Research being carried out by the Madrid Group is currently focused on the effect of dietary fatty acids during pregnancy and perinatal development in the rat on lipid metabolism, oxidative stress and the expression of PPAR and related genes. Since late pregnancy is a condition of hyperinsulinemia and insulin resistance, and insulin has been shown to downregulate beta3 adrenergic receptors in adipose tissue, within the scope of FATLINK we have been studying the relationship between insulin sensitivity in adipose tissue at different periods of pregnancy and the lipolytic responsiveness to beta3 adrenergic agonists. Hypertriglyceridemia is also a consistent feature during late pregnancy, and is the result of enhanced maternal adipose tissue lipolytic activity, liver VLDL-triglycerides production and decreased extrahepatic lipoprotein lipase activity. Since maternal hyperlipidemia seems to contribute to decreased insulin responsiveness, we are currently investigating the comparative hypolipidemic effect of fibrates in pregnant and nonpregnant rats and its relationship to liver and adipose tissue PPAR expression. This latter part of the study is being carried out in collaboration between Lyon and Madrid, and results obtained so far indicate that whereas the hypotriglyceridemic response to fibrates differ between pregnant and nonpregnant rats, their effect enhancing PPAR expression is similar, suggesting an uncoupling between the two effects.