Early intervention with probiotics and metformin alleviates liver injury in NAFLD rats via targeting gut microbiota dysbiosis and p-AKT/mTOR/LC-3II pathways

Gut microbiota-derived UDCA enhanced by metformin inhibits FXR to activate autophagy against MCD diet-induced NAFLD in mice

Nonalcoholic fatty liver disease (NAFLD), a prevalent chronic liver disease, poses a substantial global health burden. Metformin is known for its protective effects in NAFLD, but the role of gut microbiota in the underlying mechanisms remains unclear. In this study, metformin was found to mitigate methionine-choline deficient (MCD) -diet induced NAFLD through reshaping the gut microbiota to increase ursodeoxycholic acid (UDCA) level, thereby inhibiting farnesoid X receptor (FXR) accompanied with activated autophagy. Specifically, using dirty cage experiments and 16S rRNA sequencing, it identified that metformin could reshape microbiota to release liver injury as confirmed by the results of histopathology and biochemical index detection. Furthermore, the bile acids were found to be altered by metformin, in which, the UDCA, a FXR natural inhibitor, was observed a significantly increase. Meanwhile, the inhibited FXR and activated autophagy in metformin-treated mice were captured using western blot, qRT-PCR and immunofluorescence analysis. In addition, the benefit of UDCA against NAFLD was demonstrated in UDCA treated mice. Further investigation with FXR siRNA introduced to HepG2 cells revealed that inhibiting FXR can reduce oleic acids induced cell injury with the autophagy activation. In conclusion, this study highlights metformin's potential to ameliorate NAFLD by reshaping gut microbiota, thereby upregulating UDCA in the liver and restoring cholesterol synthesis capacity, possibly via inhibiting FXR to activate autophagy.

Lactobacillus rhamnosus GG Combined with Metformin Alleviates Alcohol-Induced Liver Inflammation in Mice by Maintaining the Intestinal Barrier and Regulating Treg/Th1 Cells

Disturbances of the intestinal barrier enabling bacterial translocation exacerbate alcoholic liver disease (ALD). Lactobacillus rhamnosus GG (LGG) has been shown to exert beneficial effects in gut dysbiosis and chronic liver disease. The current study assessed the combined effects of LGG and metformin, which play roles in anti-inflammatory and immunoregulatory processes, in alcohol-induced liver disease mice. A diet comprising 5% alcohol for 4 weeks was employed to develop an alcohol-induced liver injury model. Mice were orally administered LGG, metformin, or their combination on alternate days. Tight junction (TJ) proteins, gut microbiome composition, inflammatory cytokines, Jun N-terminal kinase (JNK), and p38 signals were assessed. When compared with treatment with LGG or metformin alone, combined LGG and metformin treatment substantially lowered the symptoms of inflammation, steatosis, and elevated liver enzymes caused by alcohol administration. Combination treatment significantly improved intestinal microecology, evidenced by the recovery of intestinal flora, TJ proteins, and intestinal villi. Combination treatment reduced hepatic inflammation by blocking p38 and JNK phosphorylation. The combination of LGG and metformin corrected immune-response dysregulation and improved ALD by enhancing the intestinal microbiome, restoring mucosal barrier integrity, modulating immune function, and decreasing liver injury. These results provide information for the development of intestinal microbiota-based preventive and therapeutic agents against ALD.

