Gut microbiome in alcohol use disorder: Implications for health outcomes and therapeutic strategies-a literature review

Reactive Oxygen Species as a Common Pathological Link Between Alcohol Use Disorder and Alzheimer's Disease with Therapeutic Implications

Chronic alcohol consumption leads to excessive production of reactive oxygen species (ROS), driving oxidative stress that contributes to both alcohol use disorder (AUD) and Alzheimer's disease (AD). This review explores how ROS-mediated mitochondrial dysfunction and neuroinflammation serve as shared pathological mechanisms linking these conditions. We highlight the role of alcohol-induced oxidative damage in exacerbating neurodegeneration and compare ROS-related pathways in AUD and AD. Finally, we discuss emerging therapeutic strategies, including mitochondrial antioxidants and inflammasome inhibitors, that target oxidative stress to mitigate neurodegeneration. Understanding these overlapping mechanisms may provide new insights for preventing and treating ROS-driven neurodegenerative disorders.

Effect of inulin supplementation on fecal and blood metabolome in alcohol use disorder patients: A randomised, controlled dietary intervention

BACKGROUND AND AIMS

Alcohol Use Disorder (AUD) is a psychiatric disorder characterized notably by gut microbial dysbiosis and insufficient dietary fiber (DF) intake. This study aims to investigate the effect of DF placebo-controlled intervention in patients suffering from AUD during a three-week period of alcohol withdrawal, in order to discover microbial-derived metabolites that could be involved in metabolic and behavioral status.

METHODS

A randomized, double-blind, placebo-controlled study was performed with 50 AUD patients supplemented with inulin (prebiotic DF) or maltodextrin (placebo) during 17 days. Fecal microbiota composition, plasma and fecal metabolomics (liquid chromatography coupled to mass spectrometry), blood markers of inflammation and hepatic alterations, and psychological assessment (questionnaires) were analyzed before and after the intervention.

RESULTS

Fecal metabolomics revealed 14 metabolites significantly modified by inulin versus placebo treatment (increased N8-acetylspermidine and decreased indole-3-butyric acid, 5-amino valeric acid betaine (5-AVAB) and bile acids). Thirteen plasma metabolites differentiated both treatments (higher levels of long-chain fatty acids, medium-chain acylcarnitines and sphingomyelin species, and reduced 3-methylhistidine by inulin versus placebo). Fecal Lachnoclostridium correlated with 6 of the identified fecal metabolites, whereas plasma lipidic moieties positively correlated with fecal Ruminococcus torques group and Flavonifractor. Interestingly, parameters reflecting liver alterations inversely correlated with sphingomyelin (SM 36:2).

CONCLUSIONS

Three weeks of inulin supplementation during alcohol withdrawal leads to specific and different changes in the plasma and fecal metabolome of AUD patients, some of these gut microbiota-related metabolites being correlated with liver function.

TRIAL REGISTRATION

NCT03803709, https://clinicaltrials.gov/ct2/show/NCT03803709.

The Bidirectional Relationship Between the Gut Microbiome and Mental Health: A Comprehensive Review

The gut microbiome plays a fundamental role in mental health, influencing mood, cognition, and emotional regulation through the gut-brain axis. This bidirectional communication system connects the gastrointestinal and CNS, facilitated by microbial metabolites, neurotransmitters, and immune interactions. Recent research highlights the association between gut dysbiosis and psychiatric disorders, including anxiety, depression, and stress-related conditions. Key findings indicate that altered microbial diversity, decreased short-chain fatty acid (SCFA) production, and increased neuroinflammation contribute to mental health disturbances. This paper explores the mechanism linking the gut microbiome to brain function, including microbial neurotransmitter synthesis, vagus nerve signaling, and hypothalamic-pituitary-adrenal (HPA) axis modulation. Additionally, it evaluates the potential of microbiome-targeted interventions, such as probiotics, prebiotics, dietary modifications, and fecal microbiota transplantation (FMT), in alleviating psychiatric symptoms. Microbiome sequencing and bioinformatics advances further support the development of personalized microbiome-based mental health interventions. Despite promising evidence, challenges such as inter-individual variability, methodological inconsistencies, and the need for longitudinal studies remain. Future research should focus on standardizing microbiome assessment techniques and optimizing therapeutic applications. Integrating precision psychiatry with microbiome-based diagnostics holds immense potential in transforming mental health treatment.

