Restriction of essential amino acids dictates the systemic response to dietary protein dilution

Dietary protein dilution (DPD) promotes metabolic remodelling and health but the precise nutritional components driving this response remain elusive. Here we demonstrate that dietary amino acids (AA) are sufficient and necessary to drive the response to DPD. In particular, the restriction of dietary essential AA (EAA) supply, but not non-EAA, drives the systemic metabolic response to total AA deprivation. Furthermore, systemic deprivation of Thr and Trp, independent of total AA supply, are both adequate and necessary to confer the systemic metabolic response to both diet, and genetic AA-transport loss, driven AA restriction. Thr is also potentially limiting in low-protein diet fed humans, and dietary Thr restriction (DTR) retarded the development of obesity-associated metabolic dysfunction in mice. Liver-derived fibroblast growth factor 21 was required for the metabolic remodelling with DTR. Strikingly, hepatocyte-selective establishment of Thr biosynthetic capacity reversed the systemic response to DTR. Taken together, our studies demonstrate that the restriction of EAA are sufficient and necessary to confer the systemic metabolic effects of DPD.