17:56 – Cortisol. Cortisol, the steroid hormone released in response to stress and low-blood glucose, peaks at the time when we wake up. Melatonin is the opposite, it prepares us for sleep and peaks around the time we go to bed. Cortisol regulates 10-20% of the human genome.
19:58 – People who are working or staying awake have a harder time producing the amount of melatonin needed to fall asleep. We spend a lot of time indoors; indoor lighting typically produces much less than the 10,000 Lux of light emitted from regular daylight.
22:33 – Limiting blue light exposure. Dr. Patrick uses Phillips Hue lights which can be programmed to emit the whole spectrum or only reddish yellowish at different times set by the user. F.lux is a program that can limit the blue light emitted from the computer monitor. They both seem to be fans of these things.
23:45 – Jet lag. Dr. Panda draws a parallel between those who struggle with jet lag and shift workers. An employers solution to the problems brought on by shift work is to have four days on a night shift work and three days on a day shift, this will allow the worker to spend time with friends and family. This solution is obviously not prime.
26:25 – Food. Cortisol is regulated by the circadian clock; the SCN (suprachiasmatic nucleus) sends the signal informing the body when it would be awake, eating, or fasting.
All the clocks time themselves. What Dr. Panda means by this is akin to traffic signals in a downtown area. If there are no lights, the metropolitan area will look chaotic. If there is an organization of when cars can move and when they can’t, order is restored to the whole system. This is similar to what happens when our organs are on a set clock. Not everything happens at once; there is a time for proteins to be broken down, for glucose to be made, for nucleotides to be made, and many other functions that will get their turn. What’s important to know is that these clocks time different things; when these clocks don’t work properly the body becomes similar to a downtown traffic jam.
28:52 – We have these clocks and these clocks respond to food coming in. Dr. Patrick sets the record straight for the listeners and explains that the master clock (the SCN) is regulated by light and is responsible for our sleep cycle. There are also metabolic clocks (discussed above) that are set by when we eat.
31:10 – Dr. Panda looked at which genes are regulated by CLOCK: a transcription factor that affects both the persistence and period of circadian rhythms. Some polymorphisms in the gene responsible for CLOCK have been associated with increased insomnia, weight loss difficulty, and recurrence of major depressive episodes in patients with bipolar disorder.
Dr. Panda’s research has found many instances of genes activated in certain organs at different times of the day. In the liver, there may be around 3000-5000 different genes that turn on based on the time of day.
There was an experiment with mice (who typically eat at night) where mice were given food in the middle of the day and the effects on the liver were recorded. If light regulated all the genes in question, then feeding would have no effect on which genes were expressed. But they found that there are different genes that are expressed when consuming food. So light is not the only thing that is setting our clocks.