This study found that (1) fasting and non-fasting lipid concentrations were well correlated; (2) fasting and non-fasting hypertriglyceridemia were prevalent in AIS patients; (3) fasting and non-fasting hypertriglyceridemia were associated with younger age, diabetes, and higher BMI and initial SBP; and (4) FTG and NFTG levels were not associated with the clinical outcomes.
Following food ingestion, TG is transported from the small intestines by chylomicrons through the bloodstream. Lipolysis of TG within chylomicrons, catalyzed by lipoprotein lipase, transforms these particles into atherogenic TG-remnant lipoproteins. Elevated postprandial TG levels, reflecting either higher peak levels or delay in clearance of TG-rich particles, can lead to accumulation of these atherogenic particles.13 The data presented in Supplement Table 1 corresponds to the expected time course of postprandial TG metabolism. In response to food intake, TG concentrations typically reach their peaks approximately 4 h after meals and decline thereafter.14 Thus, postprandial TG levels are more physiologic and better associated with thrombogenic conditions, such as ischemic stroke. Furthermore, our study suggests that patients with elevated FTG and NFTG levels show similar characteristics. Therefore, NFTG can replace FTG in the diagnostic evaluation of patients with AIS.
Several biological mechanisms provide plausible explanations about the associations between high FTG and NFTG concentrations and young age, higher BMI, higher SBP, and diabetes, which are components of the metabolic syndrome. Hypertriglyceridemia is a feature of dyslipidemia seen in type 2 diabetes and metabolic syndrome, which may also include insulin resistance, abdominal obesity, and hypertension.10 Hyperinsulinemia leads to an increase in the production of very-low-density lipoprotein.15 Hyperglycemia also impairs removal of TG-rich lipoproteins from circulation. Patients with poorly controlled diabetes have higher TG levels than those with well-controlled diabetes. Postprandial hyperlipidemia in diabetic patients appears to be prolonged, indicating that the arteries are exposed to atherogenic particles for extended periods.15,16
In this study, both fasting and non-fasting TG levels were not associated with the composite outcome comprising of stroke recurrence, myocardial infarction, or all-cause mortality up to one year after the index stroke. Contradicting our results, in patients with established cardiovascular disease or risk factors, higher TG levels were reportedly associated with an increased risk of recurrent vascular events17, and reducing TG levels lowered the risk of ischemic events18. There are some explanations for these discrepancies. First, it has been reported that high TG levels might be associated with milder stroke severity and better outcomes in patients with AIS.19–21 In our study, NFTG negatively correlated with the initial National Institutes of Health Stroke Scale scores (Pearson correlation coefficient = − 1.33, p < 0.001). Second, TG could paradoxically prevent lipotoxicity, and subsequently poor outcome.22,23 Third, treatment with statin at discharge might attenuate the effect of high TG on outcome. The proportion of patients treated with statin at discharge was 88.5% in our study. In a previous study that reported a significant correlation between TG and recurrent stroke, the statin prescription rate was 36%.24
Our study had several limitations. First, it only included Korean patients, and these results may not be generalizable to other populations. Second, the proportion of patients excluded from the analysis was 63%, accounting for a fairly large proportion. Particularly, when compared to patients excluded from this study, the proportion of young males, BMI, and prevalence of hyperlipidemia was relatively higher among the included patients, but the prevalence of diabetes did not differ between them (Supplemental table 5). The possibility of selection bias cannot be excluded, but the differences seemed considerably small to affect the clinical outcomes. Third, we did not have information on other possible factors affecting the lipid levels, such as foods, drugs, and nutritional state.