MECHANISMS IN ENDOCRINOLOGY: FXR signalling: a novel target in metabolic diseases

An updated review of the pharmacological effects and potential mechanisms of hederagenin and its derivatives

Hederagenin (HG) is a natural pentacyclic triterpenoid that can be isolated from various medicinal herbs. By modifying the structure of HG, multiple derivatives with superior biological activities and safety profiles have been designed and synthesized. Accumulating evidence has demonstrated that HG and its derivatives display multiple pharmacological activities against cancers, inflammatory diseases, infectious diseases, metabolic diseases, fibrotic diseases, cerebrovascular and neurodegenerative diseases, and depression. Previous studies have confirmed that HG and its derivatives combat cancer by exerting cytotoxicity, inhibiting proliferation, inducing apoptosis, modulating autophagy, and reversing chemotherapy resistance in cancer cells, and the action targets involved mainly include STAT3, Aurora B, KIF7, PI3K/AKT, NF-κB, Nrf2/ARE, Drp1, and P-gp. In addition, HG and its derivatives antagonize inflammation through inhibiting the production and release of pro-inflammatory cytokines and inflammatory mediators by regulating inflammation-related pathways and targets, such as NF-κB, MAPK, JAK2/STAT3, Keap1-Nrf2/HO-1, and LncRNA A33/Axin2/β-catenin. Moreover, anti-pathogen, anti-metabolic disorder, anti-fibrosis, neuroprotection, and anti-depression mechanisms of HG and its derivatives have been partially elucidated. The diverse pharmacological properties of HG and its derivatives hold significant implications for future research and development of new drugs derived from HG, which can lead to improved effectiveness and safety profiles.

Relationship between human serum metabolites and angina pectoris: a Mendelian randomization study

PURPOSE

We aimed to explore the causal relationship between human serum metabolites and angina pectoris.

METHODS

This study used two-sample Mendelian randomization (MR) analysis to assess the association between 486 serum metabolites and angina pectoris. The analytical methods employed to reduce study bias included inverse variance weighted, MR-Egger, and weighted median method. A comprehensive sensitivity analysis was performed using the leave-one-out method, while instrumental variable pleiotropy was tested with MR-Pleiotropy RESidual Sum and Outlier. Metabolic pathways of angina-associated metabolites were analysed on the MetaboAnalyst metabolomics analysis tool platform.

RESULTS

In this study, 42 serum metabolites were found to be strongly associated with angina pectoris. They mainly belonged to seven groups: amino acids, carbohydrates, cofactors and vitamins, lipids, nucleotides, unknown metabolites, and exogenous substances. Pipecolate posed the highest risk for the development of angina pectoris among the 42 serum metabolites. The main metabolic pathways associated with angina pectoris were glycine, serine, threonine metabolism, primary bile acid biosynthesis, and caffeine metabolism.

CONCLUSION

We identified 25 high-risk and 17 protective human serum metabolites associated with angina pectoris. Their associated major metabolic pathways were also determined. The serum metabolite pipecolate was significantly and positively correlated with the risk of angina pectoris. This finding may serve as a valuable reference for testing serum markers associated with angina pectoris.

The bile-gut axis and metabolic consequences of cholecystectomy

Cholelithiasis and cholecystitis affect individuals of all ages and are often treated by surgical removal of the gallbladder (cholecystectomy), which is considered a safe, low-risk procedure. Nevertheless, recent findings show that bile and its regulated storage and excretion may have important metabolic effects and that cholecystectomy is associated with several metabolic diseases postoperatively. Bile acids have long been known as emulsifiers essential to the assimilation of lipids and absorption of lipid-soluble vitamins, but more recently, they have also been reported to act as metabolic signaling agents. The nuclear receptor, farnesoid X receptor (FXR), and the G protein-coupled membrane receptor, Takeda G protein-coupled receptor 5 (TGR5), are specific to bile acids. Through activation of these receptors, bile acids control numerous metabolic functions. Cholecystectomy affects the storage and excretion of bile acids, which in turn may influence the activation of FXR and TGR5 and their effects on metabolism including processes leading to metabolic conditions such as metabolic dysfunction-associated steatotic liver disease and metabolic syndrome. Here, with the aim of elucidating mechanisms behind cholecystectomy-associated dysmetabolism, we review studies potentially linking cholecystectomy and bile acid-mediated metabolic effects and discuss possible pathophysiological mechanisms behind cholecystectomy-associated dysmetabolism.

