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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate further the role of cytokines in the pathogenesis of type I insulin-dependent diabetes mellitus, the effects of interleukin-1 beta (IL-1), tumour necrosis factor-alpha (TNF) and gamma-interferon (IFN) were tested on rat insulinoma INS-1 cells. Whereas TNF and IFN had, respectively, a minor or no effect on insulin production, IL-1 caused a time- and dose-dependent decrease in insulin release and lowered the insulin content as well as the preproinsulin mRNA content of INS-1 cells. Both IL-1 and TNF exerted a cytostatic effect, estimated by a decrease in [3H]thymidine incorporation, while only IL-1 decreased cell viability as measured by the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test. The glutathione content of INS-1 cells was shown to be modulated by the presence of 2-mercaptoethanol in the culture medium, but was not affected by IL-1 or TNF. In conclusion, INS-1 cell culture is considered to be a useful model for studying the effect of cytokines on insulin-producing cells. The differentiated features of these cells will permit several questions to be addressed regarding the mechanism of action of IL-1 and eventually other cytokines, both at the level of gene expression and of intracellular signalling.
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PMID:Effects of cytokines on rat insulinoma INS-1 cells. 173 60

Normal insulin secretion is oscillatory in vivo, and the oscillations are impaired in type II diabetes. We and others have shown oscillations in insulin secretion from isolated perifused islets stimulated with glucose, and in this study we show oscillations in insulin secretion from the glucose-sensitive clonal beta-cell line INS-1. We have proposed that the oscillatory insulin secretion may be caused by spontaneous oscillations of glycolysis and the ATP:ADP ratio in the beta-cell, analogous to those seen in glycolyzing muscle extracts. The mechanism of the latter involves autocatalytic activation of the key regulatory enzyme, phosphofructokinase (PFK), by its product fructose 1,6-bisphosphate (F16BP). However, of the three PFK subunit isoforms (M-[muscle], L-[liver], and C-type, predominant in fibroblasts), only M-type is activated by micromolar F16BP at near-physiological conditions. We therefore studied PFK isoforms in the beta-cell. Western analysis of PFK subunits in isolated rat islets and INS-1 cells showed the presence of M-type, as well as C-type and perhaps lesser amounts of L-type. Kinetic studies of PFK activity in INS-1 cell extracts showed strong activation by micromolar concentrations of F16BP at near-physiological concentrations of ATP (several millimolar) and AMP and fructose 6-phosphate (micromolar), indicative of the M-type isoform. Activation by submicromolar concentrations of fructose 2,6-bisphosphate (F26BP) and potent inhibition by citrate were also observed. The F16BP-stimulatable activity was about one-half of the F26BP-stimulatable activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1995 Nov
PMID:Phosphofructokinase isozymes in pancreatic islets and clonal beta-cells (INS-1). 758 25

Glucose is the main physiological regulator of insulin biosynthesis and secretion. To exert an effect on biosynthesis, stimulatory concentrations of glucose act on insulin gene expression at both transcriptional and posttranscriptional levels. The relative importance of these two effects is controversial. Studies on the effect of decreasing glucose concentrations in vitro have been contradictory as to its rapidity and magnitude. We have investigated whether a decrease in glucose concentrations from a stimulatory (11 mM) to a nonstimulatory (2 mM) level regulates insulin gene expression in both isolated rat islets and INS-1 cells, an insulinoma-derived cell line that retains a number of the differentiation characteristics of native beta-cells. We show that, in the presence of a nonstimulatory concentration of glucose, insulin mRNA levels decrease rapidly in both rat islets and INS-1 cells. Low glucose decreases insulin gene expression at the transcriptional level, and this effect is mediated by DNA sequences present within 254 base pairs of the 5'-flank of the rat insulin I gene. We conclude that lowering glucose from 11 to 2 mM decreases insulin mRNA rapidly by a transcriptional effect.
Diabetes 1994 Apr
PMID:Insulin gene transcription is decreased rapidly by lowering glucose concentrations in rat islet cells. 813 56

