Replacing device-measured sedentary time with physical activity is associated with lower risk of coronary heart disease regardless of genetic risk.

BACKGROUND: Excess sedentary time (ST) is recognized as an important modifiable risk factor for coronary heart disease (CHD). However, whether the associations of genetic susceptibility with CHD incidence can be modified by replacing wearable-device-measured ST with physical activity (PA) is unknown. OBJECTIVES: To examine the associations of wearable-device-measured ST replaced by PA with incident CHD across strata of genetic susceptibility. METHODS: This study included 77,500 White British (57% female) with valid wrist-worn accelerometry and without prevalent CHD/stroke from UK Biobank. Genetic susceptibility to CHD was quantified through weighted polygenic risk scores for CHD based on 300 single-nucleotide polymorphisms. Wrist-worn accelerometer data were used to derive ST, light PA, and moderate-to-vigorous PA (MVPA). RESULTS: Reallocation of 60 min/day of ST into the same amount of MVPA was associated with approximately 9% lower relative risk of CHD for all participants and across strata of genetic risk: replacement of 1 min/day of ST associated with <1% lower relative risk of CHD. No evidence of interaction (p: 0.784) was found between genetic risk and ST for CHD risk. Reallocating 60 min/day of ST into the same MVPA time was associated with greater absolute CHD risk reductions at high genetic risk (0.27%) versus low genetic risk (0.15%). CONCLUSIONS: Replacing any amount of ST with an equal amount of MVPA time is associated with a lower relative risk of CHD, irrespective of genetic susceptibility to CHD. Reductions in CHD absolute risk for replacing ST with MVPA are greater at high genetic risk versus low genetic risk.

Genetic susceptibility, screen-based sedentary activities and incidence of coronary heart disease.

BACKGROUND: Whether the associations of time spent in screen-based sedentary activities with CHD vary by genetic susceptibility is currently unknown. The objective of this study was to examine the interplay of genetic susceptibility to CHD and two prevalent types of screen-based sedentary activities (television [TV] viewing and computer use) for CHD incidence. METHODS: This prospective cohort study included 373,026 individuals of European ancestry without prevalent CHD/stroke from UK Biobank data. Genetic susceptibility to CHD was assessed using weighted polygenic risk scores, calculated by summing the number of risk-increasing alleles among 300 single-nucleotide polymorphisms, multiplied by their corresponding effect estimates. TV viewing and computer use were assessed through touch-screen questionnaires. CHD incidence (n=9185) was adjudicated over a median 12.6-year follow-up. RESULTS: Compared with ≥4h/day of TV viewing, the hazard ratio of CHD was 0.84 (95% confidence interval [CI] 0.79-0.90) and 0.94 (0.90-0.99) for ≤1h/day and 2-3h/day of TV viewing, respectively, after adjusting for confounders including the genetic risk. CHD hazards were higher for medium and high genetic risk than for low genetic risk. Across all levels of genetic risk including high-genetic risk, ≤1h/day of TV viewing had lower CHD hazards, compared with ≥4h/day: no evidence of interaction between genetic risk and TV viewing (p value: 0.362). Estimates of the population attributable fraction (PAF) suggested that 10.9% (95% CI 6.1-15.3%) of CHD could be prevented if TV viewing time were reduced to ≤1h/day, assuming causality. The PAF values were relatively larger for medium-to-high genetic risk than for low genetic risk, although the CIs were wide and overlapping. No associations were observed for computer use. CONCLUSIONS: Less TV viewing time was associated with lower CHD risk independently of genetic risk. Clinical trials targeted at individuals with high genetic susceptibility should consider reducing TV viewing as as a behavioural target for prevention of an early onset of cardiovascular events.

Estradiol concentrations in young healthy US versus Chinese men.

