Modulation of glucose-induced insulin secretion by cytosolic redox state in clonal beta-cells

AP Salgado, FC Pereira, RM Seica, AP Fernandes, Peter Flatt, RM Santos, LM Rosario, R Ramasamy

Research output: Contribution to journalArticle

Abstract

Nutrient stimulation of pancreatic beta-cells increases the cellular reduced pyridine nucleotide content, but the specific role of cytosolic redox state in glucose-induced insulin release (GIIR) remains undetermined. The role of cytosolic redox state has been assessed (as reflected by the lactate/pyruvate ratio) in nutrient- and non-nutrient-induced insulin release using a recently established glucose-sensitive clonal beta-cell line (BRIN-BD11). Long-term exposure to the NAD(+) precursor vitamin nicotinic acid (NA, 100 mu M) was used to promote a more oxidized state in the cytosol. Glucose (2-16 mM) evoked a dose-dependent rise in the cytosolic NADH/NAD(+) ratio which was linearly related to the extent of GIIR. NA suppressed the glucose-induced rise in the NADH/NAD(+) ratio and concomitantly reduced GIIR by 44%. It also inhibited, by 47%, the average glucose-induced rise in cytosolic free Ca2+ concentration ([Ca2+](i), assessed by fura-2 microfluorometry from single cells). The latter effect was not accounted for by a reduction in the activity of voltage-sensitive Ca2+ channels, inasmuch as both high K+- and tolbutamide-induced [Ca2+](i) rises remained insensitive to NA exposure. NA did not affect insulin release evoked by any of the depolarizing agents, indicating that steps in the stimulus-secretion coupling cascade distal to Ca2+ influx are insensitive to changes in the cytosolic redox state. It is concluded that GIIR is partially controlled by the cytosolic redox state. Moreover, the impairment in GIIR caused by a shift toward a more oxidized state in the cytosol, originates from an attenuated [Ca2+](i) response. The latter is likely mediated by the influence of cytosolic redox state on specific metabolic pathways (NADH shuttle systems and/or the malonyl-CoA pathway), leading ultimately to enhancement of the activity of ATP-sensitive K+ channels. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.
LanguageEnglish
Pages79-88
JournalMolecular and Cellular Endocrinology
Volume154
Issue number1-2
Publication statusPublished - Aug 1999

Fingerprint

Oxidation-Reduction
Insulin
Glucose
NAD
Cytosol
Malonyl Coenzyme A
Cytophotometry
Food
Tolbutamide
Fura-2
Niacin
Insulin-Secreting Cells
Metabolic Networks and Pathways
Pyruvic Acid
Lactic Acid
Nucleotides
Adenosine Triphosphate
Cell Line

Cite this

Salgado, AP., Pereira, FC., Seica, RM., Fernandes, AP., Flatt, P., Santos, RM., ... Ramasamy, R. (1999). Modulation of glucose-induced insulin secretion by cytosolic redox state in clonal beta-cells. 154(1-2), 79-88.
Salgado, AP ; Pereira, FC ; Seica, RM ; Fernandes, AP ; Flatt, Peter ; Santos, RM ; Rosario, LM ; Ramasamy, R. / Modulation of glucose-induced insulin secretion by cytosolic redox state in clonal beta-cells. 1999 ; Vol. 154, No. 1-2. pp. 79-88.
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abstract = "Nutrient stimulation of pancreatic beta-cells increases the cellular reduced pyridine nucleotide content, but the specific role of cytosolic redox state in glucose-induced insulin release (GIIR) remains undetermined. The role of cytosolic redox state has been assessed (as reflected by the lactate/pyruvate ratio) in nutrient- and non-nutrient-induced insulin release using a recently established glucose-sensitive clonal beta-cell line (BRIN-BD11). Long-term exposure to the NAD(+) precursor vitamin nicotinic acid (NA, 100 mu M) was used to promote a more oxidized state in the cytosol. Glucose (2-16 mM) evoked a dose-dependent rise in the cytosolic NADH/NAD(+) ratio which was linearly related to the extent of GIIR. NA suppressed the glucose-induced rise in the NADH/NAD(+) ratio and concomitantly reduced GIIR by 44{\%}. It also inhibited, by 47{\%}, the average glucose-induced rise in cytosolic free Ca2+ concentration ([Ca2+](i), assessed by fura-2 microfluorometry from single cells). The latter effect was not accounted for by a reduction in the activity of voltage-sensitive Ca2+ channels, inasmuch as both high K+- and tolbutamide-induced [Ca2+](i) rises remained insensitive to NA exposure. NA did not affect insulin release evoked by any of the depolarizing agents, indicating that steps in the stimulus-secretion coupling cascade distal to Ca2+ influx are insensitive to changes in the cytosolic redox state. It is concluded that GIIR is partially controlled by the cytosolic redox state. Moreover, the impairment in GIIR caused by a shift toward a more oxidized state in the cytosol, originates from an attenuated [Ca2+](i) response. The latter is likely mediated by the influence of cytosolic redox state on specific metabolic pathways (NADH shuttle systems and/or the malonyl-CoA pathway), leading ultimately to enhancement of the activity of ATP-sensitive K+ channels. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.",
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Salgado, AP, Pereira, FC, Seica, RM, Fernandes, AP, Flatt, P, Santos, RM, Rosario, LM & Ramasamy, R 1999, 'Modulation of glucose-induced insulin secretion by cytosolic redox state in clonal beta-cells', vol. 154, no. 1-2, pp. 79-88.

