scholarly journals Effects of a diabetogenic strain of encephalomyocarditis (EMC) virus on protein synthesis in mouse islets of Langerhans

1990 ◽  
Vol 270 (3) ◽  
pp. 777-781 ◽  
Author(s):  
T Ward ◽  
M J Clemens ◽  
K W Taylor
Keyword(s):  
Protein Synthesis ◽  
Insulin Release ◽  
Post Infection ◽  
Protein Biosynthesis ◽  
Insulin Biosynthesis ◽  
Mrna Levels ◽  
Gapdh Mrna ◽  
Emc Virus ◽  
Insulin Mrna ◽  
Mouse Islets

The effects of a diabetogenic strain of encephalomyocarditis (EMC) virus on total protein and insulin biosynthesis in mouse islets of Langerhans have been studied in tissue culture. In dispersed mouse islets, the rates of protein biosynthesis were assessed by measuring the incorporation of [3H]leucine into proteins. In infected dispersed islets incubated in 20 mM-glucose, both insulin and total protein biosynthesis were decreased at 6 h; only insulin biosynthesis was significantly decreased at 3 h. In whole islets, EMC virus brought about a decrease in glucose-stimulated protein and insulin biosynthesis as early as 2 h after infection without concomitant effects on insulin release. This inhibition of protein biosynthesis was still apparent at 20 h post-infection, at which time insulin release was found to be markedly elevated, and the islet insulin content was moderately decreased. At 44 h post-infection, glucose-induced insulin biosynthesis was preferentially inhibited. Infected islets at this later time point also displayed elevated levels of insulin release, and a marked loss of islet insulin content. When insulin mRNA and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA levels were assessed by dot-blot hybridization using appropriate cDNA probes, levels of insulin mRNA were shown to decrease steadily during the first 20 h of infection, in contrast with the levels of GAPDH mRNA. At 44 h post-infection, both types of mRNA were markedly decreased. It is suggested that there is an initial early ‘shut-off’ of protein synthesis without other detectable changes in islet function. This is followed by a phase where both insulin mRNA levels and insulin synthesis are dramatically decreased.

scholarly journals Effect of interferon and double-stranded RNA on B-cell function in mouse islets of Langerhans

1985 ◽  
Vol 228 (1) ◽  
pp. 87-94 ◽  
Author(s):  
C J Rhodes ◽  
K W Taylor
Keyword(s):  
Insulin Release ◽  
Cell Function ◽  
Protein Biosynthesis ◽  
Insulin Biosynthesis ◽  
Double Stranded Rna ◽  
Mouse Pancreatic Islets ◽  
Mouse Islets ◽  
Stimulation Of ◽  
Slight Inhibition

The direct effects of alpha- and beta-interferons on isolated mouse pancreatic islets were investigated in vitro and found to be similar. After 7 h incubation with interferon concentrations above 350 units/ml, glucose-stimulated (pro)insulin biosynthesis was significantly inhibited, with only a slight inhibition of total protein biosynthesis. Inhibition could be abolished in the additional presence of an anti-interferon antibody. Interferon did not affect insulin release, total insulin content, or glucose oxidation of the islets. The stimulation of (pro)insulin biosynthesis by adenosine, D-glyceraldehyde, mannose, N-acetylglucosamine and leucine was also inhibited by interferon, with no effect on insulin release. At concentrations of dsRNA (double-stranded RNA) said to induce interferon (1-100 micrograms/ml), glucose-stimulated (pro)insulin biosynthesis was inhibited without significantly affecting insulin release. The dsRNA may itself inhibit stimulated (pro)insulin biosynthesis or may function indirectly by the induction of interferon.

Lack of long-term β-cell glucotoxicity in vitro in pancreatic islets isolated from two mouse strains (C57BL/6J; C57BL/KsJ) with different sensitivities of the β-cells to hyperglycaemia in vivo

1993 ◽  
Vol 136 (2) ◽  
pp. 289-296 ◽  
Author(s):  
C. Svensson ◽  
S. Sandler ◽  
C. Hellerström
Keyword(s):  
Insulin Secretion ◽  
Glucose Metabolism ◽  
Pancreatic Islets ◽  
Insulin Release ◽  
Insulin Biosynthesis ◽  
Mouse Strains ◽  
Β Cells ◽  
Insulin Mrna

