Building an experimental nutritional model of obesity. Efects of high fat diets on lipid profile and serum enzymes activity

Abstract

Obesity is the most common nutritional disorder and is associated with a cluster of chronic metabolic disorders such as dyslipidemia, atherosclerosis, and type 2 diabetes. As a part of an institutional project that studies Obesity as a base disease for the development of chronic age-associated diseases and the search for early biomarkers with predictive potential, one of our first main objectives is to establish a nutritional model of obesity in rat. Particularly, the objective of this work was to investigate the effects of high saturated fat diets on anthropometrical parameters, lipid profile, serum enzymatic activity of alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), and glucose levels, in rats. For that, male Wistar rats weaned at 21 days of age were randomly separated and fed with a normocaloric (NC) diet containing 366 kcal from lipids/kg diet (control group) or one of two high saturated fat diets, one containing 1570 kcal from margarine/kg diet (HFM group) and other with 1698 kcal from pork fat/kg diet (HFP group), for 12 weeks. Rats were maintained under 12 h light:12 h dark and 22–24°C conditions, with food and water ad libitum, during the whole treatment period. Food consumption was recorded daily while animals’ weight and body mass index (BMI) were registered weekly. After 12 weeks animals were euthanized, and blood samples were collected. Serum ALAT and ASAT enzymatic activity were determined by kinetic assays while glucose (G), triglycerides (TG), total cholesterol (TC), HDLc and [LDLc+VLDLc] were determined by colorimetric assays. Statistical differences between groups and throughout the treatment period were analyzed by two- or one-way ANOVA, depending on data, followed by Bonferroni post-hoc test, with P < 0.05 to confirm significant differences between groups and weeks. We observed HFM and HFP diets did not modify anthropometrical parameters nor serum glucose levels, during the whole treatment period, in comparison to the control group. However, interestingly, HFM and HFP significantly increased TG (P < 0.01 and P < 0.05, respectively), TC (P < 0.001 in both cases) and [LDLc + VLDLc] levels (P < 0.001 and P < 0.01, respectively) as well as ASAT activity (P < 0.05), in the rat serum. Our results also show decreased circulating HDLc levels in the HFP group in comparison to the NC group (P < 0.05). Thus, we can conclude that feeding rats with HF diets (~400–450% higher fat’s kcal in comparison to NC) during 12 weeks from weaning, induces early metabolic alterations; though, the treatment length, or the animals age, was not enough to generate a nutritional model of obesity.