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γ-Aminobutyric acid (GABA) signalling in human pancreatic islets is altered in type 2 diabetes.

Taneera J, Jin Z, Jin Y, Muhammed SJ, Zhang E, Lang S, Salehi A, Korsgren O, Renström E, Groop L, Birnir B - Diabetologia (2012)

Bottom Line: The currents were enhanced by pentobarbital and inhibited by the GABA(A) receptor antagonist, SR95531.The effects of SR95531 on hormone release revealed that activation of GABA(A) channels (GABA(A) receptors) decreased both insulin and glucagon secretion.Interstitial GABA activates GABA(A) channels and GABA(B) receptors and effectively modulates hormone release in islets from type 2 diabetic and normoglycaemic individuals.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Sciences, Lund University Diabetes Center, University Hospital Malmö, Lund University, Malmö, Sweden.

ABSTRACT

Aims/hypothesis: γ-Aminobutyric acid (GABA) is a signalling molecule in the interstitial space in pancreatic islets. We examined the expression and function of the GABA signalling system components in human pancreatic islets from normoglycaemic and type 2 diabetic individuals.

Methods: Expression of GABA signalling system components was studied by microarray, quantitative PCR analysis, immunohistochemistry and patch-clamp experiments on cells in intact islets. Hormone release was measured from intact islets.

Results: The GABA signalling system was compromised in islets from type 2 diabetic individuals, where the expression of the genes encoding the α1, α2, β2 and β3 GABA(A) channel subunits was downregulated. GABA originating within the islets evoked tonic currents in the cells. The currents were enhanced by pentobarbital and inhibited by the GABA(A) receptor antagonist, SR95531. The effects of SR95531 on hormone release revealed that activation of GABA(A) channels (GABA(A) receptors) decreased both insulin and glucagon secretion. The GABA(B) receptor antagonist, CPG55845, increased insulin release in islets (16.7 mmol/l glucose) from normoglycaemic and type 2 diabetic individuals.

Conclusions/interpretation: Interstitial GABA activates GABA(A) channels and GABA(B) receptors and effectively modulates hormone release in islets from type 2 diabetic and normoglycaemic individuals.

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Related in: MedlinePlus

GABAA channel subunit mRNA expression and protein localisation in human pancreatic islet alpha and beta cells. a Expression of GABAA channel subunits in sorted human pancreatic islet beta cells from one normoglycaemic donor quantified by RT-qPCR. The β3 and γ2 subunits were prominently expressed, and the expression of the α1, α2, π and ρ2 subunits was somewhat lower. The relative expression of each target gene was normalised to the reference gene ACTB using the method. b Human islets were co-labelled with antibodies staining insulin (green), α1 GABAA channel subunit (purple) and glucagon (red). Scale bar, 5 μm. c Human islets were co-labelled with antibodies staining insulin (green), α2 GABAA channel subunit (purple) and glucagon (red). Scale bar, 5 μm. d Immunoreactivity of α1 GABAA channel subunit (purple) was detected in both insulin-positive cells (green) and glucagon-positive cells (red) from human islets. Scale bar, 5 μm. e Immunoreactivity of α2 GABAA channel subunit (purple) was detected in both insulin-positive cells (green) and glucagon-positive cells (red) from human islets. Scale bar, 5 μm
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Fig2: GABAA channel subunit mRNA expression and protein localisation in human pancreatic islet alpha and beta cells. a Expression of GABAA channel subunits in sorted human pancreatic islet beta cells from one normoglycaemic donor quantified by RT-qPCR. The β3 and γ2 subunits were prominently expressed, and the expression of the α1, α2, π and ρ2 subunits was somewhat lower. The relative expression of each target gene was normalised to the reference gene ACTB using the method. b Human islets were co-labelled with antibodies staining insulin (green), α1 GABAA channel subunit (purple) and glucagon (red). Scale bar, 5 μm. c Human islets were co-labelled with antibodies staining insulin (green), α2 GABAA channel subunit (purple) and glucagon (red). Scale bar, 5 μm. d Immunoreactivity of α1 GABAA channel subunit (purple) was detected in both insulin-positive cells (green) and glucagon-positive cells (red) from human islets. Scale bar, 5 μm. e Immunoreactivity of α2 GABAA channel subunit (purple) was detected in both insulin-positive cells (green) and glucagon-positive cells (red) from human islets. Scale bar, 5 μm

Mentions: To determine which specific GABAA channel subunits are present in pancreatic islet beta cells, we analysed expression of the subunits in sorted beta cells from one normoglycaemic donor using RT-qPCR. The α1, α2, α5, β3, γ2, δ, π and ρ2 GABAA channel subunits were present in the cells (Fig. 2a). To identify the cellular and subcellular location of the GABAA channel subunits, we immunostained for the α1 or α2 subunits together with insulin and glucagon in pancreatic islets (Fig. 2b–e). The results show that, in human pancreatic islets, the α1 and the α2 GABAA channel subunit proteins are present in the plasma membrane and cytoplasm of alpha and beta cells. The α2 subunit appears particularly prominent in the cells, whereas α1 expression is more limited.Fig. 2


γ-Aminobutyric acid (GABA) signalling in human pancreatic islets is altered in type 2 diabetes.