Advances in secondary prevention mechanisms of macrovascular complications in type 2 diabetes mellitus patients: a comprehensive review

Type 2 diabetes mellitus (T2DM) poses a significant global health burden. This is particularly due to its macrovascular complications, such as coronary artery disease, peripheral vascular disease, and cerebrovascular disease, which have emerged as leading contributors to morbidity and mortality. This review comprehensively explores the pathophysiological mechanisms underlying these complications, protective strategies, and both existing and emerging secondary preventive measures. Furthermore, we delve into the applications of experimental models and methodologies in foundational research while also highlighting current research limitations and future directions. Specifically, we focus on the literature published post-2020 concerning the secondary prevention of macrovascular complications in patients with T2DM by conducting a targeted review of studies supported by robust evidence to offer a holistic perspective.

Discovery of 4-aminophenylacetamide derivatives as intestine-specific farnesoid X receptor antagonists for the potential treatment of nonalcoholic steatohepatitis

Farnesoid X receptor (FXR) plays a key role in bile acid homeostasis, inflammation, fibrosis, lipid and glucose metabolism and is emerging as a promising therapeutic target for nonalcoholic steatohepatitis (NASH). Emerging evidence suggested that intestine-specific FXR antagonists exhibited remarkable metabolic improvements and slowed NASH progression. In this study, we discovered several potent FXR antagonists using a multistage ligand- and structure-based virtual screening approach. Notably, compound V023-9340, which possesses a 4-aminophenylacetamide scaffold, emerged as the most potent FXR antagonist with an IC50 value of 4.27 μM. In vivo, V023-9340 demonstrated selective accumulation in the intestine, substantially ameliorating high-fat diet (HFD)-induced NASH in mice by mitigating hepatic steatosis and inflammation. Mechanistic studies revealed that V023-9340 strongly inhibited intestinal FXR while concurrently feedback-activated hepatic FXR. Further structure-activity relationship optimization employing V023-9340 has resulted in the synthesis of a more efficacious compound V02-8 with an IC50 value of 0.89 μM, which exhibited a 4.8-fold increase in FXR antagonistic activity compared to V023-9340. In summary, 4-aminophenylacetamide derivative V023-9340 represented a novel intestine-specific FXR antagonist and showed improved effects against HFD-induced NASH in mice, which may serve as a promising lead in discovering potential therapeutic drugs for NASH treatment.

Gut microbes in metabolic disturbances. Promising role for therapeutic manipulations?

The prevalence of overweight, obesity, type 2 diabetes, metabolic syndrome and steatotic liver disease is rapidly increasing worldwide with a huge economic burden in terms of morbidity and mortality. Several genetic and environmental factors are involved in the onset and development of metabolic disorders and related complications. A critical role also exists for the gut microbiota, a complex polymicrobial ecology at the interface of the internal and external environment. The gut microbiota contributes to food digestion and transformation, caloric intake, and immune response of the host, keeping the homeostatic control in health. Mechanisms of disease include enhanced energy extraction from the non-digestible dietary carbohydrates, increased gut permeability and translocation of bacterial metabolites which activate a chronic low-grade systemic inflammation and insulin resistance, as precursors of tangible metabolic disorders involving glucose and lipid homeostasis. The ultimate causative role of gut microbiota in this respect remains to be elucidated, as well as the therapeutic value of manipulating the gut microbiota by diet, pre- and pro- synbiotics, or fecal microbial transplantation.

