Scavenger receptor class B type I polymorphisms and peripheral arterial disease

Influence of the rs4238001 Genetic Polymorphism of the SR-B1 Gene on Serum Lipid Levels and Response to Rosuvastatin in Myocardial Infarction Iraqi Patients

Scavenger receptor type B (SR-BI) is a receptor that binds both native and altered lipoproteins. It was revealed to facilitate utilization of high-density lipoprotein HDL and significantly affect the reverse transport of cholesterol. Therefore, the objectives were to identify the possible role of the genetic variant rs4238001 in patients with myocardial infarction (MI) on serum lipid level, and how this variant could impact the response of rosuvastatin drug. The genotyping of the rs4238001 genetic polymorphism of the SR-B1 gene was performed in 300 participants, including 150 MI patients treated with 20mg/day/4 weeks of rosuvastatin and 150 healthy control using Taq man probes (FAM and VIC) by Real-time PCR technique. The concentrations of the lipid profile were evaluated. The significance of the anthropometric data was revealed in the ejection fraction and smoking status (p < 0.05) between groups. The lipid profile shows either significant differences between control and MI patients (pre-treatment) or between pre-and post-treatment of MI patients (p < 0.05), but not HDL-c (p > 0.05). The minor allele frequency MAF% of the T allele and TT genotype were more frequent in MI patients than in controls (P = 0.173; OR = 3.62; 95% CI = 0.74-17.64). CC genotype was found to be associated with response to rosuvastatin therapy with a change of % (29.08 ± 53.2; p = 0.021). In the Iraqi population, the rs4238001 polymorphism of the SR-B1 gene is associated with variations in serum lipids, and the CC genotype of the SNP is related to higher HDL-C in the lipid-lowering rosuvastatin response.

Functional Deletion/Insertion Promoter Variants in SCARB1 Associated With Increased Susceptibility to Lipid Profile Abnormalities and Coronary Heart Disease

Background: Genetic variants in Scavenger receptor Class B Type 1 (SCARB1) influencing high-density lipoprotein cholesterol (HDL-C) and coronary heart disease (CHD) risk were identified by recent genome-wide association studies. Further study of potential functional variants in SCARB1 may provide new ideas of the complicated relationship between HDL-C and CHD.

Methods: 2000 bp in SCARB1 promoter region was re-sequenced in 168 participants with extremely high plasma HDL-C and 400 control subjects. Putative risk alleles were identified using bioinformatics analysis and reporter-gene assays. Two indel variants, rs144334493 and rs557348251, respectively, were genotyped in 5,002 CHD patients and 5,175 control subjects. The underlying mechanisms were investigated.

Results: Through resequencing, 27 genetic variants were identified. Results of genotyping in 5,002 CHD patients and 5,175 control subjects revealed that rs144334493 and rs557348251 were significantly associated with increased risk of CHD [odds ratio (OR): 1.28, 95% confidence interval (CI): 1.09 to 1.52, p = 0.003; OR: 2.65, 95% CI: 1.66–4.24, p = 4.4 × 10⁻⁵). Subsequent mechanism experiments demonstrated that rs144334493 deletion allele attenuated forkhead box A1 (FOXA1) binding to the promoter region of SCARB1, while FOXA1 overexpression reversely increased SR-BI expression.

Conclusion: Genetic variants in SCARB1 promoter region significantly associated with the plasma lipid levels by affecting SR-BI expression and contribute to the susceptibility of CHD.

Genomic Variants and Multilevel Regulation of ABCA1, ABCG1, and SCARB1 Expression in Atherogenesis

Atheroprotective properties of human plasma high-density lipoproteins (HDLs) are determined by their involvement in reverse cholesterol transport (RCT) from the macrophage to the liver. ABCA1, ABCG1, and SR-BI cholesterol transporters are involved in cholesterol efflux from macrophages to lipid-free ApoA-I and HDL as a first RCT step. Molecular determinants of RCT efficiency that may possess diagnostic and therapeutic meaning remain largely unknown. This review summarizes the progress in studying the genomic variants of ABCA1, ABCG1, and SCARB1, and the regulation of their function at transcriptional and post-transcriptional levels in atherosclerosis. Defects in the structure and function of ABCA1, ABCG1, and SR-BI are caused by changes in the gene sequence, such as single nucleotide polymorphism or various mutations. In the transcription initiation of transporter genes, in addition to transcription factors, long noncoding RNA (lncRNA), transcription activators, and repressors are also involved. Furthermore, transcription is substantially influenced by the methylation of gene promoter regions. Post-transcriptional regulation involves microRNAs and lncRNAs, including circular RNAs. The potential biomarkers and targets for atheroprotection, based on molecular mechanisms of expression regulation for three transporter genes, are also discussed in this review.

