Cardiac troponin-T Research Articles

New Perceptions in the Cardioprotective Effect of Metformin Against Isoproterenol Induced Cardiotoxicity in Male Rats

Background and objective: Recent clinical trials have shown that metformin improves clinical cardiovascular outcome in type-2 diabetic patients independently of its insulin-sensitizing effect. This study was sought to evaluate the potential cardioprotective effects of metformin on isoproterenol-induced cardiac stress in diabetic and non-diabetic rats. Materials and Methods: Diabetes was induced by using streptozocin (60 mg/kg, i.p.) while non-diabetic rats received saline. Rats in both experimental groups were then randomized to receive different doses of metformin (75, 150, 300 mg/kg i.p.) for 6 weeks. Cardiac stress was induced by isoproterenol (150 mg/kg i.p.) for two successive days. Specific biomarkers of tissue injury, namely brain natriuretic peptide (BNP), cardiac troponin-T (cTn-T), matrix metalloproteinase (MMP), tissue necrotic factor-α (TNF), were assessed. Data were analysed using one-way ANOVA followed by Newman Keuls post hoc test Results: The results showed that metformin significantly limited isoproterenol-induced myocardial injury in both diabetic and non-diabetic rats. Metformin significantly decreased the elevated serum levels of brain natriuretic peptide (BNP), matrix metalloproteinase (MMP), cardiac troponin t (cTn-T) which was induced by isoproterenol. It also limited expression of tissue necrotic factor-α (TNF-α) following the cardiac injury in diabetic and non-diabetic rats.

An inquest into regulatory mechanism of caveolin by ischemic preconditioning against orchidectomy-challenged rat heart.

Lower level of testosterone in men is related to major risks of cardiovascular diseases. This risk may increase due to the opening of mitochondrial permeability transition pore (mPTP). The mPTP is also regulated by ischemic preconditioning (IPC) and a membrane protein known as caveolin. The cardioprotective effect of IPC is the most effective methodologies used in testosterone deficiency. Daidzein (DDZ) a caveolin inhibitor shows cardioprotective action. The experiment has been designed to evaluate the pretreated DDZ effect in IPC-mediated cardioprotective action in orchidectomy (OCZ)-challenged rat heart. The experiment was designed on male Wistar rats with/without OCZ. The level of testosterone is decreased by OCZ which reduces general body growth. Isolated heart from normal and OCZ rat was tied up on Langendorff's perfused apparatus and followed by ischemic reperfusion (IR) and IPC cycle. To investigate the cardioprotective effect of DDZ in heart with testosterone deficiency, a total of nine groups, each consisting of six rats (n = 6) were as follows: Sham, IR, IPC, IPC + OCZ, IPC + DDZ, IPC + OCZ + DDZ, IPC + sodium nitrite, IPC + OCZ + sodium nitrite, IPC + OCZ + DDZ + sodium nitrite. Hemodynamic parameters, cellular injury (infarct size, LDH, CKMB and cardiac troponin-T), oxidative stress, mitochondrial function, integrity and immunoblot analysis were assessed for each group. The experimental data showed that DDZ potentiated IPC-mediated increase in the heart rate, left ventricular diastolic pressure, coronary flow; + dp/dtmax, and -dp/dtmax. The pretreated DDZ decreases the action of LDH and CKMB, myocyte size, cardiac collagen content, infarct size and ventricular fibrillation and attenuation in oxidative stress and mitochondrial dysfunction in OCZ-challenged rat heart in all sets of experiments. Sodium nitrite, a producer of nitric oxide (NO), enhanced potentiating effects of DDZ on IPC-mediated cardioprotection in OCZ-challenged rats. These observations show that the downregulation of caveolin through impaired opening of mPTP during reperfusion and caveolin might be a potential adjuvant to IPC against cardiac injury in OCZ-challenged rats.

