Probing the link between sensory systems and metabolism to prevent obesity

PROJECT SUMMARY The mechanism by which metabolism, diet, and olfactory function is linked is not well understood. The rising incidence of diabetes and obesity in our country is epidemic, yet little has been reported as to how chronic metabolic imbalance impacts sensory systems and whether these dysfunctions can be reversed via changes in diet, drug intervention, or selective genome editing. The work in this proposal will bridge gaps in our knowledge concerning how changes in activity of the olfactory bulb (OB) can modify energy homeostasis. To test how changes in OB excitability cause a reduction in body weight and energy metabolism, we will manipulate contribution from a voltage-dependent potassium channel, Kv1.3, exclusively in the major output neurons. Our long-term research goal is to understand how olfaction and metabolism are interrelated - to reveal how olfactory output neurons convey metabolic information. Our proposed aims are based upon the following three hypotheses: (1) Hypothesis 1 = Elimination of Kv1.3 channels in mitral/tufted cells will increase action potential firing frequency and decrease the after-hyperpolarization amplitude, selectively enhance glucose clearance, increase total energy expenditure, and decrease respiratory exchange ratio (increase fat utilization), which will produce a drop in body weight or cause a resistance to diet-induced obesity (DIO). (2) Hypothesis 2 = Odor stimulation will induce specific patterns of c-fos expression within the hypothalamus and other brain regions in mice. DIO will attenuate c-fos activation in control mice with normal Kv1.3 conduction, but not in similarly-fed, but DIO-resistant, mice in which Kv1.3 is selectively edited from mitral/tufted cells. (3) Hypothesis 3 = Restoration of Kv1.3 activity selectively in mitral/tufted cells, but not in the periphery, or decreased excitability will cause a loss in resistance to DIO as measured by body weight, glucose tolerance, and system physiology parameters. Our experiments take a multidisciplinary approach using electrophysiology, genome editing, and metabolic profiling to uncover the importance of relayed olfaction information for energy homeostasis. The knowledge generated from our proposed research defining the impact of olfactory bulb output on metabolic balance can be applied to lessen the health consequences of the rising global problem of obesity and excess food consumption. It is a high priority that we investigate coordination from extra-hypothalamic brain areas to determine their contribution to energy balance – a novel and intellectually challenging view of the olfactory system.