共查询到20条相似文献,搜索用时 3 毫秒
1.
Patrik Rorsman Lena Eliasson Takahiro Kanno Quan Zhang Sven Gopel 《Progress in biophysics and molecular biology》2011,107(2):224-235
When exposed to intermediate glucose concentrations (6–16 mol/l), pancreatic β-cells in intact islets generate bursts of action potentials (superimposed on depolarised plateaux) separated by repolarised electrically silent intervals. First described more than 40 years ago, these oscillations have continued to intrigue β-cell electrophysiologists. To date, most studies of β-cell ion channels have been performed on isolated cells maintained in tissue culture (that do not burst). Here we will review the electrophysiological properties of β-cells in intact, freshly isolated, mouse pancreatic islets. We will consider the role of ATP-regulated K+-channels (KATP-channels), small-conductance Ca2+-activated K+-channels and voltage-gated Ca2+-channels in the generation of the bursts. Our data indicate that KATP-channels not only constitute the glucose-regulated resting conductance in the β-cell but also provide a variable K+-conductance that influence the duration of the bursts of action potentials and the silent intervals. We show that inactivation of the voltage-gated Ca2+-current is negligible at voltages corresponding to the plateau potential and consequently unlikely to play a major role in the termination of the burst. Finally, we propose a model for glucose-induced β-cell electrical activity based on observations made in intact pancreatic islets. 相似文献
2.
TRPM2 is a Ca2+-permeable non-selective cation channel that can be activated by adenosine dinucleotides, hydrogen peroxide, or intracellular Ca2+. The protein is expressed in a wide variety of cells, including neurons in the brain, immune cells, endocrine cells, and endothelial cells. This channel is also well expressed in β-cells in the pancreas. Insulin secretion from pancreatic β-cells is the primary mechanism by which the concentration of blood glucose is reduced. Thus, impairment of insulin secretion leads to hyperglycemia and eventually causes diabetes. Glucose is the principal stimulator of insulin secretion. The primary pathway involved in glucose-stimulated insulin secretion is the ATP-sensitive K+ (KATP) channel to voltage-gated Ca2+ channel (VGCC)-mediated pathway. Increases in the intracellular Ca2+ concentration are necessary for insulin secretion, but VGCC is not sufficient to explain [Ca2+]i increases in pancreatic β-cells and the resultant secretion of insulin. In this review, we focus on TRPM2 as a candidate for a [Ca2+]i modulator in pancreatic β-cells and its involvement in insulin secretion and development of diabetes. Although further analyses are needed to clarify the mechanism underlying TRPM2-mediated insulin secretion, TRPM2 could be a key player in the regulation of insulin secretion and could represent a new target for diabetes therapy. 相似文献
3.
4.
Dahlhoff M Grzech M Habermann FA Wolf E Schneider MR 《Genesis (New York, N.Y. : 2000)》2012,50(5):437-442
Transgenic mouse lines expressing Cre recombinase in a cell-specific and tissue-specific manner are essential tools for studying gene function and for developing suitable models for human diseases. Here, we used an expression cassette containing the full 5' untranslated region of the porcine insulin gene to generate a mouse line expressing Cre recombinase specifically in pancreatic β-cells by pronuclear DNA microinjection. We obtained a founder animal that transmitted the construct to its descendants in a Mendelian fashion and whose descendants showed a clear activation of β-galactosidase expression in pancreatic β-cells after crossing into the ROSA26 lacZ reporter mouse line. Cre expression in other organs was negative except for the kidney, intestine, and the cerebral pons where β-galactosidase activity was detected in a small percentage of the cells. This new mouse line is a valuable tool for recombination of floxed alleles in pancreatic β-cells in vivo. 相似文献
5.
Janove Sehlin 《Bioscience reports》1987,7(1):67-72
Microdissected -cell-rich pancreatic islets fromob/ob-mice were used in studies of transmembrane36Cl– efflux. The mean rate coefficient for36Cl– efflux was stable at 0.158 min–1 during the initial 10 min. Depolarization of the -cell plasma membrane by acute increases in extracellular K+ (5–130mM) stimulated the36Cl– efflux in a concentration-dependent manner. Glucose-induced (20mM) and K+-induced increases in36Cl– efflux were largely overlapping, but even at 135.9 mM K+, glucose slightly further enhanced the36Cl– efflux rate. The data suggest (1) that pancreatic -cells are equipped with a voltage-dependent Cl– permeability, (2) that glucose-induced increase in Cl– permeability may, at least partly, be mediated by primary membrane depolarization, and (3) that glucose in addition may activate other mechanisms for -cell Cl– transport. 相似文献
6.