Impact and Determinants of High-Sensitivity Cardiac Troponin-T Concentration in Patients With COVID-19 Admitted to Critical Care

Cardiac Troponin (hs-TnT) elevation has been reported in unselected patients hospitalized with COVID-19 however the mechanism and relationship with mortality remain unclear. Consecutive patients admitted to a high-volume intensive care unit (ICU) in London with severe COVID-19 pneumonitis were included if hs-TnT concentration at admission was known. Kaplan-Meier survival analysis performed, with cohorts classified a priori by multiples of the upper limit of normal (ULN). 277 patients were admitted during a 7-week period in 2020; 176 were included (90% received invasive ventilation). hs-TnT at admission was 16.5 (9.0 to 49.3) ng/L, 56% had concentrations >ULN. 56 patients (31.8%) died during the index admission. Admission hs-TnT level was lower in survivors (12.0 (8.0-27.8) vs 28.5 (14.0 to 81.0) ng/L, p = 0.001). Univariate predictors of mortality were age, APACHE-II Score and admission hs-TnT (HR 1.73, p = 0.007). By multivariate regression, only age (HR 1.33, CI: 1.16.to 1.51, p < 0.01) and admission hs-TnT (HR 1.94, CI: 1.22 to 3.10, p = 0.006) remained predictive. Survival was significantly lower when admission hs-TnT was >ULN (log-rank p-value<0.001). Peak hs-TnT was higher in those who died but was not predictive of death after adjustment for other factors. In conclusion, in critically ill patients with COVID-19 pneumonitis, the hs-TnT level at admission is a powerful independent predictor of the likelihood of surviving to discharge from ICU. In most cases, hs-TnT elevation does not represent major myocardial injury but acts as a sensitive integrated biomarker of global stress. Whether stratification based on admission Troponin level could be used to guide prognostication and management warrants further evaluation.

Genetically Engineered Addition of a Ca2+ Buffering Capacity in Mouse Cardiac Muscle Thin Filament using a Glu-Rich Segment of Insect Troponin T Alters Cardiac Performance

In addition to a core function in Ca2+ regulation of muscle contraction, insect troponin T (TnT) has a unique glutamic acid-rich long C-terminal extension. With sequence similarity to this diverged structure, the N-terminal segment of avian flight muscle TnT binds Ca2+ with a physiologically relevant affinity (Zhang et al., Biochemistry 43:2645-55, 2004). Deletion of the C-terminal extension of Drosophila TnT significantly decreased muscle and heart functions (Cao et al., JBC 295:3794-3807, 2020). We propose a hypothesis that this structure serves as a myofilament Ca2+ reservoir to reduce the amount of Ca2+ cycled by Ca2+ pumps during muscle contraction and relaxation. A CRISP/Cas9 knock-in (KI) mouse model was constructed to replace the N-terminal variable region of cardiac TnT with 51 Glu residues derived from the C-terminal extension of bee TnT. Cardiac function is studied using ex vivo working hearts and tested for responses to beta-adrenergic stimulation or L-Ca2+ channel agonist Bay-K8644. At baseline, cTnT-51E hearts showed lower systolic velocity than that of WT control. Upon isoproterenol or Bay-K8644 treatment, cTnT-51E and wild type hearts both had positive responses in performance. However, cTnT-51E hearts exhibited significantly more increases in ventricular peak systolic pressure and diastolic velocity but still lower stroke volume as compared to that of WT controls. This phenotype is likely due to an altered response to the increase in intracellular calcium. Further analysis of Ca2+ responses of skinned muscle sections, cardiac energetic efficiency and intracellular Ca2+ transient are underway to establish the novel Ca2+ buffering capacity of TnT and its function in contractile kinetics of striated muscle.

C-Terminal Basic Residues of Troponin T Facilitate Troponin I Transitions during Activation

During activation of striated muscle, the inhibitory region of TnI moves from actin toward TnC allowing tropomyosin to adopt an activating position on actin. Basic amino acid residues within the C-terminal 14 residues of human cardiac TnT limit the extent of activation and are required for full relaxation (Johnson et al., 2018, Biophys J). FRET measurements show that those basic residues alter Ca2+-induced structural changes. With wild type TnT the distance between Cys 143 of TnI (within the inhibitory region) and Cys 190 of tropomyosin increased upon Ca2+ activation while the distance between Cys 143 of TnI and Cys 84 of TnC decreased.

