A previously unknown coupling between obesity and diabetes
obesity increases the risk of developing diabetes, but nobody knows the details of why this is the case. Researchers at the Sahlgrenska Academy in Sweden have now identified a protein that may play a role in increasing the risk. The discovery may in the long term lead to new methods of preventing type 2 diabetes.
Most people who develop type 2 diabetes are overweight. Fat can accumulate in the muscles and liver of an obese person, leading to cell damage that in turn leads to a defect in the signalling from insulin. The result is an increase in the blood sugar level, and diabetes develops.
"The faulty storage of fat in the muscle cells interferes with the signal from the insulin that should stimulate increased absorption of sugar by the cells. The fat is stored in the cells in the form of fat droplets, and we have studied in detail how these are formed and how they grow. This has enabled us to show how the insulin signal is disrupted", says Professor Sven Olof Olofsson, director of the Wallenberg Laboratory at the Sahlgrenska Academy.
The research project used several advanced microscopy techniques to study lipid droplets in cultured muscle cells. It became clear that the lipid droplets merged with each other inside the cell by a process that involved a protein known as "SNAP23". This protein has another, independent, function - that of passing the insulin signal onwards into the cell.
"It appears that the SNAP23 is being 'stolen' from the insulin signalling process when the cell starts to pack fat, and this causes the defect that subsequently leads to diabetes. If we can find out more about how this works in detail, we may be able to influence the process and protect patients from developing diabetes", says Pontus Boström, PhD student at the Sahlgrenska Academy.
Further research will be necessary before the results can be tested in patients.
Original publication: Pontus Boström, Linda Andersson, Mikale Rutberg, Jeanna Perman, Ulf Lidberg, Bengt R. Johansson, Julia Fernandez-Rodriguez, Tommy Nilsson, Jan Borén and Sven-Olof Olofsson; "SNARE proteins mediate fusion between cytosolic lipid droplets with implications for insulin sensitivity"; Nature Cell Biology.
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