ABSTRACT Previous studies have shown that 4 weeks after syngeneic transplantation of a suboptimal number of islets into either C57BL/6J (BL/6J) or C57BL/KsJ (BL/KsJ) diabetic mice there is an impaired insulin secretion by the perfused grafts. After normalization of the blood glucose level with a second islet graft, the BL/6J strain showed restored insulin secretion whilst that of the BL/KsJ strain remained impaired. The aim of the present work was to study the effects of glucose on the in-vitro function of islet β-cells from these two mouse strains, with different sensitivities of their β-cells to glucose in vivo. Isolated pancreatic islets from each strain were kept for 1 week in tissue culture at 5·6, 11, 28 or 56 mmol glucose/l and were subsequently analysed with regard to insulin release, (pro)-insulin and total protein biosynthesis, insulin, DNA and insulin mRNA contents and glucose metabolism. Islets from both strains cultured at 28 or 56 mmol glucose/l showed an increased accumulation of insulin in the culture medium and an enhanced glucose-stimulated insulin release compared with corresponding control islets cultured at 11 mmol glucose/l. After culture at either 5·6 or 56 mmol/l, rates of (pro)insulin biosynthesis were decreased in BL/KsJ islets in short-term incubations at 17 mmol glucose/l, whereas islets cultured at 56 mmol glucose/l showed a marked increase at 1·7 mmol glucose/l. In BL/6J islets, the (pro)insulin biosynthesis rates were similar to those of the BL/KsJ islets with one exception, namely that no decrease was observed at 56 mmol glucose/l. Islets of both strains showed a decreased insulin content after culture with 56 mmol glucose/l. Insulin mRNA content was increased in islets cultured in 28 or 56 mmol glucose/l from both mouse strains. Glucose metabolism showed no differences in the rates of glucose oxidation, however, in islets cultured in 56 mmol glucose/l the utilization of glucose was increased in both BL/6J and BL/KsJ animals. There were no differences in DNA content in islets cultured at different glucose concentrations, suggesting no enhancement of cell death. The present study indicates that, irrespective of genetic background, murine β-cells can adapt to very high glucose concentrations in vitro without any obvious signs of so-called glucotoxicity. Previously observed signs of glucotoxicity in vivo in BL/KsJ islets appear not to be related only to glucose but rather to an additional factor in the diabetic environment. Journal of Endocrinology (1993) 136, 289–296

scholarly journals The effect of sugars on (pro)insulin biosynthesis

1978 ◽  
Vol 174 (2) ◽  
pp. 517-526 ◽  
Author(s):  
Stephen J. H. Ashcroft ◽  
Judy Bunce ◽  
Martin Lowry ◽  
Svend E. Hansen ◽  
Carl J. Hedeskov
Keyword(s):  
Cyclic Amp ◽  
Insulin Release ◽  
Total Protein ◽  
Glucose Sensor ◽  
Protein Biosynthesis ◽  
Insulin Biosynthesis ◽  
Site Model ◽  
Low Concentrations ◽  
Glucose Analogues ◽  
Stimulation Of

Rates of incorporation of [4,5-3H]leucine into insulin plus proinsulin, designated ‘(pro)insulin’, and total protein in rat pancreatic islets were measured. Glucose stimulates rates of total protein and (pro)insulin biosynthesis, but (pro)insulin biosynthesis is stimulated preferentially. Mannose and N-acetylglucosamine also stimulate (pro)insulin and total protein biosynthesis; inosine and dihydroxyacetone stimulate (pro)insulin biosynthesis specifically. Fructose does not stimulate (pro)insulin biosynthesis when tested alone, but does so in the presence of low concentrations of glucose, mannose or N-acetylglucosamine. Many glucose analogues do not stimulate (pro)insulin biosynthesis. Mannoheptulose inhibits synthesis of (pro)insulin and total protein stimulated by glucose or mannose but not by dihydroxyacetone, inosine or N-acetylglucosamine; phloretin (9μm) inhibits N-acetylglucosamine-stimulated (pro)insulin biosynthesis preferentially. The data are in agreement with the view that the same glucose-sensor mechanism may control both insulin release and biosynthesis, and ‘substrate-site’ model is suggested. The threshold for stimulation of biosynthesis of (pro)insulin and total protein is lower than that found for glucose-stimulated insulin release; moreover the biosynthetic response to an elevation of glucose concentration is slower than that found for insulin release. The physiological implication of these findings is discussed. Caffeine and isobutylmethylxanthine, at concentrations known to increase islet 3′:5′-cyclic AMP and potentiate glucose-induced insulin release, were without effect on rates of glucose-stimulated (pro)insulin biosynthesis.

