الملخص الإنجليزي
Small dense LDL (sd LDL) is considered as an emerging cardiovascular risk factor by the National Cholesterol Education Program. It was found that the risk of coronary heart disease increases by 2-3 folds in people with high levels of sd LDL. This makes the measurement of LDL size essential. Serum oxidation status is also a very important determinant of atherosclerosis. Oxidation renders LDL particles unrecognized by LDL receptor due to the conformational changes of the Apo B-100 ligand. Therefore, oxidized LDL (ox LDL) particles stay more in the blood and can then penetrate the artery wall triggering atherosclerosis events. Methods used to measure LDL size and serum oxidation are tedious, expensive and time consuming which makes them not suitable for the use in clinical laboratories and for large number of samples.
Lipids profile surrogate measures that can predict LDL size or serum oxidation may be of significant benefit as they can be easily measured in the laboratories in routine clinical practice. One of the most widely studied ratios is triglyceride / high density lipoprotein cholesterol ratio (TG/HDL-C). Most of the studies in this field where done on patients with metabolic diseases.
In this study, we have investigated the correlation between TG/HDL-C ratio with both LDL size and serum oxidation in an attempt to investigate if this ratio could predict these parameters in healthy subjects. Eighty six serum samples were collected from apparently healthy Omani subjects with no known metabolic abnormalities. We measured their lipids profile and liver function tests. LDL size was measured by polyacrylamide gradient gel electrophoresis (PAGGE) and serum oxidation by the copper induced oxidation method measuring lag phase and baseline oxidation status.
In this study, the results showed that TG/HDL-C ratio in healthy subjects was the main predictor of serum baseline oxidation status (BOS) and significantly correlated with waist/hip ratio, TG and LDL-C. However, TG/HDL-C did not correlate with LDL size. On the other hand, LDL size was predicted by total bilirubin levels .
These results suggest that increased TG levels along with low HDL-C are significant determinants of oxidative stress in healthy subjects even before increasing atherogenic sd LDL in serum. It also means that unlike in patients with type 2 diabetes, TG/HDL C ratio does not predict LDL size in healthy subjects but it predicts their BOS.
