Peyser, Patricia A.

Background The relationship between mitochondrial DNA copy number (mtDNA CN) and cardiovascular disease remains elusive. Methods and Results We performed cross‐sectional and prospective association analyses of blood‐derived mtDNA CN and cardiovascular disease outcomes in 27 316 participants in 8 cohorts of multiple racial and ethnic groups with whole‐genome sequencing. We also performed Mendelian randomization to explore causal relationships of mtDNA CN with coronary heart disease (CHD) and cardiometabolic risk factors (obesity, diabetes, hypertension, and hyperlipidemia). P <0.01 was used for significance. We validated most of the previously reported associations between mtDNA CN and cardiovascular disease outcomes. For example, 1‐SD unit lower level of mtDNA CN was associated with 1.08 (95% CI, 1.04–1.12; P <0.001) times the hazard for developing incident CHD, adjusting for covariates. Mendelian randomization analyses showed no causal effect from a lower level of mtDNA CN to a higher CHD risk (β=0.091; P =0.11) or in the reverse direction (β=−0.012; P =0.076). Additional bidirectional Mendelian randomization analyses revealed that low‐density lipoprotein cholesterol had a causal effect on mtDNA CN (β=−0.084; P <0.001), but the reverse direction was not significant ( P =0.059). No causal associations were observed between mtDNA CN and obesity, diabetes, and hypertension, in either direction. Multivariable Mendelian randomization analyses showed no causal effect of CHD on mtDNA CN, controlling for low‐density lipoprotein cholesterol level ( P =0.52), whereas there was a strong direct causal effect of higher low‐density lipoprotein cholesterol on lower mtDNA CN, adjusting for CHD status (β=−0.092; P <0.001). Conclusions Our findings indicate that high low‐density lipoprotein cholesterol may underlie the complex relationships between mtDNA CN and vascular atherosclerosis.

Abstract With aging, somatic mutations in hematopoietic stem and progenitor cells (HSPC) can give rise to clonal hematopoiesis of indeterminate potential (CHIP), a premalignant state associated with diverse age-related diseases. Here we report the largest multi-ancestry genome-wide analysis of CHIP to date (N = 1,018,305), including individuals of African (N = 85,978), Admixed American (N = 191,371), East Asian (N = 13,532), European (N = 694,015), and South Asian (N = 13,193) ancestry. Multi-ancestry meta-analyses identified 72 genome-wide significant loci, including 44 novel associations implicating genes such as AFF1 , ATF7IP , ATP8B4 , BCL2 , CEBPA , CYRIA , DNM2 , ELF1 , NKX2-3 , PIK3CB , PRDM16 , RPN1 , TERC , and TRIM4 . Notably, variants at MECOM and PHF20L1 showed opposite allelic effects between DNMT3A - and non- DNMT3A -driven CHIP, highlighting driver-specific germline influences. Implicated loci converge on pathways regulating telomere maintenance, cell-cycle control, hematopoietic transcription, DNA damage response and immune signaling. These findings support a model in which germline variation both expands the HSPC pool and biases clonal selection in a driver-dependent manner, providing a mechanistic basis for inter-individual heterogeneity in CHIP. Phenome-wide association analyses further linked CHIP to hematologic, neoplastic, and circulatory traits, with enrichment across hematopoietic and non-hematopoietic cell types. Together, this work expands the genomic and phenomic landscape of CHIP and reveals germline–somatic interactions that shape clonal evolution during aging.

Human genetic studies support an inverse causal relationship between leukocyte telomere length (LTL) and coronary artery disease (CAD), but directionally mixed effects for LTL and diverse malignancies. Clonal hematopoiesis of indeterminate potential (CHIP), characterized by expansion of hematopoietic cells bearing leukemogenic mutations, predisposes both hematologic malignancy and CAD. TERT (which encodes telomerase reverse transcriptase) is the most significantly associated germline locus for CHIP in genome-wide association studies. Here, we investigated the relationship between CHIP, LTL, and CAD in the Trans-Omics for Precision Medicine (TOPMed) program ( n = 63,302) and UK Biobank ( n = 47,080). Bidirectional Mendelian randomization studies were consistent with longer genetically imputed LTL increasing propensity to develop CHIP, but CHIP then, in turn, hastens to shorten measured LTL (mLTL). We also demonstrated evidence of modest mediation between CHIP and CAD by mLTL. Our data promote an understanding of potential causal relationships across CHIP and LTL toward prevention of CAD.