Dietary Influences on Gut Microbiota and Their Role in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a major contributor to liver-related morbidity, cardiovascular disease, and metabolic complications. Lifestyle interventions, including diet and exercise, are first line in treating MASLD. Dietary approaches such as the low-glycemic-index Mediterranean diet, the ketogenic diet, intermittent fasting, and high fiber diets have demonstrated potential in addressing the metabolic dysfunction underlying this condition. The development and progression of MASLD are closely associated with taxonomic shifts in gut microbial communities, a relationship well-documented in the literature. Given the importance of diet as a primary treatment for MASLD, it is important to understand how gut microbiota and their metabolic byproducts mediate favorable outcomes induced by healthy dietary patterns. Conversely, microbiota changes conferred by unhealthy dietary patterns such as the Western diet may induce dysbiosis and influence steatotic liver disease through promoting hepatic inflammation, up-regulating lipogenesis, dysregulating bile acid metabolism, increasing insulin resistance, and causing oxidative damage in hepatocytes. Although emerging evidence has identified links between diet, microbiota, and development of MASLD, significant gaps remain in understanding specific microbial roles, metabolite pathways, host interactions, and causal relationships. Therefore, this review aims to provide mechanistic insights into the role of microbiota-mediated processes through the analysis of both healthy and unhealthy dietary patterns and their contribution to MASLD pathophysiology. By better elucidating the interplay between dietary nutrients, microbiota-mediated processes, and the onset and progression of steatotic liver disease, this work aims to identify new opportunities for targeted dietary interventions to treat MASLD efficiently.

Breaking the barriers: the role of gut homeostasis in Metabolic-Associated Steatotic Liver Disease (MASLD)

Obesity, insulin resistance (IR), and the gut microbiome intricately interplay in Metabolic-associated Steatotic Liver Disease (MASLD), previously known as Non-Alcoholic Fatty Liver Disease (NAFLD), a growing health concern. The complex progression of MASLD extends beyond the liver, driven by "gut-liver axis," where diet, genetics, and gut-liver interactions influence disease development. The pathophysiology of MASLD involves excessive liver fat accumulation, hepatocyte dysfunction, inflammation, and fibrosis, with subsequent risk of hepatocellular carcinoma (HCC). The gut, a tripartite barrier, with mechanical, immune, and microbial components, engages in a constant communication with the liver. Recent evidence links dysbiosis and disrupted barriers to systemic inflammation and disease progression. Toll-like receptors (TLRs) mediate immunological crosstalk between the gut and liver, recognizing microbial structures and triggering immune responses. The "multiple hit model" of MASLD development involves factors like fat accumulation, insulin resistance, gut dysbiosis, and genetics/environmental elements disrupting the gut-liver axis, leading to impaired intestinal barrier function and increased gut permeability. Clinical management strategies encompass dietary interventions, physical exercise, pharmacotherapy targeting bile acid (BA) metabolism, and microbiome modulation approaches through prebiotics, probiotics, symbiotics, and fecal microbiota transplantation (FMT). This review underscores the complex interactions between diet, metabolism, microbiome, and their impact on MASLD pathophysiology and therapeutic prospects.

Limosilactobacillus reuteri DSM 17938 reverses gut metabolic dysfunction induced by Western diet in adult rats

Introduction

Microencapsulation of probiotic bacteria is an efficient and innovative new technique aimed at preserving bacterial survival in the hostile conditions of the gastrointestinal tract. However, understanding whether a microcapsule preserves the effectiveness of the bacterium contained within it is of fundamental importance.

Methods

Male Wistar rats aged 90 days were fed a control diet or a Western diet for 8 weeks, with rats fed the Western diet divided into three groups: one receiving the diet only (W), the second group receiving the Western diet and free L. reuteri DSM 17938 (WR), and the third group receiving the Western diet and microencapsulated L. reuteri DSM 17938 (WRM). After 8 weeks of treatment, gut microbiota composition was evaluated, together with occludin, one of the tight junction proteins, in the ileum and the colon. Markers of inflammation were also quantified in the portal plasma, ileum, and colon, as well as markers for gut redox homeostasis.

Results

The Western diet negatively influenced the intestinal microbiota, with no significant effect caused by supplementation with free and microencapsulated L. reuteri. However, L. reuteri, in both forms, effectively preserved the integrity of the intestinal barrier, thus protecting enterocytes from the development of inflammation and oxidative stress.

Conclusion

From these whole data, it emerges that L. reuteri DSM 17938 can be an effective probiotic in preventing the unhealthy consequences of the Western diet, especially in the gut, and that microencapsulation preserves the probiotic effects, thus opening the formulation of new preparations to be able to improve gut function independent of dietary habits.