Inhibition of intestinal FXR activity as a possible mechanism for the beneficial effects of a probiotic mix supplementation on lipid metabolism alterations and weight gain in mice fed a high fat diet

Supplementation with probiotics has emerged as a promising therapeutic tool to manage metabolic diseases. We investigated the effects of a mix of Bifidobacterium animalis subsp. lactis LA804 and Lactobacillus gasseri LA806 on high-fat (HF) diet -induced metabolic disease in mice. Supplementation with the probiotic mix in HF diet-fed mice (HF-Pr2) reduced weight and fat mass gains, decreased hepatic lipid accumulation, and lowered plasma triglyceride peak during an oral lipid tolerance test. At the molecular level, the probiotic mix protected against HF-induced rise in mRNA levels of genes related to lipid uptake, metabolism, and storage in the liver and white adipose tissues, and strongly decreased mRNA levels of genes related to inflammation in the white adipose tissue and to oxidative stress in the liver. Regarding intestinal homeostasis, the probiotic mix did not prevent HF-induced gut permeability but slightly modified microbiota composition without correcting the dysbiosis induced by the HF diet. Probiotic supplementation also modified the cecal bile acid (BA) profile, leading to an increase in the Farnesoid-X-Receptor (FXR) antagonist/agonist ratio between BA species. In agreement, HF-Pr2 mice exhibited a strong inhibition of FXR signaling pathway in the ileum, which was associated with lipid metabolism protection. This is consistent with recent reports proposing that inhibition of intestinal FXR activity could be a potent mechanism to overcome metabolic disorders. Altogether, our results demonstrate that the probiotic mix evaluated, when administered preventively to HF diet-fed mice could limit obesity and associated lipid metabolism disorders, likely through the inhibition of FXR signaling in the intestinal tract.

THE CONNECTION BETWEEN BILE ACIDS AND TYPE 2 DIABETES MELLITUS - A REVIEW

BACKGROUND

Bile acids (BAs) are steroid molecules synthesized exclusively in the liver, being end products of cholesterol catabolism. BAs are known to be involved in several metabolic alterations, including metabolic syndrome and type 2 diabetes mellitus (DM2). DM2 is a chronic degenerative disease characterized by insulin resistance, insulin deficiency due to insufficient production of pancreatic ß-cells, and elevated serum glucose levels leading to multiple complications.

OBJECTIVE

The objective of this study is to investigate the role of BAs in the pathophysiology of DM2, highlighting the possibilities in the development of therapeutic procedures targeting BAs as an optional pathway in the treatment of DM2.

METHODS

The research was carried out through narrative review and publications on the relationship between BAs and DM2. The databases used for the search include PubMed, Scopus, and Web of Science. The keywords used for the search include bile acids, type 2 diabetes mellitus, metabolic syndrome, and metabolic disorders.

RESULTS

The studies have reported the involvement of BAs in the pathophysiology of DM2. BAs act as a ligand for the nuclear farnesoid X receptor, regulating glucose metabolism, lipid metabolism, and cellular energy production. Additionally, BAs modulate the production, elimination, and mobilization of BAs through the farnesoid X receptor. BAs also act as a signaling pathway through Takeda G protein-coupled receptor 5, further contributing to metabolic regulation. These findings suggest that targeting BAs may offer a novel therapeutic approach in the treatment of DM2.

CONCLUSION

This study highlights the important role of BAs in DM2, specifically through their interactions with key metabolic pathways. Targeting BAs may represent an innovative and effective approach to the treatment of DM2.

Function of Akkermansia muciniphila in type 2 diabetes and related diseases

The prevalence of type 2 diabetes (T2D) is increasing worldwide, with many patients developing long-term complications that affect their cardiovascular, urinary, alimentary, and other systems. A growing body of literature has reported the crucial role of gut microbiota in metabolic diseases, one of which, Akkermansia muciniphila, is considered the "next-generation probiotic" for alleviating metabolic disorders and the inflammatory response. Although extensive research has been conducted on A. muciniphila, none has summarized its regulation in T2D. Hence, this review provides an overview of the effects and multifaceted mechanisms of A. muciniphila on T2D and related diseases, including improving metabolism, alleviating inflammation, enhancing intestinal barrier function, and maintaining microbiota homeostasis. Furthermore, this review summarizes dietary strategies for increasing intestinal A. muciniphila abundance and effective gastrointestinal delivery.

