The suprachiasmatic nucleus (SCN) controls circadian rhythms in mammals. The SCN 
may also participate in regulating body metabolism and energy. Similar to other 
hypothalamic nuclei, the SCN have been reported to contain glucose-sensitive 
neurons and receptors for the adipose tissue hormone, leptin. Here we 
investigated leptin effects on the SCN clock. Our results demonstrate that the 
SCN circadian clock, when isolated in vitro, can be phase advanced by leptin in 
a dose-dependent fashion that does not require non-SCN hypothalamic tissue. 
Phase advances are induced at all circadian times except late subjective night. 
These data suggest that peripheral signals of energy and metabolism directly 
modulate the circadian pacemaker in mammals.