The pyruvate dehydrogenase kinase inhibitor dichloroacetate mitigates alcohol-induced hepatic inflammation and metabolic disturbances in mice

BACKGROUND

Dichloroacetate (DCA), a pan-pyruvate dehydrogenase kinase inhibitor, ameliorates multiple pathological conditions and tissue injury and shows strong potential for clinical applications. Here, we investigated the preventive effects of DCA in a murine model of alcohol-associated liver disease.

METHODS

C57BL/6J mice were subjected to the acute-on-chronic model of alcohol-associated liver disease and treated with DCA. Livers were assessed in liver histology, biochemistry, and gene expression. Mass spectrometry was used to compare protein expression and metabolite levels.

RESULTS

DCA inhibited hepatic expression of inflammatory genes but did not prevent steatosis and hepatocellular injury in ethanol-fed mice. Consistently, DCA repressed the expression of mRNAs for inflammatory genes in LPS-stimulated murine bone-marrow-derived macrophages and human monocytic THP-1 cells and inhibited both gene expression and protein release of interleukin-1 beta. DCA prevented hepatic accumulation of isovaleric acid in ethanol-fed mice, a short-chain fatty acid primarily produced by gut microbiota. In vitro, isovaleric acid potentiated LPS's effects, while DCA prevented this proinflammatory action. Ethanol feeding increased the expression of proteins involved in diverse metabolic pathways, including branched-chain amino acid (BCAA) degradation. In ethanol-fed mice, hepatic Fischer's ratio (the molar ratio of BCAAs to aromatic amino acids Phe and Tyr) and BTR (the molar ratio of BCAAs to Tyr) showed a decrease compared to pair-fed mice; however, this decrease was not observed in DCA-treated ethanol-fed mice. DCA blunted the ethanol-induced increase of BCKDHA, the rate-limiting enzyme in BCAA catabolism, and cytochrome P450 2E1.

CONCLUSIONS

Ethanol-induced hepatic inflammatory responses and metabolic disturbances were prevented by DCA in mice, indicating the potential to develop pyruvate dehydrogenase kinase inhibitors as an effective therapy to treat alcohol-associated liver disease.

3PM-guided innovation in treatments of severe alcohol-associated hepatitis utilizing fecal microbiota transplantation

RATIONALE

Severe alcohol-associated hepatitis (SAH) is the most critical, acute, inflammatory phenotype within the alcohol-associated liver disease (ALD) spectrum, characterized by high 30- and 90-day mortality. Since several decades, corticosteroids (CS) are the only approved pharmacotherapy offering highly limited survival benefits. Contextually, there is an evident demand for 3PM innovation in the area meeting patients' needs and improving individual outcomes. Fecal microbiota transplantation (FMT) has emerged as one of the new potential therapeutic options. In this study, we aimed to address the crucial 3PM domains in order to assess (i) the impact of FMT on mortality in SAH patients beyond CS, (ii) to identify factors associated with the outcome to be improved (iii) the prediction of futility, (iv) prevention of suboptimal individual outcomes linked to increased mortality, and (v) personalized allocation of therapy.

METHODS

We conducted a prospective study (NCT04758806) in adult patients with SAH who were non-responders (NR) to or non-eligible (NE) for CS between January 2018 and August 2022. The intervention consisted of five 100 ml of FMT, prepared from 30 g stool from an unrelated healthy donor and frozen at - 80 °C, administered daily to the upper gastrointestinal (GI) tract. We evaluated the impact of FMT on 30- and 90-day mortality which we compared to the control group selected by the propensity score matching and treated by the standard of care; the control group was derived from the RH7 registry of patients hospitalized at the liver unit (NCT04767945). We have also scrutinized the FMT outcome against established and potential prognostic factors for SAH - such as the model for end-stage liver disease (MELD), Maddrey Discriminant Function (MDF), acute-on-chronic liver failure (ACLF), Liver Frailty Index (LFI), hepatic venous-portal pressure gradient (HVPG) and Alcoholic Hepatitis Histologic Score (AHHS) - to see if the 3PM method assigns them a new dimension in predicting response to therapy, prevention of suboptimal individual outcomes, and personalized patient management.

RESULTS

We enrolled 44 patients with SAH (NR or NE) on an intention-to-treat basis; we analyzed 33 patients per protocol for associated factors (after an additional 11 being excluded for receiving less than 5 doses of FMT), and 31 patients by propensity score matching for corresponding individual outcomes, respectively. The mean age was 49.6 years, 11 patients (33.3%) were females. The median MELD score was 29, and ACLF of any degree had 27 patients (81.8%). FMT improved 30-day mortality (p = 0.0204) and non-significantly improved 90-day mortality (p = 0.4386). Univariate analysis identified MELD ≥ 30, MDF ≥ 90, and ACLF grade > 1 as significant predictors of 30-day mortality, (p = 0.031; p = 0.014; p = 0.034). Survival was not associated with baseline LFI, HVPG, or AHHS.

