Obesity is a risk factor for colorectal cancer, and hyperinsulinemia, a common condition in obese patients, may underlie this relationship. Insulin, in addition to its metabolic effects, has promitotic and antiapoptotic activity that may be tumorigenic. Insulin-like growth factor (IGF)-I, a related hormone, shares sequence homology with insulin, and has even stronger mitogenic effects. However, few prospective colorectal cancer studies directly measured fasting insulin, and none evaluated free IGF-I, or endogenous estradiol, a potential cofactor in postmenopausal women. Therefore, we conducted a case-cohort investigation of colorectal cancer among nondiabetic subjects enrolled in the Women’s Health Initiative Observational Study, a prospective cohort of 93,676 postmenopausal women. Fasting baseline serum specimens from all incident colorectal cancer cases (n = 438) and a random subcohort (n = 816) of Women’s Health Initiative Observational Study subjects were tested for insulin, glucose, total IGF-I, free IGF-I, IGF binding protein-3, and estradiol. Comparing extreme quartiles, insulin [hazard ratio (HR)q4–q1, 1.73; 95% confidence interval (CI), 1.16–2.57; ptrend = 0.005], waist circumference (HRq4–q1, 1.82; 95% CI, 1.22–2.70; ptrend = 0.001), and free IGF-I (HRq4–q1, 1.35; 95% CI, 0.92–1.98; Ptrend = 0.05) were each associated with colorectal cancer incidence in multivariate models. However, these associations each became nonsignificant when adjusted for one another. Endogenous estradiol levels, in contrast, were positively associated with risk of colorectal cancer (HR comparing high versus low levels, 1.53; 95% CI, 1.05–2.22), even after control for insulin, free IGF-I, and waist circumference. These data suggest the existence of at least two independent biological pathways that are related to colorectal cancer: one that involves endogenous estradiol, and a second pathway broadly associated with obesity, hyperinsulinemia, and free IGF-I.
Among 127 HIV-infected women, the magnitude of HDLc increases after HAART initiation predicted the magnitude of concurrent decreases in inflammation biomarkers. After HAART initiation, changes in LDLc and inflammation were unrelated. In the same population, predicted risk of coronary heart disease based upon levels of standard clinical risk factors was similar before and after HAART treatment. Thus, it remains unknown whether short-term treatment-related changes in standard risk factors may appreciably change risk of CVD.
lipids; HAART; HIV infection; inflammation
This review addresses the possible role of the insulin-like growth factor (IGF)-axis in normal glucose homoeostasis and in the etiopathogenesis of type 2 diabetes. IGF-I, a peptide hormone, shares amino acid sequence homology with insulin and has insulin-like activity; most notably, the promotion of glucose uptake by peripheral tissues. Type 2 diabetes as well as pre-diabetic states, including impaired fasting glucose and impaired glucose tolerance, are associated cross-sectionally with altered circulating levels of IGF-I and its binding proteins (IGFBPs). Administration of recombinant human IGF-I has been reported to improve insulin sensitivity in healthy individuals as well as in patients with insulin resistance and type 2 diabetes. Further, IGF-I may have beneficial effects on systemic inflammation, a risk factor for type 2 diabetes, and on pancreatic β-cell mass and function. There is considerable inter-individual heterogeneity in endogenous levels of IGF-I and its binding proteins; however, the relationship between these variations and the risk of developing type 2 diabetes has not been extensively investigated. Large prospective studies are required to evaluate this association.
insulin-like growth factor (IGF)-I; glucose; diabetes; IGFBP
Adipose tissue is considered an endocrine organ that secretes adipokines which possibly mediate the effects of obesity on risk of cardiovascular disease. However, there are yet limited prospective data on the association between circulating adipokine levels and risk of ischemic stroke. We aimed to examine the associations of three adipokines (adiponectin, leptin and resistin) with risk of ischemic stroke.
Methods and Results
We conducted a prospective nested case-control study (972 stroke cases and 972 matched controls) within the Women’s Health Initiative Observational Study cohort. The controls were matched to cases on age, race/ethnicity, date of study enrollment and follow-up time. Adipokine levels were associated with established stroke risk factors, such as obesity and systolic blood pressure. Adjusted for body mass index, the odds ratios (OR) for incident ischemic stroke comparing the highest (Q4) to the lowest quartile (Q1) were 0.81 (95% confidence intervals [CI]: 0.61–1.08; p-trend: 0.068) for adiponectin, 1.15 (95% CI: 0.83–1.59; p-trend: 0.523) for leptin, and 1.57 (95% CI: 1.18–2.08; p-trend: 0.002) for resistin. The association for resistin remained significant even after accounting for established stroke risk factors (OR: 1.39; 95% CI: 1.01–1.90; p-trend: 0.036). Further adjustment for markers for inflammation, angiogenesis, and endothelial function also did not affect our results.
