Relationship of level and type of dietary fat to fetal and maternal rat lipogenesis and lipid deposition.

Pregnant rats were pair-fed isoenergetic diets with varying fat content and varying fatty acid compositions to determine if manipulation of the maternal diet would affect fetal lipid metabolism. A mixture of tallow and lard replaced cornstarch on an equal-energy basis so that fat supplied 5 to 65% of the metabolizable energy. Fat content of the maternal diet did not affect fetal weight or fetal body composition. No differences in fetal liver fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (G6PD) activities or rate of in vivo fatty acid synthesis were noted. In vivo fatty acid synthesis was greater in fetal liver than maternal liver. Dietary manipulation did not affect in vivo fatty acid synthesis in either fetal or maternal liver. Maternal liver FAS and G6PD activities were generally greater than fetal liver FAS and G6PD activities. These enzyme activities were decreased in maternal livers when the high-fat diet was fed. A sudden decrease in food consumption 24 hours before killing may explain the apparent inconsistencies in enzyme activities and fatty acid synthesis rates. The results of this study indicate that the level of fat in the maternal diet has no effect on the amount of lipid accumulated in fetal tissues or fetal lipogenesis.