Gestational diabetes mellitus (GDM) is one of the most prevalent pregnancy complications in Australia and is associated with immediate and long-term morbidity for mothers and their babies. The placenta contributes to GDM pathogenesis by secreting factors that induce maternal insulin resistance, resulting in hyperglycaemia. The placental renin-angiotensin system (RAS) is a critical regulator of placental development however it is yet to be characterised in GDM. In non-pregnant type II diabetics, RAS activity is upregulated and mediates hyperglycaemia-induced tissue injury. Thus, we propose that the placental RAS is also dysregulated by hyperglycaemia in GDM, impacting placental structure and function.
Primary human trophoblast cells were isolated from placentae of women with uncomplicated pregnancies delivering by caesarean section at term. Trophoblast cells were cultured in normoglycaemic conditions [5mM glucose] for the initial 24h and subsequently cultured in normoglycaemic or hyperglycaemic conditions [25mM glucose] for an additional 48h (n=5 placentae in triplicate). The mRNA expression of angiotensinogen (AGT), angiotensin converting enzyme (ACE), prorenin receptor (ATP6AP2), angiotensin II type 1 receptor (AGTR1), and ACE2 was measured by qPCR. ATP6AP2 and ACE2 protein levels were also determined by Western Blot.
Exposure to hyperglycaemia significantly reduced the mRNA expression of ACE (p=0.035) and ACE2 (p=0.008), and tended to reduce the expression of AGT (p=0.077) and AGTR1 (p=0.079). The mRNA expression of ATP6AP2 was unchanged (p=0.600). ACE2 protein levels were not reduced by hyperglycaemia (p=0.149). Interestingly, despite no change in ATP6AP2 mRNA expression, protein levels of ATP6AP2 tended to decrease in hyperglycaemic conditions (p=0.061). Protein levels of additional RAS components are under investigation.
The expression of RAS components in primary human trophoblast cells is sensitive to hyperglycaemia in vitro. In cases of GDM where hyperglycaemia is poorly managed, this may supress placental RAS signalling via trophoblast cells and negatively impact placental and potentially fetal growth.