Linkage between cholesterol 7alpha-hydroxylase and high plasma low-density lipoprotein cholesterol concentrations

Betaine supplementation alleviates corticosterone-induced hepatic cholesterol accumulation through epigenetic modulation of HMGCR and CYP7A1 genes in laying hens

Excessive corticosterone (CORT) exposure could cause hepatic cholesterol accumulation in chickens and maternal betaine supplementation could decrease hepatic cholesterol deposition through epigenetic modifications in offspring chickens. Nevertheless, it remains uncertain whether providing betaine to laying hens could protect CORT-induced hepatic cholesterol accumulation via epigenetic mechanisms. This study aimed to examine the effects of dietary betaine on plasma and hepatic cholesterol contents, expression of cholesterol metabolic genes, as well as DNA methylation on their promoters in the liver of laying hens exposed to CORT. A total of 72 laying hens at 130 d of age were randomly divided into 3 groups: control (CON), CORT, and CORT+betaine (CORT+BET) groups. The experiment lasted for 35 d. Chickens in CON and CORT groups were fed a basal diet, whereas the CORT+BET group chickens were fed the basal diet supplemented with 0.1% betaine for 35 d. On d 28 of the experiment, chickens in CORT and CORT+BET groups received daily subcutaneous injections of CORT (4.0 mg/kg body weight), whereas the CON group chickens were injected with an equal volume of solvent for 7 d. The results showed that CORT administration led to a significant increase (P < 0.05) in the contents of cholesterol in plasma and liver, associated with activation (P < 0.05) of sterol regulatory element binding transcription factor 2 (SREBP2), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), lecithin-cholesterol acyltransferase (LCAT) and low-density lipoprotein receptor (LDLR) genes expression, and inhibition of cholesterol-7-alpha hydroxylase (CYP7A1) and sterol 27-hydroxylase (CYP27A1) genes expression in the liver compared to the CON. In contrast, CORT-induced up-regulation of HMGCR mRNA and protein abundances and downregulation of CYP7A1 mRNA and protein abundances were completely normalized (P < 0.05) by betaine supplementation. Besides, CORT injection led to significant hypomethylation (P < 0.05) on HMGCR promoter and hypermethylation (P < 0.05) on CYP7A1 promoter. Moreover, dietary betaine rescued (P < 0.05) CORT-induced changes in methylation status of HMGCR and CYP7A1 genes promoters. These results indicate that dietary betaine addition protects laying hens from CORT-induced hepatic cholesterol accumulation via epigenetic modulation of HMGCR and CYP7A1 genes.

[Cholesterol 7α-Hydroxylase Gene-204A/C Polymorphism in Normal and Gestational Diabetic Pregnancies]

Objective

To investigate the cholesterol 7α-hydroxylase gene ( CYP7A1)-204A/C single nucleotide polymorphism and its relationship with the blood lipid levels of pregnant women with gestational diabetes mellitus (GDM) and normal pregnant women.

Methods

The genotype and allele frequencies of CYP7A1-204A/C gene polymorphism of 1037 normal pregnant women, the normal controls, and 627 pregnant women with GDM were examined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and blood glucose (Glu) were measured by enzymatic assay. Chemiluminescence determination of plasma insulin (Ins) was conducted. Apolipoproteins A1 (apoA1) and B (apoB) were measured by the turbidimetric immunoassay.

Results

Allele frequencies of A and C at the CYP7A1-204A/C polymorphic locus were 0.586 and 0.414, respectively, in the GDM group and 0.557 and 0.443, respectively in the control group. The distribution of genotype frequencies in both groups showed conformity with the Hardy-Weinberg principle. There was no significant difference in allele and genotype frequencies between the GDM group and the control group. In the control group, carriers of the genotype AA were associated with significantly higher concentrations of apoA1 and lower levels of Ins and homeostatic model assessment of insulin resistance (HOMA-IR) compared with those with genotype CC (all P<0.05). In the non-obese subgroup of the control subjects, carriers of the genotype CC were associated with significantly higher plasma TG or apoA1 levels compared with those with genotype AA ( P<0.05). In the GDM group, carriers with genotype AA of CYP7A1-204A/C polymorphism had elevated levels of gestational weight gain (GWG) compared with those with genotype CC ( P<0.05).

Conclusion

These results suggest that 204A/C polymorphism in the CYP7A1 gene is not associated with GDM, but may be closely associated with gestational weight gain in pregnant women with GDM. Variants in this locus are strongly associated with plasma apoA1, Ins, and HOMA-IR levels in the controls and elevated plasma TG levels in non-obese controls.

Association of cholesterol 7α-hydroxylase (CYP7A1) promoter polymorphism (rs3808607) and cholesterol 24S-hydroxylase (CYP46A1) intron 2 polymorphism (rs754203) with serum lipids, vitamin D levels, and multiple sclerosis risk in the Turkish population

BACKGROUND

Patients with multiple sclerosis (MS) have significantly lower vitamin D levels. Cholesterol is known to be the precursor for vitamin D synthesis, and cholesterol removal is regulated by cholesterol 7α-hydroxylase (CYP7A1) in the liver and cholesterol 24S-hydroxylase (CYP46A1) in the brain. In this study, single nucleotide polymorphisms (SNPs) within the genes CYP7A1 (rs3808607) and CYP46A1 (rs754203) were investigated for their effects on serum lipid profiles, vitamin D levels, and the risk of developing MS.

METHODS

Patients with MS (n = 191) and controls (n = 100) were tested using the PCR-RFLP method to determine their genotypes for rs3808607 and rs754203 SNPs.

RESULTS

The minor (C) allele frequency for CYP7A1 rs3808607 variation was 0.380 in patients with MS and 0.305 in control subjects (P = .074). For CYP46A1 rs754203, the frequencies of the minor (C) allele were 0.272 and 0.250 in patients and control subjects, respectively (P = .563). Serum vitamin D (25(OH)D3) concentrations were significantly lower in patients than in control subjects (P = .002). The CYP46A1 rs754203 SNP was associated with total cholesterol levels in patients, whereas the CYP7A1 rs3808607 variant was not associated with serum lipid parameters or vitamin D levels in patients or control subjects.

CONCLUSION

CYP7A1 rs3808607 and CYP46A1 rs754203 variations are not likely to confer an independent risk for MS development in the Turkish population. To the best of our knowledge, this is the first study to investigate the association between CYP46A1 rs754203 and MS risk.

TMT-based proteomics analysis reveals the efficacy of jiangzhuo formula in improving the lipid profiles of dyslipidemia rats

ETHNOPHARMACOLOGICAL RELEVANCE

Jiangzhuo Formula (JZF) is a traditional Chinese herbal prescription that is clinically applied to treat dyslipidemia. However, the mechanism underlying its efficacy remains unexplored.

AIM OF THE STUDY

This study aims to elucidate the underlying mechanisms, explore potential pathways, and identify the key proteins of JZF for the treatment of dyslipidemia.

METHODS

In this work, Q-Orbitrap high-resolution liquid chromatography mass spectrometry was used to identify the natural ingredients in JZF, rats with dyslipidemia were established via a high-fat diet for four weeks, then the dyslipidemia rats were treated with high-dose JZF (9 g/d) and low-dose JZF (4.5 g/d) for four weeks. After treatment, serum lipid detection and Oil-red-O staining were conducted to assess the efficacy of JZF in ameliorating dyslipidemia. Tandem mass tag (TMT) -based quantitative proteomics technology was then used to evaluate the roles and importance of proteins from the extracted hepatic tissue. The differentially expressed proteins were assessed by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, Gene Ontology (GO), and protein-protein interaction (PPI) networks. Western blot and PCR analysis were used to validate the potential targets regulated by JZF.

RESULTS

JZF could significantly improve the blood lipid profiles of serum and fat deposits of the liver. A total of 123 differentially expressed proteins were detected after JZF intervention, comprising 65 up-regulated proteins and 58 down-regulated proteins. The KEGG pathway analysis revealed that cholesterol metabolism, the PPAR signaling pathway, and bile secretion were the principal pathways involved in the disordered lipid metabolism, while GO analysis suggested that proteins that are located in the cell, regulate cellular processes, and show binding activity contribute to reductions in lipids. The combination of proteomics, Western blot, and PCR suggested that Apolipoprotein B (APOB), Apolipoprotein E (APOE), cholesterol 7 alpha-hydroxylase A1 (CYP7A1), and Hydroxymethylglutaryl-CoA synthase 1 (HMGCS1) might play critical roles in JZF's lipid-lowering network.

