Efeito da dieta hipoprotéica hiperglicídica nas vias de geração de glicerol-3-fosfato e na síntese de ácidos graxos no fígado de ratos em crescimento

Abstract

Growing rats submitted to a low-protein, high-carbohydrate diet (6% protein and 76% carbohydrate), for 15 days showed an increased lipid content in the adipose tissues, carcass and liver. They showed deep metabolic and hormonal alterations, as increased levels of plasma corticosterone and leptin, low levels of seric post-prandial insulin with no glycemic alteration. The aim of this work was to investigate the effect of the low-protein, high-cabohydrate (H) diet on the synthesis of fatty acids (FA) and on the pathways of glycerol 3-phosphate (G3P) generation. The animals fed with H diet showed lower liver weight, but increased lipid content and had no difference in the glycogen content when compared with the animals fed with the normoproteic (N) diet (17% protein; 65% carbohydrate). The animals fed with H diet, also showed an increase in plasmatic tumoral necrosis factor alpha (TNF-a). The rate of the total de novo FA synthesis and of FA synthesis from glucose were determined in vivo. Total synthesis was evaluated by incorporation of 3H from 3H2O and from glucose by 14C incorporation from 14C-glucose. The evaluation of the pathways of generation of G3P was performed by: a) Rate the of synthesis of total FA de novo from glucose and glyceroneogenesis, was evaluated, in vivo, by incorporation of 14C from 14C-glucose and 3H from 3H2O b) glyceroneogenesis, was evaluated in vitro by incorporation of 1- 14C-piruvate on glycerol-glyceride in liver slices c) direct phosphorylation of glycerol, was evaluated by the GyK protein content by Western Blotting. The gluconeogenesis was evaluated by the incorporation of 1- 14C-piruvate on glucose, released in the incubation medium. The liver glyceroneogenesis/gluconeogenesis capacity was evaluated by determination of phosphoenolpyruvate carboxykinase (PEPCK) content by Western blotting. The animals fed with H diet had an increase of 150% in the synthesis of total FA de novo and 270% from glucose, respectively, when compared with N animals. The pathways of generation of G3P from glucose in vivo and by glyceroneogenesis in vitro and in vivo did not have any alterations in both groups. The GyK protein content was found elevated about 30% in H animals when compared with N animals. The H diet did not alter glyconeogenesis evaluated in vitro. However, PEPCK protein content showed XIV an increase about 70%. The results suggest that direct phosphorylation of glycerol by GyK is the main substrate for the synthesis of FA de novo and for FA esterification in TAG, contributing thus for increased TAG content on animals fed with H diet.