Gut Microbiota at the Intersection of Alcohol, Brain, and the Liver

Treating chronic stress and chronic pain by manipulating gut microbiota with diet: can we kill two birds with one stone?

Background: Chronic stress and chronic pain are closely linked by the capacity to exacerbate each other, sharing common roots in the brain and in the gut. The strict intersection between these two neurological diseases makes important to have a therapeutic strategy aimed at preventing both to maintain mental health in patients. Diet is an modifiable lifestyle factor associated with gut-brain axis diseases and there is growing interest in its use as adjuvant to main therapies. Several evidence attest the impact of specific diets or nutrients on chronic stress-related disorders and pain with a good degree of certainty. A daily adequate intake of foods containing micronutrients such as amino acids, minerals and vitamins, as well as the reduction in the consumption of processed food products can have a positive impact on microbiota and gut health. Many nutrients are endowed of prebiotic, anti-inflammatory, immunomodulatory and neuroprotective potential which make them useful tools helping the management of chronic stress and pain in patients. Dietary regimes, as intermittent fasting or caloric restriction, are promising, although further studies are needed to optimize protocols according to patient's medical history, age and sex. Moreover, by supporting gut microbiota health with diet is possible to attenuate comorbidities such as obesity, gastrointestinal dysfunction and mood disorders, thus reducing healthcare costs related to chronic stress or pain.Objective: This review summarize the most recent evidence on the microbiota-mediated beneficial effects of macro- and micronutrients, dietary-related factors, specific nutritional regimens and dietary intervention on these pathological conditions.

Therapeutic benefit of probiotic in alcohol dependence syndrome: Evidence from a tertiary care centre of India

Probiotic adjuvant has promising effects in treating alcohol induced hepatitis, depression, and anxiety. This study aimed to assess the effectiveness of adjuvant probiotic use in improving the liver functions, anxiety, and depression among patients with alcohol dependence syndrome (ADS) in a tertiary care hospital in Andhra Pradesh, India. In this prospective observational design, ADS patients with or without probiotics were followed-up at one and three months after initiation of treatment. They were assessed for liver function test (LFT), anxiety by HAM-A and depression by HAM-D scale. A total of 120 patients complied with the treatment, 60 in each group, mean age being 35.0 years (SD 9.5 years). The baseline socio-demographic and clinical characteristics were similar in both the groups. Significant reduction was noted in the probiotic group for total bilirubin (Mean difference (MD) 0.18; 95 % CI: 0.04, 0.31), AST (MD 5.0; 95 % CI: 0.5, 9.5), and ALT (MD 8.6; 95 % CI: 1.4, 15.7) at one month after treatment. Both the groups showed a considerable change in anxiety and depression scores (HAM-A and HAM-D) till three months. At three months of treatment initiation, proportional improvement of severity grade to mild form in anxiety was more in the probiotic group (35 %) than the non-probiotic group (13.3 %) (p < 0.05). Hence, probiotic supplementation can significantly reduce the hepatic enzymes and depression severity in patients with alcohol dependence syndrome but demands additional robust evidence on the causal inference.

A lupin protein hydrolysate protects the central nervous system from oxidative stress in WD-fed ApoE-/- mice

Oxidative stress plays a crucial role in neurodegenerative diseases like Parkinson's and Alzheimer's. Studies indicate the relationship between oxidative stress and the brain damage caused by a high-fat diet. It is previously found that a lupin protein hydrolysate (LPH) has antioxidant effects on human leukocytes, as well as on the plasma and liver of Western diet (WD)-fed ApoE-/- mice. Additionally, LPH shows anxiolytic effects in these mice. Given the connection between oxidative stress and anxiety, this study aimed to investigate the antioxidant effects of LPH on the brain of WD-fed ApoE-/- mice. LPH (100 mg kg-1) or a vehicle is administered daily for 12 weeks. Peptide analysis of LPH identified 101 amino acid sequences (36.33%) with antioxidant motifs. Treatment with LPH palliated the decrease in total antioxidant activity caused by WD ingestion and regulated the nitric oxide synthesis pathway in the brain of the animals. Furthermore, LPH increased cerebral glutathione levels and the activity of catalase and glutathione reductase antioxidant enzymes and reduced the 8-hydroxy-2'-deoxyguanosine levels, a DNA damage marker. These findings, for the first time, highlight the antioxidant activity of LPH in the brain. This hydrolysate could potentially be used in future nutraceutical therapies for neurodegenerative diseases.

