Effects of a desaturase inhibitor on the tissue lipid composition and dietary preference of Djungarian hamster (Phodopus sungorus)

P. sungorus changes its dietary lipid preference for saturated (SFA) or unsaturated fatty acids (UFAs) in response to changes in ambient conditions. Scientists hypothesize that organisms are able to modify their membrane fatty acid composition via dietary selection to offset direct effects of the environment on membrane fluidity or ion leakiness. Desaturases, which convert SFAs to UFAs or further desaturate UFAs, serve as an additional mechanism of regulating membrane lipid composition. This study tested the hypothesis that dietary lipid selection and desaturase activity are compensatory mechanisms by observing dietary lipid selection in P. sungorus administered sterculic oil, which contains a desaturase inhibitor. After 2 weeks of consuming chow containing 0.4% (w/w) sterculic oil, liver phospholipids & triacylglycerides and forelimb muscle triacylglycerides showed a significant decrease in mono- unsaturated fatty acid (MUFA) levels relative to SFA levels. This result is consistent with the expected effects of the desaturase inhibitor in the sterculic oil. When given the same dose of sterculic oil and presented with a choice between diets rich in SFAs or polyunsaturated fatty acids (PUFAs), hamsters significantly increased PUFA preference. Despite the shift in behavior, however, liver phospholipids and triacylglycerides still showed a significant decrease in relative MUFA and PUFA levels. The results suggest that dietary preference alone was unable to compensate fully for reduced desaturase activity in regulating membrane lipid composition. Toward future effort to measure changes in fluidity induced by inhibition of desaturase activity, this study also developed applications using ³¹p Nuclear Magnetic Resonance (NMR) and Fluorescence Polarization (FP) spectroscopies with synthetic and natural lipid extracts