Nonlinear optical responses of oxidized low-density lipoprotein: Cutoff point for z-scan peak-valley distance.

The development of new methods to assess biomarkers of cardiovascular disease is currently a subject of scientific research. This article broadens our view of nonlinear optical responses of oxidized low density lipoprotein (LDL) evaluated using the Z-scan peak-valley distance and proposes a cutoff point. We investigated the association of peak-valley distance and some cardiovascular risk factors related with sociodemographic, clinical and anthropometric profiles and plasma biomarkers such as lipid and glucose profile, apolipoprotein, lipoprotein subfractions and omega 3 fatty acids. Z-scan analysis was performed using isolated LDL after ultracentrifugation in human blood samples collected after fasting. Peak-valley distance is a parameter that decreases directly depending on the oxidizability of LDL. As peak-valley distance was associated with relevant biomarkers of cardiovascular risk, we tested cutoff points for categorization and the best results were obtained using percentile < 75 (Lowz-scan) and percentile ≥ 75 (Highz-scan). The regression logistic models tested after establishing the cutoff point for peak-valley distance showed that increased levels of plasma high-density lipoprotein cholesterol, apolipoprotein A-I, large high-density lipoprotein subfractions and docosahexaenoic acid are directly associated with HighZ-scan. Conversely, high levels of small LDL were associated with decreased odds of presenting HighZ-scan. In conclusion, the cutoff point for peak-valley distance was able to identify atherogenic characteristics of LDL and its relationship with some parameters of high-density lipoprotein functionality.