Bile acids lower triglyceride levels via a pathway involving FXR, SHP, and SREBP-1c

Different types of bile acids exhibit opposite regulatory effects on lipid metabolism in finishing pigs through bile acid receptors

The purpose of this research was to investigate how different bile acids impact lipid metabolism and carcass characteristics in finishing pigs, along with the potential mechanisms involved. Twenty-one finishing pigs (Duroc×Landrace×Yorkshire [DLY]; average BW = 144.38 ± 8.92 kg) were assigned to three dietary treatments, with each treatment containing seven replicates, each consisting of one pig. The three dietary treatments included: a basic diet, a basic diet supplemented with 500 mg/kg of hyodeoxycholic acid (HDCA), and a basic diet supplemented with 500 mg/kg of lithocholic acid (LCA). The trial lasted for 28 d. Hyodeoxycholic acid was used in the in vitro experiments and added to mature 3T3-L1 adipocytes for 4 d to elucidate the mechanism by which bile acids regulate lipid metabolism. The results suggested that HDCA tended to decrease backfat thickness in finishing pigs (P = 0.094) and reduced the size of lipid droplets in 3T3-L1 adipocytes (P = 0.012), whereas LCA increased backfat thickness (P = 0.016) and induced larger lipid droplets in the abdominal adipose tissue (P = 0.003). Furthermore, HDCA enhanced the expression of Takeda G-protein-coupled receptor 5 protein and hormone-sensitive lipase (HSL) gene in backfat of pigs (P < 0.05) and increased the protein expression of phosphorylated HSL (p-HSL) in vitro (P = 0.093). Compared to HDCA, LCA addition increased the gene and protein expression of peroxisome proliferator activated receptor gamma in backfat of pigs (P < 0.05) and enhanced the expression of hepatic genes sterol regulatory element-binding protein-1c and fatty acid synthase (P < 0.05). In conclusion, HDCA enhanced lipolysis and partially decreased backfat thickness in finishing pigs, while LCA promoted lipid synthesis and increased backfat thickness of pigs. The variations in the effects of various bile acids on bile acid receptors could explain these functional differences.

Transcription factors, metabolic dysfunction-associated fatty liver disease, and therapeutic implications

Metabolic dysfunction-associated fatty liver disease (MAFLD) encompasses a spectrum of liver diseases ranging from metabolic dysfunction-associated fatty liver to metabolic dysfunction-associated steatohepatitis, which may progress to liver cirrhosis and hepatocellular carcinoma. Several mechanisms, including obesity, insulin resistance, dyslipidemia, inflammation, apoptosis, mitochondrial dysfunction, and reactive oxygen species, have been proposed to underlie the progression of MAFLD. Transcription factors are proteins that specifically bind to DNA sequences to regulate the transcription of target genes. Numerous transcription factors regulate MAFLD by modulating the transcription of genes involved in steatosis, inflammation, apoptosis, and fibrosis. Here, we review the pathological factors associated with MAFLD, with a particular emphasis on the transcription factors that contribute to the progression of MAFLD and their therapeutic implications.

Exogenous oxidized phytosterol may modulate linoleic acid metabolism through upregulation of fatty acid desaturase in rats

Previous in vitro studies have indicated that oxidized phytosterol (OPS) exhibits some toxicity; however, the harmful effects of OPS on fatty acid metabolism are not completely understood yet. Therefore, this study examined the effects of exogenous phytosterol (PS) and OPS on growth parameters and lipid metabolism in rats. Rats were provided with AIN-76 basal diet, basal diet +0.5% PS, or basal diet +0.5% OPS. We found that the level of cholesterol and triacylglycerols in the liver was significantly lower in OPS-fed rats than in basal diet-fed rats. The ratio of Δ6 desaturation index (20:3(n-6) + 20:4(n-6))/18:2(n-6) in the plasma was significantly higher in the OPS-fed rats than in the PS-fed rats. Additionally, the proportion of arachidonic acid (20:4) in the liver was significantly higher in the OPS-fed group compared with the control group. The mRNA expression levels of Δ6 and Δ5 desaturases were significantly higher in OPS-fed rats than in basal diet-fed rats, but remained unchanged in PS-fed rats. Moreover, the protein level of Δ6 desaturase was significantly higher in both PS- and OPS-fed rats compared with basal diet-fed rats, while the protein level of Δ5 desaturase tended to be higher only in OPS-fed rats than in basal diet-fed rats. Thus, exogenous OPS, but not PS, altered fatty acid composition through the upregulation of mRNA and protein levels of fatty acid desaturation enzymes in the liver. This indicates that exogenous OPS, unlike PS, may modulate the production of eicosanoids from arachidonic acid, potentially promoting allergic reactions, inflammation, and atherosclerosis.

Zinc-Mediated Deacetylation of Farnesoid X Receptor Activates the Adipose Triglyceride Lipase Pathway to Reduce Hepatic Lipid Accumulation and Enhance Lipolysis in Yellow Catfish

BACKGROUND

High-fat diets (HFDs) can lead to excessive accumulation of lipids in the liver, leading to liver injury. Dietary zinc (Zn) has been shown to reduce HFD-induced lipid accumulation and improve lipid profiles in mammals, yet it remains unclear whether waterborne Zn maintains its lipid-lowering effects in osteichthyes.

OBJECTIVES

This study aimed to elucidate the regulatory role of Zn in HFD-induced hepatic lipid accumulation in yellow catfish (Pelteobagrus fulvidraco) and its potential mechanisms.

METHODS

Yellow catfish were fed a control diet (11.21% lipid concentration), HFD (16.10% lipid concentration), or HFD combined with waterborne Zn exposure (0.2 mg/L) for 8 wk. Various biochemical, genetic, histologic, and molecular techniques were conducted to evaluate hepatic lipid deposition and lipid metabolism and determine protein interactions between silent information regulator (SIRT) 1 and farnesoid X receptor (FXR), as well as protein-gene interactions between FXR and adipose triglyceride lipase (ATGL).

RESULTS

HFD feeding significantly increased liver fat content and induced hepatic damage in yellow catfish, but concurrent exposure to waterborne Zn alleviated these detrimental effects. Zn treatment increased mRNA and protein concentrations of SIRT1 (mean ± SEM; 97.19% ± 11.67% and 83.25% ± 28.60%, respectively) and FXR (163.90% ± 24.60% and 24.90% ± 11.12%, respectively) in yellow catfish liver (P < 0.05). Zn-activated FXR directly interacted with the promoter of ATGL, stimulating the expression of atgl (54.40% ± 16.33%; P < 0.05) and facilitating the hydrolysis of triglycerides and lipid droplets. Furthermore, Zn reduced the acetylation concentration of FXR by SIRT1 deacetylation of FXR protein K167.

CONCLUSIONS

The findings reveal that Zn protect against HFD-induced liver injury in yellow catfish by promoting the deacetylation of FXR protein K167 by SIRT1 and activating FXR, thereby promoting the transcriptional activation of ATGL to increase lipolysis.

Bile acid signaling in skeletal muscle homeostasis: from molecular mechanisms to clinical applications

The intricate relationship between bile acid metabolism and skeletal muscle function has emerged as a crucial area of research in metabolic health. This review synthesizes current evidence highlighting the fundamental role of bile acids as key signaling molecules in muscle homeostasis and their therapeutic potential in muscle-related disorders. Recent advances in molecular biology and metabolomics have revealed that bile acids, beyond their classical role in lipid absorption, function as essential regulators of muscle mass and function through multiple signaling pathways, particularly via the nuclear receptor FXR and membrane receptor TGR5. Clinical studies have demonstrated significant associations between altered bile acid profiles and muscle wasting conditions, while experimental evidence has elucidated the underlying mechanisms linking bile acid signaling to muscle protein synthesis, energy metabolism, and regeneration capacity. We critically examine the emerging therapeutic strategies targeting bile acid pathways, including receptor-specific agonists, microbiome modulators, and personalized interventions based on individual bile acid profiles. Additionally, we discuss novel diagnostic approaches utilizing bile acid-based biomarkers and their potential in early detection and monitoring of muscle disorders. This review also addresses current challenges in standardization and clinical translation while highlighting promising future directions in this rapidly evolving field. Understanding the bile acid-muscle axis may provide new opportunities for developing targeted therapies for age-related muscle loss and metabolic diseases.