CONCLUSION

JZF can effectively improve lipid profiles via multiple pathways involved in cholesterol metabolism, the PPAR signaling pathway, and bile secretion. Generally, the proteomics techniques used in this research show that JZF could be a promising drug for the treatment of dyslipidemia.

Association of Common Single Nucleotide Polymorphisms of Candidate Genes with Gallstone Disease: A Meta-Analysis

Numerous studies have investigated the relationship between various candidate gene polymorphisms and gallbladder stone disease (GSD) across ethnic populations; however, the results are often inconsistent. This meta-analysis aims to comprehensively evaluate the influence of common ABCG8 T400K, ABCG8 D19H, ABCG8 C54Y, ApoB100 EcoRI, ApoB100 XbaI, ApoE HhaI, CETP TaqI, CYP7A1 Bsa, LRPAP1 I/D and TNF-α A308G polymorphisms on the risk of gallbladder stone disease. 33 Full-text articles with 9250 cases and 12,029 healthy controls (total 21,279 subjects) were analyzed using the RevMan software (V5.1) and the Comprehensive Meta-analysis software (Version 2.0, BIOSTAT, Englewood, NJ) a Random-effects model was applied. Begg's funnel plots, Fail-safe number, Egger's regression intercept and Begg and Mazumdar rank correlation tests were performed for the potential publication bias and sensitivity analysis. The studies were also sub-grouped into European and non-European groups to find out role of ethnicity, if any, on GSD risk. Studies included in quantitative synthesis were ABCG8 T400K rs4148217 (cases/controls, n = 671/1416) (4 studies), ABCG8 D19H rs11887534 (n = 1633/2306) (8 studies), ABCG8 C54Y rs4148211 (n = 445/1194) (3 studies), ApoB100 EcoRI rs1042031 (n = 503/390) (4 studies), ApoB100 XbaI rs693 (n = 1214/1389) (9 studies), ApoE HhaI rs429358 (n = 1335/1482) (12 studies), CETP TaqI rs708272 (n = 1038/1025) (5 studies), CYP7A1 Bsa rs3808607 (n = 565/514) (3 studies), LRPAP1 I/D rs11267919 (n = 849/900) (3 studies), TNF-α A308G rs1800629 (n = 997/1413) (3 studies). The combined results displayed significant association of ABCG8 D19H (GC + CC) [OR with 95%CI = 2.2(1.7-2.8); p < 0.00001], ABCG8 Y54C (GA + GG) [OR with 95%CI = 0.65(0.5-0.9); p = 0.01]. APOB100 EcoRI (GG vs. AA) [OR with 95%CI = 0.51(0.3-0.9); p = 0.05], (GG vs. GA) [OR with 95%CI = 0.6(0.4-0.9); p = 0.04], (GA + AA) [OR with 95%CI = 0.6(0.4-0.9); p = 0.006]. APOB Xba I (X^- vs. X⁺) [OR with 95%CI = 0.53(0.3-0.8); p = 0.006. APOE Hha I (E4/E4 vs. E3/E3) [OR with 95%CI = 3.5(1.1-14.9); p = 0.04] and LRPAP1 I/D (ID + II) [OR with 95%CI = 1.27(1.0-1.6); p = 0.03] with the GSD risk. It was found that ABCG D19H was significantly associated with GSD in both European and Non-European populations. While APOB XbaI and LRPAP1 I/D markers were associated with gallstone disease only in Non- European population. Additionally, APOE HhaI and APOB 100 ECoRI were found to be associated with GSD only in European population. The results of quantitative synthesis suggest that the ABCG8 D19H polymorphism was associated with the increased risk of GSD in both European and Non-European populations, APOE Hha I and LRPAP1 I/D polymorphisms were associated with the increased risk of GSD in European and Non-European population respectively. However, no association was found in ABCG8 T400K, CETP Taq1, CYP7A1 Bsa and TNF-A308G polymorphisms with Gallstone Disease.

The relationship between CYP7A1 polymorphisms, coronary artery disease & serum lipid markers

Polymorphic variants of the CYP7A1 gene can increase the risk of atherosclerosis-based coronary artery disease (CAD) and modify serum lipid markers. Method: We studied haplotype-tagging single nucleotide polymorphisms of CYP7A1 in the Caucasian population and if they are associated with CAD, its symptoms, and any of its risk factors. Results: We did not find the genetic variants of CYP7A1 to be associated with an increased risk of CAD. However, we did find that the common rs3808607 variant is associated with modified concentrations of serum total cholesterol and LDL. We also found that the C allele and the CC genotype of the rs11786580 are more frequent in patients with myocardial infarction. This association was especially strong after the group differentiation by sex.

Current immunogenetic predisposition to tuberculosis in the Moroccan population

Tuberculosis (TB) is a serious infectious disease that kills approximately two million people per year, particularly in low- and middle-income countries. Numerous genetic epidemiology studies have been conducted of many ethnic groups worldwide and have highlighted the critical impact of the genetic environment on TB distribution. Many candidate genes associated with resistance or susceptibility to TB have been identified. In Morocco, where TB is still a major public health problem, various observations of clinical, microbiological and incidence distribution are heavily affected by genetic background and external environment. Morocco has almost the same clinical profile as do other North African countries, mainly the increase in more extrapulmonary than pulmonary forms of the diseases, when compared to European, Asian or American populations. In addition, a linkage analysis study that examined Moroccan TB patients identified a unique chromosome region that had a strong association with the risk of contracting TB. Other genes in the Moroccan population that were found to be associated seem to be involved predominantly in modulating the innate immunity. In this review, we appraise the major candidate genes that have been reported in Moroccan immunogenetic studies and discuss their updated role in TB, particularly during the first phase of the immune response to Mycobacterium tuberculosis (Mtb) infection.

Differential regulation of mRNAs and lncRNAs related to lipid metabolism in two pig breeds

Long non-coding RNAs (lncRNAs) can regulate lipid metabolism and adipogenesis. However, there is little research on the role of lncRNAs in fat deposition in pig. In this study, RNA-seq technology was used to analyze the gene expression profiles of subcutaneous adipose tissue in Laiwu (LW) and Large White (LY) pigs. Then, key lncRNAs and genes associated with lipid metabolism and adipogenic differentiation were identified. Fifty four lncRNAs and 482 known mRNAs were differentially expressed in the two pig breeds. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analyses revealed that differentially expressed genes and the target genes of differentially expressed lncRNAs were significantly enriched in PPAR signaling pathway and biological processes including fat cell differentiation and fatty acid metabolism. Key lncRNAs might regulate adipogenic differentiation and fatty acid metabolism by regulating genes involved in above signaling pathway and biological processes. Specifically, XLOC_014379, XLOC_011279, XLOC_064871, XLOC_019518 and XLOC_013639 might target SCD, LPIN1, TRIB3, EGR2 and FABP3, respectively, and then play critical regulatory role. These results are useful for understanding fat deposition in pig, breeding livestock with high quality meat, and preventing and treating lipid metabolic disease.

Diurnal variation in cholesterol 7α-hydroxylase activity is determined by the -203A>C polymorphism of the CYP7A1 gene

Aim

To determine whether the promoter polymorphism -203A>C of cholesterol-7α-hydroxylase encoding gene (CYP7A1) affects diurnal variation in CYP7A1 enzyme activity.

Methods

The study included 16 healthy male volunteers – 8 homozygous for -203A and 8 homozygous for the -203C allele of CYP7A1. Three 15-hour examinations (from 7am to 10pm) were carried out for each of the participants: after one-day treatment with cholestyramine; after one-day treatment with chenodeoxycholic acid (CDCA); and a control examination without any treatment. The plasma concentration of 7α-hydroxy-4-cholesten-3-one (C4), a marker of CYP7A1 activity, was determined in all the experiments at 90-min intervals.

Results

CYP7A1 activity was up-regulated after treatment with cholestyramine and suppressed after treatment with CDCA. There were no differences between -203A and -203C allele carriers in the response of enzyme activity to both drugs. In the control experiment, -203A allele carriers displayed diurnal variation in enzyme activity, whereas CYP7A1 activity did not change in -203C allele carriers. These results were confirmed by modeling the dynamics of C4 using polynomial regression.

