Opposite metabolic response to fenofibrate treatment in pregnant and virgin rats

The level of maternal circulating triglycerides during late pregnancy has been correlated to newborns' weight in humans. To investigate the response to fenofibrate, a hypotriglyceridemic agent, in pregnant rats, 0, 100, or 200 mg of fenofibrate/kg body weight as oral doses were given twice a day from day 16 of gestation and studied at day 20. Virgin rats were studied in parallel. Liver weight was higher in pregnant than in virgin rats, and either dose of fenofibrate increased this variable in both groups. The highest dose of fenofibrate decreased fetal weight. Although plasma triglycerides decreased during the first 2 days of fenofibrate treatment in pregnant rats, the effect disappeared on day 3, and plasma triglycerides were even enhanced at day 4. In virgin rats, fenofibrate decreased plasma triglycerides throughout the experiment. Plasma cholesterol levels in pregnant rats decreased during the first 3 days of treatment, and the effect disappeared on day 4, whereas in virgin rats, values remained decreased. Changes in plasma triglycerides paralleled those of VLDL triglycerides. In pregnant rats, VLDL cholesterol levels increased while LDL cholesterol decreased with the treatment, whereas in virgin rats, cholesterol levels decreased in all lipoprotein fractions. Only in virgin rats did liver triglyceride concentration increase with fenofibrate treatment. Lumbar adipose tissue LPL was lower in pregnant than in virgin rats, and fenofibrate treatment decreased this variable in both groups. Maternal fenofibrate treatment increased fetal plasma and liver triglyceride and cholesterol concentrations. It is proposed that the opposite effects of fenofibrate treatment in virgin and pregnant rats are a consequence of both the enhanced liver capability for VLDL triglyceride production and a rebound response to the drug in the latter.