Bile acid receptor TGR5 agonism induces NO production and reduces monocyte adhesion in vascular endothelial cells

Exploring the Impact of Intermittent Fasting on Vascular Function and the Immune System: A Narrative Review and Novel Perspective

Vascular function is a critical determinant of cardiovascular health and all-cause mortality. Recent studies have suggested that intermittent fasting, a popular dietary strategy, elicits beneficial effects on vascular function. These studies also suggest that fasting-mediated improvements in vascular function coincide with reductions in systemic inflammation. However, the mechanisms that connect fasting, the immune system, and vascular function remain largely underexplored. The current review summarizes the effects of different intermittent fasting modalities on vascular health, focusing on endothelial dysfunction and arterial stiffness, 2 critical indices of vascular function. Improvements in vascular function are associated with reduced inflammation and are mechanistically linked to decreased circulating immune cells and their accumulation within the vascular wall and perivascular tissue. Recent data show that fasting redistributes circulating and tissue-resident immune cells to the bone marrow, affecting their inflammatory actions. However, there is no direct evidence relating immune cell redistribution to cardiovascular health. By relating fasting-induced immune cell redistribution to reduced inflammation and improved vascular function, we propose an exciting avenue of further exploration is determining whether fasting-induced immune cell redistribution impacts cardiovascular health.

"Gut Microbiota as a Therapeutic Target for Hypertension: Challenges and Insights for Future Clinical Applications" "Gut Microbiota and Hypertension Therapy"

PURPOSE OF REVIEW

Systemic hypertension is a major risk factor for cardiovascular disease and remains challenging to manage despite the widespread use of antihypertensive medications and lifestyle modifications. This review explores the role of gut microbiota in hypertension development and regulation, highlighting key mechanisms such as inflammation, gut-brain axis modulation, and bioactive metabolite production. We also assess the potential of microbiota-targeted therapies for hypertension management.

RECENT FINDINGS

Emerging evidence indicates that microbial dysbiosis, high-salt diets, and gut-derived metabolites such as short-chain fatty acids (SCFAs) and bile acids significantly influence blood pressure regulation. Preclinical and early clinical studies suggest that interventions targeting gut microbiota, including probiotics, prebiotics, synbiotics, fecal microbiota transplantation (FMT), and dietary modifications, may help modulate hypertension. However, variability in gut microbiota composition among individuals and limited human trial data pose challenges to translating these findings into clinical practice. While microbiota-based therapies show promise for hypertension management, further research is needed to establish their efficacy and long-term effects. Large-scale, standardized clinical trials are crucial for understanding the therapeutic potential and limitations of gut microbiota interventions. A deeper understanding of the gut-hypertension axis could lead to novel, personalized treatment strategies for hypertension.

TGR5 Activation by Dietary Bioactives and Related Improvement in Mitochondrial Function for Alleviating Diabetes and Associated Complications

Takeda G protein-coupled receptor 5 (TGR5), also known as G protein-coupled bile acid receptor 1 (GPBAR1), is a cell surface receptor involved in key physiological processes, including glucose homeostasis and energy metabolism. Recent research has focused on the role of TGR5 activation in preventing or treating diabetes while also highlighting its potential impact on the progression of diabetic complications. Functional foods and edible plants have emerged as valuable sources of natural compounds that can activate TGR5, offering potential therapeutic benefits for diabetes management. Despite growing interest, studies on the activation of TGR5 by dietary bioactive compounds remain scattered. This Review aims to provide a comprehensive analysis of how dietary bioactives act as potential agents for TGR5 activation in managing diabetes and its complications. It explores the mechanisms of TGR5 activation through both direct agonistic effects and indirect pathways via modulation of the gut microbiota and bile acid metabolism.

Gut microbial metabolites: The bridge connecting diet and atherosclerosis, and next-generation targets for dietary interventions

Mounting evidence indicates that gut microbial metabolites are central hubs linking the gut microbiota to atherosclerosis (AS). Gut microbiota enriched with pathobiont bacteria responsible for producing metabolites like trimethylamine N-oxide and phenylacetylglutamine are related to an increased risk of cardiovascular events. Furthermore, gut microbiota enriched with bacteria responsible for producing short-chain fatty acids, indole, and its derivatives, such as indole-3-propionic acid, have demonstrated AS-protective effects. This study described AS-related gut microbial composition and how microbial metabolites affect AS. Summary findings revealed gut microbiota and their metabolites-targeted diets could benefit AS treatment. In conclusion, dietary interventions centered on the gut microbiota represent a promising strategy for AS treatment, and understanding diet-microbiota interactions could potentially be devoted to developing novel anti-AS therapies.

The Interplay Between Immunity, Inflammation and Endothelial Dysfunction

The endothelium is pivotal in multiple physiological processes, such as maintaining vascular homeostasis, metabolism, platelet function, and oxidative stress. Emerging evidence in the past decade highlighted the immunomodulatory function of endothelium, serving as a link between innate, adaptive immunity and inflammation. This review examines the regulation of the immune-inflammatory axis by the endothelium, discusses physiological immune functions, and explores pathophysiological processes leading to endothelial dysfunction in various metabolic disturbances, including hyperglycemia, obesity, hypertension, and dyslipidaemia. The final section focuses on the novel, repurposed, and emerging therapeutic targets that address the immune-inflammatory axis in endothelial dysfunction.

The bile acid receptor TGR5 inhibits platelet activation and thrombus formation

Liver failure and cirrhosis are characterized by abnormal hemostasis with aberrant platelet activation. In particular, the consequences of cholestatic liver disease and molecular mechanisms, including the role of bile acids leading to impaired platelet responses, are not well understood. Here, we demonstrate that bile acids inhibit human and murine platelet activation, adhesion and spreading, leading to reduced thrombus formation under flow conditions. We identified the G-protein coupled receptor TGR5 in platelets and provide support for its role as mediator of bile acid-induced impairment of platelet activation. In the liver, TGR5 couples to Gαs proteins, activates the adenylate cyclase to induce a transient cAMP rise and stimulates the MAPK signaling pathway to regulate cholangiocyte proliferation, hepatocyte survival and inflammation. In this report, we demonstrate that the genetic deficiency of TGR5 in mice led to enhanced platelet activation and thrombus formation, suggesting that TGR5 plays an important role in hemostasis. Mechanistically, platelet inhibition is achieved by TGR5 mediated PKA activation and modulation of AKT and ERK1/2 phosphorylation. Thus, this report provides evidence for the ability of TGR5 ligands to reduce platelet activation and identifies TGR5 agonism as a new target for the prevention of cardiovascular diseases.