Circulating levels of resistin, but not those of adiponectin or leptin, are associated with an increased risk of incident ischemic stroke in postmenopausal women, independent of obesity and other CVD risk factors.
stroke; adipokines; women
Genome-wide association studies (GWAS) offer an excellent opportunity to identify the genetic variants underlying complex human diseases. Successful utilization of this approach requires a large sample size to identify single nucleotide polymorphisms (SNPs) with subtle effects. Meta-analysis is a cost-efficient means to achieve large sample size by combining data from multiple independent GWAS; however, results from studies performed on different populations can be variable due to various reasons, including varied linkage equilibrium structures as well as gene-gene and gene-environment interactions. Nevertheless, one should expect effects of the SNP are more similar between similar populations than those between populations with quite different genetic and environmental backgrounds. Prior information on populations of GWAS is often not considered in current meta-analysis methods, rendering such analyses less optimal for the detecting association. This paper describes a test that improves meta-analysis to incorporate variable heterogeneity among populations. The proposed method is remarkably simple in computation and hence can be performed in a rapid fashion in the setting of GWAS. Simulation results demonstrate the validity and higher power of the proposed method over conventional methods in the presence of heterogeneity. As a demonstration, we applied the test to real GWAS data to identify SNPs associated with circulating Insulin-like growth factor I concentrations.
Genome-wide association study; Meta-analysis; Variance-component model; Insulin-like growth factor I
Hepatocyte growth factor (HGF) is a potent angiogenic factor and may play a role in the development and progression of atherosclerotic lesions, the underlying mechanism of cardiovascular disease. However, there have been no prospective studies examining the relationship between HGF levels and risk of stroke.
Methods and Results
We conducted a nested case-control study (972 incident stroke cases and 1:1 age- and race-matched controls) to prospectively evaluate the association between plasma HGF and risk of ischemic stroke within the Women’s Health Initiative Observational Study, a cohort of postmenopausal women aged 50–79 years. Baseline HGF levels were correlated positively with body mass index (BMI), systolic blood pressure, low-density lipoprotein cholesterol, insulin resistance, and inflammatory markers such as C-reactive protein, and inversely with high-density lipoprotein cholesterol (all P-values <0.05). Baseline HGF levels were higher among cases than controls (geometric means 601.8 vs. 523.2 pg/mL, p = 0.003). Furthermore, the risk of incident ischemic stroke was significantly greater amongst women in the highest versus lowest quartile of plasma HGF levels (odds ratio [OR] = 1.46; 95% confidence interval [CI]: 1.12–1.91; Ptrend = 0.003), in a conditional logistic regression model that adjusted for BMI. These results were only slightly attenuated after further adjustment for additional stroke risk factors (OR=1.39; 95% CI=1.04–1.85, Ptrend=0.023).
Circulating levels of HGF are associated with an increased risk of incident ischemic stroke, independent of obesity and other risk factors for cardiovascular disease among postmenopausal women aged 50–79 years.
Hepatocyte growth factor; ischemic stroke; women
We examined serum lipids in association with carotid artery intima-media thickness (CIMT) in HIV-infected and HIV-uninfected women.
In 2003–4, among 1827 Women’s Interagency HIV Study participants, we measured CIMT and lipids (high-density lipoprotein cholesterol [HDL-c], low-density lipoprotein cholesterol [LDL-c], total cholesterol [TC], non-HDL-c). A subset of 520 treated HIV-infected women had pre-1997 lipid measures. We used multivariable linear regression to examine associations between lipids and CIMT.
In HIV-uninfected women, higher TC, LDL-c and non-HDL-c were associated with increased CIMT. Among HIV-infected women, associations of lipids with CIMT were observed in treated but not untreated women. Among the HIV-infected women treated in 2003–4, CIMT was associated both with lipids measured a decade earlier in infection, and with late lipid measurements.
Among HIV-infected women, hyperlipidemia is most strongly associated with subclinical atherosclerosis in treated women. Among treated women, the association appeared strongest early in the disease course.
cardiovascular diseases; carotid arteries; HAART; HIV; lipids
To examine determinants of racial/ethnic differences in diabetes incidence among postmenopausal women participating in the Women’s Health Initiative.
RESEARCH DESIGN AND METHODS
Data on race/ethnicity, baseline diabetes prevalence, and incident diabetes were obtained from 158,833 women recruited from 1993–1998 and followed through August 2009. The relationship between race/ethnicity, other potential risk factors, and the risk of incident diabetes was estimated using Cox proportional hazards models from which hazard ratios (HRs) and 95% CIs were computed.
Participants were aged 63 years on average at baseline. The racial/ethnic distribution was 84.1% non-Hispanic white, 9.2% non-Hispanic black, 4.1% Hispanic, and 2.6% Asian. After an average of 10.4 years of follow-up, compared with whites and adjusting for potential confounders, the HRs for incident diabetes were 1.55 for blacks (95% CI 1.47–1.63), 1.67 for Hispanics (1.54–1.81), and 1.86 for Asians (1.68–2.06). Whites, blacks, and Hispanics with all factors (i.e., weight, physical activity, dietary quality, and smoking) in the low-risk category had 60, 69, and 63% lower risk for incident diabetes. Although contributions of different risk factors varied slightly by race/ethnicity, most findings were similar across groups, and women who had both a healthy weight and were in the highest tertile of physical activity had less than one-third the risk of diabetes compared with obese and inactive women.
