Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the effect of 24 h of exposure to various glucose concentrations on insulin secretion by isolated rat pancreatic islets and purified rat beta-cells. Compared with islets cultured with standard medium (5.5 mM glucose), islets cultured with 16.7 mM glucose showed a higher basal insulin release (means +/- SE, 3.0 +/- 0.5 vs. 0.7 +/- 0.2%, n = 8, P less than .005) and reduced glucose-stimulated insulin secretion (2.4 +/- 0.3 vs. 5.8 +/- 0.4%, n = 8, P less than .005). Similar results were also obtained with purified beta-cells. The effect of high glucose was time dependent (present after 12 h, maximal after 24 h) and reversible: when islets cultured with high glucose were transferred to standard medium, normal responsiveness to glucose was restored within 8 h and normal basal release within 24 h. Mannitol, 3-O-methylglucose, and 2-deoxyglucose were not able to mimic the effects of glucose. Islets or purified beta-cells cultured in the presence of high glucose had a normal response when stimulated with glyburide, dibutyryl cyclic AMP, and isobutylmethylxanthine. Tunicamycin, an inhibitor of N-terminal glycosylation, prevented glucose-induced desensitization when added during 24 h of islet culture with 16.7 mM glucose. Swainsonine, another agent that influences glycosylation, had a similar effect. Our study indicates 1) that 24 h of exposure to high glucose induces a specific and reversible impairment of insulin secretion in response to glucose, 2) that this is a direct effect of glucose on beta-cells, and 3) that islet glucose metabolism and glycosylation processes may play a critical role in determining glucose desensitization.
Diabetes 1989 Nov
PMID:Effects of high glucose on insulin secretion by isolated rat islets and purified beta-cells and possible role of glycosylation. 255 66

Hyperglycemia in diabetes mellitus is generally associated with elevated levels of glucagon in the blood. A glucagon analog, des-His1[Glu9]glucagon amide, has been designed and synthesized and found to be an antagonist of glucagon in several systems. It has been a useful tool for investigating the mechanisms of glucagon action and for providing evidence that glucagon is a contributing factor in the pathogenesis of diabetes. The in vitro and in vivo activities of the antagonist are reported here. The analog bound 40% as well as glucagon to liver membranes, but did not stimulate the release of cyclic AMP even at 10(6) higher concentration. However, it did activate a second pathway, with the release of inositol phosphates. In addition, the analog enhanced the glucose-stimulated release of insulin from pancreatic islet cells. Of particular importance were the findings that the antagonist also showed only very low activity (less than 0.2%) in the in vivo glycogenolysis assay, and that at a ratio of 100:1 the analog almost completely blocked the hyperglycemic effects of added glucagon in normal rabbits. In addition, it reduced the hyperglycemia produced by endogenous glucagon in streptozotocin diabetic rats. Thus, we have an analog that possesses properties that are necessary for a glucagon antagonist to be potentially useful in the study and treatment of diabetes.
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PMID:Biological activities of des-His1[Glu9]glucagon amide, a glucagon antagonist. 256 Jan 75

A perifusion system for the study of insulin secretory dynamics of a clonal, Simian virus 40-transformed hamster pancreatic beta cell line (HIT cells) is described. After a change from glucose-free to higher glucose levels in the perifusate, insulin secretion increased rapidly in a dose-dependent manner. The pattern of glucose-stimulated insulin release was monophasic and was not sustained during a continued glucose stimulus. Perifusing the cells with low glucose (0.3 mg/ml) before a glucose stimulus of 3.5 mg/ml resulted in more rapid insulin release with lower peak secretory rates than those seen after a glucose-free period. The combined stimulus of high glucose and 100 microM 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, significantly enhanced the acute insulin secretory response and also resulted in a biphasic secretory pattern that was sustained throughout the 60-min stimulation period. Insulin secretion stimulated by IBMX required a nonstimulatory level of glucose in the perifusing media, and, if this requirement was met, the immediate release of insulin was similar to that evoked by high glucose alone. High potassium (40 mM) also triggered a monophasic release of insulin. These studies demonstrate that glucose or high K+, which depolarizes the plasma membrane, and IBMX, an agent presumed to increase intracellular cyclic AMP levels, can signal the acute release of insulin from these beta cells. This cell line is a unique model system for studying the mechanism of insulin secretion.
Diabetes 1985 Feb
PMID:Perifusion of a clonal cell line of Simian virus 40-transformed beta cells. Insulin secretory dynamics in response to glucose, 3-isobutyl-1-methylxanthine, and potassium. 257 18

