Role of Deranged Energy Deprivation Signaling in the Pathogenesis of Cardiac and Renal Disease in States of Perceived Nutrient Overabundance.

Sodium-glucose cotransporter 2 inhibitors reduce the risk of serious heart failure and adverse renal events, but the mechanisms that underlie this benefit are not understood. Treatment with SGLT2 inhibitors is distinguished by two intriguing features - ketogenesis and erythrocytosis. Both reflect the induction of a fasting-like and hypoxia-like transcriptional paradigm that is capable of restoring and maintaining cellular homeostasis and survival. In the face of perceived nutrient and oxygen deprivation, cells activate low-energy sensors, which include sirtuin-1 (SIRT1), adenosine monophosphate-activated protein kinase (AMPK) and hypoxia inducible factors (especially HIF-2α); these enzymes and transcription factors are master regulators of hundreds of genes and proteins that maintain cellular homeostasis. The activation of SIRT1 (through its effects to promote gluconeo-genesis and fatty acid oxidation) drives ketogenesis, and working in concert with AMPK, it can directly inhibit inflammasome activation and maintain mitochondrial capacity and stability. Hypoxia inducible factors act to promote oxygen delivery (by stimulating erythropoietin and erythrocytosis) and decrease oxygen consumption. Most importantly, the activation of SIRT1, AMPK and HIF-2α enhances autophagy, a lysosome-dependent degradative pathway that removes dangerous constituents, particularly damaged mitochondria and peroxisomes, which are major sources of oxidative stress and triggers of cellular dysfunction and death. SIRT1 and AMPK also act on sodium transport mechanisms to reduce intracellular sodium concentrations. Interestingly, type 2 diabetes, obesity, chronic heart failure and chronic kidney failure are characterized by the accumulation of intracellular glucose and lipid intermediates that are perceived by cells as indicators of energy overabundance. The cells respond by down-regulating SIRT1, AMPK and HIF-2α, thus leading to an impairment of autophagic flux and acceleration of cardiomyopathy and nephropathy. SGLT2 inhibitors reverse this maladaptive signaling by triggering a state of fasting and hypoxia mimicry, which includes activation of SIRT1, AMPK and HIF-2α, enhanced autophagic flux, reduced cellular stress, decreased sodium influx into cells, and restoration of mitochondrial homeostasis. This mechanistic framework clarifies the findings of large-scale randomized trials and the close association of ketogenesis and erythrocytosis with the cardioprotective and renoprotective benefits of these drugs.