Age-related changes in echocardiographic measurements: association with variation in the estrogen receptor-alpha gene

Hepatic transcript signatures predict atherosclerotic lesion burden prior to a 2-year high cholesterol, high fat diet challenge

The purpose of this study was to identify molecular mechanisms by which the liver influences total lesion burden in a nonhuman primate model (NHP) of cardiovascular disease with acute and chronic feeding of a high cholesterol, high fat (HCHF) diet. Baboons (47 females, 64 males) were fed a HCHF diet for 2 years (y); liver biopsies were collected at baseline, 7 weeks (w) and 2y, and lesions were quantified in aortic arch, descending aorta, and common iliac at 2y. Unbiased weighted gene co-expression network analysis (WGCNA) revealed several modules of hepatic genes correlated with lesions at different time points of dietary challenge. Pathway and network analyses were performed to study the roles of hepatic module genes. More significant pathways were observed in males than females. In males, we found modules enriched for genes in oxidative phosphorylation at baseline, opioid signaling at 7w, and EIF2 signaling and HNF1A and HNF4A networks at baseline and 2y. One module enriched for fatty acid β oxidation pathway genes was found in males and females at 2y. To our knowledge, this is the first study of a large NHP cohort to identify hepatic genes that correlate with lesion burden. Correlations of baseline and 7w module genes with lesions at 2y were observed in males but not in females. Pathway analyses of baseline and 7w module genes indicate EIF2 signaling, oxidative phosphorylation, and μ-opioid signaling are possible mechanisms that predict lesion formation induced by HCHF diet consumption in males. Our findings of coordinated hepatic transcriptional response in male baboons but not female baboons indicate underlying molecular mechanisms differ between female and male primate atherosclerosis.

Left Ventricular Mass as a Risk Factor in the Oldest Old

In middle-aged and "young elderly" cohorts, higher left ventricular mass (LVM) is associated with worse outcomes. The authors examined LVM and 5-year mortality among community-dwelling 85-year-old patients. A representative sample (n=526, born 1920-1921) from the Jerusalem Longitudinal Cohort Study underwent echocardiography at age 85. LVM was indexed by body surface area (LVM-BSA) or height (LVM-Ht). Patients with higher LVM were less educated and sedentary and had poorer self-rated health, functional limitations, and increased comorbidity. Five-year mortality was 21.7% (n=114). Adjusted 5-year mortality rates were increased for the two upper quintiles of LVM-BSA (hazard ratio [HR], 1.8; 95% confidence interval [CI], 1.05-3.06) and LVM-Ht (HR, 2.2; 95% CI, 1.2-3.5). A step up in mortality occurred around the third quintile corresponding with LVM-BSA 110 g/m(2) or LVM-Ht 51 g/m(2.7). Among the oldest old, elevated LVM is significantly associated with mortality.

Estrogen signaling prevents diet-induced hepatic insulin resistance in male mice with obesity

The development of insulin resistance in the liver is a key event that drives dyslipidemia and predicts diabetes and cardiovascular risk with obesity. Clinical data show that estrogen signaling in males helps prevent adiposity and insulin resistance, which may be mediated through estrogen receptor-α (ERα). The tissues and pathways that mediate the benefits of estrogen signaling in males with obesity are not well defined. In female mice, ERα signaling in the liver helps to correct pathway-selective insulin resistance with estrogen treatment after ovariectomy. We assessed the importance of liver estrogen signaling in males using liver ERα-knockout (LKO) mice fed a high-fat diet (HFD). We found that the LKO male mice had decreased insulin sensitivity compared with their wild-type floxed (fl/fl) littermates during hyperinsulinemic euglycemic clamps. Insulin failed to suppress endogenous glucose production in LKO mice, indicating liver insulin resistance. Insulin promoted glucose disappearance in LKO and fl/fl mice similarly. In the liver, insulin failed to induce phosphorylation of Akt-Ser(473) and exclude FOXO1 from the nucleus in LKO mice, a pathway important for liver glucose and lipid metabolism. Liver triglycerides and diacylglycerides were also increased in LKO mice, which corresponded with dysregulation of insulin-stimulated ACC phosphorylation and DGAT1/2 protein levels. Our studies demonstrate that estrogen signaling through ERα in the liver helps prevent whole body and hepatic insulin resistance associated with HFD feeding in males. Augmenting hepatic estrogen signaling through ERα may lessen the impact of obesity on diabetes and cardiovascular risk in males.

