Resveratrol promotes degradation of the human bile acid transporter ASBT (SLC10A2)

Conjoint hepatobiliary-enterohepatic cycles for amyloid excretion and enhancing its drug-induced clearance: a systems biology approach to Alzheimer's disease

The liver is the major organ responsible for metabolism of amyloid-beta, the primary toxic misfolded protein responsible for Alzheimer's disease (AD). The present study focuses on the crucial role of liver in AD. We have developed a framework that formulates and integrates two reciprocal transport processes of amyloid, via hepato-biliary and enterohepatic circulations (EHC). Our system analysis approach shows that activating the liver X-receptor (LXR) can reduce amyloid-beta formation by increasing expression of the genes: ATP-binding-cassette-transporter (ABCA1) and Stearoyl-CoA-desaturase (SCD). Besides, activating the pregnane-X-receptor (PXR) can enhance the clearance of amyloid-beta by increasing the expression of the genes: ATP-Binding-Cassette-Superfamily-G-member-2 (ABCG2) and multidrug-resistance protein-1 (MDR1). We also identified receptor-like apical sodium-dependent bile-acid transporter (ASBT) of intestinal enterocyte, showing affinity towards amyloid-beta, suggesting amyloid-beta's possible reuptake from intestinal contents to the systemic circulation through this receptor. Further, we have performed protein-protein interaction to evaluate the binding affinity of amyloid-beta to these receptors. Moreover, we undertook molecular docking and molecular dynamic simulation of some repurposed drugs (rifampicin, 24-hydroxycholesterols, resveratrol, cilostazol) which can target the aforesaid receptors to enhance amyloid-beta's fecal clearance, reduce amyloid-beta formation, and prevent the reuptake of amyloid-beta from intestinal feces. Additionally, network pharmacology and synergism analysis were utilized to validate our hypothesis and identify the drug combinations, respectively. Gene-ontology investigation, network pharmacology, and consolidated pathway analysis validate the alteration of the above-mentioned gene expression profiles. Furthermore, our neuropharmacological synergism study identifies the optimal combination of the repurposed drugs. Finally, our findings on candidate drugs are substantiated by clinical-trial outcomes.Communicated by Ramaswamy H. Sarma.

Resveratrol Modulates the Redox Response and Bile Acid Metabolism to Maintain the Cholesterol Homeostasis in Fish Megalobrama amblycephala Offered a High-Carbohydrate Diet

This study aimed to characterize the effects of resveratrol on the redox balance, cholesterol homeostasis and bile acid metabolism of Megalobrama amblycephala offered a high-carbohydrate diet. Fish (35.0 ± 0.15 g) were fed four diets including one control diet (32% nitrogen-free extract), one high-carbohydrate diet (45% nitrogen-free extract, HC), and the HC diet supplemented with different levels (0.04%, HCR1; 0.08%, HCR2) of resveratrol for 12 weeks. The HC diet-induced redox imbalance is characterized by increased MDA content and decreased T-SOD and CAT activities in the liver. Resveratrol attenuated this by up-regulating the transcription of Cu/Zn-sod, and increasing the activities of T-SOD, CAT, and GPX. The HC diet enhanced the cholesterol synthesis, but decreased the bile acid synthesis via up-regulating both hmgcr and acat2, and down-regulating cyp7a1, thus resulting in excessive cholesterol accumulation. Resveratrol supplement decreased cholesterol synthesis, and increased cholesterol uptake in the liver by down-regulating both hmgcr and acat2, and up-regulating ldlr. It also increased bile acid synthesis and biliary excretion by up-regulating cyp7a1, and down-regulating mrp2, oatp1, and oatp4 in the hindgut, thereby decreasing cholesterol accumulation. In conclusion, resveratrol improves the cholesterol homeostasis of Megalobrama amblycephala fed a high-carbohydrate diet by modulating the redox response and bile acid metabolism.

