Clinical science workshop: targeting the gut-liver-brain axis

Electroacupuncture Promotes Liver Regeneration by Activating DMV Acetylcholinergic Neurons-Vagus-Macrophage Axis in 70% Partial Hepatectomy of Mice

Lack of liver regenerative capacity is the primary cause of hepatic failure and even mortality in patients undergoing hepatectomy, with no effective intervention strategies currently available. Therefore, identifying efficacious interventions to enhance liver regeneration is pivotal for optimizing clinical outcomes. Recent studies have demonstrated that vagotomy exerts an inhibitory effect on liver regeneration following partial hepatectomy, thereby substantiating the pivotal role played by the vagus nerve in the process of liver regeneration. In recent years, electroacupuncture (EA) has emerged as a non-invasive technique for stimulating the vagus nerve. However, EA on hepatic regeneration remains uncertain. In this study, a 70% partial hepatectomy (PH) mouse model is utilized to investigate the effects of EA on acute liver regeneration and elucidate its underlying molecular mechanisms. It is observed that EA at ST36 acutely activated cholinergic neurons in the dorsal motor nucleus of the vagus nerve (DMV), resulting in increased release of acetylcholine from hepatic vagal nerve endings and subsequent activation of IL-6 signaling in liver macrophages. Ultimately, these events promoted hepatocyte proliferation and facilitated liver regeneration. These findings provide insights into the fundamental brain-liver axis mechanism through which EA promotes liver regeneration, offering a novel therapeutic approach for post-hepatectomy liver regeneration disorders.

Ferroptosis: An important mechanism of disease mediated by the gut-liver-brain axis

AIMS

As a unique iron-dependent non-apoptotic cell death, Ferroptosis is involved in the pathogenesis and development of many human diseases and has become a research hotspot in recent years. However, the regulatory role of ferroptosis in the gut-liver-brain axis has not been elucidated. This paper summarizes the regulatory role of ferroptosis and provides theoretical basis for related research.

MATERIALS AND METHODS

We searched PubMed, CNKI and Wed of Science databases on ferroptosis mediated gut-liver-brain axis diseases, summarized the regulatory role of ferroptosis on organ axis, and explained the adverse effects of related regulatory effects on various diseases.

KEY FINDINGS

According to our summary, the main way in which ferroptosis mediates the gut-liver-brain axis is oxidative stress, and the key cross-talk of ferroptosis affecting signaling pathway network is Nrf2/HO-1. However, there were no specific marker between different organ axes mediate by ferroptosis.

SIGNIFICANCE

Our study illustrates the main ways and key cross-talk of ferroptosis mediating the gut-liver-brain axis, providing a basis for future research.

Hepatic Encephalopathy: Clinical Manifestations

Hepatic encephalopathy (HE) can occur as a complication of chronic liver disease as well as acute liver failure. HE is associated with significantly increased morbidity and worse patient outcomes. The clinical manifestation of HE ranges from early less-severe presentations that may only be accurately detected on dedicated psychomotor diagnostic testing to overt alterations in cognition and mental status to the most severe form of coma. Greater awareness of the clinical manifestations of HE across the spectrum of symptom severity is critical for early identification and timely initiation of appropriate therapy to improve patient outcomes.

Mitochondrial targets in hyperammonemia: Addressing urea cycle function to improve drug therapies

The urea cycle (UC) is a critically important metabolic process for the disposal of nitrogen (ammonia) produced by amino acids catabolism. The impairment of this liver-specific pathway induced either by primary genetic defects or by secondary causes, namely those associated with hepatic disease or drug administration, may result in serious clinical consequences. Urea cycle disorders (UCD) and certain organic acidurias are the major groups of inherited rare diseases manifested with hyperammonemia (HA) with UC dysregulation. Importantly, several commonly prescribed drugs, including antiepileptics in monotherapy or polytherapy from carbamazepine to valproic acid or specific antineoplastic agents such as asparaginase or 5-fluorouracil may be associated with HA by mechanisms not fully elucidated. HA, disclosing an imbalance between ammoniagenesis and ammonia disposal via the UC, can evolve to encephalopathy which may lead to significant morbidity and central nervous system damage. This review will focus on biochemical mechanisms related with HA emphasizing some poorly understood perspectives behind the disruption of the UC and mitochondrial energy metabolism, namely: i) changes in acetyl-CoA or NAD+ levels in subcellular compartments; ii) post-translational modifications of key UC-related enzymes, namely acetylation, potentially affecting their catalytic activity; iii) the mitochondrial sirtuins-mediated role in ureagenesis. Moreover, the main UCD associated with HA will be summarized to highlight the relevance of investigating possible genetic mutations to account for unexpected HA during certain pharmacological therapies. The ammonia-induced effects should be avoided or overcome as part of safer therapeutic strategies to protect patients under treatment with drugs that may be potentially associated with HA.