Despite large racial/ethnic differences in diabetes incidence, most variability could be attributed to lifestyle factors. Our findings show that the majority of diabetes cases are preventable, and risk reduction strategies can be effectively applied to all racial/ethnic groups.
Mechanistic associations between obesity and colorectal cancer remain unclear. In this study, we investigated whether adipokines are risk factors for colorectal cancer and whether they may mediate its association with obesity. In a case–cohort study nested within the Women’s Health Initiative cohort of postmenopausal women, baseline plasma samples from 457 colorectal cancer cases and 841 subcohort subjects were assayed for seven adipokines—adiponectin, leptin, plasminogen activator inhibitor-1 (PAI-1), resistin, hepatocyte growth factor, interleukin-6 (IL-6), and TNF-α. Serum insulin and estradiol values measured previously were also available for data analysis. After adjusting for age, race, smoking, colonoscopy history, and estrogen level, a low level of antiinflammatory adiponectin and high levels of proinflammatory leptin, PAI-1, and IL-6 were associated with increased colorectal cancer risk, though only leptin remained significant after further adjustment for insulin [HRs comparing extreme quartiles (HRQ4–Q1), 1.84; 95% CI, 1.17–2.90]. Mediation analyses showed that leptin and insulin partially explained the association between waist circumference and colorectal cancer and attenuated it by 25% and 37%, respectively, with insulin being a significant mediator (P = 0.041). Our findings support the conclusion that adipokines involved in inflammation are associated with colorectal cancer risk, but that their effects may be mediated mostly by insulin, with leptin exerting an independent effect. Hyperinsulinemia and hyperleptinemia may therefore partially explain the adiposity association with colorectal cancer in postmenopausal women.
Major cardiovascular diseases (CVDs) are leading causes of mortality among US Hispanic and Latino individuals. Comprehensive data are limited regarding the prevalence of CVD risk factors in this population and relations of these traits to socioeconomic status (SES) and acculturation.
To describe prevalence of major CVD risk factors and CVD (coronary heart disease [CHD] and stroke) among US Hispanic/Latino individuals of different backgrounds, examine relationships of SES and acculturation with CVD risk profiles and CVD, and assess cross-sectional associations of CVD risk factors with CVD.
Design, Setting, and Participants
Multicenter, prospective, population-based Hispanic Community Health Study/Study of Latinos including individuals of Cuban (n =2201), Dominican (n = 1400), Mexican (n=6232), Puerto Rican (n=2590), Central American (n=1634), and South American backgrounds (n = 1022) aged 18 to 74 years. Analyses involved 15 079 participants with complete data enrolled between March 2008 and June 2011.
Main Outcome Measures
Adverse CVD risk factors defined using national guidelines for hypercholesterolemia, hypertension, obesity, diabetes, and smoking. Prevalence of CHD and stroke were ascertained from self-reported data.
Age-standardized prevalence of CVD risk factors varied by Hispanic/Latino background; obesity and current smoking rates were highest among Puerto Rican participants (for men, 40.9% and 34.7%; for women, 51.4% and 31.7%, respectively); hypercholesterolemia prevalence was highest among Central American men (54.9%) and Puerto Rican women (41.0%). Large proportions of participants (80% of men, 71% of women) had at least 1 risk factor. Age- and sex-adjusted prevalence of 3 or more risk factors was highest in Puerto Rican participants (25.0%) and significantly higher (P<.001) among participants with less education (16.1%), those who were US-born (18.5%), those who had lived in the United States 10 years or longer (15.7%), and those who preferred English (17.9%). Overall, self-reported CHD and stroke prevalence were low (4.2% and 2.0% in men; 2.4% and 1.2% in women, respectively). In multivariate-adjusted models, hypertension and smoking were directly associated with CHD in both sexes as were hypercholesterolemia and obesity in women and diabetes in men (odds ratios [ORs], 1.5–2.2). For stroke, associations were positive with hypertension in both sexes, diabetes in men, and smoking in women (ORs, 1.7–2.6).
Among US Hispanic/Latino adults of diverse backgrounds, a sizeable proportion of men and women had adverse major risk factors; prevalence of adverse CVD risk profiles was higher among participants with Puerto Rican background, lower SES, and higher levels of acculturation.
Low insulin-like growth factor–1 (IGF-I) may influence the development of age-related cardiovascular diseases including congestive heart failure (CHF). Insulin-like growth factor binding protein-1 (IGFBP-1), which increases during catabolic states and inhibits anabolic IGF-I effects, is increased in CHF patients and has been associated prospectively with increased mortality among older adults and myocardial infarction survivors. We investigated the association between fasting plasma levels of IGF-I, IGFBP-1, IGFBP-3, and insulin and risk of incident CHF in the prospective Cardiovascular Health Study (CHS).
