PRKAB1 and hyperinsulinism: We report that DKI mutation of residues critical for AMPK-glycogen binding in both AMPK β subunit isoforms—AMPK β1 W100A and β2 W98A—leads to (1) increased body mass, associated with increased fat and lean mass; (2) hyperinsulinemia and glucose intolerance; (3) reduced fed liver glycogen levels and altered glycogen dynamics in skeletal muscle; and (4) reductions in AMPK protein content in the primary glycogen-storing tissues liver and skeletal muscle, as well as adipose tissue.