Recap: The hidden clock controlling your health | Professor Russell Foster
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Hello and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Today we're exploring circadian rhythms. Did you know that you could eat the exact same meal at two different times of day and your body would respond dramatically differently? It sounds like a riddle, but it actually comes down to your body clock. Every cell in your body has one, a tiny internal ticker shaped by evolution over millions of years to keep you in sync with the phases of the day. So how can we ensure we're doing the right thing at the right time?
What are circadian rhythms and why do they matter?
I'm joined by Professor Russell Foster to help us all stay in time with our natural rhythm. Circadian rhythms, you know, the body clock as it's called, what are they and why do they matter to us?
Let's start with why do they matter? If you think about our biology, what it has to achieve is the right substances at the right concentration delivered to the right tissues and organs at the right time of day. And it's the sort of temporal time structure that is delivered by our circadian system, our body clocks, that allow us to do this, that allow us to essentially optimize our biology. So they're incredibly important. Essentially, they influence every aspect of our physiology and behavior. What they are has turned out to be really fascinating. We've sort of known about rhythmicity for a very long period of time. The first sort of description of a circadian rhythm goes back to about 1729 in plants with a rhythmic opening and closing of leaves under constant conditions, under constant darkness.
In fact, this French astronomer popped a plant in a cupboard and would peek in from time to time.
Is that right? I never knew that. I assumed it was only the light that caused the flowers to move.
That was the assumption. The light-dark cycle drives this rhythmic behavior. But in fact, and he was completely puzzled by this. There must be some internal mechanism. And he was dead right. And it took us quite some time to try and understand what that mechanism was. I mean, in the early days, we knew that there was a master clock within the brain. in the hypothalamus, an area called the suprachiasmatic nuclei, mercifully abbreviated to SCN. And it comprises about 50,000 cells. And when I started in the business, it was assumed that circadian rhythms were the product of cell-cell interactions, a sort of a circuit property that would generate a 24-hour oscillation in electrical activity. And then, I mean, it was so exciting because people had isolated individual SCN neurons
and shown that they would tick away in a dish on their own in terms of electrical activity and indeed turning on and off of genes.
So to make sure I'm following this, this really is the clock, is it? So deep inside my brain is this little thing which is going tick-tock Is that a way to think about it, or have I made it too simple?
No, no, it is the master clock. And now we know that a bunch of genes, which are turned on, make their proteins, those proteins form a complex, and then they enter the nucleus and turn their genes off. The proteins are then degraded, and then the whole cycle starts again. So there's a molecular feedback loop. And we thought that it was only SCN cells that had this capacity. And then a wonderful chap called Uli Schibler, who's based in Switzerland, showed that actually lots of different sorts of cells have a clock. So you can think of a master clock within the brain coordinating the rhythmic behavior of literally billions of individual cellular clocks throughout the organ systems of the body. So you've got this incredible hierarchy.
I mean, it's sort of a bit, the analogy I've sort of used is it's a bit like the master clock in the brain is a conductor of an orchestra. She is producing a rhythmic temporal signal from which the rest of the orchestra, the body, takes its reference cue.
Can you help to explain a bit how this body clock then influences our body?
How do circadian rhythms influence our biology?
And I guess the most obvious thing to start with is sleep, which I think is what we think about.
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