Guggulsterone antagonizes farnesoid X receptor induction of bile salt export pump but activates pregnane X receptor to inhibit cholesterol 7alpha-hydroxylase gene

CXCR4 expression is elevated in TNBC patient derived samples and Z-guggulsterone abrogates tumor progression by targeting CXCL12/CXCR4 signaling axis in mice model

Environmental factors such as exposure to ionizing radiations, certain environmental pollutants, and toxic chemicals are considered as risk factors in the development of breast cancer. Triple-negative breast cancer (TNBC) is a molecular variant of breast cancer that lacks therapeutic targets such as progesterone receptor, estrogen receptor, and human epidermal growth factor receptor-2 which makes the targeted therapy ineffective in TNBC patients. Therefore, identification of new therapeutic targets for the treatment of TNBC and the discovery of new therapeutic agents is the need of the hour. In this study, CXCR4 was found to be highly expressed in majority of breast cancer tissues and metastatic lymph nodes derived from TNBC patients. CXCR4 expression is positively correlated with breast cancer metastasis and poor prognosis of TNBC patients suggesting that suppression of CXCR4 expression could be a good strategy in the treatment of TNBC patients. Therefore, the effect of Z-guggulsterone (ZGA) on the expression of CXCR4 in TNBC cells was examined. ZGA downregulated protein and mRNA expression of CXCR4 in TNBC cells and proteasome inhibition or lysosomal stabilization had no effect on the ZGA-induced CXCR4 reduction. CXCR4 is under the transcriptional control of NF-κB, whereas ZGA was found to downregulate transcriptional activity NF-κB. Functionally, ZGA downmodulated the CXCL12-driven migration/invasion in TNBC cells. Additionally, the effect of ZGA on growth of tumor was investigated in the orthotopic TNBC mice model and ZGA presented good inhibition of tumor growth and liver/lung metastasis in this model. Western blotting and immunohistochemical analysis indicated a reduction of CXCR4, NF-κB, and Ki67 in tumor tissues. Computational analysis suggested PXR agonism and FXR antagonism as targets of ZGA. In conclusion, CXCR4 was found to be overexpressed in majority of patient-derived TNBC tissues and ZGA abrogated the growth of TNBC tumors by partly targeting the CXCL12/CXCR4 signaling axis.

Theonella: A Treasure Trove of Structurally Unique and Biologically Active Sterols

The marine environment is considered a vast source in the discovery of structurally unique bioactive secondary metabolites. Among marine invertebrates, the sponge Theonella spp. represents an arsenal of novel compounds ranging from peptides, alkaloids, terpenes, macrolides, and sterols. In this review, we summarize the recent reports on sterols isolated from this amazing sponge, describing their structural features and peculiar biological activities. We also discuss the total syntheses of solomonsterols A and B and the medicinal chemistry modifications on theonellasterol and conicasterol, focusing on the effect of chemical transformations on the biological activity of this class of metabolites. The promising compounds identified from Theonella spp. possess pronounced biological activity on nuclear receptors or cytotoxicity and result in promising candidates for extended preclinical evaluations. The identification of naturally occurring and semisynthetic marine bioactive sterols reaffirms the utility of examining natural product libraries for the discovery of new therapeutical approach to human diseases.

Remodeling of white adipose tissue microenvironment against obesity by phytochemicals

Obesity is a kind of chronic disease due to a long-term imbalance between energy intake and expenditure. In recent years, the number of obese people around the world has soared, and obesity problem should not be underestimated. Obesity is characterized by changes in the adipose microenvironment, mainly manifested as hypertrophy, chronic inflammatory status, hypoxia, and fibrosis, thus contributing to the pathological changes of other tissues. A plethora of phytochemicals have been found to improve adipose microenvironment, thus prevent and resist obesity, providing a new research direction for the treatment of obesity and related diseases. This paper discusses remodeling of the adipose tissue microenvironment as a therapeutic avenue and reviews the progress of phytochemicals in fighting obesity by improving the adipose microenvironment.

Anti-cancer activity of guggulsterone by modulating apoptotic markers: a systematic review and meta-analysis

Background: Guggulsterone (pregna-4,17-diene-3,16-dione; C₂₁H₂₈O₂) is an effective phytosterol isolated from the gum resin of the tree Commiphora wightii (Family Burseraceae) and is responsible for many of the properties of guggul. This plant is widely used as traditional medicine in Ayurveda and Unani system of medicine. It exhibits several pharmacological activities, such as anti-inflammatory, analgesic, antibacterial, anti-septic and anticancer. In this article, the activities of Guggulsterone against cancerous cells were determined and summarized. Methods: Using 7 databases (PubMed, PMC, Google Scholar, Science Direct, Scopus, Cochrane and Ctri.gov), the literature search was conducted since conception until June 2021. Extensive literature search yielded 55,280 studies from all the databases. A total of 40 articles were included in the systematic review and of them, 23 articles were included in the meta-analysis.The cancerous cell lines used in the studies were for pancreatic cancer, hepatocellular carcinoma, head and neck squamous cell carcinoma, cholangiocarcinoma, oesophageal adenocarcinoma, prostrate cancer, colon cancer, breast cancer, gut derived adenocarcinoma, gastric cancer, colorectal cancer, bladder cancer, glioblastoma, histiocytic leukemia, acute myeloid leukemia and non-small cell lung cancer. The reliability of the selected studies was assessed using ToxRTool. Results: Based on this review, guggulsterone significantly affected pancreatic cancer (MiaPaCa-2, Panc-1, PC-Sw, CD18/HPAF, Capan1, PC-3), hepatocellular carcinoma (Hep3B, HepG2, PLC/PRF/5R), head and neck squamous cell carcinoma (SCC4, UM-22b, 1483), cholangiocarcinoma (HuCC-T1, RBE, Sk-ChA-1, Mz-ChA-1) and oesophageal adenocarcinoma (CP-18821, OE19), prostrate cancer (PC-3), colon cancer (HT-29), breast cancer (MCF7/DOX), gut derived adenocarcinoma (Bic-1), gastric cancer (SGC-7901), colorectal cancer (HCT116), bladder cancer (T24, TSGH8301), glioblastoma (A172, U87MG, T98G), histiocytic leukemia (U937), acute myeloid leukemia (HL60, U937) and non-small cell lung cancer (A549, H1975) by inducing apoptotic pathways, inhibiting cell proliferation, and regulating the expression of genes involved in apoptosis. Guggulsterone is known to have therapeutic and preventive effects on various categories of cancers. It can inhibit the progression of tumors and can even reduce their size by inducing apoptosis, exerting anti-angiogenic effects, and modulating various signaling cascades. In vitro studies reveal that Guggulsterone inhibits and suppresses the proliferation of an extensive range of cancer cells by decreasing intrinsic mitochondrial apoptosis, regulating NF-kB/STAT3/β-Catenin/PI3K/Akt/CHOP pathway, modulating the expression of associated genes/proteins, and inhibiting angiogenesis. Furthermore, Guggulsterone reduces the production of inflammatory markers, such as CDX2 and COX-2. The other mechanism of the Guggulsterone activity is the reversal of P-glycoprotein-mediated multidrug resistance. Twenty three studies were selected for meta-analysis following the PRISMA statements. Fixed effect model was used for reporting the odds ratio. The primary endpoint was percentage apoptosis. 11 of 23 studies reported the apoptotic effect at t = 24 h and pooled odds ratio was 3.984 (CI 3.263 to 4.865, p < 0.001). 12 studies used Guggulsterone for t > 24 h and the odds ratio was 11.171 (CI 9.148 to 13.643, 95% CI, p < 0.001). The sub-group analysis based on cancer type, Guggulsterone dose, and treatment effects. Significant alterations in the level of apoptotic markers were reported by Guggulsterone treatment. Conclusion: This study suggested that Guggulsterone has apoptotic effects against various cancer types. Further investigation of its pharmacological activity and mechanism of action should be conducted. In vivo experiments and clinical trials are required to confirm the anticancer activity.

