Student - June 21, 2007

Not all big bellies are unhealthy

Whereas doctors and health workers are constantly reminding us that a fat stomach is one of the worst signs of ill health, thousands of fatties are in fact the picture of health. And a Wageningen PhD researcher may have discovered why: the more healthy fats they store, the less dangerous thick layers of fat probably are to health.

High levels of fat reserves increase the chance of heart and circulatory disease and Type 2 diabetes, and possibly also rheumatism and some types of cancer. Dr Rinke Stienstra of the Division of Human Nutrition explains that this is because large fat reserves cause continuous inflammation in the body. If fat layers grow, they attract more immune cells. The immune cells in turn emit inflammatory proteins such as TNF-alpha and Interleukin-6, which can cause furring up of the arteries and diabetes.

Stienstra wanted to find out whether thick fat deposits always spark off more inflammatory activity, so he fattened mice and then gave them the anti-diabetic medicine rosiglitazone for a week. Rosiglitazone attaches itself in fat cells to the protein PPAR, which normally reacts to healthy unsaturated fatty acids and their metabolites. Giving rosiglitazone therefore gives an indication of what happens in a fat belly that is not composed of unhealthy fats in butter for example, but of the healthy fats in sunflower oil.

Stienstra discovered that stimulating PPAR could not prevent immune cells from transferring to the fat reserves. ‘On the contrary, the number of immune cells increased spectacularly after stimulating the protein,’ says Stienstra’s supervisor Dr Sander Kersten. ‘What was interesting was that the only immune cells involved were of a type that probably has no detrimental effects on health. They are the same immune cells as you find in muscles and undeveloped fat tissue in thin people.’

The immune cells manufacture fewer inflammatory proteins and more proteins like Interleukin-10 and arginase-1, which promote the growth and development of tissue. ‘Probably these benign immune cells stimulate the growth of fat tissue as well, so they are better able to store fatty acids,’ concludes Kersten. ‘In this way they prevent fatty acids from roaming around the body and causing damage.’ / Willem Koert

Rinke Stienstra received his PhD on 18 June. His promotor was Professor Michael Müller, chair of Nutrition, Metabolism and Genomics.

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