Interleukin-8 (IL-8) as a Potential Mediator of an Association between Trimethylamine N-Oxide (TMAO) and Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) among African Americans at Risk of Cardiovascular Disease

Trimethylamine N-oxide (TMAO)-a microbial metabolite derived from the hepatic-gut axis-is linked to inflammation, hyperlipidemia, and cardiovascular disease (CVD). Proprotein convertase subtilisin/kexin type 9 (PCSK9), which is largely hepatically expressed, blocks low-density lipoprotein (LDL) receptor recycling, also leading to hyperlipidemia. The primary objective of this study was to investigate a previously hypothesized potential relationship between TMAO and PCSK9 in order to explore novel mechanisms linking TMAO and CVD risk. African American adults at risk of CVD living in the Washington DC area were recruited to participate in a cross-sectional community-based study (n = 60, 93% female, BMI = 33). Fasting levels of inflammatory cytokines (i.e., interleukin (IL)-1 beta, tumor necrosis factor-alpha, and interleukin-8), TMAO, and PCSK9 were measured using Luminex and ELISA, respectively. Univariate and multivariate linear regression analyses and structural equation mediation analyses were conducted using STATA. All models were adjusted for body mass index (BMI) and atherosclerotic CVD risk score (ASCVD). A significant association between TMAO and PCSK9 was identified (β = 0.31, p = 0.02). Both TMAO and PCSK9 were significantly associated with IL-8 (TMAO: β = 0.45, p = 0.00; PCSK9: β = 0.23, p = 0.05) in adjusted models. Mediation analysis indicated that 34.77% of the relationship between TMAO and PCSK9 was explained by IL-8. Our findings indicate a potential PCSK9-involved pathway for TMAO and CVD risk, with potential mediation by IL-8.

The gut–microbiota–brain changes across the liver disease spectrum

Gut microbiota dysbiosis plays a significant role in the progression of liver disease, and no effective drugs are available for the full spectrum. In this study, we aimed to explore the dynamic changes of gut microbiota along the liver disease spectrum, together with the changes in cognition and brain metabolism. Sprague–Dawley rats were divided into four groups reflecting different stages of liver disease: control diet (NC); high-fat, high-cholesterol diet (HFHC), emulating non-alcoholic steatohepatitis; control diet + thioacetamide (NC + TAA), simulating acute liver failure; and high-fat, high-cholesterol diet + thioacetamide (HFHC + TAA) to assess the effect of the superimposed damages. The diet was administered for 14 weeks and the thioacetamide was administrated (100 mg/kg day) intraperitoneally over 3 days. Our results showed changes in plasma biochemistry and liver damage across the spectrum. Differences in gut microbiota at the compositional level were found among the experimental groups. Members of the Enterobacteriaceae family were most abundant in HFHC and HFHC + TAA groups, and Akkermansiaceae in the NC + TAA group, albeit lactobacilli genus being dominant in the NC group. Moreover, harm to the liver affected the diversity and bacterial community structure, with a loss of rare species. Indeed, the superimposed damage group (HFHC + TAA) suffered a loss of both rare and abundant species. Behavioral evaluation has shown that HFHC, NC + TAA, and HFHC + TAA displayed a worsened execution when discriminating the new object. Also, NC + TAA and HFHC + TAA were not capable of recognizing the changes in place of the object. Furthermore, working memory was affected in HFHC and HFHC + TAA groups, whereas the NC + TAA group displayed a significant delay in the acquisition. Brain oxidative metabolism changes were observed in the prefrontal, retrosplenial, and perirhinal cortices, as well as the amygdala and mammillary bodies. Besides, groups administered with thioacetamide presented an increased oxidative metabolic activity in the adrenal glands. These results highlight the importance of cross-comparison along the liver spectrum to understand the different gut–microbiota–brain changes. Furthermore, our data point out specific gut microbiota targets to design more effective treatments, though the liver–gut–brain axis focused on specific stages of liver disease.

