Article: article from journal or magazin.
The rate-limiting step for glucose transport into the hypothalamus is across the blood-hypothalamus interface.
Journal of Neurochemistry
Publication types: Journal Article ; Research Support, Non-U.S. Gov't Publication Status: ppublish
Specialized glucosensing neurons are present in the hypothalamus, some of which neighbor the median eminence, where the blood-brain barrier has been reported leaky. A leaky blood-brain barrier implies high tissue glucose levels and obviates a role for endothelial glucose transporters in the control of hypothalamic glucose concentration, important in understanding the mechanisms of glucose sensing We therefore addressed the question of blood-brain barrier integrity at the hypothalamus for glucose transport by examining the brain tissue-to-plasma glucose ratio in the hypothalamus relative to other brain regions. We also examined glycogenolysis in hypothalamus because its occurrence is unlikely in the potential absence of a hypothalamus-blood interface. Across all regions the concentration of glucose was comparable at a given plasma glucose concentration and was a near linear function of plasma glucose. At steady-state, hypothalamic glucose concentration was similar to the extracellular hypothalamic glucose concentration reported by others. Hypothalamic glycogen fell at a rate of approximately 1.5 micromol/g/h and remained present in substantial amounts. We conclude for the hypothalamus, a putative primary site of brain glucose sensing that: the rate-limiting step for glucose transport into brain cells is at the blood-hypothalamus interface, and that glycogenolysis is consistent with a substantial blood -to- intracellular glucose concentration gradient.
Algorithms, Animals, Biological Transport, Active/physiology, Blood Glucose/metabolism, Blood-Brain Barrier/physiology, Brain/anatomy & histology, Brain Chemistry/physiology, Glucose/metabolism, Glucose Transporter Type 1/metabolism, Glycogen/metabolism, Hypothalamus/metabolism, Kinetics, Liver Glycogen/metabolism, Male, Microwaves, Rats, Rats, Sprague-Dawley, Reproducibility of Results, Tissue Fixation
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