Farnesoid X receptor mediates macrophage-intrinsic responses to suppress colitis-induced colon cancer progression

Farnesoid X receptor‑driven metabolic plasticity: Bridging physiological adaptation and malignant transformation in lipid handling (Review)

Metabolic reprogramming represents a hallmark of malignant tumors, manifested through progressive alterations in nutrient utilization patterns during oncogenesis. As fundamental constituents of biological membranes, essential components of signaling pathways, and critical energy substrates, lipids undergo comprehensive metabolic restructuring in neoplastic cells. This lipid remodeling confers enhanced adaptability to sustain uncontrolled proliferation while promoting aggressive migratory phenotypes. Farnesoid X receptor (FXR), a ligand‑activated nuclear receptor responsive to bile acid (BA) derivatives and cholesterol metabolites, orchestrates key aspects of lipid homeostasis. Its regulatory network encompasses cholesterol/BA metabolism, fatty acid (FA) metabolism and plasma lipoprotein trafficking pathways. Emerging evidence positions FXR as a pleiotropic modulator in oncogenesis, with dysregulated expression patterns documented across multiple tumor lineages and premalignant lesions. This mechanistic understanding has propelled FXR‑targeted therapeutics into the forefront of precision oncology development. The present review critically examines the FXR‑lipid axis in lipid‑enriched malignancies, with particular emphasis on its regulatory circuitry governing BA flux and FA turnover.

Human umbilical cord mesenchymal stem cell-derived exosomes repair IBD by activating the SIRT1-FXR pathway in macrophages

BACKGROUND

Inflammatory bowel disease (IBD), a chronic immune disorder, has increasing global incidence and poor treatment outcome. Abnormal macrophage function is implicated in the pathophysiology of IBD. In this study, we investigated the mechanism by which human umbilical cord mesenchymal stem cell-derived exosomes (hucMSC-Ex) inhibit inflammation in IBD mouse and macrophage inflammation models.

METHODS

We established a dextran sodium sulfate (DSS)-induce BALB/c mice model of IBD and treated with hucMSC-Ex via tail vein to evaluate their repair effect on IBD mice. An in vitro macrophage inflammation model was established using lipopolysaccharide (LPS) and Nigericin (Nig) by stimulating mouse macrophage RAW264.7 and human myeloid leukemia mononuclear (THP-1) cells to assess the repair effect of hucMSC-Ex on macrophage inflammation. EX 527, an effective inhibitor of silent information regulator of transcription 1 (SIRT1), was employed in both the in vivo and in vitro models to explore the effect of hucMSC-Ex on the SIRT1-FXR (farnesoid X receptor) pathway in macrophages during the attenuation of inflammation.

RESULTS

HucMSC-Ex effectively inhibited inflammation in both the in vivo and in vitro models by up-regulating the expressions of SIRT1 and FXR, which reduced the acetylation level of FXR and inhibited the activation of NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome. The addition of EX 527 further proved that hucMSC-Ex can reduce the acetylation of FXR by activating the SIRT1-FXR pathway, and the decrease of FXR acetylation was directly related to the inhibition of the activity of the NLRP3 inflammasome.

CONCLUSION

HucMSC-Ex alleviates IBD by reducing the acetylation level of FXR through activating the SIRT1-FXR pathway in macrophages and directly negatively regulating the activation of NLRP3 inflammasomes, thus inhibiting the occurrence of the inflammatory process.

Crosstalk Between Bile Acids and Intestinal Epithelium: Multidimensional Roles of Farnesoid X Receptor and Takeda G Protein Receptor 5

Bile acids and their corresponding intestinal epithelial receptors, the farnesoid X receptor (FXR), the G protein-coupled bile acid receptor (TGR5), play crucial roles in the physiological and pathological processes of intestinal epithelial cells. These acids and receptors are involved in the regulation of intestinal absorption, signal transduction, cellular proliferation and repair, cellular senescence, energy metabolism, and the modulation of gut microbiota. A comprehensive literature search was conducted using PubMed, employing keywords such as bile acid, bile acid receptor, FXR (nr1h4), TGR5 (gpbar1), intestinal epithelial cells, proliferation, differentiation, senescence, energy metabolism, gut microbiota, inflammatory bowel disease (IBD), colorectal cancer (CRC), and irritable bowel syndrome (IBS), with a focus on publications available in English. This review examines the diverse effects of bile acid signaling and bile receptor pathways on the proliferation, differentiation, senescence, and energy metabolism of intestinal epithelial cells. Additionally, it explores the interactions between bile acids, their receptors, and the microbiota, as well as the implications of these interactions for host health, particularly in relation to prevalent intestinal diseases. Finally, the review highlights the importance of developing highly specific ligands for FXR and TGR5 receptors in the context of metabolic and intestinal disorders.

