Usefulness of Released Cardiac Myosin Binding Protein-C as a Predictor of Cardiovascular Events

Development and Validation of a Nomogram to Predict the Future Risk of Cardiovascular Disease

Background

Early identification of individuals at a high risk of cardiovascular disease (CVD) is crucial. This study aimed to construct a nomogram for CVD risk prediction in the general population.

Methods

This retrospective study analyzed the data between January 2012 and September 2020 at the Physical Examination Center of the Second Affiliated Hospital of Nanjing Medical University (randomized 7:3 to the training and validation cohorts). The outcome was the occurrence of CVD events, which were defined as sudden cardiac death or any death related to myocardial infarction, acute exacerbation of heart failure, or stroke. The least absolute shrinkage and selection operator (LASSO) method and multivariate logistic regression were applied to screen the significant variables related to CVD.

Results

Among the 537 patients, 54 had CVD (10.1%). The median cardiac myosin-binding protein-C (cMyBP-C) level in the CVD group was higher than in the no-CVD group (42.25 pg/mL VS 25.00 pg/mL, p = 0.001). After LASSO selection and multivariable analysis, cMyBP-C (Odds ratio [OR] = 1.004, 95% CI [CI, confidence interval]: 1.000-1.008, p = 0.035), age (OR = 1.023, 95% CI: 0.999-1.048, p = 0.062), diastolic blood pressure (OR = 1.025, 95% CI: 0.995-1.058, p = 0.103), cigarettes per day (OR = 1.066, 95% CI: 1.021-1.113, p = 0.003), and family history of CVD (OR = 2.219, 95% CI: 1.003-4.893, p = 0.047) were associated with future CVD events (p < 0.200). The model, including cMyBP-C, age, diastolic blood pressure, cigarettes per day, and family history of CVD, displayed a high predictive ability with an area under the curve (AUC) of 0.816 (95% CI: 0.714-0.918) in the training cohort (specificity and negative predictive value of 0.92 and 0.96) and 0.774 (95% CI: 0.703-0.845) in the validation cohort.

Conclusions

A nomogram based on cMyBP-C, age, diastolic blood pressure, cigarettes per day, and family history of CVD was constructed. The model displayed a high predictive ability.

Implications of S-glutathionylation of sarcomere proteins in cardiac disorders, therapies, and diagnosis

The discovery that cardiac sarcomere proteins are substrates for S-glutathionylation and that this post-translational modification correlates strongly with diastolic dysfunction led to new concepts regarding how levels of oxidative stress affect the heartbeat. Major sarcomere proteins for which there is evidence of S-glutathionylation include cardiac myosin binding protein C (cMyBP-C), actin, cardiac troponin I (cTnI) and titin. Our hypothesis is that these S-glutathionylated proteins are significant factors in acquired and familial disorders of the heart; and, when released into the serum, provide novel biomarkers. We consider the molecular mechanisms for these effects in the context of recent revelations of how these proteins control cardiac dynamics in close collaboration with Ca2+ fluxes. These revelations were made using powerful approaches and technologies that were focused on thin filaments, thick filaments, and titin filaments. Here we integrate their regulatory processes in the sarcomere as modulated mainly by neuro-humoral control of phosphorylation inasmuch evidence indicates that S-glutathionylation and protein phosphorylation, promoting increased dynamics and modifying the Frank-Starling relation, may be mutually exclusive. Earlier studies demonstrated that in addition to cTnI as a well-established biomarker for cardiac disorders, serum levels of cMyBP-C are also a biomarker for cardiac disorders. We describe recent studies approaching the question of whether serum levels of S-glutathionylated-cMyBP-C could be employed as an important clinical tool in patient stratification, early diagnosis in at risk patients before HFpEF, determination of progression, effectiveness of therapeutic approaches, and as a guide in developing future therapies.

Biomarkers of Inflammation in Left Ventricular Diastolic Dysfunction

Left ventricular diastolic dysfunction (LVDD) is an important precursor to many different cardiovascular diseases. Diastolic abnormalities have been studied extensively in the past decade, and it has been confirmed that one of the mechanisms leading to heart failure is a chronic, low-grade inflammatory reaction. The triggers are classical cardiovascular risk factors, grouped under the name of metabolic syndrome (MetS), or other systemic diseases that have an inflammatory substrate such as chronic obstructive pulmonary disease. The triggers could induce myocardial apoptosis and reduce ventricular wall compliance through the release of cytokines by multiple pathways such as (1) immune reaction, (2) prolonged cell hypoxemia, or (3) excessive activation of neuroendocrine and autonomic nerve function disorder. The systemic proinflammatory state causes coronary microvascular endothelial inflammation which reduces nitric oxide bioavailability, cyclic guanosine monophosphate content, and protein kinase G (PKG) activity in adjacent cardiomyocytes favoring hypertrophy development and increases resting tension. So far, it has been found that inflammatory cytokines associated with the heart failure mechanism include TNF-α, IL-6, IL-8, IL-10, IL-1α, IL-1β, IL-2, TGF-β, and IFN-γ. Some of them could be used as diagnosis biomarkers. The present review aims at discussing the inflammatory mechanisms behind diastolic dysfunction and their triggering conditions, cytokines, and possible future inflammatory biomarkers useful for diagnosis.

Cardiac Myosin-Binding Protein C Release Profile After Cardiac Surgery in Intensive Care Unit

BACKGROUND

Cardiac surgical procedures produce iatrogenic myocardial cell injury with necrosis that result in an obligatory release of biomarkers. Cardiac myosin binding protein C (cMyBP-C) has recently emerged as a specific and sensitive biomarker in patients with acute myocardial injury. We therefore aimed to investigate the release profiles of cMyBP-C after cardiac surgical procedures.

METHODS

Enzyme-linked immunosorbent assay to detect blood cMyBP-C was established by using two monoclonal antibodies against N-terminus of human cMyBP-C. Consecutive patients undergoing cardiac operations (N = 151) were recruited in this study. Blood cMyBP-C was assayed preoperatively, at intensive care unit arrival (0 hour after the operation), at 2 to 48 hours, and before discharge. The characteristics and detailed surgical procedure were recorded.

RESULTS

The established immunoassay was capable of detecting human cMyBP-C (0 to 1000 ng/L). The released cMyBP-C peaked immediately after cardiac surgery (0 h), attaining 3.8-fold higher than before the operation, dropped abruptly within 24 hours, and stayed at a higher level until discharge. Postoperative cMyBP-C levels correlated positively with high-sensitivity cardiac troponin T (hs-cTnT), creatine kinase, myoglobin, and creatine kinase MB isoenzyme. Different cardiac surgical procedures were characterized by different levels of release of cardiac biomarkers. Isolated off-pump coronary artery bypass grafting was associated with the smaller amount of cMyBP-C release, whereas valve replacement/plasty surgery produced higher release, in particular the multiple-valve surgery. Both cMyBP-C and hs-cTnT correlated with surgical techniques, postoperative intensive care unit stay, and hospital stay.

CONCLUSIONS

Circulating cMyBP-C is a promising novel biomarker for evaluating cardiac surgical trauma in patients undergoing a cardiac operation.