Association of genetic variation on chromosome 9p21.3 and arterial stiffness

OBJECTIVES

Genome wide association studies have consistently reported associations between a region on chromosome 9p21.3 and a broad range of vascular diseases, such as coronary artery disease (CAD), aortic and intracranial aneurysms and type-2 diabetes (T2D). However, clear associations with intermediate phenotypes have not been described so far. To shed light on a possible influence of this chromosomal region on arterial wall integrity, we analysed associations between single nucleotide polymorphisms (SNPs) and degree of stiffness of the abdominal aorta in elderly individuals.

METHODS AND RESULTS

A total of 400 subjects, 212 men and 188 women, aged 70-88 years were included. Arterial stiffness was examined at the midpoint between the renal arteries and the aortic bifurcation. Two CAD- and aneurysm-associated SNPs (rs10757274 and rs2891168) and one T2D-associated SNP (rs1081161) within the 9p21.3 region were genotyped. Aortic compliance and distensibility coefficients were higher in carriers of the rs10757274G and rs2891168G alleles in men reflecting a decrease in aortic stiffness. Adjustment for age and mean arterial pressure had no effect on these associations. The two SNPs were not associated with intima-media thickness or lumen diameter of the abdominal aorta. There were no associations between the rs10811661 SNP and any measure of aortic stiffness.

CONCLUSIONS

Impaired mechanical properties of the arterial wall may explain the association between chromosome 9p21.3 polymorphisms and vascular disease.

Identifying the susceptibility genes for coronary artery disease: from hyperbole through doubt to cautious optimism

The genetic basis of coronary artery disease (CAD) is complex, and the fact that an alarmingly high proportion of reported associations between genetic variants and CAD are not replicated has generated uncertainty as to whether molecular genetics is ever going to deliver on the promises delivered in the late 1990s. However, during 2007, the first generation of large-scale genome-wide association studies using high-density, single nucleotide polymorphism genotyping arrays have revealed genetic variants that are robustly associated with CAD and CAD-related traits such as type 2 diabetes and obesity. In particular, a robust susceptibility locus for CAD has been identified on chromosome 9p21. Also, evidence has been obtained that multiple rare alleles with fairly strong phenotypic effects may contribute to the genetic heritability of CAD, in addition to common variants with a modest impact on risk. Furthermore, new mechanistic connections have been discovered between different common complex diseases including CAD. This review focuses on the challenges and recent advances of molecular genetics in dissecting the molecular pathophysiology of atherothrombosis and defining novel targets for treatment.

Fatty acid desaturases in human adipose tissue: relationships between gene expression, desaturation indexes and insulin resistance

AIMS/HYPOTHESIS

Fatty acid desaturases introduce double bonds into growing fatty acid chains. The key desaturases in humans are Delta5-desaturase (D5D), Delta6-desaturase (D6D) and stearoyl-CoA desaturase (SCD). Animal and human data implicate hepatic desaturase activities in insulin resistance, obesity and dyslipidaemia. However, the role of desaturase activity in adipose tissue is uncertain. We therefore evaluated relationships between adipose mRNA expression, estimated desaturase activities (fatty acid ratios) in adipose tissue and insulin resistance.

METHODS

Subcutaneous adipose tissue mRNA expression of D5D (also known as FADS1), D6D (also known as FADS2) and SCD was determined in 75 individuals representative of the study population of 294 healthy 63-year-old men. Desaturation indexes (product/substrate fatty acid ratios) were generated from adipose tissue fatty acid composition in all individuals. Insulin resistance was defined as the upper quartile of the updated homeostasis model assessment (HOMA-2) index.