The glucoregulatory hormones insulin and glucagon are released from the β- and α-cells of the pancreatic islets. In both cell types, secretion is secondary to firing of action potentials, Ca(2+)-influx via voltage-gated Ca(2+)-channels, elevation of [Ca(2+)](i) and initiation of Ca(2+)-dependent exocytosis. Here we discuss the mechanisms that underlie the reciprocal regulation of insulin and glucagon secretion by changes in plasma glucose, the roles played by different types of voltage-gated Ca(2+)-channel present in α- and β-cells and the modulation of hormone secretion by Ca(2+)-dependent and -independent processes. We also consider how subtle changes in Ca(2+)-signalling may have profound impact on β-cell performance and increase risk of developing type-2 diabetes. 相似文献
7.
William F. Hopkins Sahba Fatherazi Bettina Peter-Riesch Barbara E. Corkey Daniel L. Cook 《The Journal of membrane biology》1992,129(3):287-295
Summary ATP-inhibited potassium channels (K(ATP)) were studied in excised, inside-out patches from cultured adult mouse pancreatic -cells and HIT cells. In the absence of ATP, ADP opened K(ATP) channels at concentrations as low as 10
m and as high as 500
m, with maximal activation between 10 and 100
m ADP in mouse -cell membrane patches. At concentrations greater than 500
m, ADP inhibited K(ATP) channels while 10 mm virtually abolished channel activity. HIT cell channels had a similar biphasic response to ADP except that more than 1 mm ADP was required for inhibition. The channel opening effect of ADP required magnesium while channel inhibition did not. Using creatine/creatine phosphate solutions with creatine phosphokinase to fix ATP and ADP concentrations, we found substantially different K(ATP)-channel activity with solutions having the same ATP/ADP ratio but different absolute total nucleotide levels. To account for ATP-ADP competition, we propose a new model of channel-nucleotide interactions with two kinds of ADP binding sites regulating the channel. One site specifically binds MgADP and increases channel opening. The other, the previously described ATP site, binds either ATP or ADP and decreases channel opening. This model very closely fits the ADP concentration-response curve and, when incorporated into a model of -cell membrane potential, increasing ADP in the 10 and 100
m range is predicted to compete very effectively with millimolar levels of ATP to hyperpolarize -cells.The results suggest that (i) K(ATP)-channel activity is not well predicted by the ATP/ADP ratio, and (ii) ADP is a plausible regulator of K(ATP) channels even if its free cytoplasmic concentration is in the 10–100
m range as suggested by biochemical studies.We would like to thank Mr. Louis Stamps for expert technical assistance and Dr. Wil Fujimoto and Ms. Jeanette Teague for generously providing HIT cells obtained from Dr. Robert Santerre at Eli Lilly. We would also like to thank Dr. Michel Vivaudou for providing the program ALEX. Support was provided by the NIH and the Department of Veterans Affairs. 相似文献
8.
9.
Ryanodine receptor channel model is introduced to a dynamical model of pancreatic beta-cells to discuss the effects of RyR channels and glucose concentration on membrane potential. The results show Ca(2+) concentration changes responding to enhance of glucose concentration is more quickly than that of activating RyR channels, and both methods can induce bursting action potential and increase free cytosolic Ca(2+) concentration. An interesting finding is that moderate stimulation to RyR channels will result in a kind of "complex bursting", which is more effective in enhancing average Ca(2+) concentration and insulin section. 相似文献
10.
