Adaptive oligodendrogenesis regulates blood-hypothalamus barrier permeability, hypothalamic glucose sensing and systemic glucose homeostasis in male mice

Objective: Brain glucose sensing is critical for survival during hypoglycaemia, yet how glucose-sensing neurons access circulating glucose concentrations to maintain glucose homeostasis remains poorly understood. Here we tested the hypothesis that adult oligodendrogenesis in the median eminence (ME) is responsive to changes in blood glucose levels and contributes to hypothalamic glucose sensing through regulation of the blood-hypothalamus barrier.
Methods: We used glycemic challenges and hypoinsulinaemic clamp studies to identify the effect of systemic changes in glycaemia on hypothalamic oligodendrocyte lineage cells. We used conditional knockout mouse models to dissect the respective contributions of adult oligodendrogenesis and new myelin formation to glucose homeostasis in adult male mice. Analyses combined immunofluorescence, serial electron microscopy, whole-brain tissue clearing, and transcriptomic analyses.
Results: We found that adult oligodendrogenesis in the median eminence (ME) is modulated by changes in circulating glucose levels and rapidly upregulated by hypoglycaemia. Genetic blockade of new oligodendrocyte production in adult male mice impairs the regulation of glucose homeostasis, the integrity of the ME blood-hypothalamus barrier, and hypothalamic glucose sensing. Unexpectedly, functional integrity of adult-formed myelin is not required for the maintenance of glucose homeostasis. Instead, we show that blockade of adult oligodendrogenesis disrupts hypothalamic expression of A disintegrin and metallopeptidase with thrombospondin motifs 4 (ADAMTS4), a metallopeptidase whose brain expression is restricted to the oligodendrocyte lineage and whose ME expression requires ongoing adult oligodendrogenesis. We show that ADAMTS4 regulates hypothalamic perineuronal net deposition, vascular permeability and glucose sensing. Finally, we show that ME ADAMTS4 expression is regulated by changes in peripheral glycaemia and is dysregulated in diabetes, providing a mechanism by which ME oligodendrocytes contribute to the regulation of glucose homeostasis.