Ethanol induced hepatic mitochondrial dysfunction is attenuated by all trans retinoic acid supplementation

Retinoic Acid Receptor β Loss in Hepatocytes Increases Steatosis and Elevates the Integrated Stress Response in Alcohol-Associated Liver Disease

In alcohol-associated liver disease (ALD), hepatic reductions in vitamin A and perturbations in vitamin A metabolism are common. However, the roles that the vitamin A receptors, termed retinoic acid receptors (RARs), may have in preventing the pathophysiology of ALD remains unclear. Our prior data indicate that a RARβ agonist limits the pathology of alcohol-related liver disease. Thus, we generated liver-specific AlbCre-RARβ knockout (BKO) mice and compared them to wild type (WT) mice in an early ALD model. Both strains showed similar blood ethanol concentrations and ETOH-metabolizing enzymes. However, the livers of pair-fed-BKO and ETOH-BKO mice developed higher levels of steatosis and triglycerides than pair-fed-WT and ETOH-WT mice. The increased hepatic steatosis observed in the pair-fed-BKO and ETOH-BKO mice was associated with higher lipid synthesis/trafficking transcripts and lower beta-oxidation transcripts. ETOH-BKO mice also exhibited a higher integrated stress response (ISR) signature, including higher transcript and protein levels of ATF4 and its target, 4-EBP1. In human hepatocytes (HepG2) that lack RARβ (RARβ-KO), ETOH treatments resulted in greater reactive oxygen species compared to their parental cells. Notably, even without ETOH, ATF4 and 4-EBP1 protein levels were higher in the RARβ-KO cells than in their parental cells. These 4-EBP1 increases were greatly attenuated in cultured ATF4-deficient and RARβ/ATF4-deficient HepG2, suggesting that RARβ is a crucial negative regulator of 4-EBP1 through ATF4 in cultured hepatocytes. Here, we identify RARβ as a negative regulator of lipid metabolism and cellular stress in ALD.

Endogenous ethanol produced by intestinal bacteria induces mitochondrial dysfunction in non-alcoholic fatty liver disease

BACKGROUND AND AIM

A causal relationship between changes of the gut microbiome and non-alcoholic fatty liver disease (NAFLD) remains unclear. We demonstrated that endogenous ethanol (EnEth) produced by intestinal microbiota is likely a causative agent of NAFLD.

METHODS

Two mutants with different alcohol-producing abilities, namely, W14-adh and W14Δadh, were constructed using the clinical high alcohol-producing (HiAlc) Klebsiella pneumoniae strain W14 as a parent. Damage to hepatocytes caused by bacteria with different alcohol-producing capacities was evaluated (EtOH group as positive control). The ultrastructural changes of mitochondria were assessed via transmission electron microscopy (TEM). Hepatic levels of mitochondrial reactive oxygen species (ROS), DNA damage, and adenosine triphosphate were examined.

RESULTS

The results illustrated that steatosis was most severe in the W14-adh group, followed by the W14 group, whereas the W14Δadh group had few fatty droplets. TEM and examination of related protein expression revealed that the mitochondrial integrity of HepG2 hepatocytes was considerably damaged in the EtOH and bacteria treatment groups. The impaired mitochondrial function in HepG2 hepatocytes was evidenced by reduced adenosine triphosphate content and increased mitochondrial ROS accumulation and DNA damage in the EtOH and bacteria treatment groups, especially the W14-adh group. Meanwhile, liver injury and mitochondrial damage were observed in the hepatocytes of mice. The livers of mice in the W14-adh group, which had the highest ethanol production, exhibited the most serious damage, similar to that in the EtOH group.

CONCLUSIONS

EnEth produced by HiAlc bacteria induces mitochondrial dysfunction in NAFLD.

All trans retinoic acid modulates TNF-α and CYP2E1 pathways and enhances regression of ethanol-induced fibrosis markers in hepatocytes and HSCs in abstaining rodent model

Context: Our previous studies showed that all trans retinoic acid (ATRA) ameliorates alcohol-induced toxicity. Hence, we evaluated the efficacy of ATRA and abstention in the regression of alcohol-induced hepatotoxicity. Materials and methods: After ethanol administration to rats for 90 days, the regression of alcohol-induced toxicity was studied by supplementing ATRA at a dose of 100 μg/kg body weight for 30 days. It was also compared with animals in abstention. Results and discussion: Ethanol administration enhanced oxidative stress, activated HSCs and increased collagen deposition. All these alterations were reversed to a certain extent by ATRA supplementation. Conclusions: ATRA had better efficacy than just abstention in reducing ethanol-induced toxicity. The mechanism might be downregulation of CYP2E1, leading to reduced oxidative stress in the hepatocytes and thus impeding NFκB activation, cytokine production, activation of HSC and resulting in the reduction of inflammation and remodelling of fibrosis by modulating MMP and TIMP.

Supplementation of all trans retinoic acid ameliorates ethanol-induced endoplasmic reticulum stress

CONTEXT

Molecular pathogenesis of chronic alcoholism is linked to increased endoplasmic reticulum stress. Ethanol is a competitive inhibitor of vitamin A metabolism and vitamin A supplementation aggravates existing liver problems. Hence, we probed into the impact of supplementation of all trans retinoic acid (ATRA), the active metabolite of vitamin A on ethanol-induced endoplasmic reticulcum stress.