OBJECTIVES: The role of estrogens among men has rarely been explicitly considered. We examined differences in total, free, and bioavailable estradiol (Bio E) between young men from the United States (US) and the most economically developed part of China, that is, Hong Kong (HK). METHODS: Cross-sectional analysis was conducted based on 365 young men from the Third National Health and Nutrition Examination Survey in the US and 299 young Chinese men. All participants were aged from 18 to 29 years. Main outcome measures were total estradiol (E2) and calculated Bio E and free estradiol (FE). RESULTS: In both young US and Chinese men, E2 concentrations peaked at ages 25-29 years, at 43.3 pg/ml [95% confidence interval (CI) 41.9-44.8] in US men and 29.0 pg/ml (95% CI 26.2-32.0) in Chinese men. After adjustment for age and ethnicity, in all participants, US men had higher average concentrations of E2 [39.0 (95% CI 38.6-39.4) versus 28.3 (95% CI 28.3-28.4) pg/ml], FE [72.9 (95% CI 72.7-73.7) versus 56.8 (95% CI 56.6-56.9) ng/dl], and Bio E [17.9 (95% CI 17.7-18.1) versus 14.9 (95% CI 14.8-14.9) pg/ml] than HK men. Further adjustment for height or body mass index did not change the results. CONCLUSIONS: Estradiol, and free and Bio E concentrations are much lower in young healthy Chinese men than US men. However, these findings based on comparison between the two assays in the two different locations need further confirmation.

Effects of putative metformin targets on phenotypic age and leukocyte telomere length: a mendelian randomisation study using data from the UK Biobank.

BACKGROUND: Metformin, a first-line medication for type 2 diabetes, might also have a protective effect against ageing-related diseases, but so far little experimental evidence is available. We sought to assess the target-specific effect of metformin on biomarkers of ageing in the UK Biobank. METHODS: In this drug target mendelian randomisation study, we assessed the target-specific effect of four putative targets of metformin (AMPK, ETFDH, GPD1, and PEN2), involving ten genes. Genetic variants with evidence of causation of gene expression, glycated haemoglobin A1c (HbA1c), and colocalisation were used as instruments mimicking the target-specific effect of metformin via HbA1c lowering. The biomarkers of ageing considered were phenotypic age (PhenoAge) and leukocyte telomere length. To triangulate the evidence, we also assessed the effect of HbA1c on the outcomes using a polygenic mendelian randomisation design and assessed the effect of metformin use on these outcomes using a cross-sectional observational design. FINDINGS: GPD1-induced HbA1c lowering was associated with younger PhenoAge (ß -5·26, 95% CI -6·69 to -3·83) and longer leukocyte telomere length (ß 0·28, 0·03 to 0·53), and AMPKγ2 (PRKAG2)-induced HbA1c lowering was associated with younger PhenoAge (ß -4·88, -7·14 to -2·62) but not with longer leukocyte telomere length. Genetically predicted HbA1c lowering was associated with younger PhenoAge (ß -0·96 per SD lowering of HbA1c, 95% CI -1·19 to -0·74) but not associated with leukocyte telomere length. In the propensity score matched analysis, metformin use was associated with younger PhenoAge (ß -0·36, 95% CI -0·59 to -0·13) but not with leukocyte telomere length. INTERPRETATION: This study provides genetic validation evidence that metformin might promote healthy ageing via targets GPD1 and AMPKγ2 (PRKAG2), and the effect could be in part due to its glycaemic property. Our findings support further clinical research into metformin and longevity. FUNDING: Healthy Longevity Catalyst Award, National Academy of Medicine, and Seed Fund for Basic Research, The University of Hong Kong.

Mendelian randomization analysis of vitamin D in the secondary prevention of hypertensive-diabetic subjects: role of facilitating blood pressure control.

BACKGROUND: Vitamin D (Vit-D) promotes vascular repair and its deficiency is closely linked to the development of type 2 diabetes mellitus (T2DM) and hypertension. Whether genetially predicted vitamin D status (serological 25-hydroxyvitamin D [25(OH)D]) confers secondary protection against cardiovascular diseases (CVD) among high-risk hypertensive-diabetic subjects was unknown. METHODS: This is a prospective, individual-data, two-sample Mendelian randomization study. We interrogated 12 prior GWAS-detected SNPs of comprehensive Vit-D mechanistic pathways using high-throughput exome chip analyses in a derivation subcohort (n = 1460) and constructed a genetic risk score (GRS) (rs2060793, rs4588, rs7041; F-statistic = 32, P < 0.001) for causal inference of comprehensive CVD hard clinical endpoints in an independent sample of hypertensive subjects (n = 3746) with prevailing co-morbid T2DM (79%) and serological 25(OH)D deficiency [< 20 ng/mL] 45%. RESULTS: After 55.6 ± 28.9 months, 561 (15%) combined CVD events including myocardial infarction, unstable angina, ischemic stroke, congestive heart failure, peripheral vascular disease, and cardiovascular death had occurred. Kaplan-Meier analysis showed that genetically predicted reduced vitamin D status was associated with reduced event-free survival from combined CVD events (log-rank = 13.5, P = 0.001). Multivariate-adjusted per-allele increase in GRS predicted reduced combined CVD events (HR = 0.90 [0.84 to 0.96], P = 0.002). Mendelian randomization indicates that increased Vit-D exposure, leveraged through each 1 ng/mL genetically instrumented rise of serum Vit-D, protects against combined CVD events (Wald's estimate: OR = 0.86 [95%CI 0.75 to 0.95]), and myocardial infarction (OR = 0.76 [95%CI 0.60 to 0.90]). Furthermore, genetically predicted increase in Vit-D status ameliorates risk of deviation from achieving guideline-directed hypertension control (JNC-8: systolic target < 150 mmHg) (OR = 0.89 [95%CI 0.80 to 0.96]). CONCLUSIONS: Genetically predicted increase in Vit-D status [25(OH)D] may confer secondary protection against incident combined CVD events and myocardial infarction in a hypertensive-diabetic population where serological 25(OH)D deficiency is common, through facilitating blood pressure control.

