Role of Ca2+ in impaired insulin release from islets of diabetic (C57BL/KsJ-db/db) mice

1980 ◽  
Vol 239 (2) ◽  
pp. E132-E138
Author(s):  
E. G. Siegel ◽  
C. B. Wollheim ◽  
G. W. Sharp ◽  
L. Herberg ◽  
A. E. Renold
Keyword(s):  
Tissue Culture ◽  
Beta Cell ◽  
Insulin Release ◽  
Glucose Concentration ◽  
Insulin Response ◽  
Isolated Islets ◽  
Diabetic Mice ◽  
Impaired Insulin ◽  
Insulin Response To Glucose

The involvement of Ca2+ in the impaired insulin release of diabetic C57BL/KsJ-db/db mice was studied. Twenty-week-old severely hyperglycemic mice were compared to nondiabetic C57BL/KsJ mice as controls. Collagenase-isolated islets were maintained for 46 h in tissue culture allowing for equilibration at the same glucose concentration (8.3) mM). The insulin content of both types of islets was similar. In control islets preloaded during culture with 45Ca2+ glucose-induced insulin release was associated with increased 45Ca2+ effux. Islets from diabetic mice showed markedly reduced insulin response to glucose and a smaller increase in 45Ca2+ efflux. Because insulin release was strikingly potentiated by 3-isobutyl-1-methylxanthine (IBMX), even more than in control islets, there was no generalized release defect. In both types of islets, IBMX potentiation was accompanied by a further enhanced 45Ca2+ efflux, possibly suggesting that cAMP effects are associated with increased cytosol Ca2+% concentrations. As Ca2+ uptake was stimulated by glucose in both types of islets, a defect may lie in the mechanism by which glucose uses cellulr calcium to raise cytosol Ca2+ in the beta-cell of these diabetic mice.

Effects of starvation on oxidative metabolism and insulin release by isolated mouse pancreatic islets

1982 ◽  
Vol 101 (2) ◽  
pp. 227-234 ◽  
Author(s):  
Michael Welsh ◽  
Arne Andersson
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
Oxidative Metabolism ◽  
Oxidation Rate ◽  
Insulin Response ◽  
Leucine Oxidation ◽  
Oxidation Rates ◽  
Impaired Insulin ◽  
Mouse Pancreatic Islets ◽  
Insulin Response To Glucose

Abstract. Pancreatic islets were isolated from either 60-h-starved or fed mice and subsequently incubated in order to determine the insulin release in response to various secretagogues, rates of glucose, leucine or glutamine oxidation or the acetoacetate production from leucine. It was found that in contrast to findings with islets isolated from fed mice 16.7 mm glucose, 10 mM leucine and 10 mm α-ketoisocaproic acid did not stimulate the insulin release of islets isolated from starved mice. Moreover, the insulin release in response to leucine plus glutamine or glucose plus glutamine was decreased after starvation although these values were higher than those obtained for glutamine addition alone. Theophylline, however, restored partly the impaired insulin response to glucose and completely that to leucine or α-ketoisocaproic acid. Starvation was found to inhibit the islet glucose oxidation rate but the addition of theophylline was without effect irrespective of whether the islets were prepared from fed or starved mice. On the contrary, islet leucine oxidation was increased after starvation and again theophylline did not affect the islet leucine oxidation rate. Likewise, the islet acetoacetate production was increased after starvation. The glutamine oxidation rates were not affected by starvation, either when tested alone or together with glucose or leucine. It is concluded that although the starvation-induced impairment of glucose-stimulated insulin release may well be explained by an influence on the oxidative metabolism other factors are also involved as regards leucine-stimulated insulin release.

Regulation of avian insulin secretion by isolated perfused chicken pancreas

1976 ◽  
Vol 231 (6) ◽  
pp. 1830-1839 ◽  
Author(s):  
DL King ◽  
RL Hazelwood
Keyword(s):  
Insulin Secretion ◽  
Beta Cell ◽  
Insulin Release ◽  
Transient Response ◽  
Glucose Concentration ◽  
Insulin Response ◽  
Secretory Rate ◽  
Insulin Responses ◽  
Chicken Pancreas

Chicken insulin secretory responses to glucose, glucagon, tolbutamide, and lack of Mg2+ were measured using isolated perfused in situ chicken pancreata. Although elevating perfusate glucose concentration from 100 to 250 mg/100 ml failed to increase insulin release, 500 mg glucose/100 ml provoked a transient 5-min insulin response. Additionally, 700 mg glucose/100 ml resulted in both a transient response and subsequent elevation in secretory rate that continued throughout the following 50-min stimulatory period. Glucagon (500 microgram/ml) and omission of perfusate Mg2+ potentiated glucose-stimulated insulin output by 6 and 25%, respectively. A faster release of insulin (less than 1 min) occurred during tolbutamide infusion (0.13 mg/ml) than with either 500 or 700 mg glucose per 100 ml (2-3 min); however, secretory rates declined to near basal levels within 5 min. Mammalian-like insulin responses to glucose, glucagon, Mg2+ lack, and tolbutamide suggest similarities between avian and mammalian beta-cell insulin secretory mechanisms. Nevertheless, the relatively high chicken insulin release threshold and low insulin output to glucose indicate that chicken pancreata are relatively glucose insensitive.