Vertical sleeve gastrectomy induces enteroendocrine cell differentiation of intestinal stem cells through bile acid signaling

Vertical sleeve gastrectomy (VSG) results in an increase in the number of hormone-secreting enteroendocrine cells (EECs) in the intestinal epithelium; however, the mechanism remains unclear. Notably, the beneficial effects of VSG are lost in a mouse model lacking the nuclear bile acid receptor farnesoid X receptor (FXR). FXR is a nuclear transcription factor that has been shown to regulate intestinal stem cell (ISC) function in cancer models. Therefore, we hypothesized that the VSG-induced increase in EECs is due to changes in intestinal differentiation driven by an increase in bile acid signaling through FXR. To test this, we performed VSG in mice that express EGFP in ISC/progenitor cells and performed RNA-Seq on GFP-positive cells sorted from the intestinal epithelia. We also assessed changes in EEC number (marked by glucagon-like peptide-1, GLP-1) in mouse intestinal organoids following treatment with bile acids, an FXR agonist, and an FXR antagonist. RNA-Seq of ISCs revealed that bile acid receptors are expressed in ISCs and that VSG explicitly alters expression of several genes that regulate EEC differentiation. Mouse intestinal organoids treated with bile acids and 2 different FXR agonists increased GLP-1-positive cell numbers, and administration of an FXR antagonist blocked these effects. Taken together, these data indicate that VSG drives ISC fate toward EEC differentiation through bile acid signaling.

Obeticholic acid ameliorates obesity and hepatic steatosis by activating brown fat

Obeticholic acid (OCA) is exemplified as a potent drug for treating primary biliary cirrhosis and nonalcoholic fatty liver disease by inhibiting bile acid synthesis. However, it remains unclear whether the effect of OCA is mediated by the function of brown adipose tissue (BAT). In the present study, brown adipogenesis differentiation in vitro and db/db mouse model treated with OCA were used to assess the anti-obesity function by body weight tracking, O₂ consumption, food intake, physical activity, glucose tolerance tests. In addition, uncoupling protein 1 (Ucp1) protein expression in brown adipose tissue was measured by western blotting, morphometry of brown adipose tissue was analyzed by hematoxylin and eosin staining. Hepatic steatosis was detected by Oil-Red O staining and serological analysis was performed to assess the effect of OCA on hyperlipidemia. OCA treatment enhanced brown adipocyte cell differentiation and upregulated the expression of the BAT-specific gene Ucp1) in C3H10T1/2 cells in vitro. Consistent with these findings, OCA increased whole-body energy metabolism and glucose homeostasis by enhancing BAT activity in vivo, and ultimately decreased body weight gain in db/db mice. In addition, the results demonstrated that spontaneous hepatic steatosis in db/db mice was ameliorated following OCA treatment. In summary, OCA functioned as a BAT activator to help ameliorate obesity and maintain glucose homeostasis in db/db mice. The present results may provide a novel potential therapeutic approach to activate brown fat in patients with obesity and other metabolic disorders.

Potential of guggulsterone, a farnesoid X receptor antagonist, in the prevention and treatment of cancer

Cancer is one of the most dreadful diseases in the world with a mortality of 9.6 million annually. Despite the advances in diagnosis and treatment during the last couple of decades, it still remains a serious concern due to the limitations associated with currently available cancer management strategies. Therefore, alternative strategies are highly required to overcome these glitches. The importance of medicinal plants as primary healthcare has been well-known from time immemorial against various human diseases, including cancer. Commiphora wightii that belongs to Burseraceae family is one such plant which has been used to cure various ailments in traditional systems of medicine. This plant has diverse pharmacological properties such as antioxidant, antibacterial, antimutagenic, and antitumor which mostly owes to the presence of its active compound guggulsterone (GS) that exists in the form of Z- and E-isomers. Mounting evidence suggests that this compound has promising anticancer activities and was shown to suppress several cancer signaling pathways such as NF-κB/ERK/MAPK/AKT/STAT and modulate the expression of numerous signaling molecules such as the farnesoid X receptor, cyclin D1, survivin, caspases, HIF-1α, MMP-9, EMT proteins, tumor suppressor proteins, angiogenic proteins, and apoptotic proteins. The current review is an attempt to summarize the biological activities and diverse anticancer activities (both in vitro and in vivo) of the compound GS and its derivatives, along with its associated mechanism against various cancers.

Synthesis and inhibitory effect of cis-guggulsterone on lipopolysaccharide-induced production of nitric oxide in macrophages

Guggulsterone is a bioactive plant sterol naturally found in migratory plants. It exists in various forms, and its active compounds include the isomers cis-guggulsterone (E-GS) and trans-guggulsterone (Z-GS). In this study, the anti-inflammatory effects of these two isomeric pregnadienedione steroids were investigated against lipopolysaccharide-induced inflammatory reaction in RAW264.7 mouse macrophages. Our results showed that both guggulsterones inhibited the production of NO in macrophages treated with lipopolysaccharide, with IC50 values ranging from 3.0 to 6.7 μM. E-GS exerted higher efficacy than Z-GS, and its anti-inflammatory effects was mediated through inhibition of iNOS and COX-2 expression.

Farnesoid X receptor alpha (FXRα) is a critical actor of the development and pathologies of the male reproductive system

The farnesoid-X-receptorα (FXRα; NR1H4) is one of the main bile acid (BA) receptors. During the last decades, through the use of pharmalogical approaches and transgenic mouse models, it has been demonstrated that the nuclear receptor FXRα controls numerous physiological functions such as glucose or energy metabolisms. It is also involved in the etiology or the development of several pathologies. Here, we will review the unexpected roles of FXRα on the male reproductive tract. FXRα has been demonstrated to play functions in the regulation of testicular and prostate homeostasis. Even though additional studies are needed to confirm these findings in humans, the reviewed reports open new field of research to better define the effects of bile acid-FXRα signaling pathways on fertility disorders and cancers.

A novel epigenetic mechanism of FXR inhibiting GLP-1 secretion via miR-33 and its downstream targets

Type II diabetes is a complex, chronic, and progressive disease. Previously, we demonstrate that FXR inhibits GLP-1 secretion via interacting with CREB to inhibit the transcriptional activity of CREB, thus promoting the development of type II diabetes. Epigenetic modifications, such as DNA methylation, histone acetylation, and post-transcriptional RNA regulation, are essential mediators contributing to diabetes-associated morbidity and mortality. Thus, we attempted to investigate the epigenetic mechanisms of FXR modulating GLP-1 secretion. Firstly, the involvement of histone acetylation, DNA methylation, and post-transcriptional regulation in FXR inhibiting GLP-1 secretion was verified. As FXR overexpression significantly inhibited the activity of GCG 3'-UTR, we hypothesize that miRNA might participate in the mechanism. Two online tools and real-time PCR revealed that FXR promoted miR-33 expression. Moreover, miR-33 inhibited the expression of GCG and CREB1 through direct targeting in STC-1 cells. FXR overexpression in STC-1 cells significantly reduced the mRNA expression and protein levels of both GCG and CREB1, as well as the secretion of GLP-1; miR-33 inhibition exerted opposing effects. More importantly, the effects of FXR overexpression were significantly reversed by miR-33 inhibition, indicating that FXR inhibited GLP-1 secretion through promoting miR-33 expression, therefore inhibiting the expression of miR-33 targets, GCG and CREB1. In conclusion, we provide a novel epigenetic mechanism by which FXR inhibits the secretion of GLP-1 through miR-33 and its two downstream targets, GCG and CREB1. These findings might provide innovative strategies for improving type II diabetes, which needs further in vivo and clinical investigation.

