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Of Dreams and Diabetes

By Gretchen Vogel
ScienceNOW Daily News
8 December 2008

Is there a link between sleep and type 2 diabetes? That's one implication of a new study, which has found that variants in a gene that helps regulate the body's daily rhythms increase the chance of developing the disease. The find, reported online yesterday in three papers in Nature Genetics, may suggest new ways to treat or prevent the ever more common disorder.
The body's internal clock--or circadian rhythm--is kept accurate by a hormone called melatonin, whose levels fall during the day and rise at night. Melatonin helps regulate sleep patterns, and in recent years, scientists have found that these patterns are tied to metabolism. For example, people who sleep less have a higher risk of obesity and diabetes. And experimental mice with disrupted circadian rhythms tend to gain weight.

Researchers suspect the link has something to do with another hormone, insulin: Melatonin appears to regulate the body's levels of insulin, which helps cells take up the sugar glucose from the blood. (In type 2 diabetes, the system doesn't work properly, and blood glucose is too high, damaging various organs.)

The new studies back up this link. Three groups found that people with certain variations in the so-called melatonin receptor 2 gene have higher levels of blood glucose first thing in the morning. Such high fasting glucose levels are one warning sign for type 2 diabetes. Gonçalo Abecasis of the University of Michigan, Ann Arbor, and his colleagues used data from 10 genome-wide studies involving 36,610 individuals to look for genetic variations that correlated with fasting glucose concentrations. They pinpointed a common variation in the gene called MTNR1B, which codes for one of the body's two known melatonin receptors. A study led by Leif Groop of Lund University in Sweden, using data from two long-term health studies, confirmed that result and also found that people carrying the high-blood-sugar gene variant have an increased risk of developing type 2 diabetes. Philippe Froguel of Imperial College London and his colleagues, looking at data from 2154 individuals in France, found a similar association with a different genetic variation very near the same gene.

Although previous work had suggested a connection between metabolism and circadian rhythm control, the find "will come as a big surprise to 99% of people involved in diabetes research," says Eve Van Cauter of the University of Chicago in Illinois, an expert on sleep and metabolism who was not involved in the studies. The exact biological explanation is not yet clear; however, she says one possibility is that people with the high-risk gene variant have an insulin-production system that is overly sensitive to melatonin. Understanding exactly what effect the variations have could help design more effective treatments for diabetics, says Froguel.

Gretchen Vogel
ScienceNOW Daily News




新的研究成果支持了这种联系。3个研究小组发现,每天一大早,那些所谓的退黑激素受体2型基因产生某种变异的人,其血液中的葡萄糖含量都比较高。这种空腹高血糖现象是罹患2型糖尿病的一个信号。美国安阿伯市密歇根大学的Gon?alo Abecasis和同事,利用包括36610名个体在内的10个全基因组研究的数据,寻找了与空腹血糖水平有关的遗传变异。最后研究人员在一个名为MTNR1B的基因——负责编码已知两种人体退黑激素受体中的一种——中找到了一个常见的变异。另一项由瑞典Lund大学的Leif Groop领导的研究,则利用来自两项长期健康研究的数据证明了这一结果,该研究同时发现,那些携带了高血糖基因变异的人也容易患上2型糖尿病。英国伦敦皇家学院的Philippe Froguel和他的同事利用来自法国的2154名个体的数据,在MTNR1B基因的附近又发现了一种与不同的遗传变异有关的类似关联。研究人员在最新出版的英国《自然—遗传学》杂志上报告了这3项研究成果。







作者:admin@医学,生命科学    2011-02-17 05:11