Real-Time In-Organism NMR Metabolomics Reveals Different Roles of AMP-Activated Protein Kinase Catalytic Subunits.

AMP-activated protein kinase (AMPK in human and AAK in C. elegans) is a master regulator of metabolism. It has many isotypes, but its isotype-dependent functions are largely unknown. By developing real-time in-organism NMR metabolomics for C. elegans, we were able to study different roles of the isotypic catalytic subunits of AAK/AMPK, AAK-1, and AAK-2 in live worms at the whole organism level. The aak-1 knockout animals exhibited enhanced glucose production under starvation, strikingly opposite to aak-2 knockout animals. Unusually high compensatory expression of the reciprocal isotypes in each KO strain and the results for the double KO animals suggested an unconventional phenotype-genotype relationship and the dominance of aak-2 in glucose production. The gene expression patterns showed that the differential phenotypes of aak-1 KO strain are due to reduced TCA and glycolysis and enhanced gluconeogenesis compared to the aak-2 KO strain. Subsequent 13C-isotope incorporation experiment showed that the glucose production in aak-1 KO occurs through the activation of fatty acid oxidation and glyoxylate shunt. Revealing differential roles of the isotypes of AAK/AMPK, our convenient approach is readily applicable to many C. elegans models for human metabolic diseases.