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 studied the metabolism of A14-125I-insulin in intact human fibroblasts using high performance liquid chromatography (HPLC) to detect and separate its early degradation products. The high resolving power of HPLC enabled us to separate what has been considered "intact insulin" by Sephadex G-50 chromatography or TCA precipitability into two additional peaks that had decreased biochemical properties with respect to immunoprecipitability and receptor binding but not decreased TCA precipitability. We conclude that human fibroblast is capable of metabolizing insulin within 2 min at 37 degrees C into intermediate molecules that can be detected by HPLC but not by TCA precipitability or molecular sieve chromatography.
Diabetes 1983 May
PMID:Early detection of degraded A14-125I-insulin in human fibroblasts by the use of high performance liquid chromatography. 634 Nov 31

Insulin and branched-chain amino acids are known to stimulate protein synthesis in skeletal muscle. Extracts prepared from rat diaphragms after incubation in balanced salt solution and glucose alone yielded heat- and acid-stable, TCA-precipitable, nondialyzable factor(s) that inhibit protein synthesis when added to rabbit reticulocyte lysates. Polyribosomal profiles of inhibited lysates were consistent with a defect in peptide-chain initiation. Addition of insulin and amino acids to the diaphragm incubation media partially removed the inhibition seen with the muscle extract and was accompanied by an increase in polysomes and decreased subunits. Similarly, extracts prepared from rat hindlimb muscle 48 h after induction of diabetes were much more inhibitory in rabbit reticulocyte lysates than extracts from control rats. Polyribosomal profiles were consistent with defective peptide-chain initiation. Trypsin treatment before assay abolished the inhibitory activity of muscle extracts from diabetic rats. Because translation-inhibiting peptide(s) appear to be under metabolic and/or hormonal control, their possible role in muscle protein homeostasis warrants further study.
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PMID:Muscle protein synthesis: regulation of a translational inhibitor. 637 11

To compare the metabolic characteristics and degradation of insulin tracers labeled unselectively, selectively at the A14 position (A14-monoiodoinsulin), and selectively at the B1 position (B1-monoiodoinsulin), we have followed the time course of disappearance of intact (immunoprecipitable [IP] and trichloroacetic acid [TCA] precipitable) iodoinsulin after bolus injection into greyhounds. We have used noncompartmental analysis to determine metabolic clearance rate (MCR) and apparent distribution space (DS). We have also measured the appearance of non-IP- and non-TCA-precipitable fragments, and have developed a mathematical model using compartmental analysis to explain the observed differences. B1-Monoiodoinsulin has a significantly higher MCR (16.3 ml/min/kg) than both A14-monoiodoinsulin (10.6 ml/min/kg) and unfractionated tracers (7.6 ml/min/kg) as determined by immunoprecipitation, and reaches the values observed for native insulin in greyhounds. MCR values obtained by TCA precipitation are approximately one-half of those obtained by IP for all 3 tracers. The concentration of non-IP fragments is significantly lower with B1-monoiodoinsulin than with the other tracers. Compartmental analysis suggests this to be due to greater intracellular retention of the B1 moiety during the experimental period. We conclude that: (1) by the criterion of MCR, B1-monoiodoinsulin seems to behave more like native insulin than other preparations tested; (2) the reduced MCR of A14-monoiodoinsulin raises doubts about its validity as a tracer for insulin; (3) a high-molecular-weight product of insulin degradation, which includes both the B1 and the A14-A19 regions of the molecule, is released into the circulation; and (4) smaller fragments containing A14-A19 reappear in the circulation more rapidly than fragments containing B1.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1984 Aug
PMID:Evidence for separate handling in vivo of different regions of the insulin molecule using A14- and B1-labeled insulin tracers. 637 97

Insulin binding and processing was studied in monolayer cultures of bovine aortic endothelial cells. Specific 125I-insulin binding was both time and temperature dependent. Maximum binding at 37 degrees C occurred at 90 min, and was 3.8%/mg protein and, at 15 degrees C, 7%/mg protein at 4 h. 125I-insulin was crosslinked to its receptor using disuccinimidyl suberate (DSS), and the structure of the receptor complex was identified by SDS-polyacrylamide gel electrophoresis and autoradiography; a major band with Mr = 145,000 was identified, which corresponds to the alpha-subunit of the insulin receptor reported in other tissues. Receptor-bound insulin was internalized, and both the rate and the amount of internalization were temperature dependent. The rate of internalization was slowest at 4 degrees C, and fastest at 37 degrees C, and the maximum amount of 125I-insulin internalized in 120 min was 16% at 4 degrees C, 45% at 15 degrees C, and 81% at 37 degrees C. Despite the high rate of internalization, endothelial cells do not appear to degrade insulin significantly, as determined by gel chromatography and TCA solubility (7% at 4 h) of media-associated radioactivity. In addition, the majority of internalized insulin (75%) was released by 60 min, largely as intact insulin. Chloroquine treatment at high concentration did not exert any major effect on insulin binding or degradation within the first 60 min, but thereafter produced a marked increase in cell-associated radioactivity.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1984 Aug
PMID:Processing of insulin by bovine endothelial cells in culture. Internalization without degradation. 637 2