RESULTS

The relevant desaturation indexes (16:1/16:0, 18:1/18:0, 20:4/20:3 and 18:3/18:2) reflected expression of SCD, but not of D5D or D6D in adipose tissue. Insulin-resistant individuals had a higher adipose tissue 18:1/18:0, but not 16:1/16:0 ratio than insulin-sensitive individuals. Individuals with a high adipose tissue 18:1/18:0 ratio were 4.4-fold (95% CI 1.8-11.8) more likely to be insulin resistant [threefold (95% CI 1.1-8.6) after adjustment for waist circumference and plasma triacylglycerol]. In a multiple regression model predicting HOMA-2, the independent effect of the 18:1/18:0 ratio was borderline (p=0.086).

CONCLUSIONS/INTERPRETATION

Adipose tissue desaturation indexes of SCD reflect the expression of the gene encoding the enzyme in this tissue. Elevated SCD activity within adipose tissue is closely coupled to the development of insulin resistance.

Correlation of serum IGF-I and IGFBP-1 and -3 to cardiovascular risk indicators and early carotid atherosclerosis in healthy middle-aged men

OBJECTIVES

IGF-I, IGFBP-1 and IGFBP-3 are putative mediators in cardiovascular disease. The present study examined (i) the correlations of circulating IGF-I, IGFBP-1 and IGFBP-3 to established cardiovascular risk factors and signs of early atherosclerosis as reflected by ultrasound measurement of common carotid intima-media thickness (IMT), and (ii) whether serum concentrations of these analytes are modulated during alimentary lipaemia.

DESIGN

Cross-sectional clinical study.

PATIENTS

A biobank and clinical database based on 96 healthy Caucasian men, aged 50 years, with an apolipoprotein (apo) E3/E3 genotype, who had originally undergone investigations of postprandial lipoprotein metabolism was used for the study.

MEASUREMENTS

Total IGF-I, IGFBP-1 and IGFBP-3 were determined in serum by radioimmunoassay (RIA). Free IGF-I was measured by a commercial two-site immunoradiometric assay (IRMA).

RESULTS

In multivariate analyses, fasting serum free IGF-I correlated inversely with IMT and accounted for 5% of the variation in multiple R(2). When fasting serum IGFBP-1 was entered in the models instead of IGF-I, IGFBP-1 correlated positively with IMT and accounted for 6% of the variation in IMT. IGFBP-3 and total IGF-I were unrelated to IMT. There were no associations between free IGF-I and cardiovascular risk factors, whereas IGFBP-1 behaved like a component of the insulin resistance syndrome. Serum free IGF-I increased and IGFBP-1 decreased postprandially.

CONCLUSION

The data indicate that serum free IGF-I and IGFBP-1 are implicated in early atherosclerosis.

Cardiomyopathy, pericarditis and myocarditis in a population-based cohort of inpatients with coeliac disease

OBJECTIVES

We investigated the risk of myocarditis, cardiomyopathy, and pericarditis in patients with celiac disease (CD) from a general population cohort.

SUBJECTS AND METHODS

Through the Swedish national registers we identified 9363 children and 4969 adults with a diagnosis of CD (1964-2003). These individuals were matched with upto five reference individuals for age, sex, calendar year and county (n = 69 851). Cox regression estimated hazard ratios (HRs) for later heart disease.

MAIN OUTCOME MEASURES

Myocarditis, cardiomyopathy (any or dilated), and pericarditis defined according to relevant international classification of disease codes in the Swedish national inpatient register.

RESULTS

Celiac disease diagnosed in childhood was not associated with later myocarditis (HR = 0.2; 95% CI = 0.0-1.5), cardiomyopathy of any type (HR = 0.8; 95% CI = 0.2-3.7), or pericarditis (HR = 0.4; 95% CI = 0.1-1.9). Restricting our analyses to adulthood CD and heart disease diagnosed from 1987 and onwards in departments of cardiology/internal medicine, we found no association between CD and later myocarditis (HR = 2.1; 95% CI = 0.4-11.7), dilated cardiomyopathy (HR = 1.7; 95% CI = 0.4-6.5) or pericarditis (HR = 1.5; 95% CI = 0.5-4.0).

CONCLUSION

This study found no association between CD, later myocarditis, cardiomyopathy or pericarditis.

