Cyp7a1 is continuously increased with disrupted Fxr-mediated feedback inhibition in hypercholesterolemic TALLYHO/Jng mice

Fresh and Browned Lotus Root Extracts Promote Cholesterol Metabolism in FFA-Induced HepG2 Cells through Different Pathways

Browning of fresh-cut plants is mainly attributed to the enzymatic browning of phenolic compounds induced by polyphenol oxidase (PPO), producing browning products such as anthraquinones, flavanol oxides, and glycosides, which are usually considered to be non-toxic. Could browning bring any benefits on behalf of their bioactivity? Our previous study found that browned lotus root extracts (BLREs) could reduce the cholesterol level in obese mice as fresh lotus root extracts (FLREs) did. This study aimed to compare the mechanisms of FLRE and BLRE on cholesterol metabolism and verify whether the main component's monomer regulates cholesterol metabolism like the extracts do through in vitro experiments. Extracts and monomeric compounds are applied to HepG2 cells induced by free fatty acids (FFA). Extracellular total cholesterol (TC) and triglyceride (TG) levels were also detected. In addition, RT-PCR and Western blot were used to observe cholesterol metabolism-related gene and protein expression. The in vitro results showed that BLRE and FLRE could reduce TC and TG levels in HepG2 cells. In addition, BLRE suppressed the synthesis of cholesterol. Meanwhile, FLRE promoted the synthesis of bile acid (BA) as well as the clearance and efflux of cholesterol. Furthermore, the main monomers of BLRE also decreased cholesterol synthesis, which is the same as BLRE. In addition, the main monomers of FLRE promoted the synthesis of BAs, similar to FLRE. BLRE and FLRE promote cholesterol metabolism by different pathways.

Study on the hypolipidemic effect of Inonotus obliquus polysaccharide in hyperlipidemia rats based on the regulation of intestinal flora

The purpose of this study was to observe the effect of Inonotus obliquus polysaccharide (IOP) on blood lipids and its regulation on the intestinal flora in hyperlipidemia rats, and explore the modern biological connotation of IOP in reducing blood lipids. In this study, we obtained the crude IOP by the water extraction and alcohol precipitation method, and then classified it by DEAE ion-exchange chromatography to obtain the acidic I. obliquus polysaccharide (IOP-A). After the administration of the IOP-A, the serum TC, TG, and LDL-C levels were significantly lower, while the serum HDL-C levels were significantly higher. The expression of CYP7A1 protein was considerably increased, whereas the expression of SREBP-1C protein was considerably decreased in the rat hepatic tissue. In addition, the IOP-A could significantly alleviate the hepatocyte fatty degeneration in the liver lobule of rats. We believe that the IOP-A can affect the composition of intestinal flora by reducing the relative abundance of Firmicutes and increasing the relative abundance of Bacteroidetes. These findings indicated that the IOP-A can regulate the dyslipidemia of hyperlipidemia rats, and its mechanism may be through regulating the CYP7A1 and SREBP-1C expression in the metabolism of lipids, and correcting the imbalance of intestinal flora structure caused by a high-fat diet.

iTRAQ Quantitative Proteomic Analysis of Different Expressed Proteins and Signal Pathways in Bakuchiol-Induced Hepatotoxicity

Bakuchiol (BAK) is an abundant natural compound. BAK has been reported to have several biological activities such as anticancer, antiaging, anti-inflammatory, and prevention of bone loss. However, it causes hepatotoxicity, the mechanism of which is not known. In this study, we explored the mechanism of BAK hepatotoxicity by treating rats with 52.5 mg/kg and 262.5 mg/kg of BAK, administered continuously for 6 weeks. We examined the liver pathology and biochemical composition of bile to determine toxicity. Mechanisms of BAK hepatotoxicity were analyzed based on relative and absolute quantification (iTRAQ) protein equivalent signatures and validated in vitro using LO2 cells. iTRAQ analysis revealed 281 differentially expressed proteins (DEPs) in liver tissue of the BAK-treated group, of which 215 were upregulated, and 66 were downregulated. GO and KEGG enrichment analysis revealed that bile secretion, lipid metabolism, and cytochrome P450 signaling pathways were enriched in DEPs. Among them, peroxisome proliferator-activated receptor α (PPARα), farnesoid X receptor (FXR), and cholesterol 7α-hydroxylase (CYP7a1) were closely associated with the development and progression of BAK-induced hepatic metabolic dysfunction and abnormal bile metabolism. This study shows that BAK can induce hepatotoxicity through multiple signaling pathways.