Gut-Liver-Brain Axis and Alcohol Use Disorder: Treatment Potential of Fecal Microbiota Transplantation

PURPOSE

Chronic alcohol use is a major cause of liver damage and death. In the United States, multiple factors have led to low utilization of pharmacotherapy for alcohol use disorder (AUD), including lack of provider knowledge and comfort in prescribing medications for AUD. Alcohol consumption has direct effects on the gut microbiota, altering the diversity of bacteria and leading to bacterial overgrowth. Growing evidence suggests that alcohol's effects on the gut microbiome may contribute to increased alcohol consumption and progression of alcohol-associated liver disease (ALD). This article reviews human and preclinical studies investigating the role of fecal microbiota transplantation (FMT) in ameliorating alcohol-associated alterations to the liver, gut, and brain resulting in altered behavior; it also discusses the therapeutic potential of FMT.

SEARCH METHODS

For this narrative review, a literature search was conducted in September 2022 of PubMed, Web of Science Core Collection, and Google Scholar to identify studies published between January 2012 and September 2022. Search terms used included "fecal microbiota transplantation" and "alcohol."

SEARCH RESULTS

Most results of the literature search were review articles or articles on nonalcoholic fatty liver disease; these were excluded. Of the remaining empirical manuscripts, very few described clinical or preclinical studies that were directly investigating the effects of FMT on alcohol drinking or related behaviors. Ultimately, 16 studies were included in the review.

DISCUSSION AND CONCLUSIONS

The literature search identified only a few studies that were directly investigating the effect of FMT on ALD or alcohol drinking and related behaviors. Largely proof-of-concept studies, these findings demonstrate that alcohol can alter the gut microbiome and that the microbiome can be transferred between humans and rodents to alter affective behaviors frequently associated with increased alcohol use. Other studies have shown promise of FMT or other probiotic supplementation in alleviating some of the symptoms associated with ALD and drinking. These results show that the implementation of FMT as a therapeutic approach is still in the investigatory stages.

Alcohol-related cognitive impairments in patients with and without cirrhosis

AIMS

up to 80% of patients with alcohol use disorder display cognitive impairments. Some studies have suggested that alcohol-related cognitive impairments could be worsened by hepatic damage. The primary objective of this study was to compare mean scores on the Brief Evaluation of Alcohol-Related Neurocognitive Impairments measure between alcohol use disorder patients with (CIR+) or without cirrhosis (CIR-).

METHODS

we conducted a prospective case-control study in a hepatology department of a university hospital. All patients were assessed using the Evaluation of Alcohol-Related Neuropsychological Impairments test.

RESULTS

a total of 82 patients (50 CIR+, 32 CIR-) were included in this study. CIR- patients were significantly younger than CIR+ patients (respectively, 45.5 ± 6.8 vs 60.1 ± 9.0; P < .0001). After adjusting for age and educational level, the mean Evaluation of Alcohol-Related Neuropsychological Impairments total scores in the CIR+ group were significantly lower than in the group of CIR- patients (14.1 ± 0.7 vs 7.8 ± 0.4, respectively, P < .0001). The mean subscores on delayed verbal memory, alphabetical ordination, alternating verbal fluency, visuospatial abilities, and ataxia subtests were also significantly lower in the CIR+ than in the CIR- group (respectively, 1.9 ± 0.2 vs 2.8 ± 0.2; 1.8 ± 0.2 vs 2.7 ± 0.2; 2.2 ± 0.2 vs 3.6 ± 0.2; 0.7 ± 0.2 vs 1.6 ± 0.2; 0.7 ± 0.2 vs 3.1 ± 0.2; P < .0001 for all comparisons).

CONCLUSIONS

in the present study, alcohol use disorder patients with cirrhosis presented more severe cognitive impairments than those without cirrhosis. Longitudinal studies are needed to investigate how cirrhosis can influence cognitive impairments.

