Conventional non-invasive imaging modalities of atherosclerosis such as coronary artery calcium (CAC)1 and carotid intimal medial thickness (C-IMT)2 provide information about the burden of disease. However, despite multiple validation studies of CAC3–5, and C-IMT2,6, these modalities do not accurately assess plaque characteristics7,8, and the composition and inflammatory state of the plaque determine its stability and, therefore, the risk of clinical events9–13.
[18F]-2-fluoro-2-deoxy-D-glucose (FDG) imaging using positron-emission tomography (PET)/computed tomography (CT) has been extensively studied in oncologic metabolism14,15. Studies using animal models and immunohistochemistry in humans show that FDG-PET/CT is exquisitely sensitive for detecting macrophage activity16, an important source of cellular inflammation in vessel walls. More recently, we17,18 and others have shown that FDG-PET/CT enables highly precise, novel measurements of inflammatory activity of activity of atherosclerotic plaques in large and medium-sized arteries9,16,19,20. FDG-PET/CT studies have many advantages over other imaging modalities: 1) high contrast resolution; 2) quantification of plaque volume and metabolic activity allowing for multi-modal atherosclerotic plaque quantification; 3) dynamic, real-time, in vivo imaging; 4) minimal operator dependence. Finally, vascular inflammation detected by FDG-PET/CT has been shown to predict cardiovascular (CV) events independent of traditional risk factors21,22 and is also highly associated with overall burden of atherosclerosis23. Plaque activity by FDG-PET/CT is modulated by known beneficial CV interventions such as short term (12 week) statin therapy24 as well as longer term therapeutic lifestyle changes (16 months)25.
The current methodology for quantification of FDG uptake in atherosclerotic plaque involves measurement of the standardized uptake value (SUV) of an artery of interest and of the venous blood pool in order to calculate a target to background ratio (TBR), which is calculated by dividing the arterial SUV by the venous blood pool SUV. This method has shown to represent a stable, reproducible phenotype over time, has a high sensitivity for detection of vascular inflammation, and also has high inter-and intra-reader reliability26. Here we present our methodology for patient preparation, image acquisition, and quantification of atherosclerotic plaque activity and vascular inflammation using SUV, TBR, and a global parameter called the metabolic volumetric product (MVP). These approaches may be applied to assess vascular inflammation in various study samples of interest in a consistent fashion as we have shown in several prior publications9,20,27,28
FDG-PET/CT; atherosclerosis; vascular inflammation; quantitative radiology
editorial; monocytes; cardiovascular outcomes; inflammation
genomics; genetics; coronary artery disease; genome wide association; meta-analysis
The field of vascular molecular imaging is searching for the `holy grail' of an imaging technique that will quantitatively and reliably assess vulnerable coronary plaques. Fluorescence imaging with indocyanine green specifically identifies lipid-rich plaques in rabbits and in human plaques and represents a promising, though invasive, approach.
genomics; genetics; coronary artery disease; genome wide association; metaanalysis
Genome-wide association studies (GWAS) in over 100,000 people have revealed novel loci associated with coronary artery disease (CAD) and myocardial infarction (MI) which present exciting opportunities to discover novel disease pathways. One such recently identified locus is on chromosome 10q11, near the gene for the chemokine CXCL12 which has been implicated in cardiovascular disease (CVD) in both mouse and human studies. These GWAS demonstrate that CXCL12 may emerge as a potential therapeutic target for atherosclerosis and thrombosis.
