Muscling In on Depression

Physical activity counters anxiety and stress; a recent study in mice uncovers a molecular pathway that underlies this phenomenon. The mental health benefits of physical exercise are well established, and yet the way in which exercise influences the brain to alter mood is not clearly understood. A recent study by Agudelo and colleagues 1 suggests that kynurenine metabolism in skeletal muscle mediates resilience to stress-induced behavior associated with psychiatric illnesses such as major depression. The kynurenine pathway is the principal pathway by which the amino acid tryptophan is metabolized in peripheral body tissues, including skeletal muscle, liver, and white cells, leading to the production of brain-penetrating kynurenine. Kynurenine, in turn, may be converted into metabolites, some of which have been . . .