Conclusion

The promoter polymorphism of the CYP7A1 gene has a pronounced impact on diurnal variation in CYP7A1 activity.

The effect of colesevelam treatment on bile acid and lipid metabolism and glycemic control in healthy men

The treatment of hypercholesterolemia with bile acid (BA) sequestrants results in upregulation of BA synthesis through the classical pathway initiated by cholesterol 7alpha-hydroxylase (CYP7A1). To characterize the detailed dynamics of serum lipid and BA concentrations and the BA synthesis rate in response to treatment with BA sequestrants and to determine whether the -203A/C promoter polymorphism of the CYP7A1 encoding gene (CYP7A1) affects such a response, this pilot study was carried out in healthy men (8 homozygous for the -203A allele and 8 homozygous for the -203C allele of CYP7A1). The subjects were treated for 28 days with colesevelam and blood was drawn for analysis before and on days 1, 3, 7, 14 and 28 of treatment. The response of lipids, BA, fibroblast growth factor-19 (FGF19) and 7alpha-hydroxy-4-cholesten-3-one (C4) to colesevelam did not differ between carriers of -203A and -203C alleles; their data were then aggregated for further analysis. Colesevelam treatment caused immediate suppression of FGF19 concentration and a fivefold increase in CYP7A1 activity, as assessed from C4 concentration, followed by a 17 % decrease in LDL-cholesterol. Although total plasma BA concentrations were not affected, the ratio of cholic acid/total BA rose from 0.25+/-0.10 to 0.44+/-0.16 during treatment at the expense of decreases in chenodeoxycholic and deoxycholic acid.

Common Variants in Cholesterol Synthesis- and Transport-Related Genes Associate with Circulating Cholesterol Responses to Intakes of Conventional Dairy Products in Healthy Individuals

BACKGROUND

Dairy intake has been associated with varying impacts on circulating cholesterol concentrations across nutritional epidemiology and intervention studies, with findings attributed mainly to differences in the nature of dairy products consumed or study designs. The contribution of the genomic architecture to such observations has yet to be revealed.

OBJECTIVE

We assessed the impact of multiple common genetic variations in cholesterol-related genes on responses of serum cholesterol to the recommended amount of dairy product intake in Canada.

METHODS

In a multicenter, randomized crossover design, 101 normolipidemic adults (n = 29 men and 72 women), with a mean ± SD age of 41.7 ± 16.7 y and a body mass index (BMI, in kg/m(2)) of 25.9 ± 4.3 consumed 3 servings/d of dairy [375 mL 1% milk-fat (MF) milk, 175 g 1.5% MF yogurt, and 30 g of 34% MF cheese] or energy-matched control products (juice, cashews, and cookies) provided within a prudent background diet for 4 wk each, separated by a 4- to 8-wk washout period. Serum lipid variables were determined by standard enzymatic methods by using an autoanalyzer. Candidate single nucleotide polymorphisms were assessed by TaqMan genotyping assay.

RESULTS

The responsiveness of serum total cholesterol (TC) and LDL cholesterol to the dairy compared with the control diet was associated with individuals' genotypes. The cholesterol transport gene ATP-binding cassette subfamily G, member 5 (ABCG5) rs6720173-GG homozygotes had higher concentrations of TC (+0.18 mmol/L; P = 0.0118) and LDL cholesterol (+0.17 mmol/L; P = 0.0056) relative to C-allele carriers (-0.07 and -0.06 mmol/L, respectively). The bile acid synthesis gene cholesterol 7α-hydroxylase (CYP7A1) rs3808607-G-allele carriers had higher TC (+0.20 to +0.28 mmol/L; P = 0.0026) and LDL cholesterol (+0.19 mmol/L for GT genotype; P = 0.0260) relative to TT homozygotes (-0.11 and -0.03 mmol/L, respectively). In addition, the cholesterol synthesis gene 7-dehydrocholesterol reductase (DHCR7) rs760241-A-allele carriers had higher LDL cholesterol (+0.26 mmol/L; P = 0.0399) relative to GG homozygotes (+0.06 mmol/L).

CONCLUSION

Genetic variations in ABCG5, CYP7A1, and DHCR7 may contribute to differing responses of serum cholesterol to dairy intake among healthy adults. This trial was registered at clinicaltrials.gov as NCT01444326.

Effects of pomegranate peel polyphenols on lipid accumulation and cholesterol metabolic transformation in L-02 human hepatic cells via the PPARγ-ABCA1/CYP7A1 pathway

PPPs, PC and PEA in different concentrations were found to decrease the total cholesterol (TC) content and increase the total bile acid (TBA) content of a human hepatic cell model, and so possess a lipid-lowering effect.

CYP7A1 gene polymorphism located in the 5' upstream region modifies the risk of coronary artery disease

Background. 7-Alpha cholesterol hydroxylase (CYP7A1), the first enzyme of classic conversion pathway leading from cholesterol to bile acids synthesis, is encoded by CYP7A1 gene. Its single nucleotide polymorphisms (SNPs) influence serum lipid levels and may be related to impaired lipid profile leading to coronary artery disease (CAD). The aim of the present study was to analyze the possible association between the rs7833904 CYP7A1 polymorphism and premature CAD. Material and Methods. Serum lipid levels and rs7833904 SNP were determined in 419 subjects: 200 patients with premature CAD and 219 age and sex matched controls. Results. The A allele carrier state was associated with CAD (OR = 1.76, 95% CI; 1.14–2.71, P = 0.014). The effect was even stronger in the male subgroups (OR = 2.16, 95% CI; 1.28–3.65, P = 0.003). There was no effect in the females. Risk factors of CAD and clinical phenotype of atherosclerosis were not associated with genotype variants of the rs7833904 SNP. Lipid profiles also did not differ significantly between individual genotypes. Conclusion. The CYP7A1 rs7833904 polymorphism may modify the risk of CAD. This effect is especially strong in male subjects. The studied polymorphism does not significantly influence serum lipid levels, in the present study.

Effects of dietary probiotic supplementation on LXRα and CYP7α1 gene expression, liver enzyme activities and fat metabolism in ducks

1. The objective of this study was to investigate the effects of dietary probiotic supplementation on liver X receptor alpha (LXRα) and cholesterol 7α-hydroxylase (CYP7α1) mRNA levels, protein enzymatic activities and fat metabolism in Cherry Valley Pekin ducks. 2. A total of 750 one-day-old Cherry Valley Pekin ducks were randomly divided into 5 groups with three replicates of 50 ducks each in a completely randomised experiment. Each group was fed on a basal diet supplemented with 0, 500, 1000, 1500 or 2000 mg probiotics/kg. 3. Body rate and feed conversion ratio were highest and abdominal subcutaneous fat % was lowest at 1000 mg probiotic/kg. 4. The mRNA levels of LXRα and CYP7α1 in liver tissue was estimated by RT-PCR; serum triglyceride (TG) and total cholesterol (TC) concentrations were measured by ELISA. 5. The expression levels and enzyme activity of LXRα and CYP7α1 increased in conjunction with decreases in TG and TC concentrations following probiotic supplementation to a maximum at 1000 mg probiotics/kg and decreased thereafter. 6. It is concluded that dietary probiotics can enhance LXRα and CYP7α1 enzyme activities in the liver and reduce lipid concentrations and fat deposition in ducks.

G-protein estrogen receptor as a regulator of low-density lipoprotein cholesterol metabolism: cellular and population genetic studies

OBJECTIVE

Estrogen deficiency is linked with increased low-density lipoprotein (LDL) cholesterol. The hormone receptor mediating this effect is unknown. G-protein estrogen receptor (GPER) is a recently recognized G-protein-coupled receptor that is activated by estrogens. We recently identified a common hypofunctional missense variant of GPER, namely P16L. However, the role of GPER in LDL metabolism is unknown. Therefore, we examined the association of the P16L genotype with plasma LDL cholesterol level. Furthermore, we studied the role of GPER in regulating expression of the LDL receptor and proprotein convertase subtilisin kexin type 9.