Prebiotics and Probiotics: Therapeutic Tools for Nonalcoholic Fatty Liver Disease

Alterations in the gut-liver axis and changes in the gut microbiome are among the risk factors for the pathogenesis of non-alcoholic fatty liver disease (NAFLD). These patients show increased bacterial overgrowth in the small intestine and impaired intestinal permeability. Therefore, therapeutic options such as probiotics or prebiotics have been investigated to modulate intestinal microbiota composition to improve NAFLD. Most in vivo and in vitro probiotic studies have focused on reducing hepatic fat accumulation. The beneficial effects of probiotics on NAFLD have been demonstrated in animal models, and the most widely used microorganisms are those of the Lactobacillus and Bifidobacterium genera. In animal models, probiotics help restore the intestinal microbiota and improve the integrity of the intestinal barrier. This narrative review summarizes published evidence and the likely benefits of probiotics and prebiotics as a therapeutic option for patients with NAFLD.

Si-Ni-San Reduces Hepatic Lipid Deposition in Rats with Metabolic Associated Fatty Liver Disease by AMPK/SIRT1 Pathway

Background

Metabolic associated fatty liver disease (MAFLD) is a chronic disease characterized by excessive lipid deposition in the liver without alcohol or other clear liver-damaging factors. AMP-activated protein kinase (AMPK)/silencing information regulator (SIRT)1 signaling pathway plays an important role in MAFLD development. Si-Ni-San (SNS), a traditional Chinese medicine, has shown reducing hepatic lipid deposition in MAFLD rats, however, the underlying mechanisms of SNS are barely understood.

Purpose

The aim of this research was to investigate the mechanisms of SNS in reducing hepatic lipid deposition in MAFLD rats by regulating AMPK/SIRT1 signaling pathways.

Methods

The components of SNS were determined by high performance liquid chromatography with mass spectrometry (HPLC-MS) analysis. MAFLD rats were induced by high-fat and high-cholesterol diet (HFHCD), and treated by SNS. SNS-containing serum and Compound C (AMPK inhibitor) were used to treat palmitic acid (PA)-induced HepG2 cells. To elucidate the potential mechanism, lipid synthesis-related proteins (SREBP-1c and FAS), fatty acid oxidation (PPARα and CPT-1), and AMPK/SIRT1 signaling pathway (p-AMPK and SIRT1) were assessed by Western blot.

Results

SNS improved serum lipid levels, liver function and reduced hepatic lipid deposition in MAFLD rats. SNS-containing serum reduced lipid deposition in PA-induced HepG2 cells. SNS could up-regulate protein expressions of PPARα, CPT-1, p-AMPK and SIRT1, and down-regulate protein expressions of SREBP-1c and FAS. Similar effects of SNS-containing serum were observed in PA-induced HepG2 cells. Meanwhile, Compound C weakened the therapeutic effects of SNS-containing serum on lipid deposition.

Conclusion

SNS could reduce hepatic lipid deposition by inhibiting lipid synthesis and promoting fatty acid oxidation, which might be related with activating the AMPK/SIRT1 signaling pathway. This study could provide a theoretical basis for the clinical use of SNS to treat MAFLD.

Gallic acid and metformin co-administration reduce oxidative stress, apoptosis and inflammation via Fas/caspase-3 and NF-κB signaling pathways in thioacetamide-induced acute hepatic encephalopathy in rats

BACKGROUND

Hepatic encephalopathy (HE) is a consequence of chronic or acute liver diseases. This study evaluates the combined effect of gallic acid (GA), and metformin (Met) on the liver and brain damage associated with HE.

METHODS

Acute HE was induced by a single dose of thioacetamide (TAA) (300 mg/kg) as an I.P. injection. Treated groups received GA group (100 mg/kg/day, p.o), Met (200 mg/kg/day, p.o), or their combination for 25 consecutive days before TAA injection.

