Food entrains clock genes but not metabolic genes in the liver of suprachiasmatic nucleus lesioned rats.

Hepatic circadian transcription, considered to be driven by the liver clock, is largely influenced by food even uncoupling it from the suprachiasmatic nucleus (SCN). In SCN lesioned rats (SCNx) we determined the influence of a physiological feeding schedule on the entrainment of clock and clock-controlled (CCG) genes in the liver. We show that clock genes and the CCG Rev-erbα and peroxisome proliferator-activated receptor alpha (PPARα) in food-scheduled intact and SCNx have a robust diurnal differential expression persisting after a 24h fast. However, hepatic nicotinamide phosphoribosyl transferase (Nampt) shows time dependent changes that are lost in intact animals under fasting; moreover, it is unresponsive to the nutrient status in SCNx, indicating a poor reliance on liver clock genes and highlighting the relevance of SCN-derived signals for its metabolic status-related expression.