(A) PEP can be generated from glycolytic enolase or from mitochondrial oxaloacetate conversion via PCK2 and export to the cytosol. Addition of amino acids fuels the TCA cycle and activates the PEP cycle, and pyruvate kinase activator (PKa) also activates the PEP cycle.
(B) Representative recordings of cytosolic calcium elevation in response to an amino acid ramp at 2G and in the absence (left) or presence (right) of PKa in islets isolated from 3 Con and 3 CDK2-iKO mice. At 1×, physiological amino acids (PAA) is (in μM) 2,100 alanine, 600 glutamine, 700 glycine, 550 valine, 500 leucine, 350 serine, 200 arginine, 218 lysine, and 121 threonine.
(C) Quantification of (B) by AUC at 2× mixed amino acids, normalized to Con/vehicle. (Con/vehicle, n = 44; CDK2-iKO/vehicle, n = 48; Con/PKa, n = 38; CDK2-iKO/PKa, n = 44).
Data are shown as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001 by one-way ANOVA.