The role of SNP-loop diuretic interactions in hypertension across ethnic groups in HyperGEN

Blood pressure (BP) is significantly influenced by genetic factors; however, less than 3% of the BP variance has been accounted for by variants identified from genome-wide association studies (GWAS) of primarily European-descent cohorts. Other genetic influences, including gene-environment (GxE) interactions, may explain more of the unexplained variance in BP. African Americans (AA) have a higher prevalence and earlier age of onset of hypertension (HTN) as compared with European Americans (EA); responses to anti-hypertensive drugs vary across race groups. To examine potential interactions between the use of loop diuretics and HTN traits, we analyzed systolic (SBP) and diastolic (DBP) blood BP from 1222 AA and 1231 EA participants in the Hypertension Genetic Epidemiology Network (HyperGEN). Population-specific score tests were used to test associations of SBP and DBP, using a panel of genotyped and imputed single nucleotide polymorphisms (SNPs) for AA (2.9 million SNPs) and EA (2.3 million SNPs). Several promising loci were identified through gene-loop diuretic interactions, although no SNP reached genome-wide significance after adjustment for genomic inflation. In AA, SNPs in or near the genes NUDT12, CHL1, GRIA1, CACNB2, and PYHIN1 were identified for SBP, and SNPs near ID3 were identified for DBP. For EA, promising SNPs for SBP were identified in ESR1 and for DBP in SPATS2L and EYA2. Among these SNPs, none were common across phenotypes or population groups. Biologic plausibility exists for many of the identified genes, suggesting that these are candidate genes for regulation of BP and/or anti-hypertensive drug response. The lack of genome-wide significance is understandable in this small study employing gene-drug interactions. These findings provide a set of prioritized SNPs/candidate genes for future studies in HTN. Studies in more diversified population samples may help identify previously missed variants.

Age-related changes in heart function by serial echocardiography in women aged 40-80 years

AIM

To determine if a defined set of echocardiographic parameters at entry and exit of a longitudinal study over 5 years showed changes with aging.

METHODS

The cohort consisted of 484 randomly recruited women aged 40-80. They were examined by two echocardiography cardiologists, independent of the medical information for these women.

RESULTS

Across the age decades (40-49, 50-59, 60-69, 70-79 years), body weight and body surface area (BSA) did not vary, and diastolic blood pressure (DBP) was stable; systolic blood pressure (SBP) progressively increased. There was gradual decline in left ventricular (LV) diastolic function, increase in LV muscle mass, and decrease in LV end-diastolic volume (LVEDV). The serial decrease in rate of change over 5 years in ejection fraction (ET) was small but significant across the four age decades.

CONCLUSIONS

As expected, there were age-related changes in cardiac structure and function over time in women who showed no apparent cardiovascular disease (CVD) at entry to the study. The direction of these serial changes was toward the development of LV stiffness and likelihood of subsequent heart failure. The clinical significance of the decrease in rate of change in EF remains unclear.

