ATGL and HSL have not previously been examined in placentae from women with PE. he have recently shown that ATGL mRNA was increased and HSL mRNA de- creased, with no difference in protein expression, in obese women with well controlled gestational diabetes mellitus compared to BMI matched controls(32). ATGL and HSL are both intracellular lipases. They are involved in the mobilization of triacylglycerol from lipid droplets with ATG1. mainly converting triacylglycerol to diacylglycerol and HSL converting diacylglycerol to monoacylglycerol. The decrease in ATGL and HSL mRNA and HSL protein seen here could result in reduced lipolysis of placental lipid droplets and hence reduced lipid transfer to the fetus. In the current study, LPL mRNA expression was re- duced in placentae from women with PE. However, there was no difference in protein expression or localisation. LPL mRNA expression has previously been found to be unchanged in PE 121] and unchanged 121] or increased in growth restricted infants(19, 20]. One reason for the disparity between our findings and the earlier studies with respect to growth restricted infants is the gestational age at delivery. In both the studies showing a reduced LPL mRNA expression in placentae from pregnancies with growth restricted infants, the placentae were from preg- nancies delivered at a mean gestational age of 32 weeks at
delivery, whereas delivery was at 39 weeks in the Laivouri study 1211. The mean gestational age at delivery of the pla- centae in our study is 38 weeks and the lack of change seen is consistent with the lack of change seen at the later gestation in the Laivouri study. The difference in gesta- tional age rather than the condition itself could underlie the increase in LPL mRNA seen in the studies comparing 32 week placenta to term placenta. EL mRNA expression was also reduced in placentae from women with PE, with no change in protein expres sion or localisation. EL expression has been previously found to be decreased in growth restricted infant associ ated placaentae compared with control[19]. It needs to be noted that this finding was in a cohort comparing term control and 32 week growth restricted infant re- lated placentae, and that they reported an increase in placental EL expression from the first to third trimester. Once again, in our study, with careful matching of gesta- tional age, EL protein expression was unchanged in PE. The current study found no difference in overall lipase activity measured in placental biopsies. This is consistent with the results of a previous study in preterm and term pregnancies complicated by growth restricted infants that reported no change in overall placental triglyceride hydrolase activity but reduced LPL activity in isolated
placental microvillous membrane(18). In contrast, an older study showed greater LPL but lower intracellular lipase activity in placentae from PE and UGR pregnancy[22]. The assay used in the current study is conducted a pH 7 and measures overall triglyceride hydrolase activity. The similar lipase activity levels we report are in keeping with the lack of change in protein levels for 3 of 4 lipases we examined, suggesting that in term PE. placental li- pases are unaltered.
Conclusion
The current study demonstrated a decrease in mRNA expression in all four lipases. A small decrease in HsL protein was seen, but no changes in protein expression for ATGL, LPL or El. were demonstrated. There was no difference in lipase in placentae from pregnan- cies complicated by late onset PE compared to control. This suggests that this aspect of placental lipid process- ing is not altercd in late onsct PE and does not underlic the differences seen in infant growth