A sense of time: how molecular clocks organize metabolism

Trends Endocrinol Metab. Jan-Feb 2007;18(1):4-11. doi: 10.1016/j.tem.2006.11.005. Epub 2006 Nov 30.


The discovery of an internal temporal clockwork that coordinates behavior and metabolism according to the rising and setting of the sun was first revealed in flies and plants. However, in the past decade, a molecular transcription-translation feedback loop with similar properties has also been identified in mammals. In mammals, this transcriptional oscillator programs 24-hour cycles in sleep, activity and feeding within the master pacemaker neurons of the suprachiasmatic nucleus of the hypothalamus. More recent studies have shown that the core transcription mechanism is also present in other locations within the brain, in addition to many peripheral tissues. Processes ranging from glucose transport to gluconeogenesis, lipolysis, adipogenesis and mitochondrial oxidative phosphorylation are controlled through overlapping transcription networks that are tied to the clock and are thus time sensitive. Because disruption of tissue timing occurs when food intake, activity and sleep are altered, understanding how these many tissue clocks are synchronized to tick at the same time each day, and determining how each tissue 'senses time' set by these molecular clocks might open new insight into human disease, including disorders of sleep, circadian disruption, diabetes and obesity.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Animals
  • Biological Clocks / physiology*
  • Central Nervous System / physiology
  • Circadian Rhythm
  • Gene Expression Regulation
  • Humans
  • Metabolic Networks and Pathways*
  • Models, Biological
  • Plants