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
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.
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.
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
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
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.
Insulin-like growth factor-I (IGF-I) and insulin-like growth factor-binding protein-3 (IGFBP-3) are involved in cell replication, proliferation, differentiation, protein synthesis, carbohydrate homeostasis and bone metabolism. Circulating IGF-I and IGFBP-3 concentrations predict anthropometric traits and risk of cancer and cardiovascular disease. In a genome-wide association study of 10 280 middle-aged and older men and women from four community-based cohort studies, we confirmed a known association of single nucleotide polymorphisms in the IGFBP3 gene region on chromosome 7p12.3 with IGFBP-3 concentrations using a significance threshold of P < 5 × 10−8 (P = 3.3 × 10−101). Furthermore, the same IGFBP3 gene locus (e.g. rs11977526) that was associated with IGFBP-3 concentrations was also associated with the opposite direction of effect, with IGF-I concentration after adjustment for IGFBP-3 concentration (P = 1.9 × 10−26). A novel and independent locus on chromosome 7p12.3 (rs700752) had genome-wide significant associations with higher IGFBP-3 (P = 4.4 × 10−21) and higher IGF-I (P = 4.9 × 10−9) concentrations; when the two measurements were adjusted for one another, the IGF-I association was attenuated but the IGFBP-3 association was not. Two additional loci demonstrated genome-wide significant associations with IGFBP-3 concentration (rs1065656, chromosome 16p13.3, P = 1.2 × 10−11, IGFALS, a confirmatory finding; and rs4234798, chromosome 4p16.1, P = 4.5 × 10−10, SORCS2, a novel finding). Together, the four genome-wide significant loci explained 6.5% of the population variation in IGFBP-3 concentration. Furthermore, we observed a borderline statistically significant association between IGF-I concentration and FOXO3 (rs2153960, chromosome 6q21, P = 5.1 × 10−7), a locus associated with longevity. These genetic loci deserve further investigation to elucidate the biological basis for the observed associations and clarify their possible role in IGF-mediated regulation of cell growth and metabolism.
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.
Activation of MMPs in tissues is an important component of tissue injury. Based on earlier reports that (latent) proMMP-2 is incapable of forming a complex with TIMP-1, we reasoned that the identification of MMP-2:TIMP-1 complexes in blood might serve as a surrogate marker (“smoking gun”) of MMP-2 activation in tissues. Using specific antibodies, we developed a sensitive and specific assay to detect MMP-2:TIMP-1 complexes. We were perplexed to find that approximately 40% of plasma specimens from healthy individuals had detectable levels of the MMP-2:TIMP-1 complexes. Employing recombinant TIMP-1 bound Sepharose beads and Western blots, we demonstrated binding between recombinant proMMP-2 and TIMP-1 proteins. Recombinant MMP-2 lacking the catalytic domain also bound to TIMP-1 coated beads. These data are consistent with TIMP-1 binding to the hemopexin or hinge domain of proMMP-2. The explanation for the presence of plasma proMMP-2:TIMP-1 complexes in selected healthy individuals remains to be determined. In contrast to our immunoassay and bead binding experiments, proMMP-2 failed to bind to immobilized TIMP-1 employing surface plasmon resonance technology. Additional studies are needed to clarify these contrasting results.
MMP; TIMP; MMP:TIMP complexes; ELISAs; complex formation; plasma
Human longevity and healthy aging show moderate heritability (20–50%). We conducted a meta-analysis of genome-wide association studies from nine studies from the Cohorts for Heart and Aging Research in Genomic Epidemiology Consortium for two outcomes: a) all-cause mortality and b) survival free of major disease or death. No single nucleotide polymorphism (SNP) was a genome-wide significant predictor of either outcome (p < 5 × 10−8). We found fourteen independent SNPs that predicted risk of death, and eight SNPs that predicted event-free survival (p < 10−5). These SNPs are in or near genes that are highly expressed in the brain (HECW2, HIP1, BIN2, GRIA1), genes involved in neural development and function (KCNQ4, LMO4, GRIA1, NETO1) and autophagy (ATG4C), and genes that are associated with risk of various diseases including cancer and Alzheimer’s disease. In addition to considerable overlap between the traits, pathway and network analysis corroborated these findings. These findings indicate that variation in genes involved in neurological processes may be an important factor in regulating aging free of major disease and achieving longevity.
Background and purpose
Human immunodeficiency virus (HIV)-infected persons taking highly active antiretroviral therapy (HAART) may have an increased risk for cardiovascular-related events, although the underlying mechanism remains unclear. We tested the hypothesis that carotid arterial stiffness was higher among persons taking HAART compared to HAART-naïve and HIV-uninfected persons.
Between 2004 and 2006, we performed high resolution B-mode ultrasound on 2,789 HIV-infected and HIV-uninfected participants of the Women’s Interagency HIV Study (WIHS; 1865 women) and the Multicenter AIDS Cohort Study (MACS; 924 men) and determined carotid arterial distensibility, a direct measure of carotid arterial stiffness. We used generalized estimating equations to evaluate the association between distensibility and HIV infection, CD4+ cell count, and exposure to HAART adjusted for demographic, behavioral, and clinical characteristics.
In multivariable analysis, distensibility was 4.3% lower (95% confidence interval (CI): -7.4% to -1.1%) among HIV-infected versus uninfected participants. Among HIV-infected participants with fewer than 200 CD4+ cells, distensibility was 10.5% lower (95% CI: -14.5% to -6.2%) than that among HIV-uninfected participants, and this effect did not differ significantly by cohort or race. Concurrent HAART use was independently associated with lower distensibility among MACS participants but not among WIHS participants.
