December 8, 2008
Study Links Body Clock To Diabetes And Blood Sugar
A genome-wide association study claims the workings of our internal body clock appear to be directly connected to diabetes and high levels of blood sugar.
International research found faults in a key 'clock gene' were linked to blood sugar levels and type II diabetes. People with high blood sugar levels and diabetes have a greatly increased risk of developing a range of conditions, including cardiovascular diseases.
However, unraveling the links between obesity, type II diabetes, and circadian rhythms could point the way towards new strategies to control or prevent the illness.
The 24-hour human sleep cycle is controlled partly by hormones released by the body. Melatonin, released by the pineal gland in the brain, is involved in drowsiness and the lowering of body temperature.
In healthy people, blood sugar levels are kept under control by insulin, which the pancreas releases in varying amounts at different periods during a 24-hour natural cycle.
The researchers suggest that when there is a genetic abnormality that affects melatonin levels and sleep patterns, this may also disturb the levels of insulin in the blood, preventing the body from maintaining control of blood sugar levels.
Researchers from around the world scanned the genomes of thousands of people looking for associations between particular genetic variations and type II diabetes.
A team from Imperial College London found one genetic "variation" which appeared to be linked to a 20% increase in the risk of type II diabetes. Another team discovered a second variation that could be linked to naturally higher blood sugar levels and diabetes risk.
But it was the location of these variations on the human genome that suggested the connection to the internal body clock.
They were both connected to MTNR1B, a gene that helps control the action of melatonin on different parts of the body.
The findings fit with earlier research linking sleep problems with obesity, which increases the risk of type II diabetes, according to Professor Philippe Froguel, from Imperial College.
"For example, we know that obese children tend to sleep badly and that people become more obese if they are not having enough sleep.
"Our research demonstrates that abnormalities in the circadian rhythm may partly be causing diabetes and high blood sugar levels - we hope it will ultimately provide new options for treating people."
But Dr. Jim Horne from the Sleep Research Center at Loughborough University said it was too early to be suggesting that problems with the body clock might actually be responsible for obesity and diabetes.
"There are other explanations for the link between obesity and sleep disturbance - people who eat too much may have disturbed sleep, or be drowsy or sleep during the day, and obese people may suffer from sleep apnea which can disturb sleep," said Horne.
He added that the evidence linking insufficient sleep with these changes is very contentious, and science should be cautious about drawing the wrong conclusions.
A separate study from Leeds University suggests that children with diabetes living in poorer households are less likely to have their blood sugar levels under control.
While studying blood sugar levels in 1,742 Yorkshire children, mostly with the type I form of the disease, they noticed that fewer than 15% were reaching National Institute for Clinical Excellence targets.
Children from lower-income families were less likely to hit the target than those from more affluent families.
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