Dietary β-Cryptoxanthin Inhibits High-Refined Carbohydrate Diet-Induced Fatty Liver via Differential Protective Mechanisms Depending on Carotenoid Cleavage Enzymes in Male Mice

BACKGROUND

β-Cryptoxanthin (BCX), a provitamin A carotenoid shown to protect against nonalcoholic fatty liver disease (NAFLD), can be cleaved by β-carotene-15,15'-oxygenase (BCO1) to generate vitamin A, and by β-carotene-9',10'-oxygenase (BCO2) to produce bioactive apo-carotenoids. BCO1/BCO2 polymorphisms have been associated with variations in plasma carotenoid amounts in both humans and animals.

OBJECTIVES

We investigated whether BCX feeding inhibits high refined-carbohydrate diet (HRCD)-induced NAFLD, dependent or independent of BCO1/BCO2.

METHODS

Six-week-old male wild-type (WT) and BCO1-/-/BCO2-/- double knockout (DKO) mice were randomly fed HRCD (66.5% of energy from carbohydrate) with or without BCX (10 mg/kg diet) for 24 wk. Pathological and biochemical variables were analyzed in the liver and mesenteric adipose tissues (MATs). Data were analyzed by 2-factor ANOVA.

RESULTS

Compared to their respective HRCD controls, BCX reduced hepatic steatosis severity by 33‒43% and hepatic total cholesterol by 43‒70% in both WT and DKO mice (P < 0.01). Hepatic concentrations of BCX, but not retinol and retinyl palmitate, were 33-fold higher in DKO mice than in WT mice (P < 0.001). BCX feeding increased the hepatic fatty acid oxidation protein peroxisome proliferator-activated receptor-α, and the cholesterol efflux gene ATP-binding cassette transporter5, and suppressed the lipogenesis gene acetyl-CoA carboxylase 1 (Acc1) in the MAT of WT mice but not DKO mice (P < 0.05). BCX feeding decreased the hepatic lipogenesis proteins ACC and stearoyl-CoA desaturase-1 (3-fold and 5-fold) and the cholesterol synthesis genes 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase and HMG-CoA synthase 1 (2.7-fold and 1.8-fold) and increased the cholesterol catabolism gene cholesterol 7α-hydroxylase (1.9-fold) in the DKO but not WT mice (P < 0.05). BCX feeding increased hepatic protein sirtuin1 (2.5-fold) and AMP-activated protein kinase (9-fold) and decreased hepatic farnesoid X receptor protein (80%) and the inflammatory cytokine gene Il6 (6-fold) in the MAT of DKO mice but not WT mice (P < 0.05).

CONCLUSION

BCX feeding mitigates HRCD-induced NAFLD in both WT and DKO mice through different mechanisms in the liver-MAT axis, depending on the presence or absence of BCO1/BCO2.

Dissecting the allosteric FXR modulation: a chemical biology approach using guggulsterone as a chemical tool

Guggulsterone is a promiscuous ligand for endocrine and metabolic lipid receptors traditionally used to treat a number of diseases including diabesity, hyperlipidemia, atherosclerosis, and osteoarthritis. Although relatively weak, its activity at the farnesoid X receptor (FXR) is particularly intriguing as guggulsterone acts as an antagonist with a peculiar ability of gene selective modulation. We report here a chemical biology study with the aim to further characterize the biological action of guggulsterone at the FXR and to obtain further insights into the functional role played by noncanonical FXR binding pockets S2 and S3. Our results suggest that the FXR accessory pockets might act as potential targets for small molecules able to modulate the metabolic activation of the receptor without affecting the anti-inflammatory activity thus revealing a new approach for disclosing selective FXR modulators that might bypass potential side-effects from chronic treatments.

Human cytochrome P450 enzymes 5-51 as targets of drugs and natural and environmental compounds: mechanisms, induction, and inhibition - toxic effects and benefits

Cytochrome P450 (P450, CYP) enzymes have long been of interest due to their roles in the metabolism of drugs, pesticides, pro-carcinogens, and other xenobiotic chemicals. They have also been of interest due to their very critical roles in the biosynthesis and metabolism of steroids, vitamins, and certain eicosanoids. This review covers the 22 (of the total of 57) human P450s in Families 5-51 and their substrate selectivity. Furthermore, included is information and references regarding inducibility, inhibition, and (in some cases) stimulation by chemicals. We update and discuss important aspects of each of these 22 P450s and questions that remain open.

Googling the Guggul (Commiphora and Boswellia) for Prevention of Chronic Diseases

Extensive research during last 2 decades has revealed that most drugs discovered today, although costs billions of dollars for discovery, and yet they are highly ineffective in their clinical response. For instance, the European Medicines Agency has approved 68 anti-cancer drugs, and out of which 39 has reached the market level with no indication of increased survival nor betterment of quality of life. Even when drugs did improve survival rate compared to available treatment strategies, most of these were found to be clinically insignificant. This is a fundamental problem with modern drug discovery which is based on thinking that most chronic diseases are caused by alteration of a single gene and thus most therapies are single gene-targeted therapies. However, extensive research has revealed that most chronic diseases are caused by multiple gene products. Although most drugs designed by man are mono-targeted therapies, however, those designed by "mother nature" and have been used for thousands of years, are "multi-targeted" therapies. In this review, we examine two agents that have been around for thousands of years, namely "guggul" from Commiphora and Boswellia. Although we are all familiar with the search engine "google," this is another type of "guggul" that has been used for centuries and being explored for its various biological activities. The current review summarizes the traditional uses, chemistry, in vitro and in vivo biological activities, molecular targets, and clinical trials performed with these agents.

Natural products as modulators of the nuclear receptors and metabolic sensors LXR, FXR and RXR

Nuclear receptors (NRs) represent attractive targets for the treatment of metabolic syndrome-related diseases. In addition, natural products are an interesting pool of potential ligands since they have been refined under evolutionary pressure to interact with proteins or other biological targets. This review aims to briefly summarize current basic knowledge regarding the liver X (LXR) and farnesoid X receptors (FXR) that form permissive heterodimers with retinoid X receptors (RXR). Natural product-based ligands for these receptors are summarized and the potential of LXR, FXR and RXR as targets in precision medicine is discussed.

Potential therapeutic targets of Guggulsterone in cancer

Natural compounds capable of inducing apoptosis in cancer cells have always been of considerable interest as potential anti-cancer agents. Many such compounds are under screening and development with their potential evolution as a clinical drug benefiting many of the cancer patients. Guggulsterone (GS), a phytosterol isolated gum resin of the tree Commiphora mukul has been widely used in Indian traditional medicine as a remedy for various diseses. GS has been shown to possess cancer chemopreventive and therapeutic potential as established by in vitro and in vivo studies. GS has been shown to target constitutively activated survival pathways such as PI3-kinase/AKT, JAK/STAT, and NFκB signaling pathways that are involved in the regulation of growth and inflammatory responses via regulation of antiapoptotic and inflammatory genes. The current review focuses on the molecular targets of GS, cellular responses, and the animal model studies in various cancers. The mechanistic action of GS in different types of cancers also forms a part of this review. The perspective of translating this natural compound into a clinically approved drug with its pros and cons is also discussed.

Bile acids and their receptors

Primary bile acids are synthetized from cholesterol within the liver and then transformed by the bacteria in the intestine to secondary bile acids. In addition to their involvement in digestion and fat solubilization, bile acids also act as signaling molecules. Several receptors are sensors of bile acids. Among these receptors, this review focuses on the nuclear receptor FXRα and the G-protein-coupled receptor TGR5. This review briefly presents the potential links between bile acids and cancers that are discussed in more details in the other articles of this special issue of Molecular Aspects of Medicine focused on "Bile acids, roles in integrative physiology and pathophysiology".