The effects of D-glucose, D-glyceraldehyde, glibenclamide, D-600, NH
4
+
and high concentrations of K+ on cytoplasmic pH (pH
i
) were investigated in dispersed and cultured pancreatic -cells fromob/ob mice. The cytoplasmic pH was measured with the fluorescent H+-indicator quene 1. The average pH
i
value in resting -cells was 6.71. Addition of 20 mM of the physiological stimulus D-glucose increased pH
i
with 0.05 units. Both glibenclamide and high concentrations of K+ decreased pH
i
. The latter effects were completely reversed by D-600, supporting the notion that free cytoplasmic Ca2+ can be involved in the regulation of pH
i
. In contrast to D-glucose, 10mM of D-glyceraldehyde decreased pH
i
by 0.09 units, an effect persisting even in the presence of D-600. From the present study it is evident that D-glyceraldehyde and D-glucose have opposite effects on pH
i
in pancreatic -cells. 相似文献
11.
12.
Chung SS Kim M Lee JS Ahn BY Jung HS Lee HM Park KS 《American journal of physiology. Endocrinology and metabolism》2011,301(5):E912-E921
Thiazolidinediones (TZDs) are synthetic ligands of peroxisome proliferator-activated receptor-γ (PPARγ), a member of the nuclear receptor superfamily. TZDs are known to increase insulin sensitivity and also to have an antioxidative effect. In this study, we tested whether TZDs protect pancreatic β-cells from oxidative stress, and we investigated the mechanism involved in this process. To generate oxidative stress in pancreatic β-cells (INS-1 and βTC3) or isolated islets, glucose oxidase was added to the media. The extracellular and intracellular reactive oxygen species (ROS) were measured to directly determine the antioxidant effect of TZDs. The phosphorylation of JNK/MAPK after oxidative stress was detected by Western blot analysis, and glucose-stimulated insulin secretion and cell viability were also measured. TZDs significantly reduced the ROS levels that were increased by glucose oxidase, and they effectively prevented β-cell dysfunction. The antioxidative effect of TZDs was abolished in the presence of a PPARγ antagonist, GW9662. Real-time PCR was used to investigate the expression levels of antioxidant genes. The expression of catalase, an antioxidant enzyme, was increased by TZDs in pancreatic β-cells, and the knockdown of catalase significantly inhibited the antioxidant effect of TZDs. These results suggest that TZDs effectively protect pancreatic β-cells from oxidative stress, and this effect is dependent largely on PPARγ. In addition, the expression of catalase is increased by TZDs, and catalase, at least in part, mediates the antioxidant effect of TZDs in pancreatic β-cells. 相似文献
13.
Changes in cytosolic free Ca2+ concentration ([Ca2+]c) play a crucial role in the control of insulin secretion from the electrically excitable pancreatic β-cell. Secretion is controlled by the finely tuned balance between Ca2+ influx (mainly through voltage-dependent Ca2+ channels, but also through voltage-independent Ca2+ channels like store-operated channels) and efflux pathways. Changes in [Ca2+]c directly affect [Ca2+] in various organelles including the endoplasmic reticulum (ER), mitochondria, the Golgi apparatus, secretory granules and lysosomes, as imaged using recombinant targeted probes. Because most of these organelles have specific Ca2+ influx and efflux pathways, they mutually influence free [Ca2+] in the others. In this article, we review the mechanisms of control of [Ca2+] in various compartments and particularly the cytosol, the endoplasmic reticulum ([Ca2+]ER), acidic stores and mitochondrial matrix ([Ca2+]mito), focusing chiefly on the most important physiological stimulus of β-cells, glucose. We also briefly review some alterations of β-cell Ca2+ homeostasis in Type 2 diabetes. 相似文献
14.
M. Derenzini C. M. Betts C. Busi L. Fiume 《Virchows Archiv. B, Cell pathology including molecular pathology》1978,28(1):13-20
In mice poisoned by alpha-amanitin nuclear changes typical of this toxin were observed in beta-cells of pancreatic islets. The lesions became progressively more severe and at 48 h after toxin injection some cells were necrotic. The damage to these cells could have implications in the changes in glycogen metabolism which occur after alpha-aminitin poisoning. 相似文献
15.
