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Glucagon-like peptide-1 enhances cardiac L-type Ca2+ currents via activation of the cAMP-dependent protein kinase A pathway.

Xiao YF, Nikolskaya A, Jaye DA, Sigg DC - Cardiovasc Diabetol (2011)

Bottom Line: Interestingly, preclinical and clinical evidence suggests that GLP-1 agonists produce beneficial effects on dysfunctional hearts via acting on myocardial GLP-1 receptors.Our data demonstrate that GLP-1 enhances I(Ca) in canine cardiomyocytes.The enhancement of I(Ca) is likely via the cAMP-dependent protein kinase A mechanism and may contribute, at least partially, to the prolongation of the action potential duration.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cardiac Rhythm Disease Management, Medtronic, Inc., 8200 Coral Sea Street NE, Mounds View, MN 55112, USA. yong-fu.xiao@medtronic.com

ABSTRACT

Background: Glucagon-like peptide-1 (GLP-1) is a hormone predominately synthesized and secreted by intestinal L-cells. GLP-1 modulates multiple cellular functions and its receptor agonists are now used clinically for diabetic treatment. Interestingly, preclinical and clinical evidence suggests that GLP-1 agonists produce beneficial effects on dysfunctional hearts via acting on myocardial GLP-1 receptors. As the effects of GLP-1 on myocyte electrophysiology are largely unknown, this study was to assess if GLP-1 could affect the cardiac voltage-gated L-type Ca2+ current (I(Ca)).

Methods: The whole-cell patch clamp method was used to record I(Ca) and action potentials in enzymatically isolated cardiomyocytes from adult canine left ventricles.

Results: Extracellular perfusion of GLP-1 (7-36 amide) at 5 nM increased I(Ca) by 23 ± 8% (p < 0.05, n = 7). Simultaneous bath perfusion of 5 nM GLP-1 plus 100 nM Exendin (9-39), a GLP-1 receptor antagonist, was unable to block the GLP-1-induced increase in I(Ca); however, the increase in I(Ca) was abolished if Exendin (9-39) was pre-applied 5 min prior to GLP-1 administration. Intracellular dialysis with a protein kinase A inhibitor also blocked the GLP-1-enhanced I(Ca). In addition, GLP-1 at 5 nM prolonged the durations of the action potentials by 128 ± 36 ms (p < 0.01) and 199 ± 76 ms (p < 0.05) at 50% and 90% repolarization (n = 6), respectively.

Conclusions: Our data demonstrate that GLP-1 enhances I(Ca) in canine cardiomyocytes. The enhancement of I(Ca) is likely via the cAMP-dependent protein kinase A mechanism and may contribute, at least partially, to the prolongation of the action potential duration.

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Effects of the GLP-1R inhibitor Exendin (9-39) on the GLP-1-induced enhancement of L-type Ca2+ currents in isolated canine left ventricular myocytes. A, The time course of the extracellular perfusion of Exendin (9-39, 100 nM) plus GLP-1 (5 nM) is shown. The GLP-1-induced enhancement of Ca2+ currents was not blocked by Exendin (9-39), even after washout and reperfusion of these two compounds. The currents were evoked by the depolarizing pulses from a holding potential of -40 mV to 0 mV every 10 s. C, control; E&G, Exendin (9-39) + GLP-1; W, washout. B, Compared to control, the average increase in peak ICa was statistically significant in the presence of Exendin (9-39) plus GLP-1 (n = 6, p < 0.05). Panel C shows the time course of ICa for control, the extracellular perfusion of 100 nM Exendin (9-39) alone (Exendin (9-39)) and Exendin (9-39) plus 5 nM GLP-1 (GLP-1), and washout (W). The currents were evoked by the pulses depolarizing from holding potential of -40 mV to 0 mV every 10 s. D, The averaged data show that 100 nM Exendin (9-39) applied 5 min ahead of GLP-1 (5 nM) perfusion abolished the GLP-1-induced enhancement of ICa (n = 5, p > 0.05).
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Figure 2: Effects of the GLP-1R inhibitor Exendin (9-39) on the GLP-1-induced enhancement of L-type Ca2+ currents in isolated canine left ventricular myocytes. A, The time course of the extracellular perfusion of Exendin (9-39, 100 nM) plus GLP-1 (5 nM) is shown. The GLP-1-induced enhancement of Ca2+ currents was not blocked by Exendin (9-39), even after washout and reperfusion of these two compounds. The currents were evoked by the depolarizing pulses from a holding potential of -40 mV to 0 mV every 10 s. C, control; E&G, Exendin (9-39) + GLP-1; W, washout. B, Compared to control, the average increase in peak ICa was statistically significant in the presence of Exendin (9-39) plus GLP-1 (n = 6, p < 0.05). Panel C shows the time course of ICa for control, the extracellular perfusion of 100 nM Exendin (9-39) alone (Exendin (9-39)) and Exendin (9-39) plus 5 nM GLP-1 (GLP-1), and washout (W). The currents were evoked by the pulses depolarizing from holding potential of -40 mV to 0 mV every 10 s. D, The averaged data show that 100 nM Exendin (9-39) applied 5 min ahead of GLP-1 (5 nM) perfusion abolished the GLP-1-induced enhancement of ICa (n = 5, p > 0.05).

