Faecalibacterium prausnitzii prevents hepatic damage in a mouse model of NASH induced by a high-fructose high-fat diet

The role of the microbiome in liver disease

PURPOSE OF REVIEW

The intestinal microbiome and the gut-liver axis play a major role in health and disease. The human gut harbors trillions of microbes and a disruption of the gut homeostasis can contribute to liver disease. In this review, the progress in the field within the last 3 years is summarized, focusing on metabolic dysfunction-associated steatotic liver disease (MASLD), alcohol-associated liver disease (ALD), autoimmune liver disease (AILD), and hepatocellular carcinoma (HCC).

RECENT FINDINGS

Changes in the fecal virome and fungal mycobiome have been described in patients with various liver diseases. Several microbial derived metabolites including endogenous ethanol produced by bacteria, have been mechanistically linked to liver disease such as MASLD. Virulence factors encoded by gut bacteria contribute to ALD, AILD and HCC. Novel therapeutic approaches focused on the microbiome including phages, pre- and postbiotics have been successfully used in preclinical models. Fecal microbiota transplantation has been effective in attenuating liver disease. Probiotics are safe in patients with alcohol-associated hepatitis and improve liver disease and alcohol addiction.

SUMMARY

The gut-liver axis plays a key role in the pathophysiology of liver diseases. Understanding the microbiota in liver disease can help to develop precise microbiota centered therapies.

Exploring the modulatory effects of brown seaweed meal and extracts on intestinal microbiota and morphology of broiler chickens challenged with heat stress

Brown seaweed (Ascophyllum nodosum) is known for its prebiotic roles and can improve animal intestinal health by enhancing the growth of beneficial microbes and inhibiting pathogenic ones. However, the gut health-modulatory roles of brown seaweed on chickens challenged with heat stress (HS) are rarely studied. The current study examined the effects of brown seaweed meal (SWM) and extract (SWE) on the ceca microbiota and small intestinal morphology of chickens challenged or unchallenged with HS. Three hundred and thirty-six 1-day-old Ross 308 broiler chicks were randomly assigned to either a thermoneutral (TN; 24 ± 1°C); or HS room (HS; 32-34°C, 8 h/d from d 21 to 27). All birds in each room were randomly allotted to 4 treatments - control (CON), CON + 1 mL/L seaweed extract (SWE) in drinking water, CON + 2 mL/L SWE in drinking water, and CON + 2% seaweed meal (SWM) in feed and raised for 28 d. On d 14 and 28, 12 and 24 birds per treatment group, respectively, were euthanized to collect the ceca content for gut microbiota analysis and small intestinal tissues for morphological examination. On d 14, 2% SWM increased (P = 0.047) the relative abundance of cecal Fecalibacterium and all brown seaweed treatments improved jejunal villus height (VH) and VH:CD compared to the CON diet. On d 28, HS significantly reduced (P < 0.05) ileal VH, VW, and VH:CD, and duodenal VH and VH:CD. Among the HS group, 2% SWM and 2 mL/L SWE significantly increased (P < 0.05) the relative abundance of Lactobacillus, Sellimonas, and Fournierella, compared to the CON diet. HS birds fed with 2% SWM had higher ileal VH and VH:CD compared to other treatments. In summary, SWM and SWE enhanced the abundance of beneficial microbes and improved small intestinal morphology among HS chickens. This implies that seaweed could potentially alleviate HS-induced intestinal impairment in chickens.

Bacteroides and NAFLD: pathophysiology and therapy

Non-alcoholic fatty liver disease (NAFLD) is a prevalent chronic liver condition observed globally, with the potential to progress to non-alcoholic steatohepatitis (NASH), cirrhosis, and even hepatocellular carcinoma. Currently, the US Food and Drug Administration (FDA) has not approved any drugs for the treatment of NAFLD. NAFLD is characterized by histopathological abnormalities in the liver, such as lipid accumulation, steatosis, hepatic balloon degeneration, and inflammation. Dysbiosis of the gut microbiota and its metabolites significantly contribute to the initiation and advancement of NAFLD. Bacteroides, a potential probiotic, has shown strong potential in preventing the onset and progression of NAFLD. However, the precise mechanism by which Bacteroides treats NAFLD remains uncertain. In this review, we explore the current understanding of the role of Bacteroides and its metabolites in the treatment of NAFLD, focusing on their ability to reduce liver inflammation, mitigate hepatic steatosis, and enhance intestinal barrier function. Additionally, we summarize how Bacteroides alleviates pathological changes by restoring the metabolism, improving insulin resistance, regulating cytokines, and promoting tight-junctions. A deeper comprehension of the mechanisms through which Bacteroides is involved in the pathogenesis of NAFLD should aid the development of innovative drugs targeting NAFLD.

MASLD: a systemic metabolic disorder with cardiovascular and malignant complications

Non-alcoholic fatty liver disease (NAFLD) has rapidly become the most common chronic liver disease globally and is currently estimated to affect up to 38% of the global adult population. NAFLD is a multisystem disease where systemic insulin resistance and related metabolic dysfunction play a pathogenic role in the development of NAFLD and its most relevant liver-related morbidities (cirrhosis, liver failure and hepatocellular carcinoma) and extrahepatic complications, such as cardiovascular disease (CVD), type 2 diabetes mellitus, chronic kidney disease, and certain types of extrahepatic cancers. In 2023, three large multinational liver associations proposed that metabolic dysfunction-associated steatotic liver disease (MASLD) should replace the term NAFLD; the name chosen to replace non-alcoholic steatohepatitis was metabolic dysfunction-associated steatohepatitis (MASH). Emerging epidemiological evidence suggests an excellent concordance rate between NAFLD and MASLD definitions-that is, ~99% of individuals with NAFLD meet MASLD criteria. In this narrative review, we provide an overview of the literature on (a) the recent epidemiological data on MASLD and the risk of developing CVD and malignant complications, (b) the underlying mechanisms by which MASLD (and factors strongly linked with MASLD) may increase the risk of these extrahepatic complications and (c) the diagnosis and assessment of CVD risk and potential treatments to reduce CVD risk in people with MASLD or MASH.