CYP3A deficiency alters bile acid homeostasis and leads to changes in hepatic susceptibility in rats

Cytochrome P450 3A (CYP3A) as an important enzyme metabolizes many drugs and a variety of endogenous substances. Bile acids (BA) regulate physiological function by activating BA receptors. In this study, CYP3A1/2 gene knockout (KO) and wild-type (WT) rats were used to investigate the regulatory effects of CYP3A on BA homeostasis and liver function. Compared with WT rats, BA concentrations in serum, liver and small intestine of CYP3A1/2 KO rats increased significantly, which was due to the decrease of catabolism and the increase of synthesis. In particular, the composition of serum BA (overall hydrophobicity) presented an age- and CYP3A-dependent manner. With the aging of WT rats, the serum BA became more hydrophobic, while this trend was delayed in CYP3A1/2 KO rats. Moreover, the level of serum total cholesterol, the precursor of BA synthesis, decreased by about 20% in CYP3A1/2 KO rats, which is due to the low synthesis but high biotransformation rate. The increase of BA pool further led to the change of transcription level of BA receptor in liver (pregnane X receptor) and small intestine (Takeda G-protein receptor 5), and affected the function and morphology of CYP3A1/2 KO rat liver. In conclusion, CYP3A is a key regulator of BA homeostasis in rats, especially in regulating BA pool size, composition and balance of anabolism, and prevents susceptibility to hepatotoxicity under BA overload.

LXR-Mediated Regulation of Marine-Derived Piericidins Aggravates High-Cholesterol Diet-Induced Cholesterol Metabolism Disorder in Mice

Reported as two antirenal cell carcinoma (RCC) drug candidates, marine-derived compounds piericidin A (PA) and glucopiericidin A (GPA) exhibit hepatotoxicity in renal carcinoma xenograft mice. Proteomics and transcriptomics reveal the hepatotoxicity related with cholesterol disposition since RCC is characterized by cholesterol accumulation. PA/GPA aggravate hepatotoxicity in high-cholesterol diet (HCD)-fed mice while exhibiting no toxicity in chow diet-fed mice. High cholesterol accumulation in liver is liver X receptor (LXR)-mediated cytochrome P450 family 7 subfamily a member 1 (CYP7A1) depression and low-density lipoprotein receptor (LDLR) activation. The farnesoid X nuclear receptor (FXR) is also depressed with a downregulated target gene OSTα. Different from PA directly combined with LXRα as an inhibitor, GPA exists as a prodrug in the liver and exerts toxic effects due to transformation into PA. Surface plasmon resonance (SPR) and docking results of 17 piericidins illustrate that glycosides exert no LXRα binding activity. A longer survival time of GPA-treated mice indicates that further exploration in anti-RCC drug research should focus on reducing glycosides transformed into PA and concentrating in the kidney tumor rather than the liver for lowering the risk of hepatotoxicity.

Palmatine regulates bile acid cycle metabolism and maintains intestinal flora balance to maintain stable intestinal barrier

OBJECTIVE

Palmatine (PAL) is a natural isoquinoline alkaloid that has been widely used in the pharmaceutical field. The current study aimed to investigate the function of PAL in improving hyperlipidemia induced by high-fat diet (HFD) in rats.

