Title:Current Understanding of Cardiac Troponins Metabolism: A Narrative
Review
Volume: 29
Issue: 41
Author(s): Aleksey Michailovich Chaulin*
Affiliation:
- Department of Cardiology and Cardiovascular Surgery, Medical Faculty, Samara State Medical University,
Samara, Russia
- Department of Clinical Chemistry, Samara Regional Clinical Cardiological Dispensary,
Samara, Russia
Keywords:
Troponin T, troponin I, metabolism, circulation, elimination, circadian rhythms, diagnosis.
Abstract:
Background and Aims: Current methods (highly sensitive and ultra-sensitive) of cardiospecific
troponins detection have enabled early diagnosis of myocardial infarction (MI) and selection of optimal treatment
tactics for patients early from admission. The use of these methods in real clinical practice helps to
choose the most optimal treatment tactics for patients in the early stages after admission, and this significantly
improved the further prognosis of patients suffering from MI. However, there are a number of problems
that arise when using highly sensitive or ultra-sensitive methods for determining cardiospecific troponins: frequent
and unexplained increases in serum levels of cardiospecific troponins in a number of pathological conditions
unrelated to MI; insufficient knowledge and understanding of the mechanisms of release and increase
in the levels of cardiospecific troponins; poorly understood features and mechanisms of circulation and elimination
of cardiospecific troponins; the presence of conflicting information about the influence of several factors
(gender, age and circadian characteristics) on the levels of cardiospecific troponins in blood serum;
undisclosed diagnostic potential of cardiospecific troponins in non-invasive human biological fluids. These
problems cause great difficulties and increase the risk of errors in the differential diagnosis of MI, and also
do not allow to fully unlock the diagnostic potential of cardiospecific troponins. In general, these problems
are associated with a lack of understanding of the fundamental mechanisms of the metabolism of cardiospecific
troponins. The main purpose of this narrative review is to summarize and provide detailed information
about the metabolism of cardiospecific troponins and to discuss the potential impact of metabolic features on
the diagnostic value of cardiospecific troponins and their diagnostic capabilities.
Materials and Methods: This narrative review is based on the analysis of publications in the Medline,
PubMed, and Embase databases. The terms “cardiac troponins”, “troponin T”, and “troponin I” in combination
with “mechanisms of increase”, “mechanisms of release”, “circulation”, “proteolytic cleavage”, “elimination”,
“circadian rhythms”, “saliva”, and “urine” were used to search publications.
Results: It has been reported that the metabolic features (mechanisms of release, circulation, and elimination)
of cardiospecific troponins may have an important influence on the diagnostic value of cardiospecific
troponins in a number of physiological and pathological conditions that cause cardiomyocyte damage. The
main mechanisms of cardiac troponin release are: cardiomyocyte apoptosis; myocardial cell regeneration and
renewal; increased cell membrane permeability; release of troponins by vesicular transport; increased proteolytic
degradation of cardiospecific troponin molecules within the cell which may facilitate their release from
intact myocardial cells or in the initial phase of those pathological conditions that increase the activity of enzymes
that degrade cardiospecific troponins. Besides, the formation of small fragments (troponin molecules)
may facilitate their penetration into other body fluids such as urine and/or oral fluid which may provide researchers
and practitioners with a new diagnostic opportunity. It should be noted that in addition to release
mechanisms, cardiospecific troponin elimination mechanisms may play an important diagnostic role. The
contribution of release and elimination mechanisms to different pathologies may differ significantly. Circadian
rhythms of cardiospecific troponins may be associated with fluctuations in the activity of those organ
systems which influence the mechanisms of cardiospecific troponin release or elimination. Such major systems
include: neuroendocrine, urinary, and hemostasis.
Conclusion: Cardiospecific troponins metabolism has an important influence on diagnostic value and diagnostic
capabilities. Further study of the features of cardiac troponin metabolism (mechanisms of release, circulation
and elimination) is required to improve diagnosis and differential diagnosis of diseases causing cardiomyocyte
damage. The data on the influence of circadian rhythms of cardiospecific troponins on the diagnostic
value and the possibility of determining cardiospecific troponins in body fluids that can be obtained
by noninvasive methods are very interesting. However, so far this information and valuable capabilities have
not been applied in clinical practice because of the paucity of studies conducted.