Taneera J, Jin Z, Jin Y, Muhammed SJ, Zhang E, Lang S, Salehi A, Korsgren O, Renström E, Groop L, Birnir B - Diabetologia (2012)

GABAA channel subunit mRNA expression and protein localisation in human pancreatic islet alpha and beta cells. a Expression of GABAA channel subunits in sorted human pancreatic islet beta cells from one normoglycaemic donor quantified by RT-qPCR. The β3 and γ2 subunits were prominently expressed, and the expression of the α1, α2, π and ρ2 subunits was somewhat lower. The relative expression of each target gene was normalised to the reference gene ACTB using the method. b Human islets were co-labelled with antibodies staining insulin (green), α1 GABAA channel subunit (purple) and glucagon (red). Scale bar, 5 μm. c Human islets were co-labelled with antibodies staining insulin (green), α2 GABAA channel subunit (purple) and glucagon (red). Scale bar, 5 μm. d Immunoreactivity of α1 GABAA channel subunit (purple) was detected in both insulin-positive cells (green) and glucagon-positive cells (red) from human islets. Scale bar, 5 μm. e Immunoreactivity of α2 GABAA channel subunit (purple) was detected in both insulin-positive cells (green) and glucagon-positive cells (red) from human islets. Scale bar, 5 μm
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3369140&req=5

Fig2: GABAA channel subunit mRNA expression and protein localisation in human pancreatic islet alpha and beta cells. a Expression of GABAA channel subunits in sorted human pancreatic islet beta cells from one normoglycaemic donor quantified by RT-qPCR. The β3 and γ2 subunits were prominently expressed, and the expression of the α1, α2, π and ρ2 subunits was somewhat lower. The relative expression of each target gene was normalised to the reference gene ACTB using the method. b Human islets were co-labelled with antibodies staining insulin (green), α1 GABAA channel subunit (purple) and glucagon (red). Scale bar, 5 μm. c Human islets were co-labelled with antibodies staining insulin (green), α2 GABAA channel subunit (purple) and glucagon (red). Scale bar, 5 μm. d Immunoreactivity of α1 GABAA channel subunit (purple) was detected in both insulin-positive cells (green) and glucagon-positive cells (red) from human islets. Scale bar, 5 μm. e Immunoreactivity of α2 GABAA channel subunit (purple) was detected in both insulin-positive cells (green) and glucagon-positive cells (red) from human islets. Scale bar, 5 μm
Mentions: To determine which specific GABAA channel subunits are present in pancreatic islet beta cells, we analysed expression of the subunits in sorted beta cells from one normoglycaemic donor using RT-qPCR. The α1, α2, α5, β3, γ2, δ, π and ρ2 GABAA channel subunits were present in the cells (Fig. 2a). To identify the cellular and subcellular location of the GABAA channel subunits, we immunostained for the α1 or α2 subunits together with insulin and glucagon in pancreatic islets (Fig. 2b–e). The results show that, in human pancreatic islets, the α1 and the α2 GABAA channel subunit proteins are present in the plasma membrane and cytoplasm of alpha and beta cells. The α2 subunit appears particularly prominent in the cells, whereas α1 expression is more limited.Fig. 2

Bottom Line: The currents were enhanced by pentobarbital and inhibited by the GABA(A) receptor antagonist, SR95531.The effects of SR95531 on hormone release revealed that activation of GABA(A) channels (GABA(A) receptors) decreased both insulin and glucagon secretion.Interstitial GABA activates GABA(A) channels and GABA(B) receptors and effectively modulates hormone release in islets from type 2 diabetic and normoglycaemic individuals.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Sciences, Lund University Diabetes Center, University Hospital Malmö, Lund University, Malmö, Sweden.

ABSTRACT

Aims/hypothesis: γ-Aminobutyric acid (GABA) is a signalling molecule in the interstitial space in pancreatic islets. We examined the expression and function of the GABA signalling system components in human pancreatic islets from normoglycaemic and type 2 diabetic individuals.

Methods: Expression of GABA signalling system components was studied by microarray, quantitative PCR analysis, immunohistochemistry and patch-clamp experiments on cells in intact islets. Hormone release was measured from intact islets.

Results: The GABA signalling system was compromised in islets from type 2 diabetic individuals, where the expression of the genes encoding the α1, α2, β2 and β3 GABA(A) channel subunits was downregulated. GABA originating within the islets evoked tonic currents in the cells. The currents were enhanced by pentobarbital and inhibited by the GABA(A) receptor antagonist, SR95531. The effects of SR95531 on hormone release revealed that activation of GABA(A) channels (GABA(A) receptors) decreased both insulin and glucagon secretion. The GABA(B) receptor antagonist, CPG55845, increased insulin release in islets (16.7 mmol/l glucose) from normoglycaemic and type 2 diabetic individuals.

Conclusions/interpretation: Interstitial GABA activates GABA(A) channels and GABA(B) receptors and effectively modulates hormone release in islets from type 2 diabetic and normoglycaemic individuals.

Show MeSH
Related in: MedlinePlus