The association between the rs2234693 and rs9340799 estrogen receptor alpha gene polymorphisms and risk factors for cardiovascular disease: a review

Although estrogen is primarily thought of as the hormone involved in female reproduction, it also plays a role in many additional physiological and pathological processes. Recent studies have demonstrated an association between estrogen and clustered risk factors for cardiovascular disease (CVD), such as lipid and glucose metabolism and obesity-related phenotypes, as well as occurrence and severity of CVD. Evidence suggesting a genetic basis for this link is accumulating. Several polymorphisms of the estrogen receptor (ER) alpha (ESR1) gene exist that may influence the impact of estrogen, leading to clinically relevant phenotypes. Based on the relationship ERS1 seems to exhibit with CVD risk factors, these polymorphisms may play a role in the mediation of vasoprotective effects, modulation of cardiovascular physiology, and development of risk factors for CVD. The two most frequently studied polymorphisms located in ESR1 are often identified by their restriction endonucleases Pvull (rs2234693) and Xbal (rs9340799). ln this review, we have evaluated and summarized the results of studies involving rs2234693 and rs9340799 and clustered risk factors accompanying development of CVD. Despite inconsistent findings, together these studies provide some support for a relationship between polymorphisms in ESR1 and risk factors for CVD. These summarized findings do not yet support inclusion of ESR1 genotypes in genetic testing algorithms for predisposition to CVD, but they do indicate that further investigation into the potential connection between ESR1 and risk factors for CVD is warranted.

Female adult mouse cardiomyocytes are protected against oxidative stress

Premenopausal women have less cardiovascular disease and lower cardiovascular morbidity and mortality than men the same age. Our previous studies showed that female mice have lower mortality and better preserved cardiac function after myocardial infarction. However, the precise cellular and molecular mechanisms responsible for such a sex difference are not well established. Using cultured adult mouse cardiomyocytes, we tested the hypothesis that the survival advantage of females stems from activated estrogen receptors and Akt survival signaling pathways. Adult mouse cardiomyocytes were isolated from male and female C57BL/6J mice and treated with hydrogen peroxide (100 micromol/L) for 30 minutes. Cell survival was indicated by rod ratio (rod shaped cells:total cells), cell death by lactate dehydrogenase release, and positive staining of annexin-V (a marker for apoptosis) and propidium iodide (a marker for necrosis). In response to hydrogen peroxide(,) female adult mouse cardiomyocytes exhibited a higher rod ratio, lower lactate dehydrogenase release, and fewer Annexin-V-positive and propidium iodide-positive cells compared with males. Phospho-Akt was greater in females both at baseline and after hydrogen peroxide stimulation. The downstream molecule of Akt, phosphor-GSK-3beta (inactivation), was also higher, whereas caspase 3 activity was lower in females in response to hydrogen peroxide. Bcl-2 did not differ between sexes. Estrogen receptor-alpha was the dominant isoform in females, whereas estrogen receptor-beta was low but similar in both sexes. Our findings demonstrate that female adult mouse cardiomyocytes have a greater survival advantage when challenged with oxidative stress-induced cell death. This may be attributable to activation of Akt and inhibition of GSK-3beta and caspase 3 through an estrogen receptor-alpha-mediated mechanism.

Longitudinal tracking of left ventricular mass over the adult life course: clinical correlates of short- and long-term change in the framingham offspring study

BACKGROUND

Information is limited on the longitudinal tracking of left ventricular (LV) mass over the adult life course and the determinants of such change.

METHODS AND RESULTS

We used multilevel modeling to evaluate the correlates of LV mass prospectively over a 16-year period in 4217 Framingham study participants (mean age 45 years, 53% women) using up to 4 serial routine echocardiographic observations on each individual (11 762 observations). Age, sex, body mass index, systolic blood pressure, antihypertensive treatment, smoking, and diabetes mellitus were related to longitudinal measures of LV mass. Women and participants with diabetes mellitus experienced a steeper increase in LV mass with advancing age (compared with men and those without diabetes mellitus; P for interactions <0.0001 and 0.0003, respectively). Women also displayed greater increments in LV mass with increasing body mass index (compared with men, P=0.04 for interaction). Participants with optimal values of these risk factors experienced lesser increases in LV mass over time. Analyses evaluating short-term (4-year) changes in LV mass (2605 unique individuals providing 4494 observations) identified the same key determinants that influenced its long-term trajectory (ie, body mass index, sex, systolic blood pressure, antihypertensive treatment, and smoking).

