The circadian rhythm, or body clock, controls a huge variety of bodily processes. Our 24-hour sleep-wake cycle has an effect on everything from alertness throughout the day to our digestive system and even how susceptible our skin is to sunburn. New research has revealed that it could even play a role in inflammatory diseases by affecting how much fuel our immune cells use.


“Our results add to the growing body of work showing why disruption of our body clock leads to inflammatory and infectious disease,” said Dr George Timmons, lead author on the study, “and one of the aspects is fuel usage at the level of key immune cells such as macrophages.”

Inflammation is a normal and healthy part of our immune systems. When the body gets an injury or infection, blood flow to the area is increased, which provides more blood cells and proteins, and washes away debris.

However, sometimes this system goes wrong and creates inflammation where there is no infection or injury; this is known as an inflammatory disease. This can cause pain and loss of function, such as the swollen joints common in arthritis patients. Other inflammatory diseases include heart disease, obesity and diabetes.

The study, led by researchers at the Royal College of Surgeons in Ireland, looked into circadian rhythms in a type of white blood cell called macrophages. The 24-hour cycle of these cells is controlled by a protein called BMAL1, so the researchers studied two groups of mice: those that had the gene that encodes BMAL1, and those without it. The mice without the protein represented the disrupted body clock.

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They found that when macrophages were deficient in BMAL1, they used more glucose and their mitochondria (cell power stations) broke this glucose down by a different set of processes. This resulted in the mitochondria producing reactive oxygen species – chemicals which are necessary in small amounts, but in larger amounts can cause inflammation.

"This study also shows that anything which negatively impacts on our body clocks, such as insufficient sleep and not enough daylight, can impact on the ability of our immune system to work effectively," said Dr Annie Curtis, senior author on the paper.

Read more about circadian rhythms:


Reader Q&A: What’s the best way to reset your body clock?

Asked by: Anonymous

Our body clock responds to the daily rhythm of light and dark, and so the trick to resetting it lies in knowing when to seek out light, and when to avoid it. For anyone working nights, it’s best to reduce exposure to bright light towards the end of the shift and during the journey home.

For long-distance air travel, the timings for light exposure and avoidance are more complicated, and depend on whether the destination is east or west. Fortunately, there are online calculators that can do the necessary calculations; a good one can be found here.


Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.