Inherited Variants in SCARB1 Cause Severe Early-Onset Coronary Artery Disease

[Figure: see text].

Association between a genetic variant in scavenger receptor class B type 1 and its role on codon usage bias with increased risk of developing coronary artery disease

OBJECTIVE

Coronary artery disease (CAD) as an important cause of morbidity and mortality globally. The scavenger receptor class B type 1 (SCARB1) plays an essential role in the reverse cholesterol transport. We have explored the association between a genetic variant, rs5888, in the SCARB1 gene with CAD and serum HDL-C levels.

METHODS

Patients were categorized into two groups' angiogram positive (>50% coronary stenosis) and angiogram negative (<50% coronary stenosis). Genotyping was carried out using polymerase chain reaction-amplification refractory mutation system. The association between the SNP rs5888 and serum HDL-C was analyzed using a logistic regression model.

RESULTS

The results showed that the subjects carrying a T allele was associated with a decreased serum HDL-C levels compared to the C allele in total population (p < 0.001). The risk of angiogram positivity in subjects carrying a T allele was 3.1-fold higher than for the control group (p < 0.001).

CONCLUSION

CVD patients carrying the T allele of rs5888 variant in the SCARB1 gene was associated with decreased serum level of HDL.

Effects of SR-BI rs5888 and rs4238001 variations on hypertension

Background

Scavenger receptor class B, type I (SR-BI), involved in reverse cholesterol pathway, is a multilipoprotein receptor and capable of binding HDL, LDL and VLDL. SR-BI may contribute to the development of hypertension due to accumulation of cholesterol in the vessel wall via transporting lipoproteins. Therefore, it was aimed to investigate the relationship between SR-BI rs5888 and rs4238001 variants in the patient with hypertension.

Materials and methods

Seventy three subjects diagnosed with hypertension and 76 healthy subjects constituted the patient and control group, respectively. Genomic DNA was isolated from peripheral blood samples and a real-time quantitative polymerase chain reaction protocol was performed to detect variations of rs5888 and rs4238001. The results were analyzed with the SPSS 22 program and p < 0.05 was considered statistically significant.

Results and discussion

SR-BI rs4238001 variation did not show significant difference between patient and control group (p > 0.05). In the SR-BI rs5888 variation; normal homozygous CC and heterozygous CT carriers had an average 2-fold lower risk of hypertension than those carrying the TT genotype (p < 0.05).

Conclusion

SR-BI rs5888 TT variant may increase hypertension risk by reducing lipid transport to the liver from the vessel wall.

A Novel Candidate for Prevention and Treatment of Atherosclerosis: Urolithin B Decreases Lipid Plaque Deposition in apoE-/- Mice and Increases Early Stages of Reverse Cholesterol Transport in ox-LDL Treated Macrophages Cells

SCOPE

HDL cholesterol is inversely related to the incidence of atherosclerosis. Polyphenols including ellagitannins have been shown to exert antiatherogenic properties. Urolithin B is formed from ellagitannins by components of the gut microbiota, and urolithins might be involved in beneficial effects against cardiovascular diseases in vitro. In this study, the influence of urolithin B on several parameters involved in the lipid plaque deposition and the reverse cholesterol transport is investigated.

METHODS AND RESULTS

In apoE^-/- mice and two different macrophage cell lines, the influence of urolithin B and its phase II conjugated metabolite on lipid plaque deposition, cholesterol uptake, and expression of ABCA1 and SR-BI is tested. It is shown that urolithin B decreases lipid plaque deposition, both urolithin B and urolithin B sulfate modulate expression of SR-BI and ABCA1, and cholesterol efflux increases from cholesterol laden macrophages to HDL particles as well as to reverse lipid uptake by stimulated THP-1 macrophages.