Metabolic dysfunction-associated steatotic liver disease in adults

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the umbrella term that comprises metabolic dysfunction-associated steatotic liver, or isolated hepatic steatosis, through to metabolic dysfunction-associated steatohepatitis, the progressive necroinflammatory disease form that can progress to fibrosis, cirrhosis and hepatocellular carcinoma. MASLD is estimated to affect more than one-third of adults worldwide. MASLD is closely associated with insulin resistance, obesity, gut microbial dysbiosis and genetic risk factors. The obesity epidemic and the growing prevalence of type 2 diabetes mellitus greatly contribute to the increasing burden of MASLD. The treatment and prevention of major metabolic comorbidities such as type 2 diabetes mellitus and obesity will probably slow the growth of MASLD. In 2023, the field decided on a new nomenclature and agreed on a set of research and action priorities, and in 2024, the US FDA approved the first drug, resmetirom, for the treatment of non-cirrhotic metabolic dysfunction-associated steatohepatitis with moderate to advanced fibrosis. Reliable, validated biomarkers that can replace histology for patient selection and primary end points in MASH trials will greatly accelerate the drug development process. Additionally, noninvasive tests that can reliably determine treatment response or predict response to therapy are warranted. Sustained efforts are required to combat the burden of MASLD by tackling metabolic risk factors, improving risk stratification and linkage to care, and increasing access to therapeutic agents and non-pharmaceutical interventions.

Bile acids and their receptors in hepatic immunity

Similarly to conventional steroids, bile acids function as signaling molecules, acting on a family of membrane and nuclear receptors. The best-characterized bile acid-regulated receptors are the farnesoid X receptor, activated by primary bile acids, and the G-protein-coupled bile acid receptor 1 (also known as Takeda G protein-coupled receptor 5), which is activated by secondary bile acids, such as lithocholic acid (LCA) and deoxycholic acid. Both the farnesoid X receptor and G-protein-coupled bile acid receptor 1 are expressed in cells of innate immunity, monocytes/macrophages, and natural killer cells. Their activation in these cells provides counter-regulatory signals that are inhibitory in nature and attenuate inflammation. In recent years, however, it has been increasingly appreciated that bile acids biotransformations by intestinal microbiota result in the formation of chemically different secondary bile acids that potently regulate adaptive immunity. The 3-oxoLCA and isoalloLCA, two LCA derivatives, bind receptors such as the retinoic acid receptor-related orphan receptor gamma t (RORγt) and the vitamin D receptor (VDR) that are expressed only by lymphoid cells, extending the regulatory role of bile acids to T cells, including T-helper 17 cells and type 3 innate lymphoid cells (ILC3). In this novel conceptual framework, bile acids have emerged as one of the main components of the postbiota, the waste array of chemical mediators generated by the intestinal microbiota. Deciphering the interaction of these mediators with the immune system in the intestine and liver is a novel and fascinating area of bile acid renaissance.

Effect of different Lys/Met ratios in a low-protein diet on the meat quality of Tibetan sheep: A transcriptomics- and metabolomics-based analysis

This study integrated the the effects of dietary Lys/Met ratio in a low protein diet on the meat quality in Tibetan sheep. A total of 90 weaned Tibetan sheep, 2 months old with initial weight of 15.37 ± 0.92 kg were randomly divided into 3 treatments, which were supplemented with Lys/Met ratio at 3 (LP-H), 2 (LP-M), and 1 (LP-L) in the basal diet (10 % crude protein), respectively. After slaughter (150 days of age), the growth performances and meat quality of longissimus dorsi muscle were evaluated. The LP-L group showed significantly higher final body weight compared to the LP-M group (P < 0.05). Serum albumin and total protein levels were significantly higher in the LP-L group than in the LP-H group (P < 0.05). Furthermore, meat from the LP-L group had significantly higher protein, calcium, and vitamin E content compared to the LP-M group (P < 0.05). Transcriptomic analysis revealed 3,479 differentially expressed genes enriched in pathways related to muscle growth, energy metabolism, and signaling transduction. Metabolomic analysis identified 771 differential metabolites, significantly enriched in ABC transporters, beta-alanine metabolism, and taste transduction pathways. Integrated analysis highlighted the upregulation of the ABCD4 gene and L-valine metabolite in the LP-L group, contributing to improved phenotypic traits. These findings provide molecular insights into the regulatory mechanisms underlying the effects of dietary Lys/Met ratios on Tibetan sheep meat quality and offer a basis for developing nutritional strategies to enhance premium meat production.

Pharmacological treatment for metabolic dysfunction-associated steatotic liver disease and related disorders: Current and emerging therapeutic options

Metabolic dysfunction-associated steatotic liver disease (MASLD; formerly known as nonalcoholic fatty liver disease) is a chronic liver disease affecting over a billion individuals worldwide. MASLD can gradually develop into more severe liver pathologies, including metabolic dysfunction-associated steatohepatitis (MASH), cirrhosis, and liver malignancy. Notably, although being a global health problem, there are very limited therapeutic options against MASLD and its related diseases. While a thyroid hormone receptor agonist (resmetirom) is recently approved for MASH treatment, other efforts to control these diseases remain unsatisfactory. Given the projected rise in MASLD and MASH incidence, it is urgent to develop novel and effective therapeutic strategies against these prevalent liver diseases. In this article, the pathogenic mechanisms of MASLD and MASH, including insulin resistance, dysregulated nuclear receptor signaling, and genetic risk factors (eg, patatin-like phospholipase domain-containing 3 and hydroxysteroid 17-β dehydrogenase-13), are introduced. Various therapeutic interventions against MASH are then explored, including approved medication (resmetirom), drugs that are currently in clinical trials (eg, glucagon-like peptide 1 receptor agonist, fibroblast growth factor 21 analog, and PPAR agonist), and those failed in previous trials (eg, obeticholic acid and stearoyl-CoA desaturase 1 antagonist). Moreover, given that the role of gut microbes in MASLD is increasingly acknowledged, alterations in the gut microbiota and microbial mechanisms in MASLD development are elucidated. Therapeutic approaches that target the gut microbiota (eg, dietary intervention and probiotics) against MASLD and related diseases are further explored. With better understanding of the multifaceted pathogenic mechanisms, the development of innovative therapeutics that target the root causes of MASLD and MASH is greatly facilitated. The possibility of alleviating MASH and achieving better patient outcomes is within reach. SIGNIFICANCE STATEMENT: Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease worldwide, and it can progress to more severe pathologies, including steatohepatitis, cirrhosis, and liver cancer. Better understanding of the pathogenic mechanisms of these diseases has facilitated the development of innovative therapeutic strategies. Moreover, increasing evidence has illustrated the crucial role of gut microbiota in the pathogenesis of MASLD and related diseases. It may be clinically feasible to target gut microbes to alleviate MASLD in the future.

Therapeutic Potential of Cranberry Proanthocyanidins in Addressing the Pathophysiology of Metabolic Syndrome: A Scrutiny of Select Mechanisms of Action

Metabolic syndrome (MetS) constitutes a spectrum of interconnected conditions comprising obesity, dyslipidemia, hypertension, and insulin resistance (IR). While a singular, all-encompassing treatment for MetS remains elusive, an integrative approach involving tailored lifestyle modifications and emerging functional food therapies holds promise in preventing its multifaceted manifestations. Our main objective was to scrutinize the efficacy of cranberry proanthocyanidins (PAC, 200 mg/kg/day for 12 weeks) in mitigating MetS pathophysiology in male mice subjected to standard Chow or high-fat/high-fructose (HFHF) diets while unravelling intricate mechanisms. The administration of PAC, in conjunction with an HFHF diet, significantly averted obesity, evidenced by reductions in body weight, adiposity across various fat depots, and adipocyte hypertrophy. Similarly, PAC prevented HFHF-induced hyperglycemia and hyperinsulinemia while also lessening IR. Furthermore, PAC proved effective in alleviating key risk factors associated with cardiovascular diseases by diminishing plasma saturated fatty acids, as well as levels of triglycerides, cholesterol, and non-HDL-C levels. The rise in adiponectin and drop in circulating levels of inflammatory markers showcased PAC's protective role against inflammation. To better clarify the mechanisms behind PAC actions, gut-liver axis parameters were examined, showing significant enhancements in gut microbiota composition, microbiota-derived metabolites, and marked reductions in intestinal and hepatic inflammation, liver steatosis, and key biomarkers associated with endoplasmic reticulum (ER) stress and lipid metabolism. This study enhances our understanding of the complex mechanisms underlying the development of MetS and provides valuable insights into how PAC may alleviate cardiometabolic dysfunction in HFHF mice.

Isoschaftoside in Fig Leaf Tea Alleviates Nonalcoholic Fatty Liver Disease in Mice via the Regulation of Macrophage Polarity

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a subset of fatty liver disease that is not caused by alcohol or viruses, and its increasing incidence presents a major global health concern. As few pharmacotherapies are available for NAFLD, lifestyle modifications, including diet and exercise, serve as the foundation for treatment. Therefore, NAFLD prevention is more important than cure, emphasizing the need for drugs with excellent safety and long-term efficacy. Fig leaf tea contains rutin and isoschaftoside (ISS), which may possess anti-inflammatory properties. Therefore, the aim of this murine-model-based study was to investigate the potential benefits of fig leaf tea in alleviating NAFLD and to determine the underlying mechanism by gene expression analysis.

