RESUMEN
Women with a history of gestational diabetes mellitus (GDM) have significantly greater lifetime risk of developing cardiovascular disease and type 2 diabetes compared to 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 measurement of cutaneous vascular conductance responses to graded infusion of acetylcholine (10-10 - 10-1M) and insulin (10-8 - 10-4M) in control sites and sites treated with 15mM L-NAME [NG-nitro-l-arginine methyl ester; NO-synthase (NOS) inhibitor] or 5mM 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 to 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 to 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 implicate increased endothelial oxidative stress in this microvascular insulin resistance.
RESUMEN
BACKGROUND: Chronic electronic-cigarette (EC) use is reported to decrease vascular endothelial function. However, the mechanism(s) mediating this reduction remain unclear. In this study, we examined endothelium- and NO-dependent dilation, and the role of oxidative stress in attenuating these responses, in healthy young EC users (n=20, 10 males/10 females) compared with healthy controls (n=20, 10 males/10 females). We hypothesized that EC would have reduced endothelium- and NO-dependent dilation and administration of the superoxide scavenger tempol would increase these responses in EC. We further hypothesized that female EC would have the greatest reductions in endothelium- and NO-dependent dilation. METHODS: We assessed microvascular endothelium-dependent vasodilator function in vivo by measurement of cutaneous vascular conductance (%CVCmax) responses to a standardized local heating protocol in control and 10 µM tempol-treated sites. After full expression of the local heating response, 15 mM NG-nitro-L-arginine methyl ester (NO synthase inhibition) was perfused. RESULTS: EC had significantly reduced endothelium- (73±15 versus 87±9%CVCmax; P<0.001) and NO-dependent (48±17% versus 62±15%; P=0.011) dilation. Tempol perfusion increased endothelium-dependent (84±12%CVCmax P=0.01) and NO-dependent (63±14% P=0.005) dilation in EC but had no effect in healthy control. Within female sex, EC had lower endothelium-dependent (71±13 versus 89±7%CVCmax; P=0.002) and NO-dependent (50±6 versus 69±11%; P=0.005) dilation compared with healthy control, and tempol augmented endothelium-dependent (83±13%CVCmax; P=0.002) and NO-dependent (62±13%; P=0.015) dilation. There were no group or treatment differences within male sex. CONCLUSION: Healthy young adult EC users have reduced microvascular endothelium-dependent and NO-dependent dilation, driven by greater reductions in female EC users, and mediated in part by superoxide.