APPROACH AND RESULTS

Our discovery cohort was a genetically isolated population of Northern European descent, and our validation cohort consisted of normal, healthy women aged 18 to 56 years from London, Ontario. In addition, we examined the effect of GPER on the regulation of proprotein convertase subtilisin kexin type 9 and LDL receptor expression by the treatment with the GPER agonist, G1. In the discovery cohort, GPER P16L genotype was associated with a significant increase in LDL cholesterol (mean±SEM): 3.18±0.05, 3.25±0.08, and 4.25±0.33 mmol/L, respectively, in subjects with CC (homozygous for P16), CT (heterozygotes), and TT (homozygous for L16) genotypes (P<0.05). In the validation cohort (n=339), the GPER P16L genotype was associated with a similar increase in LDL cholesterol: 2.17±0.05, 2.34±0.06, and 2.42±0.16 mmol/L, respectively, in subjects with CC, CT, and TT genotypes (P<0.05). In the human hepatic carcinoma cell line, the GPER agonist, G1, mediated a concentration-dependent increase in LDL receptor expression, blocked by either pretreatment with the GPER antagonist G15 or by shRNA-mediated GPER downregulation. G1 also mediated a GPER- and concentration-dependent decrease in proprotein convertase subtilisin kexin type 9 expression.

CONCLUSIONS

GPER activation upregulates LDL receptor expression, probably at least, in part, via proprotein convertase subtilisin kexin type 9 downregulation. Furthermore, humans carrying the hypofunctional P16L genetic variant of GPER have increased plasma LDL cholesterol. In aggregate, these data suggest an important role of GPER in the regulation of LDL receptor expression and consequently LDL metabolism.

Relationship between CYP7A1 -204A>C polymorphism with gallbladder stone disease and serum lipid levels: a meta-analysis

Background

The CYP7A1 gene polymorphism has been reported to be associated with gallbladder stone disease (GSD) and serum lipid levels, but the results were inconsistent. This meta-analysis aimed to evaluate the influence of the -204A > C polymorphism in the promoter of CYP7A1 gene on the GSD and serum lipid levels.

Methods

According to inclusion/exclusion criteria, eligible studies on CYP7A1 gene -204A > C polymorphism of serum lipid levels and the risk of GSD were retrieved. Depending on the between-study heterogeneity, the fixed- or random-effects model was applied, and the data were analyzed using the RevMan software (V5.2).

Results

Five studies totaling 830 GSD patients and 882 healthy controls were used to evaluate the relation of CYP7A1 -204A > C polymorphism with GSD. Overall comparison of alleles A with C in all study population yielded 5% but non-significant increased risk of GSD (OR = 1.05, 95% CI: 0.91 − 1.22, P = 0.48). Subgroup analysis by ethnic differences did not show any association between CYP7A1 -204A > C polymorphism and GSD either. Four studies totaling 802 cases and 691 controls were used to assess the relation of CYP7A1 -204A > C polymorphism with serum lipid levels. All the subjects were from the Asian population. The pooled effects indicated that AC genotype had higher levels of TG than AA (MD = -0.42, 95% CI: -0.76 − -0.08, P = 0.01). CC genotype in cases had higher levels of TC (MD = 0.65, 95% CI: 0.25 − 1.05, P = 0.001) and LDL-C (MD = 0.40, 95% CI: 0.06 − 0.73, P = 0.02) than AA, AA (MD = -0.35, 95% CI: -0.60 − -0.10, P = 0.007) and AC (MD = −0.35, 95% CI: -0.61 − -0.08, P = 0.01) genotypes in controls had higher levels of TC than CC, and AA genotype in controls had higher levels of HDL-C than CC (MD = -0.15, 95% CI: -0.21 − -0.09, P < 0.00001).

Conclusions

The CYP7A1 -204A > C polymorphism is significantly associated with serum lipid levels in Asian population, but not gallbladder stone disease.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-511X-13-126) contains supplementary material, which is available to authorized users.

The role of common variants of ABCB1 and CYP7A1 genes in serum lipid levels and lipid-lowering efficacy of statin treatment: a meta-analysis

BACKGROUND

The relation between the ABCB1 and CYP7A1 genes and serum lipid levels and lipid-lowering efficacy of statin treatment is inconsistent.

OBJECTIVE

The purpose of this meta-analysis was to explore the associations between the ABCB1 and CYP7A1 genes and serum lipid levels and lipid-lowering efficacy of statin treatment.

METHODS

MEDLINE, EMBASE, and the Cochrane Library databases were searched systematically for studies of associations between relevant single nucleotide polymorphisms C3435 T (ABCB1), G2677 A/T (ABCB1), and A-204C (CYP7A1) and serum lipid levels or statin treatment. Associations were assessed in pooled data by calculating mean difference with 95% confidence intervals.

RESULTS

Seventeen studies with 4890 patients were included in this meta-analysis. The "AA" group at A-204C (CYP7A1) had lower serum total cholesterol (TC) levels than "AC + CC" group. The "AA" group at A-204C (CYP7A1) had greater reduction in low-density lipoprotein cholesterol (LDL-C) with statin treatment than "AC + CC" group. The "GG" group at G2677 A/T (ABCB1) had less reduction in TC and LDL-C with statin treatment than "non-GG" group.

CONCLUSIONS

The A-204C (CYP7A1) polymorphism was associated with the level of TC and the lipid-lowering efficacy of statin treatment in the level of LDL-C. The G2677 A/T (ABCB1) polymorphism was associated with the lipid-lowering efficacy of statin treatment in the levels of LDL-C and TC.

The CYP7A1 gene rs3808607 variant is associated with susceptibility of tuberculosis in Moroccan population

Introduction

Despite the medical progress in treatment. Tuberculosis (TB) continues to be a serious global health problem. A genome-wide linkage study identified a major susceptibility locus on chromosomal region 8q12-q13 in Moroccan TB patients. The CYP7A1 gene is located in this region and codes for cholesterol 7a-hydroxylase, an enzyme involved in cholesterol catabolism.

Methods

We selected three SNPs (rs3808607, rs8192875 and rs8192879) and studied their genotype and allele frequencies distribution in patients with pulmonary (PTB) or pleural TB (pTB), and compared them to Healthy Controls (HC). Genotyping of rs8192875 and rs8192879 SNPs was carried out using the Taq Man SNP genotyping Assay while rs3808607 was investigated by PCR-RFLP.

Results

We reported here for the first time a statistically significant increase in the AA homozygote genotype frequency of rs3808607 in PTB patients compared to HC (p = 0.02, OR = 1.93, 95% CI: 1.93 (1.07;3.49). The increased risk of developing TB was maintained when we combined the groups of patients (PTB-pTB) (p = 0.01, OR= 1.91, 95% CI = (1.07 - 3.42). In contrast, no genetic association was observed between the rs8192875 or rs8192879 polymorphisms and TB.

Conclusion

Our investigations suggest that rs3808607 may play a role in susceptibility to TB in a Moroccan population.

Transport and biological activities of bile acids

Bile acids have emerged as important biological molecules that support the solubilization of various lipids and lipid-soluble compounds in the gut, and the regulation of gene expression and cellular function. Bile acids are synthesized from cholesterol in the liver and eventually released into the small intestine. The majority of bile acids are recovered in the distal end of the small intestine and then returned to the liver for reuse. The components of the mechanism responsible for the recycling of bile acids within the enterohepatic circulation have been identified whereas the mechanism for intracellular transport is less understood. Recently, the ileal lipid binding protein (ILBP; human gene symbol FABP6) was shown to be needed for the efficient transport of bile acids from the apical side to the basolateral side of enterocytes in the distal intestine. This review presents an overview of the transport of bile acids between the liver and the gut as well as within hepatocytes and enterocytes. A variety of pathologies is associated with the malfunction of the bile acid transport system.

Human cytochromes P450 in health and disease

There are 18 mammalian cytochrome P450 (CYP) families, which encode 57 genes in the human genome. CYP2, CYP3 and CYP4 families contain far more genes than the other 15 families; these three families are also the ones that are dramatically larger in rodent genomes. Most (if not all) genes in the CYP1, CYP2, CYP3 and CYP4 families encode enzymes involved in eicosanoid metabolism and are inducible by various environmental stimuli (i.e. diet, chemical inducers, drugs, pheromones, etc.), whereas the other 14 gene families often have only a single member, and are rarely if ever inducible or redundant. Although the CYP2 and CYP3 families can be regarded as largely redundant and promiscuous, mutations or other defects in one or more genes of the remaining 16 gene families are primarily the ones responsible for P450-specific diseases-confirming these genes are not superfluous or promiscuous but rather are more directly involved in critical life functions. P450-mediated diseases comprise those caused by: aberrant steroidogenesis; defects in fatty acid, cholesterol and bile acid pathways; vitamin D dysregulation and retinoid (as well as putative eicosanoid) dysregulation during fertilization, implantation, embryogenesis, foetogenesis and neonatal development.

