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In addition to their fundamental role in clearance, the kidneys release select molecules into the circulation, but whether any of these anabolic functions provides insight on kidney health is unknown. Using aptamer-based proteomics, we characterized arterial (A)-to-renal venous (V) gradients for >1,300 proteins in 22 individuals who underwent invasive sampling. Although most of the proteins that changed significantly decreased from A to V, consistent with renal clearance, several were found to increase, the most significant of which was testican-2. To assess the clinical implications of these physiologic findings, we examined proteomic data in the Jackson Heart Study (JHS), an African-American cohort (n = 1,928), with replication in the Framingham Heart Study (FHS), a White cohort (n = 1,621). In both populations, testican-2 had a strong, positive correlation with estimated glomerular filtration rate (eGFR). In addition, higher baseline testican-2 levels were associated with a lower rate of eGFR decline in models adjusted for age, gender, hypertension, type 2 diabetes, body mass index, baseline eGFR, and albuminuria. Glomerular expression of testican-2 in human kidneys was demonstrated by immunohistochemistry, immunofluorescence, and electron microscopy, while single-cell RNA sequencing of human kidneys showed expression of the cognate gene, SPOCK2, exclusively in podocytes. In vitro, testican-2 increased glomerular endothelial tube formation and motility, raising the possibility that its secretion has a functional role within the glomerulus. Taken together, our findings identify testican-2 as a podocyte-derived biomarker of kidney health and prognosis.

Heart failure (HF) is a major public health problem characterized by inability of the heart to maintain sufficient output of blood. The systematic characterization of circulating proteins across different stages of HF may provide pathophysiological insights and identify therapeutic targets. Here we report application of aptamer-based proteomics to identify proteins associated with prospective HF incidence in a population-based cohort, implicating modulation of immunological, complement, coagulation, natriuretic and matrix remodeling pathways up to two decades prior to overt disease onset. We observe further divergence of these proteins from the general population in advanced HF, and regression after heart transplantation. By leveraging coronary sinus samples and transcriptomic tools, we describe likely cardiac and specific cellular origins for several of the proteins, including Nt-proBNP, thrombospondin-2, interleukin-18 receptor, gelsolin, and activated C5. Our findings provide a broad perspective on both cardiac and systemic factors associated with HF development., Heart failure is a major health issue worldwide. Here, Egerstedt et al. perform proteomic profiling of human plasma at different stages of heart failure, providing a comprehensive analysis of changes in the plasma proteome during disease progression.

Anthracyclines and HER2-targeted antibodies are very effective for the treatment of breast cancer, but their use is limited by cardiotoxicity. In this nested case-control study, we assessed the role of intermediary metabolism in 38 women with breast cancer treated with anthracyclines and trastuzumab. Using targeted mass spectrometry to measure 71 metabolites in the plasma, we identified changes in citric acid and aconitic acid that differentiated patients who developed cardiotoxicity from those who did not. In patients with cardiotoxicity, the magnitude of change in citric acid at three months correlated with the change in left ventricular ejection fraction (LVEF) and absolute LVEF at nine months. Patients with cardiotoxicity also demonstrated more pronounced changes in purine and pyrimidine metabolism. Early metabolic changes may therefore provide insight into the mechanisms associated with the development of chemotherapy-associated cardiotoxicity.

Elevated levels of aldosterone are a modifiable contributor to clinical worsening in heart failure with reduced ejection fraction (HFrEF). Endothelin-1 (ET-1), which is increased in HFrEF, induces pulmonary endothelial aldosterone synthesis in vitro. However, whether transpulmonary aldosterone release occurs in humans or aldosterone relates to functional capacity in HFrEF is not known. Therefore, we aimed to characterize ET-1 and transpulmonary aldosterone levels in HFrEF and determine if aldosterone levels relate to peak volume of oxygen uptake (pVO2).Data from 42 consecutive HFrEF patients and 18 controls referred for invasive cardiopulmonary exercise testing were analyzed retrospectively.Radial ET-1 levels (median [interquartile range]) were higher in HFrEF patients compared with controls (17.5 [11.5-31.4] vs 11.5 [4.4-19.0] pg/ml, p = 0.04). A significant ET-1 transpulmonary gradient (pulmonary arterial [PA] - radial arterial levels) was present in HFrEF (p0.001) but not in controls (p = 0.24). Compared with controls, aldosterone levels (median [interquartile range]) were increased in HFrEF patients in the PA (364 [250-489] vs 581 [400-914] ng/dl, p0.01) and radial compartments (366 [273-466] vs 702 [443-1223] ng/dl, p0.001). Akin to ET-1, a transpulmonary increase (median [interquartile range]) in aldosterone concentration was also observed between controls and HFrEF patients at rest (7.5 [-54 to 40] vs 61.6 [-13.6 to 165] ng/dl, p = 0.01) and peak exercise (-20.7 [-39.6 to 79.1] vs 25.8 [-29.2 to 109.3] ng/dl, p = 0.02). The adjusted pVO2 correlated inversely with aldosterone levels at peak activity in the PA (r = -0.31, p = 0.01) and radial artery (r = -0.32, p = 0.01).These data provide preliminary evidence in support of increased transpulmonary aldosterone levels in HFrEF and suggest an inverse relationship between circulating aldosterone and pVO2. Future prospective studies are needed to characterize the functional effects of transpulmonary and circulating aldosterone on cardiac reserve capacity in HFrEF.