Impaired in vitro growth response of plasma-treated cardiomyocytes predicts poor outcome in patients with transthyretin amyloidosis

ObjectivesDirect toxic effects of transthyretin amyloid in patient plasma upon cardiomyocytes are discussed. However, no data regarding the relevance of this putative effect for clinical outcome are available. In this monocentric prospective study, we analyzed cellular hypertrophy after phenylephrine stimulation in vitro in the presence of patient plasma and correlated the cellular growth response with phenotype and prognosis.Methods and resultsProgress in automated microscopy and image analysis allows high-throughput analysis of cell morphology. Using the InCell microscopy system, changes in cardiomyocyte’s size after treatment with patient plasma from 89 patients suffering from transthyretin amyloidosis and 16 controls were quantified. For this purpose, we propose a novel metric that we named Hypertrophic Index, defined as difference in cell size after phenylephrine stimulation normalized to the unstimulated cell size. Its prognostic value was assessed for multiple endpoints (HTX: death/heart transplantation; DMP: cardiac decompensation; MACE: combined) using Cox proportional hazard models. Cells treated with plasma from healthy controls and hereditary transthyretin amyloidosis with polyneuropathy showed an increase in Hypertrophic Index after phenylephrine stimulation, whereas stimulation after treatment with hereditary cardiac amyloidosis or wild-type transthyretin patient plasma showed a significantly attenuated response. Hypertrophic Index was associated in univariate analyses with HTX (hazard ratio (HR) high vs low: 0.12 [0.02–0.58], p = 0.004), DMP: (HR 0.26 [0.11–0.62], p = 0.003) and MACE (HR 0.24 [0.11–0.55], p < 0.001). Its prognostic value was independent of established risk factors, cardiac TroponinT or N-terminal prohormone brain natriuretic peptide (NTproBNP).ConclusionsAttenuated cardiomyocyte growth response after stimulation with patient plasma in vitro is an independent risk factor for adverse cardiac events in ATTR patients

Corrected QT interval prolongation: A new predictor of cardiovascular risk in patients with non-St-elevation acute coronary syndrome. Algerian cohort

Recently we reported that prolongation of the corrected QT (CTc) interval is an independent risk factor in patients with unstable angina and acute ischemic changes. The aim of this study was to determine the prognostic value of the corrected QT (CTc) interval in patients with non-ST-segment elevation acute coronary syndrome who do not exhibit acute ischemic changes on admission ECG. The study included 195 patients with this syndrome. On admission, a standard 12-lead ECG was recorded, the cardiac troponin-T was measured and aTIMI (Thrombolysis in Myocardial Infarction) risk score was calculated. The primary endpoint was the combination of nonfatal acute myocardial infarction, percutaneous or surgical revascularization, and cardiac death up to 30 days after discharge. Two independent investigators measured the QT interval manually and the corrected value was derived using Bazett's formula. In the statistical analysis, the following cut-off points were used: the median TIMI risk score, a cardiac troponin-T level of 0.04 ng/mL, and a QTc of 0.458 s. Of the 74 patients (38%) who reached the primary endpoint, 59 (80%) had QTc prolongation. Binary logistic regression analysis showed that QTc prolongation was an independent predictor of the combined endpoint. This study shows that QTc prolongation is an independent predictor of cardiovascular risk in patients with non-ST-segment elevation acute coronary syndrome but without acute ischemic changes on admission ECG.

Physiological and Metabolic Responses of Amateur Spinal Cord Injured Wheelchair Racers Participating in a Marathon: A Pilot Observational Study.

ABSTRACTObjectives:We analyzed exercise-related changes in cardiac troponins and other physiological and metabolic parameters in amateur wheelchair racers with spinal cord injury (SCI) participating in a marathon event.Methods:This pilot, prospective, observational study was conducted at a community marathon event. Fifteen community-living individuals with SCI who had registered to participate in the marathon were recruited for the study. Participants with SCI used manually propelled wheelchairs (n=5) or tricycles (n=10). The outcome measures were high-sensitivity cardiac troponin-T levels (hs-cTnT), heart rate, and metabolic parameters, including body temperature, serum electrolytes, and urine osmolality. These parameters were compared with 15 age- and race-distance-matched non-SCI runners who participated in the same marathon.Results:Participants with SCI had a higher median (inter-quartile range) baseline hs-cTnT level [13.7 ng/L (10.3–25)] than did runners [4.2 ng/L (3.2–8.7; P <0.001)]. Post-race values of hs-cTnT were elevated in participants with SCI [28.0 ng/L (19.0–48.2)] and in runners [41.5 ng/L (18.4–87.1, P= 0.7)]; however, there was no significant difference between the two groups. Other parameters were not significantly different between SCI participants and runners.Conclusion:Post-race hs-cTnT levels of amateur SCI participants were elevated but were not significantly different from those of runners. Other race-induced physiological and metabolic changes in SCI participants were comparable to those of runners. The high baseline hs-cTnT levels in participants with SCI observed in this study warrant further research.

