Acute glucagon induces postprandial peripheral insulin resistance

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Abstract

Glucagon levels are often moderately elevated in diabetes. It is known that glucagon leads to a decrease in hepatic glutathione (GSH) synthesis that in turn is associated with decreased postprandial insulin sensitivity. Given that cAMP pathway controls GSH levels we tested whether insulin sensitivity decreases after intraportal (ipv) administration of a cAMP analog (DBcAMP), and investigated whether glucagon promotes insulin resistance through decreasing hepatic GSH levels. Insulin sensitivity was determined in fed male SpragueDawley rats using a modified euglycemic hyperinsulinemic clamp in the postprandial state upon ipv administration of DBcAMP as well as glucagon infusion. Glucagon effects on insulin sensitivity was assessed in the presence or absence of postprandial insulin sensitivity inhibition by administration of L-NMMA. Hepatic GSH and NO content and plasma levels of NO were measured after acute ipv glucagon infusion. Insulin sensitivity was assessed in the fed state and after ipv glucagon infusion in the presence of GSH-E. We founf that DBcAMP and glucagon produce a decrease of insulin sensitivity, in a dose-dependent manner. Glucagon-induced decrease of postprandial insulin sensitivity correlated with decreased hepatic GSH content and was restored by administration of GSH-E. Furthermore, inhibition of postprandial decrease of insulin sensitivity L-NMMA was not overcome by glucagon, but glucagon did not affect hepatic and plasma levels of NO. These results show that glucagon decreases postprandial insulin sensitivity through reducing hepatic GSH levels, an effect that is mimicked by increasing cAMP hepatic levels and requires physiological NO levels. These observations support the hypothesis that glucagon acts via adenylate cyclase to decrease hepatic GSH levels and induce insulin resistance. We suggest that the glucagon-cAMP-GSH axis is a potential therapeutic target to address insulin resistance in pathological conditions.
Original languageEnglish
Pages (from-to)Online
JournalPLoS ONE
Volume10
Issue number5
DOIs
Publication statusPublished - 1 Jan 2015

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glucagon
Glucagon
insulin resistance
Vascular Resistance
Insulin Resistance
Insulin
liver
Liver
Bucladesine
omega-N-Methylarginine
postprandial state
Plasmas
adenylate cyclase
Glucose Clamp Technique
Level control
Clamping devices
Medical problems
Adenylyl Cyclases
Glutathione
diabetes

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title = "Acute glucagon induces postprandial peripheral insulin resistance",
abstract = "Glucagon levels are often moderately elevated in diabetes. It is known that glucagon leads to a decrease in hepatic glutathione (GSH) synthesis that in turn is associated with decreased postprandial insulin sensitivity. Given that cAMP pathway controls GSH levels we tested whether insulin sensitivity decreases after intraportal (ipv) administration of a cAMP analog (DBcAMP), and investigated whether glucagon promotes insulin resistance through decreasing hepatic GSH levels. Insulin sensitivity was determined in fed male SpragueDawley rats using a modified euglycemic hyperinsulinemic clamp in the postprandial state upon ipv administration of DBcAMP as well as glucagon infusion. Glucagon effects on insulin sensitivity was assessed in the presence or absence of postprandial insulin sensitivity inhibition by administration of L-NMMA. Hepatic GSH and NO content and plasma levels of NO were measured after acute ipv glucagon infusion. Insulin sensitivity was assessed in the fed state and after ipv glucagon infusion in the presence of GSH-E. We founf that DBcAMP and glucagon produce a decrease of insulin sensitivity, in a dose-dependent manner. Glucagon-induced decrease of postprandial insulin sensitivity correlated with decreased hepatic GSH content and was restored by administration of GSH-E. Furthermore, inhibition of postprandial decrease of insulin sensitivity L-NMMA was not overcome by glucagon, but glucagon did not affect hepatic and plasma levels of NO. These results show that glucagon decreases postprandial insulin sensitivity through reducing hepatic GSH levels, an effect that is mimicked by increasing cAMP hepatic levels and requires physiological NO levels. These observations support the hypothesis that glucagon acts via adenylate cyclase to decrease hepatic GSH levels and induce insulin resistance. We suggest that the glucagon-cAMP-GSH axis is a potential therapeutic target to address insulin resistance in pathological conditions.",
keywords = "RAT-LIVER, SENSITIVITY, NITRIC-OXIDE, PHOSPHODIESTERASES, SECRETION, HEPATIC GLUTATHIONE, HYPERGLYCEMIA, PULSATILE INSULIN, BETA-CELL, GLUCOSE CLEARANCE",
author = "Patarr{\~a}o, {Rita S.} and Macedo, {M. Paula}",
note = "info:eu-repo/grantAgreement/FCT/5646-ICCMS/82956/PT# info:eu-repo/grantAgreement/FCT/3599-PPCDT/124913/PT# info:eu-repo/grantAgreement/FCT/3599-PPCDT/124357/PT# This study was supported by Fundacao para a Ciencia e Tecnologia (FCT) grant PIC/IC/82956/2007, PTDC/BIM-MET/0486/2012, PTDC/DTP-EPI/0207/2012 and by the Portuguese Diabetes Society (SPD). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.",
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Acute glucagon induces postprandial peripheral insulin resistance. / Patarrão, Rita S.; Macedo, M. Paula.