CONCLUSIONS

Urolithin B can decrease lipid plaque deposition, and urolithin B and urolithin B sulfate are able to induce reverse cholesterol transport by influencing expression of key proteins of this pathway. Urolithin B may represent the basis for development of new drugs for prevention and treatment of atherosclerosis in humans.

HDL Cholesterol Metabolism and the Risk of CHD: New Insights from Human Genetics

PURPOSE OF REVIEW

Elevated high-density lipoprotein cholesterol levels in the blood (HDL-C) represent one of the strongest epidemiological surrogates for protection against coronary heart disease (CHD), but recent human genetic and pharmacological intervention studies have raised controversy about the causality of this relationship. Here, we review recent discoveries from human genome studies using new analytic tools as well as relevant animal studies that have both addressed, and in some cases, fueled this controversy.

RECENT FINDINGS

Methodologic developments in genotyping and sequencing, such as genome-wide association studies (GWAS), exome sequencing, and exome array genotyping, have been applied to the study of HDL-C and risk of CHD in large, multi-ethnic populations. Some of these efforts focused on population-wide variation in common variants have uncovered new polymorphisms at novel loci associated with HDL-C and, in some cases, CHD risk. Other efforts have discovered loss-of-function variants for the first time in genes previously implicated in HDL metabolism through common variant studies or animal models. These studies have allowed the genetic relationship between these pathways, HDL-C and CHD to be explored in humans for the first time through analysis tools such as Mendelian randomization. We explore these discoveries for selected key HDL-C genes CETP, LCAT, LIPG, SCARB1, and novel loci implicated from GWAS including GALNT2, KLF14, and TTC39B. Recent human genetics findings have identified new nodes regulating HDL metabolism while reshaping our current understanding of known candidate genes to HDL and CHD risk through the study of critical variants across model systems. Despite their effect on HDL-C, variants in many of the reviewed genes were found to lack any association with CHD. These data collectively indicate that HDL-C concentration, which represents a static picture of a very dynamic and heterogeneous metabolic milieu, is unlikely to be itself causally protective against CHD. In this context, human genetics represent an extremely valuable tool to further explore the biological mechanisms regulating HDL metabolism and investigate what role, if any, HDL plays in the pathogenesis of CHD.

The rs5888 single nucleotide polymorphism in scavenger receptor class B type 1 (SCARB1) gene and the risk of premature coronary artery disease: a case-control study

Background

Several single nucleotide polymorphisms (SNPs) in lipid transport genes have been shown to be associated with premature coronary artery disease (PCAD). The scavenger receptor BI (SCARB1) is a key component of the reverse cholesterol transport and lipid metabolism. We aimed to examine the relationship between the rs5888 SNP within SCARB1and the risk of angiographically determined PCAD.

Methods

We used an age cut-off of 55 years for women and 45 years for men to define PCAD. Five-hundred and five patients with newly diagnosed angiographically documented PCAD (≥50 % luminal stenosis of any coronary vessel) as case group compared with 546 controls (subjects with no luminal stenosis at coronary arteries). The severity of CAD was determined by vessel score as well as Gensini score. A real-time polymerase chain reaction (PCR) and High Resolution Melting (HRM) analysis was used to distinguish between genotypes.

Results

T allele as compared to C allele was associated with increased odds of PCAD in total population (adjusted OR = 1.3, 95 % CI = 1.0 to 1.5; p = 0.020), and in women (adjusted OR = 1.3, 95 % CI = 1.0 to 1.8; p = 0.037), but not in men (adjusted OR = 1.2, 95 % CI = 0.9 to 1.5; p = 0.311). There was also no significant association between the examined polymorphism and the severity of CAD in whole or in men or women subgroups.

Conclusions

Our findings suggest that the SNP (rs5888) within SCARB1 is independently associated with PCAD in a sex-dependent manner.