An estrogen receptor β-selective agonist inhibits non-alcoholic steatohepatitis in preclinical models by regulating bile acid and xenobiotic receptors

Non-alcoholic steatohepatitis (NASH) affects 8-10 million people in the US and up to 75% of obese individuals. Despite this, there are no approved oral therapeutics to treat NASH and therefore the need for novel approaches exists. The estrogen receptor β (ER-β)-selective agonist, β-LGND2, inhibits body weight and white adipose tissue, and increases metabolism, resulting in higher energy expenditure and thermogenesis. Due to favorable effects of β-LGND2 on obesity, we hypothesized that β-LGND2 will prevent NASH directly by reducing lipid accumulation in the liver or indirectly by favorably changing body composition. Male C57BL/6 mice fed with high fat diet (HFD) for 10 weeks or methionine choline-deficient diet for four weeks and treated with vehicle exhibited altered liver weights by twofold and increased serum transaminases by 2-6-folds. These changes were not observed in β-LGND2-treated animals. Infiltration of inflammatory cells and collagen deposits, an indication of fibrosis, were observed in the liver of mice fed with HFD for 10 weeks, which were effectively blocked by β-LGND2. Gene expression studies in the liver indicate that pregnane X receptor target genes were significantly increased by HFD, and the increase was inhibited by β-LGND2. On the other hand, metabolomics indicate that bile acid metabolites were significantly increased by β-LGND2. These studies demonstrate that an ER-β agonist might provide therapeutic benefits in NASH by directly modulating the function of xenobiotic and bile acid receptors in the liver, which have important functions in the liver, and indirectly, as demonstrated before, by inhibiting adiposity. Impact statement Over 75-90% of those classified as clinically obese suffer from co-morbidities, the most common of which is non-alcoholic steatohepatitis (NASH). While there are currently no effective treatment approaches for NASH, data presented here provide preliminary evidence that an estrogen receptor β-selective ligand could have the potential to reduce lipid accumulation and inflammation, and protect liver from NASH.

Effects of triphala and guggul aqueous extracts on inhibition of protein fibrillation and dissolution of preformed fibrils

Herbal preparations such as triphala and guggul aqueous extracts have ability to inhibit protein fibrillation which is known to be an important process responsible for many neurodegenerative and other diseases.

Geniposidic acid protected against ANIT-induced hepatotoxity and acute intrahepatic cholestasis, due to Fxr-mediated regulation of Bsep and Mrp2

ETHNOPHARMACOLOGICAL RELEVANCE

Geniposidic acid (GPA) is the main constituent of Gardenia jasminoides Ellis (Rubiaceae), which has long been used to treat inflammation, jaundice and hepatic disorders. The cholagogic effect of Gardenia jasminoides Ellis (Rubiaceae) and GPA have been widely reported, but the underlying occurrence mechanism remains unclear.

AIM OF THE STUDY

This investigation was designed to evaluate the hepatoprotection effect and potential mechanisms of GPA derived from Gardenia jasminoides Ellis (Rubiaceae) on fighting against α-naphthylisothiocyanate (ANIT) caused liver injury with acute intrahepatic cholestasis.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats were intragastrically (i.g.) administered with the GPA (100, 50 and 25mg/kg B.W. every 24h) for seven consecutive days, and then they were treated with ANIT (i.g. 65mg/kg once in the 5th day) which induced liver injury with acute intrahepatic cholestasis. Serum and bile biochemical analysis, bile flow rate and liver histopathology were measured to evaluate the protective effect of GPA fight against ANIT treatment. The protein and mRNA expression levels of farnesoid X receptor (Fxr), bile-salt export pump (Bsep), multidrug resistance associated protein2 (Mrp2), were evaluated to study the effect of liver protection about GPA against ANIT induced hepatotoxicity and underlying mechanisms.

RESULTS

Some abnormalities were observed on ANIT treated rats including weight loss, reduced food intake and hair turned yellow. Obtained results demonstrated that at dose 100 and 50mg/kg B.W. (P<0.01) and 25mg/kg B.W. (P<0.05) of GPA pretreated dramatically prevented ANIT induced decreased in bile flow rate. Compared with ANIT treated group, the results of bile biochemical parameters about total bile acid (TBA) was increased by GPA at groups with any dose (P<0.01), glutathione (GSH) was increased significantly at high dose (P<0.01) and medium dose (P<0.05), total bilirubin (TB) was increased at high and medium dose (P<0.05), direct bilirubin (DB) was only increased at high dose (P<0.01). Serum levels of glutamic-Oxalacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), γ-glutamyltranspeptidase (γ-GT), TB, DB and TBA in comparison with ANIT treated group (P<0.01) were reduced by GPA (between 100 and 50mg/kg B.W.) pretreatment. Histopathology of the liver tissue showed that pathological damages and hepatic portal area filled with bile were relieved after GPA pretreatment compared with ANIT treated group. The protein and mRNA expression of Fxr, Bsep and Mrp2 were decreased in ANIT treated group. On the contrary, the protein and mRNA of Fxr, Bsep and Mrp2 were up regulated significantly pretreatment by GPA at dose of high and medium groups. On protein level of Bsep and Mrp2 the result shown no statistical difference in GPA (25mg/kg B.W.), but it was not same shown in mRNA level.

CONCLUSION

The results of this investigation have demonstrated that the GPA exerts a dose dependent hepatoprotection effect on ANIT induced liver damage with acute intrahepatic cholestasis in rats, which may due to Fxr mediated regulation of bile transporters like Bsep and Mrp2.

Guggulsterone and Its Role in Chronic Diseases

Guggulsterone is a plant sterol derived from gum resin of Commiphora wightii. The gum resin from guggul plants has been used for thousand years in Ayurveda to treat various disorders, including internal tumors, obesity, liver disorders, malignant sores and ulcers, urinary complaints, intestinal worms, leucoderma, sinuses, edema, and sudden paralytic seizures. Guggulsterone has been identified a bioactive components of this gum resin. This plant steroid has been reported to work as an antagonist of certain nuclear receptors, especially farnesoid X receptor, which regulates bile acids and cholesterol metabolism. Guggulsterone also mediates gene expression through the regulation of transcription factors, including nuclear factor-kappa B and signal transducer and activator of transcription 3, which plays important roles in the development of inflammation and tumorigenesis. Guggulsterone has been shown to downregulate the expression of proteins involved in anti-apoptotic, cell survival, cell proliferation, angiogenic, metastatic, and chemoresistant activities in tumor cells. This review aimed to clarify the cell signal pathways targeted by guggulsterone and the bioactivities of guggulsterone in animal models and humans.

Potency of individual bile acids to regulate bile acid synthesis and transport genes in primary human hepatocyte cultures

Bile acids (BAs) are known to regulate their own homeostasis, but the potency of individual bile acids is not known. This study examined the effects of cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA) and ursodeoxycholic acid (UDCA) on expression of BA synthesis and transport genes in human primary hepatocyte cultures. Hepatocytes were treated with the individual BAs at 10, 30, and 100μM for 48 h, and RNA was extracted for real-time PCR analysis. For the classic pathway of BA synthesis, BAs except for UDCA markedly suppressed CYP7A1 (70-95%), the rate-limiting enzyme of bile acid synthesis, but only moderately (35%) down-regulated CYP8B1 at a high concentration of 100μM. BAs had minimal effects on mRNA of two enzymes of the alternative pathway of BA synthesis, namely CYP27A1 and CYP7B1. BAs increased the two major target genes of the farnesoid X receptor (FXR), namely the small heterodimer partner (SHP) by fourfold, and markedly induced fibroblast growth factor 19 (FGF19) over 100-fold. The BA uptake transporter Na(+)-taurocholate co-transporting polypeptide was unaffected, whereas the efflux transporter bile salt export pump was increased 15-fold and OSTα/β were increased 10-100-fold by BAs. The expression of the organic anion transporting polypeptide 1B3 (OATP1B3; sixfold), ATP-binding cassette (ABC) transporter G5 (ABCG5; sixfold), multidrug associated protein-2 (MRP2; twofold), and MRP3 (threefold) were also increased, albeit to lesser degrees. In general, CDCA was the most potent and effective BA in regulating these genes important for BA homeostasis, whereas DCA and CA were intermediate, LCA the least, and UDCA ineffective.