From among 5,888 65+ year-old adults in the Cardiovascular Health Study (CHS), we studied 566 incident CHF cases and 1,072 comparison subjects, after exclusion of underweight individuals (BMI < 18.5 kg/m2) and insulin users. Hazard ratios (HR) with 95% confidence intervals (CIs) for CHF were estimated after adjustment for age, race, gender, hypertension, systolic blood pressure, lipid levels, left ventricular hypertrophy, coronary disease, C-reactive protein, health status, diabetes, and BMI.
High baseline IGFBP-1 level was a significant predictor of CHF, independent of established CHF risk factors and inflammation markers. The HR per SD of IGFBP-1 was 1.22 (95% CI=1.07–1.39, p < 0.01). Relative to the lowest IGFBP-1 tertile, the HR was 1.29 (95% CI=0.96–1.74, p=0.09) for the second IGFBP-1 tertile and 1.47 (95% CI=1.06–2.04; p=0.02) for the highest IGFBP-1 tertile (tertile cutpoints 19.5 and 35.8 ng/ml). Total IGF-I, IGFBP-3, or insulin levels had no association with CHF after adjustment for CHF risk factors.
High circulating IGFBP-1 may be a CHF risk factor among older adults.
IGF-I shares structural homology and in vitro metabolic activity with insulin. Laboratory models suggest that IGF-I and its binding proteins IGFBP-1 and IGFBP-2 have potentially beneficial effects on diabetes risk, whereas IGFBP-3 may have adverse effects. We therefore conducted a prospective nested case-control investigation of incident diabetes (n = 742 case subjects matched 1:1 to control subjects) and its associations with IGF-axis protein levels in the Nurses’ Health Study, a cohort of middle-aged women. The median time to diabetes was 9 years. Statistical analyses were adjusted for multiple risk factors, including insulin and C-reactive protein. Diabetes risk was fivefold lower among women with baseline IGFBP-2 levels in the top versus bottom quintile (odds ratio [OR]q5–q1 = 0.17 [95% CI 0.08–0.35]; P trend < 0.0001) and was also negatively associated with IGFBP-1 levels (ORq5–q1 = 0.37 [0.18–0.73]; P trend = 0.0009). IGFBP-3 was positively associated with diabetes (ORq5–q1 = 2.05 [1.20–3.51]; P trend = 0.002). Diabetes was not associated with total IGF-I levels, but free IGF-I and diabetes had a significant association that varied (P interaction = 0.003) by insulin levels above the median (ORq5–q1 = 0.48 [0.26–0.90]; P trend = 0.0001) versus below the median (ORq5–q1 = 2.52 [1.05–6.06]; P trend < 0.05). Thus, this prospective study found strong associations of incident diabetes with baseline levels of three IGFBPs and free IGF-I, consistent with hypotheses that the IGF axis might influence diabetes risk.
Background: Multiplex assays are available to measure an array of circulating chemokines, soluble cytokine receptors and growth factors. However, there is limited information regarding whether these analytes are suitable for large-scale epidemiological studies to assess their relationships with chronic diseases, including cancer.
Methods: We examined detectability, assay repeatability, and 3-year within-subject reproducibility of plasma levels of 25 chemokines and 11 soluble receptors of cytokines and growth factors selected from the Human Millipore Panels. Plasma samples were obtained from 36 men (average age 62 years) and 17 women (average age 32 years) who participated in two epidemiological studies. Inter-assay and within-subject reproducibility were assessed by intraclass correlation coefficients (ICC).
Results: All analytes, except lymphotactin (47% detectability), were detectable in >90% of plasma samples. Inter-assay reproducibility for all analytes in 36 men tested three times on separate days were good to excellent (ICCs: 0.71–1.00). Within-subject reproducibility in 17 women sampled three times in three years were excellent (ICC ≥ 0.75) for five chemokines (eotaxin, fractalkine, 6Ckine, eotaxin 3, and SDF-1α+β) and three soluble receptors (sIL-1R2, sIL-4R and sVEGFR2); ICCs were fair to good (0.4 ≤ ICC < 0.75) for 15 chemokines and eight soluble receptors. However, five chemokines (GRO, IP-10, MIP-1β, BCA-1, and MIP-3α) had ICC < 0.4, suggesting biological variability.
Conclusion: Multiplex assays for plasma levels of selected chemokines and soluble receptors showed good to excellent assay detectability and repeatability. Most analytes also had good 3-year within-subject reproducibility, indicating that a single measurement of these analytes may be used to assess biomarker-disease associations.
Chemokines; Soluble receptors; Within-subject variability; Biomarker; Limit of detection
Inflammation and hemostasis perturbation may be involved in vascular complications of HIV infection. We examined atherogenic biomarkers and subclinical atherosclerosis in HIV-infected adults before and after beginning highly-active antiretroviral therapy (HAART).
