Fight excess fat with fat cells?

Fat cells should help with weight loss

18/01/2012

Researchers at the Dana-Farber Cancer Institute in Boston are working to combat overweight with the help of so-called brown fat cells. In experiments with mice, Bruce Spiegelman and colleagues found that the brown fat cells promote the burning of fat and thus cause a significant reduction in body weight.

The brown fat cells, in contrast to the widely researched white fat cells store no fat, but use this to generate heat. The production of brown fat cells is controlled by the previously unknown hormone irisin, the US researchers report. Thus, an increase in the irisin level in the overweight mice caused a significant increase in the brown fat cells, which subsequently significantly reduced the weight of the animals. In normal-weight mice, however, showed no comparable effect, said Bruce Spiegelman and colleagues.

Propagation of brown fat cells helps obese people lose weight
The idea of ​​using fat cells to fight excess fat triggers fascination among researchers worldwide. By increasing the amount of brown fat cells, overweight people should be helped to reduce their weight, improve their sugar metabolism and prevent diabetes. The studies of the US researchers on the influence of brown fat cells, provide promising results here. The scientists have succeeded in using a newly discovered hormone to increase the proportion of brown fat cells in adipose tissue of mice and thus counteract the overweight of the animals. In earlier studies, researchers from the Dana-Farber Cancer Institute had already found that the mice had increased protection against obesity and diabetes from increased production of a special gene activator in their muscles. In their current study, Spiegelman and colleagues therefore looked for possible influencing factors that could be considered as a communicator between muscle and adipose tissue.

Newly discovered hormone helps to lose weight and prevents diabetes
The US scientists discovered a hitherto unknown hormone, which is released by muscle cells and enters the bloodstream with the fat. The researchers named the hormone after the Greek goddess Iris as Irisin. According to the researchers in white adipose tissue, the hormone stimulates the formation of cells with the properties of brown adipose cells and increases the energy consumption of this tissue. For example, an increase in irisin levels over a ten-day period in overweight mice resulted in significant weight loss as well as an improvement in sugar metabolism levels, which are usually considered risk factors for diabetes. The normal-weight animals, however, showed no effect on the weight when artificially increased irisin level, said the US scientists.

Endurance training increases the irisin distribution
The researchers were also able to show that irisin blood levels are markedly increased by several weeks of endurance training in both mice and humans. According to Spiegelman, the iris could be at least partially responsible for the positive effects of sport on health. While at first glance it may seem paradoxical that in an energy-depleting activity such as sport, the production of a hormone increases, which in turn increases energy consumption, but the mechanism is likely to be evolutionary, the US researchers said. For example, the effect could serve to increase the heat production known as trembling in the case of massive cold by muscle contraction. For this explanation, according to the US researchers also the fact that in mice, the proportion of brown fat cells increases when exposed to several hours of massive cold.

On the properties of brown fat cells, the US scientists said that these are not normally found in white adipose tissue in humans, but are in the separate brown adipose tissue. While mice have relatively much of this tissue type and the brown fat cells are distributed throughout the body, the existence of comparable tissue in humans was unknown until a few years ago. It was not until 2007 that researchers discovered that adults also have brown adipose tissue around the neck and clavicle.

European research project on brown fat cells
Since the discovery of brown adipose tissue, researchers worldwide are working on possible methods to increase the proportion of brown fat cells in the human body. The European research project started last year „Diabat“, in which, among other things, various active ingredients are tested, which should increase the proportion of brown fat cells in the human body. According to the scientists, 50 grams more brown fat cells would increase the energy consumption of an adult by 20 percent, said the coordinator of the „Diabat“-Research project, Stephan Herzig from the University of Heidelberg and the German Cancer Research Center. The newly discovered hormone irisin could play a decisive role here if the results from the experiments with mice are confirmed in further investigations, Herzig explained. At the same time, however, other hormones are being investigated within the scope of the research project, which are attributed to an increase in the number of brown fat cells. Thus, the researchers hope soon to be able to use the potential of brown fat cells clinically for the treatment of obesity. (Fp)

Picture: Kreuznacher Zeitung