Time-dependent supplementation of vitamin E influences leptin expression in the aortic layers of rats fed atherogenic diet.

ABSTRACT

An excessive consumption of a diet rich in saturated fatty acids is a key factor in pathogenesis of cardiovascular diseases which are strictly connected with leptin imbalance in the vessels. However, whether vitamin E supplementation would influence leptin expression in aortic layers is still unknown. For 3 or 6 weeks male Wistar rats were fed a high-fat (20% w/w) diet with lard as dietary fat source with or without vitamin E supplementation (50 mg/100 g of diet). The 6-week intake of an atherogenic diet increased total cholesterol (TC) and high density lipoprotein cholesterol (HDL) plasma levels simultaneously lowering TC/HDL ratio (ANOVA p≤0.0001 for all three parameters). After longer period of feeding it was stated that leptin expression in all three aortic layers was enhanced (ANOVA p≤0.0001 for endothelium, tunica media and adventitia, respectively) with decreased leptin plasma concentration (ANOVA p≤0.0001). After both periods of feeding vitamin E supplementation caused an increase in plasma HDL content and a decrease of TC/HDL ratio. In the 3-week experiment vitamin E addition caused a decrease in leptin plasma levels (Fisher's test, 3L versus 3LE p≤0.002) and an increase in leptin expression in all three aortic layers (Fisher's test, 3L versus 3LE p≤0.005, p≤0.01 and p≤0.05 respectively for endothelium, tunica media and adventitia). The contradictory results were observed in the 6-week experiment in which vitamin supplementation decreased leptin expression in the aortic endothelium (Fisher's test, 6L versus 6LE p≤0.001) with lack of changes in the other two layers of the aorta and plasma. The study showed that vitamin E supplementation influenced leptin expression in aortic layers in rats fed atherogenic diet differently depending on the length of feeding period. It may suggest that vitamin E consumption plays an important role in the control of leptin status in the endothelium.