King's College London

Aims:SIRT1 and AMP-activated protein kinase (AMPK) share common activators, actions and target molecules. Previous studies have suggested that a putative SIRT1-AMPK regulatory network could act as the prime initial sensor for calorie restriction-induced adaptations in skeletal muscle—the major site of insulin-stimulated glucose disposal. Our study aimed to investigate whether a feedback loop exists between AMPK and SIRT1 in skeletal muscle and how this may be involved glucose tolerance.

Main methods:To investigate this, we used skeletal muscle-specific AMPKα1/2 knockout mice (AMPKα1/2−/−) fed ad libitum (AL) or a 30% calorie restricted (CR) diet and L6 rat myoblasts incubated with SIRT1 inhibitor (EX527).Key findingsCR-AMPKα1/2−/− displayed impaired glucose tolerance (*p < 0.05), in association with down-regulated SIRT1 and PGC-1α expression (< 300% vs. CR-WT, ±±p < 0.01). Moreover, AMPK activity was decreased following SIRT1 inhibition in L6 cells (~ 0.5-fold vs. control, *p < 0.05).
Significance:This study demonstrates that skeletal muscle-specific AMPK deficiency impairs the beneficial effects of CR on glucose tolerance and that these effects may be dependent on reduced SIRT1 levels.