Background Pulmonary hypertension and associated right ventricular (RV) dysfunction are important determinants of morbidity and mortality, which are optimally characterized by invasive hemodynamic measurements. Objectives This study sought to determine whether metabolite profiling could identify plasma signatures of right ventricular-pulmonary vascular (RV-PV) dysfunction. Methods We measured plasma concentrations of 105 metabolites using targeted mass spectrometry in 71 individuals (discovery cohort) who underwent comprehensive physiological assessment with right-sided heart catheterization and radionuclide ventriculography at rest and during exercise. Our findings were validated in a second cohort undergoing invasive hemodynamic evaluations (n = 71), as well as in an independent cohort with or without known pulmonary arterial (PA) hypertension (n = 30). Results In the discovery cohort, 21 metabolites were associated with 2 or more hemodynamic indicators of RV-PV function (i.e., resting right atrial pressure, mean PA pressure, pulmonary vascular resistance [PVR], and PVR and PA pressure-flow response [ΔPQ] during exercise). We identified novel associations of RV-PV dysfunction with circulating indoleamine 2,3-dioxygenase (IDO)–dependent tryptophan metabolites (TMs), tricarboxylic acid intermediates, and purine metabolites and confirmed previously described associations with arginine–nitric oxide metabolic pathway constituents. IDO-TM levels were inversely related to RV ejection fraction and were particularly well correlated with exercise PVR and ΔPQ. Multisite sampling demonstrated transpulmonary release of IDO-TMs. IDO-TMs also identified RV-PV dysfunction in a validation cohort with known risk factors for pulmonary hypertension and in patients with established PA hypertension. Conclusions Metabolic profiling identified reproducible signatures of RV-PV dysfunction, highlighting both new biomarkers and pathways for further functional characterization.

Clinical practice guidelines currently endorse a reliance on clinical symptoms of overt left ventricular (LV) failure to time aortic valve replacement for severe aortic stenosis; however, delayed aortic valve replacement can result in irreversible LV injury and adverse outcomes. Blood metabolomic signatures possess prognostic value in heart failure; this study assesses whether they are informative in aortic stenosis.To evaluate the value of metabolomic signatures in reflecting the extent of maladaptive LV remodeling in patients with end-stage aortic stenosis undergoing transcatheter aortic valve replacement, and to assess whether this procedure reverses metabolomic aberrations.This study of 44 patients with symptomatic severe aortic stenosis who underwent transfemoral transcatheter aortic valve replacement at a single-center tertiary care hospital. Liquid chromatography-mass spectrometry-based metabolomic profiling was performed on blood samples collected before and 24 hours after the procedure, and analyses were conducted to identify metabolites related to the measures of LV remodeling.We evaluated LV ejection fraction, LV mass index, and relative wall thickness, as well as levels of the acylcarnitines C16, C18:1, C18:2, C18, C26, choline, and kynurenine.We enrolled 44 patients with severe aortic stenosis with a mean (SD) age of 81.9 (8.5) years, of whom 23 (52%) were women. The mean (SD) LV ejection fraction was 56.7% (18.2%), mean (SD) LV mass index was 117.3 (41.4) g/m2, and relative wall thickness was 0.53 (0.14). The mean β values of acylcarnitines C16, C18:1, C18:2, C18, and C26 were independently associated with LV mass index (C16: mean, 19.24; 95% CI, 5.48-33.01; P = .008; C18:1: mean, 26.18; 95% CI, 14.04-38.32; P 1.0 × 10-4; C18:2: mean, 17.42; 95% CI, 3.40-31.43; P = .02; C18: mean, 25.25; 95% CI, 10.91-39.58; P = .001; C26: mean, 19.93; 95% CI, 4.41-35.45; P = .01), even after adjustments for age, sex, diabetes status, renal function, and B-type natriuretic peptide (BNP). Circulating levels of C18:2 acylcarnitine were associated with LV ejection fraction before and after multivariable adjustment (mean, -6.11; 95% CI, -10.88 to 1.34; P = .01). Blood metabolite levels did not independently relate to relative wall thickness. Within 24 hours of transcatheter aortic valve replacement, circulating levels of C16 decreased by 30.2% (P = 7.3 × 10-6), C18:1 by 42.7% (P = 3.7 × 10-8), C18:2 by 37.3% (P = 5.1 × 10-6), and C18 by 38.3% (P = 3.4 × 10-5).In symptomatic patients with severe aortic stenosis undergoing transcatheter aortic valve replacement, circulating levels of long-chain acylcarnitines were independently associated with measures of maladaptive LV remodeling, and metabolic perturbations lessened after procedure completion. Further efforts are needed to determine the clinical applicability of these novel biomarkers.