Antioxidants ameliorate oxidative stress in alcoholic liver injury by modulating lipid metabolism and phospholipid homeostasis

Alcoholic liver disease (ALD) is a significant risk factor in the global disease burden. The antioxidants vitamin C (Vc) and N-acetyl cysteine (NAC) have shown hepatoprotective effects in preventing and treating ALD. However, the correlation between the improved effect of antioxidants and lipid metabolism is still unclear. In this study, AML12 cells and C57BL/6 mice stimulated with alcohol were used to investigate the protective effects and potential mechanisms of two antioxidants (Vc and NAC) on alcoholic liver injury. Results showed that Vc and NAC attenuated intracellular lipid accumulation and oxidative damage induced by excessive alcohol exposure in hepatic AML12 cells. The in vivo results indicated that antioxidants ameliorated alcohol-induced changes in histopathology, reducing the levels of alcohol metabolizing factors and aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglyceride (TG), and total cholesterol (TC) contents, which demonstrated that antioxidants effectively mitigated liver injury in ALD mice. Further studies showed that antioxidants reversed the disruption of fatty acid (FA) synthesis and lipid transport induced by alcohol exposure, and restored phospholipid levels. Especially, Vc and NAC increased the endogenous antioxidant plasmenyl phosphatidylethanolamine (PlsEtn). Additionally, antioxidants ameliorated the alcohol-impaired mitochondrial function and inhibited excessive oxidative stress. In conclusion, antioxidants can regulate lipid metabolism and phospholipid homeostasis, which in turn inhibit oxidative stress and thereby exert protective effects against ALD.

Acetobacter pasteurianus BP2201 alleviates alcohol-induced hepatic and neuro-toxicity and modulate gut microbiota in mice

The excessive consumption of alcohol results in a dysbiosis of the gut microbiota, which subsequently impairs the gut microbiota-brain/liver axes and induces cognitive dysfunction and hepatic injury. This study aimed to investigate the potential effect of Acetobacter pasteurianus BP2201 in reducing the negative effects of alcohol consumption on cognitive function and liver health by modulating the gut microbiota-brain/liver axes. Treatment with A. pasteurianus BP2201 improved alcohol-induced hippocampal damage, suppressed neuroinflammation, promoted neuroprotein expression in the hippocampus and enhanced cognitive function. At the same time, A. pasteurianus BP2201 can also reduce serum lipid levels, relieve oxidative stress, inhibit TLR4/MyD88/NF-κB pathway, reduce the secretion of TNF-α and IL-1β, so as to improve alcoholic liver injury. Concomitantly, the treatment with A. pasteurianus BP2201 leads to a shift in the intestinal microbiota structure towards that of healthy individuals, inhibiting the proliferation of harmful bacteria and promoting the recovery of beneficial bacteria. In addition, it also improves brain cognitive dysfunction and liver health by affecting the gut microbiota-brain/liver axes by promoting the synthesis of relevant amino acids and the metabolism of nucleotide base components. These findings demonstrate the potential of regulating the gut microbiome and gut microbiota-brain/liver axes to mitigate alcohol-induced disease.

The Role of the Gastrointestinal Microbiome in Liver Disease

Liver disease is a major global health problem leading to approximately two million deaths a year. This is the consequence of a number of aetiologies, including alcohol-related, metabolic-related, viral infection, cholestatic and immune disease, leading to fibrosis and, eventually, cirrhosis. No specific registered antifibrotic therapies exist to reverse liver injury, so current treatment aims at managing the underlying factors to mitigate the development of liver disease. There are bidirectional feedback loops between the liver and the rest of the gastrointestinal tract via the portal venous and biliary systems, which are mediated by microbial metabolites, specifically short-chain fatty acids (SCFAs) and secondary bile acids. The interaction between the liver and the gastrointestinal microbiome has the potential to provide a novel therapeutic modality to mitigate the progression of liver disease and its complications. This review will outline our understanding of hepatic fibrosis, liver disease, and its connection to the microbiome, which may identify potential therapeutic targets or strategies to mitigate liver disease.