METHODS

Male Sprague-Dawley rats were divided into four groups - I: Control; II: Ethanol; III: ATRA; IV: ATRA + Ethanol. After 90 days the animals were sacrificed to study markers of lipid peroxidation in hepatic microsomal fraction and expression of ER stress proteins and apoptosis in liver.

RESULTS AND CONCLUSION

Ethanol caused hepatic hyperlipidemia, enhanced microsomal lipid peroxidation, upregulated expression of unfolded protein response associated proteins and that of apoptosis. Ethanol also led to downregulation of retinoid receptors. ATRA supplementation reversed all these alterations indicating the decrease in ethanol-induced endoplasmic reticulum stress.

Preventive effects of indole-3-carbinol against alcohol-induced liver injury in mice via antioxidant, anti-inflammatory, and anti-apoptotic mechanisms: Role of gut-liver-adipose tissue axis

Indole-3-carbinol (I3C), found in Brassica family vegetables, exhibits antioxidant, anti-inflammatory, and anti-cancerous properties. Here, we aimed to evaluate the preventive effects of I3C against ethanol (EtOH)-induced liver injury and study the protective mechanism(s) by using the well-established chronic-plus-binge alcohol exposure model. The preventive effects of I3C were evaluated by conducting various histological, biochemical, and real-time PCR analyses in mouse liver, adipose tissue, and colon, since functional alterations of adipose tissue and intestine can also participate in promoting EtOH-induced liver damage. Daily treatment with I3C alleviated EtOH-induced liver injury and hepatocyte apoptosis, but not steatosis, by attenuating elevated oxidative stress, as evidenced by the decreased levels of hepatic lipid peroxidation, hydrogen peroxide, CYP2E1, NADPH-oxidase, and protein acetylation with maintenance of mitochondrial complex I, II, and III protein levels and activities. I3C also restored the hepatic antioxidant capacity by preventing EtOH-induced suppression of glutathione contents and mitochondrial aldehyde dehydrogenase-2 activity. I3C preventive effects were also achieved by attenuating the increased levels of hepatic proinflammatory cytokines, including IL1β, and neutrophil infiltration. I3C also attenuated EtOH-induced gut leakiness with decreased serum endotoxin levels through preventing EtOH-induced oxidative stress, apoptosis of enterocytes, and alteration of tight junction protein claudin-1. Furthermore, I3C alleviated adipose tissue inflammation and decreased free fatty acid release. Collectively, I3C prevented EtOH-induced liver injury via attenuating the damaging effect of ethanol on the gut-liver-adipose tissue axis. Therefore, I3C may also have a high potential for translational research in treating or preventing other types of hepatic injury associated with oxidative stress and inflammation.

The importance of nutrition in aiding recovery from substance use disorders: A review

BACKGROUND

Nutrition is a prerequisite for health; yet, there is no special nutritional assessment or guidance for drug and alcohol dependent individuals, despite the fact that their food consumption is often very limited, risking malnutrition. Further, the premise is examined that malnutrition may promote drug seeking and impede recovery from substance use disorders (SUD).

METHOD

A narrative review addressed the relationship between substance use disorders and nutrition, including evidence for malnutrition, as well as their impact on metabolism and appetite regulation. The implications of the biopsychology of addiction and appetite for understanding the role of nutrition in SUD were also considered.

RESULTS

The literature overwhelmingly finds that subjects with alcohol use disorder (AUD) and drug use disorder (DUD) typically suffer from nutrient deficiencies. These nutrient deficiencies may be complicit in the alcoholic myopathy, osteopenia and osteoporosis, and mood disorders including anxiety and depression, observed in AUD and DUD. These same individuals have also been found to have altered body composition and altered hormonal metabolic regulators. Additionally, brain processes fundamental for survival are stimulated both by food, particularly sweet foods, and by substances of abuse, with evidence supporting confusion (addiction transfer) when recovering from SUD between cravings for a substance and craving for food.

CONCLUSION

Poor nutritional status in AUD and DUD severely impacts their physical and psychological health, which may impede their ability to resist substances of abuse and recover their health. This review contributes to a better understanding of interventions that could best support individuals with substance use disorders.

Quercetin Attenuates Chronic Ethanol-Induced Hepatic Mitochondrial Damage through Enhanced Mitophagy

Emerging evidence suggested mitophagy activation mitigates ethanol-induced liver injury. However, the effect of ethanol on mitophagy is inconsistent. Importantly, the understanding of mitophagy status after chronic ethanol consumption is limited. This study evaluated the effect of quercetin, a naturally-occurring flavonoid, on chronic ethanol-induced mitochondrial damage focused on mitophagy. An ethanol regime to mice for 15 weeks (accounting for 30% of total calories) led to significant mitochondrial damage as evidenced by changes of the mitochondrial ultrastructure, loss of mitochondrial membrane potential and remodeling of membrane lipid composition, which was greatly attenuated by quercetin (100 mg/kg.bw). Moreover, quercetin blocked chronic ethanol-induced mitophagy suppression as denoted by mitophagosomes-lysosome fusion and mitophagy-related regulator elements, including LC3II, Parkin, p62 and voltage-dependent anion channel 1 (VDAC1), paralleling with increased FoxO3a nuclear translocation. AMP-activated protein kinase (AMPK) and extracellular signal regulated kinase 2 (ERK2), instead of AKT and Sirtuin 1, were involved in quercetin-mediated mitophagy activation. Quercetin alleviated ethanol-elicited mitochondrial damage through enhancing mitophagy, highlighting a promising preventive strategy for alcoholic liver disease.