RESULTS

The administration of TAA induced various biochemical and histopathological alterations. In contrast, treatment with GA either alone or combined with Met resulted in improved liver functions by the significant reduction in serum ALT, AST, and ALP activities, and ammonia levels. Inflammatory mediators; TNF-α, IL-6, and NFkβ levels were decreased by these treatments as well as apoptotic cascade via down-regulation of FAS and caspase-3 (CASP-3) expression in hepatic tissues. Furthermore, GA and Met either alone or combined protected the liver and brain tissues from damage by increased glutathione concentration while decreasing malondialdehyde. In addition, it was accompanied by the improvement of the brain neurotransmitter profile via the restoration of norepinephrine, dopamine, and serotonin levels. Based on our data, this is the first study to report a novel combined hepatoprotective and cognitive enhancing effect of GA and Met against TAA-induced acute liver and brain injury.

CONCLUSION

GA and Met combination resulted in a prominent improvement in HE complications, relative to monotherapy. Both agents potentiated the antioxidant, anti-inflammatory, and anti-apoptotic effects of each other.

mTOR Signaling Pathway and Gut Microbiota in Various Disorders: Mechanisms and Potential Drugs in Pharmacotherapy

The mammalian or mechanistic target of rapamycin (mTOR) integrates multiple intracellular and extracellular upstream signals involved in the regulation of anabolic and catabolic processes in cells and plays a key regulatory role in cell growth and metabolism. The activation of the mTOR signaling pathway has been reported to be associated with a wide range of human diseases. A growing number of in vivo and in vitro studies have demonstrated that gut microbes and their complex metabolites can regulate host metabolic and immune responses through the mTOR pathway and result in disorders of host physiological functions. In this review, we summarize the regulatory mechanisms of gut microbes and mTOR in different diseases and discuss the crosstalk between gut microbes and their metabolites and mTOR in disorders in the gastrointestinal tract, liver, heart, and other organs. We also discuss the promising application of multiple potential drugs that can adjust the gut microbiota and mTOR signaling pathways. Despite the limited findings between gut microbes and mTOR, elucidating their relationship may provide new clues for the prevention and treatment of various diseases.

Harnessing the potential of probiotics in the treatment of alcoholic liver disorders

In the current scenario, prolonged consumption of alcohol across the globe is upsurging an appreciable number of patients with the risk of alcohol-associated liver diseases. According to the recent report, the gut-liver axis is crucial in the progression of alcohol-induced liver diseases, including steatosis, steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Despite several factors associated with alcoholic liver diseases, the complexity of the gut microflora and its great interaction with the liver have become a fascinating area for researchers due to the high exposure of the liver to free radicals, bacterial endotoxins, lipopolysaccharides, inflammatory markers, etc. Undoubtedly, alcohol-induced gut microbiota imbalance stimulates dysbiosis, disrupts the intestinal barrier function, and trigger immune as well as inflammatory responses which further aggravate hepatic injury. Since currently available drugs to mitigate liver disorders have significant side effects, hence, probiotics have been widely researched to alleviate alcohol-associated liver diseases and to improve liver health. A broad range of probiotic bacteria like Lactobacillus, Bifidobacteria, Escherichia coli, Sacchromyces, and Lactococcus are used to reduce or halt the progression of alcohol-associated liver diseases. Several underlying mechanisms, including alteration of the gut microbiome, modulation of intestinal barrier function and immune response, reduction in the level of endotoxins, and bacterial translocation, have been implicated through which probiotics can effectively suppress the occurrence of alcohol-induced liver disorders. This review addresses the therapeutic applications of probiotics in the treatment of alcohol-associated liver diseases. Novel insights into the mechanisms by which probiotics prevent alcohol-associated liver diseases have also been elaborated.

The combination of metformin with morin alleviates hepatic steatosis via modulating hepatic lipid metabolism, hepatic inflammation, brown adipose tissue thermogenesis, and white adipose tissue browning in high-fat diet-fed mice

AIM

The valuable effects of metformin (MET) and morin (MOR) in the improvement of NAFLD have been proposed, nevertheless, their combination impacts were not investigated so far. We determined the therapeutic effects of combined MET and MOR treatment in high-fat diet (HFD)-induced Non-alcoholic fatty liver disease (NAFLD) mice.