ICAM-1 and SRD5A1 gene polymorphisms in symptomatic peripheral artery disease

The genotype distribution of two gene polymorphisms, previously associated with peripheral artery disease (PAD), has been evaluated in a population of diabetic (DPAD) and non-diabetic (NDPAD) patients affected by symptomatic PAD (stages II-IV). A decreased frequency of the AA genotype of rs5498 (ICAM-1) was observed in the PAD subjects compared to controls but this result did not reach statistical significance (p=0.06 by chi-squared test). On the contrary, a significant increase in the frequency of the GG homozygous genotype of rs248793 (SRD5A1) was observed in the PAD patient group in comparison to controls (p=0.01). These data confirm that the GG genotype of rs248793 in the SRD5A1 gene is significantly associated with symptomatic PAD and show a trend towards a stronger association with the non-diabetic status.

Functional genomics of the human high-density lipoprotein receptor scavenger receptor BI: an old dog with new tricks

PURPOSE OF REVIEW

The athero-protective role of scavenger receptor BI (SR-BI) is primarily attributed to its ability to selectively transfer cholesteryl esters from high-density lipoproteins (HDLs) to the liver during reverse cholesterol transport (RCT). In this review, we highlight recent findings that reveal the impact of SR-BI on lipid levels and cardiovascular disease in humans. Moreover, additional responsibilities of SR-BI in modulating adrenal and platelet function, as well as female fertility in humans, are discussed.

RECENT FINDINGS

Heterozygote carriers of P297S, S112F and T175A-mutant SR-BI receptors were identified in patients with high HDL-cholesterol levels. HDL from P297S-SR-BI carriers was unable to mediate macrophage cholesterol efflux, whereas hepatocytes expressing P297S-SR-BI were unable to mediate the selective uptake of HDL-cholesteryl esters. S112F and T175A-mutant receptors exhibited similar impaired cholesterol transport functions in vitro. Reduced SR-BI function in P297S carriers was also associated with decreased steroidogenesis and altered platelet function. Further, human population studies identified SCARB1 variants associated with female infertility.

SUMMARY

Identification of SR-BI variants confirms the key role of this receptor in influencing lipid levels and RCT in humans. A deeper understanding of the contributions of SR-BI to steroidogenesis, platelet function and fertility is required in light of exploration of HDL-raising therapies aimed at reducing cardiovascular risk.

Scavenger receptor class B type 1 gene rs5888 single nucleotide polymorphism and the risk of coronary artery disease and ischemic stroke: a case-control study

BACKGROUND

Our previous studies have showed that the rs5888 single nucleotide polymorphism (SNP) in Scavenger receptor class B type 1 (SCARB1) gene is associated with serum lipid levels in the general Chinese populations. The present study was undertaken to detect the associations between rs5888 SNP and the risk of coronary artery disease (CAD) and ischemic stroke (IS).

METHODS

A total of 1,716 unrelated subjects (CAD, 601; IS, 533; and healthy controls, 582) were included in this study. Genotyping of the rs5888 SNP were determined by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

The genotypic frequencies of SCARB1 rs5888 SNP were different between CAD patients and controls, the subjects with TT genotype had high risk of CAD (OR = 1.76, P = 0.038 for TT vs. CC; and OR = 1.75, P = 0.036 for TT vs. CC/CT). There was no significant association between genotypes and the risk of IS. Further analysis showed that the subjects with TT genotype in the total population had lower levels of high-density lipoprotein cholesterol than the subjects with CC/CT genotypes (P < 0.05), the subjects with TT genotype in controls but not in CAD or IS patients had higher levels of serum LDL-C and ApoB than those with CC genotype (P < 0.05 for each).

CONCLUSIONS

The present study suggests that the SCARB1 rs5888 SNP influences serum lipid levels, and is associated with the risk of CAD.

Association of three polymorphisms of scavenger receptor class BI gene (exon8, exon1, intron5) with coronary stenosis in a coronary Tunisian population

BACKGROUND

The potential role of scavenger receptor class BI (gene name SCARB1) in the regulation of lipoproteins metabolism and atherosclerosis has attracted considerable interest. We tested the relationship of SCARB1 polymorphisms with significant coronary stenosis (SCS) and lipid profile in a coronary Tunisian population.

