Hyperglycaemia and hypertriglyceridaemia are well known characteristics in women with Gestational Diabetes Mellitus (GDM). However, women with tight glucose control can still have fat babies. The aims of this study were to determine 1) if the triglyceride content/enrichment of maternal lipoproteins in women with GDM treated for blood glucose levels, could potentially provide more fatty acids to the placenta compared to normoglycaemic pregnant women and 2) if there was any evidence of fetal lipid overload that may ultimately contribute to fetal adiposity in the offspring.
Pregnant women were recruited from the Royal Brisbane and Women’s Hospital Queensland, Australia and the National Health Service Greater Glasgow and Clyde maternity units, Scotland. Fasted blood samples were collected at trimesters 2 (T2) and 3 (T3) and cord bloods were obtained at delivery. GDM was diagnosed using standard institutional clinical criteria of the time. Lipoprotein fractions were isolated from plasma via sequential ultracentrifugation (Havel et al., 1955). The fit model included the outcome (GDM status); Trimesters (T2 and T3); and GDM status and outcome*trimesters interaction, for all outcome variables. The model also included gestation at blood sampling as a covariate to correct for the difference at T2 between GDM status groups. Cord plasma means were compared using t-tests. All statistical analyses were conducted using JMP Pro and significant level was set at P<0.05. Sensitivity analyses were performed both including and excluding women of non-Caucasian ethnicity and women requiring pharmacological therapy for management of their gestational diabetes.
Plasma glucose did not differ between women with GDM and normoglycaemic women. Plasma VLDL and IDL lipids were higher in GDM compared to normoglycaemic women at T2 and reached a plateau by T3 for all women, suggesting this is related to increased insulin resistance in women with GDM. Plasma triglycerides were higher in GDM and increased from T2 to T3 in all women. VLDL- and IDL- triglyceride enrichment was 5-26% lower in GDM compared to normoglycaemic women. HDL triglyceride per HDL protein was 40% lower in GDM, suggesting this is due to reduced cholesteryl ester transfer protein activity in GDM (Liao et al 2018). This allows for more maternal VLDL-, IDL-triglyceride to be transported across the placenta to the fetus. Cord blood VLDL, IDL and LDL from women with GDM were triglyceride enriched, double that compared to normoglycaemic women.
In conclusion, despite normal blood glucose levels in women with GDM, the offspring had double the triglyceride load in their lipoproteins and tended to a 14% higher birth weight centile: highlighting the need to treat the maternal dyslipidaemia.