METHODS

C57BL/6 mice were fed on an HFD for 15 weeks. Animals were allotted into various groups and supplemented with MET (230 mg/kg), MOR (100 mg/kg), and MET + MOR (230 mg/kg + 100 mg/kg).

KEY FINDINGS

MET in combination with MOR reduced body and liver weight in HFD-fed mice. A significant decrease in fasting blood glucose and improvement in glucose tolerance was observed in HFD mice treated with MET + MOR. Supplementation with MET + MOR led to a decline in hepatic triglyceride levels and this impact was associated with diminished expression of fatty-acid synthase (FAS) and elevated expression of carnitine palmitoyl transferase 1 (CPT1) and phospho-Acetyl-CoA Carboxylase (p-ACC). Moreover, MET combined with MOR alleviates hepatic inflammation through the polarization of macrophages to the M2 phenotype, decreasing the infiltration of macrophages and lowering the protein level of NF-kB. MET and MOR in combination reduce the size and weight of epididymal white adipose tissue (eWAT), and subcutaneous WAT (sWAT), whereas improves cold tolerance, BAT activity, and mitochondrial biogenesis. Combination therapy results in stimulating brown-like adipocyte (beige) formation in the sWAT of HFD mice.

SIGNIFICANCE

These results suggest that the combination of MET and MOR has a protective effect on hepatic steatosis, which may use as a candidate therapeutic for the improvement of NAFLD.

Therapeutic efficacy of liraglutide versus metformin in modulating the gut microbiota for treating type 2 diabetes mellitus complicated with nonalcoholic fatty liver disease

Metformin and liraglutide are used in the treatment of type 2 diabetes mellitus (T2DM) complicated with nonalcoholic fatty liver disease (NAFLD). Although these drugs can alter the intestinal microbiome, clinical data are required to explore their mechanisms of action. Using 16S sequencing technology, we analyzed and compared the intestinal bacterial community structure and function between patients before and after treatment (12 weeks) with the two drugs (metformin or liraglutide, n = 15) and healthy controls (n = 15). Moreover, combined with 19 clinical indices, the potential therapeutic mechanisms of the two drugs were compared. The studied clinical indices included those associated with islet β-cell function (FPG, FINS, HbA1c, and HOMA-IR), inflammation (TNF-α, IL-6, and APN), lipid metabolism (TC, TG, and LDL-C), and liver function (ALT, AST, and GGT); the values of all indices changed significantly after treatment (p < 0.01). In addition, the effect of the two drugs on the intestinal bacterial community varied. Liraglutide treatment significantly increased the diversity and richness of the intestinal bacterial community (p < 0.05); it significantly increased the relative abundances of Bacteroidetes, Proteobacteria, and Bacilli, whereas metformin treatment significantly increased the relative abundance of Fusobacteria and Actinobacteria (p < 0.05). Metformin treatment increased the complexity and stability of the intestinal bacterial network. However, liraglutide treatment had a weaker effect on the intestinal bacterial network, and the network after treatment was similar to that in healthy controls. Correlation matrix analysis between dominant genera and clinical indicators showed that the correlation between the bacterial community and islet β-cell function was stronger after liraglutide treatment, whereas the correlation between the bacterial community and inflammation-related factors was stronger after metformin treatment. Functional prediction showed that liraglutide could significantly affect the abundance of functional genes related to T2DM and NAFLD (p < 0.05), but the effect of metformin was not significant. This study is the first to report the changes in the intestinal bacterial community in patients treated with metformin or liraglutide and the differences between the mechanisms of action of metformin and liraglutide. Metformin or liraglutide has a therapeutic value in T2DM complicated with NAFLD, with liraglutide having a weaker effect on the intestinal bacterial community but a better therapeutic efficacy.