Raised interleukin-10 is an indicator of poor outcome and enhanced systemic inflammation in patients with acute coronary syndrome

Objectives:

To re-evaluate the relation between plasma interleukin-10 (IL-10) concentration at hospital admission and outcome and to investigate the impact of single nucleotide polymorphisms (SNP) in the IL-10 gene in patients with non-ST elevation acute coronary syndrome (ACS).

Design:

Determination of IL-10 plasma concentrations and genotyping of SNPs in the IL-10 gene in a prospective trial of patients with ACS and in a group of healthy controls.

Patients:

3179 patients in the Fragmin and fast revascularisation during InStability in Coronary artery disease II (FRISC II) trial and 393 healthy controls.

Main outcome measures:

Mortality and incidence of myocardial infarction (MI) at 12 months.

Results:

The median and interquartile ranges of IL-10 were 0.8 (0.5–1.0) pg/ml in healthy controls and 1.1 (0.7–1.9) pg/ml in patients (p<0.001). In patients, IL-10 predicted a crude risk increase of death/MI, with the highest risk observed in the fourth quartile (adjusted odds ratio 1.7 (95% confidence interval 1.2 to 2.3)). Adjustment for common risk indicators, including C-reactive protein and interleukin-6, weakened the association to a non-significant level. The 1170 CC genotype weakly predicted increased plasma concentrations of IL-10 in patients (p = 0.04) and in controls (p = 0.03), which was consistent with the modest association of this variant with coronary disease (p = 0.01).

Conclusion:

In contrast with some previous reports, we conclude that IL-10 reflects a proinflammatory state in patients with ACS and we therefore suggest that IL-10 is as effective a biomarker for the risk prediction of future cardiovascular events as other markers of systemic inflammation.

Association of plasminogen activator inhibitor (PAI)-1 (SERPINE1) SNPs with myocardial infarction, plasma PAI-1, and metabolic parameters: the HIFMECH study

OBJECTIVE

The purpose of this study was to investigate the effects of plasminogen activator inhibitor-1 (PAI-1) gene (SERPINE1) single nucleotide polymorphisms (SNPs) on the risk of myocardial infarction (MI), on PAI-1 levels, and factors related to the metabolic syndrome.

METHODS AND RESULTS

Eleven SNPs capturing the common genetic variation of the SERPINE1 gene were genotyped in the HIFMECH study. In the 510 male cases and their 543 age-matched controls, a significant gene-smoking interaction was observed. In nonsmokers, the rs7242-G allele was more frequent in cases than in controls (0.486 versus 0.382, P=0.013) whereas the haplotype derived from the rs2227631 (-844A>G)-G and rs2227683-A alleles was approximately 3-fold lower in cases than in controls (0.042 versus 0.115, P=0.006). SERPINE1 haplotypes explained 3.5% (P=0.007) of the variability of PAI-1 levels, which was attributable to the combined effects of 3 SNPs, -844A>G, rs2227666, and rs2227694. The rs6092 (Ala15Thr) and rs7242 SNPs acted additively to explain 4.4% of the variability of plasma insulin levels and 1.6% of the variability of BMI (P<10(-3) and P=0.023, respectively).

CONCLUSIONS

SERPINE1 haplotypes are mildly associated with plasma levels of PAI-1 and with the risk of MI in nonsmokers. They are also associated with insulin levels and BMI.

Increased expression of the macrophage markers and of 11beta-HSD-1 in subcutaneous adipose tissue, but not in cultured monocyte-derived macrophages, is associated with liver fat in human obesity

OBJECTIVE

To determine whether increased expression of macrophage markers and of inflammatory markers in subcutaneous adipose tissue is associated with liver fat in human obesity. We also determined whether expression of TNF (gene encoding TNF-alpha), HSD11B1 (gene encoding 11beta-HSD-1) and RETN (gene encoding resistin) in cultured monocyte-derived macrophages differs between obese/overweight and non-obese subjects.

