Increased lipolysis in non-obese pregnant women studied in the third trimester

During pregnancy, metabolic adaptation takes place in the mother to provide for the supply of substrates to the growing fetus.

To determine rates and endocrine regulation of lipolysis and glucose production (GPR) in late pregnancy.

Energy substrate production was measured in healthy pregnant women by use of stable isotope-labelled compounds.

University Hospital, Uppsala, Sweden.

Eight healthy non-obese, non-smoking women with normal pregnancies were studied at 33-36 weeks of gestation after an overnight (12-14 hours) fast.

Rates of glycerol and glucose production were analysed by gas chromatography/mass spectrometry following constant rate infusion of [1,1,2,3,3-(2)H(5)]-glycerol and [6,6-(2)H(2)]-glucose.

Glycerol and glucose production in the third trimester.

The mean rate of glycerol production, reflecting lipolysis, was 3.06 (0.66) and the mean GPR was 13.2 (1.5) micromol kg(-1) minute(-1) [2.38 (0.27) mg kg(-1) minute(-1)]. There was a correlation between rate of glycerol production and GPR (r = 0.75, P = 0.033). Fasting insulin levels correlated inversely with both the rate of glycerol production (r = -0.85, P = 0.008) and GPR (r = -0.78, P= 0.021).

Our results show that lipolysis is markedly increased during late pregnancy compared with reported data for non-pregnant women. The data also confirm the occurrence of an increased GPR in pregnant women. The finding of a correlation between rate of glycerol production and GPR corroborates the view that lipolysis promotes gluconeogenesis. Although late gestation is associated with insulin resistance, the results show that insulin plays a regulatory role both in lipolysis and glucose production.