One of the central pursuits of modern human genetics is to move beyond genomic correlation. That is, to demonstrate experimentally why a specific genetic variant may be associated with a disease. New work in Nature Genetics from an international team lead by Philippe Froguel at Imperial College in London does just this – demonstrating an interesting link between saliva and obesity. Basically, all humans express amylase, a salivary enzyme that breaks down complex carbohydrates into absorbable sugars. The researchers found that people with more copies of the gene had a significantly decreased risk of developing obesity. People with fewer copies expressed less amylase, and it was hypothesized that this alteration in gastrointestinal carbohydrate metabolism affected insulin signaling, blood sugar levels, as well as the microbial community in the gut. This finding has implications for the rational design of digestive enzyme-based therapies for obesity and other metabolic disorders.

Froguel, Philippe, et al. “Low copy number of the salivary amylase gene predisposes to obesity.” Nature Genetics vol. 46, p. 492-497 (2014).