Nuclear Receptor Imaging In Vivo-Clinical and Research Advances

Nuclear receptors are transcription factors that function in normal physiology and play important roles in diseases such as cancer, inflammation, and diabetes. Noninvasive imaging of nuclear receptors can be achieved using radiolabeled ligands and positron emission tomography (PET). This quantitative imaging approach can be viewed as an in vivo equivalent of the classic radioligand binding assay. A main clinical application of nuclear receptor imaging in oncology is to identify metastatic sites expressing nuclear receptors that are targets for approved drug therapies and are capable of binding ligands to improve treatment decision-making. Research applications of nuclear receptor imaging include novel synthetic ligand and drug development by quantifying target drug engagement with the receptor for optimal therapeutic drug dosing and for fundamental research into nuclear receptor function in cells and animal models. This mini-review provides an overview of PET imaging of nuclear receptors with a focus on radioligands for estrogen receptor, progesterone receptor, and androgen receptor and their use in breast and prostate cancer.

ApoE isoform-dependent effects of xanthohumol on high fat diet-induced cognitive impairments and hippocampal metabolic pathways

Consumption of a high fat diet (HFD) is linked to metabolic syndrome and cognitive impairments. This is exacerbated in age-related cognitive decline (ACD) and in individuals with a genetic risk for Alzheimer's disease (AD). Apolipoprotein E (apoE) is involved in cholesterol metabolism. In humans, there are three major isoforms, E2, E3, and E4. Compared to E3, E4 increases ACD and AD risk and vulnerability to the deleterious cognitive effects of a HFD. The plant compound Xanthohumol (XN) had beneficial effects on cognition and metabolism in C57BL/6J wild-type (WT) male mice put on a HFD at 9 weeks of age for 13 weeks. As the effects of XN in the context of a HFD in older WT, E3, and E4 female and male mice are not known, in the current study male and female WT, E3, and E4 mice were fed a HFD alone or a HFD containing 0.07% XN for 10 or 19 weeks, starting at 6 months of age, prior to the beginning of behavioral and cognitive testing. XN showed sex- and ApoE isoform-dependent effects on cognitive performance. XN-treated E4 and WT, but not E3, mice had higher glucose transporter protein levels in the hippocampus and cortex than HFD-treated mice. E3 and E4 mice had higher glucose transporter protein levels in the hippocampus and lower glucose transporter protein levels in the cortex than WT mice. In the standard experiment, regardless of XN treatment, E4 mice had nearly double as high ceramide and sphingomyelin levels than E3 mice and male mice had higher level of glycosylated ceramide than female mice. When the differential effects of HFD in E3 and E4 males were assessed, the arginine and proline metabolism pathway was affected. In the extended exposure experiment, in E3 males XN treatment affected the arginine and proline metabolism and the glycine, serine, and threonine metabolism. Myristic acid levels were decreased in XN-treated E3 males but not E3 females. These data support the therapeutic potential for XN to ameliorate HFD-induced cognitive impairments and highlight the importance of considering sex and ApoE isoform in determining who might most benefit from this dietary supplement.

Pentacyclic triterpenes modulate farnesoid X receptor expression in colonic epithelial cells: implications for colonic secretory function

