Publications

BACKGROUND: Cardiorespiratory fitness is an integrative measure of cardiometabolic health and predictor of survival, yet little is known about its molecular underpinnings. Small molecule metabolites and lipids are increasingly recognized as exercise-stimulated signaling molecules and candidate molecular transducers of cardiorespiratory fitness.

METHODS: We performed nontargeted liquid chromatography mass spectrometry-based plasma metabolomics in 654 participants (mean age, 35 years; 55% women) from the HERITAGE Family Study (Health, Risk Factors, Exercise Training, and Genetics) who had cardiorespiratory fitness (maximal oxygen uptake [VO2max]) measured by cardiopulmonary exercise testing and underwent 20 weeks of supervised endurance training. Metabolite-VO2max relationships were assessed using linear regression and tested for replication in FHS (Framingham Heart Study) participants who also underwent cardiopulmonary exercise testing. Metabolite relationships with incident all-cause mortality ascertained in JHS (Jackson Heart Study) and MESA (Multi-Ethnic Study of Atherosclerosis) were tested using Cox regression. Experimental studies of cellular respiration and mitochondrial function were performed in C2C12 myotubes.

RESULTS: An unknown mass spectrometry peak (mass-to-charge, 385.3056; retention time, 3.69 minutes) had the strongest, positive relationship with VO2max (mL×kg-1min-1) after adjustment for age, sex, race, and lean body mass (β=1.29; false discovery rate q=5.3×10-6); was identified as N-palmitoyl glutamine (N-pal-gln) using tandem mass spectrometry and bioinformatics; and was confirmed with an authentic chemical standard. The biological role of N-pal-gln has not been described previously. The relationship of N-pal-gln with VO2max was validated in 408 participants from the FHS (β=1.2; P=3.8×10-5), and its levels increased after exercise training (log fold change=0.22; q=5.3×10-12). N-pal-gln levels were inversely associated with all-cause mortality in JHS and MESA (hazard ratio, 0.91 and 0.65 [P=0.029 and P=0.028], respectively). Previous studies have shown that structurally related biochemicals modulate energy homeostasis; thus, we performed mitochondrial experiments. N-pal-gln administration led to a dose-dependent increase in mitochondrial:nuclear DNA ratio compared with control treated cells (15% and 20% increases at 6.5 nM and 26 nM N-pal-gln, respectively [P=0.04 and P=0.02]) and improved bioenergetics (N-pal-gln at 26 nM increased the phosphate:oxygen ratio across ADP concentrations from 0 to 100 μM; ANOVA P=0.0027).

CONCLUSIONS: We identified a novel, lipidated amino acid, N-pal-gln, that is positively associated with VO2max, increases after regular aerobic exercise, and is inversely associated with incident mortality. N-pal-gln stimulates mitochondrial biogenesis and efficiency, demonstrating its potential role as an exercise-stimulated transducer of cardiorespiratory fitness.

BACKGROUND: Systematic profiling of plasma proteins in population studies offers a complementary approach to discovery of novel risk factors and may provide new insights into the causes of coronary heart disease.

METHODS: To explore relationships between the circulating proteome and coronary heart disease (CHD), we evaluated associations of 4780 plasma proteins with incident CHD in the Cardiovascular Health Study (CHS, N=2856, 575 CHD events) and replicated significant associations in the Atherosclerosis Risk in Communities Study (ARIC, N = 10456; 1375 events).

RESULTS: We find that 11 proteins significantly associate with incident CHD after adjusting for risk factors; and eight significantly replicated in ARIC. Several proteins correlate with carotid intimal medial thickness and CHD associations are attenuated in participants without subclinical atherosclerosis. Macrophage metalloelastase (MMP12) is the strongest observed association (Hazard Ratio, 1.31; 95% Confidence Interval, 1.19-1.44). Mendelian randomization (MR) identifies a causal relationship between higher MMP12 and lower CHD (Odds Ratio, OR 0.94) and ischemic stroke (OR 0.90) risk, while reverse MR found that genetic propensity to CHD increased MMP12. Taken together, multivariable MR confirms a direct protective effect of higher plasma MMP12 on CHD risk and a genetic effect of atherosclerosis and CHD on elevating MMP12.

CONCLUSIONS: Proteomic analyses reveal associations with incident CHD and genomic evidence suggests that therapeutic MMP12 inhibition may confer adverse cardiovascular effects.