IDENTIFICATION OF VDR ANTAGONISTS AMONG NUCLEAR RECEPTOR LIGANDS USING VIRTUAL SCREENING

Herein, we described the development of two virtual screens to identify new vitamin D receptor (VDR) antagonists among nuclear receptor (NR) ligands. Therefore, a database of 14330 nuclear receptor ligands and their NR affinities was assembled using the online available "Binding Database". Two different virtual screens were carried out in conjunction with a reported VDR crystal structure applying a stringent and less stringent pharmacophore model to filter docked NR ligand conformations. The pharmacophore models were based on the spatial orientation of the hydroxyl functionalities of VDR's natural ligands 1,25(OH₂)D₃ and 25(OH₂)D₃. The first virtual screen identified 32 NR ligands with a calculate free energy of VDR binding of more than -6.0 kJ/mol. All but nordihydroguaiaretic acid (NDGA) are VDR ligands, which inhibited the interaction between VDR and coactivator peptide SRC2-3 with an IC₅₀ value of 15.8 µM. The second screen identified 162 NR ligands with a calculate free energy of VDR binding of more than -6.0 kJ/mol. More than half of these ligands were developed to bind VDR followed by ERα/β ligands (26%), TRα/β ligands (7%) and LxRα/β ligands (7%). The binding between VDR and ERα ligand H6036 as well as TRα/β ligand triiodothyronine and a homoserine analog thereof was confirmed by fluorescence polarization.

Identification of 15d-PGJ2 as an antagonist of farnesoid X receptor: molecular modeling with biological evaluation

15-Deoxy-Δ(12,14)-PGJ2 (15d-PGJ2) is one of the major metabolites from prostaglandin D2 in arachidonic acid (AA) metabolic pathway. It was determined as a ligand of peroxisome proliferator-activated receptor γ (PPARγ) functioning potently in adipocyte development. However, the fact that 15d-PGJ2 exerts also PPARγ-independent biological actions has highly addressed its multi-target behavior. Here, we identified that 15d-PGJ2 was an antagonist of farnesoid X receptor (FXR), as investigated by surface plasmon resonance, fluorescence quenching and homo time-resolved fluorescence based analyses, and the coactivator-recruitment and luciferase-reporter related investigation. Assay of 15d-PGJ2 regulation on hFXRα target genes revealed that treatment of HepG2 cells with 15d-PGJ2 resulted in the stimulation of mRNA expressions of bile-salt export pump (BSEP), and the decrease of cholesterol 7a-hydroxylase (CYP7a1). In addition, functional assays indicated that 15d-PGJ2 promoted the conversion of cholesterol to bile acids in HepG2 cells. Moreover, molecular docking combined with molecular dynamics simulation was applied to develop the possible model of 15d-PGJ2 binding to hFXRα ligand binding domain (LBD) at atomic level, and the responsible residues for 15d-PGJ2/hFXRα-LBD interaction were thereby determined, which were further confirmed by SPR assays against hFXRα-LBD site-directed mutations. Given that hFXRα functions potently in the regulation of hepatic bile acid metabolism and lipid/glucose homeostasis, our current work is expected to help better understand the multi-target features of this PGD2 metabolite in biological pathways, and 15d-PGJ2 as a new discovered FXR antagonist might find its potential application in further anti-hypercholesterol research.

Enhanced antitumor effect of combination therapy with gemcitabine and guggulsterone in pancreatic cancer

OBJECTIVES

Guggulsterone is a dietary plant sterone possessing therapeutic potential against cancers. However, the antitumor effect of this natural compound on pancreatic cancer has not been determined yet. This study was designed to investigate the therapeutic efficacy of guggulsterone in pancreatic cancer.

METHODS

In this study, we examined the effect of guggulsterone on cell proliferation and apoptosis in pancreatic cancer cell lines, and then, we investigated the mechanisms responsible for the effect of guggulsterone. Finally, we investigated whether the combination of guggulsterone and gemcitabine had an additional therapeutic effect compared to gemcitabine single regimen in pancreatic cancer cell lines (in vitro) and in a xenograft model using nude mice (in vivo).

RESULTS

In vitro, the combination treatment resulted in more growth inhibition and apoptosis through the down-regulation of nuclear factor κB activity with suppression of Akt and BcL-2 and through the activation of c-Jun NH(2)-terminal kinase and Bax in pancreatic cancer cell lines. In vivo, the combination therapy augmented tumor growth inhibition through the same mechanisms in tumor tissue.

CONCLUSIONS

The combination of guggulsterone to gemcitabine enhanced antitumor efficacy through apoptosis induction by suppressing Akt and nuclear factor κB activity and by modulating apoptosis-related protein expression in pancreatic cancer.

Using resin to generate a non-invasive intestinal bile-depleted rat model was unsuccessful

The purpose of this study was to evaluate if a rat model, based upon co-administration of the anion-exchanging resin, cholestyramine, could replace surgery when evaluating the importance of bile on drug absorption. Two different formulations were used for the administration of halofantrine; polyethylene glycol 400 (PEG 400) and PEG 400/polysorbate 80 (50:50, w/w%), as a positive and negative control on the dependency of bile. No significant effect of the resin was detected after evaluation of three different pre-dosing regimes, but in line with previous studies the formulation containing polysorbate 80 showed a significant increase in the absorption of halofantrine. This study therefore demonstrates that the pre-dosing of rats with Cholestyramine can not replace surgical bile duct cannulation if a formulation needs to be evaluated for its bile dependency.

FXR and PXR: potential therapeutic targets in cholestasis

Cholestatic liver disorders encompass hepatobiliary diseases of diverse etiologies characterized by the accumulation of bile acids, bilirubin and cholesterol as the result of impaired secretion of bile. Members of the nuclear receptor (NR) family of ligand-modulated transcription factors are implicated in the adaptive response to cholestasis. NRs coordinately regulate bile acid and phospholipid transporter genes required for hepatobiliary transport, as well as the phases I and II metabolizing enzymes involved in processing of their substrates. In this review we will focus on FXR and PXR, two members of the NR family whose activities are regulated by bile acids. In addition, we also discuss the potential of pharmacological modulators of these receptors as novel therapies for cholestatic disorders.

Pharmacological properties of guggulsterones, the major active components of gum guggul

Oleo gum resin secreted by Commiphora mukul, also known as gum guggul, has been used widely as an ayurvedic drug. Commiphora mukul is a short thorny shrub that is native to the Indian subcontinent. Oleo gum resin extracted by incision of the bark is a very complex mixture of gum, minerals, essential oils, terpenes, sterols, ferrulates, flavanones and sterones. Its active constituents, the Z- and E-guggulsterones, have been demonstrated to exhibit their biological activities by binding to nuclear receptors and modulating the expression of proteins involved in carcinogenic activities. Guggulsterones have also been reported to regulate gene expression by exhibiting control over other molecular targets including transcription factors such as nuclear factor (NF)-κB, signal transducer and activator of transcription (STAT) and steroid receptors. Considerable scientific evidence indicates the use of gum guggul as a therapeutic agent in the treatment of inflammation, nervous disorders, hyperlipidaemia and associated cardiac disorders such as hypertension and ischaemia, skin disorders, cancer and urinary disorders. This review highlights the taxonomic details, phytochemical properties and pharmacological profile of gum guggul.

Discovery that theonellasterol a marine sponge sterol is a highly selective FXR antagonist that protects against liver injury in cholestasis

Background

The farnesoid-x-receptor (FXR) is a bile acid sensor expressed in the liver and gastrointestinal tract. Despite FXR ligands are under investigation for treatment of cholestasis, a biochemical condition occurring in a number of liver diseases for which available therapies are poorly effective, mice harboring a disrupted FXR are protected against liver injury caused by bile acid overload in rodent models of cholestasis. Theonellasterol is a 4-methylene-24-ethylsteroid isolated from the marine sponge Theonella swinhoei. Here, we have characterized the activity of this theonellasterol on FXR-regulated genes and biological functions.