Mentions: To determine whether the GLP-1-induced enhancement of ICa was via the activation of membrane GLP-1Rs, the GLP-1R inhibitor Exendin (9-39) was added to the GLP-1 solution. The non-mammalian peptide, Exendin (9-39 amide), is a specific and competitive antagonist of GLP-1Rs. As Exendin (9-39) has lower binding affinity to GLP-1Rs, 100 nM Exendin (9-39), at a concentration of 20 times higher than that of GLP-1, plus 5 nM GLP-1, was perfused to the canine left ventricular myocytes. Interestingly, Exendin (9-39) at 100 nM was unable to block the GLP-1-induced enhancement of ICa (Fig. 2A and 2B). These results suggest that when GLP-1 and Exendin (9-39) were applied together at the same time, GLP-1 could activate GLP-1Rs due to its higher affinity for GLP-1 receptors. After the activation of GLP-1Rs, the enhancement of ICa by GLP-1 was not blocked by 100 nM Exendin (9-39) because the activation process was already beyond the receptor stage. To test this hypothesis, we administered 100 nM Exendin (9-39) 5 min prior to GLP-1. Figure 2C and 2D clearly shows that Exendin (9-39) alone did not significantly alter the currents, but the enhancement of ICa by 5 nM GLP-1 was abolished by pre-administration of 100 nM Exendin (9-39).


Glucagon-like peptide-1 enhances cardiac L-type Ca2+ currents via activation of the cAMP-dependent protein kinase A pathway.

Xiao YF, Nikolskaya A, Jaye DA, Sigg DC - Cardiovasc Diabetol (2011)

Effects of the GLP-1R inhibitor Exendin (9-39) on the GLP-1-induced enhancement of L-type Ca2+ currents in isolated canine left ventricular myocytes. A, The time course of the extracellular perfusion of Exendin (9-39, 100 nM) plus GLP-1 (5 nM) is shown. The GLP-1-induced enhancement of Ca2+ currents was not blocked by Exendin (9-39), even after washout and reperfusion of these two compounds. The currents were evoked by the depolarizing pulses from a holding potential of -40 mV to 0 mV every 10 s. C, control; E&G, Exendin (9-39) + GLP-1; W, washout. B, Compared to control, the average increase in peak ICa was statistically significant in the presence of Exendin (9-39) plus GLP-1 (n = 6, p < 0.05). Panel C shows the time course of ICa for control, the extracellular perfusion of 100 nM Exendin (9-39) alone (Exendin (9-39)) and Exendin (9-39) plus 5 nM GLP-1 (GLP-1), and washout (W). The currents were evoked by the pulses depolarizing from holding potential of -40 mV to 0 mV every 10 s. D, The averaged data show that 100 nM Exendin (9-39) applied 5 min ahead of GLP-1 (5 nM) perfusion abolished the GLP-1-induced enhancement of ICa (n = 5, p > 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 2: Effects of the GLP-1R inhibitor Exendin (9-39) on the GLP-1-induced enhancement of L-type Ca2+ currents in isolated canine left ventricular myocytes. A, The time course of the extracellular perfusion of Exendin (9-39, 100 nM) plus GLP-1 (5 nM) is shown. The GLP-1-induced enhancement of Ca2+ currents was not blocked by Exendin (9-39), even after washout and reperfusion of these two compounds. The currents were evoked by the depolarizing pulses from a holding potential of -40 mV to 0 mV every 10 s. C, control; E&G, Exendin (9-39) + GLP-1; W, washout. B, Compared to control, the average increase in peak ICa was statistically significant in the presence of Exendin (9-39) plus GLP-1 (n = 6, p < 0.05). Panel C shows the time course of ICa for control, the extracellular perfusion of 100 nM Exendin (9-39) alone (Exendin (9-39)) and Exendin (9-39) plus 5 nM GLP-1 (GLP-1), and washout (W). The currents were evoked by the pulses depolarizing from holding potential of -40 mV to 0 mV every 10 s. D, The averaged data show that 100 nM Exendin (9-39) applied 5 min ahead of GLP-1 (5 nM) perfusion abolished the GLP-1-induced enhancement of ICa (n = 5, p > 0.05).
Mentions: To determine whether the GLP-1-induced enhancement of ICa was via the activation of membrane GLP-1Rs, the GLP-1R inhibitor Exendin (9-39) was added to the GLP-1 solution. The non-mammalian peptide, Exendin (9-39 amide), is a specific and competitive antagonist of GLP-1Rs. As Exendin (9-39) has lower binding affinity to GLP-1Rs, 100 nM Exendin (9-39), at a concentration of 20 times higher than that of GLP-1, plus 5 nM GLP-1, was perfused to the canine left ventricular myocytes. Interestingly, Exendin (9-39) at 100 nM was unable to block the GLP-1-induced enhancement of ICa (Fig. 2A and 2B). These results suggest that when GLP-1 and Exendin (9-39) were applied together at the same time, GLP-1 could activate GLP-1Rs due to its higher affinity for GLP-1 receptors. After the activation of GLP-1Rs, the enhancement of ICa by GLP-1 was not blocked by 100 nM Exendin (9-39) because the activation process was already beyond the receptor stage. To test this hypothesis, we administered 100 nM Exendin (9-39) 5 min prior to GLP-1. Figure 2C and 2D clearly shows that Exendin (9-39) alone did not significantly alter the currents, but the enhancement of ICa by 5 nM GLP-1 was abolished by pre-administration of 100 nM Exendin (9-39).

