AMPK: a nutrient and energy sensor that maintains energy homeostasis

AMPK acts as an intracellular energy sensor, as its activity is tuned by the relative levels of ATP, ADP and AMP. Therefore, it has a central role in the regulation of cellular metabolic pathways and in the control of whole-body energy balance. AMP-activated protein kinase (AMPK) is a crucial cellular energy sensor. Once activated by falling energy status, it promotes ATP production by increasing the activity or expression of proteins involved in catabolism while conserving ATP by switching off biosynthetic pathways. AMPK also regulates metabolic energy balance at the whole-body level. For example, it mediates the effects of agents acting on the hypothalamus that promote feeding and entrains circadian rhythms of metabolism and feeding behaviour. Finally, recent studies reveal that AMPK conserves ATP levels through the regulation of processes other than metabolism, such as the cell cycle and neuronal membrane excitability.