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You probably already know that ambient light regulates circadian rhythms by interacting with light-sensitive neurons in the eye.
But let’s review anyway: In full white light (which contains all colors of light), the rays of the blue and green light spectrum activate melanopsin, a photosensitive protein in specific cells of the retina in the back of the eye. When light hits these cells, a signal transmits information to the brain’s master clock. By detecting various intensities and tones of light, the brain can keep track of what time of day it is.
This is relatively well established. We also know that sunlight can stimulate the production of vitamin D and nitric oxide, both of which have important effects on health. But are these all of the effects that light has on our physiology?
It has been known for several decades that a small percentage of blue light can penetrate human skin, and can even reach white subcutaneous adipose tissue. But the relevance of this finding on our physiology was not obvious.
Curiously, it has also been reported that high OPN4 (the gene that encodes the photopigment melanopsin) mRNA levels are found in human subcutaneous fat. Kind of weird: what the heck are these light-sensitive eye proteins doing in our fat tissue? Additionally, we now know that fat cells contain transient receptor potential cation (TRPC) channels – membranes that are found in the retina that open in response to varying intensities of light.
So, we know that blue light can get to subcutaneous fat tissue, and fat cells seem to have the machinery needed to respond to the signal that is transmitted by light. Very interesting. Is it possible that visible light penetrates the skin, and exerts physiological effects by activating a melanopsin / TRPC channel signaling pathway in human fat? And if so, could exposure to visible light have an impact on the regulation of body fat? The answer appears to be yes.
My guest in this episode (inadvertently) found the answer to this novel questions…