Patients with type 2 diabetes who take Metformin seem to be at lower risk of cancer than those not treated with Metformin.

Metformin, widely given to patients with type 2 diabetes, works by reducing the amount of glucose produced by the liver and increasing the uptake of glucose by the cells of the body.

Metformin acts through activating the enzyme AMPK ( AMP activated protein kinase ), which induces muscles to take up glucose from the blood.
A recent breakthrough has found the upstream regulator of AMPK to be a protein kinase known as LKB1.
LKB1 is a well recognised tumour suppressor.
Activation of AMPK by Metformin and exercise requires LKB1, and this would also explain why exercise is beneficial in the primary and secondary prevention of certain cancers.

Investigators at University of Dundee in Scotland have hypothesized that Metformin use in patients with type 2 diabetes may reduce their risk of cancer.

They analysed databases developed in Tayside, Scotland: a diabetes clinical information system ( DARTS ) and a database of dispensed prescriptions ( MEMO ).

From 314,127 people who were resident ( or died ) in Tayside in 1993-2001, 11,876 had been newly diagnosed with type 2 diabetes.
Of these, 923 were subsequently admitted to hospital for malignant cancer.

More than half ( 53 percent ) of the patients with cancer were men. Mean age was 73 years and mean duration of diabetes was 8.5 years.

More than a third ( 36.4% ) of the cases had been given at least one prescription for Metformin in the year before the diagnosis of cancer, compared with 39.7% of the controls.

The unadjusted odds ratio ( OR ) for any exposure to Metformin since 1993 was 0.79.

According to authors, taking Metformin may be associated with reduced risk of cancer in patients with type 2 diabetes.
Of particular interest is the suggestion of a dose-response relationship.

Source: British Medical Journal, 2005


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