Triethylenetetramine (trientine): a caloric restriction mimetic with a new mode of action

Caloric restriction mimetics (CRMs) are nontoxic macroautophagy/autophagy enhancers that act through the stimulation of cytoplasmic protein deacetylation reactions. Thus far, three functional classes of CRMs have been described: inhibitors of acetyltransferases (such as spermidine), inhibitors of acetyl coenzyme (AcCoA) synthesis (such as hydroxycitrate) and activators of deacetylases/sirtuins (such as resveratrol). Triethylenetetramine (also called trientine, abbreviated TETA) is a synthetic polyamine with resemblance in its structure to spermidine, a natural polyamine reputed for its pro-autophagic, anti-obesity and anti-aging effects. TETA, which is approved for the treatment of Wilson disease, has no effects on the longevity of mice, yet does induce autophagy and reduces weight gain in mice fed a high-fat diet (HFD). Mechanistically, these effects of TETA involve an increased activity of the TETA-metabolizing enzyme, SAT1 (spermidine/spermine N1-acetyltransferase 1). SAT1 overactivation ultimately results in the depletion of intracellular AcCoA with a consequent de-acetylation of cytoplasmic proteins and induction of autophagy. Accordingly, TETA fails to induce autophagy or to control HFD-induced weight gain in SAT1-deficient mice. Altogether, these findings indicate that TETA induces autophagy through a novel mode of action, namely, by the activation of an AcCoA-depleting enzyme.