Protein kinase C activity affects glucose‐induced oscillations in cytoplasmic free Ca<sup>2+</sup> in the pancreatic B‐cell

Kindmark, Henrik; Köhler, Martin; Efendić, Suad; Rorsman, Patrik; Larsson, Olof; Berggren, Per Olof

doi:10.1016/0014-5793(92)80483-w

Cited by 31 publications

(19 citation statements)

References 28 publications

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“…The cells were loaded with 2 μM fura-2/acetoxymethylester (Molecular Probes) for 30 min and mounted on an inverted Zeiss Axiovert epifluorescence microsope connected to a Spex Fluorolog-2 system for dualwavelength excitation fluorimetry. The emissions due to the two excitation wavelengths of 340 and 380 nm were used to calculate the fluorescence ratio 340/380, reflecting changes in [Ca 2+ ] i (17).…”

Section: Methodsmentioning

confidence: 99%

Lowering apolipoprotein CIII delays onset of type 1 diabetes

Holmberg

Refai

Höög

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Serum levels of apolipoprotein CIII (apoCIII) are increased in type 1 diabetic patients, and when β cells are exposed to these diabetic sera, apoptosis occurs, an effect abolished by an antibody against apoCIII. We have investigated the BB rat, an animal model that develops a human-like type 1 diabetes, and found that apoCIII was also increased in sera from prediabetic rats. This increase in apoCIII promoted β-cell death. The endogenous levels of apoCIII were reduced by treating prediabetic animals with an antisense against this apolipoprotein, resulting in a significantly delayed onset of diabetes. ApoCIII thus serves as a diabetogenic factor, and intervention with this apolipoprotein in the prediabetic state can arrest disease progression. These findings suggest apoCIII as a target for the treatment of type 1 diabetes.W e have previously shown that there is a group of patients with type 1 diabetes (T1D) whose sera induce an increased activity of voltage-gated Ca 2+ channels in pancreatic β cells, resulting in increased cytoplasmic free Ca 2+ concentration ([Ca 2+ ] i ) and apoptosis (1). T1D serum was found to contain increased concentrations of apolipoprotein CIII (apoCIII), and we could later demonstrate that this serum factor was responsible for the [Ca 2+ ] i increase and β-cell death in vitro (2). Consequently, the effects of both T1D serum and apoCIII on [Ca 2+ ] i and β-cell death are abolished when β cells are coincubated with an antibody against apoCIII (2).To clarify the extent to which apoCIII is also involved in β-cell death in vivo, we have used the animal model diabetes-prone BB rat (DPBB), which spontaneously, at around the age of 60 d, develops T1D that resembles the human form of the disease (3, 4). Diabetes-resistant BB rats (DRBB) were developed from selective breeding from diabetes-prone (DP) forebears and were used as controls (5).This model gives an opportunity to study the impact of prediabetic interventions to prevent or delay onset of the disease. In this study, three prediabetic age groups (40, 50, and 60 d) were investigated both in vitro and in vivo, and we could demonstrate that lowering the endogenous levels of apoCIII by antisense treatment markedly delayed onset of diabetes. ResultsMorphological and Immunohistochemical Characterization. Qualitative morphological analysis showed that pancreas taken from prediabetic rats at the age of 40 d had a lower number of insulincontaining cells than the age-matched controls. The shape of the islets was round to oval with an intact thin layer of collagen around the islets. No inflammation was seen (Fig. 1A). At the age of 50 d, the number of insulin-containing cells did not differ compared with islets from control rats. Islet shape and border did not differ from control rats. No inflammation was seen (Fig. 1B). At 60 d of age, there was a clear decrease in the number of insulin-positive cells. The shape of the islet was irregular, and in some islets, exocrine cells were found. There was no distinct border between the islets and the surroun...

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Section: Methodsmentioning

confidence: 99%

Lowering apolipoprotein CIII delays onset of type 1 diabetes

Holmberg

Refai

Höög

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…These latter negative effects might simply be quantitatively unimportant or less important under physiological conditions. Another intriguing possibility is that in the context of oscillations in glycolysis, intracellular Ca 2+ and secretion [59,114,123,124,125,126], they may actually contribute to the recovery of resting cytosolic Ca 2+ after its increase, if LC-CoA oscillates out of phase with the ATP:ADP ratio. This scenario would be distinct from the incretin effects of exogenous NEFA which might be more "global" and long-lived.…”

Section: Potential Mediators and Targets Of Lc-coa Estersmentioning

confidence: 99%

Fatty acid metabolism and insulin secretion in pancreatic beta cells

2003

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Increases in glucose or fatty acids affect metabolism via changes in long-chain acyl-CoA formation and chronically elevated fatty acids increase total cellular CoA. Understanding the response of pancreatic beta cells to increased amounts of fuel and the role that altered insulin secretion plays in the development and maintenance of obesity and Type 2 diabetes is important. Data indicate that the activated form of fatty acids acts as an effector molecule in stimulus-secretion coupling. Glucose increases cytosolic long-chain acylCoA because it increases the "switch" compound malonyl-CoA that blocks mitochondrial β-oxidation, thus implementing a shift from fatty acid to glucose oxidation. We present arguments in support of the following: (i) A source of fatty acid either exogenous or endogenous (derived by lipolysis of triglyceride) is necessary to support normal insulin secretion; (ii) a rapid increase of fatty acids potentiates glucose-stimulated secretion by increasing fatty acyl-CoA or complex lipid concentrations that act distally by modulating key enzymes such as protein kinase C or the exocytotic machinery; (iii) a chronic increase of fatty acids enhances basal secretion by the same mechanism, but promotes obesity and a diminished response to stimulatory glucose; (iv) agents which raise cAMP act as incretins, at least in part, by stimulating lipolysis via beta-cell hormone-sensitive lipase activation. Furthermore, increased triglyceride stores can give higher rates of lipolysis and thus influence both basal and stimulated insulin secretion. These points highlight the important roles of NEFA, LC-CoA, and their esterified derivatives in affecting insulin secretion in both normal and pathological states. [Diabetologia (2003[Diabetologia ( ) 46:1297[Diabetologia ( -1312

