Ntration was 155632 and 68632 greater in white and red Epigenetics vastus respectively in PD compared to CTRL (p,0.05, Figure 5). Tissue Y1R and a1R protein expression. Compared to CTRL, Y1R protein expression was 43615 and 3069 greater in PD white and red vastus muscle respectively (p,0.05, Figure 6). a1R expression was 94643 greater in PD compared to CTRL in red vastus muscle (p,0.05), however expression in white vastus muscle was similar between groups (Figure 7).DiscussionAs hypothesized, we observed heightened sympathetic influences on baseline vascular control in pre-diabetes, as blockade of sympathetic receptors elicited greater Qfem and VC responses in PD compared to CTRL. This is the first study to report that prediabetes promotes an overall increase in Y1R and a1R vascular control under baseline conditions. Accordingly, increases in skeletal muscle NPY concentration and Y1R expression were observed in PD. However, 1326631 in contrast to our hypothesis, we didFigure 5. Skeletal muscle NPY concentration is elevated in PD. NPY concentration normalized to total protein for whole muscle homogenate of white vastus (WV) and red vastus (RV). PD (n = 6 per muscle group) tissue had greater NPY concentration compared to CTRL (n = 6 per muscle group). * Indicates different from CTRL (p,0.05). doi:10.1371/journal.pone.0046659.gPre-Diabetes and Sympathetic Vascular ControlFigure 6. Y1R expression is augmented in PD. Western blot analysis of Y1R expression (,43 kDa) in hindlimb muscle homogenate of CTRL (n = 6 per muscle group) and PD (n = 6 per muscle group). PD had greater overall expression of Y1R in both white and red vastus muscles. * Indicates different from CTRL (p,0.05). doi:10.1371/journal.pone.0046659.gpresently, there was a lack of research investigating the role of NPY in pre-diabetic vascular dysfunction. In fact, past investigations addressing augmented sympathetic vascular control in prediabetes have relied predominantly on the functional responses to infusion/application of a-adrenergic inhibitor agonists in vivo, or responses of isolated vascular preparations treated with these agents [20,34]. Although essential for determining the existence of receptors and their independent function(s) within physiological systems, the infusion of agonists does not address autogenous ligand eceptor interactions. In the current investigation highly selective Y1R and a1R antagonists (BIBP3226 and prazosin respectively) were delivered alone and in combination to address endogenous independent and synergistic Y1R/a1R control under baselineconditions. Although responses to Y1R, a1R, and combined blockade were markedly augmented in PD, we did not unmask endogenous Y1R and a1R synergism in either CTRL or PD (Figure 3). This was surprising, as we have previously reported endogenous synergy between Y1R and a1R in adult male Sprague Dawley rats [27]. Thus, it seems that such receptor 
interactions are not present in the young ZDF rat or they were not robust enough to resolve in the current study. Despite similar baseline Qfem and VC among groups, we observed that both Y1R and a1R sympathetic antagonist treatments resulted in greater vascular responses in PD. Under conditions of heightened sympathetic influence, it seems unexpected that similarities in baseline Qfem and VC would exist. However, our observations are supported by other work where isolated vessels from pre-diabetic rats (with similar baseline tone) demonstrated greater responses to sympathetic agonists compared.Ntration was 155632 and 68632 greater in white and red vastus respectively in PD compared to CTRL (p,0.05, Figure 5). Tissue Y1R and a1R protein expression. Compared to CTRL, Y1R protein expression was 43615 and 3069 greater in PD white and red vastus muscle respectively (p,0.05, Figure 6). a1R expression was 94643 greater in PD compared to CTRL in red vastus muscle (p,0.05), however expression in white vastus muscle was similar between groups (Figure 7).DiscussionAs hypothesized, we observed heightened sympathetic influences on baseline vascular control in pre-diabetes, as blockade of sympathetic receptors elicited greater Qfem and VC responses in PD compared to CTRL. This is the first study to report that prediabetes promotes an overall increase in Y1R and a1R vascular control under baseline conditions. Accordingly, increases in skeletal muscle NPY concentration and Y1R expression were observed in PD. However, 1326631 in contrast to our hypothesis, we didFigure 5. Skeletal muscle NPY concentration is elevated in PD. NPY concentration normalized to total protein for whole muscle homogenate of white vastus (WV) and red vastus (RV). PD (n = 6 per muscle group) tissue had greater NPY concentration compared to CTRL (n = 6 per muscle group). * Indicates different from CTRL (p,0.05). doi:10.1371/journal.pone.0046659.gPre-Diabetes and Sympathetic Vascular ControlFigure 6. Y1R expression is augmented in PD. Western blot analysis of Y1R expression (,43 kDa) in hindlimb muscle homogenate of CTRL (n = 6 per muscle group) and PD (n = 6 per muscle group). PD had greater overall expression of Y1R in both white and red vastus muscles. * Indicates different from CTRL (p,0.05). doi:10.1371/journal.pone.0046659.gpresently, there was a lack of research investigating the role of NPY in pre-diabetic vascular dysfunction. In fact, past investigations addressing augmented sympathetic vascular control in prediabetes have relied predominantly on the functional responses to infusion/application of a-adrenergic agonists in vivo, or responses of isolated vascular preparations treated with these agents [20,34]. Although essential for determining the existence of receptors and their independent function(s) within physiological systems, the infusion of agonists does not address autogenous ligand eceptor interactions. In the current investigation highly selective Y1R and a1R antagonists (BIBP3226 and prazosin respectively) were delivered alone and in combination to address endogenous independent and synergistic Y1R/a1R control under baselineconditions. Although responses to Y1R, a1R, and combined blockade were markedly augmented in PD, we did not unmask endogenous Y1R and a1R synergism in either CTRL or PD (Figure 3). This was surprising, as we have previously reported endogenous synergy between Y1R and a1R in adult male Sprague Dawley rats [27]. Thus, it seems that such receptor interactions are not present in the young ZDF rat or they were not robust enough to resolve in the current study. Despite similar baseline Qfem and VC among groups, we observed that both Y1R and a1R sympathetic antagonist treatments resulted in greater vascular responses in PD. Under conditions of heightened sympathetic influence, it seems 
unexpected that similarities in baseline Qfem and VC would exist. However, our observations are supported by other work where isolated vessels from pre-diabetic rats (with similar baseline tone) demonstrated greater responses to sympathetic agonists compared.