Measures from affinity-proteomics platforms often correlate poorly, challenging interpretation of protein associations with genetic variants and phenotypes. Here, we examine 2157 proteins measured on both SomaScan 7k and Olink Explore 3072 across 1930 participants with genetic similarity to European, African, East Asian, and Admixed American ancestry references. Inter-platform correlation coefficients for these 2157 proteins follow a bimodal distribution (median r = 0.30). We evaluate protein measure associations with genetic variants, and find approximately 25-30% of the signals on each platform are likely driven by protein-altering variants. We highlight 80 proteins that correlate differently across ancestry groups likely in part due to differing protein-altering variant frequencies by ancestry. Furthermore, adjustment for protein-altering variants with opposite directions of effect by platform improves inter-platform protein measure correlation and results in more concordant genetic and phenotypic associations. Hence, protein-altering variants need to be accounted for across ancestries to facilitate platform-concordant and accurate protein measurement.

PTER (phosphotriesterase-related) is an amidohydrolase that mediates catabolism of the anorexigenic taurine metabolite N-acetyltaurine. However, the structural basis of PTER ligand binding and catalysis remain unknown, limiting our ability to harness this pathway therapeutically. Here we solve crystal structures of a eukaryotic PTER in apo and product-bound forms. These structures uncover an unexpected pocket homology between PTER and histone deacetylase (HDAC) enzymes. We exploit this similarity to engineer a first-in-class substrate-competitive PTER inhibitor called PTERi with nanomolar potency and >100-fold selectivity for PTER over HDACs in vitro. Administration of PTERi to diet-induced obese mice reduces feeding, enhances GLP1-RA (glucagon like peptide 1 receptor agonist)-induced weight loss, and prevents weight regain after GLP1-RA discontinuation. The structure of PTER connects histone and metabolite deacetylation into a parallel conceptual framework and enables proof-of-concept data for pharmacological inhibition of PTER in obesity.

PTER (phosphotriesterase-related) is an amidohydrolase that mediates catabolism of the anorexigenic metabolite N-acetyltaurine. However, the structural basis of PTER ligand binding and catalysis remains unknown, limiting our ability to harness this pathway therapeutically. Here, we solve crystal structures of a eukaryotic PTER in apo and product-bound forms. These structures uncover an unexpected pocket homology between PTER and histone deacetylase (HDAC) enzymes. We exploit this similarity to engineer a substrate-competitive PTER inhibitor called PTERi with nanomolar potency and >100-fold selectivity for PTER over HDACs in vitro. The administration of PTERi to diet-induced obese mice reduces feeding, enhances glucagon-like peptide 1 receptor agonist (GLP1-RA)-induced weight loss, and prevents weight regain after GLP1-RA discontinuation. The structure of PTER connects histone and metabolite deacetylation into a parallel conceptual framework and enables proof-of-concept data for the pharmacological inhibition of PTER in obesity.

While the cardiometabolic benefits of exercise volume and intensity are well established, the clinical significance of exercise timing remains poorly understood, largely due to the limitations of short-term accelerometry. We leveraged minute-level heart rate data from 14,489 participants from the All of Us Research Program to define habitual exercise timing over a one-year period. Compared to daytime exercise, habitual morning exercise was associated with lower odds of coronary artery disease (OR 0.69; CI 0.55-0.87), hypertension (OR 0.82; CI 0.72-0.94), type 2 diabetes (OR 0.70; CI 0.58-0.85), hyperlipidemia (OR 0.79; CI 0.69-0.90), and obesity (OR 0.65; CI 0.55-0.77). These associations were independent of total physical activity volume and remained consistent across hour-of-day analyses, with the lowest risk nadir occurring between 07:00-08:00 for coronary artery disease. These findings suggest that exercise timing may represent a distinct, underappreciated dimension of exercise behavior linked to cardiometabolic health.

BACKGROUND: Knowledge of proteomic mechanisms explaining the link between psychosocial stress and cardiovascular disease is limited. This study aimed to (1) identify plasma proteins associated with psychosocial factors and (2) assess associational pathways between psychosocial factors, identified proteins, and incident cardiovascular disease events in a discovery cohort, JHS (Jackson Heart Study), and 2 replication cohorts, the CHS (Cardiovascular Health Study), and the MESA (Multi-Ethnic Study of Atherosclerosis).

