Microglial Fructose Metabolism and Immune Suppression in Glioblastoma

Northwestern Medicine investigators report that brain-resident microglia within glioblastoma can take up and metabolize fructose through the GLUT5 transporter, and that disrupting this pathway in mouse models was linked to heightened antitumor immune activity.

To identify which cells in the glioblastoma microenvironment could use fructose, the investigators reported analyzing microglia, macrophages, and glioma tumor cells from tumors and surrounding tissue using approaches that included flow cytometry and genetic sequencing methods. Microglia uniquely expressed the GLUT5 transporter and, among the immune cell populations evaluated, were observed to be the only immune cells capable of metabolizing fructose in the tumors examined.

In mouse experiments, tumors developing in animals genetically engineered without GLUT5 were described as showing stronger immune recognition, along with increased production of inflammatory cytokines and rapid proliferation of CD8+ T cells. The report also described activation extending beyond microglia, with investigators attributing inflammatory changes to interactions among multiple immune components in the tumor microenvironment.

The authors’ interpretation was that microglial fructose metabolism functions as a regulator of immune suppression in glioblastoma. They also described an organ-context contrast: fructose consumption has been associated with inflammatory diseases in peripheral organs, while in the brain this fructose-related activity was described as suppressing inflammation even as it supported tumor growth.

Looking ahead, next steps include identifying candidate drugs intended to block cellular fructose uptake and testing promising fructose transport inhibitors in additional preclinical studies, including in combinations with standard-of-care therapies for brain tumors and with immunotherapies, to assess whether tumors can be sensitized in those models.

Key Takeaways:

• Among immune cells assessed in glioblastoma tumors, brain-resident microglia uniquely expressed GLUT5 and were the only immune population described as metabolizing fructose.
• In GLUT5-deficient mouse tumors, investigators reported increased inflammatory signaling and CD8+ T-cell expansion.
• Next steps include finding candidate fructose transport inhibitors and evaluating them in further preclinical studies, including combination experiments with standard therapies and immunotherapies.