Bottom Line: Interestingly, preclinical and clinical evidence suggests that GLP-1 agonists produce beneficial effects on dysfunctional hearts via acting on myocardial GLP-1 receptors.Our data demonstrate that GLP-1 enhances I(Ca) in canine cardiomyocytes.The enhancement of I(Ca) is likely via the cAMP-dependent protein kinase A mechanism and may contribute, at least partially, to the prolongation of the action potential duration.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cardiac Rhythm Disease Management, Medtronic, Inc., 8200 Coral Sea Street NE, Mounds View, MN 55112, USA. yong-fu.xiao@medtronic.com

ABSTRACT

Background: Glucagon-like peptide-1 (GLP-1) is a hormone predominately synthesized and secreted by intestinal L-cells. GLP-1 modulates multiple cellular functions and its receptor agonists are now used clinically for diabetic treatment. Interestingly, preclinical and clinical evidence suggests that GLP-1 agonists produce beneficial effects on dysfunctional hearts via acting on myocardial GLP-1 receptors. As the effects of GLP-1 on myocyte electrophysiology are largely unknown, this study was to assess if GLP-1 could affect the cardiac voltage-gated L-type Ca2+ current (I(Ca)).

Methods: The whole-cell patch clamp method was used to record I(Ca) and action potentials in enzymatically isolated cardiomyocytes from adult canine left ventricles.

Results: Extracellular perfusion of GLP-1 (7-36 amide) at 5 nM increased I(Ca) by 23 ± 8% (p < 0.05, n = 7). Simultaneous bath perfusion of 5 nM GLP-1 plus 100 nM Exendin (9-39), a GLP-1 receptor antagonist, was unable to block the GLP-1-induced increase in I(Ca); however, the increase in I(Ca) was abolished if Exendin (9-39) was pre-applied 5 min prior to GLP-1 administration. Intracellular dialysis with a protein kinase A inhibitor also blocked the GLP-1-enhanced I(Ca). In addition, GLP-1 at 5 nM prolonged the durations of the action potentials by 128 ± 36 ms (p < 0.01) and 199 ± 76 ms (p < 0.05) at 50% and 90% repolarization (n = 6), respectively.

Conclusions: Our data demonstrate that GLP-1 enhances I(Ca) in canine cardiomyocytes. The enhancement of I(Ca) is likely via the cAMP-dependent protein kinase A mechanism and may contribute, at least partially, to the prolongation of the action potential duration.

Show MeSH
Related in: MedlinePlus