Loss of Glo2 alters the glucose metabolism in zebrafish

Glyoxalase 2 is the second enzyme of the glyoxalase system, catalyzing the detoxification of methylglyoxal to D-lactate via SD-Lactoylglutathione. Recent studies have suggested Glo2 as a regulator of glycolysis, but the physiological functions of Glo2 in vivo and organ specific functions of the enzyme have not yet been evaluated. Therefore, a CRISPR/Cas9 knockout of glo2 in zebrafish was created and analyzed. Consistent with its function in methylglyoxal detoxification, SD-Lactoylglutathione, but not methylglyoxal accumulated in glo2-/- larvae, with no change in longevity. Adult glo2-/- livers developed an impaired insulin signaling, indicated by a reduced hepatic P70-S6-kinase activation and reduced hepatic hexose concentration. In contrast, glo2-/- skeletal muscle remained functionally intact, compensating for the dysfunctional liver through increased glucose uptake, thereby maintaining euglycemia and preventing damage of the retina and kidney. In conclusion, the data identified Glo2 to fulfill similar but unique functions compared to Glo1 and established Glo2 as a novel target in diabetes research, regulating hepatic insulin signaling. Overall design: A CRISPR based knockout of Glyoxalase 2 was created in zebrafish. The development of the fish was analyzed, as well as organ specific glucose metabolism in skeletal muscle and liver. Imaging studies of Retina, kidney, liver and skeletal muscle were conducted. RNA sequencing was performed on adult liver tissue of glo2+/+ and glo2-/- fish by BGI in collaboration with the NGS Core facility in Mannheim, University of Heidelberg.