The association of overweight and obesity with type 2 diabetes is one of the strongest in the scientific literature. Well known to many is that the drug, metformin, is a front-line treatment for type 2 diabetes. But now come researchers with something unexpected: high levels of metformin in the Great Lakes is affecting the fish population and may be changing the expression of genes in some fish. According to a report in MedScape Today, researchers at the School of Freshwater Sciences at the University of Wiscon-Milwaukee found such high levels of metformin in the waters of Lake Michigan. There are some 180 million prescriptions written for diabetes drugs in 2013, a $213 billion market. Metformin has about 70 million prescriptions written in 2013.
The level of metformin, measured in fathead minnows in the lab, were enough to disrupt gene expression in the endocrine system of male fish but not females. The males were producing biochemical that are associated with female minnows. It has been assumed that the volume of water in the Great Lakes would dilute such a drug. The new study casts doubt on that assumption.