ABC | Volume 111, Nº6, December 2018

Original Article Santos et al OX-LDL and Oral Contraceptives Arq Bras Cardiol. 2018; 111(6):764-770 Table 2 – Comparison of fasting lipids (mg/dL) among the groups studied Variables GCOC (n = 21) CG (n = 21) p value Triglycerides 95 (73 – 112) 49 (40 – 64) < 0.01 ** Total cholesterol 210 ± 38.6 183 ± 29.7 0.01* HDL-c 58 ± 19.3 48 ± 11.5 0.04* LDL-c 134 ± 35.1 126 ± 27.7 0.42* VLDL-c 19 (15 – 22) 10 (8 – 13) < 0.01 ** TG/HDL-c ratio 1.7 ± 0.5 1.1 ± 0.5 < 0.01* GCOC: combined oral contraceptive group; CG: control group; HDL-cholesterol: high-density lipoprotein cholesterol; LDL-cholesterol: low-density lipoprotein cholesterol; VLDL-cholesterol: very low-density lipoprotein cholesterol; TG: triglycerides;*Two-way t-test for independent samples; ** Bidirectional Mann-Whitney test. In contrast to our findings, although in a population of 40‑48 years of age, different oral contraceptive formulations, and factors such as smoking, intestinal disease and physical activity, the ELAN study 3 did not identify any significant changes in plasma oxidized LDL of women who use and do not use oral contraceptives. However, it was noted that in women using this group of drugs, the lipid oxidation, marked by the highest concentration of peroxides (-OOH), was 1.7 times higher. According to the authors, this result could be explained by the higher oxidative stress induced by ethinylistradiol present in the formulations of COC. 3 In line with this observation, we can suggest, as well as other studies, that women on COC have higher oxidative stress. 3 This hypothesis can be supported by the significant increase in oxidized LDL in GCOC, because according to the literature this oxidized lipoprotein is a variable of oxidative stress. According to literature data, the estrogenic and androgenic properties of COCs have an influence on oxidative stress, because these hormones have several actions on the vascular endothelium, increasing the bioavailability of nitric oxide, a fact that does not seem to protect, but rather attacks the endothelium, due to increased oxidative stress. 27 Another fact that calls attention is that oxidized LDL has a correlationwith other lipid variables. In fact, our results, as well as other studies, indicate that oxidized LDL has amoderate positive correlation with total cholesterol, triglycerides and LDL. 8,12 This relationship may be partially justified by findings indicating that an increase of 1mg/dL in serum levels of total cholesterol or LDL-cholesterol, as well as an increase of one unit in the total cholesterol/HDL-cholesterol ratio, can predict increases of 0.22, 12.21 and 15.78 U/L at oxidized LDL levels. 28 According to the literature, triglycerides can predict, regardless of variables such as LDL-cholesterol, elevated oxidized LDL values. 27 Consistent with the literature, our study demonstrated a significant increase in serum TG, HDL-cholesterol, CRP, and systolic blood pressure values in GCOC, whereas no difference was detected in LDL-cholesterol values. 29-31 However, caution should be taken when analyzing the LDL-cholesterol and HDL‑cholesterol results, because the TG/HDL-cholesterol ratio is significantly higher in this group of women, indicating a higher atherogenic potential related to LDL cholesterol. Regarding HDL cholesterol, although in our sample its values are significantly high, it is not yet known what the effects of COC on its subfractions are, since atherogenic particles of HDL-cholesterol are present. 32 Figure 1 – The boxplot shows a higher concentration of oxidized LDL in women using combined oral contraceptives compared to those who did not use this group of drugs (p < 0.01). In addition, it is noted that in the GCOC the concentration of this oxidized lipoprotein is in the first quartile, while the CG is in the third quartile. The comparison of the median between groups was compared by bidirectional Mann-Whitney test. 800 600 400 200 0 GCOC CG Oxidized LDL (um/mL) 767