The gastrointestinal tract plays a key role in controlling eating behaviour and regulating metabolic processes. We now know that the production and release of hormones in the gastrointestinal tract play a major role in the interactions of the metabolism. A study carried out by researchers at the University of Hohenheim's Department of Nutritional Medicine led by Prof. Stephan C. Bischoff in cooperation with the eSwiss Medical and Surgical Center in St. Gallen looked into the activity of genes that produce such hormones. The researchers compared tissue samples of obese patients with those of normal-weight individuals.

“For our study, we carried out gene expression analyses using rtPCR (reverse transcriptase polymerase chain reaction) and immunohistochemical analyses of individual gene products in the respective tissue samples,” says Prof. Dr. Bernd Schultes, head of the eSwiss Medical and Surgical Center explaining the approach used. Schultes’ institute specialises in obesity treatment and frequently carries out gastric bypass operations to help people lose weight and improve their metabolic situation. The tissue samples used for the investigations were removed as part of such surgical interventions. The control group samples were provided by the university hospital Klinikum rechts der Isar's Department of Surgery in Munch.

The study analysed genes whose gene products are essential components of the serotonergic intestinal nervous system. The scientists also studied genes that play a key role in the coding of hormones that control our eating behaviour. The researchers from Hohenheim obtained preliminary data in an animal study. Based on the results of this study, they went on to study the serotonergic nervous system in a large number of human intestinal tissue samples and the expression of individual genes that are directly involved in forming hormones and other signalling molecules in the tissue. They found that obese patients and normal-weight patients differed with regard to the expression of certain intestinal tissue genes. In addition, network analyses revealed differences in the association strength between the individual genetic expression profiles of obese and normal-weight people. “Our study therefore suggests that the entire neuroendocrine intestinal network is altered in obese people,” says Prof. Schultes explaining the findings.

Above all else, the study found that the patient and control groups differed considerably from each other, in terms of dietary factors as well as changes in the bacterial composition of the individuals’ intestinal flora. “We now want to find out the causes and potential consequences of these differences. In this sense, our study has given us new starting points for further investigations,” says the head of the eSwiss Medical and Surgical Center. However, the results cannot be used to derive therapy recommendations and approaches. In a next step, the researchers are planning to identify the causal factors of the changes observed and hope to find out how the neuroendocrine intestinal system can be specifically modulated. “We still have a long way to go before our study generates new therapeutic approaches that will help obese people lose weight. But we are sure that our investigations have paved the way to some degree,” says Prof. Schultes.

The results of the study have now been published in the international journal Obesity two and a half years after the initial investigations. The next study will focus on analysing gene expression differences and finding out how these differences correlate with the metabolism of the people concerned. The researchers will also study the extent to which different dietary factors play a role in the different intestinal expression patterns. Animal experiments will be used to find out whether the expression of certain genes can be specifically modified and whether these modifications have an effect on the animals’ metabolism.

“Our study provides evidence that points to the influence of biological parameters on the development of obesity. This is very important because obesity is still regarded as a self-inflicted condition. Our results will help obese people and alleviate the heavy burden of guilt feelings,” concludes Prof. Schultes.