The nuclear bile acid receptor, farnesoid X receptor (FXR), is an important regulator of intestinal and metabolic function. Previous studies suggest that pentacyclic triterpenes (PCTs), a class of plant-derived bioactive phytochemical, can modulate FXR activity and may therefore offer therapeutic benefits. Here, we investigated the effects of a prototypical PCT, hederagenin (HG), on FXR expression, activity, and antisecretory actions in colonic epithelial cells. T₈₄ cells and murine enteroid-derived monolayers were employed to assess HG effects on FXR expression and activity in colonic epithelia. We measured mRNA levels by qRT-PCR and protein by ELISA and immunoblotting. Transepithelial Cl⁻ secretion was assessed as changes in short circuit current in Ussing chambers. We determined HG treatment (5–10 μM) alone did not induce FXR activation but significantly increased expression of the receptor, both in T₈₄ cells and murine enteroid-derived monolayers. This effect was accompanied by enhanced FXR activity, as assessed by FGF-15/19 induction in response to the synthetic, GW4064, or natural FXR agonist, chenodeoxycholic acid. Effects of HG on FXR expression and activity were mimicked by another PCT, oleanolic acid. Furthermore, we found FXR-induced downregulation of cystic fibrosis transmembrane conductance regulator Cl⁻ channels and inhibition of transepithelial Cl⁻ secretion were enhanced in HG-treated cells. These data demonstrate that dietary PCTs have the capacity to modulate FXR expression, activity, and antisecretory actions in colonic epithelial cells. Based on these data, we propose that plants rich in PCTs, or extracts thereof, have excellent potential for development as a new class of “FXR-targeted nutraceuticals”.

Targeted bile acid profiles reveal the liver injury amelioration of Da-Chai-Hu decoction against ANIT- and BDL-induced cholestasis

Multiple types of liver diseases, particularly cholestatic liver diseases (CSLDs) and biliary diseases, can disturb bile acid (BA) secretion; however, BA accumulation is currently seen as an important incentive of various types of liver diseases’ progression. Da-Chai-Hu decoction (DCHD) has long been used for treating cholestatic liver diseases; however, the exact mechanisms remain unclear. Currently, our study indicates that the liver damage and cholestasis status of the α-naphthylisothiocyanate (ANIT)-induced intrahepatic cholestasis and bile duct ligation (BDL)-induced extrahepatic cholestasis, following DCHD treatment, were improved; the changes of BA metabolism post-DCHD treatment were investigated by targeted metabolomics profiling by UPLC-MS/MS. DCHD treatment severely downregulated serum biochemical levels and relieved inflammation and the corresponding pathological changes including necrosis, inflammatory infiltration, ductular proliferation, and periductal fibrosis in liver tissue. The experimental results suggested that DCHD treatment altered the size, composition, and distribution of the BAs pool, led the BAs pool of the serum and liver to sharply shrink, especially TCA and TMCA, and enhanced BA secretion into the gallbladder and the excretion of BAs by the urinary and fecal pathway; the levels of BAs synthesized by the alternative pathway were increased in the liver, and the conjugation of BAs and the pathway of BA synthesis were actually affected. In conclusion, DCHD ameliorated ANIT- and BDL-induced cholestatic liver injury by reversing the disorder of BAs profile.

Fibroblast Growth Factor 19 Improves LPS-Induced Lipid Disorder and Organ Injury by Regulating Metabolomic Characteristics in Mice

Sepsis is extremely heterogeneous pathology characterized by complex metabolic changes. Fibroblast growth factor 19 (FGF19) is a well-known intestine-derived inhibitor of bile acid biosynthesis. However, it is largely unknown about the roles of FGF19 in improving sepsis-associated metabolic disorder and organ injury. In the present study, mice were intravenously injected recombinant human FGF19 daily for 7 days followed by lipopolysaccharide (LPS) administration. At 24 hours after LPS stimuli, sera were collected for metabolomic analysis. Ingenuity pathway analysis (IPA) network based on differential metabolites (DMs) was conducted. Here, metabolomic analysis revealed that FGF19 pretreatment reversed the increase of LPS-induced fatty acids. IPA network indicated that altered linoleic acid (LA) and gamma-linolenic acid (GLA) were involved in the regulation of oxidative stress and mitochondrial function and were closely related to reactive oxygen species (ROS) generation. Further investigation proved that FGF19 pretreatment decreased serum malondialdehyde (MDA) levels and increased serum catalase (CAT) levels. In livers, FGF19 suppressed the expression of inducible NO synthase (iNOS) and enhanced the expression of nuclear factor erythroid 2-related factor 2 (NRF2) and hemeoxygenase-1 (HO-1). Finally, FGF19 pretreatment protected mice against LPS-induced liver, ileum, and kidney injury. Taken together, FGF19 alleviates LPS-induced organ injury associated with improved serum LA and GLA levels and oxidative stress, suggesting that FGF19 might be a promising target for metabolic therapy for sepsis.