UDCA ameliorates inflammation driven EMT by inducing TGR5 dependent SOCS1 expression in mouse macrophages

Long-standing chronic inflammation of the digestive tract leads to Inflammatory Bowel Diseases (IBD), comprising Crohn's Disease (CD) and Ulcerative colitis (UC). The persistent prevalence of these conditions in the gut is a predisposing factor for Colitis-Associated Cancer (CAC), one of the most common sub-types of Colorectal Cancer (CRC), emphasizing the role of inflammation in tumorigenesis. Therefore, targeted intervention of chronic intestinal inflammation is a potential strategy for preclusion and treatment of inflammation-driven malignancies. The association between bile acids (BA) and gut immune homeostasis has been explored in the recent past. However, the exact downstream mechanism by which secondary BA successfully regulating intestinal inflammation and inflammation-dependent CAC is unclear. Our study demonstrated that Ursodeoxycholic acid (UDCA), a secondary bile acid of host gut microbial origin, finetunes the dialogue between activated macrophages and intestinal epithelial cells, modulating inflammation-driven epithelial-mesenchymal transition (EMT), a hallmark of cancer. UDCA treatment and dependency on the TGR5/GPBAR1 receptor significantly upregulated the Suppressor of Cytokine Signaling 1 (SOCS1) expression, contributing to the regulation of pro-inflammatory cytokines in activated macrophages. In this study, we also noticed heightened expression of SOCS1 in UDCA-mitigated CAC in the AOM-DSS mouse model with reduced inflammatory gene expression. Overall, our observations highlight the possible utility of UDCA for inflammation-driven intestinal cancer.

Combined analysis of cecal microbiota and metabolomics reveals the intervention mechanism of Dayuan Yin in acute lung injury

The ancient Chinese medicinal formula, Dayuan Yin (DYY), has a long history of use in treating respiratory ailments and is shown to be effective in treating acute infectious diseases. This study aims to explore how DYY may impact intestinal flora and metabolites induced by acute lung injury (ALI). ALI rats were induced with lipopolysaccharide (LPS) to serve as models for assessing the anti-ALI efficacy of DYY through multiple lung injury indices. Changes in intestinal microflora were assessed via 16SrRNA gene sequencing, while cecum contents were analyzed using non-targeted metabonomics. Differential metabolites were identified through data analysis, and correlations between metabolites, microbiota, and inflammatory markers were examined using Pearson's correlation analysis. DYY demonstrated a significant improvement in LPS-induced lung injury and altered the composition of intestinal microorganisms, and especially reduced the potential harmful bacteria and enriched the beneficial bacteria. At the gate level, DYY exhibited a significant impact on the abundance of Bacteroidota and Firmicutes in ALI rats, as well as on the regulation of genera such as Ruminococcus, Lactobacillus, and Romboutsia. Additionally, cecal metabonomics analysis revealed that DYY effectively modulated the abnormal expression of 12 key metabolic biomarkers in ALI rats, thereby promoting intestinal homeostasis through pathways such as purine metabolism. Furthermore, Pearson's analysis indicated a strong correlation between the dysregulation of intestinal microbiota, differential metabolites, and inflammation. These findings preliminarily confirm that ALI is closely related to cecal microbial and metabolic disorders, and DYY can play a protective role by regulating this imbalance, which provides a new understanding of the multi-system linkage mechanism of DYY improving ALI.

Effects of Dietary Ursolic Acid on Growth Performance and Intestinal Health of Largemouth Bass (Micropterus salmoides)

This study aimed to investigate the effects of ursolic acid (UA) on the growth performance and intestinal health of largemouth bass (Micropterus salmoides). Four diets were formulated with UA supplementation at 0, 250, 500, and 1000 mg/kg, defined as the control (CON), UA250, UA500, and UA1000, respectively. After an 8-week feeding experiment, the results showed that, in the UA500 group, the final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) increased, and the feed conversion ratio (FCR) and hepatosomatic index decreased. Total superoxide dismutase (T-SOD) activity exhibited a significant increase, and malondialdehyde (MDA) content decreased. An intestinal histological analysis revealed an improvement in the intestinal structural integrity of the UA500 group. The mRNA relative expression levels of physical barrier-related genes [occludin, claudin-1, and zonula occluden-1 (zo-1)] were upregulated. The mRNA relative expression of interlenkin 10 (il-10) increased, and the mRNA relative expression of interlenkin 1β (il-1β) and tumor necrosis factor-α (tnf-α) significantly decreased. The abundance of Firmicutes and Proteobacteria decreased, and the abundance of Tenericutes increased. The abundance of Mycoplasma, Cyanobium, and Staphylococcus decreased, while the abundance of Clostridium increased. In conclusion, dietary supplementation of UA significantly enhanced the growth performance and antioxidant capacity of largemouth bass while improving intestinal barrier function through its influence on the abundance of intestinal flora, such as Tenericutes, Firmicutes, and Mycoplasma. Optimal dietary UA levels for largemouth bass were determined to be between 498 and 520 mg/kg based on quadratic regression analyses of WGR, SGR, and FCR or T-SOD and MDA content.

TGR5-mediated lateral hypothalamus-dCA3-dorsolateral septum circuit regulates depressive-like behavior in male mice

Although bile acids play a notable role in depression, the pathological significance of the bile acid TGR5 membrane-type receptor in this disorder remains elusive. Using depression models of chronic social defeat stress and chronic restraint stress in male mice, we found that TGR5 in the lateral hypothalamic area (LHA) predominantly decreased in GABAergic neurons, the excitability of which increased in depressive-like mice. Upregulation of TGR5 or inhibition of GABAergic excitability in LHA markedly alleviated depressive-like behavior, whereas down-regulation of TGR5 or enhancement of GABAergic excitability facilitated stress-induced depressive-like behavior. TGR5 also bidirectionally regulated excitability of LHA GABAergic neurons via extracellular regulated protein kinases-dependent Kv4.2 channels. Notably, LHA GABAergic neurons specifically innervated dorsal CA3 (dCA3) CaMKIIα neurons for mediation of depressive-like behavior. LHA GABAergic TGR5 exerted antidepressant-like effects by disinhibiting dCA3 CaMKIIα neurons projecting to the dorsolateral septum (DLS). These findings advance our understanding of TGR5 and the LHAGABA→dCA3CaMKIIα→DLSGABA circuit for the development of potential therapeutic strategies in depression.

Bile Acids and Bilirubin Role in Oxidative Stress and Inflammation in Cardiovascular Diseases

Bile acids (BAs) and bilirubin, primarily known for their role in lipid metabolism and as heme catabolite, respectively, have been found to have diverse effects on various physiological processes, including oxidative stress and inflammation. Indeed, accumulating evidence showed that the interplay between BAs and bilirubin in these processes involves intricate regulatory mechanisms mediated by specific receptors and signaling pathways under certain conditions and in specific contexts. Oxidative stress plays a significant role in the development and progression of cardiovascular diseases (CVDs) due to its role in inflammation, endothelial dysfunction, hypertension, and other risk factors. In the cardiovascular (CV) system, recent studies have suggested that BAs and bilirubin have some opposite effects related to oxidative and inflammatory mechanisms, but this area of research is still under investigation. This review aims to introduce BAs and bilirubin from a biochemical and physiological point of view, emphasizing their potential protective or detrimental effects on CVDs. Moreover, clinical studies that have assessed the association between BAs/bilirubin and CVD were examined in depth to better interpret the possible link between them.

