Sex differences in glucose metabolism and mitochondrial function in glioblastoma implicate hypoxia-inducible factor 1 alpha (hif1a) activity

Abstract Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults. It is more prevalent in males and female patients have better survival. Investigating the molecular mechanisms underlying this disparity is imperative for understanding its development and progression as well as developing novel treatment paradigms. Carbohydrate (namely glucose) metabolism is a critical GBM nutrient source for biosynthesis, energetics, and reducing equivalents. Previously, our group discovered that elevated glycolytic activity uniquely predicted the outcomes of male, but not female, lower grade glioma patients. Our goal was to characterize sex differences in GBM carbohydrate metabolism and their effects on cellular phenotype. First, we discovered that male transformed murine astrocytes were more susceptible to glucose deprivation than females. We confirmed this phenotype with irreversible inhibition of hexokinase with 2-deoxyglucose as well as a GLUT1-selective inhibitor. Time-resolved stable isotope tracing of cell metabolism with carbon-13 glucose in transformed astrocytes further supported these findings; male cells had significantly higher rates of glucose uptake and metabolism than female cells. These results were validated with stable isotope metabolomics datasets from human cancer cell lines. Using additional assays of cellular metabolism, we discovered that male transformed astrocytes had a higher glycolytic rate, higher pyruvate kinase activity, higher mitochondrial respiration, and higher mitochondrial mass compared to females. This was validated by a TCGA pancancer analysis that revealed significantly higher expression of nuclear genes involved in mitochondrial regulation in males than in females. This prompted us to identify possible regulators of this metabolic phenotype. We discovered that HIF1A had robust hypoxia-inducible expression that was significantly higher in male transformed astrocytes. Moreover, HIF1A expression as well as its target transcripts were significantly higher in TCGA pancancer tumor datasets. Together, our data underscore the potential for developing sex-specific metabolic targeting approaches for patients with GBM.