PPAR-γ, TNF-α messenger RNA levels and lipase activity in the pregnant and lactating rat

Dramatic alternations in maternal metabolism occur during gestation and lactation, especially glucose and fat metabolism. For example, in rats, the amount of body fat mass increases during gestation, then decreases just prior to delivery, and remains low after parturition. To investigate the factors involved in such changes in maternal fat mass, messenger ribonucleic acid (mRNA) levels of adipocytokines, peroxisome proliferator-activated receptor-γ (PPAR-γ) and tumor necrosis factor-α (TNF-α), were examined in the intraabdominal adipose tissue of non-pregnant rats, pregnant rats and postpartum rats. We also examined the issue of whether apoptosis, which could be promoted by PPAR-γ and TNF-α, is involved in any of the changes in maternal fat mass The activity of lipoprotein lipase (LPL) and hormone sensitive lipase (HSL) in adipose tissue was also measured. PPAR-γ and TNF-α mRNA levels remained constant during the gestational and postpartum periods. Apoptosis was not detected at any time as evidenced by DNA laddering and in situ staining. LPL activity was significantly increased at day 5 and remained elevated until day 14 of gestation. HSL activity was significantly increased at day 10 of gestation and then decreased after delivery, at day 10 of lactation. In conclusion, during the gestational and postpartum period of rats, changes in maternal fat mass did not directly correlate with the levels of expression of PPAR-γ and TNF-α mRNA. Apoptosis also does not appear to influence on fat mass change. The changes in LPL and HSL activities during gestation suggest that these enzymes might be regulators of maternal adipose tissue level.