Gut-Brain Axis
The gut-brain axis refers to the bidirectional communication system between the gut and the brain, which has deep roots in evolution and embryology. The axis connects the central nervous system (brain and spinal cord) and the enteric nervous system (ENS), which is a complex network of neurons that controls the function of the gastrointestinal (GI) tract. The connections includes the vagus nerve that is responsible for relaxation and restoration. Other parts of the axis includes the immune system since 80% of immune cells are located close to the gut and they can directly communicate with the brain via cytokines and other neurochemical signals. In addition, the gut has a repertoire of dozens of hormones to speak to the brain. Finally, trillions of gut bacteria produce metabolites, including short-chain fatty acids (e.g. butyric acid) that are important for gut and brain health.
Our research delves into various aspects of the gut-brain axis and their impact on bodily functions and mental well-being by means of a large cohort study. Precisely, we examine stool-related variables like stool composition (e.g., gut bacterial diversity and neurotransmitter metabolites) and self-reported stool frequency (as a marker of constipation) for their potential effects on health outcomes, including the modulation of immune system markers and the development of unclear bowel symptoms. We also include constipation, which might not only affect gastrointestinal health but also exhibit associations with mood and cognitive alterations. We estimate vagus nerve activity as a mediator between the gut and the brain via the measurement of high-frequency heart rate variability. Another mediator might be immune system function, which we examine with the blood-based analysis of inflammatory cytokines. Dietary patterns also play an important role in shaping gut microbiota composition, with implications for mental health outcomes including depression and psychological resilience. In our research, we measure various dietary variables like mediterranean diet adherence and categorical dietary preference (omnivore, pescetarian, vegetarian, vegan, etc.).
Current Studies
GABAGEN study – a large cohort study (N=401) in which we apply various methods including neuroimaging (MRI, MRS); stool sampling; genetic, epigenetic, and transcriptomic next-generation sequencing; cytokine profiling; electrocardiogram; clinical interviews; behavioral experiments; and psychological questionnaires to explore the importance of the gut-brain connection in various health and disease states.
Publications
Breit, S., Kupferberg, A., Rogler, G., & Hasler, G. (2018). Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Frontiers in psychiatry, 9, 44. https://doi.org/10.3389/fpsyt.2018.00044
Buchmann, A., Ritter, C., Müller, S. T., Haynes, M., Ghisleni, C., Tuura, R., & Hasler, G. (2022). Associations between heart rate variability, peripheral inflammatory markers and major depressive disorder. Journal of affective disorders, 304, 93–101. https://doi.org/10.1016/j.jad.2022.02.017
Hasler, G., Buchmann, A., Haynes, M., Müller, S. T., Ghisleni, C., Brechbühl, S., & Tuura, R. (2019). Association between prefrontal glutamine levels and neuroticism determined using proton magnetic resonance spectroscopy. Translational Psychiatry, 9, 170. https://doi.org/10.1038/s41398-019-0500-z
Hasler, G., Haynes, M., Müller, S. T., Tuura, R., Ritter, C., & Buchmann, A. (2020). The Association Between Adolescent Residential Mobility and Adult Social Anxiety, BDNF and Amygdala-Orbitofrontal Functional Connectivity in Young Adults With Higher Education. Frontiers in psychiatry, 11, 561464. https://doi.org/10.3389/fpsyt.2020.561464
Müller, S. T., Buchmann, A., Haynes, M., Ghisleni, C., Ritter, C., Tuura, R., & Hasler, G. (2020). Negative association between left prefrontal GABA concentration and BDNF serum concentration in young adults. Heliyon, 6(5), e04025. https://doi.org/10.1016/j.heliyon.2020.e04025
Ritter, C., Buchmann, A., Müller, S. T., Hersberger, M., Haynes, M., Ghisleni, C., Tuura, R., & Hasler, G. (2021). Cerebral perfusion in depression: Relationship to sex, dehydroepiandrosterone sulfate and depression severity. NeuroImage. Clinical, 32, 102840. https://doi.org/10.1016/j.nicl.2021.102840
Ritter, C., Buchmann, A., Müller, S. T., Volleberg, M., Haynes, M., Ghisleni, C., Noeske, R., Tuura, R., & Hasler, G. (2022). Evaluation of Prefrontal γ-Aminobutyric Acid and Glutamate Levels in Individuals With Major Depressive Disorder Using Proton Magnetic Resonance Spectroscopy. JAMA psychiatry, 79(12), 1209–1216. https://doi.org/10.1001/jamapsychiatry.2022.3384
Tuura, R. O., Buchmann, A., Ritter, C., Hase, A., Haynes, M., Noeske, R., & Hasler, G. (2023). Prefrontal Glutathione Levels in Major Depressive Disorder Are Linked to a Lack of Positive Affect. Brain sciences, 13(10), 1475. https://doi.org/10.3390/brainsci13101475
Other Resources
In a German-language bestseller book, Prof. Gregor Hasler devotes himself to describing the gut-brain connection and its implications for health and well-being.
Hasler, G. (2020). Die Darm-Hirn-Connection. Revolutionäres Wissen für unsere psychische und körperliche Gesundheit. Klett-Cotta.
In an interview with popular influencer and writer Laura Malina Seiler, Prof. Gregor Hasler discusses the intricacies of the gut-brain connection and their personal nutrition implications
Seiler, L. M. (2020, 3. Juni). Wie dein Darm dich glücklich – oder unglücklich machen kann – Interview Special mit Gregor Hasler. https://www.youtube.com/watch?v=lqTQlQ5zJVg
