title: Hypothalamic metabolic compartmentation during appetite regulation as revealed by magnetic resonance imaging and spectroscopy methods.
abstract: We review the role of neuroglial compartmentation and transcellular neurotransmitter cycling during hypothalamic appetite regulation as detected by Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS) methods. We address first the neurochemical basis of neuroendocrine regulation in the hypothalamus and the orexigenic and anorexigenic feed-back loops that control appetite. Then we examine the main MRI and MRS strategies that have been used to investigate appetite regulation. Manganese-enhanced magnetic resonance imaging (MEMRI), Blood oxygenation level-dependent contrast (BOLD), and Diffusion-weighted magnetic resonance imaging (DWI) have revealed Mn(2+) accumulations, augmented oxygen consumptions, and astrocytic swelling in the hypothalamus under fasting conditions, respectively. High field (1)H magnetic resonance in vivo, showed increased hypothalamic myo-inositol concentrations as compared to other cerebral structures. (1)H and (13)C high resolution magic angle spinning (HRMAS) revealed increased neuroglial oxidative and glycolytic metabolism, as well as increased hypothalamic glutamatergic and GABAergic neurotransmissions under orexigenic stimulation. We propose here an integrative interpretation of all these findings suggesting that the neuroendocrine regulation of appetite is supported by important ionic and metabolic transcellular fluxes which begin at the tripartite orexigenic clefts and become extended spatially in the hypothalamus through astrocytic networks becoming eventually MRI and MRS detectable.
authors.affiliation: Department of Experimental Models of Human diseases, Laboratory of Imaging and Spectroscopy by Magnetic Resonance, Instituto de Investigaciones Biomédicas "Alberto Sols" CSIC/UAM Madrid, Spain.
authors.forename: Blanca
authors.initials: B
authors.lastname: Lizarbe
authors.forename: Ania
authors.initials: A
authors.lastname: Benitez
authors.forename: Gerardo A
authors.initials: GA
authors.lastname: Peláez Brioso
authors.forename: Manuel
authors.initials: M
authors.lastname: Sánchez-Montañés
authors.forename: Pilar
authors.initials: P
authors.lastname: López-Larrubia
authors.forename: Paloma
authors.initials: P
authors.lastname: Ballesteros
authors.forename: Sebastián
authors.initials: S
authors.lastname: Cerdán
keywords: appetite regulation; hypothalamus; magnetic resonance imaging; magnetic resonance spectroscopy; neuroendocrine signaling; neuroglial compartmentation