Effect of high carbohydrate diet on elongase and desaturase activity and accompanying gene expression in rat's liver

Background: Hepatic fatty acids (FAs) are modified through different metabolic pathways including elongation and desaturation. These processes are catalyzed by elongases and desaturases, respectively. Glucose, by transcription factors, regulates these processes. The aim of the study was to evaluate the influence of high carbohydrate diet (68%) on the expression of elongase (Elovl-2, Elovl-5, and Elovl-6) and desaturase (triangle 5D,triangle 6D, Scd 1, Scd 2) genes and the activity of the enzymes. The changes in serum lipid profile (triglycerides (TG), total cholesterol (TC), HDL cholesterol) and glucose concentration were measured. Male Wistar rats were randomized into two study groups: animals fed with high carbohydrate diet (n = 6; HiCHO) and a control group fed with a standard diet (n = 6; ST). The expression of mRNA was determinate using reverse transcription PCR (RT-PCR). Hepatic FA composition was determined by gas chromatography, and FA ratios were used to estimate the activity of enzymes. Serum lipid profile and glucose concentration were measured using spectrophotometric methods. Results: The mean values of transcript expression of all examined elongases and desaturases in liver HiCHO rats were higher as compared to ST. Higher expression did not always correspond to higher activity (as index). More monounsaturated FAs (MUFAs) were detected in the liver of HiCHO rats as compared to ST. Serum TG level was higher in the HiCHO than in ST. Conclusions: These studies support the notion that the regulation of both Elovl and desaturase expression may play an important role in managing hepatic lipid composition in response to changes in dietary status.