CONCLUSIONS AND RECOMMENDATIONS IN THE FRAMEWORK OF 3PM

In the most difficult-to-treat sub-cohort of patients with SAH (i.e., NR/NE), FMT improved 30-day mortality. Factors associated with benefit included MELD ≤ 30, MDF ≤ 90, and ACLF < 2. These results support the potential of gut microbiome as a therapeutic target in the context of 3PM research and vice versa - to use 3PM methodology as the expedient unifying template for microbiome research. The results allow for immediate impact on the innovative concepts of (i) personalized phenotyping and stratification of the disease for the clinical research and practice, (ii) multilevel predictive diagnosis related to personalized/precise treatment allocation including evidence-based (ii) prevention of futile and sub-optimally effective therapy, as well as (iii) targeted prevention of poor individual outcomes in patients with SAH. Moreover, our results add to the existing evidence with the potential to generate new research along the SAH's pathogenetic pathways such as diverse individual susceptibility to alcohol toxicity, host-specific mitochondrial function and systemic inflammation, and the role of gut dysbiosis thereof.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13167-024-00381-5.

Preclinical Evaluation of Sodium Butyrate's Potential to Reduce Alcohol Consumption: A Dose-Escalation Study in C57BL/6J Mice in Antibiotic-Enhanced Binge-Like Drinking Model

INTRODUCTION

In our earlier efforts to establish gut-brain axis during alcohol use disorder (AUD), we have demonstrated that supplementation of C57BL/6J male mice with 8 mg/mL sodium butyrate, a major short-chain fatty acid, in drinking water reduced ethanol intake and neuroinflammatory response in antibiotic (ABX)-enhanced voluntary binge-like alcohol consumption model, drinking in the dark (DID).

METHODS

To further evaluate the preclinical potential of SB, we have set a dose-escalation study in C57BL/6J male mice to test effects of ad libitum 20 mg/mL SB and 50 mg/mL SB and their combinations with ABX in the DID procedure for 4 weeks. Effects of these SB concentrations on ethanol consumption and bodily parameters were determined for the duration of the treatments. At the end of study, blood, liver, and intestinal tissues were collected to study any potential adverse effects ad to measure blood ethanol concentrations.

RESULTS

Increasing SB concentrations in the drinking water caused a loss in the protective effect against ethanol consumption and produced adverse effects on body and liver weights, reduced overall liquid intake. The hypothesis that these effects were due to aversion to SB smell/taste at these high concentrations were further tested in a follow up proof-of-concept study with intragastric gavage administration of SB. The higher gavage dose (320 mg/kg) caused reduction in ethanol consumption without any adverse effects.

CONCLUSION

Overall, these findings added more support for the therapeutic potential of SB in management of AUD, given a proper form of administration.

INTRODUCTION

In our earlier efforts to establish gut-brain axis during alcohol use disorder (AUD), we have demonstrated that supplementation of C57BL/6J male mice with 8 mg/mL sodium butyrate, a major short-chain fatty acid, in drinking water reduced ethanol intake and neuroinflammatory response in antibiotic (ABX)-enhanced voluntary binge-like alcohol consumption model, drinking in the dark (DID).

METHODS

To further evaluate the preclinical potential of SB, we have set a dose-escalation study in C57BL/6J male mice to test effects of ad libitum 20 mg/mL SB and 50 mg/mL SB and their combinations with ABX in the DID procedure for 4 weeks. Effects of these SB concentrations on ethanol consumption and bodily parameters were determined for the duration of the treatments. At the end of study, blood, liver, and intestinal tissues were collected to study any potential adverse effects ad to measure blood ethanol concentrations.

RESULTS

Increasing SB concentrations in the drinking water caused a loss in the protective effect against ethanol consumption and produced adverse effects on body and liver weights, reduced overall liquid intake. The hypothesis that these effects were due to aversion to SB smell/taste at these high concentrations were further tested in a follow up proof-of-concept study with intragastric gavage administration of SB. The higher gavage dose (320 mg/kg) caused reduction in ethanol consumption without any adverse effects.

CONCLUSION

Overall, these findings added more support for the therapeutic potential of SB in management of AUD, given a proper form of administration.