The Na/K-ATPase alpha 1/Src interaction regulates metabolic reserve and Western diet intolerance

Aim: Highly prevalent diseases such as insulin resistance and heart failure are characterized by reduced metabolic flexibility and reserve. We tested whether Na/K-ATPase (NKA)-mediated regulation of Src kinase, which requires two NKA sequences specific to the alpha 1 isoform, is a regulator of metabolic capacity that can be targeted pharmacologically. Methods: Metabolic capacity was challenged functionally by Seahorse metabolic flux analyses and glucose deprivation in LLC-PK1-derived cells expressing Src binding rat NKA alpha 1, non-Src-binding rat NKA alpha 2 (the most abundant NKA isoform in the skeletal muscle), and Src binding gain-of-function mutant rat NKA alpha 2. Mice with skeletal muscle-specific ablation of NKA alpha 1 (sk alpha 1(-/-)) were generated using a MyoD:Cre-Lox approach and were subjected to treadmill testing and Western diet. C57/Bl6 mice were subjected to Western diet with or without pharmacological inhibition of NKA alpha 1/Src modulation by treatment with pNaKtide, a cell-permeable peptide designed by mapping one of the sites of NKA alpha 1/Src interaction. Results: Metabolic studies in mutant cell lines revealed that the Src binding regions of NKA alpha 1 are required to maintain metabolic reserve and flexibility. Sk alpha 1(-/-) mice had decreased exercise endurance and mitochondrial Complex I dysfunction. However, sk alpha 1(-/-) mice were resistant to Western diet-induced insulin resistance and glucose intolerance, a protection phenocopied by pharmacological inhibition of NKA alpha 1-mediated Src regulation with pNaKtide. Conclusions: These results suggest that NKA alpha 1/Src regulatory function may be targeted in metabolic diseases. Because Src regulatory capability by NKA alpha 1 is exclusive to endotherms, it may link the aerobic scope hypothesis of endothermy evolution to metabolic dysfunction.