Effect of Cytochrome P450 7A1 (CYP7A1) Polymorphism on Lipid Responses to Simvastatin Treatment

Pharmacological modulation of cholesterol 7α-hydroxylase (CYP7A1) as a therapeutic strategy for hypercholesterolemia

Despite the availability of many therapeutic options, the prevalence of hypercholesterolemia remains high. There exists a significant unmet medical need for novel drugs and/or treatment combinations to effectively combat hypercholesterolemia while minimizing adverse reactions. The modulation of cholesterol 7α-hydroxylase (CYP7A1) expression via perturbation of the farnesoid X receptor (FXR) - dependent pathways, primarily FXR/small heterodimer partner (SHP) and FXR/ fibroblast growth factor (FGF)-19/ fibroblast growth factor receptor (FGFR)-4 pathways, presents as a potential option to lower cholesterol levels. This paper provides a comprehensive review of the important role that CYP7A1 plays in cholesterol homeostasis and how its expression can be exploited to assert differential control of bile acid synthesis and cholesterol metabolism. Additionally, the paper also summarizes the current therapeutic options for hypercholesterolemia, and positions modulators of CYP7A1 expression, namely FGFR4 inhibitors and FXR antagonists, as emerging and distinct pharmacological agents to complement and diversify the treatment regime. Their mechanistic and clinical considerations are also extensively described to interrogate the benefits and risks associated with using FXR-mediating agents, either singularly or in combination with recognised agents such as statins to target hypercholesterolemia.

High-salt diet induces dyslipidemia through the SREBP2/PCSK9 pathway in dahl salt-sensitive rats

A high-salt diet is known to increase serum cholesterol levels; however, the underlying mechanism of salt-induced dyslipidemia in patients with salt-sensitivity remains poorly understood. We aimed to investigate whether high-salt diet (HSD) can induce dyslipidemia and elucidate the underlying mechanism of salt-induced dyslipidemia in Dahl salt-sensitive (SS) rats. Metabolomic and biochemical analyses revealed that the consumption of an HSD (8 % NaCl) significantly increased the serum levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in SS rats. The enzyme-linked immunosorbent assay demonstrated an increase in circulating proprotein convertase subtilisin/kexin type 9 (PCSK9) levels, accompanied by a decrease in hepatic low-density lipoprotein receptor (LDLR) levels due to HSD consumption. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis revealed that HSD consumption activated sterol regulatory element-binding protein-2 (SREBP2) expression in the liver and kidney, resulting in upregulation of PCSK9 at the transcriptional level in the liver and at the translational level in the kidney, ultimately increasing circulating PCSK9 levels. The combined effects of HSD on the liver and kidney contributed to the development of hypercholesterolemia. Furthermore, an in vitro assay confirmed that high-salt exposure led to an increase in the protein expression of SREBP2 and PCSK9 secretion, thereby reducing low-density lipoprotein (LDL) uptake. This study, for the first time, shows that an HSD induces dyslipidemia through activation of the SREBP2/PCSK9 pathway, providing new insights into the prevention and treatment of dyslipidemia in patients with salt sensitivity.

A meta-analysis of the pooled impact of CYP7A1 single nucleotide polymorphisms on serum lipid responses to statins

Background and Aims: Various publications suggested that there is an association between CYP7A1 single nucleotide polymorphisms (SNP) and a reduced response to statin therapy, but the results were inconsistent. This study aimed to collectively review these publications to appraise the effect of statins on cholesterol control in carriers of CYP7A1 variant alleles. Methods: PUBMED, Cochrane and EMBASE were searched systematically to identify reported studies on the lipid responses to statin treatment between carriers of the variant allele versus the non-variant allele of CYP7A1 SNPs. The change from baseline in lipid responses for all included studies were calculated using weighted mean differences (WMD) (with 95% confidence interval (CI)). A meta-analysis was conducted to pool results using either the random-effects model or the fixed effects model. Results: A total of 6 publications comprising of 1,686 subjects for the assessment of total cholesterol, LDL-C and HDL-C and 1,156 subjects for the assessment of triglycerides were included in the meta-analyses. Subjects who were non-carriers of a CYP7A1 SNP (-204 A/C (rs3808607), -278 A/C (rs3808607) and rs8192875) had a greater reduction in total cholesterol (overall WMD -0.17, 95% CI -0.29, -0.06) and LDL-C levels (overall WMD -0.16, 95% CI -0.26, -0.05) as compared with subjects who borne the variant allele of CYP7A1 SNPs when administered a statin. Conclusion: The presence of variant allele of CYP7A1 SNPs may result in suboptimal control of total cholesterol and LDL-C levels as compared with individuals who do not carry the variant allele, when administered an equivalent dose of statin.

Pharmacogenomics of response to statin treatment and susceptibility to statin-induced adverse drug reactions in Asians: a scoping review

Background

Statins are the most widely used lipid-lowering agents for patients with hyperlipidemia. However, interindividual variations in efficacy and risk of adverse drug reactions to statin treatment have been widely reported. Ethnicity is well known to be one of the contributing factors to this variation, particularly among Asians.

Objectives

To identify genetic variants associated with statin treatment responses among Asian populations with a focus on four commonly prescribed statins: atorvastatin, rosuvastatin, simvastatin, and pravastatin.

Methods

A literature search was conducted in Medline and Embase databases. Studies published from 2008 to 2021 were included. The title and abstract of each article were screened by two reviewers and verified by another two reviewers. Data charted include information on authors, year of study, study population, statin studied, gene studied, study findings, and data of significant statistical value.

Results

A total of 35 articles were included from the 1,939 original studies related to treatment efficacy and 5 articles out of the 284 original studies related to adverse effects. Genetic variants in transmembrane transporters, cytochrome P450 isoenzymes, and apolipoproteins are the most extensively studied among Asian populations, with a main focus on ethnic Chinese. However, Asia consists of genetically different populations, and the results of this review indicated that there is a paucity of studies on other ethnic groups within Asia.

Conclusions

Considering the ethnicity of patients could provide a potential value to personalized medicine in statin therapy.

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.

Up to date on cholesterol 7 alpha-hydroxylase (CYP7A1) in bile acid synthesis

Cholesterol 7 alpha-hydroxylase (CYP7A1, EC1.14) is the first and rate-limiting enzyme in the classic bile acid synthesis pathway. Much progress has been made in understanding the transcriptional regulation of CYP7A1 gene expression and the underlying molecular mechanisms of bile acid feedback regulation of CYP7A1 and bile acid synthesis in the last three decades. Discovery of bile acid-activated receptors and their roles in the regulation of lipid, glucose and energy metabolism have been translated to the development of bile acid-based drug therapies for the treatment of liver-related metabolic diseases such as alcoholic and non-alcoholic fatty liver diseases, liver cirrhosis, diabetes, obesity and hepatocellular carcinoma. This review will provide an update on the advances in our understanding of the molecular biology and mechanistic insights of the regulation of CYP7A1 in bile acid synthesis in the last 40 years.