What are your general research interests?
My primary research interest is integrative human physiology.
What are your current projects and how are they funded? Who are your collaborators on these projects?
I’m interested in understanding the effects of dietary salt on blood pressure. Several years ago we initiated a study in which healthy young to middle-aged adults were placed on high and low salt diets for one week each. Despite severe variations in dietary salt, blood pressure did not change much. My colleague Dave Edwards and I began to think about the possible effects of dietary salt might blood vessel function, independent of blood pressure. Studies in rats strongly suggest that dietary salt impairs blood vessel function, even if blood pressure does not rise. For our human studies, we measure the ability of blood vessels to dilate as an index of vascular health. Our preliminary work suggests that dietary salt loading impairs blood vessel dilation, even in the absence of changes in blood pressure. Completing this project will require several years of work and will be supported by a grant from the National Heart Lung and Blood Institute.
I’m also interested in understanding the mechanisms that control blood pressure during acute exercise and how these mechanisms may be altered in those with hypertension. The blood pressure response to acute exercise in those with hypertension appears to be exaggerated (that is, it goes up too much). We specifically focus on the role of the sympathetic nervous system in driving up blood pressure and how/why this response may be heightened in those with hypertension. This work, a collaboration with Dr. Paul Fadel from the University of Missouri, is not currently funded but we just submitted an NIH proposal to move this project forward.
What are the likely “next steps” in your work?
The dietary salt studies are very labor intensive. Our current approach is to place subjects on low, medium, and high salt diets for one week each. Once we complete these studies, we want to turn our attention to longer-term dietary trials, lasting approximately six months, and examine some of the same parameters. The advantage of the three-week studies is that we can control everything the participants eat and drink by having all meals prepared for them. The disadvantage is the relatively short-term nature of the dietary perturbation. The six-month studies, which will be done in collaboration with Dr. Shannon Lennon-Edwards of UD’s Department of Behavioral Health and Nutrition, will need to be less controlled; rather than having meals prepared for the subjects, we will provide intensive dietary counseling and assess blood vessel function before and after the intervention. Shannon will also move in a new direction by focusing on the possible protective effects of dietary potassium on vascular function using a rodent model. This is an exciting future direction because it sets the stage for complementary mechanistic/animal and clinical/human studies. Translational studies such as these are generally viewed very favorably in the field.
For the acute exercise studies, we will continue to focus on the role of sensory fibers within skeletal muscle in driving up sympathetic nervous system activity and blood pressure. Our first paper in this area focused on the sensory fibers that detect changes in the skeletal muscle chemical environment during exercise (for example, changes in lactic acid concentration); our next set of experiments will focus on the sensory fibers that detect changes in muscle movement. We think both are altered in hypertension, but we need more data to test this hypothesis.
How would you describe your work’s importance to an interested lay audience?
Dietary salt studies: From a public health perspective, it is very important to determine whether high dietary salt impairs blood vessel function. We already know that this is the case in experimental animal models, but this information needs to be translated to humans.
Acute exercise studies: During exercise, it’s normal for blood pressure to increase, but it sometimes increases too much in those diagnosed with hypertension. We’re attempting to figure out the mechanisms underlying these abnormal responses.