METHODS

Three SCARB1 polymorphisms (exon8 (C/T), exon1 (G/A), intron5 (C/T)) were studied in 316 Tunisian patients undergoing coronary angiography. SCS was defined as a luminal narrowing of ≥ 50% in at least one major coronary artery. Lipid profile was measured. Genotyping was performed using PCR-RFLP.

RESULTS

Individuals with TT genotypes of exon8 were associated with higher concentrations of plasma HDL-C and ApoAI in the group without SCS. Carriers of T allele of exon8 were associated with 41% lower risk of SCS. This protective effect seemed to be particularly significant in women, nondiabetics and nonsmokers. Subjects homozygous for the variant allele of intron5 were significantly associated with an increased risk of SCS, particularly in smokers. AA genotype of exon1 was associated with an increased risk of SCS in diabetics and in patients with metabolic syndrome. The (CAT) haplotype was associated with increase in the risk of SCS compared to the wild haplotype and had a 4-fold greater risk of SCS than patients with haplotype (TGC) which seems to be the most protective against SCS.

CONCLUSION

Carriers of T allele of exon8 in SCARB1 seemed to increase HDL-C and ApoAI concentrations and reduce the risk of SCS. The intron5, exon1 and (CAT) haplotype seemed to have an atherogenic effect.

HDL scavenger receptor class B type I and platelet function

PURPOSE OF REVIEW

HDL cholesterol levels have been inversely correlated with thrombosis and HDL has been shown to mediate various antithrombotic effects. However, molecular mechanisms underlying the suppressing effect of HDL on platelet reactivity are not completely understood. The present review summarizes the recent advancements in understanding the role played by scavenger receptor class B type I (SR-BI) - an HDL receptor - in modulating platelet function and mediating platelet-HDL interactions.

RECENT FINDINGS

SR-BI is expressed on platelet surface and platelets from SR-BI knockout animals are characterized by increased free-to-total cholesterol ratio, abnormal morphology, increased reactivity to strong platelets agonists, enhanced adherence to immobilized fibrinogen, and a propensity to form arterial thrombi. Crossover incubation experiments and a bone marrow transplantation approach reveal increased wild-type platelet reactivity in plasma from SR-BI mice and normal or decreased SR-BI-deficient platelet reactivity in wild-type plasma. A similar functional platelet phenotype has been observed in human carriers of an SR-BI genetic variant. SR-BI ligands interfere with HDL binding to murine platelets and impede the agonist-induced platelet activation as effectively as native HDL. The inhibitory effects of native HDL, moderately oxidized HDL, and SR-BI ligands are abolished in SR-BI-deficient platelets but not in CD36-deficient platelets.

SUMMARY

SR-BI exerts an indirect influence on platelet reactivity via maintaining normal plasma cholesterol homeostasis. In addition, SR-BI is a functional receptor for native and moderately oxidized HDL on platelets that generates an inhibitory signal for platelet activation.

Regulation of platelet function by class B scavenger receptors in hyperlipidemia

Platelets constitutively express class B scavenger receptors CD36 and SR-BI, 2 closely related pattern recognition receptors best known for their roles in lipoprotein and lipid metabolism. The biological role of scavenger receptors in platelets is poorly understood. However, in vitro and in vivo data suggest that class B scavenger receptors modulate platelet function and contribute significantly to thrombosis by sensing pathological or physiological ligands, inducing prothrombotic signaling, and increasing platelet reactivity. Platelet CD36 recognizes a novel family of endogenous oxidized choline phospholipids that accumulate in plasma of hyperlipidemic mice and in plasma of subjects with low high-density lipoprotein levels. This interaction leads to the activation of specific signaling pathways and promotes platelet activation and thrombosis. Platelet SR-BI, on the other hand, plays a critical role in the induction of platelet hyperreactivity and accelerated thrombosis under conditions associated with increased platelet cholesterol content. Intriguingly, oxidized high-density lipoprotein, an SR-BI ligand, can suppress platelet function. These recent findings demonstrate that platelet class B scavenger receptors play roles in thrombosis in dyslipidemia and may contribute to acute cardiovascular events in vivo in hypercholesterolemia.