Loss of small heterodimer partner protects against atherosclerosis in apolipoprotein E-deficient mice

Small heterodimer partner (SHP) is involved in bile, lipid, and glucose metabolism. The aim of this study was to investigate the effect of SHP on the development of atherosclerosis. Apolipoprotein E knockout (ApoE-/-) mice were crossed with SHP knockout (SHP-/-) mice to generate double knockout (ApoE-/-SHP-/-) mice. ApoE-/- and ApoE-/-SHP-/- male mice were fed a western diet for 20 weeks. Body weight in ApoE-/-SHP-/) mice was significantly lower than that in ApoE-/- mice (37±1 g vs. 42±1 g, p<0.01). Loss of SHP in ApoE-/- mice decreased the size of adipocytes in white adipose tissue and reduced lipid accumulation in the liver. Glucose intolerance was improved in ApoE-/-SHP-/- mice as compared with ApoE-/- mice (p<0.01). There was no statistical difference in non-high density lipoprotein cholesterol levels between ApoE-/-SHP-/- mice and ApoE-/- mice despite an increase of cholesterol 7α-hydroxylase expression in the liver. The proportion of atherosclerotic lesions in the aorta was significantly lower in ApoE-/-SHP-/- mice than in ApoE-/- mice (2.8±2.0% vs. 9.1±1.9%, p<0.01). In conclusion, loss of SHP function can prevent atherosclerosis, and resistance to diet-induced obesity is the primary factor contributing to this protective effect.

The effect of CYP7A1 polymorphisms on lipid responses to fenofibrate

INTRODUCTION

CYP7A1 encodes cholesterol 7α-hydroxylase, an enzyme crucial to cholesterol homeostasis. Its transcriptional activity is downregulated by fenofibrate. The goal of this study was to determine the effect of CYP7A1 polymorphisms on lipid changes in response to fenofibrate.

METHODS

We examined the associations of 3 tagging single nuclear polymorphisms (i6782C>T, m204T>G, 3U12536A>C) at CYP7A1 with triglyceride (TG) and high-density lipoprotein cholesterol (HDL)-C responses to a 3-week treatment with 160 mg/d of fenofibrate in 864 US white participants from the Genetics of Lipid Lowering Drugs and Diet Network study.

RESULTS

The m204T>G variant was significantly associated with TG and HDL-C responses with fenofibrate. Individuals homozygous for the common T allele of m204T>G single nuclear polymorphism displayed both the greater reduction of TG (-32% for TT, -28% for GT, -25% for GG, P = 0.004) and an increase of HDL-C response compared with noncarriers (4.1% for TT, 3.4% for GT, 1.2% for GG, P = 0.01). Conversely, individuals homozygous for the minor allele of i6782C>T showed a greater increase in the HDL-C response compared with noncarriers (2.8% CC, 4.5% for CT, 5.8% for TT, P = 0.02), albeit no significant effect on TG response.

CONCLUSIONS

Our data suggest that common variants at the CYP7A1 locus modulate the TG-lowering and HDL-C-raising effects of fenofibrate, and contribute to the interindividual variation of the drug responses.

Risk modification of colorectal adenoma by CYP7A1 polymorphisms and the role of bile acid metabolism in carcinogenesis

Cholesterol 7α-hydroxylase (CYP7A1), the rate-limiting enzyme in the conversion of cholesterol to bile acids, is a postulated gene modifier of colorectal cancer risk and target for the therapeutic bile acid, ursodeoxycholic acid (UDCA). We investigated associations between CYP7A1 polymorphisms and fecal bile acids, colorectal adenoma (CRA), and UDCA efficacy for CRA prevention. Seven tagging, single-nucleotide polymorphisms (SNP) in CYP7A1 were measured in 703 (355 UDCA, 348 placebo) participants of a phase III chemoprevention trial, of which 495 had known baseline fecal bile acid concentrations. In the placebo arm, participants with two minor G(rs8192871) alleles (tag for a low activity promoter polymorphism at -204) had lower odds of high secondary bile acids (OR = 0.26, 95% CI: 0.10-0.69), and CRA at 3 years' follow-up (OR = 0.41, 95% CI: 0.19-0.89), than AA carriers. Haplotype construction from the six polymorphic SNPs showed participants with the third most common haplotype (C(rs10957057)C(rs8192879)G(rs8192877)T(rs11786580)A(rs8192871)G(rs13251096)) had higher odds of high primary bile acids (OR = 2.34, 95% CI: 1.12-4.89) and CRA (OR = 1.89, 95% CI: 1.00-3.57) than those with the most common CTACAG haplotype. Furthermore, three SNPs (rs8192877, rs8192871, and rs13251096) each modified UDCA efficacy for CRA prevention, and CCGTAG-haplotype carriers experienced 71% lower odds of CRA recurrence with UDCA treatment, an effect not present for other haplotypes (test for UDCA-haplotype interaction, P = 0.020). Our findings support CYP7A1 polymorphisms as determinants of fecal bile acids and risk factors for CRA. Furthermore, UDCA efficacy for CRA prevention may be modified by genetic variation in CYP7A1, limiting treatment benefit to a subgroup of the population.

Cytochrome P450s in the synthesis of cholesterol and bile acids--from mouse models to human diseases

The present review describes the transgenic mouse models that have been designed to evaluate the functions of the cytochrome P450s involved in cholesterol and bile acid synthesis, as well as their link with disease. The knockout of cholesterogenic Cyp51 is embrionally lethal, with symptoms of Antley-Bixler syndrome occurring in mice, whereas the evidence for this association is conflicting in humans. Disruption of Cyp7a1 from classic bile acid synthesis in mice leads to either increased postnatal death or a milder phenotype with elevated serum cholesterol. The latter is similar to the case in humans, where CYP7A1 mutations associate with high plasma low-density lipoprotein and hepatic cholesterol content, as well as deficient bile acid excretion. Disruption of Cyp8b1 from an alternative bile acid pathway results in the absence of cholic acid and a reduced absorption of dietary lipids; however, the human CYP8B1 polymorphism fails to explain differences in bile acid composition. Unexpectedly, apparently normal Cyp27a1(-/-) mice still synthesize bile acids that originate from the compensatory pathway. In humans, CYP27A1 mutations cause cerebrotendinous xanthomatosis, suggesting that only mice can compensate for the loss of alternative bile acid synthesis. In line with this, Cyp7b1 knockouts are also apparently normal, whereas human CYP7B1 mutations lead to a congenital bile acid synthesis defect in children or spastic paraplegia in adults. Mouse knockouts of the brain-specific Cyp46a1 have reduced brain cholesterol excretion, whereas, in humans, CYP46A1 polymorphisms associate with cognitive impairment. At present, cytochrome P450 family 39 is poorly characterized. Despite important physiological differences between humans and mice, mouse models prove to be an invaluable tool for understanding the multifactorial facets of cholesterol and bile acid-related disorders.

Pathway-Wide Association Study Implicates Multiple Sterol Transport and Metabolism Genes in HDL Cholesterol Regulation

Pathway-based association methods have been proposed to be an effective approach in identifying disease genes, when single-marker association tests do not have sufficient power. The analysis of quantitative traits may be benefited from these approaches, by sampling from two extreme tails of the distribution. Here we tested a pathway association approach on a small genome-wide association study (GWAS) on 653 subjects with extremely high high-density lipoprotein cholesterol (HDL-C) levels and 784 subjects with low HDL-C levels. We identified 102 genes in the sterol transport and metabolism pathways that collectively associate with HDL-C levels, and replicated these association signals in an independent GWAS. Interestingly, the pathways include 18 genes implicated in previous GWAS on lipid traits, suggesting that genuine HDL-C genes are highly enriched in these pathways. Additionally, multiple biologically relevant loci in the pathways were not detected by previous GWAS, including genes implicated in previous candidate gene association studies (such as LEPR, APOA2, HDLBP, SOAT2), genes that cause Mendelian forms of lipid disorders (such as DHCR24), and genes expressing dyslipidemia phenotypes in knockout mice (such as SOAT1, PON1). Our study suggests that sampling from two extreme tails of a quantitative trait and examining genetic pathways may yield biological insights from smaller samples than are generally required using single-marker analysis in large-scale GWAS. Our results also implicate that functionally related genes work together to regulate complex quantitative traits, and that future large-scale studies may benefit from pathway-association approaches to identify novel pathways regulating HDL-C levels.