Background: Emerging proteomic technologies using novel affinity-based reagents allow for efficient multiplexing with high-sample throughput. To identify early biomarkers of myocardial injury, we recently applied an aptamer-based proteomic profiling platform that measures 1129 proteins to samples from patients undergoing septal alcohol ablation for hypertrophic cardiomyopathy, a human model of planned myocardial injury. Here, we examined the scalability of this approach using a markedly expanded platform to study a far broader range of human proteins in the context of myocardial injury. Methods: We applied a highly multiplexed, expanded proteomic technique that uses single-stranded DNA aptamers to assay 4783 human proteins (4137 distinct human gene targets) to derivation and validation cohorts of planned myocardial injury, individuals with spontaneous myocardial infarction, and at-risk controls. Results: We found 376 target proteins that significantly changed in the blood after planned myocardial injury in a derivation cohort (n=20; P P 90% were directionally consistent and reached nominal significance in the validation cohort. Among the validated proteins that were increased within 1 hour after planned myocardial injury, 29 were also elevated in patients with spontaneous myocardial infarction (n=63; P 0 subunit component is a vasoactive peptide on its release from cells. Last, we performed aptamer-affinity enrichment coupled with mass spectrometry to technically verify aptamer specificity for a subset of the new biomarkers. Conclusions: Our results demonstrate the feasibility of large-scale aptamer multiplexing at a level that has not previously been reported and with sample throughput that greatly exceeds other existing proteomic methods. The expanded aptamer-based proteomic platform provides a unique opportunity for biomarker and pathway discovery after myocardial injury.

Background Acute kidney injury ( AKI ) occurs commonly after transcatheter aortic valve replacement ( TAVR ) and is associated with markedly increased postoperative mortality. We previously identified plasma metabolites predictive of incident chronic kidney disease, but whether metabolite profiles can identify those at risk of AKI is unknown. Methods and Results We performed liquid chromatography–mass spectrometry–based metabolite profiling on plasma from patients undergoing TAVR and subjects from the community‐based Framingham Heart Study (N=2164). AKI was defined by using the Valve Academic Research Consortium‐2 criteria. Of 44 patients (mean age 82±9 years, 52% female) undergoing TAVR , 22 (50%) had chronic kidney disease and 9 (20%) developed AKI . Of 85 metabolites profiled, we detected markedly concordant cross‐sectional metabolic changes associated with chronic kidney disease in the hospital‐based TAVR and Framingham Heart Study cohorts. Baseline levels of 5‐adenosylhomocysteine predicted AKI after TAVR , despite adjustment for baseline glomerular filtration rate (odds ratio per 1‐ SD increase 5.97, 95% CI 1.62–22.0; P =0.007). Of the patients who had AKI , 6 (66.7%) subsequently died, compared with 3 (8.6%) deaths among those patients who did not develop AKI ( P =0.0008) over a median follow‐up of 7.8 months. 5‐adenosylhomocysteine was predictive of all‐cause mortality after TAVR (hazard ratio per 1‐ SD increase 2.96, 95% CI 1.33–6.58; P =0.008), independent of baseline glomerular filtration rate. Conclusions In an elderly population with severe aortic stenosis undergoing TAVR , metabolite profiling improves the prediction of AKI. Given the multifactorial nature of AKI after TAVR , metabolite profiles may identify those patients with reduced renal reserve.