DESIGN

Cross-sectional comparison of obese/overweight and non-obese subjects with respect to adipose tissue gene expression, gene expression in monocyte-derived macrophages, liver fat content and in vivo insulin sensitivity.

SUBJECTS

Adipose tissue gene expression, gene expression in monocyte-derived macrophages, liver fat content and in vivo insulin sensitivity: 10 healthy non-obese (24.2+/-1.0 kg/m(2)) and 10 healthy obese/overweight (33.1+/-1.7 kg/m(2)) women. Gene expression in monocyte-derived macrophages: seven healthy non-obese (22.1+/-0.7 kg/m(2)) and seven healthy obese/overweight (36.9+/-2.2 kg/m(2)) women.

MEASUREMENTS

Adipose tissue biopsies and blood samples for isolation of peripheral mononuclear cells were taken after an overnight fast. Liver fat content was measured using magnetic resonance proton spectroscopy. Whole body insulin sensitivity was measured using the hyperinsulinemic euglycemic clamp technique. Expression levels of TNF, HSD11B1, RETN and the macrophage markers CD68 and ITGAM were determined by real-time PCR.

RESULTS

In adipose tissue, expression of HSD11B1, ITGAM and CD68 was significantly increased in the obese/overweight as compared to the non-obese group. Expression of all these genes was closely positively correlated with liver fat content and inversely correlated with whole body insulin sensitivity. The associations between expression of CD68, ITGAM and HSD11B1 and liver fat were independent of obesity. There were no differences in TNF, HSD11B1, RETN or CD68 gene expression basally or after stimulation with lipopolysaccharide in monocyte-derived macrophages between obese/overweight and non-obese subjects.

CONCLUSION

Accumulation of fat in the liver is associated with increased adipose tissue inflammation independent of obesity.

Elevated plasma fibrinogen gamma' concentration is associated with myocardial infarction: effects of variation in fibrinogen genes and environmental factors

BACKGROUND

Fibrinogen gamma', a fibrinogen gamma-chain variant generated via alternative mRNA processing, has been associated with susceptibility to thrombotic disease.

OBJECTIVE

The present case-control study searched for potential determinants of the plasma fibrinogen gamma' concentration and examined the relationship between this variant and risk of myocardial infarction (MI).

PATIENTS AND METHODS

The Stockholm Coronary Artery Risk Factor study, comprising 387 postinfarction patients and 387 healthy individuals, was employed. The fibrinogen gamma (FGG) 9340T > C [rs1049636], fibrinogen alpha (FGA) 2224G > A [rs2070011] and fibrinogen beta (FGB) 1038G > A [rs1800791] polymorphisms were determined. The plasma fibrinogen gamma' concentration was measured by enzyme-linked immunosorbent assay. The multifactor dimensionality reduction method was used for interaction analyses on risk of MI.

RESULTS

The FGG 9340T > C and FGA 2224G > A polymorphisms, total plasma concentrations of fibrinogen, insulin and high-density lipoprotein, and gender appeared to be independent determinants of plasma fibrinogen gamma' concentration in patients, and the corresponding determinants in controls included FGG 9340T > C and FGA 2224G > A polymorphisms and plasma fibrinogen concentration. An elevated plasma fibrinogen gamma' concentration proved to be an independent predictor of MI [adjusted odds ratio (OR) (95% CI): 1.24 (1.01, 1.52)]. The plasma fibrinogen gamma' concentration was involved in a high-order interaction with total plasma fibrinogen and the FGG 9340T > C and FGA 2224G > A polymorphisms, associated with a further increased risk of MI [OR (95% CI): 3.22 (2.35, 4.39)].

CONCLUSIONS

Plasma fibrinogen gamma' concentration influences the risk of MI, and this relationship seems to be strengthened by the presence of an elevated total plasma fibrinogen concentration and the FGG 9340T and FGA 2224G alleles.

