Full-Size and Partially Truncated Cardiac Troponin Complexes in the Blood of Patients with Acute Myocardial Infarction

Abstract

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>BACKGROUND</jats:title> <jats:p>The measurement of cardiac isoforms of troponin I (cTnI) and troponin T (cTnT) is widely used for the diagnosis of acute myocardial infarction (AMI). However, there are conflicting data regarding what forms of cTnI and cTnT are present in the blood of AMI patients. We investigated cTnI and cTnT as components of troponin complexes in the blood of AMI patients.</jats:p> </jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>Gel filtration techniques, sandwich fluoroimmunoassays, and Western blotting were used.</jats:p> </jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>Plasma samples from patients with AMI contained the following troponin complexes: (a) a cTnI-cTnT-TnC complex (ITC) composed of full-size cTnT of 37 kDa or its 29-kDa fragment and full-size cTnI of 29 kDa or its 27-kDa fragments; (b) ITC with lower molecular weight (LMW-ITC) in which cTnT was truncated to the 14-kDa C-terminal fragments; and (c) a binary cTnI-cTnC complex composed of truncated cTnI of approximately 14 kDa. During the progression of the disease, the amount of ITC in AMI samples decreased, whereas the amounts of LMW-ITC and short 16- to 20-kDa cTnT central fragments increased. Almost all full-size cTnT and a 29-kDa cTnT fragment in AMI plasma samples were the components of ITC. No free full-size cTnT was found in AMI plasma samples. Only 16- to 27-kDa central fragments of cTnT were present in a free form in patient blood.</jats:p> </jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>A ternary troponin complex exists in 2 forms in the blood of patients with AMI: full-size ITC and LMW-ITC. The binary cTnI-cTnC complex and free cTnT fragments are also present in patient blood.</jats:p> </jats:sec>

Exosomes Derived From Epigallocatechin Gallate-Treated Cardiomyocytes Attenuated Acute Myocardial Infarction by Modulating MicroRNA-30a

“…Thus, drug therapy would be an important part of the therapeutic strategies used to treat AMI more effectively and safely. Currently, myocardial infarction marker enzymes, CK-MB and cTnI, are predominant serum biomarkers used in the clinical diagnosis of AMI (Vylegzhanina et al, 2019). To confirm the successful establishment of the AMI in our model, we detected the cardiac function and the levels of CK-MB and cTnI.…”

The Importance of Cardiac Troponin Metabolism in the Laboratory Diagnosis of Myocardial Infarction (Comprehensive Review)

“…At this stage, the molecules of cardiac troponins are influenced by a number of factors (activity of proteolytic enzymes, kinases, phosphatases, the state of renal function, and the reticuloendothelial system), which can affect serum levels of cardiac troponins and, therefore, their diagnostic value. The molecules of cardiac troponins released into the bloodstream are represented by a heterogeneous fraction (a significant variety of different forms of troponin molecules): free troponins; combined complexes consisting of several free forms of cardiac troponins (for example, cardiac troponin I+troponin C and cardiac troponin T+cardiac troponin I) and small fragments of cardiac troponins [ 61 , 144 , 145 , 177 – 181 ]. All of the above forms of troponin molecules can undergo oxidation, glycosylation, phosphorylation and dephosphorylation processes, which leads to the formation of very diverse forms (varieties) of troponin proteins.…”

Сardiac troponin I for assessment of myocardial damage and prediction of complications in cardiac surgery patients

“…Степень и скорость деградации зависят от причины, вызвавшей инфаркт миокарда, и от времени появления клинических симптомов [6]. Проблемы детекции тропонина заключаются в том, что в ранних образцах крови у пациентов при ОИМ соотношение комплексов ТnI-ТnТ-ТnС, ТnI-ТnС различно и с прогрессированием заболевания это соотношение продолжает меняться [8]. Можно предположить, что после проведения кардиохирургических операций соотношение Tn комплексов также имеет отличия, но этот вопрос недостаточно изучен.…”

“…Основной формой TnI в крови является бинарный комплекс TnI-TnC, свободный TnI определяется только в следовых количествах [9], концентрация комплекса TnI-TnC эквивалентна концентрации TnI [10]. Последние исследования указывают на то, что при ОИМ в крови в основном присутствует комплекс TnI-TnC, в меньшей степени -комплекс TnI-TnT-TnC и TnT в свободной форме [8]. Получается, что разные аналитические коммерческие наборы включают в себя антитела к разным аминокислотным последовательностям, а так как в крови в течение времени происходит изменение соотношения циркулирующих тропониновых комплексов, то полученные результаты от разных производителей могут быть несопоставимы между собой.…”