Introduction: Maternal obesity, diabetes and/or dyslipidaemia are associated with adverse gestational outcomes. The placenta may adapt to protect the fetus or it may become dysfunctional and contribute to poor outcomes. The purpose of this research was to evaluate interactions between glucose and lipid metabolism in primary human trophoblasts.
Methods: The trophoblast isolation protocol from normal term placentas was optimised. Total glucose uptake, glycolysis, glycogen synthesis, glucose and palmitate oxidation were assessed after 36 h of culture over a 2 h period using radio-labelled glucose or palmitate tracers at various cold glucose concentrations +/- 0.25 mM non-esterified fatty acids (NEFA, oleate/palmitate 1:1). Lactate release into the media was measured using a colorimetric assay. Cells were also cultured for 3 days +/- epidermal growth factor (EGF) in the presence and absence of 0.1mM NEFA to measure effects on syncytialisation as assessed by E-cadherin immunofluorescence. Lipid droplet formation was assessed by oil red O staining.
Results: Trophoblast yield was 2-6x108/placenta (>95% purity). Glucose uptake increased linearly with increasing glucose concentrations without reaching plateau with a trend for attenuation in the presence of NEFA. Glycolysis, lactate release and glucose oxidation were limited and near maximum at 5mM glucose. Glycogen synthesis increased with increasing glucose concentrations with higher values at 35mM glucose in the presence of NEFA. Palmitate oxidation was reduced in presence of high glucose concentration. Lipid droplet formation was evident in the presence of NEFA with a trend for enhancement with EGF. NEFA and EGF stimulated syncytialisation (preliminary results).
Conclusion: Glucose uptake into trophoblasts and glycogen synthesis increase across a wide range of glucose concentrations, unlike glycolysis, lactate production and glucose oxidation rates, which plateau at about 5 mM. High concentrations of glucose reduce lipid oxidation. Trophoblast lipid droplet formation may be enhanced by EGF. Syncytialisation may be increased by EGF plus NEFA.