Principal Findings

Interrogation of HepG2 cells, a human hepatocyte cell line, by microarray analysis and transactivation assay shows that theonellasterol is a selective FXR antagonist, devoid of any agonistic or antagonistic activity on a number of human nuclear receptors including the vitamin D receptor, PPARs, PXR, LXRs, progesterone, estrogen, glucorticoid and thyroid receptors, among others. Exposure of HepG2 cells to theonellasterol antagonizes the effect of natural and synthetic FXR agonists on FXR-regulated genes, including SHP, OSTα, BSEP and MRP4. A proof-of-concept study carried out to investigate whether FXR antagonism rescues mice from liver injury caused by the ligation of the common bile duct, a model of obstructive cholestasis, demonstrated that theonellasterol attenuates injury caused by bile duct ligation as measured by assessing serum alanine aminostrasferase levels and extent of liver necrosis at histopathology. Analysis of genes involved in bile acid uptake and excretion by hepatocytes revealed that theonellasterol increases the liver expression of MRP4, a basolateral transporter that is negatively regulated by FXR. Administering bile duct ligated mice with an FXR agonist failed to rescue from liver injury and downregulated the expression of MRP4.

Conclusions

FXR antagonism in vivo results in a positive modulation of MRP4 expression in the liver and is a feasible strategy to target obstructive cholestasis.

Hypolipidemic agent Z-guggulsterone: metabolism interplays with induction of carboxylesterase and bile salt export pump

Z-Guggulsterone is a major ingredient in the Indian traditional hypolipidemic remedy guggul. A study in mice has established that its hypolipidemic effect involves the farnesoid X receptor (FXR), presumably by acting as an antagonist of this receptor. It is generally assumed that the antagonism leads to induction of cytochrome P450 7A1 (CYP7A1), the rate-limiting enzyme converting free cholesterol to bile acids. In this study, we tested whether Z-guggulsterone indeed induces human CYP7A1. In addition, the expression of cholesteryl ester hydrolase CES1 and bile salt export pump (BSEP) was monitored. Contrary to the general assumption, Z-guggulsterone did not induce CYP7A1. Instead, this phytosterol significantly induced CES1 and BSEP through transactivation. Z-Guggulsterone underwent metabolism by CYP3A4, and the metabolites greatly increased the induction potency on BSEP but not on CES1. BSEP induction favors cholesterol elimination, whereas CES1 involves both elimination and retention (probably when excessively induced). Interestingly, clinical trials reported the hypolipidemic response rates from 18% to 80% and showed that higher dosages actually increased VLDL cholesterol. Our findings predict that better hypolipidemic outcomes likely occur in individuals who have a relatively higher capacity of metabolizing Z-guggulsterone with moderate CES1 induction, a scenario possibly achieved by lowering the dosing regimens.

Role of farnesoid X receptor (FXR) in the process of differentiation of bone marrow stromal cells into osteoblasts

Bone tissue contains bile acids which accumulate from serum and which can be released in large amounts in the bone microenvironment during bone resorption. However, the direct effects of bile acids on bone cells remain largely unexplored. Bile acids have been identified as physiological ligands of the farnesoid X receptor (FXR, NR1H4). In the present study, we have examined the effects of FXR activation/inhibition on the osteoblastic differentiation of human bone marrow stromal cells (BMSC). We first demonstrated the expression of FXR in BMSC and SaOS2 osteoblast-like cells, and observed that FXR activation by chenodeoxycholic acid (CDCA) or by farnesol (FOH) increases the activity of alkaline phosphatase and the calcification of the extracellular matrix. In addition, we observed that FXR agonists are able to stimulate the expression of osteoblast marker genes [bone sialoprotein (BSP), osteocalcin (OC), osteopontin (OPN) and alkaline phosphatase (ALP)] (FXR involvement validated by shRNA-induced gene silencing), as well as the DNA binding activity of the bone transcription factor RUNX2 (EMSA and ChIP assay). Importantly, we observed that nitrogen-containing bisphosphonates (BPs) inhibit the basal osteoblastic differentiation of BMSC, possibly through suppression of endogenous FOH production, independently of their effects on protein prenylation. Likewise, we found that the FXR antagonist guggulsterone (GGS) inhibits ALP activity, calcium deposition, DNA binding of RUNX2, and bone marker expression, indicating that GGS interferes with osteoblastic differentiation. Furthermore, GGS induced the appearance of lipid vesicles in BMSC and stimulated the expression of adipose tissue markers (peroxisome proliferator activated receptor-gamma (PPARγ), adipoQ, leptin and CCAAT/enhancer-binding protein-alpha (C/EBPα)). In conclusion, our data support a new role for FXR in the modulation of osteoblast/adipocyte balance: its activation stimulates RUNX2-mediated osteoblastic differentiation of BMSC, whereas its inhibition leads to an adipocyte-like phenotype.

A Regioselective Synthesis of E-Guggulsterone

We have successfully prepared E-guggulsterone from 16,17-epoxy-pregnenolone in 84% yield over two steps via a hydrazine reduction and Oppenhauer oxidation. Additionally, isomerization was induced by heat, light (hν) and acid catalysis to convert E- guggulsterone into the corresponding Z isomer.

Reversal of multidrug resistance by guggulsterone in drug-resistant MCF-7 cell lines

BACKGROUND

Multidrug resistance (MDR) presents a serious problem in cancer chemotherapy. Our previous studies have shown that the MDR of K562/DOX cells could be reversed by guggulsterone through inhibiting the function and expression of P-glycoprotein. The purpose of this study was to investigate the reversal effect of guggulsterone on MDR in drug-resistant MCF-7 cells and the parental MCF-7 cells.

METHODS

MTT cytotoxicity assays, flow cytometry, and Western blot analysis were performed to investigate the antiproliferative effects of the combination of anticancer drugs with guggulsterone, to study the reversal of drug resistance and to examine the inhibitory effects on MRP1 expression.

RESULTS

The results showed that co-administration of guggulsterone (10 μM) resulted in a significant increase in chemosensitivity of MCF-7/DOX cells to doxorubicin, compared with doxorubicin treatment alone (p < 0.01). The fold reversal of 10 μM guggulsterone (11.48) was comparable to that of 10 μM verapamil (13.23). Rhodamine123 and doxorubicin accumulation in MCF-7/DOX cells was significantly enhanced after the incubation with guggulsterone (10 μM), compared with untreated MCF-7/DOX cells (p < 0.01). When doxorubicin (10 μM) was combined with guggulsterone (10 μM), the mean apoptotic population of MCF-7/DOX cells was 24.91%. It was increased by 6.15 times, compared with doxorubicin (10 μM) treatment alone. However, guggulsterone had little inhibitory effect on the expression of MRP1 proteins.

CONCLUSION

Guggulsterone is a novel and potent MDR reversal agent with the potential to be an adjunctive agent for tumor chemotherapy.

Regulation of metabolism by nuclear hormone receptors

The worldwide epidemic of metabolic disease indicates that a better understanding of the pathways contributing to the pathogenesis of this constellation of diseases need to be determined. Nuclear hormone receptors comprise a superfamily of ligand-activated transcription factors that control development, differentiation, and metabolism. Over the last 15 years a growing number of nuclear receptors have been identified that coordinate genetic networks regulating lipid metabolism and energy utilization. Several of these receptors directly sample the levels of metabolic intermediates and use this information to regulate the synthesis, transport, and breakdown of the metabolite of interest. In contrast, other family members sense metabolic activity via the presence or absence of interacting proteins. The ability of these nuclear receptors to impact metabolism and inflammation will be discussed and the potential of each receptor subfamily to serve as drug targets for metabolic disease will be highlighted.