Insulin Release and Insulin mRNA Levels in Rat Islets of Langerhans Cultured on Extracellular Matrix

Pancreas ◽  
1996 ◽  
Vol 13 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Riccardo Perfetti ◽  
Terrance E. Henderson ◽  
Yihong Wang ◽  
Chahrzad Montrose-Rafizadeh ◽  
Josephine M. Egan
Keyword(s):  
Extracellular Matrix ◽  
Insulin Release ◽  
Islets Of Langerhans ◽  
Mrna Levels ◽  
Rat Islets ◽  
Insulin Mrna ◽  
Rat Islets Of Langerhans

scholarly journals Polyamines and insulin production in isolated mouse pancreatic islets

1988 ◽  
Vol 252 (3) ◽  
pp. 701-707 ◽  
Author(s):  
N Welsh ◽  
A Sjöholm
Keyword(s):  
Insulin Release ◽  
High Glucose ◽  
Glucose Concentration ◽  
Culture Media ◽  
Protein Biosynthesis ◽  
Insulin Biosynthesis ◽  
Cell Physiology ◽  
High Glucose Concentration ◽  
Insulin Production

The aim of the present study was to evaluate the role of polyamines in the metabolism and insulin production of pancreatic-islet cells. For this purpose islets were prepared from adult mice and used either immediately or after tissue culture. There was a significant decrease in the islet content of spermidine during culture, although the effect was less pronounced in a high glucose concentration. Furthermore, a stimulatory effect of a high glucose concentration, as compared with low guclose, on the content of spermine was observed. To elucidate further the role of polyamaines in beta-cell physiology, the ornithine decarboxylase inhibitors difuoromethylornithine (DFMO) and methylacetylenic putrescine (MAP) and the S-adenosylmethionine decarboxylase inhibitor ethylglyoxal bis(guanylhydrazone) (EGBG) were added to the culture media. Addition of DFMO together with MAP decreased the cellular contents of putrescine and spermidine, whereas the content of sperimine was unaffected. When EGBG was added in combination with DFMO and MAP, there was a decrease in the content of spermine also. Cell viability in the islets depleted of their polyamine contents was not impaired, as assessed by determinations of oxygen-uptake rates and ATP contents. Depletion of putescine plus spermidine by addition of DFMO+MAP was associated with decreased biosynthesis of (pro)insulin and total protein. When the content of spermine was decreased also by the further addition of EGBG, the decrease in (pro) insulin biosynthesis was more pronounced and was paralleled by a decrease in the insulin-mRNA content. Under these conditions, the glucose-stimulated insulin release, the insulin content and the rates of islet DNA synthesis were also decreased. It is concluded that putrescine and spermidine are necessary for the maintenance of normal insulin and protein biosynthesis, whereas spermine may exert a role in some other cellular processes, such as DNA replication, RNA transcription and glucose-stimulated insulin release.

scholarly journals Translational control of insulin biosynthesis. Evidence for regulation of elongation, initiation and signal-recognition-particle-mediated translational arrest by glucose

1986 ◽  
Vol 235 (2) ◽  
pp. 459-467 ◽  
Author(s):  
M Welsh ◽  
N Scherberg ◽  
R Gilmore ◽  
D F Steiner
Keyword(s):  
Protein Synthesis ◽  
Translational Control ◽  
Blot Hybridization ◽  
Signal Recognition Particle ◽  
Chain Elongation ◽  
Insulin Biosynthesis ◽  
Signal Recognition ◽  
Insulin Synthesis ◽  
Run Off ◽  
Insulin Mrna

The biosynthesis of insulin in the islets of Langerhans is strongly controlled at the translational level by glucose. We have used a variety of experimental approaches in efforts to dissect the mechanisms underlying the stimulatory effect of glucose. To assess its effects on rates of peptide-chain elongation, isolated rat islets were labelled with [3H]leucine at different glucose concentrations in the presence or absence of low concentrations of cycloheximide. Under these conditions, at glucose concentrations up to 5.6 mM, endogenous insulin mRNA did not become rate-limiting for the synthesis of insulin, whereas stimulation of non-insulin protein synthesis was abolished by cycloheximide at all glucose concentrations, indicating either that insulin synthesis is selectively regulated at the level of elongation at glucose concentrations up to 5.6 mM, or that at these concentrations inactive insulin mRNA is transferred to an actively translating pool. Glucose-induced changes in the intracellular distribution of insulin mRNA in cultured islets were assessed by subcellular fractionation and blot-hybridization using insulin cDNA probes. At glucose concentrations above 3.3 mM, cytoplasmic insulin mRNA was increasingly transferred to fractions co-sedimenting with ribosomes, and relatively more of the ribosome-associated insulin mRNA became membrane-associated, consistent with effects of glucose above 3.3 mM on both the initiation of insulin mRNA and SRP (signal recognition particle)-mediated transfer of cytosolic nascent preproinsulin to the endoplasmic reticulum. When freshly isolated islets were homogenized and incubated with 125I-Tyr-tRNA, run-off incorporation of 125I into preproinsulin was increased by prior incubation of the islets at 16.7 mM-glucose. The addition of purified SRP receptor increased the run-off incorporation of [125I]iodotyrosine into preproinsulin, especially when the islets had been preincubated at 16.7 mM-glucose. These findings taken together suggest that glucose may stimulate elongation rates of nascent preproinsulin at concentrations up to 5.6 mM, stimulates initiation of protein synthesis involving both insulin and non-insulin mRNA at concentrations above 3.3 mM, and increases the transfer of initiated insulin mRNA molecules from the cytoplasm to microsomal membranes by an SRP-mediated mechanism that involves the modification of interactions between SRP and its receptor.