Previous data demonstrated that one rat insulinoma cell line, RINm5F cells, which is a rat beta-cell line derived from a pancreatic tumor, express mRNA coding for both the low- and the high-affinity nerve growth factor receptors. Goals of this study were to extend our data to other beta-cell lines and fetal islets in primary culture and to study further the binding characteristics of nerve growth factor receptors on beta-cells. Northern blot analysis revealed that not only a panel of endocrine beta-cell lines (RINm5F, INS-1, beta-TC3) but also fetal rat islets in primary culture express mRNA coding for trk-A, which has been proposed to be the neuronal high-affinity nerve growth factor receptors. Reverse polymerase chain reaction followed by sequencing revealed that the sequence of trk-A receptor in RINm5F cells is identical to that of trk-A expressed in PC12 cells. The expression of the low-affinity nerve growth factor receptor was examined by Northern blot analysis that showed low-affinity nerve growth factor receptor to be expressed in RINm5F and INS-1 cell lines, in fetal rat islets in primary culture, but not in beta-TC3-cells. Binding experiments revealed the presence of low- and high-affinity nerve growth factor binding sites, identical to those described for PC12 cells, on RINm5F and INS-1 cells and only high-affinity binding sites on beta-TC3 cells. Exposure of all three beta-cell lines to nerve growth factor increased NGFI-A and c-fos mRNA steady-state levels, showing that these receptors are functional.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1993 Dec
PMID:Expression of functional nerve growth factor receptors in pancreatic beta-cell lines and fetal rat islets in primary culture. 824 29

Recent studies suggest that TNF-alpha affects various biochemical and physiological processes which may be linked to the etiology of non-insulin-dependent diabetes mellitus (NIDDM). For example, TNF-alpha interferes with the signaling of the insulin receptor and the metabolism of glucose transporters. The possibility that TNF-alpha might directly reduce glucose-stimulated insulin secretion in pancreatic beta-cells was examined by using an established pancreatic beta-cell line (INS-1). TNF-alpha did not affect glucose-induced acute insulin secretion (30 min). However, over a longer time period (24 h), TNF-alpha decreased glucose-induced insulin secretion without affecting the total amount of insulin in the cell. In the presence of TNF-alpha levels of 0, 10, 100 and 1000 U/ml, the respective 20 mM glucose-induced insulin secretion was 1.736 +/- 0.166, 1.750 +/- 0.302, 1.550 +/- 0.200, and 1.400 +/- 0.112 mU/ml per 3 x 10(5) cells in 24 h.
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PMID:TNF-alpha inhibits glucose-induced insulin secretion in a pancreatic beta-cell line (INS-1). 854 58

The use of primary beta-cells in biochemical and molecular research is limited by the availability of pancreatic endocrine tissue. Numerous investigators have attempted to establish an insulin-secreting cell line that retains normal regulation of insulin secretion. Different approaches have been used, including induction of pancreatic tumors by irradiation or viral infection, immortalization of beta-cells in vitro, and development of transgenic mice with targeted expression of a recombinant oncogene in the beta-cell. Few of these attempts have proven successful, because cell differentiation and proliferation capacities are mutually exclusive. The most widely used insulin-secreting cell lines are RIN, HIT, beta TC, MIN6 and INS-1 cells. These cells contain mainly insulin and small amounts of glucagon and somatostatin. RIN cells, except for the subclone RIN-38, are not glucose-responsive. HIT cells and beta TC cells secrete insulin in response to glucose, but their dose-response curve is markedly shifted to the left MIN6, INS-1 and a newly available subclone of beta TC cells (beta TC-6 F7) are reported to retain normal regulation of glucose-induced insulin secretion. Although the behaviour of none of these cell lines perfectly mimics primary beta-cell physiology, they are extremely valuable tools for the study of molecular events underlying beta-cell function and dysfunction. In addition, insulin-secreting cell lines represent a potential source of transplantable tissue to overcome the limited availability of primary islets for this procedure.
Diabetes Metab 1996 Feb
PMID:Insulin-secreting cell lines: classification, characteristics and potential applications. 869 99