Our finding that advanced HIV-related immunosuppression was associated with increased carotid arterial stiffness independent from the effects of traditional atherosclerosis risk factors suggests that the etiologic mechanism underlying reports of an increased cardiovascular disease risk among HIV-infected individuals might involve HIV-related immunosuppression leading to vascular dysfunction and arterial stiffening.
atherosclerosis; cardiovascular disease; carotid arteries; HIV; epidemiology
The Hispanic Community Health Study (HCHS)/Study of Latinos (SOL) is a comprehensive multi-center community based cohort study of Hispanics/Latinos in the United States. Its rationale, objectives, design and implementation are described in this paper.
The HCHS/SOL will recruit 16,000 men and women who self-identify as Hispanic or Latino, age 18-74 years, from a random sample of households in defined communities in the Bronx, Chicago, Miami and San Diego. The sites were selected so that the overall sample would consist of at least 2000 persons in each of the following origin designations: Mexican, Puerto Rican and Dominican, Cuban, and Central and South American. The study includes research in the prevalence of and risk factors for heart, lung, blood and sleep disorders, kidney and liver function, diabetes, cognitive function, dental conditions, and hearing disorders.
The HCHS/SOL will 1) characterize the health status and disease burden in the largest minority population in the U.S; 2) describe the positive and negative consequences of immigration and acculturation of Hispanics/Latinos to the mainstream U.S. life-styles, environment and health care opportunities; and 3) identify likely causal factors of many diseases in a population with diverse environmental exposures, genetic backgrounds and early life experiences.
The Hispanic Community Health Study (HCHS)/Study of Latinos (SOL) is a multi-center, community based cohort study of Hispanic/Latino adults in the United States. A diverse participant sample is required that is both representative of the target population and likely to remain engaged throughout follow-up. The choice of sample design, its rationale, and benefits and challenges of design decisions are described in this paper.
The study design calls for recruitment and follow-up of a cohort of 16,000 Hispanics/Latinos aged 18-74 years, with 62.5% (10,000) over 44 years of age and adequate subgroup sample sizes to support inference by Hispanic/Latino background. Participants are recruited in community areas surrounding four field centers in the Bronx, Chicago, Miami, and San Diego. A two-stage area probability sample of households is selected with stratification and over-sampling incorporated at each stage to provide a broadly diverse sample, offer efficiencies in field operations, and ensure that the target age distribution is obtained.
Embedding probability sampling within this traditional, multi-site cohort study design enables competing research objectives to be met. However, the use of probability sampling requires developing solutions to some unique challenges in both sample selection and recruitment, as described here.
Probability sampling; Sampling diverse populations; Hispanic/Latino health
The insulin-like growth factor (IGF) axis has been hypothesized to influence the rate of human immunodeficiency virus (HIV) disease progression. This premise is based largely on laboratory models showing that IGF-I stimulates thymic growth and increases lymphocyte numbers and that IGF-binding protein (IGFBP)–3 has an opposing effect, inhibiting hematopoietic stem cell development.
We studied 1422 HIV-infected women enrolled in a large cohort that entailed semiannual follow-up (initiated in 1994). Baseline serum samples were tested for IGF-I and IGFBP-3 to determine their associations with incident clinical acquired immunodeficiency syndrome (AIDS) and CD4+ T cell count decline prior to April 1996 (before the era of highly active antiretroviral therapy [HAART]).
Low IGF-I levels (Ptrend = .02) and high IGFBP-3 levels (Ptrend = .02) were associated with rapid CD4+ T cell count decline. Only IGFBP-3, however, was significantly associated with AIDS incidence (hazard ratio for highest vs. lowest quartile, 2.65 [95% confidence interval, 1.30–5.42]; Ptrend = .02) in multivariable models.
These findings suggest that serum levels of IGFBP-3 (and possibly IGF-I) are associated with the rate of HIV disease progression in women and, more broadly, that interindividual heterogeneity in the IGF axis may influence HIV pathogenesis. If correct, the IGF axis could be a target for interventions to slow HIV disease progression and extend the time before use of HAART becomes necessary.
Obesity is a major risk factor for endometrial cancer, a relationship thought to be largely explained by the prevalence of high estrogen levels in obese women. Obesity is also associated with high levels of insulin, a known mitogen. However, no prospective studies have directly assessed whether insulin and/or insulin-like growth factor-I (IGF-I), a related hormone, are associated with endometrial cancer while accounting for estrogen levels. We therefore conducted a case-cohort study of incident endometrial cancer in the Women’s Health Initiative Observational Study, a prospective cohort of 93,676 postmenopausal women. The study involved all 250 incident cases and a random subcohort of 465 subjects for comparison. Insulin, total IGF-I, free IGF-I, IGF-binding protein-3, glucose, and estradiol levels were measured in fasting baseline serum specimens. Cox models were used to estimate associations with endometrial cancer, particularly endometrioid adenocarcinomas, the main histologic type (n = 205). Our data showed that insulin levels were positively associated with endometrioid adenocarcinoma [hazard ratio contrasting highest versus lowest quartile (HRq4-q1), 2.33; 95% confidence interval (95% CI), 1.13–4.82] among women not using hormone therapy after adjustment for age and estradiol. Free IGF-I was inversely associated with endometrioid adenocarcinoma (HRq4-q1, 0.53; 95% CI, 0.31–0.90) after adjustment for age, hormone therapy use, and estradiol. Both of these associations were stronger among overweight/obese women, especially the association between insulin and endometrioid adenocarcinoma (HRq4-q1, 4.30; 95% CI, 1.62–11.43). These data indicate that hyperinsulinemia may represent a risk factor for endometrioid adenocarcinoma that is independent of estradiol. Free IGF-I levels were inversely associated with endometrioid adenocarcinoma, consistent with prior cross-sectional data.
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