Taurocholic acid ameliorates hypertension through the activation of TGR5 in the hypothalamic paraventricular nucleus

Diets rich in taurine can increase the production of taurine-conjugated bile acids, which are known to exert antihypertensive effects. Despite their benefits to the heart, kidney and arteries, their role in the central nervous system during the antihypertensive process remains unclear. Since hypothalamic paraventricular nucleus (PVN) plays a key role in blood pressure regulation, we aimed to investigate the function of bile acids in the PVN. The concentration of bile acids in the PVN of spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats (WKY) fed with normal chow was measured using LC-MS/MS, which identified taurocholic acid (TCA) as the most down-regulated bile acid. To fully understand the mechanism of TCA's functions in the PVN, bi-lateral PVN micro-infusion of TCA was carried out. TCA treatment in the PVN led to a significant reduction in the blood pressure of SHRs, with decreased plasma levels of norepinephrine and improved morphology of cardiomyocytes. It also decreased the number of c-fos+ neurons, reduced the inflammatory response, and suppressed oxidative stress in the PVN of the SHRs. Most importantly, the TGR5 receptors in neurons and microglia were activated. PVN infusion of SBI-115, a TGR5 specific antagonist, was able to counteract with TCA in the blood pressure regulation of SHRs. In conclusion, TCA supplementation in the PVN of SHRs can activate TGR5 in neurons and microglia, reduce the inflammatory response and oxidative stress, suppress activated neurons, and attenuate hypertension.

Role of the microbiota-gut-heart axis between bile acids and cardiovascular disease

Bile acid (BA) receptors (e.g., farnesoid X-activated receptor, muscarinic receptor) are expressed in cardiomyocytes, endothelial cells, and vascular smooth muscle cells, indicating the relevance of BAs to cardiovascular disease (CVD). Hydrophobic BAs are cardiotoxic, while hydrophilic BAs are cardioprotective. For example, fetal cardiac insufficiency in maternal intrahepatic cholestasis during pregnancy, and the degree of fetal cardiac abnormality, is closely related to the level of hydrophobic BAs in maternal blood and infant blood. However, ursodeoxycholic acid (the most hydrophilic BA) can reverse/prevent these detrimental effects of increased levels of hydrophobic BAs on the heart. The gut microbiota (GM) and GM metabolites (especially secondary BAs) have crucial roles in hypertension, atherosclerosis, unstable angina, and heart failure. Herein, we describe the relationship between CVD and the GM at the BA level. We combine the concept of the "microbiota-gut-heart axis" (MGHA) and postulate the role and mechanism of BAs in CVD development. In addition, the strategies for treating CVD with BAs under the MGHA are proposed.

Bile acid metabolism and signaling in health and disease: molecular mechanisms and therapeutic targets

Bile acids, once considered mere dietary surfactants, now emerge as critical modulators of macronutrient (lipid, carbohydrate, protein) metabolism and the systemic pro-inflammatory/anti-inflammatory balance. Bile acid metabolism and signaling pathways play a crucial role in protecting against, or if aberrant, inducing cardiometabolic, inflammatory, and neoplastic conditions, strongly influencing health and disease. No curative treatment exists for any bile acid influenced disease, while the most promising and well-developed bile acid therapeutic was recently rejected by the FDA. Here, we provide a bottom-up approach on bile acids, mechanistically explaining their biochemistry, physiology, and pharmacology at canonical and non-canonical receptors. Using this mechanistic model of bile acids, we explain how abnormal bile acid physiology drives disease pathogenesis, emphasizing how ceramide synthesis may serve as a unifying pathogenic feature for cardiometabolic diseases. We provide an in-depth summary on pre-existing bile acid receptor modulators, explain their shortcomings, and propose solutions for how they may be remedied. Lastly, we rationalize novel targets for further translational drug discovery and provide future perspectives. Rather than dismissing bile acid therapeutics due to recent setbacks, we believe that there is immense clinical potential and a high likelihood for the future success of bile acid therapeutics.

The role of bile acid receptor TGR5 in regulating inflammatory signalling

Takeda G protein-coupled receptor 5 (TGR5) is a bile acid receptor, and its role in regulating metabolism after binding with bile acids has been established. Since the immune response depends on metabolism to provide biomolecules and energy to cope with challenging conditions, emerging evidence reveals the regulatory effects of TGR5 on the immune response. An in-depth understanding of the effect of TGR5 on immune regulation can help us disentangle the interaction of metabolism and immune response, accelerating the development of TGR5 as a therapeutic target. Herein, we reviewed more than 200 articles published in the last 20 years in PubMed, to discuss the roles of TGR5 in regulating inflammatory response, the molecular mechanism, as well as existing problems. Particularly, its anti-inflammation effect is emphasized.

TGR5 signalling in heart and brain injuries: focus on metabolic and ischaemic mechanisms

The heart and brain are the core organs of the circulation and central nervous system, respectively, and play an important role in maintaining normal physiological functions. Early neuronal and cardiac damage affects organ function. The relationship between the heart and brain is being continuously investigated. Evidence-based medicine has revealed the concept of the "heart- brain axis," which may provide new therapeutic strategies for certain diseases. Takeda protein-coupled receptor 5 (TGR5) is a metabolic regulator involved in energy homeostasis, bile acid homeostasis, and glucose and lipid metabolism. Inflammation is critical for the development and regeneration of the heart and brain during metabolic diseases. Herein, we discuss the role of TGR5 as a metabolic regulator of heart and brain development and injury to facilitate new therapeutic strategies for metabolic and ischemic diseases of the heart and brain.

Bile salt signaling and bile salt-based therapies in cardiometabolic disease

Bile salts have an established role in the emulsification and intestinal absorption of dietary lipids, and their homeostasis is tightly controlled by various transporters and regulators in the enterohepatic circulation. Notably, emerging evidence points toward bile salts as major modulators of cardiometabolic disease (CMD), an umbrella disease of disorders affecting the heart and blood vessels that is caused by systemic metabolic diseases such as Type 2 diabetes mellitus (T2DM) and metabolic dysfunction-associated steatotic liver disease (MASLD), the latter encompassing also metabolic dysfunction-associated steatohepatitis (MASH). The underlying mechanisms of protective effects of bile salts are their hormonal properties, enabling them to exert versatile metabolic effects by activating various bile salt-responsive signaling receptors with the nuclear farnesoid X receptor (FXR) and the Takeda G-protein-coupled receptor 5 (TGR5) as most extensively investigated. Activation of FXR and TGR5 is involved in the regulation of glucose, lipid and energy metabolism, and inflammation. Bile salt-based therapies directly targeting FXR and TGR5 signaling have been evaluated for their therapeutic potential in CMD. More recently, therapeutics targeting bile salt transporters thereby modulating bile salt localization, dynamics, and signaling, have been developed and evaluated in CMD. Here, we discuss the current knowledge on the contribution of bile salt signaling in the pathogenesis of CMD and the potential of bile salt-based therapies for the treatment of CMD.

