title: The impact of preeclampsia on fetal nutrition and offspring metabolism and cardiovascular function
Creators: name: Olivera, Sol
Publisher: name: University of Glasgow
Year: 2025

description: The incidence of pregnancy complications, including preeclampsia (PE), is increasing nowadays. PE is one of the main causes of maternal and fetal morbidity and mortality worldwide. PE can also affect the later-life health of both mother and baby by increasing the risk for the development of CVD, although the mechanisms for this remain unknown.

The development of an insulin-resistant state is a normal adaptation during late pregnancy which leads to increased adipose tissue lipolysis and presents a source of both short chain saturated fatty acids as an energy source and long-chain polyunsaturated fatty acids (LC-PUFAs) as a key nutrient for the fetus. LC-PUFAs are essential for fetal neural development and their supply depends on the delivery from the mother through the placenta. Mothers with PE have exacerbated levels of insulin resistance that lead to increased maternal adipose tissue lipolysis leading to maternal excess of plasma non-esterified fatty acids (NEFAs) and triglycerides (TGs) as well as reduced maternal and fetal levels of LC-PUFAs. There is preliminary evidence for ectopic fat accumulation in the PE placenta which may affect LC-PUFA transport to the baby, although the presence of placental lipid droplets is yet to be confirmed. Reduced LC-PUFA transport may also impact the cardiovascular development of the offspring and, consequently, increase the risk of later-life CVD. Therefore, it was hypothesised that PE impairs essential fatty acid transfer by the placenta to the growing fetus thereby limiting cardiac and vascular development in the offspring.

Firstly, this thesis aimed to investigate the cardiovascular impact on the offspring of pregnancies complicated by PE in a rat model of superimposed PE. Pregnant stroke-prone spontaneously hypertensive rats (SHRSP) were implanted with osmotic minipumps for the continuous delivery of 0.9 % saline (vehicle control) or 700 ng/kg/min angiotensin II (ANGII). Wistar Kyoto (WKY) rats were also implanted with vehicle minipumps and used as a normotensive control. Fetal growth restriction (FGR) was observed in the ANGII neonates which were significantly smaller than the SHRSP vehicle control neonates (birth weight: 5.11 ± 0.05 vs 6.00 ± 0.12 g; mean ± SEM, P&lt;0.001). Phenotyping of the offspring by echocardiography and tail-cuff plethysmography between week 5 and 17 of age showed thatANGII-exposed offspring present a worsened cardiovascular phenotype compared to controls, but without an impact on their systolic blood pressure. Fractional shortening (FSwas significantly lower in the ANGII offspring compared to vehicle controls (ANGII: 48.51 ± 0.97 ± Control: 52.12 ± 0.95; mean ± SEM, P&lt;0.001).Relative wall thickness (RWT) was also smaller in the ANGII offspring compared to vehicle controls (ANGII: 0.51 ± 0.04 vs Control: 0.58 ± 0.03 mm; mean ± SEM, P=0.024). Lower FS and RWT in the ANGII are signs of systolic dysfunction. Additionally, the early to late mitral valve flow velocity ratio (E/A) was significantly higher in the ANGII offspring compared to SHRSP vehicle control (ANGII: 1.94 ± 0.06 vs Control: 1.53 ± 0.04; mean ± SEM, P&lt;0.001), which is evidence of diastolic dysfunction. 

A lipidomics analysis of human and rat placentas was carried out to investigate the potential lipid dysregulation in PE and to further validate the ANGII animal model. Placental samples were collected at Caesarean section from women with PE and healthy pregnancies. Placental lipids were extracted and analysed via shotgun lipidomic techniques using high-resolution mass spectrometry. Lipid droplets from PE and healthy human placental cryosections were stained with Oil red O and quantitated by image analysis. TGs and cholesteryl esters (CEs)
concentrations were significantly higher in PE placentas compared to controls (TG: PE 453.6 ± 262.1 vs healthy 129.3 ± 109.4; P&lt;0.001; CE: PE 1063 ± 1004 vs healthy 425.9 ± 432.7 nmol/g; median ±IQR, P&lt;0.001), which is evidence of neutral lipid accumulation. PE placentas had a significantly higher lipid droplet area compared to healthy controls (5.56 ± 5.15 vs 1.94 ± 1.70 %; median ±IQR, P=0.009). Gene expression of lipid-droplet associated proteins perilipin 4 and 5 (PLIN4 and PLIN5) were also significantly higher in PE compared to healthy placentas, which further corroborated the presence of ectopic fat in the PE placenta. Lipidomic analyses of placentas from ANGII-treated dams and vehicle controls did not show any differences in lipid content between groups. Therefore, the ANGII model of superimposed PE does not mimic the elevated placental lipid storage accumulation observed in human PE pregnancies.

Gene expression of placental markers of fatty acid transport, lipolysis and synthesis were examined in PE in order to obtain further insights into impaired placental lipid metabolism. PE placentas had higher expression of genes involved in de novo lipogenesis (DGAT2, FASN and SREBF-1) compared to healthy controls which suggests that the elevated ectopic placental fat presence in PE is due to greater lipid synthesis. Elevated angiopoietin-like 4 (Angptl4) expression in the PE placenta was also observed, which may indicate decreased fatty acid uptake by the placenta through the inhibition of lipoprotein lipase (LPL), consequently contributing to the lower LC-PUFA status in PE. LIPE expression was higher in the PE placenta compared to controls, which may be a reflection of the elevated TG stored in intracellular lipid droplets. This dysregulated fatty acid homeostasis in the PE placenta may be caused by increased fatty acid supply due to severe insulin resistance in the mother.

Another condition characterised by elevated maternal insulin resistance during pregnancy, namely gestational diabetes mellitus (GDM), was used as a comparator to PE. GDM pregnancy did not demonstrate ectopic fat accumulation on the placenta. Placental neutral lipid content, PLIN expression and lipid droplet content were not different between healthy and GDM women, although several differences in other lipid species were identified and warrant further investigation.

Overall, the data presented in this thesis indicated that impaired placental fatty acid metabolism and storage may contribute to the pathology of PE. Despite some phenotypic similarities with PE, GDM did not have elevated ectopic fat storage in the placenta, which suggests excess fatty acids may be stored elsewhere. Due to the role of hyperlipidaemia and insulin resistance in the aetiology of PE, reducing lipid levels in the mother could potentially improve neonatal and offspring later-life outcomes. The offspring of a model of superimposed PE showed impaired cardiovascular development after ANGII intrauterine exposure, which suggests that PE offspring may benefit from long-term monitoring to ameliorate CVD risk.