Lipogenesis and pancreatic insulin release in fetal pigs.

Body composition, liver and adipose lipogenesis, and pancreatic insulin release were examined in intact and decapitated fetal pigs on d 110 of gestation. Decapitation was on d 45 of gestation. Decapitated fetuses deposited more body lipid and less body ash compared with intact fetuses. Body weight, water, dry matter and protein remained similar in intact and decapitated fetuses. Hepatic fatty acid esterification and synthesis were two- and threefold greater, respectively, in decapitated than in intact fetuses. Fatty acid synthesis in subcutaneous adipose tissue of decapitated fetuses was three times greater than values obtained in intact fetuses. The data supported the concept that substrate availability from the dam was not the rate-limiting step in fetal pig lipid synthesis and storage. High growth hormone levels in normal fetal pigs may be responsible for inhibiting lipogenesis, while fetal decapitation would remove this inhibition and be associated with greater lipid deposition. However, pancreatic insulin release was greater in decapitated than in intact fetuses; an indication that elevated lipid deposition may also be due to greater fetal insulin secretion.