Gut Microbiota Modulation for Therapeutic Management of Various Diseases: A New Perspective Using Stem Cell Therapy

Dysbiosis has been linked to various diseases ranging from cardiovascular, neurologic, gastrointestinal, respiratory, and metabolic illnesses to cancer. Restoring of gut microbiota balance represents an outstanding clinical target for the management of various multidrug-resistant diseases. Preservation of gut microbial diversity and composition could also improve stem cell therapy which now has diverse clinical applications in the field of regenerative medicine. Gut microbiota modulation and stem cell therapy may be considered a highly promising field that could add up towards the improvement of different diseases, increasing the outcome and efficacy of each other through mutual interplay or interaction between both therapies. Importantly, more investigations are required to reveal the cross-talk between microbiota modulation and stem cell therapy to pave the way for the development of new therapies with enhanced therapeutic outcomes. This review provides an overview of dysbiosis in various diseases and their management. It also discusses microbiota modulation via antibiotics, probiotics, prebiotics, and fecal microbiota transplant to introduce the concept of dysbiosis correction for the management of various diseases. Furthermore, we demonstrate the beneficial interactions between microbiota modulation and stem cell therapy as a way for the development of new therapies in addition to limitations and future challenges regarding the applications of these therapies.

The essential effect of mTORC1-dependent lipophagy in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a chronic progressive liver disease with increasing prevalence. Lipophagy is a type of programmed cell death that plays an essential role in maintaining the body's balance of fatty acid metabolism. However, the livers of NAFLD patients are abnormally dysregulated in lipophagy. mTORC1 is a critical negative regulator of lipophagy, which has been confirmed to participate in the process of lipophagy through various complex mechanisms. Therefore, targeting mTORC1 to restore failed autophagy may be an effective therapeutic strategy for NAFLD. This article reviews the main pathways through which mTORC1 participates in the formation of lipophagy and the intervention effect of mTORC1-regulated lipophagy in NAFLD, providing new therapeutic strategies for the prevention and treatment of NAFLD in the future.

Advances in metformin for the treatment of non-alcoholic fatty liver disease in children

INTRODUCTION

The increased economic and social burdens for NAFLD worldwide make treating such a disease a significant public health issue. Metformin, a kind of insulin sensitizer generally used to treat type 2 diabetes, has been recently found to have efficacy on children's NAFLD in various areas such as glucolipid metabolism, intestinal bacterial metabolism, oxidative stress, and anti-inflammatory response. This article aims to provide an overview of the possible mechanisms of NAFLD in children and the potential therapeutic application of metformin.

AREAS COVERED

The Cochrane Library, PubMed, Scopus, and EMBASE database was systematically searched on 12 April 2022, using the keywords metformin; non-alcoholic fatty liver disease; and children to identify similar studies. An additional search for recently published research was performed in June 2020.

EXPERT OPINION

Although metformin has been proved to have an excellent therapeutic effect on children's NAFLD; we can still explore its potential impacts and mechanisms from different angles, such as combined medication. At the same time, we should also pay attention to its side effects.