Mechanistic Review on the Role of Gut Microbiota in the Pathology of Cardiovascular Diseases

Cardiovascular diseases (CVDs), which stand as the primary contributors to illness and death on a global scale, include vital risk factors like hyperlipidemia, hypertension, diabetes, and smoking, to name a few. However, conventional cardiovascular risk factors offer only partial insight into the complexity of CVDs. Lately, a growing body of research has illuminated that the gut microbiome and its by-products are also of paramount importance in the initiation and progression of CVDs. The gastrointestinal tract houses trillions of microorganisms, commonly known as gut microbiota, that metabolize nutrients, yielding substances like trimethylamine-N-oxide (TMAO), bile acids (BAs), short-chain fatty acids (SCFAs), indoxyl sulfate (IS), and so on. Strategies aimed at addressing these microbes and their correlated biological pathways have shown promise in the management and diagnosis of CVDs. This review offers a comprehensive examination of how the gut microbiota contributes to the pathogenesis of CVDs, particularly atherosclerosis, hypertension, heart failure (HF), and atrial fibrillation (AF), explores potential underlying mechanisms, and highlights emerging therapeutic prospects in this dynamic domain.

Bile Acids as Signaling Molecules: Role of Ursodeoxycholic Acid in Cholestatic Liver Disease

Ursodeoxycholic acid (UDCA) is a natural substance physiologically produced in the liver. Initially used to dissolve gallstones, it is now successfully used in treating primary biliary cirrhosis and as adjuvant therapy for various hepatobiliary cholestatic diseases. However, the mechanisms underlying its beneficial effects still need to be clarified. Evidence suggests three mechanisms of action for UDCA that could benefit humans with cholestatic liver disease (CLD): protection of cholangiocytes against hydrophobic bile acid (BA) cytotoxicity, stimulation of hepatobiliary excretion, and protection of hepatocytes against BA-induced apoptosis. These mechanisms may act individually or together to potentiate them. At the molecular level, it has been observed that UDCA can generate modifications in the transcription and translation of proteins essential in the transport of BA, correcting the deficit in BA secretion in CLD, in addition to activating signaling pathways to translocate these transporters to the sites where they should fulfill their function. Inhibition of BA-induced hepatocyte apoptosis may play a role in CLD, characterized by BA retention in the hepatocyte. Thus, different mechanisms of action contribute to the improvement after UDCA administration in CLD. On the other hand, the effects of UDCA on tissues that possess receptors that may interact with BAs in pathological contexts, such as skeletal muscle, are still unclear. This work aims to describe the main molecular mechanisms by which UDCA acts in the human body, emphasizing the interaction in tissues other than the liver.

Danger-associated metabolites trigger metaflammation: A crowbar in cardiometabolic diseases

Cardiometabolic diseases (CMDs) are characterized by a series of metabolic disorders and chronic low-grade inflammation. CMDs contribute to a high burden of mortality and morbidity worldwide. Host-microbial metabolic regulation that triggers metaflammation is an emerging field of study that promotes a new perspective for perceiving cardiovascular risks. The term metaflammation denotes the entire cascade of immune responses activated by a new class of metabolites known as "danger-associated metabolites" (DAMs). It is being proposed by the present review for the first time. We summarize current studies covering bench to bedside aspects of DAMs to better understand CMDs in the context of DAMs. We have focused on the involvement of DAMs in the pathophysiological development of CMDs, including the disruption of immune homeostasis and chronic inflammation-triggered damage leading to CMD-related adverse events, as well as emerging therapeutic approaches for targeting DAM metabolism in CMDs.

Deciphering the role of gut metabolites in non-alcoholic fatty liver disease

Perturbations in microbial abundance or diversity in the intestinal lumen leads to intestinal inflammation and disruption of intestinal membrane which eventually facilitates the translocation of microbial metabolites or whole microbes to the liver and other organs through portal vein. This process of translocation finally leads to multitude of health disorders. In this review, we are going to focus on the mechanisms by which gut metabolites like SCFAs, tryptophan (Trp) metabolites, bile acids (BAs), ethanol, and choline can either cause the development/progression of non-alcoholic fatty liver disease (NAFLD) or serves as a therapeutic treatment for the disease. Alterations in some metabolites like SCFAs, Trp metabolites, etc., can serve as biomarker molecules whereas presence of specific metabolites like ethanol definitely leads to disease progression. Thus, proper understanding of these mechanisms will subsequently help in designing of microbiome-based therapeutic approaches. Furthermore, we have also focussed on the role of dysbiosis on the mucosal immune system. In addition, we would also compile up the microbiome-based clinical trials which are currently undergoing for the treatment of NAFLD and non-alcoholic steatohepatitis (NASH). It has been observed that the use of microbiome-based approaches like prebiotics, probiotics, symbiotics, etc., can act as a beneficial treatment option but more research needs to be done to know how to manipulate the composition of gut microbes.

Bile Acid Network and Vascular Calcification-Associated Diseases: Unraveling the Intricate Connections and Therapeutic Potential

Bile acids play a crucial role in promoting intestinal nutrient absorption and biliary cholesterol excretion, thereby protecting the liver from cholesterol accumulation and bile acid toxicity. Additionally, bile acids can bind to specific nuclear and membrane receptors to regulate energy expenditure and specific functions of particular tissues. Vascular calcification refers to the pathological process of calcium-phosphate deposition in blood vessel walls, which serves as an independent predictor for cardiovascular adverse events. In addition to aging, this pathological change is associated with aging-related diseases such as atherosclerosis, hypertension, chronic kidney disease, diabetes mellitus, and osteoporosis. Emerging evidence suggests a close association between the bile acid network and these aforementioned vascular calcification-associated conditions. Several bile acids have been proven to participate in calcium-phosphate metabolism, affecting the transdifferentiation of vascular smooth muscle cells and thus influencing vascular calcification. Targeting the bile acid network shows potential for ameliorating these diseases and their concomitant vascular calcification by regulating pathways such as energy metabolism, inflammatory response, oxidative stress, and cell differentiation. Here, we present a summary of the metabolism and functions of the bile acid network and aim to provide insights into the current research on the profound connections between the bile acid network and these vascular calcification-associated diseases, as well as the therapeutic potential.

How do different bile acid derivatives affect rat macrophage function - Friends or foes?

Due to an increased need for new immunomodulatory agents, many previously known molecules have been structurally modified in order to obtain new drugs, preserving at the same time some of the benevolent characteristics of the parent molecule. This study aimed to evaluate the immunomodulatory potential of a selected library of bile acid derivatives (BAD) using a broad spectrum of assays, evaluating rat peritoneal macrophages viability, cell membrane damage, lysosomal and adhesion function, and nitric oxide and cytokine production as a response to lipopolysaccharide stimulation. Also, in silico studies on two bile acid-activated receptors were conducted and the results were related to the observed in vitro effects. All tested BAD exerted significant toxicity in concentrations higher than 10 μM, which was determined based on mitochondria and cell membrane damage in a panel of assays. On the other hand, at lower concentrations, the tested BAD proved to be immunomodulatory since they affected lysosomal function, cell adhesion capacities and the ability to produce inflammatory cytokines in response to a stimulus. One of the compounds proved to exhibit significant toxicity toward macrophages, but also caused a concentration-dependent decrease in nitric oxide levels and was identified as a potential farnesoid X receptor agonist.

