The Influence of Age and Sex on Genetic Associations with Adult Body Size and Shape : A Large-Scale Genome-Wide Interaction Study

Genome-wide association studies (GWAS) have identified more than 100 genetic variants contributing to BMI, a measure of body size, or waist-to-hip ratio (adjusted for BMI, WHRadjBMI), a measure of body shape. Body size and shape change as people grow older and these changes differ substantially between men and women. To systematically screen for age-and/or sex-specific effects of genetic variants on BMI and WHRadjBMI, we performed meta-analyses of 114 studies (up to 320,485 individuals of European descent) with genome-wide chip and/or Metabochip data by the Genetic Investigation of Anthropometric Traits (GIANT) Consortium. Each study tested the association of up to similar to 2.8M SNPs with BMI and WHRadjBMI in four strata (men 50y, women 50y) and summary statistics were combined in stratum-specific meta-analyses. We then screened for variants that showed age-specific effects (G x AGE), sex-specific effects (G x SEX) or age-specific effects that differed between men and women (G x AGE x SEX). For BMI, we identified 15 loci (11 previously established for main effects, four novel) that showed significant (FDR= 50y). No sex-dependent effects were identified for BMI. For WHRadjBMI, we identified 44 loci (27 previously established for main effects, 17 novel) with sex-specific effects, of which 28 showed larger effects in women than in men, five showed larger effects in men than in women, and 11 showed opposite effects between sexes. No age-dependent effects were identified for WHRadjBMI. This is the first genome-wide interaction meta-analysis to report convincing evidence of age-dependent genetic effects on BMI. In addition, we confirm the sex-specificity of genetic effects on WHRadjBMI. These results may providefurther insights into the biology that underlies weight change with age or the sexually dimorphism of body shape.Peer reviewe

Homocysteine level is associated with aortic stiffness in elderly: cross-sectional results from the B-PROOF study

OBJECTIVE: Homocysteine has been shown to be a more accurate predictor of cardiovascular mortality in very old persons than models based on classical risk factors. Arterial stiffening is a structural abnormality involved in the pathway of cardiovascular disease. We expect this underlying pathophysiology to be a possible explanation for the association between homocysteine and cardiovascular risk, particularly in older populations. METHODS: Baseline cross-sectional data of the B-PROOF study were used to determine associations between homocysteine and outcomes of vascular function and structure. The cardiovascular subgroup of the B-PROOF study was included [n = 560, 58% men, age 72.6 ± 5.5 years, median homocysteine level 14.2 μmol/l (IQR 13.0-16.6)]. We assessed carotid distensibility coefficient, carotid compliance coefficient, aortic pulse wave velocity (aPWV), augmentation index (AIx) and aortic pulse pressure (aortic PP). Associations were tested using linear regression analysis and ANCOVA and were adjusted for possible confounders including age, sex, renal function, mean arterial pressure and heart rate. RESULTS: Ln-homocysteine was strongly associated with aPWV [β 0.005 95% confidence interval (0.001-0.009)]. Furthermore, this association was shown to be age-dependent (P = 0.02) and it was most strong in the upper tertile of age (77-98 years). No significant associations with ln-homocysteine were observed for AIx, carotid distensibility coefficient and compliance coefficient and aortic PP. Sex stratification shows the association between ln-homocysteine and aPWV is only significant in men. CONCLUSION: In older persons, homocysteine is associated with aortic stiffness, predominantly in the oldest old. This suggests that the strong association between homocysteine and cardiovascular mortality in the elderly may be mediated by aortic stiffness

Physical fitness, activity and hand-grip strength are not associated with arterial stiffness in older individuals

