Diabetes – genetically linked to the body's biological clock.PunchstockPosted on 12/07/2008 11:57:35 PM PST by neverdem
Receptor for body-clock hormone connected to disease risk.
Diabetes – genetically linked to the body's biological clock.PunchstockFresh evidence suggests that melatonin, a hormone that regulates the body's biological clock, is associated with type 2 diabetes.
Epidemiological studies have shown that shift workers have an increased risk of developing type 2 diabetes. And patients with type 1 diabetes have sometimes reported higher blood-sugar levels after taking synthetic melatonin, which can be used to ease jet lag or as a sleep aid.
Now, two separate studies by researchers based in Europe and the United States have found that variants of a gene called MTNR1B, which produces a receptor protein that binds and responds to melatonin, is linked to an increased chance of developing type 2 diabetes1,2.
In 2007, endocrinologist Leif Groop of Lund University in Sweden and his colleagues published a genetic analysis of nearly 3,000 people, half of whom had type 2 diabetes3. Further work indicated that a sequence variation in the MTNR1B gene was associated with increased levels of glucose in the blood under fasting conditions.
Although an abnormally high fasting-glucose level is a symptom of diabetes, the study did not find a link between the variant and the disease. But Groop suspected that the study may have been too small to pick up the association.
He and his colleagues joined forces with three other groups to analyze 13 studies that included 18,236 people with type 2 diabetes and 64,453 control patients without diabetes. Now, reporting in Nature Genetics, the team shows that the MTNR1B variant Groop and his colleagues identified in the 2007 study does increase the chances of developing type 2 diabetes1: by 9% when one copy of the variant gene is present and by 18% for people with two copies.
Meanwhile, a second study published in Nature Genetics reports an association between diabetes and a different genetic variant located near the MTNR1B gene2. Study author Philippe Froguel of the Pasteur Institute in Lille, France, says his team has since found additional variations within the gene that may also be associated with the disease.
Precisely how melatonin affects disease risk is still unclear. Froguel and his colleagues hope to recreate the naturally occurring MTNR1B variations in mice and study the effects on sugar metabolism. For now, he speculates that melatonin receptors in the eyes and the brain may activate signals that are transmitted to the pancreas, the organ that makes insulin.
In a further study, Groop's team reports that those who either have type 2 diabetes or carry the MTNR1B variant they worked on also express the gene at a higher level in insulin-producing β cells in the pancreas4. When grown in culture, β cells also produce less insulin when they are exposed to melatonin. The results, says Groop, suggest that the hormone acts directly on β cells, and that therapies designed to block melatonin signalling in the pancreas could one day provide a treatment for diabetes.
Such a therapy would have to be careful not to interrupt the important functions that melatonin carries out in the brain. But many drugs cannot pass through the blood–brain barrier, and Groop believes a drug could be created that would block the receptor in the pancreas without affecting the brain.
"There is mounting evidence from genetic models that there is a strong interaction between circadian regulatory pathways and glucose metabolism," says Joseph Bass, a diabetes researcher at Northwestern University in Evanston, Illinois, who was not involved with the study. "But one of the gaps has been in understanding the implications for these findings with regard to human disease and human biology."
As for those who take synthetic melatonin, there are no data to show that the tablets increase the risk of diabetes. Short-term use to treat jet lag may be less likely to have an effect on diabetes risk than long-term use, Groop says. "Theoretically, you could predict that they may be at higher risk for diabetes," he says. "But that is just a prediction: that hasn't been shown."
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BTTT
Human digestive systems aren't really efficient during sleep. Blood flow is sent to other areas of the body. Rest and repair (and growth in children). Are we disturbing/destroying our endocrine systems by eating at the wrong times?
DHEA is the hormone that is produced when the melatonin begins to wane. It would be interesting if they could study the effects of both melatonin and DHEA to see if there was a link between the effects of these substances on the pancreas and the timing of food intake .
Also, what other chemicals or nutrients would be in use by the body during the periods of time that melatonin would be produced (think rest and repair again) and how would these things interact or affect the pancreas and/or possibly affect the results of these experiments?
ping
bookmarked
Makes a lot of sense. Indicates this one arose in the Arctic.
I’ve heard that getting the right amount of sleep at the right times helps with all kinds of health issues.
Are they implying here that going to bed at a decent time and getting a good night’s sleep would be useful in warding off type II diabetes?
don’t take melatonin?
do take melatonin?
It causes diabetes?
not the most scientific of those among us, please advise, because I have been taking it for a while for sleep problems I’d hate to find out I wrecked my health for a good nights sleep.
β cells = beta cells using the Greek letter for beta. I'm sorry that I didn't catch it sooner.
Why would the pancreas have to activate and produce increased insulin when the melatonin would be signaling that the body was either ready for sleep or sleeping?
In culture, beta cells make less insulin when they are exposed to melatonin. With respect to the other questions, not to be flippant, but we don't know what we don't know.
Are they implying here that going to bed at a decent time and getting a good night’s sleep would be useful in warding off type II diabetes?
That's what I think.
I wouldn't worry about taking melatonin for a short term.
Except that type 2 diabetics have plenty of insulin.. too much, in fact. They just can’t get it into the cells. It’s the insulin resistance that causes the problems and keeps the beta cells working overtime in an attempt to compensate.
And I totally agree with your “we don’t know what we don’t know” statement. There is so much we don’t know about type 2 diabetes, that I believe we will discover that many of the current recommended treatments will be found to be useless or even harmful. *sigh* I hate this disease. It killed my dad.
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