Study links body-clock disorders to diabetes
People who have problems regulating their body clock could be at a greater risk of developing type 2 diabetes, according to new EU-funded research published in the journal Nature Genetics. The scientists found that people with a mutation in a gene involved in the production of melatonin (the hormone that helps to regulate the body clock) tend to have higher blood-sugar levels and a greater risk of developing type 2 diabetes than people without the mutation. According to the authors of the paper, the findings suggest that diabetes and high blood sugar could be treated at least in part by addressing sleep problems.
The hormone melatonin regulates the body's 24-hour cycle, including sleeping and eating patterns, by translating information on light levels from the eyes to the brain; melatonin levels tend to be low during the day and higher at night. Meanwhile levels of insulin, the hormone responsible for controlling blood-sugar levels, tend to peak during the day so that the body can process the sugar taken in during meals. The researchers suggest that if the natural cycle of melatonin production is disturbed, insulin levels could be affected, too.
As Professor Philippe Froguel of Imperial College London in the UK pointed out, there is already some evidence suggesting a link between sleep disorders and other conditions linked to diabetes, such as obesity and depression.
'We know that obese children tend to sleep badly and that people become more obese if they are not having enough sleep,' he noted. 'Our new study 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.'
In this latest study, the scientists analysed the genetic make-up of over 2,000 non-diabetic French people, including adults and children, both obese people and people of normal weight. They found that people with a mutation called rs1387153, located near the MTNR1B gene, which is involved in melatonin production, have higher blood-sugar levels and a 20% greater risk of developing type 2 diabetes than people without the mutation. Further studies involving other European populations confirmed this picture.
Professor Froguel and his team have already identified a number of genes associated with high blood-sugar levels and an increased risk of type 2 diabetes. Their analyses reveal that on average, people with more mutations associated with high blood-sugar levels tend to have higher blood-sugar levels, placing them at greater risk of developing diabetes.
For example, almost half of those carrying six or more mutations have fasting blood glucose levels over 5.6mmol/l, which the American Diabetes Association defines as 'impaired', meaning these people have a very high risk of developing diabetes.
'We have been developing quite a clear picture of the key genes involved with high blood sugar and diabetes and this allows us to better understand them and suggest new avenues for treatment,' commented Professor Froguel. 'We are also nearing the stage where we can develop tests that can identify the people at most risk of developing high blood sugar and diabetes later in their lives, so we can intervene to improve their health before they reach that point.'
EU support for the research came from three projects: EURO-BLCS ('Biological, clinical and genetic markers of future risk of cardiovascular disease'), which is financed through the 'Quality of life and management of living resources' budget line of the Fifth Framework Programme (FP5), and EURODIA ('Functional genomics of pancreatic beta cells and of tissues involved in control of the endocrine pancreas for prevention and treatment of type 2 diabetes') and EUGENE2 ('European Network on Functional Genomics of Type 2 Diabetes'), both of which are funded through the 'Life sciences, genomics and biotechnology for health' Thematic area of the Sixth Framework Programme (FP6).
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Category: Project results
Data Source Provider: Nature Genetics; Imperial College London
Document Reference: Bouatia-Naji N et al. (2008) A variant near MTNR1B is associated with increased fasting plasma glucose levels and type 2 diabetes risk. Nature Genetics, published online 7 December. DOI: 10.1038/ng.277.
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