Metformin activates the enzyme AMPK (AMP-activated protein kinase), which promotes muscles to take up glucose from the blood. It was recently discovered that the upstream regulator of AMPK is a protein kinase called LKB1, known to be a tumor suppressor.
Therefore, researchers in Scotland suggest that metformin use in patients with type 2 diabetes may reduce their risk of cancer.
Using various databases to conduct this case-control, observational study, medical records of more than 300,000 patients were analyzed. Approximately 12,000 of these patients were newly diagnosed with type 2 diabetes between 1993 and 2001, including 923 who were later diagnosed with cancer.
Information about metformin use for all cases and controls was calculated, with odds ratios adjusted for factors such as body mass index, blood pressure and smoking. During the year prior to diagnosis of cancer, 36.4 percent of cases and 39.7 percent of controls had been prescribed metformin. A dose-response relationship between metformin use and cancer was observed, indicating a decreased risk of cancer with longer duration of metformin treatment and total dosage.
The researchers note limitations to the findings of this pilot study and state they are planning a large cohort study to further explore the relationship of metformin use in diabetics and the possible decreased risk of cancer. The new study will focus on specific types of cancer and use more precise dates of cancer diagnosis.
—British Medical Journal, April 22, 2005