Positive effects on lipid metabolism in Wistar rats of hypercholesterolemic diets enhanced by onion intake

Abstract

The complex biochemical composition of onions has been studied as a source of biological components with health-related properties. The evolution of hypercholesterolemia is associated with a large range of alterations considered as strong risk factors for many cardiovascular events. The objective of this study was to investigate the effects of an onion functional ingredient on plasma, erythrocytes, liver and adipose tissue fatty acid composition in hypercholesterolemic male Wistar rats. Rats (n=24) were randomly divided into three groups: control (C), high-cholesterol (HC), and high-cholesterol enriched with onion (HCO) groups. At the end of 7 weeks, animals were anaesthetized and euthanized by extracting blood by cardiac puncture. Plasma, erythrocytes, liver and adipose tissue were collected and immediately stored at -80 ºC. Fatty acids methyl esters were obtained by direct transmethylation using methanolic sulphuric acid and were identified and quantified by GC/MS. A significant variation of fatty acid composition was showed in HC and HCO compared with C in all tissues. Total lipid concentration significantly decreased in liver and adipose tissue in HC and HCO. SFA content was significantly higher in plasma (31.3%±0.9), erythrocytes (50.6%±0.6) and liver (64.2%±0.7) in C compared with HC and HCO, representing about 24%, 45%, and 47%, respectively. In contrast, SFA increased in adipose tissue both in HC and HCO compared with C. A significant increase in MUFA content in plasma was found in HC (24.4%±1.4) and HCO (27.2% ±1.6) compared with C (12.2%±0.7); in erythrocytes and liver the increase was lower. In plasma, PUFA content was significantly lower in HC and HCO compared with C. Interestingly, in liver and adipose tissue, PUFA increased in HC and HCO compared with C. Results showed unexpected positive effects on the lipid metabolism when assaying high-cholesterol diets in rats, enhanced by onion. Further research is needed to deepen in the involved mechanisms/pathways.