Perioperative Outcomes of Patients Who Were Not Candidates for Additional Nonsteroidal Anti-inflammatory Drugs in a Multimodal Pain Control Regimen for Total Knee Arthroplasty.

BackgroudPostoperative pain following total knee arthroplasty (TKA) may hamper patients from a rapid recovery and increase perioperative blood loss and stress on the cardiovascular system. Therefore, our objective was to assess perioperative outcomes after TKA in patients who were not candidates for the additional nonsteroidal anti-inflammatory drugs (NSAIDs) in a multimodal pain control regimen.MethodsPropensity score matching for age, sex, body mass index, American Society of Anesthesiologists class, and preoperative hemoglobin level was conducted on patients undergoing unilateral TKA, and thereby 52 patients remained in each group. The control group comprised patients who received parenteral parecoxib every 12 hours during the first 48 hours after TKA. The No-NSAIDs group did not receive NSAIDs because of known contraindications. Identical postoperative pain control including intravenous patient-controlled analgesia was applied for all patients. Visual analog scale (VAS) score for pain, knee flexion, blood loss, serum cardiac troponin-T (cTnT), and length of stay (LOS) were determined.ResultsThe No-NSAIDs group had significantly higher VAS scores in 6–96 hours and consumed more morphine at 24 hours and 48 hours after the surgery than the control group. The No-NSAIDs group had significantly less knee flexion at 48 hours (p = 0.045) and tended to have more emesis and longer LOS than the control group. The blood loss of the No-NSAIDs and control group was 552.52 mL and 397.65 mL (p = 0.02), respectively, and blood transfusion rate was 23.1% and 17.3% (p = 0.63), respectively. The cTnT of the No-NSAIDs group rose over the first 48 hours and was significantly higher than that of the control group at 48 hours.ConclusionsPatients who were not candidates for NSAIDs had significantly higher pain scores and consumed more morphine after TKA. They also tended to have greater blood loss and the rising of cardiac biomarkers during the first 48 hours after TKA. Hence, these patients may benefit from supplementary analgesia and appropriate perioperative monitoring.

Clinical Outcomes of Myocarditis after Moderate-Dose Steroid Therapy in Systemic Sclerosis: A Pilot Study.

Background Myocarditis is reported in systemic sclerosis (SSc); however, treatment options and outcomes are limited. Our objective was to define cardiac outcomes after moderate-dose steroid therapy in SSc patients with myocarditis. Method An open-label study was conducted among SSc patients with myocarditis—as defined by cardiovascular magnetic resonance (CMR), disease onset <5 years, and a NYHA functional class ≥II. All enrolled patients received prednisolone (30 mg/d) which would be tapered off by week 24, and CMR was followed up at the end of treatment. Results A total of 20 SSc patients were enrolled which 12 patients completed the study. At week 24, 8 of the 12 cases experienced improvement of myocarditis. Compared to those with no improvement, these 8 patients had significantly longer disease duration (p = 0.03), higher heart rate at baseline (p = 0.049) and week 24 (p = 0.04), lower left ventricular (LV) and right ventricular (RV) stroke volume at baseline (p = 0.002 and p = 0.01) and week 24 (p = 0.01 and p = 0.02), and lower LV and RV cardiac output at week 24 (p = 0.01 and p = 0.01). Four cases died during follow-up (3 due to cardiac complications, 1 due to renal crisis). The two who died from heart failure had very high NT-prohormone-brain natriuretic peptide (NT-proBNP) and impaired LV ejection fraction (LVEF), and the one who died from arrhythmia had very high sensitivity of cardiac Troponin-T (hs-cTnT). Conclusions Moderate-dose steroid therapy may improve myocarditis in SSc. A proportion of patients died due to cardiac complications during treatment, particularly those with high hs-cTnT, high NT-proBNP, and impaired LVEF. This trial is registered with NCT03607071.

