Glucokinase in pancreatic B-cells and its inhibition by alloxan

1987 ◽  
Vol 115 (1) ◽  
pp. 21-29 ◽  
Author(s):  
Sigurd Lenzen ◽  
Markus Tiedge ◽  
Uwe Panten
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
B Cell ◽  
Metabolic Flux ◽  
Inhibitory Concentration ◽  
Pancreatic B Cell ◽  
High K ◽  
Pancreatic B Cells ◽  
Low K

Abstract. Characterization of glucokinase in pancreatic B-cells from ob/ob mice and from rat liver revealed identical characteristics. A narrow substrate specificity; high Km values for the two substrates, D-glucose and D-mannose, in the range of 10 and 20 mmol/l, respectively; higher Vmax values for D-glucose than for D-mannose; inhibition of glucokinase activities by D-mannoheptulose and by a specific glucokinase antibody. These characteristics distinguish glucokinase in soluble cytoplasmic fractions of pancreatic B-cells and liver from low Km hexokinases. Alloxan is a pancreatic B-cell cytotoxic agent, which has been widely used as a tool for the elucidation of the mechanisms of insulin secretion, because its inhibitory action on insulin secretion has been presumed to be intimately related to the mechanism of glucose-induced insulin secretion. Alloxan inhibited glucokinase but not hexokinase activity in cytoplasmic fractions of pancreatic B-cells and liver. The half maximal inhibitory concentration of alloxan was 5 μmol/l. Glucokinase activity was protected from alloxan toxicity only by D-glucose and D-mannose; the α anomer of D-glucose provided significantly greater protection than the β anomer. The non-metabolizable sugar 3-0-methyl-D-glucose did not provide protection of glucokinase activity against inhibition by alloxan. Thus, inhibition of pancreatic B-cell glucokinase may contribute to the inhibition of glucose-induced insulin secretion by alloxan. These results support the contention that glucokinase regulates the metabolic flux rate through the glycolytic chain in the pancreatic B-cell and thereby generates the signal for glucose-induced insulin secretion.

3-Ketoglutarate generation in pancreatic B-cell mitochondria regulates insulin secretory action of amino acids and 2-keto acids

1986 ◽  
Vol 6 (2) ◽  
pp. 163-169 ◽  
Author(s):  
S. Lenzen ◽  
W. Schmidt ◽  
I. Rustenbeck ◽  
U. Panten
Keyword(s):  
Amino Acids ◽  
Insulin Secretion ◽  
B Cell ◽  
Common Denominator ◽  
Pancreatic B Cell ◽  
Stimulate Insulin Secretion ◽  
Neutral Amino Acids ◽  
Keto Acids ◽  
Secretory Action ◽  
Pancreatic B Cells

The various neutral amino acids and aliphatic 2-keto acids exhibit differential effects on insulin secretion. The common denominator for all these effects is the 2-ketoglutarate generation in the pancreatic B-cell mitochondria. The neutral amino acids l-leucine and l-norvaline and the aliphatic ketomonocarboxylic acids 2-ketoisocaproate, 2-ketocaproate, 2-ketovalerate, and 2-keto-3-methylvalerate all stimulate insulin secretion and increase 2-ketoglutarate generation in pancreatic B-cell mitochondria through activation of glutamate dehydrogenase and transamination with l-glutamate and l-glutamine, respectively. The neutral amino acids l-valine, l-norleucine, and l-alanine and the aliphatic 2-keto acids 2-ketoisovalerate and pyruvate do not stimulate insulin secretion and do not increase 2-ketoglutarate generation in pancreatic B-cell mitochondria. Inhibition of 2-keto acid induced insulin secretion by l-valine and l-isoleucine is accompanied by reduced 2-ketoglutarate generation in pancreatic B-cell mitochondria. Thus intramitochondrial 2-ketoglutarate generation in pancreatic B-cells may regulate the insulin secretory potency of amino acids and 2-keto acids.

scholarly journals Regulation of glucokinase and GLUT-2 glucose-transporter gene expression in pancreatic B-cells

1991 ◽  
Vol 279 (3) ◽  
pp. 899-901 ◽  
Author(s):  
M Tiedge ◽  
S Lenzen
Keyword(s):  
Insulin Secretion ◽  
B Cells ◽  
B Cell ◽  
Glucose Transporter ◽  
Transcriptional Level ◽  
Signal Recognition ◽  
Transporter Gene ◽  
Physiological Regulation ◽  
Mrna Species ◽  
Pancreatic B Cells

