990: Are changes in maternal glucose metabolism related to changes in gestational weight gain?

Abstract

Increasing gestational weight gain (BW) has been associated with an increased risk of gestational diabetes (GDM). Based on previous research from our group, we hypothesize that maternal pregravid metabolic condition and NOT changes in BW or more specifically fat mass (FM) correlate with changes in Insulin Sensitivity (ΔIS) and Insulin Response (ΔIR) during pregnancy. Thirty normal glucose tolerant (NGT) and seventeen GDM were evaluated before conception and 34-36 weeks gestation. Both change (Δ) and percent change, %Δ in IS and IR were assessed. IS was estimated with euglycemic clamp (40mU/m2/min). We defined IS as the Glucose Disposal Rate (ΔGDR; glucose infusion mg.min/insulin) to account for BW and FFM as interdependent factors. IR, a measurement of β cell function, was assessed with an intravenous glucose tolerance test. We calculated the relationship between IS and IR (Disposition Index (ΔDI)) (ISxIR). Body composition (ΔFM) was estimated using densitometry and serum leptin (ΔLEP) using ELISA. NGT and GDM were matched prior to conception and there was no significant difference in the demographic characteristics or body composition. Results are presented combined and separately as NGT and GDM. The associations between %ΔIS, %ΔIR, and % ΔDI compared with %ΔBW and %ΔFM are shown in Table 1. These associations were also estimated using the absolute change in ΔIS, ΔIR, and ΔDI and results were similar to relative changes (data not shown). Additionally there was an association between %ΔIR and %ΔLEP (coef=0.563, p=0.032). This association was stronger using absolute ΔIR (coef=0.499, p= 0.008). Changes in glucose metabolism, i.e. %ΔIS, %ΔIR, %ΔDI, in pregnancy are not associated with %ΔFM in either NGT or GDM. The association between %ΔIS and %ΔBW, accounted for only ∼10% of the variance in IS. The association between ΔIR and ΔLEP may relate to the independent effect of placental leptin on pancreatic β cell function. These data suggest that placental hormones rather than maternal gestational weight gain account for the majority of changes in glucose metabolism during human pregnancy.