Gut microbiota in alcohol-related liver disease: pathophysiology and gut-brain cross talk

Alcohol-related liver disease (ALD) from excessive alcohol intake has a unique gut microbiota profile. The disease progression-free survival in ALD patients has been associated with the degree of gut dysbiosis. The vicious cycles between gut dysbiosis and the disease progression in ALD including: an increase of acetaldehyde production and bile acid secretion, impaired gut barrier, enrichment of circulating microbiota, toxicities of microbiota metabolites, a cascade of pro-inflammatory chemokines or cytokines, and augmentation in the generation of reactive oxygen species. The aforementioned pathophysiology process plays an important role in different disease stages with a spectrum of alcohol hepatitis, ALD cirrhosis, neurological dysfunction, and hepatocellular carcinoma. This review aims to illustrate the pathophysiology of gut microbiota and clarify the gut-brain crosstalk in ALD, which may provide the opportunity of identifying target points for future therapeutic intervention in ALD.

Therapeutic strategies of small molecules in the microbiota-gut-brain axis for alcohol use disorder

The microbiota-gut-brain axis (MGBA) is important in maintaining the structure and function of the central nervous system (CNS) and is regulated by the CNS environment and signals from the peripheral tissues. However, the mechanism and function of the MGBA in alcohol use disorder (AUD) are still not completely understood. In this review, we investigate the underlying mechanisms involved in the onset of AUD and/or associated neuronal deficits and create a foundation for better treatment (and prevention) strategies. We summarize recent reports focusing on the alteration of the MGBA in AUD. Importantly, we highlight the properties of small-molecule short-chain fatty acids (SCFAs), neurotransmitters, hormones, and peptides in the MGBA and discusses their usage as therapeutic agents against AUD.

Gut Microbiota Deficiency Exacerbates Liver Injury in Bile Duct Ligated Mice via Inflammation and Lipid Metabolism

Bile components play a critical role in maintaining gut microbiota homeostasis. In cholestasis, bile secretion is impaired, leading to liver injury. However, it remains to be elucidated whether gut microbiota plays a role in cholestatic liver injury. Here, we performed a sham operation and bile duct ligation (BDL) in antibiotic-induced microbiome depleted (AIMD) mice and assessed liver injury and fecal microbiota composition in these mice. Significant reductions in gut microbiota richness and diversity were found in AIMD-sham mice when compared to sham controls. Three-day BDL leads to great elevation of plasma ALT, ALP, total bile acids, and bilirubin where reduced diversity of the gut microbiota was also found. AIMD further aggravated cholestatic liver injury evidenced by significantly higher levels of plasma ALT and ALP, associated with further reduced diversity and increased Gram-negative bacteria in gut microbiota. Further analyses revealed increased levels of LPS in the plasma of AIMD-BDL mice where elevated expression of inflammatory genes and decreased expression of hepatic detoxification enzymes were also found in liver when compared to the BDL group. These findings indicate that gut microbiota plays a critical role in cholestatic liver injury. Maintaining its homeostasis may alleviate liver injury in patients with cholestasis.

Alterations and correlations of gut microbiota, fecal, and serum metabolome characteristics in a rat model of alcohol use disorder

Background

Growing evidence suggests the gut microbiota and metabolites in serum or fecal may play a key role in the process of alcohol use disorder (AUD). However, the correlations of gut microbiota and metabolites in both feces and serum in AUD subjects are not well understood.

Methods

We established a rat model of AUD by a chronic intermittent ethanol voluntary drinking procedure, then the AUD syndromes, the gut microbiota, metabolomic profiling in feces and serum of the rats were examined, and correlations between gut microbiota and metabolites were analyzed.

Results

Ethanol intake preference increased and maintained at a high level in experimental rats. Anxiety-like behaviors was observed by open field test and elevated plus maze test after ethanol withdraw, indicating that the AUD rat model was successfully developed. The full length 16S rRNA gene sequencing showed AUD significantly changed the β-diversity of gut microbial communities, and significantly decreased the microbial diversity but did not distinctly impact the microbial richness. Microbiota composition significantly changed in AUD rats, such as the abundance of Romboutsia and Turicibacter were significantly increased, whereas uncultured_bacterium_o_Mollicutes_RF39 was decreased. In addition, the untargeted metabolome analysis revealed that many metabolites in both feces and serum were altered in the AUD rats, especially involved in sphingolipid metabolism and glycerophospholipid metabolism pathways. Finally, multiple correlations among AUD behavior, gut microbiota and co-changed metabolites were identified, and the metabolites were directly correlated with the gut microbiota and alcohol preference.

Conclusion

The altered metabolites in feces and serum are important links between the gut microbiota dysbiosis and alcohol preference in AUD rats, and the altered gut microbiota and metabolites can be potentially new targets for treating AUD.

