**3.1 Aim**

Given the demonstrated role-playing of blood cholesterol in the atherosclerotic continuum, we designed two studies to ascertain the usefulness of the LDL-cholesterol/HDLcholesterol, Triglycerides/HDL-cholesterol and Total-cholesterol/HDL-cholesterol ratios in predicting cardiovascular risk, through its relation to cardiovascular events and peripheral arterial disease (PAD) in two different clinical and experimental settings.

#### **3.2 Study 1 – Usefulness of the lipidic ratios predicting peripheral artery disease in hypertensive patients: A retrospective analysis**

The importance of the lipidic profile is well established in atherosclerotic processes related to coronary artery disease. Its relation with atherosclerosis in other vascular territories, particularly the inferior limbs has also received strong support from several experimental settings and in different clinical contexts. In order to address wether the lipid ratios can predict the occurrence of obstructive peripheral artery disease (PAD) we conducted a crosssectional study in a sample of hypertensive patients. The study population consisted of 920 Portuguese nationals, aged between 20 and 91 years (mean 64.23 + 12.30 years).

#### **3.2.1 Methods**

A total of 920 hypertensive patients (51.3% female, age 64.22 ± 12.01 years) were consecutively included in the study. None of the patients were taking drugs or were in situations known to affect lipoprotein metabolism. Total cholesterol, triglycerides and HDL cholesterol were measured. LDL cholesterol was obtained by Friedewald's formula (if triglycerides <3.39 mmol/l) or by ultracentrifugation. The LDL-Cholesterol/HDL-Cholesterol, Total Cholesterol/HDL-Cholesterol and Triglycerides/HDL-Cholesterol ratios were calculated in all patients. Blood pressure and heart rate were measured in standard conditions. Ankle-Brachial index (ABI) was estimated bilaterally as the ratio of ankle (left and right) systolic blood pressure and brachial (highest upper limb) systolic blood pressure. The normal range for ABI was 0.9-1.3 mmHg, and individuals with ABI<0.9 were classified as having peripheral arterial disease.

All data was processed using STATA for Windows, version 11.1. The distribution of the variables was tested for normality using the Kolmogorov-Smirnov test, and for homogeneity of variance by Levene's test. Simple descriptive statistics were used to characterize the sample and the distribution of variables. Logistic regression analysis was used to determine the influence of the lipidic parameters on the occurrence of PAD.

Groups were compared using the χ2 test for categorical variables and the Student's t test (2 groups) or ANOVA with the post-hoc Tukey test (3 groups) for quantitative variables. A value of P≤0.05 was taken as the criterion of statistical significance for a 95% confidence interval.
