This is the first study revealed a significant association between the TyG index and CAD severity in CHD patients and assessed this association according to the states of glucose metabolism. In the present study, the TyG index was significantly associated with CAD severity and the risk of 3-VD in patients with CHD. Among different states of glucose metabolism, the association between the TyG index and 3-VD observed was significant in diabetes. Furthermore, the accuracy of TyG index in detecting the CAD severity was also evaluated. A TyG index threshold for predicting 3-VD in CHD patients was 7.0 and was 8.1 in diabetes state.
Previous literature has suggested that the TyG index could identify individuals in asymptomatic patients with T2DM who are at high risk of coronary disease. The study mainly compared patients with the severity of CS in diabetic patients; the evidence was provided to the TyG index was related to the degree of coronary artery stenoses in patients with T2DM and without cardiovascular disease. In line with the study, the results of our research analysis supported the notion that increased TyG index is associated with the number of vessels and the degree of CS, and our study builds on this with a more in-depth study of the severity of CAD in patients with CHD in different states of metabolic status.
The TyG index is a proven independent predictor of coronary artery calcification progression[15, 21]. A large-scale population study whose date form 5,593,134 Korean participants were evaluated to indicate that TyG index as a simple and low-cost marker was associated with atherosclerotic cardiovascular disease. The TyG index is also associated with carotid arterial stenosis and our previous study revealed that the relationship between the TyG index and carotid artery plaque is significant in CHD patients[22, 23]. Additionnally, the elevated TyG index plays a potentially valuable role in early recognizing the individuals at high risk of CVD.
Patients with IR result in the disappearance of the normal coordinated hypoglycaemic response and the loss of, for example, inhibition of endogenous glucose production, inhibition of endogenous glucose lipolysis, cellular uptake of available blood glucose, and net glycogen synthesis. Triglycerides stored in adipose tissue increase as IR begins to lipolysis and produce more fatty acids before raising blood glucose levels. The TyG index, a product calculated from FPG and TG, has also become a simple surrogate marker for IR and is inversely related to IR as determined using the euglycemic-hyperinsulinemic clamp test. Among the traditional risk factors, FBG and TG levels have been associated with an increased risk of T2DM[28, 29]. In addition to the well-known fact that IR accelerates the decline in pancreatic β cell function leading to the development of diabetes on the one hand. The above theory could explain the relationship between IR and diabetes in another way. Previous evidence reported that patients with metabolism disorder had more severe coronary artery lesion in the coronary artery stenosis population. IR, a severe metabolic syndrome that can cause diabetes, is a collection of pathological conditions associated with systemic inflammation, endothelial dysfunction, oxidative stress and prothrombotic states. Moreover, IR is also considered a pivotal risk factor for cardiometabolic diseases. IR plays an essential role in the atherosclerotic process with associated clustering of risk factors increasing the risk of atherogenic damage. Compared with the homeostasis model assessment of insulin resistance (HOMA-IR), the TyG index is better for predicting subclinical atherosclerosis. It may be ascribed to the myocardium generating damage and atherosclerotic plaque generation due to IR. Based on the above rationale, we can better understand the association between the TyG index and CAD severity that emerged in the analysis of the study.
In this retrospective cohort study, we observed that the prevalence and incidence of abnormalities in clinical and biological characteristics were higher than in the general population. The results showed that an elevated TyG index was also associated with more severe dyslipidemia, progressively impaired glucose metabolic status and progression of coronary stenoses. CHD patients were detected 2-VD with stenosis ≥ 50% in 36.9% and 3-VD in 28.0%. This may be due to the fact that our study was a hospital-based study in which subjects had CHD with more risk factors, such as diagnosed diabetes, dyslipidemia, and hypertension. The results of epidemiological studies have identified multiple important risk factors responsible for the progression of CAD, such as hypertension, hyperlipidemia, IR and obesity[35, 36]. Our results corroborate this view that CHD patients showed more abnormal biochemical parameters and glucose metabolic status with developing severity of CAD.
This study demonstrated that the number of coronary lesions was associated with levels of the TyG index and the associativity was higher than the relationship between other risk factors and CAD severity and CS degree regardless of the confounders such as age, sex, BMI, SBP, DBP, smoking, drinking and drug therapy, further emphasizing the consistency of this association. IR has been present for an extended period before the diagnosis of diabetes and it is a critical pathophysiological pathway leading to DM. The TyG index can similarly indicate IR in non-diabetic individuals. This theory is consistent with our results: The TyG index could be of value for detecting the severity of CAD across all CHD patients.
It is well known that 3-VD, the three major vessels lesions of the coronary arteries involving left anterior descending, left circumflex and right coronary arteries, is the type of CHD with the highest risk of death and adverse events and is a clinical indication for coronary artery bypass grafting (CABG). This study showed that the TyG index of CHD patients was significantly associated with the risk of 3-VD. In the meantime, the CHD patients in the DM state had their TyG index significantly related to 3-VD. The present study's findings showed that the incidence of three branch lesions is higher in the DM state than in the NGR and Pre-DM states (34.6%>22.3%>18.3%). Studies have indicated that DM usually exists with dyslipidemia and increases CHD risk[3, 39]. DM may increase cardiovascular risk in individuals by accelerating the development of atherosclerosis, including through polygenic risk[40, 41]. Unfortunately, we did not find a statistical association between the TyG index and the presence of 3-VD in CHD patients without diabetes. This may be associated with higher levels of the TyG index in 3-VD but lower levels of the TyG index in NGR and Pre-DM states, which needs to be further explored in future studies.