Targeting gut microbiota and immune crosstalk: potential mechanisms of natural products in the treatment of atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory reaction that primarily affects large and medium-sized arteries. It is a major cause of cardiovascular disease and peripheral arterial occlusive disease. The pathogenesis of AS involves specific structural and functional alterations in various populations of vascular cells at different stages of the disease. The immune response is involved throughout the entire developmental stage of AS, and targeting immune cells presents a promising avenue for its treatment. Over the past 2 decades, studies have shown that gut microbiota (GM) and its metabolites, such as trimethylamine-N-oxide, have a significant impact on the progression of AS. Interestingly, it has also been reported that there are complex mechanisms of action between GM and their metabolites, immune responses, and natural products that can have an impact on AS. GM and its metabolites regulate the functional expression of immune cells and have potential impacts on AS. Natural products have a wide range of health properties, and researchers are increasingly focusing on their role in AS. Now, there is compelling evidence that natural products provide an alternative approach to improving immune function in the AS microenvironment by modulating the GM. Natural product metabolites such as resveratrol, berberine, curcumin, and quercetin may improve the intestinal microenvironment by modulating the relative abundance of GM, which in turn influences the accumulation of GM metabolites. Natural products can delay the progression of AS by regulating the metabolism of GM, inhibiting the migration of monocytes and macrophages, promoting the polarization of the M2 phenotype of macrophages, down-regulating the level of inflammatory factors, regulating the balance of Treg/Th17, and inhibiting the formation of foam cells. Based on the above, we describe recent advances in the use of natural products that target GM and immune cells crosstalk to treat AS, which may bring some insights to guide the treatment of AS.

Research Progress of Takeda G Protein-Coupled Receptor 5 in Metabolic Syndrome

Bile acids are acknowledged as signaling molecules involved in metabolic syndrome. The Takeda G protein-coupled receptor 5 (TGR5) functions as a significant bile acid receptor. The accumulated evidence suggests that TGR5 involves lipid homeostasis, glucose metabolism, and inflammation regulation. In line with this, recent preclinical studies also demonstrate that TGR5 plays a significant role in the generation and progression of metabolic syndrome, encompassing type 2 diabetes mellitus, obesity, atherosclerosis, and non-alcoholic fatty liver disease (NAFLD). In this review, we discuss the role of TGR5 in metabolic syndrome, illustrating the underlying mechanisms and therapeutic targets.

Emerging Roles of Gut Microbial Modulation of Bile Acid Composition in the Etiology of Cardiovascular Diseases

Despite advances in preventive measures and treatment options, cardiovascular disease (CVD) remains the number one cause of death globally. Recent research has challenged the traditional risk factor profile and highlights the potential contribution of non-traditional factors in CVD, such as the gut microbiota and its metabolites. Disturbances in the gut microbiota have been repeatedly associated with CVD, including atherosclerosis and hypertension. Mechanistic studies support a causal role of microbiota-derived metabolites in disease development, such as short-chain fatty acids, trimethylamine-N-oxide, and bile acids, with the latter being elaborately discussed in this review. Bile acids represent a class of cholesterol derivatives that is essential for intestinal absorption of lipids and fat-soluble vitamins, plays an important role in cholesterol turnover and, as more recently discovered, acts as a group of signaling molecules that exerts hormonal functions throughout the body. Studies have shown mediating roles of bile acids in the control of lipid metabolism, immunity, and heart function. Consequently, a picture has emerged of bile acids acting as integrators and modulators of cardiometabolic pathways, highlighting their potential as therapeutic targets in CVD. In this review, we provide an overview of alterations in the gut microbiota and bile acid metabolism found in CVD patients, describe the molecular mechanisms through which bile acids may modulate CVD risk, and discuss potential bile-acid-based treatment strategies in relation to CVD.

Pulmonary Arterial Hypertension Patients Have a Proinflammatory Gut Microbiome and Altered Circulating Microbial Metabolites

Rationale: Inflammation drives pulmonary arterial hypertension (PAH). Gut dysbiosis causes immune dysregulation and systemic inflammation by altering circulating microbial metabolites; however, little is known about gut dysbiosis and microbial metabolites in PAH. Objectives: To characterize the gut microbiome and microbial metabolites in patients with PAH. Methods: We performed 16S ribosomal RNA gene and shotgun metagenomics sequencing on stool from patients with PAH, family control subjects, and healthy control subjects. We measured markers of inflammation, gut permeability, and microbial metabolites in plasma from patients with PAH, family control subjects, and healthy control subjects. Measurements and Main Results: The gut microbiome was less diverse in patients with PAH. Shannon diversity index correlated with measures of pulmonary vascular disease but not with right ventricular function. Patients with PAH had a distinct gut microbial signature at the phylogenetic level, with fewer copies of gut microbial genes that produce antiinflammatory short-chain fatty acids (SCFAs) and secondary bile acids and lower relative abundances of species encoding these genes. Consistent with the gut microbial changes, patients with PAH had relatively lower plasma concentrations of SCFAs and secondary bile acids. Patients with PAH also had enrichment of species with the microbial genes that encoded the proinflammatory microbial metabolite trimethylamine. The changes in the gut microbiome and circulating microbial metabolites between patients with PAH and family control subjects were not as substantial as the differences between patients with PAH and healthy control subjects. Conclusions: Patients with PAH have proinflammatory gut dysbiosis, in which lower circulating SCFAs and secondary bile acids may facilitate pulmonary vascular disease. These findings support investigating modulation of the gut microbiome as a potential treatment for PAH.

G protein-coupled bile acid receptor 1 reduced hepatic immune response and inhibited NFκB, PI3K/AKT, and PKC/P38 MAPK signaling pathway in hybrid grouper

The mammalian G protein-coupled bile acid receptor 1 (TGR5) is involved in the inflammatory response. However, the functions of TGR5 in the immune response of fish remain unclear. In this study, the full-length sequence of tgr5 from hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) was cloned, and the function of TGR5 in the immune response was explored. The results showed that the ORF of tgr5 gene in hybrid grouper was 1029 bp and encoded 342 amino acids. Activation of TGR5 by INT-777 significantly decreased the activities and mRNA expression of TNFα and IL1β, whereas inhibition of TGR5 by SBI-115 showed the opposite effect. SBI-115 treatment significantly increased the expression of phosphorylated inhibitor κB α (p-IKBα) protein. After the INT-777 treatment, the concentration of protein kinase C (PKC) and expression of the p38 mitogen-activated protein kinases (p38a), p38b and p38c, were significantly decreased in vivo. INT-777 agonist significantly decreased the expression of phosphorylated phosphoinositide 3-kinase (p-PI3K) protein and the ratio of phosphorylated and nonphosphorylated serine/threonine-protein kinase (p-AKT/AKT). In conclusion, activation of hepatic TGR5 inhibited the PKC/P38 MAPK, PI3K/AKT, NFκB signaling pathway and improved hepatic immune responses of hybrid grouper in vivo and in vitro.