CONCLUSIONS

Our longitudinal observations on a large community-based sample identified higher blood pressure, excess adiposity, smoking, and diabetes mellitus as fundamental determinants of LV mass tracking over the adult life course. These observations are consistent with the notion that maintenance of optimal levels of these risk factors in midlife will reduce the burden of LV hypertrophy, and possibly heart failure, in older age.

Association between arterial stiffness and variations in oestrogen-related genes

Increased arterial stiffness and wave reflection have been identified as cardiovascular disease risk factors. In light of significant sex differences and the moderate heritability of vascular function measures, we hypothesized that variation in the genes coding for estrogen receptors alpha (ESR1) and beta (ESR2) and aromatase (CYP19A1) is associated with aortic stiffness and pressure wave reflection as measured by noninvasive arterial tonometry. 1261 unrelated Framingham Offspring Study participants who attended the 7^th examination cycle (mean age 62±10 years, 52% women) and had arterial tonometry and genotyping data were included in the study. ANCOVA was used to assess the association of polymorphisms with forward wave amplitude, augmented pressure, augmentation index, carotid-femoral pulse wave velocity, and mean arterial pressure with adjustment for potential confounders. In the sex-pooled analysis, those homozygous for the minor allele at any of four ESR1 variants that were in strong linkage disequilibrium ((TA)_n, rs2077647, rs2234693 and rs9340799) had on average 18% higher augmented pressure and 16% greater augmentation index compared to carriers of one or two major alleles (p=0.0002–0.01). A similar magnitude of association was detected in those homozygous for the common allele at two ESR2 SNPs (p=0.007–0.02). Our results are consistent with the hypothesis that variation in ESR1 and ESR2, but not CYP19A1, is associated with increased wave reflection, which may contribute to previously demonstrated associations between these variants and adverse clinical events. Our findings will need to be replicated in additional cohorts.

Variation in estrogen-related genes associated with cardiovascular phenotypes and circulating estradiol, testosterone, and dehydroepiandrosterone sulfate levels

BACKGROUND

Younger age at the onset of menopause and lower circulating levels of estrogen are risk factors for cardiovascular disease. Several studies have detected associations between variations in genes encoding estrogen receptors alpha (ESR1) and beta (ESR2), and enzyme aromatase (CYP19A1), which regulates the estrogen to testosterone ratio, and cardiovascular phenotypes in the Framingham Heart Study. To explore potential mechanisms by which these gene variants may contribute to cardiovascular disease, we tested the hypothesis that the polymorphisms were associated with endogenous steroid hormone levels.

METHODS

Multiple regression analysis was used to assess the relation between reported polymorphisms and total serum estradiol, testosterone, and dehydroepiandrosterone sulfate levels in 834 men and 687 women who attended the third and fourth Framingham Heart Study examination cycles.

RESULTS

In men, significant associations were detected between CYP19A1 polymorphisms and estradiol and testosterone levels, and the estradiol to testosterone ratio (P ranges 0.0005-0.01). Specifically, carriers of common haplotype rs700518[G]-(TTTA)(n) [L]-rs726547[C] had higher estradiol levels (5% per copy; P = 0.0004), lower testosterone levels (17% per copy; P = 0.036), and a higher estradiol to testosterone ratio (24% per copy; P < 0.0001) compared with the rs700518[A]-(TTTA)(n) [S]-rs726547[C] carriers. In addition, postmenopausal carriers of the ESR2 (CA)(n) long allele and rs1256031 [C] allele had moderately higher estradiol levels (P < or = 0.03). No significant associations with the ESR1 variants were detected.

CONCLUSIONS

Our findings suggest that variations in CYP19A1 correlate with steroid hormone levels in men. Knowledge that a specific carrier status may predispose to altered steroid hormone levels may lead to targeted intervention strategies to reduce health risks in genetically susceptible individuals.