Takeda Y Amano A Noma A Nakamura Y Fujimoto S Inagaki N 《American journal of physiology. Cell physiology》2011,301(4):C792-C803
Glucagon-like peptide-1 (GLP-1) elevates intracellular concentration of cAMP ([cAMP]) and facilitates glucose-dependent insulin secretion in pancreatic β-cells. There has been much evidence to suggest that multiple key players such as the GLP-1 receptor, G(s) protein, adenylate cyclase (AC), phosphodiesterase (PDE), and intracellular Ca(2+) concentration ([Ca(2+)]) are involved in the regulation of [cAMP]. However, because of complex interactions among these signaling factors, the kinetics of the reaction cascade as well as the activities of ACs and PDEs have not been determined in pancreatic β-cells. We have constructed a minimal mathematical model of GLP-1 receptor signal transduction based on experimental findings obtained mostly in β-cells and insulinoma cell lines. By fitting this theoretical reaction scheme to key experimental records of the GLP-1 response, the parameters determining individual reaction steps were estimated. The model reconstructed satisfactorily the dynamic changes in [cAMP] and predicted the activities of cAMP effectors, protein kinase A (PKA), and cAMP-regulated guanine nucleotide exchange factor [cAMP-GEF or exchange protein directly activated by cAMP (Epac)] during GLP-1 stimulation. The simulations also predicted the presence of two sequential desensitization steps of the GLP1 receptor that occur with fast and very slow reaction rates. The cross talk between glucose- and GLP-1-dependent signal cascades for cAMP synthesis was well reconstructed by integrating the direct regulation of AC and PDE by [Ca(2+)]. To examine robustness of the signaling system in controlling [cAMP], magnitudes of AC and PDE activities were compared in the presence or absence of GLP-1 and/or the PDE inhibitor IBMX.(1). 相似文献
16.
Masashi Yoshida Shiho Yamato Hitoshi Sugawara Masanobu Kawakami Masafumi Kakei 《Biochemical and biophysical research communications》2010,396(2):304-4132
Voltage-gated potassium channels (Kv channels) play a crucial role in formation of action potentials in response to glucose stimulation in pancreatic β-ells. We previously reported that the Kv channel is regulated by glucose metabolism, particularly by MgATP. We examined whether the regulation of Kv channels is voltage-dependent and mechanistically related with phosphorylation of the channels. In rat pancreatic β-cells, suppression of glucose metabolism with low glucose concentrations of 2.8 mM or less or by metabolic inhibitors decreased the Kv2.1-channel activity at positive membrane potentials, while increased it at potentials negative to −10 mV, suggesting that modulation of Kv channels by glucose metabolism is voltage-dependent. Similarly, in HEK293 cells expressing the recombinant Kv2.1 channels, 0 mM but not 10 mM MgATP modulated the channel activity in a manner similar to that in β-cells. Both steady-state activation and inactivation kinetics of the channel were shifted toward the negative potential in association with the voltage-dependent modulation of the channels by cytosolic dialysis of alkaline phosphatase in β-cells. The modulation of Kv-channel current-voltage relations were also observed during and after glucose-stimulated electrical excitation. These results suggest that the cellular metabolism including MgATP production and/or channel phosphorylation/dephosphorylation underlie the physiological modulation of Kv2.1 channels during glucose-induced insulin secretion. 相似文献
17.
《Saudi Journal of Biological Sciences》2021,28(9):5338-5348
Cyanidin-3-glucoside (C3Ghv) compounds were purified and isolated from the anthocyanins extract of Haematocarpus validus. C3Ghv were studied for antioxidant and cytoprotective properties on pancreatic β-cells of rat insulinoma cells (RINm5F) against the oxidative stress induced by streptozotocin (STZ). The exposure of RINm5F cells to C3Ghv at concentration of 100 and 200 μg/mL for 24 h reduced 10% and 23% cell viability, respectively, as compared to control cells. The pre-treatment of RINm5F cells with C3Ghv (50 µg/mL) increased the cell viability by 29% as compared to control, on being treated with STZ (10 mM) for 24 h. The pre-treatment of RINm5F cells with C3Ghv (50 µg/mL) for 24 h followed by exposure to STZ (10 mM) for 1 h decreased the generation of reactive oxygen species (ROS) by 57%, generation of nitric oxide by 22.8%, generation of malondialdehyde (MDA) by 32%, the production of p-ERK ½ by 83%, p-JNK by 82.6%, p-MEK by 57%, and p-p38 MAPK by 64%. The C3Ghv treatment also decreased the ratio of apoptotic proteins Bax to Bcl-2 by 61%, and improved the M2 phase of cell cycle by 75% as compared to STZ treated cells. The overall results suggest that C3Ghv protects pancreatic β-cells against oxidative stress-induced apoptosis, thereby implicating the significant role of C3Ghv as an antidiabetic agent. 相似文献
18.
