¹Tokyo Metropolitan Institute of Medical Science, Frontier Research Laboratory, Brain Metabolism Group, Tokyo, Japan

Background: Glucose transporter 1 (GLUT1, SLC2A1) is essential for glucose uptake into the brain. GLUT1 deficiency syndrome (GLUT1-DS) is characterized by hypoglycorrhachia, seizures, and cognitive and motor impairments, and has been primarily attributed to reduced GLUT1 in brain endothelial cells at the blood–brain barrier. Previous reports also indicated that GLUT1 localizes to astrocytic perivascular endfeet; however, its functional significance has not been fully understood.

Aims & Objectives: This study aimed to investigate the role of astrocytic GLUT1 in glucose uptake into the brain and its contribution to the development of GLUT1-DS symptoms.

Method: We generated astrocyte-specific Glut1 haploinsufficient mice (Aldh1l1-Cre; Glut1 flox/+) and compared them with systemic Glut1 haploinsufficient mice (Glut1 del/+) and endothelial cell–specific GLUT1 haploinsufficient mice (Tie2-cre; Glut1 flox/+). As an evaluation of GLUT1-DS–like features, glucose concentrations in cerebrospinal fluid (CSF) and interstitial fluid (ISF) were measured, and motor coordination as well as memory performance were assessed. To evaluate therapeutic relevance, we restored GLUT1 at postnatal days 15–19 under three conditions: endothelial cells only, astrocytes only, or both endothelial cells and astrocytes. We employed a novel astrocyte-targeted viral vector we developed for astrocyte-targeted repair.

Results: Our analysis revealed that astrocytic GLUT1 is not restricted to perivascular endfeet, as previously believed, but is widely distributed throughout the entire astrocytes. Astrocyte-specific Glut1 haploinsufficient mice exhibited significantly reduced CSF and ISF glucose concentrations and showed motor and memory deficits, closely resembling the phenotype of systemic Glut1 deficiency and endothelial cell–specific Glut1 deficiency. Furthermore, restoration of GLUT1 in both astrocytes and endothelial cells was required to normalize CSF and ISF glucose levels and to partially rescue behavioral deficits.

Discussion & Conclusions: This study demonstrates that astrocytic GLUT1 is indispensable for brain glucose homeostasis and neurological function, in coordination with endothelial GLUT1. We propose that effective therapeutic strategies should target both endothelial cells and astrocytes, thereby redefining the therapeutic framework for GLUT1-DS. Furthermore, under the conditions of this study, the improvement in motor dysfunction achieved by GLUT1 restoration was insufficient, suggesting that further optimization may be necessary, such as earlier GLUT1 supplementation.