The association between fibrinogen haplotypes and myocardial infarction in men is partly mediated through pleiotropic effects on the serum IL-6 concentration

BACKGROUND AND OBJECTIVES

Fibrinogen haplotypes have been associated with risk of myocardial infarction (MI), independently of plasma fibrinogen concentration, and experimental data indicate that fibrinogen exerts pleiotropic effects on interleukin 6 (IL-6) production. Also, the coagulation factor XIII (gene symbol F13A1) Val34Leu haplotype tag single nucleotide polymorphism (htSNP) has been reported to exert pleiotropic effects on serum IL-6 concentration and to be associated with risk of MI. Therefore, in the present case-control study (a substudy to the Stockholm Heart Epidemiology Program), the effects of the fibrinogen gamma (FGG) 9340T>C [rs1049636], fibrinogen alpha (FGA) 2224G>A [rs2070011] and F13A1 Val34Leu [rs5985] htSNPs on concentrations of plasma fibrinogen and serum IL-6 and risk of MI were assessed.

RESULTS

There were no associations between these SNPs and the plasma fibrinogen concentration. In contrast, in male controls the FGA 2224G>A htSNP was significantly associated with serum IL-6 concentration (P < 0.05). Also, in men the FGG-FGA*1 haplotype (containing the major FGG 9340T and FGA 2224G alleles) was associated with increased risk of MI [adjusted odds ratio (OR) 95% confidence interval (CI): 1.29 (1.02, 1.62)] and with higher IL-6 concentrations, whereas the least common FGG-FGA*4 haplotype (containing the minor FGG 9340C and FGA 2224A alleles) conferred lowered risk [adjusted OR (95% CI): 0.70 (0.57, 0.86)] and lowered IL-6 concentrations. In women, fibrinogen haplotypes were not associated with risk of MI after adjusting for cardiovascular risk factors.

CONCLUSION

In healthy men, fibrinogen haplotypes are associated with serum IL-6 concentrations in a manner consistent with their impact on MI risk.

Human evidence for the involvement of insulin-induced gene 1 in the regulation of plasma glucose concentration

AIMS/HYPOTHESIS

Insulin-induced gene 1 (INSIG1) is a protein that blocks proteolytic activation of sterol regulatory element-binding proteins (SREBPs), transcription factors that activate genes regulating cholesterol and fatty acid metabolism and possibly genes involved in glucose homeostasis. In search of genetic regulation of these processes we examined human INSIG1 for common polymorphisms and analysed their associations with biochemical parameters related to lipid and glucose metabolism.

METHODS

Associations between common polymorphisms in INSIG1 and several biochemical parameters were analysed in a group of 618 healthy, 50-year-old men. A replication analysis was performed in a cohort of 472 healthy, middle-aged men. The impact of one promoter polymorphism on oral glucose tolerance was analysed in a subset of 181 subjects. Small interfering RNA (siRNA) inhibition was used to test the significance of INSIG1 for gene expression in human Huh7 hepatoma cells.

RESULTS

A potentially functional polymorphism, a C to T substitution at position -169, was discovered in a highly conserved section of the promoter. Significant relationships between the -169C>T polymorphism and plasma glucose concentration were found in two cohorts of healthy, middle-aged men (p < 0.01 and p < 0.02, respectively). The -169T allele was associated with significantly lower post-load plasma glucose concentrations. A significant (p = 0.02) reduction in expression of phosphoenolpyruvate carboxykinase (PCK2) was observed following siRNA inhibition of INSIG1 in human Huh7 hepatoma cells.

CONCLUSIONS/INTERPRETATION

Population studies demonstrate that INSIG1 plays a role in glucose homeostasis. Experiments with siRNA suggest that this action of INSIG1 is related to SREBP-mediated regulation of PCK2.

Fatty acid handling protein expression in adipose tissue, fatty acid composition of adipose tissue and serum, and markers of insulin resistance

OBJECTIVE

Proteins involved in cellular fatty acid (FA) uptake and metabolism may be of relevance in the context of disturbed FA metabolism associated with insulin resistance. Therefore this study investigated relationships between FA handling protein mRNA expression in adipose tissue, FA composition of adipose tissue and serum, and markers of insulin resistance.