CXCL12; atherosclerosis; GWAS; cardiovascular disease; inflammation
Objective: Psoriasis (PSO) and rheumatoid arthritis (RA) increase cardiovascular diseases (CVD) beyond traditional risk factors. Vascular inflammation has previously been demonstrated to be present in PSO and RA using [18F]-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) imaging. However, vascular inflammation has not been compared in these two disorders relative to a healthy reference population. Thus, vascular inflammation was quantitatively assessed in patients with PSO (n=10), RA (n=5), and healthy subjects (n=10) using FDG-PET/CT. Methods: FDG-PET/CT mean standardized uptake value (SUVmean) was determined slice by slice within the ascending, aortic arch, descending thoracic, suprarenal abdominal, and infrarenal abdominal aorta, and the mean metabolic volumetric product (MVPmean) was then calculated for each aortic subsegment. Plasma lipids and metabolic and inflammatory markers were also assessed. Results: CVD risk profiles were largely similar across groups. After adjustment for CV risk factors, regional aortic vascular inflammation based on MVPmean was elevated for both PSO (beta coefficients 0.31-1.47, p<0.001) and RA (beta coefficients 0.15-0.69, p<0.05) compared to healthy subjects. Conclusions: These observations using FDG-PET/CT to estimate vascular inflammation support epidemiological findings of premature atherosclerosis in PSO and RA. The use of FDG-PET/CT to investigate vascular inflammation across systemic inflammatory diseases warrants further examination in larger study populations.
Psoriasis; rheumatoid arthritis; atherosclerosis; vascular inflammation; FDG-PET/CT
Psoriasis is a Th-1/17 mediated inflammatory disease associated with increased risk of cardiovascular disease (CVD). Inflammation may modulate lipoprotein particle number and directly impair HDL functions, in particular reverse cholesterol transport (RCT). We sought to study how chronic in vivo inflammation modulates lipoprotein particle composition using nuclear magnetic resonance spectroscopy (NMR) and HDL efflux in psoriasis.
Methods and Results
We prospectively enrolled a consecutive sample of patients with psoriasis (n=122) and compared lipoprotein and metabolic risk factors to patients without psoriasis (n=134). Fasting lipids, insulin, glucose were measured by standard assays, and lipoprotein concentration and size were measured by NMR. In a random subset (n=100 each group), HDL efflux capacity was quantified using a validated ex vivo system involving the incubation of macrophages with apolipoprotein B-depleted serum from patients. Traditional lipid concentrations were similar in both groups except for HDL concentration which was lower in psoriasis (43 mg/dL (36–58) vs 50 (42–62), p<0.01). However, NMR showed an atherogenic profile in psoriasis similar to that observed in diabetes, with significant increase in LDL particle concentration [1210.5 (1002–1498) vs 1115 (935–1291), p=0.03] with decrease in LDL size [20.6 (20.3–21.1) vs 21.3 (20.6–21.1), p<0.001] beyond CV risk factors and HOMA-IR (p=0.001). Finally, HDL efflux capacity was lower in psoriasis compared to controls in fully adjusted models (beta −0.14, p=0.001).
These data support a more atherogenic lipoprotein profile by NMR and decreased HDL efflux capacity in psoriasis patients compared to controls beyond CVD risk factors. The abnormal lipoprotein particle composition and HDL efflux capacity in psoriasis may provide a link between psoriasis and CVD.
inflammation; atherosclerosis; HDL efflux; cholesterol; lipoprotein particles
Moderate-to-severe psoriasis is associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD); however, the link is poorly understood.
Skin and serum from patients with psoriasis were evaluated to understand if there was evidence of dysregulation in a targeted group of inflammatory and lipid genes related to ASCVD. Microarray analyses of expression of targeted ASCVD genes from skin in 89 patients with moderate-to-severe psoriasis from the ACCEPT trial were compared with non-diseased skin from healthy controls (n = 25). Serum (n = 149) was tested at baseline for monocyte chemoattractant protein-1 (MCP-1), macrophage-derived chemokine (MDC), and apolipoprotein-A1 (Apo-A1) comparing to healthy controls (n=162).
An increase in skin gene expression for MCP-1 (7.98-fold) and MDC (6.66-fold) (p < 0.001 each) was observed in lesional versus healthy skin. Significant decreases in liver X receptor-alpha (LXR-α) (−5.94-fold), a protective lipoprotein metabolism gene, and in peroxisome proliferator-activated receptor-alpha (PPAR-α) (−7.58-fold), a protective anti-inflammatory and lipid modulating gene, were observed in lesional versus healthy skin (p < 0.001 each). Serum analyses revealed that MCP-1 (502 vs. 141 pg/mL) and MDC (1240 vs. 409 pg/mL) levels were significantly elevated in psoriasis compared with healthy controls (p < 0.001 each). Dysregulated lipid metabolism was also evident in the serum, as Apo-A1, a protein product related to PPAR-α activation, was significantly decreased in patients with psoriasis compared with healthy controls (25.2 vs. 38.9 mg/dL; p < 0.001).