Huntington's disease (HD) is a neurodegenerative disease caused by expansion of a polyglutamine tract within the huntingtin protein. Transcriptional dysregulation has been implicated in HD pathogenesis; recent evidence suggests a defect in Sp1-mediated transcription. We used chromatin immunoprecipitation (ChIP) assays followed by real-time PCR to quantify the association of Sp1 with individual genes. We find that, despite normal protein levels and normal to increased overall nuclear binding activity, Sp1 has decreased binding to specific promoters of susceptible genes in transgenic HD mouse brain, in striatal HD cells, and in human HD brain. Genes whose mRNA levels are decreased in HD have abnormal Sp1-DNA binding, whereas genes with unchanged mRNA levels have normal levels of Sp1 association. Moreover, the altered binding seen with Sp1 is not found with another transcription factor, NF-Y. These findings suggest that mutant huntingtin dissociates Sp1 from target promoters, inhibiting transcription of specific genes.

Elevated pulmonary arterial aldosterone levels (PA-ALDO) are associated with decreased exercise capacity in pulmonary hypertension patients despite normal left ventricular (LV) function. Pulmonary endothelial ALDO synthesis occurs in vitro under experimental conditions akin to LV systolic heart failure (HFrEF); however, the relevance of PA-ALDO to the clinical profile of HFrEF is not known. Therefore, we analyzed PA and radial arterial plasma in control and HFrEF patients to assess for transpulmonary ALDO release and determine if circulating ALDO is related to hemodynamic indices of cardiac reserve capacity during exercise. Data from 20 controls (51 ± 13 y, 13 females, LVEF=0.66 ± 0.9, volume of oxygen uptake at peak exercise [pVO2]=94.1 ± 11.5 % predicted) and 42 consecutive HFrEF patients (57 ± 13 y, 20 females, LVEF=0.36 ± 0.1, pVO2=47.1 ± 2.5 % predicted) undergoing invasive cardiopulmonary exercise testing were analyzed. At rest, HFrEF patients had increased PA-ALDO (714 ± 450 vs. 380 ± 187 ng/dl, P

Background: It is sometimes challenging to distinguish hypertrophic cardiomyopathy (HCM) from other cardiac conditions such as hypertensive heart disease. The present study utilized metabolite profiling, a novel technology that measures serum concentrations of biochemical substances, to distinguish

We developed a pipeline to integrate the proteomic technologies used from the discovery to the verification stages of plasma biomarker identification and applied it to identify early biomarkers of cardiac injury from the blood of patients undergoing a therapeutic, planned myocardial infarction (PMI) for treatment of hypertrophic cardiomyopathy. Sampling of blood directly from patient hearts before, during and after controlled myocardial injury ensured enrichment for candidate biomarkers and allowed patients to serve as their own biological controls. LC-MS/MS analyses detected 121 highly differentially expressed proteins, including previously credentialed markers of cardiovascular disease and >100 novel candidate biomarkers for myocardial infarction (MI). Accurate inclusion mass screening (AIMS) qualified a subset of the candidates based on highly specific, targeted detection in peripheral plasma, including some markers unlikely to have been identified without this step. Analyses of peripheral plasma from controls and patients with PMI or spontaneous MI by quantitative multiple reaction monitoring mass spectrometry or immunoassays suggest that the candidate biomarkers may be specific to MI. This study demonstrates that modern proteomic technologies, when coherently integrated, can yield novel cardiovascular biomarkers meriting further evaluation in large, heterogeneous cohorts.

Dyslipidemia is an independent risk factor for type 2 diabetes, although exactly which of the many plasma lipids contribute to this remains unclear. We therefore investigated whether lipid profiling can inform diabetes prediction by performing liquid chromatography/mass spectrometry-based lipid profiling in 189 individuals who developed type 2 diabetes and 189 matched disease-free individuals, with over 12 years of follow up in the Framingham Heart Study. We found that lipids of lower carbon number and double bond content were associated with an increased risk of diabetes, whereas lipids of higher carbon number and double bond content were associated with decreased risk. This pattern was strongest for triacylglycerols (TAGs) and persisted after multivariable adjustment for age, sex, BMI, fasting glucose, fasting insulin, total triglycerides, and HDL cholesterol. A combination of 2 TAGs further improved diabetes prediction. To explore potential mechanisms that modulate the distribution of plasma lipids, we performed lipid profiling during oral glucose tolerance testing, pharmacologic interventions, and acute exercise testing. Levels of TAGs associated with increased risk for diabetes decreased in response to insulin action and were elevated in the setting of insulin resistance. Conversely, levels of TAGs associated with decreased diabetes risk rose in response to insulin and were poorly correlated with insulin resistance. These studies identify a relationship between lipid acyl chain content and diabetes risk and demonstrate how lipid profiling could aid in clinical risk assessment.