Role of Gut Microbiome in Atherosclerosis: Molecular and Therapeutic Aspects

Atherosclerosis is one of the most relevant and prevalent cardiovascular diseases of our time. It is one of the pathological entities that increases the morbidity and mortality index in the adult population. Pathophysiological connections have been observed between atherosclerosis and the gut microbiome (GM), represented by a group of microorganisms that are present in the gut. These microorganisms are vital for metabolic homeostasis in humans. Recently, direct and indirect mechanisms through which GM can affect the development of atherosclerosis have been studied. This has led to research into the possible modulation of GM and metabolites as a new target in the prevention and treatment of atherosclerosis. The goal of this review is to analyze the physiopathological mechanisms linking GM and atherosclerosis that have been described so far. We also aim to summarize the recent studies that propose GM as a potential target in atherosclerosis management.

The gut microbiota-artery axis: A bridge between dietary lipids and atherosclerosis?

Atherosclerotic cardiovascular disease is one of the major leading global causes of death. Growing evidence has demonstrated that gut microbiota (GM) and its metabolites play a pivotal role in the onset and progression of atherosclerosis (AS), now known as GM-artery axis. There are interactions between dietary lipids and GM, which ultimately affect GM and its metabolites. Given these two aspects, the GM-artery axis may play a mediating role between dietary lipids and AS. Diets rich in saturated fatty acids (SFAs), omega-6 polyunsaturated fatty acids (n-6 PUFAs), industrial trans fatty acids (TFAs), and cholesterol can increase the levels of atherogenic microbes and metabolites, whereas monounsaturated fatty acids (MUFAs), ruminant TFAs, and phytosterols (PS) can increase the levels of antiatherogenic microbes and metabolites. Actually, dietary phosphatidylcholine (PC), sphingomyelin (SM), and omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been demonstrated to affect AS via the GM-artery axis. Therefore, that GM-artery axis acts as a communication bridge between dietary lipids and AS. Herein, we will describe the molecular mechanism of GM-artery axis in AS and discuss the complex interactions between dietary lipids and GM. In particular, we will highlight the evidence and potential mechanisms of dietary lipids affecting AS via GM-artery axis.

Altered serotonin metabolism in Takeda G protein-coupled receptor 5 knockout mice protects against diet-induced hepatic fibrosis

Background and aims

Diet-induced obesity and metabolic syndrome can trigger the progression of fatty liver disease to non-alcoholic steatohepatitis and fibrosis, which is a major public health concern. Bile acids regulate metabolic homeostasis and inflammation in the liver and gut via the activation of nuclear farnesoid X receptor (Fxr) and the membrane receptor Takeda G protein-coupled receptor 5 (Tgr5). Tgr5 is highly expressed in the gut and skeletal muscle, and in cholangiocytes and Kupffer cells of the liver. Tgr5 is implicated in the mediation of liver and gut inflammation, as well as the maintenance of energy homeostasis. Here, we used a high fat, high fructose, and high sucrose (HFS) diet to determine how bile acid signaling through Tgr5 may regulate metabolism during the progression from fatty liver to non-alcoholic steatohepatitis and fibrosis.

Materials and methods

Female C57BL/6J control wild type (WT) and Tgr5 knockout (Tgr5 -/-) mice were fed HFS (high fat (40% kcal), high fructose, and 20% sucrose water) diet for 20 weeks. Metabolic phenotypes were characterized through examination of bile acid synthesis pathways, lipid and cholesterol metabolism pathways, and fibrosis and inflammation pathways.

Results

Tgr5 -/- mice were more glucose intolerant when fed HFS diet, despite gaining the same amount of weight as WT mice. Tgr5 -/- mice accumulated significantly more hepatic cholesterol and triglycerides on HFS diet compared to WT mice, and gene expression of lipogenic genes was significantly upregulated. Hepatic cholesterol 7alpha-hydroxylase (Cyp7a1) gene expression was consistently elevated in Tgr5 -/- mice, while oxysterol 7alpha-hydroxylase (Cyp7b1), sterol 27-hydroxylase (Cyp27a1), Fxr, and small heterodimer partner (Shp) were downregulated by HFS diet. Surprisingly, hepatic inflammation and fibrosis were also significantly reduced in Tgr5 -/- mice fed HFS diet, which may be due to altered serotonin signaling in the liver.

Conclusions

Tgr5 -/- mice may be protected from high fat, high sugar-induced hepatic inflammation and injury due to altered serotonin metabolism.

The role of TGR5 as an onco-immunological biomarker in tumor staging and prognosis by encompassing the tumor microenvironment

The relationship between G protein–coupled bile acid receptor 1 (TGR5, GPBAR1) and, specifically, cancer has been studied in in vivo and in vitro experiments, but there is still a lack of pan-cancer analysis to understand the prognostic significance and functioning mechanism of TGR5 in different cancer-driving oncogenic processes. Here, we used Gene Expression Integration, Human Protein Atlas, and The Cancer Genome Atlas (TCGA) to perform a pan-cancer analysis of the role of TGR5 in all 33 tumors. In all TCGA tumors, the TGR5 gene expression has been assessed, and we found that the high TGR5 gene expression in most cancers is associated with poor prognosis of overall survival for cancers such as glioblastoma multiforme (p = 0.0048), kidney renal papillary cell carcinoma (p = 0.033), lower grade glioma (p = 0.0028), thymoma (p = 0.048), and uveal melanoma (p = 0.004), and then the lower expression of TGR5 was linked with poor prognosis in cervical squamous cell carcinoma and endocervical adenocarcinoma (p = 0.014), malignant mesothelioma (MESO) (p = 0.048), sarcoma (p = 0.018), and skin cutaneous melanoma (p = 0.0085). The TGR5 expression was linked with the immune infiltration level of the macrophage M2_TIDE and was also associated with DNA methylation in ovarian and breast cancers. The regulation of hormone secretion, Rap1 pathway, osteoclast differentiation, and bile acid pathway was involved in the functional mechanism of TGR5. Besides, gene expressions were different in different tumors detected by RT-PCR, and cell activity experiments have also found that TGR5 can increase the activity of renal cell carcinoma and reduce the activity of skin cancer and osteosarcoma cells. In this investigation, the aim was to assess the comprehensive overview of the oncogenic roles of TGR5 in all TCGA tumors using pan-analysis.

