Triglyceride Hydrolase Activities and Expression of Fatty Acid Binding Proteins in the Human Placenta in Pregnancies Complicated by Intrauterine Growth Restriction and Diabetes

Abstract

Triglyceride (TG) hydrolases in the placental microvillous plasma membrane (MVM) release fatty acids from circulating lipoproteins and represent the critical initial step in transplacental fatty acid transfer. We investigated the activity of two TG hydrolases in MVM isolated from placentas of appropriately grown for gestational age pregnancies and pregnancies complicated by intrauterine growth restriction (IUGR), insulin-dependent diabetes mellitus (IDDM) or gestational diabetes mellitus (GDM). In addition, we measured protein expression of lipoprotein lipase (LPL) in MVM and two fatty acid binding proteins (L- and C-FABP) in placental homogenates. The TG hydrolase activities were assessed by measuring hydrolysis of (3)H-trioleic acid incorporated into intralipid micelles after incubation with MVM. The placenta-specific TG hydrolase activity (optimum at pH 6) did not differ in the patient groups studied. MVM LPL activity (optimum at pH 8) was reduced by 47% in preterm IUGR (n = 8, P < 0.05), compared with gestational age-matched controls. The LPL activity in placentas of IDDM pregnancies was increased by 39% (n = 8, P < 0.05), compared with controls. No significant differences were observed in cases of GDM. We found no alteration in protein expression of LPL or C-FABP. The expression of L-FABP was increased by 112% (n = 8, P < 0.05) in IDDM and 64% (n = 8, P < 0.05) in GDM. These results indicate that alterations in MVM LPL activity and expression of L-FABP may contribute to the altered lipid deposition and metabolism in IUGR and diabetic pregnancies.