Short-term fasting increases the levels of glucose transporters in the male rat hypothalamus

Abstract

Introduction. Different isoforms of glucose transporters (GLUTs) are present in the brain and they exhibit cell-specific expression and distinct anatomical localization. GLUT1 and GLUT3 are the predominant types of glucose transporters in the brain, whereas other forms are less abundant and are involved in glucose sensing only in certain brain regions. Here we examined the effect of six-hour fasting on the levels and anatomical distribution of GLUT1, GLUT2, and GLUT3 in the rat hypothalamus. Methods. Food was removed at 6 pm and male Wistar rats were sacrificed at midnight. Control animals had ad libitum access to food and they were sacrificed simultaneously with the fasting rats. The hypothalamic membrane protein fraction was isolated using subcellular protein fractionation kit for tissues. The amount of GLUT1, 2, and 3 was estimated by immunoblotting. Immunofluorescence was used to determine cell types expressing each of the examined GLUTs as well as their anatomical localizations within the hypothalamus. Results. Short-term food deprivation increased content of all three examined GLUT isoforms in the hypothalamic membrane protein fraction. GLUT1 and GLUT2 immunopositivity was observed in neuronal cell bodies and in the ependymal cells surrounding the third ventricle. GLUT1 was detected throughout the entire hypothalamic region, while strong GLUT2 immunoreactivity was restricted to paraventricular and ventromedial nucleus. GLUT3 positivity was detected in the subventricular zone glial cells located in the vicinity of ependymal cells. Conclusion. In conclusion, although the short-term fasting increased the hypothalamic levels of the examined GLUTs, it did not result in changing their regional distribution in this brain region.