Research on lipid metabolism in murine brain
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1 LIMES (Life and Medical Sciences Institute), University of Bonn |
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The balance between food consumption and utilization is essential for homeostasis. Therefore, organisms need to adapt to constant changes of food availability and energy requirements. An important role in controlling the metabolic system plays the hypothalamus – one of the satiety centers in the brain found to be differentially targeted by saturated and unsaturated fatty acids. Since the blood-brain barrier displays special characteristics in this region it was suggested that other circumventricular organs could also take up circulating lipids for sensing purposes. In order to observe the uptake of saturated and unsaturated lipids into various brain regions, acute brain slices were cultured either with alkyne-oleate or alkyne-palmitate, followed by click-reaction with fluorescent azide-reporter and microscopy. Distribution of lipid droplets was observed in separate experiment using the lipophilic dye LD540. The key discoveries are: (I) alkyne-oleate in situ targets ependymal cells of the choroid plexus, subfornical organ, median eminence, cerebellar Bergmann glia, optic chiasma, pyramidal tracts, fimbria of the hippocampus, stria terminalis, corpus callosum, trapezoid body, transverse fibers of the pons, spinal trigeminal tract, spinal nucleus of trigeminal nerve, periaqueductal grey, external cuneate nucleus and the gracile nucleus. (II) Astrocytes and the capillary endothelium show more intense staining by alkyne-oleate than alkyne-palmitate. (III) Lipid droplets are located primarily in the ependymal cell layer of the lateral and 4th ventricles.