Muricholic Acids Promote Resistance to Hypercholesterolemia in Cholesterol-Fed Mice

Hepatic HKDC1 deletion alleviates western diet-induced MASH in mice

The global prevalence of Metabolic Dysfunction-Associated Steatohepatitis (MASH) has been rising sharply, closely mirroring the increasing rates of obesity and metabolic syndrome. MASH exhibits a strong sexual dimorphism where females are affected with more severe forms after menopause. Hexokinase domain-containing protein 1 (HKDC1) has recently been recognized for its role in liver diseases, where its expression is minimal under normal conditions but significantly increases in response to metabolic stressors like obesity and liver injury. This selective upregulation suggests HKDC1's potential specialization in hepatic glucose and lipid dysregulation, linking it closely to the progression of MASH. This study aims to clarify the role of HKDC1 in Western diet-induced MASH in female mice by examining its impact on hepatic glucose and lipid metabolism, offering insights into its potential as a therapeutic target and addressing the need for sex-specific research in liver disease. This study reveals that HKDC1 expression is elevated in obese women with MASH and correlates with liver pathology. In a mouse model, liver-specific HKDC1 knockout (HKDC1LKO) protected against Western diet-induced obesity, glucose intolerance, and MASH features, including steatosis, inflammation, and fibrosis. Transcriptomic analysis showed that HKDC1 deletion reduced pro-inflammatory and pro-fibrotic gene expression, while gut microbiome analysis indicated a shift toward MASH-protective bacteria. These findings suggest that HKDC1 may exacerbate MASH progression through its role in metabolic and inflammatory pathways, making it a potential therapeutic target.

Bile Acids and Farnesoid X Receptor in Renal Pathophysiology

BACKGROUND

Bile acids (BAs) act not only as lipids and lipid-soluble vitamin detergents but also function as signaling molecules, participating in diverse physiological processes. The identification of BA receptors in organs beyond the enterohepatic system, such as the farnesoid X receptor (FXR), has initiated inquiries into their organ-specific functions. Among these organs, the kidney prominently expresses FXR.

SUMMARY

This review provides a comprehensive overview of various BA species identified in kidneys and delves into the roles of renal apical and basolateral BA transporters. Furthermore, we explore changes in BAs and their potential implications for various renal diseases, particularly chronic kidney disease. Lastly, we center our discussion on FXR, a key BA receptor in the kidney and a potential therapeutic target for renal diseases, providing current insights into the protective mechanisms associated with FXR agonist treatments.

KEY MESSAGES

Despite the relatively low concentrations of BAs in the kidney, their presence is noteworthy, with rodents and humans exhibiting distinct renal BA compositions. Renal BA transporters efficiently facilitate either reabsorption into systemic circulation or excretion into the urine. However, adaptive changes in BA transporters are evident during cholestasis. Various renal diseases are accompanied by alterations in BA concentrations and FXR expression. Consequently, the activation of FXR in the kidney could be a promising target for mitigating kidney damage.

Protective effect and mechanism of lactoferrin combined with hypoxia against high-fat diet induced obesity and non-alcoholic fatty liver disease in mice

Obesity is a global epidemic, it can induce glucose and lipid metabolism disorder and non-alcoholic fatty liver disease (NAFLD). This study explored a new way to control weight and improve fatty liver, namely, living in hypoxia environment and supplement with lactoferrin (Lf). Sixty male C57BL/6J mice were divided into six groups, namely, control, hypoxia, high-fat diet, hypoxia + high-fat diet, hypoxia + high-fat diet + low dose Lf intervention, and hypoxia + high-fat diet + high-dose Lf intervention. Mice in the hypoxia treatment groups were treated with approximately 11.5 % oxygen for 6 h every day for 8 weeks. Results showed that interventions combining Lf and hypoxia treatments showed better effect against obesity and NAFLD than hypoxia treatment alone. The interventions controlled weight gain in mice, improved glucolipid metabolism in mice. The combination intervention reduced cholesterol absorption by reducing the level of hydrophobic bile acids, and elevating the level of hydrophilic bile acids. Gut microbiota analysis revealed that the combination intervention considerably elevated short chain fatty acids (SCFAs)-producing bacteria level, and reduced the Desulfovibrionaceae_unclassified level. Thus, Lf combined with hypoxia intervention effectively prevents obesity and NAFLD by restoring gut microbiota composition and bile acid profile.

