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Diabetes Research
19.06.2017

How Insulin in the Brain May Suppress the Subjective Feeling of Hunger

Insulin in the brain may help regulate the hunger sensation and improve functional connectivity in certain cognitive brain regions as well as in the hippocampus and hypothalamus. This is the finding of a new ‚Scientific Reports’ study by researchers at the Helmholtz Zentrum München, partner in the German Center for Diabetes Research (DZD).

Image Brain Regions

Intranasal insulin enhances functional connectivity in specific cognitive brain regions (default-mode network, DMN) as well as in the hippocampus and the hypothalamus. Image source: IDM

Eating behavior and the subjective feeling of hunger are regulated by a variety of hormones. Here a key role is played by the hormone insulin because it is not only active in the body, but also in the brain. It was previously known that insulin acts on the homeostatic region (hypothalamus*). Now, however, scientists have found that the hormone is also active in other brain regions. Researchers at the Institute for Diabetes Research and Metabolic Diseases of Helmholtz Zentrum München at the University of Tübingen, a partner of the DZD, have further deciphered the function of insulin in the brain as well as its influence on the subjective feeling of hunger.

To better understand the mechanism of action of insulin, the researchers administered insulin intranasally to healthy young adults. Through the application of the hormone via a nasal spray, the blood-brain barrier is bypassed and the insulin reaches the brain directly. In the study, 25 lean, ten overweight and 12 obese participants “sniffed” insulin or the placebo. Brain activity was then visualized and recorded by means of a functional magnetic resonance imaging (fMRI) scan. The result in all study participants: Intranasal insulin improves functional connectivity in the prefrontal regions of the default-mode network (DMN), a group of brain regions that are activated when a person is at rest and is not performing any tasks. This region is central to cognitive processes. In addition, the functional connectivity between the DMN and the hippocampus as well as the hypothalamus is strengthened.

These changes in the brain also influence eating behavior and alter the relationship between adiposity and the hunger sensation. Actually, people with a lot of visceral adipose tissue** have an increased sensation of hunger. "Insulin-enhanced connectivity between the DMN and the hippocampus suppresses the relationship between adipose tissue and the subjective hunger feeling," said Stephanie Kullmann, author of the study. The study participants felt less hunger after being administered intranasal insulin.

In addition, the scientists observed that insulin in the brain also improves the effect of the hormone in the body. Study participants with insulin-induced increased functional connectivity in the DMN have higher insulin sensitivity in the body. This counteracts obesity and type 2 diabetes.

The current results show that insulin in the brain – due to increased functional connectivity between cognitive and homeostatic regions – may help regulate eating behavior and facilitate weight loss.

Further Information

* The hypothalamus is the supreme regulatory center for all vegetative and endocrine processes. The hypothalamus coordinates water and saline balance as well as blood pressure. It ensures the maintenance of the inner milieu (homeostasis) and regulates food intake.

** The fatty tissue on and especially in the abdomen is called visceral fat. It is stored in the free abdominal cavity and envelops the internal organs – especially the organs of the digestive system. There is a relationship between visceral adipose tissue and the subjective feeling of hunger.

Original Publication:
Kullmann, S. et al. (2017): Intranasal insulin enhances brain functional connectivity mediating the relationship between adiposity and subjective feeling of hunger. Scientific Reports, DOI:10.1038/s41598-017-01907-w

As German Research Center for Environmental Health, Helmholtz Zentrum München pursues the goal of developing personalized medical approaches for the prevention and therapy of major common diseases such as diabetes mellitus and lung diseases. To achieve this, it investigates the interaction of genetics, environmental factors and lifestyle. The Helmholtz Zentrum München has about 2,300 staff members and is headquartered in Neuherberg in the north of Munich. Helmholtz Zentrum München is a member of the Helmholtz Association, a community of 18 scientific-technical and medical-biological research centers with a total of about 37,000 staff members. 

The primary research objective of the research groups working in the Institute for Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Zentrum München at the University of Tübingen is personalized prediction of diabetes risk and diabetes prevention as well as personalized therapy. Here special focus is placed on gene-environment interaction. 

The German Center for Diabetes Research (DZD) is a national association that brings together experts in the field of diabetes research and combines basic research, translational research, epidemiology and clinical applications. The aim is to develop novel strategies for personalized prevention and treatment of diabetes. Members are Helmholtz Zentrum München – German Research Center for Environmental Health, the German Diabetes Center in Düsseldorf, the German Institute of Human Nutrition in Potsdam-Rehbrücke, the Paul Langerhans Institute Dresden of the Helmholtz Zentrum München at the University Medical Center Carl Gustav Carus of the TU Dresden and the Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Zentrum München at the Eberhard-Karls-University of Tuebingen together with associated partners at the Universities in Heidelberg, Cologne, Leipzig, Lübeck and Munich.