Abstract 14182: Genome Wide Association Study for High Sensitive Cardiac Troponin T Levels Identifies a Novel Gene in Europeans With Type 1 Diabetes

Introduction: Adults with diabetes have a two to four folds increased risk of dying with heart disease compared to those without diabetes. Higher cardiac troponins, especially Troponin T (TnT) is a specific biomarker for cardiac injury also guiding management of chest pain and associated with increased risk of heart failure. Hypothesis: There is limited knowledge on genes regulating cardiac TnT levels. We conducted a genome wide association study (GWAS) for circulating cardiac TnT levels among individuals with type 1 diabetes (T1D). Methods: The study included 849 T1D individuals recruited from the outpatient clinic at Steno Diabetes Center Copenhagen, Denmark. Serum high sensitive TnT (hsTnT) levels were measured and log transformed for normalization after check for outliers (mean ± 4 SD). Genotyping on 538,448 single nucleotide variants (SNVs) was done using Illumina Human Core Exome Chip. After quality control filters: hardy weinberg equilibrium (p &gt;10 -6 ), European ancestry, genotype call rates &gt;95%, common variants were examined in 740 individuals with hs TnT data. We ran linear regression based additive genetic models adjusting for age, sex, diabetes duration and population sub structure using Plink and R statistical programs. P &lt;5 x 10 -8 was genome wide significant (GWS) while 5 x 10 -8 &lt; p &lt; 1 x 10 -6 was considered suggestive. Results: Participants had a mean (SD) age of 43.7 (11.1) years, 57.4% were men, with diabetes duration of 28.0 (9.5) years, HbA1c 8.9 (1.3) % and 50.5% with diabetic nephropathy. Median (IQR) hsTnT levels were 64.7 (29.2-175.6) pg/ml. We identified a GWS missense common variant in the CISD3 gene locus on chromosome 17 (p=1.7 x 10 -8 ) for cardiac hsTnT levels. This gene codes CDGSH Iron Sulfur Domain 3 protein also called Mitochondrial Inner NEET Protein. Two suggestive loci were PTPRD (Protein Tyrosine Phosphatase Receptor Type D; p=4.9 x 10 -7 ) and DCC (DCC Netrin 1 Receptor; 6.6 x 10 -7 ) on chromosomes 9 and 18. PTPRD is a known GWS locus for hsTnT that we reconfirm among T1D individuals. Conclusions: We identify a novel gene locus for circulating cardiac hsTnT levels among T1D individuals of European ancestry. CISD3 is expressed in heart tissue regulating mitochondrial functions. Further validation is suggested.

Abstract 13919: Race and Gender Specific High Sensitivity Troponin-t Cutoff Values Improve Detection in Patients’ With Ischemic Heart Disease

Introduction: Death rates from acute coronary syndrome events (ASCE) are 30% higher in African Americans than in Caucasians. A potential reason for this disparity is the underdiagnosis of ACSE due to race-specific differences in blood levels of cardiac troponin-T (cTnT), the biomarker of choice for the exclusion of myocardial injury. Hypothesis: Race- and gender-specific high-sensitivity cTnT (hs-cTnT) cutoff values will improve the detection of myocardial injury. Methods: Emergency Department encounters at the University of Chicago from June 2018 through April 2019 with at least 1 hs-cTnT value were included. Race- and gender-specific 99 th percentiles for hs-cTnT were determined for patients without a history of hypertension, heart failure, coronary artery disease, diabetes, or chronic kidney disease, and used as the threshold for a positive result. These threshold values were compared against manufacturer’s recommended gender-only values (male ≥ 22 ng/dL, female ≥ 14 ng/dL). Confusion matrices were used to calculate test characteristics. The presence of ischemic heart disease was determined by the corresponding International Statistical Classification of Diseases. Results: Among 10,934 included encounters, 89.9% were African American. The 99 th percentile values for African American were lower than for matched white counterparts. Race and gender specific cutoffs had higher specificity (83.1% vs 75.2%), greater positive predictive value (91.9% vs 90.7%), and lower false negative rates (16.9% vs. 24.8%) compared with traditional gender-only cutoff values. During the 10 months of data collection, race- and gender-specific cutoffs would have correctly identified 215 additional encounters as having ischemic heart disease, all of them African Americans. The net reclassification rate was +7.91%. Conclusions: Using race-specific, in addition to traditional gender-specific, hs-cTnT cutoff values resulted in higher specificity, greater positive predictive value, and lower false negative rates. Nearly 8% of patients with eventual diagnosis of ischemic heart disease would have been correctly reclassified using race- and gender-specific cutoffs. These findings suggest that race- and gender-specific cutoffs should be further explored.

