Impaired microvascular insulin-dependent dilation in women with a history of gestational diabetes.

Women with a history of gestational diabetes mellitus (GDM) have a significantly greater lifetime risk of developing cardiovascular disease and type 2 diabetes compared with women who had an uncomplicated pregnancy (HC). Microvascular endothelial dysfunction, mediated via reduced nitric oxide (NO)-dependent dilation secondary to increases in oxidative stress, persists after pregnancy complicated by GDM. We examined whether this microvascular dysfunction reduces insulin-mediated vascular responses in women with a history of GDM. We assessed in vivo microvascular endothelium-dependent vasodilator function by measuring cutaneous vascular conductance responses to graded infusions of acetylcholine (10 ^-10 -10 ^-1 M) and insulin (10 ^-8 -10 ^-4 M) in control sites and sites treated with 15 mM l-NAME [ N ^G -nitro-l-arginine methyl ester; NO-synthase (NOS) inhibitor] or 5 mM l-ascorbate. We also measured protein expression of total endothelial NOS (eNOS), insulin-mediated eNOS phosphorylation, and endothelial nitrotyrosine in isolated endothelial cells from GDM and HC. Women with a history of GDM had reduced acetylcholine ( P < 0.001)- and insulin ( P < 0.001)-mediated dilation, and the NO-dependent responses to both acetylcholine ( P = 0.006) and insulin ( P = 0.006) were reduced in GDM compared with HC. Insulin stimulation increased phosphorylated eNOS content in HC ( P = 0.009) but had no effect in GDM ( P = 0.306). Ascorbate treatment increased acetylcholine ( P < 0.001)- and insulin ( P < 0.001)-mediated dilation in GDM, and endothelial cell nitrotyrosine expression was higher in GDM compared with HC ( P = 0.014). Women with a history of GDM have attenuated microvascular vasodilation responses to insulin, and this attenuation is mediated, in part, by reduced NO-dependent mechanisms. Our findings further implicate increased endothelial oxidative stress in this microvascular insulin resistance. NEW & NOTEWORTHY Women who have gestational diabetes during pregnancy are at a greater risk for cardiovascular disease and type 2 diabetes in the decade following pregnancy. The mechanisms mediating this increased risk are unclear. Herein, we demonstrate that insulin-dependent microvascular responses are reduced in women who had gestational diabetes, despite the remission of glucose intolerance. This reduced microvascular sensitivity to insulin may contribute to increased cardiovascular disease and type 2 diabetes risk in these women.