Dietary fat influences testosterone, cholesterol, aminopeptidase A, and blood pressure in male rats.

Introduction & A high intake of monounsaturated fat (MUFA) has been proposed to be a dietary factor able to decrease the incidence of cardiovascular disease and hypertension [1] . It has been shown that an increase in the saturation of dietary fat results in increased concentrations of total plasma cholesterol [2] and higher blood pressure [3] . It was previously shown that serum total cholesterol levels were higher in mice fed diets containing saturated oils than in those consuming unsaturated fat. In addition, angiotensin II – degrading (aminopeptidase A) activity increased progressively with the degree of saturation of dietary fatty acids [4] . A subsequent study found that dietary fatty acid composition affected aminopeptidase A activity in the testes of mice, suggesting a role for fatty acids in male reproductive functions, including androgen synthesis [5] . It was recently observed that a diet enriched with Iberian pig lard remarkably increased serum testosterone levels in comparison to diets containing other types of fatty acids with different degrees of saturation [6] . This and other studies suggested an infl uence of gonadal steroids and cholesterol on angiotensin-degrading activities [7] . Other actions of gonadal steroids by nongenomic-dependent mechanisms have been reported, such as stimulation of insulin secretion and Ca 2 + uptake as well as vasodilatory effects [8, 9] . In the present report we analyze the effect of various diets enriched in fatty acids with different degrees of saturation on systolic blood pressure, plasma levels of testosterone, total cholesterol, HDL cholesterol, LDL cholesterol, and angiotensin II – degrading activity. Materials and Methods & Six groups of adult male Wistar rats (200 – 250 g, n = 8 in each group) were fed with isocaloric diets for 16 weeks. Each diet was supplemented with 10 % of the oil under investigation: sesame oil, sunfl ower oil, fi sh oil, olive oil, Iberian pig lard, or coconut oil. The characteristics of the different types of dietary fat compared in this study are summarized in Table 1 [10, 11] . At the end of the feeding period, systolic blood pressure in each rat was recorded, and then the animals were killed by Equithesin anesthesia. Blood samples were obtained and plasma was isolated by centrifugation for 10 minutes at 2000 g and stored at − 20 ° C. Plasma testosterone levels were measured by radioimmunoassay as previously reported [6] and expressed as nanograms per milliliter. Cholesterol levels were determined colorimetrically with a commercial kit purchased from Sigma. Aminopeptidase A activity was determined with a fl uorometric assay using glutamyl-naphthylamide as the substrate, as previously described [12] . Systolic blood pressure was measured with a tail-cuff plethysmograph (LE 5001 Pressure Meter, Letica SA, Barcelona, Spain) in trained, unanesthetized animals as previously reported [13] . For the statistical analysis we used one-way analysis of variance to analyze differences between groups. Post-hoc comparisons were made with Tukey ’ s test. P-values below 0.05 were considered signifi cant.