Scientists have figured out how a light-sensitive protein called opsin 3 regulates food consumption in mice. The findings raise new questions about the mechanisms involved in regulating human metabolism.

The study, co-led by Brown researchers and published in PNAS, uncovers a mechanism by which opsin 3 controls food intake via a receptor, MC4R, that is critical to the regulation of energy balance and feeding behavior.

“This finding is interesting because loss-of-function mutations in MC4R are a known genetic cause of obesity in humans,” says senior author Elena Oancea, PhD, a professor of medical science. “We’re very excited to have, for the first time, a cellular mechanism of what [opsin 3]is doing in the brain.”

The research team reported that opsin 3 functions together with MC4R and a potassium channel to regulate certain cell signals as well as neuronal firing in a key area that controls energy balance. Notably, mice that were engineered to lack opsin 3 ate significantly less and were less active than control mice.

While their findings add an important insight into the function of opsin 3, the researchers say more study is necessary to address whether the mechanism performs similarly in the human brain. The regulation of eating behavior and body weight is extremely complex, Oancea adds.

“Figuring out how to address these complex issues requires a broader understanding of the cellular processes involved,” she says.