Circulating chemerin levels in metabolic-associated fatty liver disease: a systematic review and meta-analysis

Background and objectives

Chemerin is a brand-new adipokine that has been linked to both inflammation and metabolic dysfunction. Even though a rising number of studies have connected chemerin to metabolic-associated fatty liver disease (MAFLD), formerly referred to as non-alcoholic fatty liver disease (NAFLD), this association has been controversial.

Methods

A comprehensive literature search was undertaken up to February 1, 2022, in the PubMed, Embase, Web of Science, CNKI, WANFANG, and CBM library databases. Circulating chemerin levels were obtained and summarized using the standardized mean difference (SMD) and 95% confidence interval (CI). Subgroup and meta-regression analyses were conducted to examine the possibility of heterogeneity.

Results

A total of 17 studies involving 2580 participants (1584 MAFLD patients and 996 controls) evaluated circulating chemerin levels in patients with MAFLD. The present study showed that higher chemerin levels were found in patients with MAFLD (SMD: 1.32; 95% CI: 0.29, 2.35) and nonalcoholic fatty liver (NAFL) (SMD: 0.75; 95% CI: 0.01, 1.50) compared to controls. However, circulating chemerin levels did not differ significantly in the following comparisons: nonalcoholic steatohepatitis (NASH) patients and controls (SMD: 0.75; 95% CI: -0.52, 2.03); NASH patients and NAFL patients (SMD: 0.16; 95% CI: -0.39, 0.70); moderate to severe steatosis and mild steatosis (SMD: 0.55; 95% CI: -0.59, 1.69); present liver fibrosis and absent liver fibrosis (SMD: 0.66; 95% CI: -0.42, 1.74); present lobular inflammation and absent lobular inflammation (SMD: 0.45; 95% CI: -0.53, 1.42); and present portal inflammation and absent portal inflammation (SMD: 1.92; 95% CI: -0.85, 4.69).

Conclusions

Chemerin levels were considerably greater in patients with MAFLD than in controls, despite the fact that they were not significantly linked to different liver tissue lesions of MAFLD. In different subtypes of MAFLD, in comparison to healthy controls, the chemerin levels of NAFL patients were higher, whereas, there was no obvious difference in chemerin levels between NASH patients and controls. It is possible that chemerin will be used as a biomarker in the future to track the development and progression of MAFLD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-022-01637-7.

Microbiome Metabolites and Thyroid Dysfunction

Thyroid diseases are common conditions that have a negative impact on the health of all populations. The literature sheds light on the differences in the composition of the intestinal microbiota in patients suffering from thyroid diseases compared to healthy individuals. The microbiome affects the proper functioning of the thyroid gland, and the existence of the gut–thyroid axis is discussed in the context of both thyroid diseases and intestinal dysbiosis. The purpose of this review is to describe associations between the microbiome and its metabolites and thyroid dysfunction. We try to explain the role of the microbiome in the metabolism of thyroid hormones and the impact of thyroid autoimmune diseases. In addition, we raise issues related to the influence of bacterial metabolites, such as short-chain fatty acids or secondary bile acids, in the functioning of the thyroid gland. Last but not least, we explored the interactions between the gut microbiota and therapeutics and supplements typically administered to patients with thyroid diseases.

Roles of Gut Microbial Metabolites in Diabetic Kidney Disease

Diabetes is a highly prevalent metabolic disease that has emerged as a global challenge due to its increasing prevalence and lack of sustainable treatment. Diabetic kidney disease (DKD), which is one of the most frequent and severe microvascular complications of diabetes, is difficult to treat with contemporary glucose-lowering medications. The gut microbiota plays an important role in human health and disease, and its metabolites have both beneficial and harmful effects on vital physiological processes. In this review, we summarize the current findings regarding the role of gut microbial metabolites in the development and progression of DKD, which will help us better understand the possible mechanisms of DKD and explore potential therapeutic approaches for DKD.