METHODS

Biochemical analysis of triglyceride (TG), total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDLC) was performed on rats. Total bile acid (TBA) and stool TC and TBA were also measured to assess the changes in total bile acid excretion. RT-qPCR was employed to detect the expression of genes related to bile acid metabolism, and the Western blot assay was used to detect the levels of CYP7A1, ZO-1, ZO-2, and Claudin-1. The siRNA experiment was employed to further investigate whether PAL regulated CYP7A1 through PPARα. Lipopolysaccharide (LPS) and FITC-dextran (FD-4) were also tested to assess the intestinal permeability.

RESULTS

AL-treated rats had lower TC, TG, LDL-C levels, lower serum TBA levels, and increased fecal TBA and TC levels. Furthermore, CYP7A1 protein expression was up-regulated in PAL-treated rats. Additionally, PAL regulated bile acid metabolism by up-regulating the expression of CYP7A1 and PPARα and down-regulating the expression of FXR. Besides, the area of plasma FD-4 and LPS content in the PAL group were reduced, and the expression of proteins ZO-1, ZO-2 and Claudin-1 related to intestinal permeability was increased.

CONCLUSION

All in all, PAL could mediate the PPARα-CYP7A1 pathway to maintain the balance of intestinal flora, regulate the bile acid metabolism, and reduce the blood lipids of rats, thereby protecting against hyperlipidemia.

PL-S2, a homogeneous polysaccharide from Radix Puerariae lobatae, attenuates hyperlipidemia via farnesoid X receptor (FXR) pathway-modulated bile acid metabolism

Polysaccharides are important active constituents of Radix Puerariae lobatae (RPL). In this study, a novel homogeneous polysaccharide from RPL was successfully obtained by HP-20 macroporous resin and purified by Sepharose G-100 column chromatography. Nuclear magnetic resonance (NMR) analysis showed that the main glycosidic bonds were composed of α-1,3-linked and α-1,4-linked glucose. The molecular weight of PL-S2 was 18.73 kDa. The hypolipidemic effect of PL-S2 on hyperlipidemic rats was evaluated in histopathology and metabolomics analyses. PL-S2 significantly reduced plasma lipid levels and inhibited bile acid metabolism. We also demonstrated that treatment with PL-S2 activated FXR, CYP7A1, BESP, and MRP2 in rat liver. Our findings first indicate that PL-S2 decreases plasma lipid levels in hyperlipidemic rats by activating the FXR signaling pathway and promoting bile acid excretion. Therefore, PL-S2 derived from RPL is implicated as a functional food factor with lipid-regulating activity, and highlighted as a potential food supplement for the treatment of hyperlipidemia.

Structure-guided modification of isoxazole-type FXR agonists: Identification of a potent and orally bioavailable FXR modulator

Farnesoid X receptor (FXR) agonists are emerging as potential therapeutics for the treatment of various metabolic diseases, as they display multiple effects on bile acid, lipid, and glucose homeostasis. Although the steroidal obeticholic acid, a full FXR agonist, was recently approved, several side effects probably due to insufficient pharmacological selectivity impede its further clinical application. Activating FXR in a partial manner is therefore crucial in the development of novel FXR modulators. Our efforts focusing on isoxazole-type FXR agonists, common nonsteroidal agonists for FXR, led to the discovery a series of novel FXR agonists bearing aryl urea moieties through structural simplification of LJN452 (phase 2). Encouragingly, compound 11k was discovered as a potent FXR agonist which exhibited similar FXR agonism potency but lower maximum efficacy compared to full agonists GW4064 and LJN452 in cell-based FXR transactivation assay. Extensive in vitro evaluation further confirmed partial efficacy of 11k in cellular FXR-dependent gene modulation, and revealed its lipid-reducing activity. More importantly, orally administration of 11k in mice exhibited desirable pharmacokinetic characters resulting in promising in vivo FXR agonistic activity.