Glucokinase (EC 2.7.1.2) is the signal-recognition enzyme in pancreatic B-cells for initiation of glucose-induced insulin secretion. We show here that both the glucokinase and glucose-transporter GLUT-2 genes are regulated physiologically. Fasting decreased B-cell glucokinase and glucose-transporter GLUT-2 mRNA in pancreatic B-cells as well as in liver, whereas refeeding induced expression of both genes. In pancreatic B-cells a approximately 4.4 kb glucokinase-related mRNA was detectable, in addition to the 2.8 kb form. This approximately 4.4 kb glucokinase transcript was drastically decreased during refeeding. The 2.8 kb mRNA, which is typical for pancreatic B-cells, was accompanied after refeeding by a 2.4 kb mRNA species typical for liver glucokinase. Starvation primarily decreased the 2.8 kb pancreatic B-cell glucokinase mRNA species. The concordant regulation of both genes may represent the basis for the physiological regulation of glucose-induced insulin secretion at a transcriptional level.

Mechanisms of amino acid-induced insulin secretion from the glucose-responsive BRIN-BD11 pancreatic B-cell line

1996 ◽  
Vol 151 (3) ◽  
pp. 349-357 ◽  
Author(s):  
N H McClenaghan ◽  
C R Barnett ◽  
F P M O'Harte ◽  
P R Flatt
Keyword(s):  
Amino Acids ◽  
Insulin Secretion ◽  
Amino Acid ◽  
B Cell ◽  
Cell Line ◽  
Future Research ◽  
Nutrient Regulation ◽  
Pancreatic B Cell ◽  
Voltage Dependent ◽  
Pancreatic B Cells

Abstract The effects of different classes of amino acids known to be transported and utilized by pancreatic B-cells were examined using the novel glucose-responsive pancreatic B-cell line, BRIN-BD11. Amino acids tested included α-aminoisobutyric acid, l-alanine, l-arginine, l-glutamine, glycine, l-leucine, l-lysine, l-proline and l-serine. At non-stimulatory (1·1 mmol/l) glucose, acute incubations with either 1 or 10 mmol/l amino acid evoked 1·3- to 4·7-fold increases of insulin release. Raising glucose to 16·7 mmol/l enhanced the effects of all amino acids except l-glutamine, and increased insulin output at 10 mmol/l compared with 1 mmol/l amino acid. Glyceraldehyde (10 mmol/l) also served to promote 10 mmol/l amino acid-induced insulin secretion with the exceptions of l-arginine, glycine, l-lysine and l-proline. At 16·7 mmol/l glucose, diazoxide (300 μmol/l) significantly decreased the secretory response to all amino acids except l-glutamine. Likewise, verapamil (20 μmol/l) or depletion of extracellular Ca2+ reduced insulin output indicating the importance of Ca2+ influx in the actions of amino acids. These data indicate that BRIN-BD11 cells transport and utilize amino acids, acting in association with glycolysis, K+-ATP channels and/or voltage-dependent Ca2+ channels to promote Ca2+ influx and insulin secretion. The response of BRIN-BD11 cells to glucose and amino acids indicates that this is a useful cell line for future research on the mechanisms of nutrient regulation of insulin secretion. Journal of Endocrinology (1996) 151, 349–357

scholarly journals Evidence for two different types of P2 receptors stimulating insulin secretion from pancreatic B cell

1998 ◽  
Vol 125 (6) ◽  
pp. 1368-1374 ◽  
Author(s):  
P Petit ◽  
D Hillaire-Buys ◽  
M Manteghetti ◽  
S Debrus ◽  
J Chapal ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
B Cell ◽  
P2 Receptors ◽  
Pancreatic B Cell ◽  
Different Types

scholarly journals Characterization of human FDCs reveals regulation of T cells and antigen presentation to B cells

2021 ◽  
Vol 218 (10) ◽  
Author(s):  
Balthasar A. Heesters ◽  
Kyah van Megesen ◽  
Ilhan Tomris ◽  
Robert P. de Vries ◽  
Giuliana Magri ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
Intimate Contact ◽  
Expression Of Genes ◽  
T Cell Regulation ◽  
Native Antigen ◽  
Reticular Cells ◽  
Molecular Patterns

Stromal-derived follicular dendritic cells (FDCs) are essential for germinal centers (GCs), the site where B cells maturate their antibodies. FDCs present native antigen to B cells and maintain a CXCL13 gradient to form the B cell follicle. Yet despite their essential role, the transcriptome of human FDCs remains undefined. Using single-cell RNA sequencing and microarray, we provided the transcriptome of these enigmatic cells as a comprehensive resource. Key genes were validated by flow cytometry and microscopy. Surprisingly, marginal reticular cells (MRCs) rather than FDCs expressed B cell activating factor (BAFF). Furthermore, we found that human FDCs expressed TLR4 and can alter antigen availability in response to pathogen-associated molecular patterns (PAMPs). High expression of PD-L1 and PD-L2 on FDCs activated PD1 on T cells. In addition, we found expression of genes related to T cell regulation, such as HLA-DRA, CD40, and others. These data suggest intimate contact between human FDCs and T cells.

