Type 2 Diabetes

Over 300 million people worldwide have type 2 diabetes. Exercising more, losing weight and taking certain medicines can slow the progression of the disease and sometimes even reverse it, but many people need more effective treatments.

In 2009 research that was based on a genetic analysis of patients in Sweden and Finland revealed that mutations in gene SLC30A8 reduce the risk of type 2 diabetes. The study looked at people who were at very high risk for diabetes, because of factors such as advanced age or obesity, but never developed the disease. They looked at a set of genes that were known to play a role in type 2 diabetes and searched for rare mutations within them, identifying one that appeared to abolish the function of the SLC30A8 gene. Then in 2012 the unpublished results of this study were shared with the company, deCODE Genetics, who uncovered a second mutation among Icelandic people that accomplished the same thing.

A current study led by researchers at the Broad Institute and Massachusetts General Hospital have looked at the genetic analysis of 150,000 patients and again identified mutations in gene SLC30A8 that decrease the chances of developing type 2 diabetes even in people at high risk for the disease.
Unlike the other studies, this research was conducted among varied ethnic groups, suggesting that if a drug was developed that mimicked the effect of the mutation it could be used widely throughout the world. In the end 10 more mutations in the same gene in addition to the two from the previous studies were found to have a protective effect. When all of the results were combined it was shown that having one copy of a defective version of SLC30A8 provided a 65% reduction in the risk of becoming a type 2 diabetic.

David Altshuler co-senior study author said, "This work underscores that human genetics is not just a tool for understanding biology: it can also powerfully inform drug discovery by addressing one of the most challenging and important questions - knowing which targets to go after."

Despite huge investments of time and effort new drugs are being developed at a slow pace. "Almost everything we put into patients fails," said Altshuler, a professor of genetics and medicine at Harvard Medical School. "There's something wrong with what we are doing." He believes that "broken genes", such as SLC30A8, those that offer protection from disease by shutting off, offer great promise. Creating a drug to stop a gene from working is much easier than making one to turn one on or change how it functions.

At a recent Broad Institute lecture, Altshuler said that we used to find successful drugs by investigating "experiments of nature". These are disease outcomes that differ in different people and can be linked to a specific physiological trait. For example, Altshuler said, the use of cortisol to treat rheumatoid arthritis came from observations that the condition would improve in patients with Cushings' syndrome, marked by too much cortisol, and get worse in those with Addison's disease, marked by too little. He believes that by using genetics, as was done in the diabetes studies, we can see the same sort of natural experiments which will lead to more effective drug development.