The fungicide prothioconazole and its metabolite prothioconazole-desthio disturbed the liver-gut axis in mice

The triazole fungicide prothioconazole (PTC) can cause adverse effects in animals, and its main metabolite prothioconazole-desthio (PTC-d) is even much more harmful. However, the toxic effects of PTC and PTC-d on the liver-gut axis of mice are still unknown. In the present experiment, we found that oral exposure to PTC and PTC-d increased total bile acids (TBAs) levels in the serum, liver, and feces. Correspondingly, the transcription of genes involved in bile acids (BAs) disposition was significantly influenced by PTC or PTC-d exposure. Furthermore, the BAs composition of serum BAs was analyzed by LC-MS, and the results indicated that PTC and PTC-d exposure changed the BAs composition, lowered the ratio of conjugated/unconjugated BAs, elevated the ratio of CA/b-MCA, and enhanced the hydrophobicity of BAs pool. 16s RNA gene sequencing of the DNA from colonic contents uncovered that PTC and PTC-d exposure altered the relative abundance and constitution of intestinal microbiota, increasing the relative level of Lactobacillus with bile salt hydrolase (BSH) activity. Furthermore, PTC and PTC-d exposure impaired the gut barrier function, causing an increase in mucus secretion. In particular, the effects of PTC-d on some endpoints in the BAs metabolism and gut barrier function had been proven to be more significant than the parent compound PTC. All these findings draw attention to the health risk of PTC and PTC-d exposure in regulating BAs metabolism, which might lead to some metabolic disorders and occur of related diseases in animals.

Nutritional and Chemical Composition of Sargassum zhangii and the Physical and Chemical Characterization, Binding Bile Acid, and Cholesterol-Lowering Activity in HepG2 Cells of Its Fucoidans

Fucoidan is a marine sulfated polysaccharide that is rich in Sargassum and has a wide range of biological activities. In this study, the chemical composition and bile acid binding ability of six crude fucoidans were compared, the nutrition and chemical composition of Sargassum zhangii were analyzed, and fucoidan from Sargassum zhangii was extracted and purified. The purified fractions (ZF1, ZF2, and ZF3) were analyzed by physicochemical characterization, and the ability of binding bile acid and cholesterol lowering in HepG2 cells were evaluated. The results showed that the contents of sulfate in crude fucoidan from Sargassum Zhangii (ZF) was as high as13.63%. Its ability of binding bile acid was better than other five crude fucoidans. Sargassum zhangii was a kind of brown seaweed with high carbohydrate, and low fat and rich in minerals. The sulfate content of ZF1, ZF2, and ZF3 was 3.29%, 19.39%, and 18.89% respectively, and the molecular weight (Mw) was 4.026 × 10⁵, 2.893 × 10⁵, and 3.368 × 10⁵, respectively. Three fucoidans all contained the characteristic absorption bands of polysaccharides and sulfate groups and were rich in fucose. Three fucoidans can bind to bile acid, and ZF2 showed the best binding capability. In vitro experiments showed that ZF1, ZF2, and ZF3 could reduce intracellular total cholesterol (TC) content in HepG2 cells without affecting their viability. ZF2 showed the best ability to reduce TC.

Atorvastatin protects against liver and vascular damage in a model of diet induced steatohepatitis by resetting FXR and GPBAR1 signaling

Farnesoid-x-receptor (FXR) agonists, currently trialed in patients with non-alcoholic steatosis (NAFLD), worsen the pro-atherogenic lipid profile and might require a comedication with statin. Here we report that mice feed a high fat/high cholesterol diet (HFD) are protected from developing a pro-atherogenic lipid profile because their ability to dispose cholesterol through bile acids. This protective mechanism is mediated by suppression of FXR signaling in the liver by muricholic acids (MCAs) generated in mice from chenodeoxycholic acid (CDCA). In contrast to CDCA, MCAs are FXR antagonists and promote a CYP7A1-dependent increase of bile acids synthesis. In mice feed a HFD, the treatment with obeticholic acid, a clinical stage FXR agonist, failed to improve the liver histopathology while reduced Cyp7a1 and Cyp8b1 genes expression and bile acids synthesis and excretion. In contrast, treating mice with atorvastatin mitigated liver and vascular injury caused by the HFD while increased the bile acids synthesis and excretion. Atorvastatin increased the percentage of 7α-dehydroxylase expressing bacteria in the intestine promoting the formation of deoxycholic acid and litocholic acid, two GPBAR1 agonists, along with the expression of GPBAR1-regulated genes in the white adipose tissue and colon. In conclusion, present results highlight the central role of bile acids in regulating lipid and cholesterol metabolism in response to atorvastatin and provide explanations for limited efficacy of FXR agonists in the treatment of NAFLD.

Linking liver metabolic and vascular disease via bile acid signaling

Non-alcoholic fatty liver disease (NAFLD) is a metabolic disorder affecting over one quarter of the global population. Liver fat accumulation in NAFLD is promoted by increased de novo lipogenesis leading to the development of a proatherosclerotic lipid profile and atherosclerotic cardiovascular disease (CVD). The CVD component of NAFLD is the main determinant of patient outcome. The farnesoid X receptor (FXR) and the G protein bile acid-activated receptor 1 (GPBAR1) are bile acid-activated receptors that modulate inflammation and lipid and glucose metabolism in the liver and CV system, and are thus potential therapeutic targets. We review bile acid signaling in liver, metabolic tissues, and the CV system, and we propose the development of dual FXR/GPBAR1 ligands, intestine-restricted FXR ligands, or statin combinations to limit side effects and effectively manage the liver and CV components of NAFLD.