In our study, we examined the relationship
between the coronary collateral index and TyG
index in patients with stable or unstable angina
pectoris who underwent coronary angiography
procedures. To the best of our knowledge, there
is no study regarding the TyG index and CTO.
Early identification of diabetic patients with acute
coronary syndrome (ACS) is important to reduce
future cardiovascular events. Insulin resistance is an
increasingly common metabolic disorder caused by an
impaired physiological response to insulin. For many
years, insulin resistance and hypertriglyceridemia have
been related to metabolic disorders, type 2 diabetes,
and atherosclerotic cardiovascular diseases.[
16-
19] In
the onset of diabetes, insulin resistance develops
first. Causes of insulin resistance include reduction of glycogen synthesis in skeletal muscles by glucose
transporter type-4 (GLUT 4), impaired insulin
receptor binding or intracellular signal transduction,
as well as the presence of high amounts of circulating
free fatty acids. Patients with type 2 diabetes have
insulin resistance and decreased β-cell function.
Hyperglycemia causes islet cells to be constantly
exposed to oxidative stress. Islet cells in the pancreas
have a weaker antioxidant capacity. Long-term
glucose toxicity and lipotoxicity cause β-cell failure.
Insulin resistance is related to the chronic increase
of plasma glucose and triglycerides.[19] The TyG
index, which is an indicator of insulin resistance, is
related to cardiovascular mortality and morbidity
in patients with and without diabetes in many
studies.[20] The sensitivity and specificity of the TyG
index for determining insulin resistance were 84.0%
and 45.0%, respectively, in the study reported by
Simental-Mendia et al.[21] Zhao et al.[22] revealed
that the TyG index could be a better predictor of
cardiovascular risk than FPG or HbA1C for patients
with ACS.
In their study, da Silva et al.[23] found that the TyG
index could be used as a marker in determining the
intensity of atherosclerosis in patients with symptomatic
CAD. Mao et al.[24] revealed that the TyG index could
be a detached predictor of CAD severity as assessed
by the SYNTAX score in patients with ACS. Luo et
al.[25] also observed that a TYG increase index could
be a potent indicator of the worst prognosis in patients
with acute ST-segment elevation myocardial infarction
cured with percutaneous coronary intervention for
one-year follow-up. In a cross-sectional study, patients
with type 2 diabetes, but without a CAD history
were found to have a higher TyG index related to an
increased risk of significant coronary artery stenosis.[26]
In another study involving Korean adults, the TyG
index was associated with the progression of coronary
artery calcification.[27]
Recent studies have revealed that insulin resistance
takes part in macrophage, endothelial, and vascular
smooth muscle cell destruction, which contributes
to plaque progression.[28] Impaired glucose tolerance,
increased insulin resistance increases oxidative stress
in the long-term and damages vascular endothelial
cells. Moreover, insulin resistance, hyperglycemia,
and dyslipidemia increase plasminogen activator
inhibitor-1 levels, resulting in reduced fibrinolytic
activity and raised thrombotic events.[29,30] Again, in several studies, insulin resistance causes both structural
and functional deterioration such as increased intimamedia
thickness, coronary artery calcification, and
arterial stiffness in the vessel wall.[31]
In different studies, cardiovascular diseases and
complications were found to be higher in diabetic
patients.[32,33] On the other hand, a higher level of TyG
index can expedite atherosclerosis in patients with
CABG that causes graft failure, as insulin resistance
has a proinflammatory and procoagulatory effect,
and TyG index is related to endothelial dysfunction.
In previous studies, increased insulin resistance levels
were associated with the decreased circulation at the
microvascular level.[34]
Insulin resistance was associated with an
increased infarct area of single-photon emission
computed tomography and myocardial perfusion
imaging in a study that included non-diabetic
patients with ST-segment elevation myocardial
infarction.[35] In our study, the TyG index was found
to be higher in the group with poor CCC. This
situation may have been the result of endothelial
dysfunction as a result of the proinflammatory and
procoagulatory effects of IR.[36,37]
The main limitation to this study is that it was
conducted with a small group of patients in a single
center. In addition, the retrospective nature of our study,
including a small group of patients, reduces the power of
the study. The findings may not cover other demographic
groups. The TyG index of patients was calculated only
once during hospitalization. Also, we could not reach
the HbA1c results of all patients. Therefore, we did
not include HbA1c results in the table as the statistical
data. Calculating the changes in the TyG index during
follow-up may be better in predicting the prognosis.
Further multi-center, large-scale prospective studies are
required to confirm our results.
In conclusion, high TyG index levels are related
to poor collateral circulation in patients with CTO.
A high TyG index is an important predictor of a low
CCC grade. Based on these findings, TyG index can
be a beneficial marker for prognosis in patients with
type 2 diabetes and ACS undergoing percutaneous
coronary intervention. For CTO interventions, these
and similar markers can be a guide in the patient
selection.
Declaration of conflicting interests
The authors declared no conflicts of interest with respect
to the authorship and/or publication of this article.
Funding
The authors received no financial support for the research
and/or authorship of this article.