Transcriptomic and Metabonomic Profiling Reveals the Antihyperlipidemic Effects of Tartary Buckwheat Sprouts in High-Fat-Diet-Fed Mice

Flavonoids are known for potent antioxidant activity and antihyperlipidemia. As a result of the few antinutritional factors and high bioactive substances, such as flavonoids, sprouts of tartary buckwheat (Fagopyrum tataricum, STB) have become healthy food. This study aims to unravel the antihyperlipidemic effects of STB in vivo and its potential mechanism through transcriptomic and metabonomic analysis. The physiological parameters of mice administered the high-fat diet with or without 2.5 and 5% of STB for 10 weeks were recorded. Liquid chromatography-tandem mass spectrometry and RNA sequencing were applied to obtain the serum lipid metabolomic and hepatic transcriptomic profiling, respectively. Results revealed that STB could significantly alleviate the increase of body weight, liver, and abdominal adipose while ameliorating the lipid content in serum and insulin resistance of mice fed with a high-fat diet. Notably, the metabonomic analysis identified the core differential metabolites mainly enriched in the pathways, such as fat digestion and absorption, insulin resistance, and other processes. Transcriptomic results revealed that STB significantly altered the expression levels of PIK3R1, LRP5, SLC10A2, and FBXO21. These genes are involved in the PI3K-AKT signaling pathway, digestion and absorption of carbohydrates, and type II diabetes mellitus pathways. In this study, STB exhibited remarkable influence on the metabolism of lipids and glucose, exerting antihyperlipidemic effects. STB have the potential for the development and application of a lipid-lowering health food.

Enantioselective bioaccumulation and detoxification mechanisms of earthworms (Eisenia fetida) exposed to mandipropamid

As a novel chiral amide fungicide, the enantioselective behaviors of mandipropamid in the soil environment are unclear. Furthermore, there is a need to understand the stress response mechanisms of soil organisms exposed to mandipropamid isomers. Therefore, the selective bioaccumulation of mandipropamid isomers and detoxification mechanisms of earthworms (Eisenia fetida) were investigated in this study. Our results suggested that the enantioselective bioaccumulation of mandipropamid in earthworms occurred with the preferential enrichment of S-(+)-isomer. The activities of detoxification enzymes, such as cytochrome P450 (CYP450), glutathione-S-transferases (GST), and carboxylesterase (CarE), changed significantly upon exposure to S-(+)- and R-(-)-mandipropamid (particularly for CYP450 and GST). A transcriptome analysis revealed that more differentially expressed genes (DEGs) were observed under S-(+)-isomer exposure (15,798) than those under R-(-)-isomer exposure (12,222), as compared to the control group. These DEGs were mainly enriched in bile secretion and thyroid hormone signaling pathways, which were related to the detoxification process in earthworms. Moreover, the 20 DEGs, which exhibited the most profound changes (such as CYP2 and CYP3A4) in these pathways, were screened, clustered, and observed to be mainly involved in regulating the detoxification function of earthworm cells. These results indicated that detoxification systems played an essential role in the stress response to mandipropamid exposure. Additionally, earthworms were more sensitive to the stress induced by S-(+)-mandipropamid than that induced by R-(-)-mandipropamid. This is the first study to elucidate the mandipropamid detoxification mechanism of earthworms at the enantiomer level, which can be beneficial for remediating chiral pollutants.

Bioactivity of Dietary Polyphenols: The Role in LDL-C Lowering

Cardiovascular diseases are the leading causes of the death around the world. An elevation of the low-density lipoprotein cholesterol (LDL-C) level is one of the most important risk factors for cardiovascular diseases. To achieve optimal plasma LDL-C levels, clinal therapies were investigated which targeted different metabolism pathways. However, some therapies also caused various adverse effects. Thus, there is a need for new treatment options and/or combination therapies to inhibit the LDL-C level. Dietary polyphenols have received much attention in the prevention of cardiovascular diseases due to their potential LDL-C lowering effects. However, the effectiveness and potential mechanisms of polyphenols in lowering LDL-C is not comprehensively summarized. This review focused on dietary polyphenols that could reduce LDL-C and their mechanisms of action. This review also discussed the limitations and suggestions regarding previous studies.

