Impaired decline in renal threshold for glucose during pregnancy - a possible novel mechanism for gestational diabetes mellitus

BackgroundThe renal threshold for glucose (RTG) is determined by the nephron's reabsorptive capacity. Glucose is reabsorbed through sodium-coupled glucose cotransporters in the proximal tubules. During pregnancy, renal glucose reabsorptive capacity decreases, possibly, due to reduced glucose transporter expression. Our hypothesis is that inadequate decrease in RTG during pregnancy will make women more prone to develop gestational diabetes mellitus (GDM). MethodsPregnant women (n=40) who were referred to our center for oral glucose tolerance test (OGTT) were included in the analysis. Plasma glucose levels and urinary glucose excretion were measured for 4h after 100g oral glucose load. These data were used to calculate RTG. The subjects were divided into two cohorts, GDM and non-GDM, according to the OGTT results. Mean RTG was compared between the two groups. ResultsFifteen (37.5%) of the women were diagnosed with GDM. Seventeen participants had only trace amounts of urinary glucose excretion, and no value of RTG could be determined; RTG was determined in the other 23 subjects. Among these 23 women, 13 were diagnosed as GDM, and 10 had normal OGTT. RTG was lower in the non-GDM women (14614mg/dL) than in the GDM women (182 +/- 18mg/dL), p<0.001. ConclusionsGestational diabetes mellitus is associated with higher RTG during pregnancy compared with non-GDM. These results support our hypothesis that inadequate decrease of the RTG may have a pathophysiological role in the development of GDM. Copyright (c) 2013 John Wiley & Sons, Ltd.