[Gut microbiota and depression : Pathophysiology of depression: hypothalamic-pituitary-adrenal axis and microbiota-gut-brain axis]. / Darmflora und Depression : Pathophysiologie der Depression: Hypothalamus-Hypophysen-Nebennierenrinden- und Mikrobiota-Darm-Hirn-Achse.

Depression is a chronic disease with a complex multifactorial and still not fully clarified etiology. Due to new insights after recent investigations of the microbiota-gut-brain (MGB) axis, a relationship between a disrupted gut microbiota composition and the probability to develop a depression can be assumed. This hypothesis is supported by evidence that there is a strong communication between gut microbiota and the central nervous system (CNS) and that this communication is mediated through the MGB axis. Apparently, this bidirectional axis can be modulated by environmental factors, such as stress, pharmaceuticals (in particular antibiotics) and dietary habits. Moreover, modulation of this axis can also result in mood alterations. As the hypothalamic-pituitary-adrenal (HPA) axis is a key element regulating the MGB axis and is also related to the pathophysiology of depression, it is important to understand the relationship between both biological systems. An English language literature search was conducted using the biomedical database PubMed. We used combined terms, such as "gut microbiota", "depression", "hypothalamic-pituitary-adrenal axis" or "microbiota-gut-brain axis". The current literature supports the idea that the MGB axis has an impact on the risk to develop depression and that stress modulation through the HPA axis plays a key role in this context.

Translocator Protein (TSPO) Expression in Platelets of Depressed Patients Decreases during Antidepressant Therapy.

Introduction: A promising candidate in the field of pharmacological treatment options regarding major depressive disorder (MDD) is the mitochondrial translocator protein (18 kDa) (TSPO). TSPO is crucial for neurosteroid synthesis, which is in turn important for the regulation of emotions. It has already been shown that TSPO expression in platelets of depressed patients is reduced compared to healthy subjects. Methods: We measured TSPO levels in platelets of 37 depressed patients before and after 6 weeks of pharmacological treatment to test the hypotheses that i) such treatment would increase TSPO expression and ii) that this increase would be correlated with therapeutic response. Results: Surprisingly, TSPO levels in platelets of all patients were significantly reduced after 6 weeks of treatment (p=0.044). Within the responder group, a non-significant trend towards greater TSPO level reduction could be observed. Discussion: These results challenge our hypotheses that TSPO levels might increase during antidepressant therapy along with a decrease in depressive symptoms. Thus, we assume that TSPO expression in platelets is not a suitable state marker for MDD.

Significant increase in anxiety during aging in mGlu5 receptor knockout mice.

Glutamatergic mechanisms regulate neuronal circuits implicated in mood and anxiety. Emotional disorders as anxiety and depression are particularly difficult to treat during aging and mechanisms underlying emotional disturbances in the brain of the elderly are poorly understood. This may result from the small number of studies investigating these disorders in aged animals. Among glutamate receptors, metabotropic mGlu5 receptors are thought to play an important role, since their pharmacological blockade induces strong anxiolytic effects. However, the implication of mGlu5 in regulating anxiety is not yet completely understood. Here we analyzed both young adult and aged mice lacking mGlu5 receptors, to clarify, if genetic deletion of the receptor induces similar to pharmacological blockade anxiolytic effects. Unexpectedly, mGlu5 receptor knockout (KO) mice showed increased anxiety accentuating with aging. In contrast, young adult mice displayed an anti-depressive-like phenotype that was no longer detectable in aged animals. Our data support important distinct roles of mGlu5 receptors in modulating anxiety and depression during aging.