Sclerocarya birrea (Marula) Extract Inhibits Hepatic Steatosis in db/db Mice

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of hepatic metabolic perturbations ranging from simple steatosis to steatohepatitis, cirrhosis and hepatocellular carcinoma. Currently, lifestyle modifications to reduce weight gain are considered the most effective means of preventing and treating the disease. The aim of the present study was to determine the therapeutic benefit of Sclerocarya birrea (Marula leaf extract, MLE) on hepatic steatosis. Obese db/db mice were randomly stratified into the obese control, metformin (MET) or MLE-treated groups. Mice were treated daily for 29 days, at which point all mice were euthanized and liver samples were collected. Hematoxylin and eosin staining was used for histological assessment of the liver sections, while qRT-PCR and Western blot were used to determine hepatic mRNA and protein expression, respectively. Thereafter, the association between methylenetetrahydrofolate reductase (Mthfr a key enzyme in one-carbon metabolism and DNA-methylation-induced regulation of gene transcription) and lipogenic genes was evaluated using Pearson's correlation coefficient. Mice treated with MLE presented with significantly lower body and liver weights as compared with the obese control and MET-treated mice (p ≤ 0.05). Further, MLE treatment significantly inhibited hepatic steatosis as compared with the obese control and MET-treated mice (p ≤ 0.05). The reduced lipid accumulation was associated with low expression of fatty acid synthase (Cpt1; p ≤ 0.05) and an upregulation of the fatty acid oxidation gene, carnitine palmitoyltransferase (Cpt1; p ≤ 0.01), as compared with the obese control mice. Interestingly, MLE treatment improved the correlation between Mthfr and Cpt1 mRNA expression (r = 0.72, p ≤ 0.01). Taken together, the results suggest that Marula leaf extracts may inhibit hepatic steatosis by influencing the association between Mthfr and genes involved in hepatic lipid metabolism. Further studies are warranted to assess DNA methylation changes in lipid metabolism genes.

Reciprocal interactions between gut microbiota and autophagy

A symbiotic relationship has set up between the gut microbiota and its host in the course of evolution, forming an interkingdom consortium. The gut offers a favorable ecological niche for microbial communities, with the whole body and external factors (e.g., diet or medications) contributing to modulating this microenvironment. Reciprocally, the gut microbiota is important for maintaining health by acting not only on the gut mucosa but also on other organs. However, failure in one or another of these two partners can lead to the breakdown in their symbiotic equilibrium and contribute to disease onset and/or progression. Several microbial and host processes are devoted to facing up the stress that could alter the symbiosis, ensuring the resilience of the ecosystem. Among these processes, autophagy is a host catabolic process integrating a wide range of stress in order to maintain cell survival and homeostasis. This cytoprotective mechanism, which is ubiquitous and operates at basal level in all tissues, can be rapidly down- or up-regulated at the transcriptional, post-transcriptional, or post-translational levels, to respond to various stress conditions. Because of its sensitivity to all, metabolic-, immune-, and microbial-derived stimuli, autophagy is at the crossroad of the dialogue between changes occurring in the gut microbiota and the host responses. In this review, we first delineate the modulation of host autophagy by the gut microbiota locally in the gut and in peripheral organs. Then, we describe the autophagy-related mechanisms affecting the gut microbiota. We conclude this review with the current challenges and an outlook toward the future interventions aiming at modulating host autophagy by targeting the gut microbiota.

Bacillus amyloliquefaciens SC06 Induced AKT-FOXO Signaling Pathway-Mediated Autophagy to Alleviate Oxidative Stress in IPEC-J2 Cells

Autophagy is a conserved proteolytic mechanism, which degrades and recycles damaged organs and proteins in cells to resist external stress. Probiotics could induce autophagy; however, its underlying molecular mechanisms remain elusive. Our previous study has found that BaSC06 could alleviate oxidative stress by inducing autophagy in rats. This research aimed to verify whether Bacillus amyloliquefaciens SC06 can induce autophagy to alleviate oxidative stress in IPEC-J2 cells, as well as explore its mechanisms. IPEC-J2 cells were first pretreated with 10⁸ CFU/mL BaSC06, and then were induced to oxidative stress by the optimal dose of diquat. The results showed that BaSC06 significantly triggered autophagy, indicated by the up-regulation of LC3 and Beclin1 along with downregulation of p62 in IPEC-J2 cells. Further analysis revealed that BaSC06 inhibited the AKT-FOXO signaling pathway by inhibiting the expression of p-AKT and p-FOXO and inducing the expression of SIRT1, resulting in increasing the transcriptional activity of FOXO3 and gene expression of the ATG5-ATG12 complex to induce autophagy, which alleviated oxidative stress and apoptosis. Taken together, BaSC06 can induce AKT-FOXO-mediated autophagy to alleviate oxidative stress-induced apoptosis and cell damage, thus providing novel theoretical support for probiotics in the prevention and treatment of oxidative damage.