (other than removing potentially hepatotoxic drugs) remains limited. More translational research to unravel the pathogenesis, inclusive of the underlying molecular basis, regarding antituberculosis drug-induced hepatotoxicity is needed, and so is clinical research pertaining to the advances in therapy with antioxidants and drugs related to antioxidants, especially those for management of mitochondrial dysfunction. The role of pharmacogenetics in the clinical management of drug-induced hepatotoxicity also likely merits further evaluation.

Genetic Variants in the Manganese Superoxide Dismutase 2 Gene and in the Catalase Gene are not Associated With Alcoholic Chronic Pancreatitis

Aims

Oxidative stress may contribute to the development of chronic pancreatitis (CP). The enzymes manganese superoxide dismutase 2 (MnSOD, SOD2) and catalase (CAT) counteract free radical activity within the mitochondria and the cytosol. Moreover, CAT activity contributes to the transformation of ethanol to acetaldehyde, a toxic intermediate product of ethanol metabolism, which has been associated with pancreatic damage. Common functional polymorphisms have been described in the MnSOD gene [rs4880, NM_000636.3:c.47 T > C, alanine (ALA) to valine (Val)] and in the CAT promoter region [rs1001179, NG_013339.1:g.4760 C > T]. We investigated whether these polymorphisms are associated with alcoholic CP.

Methods

We genotyped 470 patients with alcoholic CP for these MnSOD and CAT polymorphisms. We also analysed these variants in 357 healthy control subjects, and in an additional control group of 113 individuals with non-alcoholic CP. We used the age at onset of CP as marker of disease severity and investigated whether different genotypes are associated with different ages at onset. In patients with alcoholic CP, we investigated whether an interaction exists between smoking behaviour and genotypes by comparing genotype distributions in smokers and non-smokers.

Results

We did not observe significant differences of genotype frequencies between patient groups and controls. In patient groups, we did not find significant differences in the ages at onset between different genotypes. We did not observe an interaction between these polymorphisms. We did not find an association of these variants with smoking behaviour.

Conclusions

The investigated MnSOD and CAT polymorphisms do not predispose to the development of alcoholic CP.

Short summary

Patients with alcoholic pancreatitis and controls were genotyped for polymorphisms in oxidative stress genes. There were no significant differences of genotype frequencies between patients and controls, and no association with the age at onset of disease was observed. The polymorphisms are not associated with the development of alcoholic pancreatitis.