Analyses of targeted genes and their products known to be associated with ASCVD revealed dysregulation of inflammatory (MCP-1 and MDC) and lipid metabolism (LXR-α, PPAR-α) genes in psoriasis. These findings provide evidence of a potential shared pathophysiology linking psoriasis to cardiometabolic diseases.
Inflammation; Atherosclerosis; Lipid metabolism; Psoriasis
Inflammation may directly impair HDL functions, in particular reverse cholesterol transport (RCT), but limited data support this concept in humans.
Methods and Results
We employed low-dose human endotoxemia to assess the effects of inflammation on HDL and RCT-related parameters in vivo. Endotoxemia induced remodelling of HDL with depletion of pre-β1a HDL particles determined by 2-D gel electrophoresis (-32.2 ± 9.3% at 24h, p<0.05) as well as small (-23.0 ± 5.1%, p<0.01, at 24h) and medium (-57.6 ± 8.0% at 16h, p<0.001) HDL estimated by nuclear magnetic resonance (NMR). This was associated with induction of class II secretory phospholipase A2 (~36 fold increase) and suppression of lecithin:cholesterol acyltransferase activity (-20.8 ± 3.4% at 24h, p<0.01) and cholesterol ester transfer protein mass (-22.2 ± 6.8% at 24h, p<0.001). The HDL fraction, isolated following endotoxemia, had reduced capacity to efflux cholesterol in vitro from SR-BI and ABCA1, but not ABCG1 transporter cell models.
These data support the concept that “atherogenic-HDL dysfunction” and impaired RCT occur in human inflammatory syndromes, largely independent of changes in plasma HDL-C and ApoA-I levels.
inflammation; atherosclerosis; cholesterol; lipoproteins; macrophages
To examine the role of lipoprotein-associated phospholipase A2 (Lp-PLA2/PLA2G7) in human inflammation and coronary atherosclerosis.
Lp-PLA2 has emerged as a potential therapeutic target in coronary heart disease (CHD). Data supporting Lp-PLA2 are indirect and confounded by species differences; whether Lp-PLA2 is causal in CHD remains in question.
We examined inflammatory regulation of Lp-PLA2 during experimental endotoxemia in human, probed the source of Lp-PLA2 in human leukocytes under inflammatory conditions, and assessed the relationship of variation in PLA2G7, the gene encoding Lp-PLA2, with coronary artery calcification (CAC).
In contrast to circulating TNFα and CRP, blood and monocyte Lp-PLA2 mRNA decreased transiently, and plasma Lp-PLA2 mass declined modestly during endotoxemia. In vitro, Lp-PLA2 expression increased dramatically during human monocyte to macrophage differentiation and further in inflammatory macrophages and foam like-cells. Despite only a marginal association of SNPs in PLA2G7 with Lp-PLA2 activity or mass, numerous PLA2G7 SNPs were associated with CAC. In contrast, several SNPs in CRP were significantly associated with plasma CRP levels but had no relation with CAC.
Circulating Lp-PLA2 did not increase during acute phase response in human, while inflammatory macrophages and foam cells, but not circulating monocytes, are major leukocyte sources of Lp-PLA2. Common genetic variation in PLA2G7 is associated with sub-clinical coronary atherosclerosis. These data link Lp-PLA2 to atherosclerosis in human while highlighting the challenge in using circulating Lp-PLA2 as a biomarker of Lp-PLA2 actions in the vasculature.
