Obesity and type 2 diabetes are known to raise the risk of pancreatic cancer, but until recently it has not been clear what the source of the connection is.

It now appears that there is a direct link between high levels of insulin in the blood and the risk of pancreatic cancer, particularly among patients with obesity and type 2 diabetes, according to the findings of a new Canadian study done on mice.

Pancreatic cancer rates have risen along with increases in type 2 diabetes and obesity, said study author, James Johnson, a professor of cellular and physiological sciences at the University of British Columbia. Johnson explained in a statement that, “These findings help us understand how this is happening, and highlight the importance of keeping insulin levels within a normal range, which can be accomplished with diet, exercise and, in some cases, medications.”

“Hyperinsulinemia doesn't cause cancer, it just creates an environment that makes it more likely.”

Insulin is one of the most studied hormones in science and clinical practice, Janel Kopp, co-senior author of the study, told TheDoctor. Hopefully, she added, this work will change clinical practice and promote lifestyle interventions that can lower pancreatic cancer risk in the general population. It might also pave the way for therapies that target insulin receptors in the pancreas to slow the development of, or prevent, cancer.

The research team found that high levels of insulin, or hyperinsulinemia, in obese mice overstimulated acinar cells in the pancreas. These cells produce trypsinogen, the inactive form of the digestive enzyme trypsin. The overstimulation of acinar cells caused the production of excess trypsinogen, increasing the risk of damage to the acinar cells. The inflammation caused by this damage converted acinar cells into precancerous cells.

The researchers were surprised at the number of precancerous lesions formed in the mouse model, said Kopp, an assistant professor of cellular and physiological sciences at the University of British Columbia. “Hyperinsulinemia doesn't cause cancer, it just creates an environment that makes it more likely,” she noted.

Kopp and her team currently have funding from the Lustgarten Foundation to determine the role of insulin in patients who have already been diagnosed with pancreatic cancer. High insulin levels or uncontrolled diabetes may affect how their tumors grow.

The clinical effects of diabetes are chronic and long term, Kopp explained. However, these effects are not usually considered in those with pancreatic cancer, because patients typically don't live longer than five years, and most are diagnosed when they already have metastatic disease. Controlling blood sugar and insulin levels may eventually be found to improve the quality of life in those with pancreatic cancer.

The study is published in the journal Cell Metabolism.