Dr. Michael Overton

Research Interest

The incidence of both obesity and hypertension continue to increase throughout many parts of the world. The primary focus of my research program is to discover and understand the neuroendocrine mechanisms by which energy homeostasis and cardiovascular function are regulated. We utilize chronically instrumented pre-clinical approaches (rodent models) to determine how metabolism, behavior and cardiovascular physiology respond to a number of nutrition and pharmacologic interventions. We are also able to advance our understanding of these problems via state of the art studies of mouse physiology. Since the discovery of leptin in 1994, there has been a remarkable advancement in our understanding of hypothalamic systems that regulate energy homeostasis. One of our main goals is to understand the biologic adaptations to weight loss to assist in developing more effective therapies for obesity.

Current Research

Mechanisms by which reduced energy consumption produces marked reductions in blood pressure and sympathetic activity. We use chronically instrumented rats to assess cardiovascular status while manipulating caloric intake. CNS lesions and microinjection strategies are employed to evaluate specific neuroanatomic and neurochemical substrates which modulate blood pressure during negative energy balance. In collaboration with Mike Rashotte, we are examining blood pressure, metabolic rate, and feeding responses to long term modulation of caloric availability or CNS infusion of peptides such as NPY.

Publications

• Knight WD, Seth R, Boron J, Overton JM. Short-term physiological hyperleptinemia decreases arterial blood pressure. Regul Pept. 154(1-3):60-8. (2009)
• Tucker K, Overton JM, Fadool DA. Kv1.3 gene-targeted deletion alters longevity and reduces adiposity by increasing locomotion and metabolism in melanocortin-4 receptor-null mice. Int J Obesity. 32(8): 1222-123. (2008) PDF
• Swoap SJ, Li C, Wess J, Parsons AD, Williams TD, Overton JM. Vagal tone dominates autonomic control of mouse heart rate at thermoneutrality. Am J Physiol Heart Circ Physiol. 294(4):H1581-8. (2008)
• Messina MM, Overton JM. Cardiovascular effects of melanin-concentrating hormone. Regul Pept. 139(1-3):23-30. (2007)
• Messina MM, Boersma G, Overton JM, Eckel LA. Estradiol decreases the orexigenic effect of melanin-concentrating hormone in ovariectomized rats. Physiol Behav. 88(4-5):523-8. (2006)
• Knight WD, Swoap SJ, Parsons AD, Overton JM. Central thyrotropin-releasing hormone infusion opposes cardiovascular and metabolic suppression during caloric restriction. Neuroendocrinology. 83(2):69-76. (2006)
• Das P, Parsons AD, Scarborough J, Hoffman J, Wilson J, Thompson RN, Overton JM, Fadool DA. Electrophysiological and behavioral phenotype of insulin receptor defective mice. Physiol Behav. 86(3):287-96. (2005)
• Messina MM, Evans SA, Swoap SJ, Overton JM. Perinatal MSG treatment attenuates fasting-induced bradycardia and metabolic suppression. Physiol Behav. 86(3):324-30. (2005)
• Evans SA, Parsons AD, Overton JM. Homeostatic responses to caloric restriction: influence of background metabolic rate. J Appl Physiol. 99(4):1336-42. (2005)
• Evans SA, Messina MM, Knight WD, Parsons AD, Overton JM. Long-Evans and Sprague-Dawley rats exhibit divergent responses to refeeding after caloric restriction. Am J Physiol Regul Integr Comp Physiol. 288(6):R1468-76. (2005)
• Fadool DA, Tucker K, Perkins R, Fasciani G, Thompson RN, Parsons AD, Overton JM, Koni PA, Flavell RA, Kaczmarek LK. Kv1.3 channel gene-targeted deletion produces "super-smeller mice" with altered glomeruli, interacting scaffolding proteins, and biophysics. Neuron. 41(3): 389-404. (2004)
• Evans SA, Overton JM, Alshingiti A, Levenson CW. Regulation of metabolic rate and substrate utilization by zinc deficiency. Metabolism. 53(6):727-32. (2004)
• DeRuisseau LR, Parsons AD, Overton JM. Adaptive thermogenesis is intact in B6 and A/J mice studied at thermoneutrality. Metabolism. 53(11):1417-23. (2004)
• Overton JM, Williams TD. Behavioral and physiologic responses to caloric restriction in mice. Physiol Behav. 81(5):749-54. (2004)
• Evans SA, Overton JM, Alshingiti A, Levenson CW. Regulation of metabolic rate and substrate utilization by zinc deficiency. Metabolism. 53(6):727-32. (2004)
• Swoap SJ, Overton JM, Garber G. Effect of ambient temperature on cardiovascular parameters in rats and mice: a comparative approach. Am J Physiol Regul Integr Comp Physiol. 287(2):R391-6. (2004)