Response of peripheral rhythms to the timing of food intake

Metabolism and physiology in animals show diurnal rhythm to adapt to the daily cycles of activity-rest and the associated rhythm in feeding and fasting. Accordingly, gene expression, protein activities, and numerous metabolites show daily rhythm in abundance. The significance of these rhythms in promoting healthy lifespan and preventing disease has recently come to light. Mice with genetic disruption of circadian rhythm, mice, and humans under shift-work paradigm, and mice fed high-fat diet ad libitum exhibit chronic disruption of feeding-fasting rhythm and dampened daily rhythms in physiology, metabolism, and gene expression. These dampened rhythms are associated with metabolic diseases. Conversely, time-restricted feeding, in which mice are fed for certain number of hours every day, restores rhythms and can prevent obesity and metabolic diseases even when mice are fed high-fat diet. These observations seek mechanistic explanations, which will require careful experiments in which feeding duration, genotype, nutrient, and feeding time relative to light:dark cycle will be manipulated and molecular changes in peripheral organs and a few brain regions will be assessed. This chapter will primarily focus on the use of mouse as an experimental animal and the experimental setup so that the molecular readouts can be better interpreted.