Deng B 《Journal of mathematical biology》1999,38(1):21-78
In the presence of stimulatory concentrations of glucose, the membrane potential of pancreatic β-cells may experience a transition
from periods of rapid spike-like oscillations alternating with a pseudo-steady state to spike-only oscillations. Insulin secretion
from β-cells closely correlates the periods of spike-like oscillations. The purpose of this paper is to study the mathematical
structure which underlines this transitional stage in a pancreatic β-cell model. It is demonstrated that the transition can
be chaotic but becomes more and more regular with increase in glucose. In particular, the system undergoes a reversed period-doubling
cascade leading to the spike-only oscillations as the glucose concentration crosses a threshold. The transition interval in
glucose concentration is estimated to be extremely small in terms of the rate of change for the calcium dynamics in the β-cells.
The methods are based on the theory of unimodal maps and the geometric and asymptotic theories of singular perturbations.
Received: 25 October 1996/Revised version: 18 August 1997 相似文献
19.
Ropero AB Alonso-Magdalena P Soriano S Juan-Picó P Roepke TA Kelly MJ Nadal Á 《PloS one》2012,7(4):e34650
The non-steroidal compound STX modulates the hypothalamic control of core body temperature and energy homeostasis. The aim of this work was to study the potential effects of STX on pancreatic β-cell function. 1-10 nM STX produced an increase in glucose-induced insulin secretion in isolated islets from male mice, whereas it had no effect in islets from female mice. This insulinotropic effect of STX was abolished by the anti-estrogen ICI 182,780. STX increased intracellular calcium entry in both whole islets and isolated β-cells, and closed the K(ATP) channel, suggesting a direct effect on β-cells. When intraperitoneal glucose tolerance test was performed, a single dose of 100 μg/kg body weight STX improved glucose sensitivity in males, yet it had a slight effect on females. In agreement with the effect on isolated islets, 100 μg/kg dose of STX enhanced the plasma insulin increase in response to a glucose load, while it did not in females. Long-term treatment (100 μg/kg, 6 days) of male mice with STX did not alter body weight, fasting glucose, glucose sensitivity or islet insulin content. Ovariectomized females were insensitive to STX (100 μg/kg), after either an acute administration or a 6-day treatment. This long-term treatment was also ineffective in a mouse model of mild diabetes. Therefore, STX appears to have a gender-specific effect on blood glucose homeostasis, which is only manifested after an acute administration. The insulinotropic effect of STX in pancreatic β-cells is mediated by the closure of the K(ATP) channel and the increase in intracellular calcium concentration. The in vivo improvement in glucose tolerance appears to be mostly due to the enhancement of insulin secretion from β-cells. 相似文献
20.
Type III galactosemia results from reduced activity of the enzyme UDP-galactose 4′-epimerase. Five disease-associated alleles (G90E, V94M, D103G, N34S and L183P) and three artificial alleles (Y105C, N268D, and M284K) were tested for their ability to alleviate galactose-induced growth arrest in a Saccharomyces cerevisiae strain which lacks endogenous UDP-galactose 4′-epimerase. For all of these alleles, except M284K, the ability to alleviate galactose sensitivity was correlated with the UDP-galactose 4′-epimerase activity detected in cell extracts. The M284K allele, however, was able to substantially alleviate galactose sensitivity, but demonstrated near-zero activity in cell extracts. Recombinant expression of the corresponding protein in Escherichia coli resulted in a protein with reduced enzymatic activity and reduced stability towards denaturants in vitro. This lack of stability may result from the introduction of an unpaired positive charge into a bundle of three α-helices near the surface of the protein. The disparities between the in vivo and in vitro data for M284K-hGALE further suggest that there are additional, stabilising factors present in the cell. Taken together, these results reinforce the need for care in the interpretation of in vitro, enzymatic diagnostic tests for type III galactosemia. 相似文献