Lp-PLA2; PLA2G7; CAC
Psoriasis is a model Th1-mediated inflammatory disease associated with increased incidence of stroke and cardiovascular disease (CVD). The mechanism behind these associations is unknown, however abnormal HDL particle composition measured by nuclear magnetic resonance (NMR) spectroscopy has been shown to be associated with CVD. Using [18F]-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT), a validated surrogate marker of CVD, we assessed whether HDL particle size and concentration were associated with vascular inflammation in patients with psoriasis. Patients with psoriasis were prospectively enrolled (439 aortic samples from 10 patients). Lipoprotein profiles using NMR spectroscopy were obtained and the relationship between vascular inflammation within the thoracic aorta by FDG-PET/CT was analyzed for association with lipoprotein particle characteristics. The plasma total cholesterol (206 mg/dL (IQR 154-229)), LDL (105 (90-161)), and triglyceride levels were within normal range (151 (94-191)) while HDL levels were low (28.9 (27.2-31.3)); however, the NMR profile demonstrated an atherogenic profile with increased small LDL and HDL particles. Total HDL particle concentration (p<0.001) and HDL particle size (p<0.001) were associated with decreased aortic inflammation, while concentration of small HDL particles was associated with increased inflammation (p<0.001). The association of total HDL particle concentration (β -0.0113, p=0.002) and small HDL particle concentration (β 0.026, p<0.001) with aortic inflammation persisted following adjustment for CVD risk factors. Total HDL particle concentration and small HDL particle concentration were associated with vascular inflammation within the thoracic aorta in psoriasis. These findings suggest that HDL particle characteristics may play an important role in psoriatic vascular inflammation and CVD.
Psoriasis; inflammation; atherosclerosis; high-density lipoprotein cholesterol particle; FDG PET CT
Introducing the Cardiovascular, metabolic and lipoprotein translation section of journal of translational medicine.
The relationship between glycemic control and lipid abnormalities with urinary albumin-creatinine ratio (ACR) in chronic kidney disease (CKD) patients with diabetes mellitus (DM) is unknown. We sought to investigate the association of dyslipidemia and glycemic control with levels of albuminuria in the National Kidney Foundation (NKF) Kidney Early Evaluation Program (KEEP) participants with DM and CKD stage 3 or higher.
We performed a cross-sectional study of 6639 eligible KEEP patients with DM and CKD Stage 3 to 5 from June 2008 to December 2009. Multivariate logistic regression was used to evaluate the association of lipid parameters (per 10 mg/dl change in serum level) and glycosylated hemoglobin (HbA1c) values with three degrees of albuminuria normo (<30 mg⁄g), micro (30 to 300 mg⁄g) and macro (>300 mg⁄g).
2141 KEEP participants were included. HbA1c levels were strongly associated with micro-albuminuria (compared to normo-albuminuria) and macro-albuminuria (compared to normo-albuminuria and micro-albuminuria). Each 1.0% increase in HbA1c increased the odds of micro-albuminuria by 32% (OR 1.32, 95% CI 1.23-1.42) and the odds of macro-albuminuria (vs. microalbuminuria) by 16% (OR 1.16, 95% CI 1.05-1.28). Only increases in serum HDL were associated with decreased odds of micro-albuminuria; otherwise, the association between other components of the serum lipid profile with urinary ACR did not reach statistical significance.
In this cross-sectional study of 2141 KEEP participants with DM and CKD stages 3–5, overall glycemic control but not lipids were associated with abnormal urinary albumin excretion, a marker of increased risk for progressive disease.
Chronic Kidney Disease; Diabetes Mellitus; Proteinuria; Dyslipidemia; Glycosylated hemoglobin
Increasing epidemiological evidence suggests independent associations between psoriasis and cardiovascular and metabolic disease. Our objective was to test the hypothesis that directly-assessed psoriasis severity relates to the prevalence of metabolic syndrome and its components.
Population-based, cross-sectional study using computerized medical records from The Health Improvement Network Study population included individuals aged 45-65 years with psoriasis and practice-matched controls. Psoriasis diagnosis and extent were determined using provider-based questionnaires. Metabolic syndrome was defined using National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III criteria.
44,715 individuals were included: 4,065 with psoriasis and 40,650 controls. 2,044 participants had mild psoriasis (≤2% body surface area (BSA)), 1,377 had moderate (3-10% BSA), and 475 had severe psoriasis (>10% BSA). Psoriasis was associated with metabolic syndrome, adjusted odds ratio (OR) 1.41 (95% CI 1.31-1.51), varying in a “dose-response” manner, from mild (adj. OR 1.22, 95% CI 1.11-1.35) to severe psoriasis (adj. OR 1.98, 95% CI 1.62-2.43).