In the Women's Interagency HIV Study (WIHS), 127 HIV-infected women studied pre- and post-HAART were matched to HIV-uninfected controls. Six semi-annual measurements of soluble CD14, tumor necrosis factor (TNF)-alpha, soluble interleukin (IL)-2 receptor, IL-6, IL-10, monocyte chemoattractant protein (MCP)-1, D-dimer, and fibrinogen were obtained. Carotid artery intima-media thickness (CIMT) was measured by B-mode ultrasound.
Relative to HIV-uninfected controls, HAART-naïve HIV-infected women had elevated levels of soluble CD14 (1945 vs 1662 ng/mL, Wilcoxon signed rank P<0.0001), TNF-alpha (6.3 vs 3.4 pg/mL, P<0.0001), soluble IL-2 receptor (1587 vs 949 pg/mL, P<0.0001), IL-10 (3.3 vs 1.9 pg/mL, P<0.0001), MCP-1 (190 vs 163 pg/mL, P<0.0001) and D-dimer (0.43 vs 0.31 µg/mL, P<0.01). Elevated biomarker levels declined after HAART. While most biomarkers normalized to HIV-uninfected levels, in women on effective HAART, TNF-alpha levels remained elevated compared to HIV-uninfected women (+0.8 pg/mL, P=0.0002). Higher post-HAART levels of soluble IL-2 receptor (P=0.02), IL-6 (P=0.05), and D-dimer (P=0.03) were associated with increased CIMT.
Untreated HIV infection is associated with abnormal hemostasis (e.g., D-dimer), and pro-atherogenic (e.g., TNF-alpha) and anti-atherogenic (e.g., IL-10) inflammatory markers. HAART reduces most inflammatory mediators to HIV-uninfected levels. Increased inflammation and hemostasis are associated with subclinical atherosclerosis in recently treated women. These findings have potential implications for long-term risk of cardiovascular disease in HIV-infected patients, even with effective therapy.
antiretroviral therapy; cardiovascular diseases; cytokines; hemostasis; HIV; inflammation
Background. Cytomegalovirus (CMV) infection has been implicated in immune activation and accelerated progression of immunodeficiency from human immunodeficiency virus (HIV) coinfection. We hypothesized that CMV is associated with vascular disease in HIV-infected adults.
Methods. In the Women's Interagency HIV Study, we studied 601 HIV-infected and 90 HIV-uninfected participants. We assessed the association of CMV immunoglobulin G (IgG) level with carotid artery intima-media thickness, carotid artery distensibility, Young's elastic modulus, and blood pressures. Multivariable models adjusted for age, race/ethnicity, smoking, diabetes, and body mass index.
Results. Mean CMV IgG levels were higher in HIV-infected women compared with HIV-uninfected women (P < .01). Among HIV-infected women, higher CMV IgG level was associated with decreased carotid artery distensibility (P < .01) and increased Young's modulus (P = .02). Higher CMV IgG antibody level was associated with increased prevalence of carotid artery lesions among HIV-infected women who achieved HIV suppression on antiretroviral therapy, but not among viremic or untreated HIV-infected women. Adjustment for Epstein–Barr virus antibody levels and C-reactive protein levels had no effect on the associations between CMV IgG levels and vascular parameters.
Conclusions. Cytomegalovirus antibody titers are increased in HIV-infected women and associated with subclinical cardiovascular disease. Host responses to CMV may be abnormal in HIV infection and associated with clinical disease.
Candidate gene association studies for peripheral artery disease (PAD), including subclinical disease assessed with the ankle-brachial index (ABI), have been limited by the modest number of genes examined. We conducted a two stage meta-analysis of ~50,000 SNPs across ~2100 candidate genes to identify genetic variants for ABI.
Methods and results
We studied subjects of European ancestry from 8 studies (n = 21,547, 55% women, mean age 44–73 years) and African American ancestry from 5 studies (n = 7267, 60% women, mean age 41–73 years) involved in the candidate gene association resource (CARe) consortium. In each ethnic group, additive genetic models were used (with each additional copy of the minor allele corresponding to the given beta) to test each SNP for association with continuous ABI (excluding ABI > 1.40) and PAD (defined as ABI < 0.90) using linear or logistic regression with adjustment for known PAD risk factors and population stratification. We then conducted a fixed-effects inverse-variance weighted meta-analyses considering a p < 2 × 10−6 to denote statistical significance.
In the European ancestry discovery meta-analyses, rs2171209 in SYTL3 (β = −0.007, p = 6.02 × 10−7) and rs290481 in TCF7L2 (β = −0.008, p = 7.01 × 10−7) were significantly associated with ABI. None of the SNP associations for PAD were significant, though a SNP in CYP2B6 (p = 4.99 × 10−5) was among the strongest associations. These 3 genes are linked to key PAD risk factors (lipoprotein(a), type 2 diabetes, and smoking behavior, respectively). We sought replication in 6 population-based and 3 clinical samples (n = 15,440) for rs290481 and rs2171209. However, in the replication stage (rs2171209, p = 0.75; rs290481, p = 0.19) and in the combined discovery and replication analysis the SNP–ABI associations were no longer significant (rs2171209, p = 1.14 × 10−3; rs290481, p = 8.88 × 10−5). In African Americans, none of the SNP associations for ABI or PAD achieved an experiment-wide level of significance.
