Relationship between insulin responses tod-glucose and tol-arginine in women with a history of gestational diabetes

The relationship between insulin responses to glucose and to arginine was studied in non-obese women with previous gestational diabetes (PGD). One group,n=10, had normal glucose tolerance (NGT) by WHO criteria and another,n=8, had impaired glucose tolerance (IGT). A third group of women without PGD,n=12, was also studied. A hyperglycaemic clamp (blood glucose level 11 mM) and an arginine stimulation test (150 mg/kgl-arginine followed by 10 mg/kg · min) were performed on separate days. The ratios of arginine to glucose responses 0–10 min differed: they were 1.00 for non-PGD, 1.29 for NGT and 1.46 for IGT (P<0.02 vs non-PGD). A further difference between groups was the ratio between first- and second-phase glucose-induced insulin secretion, which was significantly decreased in IGT, 0.72, compared with NGT, 0.98 (P<0.01), and non-PGD, 1.05 (P<0.005). However, within each group insulin responses 0–10 min to glucose and arginine were strongly correlated: for NGT (r=0.75,P<0.05), for IGT (r=0.85,P<0.01) and for women without PGD (r=0.69,P<0.05). Insulin sensitivity, as assessed by the M/I ratio, was non-significantly decreased in IGT (0.18±0.03 mg/kg·min per mU/l vs 0.26 ±0.03 in NGT and 0.28±0.03 in non-PGD,P<0.1). Conclusions are: (1) insulin responses to glucose and arginine are linked both in PGD and non-PGD women, but (2) the relative potency of these secretagogues as well as the time-dynamics of glucose-induced insulin secretion may be altered in PGD with IGT.