SUBJECTS

75 subjects with a range of insulin sensitivities recruited from a cohort of 294 healthy 63-year-old Swedish men.

MEASUREMENTS

Anthropometric and biochemical variables (e.g. waist-hip-ratio (WHR) and homeostasis model assessment (HOMA) index of insulin sensitivity), FA composition of the subcutaneous (s.c.) gluteal adipose tissue, serum nonesterified FA (NEFA) and serum phospholipid compartments (by gas-liquid chromatography; n = 294), and mRNA levels of FA handling proteins (adipocyte and keratinocyte lipid binding proteins, fatty acid transport protein (FATP) -1 and -4, CD36/fatty acid translocase, plasma membrane fatty acid binding protein, and acyl-CoA synthase-1 (ACS1)) in s.c. gluteal adipose tissue (by quantitative real-time polymerase chain reaction; n = 75).

RESULTS

ACS1 expression was negatively correlated with measures of insulin resistance and central obesity (ACS1 versus HOMA: r = -0.28, P<0.05; ACS1 versus WHR: r = -0.23, P<0.05), with an opposite trend for FATP4. Further analysis of ACS1 expression levels revealed correlations with adipose tissue 16:0 (r = -0.27, P<0.05) and NEFA 16:1 (r = 0.29, P<0.05), FA composition variables which in turn correlated with HOMA index (r = 0.39, P<0.001 and r = -0.23, P<0.05, respectively, n = 75). Moreover, NEFA 16:1 predicted ACS1 expression independently of HOMA, WHR and adipose tissue 16:0 in multiple regression analysis (standardized coefficient = 0.27, P<0.05).

CONCLUSION

Significant associations were found between measures of insulin sensitivity, adipose tissue FA handling protein expression, and specific FA composition variables. Although causal relationships could not be identified these findings suggest a role of FA handling proteins in relation to insulin sensitivity, via their involvement in FA trafficking and metabolism. In particular they indicate links between ACS1 activity, the distribution of 16:0 and 16:1, and insulin sensitivity, which may be of physiological relevance.

Lower serum concentration of matrix metalloproteinase-3 in the acute stage of myocardial infarction

OBJECTIVES

The importance of matrix metalloproteinases (MMPs) in the progression and rupture of the atherosclerotic plaque is gaining increasing recognition but the mechanisms are not yet fully understood. The aim of this study was to investigate the significance of MMP-3 in the acute phase of myocardial infarction (MI) and the influence of the -1612 5A/6A MMP-3 gene promoter polymorphism on serum MMP-3 concentration.

SUBJECTS

One-hundred and sixty-four patients admitted with ST-elevation MI and receiving thrombolysis treatment were included in this study. Serum MMP-3 was analysed at admission, after 48 h and at 3 months.

RESULTS

Serum MMP-3 concentration was significantly increased at 3 months when compared with admission and 48 h (19.5 ng mL(-1) [14.4-24.7] vs. 15.5 ng mL(-1) [10.5-21.8] at admission, P < 0.001; and 14.7 ng mL(-1) [9.9-23.8] at 48 h, P < 0.001). Furthermore, we found the -1612 5A/6A polymorphism to influence the serum concentration of MMP-3 at all time-points: 14.1 ng mL(-1) [10.2-18.8] in 5A/5A; 19.6 ng mL(-1) [15.0-24.4] in 5A/6A; and 24.0 ng mL(-1) [20.1-32.3] in 6A/6A genotype at 3 months (P < 0.001 between all groups). Female patients had lower serum MMP-3 concentration than male patients at all time-points (14.8 ng mL(-1) [9.4-20.8] vs. 19.9 ng mL(-1) [16.0-26.9], P < 0.0001 at 3 months).