RESULTS

We found that in mice with NAFLD induced by a high-fat diet, the administration of high concentration fig leaf tea or 50 µM ISS significantly ameliorated lobule inflammation. In contrast, low concentration fig leaf tea containing 75 µM ISS did not improve inflammation. The balance between the NAFLD-promoting component of fig leaf tea and the inhibitory effect of ISS was thought to be affected. Gene expression analysis of the liver showed that high concentration fig leaf tea or ISS significantly suppressed the expression of M1 macrophage markers such as CD antigens, toll-like receptors (TLR), chemokines, and cytokines. Further, ISS suppressed the amount of TNF-α released during the M1 polarization of macrophage cells upon lipopolysaccharide (LPS) stimulation.

CONCLUSIONS

Overall, these results suggest that controlling macrophage polarization may improve NAFLD. Furthermore, these findings highlight the potential clinical applicability of ISS.

Current Therapeutic Landscape for Metabolic Dysfunction-Associated Steatohepatitis

In recent years, "metabolic dysfunction-associated steatotic liver disease" (MASLD) has been proposed to better connect liver disease to metabolic dysfunction, which is the most common chronic liver disease worldwide. MASLD affects more than 30% of individuals globally, and it is diagnosed by the combination of hepatic steatosis and obesity, type 2 diabetes, or two metabolic risk factors. MASLD begins with the buildup of extra fat, often greater than 5%, within the liver, causing liver hepatocytes to become stressed. This can proceed to a more severe form, metabolic dysfunction-associated steatohepatitis (MASH), in 20-30% of people, where inflammation in the liver causes tissue fibrosis, which limits blood flow over time. As fibrosis worsens, MASH may lead to cirrhosis, liver failure, or even liver cancer. While the pathophysiology of MASLD is not fully known, the current "multiple-hits" concept proposes that dietary and lifestyle factors, metabolic factors, and genetic or epigenetic factors contribute to elevated oxidative stress and inflammation, causing liver fibrosis. This review article provides an overview of the pathogenesis of MASLD and evaluates existing therapies as well as pharmacological drugs that are currently being studied in clinical trials for MASLD or MASH.

The Potential Role of Intestinal Microbiota on the Intestine-Protective and Lipid-Lowering Effects of Berberine in Zebrafish (Danio rerio) Under High-Lipid Stress

Background: Berberine has extremely low oral bioavailability, but shows a potent lipid-lowering effect, indicating its potential role in regulating intestinal microbiota, which has not been investigated. Methods: In the present study, five experimental diets, a control diet (Con), a high-lipid diet (HL), and high-lipid·diets·supplemented with an antibiotic cocktail (HLA), berberine (HLB), or both (HLAB) were fed to zebrafish (Danio rerio) for 30 days. Results: The HLB group showed significantly greater weight gain and feed intake than the HLA and other groups, respectively (p < 0.05). Hepatic triglyceride (TG) and total cholesterol (TC) levels, lipogenesis, and proinflammatory cytokine gene expression were significantly upregulated by the high-lipid diet, but significantly downregulated by berberine supplementation. Conversely, the expression levels of intestinal and/or hepatic farnesoid X receptor (fxr), Takeda G protein-coupled receptor 5 (tgr5), lipolysis genes, and zonula occludens 1 (zo1) exhibited the opposite trend. Compared with the HLB group, the HLAB group displayed significantly greater hepatic TG content and proinflammatory cytokine expression, but significantly lower intestinal bile salt hydrolase (BSH) activity and intestinal and/or hepatic fxr and tgr5 expression levels. The HL treatment decreased the abundance of certain probiotic bacteria (e.g., Microbacterium, Cetobacterium, and Gemmobacter) and significantly increased the pathways involved in cytochrome P450, p53 signaling, and ATP-binding cassette (ABC) transporters. The HLB group increased some probiotic bacteria abundance, particularly BSH-producing bacteria (e.g., Escherichia Shigella). Compared with the HLB group, the abundance of BSH-producing bacteria (e.g., Bifidobacterium and Enterococcus) and pathways related to Notch signaling and Wnt signaling were reduced in the HLAB group. Conclusions: This study revealed that berberine's lipid-lowering and intestine-protective effects are closely related to the intestinal microbiota, especially BSH-producing bacteria.

Galactooligosaccharide-Metabolism-Related Genes of Bifidobacterium pseudocatenulatum Contribute to the Regulation of Glucose and Lipid Metabolism in Type 2 Diabetic Mice

This study investigated whether the galactooligosaccharide (GOS)-metabolism-related genes (GOS-cluster) in Bifidobacterium pseudocatenulatum contribute to alleviating glucose and lipid metabolic disorders in type 2 diabetic mice. Genomic analysis of 69 B. pseudocatenulatum strains based on the GOS-cluster, combined with in vitro fermentation experiments, revealed that high-GOS-cluster strains (≥24 MFS, ≥39 GOS-cluster) demonstrated superior GOS utilization and bile salt tolerance. In vivo, the high-GOS-cluster strains resulted in a significant reduction of blood glucose levels by 18.52 to 32.01% compared to the model group. Mechanistic studies showed that these strains significantly activated the FXR/FGF15/GSK3β and FXR/SREBP1/FAS signaling pathways. Species-specific quantification of B. pseudocatenulatum, metabolomics, and network analysis suggested that GOS treatment increased the abundance of B. pseudocatenulatum, particularly strains rich in the GOS-cluster, with a 32.03% increase compared to strains with a low GOS-cluster. This indirectly increased choloylglycine hydrolase levels and altered the profiles of primary and secondary bile acids, resulting in an increase in FXR agonists, such as glycocholic acid, cholic acid, and deoxycholic acid. These findings suggest that the presence of the GOS-cluster is a crucial factor in determining whether a B. pseudocatenulatum strain can prevent or ameliorate type 2 diabetes.

A Collection of Novel Antitumor Agents That Regulate Lipid Metabolism in the Tumor Microenvironment

Lipid metabolism disorder is the cause of one of the most significant metabolic changes in tumors. In the process of tumor occurrence and development, tumor cells choose a continuous metabolic adaptation to accommodate the changing environment to the maximum extent possible. In a variety of tumors, the uptake, production, and storage of lipids are generally upregulated. Tumor cells take advantage of lipid metabolism to access basic energy, biofilm components, and signal molecules of the tumor microenvironment required for proliferation, survival, invasion, and metastasis. This Perspective briefly uncovers the main metabolic processes and key factors involved in lipid metabolism reprogramming, mainly related to lipid uptake, de novo synthesis and storage of fatty acids, oxidation of fatty acids, cholesterol synthesis, and related regulatory factors. From a medicinal chemistry perspective, agents against related key targets are reviewed, expecting to pave the way for promising antitumor drugs with prospects for application through lipid metabolism reprogramming.

Bioactive metabolites: A clue to the link between MASLD and CKD?

Metabolites produced as intermediaries or end-products of microbial metabolism provide crucial signals for health and diseases, such as metabolic dysfunction-associated steatotic liver disease (MASLD). These metabolites include products of the bacterial metabolism of dietary substrates, modification of host molecules (such as bile acids [BAs], trimethylamine-N-oxide, and short-chain fatty acids), or products directly derived from bacteria. Recent studies have provided new insights into the association between MASLD and the risk of developing chronic kidney disease (CKD). Furthermore, alterations in microbiota composition and metabolite profiles, notably altered BAs, have been described in studies investigating the association between MASLD and the risk of CKD. This narrative review discusses alterations of specific classes of metabolites, BAs, fructose, vitamin D, and microbiota composition that may be implicated in the link between MASLD and CKD.

Bile acid metabolism and signalling in liver disease

Bile acids (BAs) serve as signalling molecules, efficiently regulating their own metabolism and transport, as well as key aspects of lipid and glucose homeostasis. BAs shape the gut microbial flora and conversely are metabolised by microbiota. Disruption of BA transport, metabolism and physiological signalling functions contribute to the pathogenesis and progression of a wide range of liver diseases including cholestatic disorders and MASLD (metabolic dysfunction-associated steatotic liver disease), as well as hepatocellular and cholangiocellular carcinoma. Additionally, impaired BA signalling may also affect the intestine and kidney, thereby contributing to failure of gut integrity and driving the progression and complications of portal hypertension, cholemic nephropathy and the development of extrahepatic malignancies such as colorectal cancer. In this review, we will summarise recent advances in the understanding of BA signalling, metabolism and transport, focusing on transcriptional regulation and novel BA-focused therapeutic strategies for cholestatic and metabolic liver diseases.