The degradation of intracellular protein and other cytoplasmic macromolecules in liver is an ongoing process that regulates cytoplasmic mass and provides amino acids for energy and other metabolic uses early in starvation. Cellular proteins are conveniently divided into two general classes according to readily discernable differences in average rates of turnover. A short-lived class, having a half-life of approximately 10 min, comprises about 0.6% of total protein. Its degradation is not physiologically controlled, and the mechanism is probably nonlysosomal in nature. The second or long-lived group, with an average half-life 250 times greater, constitutes more than 99% of the cell's protein. By contrast, its breakdown is strongly regulated, and the site of catabolism is believed to be the vacuolar-lysosomal system. Cytoplasmic sequestration by lysosomes can be divided into two categories; macro- and microautophagy. The first is induced by amino acid and/or insulin deprivation. Amino acids are considered to be primary regulators, since they can control this process over the full range of induced proteolysis in the absence of hormones. Glucagon, cyclic AMP, and beta-agonists also stimulate macroautophagy in hepatocytes but have opposite effects in myocytes. Micrautophagy differs from the former in that the cytoplasmic "bite" is smaller and the uptake process is not acutely regulated. However, the latter does decrease during starvation in parallel with basal proteolysis, effects that might be linked to the loss of endoplasmic reticulum. The primary control of macroautophagy is accomplished through a small group of direct regulators (Leu, Tyr/Phe, Gln, Pro, Met, His, and Trp) and a specific coregulatory action of alanine. As a group, regulatory amino acids produce direct inhibitory responses in the perfused rat liver that are identical to those of the complete amino acid mixture at 0.5x and 4x (times) normal plasma concentrations. However, they lose effectiveness almost completely within a narrow zone centered at normal levels, a loss that can be abolished by the addition of alanine at its normal plasma concentration (0.5 mM). At this level, alanine does not inhibit directly. Interestingly, this zonal loss is also eliminated by insulin. Glucagon, though, specifically blocks the initial inhibition evoked by 0.5x amino acid mixtures and thus induces maximal rates of protein degradation at normal amino acid concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)
Diabetes Metab Rev 1989 Feb
PMID:Mechanism and regulation of protein degradation in liver. 264 36

For the metabolic characterization of immunocompetent cells which are involved in the development of an insulin-dependent diabetes, a method for measurement of adenine uptake by mononuclear and macrophage-depleted mononuclear cell populations and of incorporation rates into the ATP, ADP, AMP and hypoxanthine fractions of these cells is presented and examined for its informative value in a cross-sectional study of individuals at risk of developing insulin-dependent diabetes. Values of 30 controls were compared with those of 53 risk persons. In controls and in 28 of the risk persons the adenine uptake by mononuclear cells was two to three times higher than that by the macrophage-depleted mononuclear cell population, suggesting high adenine metabolic activity of phagocytic cells. This activity was significantly decreased in the phagocytic cells of the remaining 25 risk persons. Additionally, the adenine incorporation rates into the adenine nucleotides of mononuclear cells were reduced by approximately 50% in these 25 risk persons. The alterations of purine metabolism were found associated with clinical symptoms of transient alterations of glucose tolerance and in the case of manifestation with a mild (HLA DR 3) type of insulin-dependent diabetes.
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PMID:Alterations of purine metabolism in mononuclear cells of individuals at risk of developing type I (insulin-dependent) diabetes mellitus. 280 59