Risk Factors for Hepatic Encephalopathy in Hepatocellular Carcinoma After Sorafenib or Lenvatinib Treatment: A Real-World Study

Purpose

This study aimed to investigate the incidence rate and risk factors for hepatic encephalopathy (HE) among unresectable hepatocellular carcinoma (uHCC) patients with liver cirrhosis who received sorafenib or lenvatinib treatment.

Patients and Methods

uHCC patients with cirrhosis who received first-line sorafenib or lenvatinib treatment between September 2014 and February 2021 were continually reviewed in our single-center retrospective study. The Hepatic Encephalopathy Scoring Algorithm was used to evaluate the occurrence and grade of HE during treatment, and logistic regression models were used to further explore the risk factors for HE.

Results

A total of 454 eligible patients were enrolled in our study, with 214 and 240 patients in the sorafenib and lenvatinib groups, respectively. At time of data cut-off (2021-12), the incidence of HE in sorafenib group (4.2%, 95% CI:2-7%) was significantly lower than that in lenvatinib group (11.3%,95% CI:7-15%) (p = 0.006), with alcoholic cirrhosis [OR: 5.857 (95% CI: 1.519-22.591)], Child-Pugh >7 [OR: 3.023 (95% CI: 1.135-8.053)], blood ammonia ≥38.65 μmol/L [OR: 4.693 (95% CI: 1.782-12.358)], total bile acid ≥29.5 μmol/L [OR: 11.047 (95% CI: 4.414-27.650)] and duration of treatment ≥5.6 months [OR: 4.350 (95% CI: 1.701-11.126)] to be risk factors for the occurrence of HE during first-line systemic therapy.

Conclusion

In our study, for off-label uHCC patients (Child-Pugh >7) with alcoholic cirrhosis, hyperammonemia, hypercholesterolemia, and estimated longer duration of treatment, the application of lenvatinib has to be cautious, which needs to be confirmed in future clinical trials.

Trimethylamine N-Oxide (TMAO) and Indoxyl Sulfate Concentrations in Patients with Alcohol Use Disorder

Background: Trimethylamine N-oxide (TMAO) and indoxyl sulfate (IS) are produced by the microbiota and the liver, and can contribute to brain aging and impaired cognitive function. This study aims to examine serum TMAO and IS concentrations in patients with alcohol-use disorder (AUD) at the entry for alcohol withdrawal, and the relationships with several biological, neuropsychological, and clinical parameters. Methods: TMAO and IS were quantified in thirty AUD inpatients and fifteen healthy controls (HC). The severities of AUD and alcohol withdrawal syndrome (AWS), and general cognitive abilities were assessed in AUD patients. Results: TMAO concentrations did not differ between HC and AUD patients. Several biomarkers assessing nutritional status and liver function were significantly different in AUD patients with the lowest TMAO concentrations compared to other AUD patients. IS concentration was significantly lower in AUD patients and a significant positive predictor of serum prealbumin variation during the acute phase of alcohol withdrawal. No relationship was observed between the concentrations of these metabolites and the severities of alcohol dependence, AWS, or cognitive deficits. Conclusions: Our data suggest that AUD patients with low concentrations of TMAO or IS should probably benefit from a personalized refeeding program during the acute phase of alcohol withdrawal.

Gut Microbiome and Alcohol-associated Liver Disease

Changes in gut microbiota (GM) may be associated with the causation and progression of multiple liver diseases such as metabolic-associated liver disease, alcohol-associated liver disease (ALD), alcohol-associated hepatitis (AH), primary biliary cholangitis, primary sclerosing cholangitis, autoimmune liver disease, and most importantly, complications of cirrhosis and portal hypertension such as hepatic encephalopathy (HE), infection, and hepatocellular carcinoma. ALD includes simple steatosis, steatohepatitis, AH, cirrhosis, and acute-on-chronic liver failure. Alcohol consumption is associated with GM changes even before ALD development, and continued alcohol intake results in progressive dysbiosis and development of clinical events such as AH, infection, and HE. The composition and function of GM, specific changes in bacterial communities, and the functional metabolism of GM are affected in the spectrum of ALD, as revealed using high-throughput sequencing. It was reported in preliminary studies that modulation of disrupted GM improves adverse clinical events and ameliorates disease progression in ALD. In this review, we exhaustively discuss the preclinical and clinical studies on GM in ALD and critically discuss GM modulation and its effects based on various human and animal models of ALD.