CONCLUSIONS

Serum concentration of MMP-3 is significantly lower in the acute stage of MI than during recovery and is significantly influenced by -1612 5A/6A genotype and gender. Together with previous findings, these results primarily implicate MMP-3 in atherosclerosis progression rather than in acute MI.

Triglyceride-rich lipoproteins from hypertriglyceridemic subjects induce a pro-inflammatory response in the endothelium: Molecular mechanisms and gene expression studies

Triglyceride-rich lipoproteins (TGRLs) are a cardiovascular risk factor and induce endothelial dysfunction. In the present study we investigated the effects of TGRLs from type IV hyperlipidemic and normolipidemic subjects on endothelial activation focusing on the effects on intracellular pathways and gene expression. A total of 54 subjects, 30 hypertriglyceridemic (triglyceride (TG) levels 284+/-101 mg/dl) and 23 normotriglyceridemic (TG levels 109+/-40 mg/dl) were enrolled as lipoprotein donors. TGRLs were isolated from hypertriglyceridemic (H-TGRL) and normotriglyceridemic (N-TGRL) subjects. RNA from human endothelial cells incubated with N-TGRL or H-TGRL was prepared for cDNA microarray analyses. Western blotting was used to study intracellular signaling pathways. Regulated genes were further studied with real-time PCR, immunofluorescence and FACS. Furthermore, a protein/DNA array and chromatin-immunoprecipitation were used to identify transcription factors involved in the observed effects. Both N-TGRL and H-TGRL activated ERK1/2 and p38 MAPK. However, there were differences in the pattern of upregulated target genes between the two types of lipoproteins in HUVECs and/or HAECs: PAI-1, VCAM-1, ELAM-1 and MCP-1 were upregulated by both N-TGRL and H-TGRL, while PECAM-1, IL-6 and ADAMTs1 were selectively upregulated by H-TGRL. Chromatin immunoprecipitation analysis demonstrated the involvement of transcription factors NF-kB and CREB in the activation of these genes. These results support the possible involvement of hypertriglyceridemic TGRLs in endothelial dysfunction via induction of a pro-inflammatory and pro-thrombotic state.

EPCR Ser219Gly: elevated sEPCR, prothrombin F1+2, risk for coronary heart disease, and increased sEPCR shedding in vitro

We have progressively analysed three studies of coronary heart disease (CHD) for a variant in EPCR (Ser219Gly). Initially, in a prospective study, NPHSII, while no overall CHD-risk was identified in heterozygotes, homozygotes for 219Gly exhibited a three-fold elevated risk (HR 3.3, CI 1.22-8.96). In diabetics within NPHSII, there was a suggestion that 219Gly+ was associated with elevated CHD-risk (HR 1.89, CI 0.39-9.06) although numbers were small. To further assess the effect of the variant in diabetes, a case-control study of MI, HIFMECH, was used, in which previous analysis had defined a group with metabolic syndrome, by factor analysis. A significant CHD-risk interaction was identified between genotype and the 'metabolic syndrome' factor (interaction p=0.009). To further assess CHD-risk for this variant in type-2 diabetes and to assess the effect of the variant upon thrombin generation and plasma levels of soluble EPCR, a cross-sectional study of type-2 diabetes was used. A significant CHD-risk was identified for European Whites (OR 2.84, CI 1.38-5.85) and Indian Asians in this study (OR 1.6, CI 1.00-2.57) and the frequency of 219Gly was two-fold higher in Indian Asians. Soluble EPCR levels were strongly associated with genotype, with homozygotes for 219Gly having four-fold higher levels (p<0.0001). In vitro studies of EPCR-transfected cells suggested increased basal release of sEPCR from cells expressing the 219Gly EPCR phenotype. Furthermore, in base-line samples from NPHSII and in the diabetic study, a significant increase in prothrombin F1+2 level was observed for 219Gly. The increased CHD-risk and thrombin generation appears to be acting through increased shedding of the Gly allele from the cell surface.