Genetic determinants of ABI and PAD remain elusive. Follow-up of these preliminary findings may uncover important biology given the known gene-risk factor associations. New and more powerful approaches to PAD gene discovery are warranted.
Ankle brachial index; Peripheral artery disease; Genetics; Candidate gene array; Meta-analysis; Ethnicity
Inflammatory and hemostasis-related biomarkers may identify women at risk of stroke.
Hormones and Biomarkers Predicting Stroke is a study of ischemic stroke among postmenopausal women participating in the Women’s Health Initiative Observational Study (n = 972 case-control pairs). A Biomarker Risk Score was derived from levels of seven inflammatory and hemostasis-related biomarkers that appeared individually to predict risk of ischemic stroke: C-reactive protein, interleukin-6, tissue plasminogen activator, D-dimer, white blood cell count, neopterin, and homocysteine. The c index was used to evaluate discrimination.
Of all the individual biomarkers examined, C-reactive protein emerged as the only independent single predictor of ischemic stroke (adjusted odds ratio comparing Q4 versus Q1 = 1.64, 95% confidence interval: 1.15–2.32, p = 0.01) after adjustment for other biomarkers and standard stroke risk factors. The Biomarker Risk Score identified a gradient of increasing stroke risk with a greater number of elevated inflammatory/hemostasis biomarkers, and improved the c index significantly compared with standard stroke risk factors (p = 0.02). Among the subset of individuals who met current criteria for “high risk” levels of C-reactive protein (> 3.0 mg/L), the Biomarker Risk Score defined an approximately two-fold gradient of risk. We found no evidence for a relationship between stroke and levels of E-selectin, fibrinogen, tumor necrosis factor-alpha, vascular cell adhesion molecule-1, prothrombin fragment 1+2, Factor VIIC, or plasminogen activator inhibitor-1 antigen (p >0.15).
The findings support the further exploration of multiple-biomarker panels to develop approaches for stratifying an individual’s risk of stroke.
stroke; epidemiology; women
We assessed the association of genetic variation in MMP3 and MMP9 with risk of myocardial infarction and stroke.
A case-control study was conducted among members of Group Health (GH), a large integrated health care delivery system. Case subjects with incident non-fatal myocardial infarction (n = 854), ischemic stroke (n = 367), and hemorrhagic stroke (n = 66) were identified and validated. A matched control group was selected from among GH members without myocardial infarction or stroke (n=2696). Haplotype-tagging sets of single nucleotide polymorphisms (SNPs) in MMP3 and MMP9 were genotyped.
MMP3 haplotype 2 was associated with reduced risk of myocardial infarction (adjusted odds ratio [OR] per copy = 0.80, 95% confidence interval 0.66, 0.98) and increased risk of hemorrhagic stroke (OR = 1.69, 95% confidence interval 1.05, 2.75). Results for MMP3 haplotype 2 and ischemic stroke resembled those for myocardial infarction but did not achieve statistical significance (OR = 0.85, 95% confidence interval 0.64, 1.12). No individual SNP identified MMP3 haplotype 2, and none of the individual MMP3 SNPs were associated with myocardial infarction or stroke. MMP9 haplotypes or SNPs were not associated with myocardial infarction or stroke.
MMP3 haplotype may predict both cardiac events and stroke.
Myocardial infarction; stroke; genetics
Individuals with HIV infection exhibit high cytomegalovirus (CMV) IgG levels, but there are few data regarding the association of hepatitis C virus (HCV) with the immune response against CMV.
Associations of HCV with CMV seropositivity and CMV IgG levels were studied in 635 HIV-infected women, 187 of whom were HCV-seropositive, with adjustment in multivariable models for age, race/ethnicity, and HIV disease characteristics. Eighty one percent of the women reported receipt of highly active antiretroviral therapy (HAART) prior to or at CMV testing.
In adjusted models women with chronic HCV had higher CMV IgG levels than those without HCV RNA (β = 2.86, 95% CI:0.89 – 4.83; P = 0.004). The association of HCV RNA with CMV IgG differed by age (Pinteraction = 0.0007), with a strong association observed among women in the low and middle age tertiles (≤45.3 years of age; β = 6.21, 95% CI:3.30 – 9.11, P<0.0001) but not among women in the high age tertile. CMV IgG levels were not associated with non-invasive measures of liver disease, APRI and FIB-4, or with HCV RNA level and adjustment for Epstein-Barr virus (EBV) IgG levels did not affect the association between HCV and CMV.
