The comprehensive electrophysiological study of curcuminoids on delayed-rectifier K+ currents in insulin-secreting cells

Ping-Chung Kuo, Chia Jung Yang, Yu Chi Lee, Pei-chun Chen, Yen-Chin Liu, Sheng-Nan Wu

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Abstract

Curcumin (CUR) has been demonstrated to induce insulin release from pancreatic β-cells; however, how curcuminoids (including demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC)) exert any possible effects on membrane ion currents inherently in insulin-secreting cells remains largely unclear. The effects of CUR and other structurally similar curcuminoids on ion currents in rat insulin-secreting (INS-1) insulinoma cells were therefore investigated in this study. The effects of these compounds on ionic currents and membrane potential were studied by patch-clamp technique. CUR suppressed the amplitude of delayed-rectifier K+ current (IK(DR)) in a time-, state- and concentration-dependent manner in these cells and the inhibition was not reversed by diazoxide, nicorandil or chlorotoxin. The value of dissociation constant for CUR-induced suppression of IK(DR) in INS-1 cells was 1.26 μM. Despite the inability of CUR to alter the activation rate of IK(DR), it accelerated current inactivation elicited by membrane depolarization. Increasing CUR concentrations shifted the inactivation curve of IK(DR) to hyperpolarized potential and slowed the recovery of IK(DR) inactivation. CUR, DMC, and BDMC all exerted depressant actions on IK(DR) amplitude to a similar magnitude, although DMC and BDMC did not increase current inactivation clearly. CUR slightly suppressed the peak amplitude of voltage-gated Na+ current. CUR, DMC and BDMC depolarized the resting potential and increased firing frequency of action potentials. The CUR-mediated decrease of IK(DR) and the increase of current inactivation also occurred in βTC-6 INS-1 cells. Taken these results together, these effects may be one of the possible mechanisms contributing their insulin-releasing effect.

Original languageEnglish
Pages (from-to)233-241
Number of pages9
JournalEuropean Journal of Pharmacology
Volume819
DOIs
Publication statusPublished - 2018 Jan 15

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Curcumin
Insulin-Secreting Cells
Insulin
Membrane Potentials
Nicorandil
Ions
Diazoxide
Insulinoma
Membranes
Patch-Clamp Techniques
Action Potentials

All Science Journal Classification (ASJC) codes

  • Pharmacology

Cite this

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title = "The comprehensive electrophysiological study of curcuminoids on delayed-rectifier K+ currents in insulin-secreting cells",
abstract = "Curcumin (CUR) has been demonstrated to induce insulin release from pancreatic β-cells; however, how curcuminoids (including demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC)) exert any possible effects on membrane ion currents inherently in insulin-secreting cells remains largely unclear. The effects of CUR and other structurally similar curcuminoids on ion currents in rat insulin-secreting (INS-1) insulinoma cells were therefore investigated in this study. The effects of these compounds on ionic currents and membrane potential were studied by patch-clamp technique. CUR suppressed the amplitude of delayed-rectifier K+ current (IK(DR)) in a time-, state- and concentration-dependent manner in these cells and the inhibition was not reversed by diazoxide, nicorandil or chlorotoxin. The value of dissociation constant for CUR-induced suppression of IK(DR) in INS-1 cells was 1.26 μM. Despite the inability of CUR to alter the activation rate of IK(DR), it accelerated current inactivation elicited by membrane depolarization. Increasing CUR concentrations shifted the inactivation curve of IK(DR) to hyperpolarized potential and slowed the recovery of IK(DR) inactivation. CUR, DMC, and BDMC all exerted depressant actions on IK(DR) amplitude to a similar magnitude, although DMC and BDMC did not increase current inactivation clearly. CUR slightly suppressed the peak amplitude of voltage-gated Na+ current. CUR, DMC and BDMC depolarized the resting potential and increased firing frequency of action potentials. The CUR-mediated decrease of IK(DR) and the increase of current inactivation also occurred in βTC-6 INS-1 cells. Taken these results together, these effects may be one of the possible mechanisms contributing their insulin-releasing effect.",
author = "Ping-Chung Kuo and Yang, {Chia Jung} and Lee, {Yu Chi} and Pei-chun Chen and Yen-Chin Liu and Sheng-Nan Wu",
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AU - Kuo, Ping-Chung

AU - Yang, Chia Jung

AU - Lee, Yu Chi

AU - Chen, Pei-chun

AU - Liu, Yen-Chin

AU - Wu, Sheng-Nan

PY - 2018/1/15

Y1 - 2018/1/15

N2 - Curcumin (CUR) has been demonstrated to induce insulin release from pancreatic β-cells; however, how curcuminoids (including demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC)) exert any possible effects on membrane ion currents inherently in insulin-secreting cells remains largely unclear. The effects of CUR and other structurally similar curcuminoids on ion currents in rat insulin-secreting (INS-1) insulinoma cells were therefore investigated in this study. The effects of these compounds on ionic currents and membrane potential were studied by patch-clamp technique. CUR suppressed the amplitude of delayed-rectifier K+ current (IK(DR)) in a time-, state- and concentration-dependent manner in these cells and the inhibition was not reversed by diazoxide, nicorandil or chlorotoxin. The value of dissociation constant for CUR-induced suppression of IK(DR) in INS-1 cells was 1.26 μM. Despite the inability of CUR to alter the activation rate of IK(DR), it accelerated current inactivation elicited by membrane depolarization. Increasing CUR concentrations shifted the inactivation curve of IK(DR) to hyperpolarized potential and slowed the recovery of IK(DR) inactivation. CUR, DMC, and BDMC all exerted depressant actions on IK(DR) amplitude to a similar magnitude, although DMC and BDMC did not increase current inactivation clearly. CUR slightly suppressed the peak amplitude of voltage-gated Na+ current. CUR, DMC and BDMC depolarized the resting potential and increased firing frequency of action potentials. The CUR-mediated decrease of IK(DR) and the increase of current inactivation also occurred in βTC-6 INS-1 cells. Taken these results together, these effects may be one of the possible mechanisms contributing their insulin-releasing effect.

AB - Curcumin (CUR) has been demonstrated to induce insulin release from pancreatic β-cells; however, how curcuminoids (including demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC)) exert any possible effects on membrane ion currents inherently in insulin-secreting cells remains largely unclear. The effects of CUR and other structurally similar curcuminoids on ion currents in rat insulin-secreting (INS-1) insulinoma cells were therefore investigated in this study. The effects of these compounds on ionic currents and membrane potential were studied by patch-clamp technique. CUR suppressed the amplitude of delayed-rectifier K+ current (IK(DR)) in a time-, state- and concentration-dependent manner in these cells and the inhibition was not reversed by diazoxide, nicorandil or chlorotoxin. The value of dissociation constant for CUR-induced suppression of IK(DR) in INS-1 cells was 1.26 μM. Despite the inability of CUR to alter the activation rate of IK(DR), it accelerated current inactivation elicited by membrane depolarization. Increasing CUR concentrations shifted the inactivation curve of IK(DR) to hyperpolarized potential and slowed the recovery of IK(DR) inactivation. CUR, DMC, and BDMC all exerted depressant actions on IK(DR) amplitude to a similar magnitude, although DMC and BDMC did not increase current inactivation clearly. CUR slightly suppressed the peak amplitude of voltage-gated Na+ current. CUR, DMC and BDMC depolarized the resting potential and increased firing frequency of action potentials. The CUR-mediated decrease of IK(DR) and the increase of current inactivation also occurred in βTC-6 INS-1 cells. Taken these results together, these effects may be one of the possible mechanisms contributing their insulin-releasing effect.

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