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“…Metabolism of glucose leads to an increase in the cytosolic ATP/ADP ratio, closure of ATP-dependent K ϩ channels (K ATP channels) 1 in the plasma membrane, and thus depolarization of the ␤-cell (1,2 (3)(4)(5). The detailed regulation of these oscillations at the single cell level is not clear.…”

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Glucose-induced Oscillations in Cytoplasmic Free Ca2+Concentration Precede Oscillations in Mitochondrial Membrane Potential in the Pancreatic β-Cell

Kindmark

Köhler

Brown

et al. 2001

Journal of Biological Chemistry

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Using dual excitation and fixed emission fluorescence microscopy, we were able to measure changes in cytoplasmic free Ca 2؉ concentration ([Ca 2؉ ] i ) and mitochondrial membrane potential simultaneously in the pancreatic ␤-cell. The ␤-cells were exposed to a combination of the Ca 2؉ indicator fura-2/AM and the indicator of mitochondrial membrane potential, rhodamine 123 (Rh123 [Ca 2ϩ ] i in pancreatic ␤-cells using the dye fura-2 (4, 6, 7). Measurements of mitochondrial membrane potential in these cells, using the lipophilic cationic dye rhodamine 123 (Rh123), have also been reported (8). Simultaneous measurements of [Ca 2ϩ ] i and mitochondrial membrane potential in the pancreatic ␤-cell would be of great interest and could provide important information about the possible correlation between mitochondrial responses to glucose stimulation and events at the plasma membrane of the ␤-cell. Such simultaneous measurements have recently been performed in neurons (9, 10) and in mouse ␤-cells (11). To investigate the relationship between mitochondrial membrane potential and [Ca 2ϩ ] i in the ␤-cell, we loaded ␤-cells with fura-2 and Rh123 and applied the method of simultaneous measurements of these two parameters. Our methodological evaluation included an investigation of cellular Rh123 distribution as observed with confocal microscopy. We also estimated the contribution to emitted light from both dyes at the respective excitation wavelength, allowing us to correct for contaminating fluorescence. EXPERIMENTAL PROCEDURESAll reagents were of analytical grade and Millipore water was used. Bovine serum albumin fraction V was from Sigma, collagenase was from Roche Molecular Biochemicals, and fura-2/AM as well as Rh123 were from Molecular Probes Europe BV (Leiden, The Netherlands). Statistical summaries of data are expressed as the mean Ϯ S.E. Where appropriate, the possible statistical significance of differences between two sets of data was tested using Student's t test for unpaired data. In all experimental protocols, ␤-cells from at least three different animals were used, if not otherwise specified.Animals and Preparation of Cells-Adult obese mice (gene symbol ob/ob) of both sexes were obtained from a local colony and starved for 24 h. The animals were killed by decapitation and the islets isolated using a collagenase technique (12). The islets of these mice contain more than 90% ␤-cells (13). A cell suspension was prepared and washed essentially as described previously (14). The cells were suspended in RPMI 1640 culture medium (Flow Laboratories) containing 11 mM glucose supplemented with 10% (v/v) fetal bovine serum, 2 mM Lglutamine, 50 IU/ml penicillin, and 50 g/ml streptomycin (Life Technologies, Inc.). The cell suspension was seeded onto coverslips, and the cells allowed to attach for 2 h and then cultured for up to 3 days in the above medium.Media-The basal medium used for preparation of cells as well as experiments was a HEPES buffer, pH 7.4, with Cl Ϫ as the sole anion (15), containing 3 mM glucose, 1.28 ...

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Protein kinase C activity affects glucose‐induced oscillations in cytoplasmic free Ca²⁺ in the pancreatic B‐cell

Cited by 31 publications

References 28 publications

Lowering apolipoprotein CIII delays onset of type 1 diabetes

Lowering apolipoprotein CIII delays onset of type 1 diabetes

Fatty acid metabolism and insulin secretion in pancreatic beta cells

Glucose-induced Oscillations in Cytoplasmic Free Ca2+Concentration Precede Oscillations in Mitochondrial Membrane Potential in the Pancreatic β-Cell

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Protein kinase C activity affects glucose‐induced oscillations in cytoplasmic free Ca2+ in the pancreatic B‐cell

Cited by 31 publications

References 28 publications

Lowering apolipoprotein CIII delays onset of type 1 diabetes

Lowering apolipoprotein CIII delays onset of type 1 diabetes

Fatty acid metabolism and insulin secretion in pancreatic beta cells

Glucose-induced Oscillations in Cytoplasmic Free Ca2+Concentration Precede Oscillations in Mitochondrial Membrane Potential in the Pancreatic β-Cell

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Protein kinase C activity affects glucose‐induced oscillations in cytoplasmic free Ca²⁺ in the pancreatic B‐cell