CMV IgG levels are higher in HCV/HIV co-infected women than in HIV mono-infected women. Further research on the association of HCV with CMV IgG is indicated because prior studies have found CMV IgG to be associated with morbidity and mortality in the general population and subclinical carotid artery disease in HIV-infected patients.
Few studies simultaneously investigated lipids and lipoprotein biomarkers as predictors of ischemic stroke. The value of these biomarkers as independent predictors of ischemic stroke remains controversial.
We conducted a prospective nested case-control study among postmenopausal women from the Women’s Health Initiative Observational Study to assess the relationship between fasting lipids (total cholesterol, LDL-C, HDL-C, and triglycerides), lipoproteins (LDL, HDL and VLDL particle number and size, IDL particle number, and lipoprotein [a]) and risk of ischemic stroke. Among women free of stroke at baseline, 774 ischemic stroke patients were matched according to age and race to controls using a 1:1 ratio.
In bivariate analysis, baseline triglycerides (P<0.001), IDL particles (P<0.01), LDL particles (P<0.01), VLDL triglyceride (P<0.001), VLDL particles (P<0.01), VLDL size (P<0.001), LDL size (P=0.03), and total/HDL cholesterol ratio (P<0.01) were significantly higher among women with incident ischemic stroke, while levels of HDL-C (P<0.01) and HDL size (P<0.01) were lower. No significant baseline difference for total cholesterol (P=0.15), LDL-C (P=0.47), and lipoprotein (a) (P=0.11) was observed. In multivariable analysis, triglycerides, (OR for the highest vs lowest quartile, 1.56; 95% CI, 1.13-2.17, P for trend =0.02), VLDL size (OR 1.59, 95% CI, 1.10-2.28, P for trend =0.03) and IDL particle number (OR 1.46, 95% CI, 1.04-2.04, P for trend =0.02) were significantly associated with ischemic stroke.
Among a panel of lipid and lipoprotein biomarkers, baseline triglycerides, VLDL size and IDL particle number were significantly associated with incident ischemic stroke in postmenopausal women.
Lipids; Lipoproteins; Ischemic Stroke; Women; Triglycerides
To assess associations between abacavir (ABC) use and systemic inflammation.
Retrospective case-control study.
MACS & WIHS cohort participants who initiated ABC were matched, using propensity score methods, to ABC-unexposed persons. Levels of hsCRP(μg/mL), IL-6(pg/mL), and D-dimer (μg/mL) were measured from pre-HAART and on-HAART plasma. Random-effects models compared markers by ABC exposure and by changes from pre-HAART levels.
Biomarkers were measured in N=508 matched pairs (328 women; 180 men). Pre-HAART levels did not differ by exposure group except that hsCRP levels were higher among WIHS women who subsequently used ABC (p=0.04). Regardless of ABC use, mean hsCRP increases and D-dimer reductions were seen when comparing pre- to on-HAART levels, in the overall group (28% and -27%), for MACS men (28% and -31%) and for WIHS women (29% and -24% (p<0.01 for all); IL-6 levels declined in MACS men (p=0.02). No adjusted biomarker level differences existed by ABC exposure at the on-HAART visit. HIV RNA reductions correlated with D-dimer (r = 0.14, p < 0.01) and IL-6 (r = 0.12, p < 0.01) reductions. Associations between ABC use and mean biomarker levels were modified by pre-HAART ART experience. Renal dysfunction was equally likely among non-ABC and ABC recipients.
ABC use was not associated with plasma elevations in hsCRP, IL-6 and d-dimer. Mechanisms other than increased systemic inflammation may account for ABC’s reported association with increased cardiovascular disease. HAART -associated reductions in D-dimer and IL-6 were apparent regardless of ABC use and were correlated with HIV RNA reductions.
HIV infection; inflammation; HAART; abacavir; cytokines
Despite use of HAART, cognitive impairment remains prevalent in HIV. Indeed, a recent study suggested that in certain instances, stopping HAART was associated with improved cognitive function (Robertson et al. 2010). HAART is occasionally associated with cardiovascular pathology and such pathology may be associated with cognitive impairment. To explore these associations, we assessed the relative contributions of cardiovascular variables such as hypertension and atherosclerosis, of HIV and HAART to cognition. Participants were members of the Women’s Interagency HIV Study (WIHS). In analysis of cross-sectional data using general linear models we assessed the relationship between each cardiovascular variable and Stroop interference time and symbol digit modalities test while adjusting for age, HIV, education, depression, and race/ethnicity. We also analyzed the association of summary measures of HAART use with cognition. In multivariate models significance was limited to carotid lesions and carotid intima-medial thickness quintile (CIMT) with Stroop interference time (for carotid lesions, coefficient = 10.5, CI: 3.5 to 17.5, p = 0.003, N = 1130; for CIMT quintile, coefficient = 8.6, CI = 1.7 to 15.4, p = 0.025, N = 1130). Summary measures of protease inhibitor use and other HAART measures were in most cases not associated with cognitive score in multivariate models. We conclude that in the HAART era among middle-aged women with HIV, carotid disease may be significantly associated with some measures of cognitive impairment. In this cross-sectional study, we could detect neither positive nor negative effects of HAART on cognition.