High sensitivity Troponin-T for prediction of adverse events in patients with COVID-19

Background High sensitivity cardiac troponin-T (hs-TnT) has been associated with mortality in patients hospitalized with COVID-19. We aimed to determine if hs-TnT levels and their timing are independent predictors of adverse events in these patients. Design Retrospective chart review was performed for all patients hospitalized at our institution between 23 March 2020 and 13 April 2020 who were found to be COVID-19-positive. Clinical, demographic, and laboratory variables including initial and peak hs-TnT were recorded. Univariable and multivariable analyses were completed for a primary composite endpoint of in-hospital death, intubation, need for critical care, or cardiac arrest. Results In the 276 patients analysed, initial hs-TnT above the median (≥17 ng/L) was associated with increased length of stay, need for vasoactive medications, and death, along with the composite endpoint (OR 3.92, p < 0.001). Multivariable analysis demonstrated that elevated initial hs-TnT was independently associated with the primary endpoint (OR 2.92, p = 0.01). Late-peaking hs-TnT (OR 2.19 for each additional day until peak, p < 0.001) was also independently associated with the composite endpoint. Conclusions In patients hospitalized with COVID-19, hs-TnT identifies patients at high risk for adverse in-hospital events, and trends of hs-TnT over time, particularly during the first day, provide additional prognostic information.

Ultrafast, Ultrasensitive Detection and Imaging of Single Cardiac Troponin-T Molecules.

The fluorescence-based methods of single-molecule optical detection have opened up unprecedented possibilities for imaging, monitoring, and sensing at a single-molecule level. However, single-molecule detection methods are very slow, making them practically inapplicable. In this paper, we show how to overcome this key limitation using the expanded laser spot, laser excitation in a nonfluorescent spectral window of biomolecules, and more binding fluorescent molecules on a biomolecule that increases the detection volume and the number of collected photons. We demonstrate advantages of the developed approach unreachable by any other technique using detection of single cardiac troponin-T molecules: (i) 1000-fold faster than by known approaches, (ii) real-time imaging of single troponin-T molecules dissolved in human blood serum, (iii) measurement of troponin-T concentration with a clinically important sensitivity of about 1 pg/mL. The developed approach can be used for ultrafast, ultrasensitive detection, monitoring, and real-time imaging of other biomolecules as well as of larger objects including pathogenic viruses and bacteria.

Prognostic value of DCTA scoring system in heart failure.

The aim of this study was to evaluate the prognostic value of anovel scoring system, based on D‑dimer, total cholesterol, high-sensitivity cardiac troponinT (hs-cTnT), and serum albumin levels, in patients with heart failure. Atotal of 221patients diagnosed with heart failure between May 2016 to January 2020 were enrolled in this retrospective study. The prognostic significance of the biomarkers D‑dimer, total cholesterol, hs-cTnT, and serum albumin was determined with univariate and multivariate Cox proportional hazard models. Anovel prognostic score based on these predictors was established. The Kaplan-Meier method and log-rank test were used to compare the adverse outcomes of patients in different risk groups. Results from univariate and multivariate analyses showed that high D‑dimer, low serum albumin, high hs-cTnT, and low total cholesterol levels were independent prognostic factors for adverse outcomes (D-dimer >0.63 mg/l, HR = 1.84, 95% CI = 1.16-2.94, p = 0.010; serum albumin >34 g/l, HR = 0.67, 95% CI = 0.45-0.99, p = 0.046; hs-cTnT >24.06 pg/ml, HR = 1.65, 95% CI = 1.08-2.53, p = 0.020; total cholesterol >3.68 mmol/l, HR = 0.63, 95% CI = 0.43-0.92, p = 0.017). Moreover, all the patients were stratified into low-risk or high-risk group according to ascoring system based on these four markers. Kaplan-Meier analyses demonstrated that patients in the high-risk group were more prone to having adverse outcomes compared with patients in the low-risk group. D‑dimer, total cholesterol, hs-cTnT, and serum albumin levels were independent prognostic factors in the setting of heart failure. Anovel and comprehensive scoring system based on thesebiomarkers is an easily available and effective tool for predicting the adverse outcomes of patients with heart failure.