The ability of beta cells to endure assaults by various environmental agents, including toxins and viruses, may be relevant to the development of diabetes. We have examined the mode of cell death caused by streptozotocin (STZ) in a murine pancreatic beta cell line, INS-1. Apoptosis was identified by detection of initial endonuclease-mediated DNA strand breaks by DNA gel electrophoresis. Apoptosis and necrosis were distinguished morphologically by light and electron microscopy. Higher rates of apoptosis, as compared to necrosis, were observed when cells were exposed to 15 mM STZ for 1 hr followed by a 24 hrs recovery period. Higher doses of STZ (30 mM) caused the cells to undergo necrosis (22%) as well as apoptosis (17%). These results suggest that the cytotoxic effect of STZ, at low doses, on beta cells involves the activation of the apoptotic pathway, whereas, at high doses, the mode of beta cell death is predominantly necrosis.
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PMID:Streptozotocin at low doses induces apoptosis and at high doses causes necrosis in a murine pancreatic beta cell line, INS-1. 887 77

Interleukin-1beta (IL-1beta) has been shown to inhibit glucose-induced insulin secretion from rat islets and purified beta-cells, primarily through the generation of nitric oxide (NO). However, the mechanisms by which NO exerts its effects remain unclear. To examine the role of purine nucleotides, we cultured intact rat islets or INS-1 (glucose-responsive transformed rat) beta-cells for 18 h in the presence or absence of IL-1beta. In islets, the exposure to IL-1beta (100 pmol/l) inhibited subsequent glucose-induced insulin secretion by 91% with no significant effect on insulin content or basal insulin release. IL-1beta also diminished insulin secretion induced by pure mitochondrial fuels, 40 mmol/l K+, or a phorbol ester. Concomitantly, IL-1beta significantly decreased islet ATP (-45%), GTP (-33%), ATP/ADP (-54%), and GTP/GDP (-46%). These effects were totally reversed by provision of N(omega)-nitro-L-arginine methyl ester (NAME) in arginine-free media that inhibited NO production. In contrast, in INS-1 cells, IL-1beta (10 or 100 pmol/l) reduced both basal and glucose-induced insulin secretion by 50%, but insulin content was also reduced by 35%. Therefore, the INS-1 cells were still able to respond to glucose stimulation with a 1.8-2.0-fold increase in insulin release in either the presence or absence of IL-1beta. Concomitantly, in INS-1 cells, IL-1beta had no effect on ATP/ADP or GTP/GDP ratios, although it modestly decreased ATP (-25%) and GTP (-22%). As in islets, all effects of IL-1beta in INS-1 cells were prevented by NAME. Thus, in rat islets, IL-1beta (via the generation of NO) abolishes insulin exocytosis in association with large decreases in the ATP/ADP (and GTP/GDP) ratio, implying the impairment of mitochondrial function. Furthermore, IL-1beta inhibits cytosolic synthesis of new purine nucleotides (via the salvage pathway), as assessed by a decrease in their specific activity after labeling with [3H]hypoxanthine. In contrast, in INS-1 cells, IL-1beta appears to impair cytosolic synthesis of purine nucleotides and insulin biosynthesis selectively (both possibly reflecting decreased glycolysis) with little direct effect on insulin exocytosis itself.
Diabetes 1996 Dec
PMID:Dual functional effects of interleukin-1beta on purine nucleotides and insulin secretion in rat islets and INS-1 cells. 892 66

