Nitrative stress and poly(ADP-ribose) polymerase activation in healthy and gestational diabetic pregnancies

Increased oxidative-nitrosative stress, poly(ADP-ribose) polymerase (PARP) activation and subsequent cellular damage play important roles in the complications of both diabetes mellitus and pregnancy. Our aim was to investigate nitrative stress and PARP activity levels during normal and gestational diabetic (GDM) pregnancy in both maternal and fetal tissues.

Blood samples were collected during pregnancy (weeks 16-29 and 36-40), and placental and umbilical cord tissues were harvested after delivery from healthy volunteers and GDM patients subjected to a carbohydrate-restricted diet or insulin treatment. Immunohistochemical staining was performed on leucocytes and tissue sections using anti-nitrotyrosine (NT), anti-poly(ADP-ribose) (PAR) and anti-apoptosis inducing factor antibodies.

In healthy pregnancies the intensity of NT and PAR staining of leucocytes correlated positively with gestational week (R (2) = 0.43, p < 0.01 and R (2) = 0.49, p < 0.001, respectively). In patients on a carbohydrate-restricted diet PAR staining was already strong in weeks 16-29 (p < 0.001 vs control) and did not increase further. In weeks 16-29 there was a correlation between PAR staining and the 2 h value of the oral glucose tolerance test (R (2) = 0.49, p < 0.001). Patients with the highest level of leucocyte PARP activity later required insulin therapy, which decreased the intensity of NT and PAR staining. Placental and umbilical cord tissues also had a higher level of nitrative stress markers in GDM pregnancies, but the highest level of PARP activity was observed after insulin therapy.

Continuous elevation of tyrosine nitration and PARP activation may be considered physiological during pregnancy. However, the high level of PARP activity in early pregnancy may signal the subsequent development of severe GDM.