Objectives: Whereas evidence exists about the benefits of intensive exercise on cardiovascular outcomes in older adults, data are lacking regarding long-term effects of physical fitness and physical activity on cardiovascular health. Therefore, we aimed to investigate the longitudinal association of physical fitness, physical activity and muscle strength with arterial stiffness measures. Design: a longitudinal follow-up study (2 years) of data from the B-PROOF study. Setting: a subgroup of the B-PROOF study (n=497). Participants: Four hundred ninety-seven participants with a mean age of 72.1 years (SD 5.4) of which 57% was male. Measurements: All performed at baseline and after two-year follow-up. Arterial stiffness was estimated by pulse wave velocity (PWV) measured with applanation tonometry. Furthermore, augmentation index (AIx) and aortic pulse pressure (PP) were assessed. Physical activity was estimated using a validated questionnaire regarding daily activities. Physical fitness was measured with a physical performance score, resulting from a walking, chair-stand and balance test. Muscle strength was assessed with hand-grip strength using a handheld dynamometer. Results: The median performance score was 9.0 [IQR 8.0–11.0], the mean physical activity was 744.4 (SD 539.4) kcal/day and the mean hand-grip strength was 33.1 (SD 10.2) kg. AIx differed between the baseline and follow-up measurement (26.2% (SD 10.1) vs. 28.1% (SD 9.9); p < 0.01), whereas PWV and aortic PP did not. In multivariable linear regression analysis, physical performance, physical activity and hand-grip strength at baseline were not associated with the amount of arterial stiffness after two years of follow-up. Conclusion: Physical fitness, activity and muscle strength were not associated with arterial stiffness. More research is warranted to elucidate the long-term effects of daily and intensive physical activity on arterial stiffness in an elderly population

Homocysteine level is associated with aortic stiffness in elderly: cross-sectional results from the B-PROOF study

OBJECTIVE:: Homocysteine has been shown to be a more accurate predictor of cardiovascular mortality in very old persons than models based on classical risk factors. Arterial stiffening is a structural abnormality involved in the pathway of cardiovascular disease. We expect this underlying pathophysiology to be a possible explanation for the association between homocysteine and cardiovascular risk, particularly in older populations. METHODS:: Baseline cross-sectional data of the B-PROOF study were used to determine associations between homocysteine and outcomes of vascular function and structure. The cardiovascular subgroup of the B-PROOF study was included [n¿=¿560, 58% men, age 72.6¿±¿5.5 years, median homocysteine level 14.2¿µmol/l (IQR 13.0-16.6)]. We assessed carotid distensibility coefficient, carotid compliance coefficient, aortic pulse wave velocity (aPWV), augmentation index (AIx) and aortic pulse pressure (aortic PP). Associations were tested using linear regression analysis and ANCOVA and were adjusted for possible confounders including age, sex, renal function, mean arterial pressure and heart rate. RESULTS:: Ln-homocysteine was strongly associated with aPWV [ß 0.005 95% confidence interval (0.001-0.009)]. Furthermore, this association was shown to be age-dependent (P¿=¿0.02) and it was most strong in the upper tertile of age (77-98 years). No significant associations with ln-homocysteine were observed for AIx, carotid distensibility coefficient and compliance coefficient and aortic PP. Sex stratification shows the association between ln-homocysteine and aPWV is only significant in men. CONCLUSION:: In older persons, homocysteine is associated with aortic stiffness, predominantly in the oldest old. This suggests that the strong association between homocysteine and cardiovascular mortality in the elderly may be mediated by aortic stiffnes

Effects of 2-year vitamin B12 and folic acid supplementation in hyperhomocysteinemic elderly on arterial stiffness and cardiovascular outcomes within the B-PROOF trial

