Validation and Mechanistic Studies of Gluconeogenesis Regulators Identified from Zebrafish Chemical Genetic Screens

Phosphoenolypyruvate carboxykinase (PEPCK) is the rate limiting enzyme in hepatic gluconeogenesis, which produces glucose from pyruvate to maintain circulating glucose level according to the bodyâ s needs. Cytosolic PEPCK (pck1) is widely studied for its crucial role in hepatic gluconeogenesis. High levels of pck1 are associated with the development of type 2 diabetes; conversely, improved insulin sensitivity is observed in mice with decreased pck1 level. Ten potential lead compounds from previous screening of 727 FDA-approved compounds were examined using pck1 zebrafish reporter lines, Tg(pck1:luc2) and Tg(pck1:Venus). Compounds were tested in larval zebrafish and ranked based on their ability to regulate pck1 expression and glucose levels. Subsequently, a diabetic mouse model was used to further validate the potential anti-hyperglycemic effects of the selected compound (Esomeprazole, Eso). Eso treatment improved glucose homeostasis in diabetic mice as determined by pyruvate tolerance tests. Here we describe a possible mechanism of action of Eso, which involves regulation of hepatic gluconeogenesis through insulin-dependent down-regulation of pck1.