Diverting hepatic lipid fluxes with lifestyles revision and pharmacological interventions as a strategy to tackle steatotic liver disease (SLD) and hepatocellular carcinoma (HCC)

Steatotic liver disease (SLD) and Hepatocellular Carcinoma (HCC) are characterised by a substantial rewiring of lipid fluxes caused by systemic metabolic unbalances and/or disrupted intracellular metabolic pathways. SLD is a direct consequence of the interaction between genetic predisposition and a chronic positive energy balance affecting whole-body energy homeostasis and the function of metabolically-competent organs. In this review, we discuss how the impairment of the cross-talk between peripheral organs and the liver stalls glucose and lipid metabolism, leading to unbalances in hepatic lipid fluxes that promote hepatic fat accumulation. We also describe how prolonged metabolic stress builds up toxic lipid species in the liver, and how lipotoxicity and metabolic disturbances drive disease progression by promoting a chronic activation of wound healing, leading to fibrosis and HCC. Last, we provide a critical overview of current state of the art (pre-clinical and clinical evidence) regarding mechanisms of action and therapeutic efficacy of candidate SLD treatment options, and their potential to interfere with SLD/HCC pathophysiology by diverting lipids away from the liver therefore improving metabolic health.

Metabolic disorders, inter-organ crosstalk, and inflammation in the progression of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents a global health concern, affecting over 30 % of adults. It is a principal driver in the development of cirrhosis and hepatocellular carcinoma. The complex pathogenesis of MASLD involves an excessive accumulation of lipids, subsequently disrupting lipid metabolism and prompting inflammation within the liver. This review synthesizes the recent research progress in understanding the mechanisms contributing to MASLD progression, with particular emphasis on metabolic disorders and interorgan crosstalk. We highlight the molecular mechanisms linked to these factors and explore their potential as novel targets for pharmacological intervention. The insights gleaned from this article have important implications for both the prevention and therapeutic management of MASLD.

Structure-guided discovery of bile acid derivatives for treating liver diseases without causing itch

Chronic itch is a debilitating symptom profoundly impacting the quality of life in patients with liver diseases like cholestasis. Activation of the human G-protein coupled receptor, MRGPRX4 (hX4), by bile acids (BAs) is implicated in promoting cholestasis itch. However, the detailed underlying mechanisms remain elusive. Here, we identified 3-sulfated BAs that are elevated in cholestatic patients with itch symptoms. We solved the cryo-EM structure of hX4-Gq in a complex with 3-phosphated deoxycholic acid (DCA-3P), a mimic of the endogenous 3-sulfated deoxycholic acid (DCA-3S). This structure revealed an unprecedented ligand-binding pocket in MRGPR family proteins, highlighting the crucial role of the 3-hydroxyl (3-OH) group on BAs in activating hX4. Guided by this structural information, we designed and developed compound 7 (C7), a BA derivative lacking the 3-OH. Notably, C7 effectively alleviates hepatic injury and fibrosis in liver disease models while significantly mitigating the itch side effects.

Exploring the role and therapeutic potential of lipid metabolism in acute kidney injury

Acute kidney injury (AKI) is a prevalent condition, yet no specific treatment is available. Extensive research has revealed the pivotal role of lipid-related alterations in AKI. Lipid metabolism plays an essential role in the sustenance of the kidneys. In addition to their energy-supplying function, lipids contribute to the formation of renal biomembranes and the establishment of the renal microenvironment. Moreover, lipids or their metabolites actively participate in signal transduction, which governs various vital biological processes, such as proliferation, differentiation, apoptosis, autophagy, and epithelial-mesenchymal transition. While previous studies have focused predominantly on abnormalities in lipid metabolism in chronic kidney disease, this review focuses on lipid metabolism anomalies in AKI. We explore the significance of lipid metabolism products as potential biomarkers for the early diagnosis and classification of AKI. Additionally, this review assesses current preclinical investigations on the modulation of lipid metabolism in the progression of AKI. Finally, on the basis of existing research, this review proposes future directions, highlights challenges, and presents novel targets and innovative ideas for the treatment of and intervention in AKI.

Dietary high lipid and high plant-protein affected growth performance, liver health, bile acid metabolism and gut microbiota in groupers

High lipid diets (HLD) and high plant-protein diets (HPD) exhibit potential fishmeal-saving effects but negatively impact liver health and growth performance in fish. We hypothesized that HLD and HPD impair liver health in pearl gentian groupers (Epinephelus fuscoguttatus♂ × Epinephelus lanceolatus♀) through the modulation of intestinal microbiota and bile acid (BA) metabolism. Four diet groups were tested: control diet (CD, 46.21% crude protein, 9.48% crude lipid), HLD (46.37% crude protein, 16.70% crude lipid), HPD (46.50% crude protein, 9.38% crude lipid), and high lipid-high plant-protein diet (HLPD, 46.54% crude protein, 16.67% crude lipid). A total of 300 fish (average body weight = 15.22 ± 0.03 g) were randomly divided into 4 diet treatments (ensuring 3 tanks replicates of each diet treatment, each tank containing 25 fish). After an eight-week feeding period, the HLD and HPD significantly decreased the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR) and feed intake (FI) in comparison to CD group, with HLPD exacerbating these indicators (P < 0.05). Compared to CD group, the content of total cholesterol (T-CHO) and triglyceride (TG) in liver and serum were significantly increased in HLD group (P < 0.05). Compared to HPD group, the content of T-CHO in liver was significantly decreased, the content of TG in liver and serum were significantly increased in HLPD group (P < 0.05). HLD, HPD, and HLPD impaired liver health by inducing histological damage, inflammation, and oxidative stress. Compared to CD group, the mRNA relative expression of bile salt export pump (bsep) and multidrug resistance protein 3 (mdr3) were significantly increased in HLD group, whereas the mRNA relative expression of sterol-27-hydroxylase (cyp27a1), microsomal epoxide hydrolase (meh), apical sodium-dependent bile acid transporter (asbt), multidrug resistance-associated protein 3 (mrp3), farnesoid X receptor (fxr) and G protein-coupled bile acid receptor 5 (tgr5) were significantly decreased (P < 0.05). Compared to CD group, the mRNA relative expression of mdr3, asbt, mrp3, organic anion transporters 1 (oatp1), meh, fxr and tgr5 were significantly decreased in HPD group (P < 0.05). In summary, HLD affects intestinal microbiota, BA metabolism, and lipid metabolism, leading to lipid deposition and liver damage. HPD regulates gut microbiota, BA metabolism, inflammatory responses, and BA receptor expression, impairing grouper liver health. HLPD synergistically combines the adverse effects of HLD and HPD on grouper liver health.

An integrative lipidomics and transcriptomics study revealing Bavachin and Icariin synergistically induce idiosyncratic liver injury

Objectives: Reports of traditional Chinese medicine (TCM)-related liver injury have increased over recent years; however, identifying susceptibility-related components and biomarkers remains challenging due to the heterogeneous nature of TCM and idiosyncratic drug-induced liver injury (IDILI). Psoraleae Fructus (PF) and Epimedii Folium (EF), commonly found in TCM prescriptions, have been implicated in IDILI, but their constituents and underlying mechanisms are poorly understood.

Methods: In this study, we identified bavachin (Bav) and icariin (Ica) as susceptibility components for IDILI in PF and EF using a TNF-α-mediated mouse model. Lipidomics and transcriptomics were used to investigate their related mechanism.

Results: Liver biochemistry and histopathology analyses revealed that co-exposure to Bav, Ica, and a non-toxic dose of TNF-α prestimulation induced significant liver injury, while Bav and Ica alone did not. Lipidomics identified seven differentially abundant metabolites in the Bav/Ica/TNF-α group compared to the Ica/TNF-α or Bav/TNF-α groups, mainly enriched in alpha-linolenic acid (ALA), arachidonic acid (AA), and linoleic acid (LA) metabolic pathways. Additionally, transcriptomics revealed 49 differentially expressed genes (DEGs) in the Bav/TNF-α vs Bav/Ica/TNF-α and Ica/TNF-α vs Bav/Ica/TNF-α groups, primarily associated with the PI3K/AKT/mTOR signaling pathway and sphingolipid metabolism. Integrative lipidomics and transcriptomics analyses identified significant positive correlations between five differential metabolites (DMs) - PC (O-16:0_14:1), PG (22:1_20:3), PI (16:0_14:1), PS (18:0_19:2), and TG (17:0_18:2_22:5) - and ten DEGs - Nr0b2, Btbd19, Btg2, Fam222a, Fam83f, Gtse1, Anln, Gja4, Srrm4, and Zfp13.

Conslusions: Collectively, these results suggest that alterations in intracellular metabolism and gene expression levels may contribute to the synergistic induction of IDILI by the incompatible pair Bav and Ica in the presence of TNF-α.

