Unexpected link between glioma and blood sugar levels helps understand brain cancer

Glioma is one of the most common cancers that arise in the brain and is usually diagnosed in middle age. It accounts for nearly a quarter of all primary brain tumors and three quarters of all malignant tumors

Having high blood sugar or diabetes is linked to a higher risk of developing most cancers. However, studies have found that brain cancers such as glioma are less common in people with diabetes and high blood sugar. Now, a new study begins to shed light on this surprising link. Could it be, the researchers ask, that brain tumors have a strong effect on blood glucose levels?

The findings of this new study were reported in the journal Scientific Reports by researchers which included members from Ohio State University (OSU) at Columbus, Ohio.

Diabetes and elevated blood sugar increase the risk of cancer at several sites including the colon, breast, and bladder.” said co-lead author Judith Schwartzbaum, associate professor of epidemiology at OSU.

This isn’t the case with brain cancer such as glioma. Instead, “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.”

The new study has built upon previous work by Prof. Schwartzbaum which found a link between high blood sugar and reduced risk of meningioma – a non-malignant brain tumour.

Glioma is one of the most common cancers that arise in the brain. It accounts for nearly a quarter of all primary brain tumors and three quarters of all malignant tumors.

Indicators of pre-symptomatic glioma much needed

Glioma begins in the glia cells in the brain. Glia cells are more abundant and very different from neurons or nerve cells.

Glia cells do not send the electrical signals that we normally associate with brain function as neurons do; instead, they protect, maintain, and support neurons.

Glioma is typically diagnosed in middle age. The researchers explain that there are currently no treatments capable of ensuring long-term survival, although some options are currently being researched.

The average survival for patients diagnosed with glioblastoma – the most common adult form of glioma – is only 14 months.

Also, as symptoms typically occur only 3 months prior to diagnosis, the authors note that “it is therefore important that indicators of the preclinical tumour be identified before the onset of symptoms.”

The new study examines data from two large long-term investigations: AMORIS and Me-Can, which together totalled 797,945 participants among whom 812 developed gliomas.

The team analysed the data on blood sugar levels and diabetes – including that related to the period preceding diagnosis – and how this related to subsequent diagnosis of glioma.

‘Could the glioma itself affect blood glucose levels?’

The results showed that participants with high blood sugar and diabetes were less likely to develop glioma. Also, the link was strongest in the year leading up to the diagnosis.

Prof. Schwartzbaum says that this result got the team wondering: “Why is the association between blood glucose levels and brain cancer the opposite of that for several other cancerous tumors?”

In their paper, they discuss a number of factors that might shed some light on this question.

For example, could the tumour itself affect blood sugar levels? It is known, for instance, that insulin-like growth factor is related to recurrence of glioma, and people with diabetes have less of it than people without diabetes.

Another explanation might arise from looking at how the brain uses glucose. Although it accounts for a mere 2 percent of body mass, the human brain consumes around 20 percent of available glucose, says Prof. Schwartzbaum.

It is up to further studies to investigate these questions and see if there is anything in the relationship between blood and brain tumors that can be used to develop new treatments for brain cancer.

“Our research raises questions that, when answered, will lead to a better understanding of the mechanisms involved in glioma development.” said Prof. Judith Schwartzbaum

Source: Medical News Today