An Elevated FIB-4 Score Is Associated with an Increased Incidence of Depression among Outpatients in Germany

Background: Liver disease and depression are known to be closely associated. Non-invasive tests (NIT), such as the FIB-4 score, have been recommended by different guidelines to rule out advanced fibrosis and to stratify the risk of liver-related outcomes in patients with chronic liver diseases. However, the predictive value of an elevated FIB-4 score regarding the development of depression and/or anxiety disorders among the general population is unknown. Methods: By using the Disease Analyzer database (IQVIA), which compiles diagnoses and laboratory values as well as basic medical and demographic data of patients followed in general practices in Germany, we identified 370,756 patients with available lab values for FIB-4 score calculation between 2005 and 2019. Patients with an FIB-4 score < 2 were matched 1:1 to patients with an FIB-4 index ≥ 2 by age, sex and yearly consultation frequency. Results: In regression analysis, the incidence rate ratio (IRR) of depression was significantly higher among patients with an FIB-4 score ≥ 2.0 compared to patients with a lower FIB-4 score <2.0 (IRR: 1.12, p < 0.001). This association was significant for both female (IRR: 1.10, p = 0.004) and male (IRR: 1.15, p < 0.001) patients and strongest in the age groups ≤50 years (IRR: 1.42, p < 0.001) and 51-60 years (IRR: 1.34, p < 0.001). There was no significant association between an elevated FIB-4 score ≥ 2.0 and the incidence of depression among patients aged 60 years and older. There was no significant increase in the IRR of anxiety disorders for patients with high or low FIB-4 scores. Conclusion: Our study suggests a previously unknown association between an elevated FIB-4 score and an increased incidence of depression. This finding suggests that the FIB-4 score is not only a valuable tool for the prediction of liver-specific endpoints but also may be of relevance for the prediction of extrahepatic comorbidities, which in turn may argue for clinical screening programs in patients with an elevated FIB-4.

Gut Microbiome in Non-Alcoholic Fatty Liver Disease: From Mechanisms to Therapeutic Role

Non-alcoholic fatty liver disease (NAFLD) is considered to be a significant health threat globally, and has attracted growing concern in the research field of liver diseases. NAFLD comprises multifarious fatty degenerative disorders in the liver, including simple steatosis, steatohepatitis and fibrosis. The fundamental pathophysiology of NAFLD is complex and multifactor-driven. In addition to viruses, metabolic syndrome and alcohol, evidence has recently indicated that the microbiome is related to the development and progression of NAFLD. In this review, we summarize the possible microbiota-based therapeutic approaches and highlight the importance of establishing the diagnosis of NAFLD through the different spectra of the disease via the gut–liver axis.

Probiotics attenuate alcohol-induced muscle mechanical hyperalgesia: Preliminary observations

Alcohol use disorder (AUD) is a major health problem that causes millions of deaths annually world-wide. AUD is considered to be a chronic pain disorder, that is exacerbated by alcohol withdrawal, contributing to a high (∼80%) relapse rate. Chronic alcohol consumption has a marked impact on the gut microbiome, recognized to have a significant effect on chronic pain. We tested the hypothesis that modulating gut microbiota through feeding rats with probiotics can attenuate alcohol-induced muscle mechanical hyperalgesia. To test this hypothesis, rats were fed alcohol (6.5%, 4 days on 3 days off) for 3 weeks, which induced skeletal muscle mechanical hyperalgesia. Following alcohol feeding, at which time nociceptive thresholds were ∼37% below pre-alcohol levels, rats received probiotics in their drinking water, either Lactobacillus Rhamnosus GG (Culturelle) or De Simone Formulation (a mixture of 8 bacterial species) for 8 days; control rats received plain water to drink. When muscle mechanical nociceptive threshold was evaluated 1 day after beginning probiotic feeding, nociceptive thresholds were significantly higher than rats not receiving probiotics. Mechanical nociceptive thresholds continued to increase during probiotic feeding, with thresholds approaching pre-alcohol levels 5 days after starting probiotics; nociceptive threshold in rats not receiving probiotics remained low. After probiotics were removed from the drinking water, nociceptive thresholds gradually decreased in these two groups, although they remained higher than the group not treated with probiotic (21 days after ending alcohol feeding). These observations suggest that modification of gut microbiota through probiotic feeding has a marked effect on chronic alcohol-induced muscle mechanical hyperalgesia. Our results suggest that administration of probiotics to individuals with AUD may reduce pain associated with alcohol consumption and withdrawal, and may be a novel therapeutic intervention to reduce the high rate of relapse seen in individuals with AUD attempting to abstain from alcohol.

