PROJECT 1 (HOLWERDA): PROJECT SUMMARY Obesity is highly prevalent in the U.S. and has significant consequences for mortality and quality of life. Obesity is the primary gateway to additional cardiovascular disease (CVD) risk factors such as increased insulin resistance, dyslipidemia, and hypertension. Prospective studies have estimated that nearly 75% of cases of hypertension can be attributed to obesity. Hallmarks of obesity-related hypertension are oxidative stress, chronic inflammation, and vascular dysfunction. However, our understanding of the precise mechanisms underlying the development of hypertension in obesity and insulin resistance remains incomplete. We hypothesize that vascular sensitivity to single bursts of sympathetic nerve activity (SNA) is augmented by oxidative stress in obesity and heightens blood pressure variability. Using a randomized, double-blinded, cross-over study design, we hypothesize that elevated SVT will be attenuated by suppression of oxidative stress via ascorbic acid I.V. infusion at supraphysiological concentration compared with saline I.V. infusion (placebo) in obese adults with insulin resistance. Given our innovative approach, these studies provide direct insight into the ability of single bursts of SNA to dynamically regulate vascular tone and blood pressure. We will also test the novel hypothesis that sympathetic blockade mitigates the pro-inflammatory phenotype of obesity. Obesity is also characterized by chronic inflammation, which is mediated in part by the sympathetic nervous system. Expression of pro- inflammatory cytokines such as tumor necrosis factor alpha (TNF-α) can be regulated by norepinephrine. We propose sympathetic blockade as a novel approach to mitigating the pro-inflammatory phenotype of obesity and hypertension. To demonstrate feasibility of our hypothesis, we have performed pilot studies using a randomized, double-blinded, parallel study design in a small group of overweight/obese adults using 4 weeks of oral clonidine to reduce central sympathetic outflow and observed significant reductions in MSNA and circulating TNF-α but no change in MSNA and circulating TNF-α following 4 weeks of placebo or hydrochlorothiazide (HCTZ) as a BP- lowering control condition. We plan to extend these preliminary data in our outlined studies to achieve sufficient power to observe signficant and clinically meaningful group differences in circulating and endothelial cell pro- inflammatory cytokines. The long-term goal of our research is to identify unique mechanisms that can be targeted to limit increases in vascular dysfunction in obesity and insulin resistance and reduce the excessively high prevalence of hypertension and risk for CVD in obesity.