Immunomodulatory functions of FXR

The Farnesoid-x-receptor (FXR) is a bile acids sensor activated in humans by primary bile acids. FXR is mostly expressed in liver, intestine and adrenal glands but also by cells of innate immunity, including macrophages, liver resident macrophages, the Kupffer cells, natural killer cells and dendritic cells. In normal physiology and clinical disorders, cells of innate immunity mediate communications between liver, intestine and adipose tissues. In addition to FXR, the G protein coupled receptor (GPBAR1), that is mainly activated by secondary bile acids, whose expression largely overlaps FXR, modulates chemical communications from the intestinal microbiota and the host's immune system, integrating epithelial cells and immune cells in the entero-hepatic system, providing a mechanism for development of a tolerogenic state toward the intestinal microbiota. Disruption of FXR results in generalized inflammation and disrupted bile acids metabolism. While FXR agonism in preclinical models provides counter-regulatory signals that attenuate inflammation-driven immune dysfunction in a variety of liver and intestinal disease models, the clinical relevance of these mechanisms in the setting of FXR-related disorders remain poorly defined.

Bile acids and their receptors: modulators and therapeutic targets in liver inflammation

Bile acids participate in the intestinal emulsion, digestion, and absorption of lipids and fat-soluble vitamins. When present in high concentrations, as in cholestatic liver diseases, bile acids can damage cells and cause inflammation. After the discovery of bile acids receptors about two decades ago, bile acids are considered signaling molecules. Besides regulating bile acid, xenobiotic, and nutrient metabolism, bile acids and their receptors have shown immunomodulatory properties and have been proposed as therapeutic targets for inflammatory diseases of the liver. This review focuses on bile acid-related signaling pathways that affect inflammation in the liver and provides an overview of the preclinical and clinical applications of modulators of these pathways for the treatment of cholestatic and autoimmune liver diseases.

The Activity of Prebiotics and Probiotics in Hepatogastrointestinal Disorders and Diseases Associated with Metabolic Syndrome

The components of metabolic syndrome (MetS) and hepatogastrointestinal diseases are widespread worldwide, since many factors associated with lifestyle and diet influence their development and correlation. Due to these growing health problems, it is necessary to search for effective alternatives for prevention or adjuvants in treating them. The positive impact of regulated microbiota on health is known; however, states of dysbiosis are closely related to the development of the conditions mentioned above. Therefore, the role of prebiotics, probiotics, or symbiotic complexes has been extensively evaluated; the results are favorable, showing that they play a crucial role in the regulation of the immune system, the metabolism of carbohydrates and lipids, and the biotransformation of bile acids, as well as the modulation of their central receptors FXR and TGR-5, which also have essential immunomodulatory and metabolic activities. It has also been observed that they can benefit the host by displacing pathogenic species, improving the dysbiosis state in MetS. Current studies have reported that paraprobiotics (dead or inactive probiotics) or postbiotics (metabolites generated by active probiotics) also benefit hepatogastrointestinal health.

Investigation of the potential role of TGR5 in pancreatic cancer by a comprehensive molecular experiments and the liquid chromatography mass spectrometry (LC-MS) based metabolomics

BACKGROUND

Takeda G protein receptor 5 (TGR5) is widely recognized as a potential drug target for the treatment of metabolic diseases. TGR5 is not only a metabolic regulator, but also has a potential role that participating in developing and progressing of gastrointestinal cancer. We aimed to investigate the potential role of TGR5 in pancreatic cancer by utilizing molecular experiments and the liquid chromatography mass spectrometry (LC-MS) based metabolomics.

METHODS

Herein, we assessed pancreatic cancer proliferation, migration and invasion in response to TGR5 antagonist SBI-115 in vitro experiments. Cell death was examined by using TUNEL assay on agarose-embedded sections. Then we investigated the effects of TGR5 on PANC-1 and BXPC3 cells via transmission electron microscopy (TEM). Moreover, LC-MS-based metabolomics was performed to explore the potential underlying mechanisms of TGR5 in pancreatic cancer. The correlations between TGR5 and the metabolism-related genes were further analysed by GEPIA 2 database.

RESULTS

We found the proliferation capacities were decreased significantly in PANC-1 and BXPC3 cells after the treatment of SBI-115 for 48 h. The results of TUNEL assay showed that antagonism of TGR5 by SBI-115 had a remarkable effect on inducing cell death. Analysis of TEM demonstrated that SBI-115 treatment could impair the morphology of mitochondria in most PANC-1 and BXPC3 cells. The LC-MS-based analyses revealed that antagonism of TGR5 could alter the metabolic profiles of PANC-1 cells in vitro. Moreover, TGR5 was associated with some metabolism-related genes in pancreatic cancer.

CONCLUSION

Our data suggests that antagonism of TGR5 may suppress cell proliferation and induce apoptosis in pancreatic cancer cells. TGR5 may affect the metabolism of pancreatic cancer, and TGR5 would be an attractive target for pancreatic cancer treatment.

Discovery of farnesoid X receptor and its role in bile acid metabolism

In 1995, the nuclear hormone orphan receptor farnesoid X receptor (FXR, NR1H4) was identified as a farnesol receptor expressed mainly in liver, kidney, and adrenal gland of rats. In 1999, bile acids were identified as endogenous FXR ligands. Subsequently, FXR target genes involved in the regulation of hepatic bile acid synthesis, secretion, and intestinal re-absorption were identified. FXR signaling was proposed as a mechanism of feedback regulation of the rate-limiting enzyme for bile acid synthesis, cholesterol 7⍺-hydroxylase (CYP7A1). The primary bile acids synthesized in the liver are transformed to secondary bile acids by the gut microbiota. The gut-to-liver axis plays a critical role in the regulation of bile acid synthesis, composition and circulating bile acid pool size, which in turn regulates glucose, lipid, and energy metabolism. Dysregulation of bile acid metabolism and FXR signaling in the gut-to-liver axis contributes to metabolic diseases including obesity, diabetes, and non-alcoholic fatty liver disease. This review will cover the discovery of FXR as a bile acid sensor in the regulation of bile acid metabolism and as a metabolic regulator of lipid, glucose, and energy homeostasis. It will also provide an update of FXR functions in the gut-to-liver axis and the drug therapies targeting bile acids and FXR for the treatment of liver metabolic diseases.

Bile acids and salt-sensitive hypertension: a role of the gut-liver axis

Salt-sensitivity of blood pressure (SSBP) affects 50% of the hypertensive and 25% of the normotensive populations. Importantly, SSBP is associated with increased risk for mortality in both populations independent of blood pressure. Despite its deleterious effects, the pathogenesis of SSBP is not fully understood. Emerging evidence suggests a novel role of bile acids in salt-sensitive hypertension and that they may play a crucial role in regulating inflammation and fluid volume homeostasis. Mechanistic evidence implicates alterations in the gut microbiome, the epithelial sodium channel (ENaC), the farnesoid X receptor, and the G protein-coupled bile acid receptor TGR5 in bile acid-mediated effects on cardiovascular function. The mechanistic interplay between excess dietary sodium-induced alterations in the gut microbiome and immune cell activation, bile acid signaling, and whether such interplay may contribute to the etiology of SSBP is still yet to be defined. The main goal of this review is to discuss the potential role of bile acids in the pathogenesis of cardiovascular disease with a focus on salt-sensitive hypertension.