Design, synthesis and FXR partial agonistic activity of anthranilic acid derivatives bearing aryloxy moiety as therapeutic agents for metabolic dysfunction-associated steatohepatitis

Farnesoid X receptor (FXR) is considered a promising therapeutic target for the treatment of metabolic dysfunction-associated steatohepatitis (MASH). Increasing evidence suggests that targeting FXR with full agonists may lead to side effects. FXR partial agonists, which moderately activate FXR signaling, are emerging as a feasible approach to mitigate side effects and address MASH. Herein, a series of novel anthranilic acid derivatives bearing aryloxy moiety were designed and synthesized using a hybrid strategy from the previously identified FXR partial agonists DM175 and AIV-25. Particularly, compound 26 exhibited potent FXR partial agonistic activity in a dual-luciferase reporter gene assay with an EC50 value of 0.09 ± 0.02 µM (75.13 % maximum efficacy relative to OCA). In the MASH mice model, compound 26 significantly ameliorated the pathological features of the liver, including steatosis, inflammation, and fibrosis. In addition, compound 26 displayed high selectivity, good oral bioavailability, high liver distribution, as well as an acceptable safety profile. Molecular simulation studies showed that compound 26 fitted well with the binding site of FXR. Collectively, these findings demonstrated that compound 26 might serve as a promising candidate targeting FXR for MASH treatment.

Replacement of fish meal with full fat Hermetia illucens modulates hepatic FXR signaling in juvenile rainbow trout (Oncorhynchus mykiss): Exploring a potential role of ecdysteroids

The present study was conducted to investigate the effects of fish meal (FM) replacement with full fat Hermetia illucens (HI) on the molecular mechanisms regulating lipid and bile salt (BA) homeostasis in rainbow trout (Oncorhynchus mykiss) juveniles. We thus explore the presence of 20-hydroxyecdysone (20E) in an insect meal-based diet and evaluate its potential involvement in regulating the molecular mechanisms/basis of FXR:RXR axis signaling. Ecdysteroids are a category of steroid hormones which bind a nuclear-receptor complex composed of ecdysone receptor (EcR) and ultraspiracle protein (USP) and regulate insect molting and metamorphosis. In all vertebrates, including fish, EcR-USP homologs are the Farnesoid X receptors (FXR) and the Retinoid X receptors (RXR), which are known to regulate crucial physiological and metabolic aspects, including BA synthesis and cholesterol homeostasis. In silico prediction indicates that 20E binds the heterodimeric complex with a binding affinity constant Kd equals to 610 ± 60 nM and affects positively the dimerization process. Results also demonstrated the coordinated increased expression of FXR and RXR, as well as their downstream target genes (i.e. short heterodimer partner 1 and 2) in rainbow trout fed diets containing HI meal. This latter finding was paralleled by a significant down-regulation of CYP7a1 and CYP8b1 gene expression together with a decrease in hepatic total cholesterol, triglyceride, and BA levels. Overall, our study suggested that FXR is a potential target for 20E content in insect meal and provided preliminary data on the potential role of ecdysteroids in regulating the metabolic status of teleost fish through modulation of FXR signaling in the enterohepatic system.

Metabolic Dysfunction Associated Fatty Liver Disease in Long-Term Cholecystectomy Patients: A Cross-Sectional Study

Background/Aims

Cholecystectomy, while generally safe with low perioperative morbidity and mortality, has been linked to an increase in metabolic disorders. Metabolic dysfunction-associated fatty liver disease (MAFLD) is a globally prevalent condition that leads to both hepatic and systemic complications. This study aimed to investigate the association between cholecystectomy and MAFLD.

Materials and Methods

This cross-sectional study was designed to evaluate the relationship between cholecystectomy and MAFLD. Metabolic dysfunction-associated fatty liver disease was defined by the presence of hepatic steatosis in combination with any of the following conditions: diabetes mellitus (fasting plasma glucose ≥126 mg/dL), overweight (body mass index (BMI) ≥25 kg/m2), or metabolic dysregulation.

Results

A total of 163 participants with BMI ≥25 kg/m2, including consecutive cholecystectomized (N = 83) and non-cholecystectomized (N = 80) subjects, were included. The prevalence of MAFLD was found in 64 out of 83 (77.1%) cholecystectomized patients and in 30 out of 80 (37.5%) non-cholecystectomized subjects (P < .001). When age, gender, BMI, exercise habits, hypertension, diabetes mellitus, and cholecystectomy status were included in regression analyses, we found that only BMI [odds ratio (OR) = 1.155 (95% CI: 1.040-1.283)] and cholecystectomy [OR = 4.540 (95% CI: 2.200-9.370)] were independently associated with MAFLD (both P < .01). ROC analysis identified 10 years as the cut-off, with MAFLD risk being 2.7-7.3 times higher in patients with cholecystectomy for ≤10 and >10 years.

Conclusion

In our study, MAFLD was found to be 4.5 times more likely in cholecystectomized patients compared to those without cholecystectomy, with a significant increase in frequency observed after 10 years. These results suggest that cholecystectomized patients should be monitored for MAFLD.

Lactiplantibacillus plantarum Y44 Complex Fermented Milk Regulates Lipid Metabolism in Mice Fed with High-Fat Diet by Modulating Gut Microbiota

The benefits of fermented milk containing Lactiplantibacillus plantarum (L. plantarum) Y44, known for its weight loss properties, remain unclear. For this, we evaluated the effects of the complex fermented milk (Y44-CFM), obtained through the cofermentation of cow's milk and soybean milk with L. plantarum Y44 and traditional starters, on high-fat diet (HFD)-fed C57BL/6 mice. Our study found that the oral administration of Y44-CFM significantly reduced body weight gain and hepatic lipid accumulation in HFD-fed mice while also mitigating liver injury. Additionally, Y44-CFM regulated the expression of enzymes associated with lipid metabolism in the serum, as well as the corresponding or related genes in the liver, such as fatty acid synthase. Furthermore, HFD-induced systemic inflammation, oxidative stress, and intestinal barrier dysfunction were improved. The primary alterations in hepatic metabolism involved glycerophospholipids and amino acids, including the biosynthesis of valine, leucine, and isoleucine. The diversity and overall structure of the gut microbiota were also regulated, resulting in a significant decrease in the ratio of Firmicutes to Bacteroidetes (F/B) and unclassified_f_Lachnospiraceae, along with a notable increase in Oscillospiraceae. The correlation analysis indicated that Y44-CFM influenced hepatic lipid metabolism by mediating intestinal flora and its production of short-chain fatty acids, ultimately leading to weight reduction.

Aristolochic acid-induced dyslipidemia and hepatotoxicity: The potential role of FXR and AHR receptors

Aristolochic acids (AAs) represent a class of nitrophenanthrene carboxylic acids naturally existing or accidentally mixed in herbal medicines or crops, which have long been recognized for causing nephropathy. Recently, the linkage between AAs and liver injury has become a concern; however, the current understanding of the mechanism or mode of action (MOA) is limited. In the present study, we investigated nuclear receptor-mediated MOA associated with AAs-induced liver injury including dyslipidemia and hepatotoxicity. Bioinformatic analysis of AAI-interacting genes indicated nuclear receptor-mediated metabolizing pathways; Transcriptomic profiling of AAs-exposed rats with liver injury suggested FXR-, NRF2-, and AHR- mediated pathways in the injured livers of the rats. Mechanistic investigation using HepG2 cells indicated AAI-induced hepatic lipid accumulation by elevating Triglyceride (TG) through inhibition of the FXR. In addition, AAI-induced hepatocellular damage by activating the AHR pathway, which further generated ROS and activated the NRF2 pathway. Together, these results provided new clues for researchers who are interested in chemical-induced liver injury.

Biological functions and pharmacological behaviors of bile acids in metabolic diseases

BACKGROUND

Bile acids, synthesized endogenously from cholesterol, play a central role in metabolic regulation within the enterohepatic circulatory system. Traditionally known as emulsifying agents that facilitate the intestinal absorption of vitamins and lipids, recent research reveals their function as multifaceted signal modulators involved in various physiological processes. These molecules are now recognized as key regulators of chronic metabolic diseases and immune dysfunction. Despite progress in understanding their roles, their structural diversity and the specific functions of individual bile acids remain underexplored.

AIM OF REVIEW

This study categorizes the bile acids based on their chemical structures and their roles as signaling molecules in physiological processes. It consolidates current knowledge and provides a comprehensive overview of the current research. The review also includes natural and semisynthetic variants that have demonstrated potential in regulating metabolic processes in animal models or clinical contexts.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Bile acids circulate primarily within the enterohepatic circulation, where they help maintain a healthy digestive system. Disruptions in their balance are linked to metabolic disorders, hepatobiliary diseases and intestinal inflammation. Through receptor-mediated pathways, bile acids influence the progression of metabolic diseases by regulating glucose and lipid metabolism, immune function, and energy expenditure. This review aims to provide a comprehensive, systematic foundation to for understanding their physiological roles and supporting future therapeutic developments for metabolic and inflammatory diseases.