METHODS: JHS participants from exam 1 (2000-2004) with SomaScan 1.3k platform proteomics data were included (n=2143, mean age=55.3). Depressive symptoms and perceived stress scores were measured via the 20-item Center for Epidemiological Studies scale and an 8-item perceived stress scale adapted for the JHS, respectively. Multivariable linear regression models were used to test the association between psychosocial factors and plasma proteins, controlling for age, sex, proteomics batch, and estimated glomerular filtration rate. Bonferroni correction was used for multiple testing (P<3.782×10-5) and meta-analyses were performed across cohorts. Mediation analyses with Cox proportional hazards models were used to evaluate potential proteomic pathways in the association between psychosocial factors and coronary heart disease, heart failure, and stroke in JHS.

RESULTS: Angiopoietin-2 (β=0.014, SE=0.003, P<0.001), contactin-5 (β=-0.017, SE=0.003, P<0.001), growth/differentiation factor 15 or macrophage inhibitory cytokine 1 (β=0.014, SE=0.002, P<0.001), neural cell adhesion molecule 120 (β=-0.016, SE=0.003, P<0.001), and KYNU (kynureninase; β=0.014, SE=0.003, P<0.001) were each significantly associated with depressive symptoms, with angiopoietin-2, contactin-5, macrophage inhibitory cytokine 1, and neural cell adhesion molecule 120 replicating in CHS and MESA. Leukotriene A-4 hydrolase was associated with perceived stress (β=0.0235, SE=0.005, P<0.001). Macrophage inhibitory cytokine 1 partially accounted for the association between depressive symptoms and incident coronary heart disease in JHS (23%; P<0.001).

CONCLUSIONS: Novel associations between psychosocial factors, plasma proteins, and cardiovascular disease were identified in JHS. Circulating proteomic profiles across 3 cardiovascular disease cohorts showed differences in protein concentrations by psychosocial measures. Future investigations should identify additional potentially targetable proteomic mechanisms by which psychosocial factors contribute to disease.

Protein profiling and genetic findings can be integrated to define the genetic architecture of the circulating proteome in chronic diseases. Most self-identified African American (AA) individuals have both African and European genetic ancestry. Admixture mapping can detect genomic association regions in which causal variants exist with substantial differences in allele frequency or effect sizes between genetic ancestries. We performed admixture mapping of the circulating proteome in 1,989 participants from the Jackson Heart Study (JHS), investigating the relation of local African ancestry within genomic regions with levels of circulating proteins. We conditioned protein-local ancestry association models on variants previously found to be associated with those proteins in genome-wide association studies (GWASs). We replicated findings in 196 AA participants from the Multi-Ethnic Study of Atherosclerosis (MESA). 62 proteins were associated with local African ancestry. 21 of 62 remained statistically significant after conditioning on protein-associated variants observed in previous GWASs. 48 of 54 available protein-local ancestry associations were replicated in the MESA. Proteins associated with local African ancestry included chemokines, factors associated with vascular biology and inflammation, and other biologically interesting proteins. Admixture associations unexplained by previously reported protein-associated variants in conditional analysis suggest the existence of causal variants missed by standard GWAS techniques.

Plasma proteomic profiles associated with subclinical somatic mutations in blood cells may offer insights into downstream clinical consequences. Here we explore these patterns in clonal hematopoiesis of indeterminate potential (CHIP), which is linked to several cancer and non-cancer outcomes, including coronary artery disease (CAD). Among 61,833 participants (3881 with CHIP) from TOPMed and UK Biobank (UKB) with blood-based DNA sequencing and proteomic measurements (1,148 proteins by SomaScan in TOPMed and 2917 proteins by Olink in UKB), we identify 32 and 345 proteins from TOPMed and UKB, respectively, associated with CHIP and most prevalent driver genes (DNMT3A, TET2, and ASXL1). These associations show substantial heterogeneity by driver genes, sex, and race, and were enriched for immune response and inflammation pathways. Mendelian randomization in humans, coupled with ELISA in hematopoietic Tet2-/- vs wild-type mice validation, disentangle causal proteomic perturbations from TET2 CHIP. Lastly, we identify plasma proteins shared between CHIP and CAD.

Proteomic profiling may provide insights into new biomarkers and pathways in coronary heart disease (CHD). We profiled ∼1,300 proteins in 1,967 Black individuals in the Jackson Heart Study and found Secreted and Transmembrane Protein 1 (SECTM1), a monocyte chemoattractant, to be our top novel finding associated with incident CHD. We validated our findings in the Cardiovascular Health Study. The top variant (rs116473040) associated with SECTM1 was associated with circulating monocyte percentage of white blood cells in a genomic database. In vivo studies demonstrated that recombinant SECTM1a increased the proportion of proatherogenic Ly6Chi monocytes, suggesting a pathway by which SECTM1 may contribute to CHD.