Psoriasis is associated with metabolic syndrome and the association increases with increasing disease severity. Furthermore, associations with obesity, hypertriglyceridemia and hyperglycemia increase with increasing disease severity independent of other metabolic syndrome components. These findings suggest that screening for metabolic disease should be considered for psoriasis, especially when extensive.
The Psoralen plus Ultraviolet-A (PUVA) cohort study has been a tremendous success in determining how a novel treatment (i.e. PUVA) impacts the long-term risk of keratinocyte carcinoma. The ability to follow patients from the initial multi-center clinical trial for over three decades has been a remarkable achievement in dermatoepidemiology. In this issue, Stern and Huibregste report results from the PUVA follow-up study and conclude that only patients with exceptionally severe psoriasis have an increased overall mortality risk and that there is no significant risk of cardiovascular mortality associated with psoriasis. The results are in contrast to a large and growing body of literature that suggests patients with more severe psoriasis have a clinically significant increased risk of mortality in general, and cardiovascular disease in particular. In addition, the authors found no association between severe psoriasis and obesity or between obesity and cardiovascular mortality, despite extensive literature establishing these associations. Basic principles of epidemiological study design may explain these discrepancies. Ultimately, however, , randomized clinical trials will be necessary to determine whether severe psoriasis is in fact a “visible killer”, as four decades ago (after many years of controversy), hypertension was recognized to be a “silent killer”.
Data conflict with regard to whether peroxisome proliferator–activated receptor-α agonism suppresses inflammation in humans. We hypothesized that in healthy adults peroxisome proliferator–activated receptor-α agonism with fenofibrate would blunt the induced immune responses to endotoxin (lipopolysaccharide [LPS]), an in vivo model for the study of cardiometabolic inflammation.
Methods and Results
In the Fenofibrate and omega-3 Fatty Acid Modulation of Endotoxemia (FFAME) trial, 36 healthy volunteers (mean age 26±7 years, mean body mass index 24±3 kg/m2, 44% female, 72% white) were randomized to fenofibrate 145 mg or placebo daily. After 6 to 8 weeks of treatment, subjects underwent a low-dose LPS challenge. Clinical and blood measurements were collected at randomization, before LPS administration, and serially for 24 hours after LPS administration. We examined area under the curve for evoked responses by treatment group. Compared to placebo, but before LPS challenge, fenofibrate reduced total cholesterol and tended to decrease triglycerides, consistent with achieved therapeutic plasma levels of fenofibric acid. In the placebo group, LPS induced a modest inflammatory response with increased cytokines and chemokines (2- to 4-hour post-LPS 8-fold increase in tumor necrosis factor-α, 9-fold increase in interleukin-6, 9-fold increase in interleukin-10, and 10-fold increase in monocyte chemotactic protein-1; all P<0.001) and acute-phase reactants (24-hour post-LPS 15-fold increase in serum amyloid A and 9-fold increase in C-reactive protein; both P<0.001). Compared to placebo, however, fenofibrate did not significantly attenuate LPS-induced levels of plasma cytokines, chemokines, or acute-phase proteins.
These data suggest a lack of systemic antiinflammatory properties of fenofibrate at clinically relevant dosing in humans.
Clinical Trial Registration
URL: http://clinicaltrials.gov/ct2/show/NCT01048502. Unique identifier: NCT01048502. (J Am Heart Assoc. 2012;1:e002923 doi: 10.1161/JAHA.112.002923.)
clinical trials; cytokines; endotoxemia; fenofibrate; inflammation
Chronic inflammation may contribute to insulin resistance (IR), metabolic syndrome and atherosclerosis although evidence of causality is lacking in humans. We hypothesized that very low-dose experimental endotoxemia would induce adipose tissue inflammation and systemic IR during a low-grade but asymptomatic inflammatory response and thus provide an experimental model for future tests of pharmacologic and genomic modulation of cardio-metabolic traits in humans.