Free fatty acids induce bile acids overproduction and oxidative damage of bovine hepatocytes via inhibiting FXR/SHP signaling

Hepatic oxidative injury induced by free fatty acids (FFA) and metabolic disorders of bile acids (BA) increase the risk of metabolic diseases in dairy cows during perinatal period. However, the effects of FFA on BA metabolism remained poorly understood. In present study, high concentrations of FFA caused cell impairment, oxidative stress and BA overproduction. FFA treatment increased the expression of BA synthesis-related genes [cholesterol 7a-hydroxylase (CYP7A1), hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 7, sterol 12α-hydroxylase, sterol 27-hydroxylase and oxysterol 7α-hydroxylase], whereas reduced BA exportation gene (ATP binding cassette subfamily C member 1) and inhibited farnesoid X receptor/small heterodimer partner (FXR/SHP) pathway in bovine hepatocytes. Knockdown of nuclear receptor subfamily 1 group H member 4 (NR1H4) worsened FFA-caused oxidative damage and BA production, whereas overexpression NR1H4 ameliorated FFA-induced BA production and cell oxidative damage. Besides, reducing BA synthesis through knockdown of CYP7A1 can alleviate oxidative stress and hepatocytes impairment caused by FFA. In summary, these data demonstrated that regulation of FXR/SHP-mediated BA metabolism may be a promising target in improving hepatic oxidative injury of dairy cows during high levels of FFA challenges.

Intrauterine exposure to long-chain perfluorocarboxylic acids (PFCAs) were associated with reduced primary bile acids in three-year-old children: Findings from a prospective birth cohort study

Bile acids (BAs) play a crucial role in lipid metabolism of children. However, the association between per- and polyfluoroalkyl substance (PFAS) exposure and BAs in children is scarce. To address this need, we selected 252 children from the Maoming Birth Cohort and measured 32 PFAS, encompassing short- and long-chain perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) in the cord blood. Additionally, we analyzed nine primary and eight secondary BAs in the serum of three-year-old children. Generalized linear models with FDR-adjusted and Bayesian kernel machine regression (BKMR) were used to explore the associations of individual and mixture effects of PFAS and BAs. We found negative associations between cord blood long-chain PFCAs exposure and serum primary BAs in three-year-old children. For example, one ln-unit (ng/mL) increase of perfluoro-n-tridecanoic acid (PFTrDA), perfluoro-n-undecanoic acid (PFUnDA) and perfluoro-n-decanoic acid (PFDA) were associated with decreased taurochenodeoxycholic acid, with estimated percentage change of -24.28% [95% confidence interval (CI): -36.75%, -9.35%], -25.84% (95% CI: -39.67%, -8.83%), and -22.97% (95% CI: -34.45%, -9.47%) respectively. Notably, the observed associations were more pronounced in children with lower vegetable intake. Additionally, the BKMR model also demonstrated a monotonical decline in primary BAs as the PFAS mixture increased. We provided the first evidence of the association between intrauterine exposure to PFAS and its mixture with BAs in children. Further large-sample-size studies are needed to verify this finding.

Silibinin, a commonly used therapeutic agent for non-alcohol fatty liver disease, functions through upregulating intestinal expression of fibroblast growth factor 15/19

BACKGROUND AND PURPOSE

Silibinin is used to treat non-alcohol fatty liver disease (NAFLD) despite having rapid liver metabolism. Therefore, we investigated the role of the intestine in silibinin mechanism of action.

EXPERIMENTAL APPROACH

NAFLD mice model was established by feeding them with a high-fat diet (HFD). Liver pathological were examined using H&E and oil red O staining. Tissue distribution of silibinin was detected by LC-MS/MS. SiRNA was employed for gene silencing and plasmid was used for gene overexpression. ChIP-qPCR assay was performed to detect the levels of histone acetylation. Recombinant adeno-associated virus 9-short hairpin-fibroblast growth factor (FGF)-15 and -farnesoid X receptor (FXR; NR1H4) were used to knockdown expression of FGF-15 and FXR.

KEY RESULTS

Oral silibinin significantly reversed NAFLD in mice, although liver concentration was insufficient for reduction of lipid accumulation in hepatocytes. Among endogenous factors capable of reversing NAFLD, the expression of Fgf-15 was selectively up-regulated by silibinin in ileum and colon of mice. When intestinal expression of Fgf-15 was knocked down, protection of silibinin against lipid accumulation and injury of livers nearly disappeared. Silibinin could reduce activity of histone deacetylase 2 (HDAC2), enhance histone acetylation in the promoter region of FXR and consequently increase intestinal expression of FGF-15/19.

CONCLUSION AND IMPLICATIONS

Oral silibinin selectively promotes expression of FGF-15/19 in ileum by enhancing transcription of FXR via reduction of HDAC2 activity, and FGF-15/19 enters into circulation to exert anti-NAFLD action. As the site of action is the intestine this would explain the discrepancy between pharmacodynamics and pharmacokinetics of silibinin.

Potential therapeutic strategies for MASH: from preclinical to clinical development

Current treatment paradigms for metabolic dysfunction-associated steatohepatitis (MASH) are based primarily on dietary restrictions and the use of existing drugs, including anti-diabetic and anti-obesity medications. Given the limited number of approved drugs specifically for MASH, recent efforts have focused on promising strategies that specifically target hepatic lipid metabolism, inflammation, fibrosis, or a combination of these processes. In this review, we examined the pathophysiology underlying the development of MASH in relation to recent advances in effective MASH therapy. Particularly, we analyzed the effects of lipogenesis inhibitors, nuclear receptor agonists, glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) agonists, fibroblast growth factor mimetics, and combinatorial therapeutic approaches. We summarize these targets along with their preclinical and clinical candidates with the ultimate goal of optimizing the therapeutic prospects for MASH.

Exploring the role of a novel postbiotic bile acid: Interplay with gut microbiota, modulation of the farnesoid X receptor, and prospects for clinical translation

The gut microbiota, mainly resides in the colon, possesses a remarkable ability to metabolize different substrates to create bioactive substances, including short-chain fatty acids, indole-3-propionic acid, and secondary bile acids. In the liver, bile acids are synthesized from cholesterol and then undergo modification by the gut microbiota. Beyond those reclaimed by the enterohepatic circulation, small percentage of bile acids escaped reabsorption, entering the systemic circulation to bind to several receptors, such as farnesoid X receptor (FXR), thereby exert their biological effects. Gut microbiota interplays with bile acids by affecting their synthesis and determining the production of secondary bile acids. Reciprocally, bile acids shape out the structure of gut microbiota. The interplay of bile acids and FXR is involved in the development of multisystemic conditions, encompassing metabolic diseases, hepatobiliary diseases, immune associated disorders. In the review, we aim to provide a thorough review of the intricate crosstalk between the gut microbiota and bile acids, the physiological roles of bile acids and FXR in mammals' health and disease, and the clinical translational considerations of gut microbiota-bile acids-FXR in the treatment of the diseases.

Isorhamnetin in Quinoa Whole-Grain Flavonoids Intervenes in Non-Alcoholic Fatty Liver Disease by Modulating Bile Acid Metabolism through Regulation of FXR Expression

Non-alcoholic fatty liver disease (NAFLD) is a severe hepatic health threat with no effective treatment. Based on the results that Chenopodium quinoa Willd. flavonoids eluted with 30% ethanol (CQWF30) can effectively alleviate NAFLD, this study employed ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) to analyze the components of CQWF30., and screened for flavonoids with potential NAFLD-mitigating effects through network pharmacology. In vitro models using HepG2 and BEL-7402 cell lines induced with free fatty acid (FFA) showed that isorhamnetin administration reduced intracellular lipid deposition and reversed elevated triglyceride (TG) and total cholesterol (T-CHO) levels. In vivo experiments in high-fat diet (HFD) mice demonstrated that isorhamnetin significantly lowered serum and liver fat content, mitigated liver damage, and modulated bile acid metabolism by upregulating FXR and BSEP and downregulating SLCO1B3. Consequently, isorhamnetin shows promise as a treatment for NAFLD due to its lipid-lowering and hepatoprotective activities.

Nogo-B inhibition facilitates cholesterol metabolism to reduce hypercholesterolemia

The strategy of lowering cholesterol levels by promoting cholesterol excretion is still lacking, and few molecular targets act on multiple cholesterol metabolic processes. In this study, we find that Nogo-B deficiency/inhibition simultaneously promotes hepatic uptake of cholesterol and cholesterol excretion. Nogo-B deficiency decreases cholesterol levels by activating ATP-binding cassette transporters (ABCs), apolipoprotein E (ApoE), and low-density lipoprotein receptor (LDLR) expression. We discover that Nogo-B interacts with liver X receptor α (LXRα), and Nogo-B deficiency inhibits ubiquitination degradation of LXRα, thereby enhancing its function on cholesterol excretion. Decreased cellular cholesterol levels further activate SREBP2 and LDLR expression, thereby promoting hepatic uptake of cholesterol. Nogo-B inhibition decreases atherosclerotic plaques and cholesterol levels in mice, and Nogo-B levels are correlated to cholesterol levels in human plasma. In this study, Nogo-B deficiency/inhibition not only promotes hepatic uptake of blood cholesterol but also facilitates cholesterol excretion. This study reports a strategy to lower cholesterol levels by inhibiting Nogo-B expression to promote hepatic cholesterol uptake and cholesterol excretion.

