In a recent perspective piece published in the journal Nature Metabolism , Chinese researchers discussed evidence from recent studies on the non-rhythmic impact of light deprivation or exposure on metabolic activities such as thermogenesis or glucose homeostasis in a manner that is not dependent on the circadian clock. Perspective: Circadian-independent light regulation of mammalian metabolism . Image Credit: vetre / Shutterstock Sunlight is the energy source that powers most ecosystems, with primary producers or autotrophs harvesting the energy from light to produce the biomass that fuels most heterotrophs.
Furthermore, while animals do not directly harvest the energy from light, photoreceptors expressing opsins in the chromophores and peripheral tissues help them sense light, which acts as an environmental cue for various biological functions. Mammalian systems largely depend on the eye, which contains rod and cone opsins, to perceive light. However, observations of light detection in animals that do not have functional rod and cone opsins led to the detection of intrinsically photosensitive retinal ganglion cells (ipRGCs).
Through non-visual melanopsin, an evolutionarily conserved and primordial light sensor, ipRGCs modulate processes such as mood regulation and pupillary reflexes. While ipRGCs are involved in setting the circadian rhythm through the suprachiasmatic nucleus of the hypothalamus, recent studies have shown that ipRGCs are also involved in conveying photic sig.