The Positively Charged C-Terminal Region of Human Skeletal Troponin T Retards Activation and Decreases Calcium Sensitivity

Calcium binding to troponin C (TnC) activates striated muscle contraction by removing TnI (troponin I) from its inhibitory site on actin. Troponin T (TnT) links TnI with tropomyosin, causing tropomyosin to move from an inhibitory position on actin to an activating position. Positive charges within the C-terminal region of human cardiac TnT limit Ca2+ activation. We now show that the positively charged region of TnT has an even larger impact on skeletal muscle regulation. We prepared one variant of human skeletal TnT that had the C-terminal 16 residues truncated (Δ16) and another with an added C-terminal Cys residue and Ala substituted for the last 6 basic residues (251C-HAHA). Both mutants reduced (based on S1 binding kinetics) or eliminated (based on acrylodan-tropomyosin fluorescence) the first inactive state of actin at <10 nM free Ca2+. 251C-HAHA-TnT and Δ16-TnT mutants greatly increased ATPase activation at 0.2 mM Ca2+, even without high-affinity cross-bridge binding. They also shifted the force-pCa curve of muscle fibers to lower Ca2+ by 0.8-1.2 pCa units (the larger shift for 251C-HAHA-TnT). Shifts in force-pCa were maintained in the presence of para-aminoblebbistatin. The effects of modification of the C-terminal region of TnT on the kinetics of S1 binding to actin were somewhat different from those observed earlier with the cardiac analogue. In general, the C-terminal region of human skeletal TnT is critical to regulation, just as it is in the cardiac system, and is a potential target for modulating activity.

Serum high-density lipoprotein cholesterol serves as a prognostic marker for light-chain cardiac amyloidosis

BackgroundOxidative stress and inflammation are central in the pathophysiology of light-chain amyloid cardiomyopathy (AL-CM). High-density lipoprotein cholesterol (HDLC) is an antioxidant and acts as an anti-inflammatory regulator. In this study, the prognostic value of serum HDL-C was explored in AL-CM. MethodIn this prospective single-center study, two hundred consecutive patients with biopsy-confirmed light-chain amyloidosis (AL) and cardiac involvement were enrolled. Patients were classified into low or normal serum HDL-C groups (HDL-C < 40 mg/dL and HDL-C ≥ 40 mg/dL, respectively). Univariate and multivariate Cox models were used to identify predictors of survival. Kaplan-Meier analysis was performed to compare survival between patients with low or normal serum HDL-C. ResultsPatients with low serum HDL-C were more likely to present with higher levels of cardiac troponin-T (123.4 ng/L vs. 79.1 ng/L, p = 0.026) and higher levels of N-terminal pro-B-type natriuretic peptide (9146 pg/mL vs. 4945 pg/mL, p = 0.011). Patients were followed for a median follow-up period of 19 months, in which 118 (59%) patients died. The median overall survival times for patients with low or normal serum HDL-C were 7 and 16 months, respectively (p = 0.002). Multivariate analysis demonstrated that serum HDL-C (HR 0.984, 95% CI 0.973–0.994, p = 0.003) was independently associated with prognosis, after adjusting for nephrotic syndrome, hepatic involvement, nutritional state, renal function, SBP, DBP, serum uric acid, total cholesterol, Mayo AL 2004 stage, and treatment with chemotherapy. ConclusionsHDL-C is a novel serum biomarker for disease severity and prognosis in light-chain cardiac amyloidosis.

Postmortem Cardiac Troponin-T levels in Heart Blood as a Marker to Diagnose Acute Myocardial Infarction

Sudden death accounts for approximately two-thirds of autopsies in Forensic Medicine. Natural deathwithin 1 hour after the beginning of acute symptoms, is defined as Sudden Cardiac Death. Acute Myocardialinfarction (AMI) is a serious and potentially lethal manifestation of coronary artery disease, affecting morethan 7 million people worldwide each year and was proved to be a cause of sudden death. This studyquantitatively analyzed the heart blood for Cardiac Troponin T (cTnT) levels within 48hours after death &amp;correlated with the histological changes of myocardium

Scalable Biomimetic Coaxial Aligned Nanofiber Cardiac Patch: A Potential Model for "Clinical Trials in a Dish".