Comparative Effectiveness and Safety of Polyethylene Glycol Electrolyte Solution Versus Lactulose for Treatment of Hepatic Encephalopathy: A Systematic Review and Meta-analysis

BACKGROUND

Hepatic encephalopathy (HE) is a complex neuropsychiatric syndrome associated with liver failure and/or portal systemic shunting. Polyethylene glycol (PEG) electrolyte solution is a commonly used for catharsis of gut, which has been demonstrated to relieve HE in a number of randomized controlled trials. The aim of this paper was to evaluate the comparative efficacy and safety of PEG with lactulose for current HE treatment.

METHODS

PEG electrolyte solution versus lactulose of HE was deeply studied by conducting a systematic search in electronic databases and other sources until December 31, 2020. The PRISMA statement recommended the use of meta-analysis with 95% confidence interval (CI), relative risk (RR), and weighted mean deviation (WMD) as the estimated effect size. A sensitivity analysis was performed comprehensively to present the risk of bias and the source of heterogeneity.

RESULTS

A total of 434 patients were involved in 7 randomized studies. It is found that there was a significant advantage of PEG therapy in the increase of clinical efficacy (RR=1.46; 95% CI: 1.26-1.68; P=0.000; I2=0.0%) and the decrease of hospital stay (WMD=-1.78; 95% CI: -2.72 to 0.85; P=0.000; I2=90.1%). There was no significant difference in the incidence of adverse events (RR=0.75; 95% CI: 0.48-1.19; P=0.222>0.05; I2=7.2%) and the level of serum ammonia (WMD=9.02; 95% CI: -14.39 to 32.43; P=0.45>0.05; I2=84.9%) after 24 hours between the 2 groups.

CONCLUSIONS

The results prove that PEG has a beneficial effect on the treatment of HE. Compared with lactulose, PEG can lead to more rapid HE resolution during the first 24 hours and shorten the length of stay without increasing the rate of adverse effects.

Gut Microbiota and Neuroplasticity

The accumulating evidence linking bacteria in the gut and neurons in the brain (the microbiota-gut-brain axis) has led to a paradigm shift in the neurosciences. Understanding the neurobiological mechanisms supporting the relevance of actions mediated by the gut microbiota for brain physiology and neuronal functioning is a key research area. In this review, we discuss the literature showing how the microbiota is emerging as a key regulator of the brain's function and behavior, as increasing amounts of evidence on the importance of the bidirectional communication between the intestinal bacteria and the brain have accumulated. Based on recent discoveries, we suggest that the interaction between diet and the gut microbiota, which might ultimately affect the brain, represents an unprecedented stimulus for conducting new research that links food and mood. We also review the limited work in the clinical arena to date, and we propose novel approaches for deciphering the gut microbiota-brain axis and, eventually, for manipulating this relationship to boost mental wellness.

Psychosomatic Disorders in Patients with Gastrointestinal Diseases: Single-Center Cross-Sectional Study of 1186 Inpatients

OBJECTIVE

To investigate the prevalence of anxiety and depression in hospitalized patients in the Department of Gastroenterology and to explore the risk factors affecting psychosomatic conditions in patients with digestive disorders.

METHODS

Patients hospitalized with gastrointestinal diseases were enrolled by the Department of Gastroenterology of Xiangya Hospital of Central South University from November 2017 to June 2018 and completed a cross-sectional questionnaire survey. According to anxiety/nonanxiety, depression/nondepression, the subjects were divided into two groups, respectively, and the risk factors of anxiety/depression were analyzed.

