Saxagliptin but Not Sitagliptin Inhibits CaMKII and PKC via DPP9 Inhibition in Cardiomyocytes

Abstract

Some oral anti-hyperglycemic drugs, including gliptins that inhibit dipeptidyl peptidase 4 (DPP4), have been linked to the increased risk of heart failure (HF) in type-2 diabetic patients. While the cardiovascular safety trial, TECOS, revealed no link between sitagliptin and the risk of HF, a substantial 27% increase in the hospitalization for HF was observed in type-2 diabetic patients treated with saxagliptin within the SAVOR-TIMI 53 trial. A previous in vitro study revealed that saxagliptin impairs the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-phospholamban (PLB)-sarcoplasmic reticulum Ca2+-ATPase 2a axis and protein kinase C (PKC) activity in cardiomyocytes leading to impaired cardiac contractility and electrophysiological function. However, the link between saxagliptin and its target proteins (CaMKII and PKC) remains to be explored. Since DPP8 and DPP9 (but not DPP4) are expressed by cardiomyocytes and saxagliptin is internalized by cardiomyocytes, we investigated whether DPP8/9 contribute to saxagliptin-mediated inhibition of CaMKII and PKC activity. Structural analysis revealed that the DPP4-saxagliptin interaction motif (S630, Y547) for the cyanopyrrolidine group is conserved in DPP8 (S755, Y669) and DPP9 (S730, Y644). Conversely, F357 that facilitates binding of the anchor lock domain of sitagliptin in the S2 extensive subsite of DPP4 is not conserved in DPP8/9. In parallel, unlike saxagliptin, sitagliptin did not affect phosphorylation of CaMKII/PLB or activity of PKC in HL-1 cardiomyocytes. These findings were recapitulated by pharmacological inhibition (TC-E-5007, a DPP8/9 antagonist) and knock-down of DPP9 (but not DPP8). In primary mouse ventricular cardiomyocytes, saxagliptin (but not sitagliptin) impaired Ca2+ transient relaxation and prolonged action potential duration (APD). These results suggest that saxagliptin-DPP9 interaction impairs the CaMKII-PLB and PKC signaling in cardiomyocytes. We reveal a novel and potential role of DPP9 in cardiac signaling. The interaction of saxagliptin with DPP9 may represent an underlying mechanism for the link between saxagliptin and HF. Elucidation of saxagliptin-DPP9 interaction and downstream events may foster a better understanding of the role of gliptins as modulators of cardiac signaling.

Physiology and Pharmacology of DPP-4 in Glucose Homeostasis and the Treatment of Type 2 Diabetes

“…However, it cannot be excluded that it could also be associated with some property of the saxagliptin molecule, unrelated to its action as a DPP-4 inhibitor. Accordingly, in vitro and ex vivo studies have shown that exposure to saxagliptin (135, 136) but not sitagliptin (136), results in altered cardiac electrophysiology and is associated with impaired cardiomyocyte contractility. The mechanism has been suggested to involve inhibition of cardiac intracellular signaling pathways (Ca 2+ /calmodulin-dependent protein kinase II and protein kinase C) due to saxagliptin-mediated inhibition DPP-9 (136).…”

“…Accordingly, in vitro and ex vivo studies have shown that exposure to saxagliptin (135, 136) but not sitagliptin (136), results in altered cardiac electrophysiology and is associated with impaired cardiomyocyte contractility. The mechanism has been suggested to involve inhibition of cardiac intracellular signaling pathways (Ca 2+ /calmodulin-dependent protein kinase II and protein kinase C) due to saxagliptin-mediated inhibition DPP-9 (136). DPP-9 belongs to the same family as DPP-4, and it is known that saxagliptin is a less selective inhibitor, whereas sitagliptin is highly selective for DPP-4 (35) and does not alter DPP-9 activity (136).…”

“…The mechanism has been suggested to involve inhibition of cardiac intracellular signaling pathways (Ca 2+ /calmodulin-dependent protein kinase II and protein kinase C) due to saxagliptin-mediated inhibition DPP-9 (136). DPP-9 belongs to the same family as DPP-4, and it is known that saxagliptin is a less selective inhibitor, whereas sitagliptin is highly selective for DPP-4 (35) and does not alter DPP-9 activity (136). Nevertheless, although off-target inhibition of DPP-9 could be one potential explanation for the association between saxagliptin and heart failure in an experimental setting, it is uncertain whether mean exposure levels of saxagliptin reach a high enough level to affect DPP-9 activity when used at its therapeutic dose in humans.…”

Linagliptin prevents left ventricular stiffening by reducing titin cleavage and hypophosphorylation

“…While DPP‐4 was predominantly expressed by coronary capillaries and immune cells, some cardiomyocytes also express DPP‐4 within the cytosol (Figure A; black arrows), as published previously 35,36 . Furthermore, gliptins (saxagliptin and sitagliptin) are internalized by cardiomyocytes and localize to the cytosol 37,38 . As such, we first investigated whether linagliptin could directly affect cardiomyocyte F passive in vitro in human cardiomyocytes in the absence of cardiometabolic risk factors.…”

Repurposing Antidiabetic Drugs for Cardiovascular Disease

“…Moreover, the structural differences of the compounds within the class of DPP4i are relevant for the treatment effect. Saxagliptin, but not sitagliptin, was shown to affect CaMKII/PLB phosphorylation in cardiomyocytes through off-target inhibition of DPP9, which leads to prolonged action potential duration and may trigger arrhythmic events (Koyani et al, 2018). These results indicate that off-target activities of DPP4i on other DPPs may contribute to the different outcome of DPP4i in the clinical trials.…”