In: PLoS ONE, Vol. 10, No. 5, 01.01.2015, p. Online.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Acute glucagon induces postprandial peripheral insulin resistance

AU - Patarrão, Rita S.

AU - Macedo, M. Paula

N1 - info:eu-repo/grantAgreement/FCT/5646-ICCMS/82956/PT# info:eu-repo/grantAgreement/FCT/3599-PPCDT/124913/PT# info:eu-repo/grantAgreement/FCT/3599-PPCDT/124357/PT# This study was supported by Fundacao para a Ciencia e Tecnologia (FCT) grant PIC/IC/82956/2007, PTDC/BIM-MET/0486/2012, PTDC/DTP-EPI/0207/2012 and by the Portuguese Diabetes Society (SPD). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

PY - 2015/1/1

Y1 - 2015/1/1

N2 - Glucagon levels are often moderately elevated in diabetes. It is known that glucagon leads to a decrease in hepatic glutathione (GSH) synthesis that in turn is associated with decreased postprandial insulin sensitivity. Given that cAMP pathway controls GSH levels we tested whether insulin sensitivity decreases after intraportal (ipv) administration of a cAMP analog (DBcAMP), and investigated whether glucagon promotes insulin resistance through decreasing hepatic GSH levels. Insulin sensitivity was determined in fed male SpragueDawley rats using a modified euglycemic hyperinsulinemic clamp in the postprandial state upon ipv administration of DBcAMP as well as glucagon infusion. Glucagon effects on insulin sensitivity was assessed in the presence or absence of postprandial insulin sensitivity inhibition by administration of L-NMMA. Hepatic GSH and NO content and plasma levels of NO were measured after acute ipv glucagon infusion. Insulin sensitivity was assessed in the fed state and after ipv glucagon infusion in the presence of GSH-E. We founf that DBcAMP and glucagon produce a decrease of insulin sensitivity, in a dose-dependent manner. Glucagon-induced decrease of postprandial insulin sensitivity correlated with decreased hepatic GSH content and was restored by administration of GSH-E. Furthermore, inhibition of postprandial decrease of insulin sensitivity L-NMMA was not overcome by glucagon, but glucagon did not affect hepatic and plasma levels of NO. These results show that glucagon decreases postprandial insulin sensitivity through reducing hepatic GSH levels, an effect that is mimicked by increasing cAMP hepatic levels and requires physiological NO levels. These observations support the hypothesis that glucagon acts via adenylate cyclase to decrease hepatic GSH levels and induce insulin resistance. We suggest that the glucagon-cAMP-GSH axis is a potential therapeutic target to address insulin resistance in pathological conditions.

AB - Glucagon levels are often moderately elevated in diabetes. It is known that glucagon leads to a decrease in hepatic glutathione (GSH) synthesis that in turn is associated with decreased postprandial insulin sensitivity. Given that cAMP pathway controls GSH levels we tested whether insulin sensitivity decreases after intraportal (ipv) administration of a cAMP analog (DBcAMP), and investigated whether glucagon promotes insulin resistance through decreasing hepatic GSH levels. Insulin sensitivity was determined in fed male SpragueDawley rats using a modified euglycemic hyperinsulinemic clamp in the postprandial state upon ipv administration of DBcAMP as well as glucagon infusion. Glucagon effects on insulin sensitivity was assessed in the presence or absence of postprandial insulin sensitivity inhibition by administration of L-NMMA. Hepatic GSH and NO content and plasma levels of NO were measured after acute ipv glucagon infusion. Insulin sensitivity was assessed in the fed state and after ipv glucagon infusion in the presence of GSH-E. We founf that DBcAMP and glucagon produce a decrease of insulin sensitivity, in a dose-dependent manner. Glucagon-induced decrease of postprandial insulin sensitivity correlated with decreased hepatic GSH content and was restored by administration of GSH-E. Furthermore, inhibition of postprandial decrease of insulin sensitivity L-NMMA was not overcome by glucagon, but glucagon did not affect hepatic and plasma levels of NO. These results show that glucagon decreases postprandial insulin sensitivity through reducing hepatic GSH levels, an effect that is mimicked by increasing cAMP hepatic levels and requires physiological NO levels. These observations support the hypothesis that glucagon acts via adenylate cyclase to decrease hepatic GSH levels and induce insulin resistance. We suggest that the glucagon-cAMP-GSH axis is a potential therapeutic target to address insulin resistance in pathological conditions.

KW - RAT-LIVER

KW - SENSITIVITY

KW - NITRIC-OXIDE

KW - PHOSPHODIESTERASES

KW - SECRETION

KW - HEPATIC GLUTATHIONE

KW - HYPERGLYCEMIA

KW - PULSATILE INSULIN

KW - BETA-CELL

KW - GLUCOSE CLEARANCE

U2 - 10.1371/journal.pone.0127221

DO - 10.1371/journal.pone.0127221

M3 - Article

VL - 10

SP - Online

JO - PlosOne

JF - PlosOne

SN - 1932-6203

IS - 5

ER -