The effects of glucose (16.7 mM), potassium (50 mM), forskolin (20 microM), dibutyryl cyclic AMP (1 mM) and arachidonic acid (82 microM) upon insulin release and cytosolic free calcium concentrations ([Ca2+]i) were investigated in normal rat pancreatic islets. Potassium, forskolin and dibutyryl cyclic AMP significantly raised [Ca2+]i, but elicited only minimal insulin release. In the absence of extracellular Ca2+, glucose evoked insulin release, but failed to augment [Ca2+]i. Arachidonic acid increased [Ca2+]i both in Ca-depleted and -repleted medium, but promoted insulin release only in Ca2+-repleted environment. These new observations clearly demonstrate by direct measurements that although [Ca2+]i is an important factor in exocytotic insulin release, its effect is subject to amplification or antagonism.
Diabetes Res Clin Pract
PMID:Measurement of cytosolic free calcium concentration in relation to insulin release in normal rat pancreatic islets. 282 70

The influence of cyclic AMP (cAMP) and extracellular calcium on phosphoinositide (PI) hydrolysis in isolated islets was assessed and related to insulin output. Three stimulants were chosen to activate the beta-cell: sulfated cholecystokinin (CCK-8S, 200 nM), high-level glucose (20 mM), and the sulfonylurea tolbutamide (200 microM). The insulin secretory response to all three agonists was amplified by forskolin (which increases cAMP levels) and reduced by nitrendipine (which decreases calcium influx). All three stimulants increased the hydrolysis of inositol-containing phospholipids, an event monitored by an increase in [3H]inositol efflux from [3H]inositol-prelabeled islets and by the accumulation of labeled inositol phosphates. Forskolin, despite its positive impact on insulin secretion, reduced [3H]inositol efflux and inositol phosphate accumulation in response to all agonists. A similar inhibitory effect on these parameters was noted with nitrendipine; however, nitrendipine abolished secretion in response to all agonists. These findings support the following conclusions: 1) an increase in cellular cAMP levels reduces the quantitative impact of various agonists on these indices of PI hydrolysis; 2) despite this inhibitory effect, cAMP amplifies the insulin secretory response to these agonists; and 3) extracellular calcium is a crucial determinant of both PI hydrolysis and the ensuing insulin secretory response.
Diabetes 1988 Nov
PMID:Influence of cAMP and calcium on [3H]inositol efflux, inositol phosphate accumulation, and insulin release from isolated rat islets. 284 90

Fifteen week old male Wistar rats (n = 7) were made diabetic by intravenous injection of streptozotocin (50 mg/kg). Age-matched, untreated male Wistar rats (n = 9) served as controls. Hearts were removed after 5-6 weeks of diabetes, and the isometric developed tension (T) of isolated left ventricular papillary muscles and its first derivative (dT/dt) were measured at a frequency of 0.2 Hz. During testing, the muscles were perfused with Tyrode's solution (Ca2+ concentration was half of normal Tyrode's solution, pH 7.4, 32 degrees C, bubbled with 95% O2 and 5% CO2). In addition, the left ventricular isoenzyme pattern, which is related to myocardial energetics, was determined by pyrophosphate gel electrophoresis. There was no significant difference in isometric developed tension between diabetic and control rats (DM: 2.90 +/- 0.89 vs controls: 2.87 +/- 0.85 g/mm2, mean +/- SD), but in diabetic rats, dT/dtmax decreased significantly as compared with controls (DM: 23.5 +/- 4.2 vs controls: 31.9 +/- 7.9 g/mm2.s, p less than 0.05). Myocardial mechanical responses to isoproterenol (10(-7)M) and dibutyryl cyclic AMP (10(-5)M) also decreased in diabetic rats. The left ventricular myosin isoenzyme pattern shifted toward VM-3 in diabetic rats (VM-3: DM: 74.9 +/- 10.7 vs controls: 9.5 +/- 4.1%, p less than 0.001). These results indicate that diabetes influences myocardial contractility and changes cardiac energetics. Post-receptor processes may play a role in myocardial mechanical responses to catecholamines in streptozotocin-diabetic rats.
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PMID:Myocardial mechanical and myosin isoenzyme alterations in streptozotocin-diabetic rats. 284 6

