ABC | Volume 111, Nº6, December 2018

Original Article Santos et al OX-LDL and Oral Contraceptives Arq Bras Cardiol. 2018; 111(6):764-770 use and do not use COC was tested, and the correlation between oxidized LDL and the fasting lipid profile variables and C-reactive protein were evaluated. Methods Sample The research is characterized as a cross-sectional analytical study, which has as a predictor variable the use of COC, and as an outcome variable, the oxidized LDL. The study population consisted of 42 self-reported healthy, eutrophic, irregularly active women aged 19 to 30 years, nulliparous, with fasting values of triglycerides < 150 mg/dL, blood glucose < 100 mg/dL, and who used COC or not. All participants were students of a private college located in the city of Salvador, BA - Brazil. The sample was divided into two groups: COC group (GCOC) consisting of 21 women using COC of low dose of ethinylestradiol (15 to 30 mcg) for at least 1 year; and control group (CG), consisting of 21 women who had not used any type of hormonal contraceptive for at least 1 year. To determine if participants were irregularly active, the International Physical Activity Questionnaire (long version), developed by the World Health Organization and the US Centers for Disease Control and Prevention was used. 18 Women who reported familial dyslipidemia, hypo- or hyperthyroidism, history of alcoholism or smoking, polycystic ovarian syndrome, hypo- or hyperlipidic diet, use of dietary or anabolic supplements, hypolipidemic agents, corticosteroids, diuretics or beta blockers were excluded. Those who presented, on the physical evaluation, values of SBP ≥ 140/90 mmHg, abdominal circumference ≥ 80 cm or, in the laboratory examination, alteration of pyruvic (TGP) or oxidative (TGO) glutamic transaminase, or creatininewere also excluded. TGP and TGOwere evaluated to identify pancreatic and hepatic diseases, and creatinine, to identify the presence of renal dysfunction. All the participants answered the semi-structured questionnaire, elaborated by the authors of the research and underwent physical examination. The latter consisted of resting blood pressure (BP), total body mass, height and waist circumference. Body mass index (BMI) was calculated with mass and height measurements, according to the Quetelet equation: mass (kg)/height 2 (cm). The BMI cutoff points adopted were those recommended by the IV Brazilian Guidelines on Dyslipidemias and Prevention of Atherosclerosis of the Department of Atherosclerosis of the Brazilian Society of Cardiology (SBC), 19 that is, low weight (BMI < 18.5); eutrophy (BMI 18.5-24.9); overweight (BMI 25-29.9), and obesity (BMI ≥ 30). The abdominal circumference was obtained with a Starrett ® metric and inelastic tape, with a measurement definition of 0.1 cm. It was measured at the lowest curvature located between the last rib and the iliac crest without compressing the tissues. 20 Laboratory Data Collection Protocol To collect the laboratory data, the volunteers were referred to the Laboratory of Clinical Pathology in the city of Salvador, state of Bahia - Brazil, where blood samples were collected. Following antecubital vein puncture, 10 mL of blood were collected for triglycerides (TG), oxidized LDL, high-density lipoprotein (HDL-cholesterol), total cholesterol (TC), blood glucose, pyruvic glutamic and oxidative transaminase. LDL-cholesterol and the very low density cholesterol (VLDL‑cholesterol) were calculated by the Friedewald equation: 21 TC = HDL-cholesterol + LDL-cholesterol + VLDL-cholesterol, with VLDL-cholesterol being equal to TG/5. The collections were performed with the volunteers fasting for 12 hours. All were instructed not to change their diet during the week of the test, not to perform any physical exertion other than usual, and not to drink alcoholic beverages 24 hours before the laboratory examination. For the CG, the collections were performed between the 5th and 10th day of the menstrual cycle, considering the lower hormonal fluctuations, as recommended by Casazza et al. 22 Blood samples were collected by a trained professional and in a laboratory environment suitable for this type of procedure. For determination of oxidized LDL in the serum samples, the ELISA kit was used. In this analysis, the oxidized LDL values considered normal were between 100 and 700 mU/mL. The triglycerides, HDL-cholesterol, total cholesterol and blood glucose values were obtained by the Trinder colorimetric enzyme method. 23 TGP and TGO were measured by the Reitman-Frankel colorimetric method. 24 The sample adequacy calculation was performed in the GraphPad StatMate 2.0 for Windows software, which considered a difference between the means of 63 MU/mL and standard deviations of 119.5MU/mL (GCOC) and 43.6MU/mL (CG), both extracted from a previous pilot study (n = 12). In order to eliminate the bias of the laboratory variation coefficient of oxidized LDL dosage, which was of 3%, a significant difference was considered between the groups, of 20% for alpha and beta of 0.05 (bidirectional) and 0.80, respectively. Thus, 20 women were needed in each group. Statistical analysis Initially, symmetry and kurtosis tests and the Shapiro-Wilk test were applied to check data distribution. The variables values with normal behavior were described in mean and standard deviation and the values of nonparametric variables in median and interquartile range. Categorical variables were presented as absolute and relative frequencies. For the intergroup comparison of the parametric variables, we used the unpaired bidirectional Student t test, and for the non-parametric variables, the Mann-Whitney test. The correlation between the oxidized LDL values and all variables of the lipid profile - triglycerides, total cholesterol, HDL‑cholesterol and LDL-cholesterol, and CRP was also verified. In the correlation analysis, the Spearman correlation coefficient was used. In addition to the inter-group comparisons of oxidized LDL, the sample was categorized based on the median of oxidized LDL in women with LDL-oxidized values above and below the median. After the categorization, Fisher's exact test was used. All analyzes were performed in the BioStat 5.0 statistical package, adopting a significance level of 5%. 765