Modulation of glucose-induced insulin secretion by cytosolic redox state in clonal beta-cells. / Salgado, AP; Pereira, FC; Seica, RM; Fernandes, AP; Flatt, Peter; Santos, RM; Rosario, LM; Ramasamy, R.

Vol. 154, No. 1-2, 08.1999, p. 79-88.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Modulation of glucose-induced insulin secretion by cytosolic redox state in clonal beta-cells

AU - Salgado, AP

AU - Pereira, FC

AU - Seica, RM

AU - Fernandes, AP

AU - Flatt, Peter

AU - Santos, RM

AU - Rosario, LM

AU - Ramasamy, R

PY - 1999/8

Y1 - 1999/8

N2 - Nutrient stimulation of pancreatic beta-cells increases the cellular reduced pyridine nucleotide content, but the specific role of cytosolic redox state in glucose-induced insulin release (GIIR) remains undetermined. The role of cytosolic redox state has been assessed (as reflected by the lactate/pyruvate ratio) in nutrient- and non-nutrient-induced insulin release using a recently established glucose-sensitive clonal beta-cell line (BRIN-BD11). Long-term exposure to the NAD(+) precursor vitamin nicotinic acid (NA, 100 mu M) was used to promote a more oxidized state in the cytosol. Glucose (2-16 mM) evoked a dose-dependent rise in the cytosolic NADH/NAD(+) ratio which was linearly related to the extent of GIIR. NA suppressed the glucose-induced rise in the NADH/NAD(+) ratio and concomitantly reduced GIIR by 44%. It also inhibited, by 47%, the average glucose-induced rise in cytosolic free Ca2+ concentration ([Ca2+](i), assessed by fura-2 microfluorometry from single cells). The latter effect was not accounted for by a reduction in the activity of voltage-sensitive Ca2+ channels, inasmuch as both high K+- and tolbutamide-induced [Ca2+](i) rises remained insensitive to NA exposure. NA did not affect insulin release evoked by any of the depolarizing agents, indicating that steps in the stimulus-secretion coupling cascade distal to Ca2+ influx are insensitive to changes in the cytosolic redox state. It is concluded that GIIR is partially controlled by the cytosolic redox state. Moreover, the impairment in GIIR caused by a shift toward a more oxidized state in the cytosol, originates from an attenuated [Ca2+](i) response. The latter is likely mediated by the influence of cytosolic redox state on specific metabolic pathways (NADH shuttle systems and/or the malonyl-CoA pathway), leading ultimately to enhancement of the activity of ATP-sensitive K+ channels. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.

AB - Nutrient stimulation of pancreatic beta-cells increases the cellular reduced pyridine nucleotide content, but the specific role of cytosolic redox state in glucose-induced insulin release (GIIR) remains undetermined. The role of cytosolic redox state has been assessed (as reflected by the lactate/pyruvate ratio) in nutrient- and non-nutrient-induced insulin release using a recently established glucose-sensitive clonal beta-cell line (BRIN-BD11). Long-term exposure to the NAD(+) precursor vitamin nicotinic acid (NA, 100 mu M) was used to promote a more oxidized state in the cytosol. Glucose (2-16 mM) evoked a dose-dependent rise in the cytosolic NADH/NAD(+) ratio which was linearly related to the extent of GIIR. NA suppressed the glucose-induced rise in the NADH/NAD(+) ratio and concomitantly reduced GIIR by 44%. It also inhibited, by 47%, the average glucose-induced rise in cytosolic free Ca2+ concentration ([Ca2+](i), assessed by fura-2 microfluorometry from single cells). The latter effect was not accounted for by a reduction in the activity of voltage-sensitive Ca2+ channels, inasmuch as both high K+- and tolbutamide-induced [Ca2+](i) rises remained insensitive to NA exposure. NA did not affect insulin release evoked by any of the depolarizing agents, indicating that steps in the stimulus-secretion coupling cascade distal to Ca2+ influx are insensitive to changes in the cytosolic redox state. It is concluded that GIIR is partially controlled by the cytosolic redox state. Moreover, the impairment in GIIR caused by a shift toward a more oxidized state in the cytosol, originates from an attenuated [Ca2+](i) response. The latter is likely mediated by the influence of cytosolic redox state on specific metabolic pathways (NADH shuttle systems and/or the malonyl-CoA pathway), leading ultimately to enhancement of the activity of ATP-sensitive K+ channels. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.

M3 - Article

VL - 154

SP - 79

EP - 88

IS - 1-2

ER -

Salgado AP, Pereira FC, Seica RM, Fernandes AP, Flatt P, Santos RM et al. Modulation of glucose-induced insulin secretion by cytosolic redox state in clonal beta-cells. 1999 Aug;154(1-2):79-88.