Limits...
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.

Show MeSH

Related in: MedlinePlus

Gene expression of GABA signalling system components in human islets determined by RT-qPCR. a In islets from normoglycaemic donors (grey bar, n = 14) and donors with type 2 diabetes (black bar, n = 9), 18 out of 19 GABAA channel subunits were detected, with the most prominent expression level for α1, α2, β3, γ2, π and ρ2. In islets from individuals with type 2 diabetes, expression of the α1, α2, β2 and β3 GABAA channel subunits was significantly downregulated compared with normoglycaemic donors. b Gene expression of GABA signalling system accessory proteins, receptors, enzymes and transporters from normoglycaemic donors (grey bar, n = 14) and donors with type 2 diabetes (black bar, n = 9). The most prominent expression was detected for GEPHRYN, GABARAP, RADIXIN, GAD65 and the chloride transporter, NKCC1 (also known as SLC12A2). c In islets from hyperglycaemic donors (open bar, n = 6), expression of the α2 GABAA channel subunit was downregulated compared with normoglycaemic donors (grey bar, n = 14). The relative expression of each target gene was normalised to reference gene ACTB using the method. All individual experiments were run in duplicate, and the data presented as mean ± SEM. Differences in expression levels were analysed by Student's t test: *p < 0.05, **p < 0.01, ***p < 0.001
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3369140&req=5

Fig1: Gene expression of GABA signalling system components in human islets determined by RT-qPCR. a In islets from normoglycaemic donors (grey bar, n = 14) and donors with type 2 diabetes (black bar, n = 9), 18 out of 19 GABAA channel subunits were detected, with the most prominent expression level for α1, α2, β3, γ2, π and ρ2. In islets from individuals with type 2 diabetes, expression of the α1, α2, β2 and β3 GABAA channel subunits was significantly downregulated compared with normoglycaemic donors. b Gene expression of GABA signalling system accessory proteins, receptors, enzymes and transporters from normoglycaemic donors (grey bar, n = 14) and donors with type 2 diabetes (black bar, n = 9). The most prominent expression was detected for GEPHRYN, GABARAP, RADIXIN, GAD65 and the chloride transporter, NKCC1 (also known as SLC12A2). c In islets from hyperglycaemic donors (open bar, n = 6), expression of the α2 GABAA channel subunit was downregulated compared with normoglycaemic donors (grey bar, n = 14). The relative expression of each target gene was normalised to reference gene ACTB using the method. All individual experiments were run in duplicate, and the data presented as mean ± SEM. Differences in expression levels were analysed by Student's t test: *p < 0.05, **p < 0.01, ***p < 0.001

Mentions: We further examined and compared gene expression in islets from individuals with and without type 2 diabetes using RT-qPCR analysis (Fig. 1). The highest level of expression was obtained for the genes for α1, α2, β3, γ2, π and ρ2 GABAA channel subunits in islets from normoglycaemic individuals (n = 14). In islets from type 2 diabetic donors, the α1, α2, β2 and β3 GABAA subunits were significantly downregulated (Fig. 1a). The other genes in the GABA signalling cascade (Fig. 1b) were all similarly expressed and did not differ significantly between islets from individuals with type 2 diabetes and those from normoglycaemic donors. We further examined whether we could detect downregulation of genes in the islets from hyperglycaemic donors (not diagnosed with type 2 diabetes; n = 6). Only the α2 GABAA channel subunit was significantly downregulated in islets from hyperglycaemic individuals compared with normoglycaemic individuals (Fig. 1c, α1, p = 0.127; β2, p = 0.536; β3, p = 0.386).Fig. 1


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)

Gene expression of GABA signalling system components in human islets determined by RT-qPCR. a In islets from normoglycaemic donors (grey bar, n = 14) and donors with type 2 diabetes (black bar, n = 9), 18 out of 19 GABAA channel subunits were detected, with the most prominent expression level for α1, α2, β3, γ2, π and ρ2. In islets from individuals with type 2 diabetes, expression of the α1, α2, β2 and β3 GABAA channel subunits was significantly downregulated compared with normoglycaemic donors. b Gene expression of GABA signalling system accessory proteins, receptors, enzymes and transporters from normoglycaemic donors (grey bar, n = 14) and donors with type 2 diabetes (black bar, n = 9). The most prominent expression was detected for GEPHRYN, GABARAP, RADIXIN, GAD65 and the chloride transporter, NKCC1 (also known as SLC12A2). c In islets from hyperglycaemic donors (open bar, n = 6), expression of the α2 GABAA channel subunit was downregulated compared with normoglycaemic donors (grey bar, n = 14). The relative expression of each target gene was normalised to reference gene ACTB using the method. All individual experiments were run in duplicate, and the data presented as mean ± SEM. Differences in expression levels were analysed by Student's t test: *p < 0.05, **p < 0.01, ***p < 0.001
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369140&req=5

Fig1: Gene expression of GABA signalling system components in human islets determined by RT-qPCR. a In islets from normoglycaemic donors (grey bar, n = 14) and donors with type 2 diabetes (black bar, n = 9), 18 out of 19 GABAA channel subunits were detected, with the most prominent expression level for α1, α2, β3, γ2, π and ρ2. In islets from individuals with type 2 diabetes, expression of the α1, α2, β2 and β3 GABAA channel subunits was significantly downregulated compared with normoglycaemic donors. b Gene expression of GABA signalling system accessory proteins, receptors, enzymes and transporters from normoglycaemic donors (grey bar, n = 14) and donors with type 2 diabetes (black bar, n = 9). The most prominent expression was detected for GEPHRYN, GABARAP, RADIXIN, GAD65 and the chloride transporter, NKCC1 (also known as SLC12A2). c In islets from hyperglycaemic donors (open bar, n = 6), expression of the α2 GABAA channel subunit was downregulated compared with normoglycaemic donors (grey bar, n = 14). The relative expression of each target gene was normalised to reference gene ACTB using the method. All individual experiments were run in duplicate, and the data presented as mean ± SEM. Differences in expression levels were analysed by Student's t test: *p < 0.05, **p < 0.01, ***p < 0.001
Mentions: We further examined and compared gene expression in islets from individuals with and without type 2 diabetes using RT-qPCR analysis (Fig. 1). The highest level of expression was obtained for the genes for α1, α2, β3, γ2, π and ρ2 GABAA channel subunits in islets from normoglycaemic individuals (n = 14). In islets from type 2 diabetic donors, the α1, α2, β2 and β3 GABAA subunits were significantly downregulated (Fig. 1a). The other genes in the GABA signalling cascade (Fig. 1b) were all similarly expressed and did not differ significantly between islets from individuals with type 2 diabetes and those from normoglycaemic donors. We further examined whether we could detect downregulation of genes in the islets from hyperglycaemic donors (not diagnosed with type 2 diabetes; n = 6). Only the α2 GABAA channel subunit was significantly downregulated in islets from hyperglycaemic individuals compared with normoglycaemic individuals (Fig. 1c, α1, p = 0.127; β2, p = 0.536; β3, p = 0.386).Fig. 1

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