Role of Gut Microbial Metabolites in Cardiovascular Diseases-Current Insights and the Road Ahead

Cardiovascular diseases (CVDs) are the leading cause of premature morbidity and mortality globally. The identification of novel risk factors contributing to CVD onset and progression has enabled an improved understanding of CVD pathophysiology. In addition to the conventional risk factors like high blood pressure, diabetes, obesity and smoking, the role of gut microbiome and intestinal microbe-derived metabolites in maintaining cardiovascular health has gained recent attention in the field of CVD pathophysiology. The human gastrointestinal tract caters to a highly diverse spectrum of microbes recognized as the gut microbiota, which are central to several physiologically significant cascades such as metabolism, nutrient absorption, and energy balance. The manipulation of the gut microbial subtleties potentially contributes to CVD, inflammation, neurodegeneration, obesity, and diabetic onset. The existing paradigm of studies suggests that the disruption of the gut microbial dynamics contributes towards CVD incidence. However, the exact mechanistic understanding of such a correlation from a signaling perspective remains elusive. This review has focused upon an in-depth characterization of gut microbial metabolites and their role in varied pathophysiological conditions, and highlights the potential molecular and signaling mechanisms governing the gut microbial metabolites in CVDs. In addition, it summarizes the existing courses of therapy in modulating the gut microbiome and its metabolites, limitations and scientific gaps in our current understanding, as well as future directions of studies involving the modulation of the gut microbiome and its metabolites, which can be undertaken to develop CVD-associated treatment options. Clarity in the understanding of the molecular interaction(s) and associations governing the gut microbiome and CVD shall potentially enable the development of novel druggable targets to ameliorate CVD in the years to come.

Nonlipogenic ABCA1 Inducers (NLAI) for Alzheimer's Disease Validated in a Mouse Model Expressing Human APOE3/APOE4

Therapeutics enhancing apolipoprotein (APOE) positive function are a priority, because APOE4 is the major genetic risk factor for Alzheimer's disease (AD). The function of APOE, the key constituent of lipoprotein particles that transport cholesterol and lipids in the brain, is dependent on lipidation by ABCA1, a cell-membrane cholesterol transporter. ABCA1 transcription is regulated by liver X receptors (LXR): agonists have been shown to increase ABCA1, often accompanied by unwanted lipogenesis and elevated triglycerides (TG). Therefore, nonlipogenic ABCA1-inducers (NLAI) are needed. Two rounds of optimization of an HTS hit, derived from a phenotypic screen, gave lead compound 39 that was validated and tested in E3/4FAD mice that express human APOE3/4 and five mutant APP and PSEN1 human transgenes. Treatment with 39 increased ABCA1 expression, enhanced APOE lipidation, and reversed multiple AD phenotypes, without increasing TG. This NLAI/LXR-agonist study is the first in a human APOE-expressing model with hallmark amyloid-β pathology.

Natural bioactive compounds-The promising candidates for the treatment of intestinal failure-associated liver disease

Parenteral nutrition (PN) is a life-saving procedure conducted to maintain a proper nutritional state in patients with severe intestinal failure who cannot be fed orally. A serious complication of PN therapy is liver failure, known as intestinal failure-associated liver disease (IFALD). The pathogenesis of IFALD is multifactorial and includes inhibition of the farnesoid X receptor (FXR) by PN components, bacteria translocation from impaired intestines, and intravenous line-associated bloodstream infection. Currently, the most frequently researched therapeutic option for IFALD is using lipid emulsions based on soy or fish oil and, therefore, free from phytosterols known as FXR antagonists. Nevertheless, the potential side effects of the lack of soybean oil delivery seem to outweigh the benefits, especially in the pediatric population. PN admixture provides all the necessary nutrients; however, it is deprived of exogenous natural bioactive compounds (NBCs) of plant origin, such as polyphenols, characterized by health-promoting properties. Among them, many substances have already been known to demonstrate the hepatoprotective effect in various liver diseases. Therefore, searching for new therapeutic options for IFALD among NBCs seems reasonable and potentially successful. This review summarizes the recent research on polyphenols and their use in treating various liver diseases, especially metabolic dysfunction-associated steatotic liver diseases (MASLD). Furthermore, based on scientific reports, we have described the molecular mechanism of action of selected NBCs that exert hepatoprotective properties. We also summarized the current knowledge on IFALD pathogenesis, described therapeutic options undergoing clinical trials, and presented the future perspective of the potential use of NBCs in PN therapy.

High-fat diet modulates bile acid composition and gut microbiota, affecting severe cholangitis and cirrhotic change in murine primary biliary cholangitis

Increasing evidence suggests that, in addition to a loss of tolerance, bile acid (BA) modulates the natural history of primary biliary cholangitis (PBC). We focused on the impacts of dietary changes on the immunopathology of PBC, along with alterations in BA composition and gut microbiota. In this study, we have taken advantage of our unique PBC model, a Cyp2c70/Cyp2a12 double knockout (DKO), which includes a human-like BA composition, and develops progressive cholangitis following immunization with the PDC-E2 mimic, 2-octynoic acid (2OA). We compared the effects of a ten-week high-fat diet (HFD) (60 % kcal from fat) and a normal diet (ND) on 2OA-treated DKO mice. Importantly, we report that 2OA-treated DKO mice fed HFD had significantly exacerbated cholangitis, leading to cirrhosis, with increased hepatic expression of Th1 cytokines/chemokines and hepatic fibrotic markers. Serum lithocholic acid (LCA) levels and the ratio of chenodeoxycholic acid (CDCA)-derived BAs to cholic acid-derived BAs were significantly increased by HFD. This was also associated with downregulated expression of key regulators of BA synthesis, including Cyp8b1, Cyp3a11, and Sult2a1. In addition, there were increases in the relative abundances of Acetatifactor and Lactococcus and decreases in Desulfovibrio and Lachnospiraceae_NK4A136_group, which corresponded to the abundances of CDCA and LCA. In conclusion, HFD and HFD-induced alterations in the gut microbiota modulate BA composition and nuclear receptor activation, leading to cirrhotic change in this murine PBC model. These findings have significant implications for understanding the progression of human PBC.

Gypensapogenin A-Liposomes Efficiently Ameliorates Hepatocellular Lipid Accumulation via Activation of FXR Receptor

Non-alcoholic fatty liver disease (NAFLD) is one of the most common metabolic diseases encountered in clinical practice, which is characterized by the excessive accumulation of triglycerides (steatosis), and a variety of metabolic abnormalities including lipid metabolism and bile acid metabolism are closely related to NAFLD. In China, Gynostemma pentaphyllum is used as functional food and Chinese medicine to treat various diseases, especially NAFLD, for a long time. However, the active components that exert the main therapeutic effects and their mechanisms remain unclear. In this study, Gypensapogenin A was isolated from the total saponins of G. pentaphyllum and prepared as a liposomal delivery system. Gypensapogenin A liposomes could activate FXR, inhibit the expression of CYP7A1 and CYP8B1, increase the expression of CYP27A1, modulate the ratio of CA and CDCA, decrease the content of CA, and increase the content of CDCA, thus forming a virtuous cycle of activating FXR to play a role in lowering blood lipid levels.

Correlation between ZJU index and hepatic steatosis and liver fibrosis in American adults with NAFLD

Background

ZJU index, a novel calculation combining blood glucose, body mass index (BMI), lipids and liver functions, is closely related with non-alcoholic fatty liver disease (NAFLD). However, the correlation between ZJU index and hepatic steatosis and liver fibrosis has not been reported in the studies. This study aims to examine the correlation between these variables.

Methods

Data from the 2017-2020 NHANES were collected for a cross-sectional study, to explore the linear relationship between ZJU, liver stiffness measurements (LSM) and controlled attenuation parameters (CAP) with multivariate linear regression models. Restricted cubic spline (RCS) regression and threshold effect analyses were utilized to describe the nonlinear relationship. The correlation in subgroups was analyzed based on race, gender, drinking, age, BMI, diabetes and moderate activities.