Cognition; HIV; Women; Hypertension; Atherosclerosis; Middle-Aged
To assess the association of HIV infection, HIV disease parameters (including CD4+ T-cell counts, HIV viral load, and AIDS) and antiretroviral medication use with subclinical carotid artery atherosclerosis.
Cross-sectional study nested within a prospective cohort study
Among participants in the Women's Interagency HIV Study (1,331 HIV-infected women, 534 HIV-uninfected women) and Multicenter AIDS Cohort Study (600 HIV-infected men, 325 HIV-uninfected men), we measured subclinical carotid artery lesions and common carotid artery intima-media thickness (CIMT) using B-mode ultrasound. We estimated adjusted mean CIMT differences and prevalence ratios (PRs) for carotid lesions associated with HIV-related disease and treatments, with multivariate adjustment to control for possible confounding variables.
Among HIV-infected individuals, a low CD4+ T cell count was independently associated with an increased prevalence of carotid lesions. Compared to the reference group of HIV-uninfected individuals, the adjusted PR for lesions among HIV-infected individuals with CD4+ T-cell count <200 cells/mm3 was 2.00 (95% confidence interval 1.22, 3.28) in women and 1.74 (95% confidence interval 1.04, 2.93) in men. No consistent association of antiretroviral medications with carotid atherosclerosis was observed, except for a borderline significant association between protease inhibitor use and carotid lesions in men (with no association among women). History of clinical AIDS and HIV viral load were not significantly associated with carotid atherosclerosis.
Beyond traditional cardiovascular disease risk factors, low CD4+ T-cell count is the most robust risk factor for increased subclinical carotid atherosclerosis in HIV-infected women and men.
HIV disease is associated with increased arterial stiffness, which may be related to inflammation provoked by HIV-related immune perturbation. We assessed the association of T cell markers of immune activation and immunosenescence with carotid artery stiffness among HIV-infected women.
Among 114 HIV-infected and 43 HIV-uninfected women, we measured CD4+ and CD8+ T cell populations expressing activation (CD38+HLA-DR+) and senescence (CD28-CD57+) markers. We then related these measures of immune status with parameters of carotid artery stiffness, including decreased distensibility, and increased Young’s elastic modulus, as assessed by B-mode ultrasound.
HIV infection was associated with increased CD4+ T cell activation, CD8+ T cell activation and CD8+ T cell senescence. Among HIV-infected women, adjusted for age, HIV medications, and vascular risk factors, higher CD4+CD38+HLA-DR+ T cell frequency was associated with decreased carotid artery distensibility (β= −2.00, 95% confidence interval [CI]= −3.86,−0.14, P=0.04) and increased Young’s modulus (β=1.00, 95% CI=0.03,1.97, P=0.04). These associations were affected little by further adjustment for CD4+ T cell count and viral load. Among HIV-infected women, higher frequencies of immunosenescent T cells, including CD4+CD28-CD57+ and CD8+CD28-CD57+ T cells, were also associated with decreased arterial distensibility. Among HIV-uninfected women, frequencies of activated or senescent T cells were not significantly associated with measures of carotid stiffness.
T cell activation and senescence are associated with arterial stiffness, suggesting that pro-inflammatory populations of T cells may produce functional or structural vascular changes in HIV-infected women.
It is hypothesized that inflammation may mediate the relationship between obesity and endometrial cancer risk. We examined the associations of three inflammation markers, C-reactive protein (CRP), interleukin (IL)-6, and tumor necrosis factor (TNF)-α, with risk of endometrial cancer.
A case-cohort study was nested within the Women’s Health Initiative, a cohort of postmenopausal women. Baseline plasma samples of 151 incident endometrial cancer cases and 301 subcohort subjects not using hormones were assayed.
CRP, but not IL-6 or TNF-α, was positively associated with endometrial cancer risk after adjusting for age and BMI [hazard ratio comparing extreme quartiles (HRq4-q1) = 2.29; 95% confidence interval (CI) = 1.13–4.65; ptrend = 0.012). After additional adjustment for estradiol and insulin, this association was attenuated (HRq4-q1 = 1.70;95% CI= 0.78–3.68; ptrend = 0.127). Obesity (BMI ≥ 30 kg/m2) was associated with endometrial cancer risk in an age-adjusted model. The obesity effect was reduced by 48%, 67%, and 77% when either estradiol, CRP, or insulin, respectively, was included in the model, and it became null when all three factors were adjusted for simultaneously.
The association between inflammation, as indicated by a relatively high level of CRP, and endometrial cancer risk may partially be explained by hyperinsulinemia and elevated estradiol. Nevertheless, all three factors contribute to and mediate the link between obesity and endometrial cancer in postmenopausal women not using hormones.
The association between obesity and endometrial cancer risk in postmenopausal women may be attributed to inflammation, insulin resistance, and elevated estrogen.