Regulation of lipid metabolism and oxidative stress in BioF1B hamsters : a comparison of fish oil and seal oil rich diets

Dubey, Pratibha. (2010) Regulation of lipid metabolism and oxidative stress in BioF1B hamsters : a comparison of fish oil and seal oil rich diets. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (8MB)

Abstract

Dietary supplementation of fish oil has been associated with reduced risk of cardiovascular disease. However, previous studies from our lab showed severe hyperlipidemia and elevated oxidative stress levels in BioF1B hamsters fed 20% (w/w) fish oil supplemented diet. BioF1B hamster, an inbred strain from Bio87.2 and Bio1.5 parent strains, is an animal model for diet induced hyperlipidemia and atherosclerosis. BioF1B hamsters have significantly lower post-heparin lipoprotein lipase (LPL) activity as compared to Golden Syrian hamsters, which is further reduced in response to 20% (w/w) fish oil diet. Reduced LPL activity in BioF1B hamsters is believed to interfere with the clearance of chylomicron-like particles and thus responsible for fish oil induced hyperlipidemia. In the present study we compared the effects of two ω-3 PUFA-rich sources, fish oil and seal oil, on regulation of lipid metabolism and oxidative stress in BioF1B hamsters. The two marine sources of ω-3 PUFA differ in the intramolecular distribution of ω-3 PUFA on their triglyceride (TG) molecules. While EPA and DHA are primarily located in sn-2 position in fish oil TG, these are distributed in sn-1 and sn-3 positions in seal oil TG. Fish oil and seal oil further differ in their fatty acid composition with significantly higher levels of DP A and MUFA in seal oil as compared to fish oil. We hypothesized that BioF1B hamsters will be able to tolerate seal oil better than fish oil due to differences in positional distribution of ω-3 PUFA in TG molecule as well as differences in the fatty acid composition. Moreover, increased resistance to oxidation has been reported with seal oil. Significantly lower plasma and liver lipid levels were observed with 20% (w/w) seal oil fed BioF1B hamsters as compared to 20% (w/w) fish oil fed BioF1B hamsters. RT-PCR analysis showed significantly reduced SREBP-1cmRNA expression levels in seal oil fed hamsters which can partially explain the suppression of lipogenesis in response to dietary seal oil compared to fish oil. Seal oil fed BioF1B hamsters also showed significantly lower plasma and liver TBARS levels, thus suggesting reduced oxidative stress relative to fish oil fed hamsters. Since fish oil fed hamsters showed elevated levels of oxidative stress, we wanted to investigate possible beneficial effects of antioxidant supplementation in hamsters fed high fat diets. Berry extract rich in anthocyanins has gained prominence as a potent antioxidant in recent years. Study of the role of anthocyanin enriched (25% w/w) elderberry extract supplementation on plasma lipid levels in marine oil fed BioF1B hamsters also revealed significant reduction in all plasma lipid parameters upon addition of elderberry extract to respective marine oil fed BioF1B hamsters. While cosupplementation with elderberry extract resulted in significantly lower hepatic total cholesterol and cholesterol ester concentrations in both fish oil and seal oil fed BioF1B hamsters, reductions in hepatic TG and free cholesterol levels was seen in fish oil fed group alone. Moreover, both plasma and hepatic TBARS levels showed significant reductions upon elderberry extract supplementation in fish oil fed BioF1B hamsters. Thus, current findings suggest that seal oil may confer greater benefits compared to fish oil in lowering lipid and oxidative stress levels under certain genetic conditions. Furthermore, co-supplementation of fish oil with anthocyanin enriched elderberry extract may be beneficial under these conditions than fish oil alone.

Actions (login required)

View Item