Ethnic differences in the prevalence of polymorphisms in CYP7A1, CYP7B1 AND CYP27A1 enzymes involved in cholesterol metabolism

It is well known that drug disposition and response are greatly determined by the activities of drug metabolizing enzymes, which are polymorphic. Some of these polymorphisms are clinically relevant and presented an ethnic-dependent pattern of distribution. The characterization of the genetic distribution of different populations allows the selection of therapeutic options in accordance with the genetic background, with the objective to avoid adverse reactions and inefficacy of the treatment. In this work, we studied selected genetic polymorphisms in drug metabolizing enzymes in three different ethnic groups - Portugal, Mozambique and Colombia. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) genotyping methods were developed for drug metabolizing enzymes, namely, cholesterol 7α-hydroxylase (CYP7A1) (-203A>C, -346C>T, -496C>T, N233S, G347S), sterol 27-hydroxylase (CYP27A1) (R164W, A169V, D273N, V400A) and oxysterol 7α-hydroxylase (CYP7B1) (-116C>G, R324H, 1774C>T) to characterize the allelic distribution of these polymorphisms among three different ethnic/geographic origins. A total of 12 CYP7A1, CYP27A1 and CYP7B1 genetic variants were genotyped in a sample of 92 Portuguese, 151 Mozambican and 91 Colombian subjects. The variants N233S in CYP7A1 and 1774C>T in CYP7B1 were not detected in any population studied. The promoter polymorphisms in CYP7A1 (-203A>C, -346C>T, -496C>T) had high frequency in the three ethnic groups. G347S (CYP7A1), R164W, A169V and V400A (CYP27A1) were present in a low frequency but with a similar distribution in the three ethnic groups. Significant differences were observed for D273N (CYP27A1), -346C>T (CYP7A1), -116C>G and R324H (CYP7B1)Our results demonstrate a high variability of drug metabolizing enzymes between the different populations analyzed, indicating that at least some of these polymorphisms are ethnic specific.

CYP7A1 genotypes and haplotypes associated with hypertension in an obese Han Chinese population

This study investigated the association between single-nucleotide polymorphisms (SNPs; rs3808607 and rs1125226) within the CYP7A1 promoter and hypertension susceptibility in a Han Chinese population. From 2003 through 2006, a population-based case-control study was performed in a cohort of 1187 randomly selected Han Chinese subjects. A sib-pair study for a transmission disequilibrium test analysis was carried out in 76 hypertensive (HT) families (n=312) from northeastern Liaoning province. SNPs were detected using real-time PCR. No significant differences were found in the genotype or allele frequencies of either SNP (P>0.05), with no excessive allele sharing. For rs3808607, the frequency of the AA genotype in obese hypertensive patients was 31.91%, significantly higher than in normotensive (NT) subjects (12.73%; odds ratio (OR)=3.21, 95% confidence interval (CI)=1.35-7.66). For rs3808607, the AA genotype frequency was significantly higher in obese male HT subjects (27.87%) than in matched NTs (7.41%; OR=4.83, 95% CI=1.03-22.65). After adjustment for environmental risk factors in obese participants, the AA genotype was associated with hypertension (OR=3.395, 95% CI=1.412-8.162). Among subjects with body mass index 28 kg m(-2), the HT and NT groups had significantly different frequencies of Hap I (C/C) and Hap IV (A/A). The frequencies of rs3808607 alleles in the CYP7A1 gene differed significantly between obese HT and NT men. Haplotypes I and IV were associated with hypertension in obese participants.

Common variants of HMGCR, CETP, APOAI, ABCB1, CYP3A4, and CYP7A1 genes as predictors of lipid-lowering response to atorvastatin therapy

There is interindividual variation in lipid-lowering response to statins. The objective of this study was to investigate whether common variation in genes involved in lipid and statin metabolism modify the effect of statins on serum total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol concentration in coronary artery disease (CAD) patients. We studied the association between 18 single-nucleotide polymorphisms (SNPs) in six genes (HMGCR, CETP, APOAI, ABCB1, CYP3A4, CYP7A1) in response to atorvastatin therapy (20 mg/day) in 265 newly diagnosed CAD patients using multivariable adjusted general linear regression. Variant alleles of ABCB1 (-41A/G), HMGCR SNP29 G/T, rs5908A/G, rs12916C/T, and CYP7A1-204A/C polymorphisms were significantly associated with attenuated LDL-C reduction and variant alleles of CETP TaqI, -629C/A, and APOAI PstI polymorphisms were associated with higher increase in high-density lipoprotein-cholesterol. A three-loci interaction model consisting of CYP7A1rs892871AA/APOAIPstIP1P1/HMGCR rs12916CT was a better predictor for LDL-C lowering, when compared with single polymorphisms analysis on statin response. Variant genotypes of APOAI -2500C/T, CETP 405I/V, and ABCB1 3435C/T showed higher risk of myocardial infarction events (p < 0.05) in a 1-year follow-up of CAD patients. These results suggest that SNPs in lipid and statin pathway genes are associated with reduced LDL-C lowering by statins and identify individuals who may be resistant to maximal LDL-C lowering by statins.

CYP7A1 (-204 A>C; rs3808607 and -469 T>C; rs3824260) promoter polymorphisms and risk of gallbladder cancer in North Indian population

Cholesterol 7-alpha hydroxylase (CYP7A1), which is a rate-limiting enzyme for cholesterol catabolism and bile acid synthesis, may affect cholesterol homeostasis and result in gallstone formation that is a major risk factor for gallbladder cancer (GBC) pathogenesis. Genetic variations in CYP7A1 may influence its expression and thus may affect the risk of gallstone disease and GBC. We aimed to study the association of 2 promoter polymorphisms of CYP7A1 (-204 A>C [rs3808607] and -469 T>C [rs3824260]) in gallstone and GBC susceptibility in North Indian population. The study included 185 GBC patients, 195 symptomatic gallstone patients, and 200 healthy controls. Genotyping for both polymorphisms was done by polymerase chain reaction-restriction fragment length polymorphism method. Although the CC genotype of CYP7A1 -204 A>C was not significantly associated with gallstone disease (P = .083, odds ratio [OR] = 1.69, 95% confidence interval [CI] = 0.9-3.0), it was conferring higher risk for GBC (P = .018, OR = 2.05, 95% CI = 1.1-3.7). However, CYP7A1 -469 T>C was not associated with gallstone disease and GBC risk in our population. After subgroup stratifications on the basis of sex and gallstone status, CC genotype and variant allele of CYP7A1 -204 A>C imparted higher risk for GBC in women (P = .003, OR = 3.30, 95% CI = 1.5-7.2) and patients without gallstones (P = .045, OR = 1.91, 95% CI = 1.2-3.6). Haplotype analysis of the 2 polymorphisms showed that C,T (P = .045, OR = 1.84, 95% CI = 1.0-3.3) and C,C (P = .0001, OR = 3.10, 95% CI = 1.6-6.0) haplotypes had elevated risk of GBC predisposition. CYP7A1 -469 T>C is not associated with gallstone disease or GBC risk. Although CYP7A1 -204 A>C might play a modest role in gallstone susceptibility, it is an independent risk factor for GBC in North Indian population. Underlying mechanism for GBC susceptibility by CYP7A1 (-204 A>C and -469 T>C) haplotype appears to be independent of gallstone pathway and is believed to involve genotoxicity resulting from subnormal bile acid production.