RESULTS

A total of 1186 patients were included in this study. The overall detection rate was 20.74% for anxiety symptoms alone, 31.78% for depressive symptoms alone, 13.99% for both anxiety and depressive symptoms, and 38.53% for either depression or anxiety symptoms. The prevalence of anxiety symptoms was higher in female than in male patients and inversely correlated with levels of education. There was no significant difference in the detection rate of anxiety and depression between patients with functional and organic digestive diseases. Sleep quality and quality of life were inversely correlated with the severity of anxiety and depression. Notably, among the patients with abnormal psychological conditions, only 7.6% of them were willing to receive psychological treatment. Gender, sleep quality, and life quality are independent risk factors for anxiety and depression symptoms for inpatients with gastrointestinal diseases.

CONCLUSION

Paying more attention to the education level, sleep quality, and quality of life in patients with gastrointestinal diseases will help doctors to identify the risk of psychological abnormalities and improve medical care.

Probiotics improve the neurometabolic profile of rats with chronic cholestatic liver disease

Chronic liver disease leads to neuropsychiatric complications called hepatic encephalopathy (HE). Current treatments have some limitations in their efficacy and tolerability, emphasizing the need for alternative therapies. Modulation of gut bacterial flora using probiotics is emerging as a therapeutic alternative. However, knowledge about how probiotics influence brain metabolite changes during HE is missing. In the present study, we combined the advantages of ultra-high field in vivo 1H MRS with behavioural tests to analyse whether a long-term treatment with a multistrain probiotic mixture (VIVOMIXX) in a rat model of type C HE had a positive effect on behaviour and neurometabolic changes. We showed that the prophylactic administration of this probiotic formulation led to an increase in gut Bifidobacteria and attenuated changes in locomotor activity and neurometabolic profile in a rat model of type C HE. Both the performance in behavioural tests and the neurometabolic profile of BDL + probiotic rats were improved compared to the BDL group at week 8 post-BDL. They displayed a significantly lesser increase in brain Gln, a milder decrease in brain mIns and a smaller decrease in neurotransmitter Glu than untreated animals. The clinical implications of these findings are potentially far-reaching given that probiotics are generally safe and well-tolerated by patients.

The Gut Barrier, Intestinal Microbiota, and Liver Disease: Molecular Mechanisms and Strategies to Manage

Liver disease encompasses pathologies as non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, alcohol liver disease, hepatocellular carcinoma, viral hepatitis, and autoimmune hepatitis. Nowadays, underlying mechanisms associating gut permeability and liver disease development are not well understood, although evidence points to the involvement of intestinal microbiota and their metabolites. Animal studies have shown alterations in Toll-like receptor signaling related to the leaky gut syndrome by the action of bacterial lipopolysaccharide. In humans, modifications of the intestinal microbiota in intestinal permeability have also been related to liver disease. Some of these changes were observed in bacterial species belonging Roseburia, Streptococcus, and Rothia. Currently, numerous strategies to treat liver disease are being assessed. This review summarizes and discusses studies addressed to determine mechanisms associated with the microbiota able to alter the intestinal barrier complementing the progress and advancement of liver disease, as well as the main strategies under development to manage these pathologies. We highlight those approaches that have shown improvement in intestinal microbiota and barrier function, namely lifestyle changes (diet and physical activity) and probiotics intervention. Nevertheless, knowledge about how such modifications are beneficial is still limited and specific mechanisms involved are not clear. Thus, further in-vitro, animal, and human studies are needed.