Farnesoid X Receptor Agonists as Therapeutic Target for Cardiometabolic Diseases

Cardiometabolic diseases are characterized as a combination of multiple risk factors for cardiovascular disease (CVD) and metabolic diseases including diabetes mellitus and dyslipidemia. Cardiometabolic diseases are closely associated with cell glucose and lipid metabolism, inflammatory response and mitochondrial function. Farnesoid X Receptor (FXR), a metabolic nuclear receptor, are found to be activated by primary BAs such as chenodeoxycholic acid (CDCA), cholic acid (CA) and synthetic agonists such as obeticholic acid (OCA). FXR plays crucial roles in regulating cholesterol homeostasis, lipid metabolism, glucose metabolism, and intestinal microorganism. Recently, emerging evidence suggests that FXR agonists are functional for metabolic syndrome and cardiovascular diseases and are considered as a potential therapeutic agent. This review will discuss the pathological mechanism of cardiometabolic disease and reviews the potential mechanisms of FXR agonists in the treatment of cardiometabolic disease.

Effects of Agaricus blazei Murrill polysaccharides on hyperlipidemic rats by regulation of intestinal microflora

The present research envisaged the effects of Agaricus blazei Murrill polysaccharides (ABPs) on blood lipids and its role in regulation of the intestinal microflora in hyperlipidemic rats. The acidic polysaccharide fraction of Agaricus blazei Murrill was obtained by DEAE-cellulose ion exchange column chromatography. The sugar content of ABP was 75.1%. Compared with the model group (MG), the serum TC, TG, and LDL-C levels decreased (p < .05 or p < .01) and the HDL-C levels increased (p < .01) significantly in the ABP group. Expression of CYP7A1 was up-regulated (p < .01), and that of SREBP-1C (p < .05) was down-regulated significantly in the liver tissue of rats in the ABP group. Additionally, the disordered hepatic lobules and the steatosis of hepatocytes were found to be significantly alleviated in the ABP group. We believe that ABP can reduce the ratio of Firmicutes/Bacteroidetes and reduce the relative abundance of Firmicutes, Ruminococcaceae_unclassified, and Ruminococcaceae, increasing the relative abundance of Proteobacteria, Clostridium_sensu_stricto, Allobaculum, Peptostreptococcaceae, Clostridiaceae_1, and Erysipelotrichaceae as targets to regulate blood lipids. The results showed ABP could regulate the dyslipidemia in rats with hyperlipidemia. The mechanism may be through the regulation of the imbalance of intestinal microflora induced by the high-fat diet in rats, which may be one of the important ways of its intervention on the dyslipidemia induced by high-fat diet.

Polyphenol Effects on Cholesterol Metabolism via Bile Acid Biosynthesis, CYP7A1: A Review

Atherosclerosis, the main contributor to coronary heart disease, is characterised by an accumulation of lipids such as cholesterol in the arterial wall. Reverse cholesterol transport (RCT) reduces cholesterol via its conversion into bile acids (BAs). During RCT in non-hepatic peripheral tissues, cholesterol is transferred to high-density lipoprotein (HDL) particles and returned to the liver for conversion into BAs predominantly via the rate-limiting enzyme, cholesterol 7 α-hydroxylase (CYP7A1). Numerous reports have described that polyphenol induced increases in BA excretion and corresponding reductions in total and LDL cholesterol in animal and in-vitro studies, but the process whereby this occurs has not been extensively reviewed. There are three main mechanisms by which BA excretion can be augmented: (1) increased expression of CYP7A1; (2) reduced expression of intestinal BA transporters; and (3) changes in the gut microbiota. Here we summarise the BA metabolic pathways focusing on CYP7A1, how its gene is regulated via transcription factors, diurnal rhythms, and microRNAs. Importantly, we will address the following questions: (1) Can polyphenols enhance BA secretion by modulating the CYP7A1 biosynthetic pathway? (2) Can polyphenols alter the BA pool via changes in the gut microbiota? (3) Which polyphenols are the most promising candidates for future research? We conclude that while in rodents some polyphenols induce CYP7A1 expression predominantly by the LXRα pathway, in human cells, this may occur through FXR, NF-KB, and ERK signalling. Additionally, gut microbiota is important for the de-conjugation and excretion of BAs. Puerarin, resveratrol, and quercetin are promising candidates for further research in this area.