P724Antibody treatment against pathological pancreatic islet amyloid polypeptide (IAPP) aggregates restores endothelial dysfunction in human-IAPP transgenic rats

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
A Taheri ◽  
P Doytcheva ◽  
E Tarasco ◽  
W Gut ◽  
M Engeli ◽  
...  
Keyword(s):  
B Cells ◽  
Endothelial Dysfunction ◽  
Glucose Tolerance ◽  
B Cell ◽  
Aortic Arch ◽  
Islet Amyloid Polypeptide ◽  
Oral Glucose ◽  
Oral Glucose Tolerance ◽  
Islet Amyloid ◽  
Pancreatic B Cells

Abstract Background Islet amyloid polypeptide (IAPP; or amylin) is produced in pancreatic B-cells and co-secreted with insulin in response to nutrients. In insulin resistance and type 2 diabetes (T2D), higher secretion and impaired processing of IAPP results in its aggregation, contributing to amyloid-induced apoptosis of pancreatic B-cells. Insight into IAPP's role in diabetic endothelial dysfunction is scarce. Purpose Rats transgenic for human IAPP (hIAPP), which in contrast to rodent IAPP produces amyloid deposits and contributes to diabetes due to B-cell failure, were studied to understand the mechanisms of endothelial dysfunction in T2D and test the vasoprotective actions of an anti-hIAPP antibody. Methods Male hemizygous transgenic Sprague-Dawley rats with islet B-cell expression of hIAPP (TG) and wild-type (WT) controls were sacrificed at 2, 3, 6- and 9-months age to assess endothelial function. In a second experiment, TG rats received weekly injections of antibody against aggregated hIAPP (3 mg/kg; TG-Ab) from 3–12 months of age; TG and WT controls received PBS. Oral glucose tolerance was assessed before harvesting. At the respective time points (12 mts in exp. 2), thoracic aortic rings were isolated and subjected to ex vivo isometric tension recording. After contraction with norepinephrine (NE 1x10–7 mol/L), cumulative relaxation responses were performed to glucagon-like peptide-1 (GLP-1; 10–12 to 10–6 mol/L) and insulin (10–11 to 10–6 mol/L). Pancreas and aortic arch samples were used for immunostaining of hIAPP antibody engagement. Results GLP-1 and insulin-mediated vasodilation was impaired in 3 month-old TG rats compared to WT. Glucose intolerance appeared in TG rats at 6 months in comparison to WT (p<0.0001), indicating that endothelial dysfunction in TG rats precedes the onset of glucose intolerance. Anti-hIAPP antibody showed selectivity against aggregated IAPP in pancreatic islets, but there was no target engagement in the aortic arch, questioning a pathogenic role of IAPP deposition in the aortic wall. At 12 months, glucose control in TG-Ab rats was improved in comparison to TG control rats (p<0.013). Vasodilatation in TG-Ab rats was restored in response to GLP-1 (35.5% ± 4.6 vs. 16.0% ± 3.1 in TG controls), similar to that of WT rats (35.5% ± 6.5). Vasodilatation in response to insulin (48.9% ± 4.2) was improved in comparison to both TG (29.4% ± 3.0) and WT controls (32.5% ± 5.7) (p<0.0001; 2-way ANOVA, n=6–11 for all groups. Conclusion Early endothelial dysfunction develops in hIAPP rats compared to WT. Endothelial dysfunction is restored by the anti-hIAPP antibody treatment via improved oral glucose tolerance, but it remains unclear whether this effect is due to a local action in the aorta or a secondary effect, e.g. due to a reduction in pancreatic IAPP deposition.

scholarly journals Characterization of marginal zone B cell precursors

2005 ◽  
Vol 202 (9) ◽  
pp. 1225-1234 ◽  
Author(s):  
Bhaskar Srivastava ◽  
William J. Quinn ◽  
Kristin Hazard ◽  
Jan Erikson ◽  
David Allman
Keyword(s):  
B Cells ◽  
B Cell ◽  
Marginal Zone ◽  
Environmental Cues ◽  
Developmental Potential ◽  
B Cell Maturation ◽  
B Cell Precursors ◽  
Follicular B Cells ◽  
Selection Of

Selection of recently formed B cells into the follicular or marginal zone (MZ) compartments is proposed to occur by way of proliferative intermediates expressing high levels of CD21/35 and CD23. However, we show that CD21/35high CD23+ splenocytes are not enriched for proliferative cells, and do not contribute substantially to the generation of follicular B cells. Instead, ontogenic relationships, steady-state labeling kinetics, and adoptive transfer experiments suggest that CD21/35high CD23+ splenocytes serve primarily as precursors for MZ B cells, although their developmental potential seems to be broader and is influenced by environmental cues that are associated with lymphopenia. Furthermore, CD21/35high CD23+ splenocytes share several key functional characteristics with MZ B cells, including their capacity to trap T-independent antigen and a heightened proliferative response to LPS. These observations challenge previous models of peripheral B cell maturation, and suggest that MZ B cells develop by way of CD21/35high CD23+ intermediates.