Introduction: Hyperhomocysteinemia is an important cardiovascular risk indicator in the oldest old, and is associated with elevated arterial stiffness in this age group. Since several intervention trials reported a lack of benefit of B-vitamin supplementation on cardiovascular outcomes, we aimed to investigate the effect of B-vitamin supplementation on arterial stiffness and atherosclerosis in hyperhomocysteinemic elderly patients. Methods: The B-PROOF study is a double-blind, randomized controlled trial, including 2919 elderly aged at least 65 years, with hyperhomocysteinemia (12-50 mmol/l), treated with B-vitamins (500 mg vitamin B12 and 400 mg folic acid) or placebo for 2 years. In a subgroup (n=569), the effect of B-vitamins on pulse wave velocity (PWV) was investigated as a measurement of arterial stiffness. To measure atherosclerosis, carotid intima-media thickness (IMT) measures had been used. Incidents of cardiovascular and cerebrovascular events were determined via structured questionnaires, and blood pressure was also measured. Results: Compared to placebo, B-vitamin supplementation lowered serum homocysteine by 3.6 mmol/l (P<0.001). Analysis of covariance showed no effect of supplementation on PWV levels, and this was not different for patients without increased arterial stiffness at baseline. Furthermore, no effect on carotid IMT was observed. Discussion: Vitamin B12 and folic acid supplementation in hyperhomocysteinemic elderly patients have no effect on PWV or carotid IMT. Further research will still be necessary to unravel the effects and pathways of homocysteine-lowering treatment on cardiovascular outcomes

Arterial stiffness is not associated with bone parameters in an elderly hyperhomocysteinemic population

Several studies have observed positive associations between bone disease and cardiovascular disease. A potential common pathway is hyperhomocysteinemia; however, to date, there is a lack of data regarding hyperhomocysteinemic populations. Therefore, we examined both cross-sectionally and longitudinally, whether there is an association between bone parameters and arterial stiffness in a hyperhomocysteinemic population, and investigated the potential common role of homocysteine (hcy) level on these associations. Cross-sectional and longitudinal data of the B-PROOF study were used (n = 519). At both baseline and 2-year follow-up we determined bone measures—incident fractures and history of fractures, bone-mineral density (BMD) and quantitative ultrasound (QUS) measurement. We also measured arterial stiffness parameters at baseline—pulse wave velocity, augmentation index and aortic pulse pressure levels with applanation tonometry. Linear regression analysis was used to examine these associations and we tested for potential interaction of hcy level. The mean age of the study population was 72.3 years and 44.3 % were female. Both cross-sectionally and longitudinally there was no association between arterial stiffness measures and BMD or QUS measurements or with incident fractures (n = 16) within the 2–3 years of follow-up. Hcy level did not modify the associations and adjustment for hcy did not change the results. Arterial stiffness was not associated with bone parameters and fractures, and hcy neither acted as a pleiotropic factor nor as a mediator. The potential association between bone and arterial stiffness is therefore not likely to be driven by hyperhomocysteinemia

B-vitamin levels and genetics of hyperhomocysteinemia are not associated with arterial stiffness

Hyperhomocysteinemia is associated with arterial stiffness, but underlying pathophysiological mechanisms explaining this association are to be revealed. This study was aimed to explore two potential pathways concerning the one-carbon metabolism. A potential causal effect of homocysteine was explored using a genetic risk score reflecting an individual's risk of having a long-term elevated plasma homocysteine level and also associations with B-vitamin levels were investigated. Baseline cross-sectional data of the B-PROOF study were used. In the cardiovascular subgroup (n = 567, 56% male, age 72.6 ± 5.6 yrs) pulse wave velocity (PWV) was determined using applanation tonometry. Plasma concentrations of vitamin B12, folate, methylmalonic acid (MMA) and holo transcobalamin (holoTC) were assessed and the genetic risk score was based on 13 SNPs being associated with elevated plasma homocysteine. Associations were examined using multivariable linear regression analysis. B-vitamin levels were not associated with PWV. The genetic risk score was also not associated with PWV. However, the homocysteine-gene interaction was significant (p < 0.001) in the association of the genetic risk score and PWV. Participants with the lowest genetic risk of having long-term elevated homocysteine levels, but with higher measured homocysteine levels, had the highest PWV levels. Homocysteine is unlikely to be causally related to arterial stiffness, because there was no association with genetic variants causing hyperhomocysteinemia, whereas non-genetically determined hyperhomocysteinemia was associated with arterial stiffness. Moreover, the association between homocysteine and arterial stiffness was not mediated by B-vitamins. Possibly, high plasma homocysteine levels reflect an unidentified factor, that causes increased arterial stiffnes