Recent advances in cardiac tissue engineering have shown that human induced-pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) cultured in a three-dimensional (3D) micro-environment exhibit superior physiological characteristics compared with their two-dimensional (2D) counterparts. These 3D cultured hiPSC-CMs have been used for drug testing as well as cardiac repair applications. However, the fabrication of a cardiac scaffold with optimal biomechanical properties and high biocompatibility remains a challenge. In our study, we fabricated an aligned polycaprolactone (PCL)-Gelatin coaxial nanofiber patch using electrospinning. The structural, chemical, and mechanical properties of the patch were assessed by scanning electron microscopy (SEM), immunocytochemistry (ICC), Fourier-transform infrared spectroscopy (FTIR)-spectroscopy, and tensile testing. hiPSC-CMs were cultured on the aligned coaxial patch for 2 weeks and their viability [lactate dehydrogenase (LDH assay)], morphology (SEM, ICC), and functionality [calcium cycling, multielectrode array (MEA)] were assessed. Furthermore, particle image velocimetry (PIV) and MEA were used to evaluate the cardiotoxicity and physiological functionality of the cells in response to cardiac drugs. Nanofibers patches were comprised of highly aligned core-shell fibers with an average diameter of 578 ± 184 nm. Acellular coaxial patches were significantly stiffer than gelatin alone with an ultimate tensile strength of 0.780 ± 0.098 MPa, but exhibited gelatin-like biocompatibility. Furthermore, hiPSC-CMs cultured on the surface of these aligned coaxial patches (3D cultures) were elongated and rod-shaped with well-organized sarcomeres, as observed by the expression of cardiac troponin-T and α-sarcomeric actinin. Additionally, hiPSC-CMs cultured on these coaxial patches formed a functional syncytium evidenced by the expression of connexin-43 (Cx-43) and synchronous calcium transients. Moreover, MEA analysis showed that the hiPSC-CMs cultured on aligned patches showed an improved response to cardiac drugs like Isoproterenol (ISO), Verapamil (VER), and E4031, compared to the corresponding 2D cultures. Overall, our results demonstrated that an aligned, coaxial 3D cardiac patch can be used for culturing of hiPSC-CMs. These biomimetic cardiac patches could further be used as a potential 3D in vitro model for “clinical trials in a dish” and for in vivo cardiac repair applications for treating myocardial infarction.

5-Azacytidine-Induced Cardiomyocyte Differentiation of Very Small Embryonic-Like Stem Cells.

The use of stem cells in generating cell-based pacemaker therapies for bradyarrhythmia is currently being considered. Due to the propensity of stem cells to form tumors, as well as ethical issues surrounding their use, the seed cells used in cardiac biological pacemakers have limitations. Very small embryonic-like stem cells (VSELs) are a unique and rare adult stem cell population, which have the same structural, genetic, biochemical, and functional characteristics as embryonic stem cells without the ethical controversy. In this study, we investigated the ability of rat bone marrow- (BM-) derived VSELs to differentiate in vitro into cardiomyocytes by 5-Azacytidine (5-AzaC) treatment. The morphology of VSELs treated with 10 μM 5-AzaC increased in volume and gradually changed to cardiomyocyte-like morphology without massive cell death. Additionally, mRNA expression of the cardiomyocyte markers cardiac troponin-T (cTnT) and α-sarcomeric actin (α-actin) was significantly upregulated after 5-AzaC treatment. Conversely, stem cell markers such as Nanog, Oct-4, and Sox2 were continuously downregulated posttreatment. On day 14 post-5-AzaC treatment, the positive expression rates of cTnT and α-actin were 18.41 ± 1.51% and 19.43 ± 0.51%, respectively. Taken together, our results showed that rat BM-VSELs have the ability to differentiate into cardiomyocytes in vitro. These findings suggest that VSELs would be useful as seed cells in exploring the mechanism of biological pacemaker activity.