S-acylation status of bile acid transporter hASBT regulates its function, metabolic stability, membrane expression, and phosphorylation state

The human apical sodium-dependent bile acid transporter (hASBT, SLC10A2) is the rate-limiting step of intestinal bile acid absorption in the enterohepatic circulation system of bile acids. Therefore, the regulation and stability of hASBT is vital in maintaining bile acid and cholesterol homeostasis and may serve as a potential target for cholesterol-related disorders. We hypothesized that post-translational mechanisms that govern hASBT function and regulation will provide novel insight on intestinal bile acid transport and homeostasis. In this study, we confirm the S-acylation status of hASBT via acyl biotin exchange in COS-1 cells and its impact on hASBT expression, function, kinetics, and protein stability. Using the acylation inhibitor, 2-bromopalmitate, we show that S-acylation is an important modification which modulates the function, surface expression, and maximal transporter flux (J_max) of hASBT. By means of proteasome inhibitors, S-acylated hASBT was found to be cleared via the proteasome whereas a reduction in the palmitoylation status of hASBT resulted in rapid proteolytic degradation compared to the unmodified transporter. Screening of cysteine mutants in and or near transmembrane domains, some of which are exposed to the cytosol, confirmed Cys314 to be the predominate S-acylated residue. Lastly, we show that S-acylation was reduced in a mutant form of hASBT devoid of cytosolic facing tyrosine residues, suggestive of crosstalk between acylation and phosphorylation post-translational modification mechanisms.

[The inhibitors of the apical sodium-dependent bile acid transporter (ASBT) as promising drugs]

Inhibition of the apical sodium-dependent bile acid transporter (ASBT, also known as IBAT - ileal bile acid transporter, SLC10A2) leads to disruption of the enterohepatic circulation of bile acids and their excretion with fecal masses. This is accompanied by cholesterol utilization for synthesis of new bile acids. ASBT inhibitors are promising drugs for the treatment of such diseases as non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, type 2 diabetes mellitus, necrotic enterocolitis, chronic constipation, atherosclerosis. To date the most known chemically synthesized inhibitors are: A3309, SHP626, A4250, 264W94, GSK2330672, SC-435. All of them are at different stages of clinical trials, which confirm the high efficacy and good tolerance of these inhibitors. Current trends in this field also include directed chemical synthesis of ASBT inhibitors, as well as their search among substances of plant origin.

ASBT(SLC10A2): A promising target for treatment of diseases and drug discovery

Bile acids has gradually become a new focus in various diseases, and ASBT as a transporter responsible for the reabsorption of ileal bile acids, is a key hinge associated to the bile acids-cholesterol balance and bile acids of enterohepatic circulation. The cumulative studies have also shown that ASBT is a promising target for treatment of liver, gallbladder, intestinal and metabolic diseases. This article briefly reviewed the process of bile acids enterohepatic circulation, as well as the regulations of ASBT expression, covering transcription factors, nuclear receptors and gut microbiota. In addition, the relationship between ASBT and various diseases were discussed in this paper. According to the structural classification of ASBT inhibitors, the research status of ASBT inhibitors and potential ASBT inhibitors of traditional Chinese medicine (such resveratrol, jatrorrhizine in Coptis chinensis) were summarized. This review provides a basis for the development of ASBT inhibitors and the treatment strategy of related diseases.

Bile Acid Transporters Are Expressed and Heterogeneously Distributed in Rat Bile Ducts

Background/Aims

Cholangiocytes are capable of reabsorbing bile salts from bile, but the pathophysiological significance of this process is unclear. To this end, we detected the expression and distribution of bile acid transport proteins in cholangiocytes from normal rat liver and analyzed the possible pathophysiological significance.

Methods

Bile duct tissues of Sprague-Dawley rats were isolated by enzymatic digestion and mechanical isolation, and then divided into large and small bile duct tissues. Immunohistochemistry, real-time polymerase chain reaction and Western blotting were used to determine the expression of the apical sodium-dependent bile acid transporter (ASBT), ileal bile acid binding protein (IBABP), and basolateral organic solute transporter α (Ostα) in the biliary tract system of rats. Differences in the expression and distribution of these proteins were analyzed.

Results

In cholangiocytes, ASBT and IBABP were mainly expressed in cholangiocytes of the large bile ducts, in which the expression of both was significantly higher than that in the small ducts (p<0.05). Ostα was simultaneously expressed in cholangiocytes of both the large and small bile ducts, showing no significant difference in expression between the two groups of bile ducts (p>0.05).

Conclusions

Bile acid transporters are expressed and heterogeneously distributed in rat bile ducts, indicating that bile acid reabsorption by cholangiocytes might mainly occur in the large bile ducts. These findings may help explore the physiology of bile ducts and the pathogenesis of various cholangiopathies.

