Scientists believe they have discovered why Alzheimer’s disease sufferers
have terrible sleeping patterns.
One common symptom of the condition is being awake at night and dozing
during the day, which can become stressful for both sufferers and carers.
Until now, it was believed that Alzheimer’s affected a sufferer’s biological
clock.
But a new study by Cambridge researchers – using fruit flies – has
discovered disrupted sleep is actually caused by behavioural factors.
They added a protein to the flies’ brains which lies behind the initial
stages of Alzheimer’s – essentially giving them the disease.
They were put in a tube next to another containing healthy flies and laser
beams were used to record the flies’ movements.
As predicted, the flies with Alzheimer’s were more active at night and less
so in the day.
The scientists then attached another protein, which emits light and is seen
in fireflies, to all the flies’ biological clock proteins in their brains.
Unlike mice and humans, flies are perfect for the study as they do not have
thick skulls so the lights could be seen in the dark.
The scientists predicted the flies with Alzheimer’s would glow brighter at
night and less in the day compared to the healthy flies because their
biological clocks were not working.
However they were shocked to see they glowed in exactly the same way the
healthy flies glowed.
They concluded that the biological clock had not stopped ticking and that
the Alzheimer’s sufferers have not stopped responding to the clock, but that
it is more of a behavioural issue.
Dr Damian Crowther of Cambridge University’s Department of Genetics said:
“Until now, the prevailing view was that Alzheimer’s destroyed the
biological clock.
“A lot of effort has gone into dimming lights for people with Alzheimer’s
and working around them after thinking they do not have the same biological
clock as everyone else.
“What we have shown in flies with Alzheimer’s is that the clock is still
ticking but is being ignored by other parts of the brain and body that
govern behaviour.
“This research shows all that effort may actually have been pointless and
the behavioural side is what needs to be looked at.
“If we can understand this, it could help us develop new therapies to tackle
sleep disturbances in people with Alzheimer’s.
“We now need to find the link between the biological clock and behavioural
cause.”
The scientists fused the biological clock’s protein – the period protein –
with luciferase – the glowing protein.
The flies given the Alzheimer’s were bred with an A-beta peptide, the
protein which helps to form plaques in the brain which show up in those with
Alzheimer’s.
Flies are a cheap way of doing research for Alzheimer’s – a small sample of
flies were given the proteins and then bred – with just an 11-day turnover
for offspring.
Dr Simon Ridley, head of research at Alzheimer’s Research UK, which helped
to fund the study, said: “Understanding the biology behind distressing
symptoms like sleep problems is important to guide the development of new
approaches to manage or treat them.
“This study sheds more light on the how features of Alzheimer’s can affect
the molecular mechanisms controlling sleep-wake cycles in flies.
“We hope these results can guide further studies in people to ensure that
progress is made for the half a million people in the UK with the disease.”
The research is published in Disease Models & Mechanisms.
