POLYUNSATURATED FATTY ACIDS (n-3) FROM VEGETABLE SOURCE IMPROVE LIPID METABOLISM IN DYSLIPEMIC INSULIN RESISTANT RATS

MARÍA CECILIA BERNARD; GUSTAVO HEIN; ADRIANA CHICCO; YOLANDA B LOMBARDO

LLOYD`S BAIA HOTEL SALERNO, ITALY.

Congreso; 24th INTERNATIONAL SYMPOSIUM ON DIABETES AND NUTRITION.; 2006

We have previously shown that hypertriglyceridemia and insulin resistance which developed in rats fed a sucrose rich diet (SRD) for long-time (6months) was completely normalized when corn oil (CO) was replaced by fish oil (rich in n-3 fatty acids: EPA and DHA) as a source of fat in the diet during the last 2 months of the feeding period. Soybean oil (SO) is an important vegetable source of α linolenic acid (18:3, n-3, ALA) which is a precursor of 20 and 22 carbon n-3 long chain PUFAs: EPA and DHA. The purpose of this work was to study the effect of replacing the source of fat in the diet from CO to SO upon the dislipidemia and impaired glucose homeostasis present in long-term SRD fed rats. Methodology: To achieve this goal a group of 40 male Wistar rats was fed a SRD (w/w: 61% sucrose, 17% protein, 10% CO) for 4 months. At that time, one half of the rats (n=20) continued consuming the SRD for 2 more months. The other half received for 2 months a SRD in which the source of fat CO (10% w/w) has been replaced by SO (10% w/w, SRD+SO). The reference group of rats (n=20) was fed a control diet (CD) (w/w: 61% corn starch, 17% protein, 10% CO) throughout the experimental period. In all groups the following parameters were evaluated: i) Plasma glucose control (glycemia, insulinemia), plasma lipids: triglyceride (Tg), free fatty acids (FFA), total cholesterol (Ch). High density lipoprotein cholesterol (HDL-Ch) and liver and heart Tg content; ii) “In vivo” triglyceride secretion rate (TGSR), and the fractional removal rate of the intravenous fat emulsion from the circulation (IVFT). Results: At the end of the nutritional period, SRD-fed rats compared with the reference group (CD) showed: 1) Significant increase (p<0.05) of plasma glucose, Tg, FFA and Ch levels and a decrease of HDL-Ch. Tg contents increase (p<0.05) in heart muscle and liver. 2) The TGSR was significantly higher (p<0.05) while the IVFT decreased (p<0.05). Rats fed a SRD+SO compared to SRD significantly decrease (p<0.05) plasma Tg, FFA, Ch as well as heart and liver Tg contents although values are still significantly above those recorded in the control group (CD). The altered TGSR and IVFT were both improved without significant changes in plasma insulin and glucose levels. Conclusion: These results indicate that the administration of SO improve the altered lipid metabolism in the SRD fed rats possibly through the conversion of ALA to long-chain n-3 PUFA, and suggest that the increase of ALA in the diet could be important in terms of long-term dietary intake.