Results

In this population-based study, a total of 2,122 adults aged 18-80 years old with NAFLD were included. According to the multivariate linear regression analysis, ZJU had a significant positive correlation with liver fibrosis (LSM, β = 0.182, 95%CI = 0.154-0.211, p < 0.001) and hepatic steatosis (CAP, β = 2.35, 95%CI = 2.14-2.56, p < 0.001), which was stronger in males. According to the RCS analysis, an inverted L-shaped relationship between ZJU and CAP (inflection point at 60.56) and a J-shaped relationship between ZJU index and LSM (inflection point at 51.27) were observed.

Conclusion

ZJU had a positive correlation with CAP and LSM in American adults with NAFLD. The findings suggest that ZJU may be a valuable biomarker for assessing the severity of liver fibrosis and hepatic steatosis in individuals with NAFLD.

Dietary fiber alleviates alcoholic liver injury via Bacteroides acidifaciens and subsequent ammonia detoxification

The gut microbiota and diet-induced changes in microbiome composition have been linked to various liver diseases, although the specific microbes and mechanisms remain understudied. Alcohol-related liver disease (ALD) is one such disease with limited therapeutic options due to its complex pathogenesis. We demonstrate that a diet rich in soluble dietary fiber increases the abundance of Bacteroides acidifaciens (B. acidifaciens) and alleviates alcohol-induced liver injury in mice. B. acidifaciens treatment alone ameliorates liver injury through a bile salt hydrolase that generates unconjugated bile acids to activate intestinal farnesoid X receptor (FXR) and its downstream target, fibroblast growth factor-15 (FGF15). FGF15 promotes hepatocyte expression of ornithine aminotransferase (OAT), which facilitates the metabolism of accumulated ornithine in the liver into glutamate, thereby providing sufficient glutamate for ammonia detoxification via the glutamine synthesis pathway. Collectively, these findings uncover a potential therapeutic strategy for ALD involving dietary fiber supplementation and B. acidifaciens.

Pathophysiological Relationship between Type 2 Diabetes Mellitus and Metabolic Dysfunction-Associated Steatotic Liver Disease: Novel Therapeutic Approaches

Type 2 diabetes mellitus (T2DM), often featuring hyperglycemia or insulin resistance, is a global health concern that is increasing in prevalence in the United States and worldwide. A common complication is metabolic dysfunction-associated steatotic liver disease (MASLD), the hepatic manifestation of metabolic syndrome that is also rapidly increasing in prevalence. The majority of patients with T2DM will experience MASLD, and likewise, individuals with MASLD are at an increased risk for developing T2DM. These two disorders may act synergistically, in part due to increased lipotoxicity and inflammation within the liver, among other causes. However, the pathophysiological mechanisms by which this occurs are unclear, as is how the improvement of one disorder can ameliorate the other. This review aims to discuss the pathogenic interactions between T2D and MASLD, and will highlight novel therapeutic targets and ongoing clinical trials for the treatment of these diseases.

Altered lipid metabolism and the development of metabolic-associated fatty liver disease

PURPOSE OF REVIEW

An increasing amount of research has underscored the significant role of lipoproteins in the pathogenesis of metabolic-associated fatty liver disease (MAFLD). This comprehensive review examines the intricate relationship between lipoprotein abnormalities and the development of MAFLD.

RECENT FINDINGS

Atherogenic dyslipidemia seen in insulin resistance states play a significant role in initiating and exacerbating hepatic lipid accumulation. There are also specific genetic factors ( PNPLA3 , TM6SF2 , MBOAT7 , HSD17B13 , GCKR- P446L) and transcription factors (SREBP-2, FXR, and LXR9) that increase susceptibility to both lipoprotein disorders and MAFLD. Most monogenic primary lipid disorders do not cause hepatic steatosis unless accompanied by metabolic stress. Hepatic steatosis occurs in the presence of secondary systemic metabolic stress in conjunction with predisposing environmental factors that lead to insulin resistance. Identifying specific aberrant lipoprotein metabolic factors promoting hepatic fat accumulation and subsequently exacerbating steatohepatitis will shed light on potential targets for therapeutic interventions.

SUMMARY

The clinical implications of interconnection between genetic factors and an insulin resistant environment that predisposes MAFLD is many fold. Potential therapeutic strategies in preventing or mitigating MAFLD progression include lifestyle modifications, pharmacological interventions, and emerging therapies targeting aberrant lipoprotein metabolism.

Farnesoid X receptor: From Structure to Function and Its Pharmacology in Liver Fibrosis

The farnesoid X receptor (FXR), a ligand-activated transcription factor, plays a crucial role in regulating bile acid metabolism within the enterohepatic circulation. Beyond its involvement in metabolic disorders and immune imbalances affecting various tissues, FXR is implicated in microbiota modulation, gut-to-brain communication, and liver disease. The liver, as a pivotal metabolic and detoxification organ, is susceptible to damage from factors such as alcohol, viruses, drugs, and high-fat diets. Chronic or recurrent liver injury can culminate in liver fibrosis, which, if left untreated, may progress to cirrhosis and even liver cancer, posing significant health risks. However, therapeutic options for liver fibrosis remain limited in terms of FDA-approved drugs. Recent insights into the structure of FXR, coupled with animal and clinical investigations, have shed light on its potential pharmacological role in hepatic fibrosis. Progress has been achieved in both fundamental research and clinical applications. This review critically examines recent advancements in FXR research, highlighting challenges and potential mechanisms underlying its role in liver fibrosis treatment.

Modulation of the Serum Metabolome by the Short-Chain Fatty Acid Propionate: Potential Implications for Its Cholesterol-Lowering Effect

(1) Background: Dyslipidemia represents a major risk factor for atherosclerosis-driven cardiovascular disease. Emerging evidence suggests a close relationship between cholesterol metabolism and gut microbiota. Recently, we demonstrated that the short-chain fatty acid (SCFA) propionate (PA) reduces serum cholesterol levels through an immunomodulatory mechanism. Here, we investigated the effects of oral PA supplementation on the human serum metabolome and analyzed changes in the serum metabolome in relation to the cholesterol-lowering properties of PA. (2) Methods: The serum metabolome of patients supplemented with either placebo or propionate orally for 8 weeks was assessed using a combination of flow injection analysis-tandem (FIA-MS/MS) as well as liquid chromatography (LC-MS/MS) and mass spectrometry using a targeted metabolomics kit (MxP®Quant 500 kit: BIOCRATES Life Sciences AG, Innsbruck, Austria). A total of 431 metabolites were employed for further investigation in this study. (3) Results: We observed a significant increase in distinct bile acids (GCDCA: fold change = 1.41, DCA: fold change = 1.39, GUDCA: fold change = 1.51) following PA supplementation over the study period, with the secondary bile acid DCA displaying a significant negative correlation with the serum cholesterol levels. (4) Conclusions: Oral supplementation with PA modulates the serum metabolome with a particular impact on the circulatory bile acid profile. Since cholesterol and bile acid metabolism are interconnected, the elevation of the secondary bile acid DCA may contribute to the cholesterol-lowering effect of PA.

New advances in drug development for metabolic dysfunction-associated diseases and alcohol-associated liver disease

Metabolic disorders are currently threatening public health worldwide. Discovering new targets and developing promising drugs will reduce the global metabolic-related disease burden. Metabolic disorders primarily consist of lipid and glucose metabolic disorders. Specifically, metabolic dysfunction-associated steatosis liver disease (MASLD) and alcohol-associated liver disease (ALD) are two representative lipid metabolism disorders, while diabetes mellitus is a typical glucose metabolism disorder. In this review, we aimed to summarize the new drug candidates with promising efficacy identified in clinical trials for these diseases. These drug candidates may provide alternatives for patients with metabolic disorders and advance the progress of drug discovery for the large disease burden.

Genipin improves obesity through promoting bile secretion and changing bile acids composition in diet-induced obese rats

OBJECTIVES

Bile acids (BAs), as signaling molecules to regulate metabolism, have received considerable attention. Genipin is an iridoid compound extracted from Fructus Gradeniae, which has been shown to relieve adiposity and metabolic syndrome. Here, we investigated the mechanism of genipin counteracting obesity and its relationship with BAs signals in diet-induced obese (DIO) rats.

METHODS

The DIO rats were received intraperitoneal injections of genipin for 10 days. The body weight, visceral fat, lipid metabolism in the liver, thermogenic genes expressions in brown fat, BAs metabolism and signals, and key enzymes for BAs synthesis were determined.

KEY FINDINGS

Genipin inhibited fat synthesis and promoted lipolysis in the liver, and upregulated thermogenic gene expressions in brown adipose tissue of DIO rats. Genipin increased bile flow rate and upregulated the expressions of aquaporin 8 and the transporters of BAs in liver. Furthermore, genipin changed BAs composition by promoting alternative pathways and inhibiting classical pathways for BAs synthesis and upregulated the expressions of bile acid receptors synchronously.

CONCLUSIONS

These results suggest that genipin ameliorate obesity through BAs-mediated signaling pathways.