scholarly journals Defective Glucose-Stimulated Insulin Release in the Diabetic Goto-Kakizaki (GK) Rat Coincides with Reduced Activity of the Islet Carbon Monoxide Signaling Pathway

Endocrinology ◽  
2005 ◽  
Vol 146 (3) ◽  
pp. 1553-1558 ◽  
Author(s):  
Henrik Mosén ◽  
Albert Salehi ◽  
Per Alm ◽  
Ragnar Henningsson ◽  
Javier Jimenez-Feltström ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Signaling Pathway ◽  
Insulin Release ◽  
Insulin Response ◽  
Isolated Islets ◽  
Compensatory Mechanism ◽  
Gk Rat ◽  
Β Cell ◽  
Glucose Signaling ◽  
Insulin Response To Glucose

The Goto-Kakizaki (GK) rat displays a markedly reduced insulin response to glucose, a defect that is thought to be coupled to an impaired glucose signaling in the β-cell. We have examined whether carbon monoxide (CO), derived from β-cell heme oxygenase (HO), might be involved in the secretory dysfunction. Immunocytochemical labeling of constitutive HO (HO-2) showed no overt difference in fluorescence pattern in islets from GK vs. Wistar controls. However, isolated islets from GK rats displayed a markedly impaired HO activity measured as CO production (−50%), and immunoblotting revealed an approximately 50% reduction of HO-2 protein expression compared with Wistar controls. Furthermore, there was a prominent expression of inducible HO (HO-1) in GK islets. Incubation of isolated islets showed that the glucose-stimulated CO production and the glucose-stimulated insulin response were considerably reduced in GK islets compared with Wistar islets. Addition of the HO activator hemin or gaseous CO to the incubation media brought about a similar amplification of glucose-stimulated insulin release in GK and Wistar islets, suggesting that distal steps in the HO-CO signaling pathway were not appreciably affected. We conclude that the defective insulin response to glucose in the GK rat can be explained, at least in part, by a marked impairment of the glucose-HO-CO signaling pathway as manifested by a prominent decrease in glucose stimulation of islet CO production and a reduced expression of HO-2. A possible role of HO-1 expression as a compensatory mechanism in the GK islets is presently unclear.

scholarly journals Long-term effects of glucose on insulin release and glucose oxidation by mouse pancreatic islets maintained in tissue culture

1974 ◽  
Vol 140 (3) ◽  
pp. 377-382 ◽  
Author(s):  
Arne Andersson
Keyword(s):  
Tissue Culture ◽  
B Cells ◽  
Pancreatic Islets ◽  
Insulin Release ◽  
High Glucose ◽  
Glucose Concentration ◽  
Glucose Oxidation ◽  
Extracellular Glucose Concentration ◽  
Extracellular Glucose ◽  
Mouse Pancreatic Islets

Rates of glucose oxidation and insulin release in response to a wide range of glucose concentrations were studied in short-term experiments in isolated mouse pancreatic islets maintained in tissue culture for 6 days at either a physiological glucose concentration (6.7mm) or at a high glucose concentration (28mm). The curves relating glucose oxidation or insulin release to the extracellular glucose concentration obtained with islets cultured in 6.7mm-glucose displayed a sigmoid shape similar to that observed for freshly isolated non-cultured islets. By contrast islets that had been cultured in 28mm-glucose showed a linear relationship between the rate of glucose oxidation and the extracellular glucose concentration up to about 8mm-glucose. The maximal oxidative rate was twice that of the non-cultured islets and the glucose concentration associated with the half-maximal rate considerably decreased. In islets cultured at 28mm-glucose there was only a small increase in the insulin release in response to glucose, probably due to a depletion of stored insulin in those B cells that had been cultured in a high-glucose medium. It is concluded that exposure of B cells for 6 days to a glucose concentration comparable with that found in diabetic individuals causes adaptive metabolic alterations rather than degeneration of these cells.

Prevalence of Diabetes-associated Antibodies and Impaired Insulin Response to Glucose in First Degree Relatives of Diabetic Patients

2006 ◽  
Vol 6 (2) ◽  
pp. 139-148
Author(s):  
Ebtissam M. Salah ◽  
Hesham El-Hafnawy . ◽  
Mona Anwar M. . ◽  
Samar M.E. Salem . ◽  
Mai M. Youssef . ◽  
...  
Keyword(s):  
Insulin Response ◽  
Diabetic Patients ◽  
First Degree Relatives ◽  
Impaired Insulin ◽  
Insulin Response To Glucose

POTENTIATION OF INSULIN RELEASE BY GLUCOSE IN MAN

1975 ◽  
Vol 79 (3) ◽  
pp. 502-510 ◽  
Author(s):  
Erol Cerasi
Keyword(s):  
Glucose Metabolism ◽  
Adenylate Cyclase ◽  
Beta Cell ◽  
Insulin Release ◽  
Insulin Response ◽  
Glucose Infusion ◽  
Insulin Responses