Ten healthy, human volunteers (50% male, 90% Caucasian, mean age 22.7 ± 3.8) were randomized in a double-masked, placebo-controlled, crossover study to separate 36-hour inpatient visits (placebo versus intravenous-LPS 0.6 ng/kg). We measured clinical symptoms via the McGill pain questionnaire and serial vital signs. Plasma and serum were collected for measurement of cytokines, C-reactive protein, insulin and glucose, serial whole blood & subcutaneous adipose tissue mRNA expression were measured by real-time PCR. HOMA-IR, a well-validated measure of IR was calculated to estimate insulin resistance, and frequently sampled intravenous glucose tolerance testing (FSIGTT) was performed to confirm an insulin resistant state. We performed ANOVA and within subject ANOVA to understand the differences in cytokines, adipose tissue inflammation and IR before and after LPS or placebo.
There was no significant difference between placebo and LPS in clinical responses of symptom scores, body temperature or heart rate. However, low-dose endotoxemia induced a rapid and transient 25-fold induction of plasma TNF-alpha and 100-fold increase in plasma IL-6 (Figure 1B) (p < 0.001 for both) both peaking at two hours, followed by modest inflammation in adipose tissue with increases in mRNA levels of several inflammatory genes known to modulate adipose and systemic insulin resistance. Adipose tissue mRNA levels of IL-6 (peak 6-fold, ANOVA F = 27.5, p < 0.001) and TNF-alpha (peak 1.8-fold, F = 2.9, p = 0.01) increased with MCP-1 (peak 10-fold, F = 5.6, p < 0.01) and fractalkine (CX3CL1) (peak 15-fold, F = 13.3, p < 0.001). Finally, HOMA-IR was 32% higher following LPS compared to placebo (p < 0.01) and insulin sensitivity declined by 21% following LPS compared to placebo (p < 0.05).
We present a low dose human endotoxemia model of inflammation which induces adipose tissue inflammation and systemic insulin resistance in the absence of overt clinical response. Such a model has the potential for broad and safe application in the study of novel therapeutics and genomic influences in cardio-metabolic disease.
Inflammation; Obesity; Atherosclerosis; Insulin resistance
Leukocyte infiltration of adipose is a critical determinant of obesity-related metabolic diseases. Fractalkine (CX3CL1) and its receptor (CX3CR1) comprise a chemokine system involved in leukocyte recruitment and adhesion in atherosclerosis, but its role in adipose inflammation and type 2 diabetes is unknown.
RESEARCH DESIGN AND METHODS
CX3CL1 mRNA and protein were quantified in subcutaneous adipose and blood during experimental human endotoxemia and in lean and obese human adipose. CX3CL1 cellular source was probed in human adipocytes, monocytes, and macrophages, and CX3CL1-blocking antibodies were used to assess its role in monocyte-adipocyte adhesion. The association of genetic variation in CX3CR1 with metabolic traits was determined in a community-based sample. Finally, plasma CX3CL1 levels were measured in a case-control study of type 2 diabetes.
Endotoxemia induced adipose CX3CL1 mRNA (32.7-fold, P < 1 × 10−5) and protein (43-fold, P = 0.006). Obese subjects had higher CX3CL1 levels in subcutaneous adipose compared with lean (0.420 ± 0.387 vs. 0.228 ± 0.187 ng/mL, P = 0.04). CX3CL1 was expressed and secreted by human adipocytes and stromal vascular cells. Inflammatory cytokine induction of CX3CL1 in human adipocytes (27.5-fold mRNA and threefold protein) was completely attenuated by pretreatment with a peroxisome proliferator–activated receptor-γ agonist. A putative functional nonsynonymous single nucleotide polymorphism (rs3732378) in CX3CR1 was associated with adipose and metabolic traits, and plasma CX3CL1 levels were increased in patients with type 2 diabetes vs. nondiabetics (0.506 ± 0.262 vs. 0.422 ± 0.210 ng/mL, P < 0.0001).
CX3CL1-CX3CR1 is a novel inflammatory adipose chemokine system that modulates monocyte adhesion to adipocytes and is associated with obesity, insulin resistance, and type 2 diabetes. These data provide support for CX3CL1 as a diagnostic and therapeutic target in cardiometabolic disease.
