REFEEDING AFTER FASTING INCREASES APPARENT OXIDATION OF N-3 AND N-6 FATTY-ACIDS IN PREGNANT RATS

The intake, excretion, and accumulation of long-chain fatty acids was analyzed to test the hypothesis that during pregnancy in the rat whole-body partitioning of n-6 and n-3 fatty acids between net accumulation or disappearance (apparent oxidation) is determined by both maternal energy status and fetal development. From midpregnancy to term in ad libitum-fed rats consuming rodent chow, 30% more saturates and monounsaturates accumulated in the whole body than were consumed, whereas 28% of dietary n-6 fatty acids and 55% of dietary n-3 fatty acids were apparently oxidized. After 48 hours of fasting during midpregnancy (days 13 to 15) followed by refeeding to term, net accumulation of saturates and monounsaturates was equivalent to intake, but whole-body disappearance of n-6 fatty acids exceeded intake by 6% (NS), whereas n-3 fatty acid disappearance exceeded intake by 43%. Thus during refeeding after fasting, dietary n-6 and n-3 fatty acids were apparently completely oxidized and there was actually a net loss of n-3 fatty acids from whole-body stores. Fasting during midpregnancy did not significantly affect fetal weight gain or maternal gestational hyperlipidemia toward term. We conclude that during pregnancy n-6 and n-3 fatty acids are not only required for maternal and fetal structural and storage lipids, but are also used to meet energy requirements, especially during refeeding after fasting. © 1993.