Insulin resistance in diabetes and other metabolic disorders could be treated by a naturally occurring molecule with insulin-like effects, studies by French researchers suggest.
The mechanisms that regulate apelin, a peptide found in a variety of tissues in the body and in the bloodstream, and those that regulate insulin are known to be closely related, but researchers had not previously looked at how apelin affects glucose metabolism in the body.
Professor Isabelle Castan-Laurell and colleagues from the University of Toulouse injected mice intravenously with apelin and found that it rapidly reduced glucose levels in the blood.
They then went on to examine how apelin affected the way that glucose was metabolised in the body. They found that apelin increased glucose turnover and, in response, liver tissue adjusted its glucose production so that normal blood glucose levels were maintained.
In addition, apelin was able to increase insulin-stimulated glucose transport, suggesting that the effects of apelin and insulin are mediated by different mechanisms and can be additive.
'Apelin could represent a promising target in the management of insulin resistance,' Professor Castan-Laurell said.
'Improvement of insulin sensitivity and reduction of blood glucose levels are expected goals for the treatment of type-2 diabetes. We demonstrated that acute injection of apelin was able to improve glucose tolerance in insulin-resistant mice and to increase glucose utilisation in white adipose tissue, skeletal muscles and the heart.'
The effect of long-term treatment with apelin will now need to be studied to provide further insight into the precise role the peptide plays in treating insulin resistance, the researchers said.
The findings may also have wider benefits, they pointed out. 'The contribution of apelin should yield new insights into the physiology and physiopathology of glucose and lipid metabolism.'
Cell Metabolism 2008; 8: 437-45
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