CV Protection in the EMPA-REG OUTCOME Trial: A "Thrifty Substrate" Hypothesis.
The striking and unexpected relative risk reductions in cardiovascular (CV) mortality (38%), hospitalization for heart failure (35%), and death from any cause (32%) observed in the EMPA-REG OUTCOME trial using an inhibitor of sodium-glucose cotransporter 2 (SGLT2) in patients with type 2 diabetes and high CV risk have raised the possibility that mechanisms other than those observed in the trial-modest improvement in glycemic control, small decrease in body weight, and persistent reductions in blood pressure and uric acid level-may be at play. We hypothesize that under conditions of mild, persistent hyperketonemia, such as those that prevail during treatment with SGLT2 inhibitors, β-hydroxybutyrate is freely taken up by the heart (among other organs) and oxidized in preference to fatty acids. This fuel selection improves the transduction of oxygen consumption into work efficiency at the mitochondrial level. In addition, the hemoconcentration that typically follows SGLT2 inhibition enhances oxygen release to the tissues, thereby establishing a powerful synergy with the metabolic substrate shift. These mechanisms would cooperate with other SGLT2 inhibition-induced changes (chiefly, enhanced diuresis and reduced blood pressure) to achieve the degree of cardioprotection revealed in the EMPA-REG OUTCOME trial. This hypothesis opens up new lines of investigation into the pathogenesis and treatment of diabetic and nondiabetic heart disease.
CNR Institute of Clinical Physiology, Pisa, Italy ferranni@ifc.cnr.it.
Ele
E
Ferrannini
Cardiometabolic Disease Research, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach, Germany.
Michael
M
Mark
Cardiometabolic Disease Research, Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach, Germany.
Eric
E
Mayoux
D020155:3-Hydroxybutyric Acid / Q000378:metabolism / Q000502:physiology*; D001559:Benzhydryl Compounds / Q000627:therapeutic use*; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D002318:Cardiovascular Diseases / Q000517:prevention & control*; D002986:Clinical Trials as Topic / Q000379:methods; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D003925:Diabetic Angiopathies / Q000517:prevention & control; D005960:Glucosides / Q000627:therapeutic use*; D006321:Heart / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008954:Models, Biological; D012107:Research Design; D051297:Sodium-Glucose Transporter 2; D000077203:Sodium-Glucose Transporter 2 Inhibitors; D016896:Treatment Outcome
D001559:Benzhydryl Compounds; D001786:Blood Glucose; D005960:Glucosides; D007004:Hypoglycemic Agents; C089180:SLC5A2 protein, human; D051297:Sodium-Glucose Transporter 2; D000077203:Sodium-Glucose Transporter 2 Inhibitors; C570240:empagliflozin; D020155:3-Hydroxybutyric Acid