Scavenger receptor BI modulates platelet reactivity and thrombosis in dyslipidemia

Hypercholesterolemia is associated with increased platelet sensitivity to agonists and a prothrombotic phenotype. Mechanisms of platelet hypersensitivity are poorly understood; however, increased platelet cholesterol levels associated with hypercholesterolemia were proposed as leading to hypersensitivity. Scavenger receptor class B type I (SR-BI) in the liver controls plasma high-density lipoprotein (HDL) levels, and SR-BI-deficient mice display a profound dyslipoproteinemia. SR-BI is also expressed on platelets, and recent studies have suggested a role for SR-BI in platelet function; however, its role in hemostasis is unknown. Our present studies demonstrated that non-bone marrow-derived SR-BI deficiency and the dyslipidemia associated with it lead to platelet hyperreactivity that was mechanistically linked to increased platelet cholesterol content. Platelet-specific deficiency of SR-BI, on the other hand, was associated with resistance to hyperreactivity induced by increased platelet cholesterol content. Intravital thrombosis studies demonstrated that platelet SR-BI deficiency protected mice from prothrombotic phenotype in 2 types of dyslipidemia associated with increased platelet cholesterol content. These novel findings demonstrate that SR-BI plays dual roles in thrombosis and may contribute to acute cardiovascular events in vivo in hypercholesterolemia.

Influence of SCARB1 polymorphisms on serum lipids of hypercholesterolemic individuals treated with atorvastatin

BACKGROUND

The SR-BI is a key component on the cholesterol metabolism. Polymorphisms in the SR-BI gene (SCARB1) were related with variations on plasma lipoprotein profile and other risk factors for cardiovascular disease. We tested the relationship of 3 SCARB1 single nucleotide polymorphisms (SNPs) with hypercholesterolemia in a Brazilian population and whether these variants can influence lipid-lowering response to atorvastatin.

METHODS

c.4G>A, c.726+54C>T and c.1050C>T SNPs and serum concentrations of lipid and apolipoproteins were evaluated in 147 hypercholesterolemic (HC) and 185 normolipidemic (NL) unrelated Brazilian subjects. HC patients were treated with atorvastatin (10 mg/day/4 weeks).

RESULTS

Frequencies of SCARB1 polymorphisms were similar between the HC and NL groups (p>0.05). The T allele for c.726+54C>T was associated with higher LDL-c in NL and with higher apoB and apoB/apoAI in HC (p<0.05). HC individuals carrying c.1050C allele carriers (CC and CT genotypes) had lower change of total cholesterol, LDL-c, apoB and apoB/apoAI ratio (p<0.05) than the TT genotype carriers in response to atorvastatin.

CONCLUSION

The SCARB1 polymorphisms are related with variations in serum lipids in the Brazilian population and c.1050C>T SNP is associated with lipid-lowering atorvastatin response.

rs5888 variant of SCARB1 gene is a possible susceptibility factor for age-related macular degeneration

Major genetic factors for age-related macular degeneration (AMD) have recently been identified as susceptibility risk factors, including variants in the CFH gene and the ARMS2 LOC387715/HTRA1locus. Our purpose was to perform a case-control study in two populations among individuals who did not carry risk variants for CFHY402H and LOC387715 A69S (ARMS2), called “study” individuals, in order to identify new genetic risk factors. Based on a candidate gene approach, we analyzed SNP rs5888 of the SCARB1 gene, coding for SRBI, which is involved in the lipid and lutein pathways. This study was conducted in a French series of 1241 AMD patients and 297 controls, and in a North American series of 1257 patients with advanced AMD and 1732 controls. Among these individuals, we identified 61 French patients, 77 French controls, 85 North American patients and 338 North American controls who did not carry the CFH nor ARMS2 polymorphisms. An association between AMD and the SCARB1 gene was seen among the study subjects. The genotypic distribution of the rs5888 polymorphism was significantly different between cases and controls in the French population (p<0.006). Heterozygosity at the rs5888 SNP increased risk of AMD compared to the CC genotypes in the French study population (odds ratio (OR) = 3.5, CI95%: 1.4–8.9, p<0.01) and after pooling the 2 populations (OR = 2.9, 95% CI: 1.6–5.3, p<0.002). Subgroup analysis in exudative forms of AMD revealed a pooled OR of 3.6 for individuals heterozygous for rs5888 (95% CI: 1.7–7.6, p<0.0015). These results suggest the possible contribution of SCARB1, a new genetic factor in AMD, and implicate a role for cholesterol and antioxidant micronutrient (lutein and vitamin E) metabolism in AMD.