Akkermansia muciniphila and its outer membrane protein Amuc_1100 prevent high-fat diet-induced nonalcoholic fatty liver disease in mice

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. A. muciniphila and its outer membrane protein Amuc_1100 ameliorate metabolic disorders, enteritis, depression, and other diseases in mice. The NAFLD mouse model was established by feeding a high-fat diet (HFD) for 10 weeks. To assess the effect of A. muciniphila and Amuc_1100 on NAFLD, we used atorvastatin, a common lipid-lowering drug, as a positive control. A. muciniphila and Amuc_1100 significantly reduced body weight and serum ALT and AST levels, and improved serum lipid levels in NAFLD mice, which had similar effects to Ator. In addition, A. muciniphila and Amuc_1100 decreased the concentration of LPS in the serum and upregulated the mRNA expression of the colonic tight junction proteins. In the liver, A. muciniphila and Amuc_1100 significantly reduced the mRNA expression levels of nodular receptor protein 3 (NLRP3) and Toll-like receptor 4 (TLR4)/nuclear factor κB (NF-κB), and the protein and mRNA expression levels inflammatory cytokines. At the genus level, Amuc_1100 treatment significantly reduced the abundance of Coriobacteriaceae_UCG-002 produced by the HFD. The abundances of Blautia, norank_f__Ruminococcaceae, Lachnoclostridium, GCA-900066575 and Lachnospiraceae_UCG-006 increased dramatically. Together, A. muciniphila and Amuc_1100 alleviate HFD-induced NAFLD by acting on the gut-liver axis and regulating gut microbes.

Roles of gut microbes in metabolic-associated fatty liver disease

Metabolic-associated fatty liver disease (MAFLD) is the most common chronic liver disease. Gut dysbiosis is considered a significant contributing factor in disease development. Increased intestinal permeability can be induced by gut dysbiosis, followed by the entry of lipopolysaccharide into circulation to reach peripheral tissue and result in chronic inflammation. We reviewed how microbial metabolites push host physiology toward MAFLD, including short-chain fatty acids (SCFAs), bile acids, and tryptophan metabolites. The effects of SCFAs are generally reported as anti-inflammatory and can improve intestinal barrier function and restore gut microbiota. Gut microbes can influence intestinal barrier function through SCFAs produced by fermentative bacteria, especially butyrate and propionate producers. This is achieved through the activation of free fatty acid sensing receptors. Bile is directly involved in lipid absorption. Gut microbes can alter bile acid composition by bile salt hydrolase-producing bacteria and bacterial hydroxysteroid dehydrogenase-producing bacteria. These bile acids can affect host physiology by activating farnesoid X receptor Takeda G protein-coupled receptor 5. Gut microbes can also induce MAFLD-associated symptoms by producing tryptophan metabolites kynurenine, serotonin, and indole-3-propionate. A summary of bacterial genera involved in SCFAs production, bile acid transformation, and tryptophan metabolism is provided. Many bacteria have demonstrated efficacy in alleviating MAFLD in animal models and are potential therapeutic candidates for MAFLD.

Supplementation of Lactobacillus plantarum ATCC14917 mitigates non-alcoholic fatty liver disease in high-fat-diet-fed rats

Atherosclerosis and non-alcoholic fatty liver disease (NAFLD) have been increasing at an alarming rate worldwide. Many clinical studies have underlined the link between NAFLD and atherosclerosis. Our previous experiments have discovered that Lactobacillus (L.) plantarum ATCC14917 supplementation could decrease the progression of atherosclerotic lesion formation. In this study, we aimed to investigate the role of supplementation of L. plantarum ATCC14917 mitigates liver injury in rats fed with a high-fat diet (HFD, 45% kcal from fat). A total of 32 rats were randomly divided into four groups, including two intervention groups, who fed with HFD and administering either 1 × 10⁷ or 1 × 10⁹ colony forming units (CFU) of L. plantarum ATCC14917, the normal control group, and the HFD control group. The results showed that supplementation with low-dose and high-dose of L. plantarum ATCC14917 for 8 weeks could alleviate the body weight gain (p < 0.05), hepatic steatosis, and serum lipid metabolism (p < 0.05) in HFD-fed rats. Moreover, supplementation of L. plantarum ATCC 14917 decreased total cholesterol (TC), triglyceride (TG), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) levels (p < 0.05) in serum, and improved HFD-associated inflammation (p < 0.05). Furthermore, cecal contents were analyzed by high-throughput 16S ribosomal RNA sequencing. The results indicated that supplementation of L. plantarum ATCC 14917 could ameliorate HFD-induced gut dysbiosis. In summary, our findings suggest that supplementation of L. plantarum ATCC 14917 could mitigate NAFLD in rats, suggesting it may be considered as a probiotic agent for preventing HFD-induced obesity.