A mitochondrial peptide kept mice lean on junk food

Researchers at the University of Southern California identified a peptide called MOTS-c, encoded in a stretch of mitochondrial DNA long assumed to do nothing else, and tested whether injecting it could change how mice responded to a high-fat diet.

In the peer-reviewed study, mice fed a diet in which 60 percent of calories came from fat were given daily MOTS-c injections while on the diet. Treated mice gained markedly less weight than untreated mice on the same diet, without eating less food, and avoided the high blood insulin levels the untreated mice developed.

Eating the same food while weighing less meant the treated mice were spending more energy, including as body heat, without moving around more, which is what led the researchers to describe MOTS-c as a hormone-like signal rather than a housekeeping molecule. The effect was shown only in mice given daily injections, and no human trial has tested whether a MOTS-c injection changes weight or insulin sensitivity in people.

A mitochondrial afterthought turned out to talk.