Two single-nucleotide polymorphisms (SNPs), rs1746048 and rs501120, from genome wide association studies of coronary artery disease (CAD) map to chromosome 10q11 ∼80 kb downstream of chemokine CXCL12. Therefore, we examined the relationship between these two SNPs and plasma CXCL12 levels.
Methods and Results
We tested the association of two SNPs with plasma CXCL12 levels in a two-stage study (n= 2939): first in PennCath (n= 1182), a Caucasian, angiographic CAD case–control study, and second in PennCAC (n= 1757), a community-based study of CAD risk factors. Plasma CXCL12 levels increased with age and did not vary by gender. There was no linkage disequilibrium between these two SNPs and SNPs within CXCL12 gene. However, CAD risk alleles at rs1746048 (C allele, P= 0.034; CC 2.33 ± 0.49, CT 2.27 ± 0.46, and TT 2.21 ± 0.52 ng/mL) and rs501120 (T allele, P= 0.041; TT 2.34 ± 0.49, CT 2.28 ± 0.46, and CC 2.23 ± 0.53 ng/mL) were associated with higher plasma levels of CXCL12 in age and gender adjusted models. In Stage 2, we confirmed this association (rs501120, T allele, P= 0.007), and meta-analysis strengthened this finding (n= 2939, P= 6.0 × 10−4). Finally, in exploratory analysis, the rs1746048 risk allele tended to have higher transcript levels of CXCL12 in human natural killer cells and the liver.
Coronary artery disease risk alleles downstream of CXCL12 are associated with plasma protein levels of CXCL12 and appear to be related to CXCL12 transcript levels in two human cell lines. This implicates CXCL12 as potentially causal and supports CXCL12 as a potential therapeutic target for CAD.
Myocardial infarction; Cardiovascular genomics; Chemokines; CXCL12; Inflammation
We tested whether genetic factors distinctly contribute to either development of coronary atherosclerosis or, specifically, to myocardial infarction in existing coronary atherosclerosis.
We did two genome-wide association studies (GWAS) with coronary angiographic phenotyping in participants of European ancestry. To identify loci that predispose to angiographic coronary artery disease (CAD), we compared individuals who had this disorder (n=12 393) with those who did not (controls, n=7383). To identify loci that predispose to myocardial infarction, we compared patients who had angiographic CAD and myocardial infarction (n=5783) with those who had angiographic CAD but no myocardial infarction (n=3644).
In the comparison of patients with angiographic CAD versus controls, we identified a novel locus, ADAMTS7 (p=4·98×10−13). In the comparison of patients with angiographic CAD who had myocardial infarction versus those with angiographic CAD but no myocardial infarction, we identified a novel association at the ABO locus (p=7·62×10−9). The ABO association was attributable to the glycotransferase-deficient enzyme that encodes the ABO blood group O phenotype previously proposed to protect against myocardial infarction.
Our findings indicate that specific genetic predispositions promote the development of coronary atherosclerosis whereas others lead to myocardial infarction in the presence of coronary atherosclerosis. The relation to specific CAD phenotypes might modify how novel loci are applied in personalised risk assessment and used in the development of novel therapies for CAD.
The PennCath and MedStar studies were supported by the Cardiovascular Institute of the University of Pennsylvania, by the MedStar Health Research Institute at Washington Hospital Center and by a research grant from GlaxoSmithKline. The funding and support for the other cohorts contributing to the paper are described in the webappendix.
