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Keywords
- depression (2)
- Axonal degeneration (1)
- Diabetic polyneuropathy (1)
- Fabry disease (1)
- Fabry-associated pain (1)
- Motor nerve biopsy (1)
- Neuropathy (1)
- Neurotrophic factors (1)
- Serotonin (1)
- Tryptophan hydroxylase-2 (Tph2) (1)
Institute
Rationale
While brain serotonin (5-HT) function is implicated in gene-by-environment interaction (GxE) impacting the vulnerability-resilience continuum in neuropsychiatric disorders, it remains elusive how the interplay of altered 5-HT synthesis and environmental stressors is linked to failure in emotion regulation.
Objective
Here, we investigated the effect of constitutively impaired 5-HT synthesis on behavioral and neuroendocrine responses to unpredictable chronic mild stress (CMS) using a mouse model of brain 5-HT deficiency resulting from targeted inactivation of the tryptophan hydroxylase-2 (Tph2) gene.
Results
Locomotor activity and anxiety- and depression-like behavior as well as conditioned fear responses were differentially affected by Tph2 genotype, sex, and CMS. Tph2 null mutants (Tph2\(^{−/−}\)) displayed increased general metabolism, marginally reduced anxiety- and depression-like behavior but strikingly increased conditioned fear responses. Behavioral modifications were associated with sex-specific hypothalamic-pituitary-adrenocortical (HPA) system alterations as indicated by plasma corticosterone and fecal corticosterone metabolite concentrations. Tph2\(^{−/−}\) males displayed increased impulsivity and high aggressiveness. Tph2\(^{−/−}\) females displayed greater emotional reactivity to aversive conditions as reflected by changes in behaviors at baseline including increased freezing and decreased locomotion in novel environments. However, both Tph2\(^{−/−}\) male and female mice were resilient to CMS-induced hyperlocomotion, while CMS intensified conditioned fear responses in a GxE-dependent manner.
Conclusions
Our results indicate that 5-HT mediates behavioral responses to environmental adversity by facilitating the encoding of stress effects leading to increased vulnerability for negative emotionality.
Dysregulated IGFBP5 expression causes axon degeneration and motoneuron loss in diabetic neuropathy
(2015)
Diabetic neuropathy (DNP), afflicting sensory and motor nerve fibers, is a major complication in diabetes.The underlying cellular mechanisms of axon degeneration are poorly understood. IGFBP5, an inhibitory binding protein for insulin-like growth factor 1 (IGF1) is highly up-regulated in nerve biopsies of patients with DNP. We investigated the pathogenic relevance of this finding in transgenic mice overexpressing IGFBP5 in motor axons and sensory nerve fibers. These mice develop motor axonopathy and sensory deficits similar to those seen in DNP. Motor axon degeneration was also observed in mice in which the IGF1 receptor(IGF1R) was conditionally depleted in motoneurons, indicating that reduced activity of IGF1 on IGF1R in motoneurons is responsible for the observed effect. These data provide evidence that elevated expression of IGFBP5 in diabetic nerves reduces the availability of IGF1 for IGF1R on motor axons, thus leading to progressive neurodegeneration. Inhibition of IGFBP5 could thus offer novel treatment strategies for DNP.
Background
Fabry-associated pain may be the first symptom of Fabry disease (FD) and presents with a unique phenotype including mostly acral burning triggerable pain attacks, evoked pain, pain crises, and permanent pain. We recently developed and validated the first Fabry Pain Questionnaire (FPQ) for adult patients. Here we report on the validation of the self-administered version of the FPQ that no longer requires a face-to-face interview but can be filled in by the patients themselves allowing more flexible data collection.
Methods
At our Würzburg Fabry Center for Interdisciplinary Treatment, Germany, we have developed the self-administered version of the FPQ by adapting the questionnaire to a self-report version. To do this, consecutive Fabry patients with current or past pain history (n = 56) were first interviewed face-to-face. Two weeks later patients’ self-reported questionnaire results were collected by mail (n = 55). We validated the self-administered version of the FPQ by assessing the inter-rater reliability agreement of scores obtained by supervised administration and self-administration of the FPQ.
Results
The FPQ contains 15 questions on the different pain phenotypes, on pain development during life with and without therapy, and on impairment due to pain. Statistical analysis showed that the majority of questions were answered in high agreement in both sessions with a mean AC1-statistic of 0.857 for 55 nominal-scaled items and a mean ICC of 0.587 for 9 scores.
Conclusions
This self-administered version of the first pain questionnaire for adult Fabry patients is a useful tool to assess Fabry-associated pain without a time-consuming face-to-face interview but via a self-reporting survey allowing more flexible usage.
Background
Fibromyalgia syndrome (FMS) is a chronic condition characterized by widespread pain and associated symptoms. We investigated cerebral activation in FMS patients by functional near-infrared spectroscopy (fNIRS).
Methods
Two stimulation paradigms were applied: a) painful pressure stimulation at the dorsal forearm; b) verbal fluency test (VFT). We prospectively recruited 25 FMS patients, ten patients with unipolar major depression (MD) without pain, and 35 healthy controls. All patients underwent neurological examination and all subjects were investigated with questionnaires (pain, depression, FMS, empathy).
Results
FMS patients had lower pressure pain thresholds than patients with MD and controls (p < 0.001) and reported higher pain intensity (p < 0.001). Upon unilateral pressure pain stimulation fNIRS recordings revealed increased bilateral cortical activation in FMS patients compared to controls (p < 0.05). FMS patients also displayed a stronger contralateral activity over the dorsolateral prefrontal cortex in direct comparison to patients with MD (p < 0.05). While all three groups performed equally well in the VFT, a frontal deficit in cortical activation was only found in patients with depression (p < 0.05). Performance and cortical activation correlated negatively in FMS patients (p < 0.05) and positively in patients with MD (p < 0.05).
Conclusion
Our data give further evidence for altered central nervous processing in patients with FMS and the distinction between FMS and MD.