ABSTRACT If two consecutive glucose infusions are administered with 40 min of rest between, the insulin response to the second challenge is markedly potentiated. When the insulin response to the first glucose infusion was suppressed by 65 % with the aid of adrenaline, potentiation of the insulin response to the second infusion was not modified. This suggests that the generation of a state of enhancement in the islet does not necessitate that glucose exerts its insulin releasing action. It is postulated that islet glucose metabolism may be involved in producing the potentiation. Pretreatment of the subjects with a glucose infusion enhanced also the insulin responses to glucagon and to tolbutamide, given intravenously 50 min later. Thus, the potentiation generated by glucose is not restricted to the insulinogenic signal induced by glucose. The eventual role that the beta-cell adenylate cyclase may play in this respect is discussed.

Effect of fatty acids on insulin release: role of chain length and degree of unsaturation

1994 ◽  
Vol 266 (4) ◽  
pp. E635-E639 ◽  
Author(s):  
E. C. Opara ◽  
M. Garfinkel ◽  
V. S. Hubbard ◽  
W. M. Burch ◽  
O. E. Akwari
Keyword(s):  
Fatty Acids ◽  
Insulin Secretion ◽  
Fatty Acid ◽  
Insulin Release ◽  
Glucose Concentration ◽  
Basal Insulin ◽  
Degree Of Unsaturation ◽  
Structural Differences ◽  
Basal Insulin Secretion

The purpose of the present study was to examine the role played by structural differences among fatty acids in their effect on insulin secretion by isolated perifused murine islets. Insulin secretion measured by radioimmunoassay was assessed either as total insulin output (ng.6 islets-1.20 min-1) or as percent of basal insulin secretion. Raising the glucose concentration from a basal 5.5 to 27.7 mM caused an increase of insulin output from 6.69 +/- 1.59 to 19.92 +/- 4.99 ng.6 islets-1.20 min-1 (P < 0.05) in control (untreated) islets. However, after 20-min exposure of islets to 5 mM 16:0 or 18:2, the effect of 27.7 mM glucose was enhanced or diminished, respectively. Basal insulin output (100% basal) changed to 44 +/- 10% basal (P < 0.005) with the addition of 5 mM 4:0 but was not altered when 4:0 was replaced by 6:0. Insulin output increased modestly with 5 mM 8:0 but significantly (P < 0.05) with 10:0 until a maximal of 280 +/- 24% basal with 12:0 (P < 0.01), then fell to 110 +/- 18 and 93 +/- 15% basal (P < 0.05) with 14:0 and 16:0, respectively. The addition of 5 mM 18:0 inhibited insulin secretion to 30 +/- 10% of basal (P < 0.003), and this effect was not caused by fatty acid interference with insulin assay.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Glucose Tolerance and Insulin Release in Malnourished Rats

1976 ◽  
Vol 50 (3) ◽  
pp. 153-163 ◽  
Author(s):  
C. Weinkove ◽  
E. A. Weinkove ◽  
B. L. Pimstone
Keyword(s):  
Blood Glucose ◽  
Glucose Tolerance ◽  
Insulin Release ◽  
Glucose Concentration ◽  
Plasma Insulin ◽  
Blood Glucose Concentration ◽  
Protein Energy Malnutrition ◽  
Insulin Response ◽  
Intravenous Glucose ◽  
Protein Energy

1. Young Wistar rats were used as an experimental model to determine the effects of protein-energy malnutrition on glucose tolerance and insulin release. 2. Malnourished rats presented some of the features commonly found in human protein-energy malnutrition, such as failure to gain weight, hypoalbuminaemia, fatty infiltration of the liver and intolerance of oral and intravenous glucose loads. 3. The rate of disappearance of glucose from the gut lumen was greater in the malnourished rats but there was no significant difference in portal blood glucose concentration between normal and malnourished rats 5 and 10 min after an oral glucose load. 4. Insulin resistance was not thought to be the cause of the glucose intolerance in the malnourished animals since these rats had a low fasting plasma insulin concentration with a normal fasting blood glucose concentration and no impairment in their hypoglycaemic response to exogenous insulin administration. Furthermore, fasting malnourished rats were unable to correct the insulin-induced hypoglycaemia despite high concentrations of hepatic glycogen. 5. Malnourished rats had lower peak plasma insulin concentrations than normal control animals after provocation with oral and intravenous glucose, intravenous tolbutamide and intravenous glucose plus aminophyllin. This was not due to a reduction in the insulin content of the pancreas or potassium deficiency. Healthy weanling rats, like the older malnourished rats, had a diminished insulin response to intravenous glucose and intravenous tolbutamide. However, their insulin response to stimulation with intravenous glucose plus aminophyllin far exceeded that of the malnourished rats. Thus the impairment of insulin release demonstrated in the malnourished rats cannot be ascribed to a ‘functional immaturity’ of the pancreas.

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