Intestinal Absorption of Bile Acids in Health and Disease

The intestinal reclamation of bile acids is crucial for the maintenance of their enterohepatic circulation. The majority of bile acids are actively absorbed via specific transport proteins that are highly expressed in the distal ileum. The uptake of bile acids by intestinal epithelial cells modulates the activation of cytosolic and membrane receptors such as the farnesoid X receptor (FXR) and G protein-coupled bile acid receptor 1 (GPBAR1), which has a profound effect on hepatic synthesis of bile acids as well as glucose and lipid metabolism. Extensive research has focused on delineating the processes of bile acid absorption and determining the contribution of dysregulated ileal signaling in the development of intestinal and hepatic disorders. For example, a decrease in the levels of the bile acid-induced ileal hormone FGF15/19 is implicated in bile acid-induced diarrhea (BAD). Conversely, the increase in bile acid absorption with subsequent overload of bile acids could be involved in the pathophysiology of liver and metabolic disorders such as fatty liver diseases and type 2 diabetes mellitus. This review article will attempt to provide a comprehensive overview of the mechanisms involved in the intestinal handling of bile acids, the pathological implications of disrupted intestinal bile acid homeostasis, and the potential therapeutic targets for the treatment of bile acid-related disorders. Published 2020. Compr Physiol 10:21-56, 2020.

Post-translational modifications of transporters

Drug transporter proteins are critical to the distribution of a wide range of endogenous compounds and xenobiotics such as hormones, bile acids, peptides, lipids, sugars, and drugs. There are two classes of drug transporters- the solute carrier (SLC) transporters and ATP-binding cassette (ABC) transporters -which predominantly differ in the energy source utilized to transport substrates across a membrane barrier. Despite their hydrophobic nature and residence in the membrane bilayer, drug transporters have dynamic structures and adopt many conformations during the translocation process. Whereas there is significant literature evidence for the substrate specificity and structure-function relationship for clinically relevant drug transporters proteins, there is less of an understanding in the regulatory mechanisms that contribute to the functional expression of these proteins. Post-translational modifications have been shown to modulate drug transporter functional expression via a wide range of molecular mechanisms. These modifications commonly occur through the addition of a functional group (e.g. phosphorylation), a small protein (e.g. ubiquitination), sugar chains (e.g. glycosylation), or lipids (e.g. palmitoylation) on solvent accessible amino acid residues. These covalent additions often occur as a result of a signaling cascade and may be reversible depending on the type of modification and the intended fate of the signaling event. Here, we review the significant role in which post-translational modifications contribute to the dynamic regulation and functional consequences of SLC and ABC drug transporters and highlight recent progress in understanding their roles in transporter structure, function, and regulation.

Bexarotene inhibits the viability of non-small cell lung cancer cells via slc10a2/PPARγ/PTEN/mTOR signaling pathway

Background

Thirty to 40 % of non-small cell lung cancer (NSCLC) patients developed higher hypertriglyceridemia in the process of treatment with bexarotene. And bioinformatics studies discovered that the expression of slc10a2 was increased in high-grade hypertriglyceridemia patients. So, we will explore the mechanism which may involve in this process.

Methods

We constructed slc10a2 overexpressed A549 cells and H1299 cells as cell models, normal A549 cells and H1299 cells as control. Then we explored the effects of slc10a2 on A549 cells and H1299 cells behaviors, including proliferation, invasion and apoptosis. The expression of apoptotic related genes and anti-cancer genes also been detected.

Results

We found that the proliferation and migration were inhibited and the apoptosis of NSCLC cells was accelerated by bexarotene. In addition, overexpressed slc10a2 in NSCLC cells can further suppress the proliferation and migration, and promote apoptosis under the treatment of bexarotene. On the contrary, the opposite results were obtained after slc10a2 gene was silenced in NSCLC cells treated with bexarotene. Moreover, the expression of caspase 3, caspase 7, PTEN, P21, P53, LKB1, TSC2 were increased and the expression of Bcl-2, cyclin D1, c-FLIP were declined in NSCLC cells and slc10a2 overexpressed NSCLC cells with the treatment of bexarotene, and the opposite situations were seen after slc10a2 gene was silenced in NSCLC cells. The further studies revealed the increased expression of slc10a2 activated the expression of peroxisome proliferator-activated receptor γ (PPARγ), then up-regulated PTEN expression and down-regulated mTOR expression.

