High blood sugar is a risk factor for diabetes, but for some reason, the elevated sugar levels seem to reduce the risk for brain tumors called meningiomas. The surprising link between the conditions has prompted researchers to reexamine the mechanisms driving brain tumor growth.
"Diabetes and elevated blood sugar increase the risk of cancer at several sites including the colon, breast and bladder. But in this case, these rare malignant brain tumors are more common among people who have normal levels of blood glucose than those with high blood sugar or diabetes," said Judith Schwartzbaum, an associate professor of epidemiology and a researcher in Ohio State's Comprehensive Cancer Center.
Of note, gliomas make up about 27 percent of all brain cancers, which result in 13,000 deaths every year. In particular, the GBM form of glioma is particularly aggressive and notorious for the dismally grim 5-year survival rate of less than 10 percent.
To study the link between blood sugar levels and gliomas, Schwartzbaum and her team analyzed data from two large studies that totaled nearly 798,000 individuals. Of these 812 patients developed the brain tumors. In those patients who had high blood sugar and diabetes, Schwartzbaum found that the risk for glioma was actually lowered.
"This really prompts the question, 'Why is the association between blood glucose levels and brain cancer the opposite of that for several other cancerous tumors?" she said. "Our research raises questions that, when answered, will lead to a better understanding of the mechanisms involved in glioma development.”
The findings are surprising and challenges our basic assumption that cancer cells are glutton for sugar. In fact, some cancer treatments are centered on choking the tumor cells from the body’s glucose supply. But when deprived of one nutrient source, some cancers can still thrive by leeching on other nutrients, like fat, for its survival. Fat-loving cancers include acute myeloid leukemia and prostate cancer – two of the more common cancer types that can’t be starved by cutting the glucose supply.
In that context, perhaps Schwartzbaum’s results hint at glioma’s preference for another nutrient source, or that high glucose is actually dangerous to the tumor.
"This may suggest that the tumor itself affects blood glucose levels or that elevated blood sugar or diabetes may paradoxically be associated with a protective factor that reduces brain tumor risk," Schwartzbaum said. "For example, insulin-like growth factor is associated with glioma recurrence and is found in lower levels in people with diabetes than those who don't have the disease."
As researchers further investigate the mechanism behind this unusual link, they can potentially develop more targeted and effective therapies to squelch the growth of brain tumors.
Additional source: Ohio State University