Bile acids: regulation of synthesis

Bile acids are physiological detergents that generate bile flow and facilitate intestinal absorption and transport of lipids, nutrients, and vitamins. Bile acids also are signaling molecules and inflammatory agents that rapidly activate nuclear receptors and cell signaling pathways that regulate lipid, glucose, and energy metabolism. The enterohepatic circulation of bile acids exerts important physiological functions not only in feedback inhibition of bile acid synthesis but also in control of whole-body lipid homeostasis. In the liver, bile acids activate a nuclear receptor, farnesoid X receptor (FXR), that induces an atypical nuclear receptor small heterodimer partner, which subsequently inhibits nuclear receptors, liver-related homolog-1, and hepatocyte nuclear factor 4alpha and results in inhibiting transcription of the critical regulatory gene in bile acid synthesis, cholesterol 7alpha-hydroxylase (CYP7A1). In the intestine, FXR induces an intestinal hormone, fibroblast growth factor 15 (FGF15; or FGF19 in human), which activates hepatic FGF receptor 4 (FGFR4) signaling to inhibit bile acid synthesis. However, the mechanism by which FXR/FGF19/FGFR4 signaling inhibits CYP7A1 remains unknown. Bile acids are able to induce FGF19 in human hepatocytes, and the FGF19 autocrine pathway may exist in the human livers. Bile acids and bile acid receptors are therapeutic targets for development of drugs for treatment of cholestatic liver diseases, fatty liver diseases, diabetes, obesity, and metabolic syndrome.

Role of bile acids and bile acid receptors in metabolic regulation

The incidence of the metabolic syndrome has taken epidemic proportions in the past decades, contributing to an increased risk of cardiovascular disease and diabetes. The metabolic syndrome can be defined as a cluster of cardiovascular disease risk factors including visceral obesity, insulin resistance, dyslipidemia, increased blood pressure, and hypercoagulability. The farnesoid X receptor (FXR) belongs to the superfamily of ligand-activated nuclear receptor transcription factors. FXR is activated by bile acids, and FXR-deficient (FXR(-/-)) mice display elevated serum levels of triglycerides and high-density lipoprotein cholesterol, demonstrating a critical role of FXR in lipid metabolism. In an opposite manner, activation of FXR by bile acids (BAs) or nonsteroidal synthetic FXR agonists lowers plasma triglycerides by a mechanism that may involve the repression of hepatic SREBP-1c expression and/or the modulation of glucose-induced lipogenic genes. A cross-talk between BA and glucose metabolism was recently identified, implicating both FXR-dependent and FXR-independent pathways. The first indication for a potential role of FXR in diabetes came from the observation that hepatic FXR expression is reduced in animal models of diabetes. While FXR(-/-) mice display both impaired glucose tolerance and decreased insulin sensitivity, activation of FXR improves hyperglycemia and dyslipidemia in vivo in diabetic mice. Finally, a recent report also indicates that BA may regulate energy expenditure in a FXR-independent manner in mice, via activation of the G protein-coupled receptor TGR5. Taken together, these findings suggest that modulation of FXR activity and BA metabolism may open new attractive pharmacological approaches for the treatment of the metabolic syndrome and type 2 diabetes.

Identification of a novel agonist of peroxisome proliferator-activated receptors alpha and gamma that may contribute to the anti-diabetic activity of guggulipid in Lep(ob)/Lep(ob) mice

The ethyl acetate extract of the gum of the guggul tree, Commiphora mukul (guggulipid), is marketed for the treatment of dyslipidaemia and obesity. We have found that it protects Lep(ob)/Lep(ob) mice from diabetes and have investigated possible molecular mechanisms for its metabolic effects, in particular those due to a newly identified component, commipheric acid. Both guggulipid (EC(50)=0.82 microg/ml) and commipheric acid (EC(50)=0.26 microg/ml) activated human peroxisome proliferator-activated receptor alpha (PPARalpha) in COS-7 cells transiently transfected with the receptor and a reporter gene construct. Similarly, both guggulipid (EC(50)=2.3 microg/ml) and commipheric acid (EC(50)=0.3 microg/ml) activated PPARgamma and both promoted the differentiation of 3T3 L1 preadipocytes to adipocytes. Guggulipid (EC(50)=0.66 microg/ml), but not commipheric acid, activated liver X receptor alpha (LXRalpha). E- and Z-guggulsterones, which are largely responsible for guggulipid's hypocholesterolaemic effect, had no effects in these assays. Guggulipid (20 g/kg diet) improved glucose tolerance in female Lep(ob)/Lep(ob) mice. Pure commipheric acid, given orally (960 mg/kg body weight, once daily), increased liver weight but did not affect body weight or glucose tolerance. However, the ethyl ester of commipheric acid (150 mg/kg, twice daily) lowered fasting blood glucose and plasma insulin, and plasma triglycerides without affecting food intake or body weight. These results raise the possibility that guggulipid has anti-diabetic activity due partly to commipheric acid's PPARalpha/gamma agonism, but the systemic bioavailability of orally dosed, pure commipheric acid appears poor. Another component may contribute to guggulipid's anti-diabetic and hypocholesterolaemic activity by stimulating LXRalpha.

Resin from the mukul myrrh tree, guggul, can it be used for treating hypercholesterolemia? A randomized, controlled study

BACKGROUND

Guggul, herbal extract from resin of the Commiphora mukul tree, is widely used in Asia as a cholesterol-lowering agent based on Indian Ayurvedic medicine. Its popularity for this use is increasing in the US and Western Europe. Guggulsterones, the presumed bioactive compounds of guggul, may antagonise two nuclear hormone receptors involved in cholesterol metabolism, which is a possible explanation for hypolipidemic effects of these extracts. However, publications of efficacy data on the use of guggul extracts in Western populations are scarce.

OBJECTIVE

To study the efficacy of a guggul-based formulation (short: guggul) on blood lipids in healthy adults with moderately increased cholesterol.

METHODS

Double-blind, randomised, placebo controlled trial in Norwegian general practice. 43 women and men, age 27-70, with moderately increased cholesterol, randomised to use 2160mg guggul (4 capsules) daily, or placebo for 12 weeks.

OUTCOME MEASURES

Mean change in total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglycerides, high-density lipoprotein cholesterol (HDL-C) and total cholesterol/HDL-C ratio compared with baseline. Lipids were analysed at baseline, and at 6 and 12 weeks. In addition, unexpected events and adverse effects were recorded.

RESULTS

Two dropouts, one withdrawal, and incomplete lab results for six persons left 34 participants to accomplish the trial (18-guggul, 16-placebo) with complete lab test data. After 12 weeks, mean levels of total cholesterol and HDL-C in the active group were significantly reduced compared with the placebo group. However, the mean levels of LDL-C, triglycerides, and total cholesterol/HDL-C ratio between the two groups did not change significantly. Ten guggul users (vs. four in the placebo group) reported side effects: mild gastrointestinal discomfort (n=7), possible thyroid problems (n=2), and generalized skin rash (n=1). The latter resulted in withdrawal from trial.

CONCLUSIONS

Even if total cholesterol and HDL-C were significantly reduced, the clinical magnitude of this remains obscure. More and larger studies are needed to establish effects and safety of guggul-based formulations in the treatment for hypercholesterolemia.

