title: Differential acute and chronic effects of leptin on hypothalamic astrocyte morphology and synaptic protein levels.
abstract: Astrocytes participate in neuroendocrine functions partially through modulation of synaptic input density in the hypothalamus. Indeed, glial ensheathing of neurons is modified by specific hormones, thus determining the availability of neuronal membrane space for synaptic inputs, with the loss of this plasticity possibly being involved in pathological processes. Leptin modulates synaptic inputs in the hypothalamus, but whether astrocytes participate in this action is unknown. Here we report that astrocyte structural proteins, such as glial fibrillary acidic protein (GFAP) and vimentin, are induced and astrocyte morphology modified by chronic leptin administration (intracerebroventricular, 2 wk), with these changes being inversely related to modifications in synaptic protein densities. Similar changes in glial structural proteins were observed in adult male rats that had increased body weight and circulating leptin levels due to neonatal overnutrition (overnutrition: four pups/litter vs. control: 12 pups/litter). However, acute leptin treatment reduced hypothalamic GFAP levels and induced synaptic protein levels 1 h after administration, with no effect on vimentin. In primary hypothalamic astrocyte cultures leptin also reduced GFAP levels at 1 h, with an induction at 24 h, indicating a possible direct effect of leptin. Hence, one mechanism by which leptin may affect metabolism is by modifying hypothalamic astrocyte morphology, which in turn could alter synaptic inputs to hypothalamic neurons. Furthermore, the responses to acute and chronic leptin exposure are inverse, raising the possibility that increased glial activation in response to chronic leptin exposure could be involved in central leptin resistance.
authors.affiliation: Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Avenida Menéndez Pelayo, 65, 28009 Madrid, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: García-Cáceres
authors.forename: Esther
authors.initials: E
authors.lastname: Fuente-Martín
authors.forename: Emma
authors.initials: E
authors.lastname: Burgos-Ramos
authors.forename: Miriam
authors.initials: M
authors.lastname: Granado
authors.forename: Laura M
authors.initials: LM
authors.lastname: Frago
authors.forename: Vicente
authors.initials: V
authors.lastname: Barrios
authors.forename: Tamas
authors.initials: T
authors.lastname: Horvath
authors.forename: Jesús
authors.initials: J
authors.lastname: Argente
authors.forename: Julie A
authors.initials: JA
authors.lastname: Chowen
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015153:Blotting, Western; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism*; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007150:Immunohistochemistry; D057967:Infusions, Intraventricular; D020738:Leptin / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D050765:Qa-SNARE Proteins / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016704:Synapsins / Q000378:metabolism; D013997:Time Factors; D014746:Vimentin / Q000378:metabolism*
chemical_list: D005904:Glial Fibrillary Acidic Protein; D020738:Leptin; D050765:Qa-SNARE Proteins; D016704:Synapsins; D014746:Vimentin