The mechanism whereby long-term exposure of the beta-cell to fatty acids alters the beta-cell response to glucose is not known. We hypothesized that fatty acids may alter beta-cell function by changing the expression level of metabolic enzymes implicated in the regulation of insulin secretion, in particular acetyl-CoA carboxylase (ACC). This enzyme catalyzes the formation of malonyl-CoA, a key regulator of fatty acid oxidation. Using the beta-cell line INS-1 as a model, the results show that the polyunsaturated fatty acid linoleate (C18:2) inhibited both basal and glucose-stimulated ACC mRNA induction. The inhibition was detected by 4-6 h, and a maximal 60% effect occurred at 12 h after cell exposure to the fatty acid. Linoleate, as glucose, did not modify the half-life of the ACC transcript. Prolonged exposure of INS-1 cells to linoleate also inhibited ACC protein accumulation at low and high glucose. The saturated fatty acids myristate (C14:0), palmitate (C16:0), and stearate (C18:0) were also effective as well as the monounsaturated oleate (C18:1) and the short-chain fatty acids butyrate (C4:0) and caproate (C6:0); long-chain omega3 fatty acids were ineffective. The threshold concentration for long-chain fatty acids was 0.05 mmol/l, and maximal inhibition occurred at 0.3 mmol/l. 2-bromopalmitate, a nonmetabolizable analog, had no effect, suggesting that fatty acids must be metabolized to change ACC gene expression. Prolonged exposure of INS-1 cells to palmitate, oleate, and linoleate markedly altered the glucose-induced insulin response, resulting in high basal insulin release and a suppression of glucose-induced insulin secretion. This was associated with an exaggerated (twofold to threefold) rate of fatty acid oxidation at all tested glucose concentrations. The data provide a possible mechanism to at least partially explain how fatty acids cause beta-cell insensitivity to glucose, i.e., by downregulating ACC with a resulting exaggerated fatty acid oxidation.
Diabetes 1997 Mar
PMID:Long-chain fatty acids inhibit acetyl-CoA carboxylase gene expression in the pancreatic beta-cell line INS-1. 903 94

To study the regulation of growth and differentiated function of insulin-secreting cells, the rat insulinoma cell line INS-1 was cultured in a defined serum-free medium containing prolactin, IGF-I, and triiodothyronine, which was originally reported to maintain insulin secretion of islet cells. Growth and viability, as well as cellular insulin content of INS-1 cells in the defined medium, were comparable to the control cells cultured in the complete medium containing 10% fetal calf serum. However, after a 3-day culture in this medium, insulin secretion in response to glucose, pyruvate, and leucine was markedly blunted compared with the control cells (-78, -68, and -56%, respectively), whereas the response to 30 mmol/l K+ was only slightly decreased. In these cells: 1) nutrient metabolism assessed by tetrazolium salt reduction was reduced in response to pyruvate and leucine, which are mainly metabolized in the mitochondria; 2) oxidation of both [3,4-(14)C]glucose and [1-(14)C]pyruvate was decreased (-22 and -32%, respectively); 3) glucose failed to depolarize the membrane potential, whereas tolbutamide was fully active; 4) video imaging analysis of cytosolic Ca2+ showed a decrease in the population of glucose-responsive cells, while the response to 30 mmol/l K+ was preserved; 5) serum replenishment for 3 days restored glucose-induced insulin secretion. Interestingly, conditioned serum-free medium from rat islets maintained the insulin secretory function of INS-1 cells, although glucagon, somatostatin, and some other factors failed to restore the function. In contrast, conditioned media from HepG2, PC12, and human umbilical vein endothelial cells did not substitute for serum. Thus, the impaired insulin secretion of the cells cultured in the defined medium is best explained by defective mitochondrial metabolism. Islet cells, but not INS-1 cells, produce factors required for normal signal generation by nutrient secretagogues.
Diabetes 1997 Sep
PMID:Glucose-induced insulin secretion in INS-1 cells depends on factors present in fetal calf serum and rat islet-conditioned medium. 928 42


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