Physiological and behavioral processes exhibit daily oscillations under the control of an internal circadian timing mechanism. A key function of the circadian system is to ensure that feeding occurs at specific times of day and that metabolic processes are coordinated with periods of increased food intake. The importance of this is evidenced by the fact that circadian disruption, which commonly occurs in modern society as a result of aberrant feeding and sleeping schedules that are facilitated by artificial lighting, is associated with profound cognitive and metabolic consequences. Furthermore, behavioral interventions that restrict feeding to appropriate times of day counteract the metabolic consequences of high-fat diets and ameliorate age-related organismal decline. Because the circadian clock oscillates with an intrinsic period that is not exactly 24-hrs, it must be synchronized to daily environmental cycles through a process called entrainment. Notably, time- restricted feeding (TRF), in which food availability is limited to a small window of time each day, exerts powerful control over circadian processes and serves as a dominant entrainment signal for both behavioral and physiological rhythms. Animals exposed to TRF exhibit increased locomotor activity in anticipation of food availability, which persists during periods of total food deprivation, demonstrating the ability of TRF to entrain rest:activity rhythms. Furthermore, clocks in peripheral tissues become time-locked to the food availability cycle, even in the presence of conflicting light-dark schedules. However, despite its central role in the circadian modulation of behavior and physiology, fundamental questions remain regarding the molecular and cellular mechanisms through which food entrainment occurs. Studies in the fruit fly, Drosophila melanogaster, have been integral in our understanding of circadian rhythms, and Drosophila research led to the identification of the transcriptional-translational feedback loop through which cells keep time. We hypothesize that experiments in Drosophila will similarly provide fundamental insight into the process of food entrainment, but major technological limitations have thus far prevented such experiments. Most notably, TRF paradigms in flies are laborious and time-consuming and require manual switching of flies between food-containing and non-food- containing vials multiple times a day, which disrupts fly behavior. The primary goal of this proposal is therefore the development and characterization of a novel research technology that allows for programmable control over food access while simultaneously recording locomotor activity data. We will use this system in pilot experiments to confirm the presence of food entrainment in Drosophila (Aim 1), and will furthermore apply the powerful genetic and experimental tools available in flies to identify neuronal and molecular mechanisms underlying food entrainment (Aim 2). In addition to providing insight into circadian regulation of behavior, our system will be generally useful to research aimed at understanding the link between neuronal and metabolic processes and in determining how TRF improves overall organismal health.
The internal circadian clock ensures that behavioral and physiological processes are coordinated with respect to one another and the external environment so that they occur at appropriate times of day. Our research will lead to the development of novel research technology that will facilitate investigations into the cellular and molecular mechanisms through which circadian processes become synchronized to daily cycles of food availability, which allows organisms to adapt neuronal and metabolic processes to coincide with periods of increased food intake. These experiments will enhance understanding of fundamental principles underlying the function and regulation of the circadian system and will shed light on the profound cognitive and behavioral consequences associated with circadian rhythm disruptions that commonly occur due to the aberrant sleeping and feeding cycles present in modern society.