Sodium Butyrate Protects Against Ethanol-Induced Toxicity in SH-SY5Y Cell Line

Alcohol use disorder (AUD), brought about by excessive alcohol use, is associated with damages to several organs including the brain. Chronic excessive use of alcohol can compromise intestinal integrity, leading to changes in gut microbiota (GM) composition known as dysbiosis. Dysbiosis, by disruption of the gut-brain axis (GBA), further exacerbates the deleterious effects of alcohol. One of the fermentation by-products of GM is butyrate (BUT), a short-chain fatty acid (SCFA) that plays an important role in maintaining homeostasis of the GBA. Alcohol metabolism results in formation of acetaldehyde, a highly reactive compound that reacts with dopamine in the brain to form toxic adducts such as salsolinol. Recent studies indicate potential neuro-protective effects of BUT against various toxicants including salsolinol. Here, we sought to investigate whether BUT can also protect against alcohol toxicity. Pretreatment of neuroblastoma-derived SH-SY5Y cells with 500 mM ethanol (ETOH) for 24 h resulted in approximately 40% reduction in cell viability, which was totally blocked by 10 µM of either BUT or AR 420,626 (AR), a selective fatty acid 3 receptor (FA3R) agonist. The neuro-protective effects of both BUT and AR were significantly (80%) attenuated by beta-hydroxy butyrate (BHB), a selective FA3R antagonist. Interestingly, combination of BUT and AR resulted in synergistic protection against ETOH, which was totally blocked by BHB. These findings suggest potential utility of butyrate and/or FA3R agonists against ETOH-induced toxicity.

Probiotics-Based Treatment as an Integral Approach for Alcohol Use Disorder in Alcoholic Liver Disease

Alcoholic liver disease (ALD) is one of the leading causes of morbidity among adults with alcohol use disorder (AUD) worldwide. Its clinical course ranges from steatosis to alcoholic hepatitis, progressing to more severe forms of liver damage, such as cirrhosis and hepatocellular carcinoma. The pathogenesis of ALD is complex and diverse elements are involved in its development, including environmental factors, genetic predisposition, the immune response, and the gut-liver axis interaction. Chronic alcohol consumption induces changes in gut microbiota that are associated with a loss of intestinal barrier function and inflammatory responses which reinforce a liver damage progression triggered by alcohol. Alcohol metabolites such as acetaldehyde, lipid peroxidation-derived aldehyde malondialdehyde (MDA), and protein-adducts act as liver-damaging hepatotoxins and potentiate systemic inflammation. Additionally, ethanol causes direct damage to the central nervous system (CNS) by crossing the blood-brain barrier (BBB), provoking oxidative stress contributing to neuroinflammation. Overall, these processes have been associated with susceptibility to depression, anxiety, and alcohol craving in ALD. Recent evidence has shown that probiotics can reverse alcohol-induced changes of the microbiota and prevent ALD progression by restoring gut microbial composition. However, the impact of probiotics on alcohol consumption behavior has been less explored. Probiotics have been used to treat various conditions by restoring microbiota and decreasing systemic and CNS inflammation. The results of some studies suggest that probiotics might improve mental function in Alzheimer’s, autism spectrum disorder, and attenuated morphine analgesic tolerance. In this sense, it has been observed that gut microbiota composition alterations, as well as its modulation using probiotics, elicit changes in neurotransmitter signals in the brain, especially in the dopamine reward circuit. Consequently, it is not difficult to imagine that a probiotics-based complementary treatment to ALD might reduce disease progression mediated by lower alcohol consumption. This review aims to present an update of the pathophysiologic mechanism underlying the microbiota-gut-liver-brain axis in ALD, as well as to provide evidence supporting probiotic use as a complementary therapy to address alcohol consumption disorder and its consequences on liver damage.