Leptin-induced suppression of cardiomyocyte contraction is amplified by ceramide

Abstract

Uncorrected obesity is often accompanied by ventricular contractile dysfunction, elevation of the lipotoxic mediator ceramide and the obesity gene product leptin. Both ceramide and leptin participate in the regulation of cardiac function and are speculated to play roles in obesity-related cardiac dysfunctions. The purpose of this study was to examine the effect of ceramide on leptin-elicited cardiac contractile response. Adult rat left ventricular myocytes were incubated for 24 h with low (5 nM) or high (50 nM) concentration of leptin in the absence or presence of the active ceramide analog C 2-dihydroceramide (25 μM). Contractile and intracellular Ca 2+ properties were evaluated using an IonOptix MyoCam ® system including peak shortening (PS), maximal velocity of shortening/relengthening (±d L/d t), time-to-PS (TPS), time-to-90% relengthening (TR 90), intracellular Ca 2+ rise (Δ[Ca 2+]) and intracellular Ca 2+ decay. While ceramide did not elicit any effect on cell mechanics and intracellular Ca 2+ transients, it sensitized leptin-induced effects on myocyte shortening and intracellular Ca 2+ transients. In the absence of ceramide, 5 nM leptin had no effect on cell mechanics while 50 nM depressed PS, ±d L/d t, Δ[Ca 2+] and prolonged TR 90. With ceramide co-incubation, 5 nM leptin depressed PS, ±d L/d t, Δ[Ca 2+] and prolonged TR 90 whereas 50 nM leptin-elicited effects on PS, ±d L/d t, Δ[Ca 2+] and TR 90 were significantly potentiated in addition to slowing intracellular Ca 2+ decay. In summary, our data demonstrated that ceramide sensitizes cardiac depressive effects of leptin and may contribute to hyperleptinemia-related cardiac contractile dysfunction.