Crosstalk between the microbiota-gut-brain axis and depression

Nutritional and microbiological psychiatry, especially the contribution of the gut microbiota to depression, has become a promising research field over the past several decades. An imbalance in the "microbiota-gut-brain axis", which reflects the constant bidirectional communication between the central nervous system and the gastrointestinal tract, has been used as a hypothesis to interpret the pathogenesis of depression. Alterations in gut microbiota composition could increase the permeability of the gut barrier, activate systemic inflammation and immune responses, regulate the release and efficacy of monoamine neurotransmitters, alter the activity and function of the hypothalamic-pituitary-adrenal (HPA) axis, and modify the abundance of brain-derived neurotrophic factor (BDNF), eventually leading to depression. In this article, we review changes in gut microbiota in depressive states, the association between these changes and depression-like behavior, the potential mechanism linking gut microbiota disruptions and depression, and preliminary attempts at using gut microbiota intervention for the treatment of depression. In summary, although the link between gut microbiota and depression and the potential mechanism have been discussed, a more detailed mechanistic understanding is needed to fully realize the importance of the microbiota-gut-brain axis in depression. Future efforts should aim to determine the potential causative mechanisms, which will require further animal and clinical research as well as the development of analytical approaches.

Modulating the Intestinal Microbiota: Therapeutic Opportunities in Liver Disease

Gut microbiota has been demonstrated to have a significant impact on the initiation, progression and development of complications associated with multiple liver diseases. Notably, nonalcoholic fatty liver diseases, including nonalcoholic steatohepatitis and cirrhosis, severe alcoholic hepatitis, primary sclerosing cholangitis and hepatic encephalopathy, have strong links to dysbiosis - or a pathobiological change in the microbiota. In this review, we provide clear and concise discussions on the human gut microbiota, methods of identifying gut microbiota and its functionality, liver diseases that are affected by the gut microbiota, including novel associations under research, and provide current evidence on the modulation of gut microbiota and its effects on specific liver disease conditions.

Analysis of Risk Factors for Postoperative Delirium After Liver Transplantation

PURPOSE

The study aimed to analyze the incidence of postoperative delirium (POD) and associated risk factors after liver transplantation (LT).

PATIENTS AND METHODS

We identified and enrolled patients undergoing LT at the Second Xiangya Hospital, Central South University between August 2018 and May 2019. We abstracted their relevant clinical information and assigned the patients into a POD group and non-POD group to compare differences in clinical information. Risk factors of POD were analyzed using logistic regression.

RESULTS

A total of 159 LT patients were enrolled. Forty-two patients exhibited delirium (26.4%). Of the 42 with delirium, 33 (78.6%) had delirium within 3 days postoperatively and a median duration of 5 days (quartile 3-7 days). The results of binary logistic regression are as follows: preoperative ammonia (≥46 vs <46 μmol/L; OR 3.51, 95% CI [1.31-9.46], P<0.05), Model for End-Stage Liver Disease (MELD) score (≥15 vs.<15; OR 3.33, 95% CI [1.27-8.79], P<0.05), presence of hepatic encephalopathy (OR 3.30, 95% CI [1.20-9.07], P<0.05), aspartate aminotransferase (AST) on day 1 postoperatively (OR 1.33, 95% CI [1.06 -1.68], P<0.05), anhepatic period (OR 1.04, 95% CI [1.02 -1.06], P<0.01). The POD group had a longer intubation time (2925.0 vs 1410.0 min, P<0.01), ICU length of stay (6 vs 4 d, P<0.01) and increased medical costs (43.96 vs 33.74 ten thousand yuan, P<0.01).

CONCLUSION

The incidence of POD in LT patients is a significant clinical feature. Ammonia ≥46 μmol/l, MELD score ≥15, hepatic encephalopathy, anhepatic period, and AST at 1 day postoperatively were independent risk factors for POD.

Combination of rifaximin and lactulose improves clinical efficacy and mortality in patients with hepatic encephalopathy

Background

Rifaximin and lactulose are common effective agents for hepatic encephalopathy (HE). Whether a combination of rifaximin and lactulose improves the efficacy and mortality in patients with HE compared with lactulose alone needs to be analyzed.

Methods

A systematic search was performed in electronic databases and other sources for possible studies focusing on combination therapy of rifaximin and lactulose for HE between January 2000 and February 2018. A meta-analysis was performed by the method recommended by the Cochrane Collaboration, and estimated effect size was presented as risk difference (RD), 95% CI, and the number needed to treat (NNT). Subgroup analysis, sensitivity analysis, and Trial Sequence Analysis were comprehensively performed to indicate the source of heterogeneity and risk of bias.