Role of Protein Regulators of Cholesterol Homeostasis in Immune Modulation and Cancer Pathophysiology

Cholesterol metabolism and homeostasis have emerged as important factors governing various aspects of cancer biology. Clinical associations between circulating cholesterol and poor prognosis or use of cholesterol-lowering medication and improved prognosis have been noted for several different solid tumors. Mechanistically, cholesterol has many different direct and indirect effects on cancer cells themselves but is also critically involved in shaping the function of other cells of the tumor microenvironment, especially immune cells. There are 2 major feedback loops regulating cholesterol homeostasis. Here we highlight the major proteins involved in the so-called oxysterol-bile acid feedback loop and discuss how each has been implicated in cancer biology. We focus on roles within the immune system with implications for cancer. Given that many of these proteins are enzymes or nuclear receptors, both of which are amenable to small molecule intervention, we posit that this axis may represent a promising area for therapeutic intervention.

Long-term effects of Nε-carboxymethyllysine intake on intestinal barrier permeability: Associations with gut microbiota and bile acids

Advanced glycation end products (AGEs) in processed foods are closely linked to intestinal injury. However, the long-term effects of exposure to free Nɛ-carboxymethyl lysine (CML), a prevalent AGE molecule, on intestinal barrier integrity have been rarely evaluated. This study investigated the temporal effects of CML exposure on intestinal barrier permeability in C57BL/6N mice at diet-related doses over 12, 14, and 16 weeks. No significant changes were observed at 12 weeks, but CML exposure significantly increased intestinal permeability at 14 and 16 weeks, accompanied by elevated serum LPS levels, colonic histological damage, and reduced tight junction protein expression at 16 weeks. CML exposure also altered gut microbiota composition and intestinal bile acid (BA) profiles, specifically reducing TDCA, GDCA, and GCDCA levels. Given the important role of colonic BA receptor signaling in maintaining the intestinal barrier integrity, the impact of CML on BA receptor signaling was assessed. CML exposure significantly downregulated BA receptor TGR5-YAP signaling in mice, while no significant effects were observed in vitro, suggesting that the changes observed in TGR5-YAP signaling in vivo may not result from the direct effects of CML. Spearman's correlation analysis revealed strong associations between altered gut microbiota, BA levels, TGR5-YAP signaling, and intestinal barrier injury. This study highlighted the chronic health risks of long-term CML intake and provided new insights into the links between CML-induced intestinal toxicity, gut microbiota, BA profiles, and BA receptor signaling.

Bile Acids in Inflammatory Bowel Disease: From Pathophysiology to Treatment

Inflammatory bowel disease (IBD) is a chronic condition that affects about 7 million people worldwide, and new therapies are needed. Understanding the complex roles that bile acids (BAs) play in IBD may lead to the development of novel IBD treatments independent of direct immunosuppression. This review discusses the latest discoveries in the roles BAs play in IBD pathogenesis and explores how these discoveries offer promising new therapeutic targets to treat IBD and improve patient outcomes. Several therapies discussed include specific BA receptor (BAR) agonists, dietary therapies, supplements, probiotics, and mesenchymal stem cell therapies that have all been shown to decrease IBD disease activity.

Regulation of gut microbiota on immune cell ferroptosis: A novel insight for immunotherapy against tumor

Gut microbiota contributes to the homeostasis of immune system and is related to various diseases such as tumorigenesis. Ferroptosis, a new type of cell death, is also involved in the disease pathogenesis. Recent studies have found the correlations of gut microbiota mediated ferroptosis and immune cell death. Gut microbiota derived immunosuppressive metabolites, which can promote differentiation and function of immune cells, tend to inhibit ferroptosis through their receptors, whereas inflammatory metabolites from gut microbiota also affect the differentiation and function of immune cells and their ferroptosis. Thus, it is possible for gut microbiota to regulate immune cell ferroptosis. Indeed, gut microbiota metabolite receptor aryl hydrocarbon receptor (AhR) can affect ferroptosis of intestinal intraepithelial lymphocytes, leading to disease pathogenesis. Since immune cell ferroptosis in tumor microenvironment (TME) affects the occurrence and development of tumor, the modulation of gut microbiota in these cell ferroptosis might influence on the tumorigenesis, and also immunotherapy against tumors. Here we will summarize the recent advance of ferroptosis mediated by gut microbiota metabolites, which potentially acts as regulator(s) on immune cells in TME for therapy against tumor.

The role of the gut microbiota in tumor, immunity, and immunotherapy

In recent years, with the deepening understanding of the gut microbiota, it has been recognized to play a significant role in the development and progression of diseases. Particularly in gastrointestinal tumors, the gut microbiota influences tumor growth by dysbiosis, release of bacterial toxins, and modulation of host signaling pathways and immune status. Immune checkpoint inhibitors (ICIs) have greatly improved cancer treatment efficacy by enhancing immune cell responses. Current clinical and preclinical studies have demonstrated that the gut microbiota and its metabolites can enhance the effectiveness of immunotherapy. Furthermore, certain gut microbiota can serve as biomarkers for predicting immunotherapy responses. Interventions targeting the gut microbiota for the treatment of gastrointestinal diseases, especially colorectal cancer (CRC), include fecal microbiota transplantation, probiotics, prebiotics, engineered bacteria, and dietary interventions. These approaches not only improve the efficacy of ICIs but also hold promise for enhancing immunotherapy outcomes. In this review, we primarily discuss the role of the gut microbiota and its metabolites in tumors, host immunity, and immunotherapy.