Conclusion

These results suggest that bexarotene inhibits the viability of lung cancer cells via slc10a2/PPARγ/PTEN/mTOR signaling pathway.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4224-x) contains supplementary material, which is available to authorized users.

Human bile acid transporter ASBT (SLC10A2) forms functional non-covalent homodimers and higher order oligomers

The human apical sodium-dependent bile acid transporter, hASBT/SLC10A2, plays a central role in cholesterol homeostasis via the efficient reabsorption of bile acids from the distal ileum. hASBT has been shown to self-associate in higher order complexes, but while the functional role of endogenous cysteines has been reported, their implication in the oligomerization of hASBT remains unresolved. Here, we determined the self-association architecture of hASBT by site-directed mutagenesis combined with biochemical, immunological and functional approaches. We generated a cysteine-less form of hASBT by creating point mutations at all 13 endogenous cysteines in a stepwise manner. Although Cysless hASBT had significantly reduced function correlated with lowered surface expression, it featured an extra glycosylation site that facilitated its differentiation from wt-hASBT on immunoblots. Decreased protein expression was associated with instability and subsequent proteasome-dependent degradation of Cysless hASBT protein. Chemical cross-linking of wild-type and Cysless species revealed that hASBT exists as an active dimer and/or higher order oligomer with apparently no requirement for endogenous cysteine residues. This was further corroborated by co-immunoprecipitation of differentially tagged (HA-, Flag-) wild-type and Cysless hASBT. Finally, Cysless hASBT exhibited a dominant-negative effect when co-expressed with wild-type hASBT which validated heterodimerization/oligomerization at the functional level. Combined, our data conclusively demonstrate the functional existence of hASBT dimers and higher order oligomers irrespective of cysteine-mediated covalent bonds, thereby providing greater understanding of its topological assembly at the membrane surface.

An important intestinal transporter that regulates the enterohepatic circulation of bile acids and cholesterol homeostasis: The apical sodium-dependent bile acid transporter (SLC10A2/ASBT)

The enterohepatic circulation of bile acids (BAs) is governed by specific transporters expressed in the liver and the intestine and plays a critical role in the digestion of fats and oils. During this process, the majority of the BAs secreted from the liver is reabsorbed in intestinal epithelial cells via the apical sodium-dependent bile acid transporter (ASBT/SLC10A2) and then transported into the portal vein. Previous studies revealed that regulation of the ASBT involves BAs and cholesterol. In addition, abnormal ASBT expression and function might lead to some diseases associated with disorders in the enterohepatic circulation of BAs and cholesterol homeostasis, such as diarrhoea and gallstones. However, decreasing cholesterol or BAs by partly inhibiting ASBT-mediated transport might be used for treatments of hypercholesterolemia, cholestasis and diabetes. This review mainly discusses the regulation of the ASBT by BAs and cholesterol and its relevance to diseases and treatment.

Loops and layers of post-translational modifications of drug transporters

Drug transporters encoded by solute carrier (SLC) family are distributed in multiple organs including kidney, liver, placenta, brain, and intestine, where they mediate the absorption, distribution, and excretion of a diverse array of environmental toxins and clinically important drugs. Alterations in the expression and function of these transporters play important roles in intra- and inter-individual variability of the therapeutic efficacy and the toxicity of many drugs. Consequently, the activity of these transporters must be highly regulated to carry out their normal functions. While it is clear that the regulation of these transporters tightly depends on genetic mechanisms, many studies have demonstrated that these transporters are the target of various post-translational modifications. This review article summarizes the recent advances in identifying the posttranslational modifications underlying the regulation of the drug transporters of SLC family. Such mechanisms are pivotal not only in physiological conditions, but also in diseases.

Two novel loci, COBL and SLC10A2, for Alzheimer's disease in African Americans

INTRODUCTION

African Americans' (AAs) late-onset Alzheimer's disease (LOAD) genetic risk profile is incompletely understood. Including clinical covariates in genetic analyses using informed conditioning might improve study power.

METHODS

We conducted a genome-wide association study (GWAS) in AAs employing informed conditioning in 1825 LOAD cases and 3784 cognitively normal controls. We derived a posterior liability conditioned on age, sex, diabetes status, current smoking status, educational attainment, and affection status, with parameters informed by external prevalence information. We assessed association between the posterior liability and a genome-wide set of single-nucleotide polymorphisms (SNPs), controlling for APOE and ABCA7, identified previously in a LOAD GWAS of AAs.

