Thursday, 23 February 2012

Old fruit flies and broken body clocks

Sleeping problems can get worse with age but they are often exacerabated in age-related diseases that involve damage to the brain such as Alzheimer's, Parkinson's and Huntingtons Disease [1]. Why does the body clock get disrupted? Indeed, is a disrupted body clock the result or the cause of these diseases, or a bit of both? Could a fully-working healthy body clock protect against these brain diseases?

A recent study in fruit flies being published next month aimed to address some of these questions [2]. The fruit fly has a body clock with behavioural rhythms and many similar genes to the human body clock. They also can suffer brain related ageing diseases, and as they typically only live for 2-3 months it doesn't take too long for researchers to study these.

Fruit flies (Drosophila Melanogaster) who live for 2-3 months are being used to study the effect of the body clock on age related diseases (C) Marcos Teixeira de Freitas

The researchers have certain fruit flies where a specific gene known to act in protecting the brain is removed, these flies die younger due to brain defects. They also have flies that don't have a functional body clock, these are lacking a gene called "period" and causes the fly to have no body clock rhythms, in gene expression or in behaviour.

They wanted to determine the effect the body clock has in protecting the brain from age-related diseases. Therefore they took their mutant flies that suffer age-related brain damage and bred them with the flies that have no body clock. 

What they saw was that if you take away the body clock from a fly that has age-related brain damage, they die even younger. So a functional body clock is being protective against these age-related brain diseases. 

Fruit flies that are prone to old age brain disease are more likely to die younger if their body clock is disrupted.   Adapted from Krishnan, 2012

To rule out any effects of the gene "period" working in another way other than to maintain a healthy body clock they also tested the effects of raising the age-related brain defect mutant fruit flies in constant light. Constant light also stops behavioural rhythms and the molecular body clock.

Stopping the body clock with constant light also caused the brain damage to be worse, so it wasn't due to other functions of the period gene.

This research doesn't fully resolve the question of the cause or effect of a disrupted body clock in age-related brain diseases, though it does suggest it to cause the brain damage to be worse.

However, the results do show how maintaining a healthy body clock can increase chances of survival in animals prone to age-related brain diseases. My hope is that research in this field will further our understanding of human ageing.

Enjoyed this post? Check out Young or old: who can stay awake better at the wheel? and Around the Clock Doc

[1] Vitiello, M. V. "Sleep and Circadian Rhythm Disorders in Human Aging and Dementia", Encyclopedia of Neuroscience, Pages 887–893

[2] Krishnan, N., et al., "Loss of circadian clock accelerates aging in neurodegeneration-prone mutants", Neurobiology of Disease, Vol 45, Issue 3, March 2012, Pages 1129–1135, doi:10.1016/j.nbd.2011.12.034

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