The role of cytoplasmic activator of adenylate cyclase in rat lung metabolism was investigated. Mouse adrenal tumor (MAT) cells undergo differentiation in response to choleratoxin which acts through cyclic AMP. The activator of adenylate cyclase from rat lung also produced cyclic AMP in a disrupted MAT cell preparation. However, unlike choleratoxin, it did not induce MAT cell differentiation in whole cells. These results suggest impermeability of MAT cells, and possibly other cells, to the activator. Thus, means of altering activator activity in lung cytoplasm were sought, and changes in activator activity were related to lung glycogen. Adrenalectomy (ADX) in rats led to a reduction in activator activity that was accompanied by an elevation in lung glycogen. Dexamethasone treatment of adrenalectomized rats reversed both of these effects. Streptozotocin-induced diabetes in rats elevated activator activity and lowered lung glycogen. Insulin treatment of the diabetic rats restored activator activity to the normal control values. Preweaning of rats on day 16 instead of day 22 increased activator activity on the 19th day over the controls and there was a concomitant decrease in lung glycogen. Feeding the separated pups with homogenized milk restored glycogen and activator activity to the control values. These results indicate that activator activity in rat lung cytoplasm was dependent on the circulating levels of cortisol and insulin, and that there appeared to be an inverse relationship between activator activity and glycogen level in rat lungs.
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PMID:Relationship between the cytoplasmic activator of adenylate cyclase and glycogen metabolism in rat lung. 285 15

To clarify the role of the sympatho-adrenomedullary and renin-angiotensin-aldosterone systems, and catecholamine receptors, in the pathogenesis of orthostatic hypotension in diabetes mellitus (DM), urinary excretion of catecholamines, and plasma levels of norepinephrine (PNE), epinephrine (PE), renin activity (PRA), aldosterone (PAC), cyclic AMP (PcAMP) and cyclic GMP (PcGMP) were measured in 16 normal subjects (N) and 50 diabetic patients with or without orthostatic hypotension (DMOH(+), DMOH(-)). Changes in PNE, PE, PRA, PAC, PcAMP and PcGMP by standing, glucagon (G) administration and cold pressor test were examined. Furthermore, the effect of metoclopramide on catecholamine levels and blood pressure was investigated before and after cold pressor test. The results were following; (1) Urinary free norepinephrine excretion was significantly lower in DMOH(+), while urinary total norepinephrine excretion was normal in the two DM groups. Urinary free and total epinephrine excretions were lower in DMOH(+) than in N and DMOH(-). (2) PNE and PE were elevated after standing in all groups tested, and more pronounced in some cases of DMOH(+). Although PRA and PAC were elevated normally after standing in all groups, a dissociation between the two parameters was seen in some cases of DM. PcAMP after standing was correlated with PE(r = 0.829). Basal PcGMP was high in many cases of DMOH(+). However, no difference in the elevation of PcGMP after standing was noted between N and the two DM groups. (3) Systolic blood pressure (SBP) rose markedly in only DMOH(+) from 146 +/- 27mmHg to 178 +/- 34mmHg 5 minutes after G administration. The increment of PNE and PE 5 minutes after G administration were similar in all groups. In only DMOH(+), the increase in PcAMP 15 minutes after G test was proportional (r = 0.498) to that of epinephrine. (4) Responses of SBP, PNE, PE and PAC to cold pressor test apparently improved after administration of metoclopramide (MC) in some patients with DM. These results suggest that not only organic disturbance of sympathetic nerves but also functional inhibition of norepinephrine release mediated by dopamine receptor, may play an important role in the pathogenesis of orthostatic hypotension in diabetes mellitus. It is considered that catecholamine secretion from the adrenal medulla in DMOH(+) is increased by hypotension induced by standing. Furthermore, the vascular response to catecholamines may be accelerated through the increment of the extrajunctional receptor in DMOH(+).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[The role of the sympatho-adrenomedullary system and adrenergic receptors in the pathogenesis of orthostatic hypotension in diabetes mellitus]. 285 93


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