Obesity hypertension in African American women: Neuro-metabolic mechanisms

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DESCRIPTION (provided by applicant): The purpose of this proposal is to foster the scientific development and research skills of Dr. Cyndya Shibao in order to support her transition into an independent investigator. The Department of Medicine and the Division of Clinical Pharmacology at Vanderbilt University will provide Dr. Shibao with the ideal setting in which to investigate the neuro-metabolic mechanisms underlying obesity-associated hypertension in African American women. Through the collaboration of Dr. Shibao's mentor (Dr. Italo Biaggioni) and co-mentor (Dr. Naji Abumrad) and her Advisory Committee composed by an extensive network of experienced scientific and clinical researchers, Dr. Shibao will obtain the foundation for the development of an independent academic career. During her postdoctoral fellowship Dr. Shibao has acquired the necessary experience and research skills to successfully conduct the studies proposed in her application. This award will be critical for her to learn new scientific approaches and research techniques in the area of metabolism, and expand her previous experience on cardiovascular and autonomic research. Furthermore, this award will provide Dr. Shibao with a solid foundation to develop her research interest in the cardiovascular and metabolic derangement associated with obesity, and complement her training with formal didactic courses through her participation in the Master of Science and Clinical Investigation at Vanderbilt University. African American women have the highest prevalence of obesity, hypertension and insulin resistance compared to African American men or Caucasians of either gender. The underlying mechanisms accounting for these abnormalities are unknown. The overall goal of this proposal is to determine the contribution of the sympathetic and nitric oxide systems to obesity-associated hypertension. In specific aim 1a we propose to test the hypothesis that the sympathetic contribution to blood pressure is lower in obese African American women as compared to Caucasians. This is based on our preliminary studies in which African American women have less of an increase in sympathetic activation as compared to Caucasians. In this specific aim we will use autonomic ganglionic blockade with trimethaphan to address this question, and explore possible underlying mechanisms for these differences such as visceral fat mass. Even though we found that obese African American women have less sympathetic activation, they still have the same increase in blood pressure as compared to Caucasian women of the same body mass index. Our preliminary results indicate that nitric oxide (NO) is arguably the most important metabolic modulator of blood pressure in humans, tonically restraining it by at least 30 mm Hg. Moreover, there is substantial evidence in the literature for impaired NO function in African Americans. Therefore, in Specific aim 1b we will test the hypothesis that in African American women impaired NO vascular function contributes to obesity-associated hypertension. In specific aim 2 we will test the hypothesis that increasing NO function with the phosphodiesterase-5 inhibitor, sildenafil, will reverse the cardiovascular and metabolic alterations in African American women. Upon completion of this project, we will have obtained important knowledge about the differences in the underlying mechanisms of obesity-associated hypertension among racial groups and we will also identify potential targets for therapies aimed at reversing these abnormalities.