Association of CYP7A1 -278A>C polymorphism and the response of plasma triglyceride after dietary intervention in dyslipidemic patients

We investigated the effect of the -278A>C polymorphism in the CYP7A1 gene on the response of plasma lipids to a reduced-fat diet for 6 to 8 weeks in a group of 82 dyslipidemic males with a mean age of 46.0 +/- 11.7 years. Individuals who presented at least one high alteration in total cholesterol, low-density lipoprotein cholesterol or triglyceride values were considered to be dyslipidemic. Exclusion criteria were secondary dyslipidemia due to diabetes mellitus, renal, liver, or thyroid disease. None of the subjects were using lipid-lowering medication. Baseline and follow-up lipid concentrations were measured. The genotypes were determined by the digestion of PCR products with the BsaI restriction endonuclease. There were statistically significant reductions in plasma total cholesterol, low-density lipoprotein cholesterol and triglyceride concentrations after dietary intervention. The minor allele C has a frequency of 43%. Carriers of the C allele had significantly lower triglyceride concentrations (P = 0.02) than AA homozygotes. After adjustment of covariates, subjects with the AC and CC genotypes showed a greater reduction in triglyceride concentrations compared to subjects with the AA genotype. Multiple linear regression analyses showed that the AC and CC CYP7A1 genotypes accounted for 5.2 and 6.2% of triglyceride concentration during follow-up and adjusted percent of change of triglyceride concentration, respectively. The present study provides evidence that -278A>C polymorphism in the CYP7A1 gene can modify triglyceride concentrations in response to a reduced fat diet in a dyslipidemic male population. This gene represents a potential locus for a nutrigenetic directed approach.

The potential influence of genetic variants in genes along bile acid and bile metabolic pathway on blood cholesterol levels in the population

The liver is currently known to be the major organ to eliminate excess cholesterol from our body. It accomplishes this function in two ways: conversion of cholesterol molecules into bile acids (BAs) and secretion of unesterified cholesterol molecules into bile. BAs are synthesized in the hepatocytes, secreted into bile and delivered to the lumen of the small intestine where they act as detergents to facilitate absorption of fats and fat-soluble vitamins. About 95% of BAs are recovered in the ileum during each cycle of the enterohepatic circulation. Five percent are lost and replaced by newly synthesized BAs, which amounts to approximately 500 mg/day in adult humans. In contrast to the efficiency of the BAs' enterohepatic circulation, 50% of the 1000 mg of cholesterol secreted daily into bile is lost in feces. It is known that rare human mutations in certain genes in bile acid and bile metabolic pathway influence blood cholesterol levels. With the recent success of genome-wide association studies, we are convinced that common genetic variants also play a role in the genetic architecture of plasma lipid traits. In this review, we summarized the current state of knowledge about genetic variations in bile acid and bile metabolic pathway, and assessed their impact on blood cholesterol levels and cholesterol metabolic kinetics in the population.

Association between CYP7A1 and the risk of proximal colon cancer in Japanese

Bile acids have long been implicated in the etiology of colorectal carcinogenesis by their genotoxicity as well as cytotoxicity. Cholesterol 7-alfa-hydroxylase (CYP7A1) is the rate-limiting enzyme that converts cholesterol into cholesterol 7-alfa-hydroxycholesterol in the first step of the classical pathway of bile acid synthesis. Recently, an association between a polymorphism (-204A>C, rs3808607) in CYP7A1 and proximal colon cancer/adenoma has been reported, which was not observed with distal colon or rectal cancer/adenoma. In this case-control study, we examined the association between haplotypes of CYP7A1 and proximal or distal colon/rectal cancer risk in a Japanese population. Subjects were 96 cases of proximal colon cancer, 357 of distal colon/rectal cancer and 961 age- and sex-matched non-cancer controls at Aichi Cancer Center. We examined five loci, including rs3808607, and evaluated the impact of haplotype on risk. In locus-specific analyses, we saw no association with rs3808607 for any site. Haplotype analyses revealed that the TAAGG haplotype was positively associated with proximal colon cancer [confounder-adjusted odds ratio: 1.72 (95% confidence interval: 1.10-2.71), p=0.018] but not with distal colon and rectal cancer combined. This association was consistently observed in analyses stratified by potential confounders. Our results indicate that CYP7A1 plays a role in the carcinogenesis of colorectal cancer specifically in the proximal colon. Confirmation of this association in other epidemiologic studies and biological evaluation of the TAAGG haplotype are warranted.

A combination of proatherogenic single-nucleotide polymorphisms is associated with increased risk of coronary artery disease and myocardial infarction in Asian Indians

Common single-nucleotide polymorphisms (SNPs) in genes of lipid metabolism modestly influence plasma low-density lipoprotein cholesterol (LDL-C) and risk of coronary artery disease (CAD). We evaluated a panel of LDL-C-modulating SNPs for potential association with risk of CAD in Asian Indians. Fifteen SNPs of CETP, ABCB1, APOAI, CYP7A1, and HMGCR genes were genotyped in 265 CAD patients and 150 controls of North Indian origin. A proatherogenic genotype score was formulated based on number of alleles associated with LDL-C and was evaluated for association with risk of CAD. We observed 12 SNPs from CETP, APOAI, ABCB1, CYP7A1, and HMGCR genes to be associated with baseline LDL-C and high-density lipoprotein cholesterol levels and increased risk of CAD (p < 0.05). Co-occurrence of three or more risk alleles (proartherogenic genotype score >or=3) was associated with increased risk of CAD and myocardial infarction. Analysis of epistatic interactions revealed CETPTaqIB1B1/405II/APOAI-75GA to be best model of CAD risk prediction in our population. Our study highlights synergistic association of multiple SNPs of lipid pathway with LDL-C levels and risk of CAD, and indicates that co-occurrence of proatherogenic risk alleles may provide incremental information about CAD risk beyond lipid concentrations.

Cholesterol-metabolizing cytochromes P450: implications for cholesterol lowering

Cardiovascular disease (CVD) continues to be a leading cause of death worldwide. Elevated serum cholesterol is one of the classical risk factors for CVD, which also include age, hypertension, smoking, diabetes mellitus, obesity and family history. Several therapeutic drug classes have been developed to treat hypercholesterolemia; yet, an important percentage of patients do not reach their treatment goals. Therefore, new cholesterol-lowering medications that have sites of action different from that of drugs available at present need to be developed. This review summarizes new information about cytochrome P450 enzymes 7A1, 27A1 and 46A1. These enzymes play key roles in cholesterol elimination and have the potential to serve as targets for cholesterol-lowering.

Loss of small heterodimer partner expression in the liver protects against dyslipidemia

Multiple studies suggest increased conversion of cholesterol to bile acids by cholesterol 7alpha-hydroxylase (CYP7A1) protects against dyslipidemia and atherosclerosis. CYP7A1 expression is repressed by the sequential activity of two nuclear hormone receptors, farnesoid X receptor (FXR) and small heterodimer partner (SHP). Here we demonstrate 129 strain SHP(-/-) mice are protected against hypercholesterolemia resulting from either a cholesterol/cholic acid (chol/CA) diet or from hypothyroidism. In a mixed 129-C57Bl/6 background, LDLR(-/-) and LDLR(-/-)SHP(-/-) mice had nearly identical elevations in hepatic cholesterol content and repression of cholesterol regulated genes when fed a Western diet. However, the LDLR(-/-)SHP(-/-) mice had greatly reduced elevations in serum VLDL and LDL cholesterol levels and triglyceride (TG) levels as compared with LDLR(-/-) mice. Additionally, the hepatic inflammation produced by the Western diet in the LDLR(-/-) mice was abolished in the LDLR(-/-)SHP(-/-) mice. CYP7A1 expression was induced 10-fold by the Western diet in the LDLR(-/-)SHP(-/-) mice but not in the LDLR(-/-) mice. Finally, hepatocyte-specific deletion of SHP expression was also protective against dyslipidemia induced by either a chol/CA diet or by hypothyroidism. While no antagonist ligands have yet been identified for SHP, these results suggest selective inhibition of hepatic SHP expression may provide protection against dyslipidemia.

CYP7A1 promoter polymorphism -203A>C affects bile salt synthesis rate in patients after ileal resection

Cholesterol 7alpha-hydroxylase (CYP7A1) plays a crucial role in cholesterol metabolism and has been implicated in genetic susceptibility to atherosclerosis. Thus, an understanding of its transcriptional regulation is of considerable importance. We evaluated the effect of a common -203A>C polymorphism in the CYP7A1 promoter region on the activity of CYP7A1, estimated as the ratios of serum 7alpha-hydroxycholest-4-en-3-one (C4) to either total or non-HDL-cholesterol. The study was performed on patients after resection of the distal ileum, leading to upregulation of CYP7A1 activity (n = 65). Healthy volunteers served as the control group (n = 66). Whereas higher CYP7A1 activity was associated with the -203A allele in the patient group (C4/cholesterol ratio, 29.0 vs. 14.8 microg/mmol, P = 0.032; C4/non-HDL-cholesterol ratio, 53.3 vs. 21.3 microg/mmol in -203AA and -203CC, P = 0.017, respectively), no differences were observed in the healthy controls. We conclude that under physiological conditions, the -203A>C polymorphism in the CYP7A1 gene promoter region does not seem to have any clinically relevant effect. However, in patients with severe bile salt malabsorption, this polymorphism markedly affects CYP7A1 activity.