scholarly journals Antigen-initiated B-lymphocyte differentiation. VIII. Sedimentation velocity and buoyant density characterization of virgin antibody-forming cell progenitors in the adoptive immune response of unprimed CBA mice to 4-hydroxy-3-iodo-5-nitrophenylacetic acid-polymerized bacterial flagellin antigen.

1976 ◽  
Vol 143 (5) ◽  
pp. 1220-1238 ◽  
Author(s):  
J M Fidler ◽  
M C Howard ◽  
K Shortman
Keyword(s):  
B Cells ◽  
Physical Properties ◽  
B Cell ◽  
B Lymphocytes ◽  
Buoyant Density ◽  
Specific Antigen ◽  
Significant Proportion ◽  
Sedimentation Velocity ◽  
Cba Mice

The characteristics of antibody-forming cell (AFC) progenitors lacking previous contact with specific antigen (virgin AFC progenitors) has been studied using sedimentation velocity and buoyant density separation for the investigation of physically distinct B-cell subpopulations. Functional characterization of isolated subsets was made using a quantitative adoptive immune assay for the IgM AFC progenitors responding to the antigen 4-hydroxy-3-iodo-5-nitrophenylacetic acid conjugated polymerized bacterial flagellin. Extensive heterogeneity is present among B lymphocytes, only some subpopulations of which exhibit AFC progenitor function. In the spleen of adult conventional CBA mice, atypically fast sedimenting cells of low buoyant density are active, while typical small B lymphocytes do not appear to be progenitors of IgM AFC. Spleen of adult specific pathogen-free (SPF), germfree, and athymic nude mice give similar results, although a minor population of typical slowly sedimenting dense cells are active in the latter two sources. Adult conventional bone marrow cells are as physically and functionally heterogeneous as splenic B cells, and although a significant proportion of AFC progenitor activity is found among dense, slowly sedimenting cells, most of the activity is among low density, faster sedimenting cells. In contrast to this situation in adult animals, where most of the unprimed AFC progenitors are large, atypical B cells, the spleens of neonatal mice provide a site where virgin AFC progenitors with the physical properties of typical small B lymphocytes are found. While being present in conventional and SPF neonatal spleens, these virgin cells are predominant in 7-day-old germfree mouse spleen. These findings suggest that the newborn virgin B cell is a typical small lymphocyte. However, few cells of this type are found in the adult animal. The unprimed AFC-progenitor population in the adult consists of large, fast sedimenting, low buoyant density, adherent cells, the physical properties of which are characteristic of activated B lymphocytes. It is suggested that these atypical cells are derived from the small newborn virgin B cell by the nonspecific effects of environmental antigenic stimuli.

Diabetes is not associated with a change in the elemental composition of the pancreatic B cell in diabetic C57BL KsJ-db/db mice

1990 ◽  
Vol 10 (2) ◽  
pp. 217-223 ◽  
Author(s):  
Lisa Juntti-Berggren ◽  
Ulf Lindh ◽  
Per-Olof Berggren ◽  
Ove Berglund ◽  
Barbara J. Frankel
Keyword(s):  
B Cells ◽  
B Cell ◽  
Elemental Composition ◽  
Exocrine Pancreas ◽  
X Rays ◽  
Proton Bombardment ◽  
Pancreatic B Cell ◽  
Freeze Dried ◽  
Different Ages ◽  
Onset Of Diabetes

Freeze-dried pancreas sections from 7-, 17-and 27-week-old genetically diabetic (db/db) and normal (±/±) mice were subjected to proton bombardment and the concentrations of 15 elements in B cells and exocrine pancreas were calculated from the characteristic X-rays emitted. In the 7-week-old diabetic animals, B cells contained significantly above-normal levels of Na and S, while exocrine pancreas contained subnormal levels of Ca, and excess Mn. The B cells from the 17-week-old diabetic animals contained subnormal levels of Cu and the exocrine pancreas of the 27-week-old diabetic animals was deficient in Cd. The 7-, 17- and 27-week-old, genetically diabetic (db/db) mice were hyperglycemic, hyperinsulinemic and heavier than age-matched normal (±/±) mice. Although significant changes were found in elemental composition when comparing both B cells and exocrine pancreas at different ages, the changes were not consistent. Therefore, it appears as if the measured elemental changes were random and not related to the onset of diabetes.

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