Meeting Abstract

P2.126  Friday, Jan. 4  Effects of a desaturase inhibitor on tissue lipid composition and dietary self-selection by the Djungarian hamster (Phodopus sungorus) ZEE, B.M.*; HIEBERT, S.M.; Swarthmore College; Swarthmore College shieber1@swarthmore.edu

Organisms change the levels of tissue saturated and unsaturated fatty acids in response to ambient conditions. Since unsaturated fatty acids increase the steric hindrance between lipids, homeoviscous adaptation and membrane pacemaker theories posit that organisms maintain a physiologically favorable membrane fluidity and leakiness, respectively, by changing ratios of saturated to unsaturated fatty acids in membranes. Past work has shown that P. sungorus increase their preferences for chow rich in polyunsaturated fatty acids (PUFAs) when exposed to cold, short days, or short-day mimicking melatonin treatments, in a manner consistent with both hypotheses. In addition to dietary lipid selection, delta 9-desaturase activity, which converts the saturated fatty acids (SFAs), palmitic (16:0) and stearic (18:0), to the monounsaturated fatty acids, palmitoleic (16:1) and oleic (18:1), respectively, is expected to increase membrane fluidity and leakiness, both of which are adaptations to decreased ambient temperature in endotherms experiencing regional or temporal heterothermy. To determine how delta 9-desaturase activity and dietary selection complement each other in adjusting membrane composition, we compared the dietary lipid preference and lipid composition of muscle and liver in experimental hamsters fed 0.4% sterculic oil (a known delta 9-desaturase inhibitor) with those of controls fed 0.4% sterculic oil that had been heated to reduce delta 9-desaturase inhibitor activity. Results confirm the delta 9-desaturase inhibiting activity of sterculic oil and support the hypothesis that dietary lipid choice and endogenous desaturase activity complement one another in the regulation of tissue lipid composition.