Adipose tissue endangers physical and mental health

The adipose tissue in people with severe overweight (adiposity or obesity) is more than an energy reservoir. It affects metabolism, immune defense, and even the individual’s psyche. Here certain signaling transmitters of the immune system (cytokines) play a decisive role.

An interdisciplinary study of the Integrated Research and Treatment Center (IFB) AdiposityDiseases shows that in obesity more signaling transmitters of the immune system are being produced in the adipose tissue than has been assumed so far. These so-called cytokines can lead to inflammatory processes in the whole body. The researchers furthermore found evdidence that physical activity can lower the levels of these pro-inflammatory cytokines also in obese patients. The results of the study were published on the science portal PLOS One in March 2015 (1).

The inflammatory processes in obesity are associated with a higher risk to develop type-2-diabetes or cardio-vascular diseases. Researchers of the IFB, the hospital for psychiatry and psychotherapy at the university hospital Leipzig, of the Ludwigs-Maxilimilans University Munich and of the Australian Tasmanian University examined cytokine levels in the blood of 200 normal weight and obese persons as well as their exact amount of exercise and energy consumption.

Increased production of inflammation-mediating cytokines

“An interesting result of the study was, that for the first time we measured levels of certain cytokines in obesity that are known for being crucial in inflammatory diseases such as asthma, which have so far not been associated with obesity and its sequelae. Now we have a better understanding why we find those diseases more often in obese patients,” underlines the psychiatrist and obesity researcher, Prof. Hubertus Himmerich. In normal weight study participants the serum levels of cytokines such as interleukin-5 and interleukin-13 were lower than in obese patients, the highest levels could be found in visceral obesity. Scientists know already that increased amounts of abdominal or visceral adipose tissue are associated with a higher morbidity of metabolic disorders, type-2-diabetes, and cardio-vascular diseases.

Obese participants who had much exercise showed lower levels of cytokines than those who were more passive. These scientific results make clear that more physical exercise can protect from the diseases associated with adiposity. Another therapeutic approach could be the blocking of cytokines with special medications, similar to the approach in autoimmune disorders.

Impact on the psyche

An elevated cytokine production can also contribute to the development of depression, since cytokines influence neuronal transmitters in the brain. They decrease e. g. the secretion of serotonin, a transmitter which is responsible for a positive mood and motivation. A lack of serotonin is one of the causes of depression. Further study results of the IFB on cytokine levels in healthy and depressed probands showed higher levels in the latter (2). Depressed probands who are additionally obese showed the highest serum concentrations of certain cytokines. “The higher secretion of cytokines in the adipose tissue can explain why obese patients more often suffer from a depression than normal weight persons”, said Prof. Himmerich. This connection may also shed light on the fact that a growing number of people in Germany are obese, and an also growing number suffers from depression.

The excess adipose tissue in obesity furthermore influences the metabolism, the energy homeostasis, and the sensation of hunger via hormones produced in the fat cells, the so called adipokines. The IFB has a special research field devoted to adipokines.

Besides the known sequelae of severe overweight such as arthrosis, diabetes, high blood pressure or fatty liver there is a growing number of disorders associated with obesity. Researching the mechanisms behind these disorders is prerequisite for improved prevention and therapy approaches.

 

Publications

(1) Schmidt FM, Weschenfelder J, Sander C, Minkwitz J, Thormann J, Chittka T, Mergl R, Kirkby KC, Faßhauer M, Stumvoll M, Holdt LM, Teupser D, Hegerl U, Himmerich H. Inflammatory cytokines in general and central obesity and modulating effects of physical activity. PLoS One 2015;10(3):e0121971.  Published: March 17, 2015      DOI: 10.1371/journal.pone.0121971

(2) Schmidt FM, Lichtblau N, Minkwitz J, Chittka T, Thormann J, Kirkby KC, Sander C, Mergl R, Faßhauer M, Stumvoll M, Holdt LM, Teupser D, Hegerl U, Himmerich H. Cytokine levels in depressed and non-depressed subjects, and masking effects of obesity. J Psychiatr Res 2014;55:29-34.  Epub 2014 May 8       DOI: 10.1016/j.jpsychires.2014.04.021.   

Doris Gabel