ESRD is a state of small-molecule disarray. We applied liquid chromatography/tandem mass spectrometry-based metabolite profiling to survey350 small molecules in 44 fasting subjects with ESRD, before and after hemodialysis, and in 10 age-matched, at-risk fasting control subjects. At baseline, increased levels of polar analytes and decreased levels of lipid analytes characterized uremic plasma. In addition to confirming the elevation of numerous previously identified uremic toxins, we identified several additional markers of ESRD, including dicarboxylic acids (adipate, malonate, methylmalonate, and maleate), biogenic amines, nucleotide derivatives, phenols, and sphingomyelins. The pattern of lipids was notable for a universal decrease in lower-molecular-weight triacylglycerols, and an increase in several intermediate-molecular-weight triacylglycerols in ESRD compared with controls; standard measurement of total triglycerides obscured this heterogeneity. These observations suggest disturbed triglyceride catabolism and/or beta-oxidation in ESRD. As expected, the hemodialysis procedure was associated with significant decreases in most polar analytes. Unexpected increases in several metabolites, however, indicated activation of a broad catabolic program, including glycolysis, lipolysis, ketosis, and nucleotide breakdown. In summary, this study demonstrates the application of metabolite profiling to identify markers of ESRD, provide perspective on uremic dyslipidemia, and broaden our understanding of the biochemical effects of hemodialysis.

Emerging metabolomic tools have created the opportunity to establish metabolic signatures of myocardial injury. We applied a mass spectrometry–based metabolite profiling platform to 36 patients undergoing alco-hol septal ablation treatment for hypertrophic obstructive cardiomyopathy, a human model of planned myo-cardial infarction (PMI). Serial blood samples were obtained before and at various intervals after PMI, with patients undergoing elective diagnostic coronary angiography and patients with spontaneous myocardial infarction (SMI) serving as negative and positive controls, respectively. We identified changes in circulating levels of metabolites participating in pyrimidine metabolism, the tricarboxylic acid cycle and its upstream con-tributors, and the pentose phosphate pathway. Alterations in levels of multiple metabolites were detected as early as 10 minutes after PMI in an initial derivation group and were validated in a second, independent group of PMI patients. A PMI-derived metabolic signature consisting of aconitic acid, hypoxanthine, trimethylamine N-oxide, and threonine differentiated patients with SMI from those undergoing diagnostic coronary angiogra-phy with high accuracy, and coronary sinus sampling distinguished cardiac-derived from peripheral metabolic changes. Our results identify a role for metabolic profiling in the early detection of myocardial injury and sug-gest that similar approaches may be used for detection or prediction of other disease states.

Transcriptional dysregulation is a central pathogenic mechanism in Huntington's disease (HD); HD and transgenic mouse models of HD demonstrate down-regulation of specific genes at the level of mRNA expression. Furthermore, neuronal intranuclear inclusions (NIIs) have been identified in the brains of R6/2 mice and HD patients. One possibility is that NIIs contribute to transcriptional dysregulation by sequestering transcription factors. We therefore assessed the relationship between NIIs and transcriptional dysregulation in the R6/2 mouse, using double-label in situ hybridization combined with immunohistochemistry, and laser capture microdissection combined with quantitative real-time PCR. There was no difference in transcript levels of specific genes between NII-positive and NII-negative neurons. These results demonstrate that NIIs do not cause decreases in D2, PPE and PSS mRNA levels in R6/2 striatum and therefore are not involved in the down-regulation of these specific genes in this HD model. In addition, these observations argue against the notion that NIIs protect against transcriptional dysregulation in HD.

Recent advances in proteomic technologies have made high-throughput profiling of low-abundance proteins in large epidemiological cohorts increasingly feasible. We investigated whether aptamer-based proteomic profiling could identify biomarkers associated with future development of type 2 diabetes (T2DM) beyond known risk factors. We identified dozens of markers with highly significant associations with future T2DM across 2 large longitudinal cohorts (n = 2839) followed for up to 16 years. We leveraged proteomic, metabolomic, genetic, and clinical data from humans to nominate 1 specific candidate to test for potential causal relationships in model systems. Our studies identified functional effects of aminoacylase 1 (ACY1), a top protein association with future T2DM risk, on amino acid metabolism and insulin homeostasis in vitro and in vivo. Furthermore, a loss-of-function variant associated with circulating levels of the biomarker WAP, Kazal, immunoglobulin, Kunitz, and NTR domain–containing protein 2 (WFIKKN2) was, in turn, associated with fasting glucose, hemoglobin A1c, and HOMA-IR measurements in humans. In addition to identifying potentially novel disease markers and pathways in T2DM, we provide publicly available data to be leveraged for insights about gene function and disease pathogenesis in the context of human metabolism.