RESULTS

Two SNPs at novel loci, rs112404845 (P = 3.8 × 10-8), upstream of COBL, and rs16961023 (P = 4.6 × 10-8), downstream of SLC10A2, obtained genome-wide significant evidence of association with the posterior liability.

DISCUSSION

An informed conditioning approach can detect LOAD genetic associations in AAs not identified by traditional GWAS.

Sirtuin 1 activation alleviates cholestatic liver injury in a cholic acid-fed mouse model of cholestasis

Sirtuin1 (Sirt1; mammalian homolog of Saccharomyces cerevisiae enzyme Sir2) is a transcriptional and transactivational regulator of murine farnesoid X receptor (Fxr), which is the primary bile acid (BA) sensor, and critical regulator of BA metabolism in physiological and pathophysiological conditions. Previous studies have suggested compromised Sirt1 expression in rodent models of cholestatic liver injury. We hypothesized that Sirt1 could be potentially targeted to alleviate cholestatic liver injury. In cultured primary human hepatocytes, SIRT1 messenger RNA was down-regulated after GCA treatment, potentially through induction of microRNA (miR)-34a, whereas tauroursodeoxycholic acid induced SIRT1 expression without affecting miR-34a expression. Sirt1 expression was also significantly down-regulated in three mouse models of liver injury (bile duct ligation, 1% cholic acid [CA] fed, and the Mdr2^-/- mouse). Mice fed CA diet also demonstrated hepatic FXR hyperacetylation and induction of the Janus kinase/p53 pathway. Mice fed a CA diet and concurrently administered the Sirt1 activator, SRT1720 (50 mg/kg/day, orally), demonstrated 40% and 45% decrease in plasma alanine aminotransferase and BA levels, respectively. SRT1720 increased hepatic BA hydrophilicity by increasing tri- and tetrahydroxylated and decreasing the dihydroxylated BA fraction. SRT1720 administration also inhibited hepatic BA synthesis, potentially through ileal fibroblast growth factor 15- and Fxr-mediated inhibition of cytochrome p450 (Cyp) 7a1 and Cyp27a1, along with increased hepatic BA hydroxylation in association with Cyp2b10 induction. SRT1720 administration significantly induced renal multidrug resistance-associated protein 2 and 4, peroxisome proliferator-activated receptor gamma coactivator 1-α, and constitutive androstance receptor expression along with ∼2-fold increase in urinary BA concentrations.

CONCLUSION

SRT1720 administration alleviates cholestatic liver injury in mice by increasing hydrophilicity of hepatic BA composition and decreasing plasma BA concentration through increased BA excretion into urine. Thus, use of small-molecule activators of Sirt1 presents a novel therapeutic target for cholestatic liver injury. (Hepatology 2016;64:2151-2164).

Posttranslational Regulation of Organic Anion Transporters by Ubiquitination: Known and Novel

Organic anion transporters (OATs) encoded by solute carrier 22 family are localized in the epithelia of multiple organs, where they mediate the absorption, distribution, and excretion of a diverse array of negatively charged environmental toxins and clinically important drugs. Alterations in the expression and function of OATs play important roles in intra- and interindividual variability of the therapeutic efficacy and the toxicity of many drugs. As a result, the activity of OATs must be under tight regulation so as to carry out their normal functions. The regulation of OAT transport activity in response to various stimuli can occur at several levels such as transcription, translation, and posttranslational modification. Posttranslational regulation is of particular interest, because it usually happens within a very short period of time (minutes to hours) when the body has to deal with rapidly changing amounts of substances as a consequence of variable intake of drugs, fluids, or meals as well as metabolic activity. This review article highlights the recent advances from our laboratory in uncovering several posttranslational mechanisms underlying OAT regulation. These advances offer the promise of identifying targets for novel strategies that will maximize therapeutic efficacy in drug development.

