Anorexia disrupts glutamate-glutamine homeostasis associated with astroglia in the prefrontal cortex of young female rats

Anorexia nervosa (AN) is an eating disorder characterized by self-starvation and excessive weight loss with a notorious prevalence in young women. The neurobiology of AN is unknown but murine models, like dehydration induced anorexia (DIA), reproduce weight loss and avoidance of food despite its availability. Astrocytes are known to provide homeostatic support to neurons, but it is little explored if anorexia affects this function. In this study, we tested if DIA disrupts glutamate-glutamine homeostasis associated with astrocytes in the prefrontal cortex (PFC) of young female rats. Our results showed that anorexia reduced the redox state, as well as endogenous glutamate and glutamine. These effects correlated with a reduced expression of the glutamate transporters (GLT-1 and GLAST) and glutamine synthetase, all of them are preferentially expressed by astrocytes. Accordingly, the expression of GFAP was reduced. Anorexia reduced the astrocyte density, promoted a de-ramified morphology, and augmented the de-ramified/ramified astrocyte ratio in the medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC), but not in the motor cortex (M2). The increase of a de-ramified phenotype correlated with increased expression of vimentin and nestin. Based on these results, we conclude that anorexia disrupts glutamate-glutamine homeostasis and the redox state associated with astrocyte dysfunction.

A Functional Signature in the Developing Cerebellum: Evidence From a Preclinical Model of Autism

Autism spectrum disorders (ASD) are pervasive neurodevelopmental conditions detected during childhood when delayed language onset and social deficits are observed. Children diagnosed with ASD frequently display sensorimotor deficits associated with the cerebellum, suggesting a dysfunction of synaptic circuits. Astroglia are part of the tripartite synapses and postmortem studies reported an increased expression of the glial fibrillary acidic protein (GFAP) in the cerebellum of ASD patients. Astroglia respond to neuronal activity with calcium transients that propagate to neighboring cells, resulting in a functional response known as a calcium wave. This form of intercellular signaling is implicated in proliferation, migration, and differentiation of neural precursors. Prenatal exposure to valproate (VPA) is a preclinical model of ASD in which premature migration and excess of apoptosis occur in the internal granular layer (IGL) of the cerebellum during the early postnatal period. In this study we tested calcium wave propagation in the IGL of mice prenatally exposed to VPA. Sensorimotor deficits were observed and IGL depolarization evoked a calcium wave with astrocyte recruitment. The calcium wave propagation, initial cell recruitment, and mean amplitude of the calcium transients increased significantly in VPA-exposed mice compared to the control group. Astrocyte recruitment was significantly increased in the VPA model, but the mean amplitude of the calcium transients was unchanged. Western blot and histological studies revealed an increased expression of GFAP, higher astroglial density and augmented morphological complexity. We conclude that the functional signature of the IGL is remarkably augmented in the preclinical model of autism.