scholarly journals 1202. Subinhibitory Concentrations of Omadacycline Inhibit Staphylococcus aureus Hemolytic Activity in Vitro

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S622-S623
Author(s):  
Alisa W Serio ◽  
S Ken Tanaka ◽  
Kelly Wright ◽  
Lynne Garrity-Ryan
Keyword(s):  
Staphylococcus Aureus ◽  
Protein Synthesis ◽  
Virulence Factors ◽  
Hemolytic Activity ◽  
Protein Biosynthesis ◽  
The United States ◽  
Aureus Strain ◽  
Protein Synthesis Inhibitors ◽  
Subinhibitory Concentrations

Abstract Background In animal models of Staphylococcus aureus infection, α-hemolysin has been shown to be a key virulence factor. Treatment of S. aureus with subinhibitory levels of protein synthesis inhibitors can decrease α-hemolysin expression. Omadacycline, a novel aminomethylcycline antibiotic in the tetracycline class of bacterial protein biosynthesis inhibitors, is approved in the United States for treatment of community-acquired bacterial pneumonia (CABP) and acute bacterial skin and skin structure infections (ABSSSI) in adults. This study was performed to determine the durability of inhibition and effect of subinhibitory concentrations of omadacycline on S. aureus hemolytic activity. Methods All experiments used the methicillin-sensitive S. aureus strain Wood 46 (ATCC 10832), a laboratory strain known to secrete high levels of α-hemolysin. Minimum inhibitory concentrations (MICs) of omadacycline and comparator antibiotics (tetracycline, cephalothin, clindamycin, vancomycin, linezolid) were determined. Growth of S. aureus with all antibiotics was determined and the percentage of hemolysis assayed. “Washout” experiments were performed with omadacycline only. Results S. aureus cultures treated with 1/2 or 1/4 the MIC of omadacycline for 4 hours showed hemolysis units/108 CFU of 47% and 59% of vehicle-treated cultures, respectively (Fig. 1A, 1B). In washout experiments, treatment with as little as 1/4 the MIC of omadacycline for 1 hour decreased the hemolysis units/108 CFU by 60% for 4 hours following removal of the drug (Table 1). Figure 1 Table 1 Conclusion Omadacycline inhibited S. aureus hemolytic activity in vitro at subinhibitory concentrations and inhibition was maintained for ≥ 4 hours after removal of extracellular drug (Fig. 2). The suppression of virulence factors throughout the approved omadacycline dosing interval, in addition to the in vitro potency of omadacycline, may contribute to the efficacy of omadacycline for ABSSSI and CABP due to virulent S. aureus. This finding may apply to other organisms and other virulence factors that require new protein synthesis to establish disease. Figure 2 Disclosures Alisa W. Serio, PhD, Paratek Pharmaceuticals, Inc. (Employee, Shareholder) S. Ken Tanaka, PhD, Paratek Pharmaceuticals, Inc. (Employee, Shareholder) Kelly Wright, PharmD, Paratek Pharmaceuticals, Inc. (Employee, Shareholder) Lynne Garrity-Ryan, PhD, Paratek Pharmaceuticals, Inc. (Employee, Shareholder)

scholarly journals Vanadate stimulation of insulin release in normal mouse islets.

1991 ◽  
Vol 266 (32) ◽  
pp. 21649-21656
Author(s):  
A.Q. Zhang ◽  
Z.Y. Gao ◽  
P. Gilon ◽  
M. Nenquin ◽  
G. Drews ◽  
...  
Keyword(s):  
Insulin Release ◽  
Normal Mouse ◽  
Mouse Islets ◽  
Stimulation Of
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