The drug metformin is given to patients who have type 2 diabetes, but until recently, no one knew exactly how it worked. What they did know was that it doesn’t affect blood sugar directly, instead helping insulin in the body to work properly. That is, metformin does nothing to directly lower blood glucose. Rather, it interacts with insulin in a way that means the insulin gets used properly, and the insulin, restored to full function as long as the drug is effective, lowers glucose levels, as it is supposed to do. Now researchers have discovered the mechanism by which metformin performs this feat. The drug works in the liver, where it suppresses fatty tissue.
Nonalcoholic fatty liver disease—which occurs, as the name suggests, when fat deposits collect in the liver other than as a result of alcohol consumption—is generally caused by obesity, and has been implicated in the development of type 2 diabetes. The damaged liver is less efficient at using insulin to regulate blood sugar levels. Metformin attacks these fatty deposits, eroding them and letting the liver better do its job.
In the wake of this discovery, researchers are taking a closer look at what other tricks metformin might be able to perform. In one study, metformin had a beneficial effect on the weights of obese children who ate healthy diets and followed an exercise plan. While diet and exercise played a large role. the metformin helped enhance the effectiveness of these interventions. Metformin is given to children over age ten with type 2 diabetes, but is not officially used for non-diabetic children. The study confirmed what doctors prescribing metformin off-label had already recognized, that the drug helps children lose weight, though the study found the effect was small in the long term.
Another line of investigation did not pan out at all. A research team in the Netherlands gave metformin to heart attack survivors who were not diabetic. People who have the specific sort of myocardial infarction the test subjects had experienced often develop heart dysfunction. The researchers thought metformin might have properties that could prevent this dysfunction. Sadly, in the study, patients who were taking metformin fared no better than those who were not. However, metformin is still being studied to see what else it may be able to do.