Platelet Glycoprotein Ib α-Chain as a Putative Therapeutic Target for Juvenile Idiopathic Arthritis: A Mendelian Randomization Study.

OBJECTIVE: To ascertain the role of platelet glycoprotein Ib α-chain (GPIbα) plasma protein levels in cardiovascular, autoimmune, and autoinflammatory diseases and whether its effects are mediated by platelet count. METHODS: We performed a two-sample Mendelian randomization (MR) study, using both a cis-acting protein quantitative trait locus (cis-pQTL) and trans-pQTL near the GP1BA and BRAP genes as instruments. To assess if platelet count mediated the effect, we then performed a two-step MR study. Putative associations (GPIbα/platelet count/disease) detected by MR analyses were subsequently assessed using multiple-trait colocalization analyses. RESULTS: After correction for multiple testing (Bonferroni-corrected threshold P ≤ 2 × 10-3 ), GPIbα, instrumented by either cis-pQTL or trans-pQTL, was causally implicated with an increased risk of oligoarticular and rheumatoid factor (RF)-negative polyarticular juvenile idiopathic arthritis (JIA). These effects of GPIbα appeared to be mediated by platelet count and were supported by strong evidence of colocalization (probability of all 3 traits sharing a common causal variant ≥0.80). GPIbα instrumented by cis-pQTL did not appear to affect cardiovascular risk, although the GPIbα trans-pQTL was associated with an increased risk of cardiovascular diseases and autoimmune diseases but a decreased risk of autoinflammatory diseases, suggesting that this trans-acting instrument operates through other pathways. CONCLUSION: The role of platelets in thrombosis is well-established; however, our findings provide some novel genetic evidence that platelets may be causally implicated in the development of oligoarticular and RF-negative polyarticular JIA, and indicate that GPIbα may serve as a putative therapeutic target for these JIA subtypes.

Genetically predicted testosterone and systemic inflammation in men: a separate-sample Mendelian randomization analysis in older Chinese men.

OBJECTIVES: Observationally, testosterone is negatively associated with systemic inflammation, but this association is open to both residual confounding and reverse causality. Large-scale randomized controlled trials (RCTs), assessing exogenous effects, are presently unavailable. We examined the association of endogenous testosterone with well-established systemic inflammatory markers (white blood cell, granulocyte, lymphocyte and high-sensitivity C-reactive protein (hsCRP)) using a separate-sample Mendelian randomization analysis to minimize reverse causality. METHODS: A genetic prediction rule for serum testosterone was developed in 289 young Chinese men with mean age of 21.0, using selected testosterone-related SNPs (rs10046, rs1008805 and rs1256031). Multivariable linear regression was used to examine the association of genetically predicted serum testosterone with inflammatory markers among 4,212 older Chinese men from the Guangzhou Biobank Cohort Study. RESULTS: Genetically predicted testosterone was unrelated to white blood cell count (-0.01 109/L per nmol/L testosterone, 95% confidence interval (CI) -0.05 to 0.04), granulocyte count (-0.02 109/L, 95% CI -0.06 to 0.02), lymphocyte count (0.005 109/L, 95% CI -0.01 to 0.02) and hsCRP (-0.05 mg/L, 95% CI -0.15 to 0.06). CONCLUSION: Our findings did not corroborate any anti-inflammatory effects of testosterone or corresponding potentially protective effects of testosterone on chronic diseases resulting from reduced low-grade systemic inflammation.