P10 Coronary artery calcification (CAC), quantified by electron beam computed tomography, provides a measure of extent of coronary atherosclerosis in asymptomatic and symptomatic individuals. It is well recognized that coronary artery disease and CAC are complex processes that are influenced by many genetic and environmental factors. Several aspects of CAC quantity make genetic studies of it particularly challenging. These include the non-normality of CAC frequency distributions and the strong age- and sex-dependence of CAC levels. To search for regions that may contain genes influencing CAC quantity, a genome-wide scan was conducted on a sample enriched for hypertension from the Epidemiology of Coronary Artery Calcification Study. The genome-wide linkage scan was based on 370 anonymous markers spanning the 22 autosomal chromosomes in 29 families. The analysis sample consisted of 20 affected sib-pairs, 8 affected sib-trios and 1 family with 6 affected siblings. Here, affection status was defined as being above the 70th sex- and age-specific percentile based on a reference population. Mode-of-inheritance-free qualitative linkage analysis was used to analyze sib-pair data. Maximum multipoint lod scores were calculated using the computer software Genehunter-2. Weighted analyses were conducted using Holmans “possible triangle” constraint. The overall maximum lod scores were observed on chromosomes 6 (lod=2.22) and 10 (lod=3.24). Additional lod scores greater than 1.0 were observed on chromosomes 2, 14, 15 and 17. These results identify regions that may harbor genes involved in high sex- and age-specific levels of CAC (supported by HL46292).

Objectives: Determine relationships between calcification and cognitive function. Background: Dementia affects over 5.4 million Americans; prevalence will quadruple in the next 50 years. Coronary artery calcification (CAC), a measure of subclinical atherosclerosis, may affect cognitive function through microvascular brain effects. Abdominal aortoiliac calcification (AAC) generally precedes CAC and may provide earlier risk determination. Effects of calcification on cognition have not been studied in African Americans (AA). Methods: The 2008-2011 GENOA CAC cohort consists of AA sibships (n=657, mean age 69 [range 40-98], 74% women, 82% hypertensive) enriched with hypertension from Jackson, MS with computed tomography (CT) Agatston calcification measures. Cognition was assessed in 4 domains: global cognitive function (Mini-Mental State Examination); processing speed (Digit Symbol Substitution and Trail Making A); memory (RAVLT and WAIS-III Incidental Learning); and executive function (Trail Making B). Relationships of cognition (standardized) and calcification (log base 2 scale accounting for skewness) were examined using linear regressions with GEE to account for sibship clustering, adjusting parsimoniously for age, sex, and education. Results: Doublings of CAC were significantly associated with poorer processing speed (ß=-0.049 [-0.072, -0.025] p=0.000) and executive function (ß=-0.037 [-0.070, -0.003] p=0.031) in younger subjects and with poorer global function (ß=-0.0648 [-0.096, -0.020] p=0.000), memory (ß=-0.034 [-0.060, -0.007] p=0.013), and processing speed (ß=-0.051 [-0.076, -0.025] p=0.000) in older subjects. Doublings of AAC were significantly associated with poorer processing speed (ß=-0.0381 [-0.056, -0.020] p=0.000) and executive function (ß=-0.045 [-0.070, -0.020] p=0.000) in younger subjects and poorer processing speed (ß=-0.050 [-0.075, -0.025] p=0.000) in older subjects. Conclusions: Calcification is associated with processing speed in young and old AA with prevalent cardiovascular risk factors and may be differentially associated with other cognitive domains by age. Processing speed in particular may be a domain affected early in the calcification process, warranting further study. This supports existing literature addressing the relationship between calcification and cognitive function in ethnically diverse cohorts. Further studies can focus on the temporal and causal relationships between calcification and cognition across age in AA samples enriched for hypertension to identify predictive factors associated with future cognitive decline.