Resveratrol Attenuates Trimethylamine-N-Oxide (TMAO)-Induced Atherosclerosis by Regulating TMAO Synthesis and Bile Acid Metabolism via Remodeling of the Gut Microbiota

The gut microbiota is found to be strongly associated with atherosclerosis (AS). Resveratrol (RSV) is a natural phytoalexin with anti-AS effects; however, its mechanisms of action remain unclear. Therefore, we sought to determine whether the anti-AS effects of RSV were related to changes in the gut microbiota. We found that RSV attenuated trimethylamine-N-oxide (TMAO)-induced AS in ApoE^−/− mice. Meanwhile, RSV decreased TMAO levels by inhibiting commensal microbial trimethylamine (TMA) production via gut microbiota remodeling in mice. Moreover, RSV increased levels of the genera Lactobacillus and Bifidobacterium, which increased the bile salt hydrolase activity, thereby enhancing bile acid (BA) deconjugation and fecal excretion in C57BL/6J and ApoE^−/− mice. This was associated with a decrease in ileal BA content, repression of the enterohepatic farnesoid X receptor (FXR)-fibroblast growth factor 15 (FGF15) axis, and increased cholesterol 7a-hydroxylase (CYP7A1) expression and hepatic BA neosynthesis. An FXR antagonist had the same effect on FGF15 and CYP7A1 expression as RSV, while an FXR agonist abolished RSV-induced alterations in FGF15 and CYP7A1 expression. In mice treated with antibiotics, RSV neither decreased TMAO levels nor increased hepatic BA synthesis. Additionally, RSV-induced inhibition of TMAO-caused AS was also markedly abolished by antibiotics. In conclusion, RSV attenuated TMAO-induced AS by decreasing TMAO levels and increasing hepatic BA neosynthesis via gut microbiota remodeling, and the BA neosynthesis was partially mediated through the enterohepatic FXR-FGF15 axis.

Recently, trimethylamine-N-oxide (TMAO) has been identified as a novel and independent risk factor for promoting atherosclerosis (AS) partially through inhibiting hepatic bile acid (BA) synthesis. The gut microbiota plays a key role in the pathophysiology of TMAO-induced AS. Resveratrol (RSV) is a natural phytoalexin with prebiotic benefits. A growing body of evidence supports the hypothesis that phenolic phytochemicals with poor bioavailability are possibly acting primarily through remodeling of the gut microbiota. The current study showed that RSV attenuated TMAO-induced AS by decreasing TMAO levels and increasing hepatic BA neosynthesis via gut microbiota remodeling. And RSV-induced hepatic BA neosynthesis was partially mediated through downregulating the enterohepatic farnesoid X receptor-fibroblast growth factor 15 axis. These results offer new insights into the mechanisms responsible for RSV’s anti-AS effects and indicate that the gut microbiota may become an interesting target for pharmacological or dietary interventions to decrease the risk of developing cardiovascular diseases.

Analysis of influence of baicalin joint resveratrol retention enema on the TNF-α, SIgA, IL-2, IFN-γ of rats with respiratory syncytial virus infection

Explore the influence of baicalin joint resveratrol retention enema on TNF-α, SIgA, IL-2, and IFN-γ of rats with respiratory syncytial virus (RSV) infection. The 60 SD rats were randomly divided into normal group, model group, baicalin group, resveratrol group, joint group, and ribavirin group. For model group, baicalin group, resveratrol group, joint group, and ribavirin group, rats were given RSV virus suspension intranasally for 3 days, and model group was not given administration. Baicalin group, resveratrol group, joint group, and ribavirin group were, respectively, given baicalin 100 mg/kg/day, resveratrol 30 mg/kg/day, baicalin joint resveratrol, and ribavirin 1 g/kg/day retention enema. After continuously given administration 7 days, rats were measured in serum TNF-α, IL-2, IFN-γ levels and SIgA levels in bronchoalveolar lavage fluid. Model group, TNF-α, IL-2, IFN-γ, and SIgA were significantly higher than the normal group (P < 0.05); Baicalin group, resveratrol group, ribavirin group, TNF-α, IL-2, IFN-γ, and SIgA were significantly higher than the model group (P < 0.05); TNF-α, IL-2 between baicalin group, resveratrol group, ribavirin group, have no significant difference (P > 0.05); Baicalin group, resveratrol group, joint group, IFN-γ, and SIgA were significantly higher than the ribavirin group (P < 0.05); Joint group TNF-α, IL-2, IFN-γ, and SIgA were significantly higher than baicalin group, resveratrol group, and ribavirin group (P < 0.05). Baicalin joint resveratrol retention enema can increase RSV infection model in rats serum TNF-α, IL-2, IFN-γ levels and SIgA levels in bronchoalveolar lavage fluid, which may anti-virus through this mechanism.