Microbiome and Cardiovascular Disease

Atherosclerotic cardiovascular disease (ASCVD) is a prime example of a systems disease. In the initial phase, apolipoprotein B-containing cholesterol-rich lipoproteins deposit excess cholesterol in macrophage-like cells that subsequently develop into foam cells. A multitude of systemic as well as environmental factors are involved in further progression of atherosclerotic plaque formation. In recent years, both oral and gut microbiota have been proposed to play an important role in the process at different stages. Particularly bacteria from the oral cavity may easily reach the circulation and cause low-grade inflammation, a recognized risk factor for ASCVD. Gut-derived microbiota on the other hand can influence host metabolism on various levels. Next to translocation across the intestinal wall, these prokaryotes produce a great number of specific metabolites such as trimethylamine and short-chain fatty acids but can also metabolize endogenously formed bile acids and convert these into metabolites that may influence signal transduction pathways. In this overview, we critically discuss the novel developments in this rapidly emerging research field.

The Role of Bile Acids in Cardiovascular Diseases: from Mechanisms to Clinical Implications

Bile acids (BAs), key regulators in the metabolic network, are not only involved in lipid digestion and absorption but also serve as potential therapeutic targets for metabolic disorders. Studies have shown that cardiac dysfunction is associated with abnormal BA metabolic pathways. As ligands for several nuclear receptors and membrane receptors, BAs systematically regulate the homeostasis of metabolism and participate in cardiovascular diseases (CVDs), such as myocardial infarction, diabetic cardiomyopathy, atherosclerosis, arrhythmia, and heart failure. However, the molecular mechanism by which BAs trigger CVDs remains controversial. Therefore, the regulation of BA signal transduction by modulating the synthesis and composition of BAs is an interesting and novel direction for potential therapies for CVDs. Here, we mainly summarized the metabolism of BAs and their role in cardiomyocytes and noncardiomyocytes in CVDs. Moreover, we comprehensively discussed the clinical prospects of BAs in CVDs and analyzed the clinical diagnostic and application value of BAs. The latest development prospects of BAs in the field of new drug development are also prospected. We aimed to elucidate the underlying mechanism of BAs treatment in CVDs, and the relationship between BAs and CVDs may provide new avenues for the prevention and treatment of these diseases.

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.

The gut-cardiovascular connection: new era for cardiovascular therapy

Our gut microbiome is constituted by trillions of microorganisms including bacteria, archaea and eukaryotic microbes. Nowadays, gut microbiome has been gradually recognized as a new organ system that systemically and biochemically interact with the host. Accumulating evidence suggests that the imbalanced gut microbiome contributes to the dysregulation of immune system and the disruption of cardiovascular homeostasis. Specific microbiome profiles and altered intestinal permeability are often observed in the pathophysiology of cardiovascular diseases. Gut-derived metabolites, toxins, peptides and immune cell-derived cytokines play pivotal roles in the induction of inflammation and the pathogenesis of dysfunction of heart and vasculature. Impaired crosstalk between gut microbiome and multiple organ systems, such as gut-vascular, heart-gut, gut-liver and brain-gut axes, are associated with higher cardiovascular risks. Medications and strategies that restore healthy gut microbiome might therefore represent novel therapeutic options to lower the incidence of cardiovascular and metabolic disorders.

Mechanistic insights into the pathophysiology of cirrhotic cardiomyopathy

Myocardial dysfunction in end stage cirrhotic liver disease, termed cirrhotic cardiomyopathy, is a long known, but little understood comorbidity seen in ∼50% of adults and children who present for liver transplantation. Structural, functional, hemodynamic and electrocardiographic aberrations that occur in the heart as a direct consequence of a damaged liver, is associated with multi-organ failure and increased mortality and morbidity in patients undergoing surgical procedures such as porto-systemic shunt placement and liver transplantation. Despite its clinical significance and rapid advances in science and pharmacotherapy, there is yet no specific treatment for this disease. This may be due to a lack of understanding of the pathogenesis and mechanisms behind how a cirrhotic liver causes cardiac pathology. This review will focus specifically on insights into the molecular mechanisms that drive this liver-heart interaction. Deeper understanding of the etio-pathogenesis of cirrhotic cardiomyopathy will allow us to design and test treatments that can be targeted to prevent and/or reverse this co-morbid consequence of liver failure and improve health care delivery and outcomes in patients with cirrhosis.

Redox-Dependent Effects in the Physiopathological Role of Bile Acids

Bile acids (BA) are recognized by their role in nutrient absorption. However, there is growing evidence that BA also have endocrine and metabolic functions. Besides, the steroidal-derived structure gives BA a toxic potential over the biological membrane. Thus, cholestatic disorders, characterized by elevated BA on the liver and serum, are a significant cause of liver transplant and extrahepatic complications, such as skeletal muscle, central nervous system (CNS), heart, and placenta. Further, the BA have an essential role in cellular damage, mediating processes such as membrane disruption, mitochondrial dysfunction, and the generation of reactive oxygen species (ROS) and oxidative stress. The purpose of this review is to describe the BA and their role on hepatic and extrahepatic complications in cholestatic diseases, focusing on the association between BA and the generation of oxidative stress that mediates tissue damage.

Bile acid activated receptors: Integrating immune and metabolic regulation in non-alcoholic fatty liver disease

Bile acids are a family of atypical steroids generated at the interface of liver-intestinal microbiota acting on a ubiquitously expressed family of membrane and nuclear receptors known as bile acid activated receptors. The two best characterized receptors of this family are the nuclear receptor, farnesoid X receptor (FXR) and the G protein-coupled receptor, G protein-coupled bile acid receptor 1 (GPBAR1). FXR and GPBAR1 regulate major aspects of lipid and glucose metabolism, energy balance, autophagy and immunity and have emerged as potential pharmaceutical targets for the treatment of metabolic and inflammatory disorders. Clinical trials in non-alcoholic fatty liver disease (NAFLD), however, have shown that selective FXR agonists cause side effects while their efficacy is partial. Because FXR and GPBAR1 exert additive effects, dual FXR/GPBAR1 ligands have been developed for the treatment of metabolic disorders and are currently advanced to clinical trials. Here, we will review the role of FXR and GPBAR1 agonism in NAFLD and how the two receptors could be exploited to target multiple components of the disease.

Bile Acids, Liver Cirrhosis, and Extrahepatic Vascular Dysfunction

The bile acid pool with its individual bile acids (BA) is modulated in the enterohepatic circulation by the liver as the primary site of synthesis, the motility of the gallbladder and of the intestinal tract, as well as by bacterial enzymes in the intestine. The nuclear receptor farnesoid X receptor (FXR) and Gpbar1 (TGR5) are important set screws in this process. Bile acids have a vasodilatory effect, at least according to in vitro studies. The present review examines the question of the extent to which the increase in bile acids in plasma could be responsible for the hyperdynamic circulatory disturbance of liver cirrhosis and whether modulation of the bile acid pool, for example, via administration of ursodeoxycholic acid (UDCA) or via modulation of the dysbiosis present in liver cirrhosis could influence the hemodynamic disorder of liver cirrhosis. According to our analysis, the evidence for this is limited. Long-term studies on this question are lacking.