Dementia affects approximately 5 million people in the United States and cost $183 billion in 2011, with African Americans (AA) experiencing a disproportionate burden of dementia compared to European Americans (EA). Inflammation is considered by many to be a potential mediator in the development of cognitive dysfunction. High sensitivity C-reactive protein (CRP) and tumor necrosis factor-α (TNF-α), increasingly measured by the soluble TNF receptors 1 & 2 (sTNFRI1, sTNFR2), are among the most frequently cited inflammatory markers associated with dementia and are also elevated in vascular disease. Few studies have compared associations of inflammatory markers with cognitive function in EA and AA. We examined the association of CRP, sTNFR1 and sTNFR2 with cognitive function using detailed neuropsychological assessments in the Genetic Epidemiology Network of Arteriopathy (GENOA)-Genetics of Microangiopathic Brain Injury (GMBI) participants, a cohort considered at high risk of vascular disease due to family history (> 2 individuals in sibships with hypertension at age <60 years) and high prevalence rates of hypertension (74%), diabetes (27%), and obesity (51%). Cognitive function was measured across 5 cognitive domains: global cognitive function, processing speed, language, memory, and executive function. In AA, higher sTNFR2 was associated with poorer performance across all five domains. Higher sTNFR1 and CRP were associated with slower processing speed. In EA, higher sTNFR1 was associated with slower processing speed. CRP and sTNFR2 were not associated with cognitive function in EA. Inflammatory markers in this cohort were associated differentially across cognitive domains in AA and EA, and may reflect racial differences in vascular responses to inflammation.

Background Bone-marrow derived progenitor cells (PCs) may play a role in maintaining vascular health by actively repairing damaged endothelium. The purpose of this study in asymptomatic Old Order Amish men (n = 90) without hypertension or diabetes was to determine if PC count, as determined by CD34+ cell count in peripheral blood, was associated with 10-year risk of cardiovascular disease (CVD) and measures of subclinical atherosclerosis. Methods and Results CD34+ cell count by fluorescence-activated cell sorting, coronary artery calcification (CAC) by electron beam computed tomography, and CVD risk factors were obtained. Carotid intimal-medial thickness (CIMT) also was obtained in a subset of 57 men. After adjusting for 10-year CVD risk, CD34+ cell count was significantly associated with CAC quantity ( p =0.03) and CIMT ( p < 0.0001). A 1-unit increase in natural-log transformed CD34+ cell count was associated with an estimated 55.2% decrease (95% CI: −77.8% to −9.3%) in CAC quantity and an estimated 14.3% decrease (95% CI: −20.1% to −8.1%) in CIMT. Conclusions Increased CD34+ cell count was associated with a decrease in extent of subclinical atherosclerosis in multiple arterial beds, independent of 10-year CVD risk. Further investigations of associations of CD34+ cell count with subclinical atherosclerosis in asymptomatic individuals could provide mechanistic insights into the atherosclerotic process.

Objectives To examine associations between specific inflammatory biomarkers and cognitive function in African Americans (AAs) and European Americans (EAs) with prevalent vascular risk factors. Design Cross‐sectional analysis using generalized estimating equations to account for familial clustering; standardized β‐coefficients, adjusted for age, sex, and education are reported. Setting Community cohort study in Jackson, Mississippi, and Rochester, Minnesota. Participants Genetic Epidemiology Network of Arteriopathy (GENOA)–Genetics of Microangiopathic Brain Injury (GMBI) Study participants. Measurements Associations between inflammation (high‐sensitivity C‐reactive protein (CRP), interleukin (IL)‐6, soluble tumor necrosis factor (TNF) receptor 1 and 2 (sTNFR1, sTNFR2)) and cognitive function (global, processing speed, language, memory, and executive function) were examined in AAs and EAs (N = 1,965; aged 26–95, 64% women, 52% AA, 75% with hypertension). Results In AAs, higher sTNFR2 was associated with poorer cognition in all domains (global: −0.11, P = .009; processing speed: −0.11, P < .001; language: −0.08, P = .002; memory: −0.09, P = .008; executive function: −0.07, P = .03); sTNFR1 was associated with slower processing speed (−0.08, P < .001) and poorer executive function (−0.08, P = .008); higher CRP was associated with slower processing speed (−0.04, P = .024), and higher IL6 was associated with poorer executive function (−0.07, P = .02). In EA, only higher sTNFR1 was associated with slower processing speed (−0.05, P = .007). Associations were not found between cognition and sTNFR2, CRP, or IL6 in EA. Conclusion In a population with high vascular risk, adverse associations between inflammation and cognitive function were especially apparent in AAs, primarily involving markers of TNFα activity.

Genetic College Many genomic elements in humans are associated with behavior, including educational attainment. In a genome-wide association study including more than 100,000 samples, Rietveld et al. (p. 1467 , published online 30 May; see the Perspective by Flint and Munafò ) looked for genes related to educational attainment in Caucasians. Small genetic effects at three loci appeared to impact educational attainment.