A field synopsis and meta-analysis of genetic association studies in peripheral arterial disease: The CUMAGAS-PAD database

In an electronic search of the literature, the authors systematically retrieved all published studies that investigated genetic susceptibility to peripheral arterial disease (PAD). They created a comprehensive database of all eligible studies, collecting detailed genetic and bioinformatics data on each polymorphism. Data from eligible studies were synthesized using meta-analysis techniques. Gene variants were classified into distinct pathophysiologic pathways, and their potential involvement in PAD pathogenesis was determined. Forty-one publications that examined 44 gene polymorphisms were included. For 37 polymorphisms, the variant form had a functional effect. Twenty-three polymorphisms in 22 potential PAD candidate genes (F2, FGB, MTHFR, ITGB3, ACE, AGT, IL6, CCL2, ICAM1, SELE, MMP9, PPARG, MMP1, ADD1, P2RY12, LIPC, PLA2G7, SCARB1, MMP3, MTTP, LPA, CHRNA3) showed a significant association in individual studies. Eighty-eight percent of the studies had statistical power of less than 50%, and in 15 studies the genotype distribution in the control group did not conform to Hardy-Weinberg equilibrium. Data on 12 polymorphisms (F5 1691 G/A, MTHFR 677C/T, F2 20210 G/A, ITGB3 1565 T/C, ACE I/D, AGT 704C/T, AGT -6G/A, AGT 733C/T, IL6 -174 G/C, MMP9 -1562C/T, ICAM1 1462A/G, CHRNA3 831C/T) were synthesized, and a positive association was found for 3 (IL6 -174 G/C, ICAM1 1462A/G, CHRNA3 831C/T).

Scavenger receptor class B type I protein as an independent predictor of high-density lipoprotein cholesterol levels in subjects with hyperalphalipoproteinemia

CONTEXT

In mice, scavenger receptor class B, type I (SR-BI) receptor protein deficiency is associated with elevated high-density lipoprotein (HDL)-cholesterol (HDL-C) levels.

OBJECTIVE

Our objective was to determine the relationship between SR-BI protein and HDL-C levels in humans.

DESIGN

This was a prospective study of adults with hyperalphalipoproteinemia. Fasting blood was obtained for lipid and lipoprotein measurement, genomic DNA, and monocyte-derived macrophages. SR-BI protein levels were measured by Western blots, and SR-BI activity was measured by cholesteryl ester (CE) uptake of each donor's radiolabeled HDL with their monocyte-derived macrophages, or by degradation and specific cell association of dual-labeled HDL in vitro.

SETTING

The study was performed in a tertiary university teaching hospital.

RESULTS

The mean age was 57.2 +/- 10.9 yr (n = 65). SR-BI protein levels were inversely associated with HDL-C levels (P < 0.002), HDL particle size (P < 0.05), and positively associated with CE uptake (P < 0.004); there was no association with plasma apolipoprotein levels. SR-BI protein levels (P = 0.01) were independent predictors of HDL-C levels. Subjects who were carriers of the A allele for the rs4238001 (glycine to serine at position 2) polymorphism [single nucleotide polymorphism (SNP)] had lower SR-BI protein levels (P = 0.01), whereas carriers of the C allele for the rs2278986 SNP also had lower SR-BI protein levels (P = 0.02). Body mass index (P = 0.05), rs4238001 (P = 0.01), and rs2278986 (P = 0.01) SNPs were independent predictors of SR-BI protein levels. In vitro studies of murine macrophages stably expressing the glycine to serine at position 2 SNP showed less degradation (P < 0.0004) and specific cell association (P < 0.0004) of [(125)I, (3)H]-CE-labeled HDL.

CONCLUSIONS

SR-BI protein has an independent effect on HDL-C levels in women with hyperalphalipoproteinemia. Two SNPs were significantly associated with lower SR-BI protein levels.