Results

Five randomized and five observational studies involving 2,276 patients were included. Combination therapy had a significant advantage in both clinical efficacy increase (RD 0.26, 95% CI 0.19–0.32, NNT 5) and mortality decrease (RD −0.16, 95% CI −0.20–0.11, NNT 9) in overall analysis. In the pooled analysis of randomized studies, combination therapy showed similar results in clinical efficacy (RD 0.25, 95% CI 0.16–0.35, NNT 4) and mortality (RD −0.22, 95% CI −0.33–0.12, NNT 5). Compared with lactulose, hospital stay was also reduced in combination therapy, and there was no significant difference in treatment-related adverse events between the two groups.

Conclusion

Combination of rifaximin and lactulose has beneficial effects on HE. Compared with lactulose alone, additional rifaximin increases clinical efficacy and decreases mortality. However, its effects on different types of HE are still uncertain.

Clinical impact of microbiome in patients with decompensated cirrhosis

Cirrhosis is an increasing cause of morbidity and mortality. Recent studies are trying to clarify the role of microbiome in clinical exacerbation of patients with decompensated cirrhosis. Nowadays, it is accepted that patients with cirrhosis have altered salivary and enteric microbiome, characterized by the presence of dysbiosis. This altered microbiome along with small bowel bacterial overgrowth, through translocation across the gut, is associated with the development of decompensating complications. Studies have analyzed the correlation of certain bacterial families with the development of hepatic encephalopathy in cirrhotics. In general, stool and saliva dysbiosis with reduction of autochthonous bacteria in patients with cirrhosis incites changes in bacterial defenses and higher risk for bacterial infections, such as spontaneous bacterial peritonitis, and sepsis. Gut microbiome has even been associated with oncogenic pathways and under circumstances might promote the development of hepatocarcinogenesis. Lately, the existence of the oral-gut-liver axis has been related with the development of decompensating events. This link between the liver and the oral cavity could be via the gut through impaired intestinal permeability that allows direct translocation of bacteria from the oral cavity to the systemic circulation. Overall, the contribution of the microbiome to pathogenesis becomes more pronounced with progressive disease and therefore may represent an important therapeutic target in the management of cirrhosis.

Nonabsorbable disaccharides for hepatic encephalopathy: A systematic review and meta-analysis

Nonabsorbable disaccharides (NADs) have been used to treat hepatic encephalopathy (HE) since 1966. However, a Cochrane Review, published in 2004, found insufficient evidence to recommend their use in this context. This updated systematic review evaluates the effects of the NADs, lactulose and lactitol, for the treatment and prevention of HE in patients with cirrhosis. Thirty-eight randomized controlled trials, involving 1,828 patients, were identified through electronic and manual searches; 31 randomized controlled trials looked at the treatment of HE, while seven looked at its primary/secondary prevention. Random-effects meta-analyses showed that, compared to placebo/no intervention, NADs had a beneficial effect on HE (relative risk [RR] = 0.63, 95% confidence interval [CI] 0.53-0.74, number needed to treat [NNT] = 4) and serious liver-related adverse events such as liver failure, variceal bleeding, serious infections, spontaneous bacterial peritonitis, and hepatorenal syndrome (RR = 0.42, 95% CI 0.26-0.69, NNT = 50). Treatment was also associated with a reduction in mortality in patients with overt HE (RR = 0.36, 95% CI 0.14-0.94, NNT = 20), although not in patients with minimal HE. Meta-analyses of the prevention randomized controlled trials showed that NADs prevented the development of HE (RR = 0.47, 95% CI 0.33-0.68, NNT = 6), the risk of developing serious liver-related adverse events (RR = 0.48, 95% CI 0.33-0.70, NNT = 6), and reduced mortality (RR = 0.63, 95% CI 0.40-0.98, NNT = 20). Use of NADs was associated with nonserious gastrointestinal adverse events. There were no differences in the efficacy or safety of lactulose and lactitol.

CONCLUSIONS

NADs have beneficial effects in the treatment and prevention of HE; their use, in this context, confers additional benefits including a reduction in serious liver-related morbidities and all-cause mortality. (Hepatology 2016;64:908-922).