A total of 9,944 subjects were included in this study, and the cross-sectional study was conducted data from a full population. It was found that HDL-C and non-HDL-C were correlated with the incidence of acute myocardial infarction in the whole sample population. This association remained significant even after adjusting for age, sex, hypertension, diabetes, smoking and BMI. Many observational studies in western populations have shown a significant association between non-HDL-C and coronary heart disease[22–24]. Similarly, a Prospective study involving 27,020 participants in China found that higher levels of non-HDL-C were associated with an increased incidence of cardiovascular disease, and the extent to which LDL-C predicted the risk of CVD in Chinese people was similar. In addition, most of the lipid results of the patients included in this study were in the non-fasting status, indicating that the non-HDL-C level was associated with the occurrence of acute myocardial infarction even in the non-fasting status. Additionally, A study from Japan followed for up to 20 years reported that non-HDL-C levels were clearly associated with future mortality by coronary heart disease, but not by stroke (The subjects were mostly in the non-fasting status).
The total sample population was subdivided according to whether or not they had diabetes. It was found that LDL-C, HDL-C, and non-HDL-C were associated with the occurrence of acute myocardial infarction in the non-diabetic population after adjustment for age, sex, smoking and other factors, similar to the results in the whole sample population. However, in diabetic patients, non-HDL-C was still associated with the occurrence of AMI after adjustment for gender, age, smoking, hypertension, and body mass index. Conversely, there were no significant associations between HDL-C and LDL-C and the occurrence of AMI. In a meta-analysis of 156,381 patients with non-HDL-C, the combined RR of coronary heart disease in the general population and patients with type 2 diabetes was 1.59(95%CI, 1.46 to 1.72) and 1.99(95%CI, 1.57 to 2.51), and indicated that elevated serum non-HDL-C level was independently associated with an increased risk of CVD in the general population and individuals with type 2 diabetes. When comparing the highest with the reference lower non-HDL-C level, CVD risk increased by 62% and 99% in the general population and type 2 diabetes patients, respectively.
In terms of the results of this study, low levels of HDL-C did not differ statistically between the AMI group and non-AMI group in diabetic subjects. Several studies have shown that an inverse relationship between the antiatherosclerotic effects of HDL and the incidence of cardiovascular events, particularly concerning reverse cholesterol transport (RCT), is increasingly being established. In addition to this protective effect, HDL is also associated with other important functions, such as antioxidant protection, regulation of cholesterol efflux, inhibition of cell adhesion molecule expression and leukocyte activation, and induction of nitric oxide production. Therefore, low HDL concentrations in patients with diabetes are considered to be one of the major causes of increased cardiovascular risk. However, there have been studies that increased patients’ HDL-C levels by using CETP inhibitors, and no significant reduction in cardiovascular events was observed. This suggests that there may be other factors besides HDL concentration that contribute to the increased risk of cardiovascular disease in diabetic patients.
In the last few decades, low-density lipoprotein cholesterol (LDL-C) was recommended as the primary treatment target on lipid management in CHD patients[28–30]. Selected worldwide dyslipidemia guidelines and expert recommendations, including the American Diabetes Association/American College of Cardiology (ADA/ACC) guidelines, Canadian Cardiovascular Society (CCS) guidelines and European Society of Cardiology/European Atherosclerosis Society (ESC/EAS) guidelines, have all identified LDL-C targets of < 70 and < 100 mg/dl for patients at very high- and high-risk for CHD, respectively, and recommended that first-line therapy should target LDL-C reduction. However, trials on the effectiveness of lipid-lowering treatments suggest that the cardiovascular benefits of statins may outweigh their effect on LDL-C levels. Studies have shown that lowering LDL-C in patients with diabetes is insufficient to reduce cardiovascular events to the level of those without diabetes, and intravascular ultrasound studies have shown less plaque regression in patients with diabetes after cholesterol reduction. Residual cardiovascular disease risk appears to be partially related to elevated plasma triglycerides and abnormal metabolism of triglyceride-rich lipoproteins (TRLs). These lipoproteins are generally thought to be composed of chylous, VLDLs, and their respective residual lipoproteins (residual lipoprotein particles), many of which are present in intermediate-density lipoproteins[35–36]. In 2011, the Joint Committee of the European Society of Cardiology (ESC)/ European Atherosclerosis Society (EAS) issued guidelines similar to the updated US 2004 guidelines (i.e., diabetes is a high-risk state with an LDL-C target < 70 mg/dl). However, it included non-HDL-C and apolipoprotein B as alternative targets to LDL-C, mainly in patients with T2DM. Several studies in Chinese populations have shown that the association between non-HDL-C and cardiovascular disease remains a stronger predictor of LDL-C for coronary heart disease and ischemic stroke in urban populations and in the occupational cohorts. In this study, it was found that among diabetic participants, HDL-C, LDL-C and non-HDL-C were included in the model, and LDL-C was not associated with the occurrence of acute myocardial infarction after adjusting for age, sex, hypertension, BMI, smoking and other factors. Even if only HDL-C, LDL-C and non-HDL-C were mutually adjusted, the correlation between LDL-C and the occurrence of acute myocardial infarction was not observed.
Compared with HDL-C, non-HDL-C is associated with the occurrence of acute myocardial infarction in the diabetic population, so more attention should be paid to non-HDL-C in diabetic patients.
Several potential limitations of this study should be considered. First, this study is a single-center study, and the sample population is mainly Han people in the Hengyang region of China, so the generality of other regions and races is limited. Second, data on blood pressure control at admission and history of ACEI/ARB and β-blocker use were missing. Therefore, we cannot rule out the possible influence of the drug on the results of the study. Third, participants in the non-AMI group were excluded from myocardial infarction only by coronary angiography, and the presence of other diseases that may affect the outcome was not excluded. Finally, due to the cross-sectional nature of the study, the current results only show an association between non-HDL-C and acute myocardial infarction. Prospective basic and clinical studies are needed to further confirm causality.