Metabolic syndrome (MS) definitions predict cardiovascular events beyond traditional risk factors in type 2 diabetic (DM) as well as non-diabetics subjects. We and other have shown that apolipoprotein B (apoB) and non-HDL cholesterol (non-HDL-C) are associated with coronary artery calcification (CAC) in DM. However, the relative value of MS, apoB lipoproteins and estimates of insulin resistance is unknown in predicting atherosclerosis in DM. We performed cross sectional analyses of white subjects in 2 community based studies (N= 611 type 2 diabetic subjects, N= 803 non-diabetic subjects) using multivariate analysis of traditional risk factors and then adding MS, apoB and homeostatic model assessment for insulin resistance (HOMA-IR). Incremental value was tested with likelihood ratio testing. Beyond traditional risk, HOMA-IR [Tobit regression ratio 1.86 (p=0.002)], apoB [1.55 (p=0.001)] and MS [2.37 (p=0.007)] were independently associated with CAC. In nested models, HOMA-IR added value to apoB [1.72 (p=0.008)], MS [1.72 (p=0.011)] and both apoB and MS [1.64 (p=0.021)]. ApoB showed a similar pattern when added to HOMA-IR [1.51 (p=0.004)], MS [1.46 (p=0.005)] and both HOMA-IR and MS [1.48 (p=0.006)]. MS added to apoB [1.99 (p=0.032)], but not HOMA-IR [1.54 (p=0.221)] or both apoB and HOMA-IR [1.32 (p=0.434)]. In conclusion, insulin resistance estimates add value to MS and apoB in predicting CAC scores in DM and warrant further evaluation in clinic for identification of DM patients at higher risk for atherosclerotic cardiovascular disease.
insulin resistance; apolipoprotein B; coronary artery calcification; type 2 diabetes
Plasma C-reactive protein (CRP) is associated with cardiovascular disease (CVD) but effects may vary by gender and degree of CVD risk. Whether CRP has value as a CVD risk marker in type-2 diabetes (T2DM) is unclear. We examined whether CRP has gender differences in the association of coronary artery calcium (CAC) in diabetic and non diabetic samples without clinical CVD.
We performed cross-sectional analyses of gender influence on CRP association with CAC in the Penn Diabetes Heart Study (N = 1299 with T2DM), the Study of Inherited Risk of Coronary Atherosclerosis (N = 860 non diabetic subjects), and a combined sample.
Female gender was associated with higher plasma CRP in diabetic and non-diabetic samples after adjustment for covariates. There was a strong interaction by gender in the association of CRP with CAC (interaction p < 0.001). In diabetic women, CRP was associated with higher CAC even after further adjustment for age, race, medications, metabolic syndrome, Framingham risk score, and body mass index [Tobit ratio 1.60, 95% CI (1.03-2.47)]. Although this relationship was attenuated in non diabetic women, the combined sample maintained this association in fully adjusted models [1.44, 95% CI (1.13-1.83)]. There was no association of CRP with CAC in either diabetic or non diabetic men.
CRP may be a useful marker of cardiovascular risk in women, particularly in diabetic women who otherwise have no known CVD. Prospective studies are needed to better assess gender differences in CRP utility and the use of CRP in T2DM.
Coronary artery calcium; C-reactive protein; Diabetes; Gender
The Vitamin D endocrine system is essential for calcium homeostasis, and low levels of vitamin D metabolites have been associated with cardiovascular disease risk. We hypothesized that DNA sequence variation in genes regulating vitamin D metabolism and signaling pathways might influence variation in coronary artery calcification (CAC).
Methods and Results
We genotyped single nucleotide polymorphisms (SNPs) in GC, CYP27B1, CYP24A1, and VDR and tested their association with CAC quantity, as measured by electron beam computed tomography. Initial association studies were carried out in a discovery sample comprised of 697 Amish subjects and SNPs nominally associated with CAC quantity (4 SNPs in CYP24A1, P = 0.008-0.00003) were then tested for association with CAC quantity in two independent cohorts of subjects of European Caucasian ancestry (Genetic Epidemiology Network of Arteriopathy (GENOA) Study (n = 916) and The Penn Coronary Artery Calcification (PennCAC) sample (n = 2,061)). One of the four SNPs, rs2762939, was associated with CAC quantity in both GENOA (P = 0.007) and PennCAC (P = 0.01). In all three populations the rs2762939 C allele was associated with lower CAC quantity. Meta-analysis for the association of this SNP with CAC quantity across all three studies yielded a P value of 2.9 × 10-6.
A common SNP in the CYP24A1 gene was associated with CAC quantity in three independent populations. This result suggests a role for vitamin D metabolism in the development of CAC quantity.