PERSISTENCE OF METABOLIC RHYTHMICITY DURING FASTING AND ITS ENTRAINMENT BY RESTRICTED FEEDING SCHEDULES IN RATS

The presence of a food-entrainable oscillator (FEO) independent from t he SCN is now well established, but until now its location and charact erization have been elusive. Because its expression requires priming o f the animal's metabolism toward a catabolic state, it is possible tha t metabolic rhythms may be related to FEO. The present study was desig ned to determine whether metabolic rhythms persist during fasting and whether such rhythms could be entrained to a restricted feeding schedu le. The results indicate persistent rhythms of triacylglycerides, free fatty acids, glucose, and proteins during fasting, whereas ketone bod ies and liver glycogen changed their concentration as a function of fa sting. Daily food pulses of 2 h entrained the rhythms of triacylglycer ides and free fatty acids and restored ketone bodies and liver glycoge n to similar levels as controls. Neither glucose nor proteins were aff ected by the food pulse. These results indicate the relevance of lipid metabolism as a phenomenon associated with the FEO.