Cholesterol 7alpha-hydrolase (CYP7A1) c.-278A>C promoter polymorphism in gallstone disease patients

There is growing evidence that gallstone formation may be genetically determined. Cholesterol 7alpha-hydrolase (CYP7A1) is an enzyme that catalyzes the first, rate-limiting reaction of cholesterol catabolic pathway. Recently, a common c.-278A>C polymorphism (rs3808607:G>T) has been described in CYP7A1 gene, associated with altered plasma lipid levels. The aim of this study was to verify the finding that CYP7A1 polymorphism may be associated with gallstone disease. Frequency and distribution of the studied alleles did not differ significantly between the patients (-278C; minor allele frequency: 0.45) and the controls (0.48). No significant gender-related differences of allele frequencies or distribution were noted. We conclude that CYP7A1 promoter polymorphism is not a valuable marker of gallstone disease susceptibility in a Polish population.

Role of genetic variant A-204C of cholesterol 7alpha-hydroxylase (CYP7A1) in susceptibility to gallbladder cancer

Gallbladder carcinoma (GBC) usually arises in the background of gallstone disease. Cholesterol 7alpha-hydroxylase (CYP7A1) is a rate-limiting enzyme for cholesterol catabolism and bile acid synthesis. A-204C genetic polymorphism in CYP7A1 may influence gene expression and thus affect the risk of gallstone disease and GBC. We aimed to study the association of A-204C variation of CYP7A1 gene promoter polymorphism in GBC patients, gallstone patients and healthy subjects. The study included 141 histopathologically proven GBC patients, ultrasonographically proven 185 symptomatic gallstone patients and 200 gallstone-free healthy subjects. Genotyping was done by PCR-RFLP method. CYP7A1 A-204C genotypes in control population were in Hardy-Weinberg equilibrium. The CC genotype conferred marginally significant risk for gallstone disease (p=0.051; OR=1.54; 95% CI=0.9-3.4). In GBC patients, the CYP7A1 A-204C polymorphism conferred high risk for GBC at genotype (p=0.005; OR=2.78; 95% CI: 1.3-5.6) as well as allele levels (p=0.008; OR=1.58 and 95% CI: 1.1-2.2). After stratification of GBC patients on the basis of presence or absence of gallstones, CC genotype imparted higher risk for GBC without stones (p=0.002; OR=4.44: 95% CI=1.7-11.3). The association of the polymorphism with GBC was more pronounced in female GBC patients, and also in cancer patients who developed GBC at advanced age. The CC genotype of CYP7A1 is an independent genetic risk factor for GBC but plays a modest role in susceptibility to gallstone disease. The GBC pathogenesis by CYP7A1 polymorphism appears to be independent of gallstone pathway and probably involves genotoxicity due to lipid peroxidation mechanisms.

Genetic variation and atherosclerosis

A family history of atherosclerosis is independently associated with an increased incidence of cardiovascular events. The genetic factors underlying the importance of inheritance in atherosclerosis are starting to be understood. Genetic variation, such as mutations or common polymorphisms has been shown to be involved in modulation of a range of risk factors, such as plasma lipoprotein levels, inflammation and vascular calcification. This review presents examples of present studies of the role of genetic polymorphism in atherosclerosis.

Genetic determinants of plasma lipoproteins

The search for common genetic determinants of plasma lipoproteins began in the early 1980s. Despite some exceptions, these efforts have not yet yielded a set of biological markers that can be used in clinical practice. By contrast, successes in defining the molecular basis of rare single-gene disorders, such as familial hypoalphalipoproteinemia, have shown the value of experimental designs that focus on genomic analysis of individuals within the tails of Gaussian distributions of quantitative lipoprotein traits. For example, this strategy showed that a small but relevant proportion of individuals within the <5% tail of plasma HDL-cholesterol distribution have mutations in genes that cause familial hypoalphalipoproteinemia. The value of clinical testing for genomic variants as an adjunct to a biochemical measurement of plasma lipoproteins, however, is at best questionable. A more direct impact of genetic studies is that definitions of 'common' and 'large genetic effects' have become more tempered, reflecting perhaps the biological reality that plasma lipoproteins are probably determined by the aggregate of numerous modest and occasional large genetic effects in addition to environmental factors. Here, we review recent progress on genomic variants and cholesterol metabolism, and discuss the impact these genetic studies will have on clinical cardiology.

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.

Pharmacogenetics and pharmacogenomics of cholesterol-lowering therapy

PURPOSE OF REVIEW

To summarize recent findings on pharmacokinetics, pharmacodynamics, drug-drug interactions and influence of lifestyle heterogeneity on adverse events in cholesterol-lowering therapy

RECENT FINDINGS

The prevention of cardiovascular disease is critically dependent on lipid-lowery therapy, including statins, cholesterol absorption inhibitors, fibrates and nicotinic acid. Statins are the most prescribed drugs in lipid lowering therapy with variability in response and almost one third of the patients do not meet their treatment goals. The severe adverse effects of treatment with cerivastatin stimulated the search for new genes and gene variations affecting pharmacokinetics, drug-drug interactions and pharmacodynamics. Moreover, instead of monotherapy, combined therapy of statins with ezetemibe and niacin was considered. This led to the identification of CD13, NPC1L1 and HM74A as new targets and CYP2C8 and glucuronidation enzymes as potential targets for drug-drug interactions. Moreover multiple polymorphic sites and pleiotrophic gene targets were reinvestigated in larger cohorts and the relevant pathogenetic factors start to evolve.

SUMMARY

Statin therapy is widely used and well tolerated by the majority of patients. To further reduce potential adverse effects and to increase efficacy, combined therapy concepts with ezetimibe or niacin are underway.

Cytochrome P450s and cholesterol homeostasis

By participating in pathways of cholesterol biosynthesis and elimination, different cytochrome P450 (P450 or CYP) enzymes play an important role in maintenance of cholesterol homeostasis. CYP51 is involved in cholesterol biosynthesis, whereas CYP 7A1, 27A1, 46A1, 7B1, 39A1, and 8B1 are the key enzymes in cholesterol catabolism to bile acids, the major route of cholesterol elimination in mammals. Cholesterol transformations to steroid hormones are also initiated by the P450 enzyme CYP11A1. Finally, one of the major drug-metabolizing P450s CYP3A4 seems to contribute to bile acid biosynthesis as well. The 9 P450s will be the focus of this review and assessed as drug targets for cholesterol lowering.

The nuclear hormone receptor farnesoid X receptor (FXR) is activated by androsterone

Farnesoid X receptor (FXR) uses bile acids as endogenous ligands. Here, we demonstrate that androsterone, a metabolic product of testosterone, is also an FXR ligand. Treatment of castrated male mice with androsterone induced expression of the FXR target gene small heterodimer partner (SHP). In mouse AML-12 hepatocytes, chenodeoxycholic acid (CDCA) or androsterone induced SHP expression with a similar kinetic pattern. The FXR antagonist guggulsterone blocked the induction of SHP by androsterone in AML-12 cells. Nuclear magnetic resonance spectroscopy demonstrated the direct binding of androsterone to purified human FXR (hFXR) ligand-binding domain (LBD) protein, resulting in the recruitment of steroid receptor coactivator protein-1 (SRC-1) coactivator peptide. In HEK293 cells, androsterone activated gal4-mouse FXR-LBD and gal4-hFXR-LBD fusion proteins, although in contrast to CDCA, androsterone activation was significantly greater for the mouse FXR-LBD than for the hFXR-LBD. Site-directed mutagenesis of the hFXR-LBD defined amino acids Asn354 and Ser345 as critical for differential species sensitivity to CDCA and androsterone, respectively. Crystal structure studies suggest that the orientation of the steroid nucleus of bile acids within the binding pocket of FXR is reversed from all other nuclear hormone receptors. In support of this model, we show here that mutations M265I or R331H, residues predicted by crystal structure to interact with the carboxylic acid tail of CDCA but not with androsterone, altered CDCA activation but had no effect on androsterone activation. Activation of FXR by androsterone may provide an additional means for physiological or pharmacological modulation of FXR.