Therapeutic effects of guggul and its constituent guggulsterone: cardiovascular benefits

Oleogum resin (known as guggul) from the guggul tree, Commiphora mukul, found in India, Bangladesh, and Pakistan, has been used to treat various diseases including hyper-cholesterolemia, atherosclerosis, rheumatism, and obesity over several thousands of years. Guggulsterone isolated from guggul has been identified as the bioactive constituent responsible for guggul's therapeutic effects. Since the first study demonstrating the therapeutic effects of guggul in an animal model in 1966, numerous preclinical and clinical trails have been carried out. Although differences in study design, methodological quality, statistical analysis, sample size, and subject population result in certain inconsistencies in the response to therapy, the cumulative data from in vitro, preclinical, and clinical studies largely support the therapeutic claims for guggul described in the ancient Ayurvedic text. However, future clinical studies with much larger size and longer term are required to confirm these claims. The cardiovascular benefits of the therapy are derived from the multiple pharmacological activities associated with guggul or guggulsterone, notably its hypolipidemic, antioxidant, and antiinflammatory activities. It has been established that guggulsterone is an antagonist at farnesoid x receptor (FXR), a key transcriptional regulator for the maintenance of cholesterol and bile acid homeostasis. The FXR antagonism by guggulsterone has been proposed as a mechanism for its hypolipidemic effect. A recent study demonstrates that guggulsterone upregulates the bile salt export pump (BSEP), an efflux transporter responsible for removal of cholesterol metabolites, bile acids from the liver. Such upregulation of BSEP expression by guggulsterone favors cholesterol metabolism into bile acids, and thus represents another possible mechanism for its hypolipidemic activity. Guggulsterone has been found to potently inhibit the activation of nuclear factor-kappaB (NF-kappaB), a critical regulator of inflammatory responses. Such repression of NF-kappaB activation by guggulsterone has been proposed as a mechanism of the antiinflammatory effect of guggulsterone.

The tangle of nuclear receptors that controls xenobiotic metabolism and transport: crosstalk and consequences

The expression of many genes involved in xenobiotic/drug metabolism and transport is regulated by at least three nuclear receptors or xenosensors: aryl hydrocarbon receptor (AhR), constitutive androstane receptor (CAR), and pregnane X receptor (PXR). These receptors establish crosstalk with other nuclear receptors or transcription factors controlling signaling pathways that regulate the homeostasis of bile acids, lipids, glucose, inflammation, vitamins, hormones, and others. These crosstalks are expected to modify profoundly our vision of xenobiotic/drug disposition and toxicity. They provide molecular mechanisms to explain how physiopathological stimuli affect xenobiotic/drug disposition, and how xenobiotics/drugs may affect physiological functions and generate toxic responses. In addition, the possibility that xenosensors may control other signaling pathways opens the way to new pharmacological opportunities.

Synthesis, characterization, and receptor interaction profiles of enantiomeric bile acids

Bile acids are endogenous steroid detergents with receptor-mediated physiologic actions including activation of the G-protein coupled receptor TGR5 and gene regulation mediated by nuclear receptors. In this study, we report the first synthesis of enantiomeric lithocholic acid (ent-LCA, ent-1) and chenodeoxycholic acid (ent-CDCA, ent-2) via ent-testosterone (3). ent-1 was synthesized in 21 total steps in 4.2% yield, whereas ent-2 was obtained in 23 total steps in 0.8% yield. Critical micelle concentrations of the enantiomeric bile acids were found to be identical to their natural counterparts. Furthermore, enantiomeric bile acids were also tested for their ability to modulate bile acid activated proteins: farnesoid X receptor, vitamin D receptor, pregnane X receptor, and TGR5. Interestingly, ent-1 and ent-2 showed differential interactions with these proteins as compared to their corresponding natural bile acids. These data highlight the potential for using enantioselectivity as a way to distinguish between receptor and nonreceptor-mediated functions of natural bile acids.

Activated pregnenolone X-receptor is a target for ketoconazole and its analogs

PURPOSE

Variations in biotransformation and elimination of microtubule-binding drugs are a major cause of unpredictable side effects during cancer therapy. Because the orphan receptor, pregnenolone X-receptor (PXR), coordinately regulates the expression of paclitaxel metabolizing and transport enzymes, controlling this process could improve therapeutic outcome.

EXPERIMENTAL DESIGN

In vitro RNA-, protein-, and transcription-based assays in multiple cell lines derived from hepatocytes and PXR wild-type and null mouse studies were employed to show the effects of ketoconazole and its analogues on ligand-activated PXR-mediated gene transcription and translation.

RESULTS

The transcriptional activation of genes regulating biotransformation and transport by the liganded human nuclear xenobiotic receptor, PXR, was inhibited by the commonly used antifungal ketoconazole and related azole analogs. Mutations at the AF-2 surface of the human PXR ligand-binding domain indicate that ketoconazole may interact with specific residues outside the ligand-binding pocket. Furthermore, in contrast to that observed in PXR (+/+) mice, genetic loss of PXR results in increased (preserved) blood levels of paclitaxel.

CONCLUSIONS

These studies show that some azole compounds repress the coordinated activation of genes involved in drug metabolism by blocking PXR activation. Because loss of PXR maintains blood levels of paclitaxel upon chronic dosing, ketoconazole analogues may also serve to preserve paclitaxel blood levels on chronic dosing of drugs. Our observations may facilitate new strategies to improve the clinical efficacy of drugs and to reduce therapeutic side effects.

The pharmacological exploitation of cholesterol 7alpha-hydroxylase, the key enzyme in bile acid synthesis: from binding resins to chromatin remodelling to reduce plasma cholesterol

Mammals dispose of cholesterol mainly through 7alpha-hydroxylated bile acids, and the enzyme catalyzing the 7alpha-hydroxylation, cholesterol 7alpha-hydroxylase (CYP7A1), has a deep impact on cholesterol homeostasis. In this review, we present the study of regulation of CYP7A1 as a good exemplification of the extraordinary contribution of molecular biology to the advancement of our understanding of metabolic pathways that has taken place in the last 2 decades. Since the cloning of the gene from different species, experimental evidence has accumulated, indicating that the enzyme is mainly regulated at the transcriptional level and that bile acids are the most important physiological inhibitors of CYP7A1 transcription. Multiple mechanisms are involved in the control of CYP7A1 transcription and a variety of transcription factors and nuclear receptors participate in sophisticated regulatory networks. A higher order of transcriptional regulation, stemming from the so-called histone code, also applies to CYP7A1, and recent findings clearly indicate that chromatin remodelling events have profound effects on its expression. CYP7A1 also acts as a sensor of signals coming from the gut, thus representing another line of defence against the toxic effects of bile acids and a downstream target of agents acting at the intestinal level. From the pharmacological point of view, bile acid binding resins were the first primitive approach targeting the negative feed-back regulation of CYP7A1 to reduce plasma cholesterol. In recent years, new drugs have been designed based on recent discoveries of the regulatory network, thus confirming the position of CYP7A1 as a focus for innovative pharmacological intervention.

Guggulsterone production in cell suspension cultures of the guggul tree, Commiphora wightii, grown in shake-flasks and bioreactors

Cell suspension cultures of Commiphora wightii, grown in modified MS medium containing 2,4-dichlorophenoxyacetic acid (0.5 mg l(-1)) and kinetin (0.25 mg l(-1)), produced approximately 5 microg guggulsterone g(-1) dry wt. In a 2 l stirred tank bioreactor, the biomass was 5.5 g l(-1) and total guggulsterone was 36 microg l(-1).

Design, synthesis, and evaluation of non-steroidal farnesoid X receptor (FXR) antagonist

A series of substituted-isoxazole derivatives was prepared as candidate farnesoid X receptor (FXR) antagonists, based on our previously proposed ligand superfamily concept. Structure-activity relationship studies indicated that the shape and the structural bulkiness of the substituent at the 5-position of the isoxazole ring affected FXR-antagonistic activity. Compounds 15 g (5-substituent: 2-naphthyl) and 15 h (5-substituent: 4-biphenyl) were identified as potent antagonists with higher selectivity for FXR over progesterone receptor than the naturally occurring FXR antagonist GS. The 5-substituent is also a critical determinant of the characteristic corepressor recruitment profile of this class of FXR antagonists, though distinct mechanisms appear to be involved: 15 h stabilizes the corepressor-nuclear receptor interaction, while 15 g inhibits coactivator recruitment.