Depleting inositol pyrophosphate 5-InsP₇ protected the heart against ischaemia-reperfusion injury by elevating plasma adiponectin

Aims Adiponectin is an adipocyte-derived circulating protein that exerts cardiovascular and metabolic protection. Due to the futile degradation of endogenous adiponectin and the challenges of exogenous administration, regulatory mechanisms of adiponectin biosynthesis are of significant pharmacological interest. Methods and results Here, we report that 5-diphosphoinositol 1,2,3,4,6-pentakisphosphate (5-InsP(7) ) generated by inositol hexakisphosphate kinase 1 (IP6K1) governed circulating adiponectin levels via thiol-mediated protein quality control in the secretory pathway. IP6K1 bound to adiponectin and DsbA-L and generated 5-InsP(7) to stabilize adiponectin/ERp44 and DsbA-L/Ero1-L alpha interactions, driving adiponectin intracellular degradation. Depleting 5-InsP(7) by either IP6K1 deletion or pharmacological inhibition blocked intracellular adiponectin degradation. Whole-body and adipocyte-specific deletion of IP6K1 boosted plasma adiponectin levels, especially its high molecular weight forms, and activated AMPK-mediated protection against myocardial ischaemia-reperfusion injury. Pharmacological inhibition of 5-InsP(7) biosynthesis in wild-type but not adiponectin knockout mice attenuated myocardial ischaemia-reperfusion injury. Conclusion Our findings revealed that 5-InsP(7) is a physiological regulator of adiponectin biosynthesis that is amenable to pharmacological intervention for cardioprotection. [GRAPHICS] .