Increase in placental apolipoprotein D as an adaptation to human gestational diabetes

The expression of apolipoprotein D (apo D), a lipocalin involved in defense mechanisms against oxidative stress, in placental tissue samples of pregnancies with gestational diabetes mellitus (GDM) was compared to non-diabetic controls. We have investigated the relationship of apo D with 4-HNE, a major propagation product of lipid peroxidation, in stressed tissues. We included 20 pregnant women with GDM and 30 women with normal ongoing pregnancies as the control group. Placentas were collected and frozen for Western blot or included in paraffin for immunohistochemistry. The intensity of immunostaining was higher for apo D and 4-HNE in GDM samples; however, the differences in expression between the groups was more intense for apo D. Positive signals for both antibodies was detected in the villous trophoblast and adventitia tunica around the large blood vessels for all groups. Specific immunostaining for apo D was noted in some mesenchymal and macrophagic-like cells and this signal increased in diabetic placentas. Densitometry analysis of Western blots showed no significant difference for 4-HNE, but was significantly more intense for apo D in diabetic women. The contradictory results for 4-HNE could be due to changes which are too small and are masked in tissue homogenates. The results for apo D showed a strong relationship with GDM in the placenta that may reflect its suggested function in defense mechanisms against oxidative stress.