The stability of the perfused mouse hindquarter was assessed for a period of 5 h, and the preparation shown to remain stable for metabolic studies over this time period. Muscle protein synthesis and degradation rates in lean and diabetic-obese (db/db) mice were measured using the in situ perfused hindquarter preparation. The rates of protein synthesis were 48% lower in the muscles of intact db/db mice than in the lean controls when expressed per gram TCA precipitable protein and 46% lower when expressed per gram dry weight. Adrenalectomy, which has been shown to restore the lean body mass of the db/db mice to normal, had the effect of returning protein synthesis rate in muscle of db/db mice to lean control values. Insulin at a dose of 1 mU/ml stimulated protein synthesis in lean mice only, showing that the process of protein synthesis in the db/db mice is also insensitive to insulin. Measurements of the rates of degradation of muscle protein showed no differences between lean and db/db mice. These findings suggest that the decreased lean body mass of db/db mice is the result of a defect in protein synthesis rather than due to altered degradation.
Diabetes 1984 Dec
PMID:Muscle protein turnover in the perfused hindquarters of lean and genetically obese-diabetic (db/db) mice. 650 Jan 91

The incorporation of radioactively labeled leucine into TCA-precipitable proteins by submandibular gland tissue slices from control, alloxan diabetic, and insulin supplemented diabetic rats was measured in vitro. Incorporation decreased in alloxan diabetes and could be restored to control levels within three hours after insulin administration. The effects of alloxan diabetes and insulin on 3H-leucine incorporation paralleled their effects on a secretory enzyme, peroxidase. Insulin in vitro stimulated the incorporation of 3H-leucine within 15 minutes of addition to the incubation medium. Further, the response to insulin was found to be dose-related. The conclusion drawn from these results is that insulin has a rapid, direct effect on the rate of protein synthesis in the rat submandibular gland.
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PMID:The effect of alloxan diabetes and insulin on the rate of protein synthesis in the rat submandibular gland. 698 29

Mononuclear cells from peripheral blood possess insulin receptors that are altered in number or binding affinity in certain metabolic diseases as obesity. The monocyte, and not the lymphocyte, is the cell with the capacity to specifically bind insulin. Furthermore, this binding appears to mirror the receptor status on such insulin target tissues as liver, muscle, and fat. Since liver, muscle, and fat also degrade insulin, mononuclear cells from the blood of normal volunteers were examined for insulin-degrading activity. Intact cells were incubated with 125I-insulin and the amount of degraded insulin was measured by the trichloroacetic acid-precipitation technique. Insulin-degrading activity increased when the number of cells and the time of incubation were increased. Total insulin binding behaved in a similar fashion. Very little degradation was seen at 4 degrees or 15 degrees. The Km for insulin-degrading activity was 7.03 X 10(-8) M. Homogenized mononuclear cells degraded two to five times more insulin than did intact cells and also demonstrated cell concentration, time, and temperature dependence for degradation. The Km of degradation for homogenized mononuclear cells was 2.2 X 10(-8) M. Subcellular fractionation revealed significant degrading activity in the 100,000 X g supernatant, but little activity in the 100,000 X g pellet. A purified lymphocyte preparation did not bind insulin and contained little insulin-degrading activity.
Diabetes 1980 Jan
PMID:Insulin degradation by mononuclear cells. 699 13

In this study we used chloroquine to characterize the interalization and lysosomal degradation of receptor-bound 125I-insulin by rat adipocytes and to determine the role of lysosomal processing of insulin in the short-term biologic effects of the hormone. Chloroquine inhibited the degradation of 125I-insulin bound to adipocytes by both association and disslociation experiments. In the former experiments, chloroquine caused a time- and concentration-dependent increase in specifically bound insulin owing to an increase in intact insulin and a decrease in degradation products, as determined by trichloroacetic acid precipitability and gel chromatographic analysis of material extracted from the cells. In the dissociation experiments, 50 microM chloroquine decreased the rate of degradation by two third, as reflected in the release of degradation to or degraded by isolated plasma membranes, on the degradation of 125I-insulin by proteases in the incubation medium, or on the endocytotic uptake of receptor-bound insulin. Quantitative electron miroscopy, using monomeric ferritin-insulin, showed 50 microM chloroquine doubled the number of lysosomal structures containing ferritin. These findings are consistent with an inhibition by chloroquine of lysosomal degradation of internalized receptor-bound insulin. Chloroquine, at these same concentrations, had no effect on the ability of insulin to stimulate glucose transport and oxidation or to inhibit epinephrine-stimulated lipolysis. In these studies, we show that lysosomal degradation of internalized receptor-bound insulin is not necessary for insulin to cause short-term biologic effects in the adipocyte.
Diabetes 1980 Jun
PMID:Lysosomal degradation of receptor-bound 125I-labeled insulin by rat adipocytes: its characterization and dissociation from the short-term biologic effects of insulin. 699 35

Rat pancreatic islets were incubated in vitro with L-[4,5-3H]leucine or with L-[2,3-3H]tryptophan in Krebs-Ringer bicarbonate buffer, containing 0, 5, or 20 mM glucose. Incorporation of labeled amino acids in islet cells was evaluated quantitatively by a validated radioautographic procedure. Incorporation of labeled leucine into [3H]proinsulin and [3H]insulin was measured by immunoprecipitation and into other islet proteins by trichloroacetic acid precipitation. Incorporation of labeled amino acids in pancreatic beta cells was patchy and not uniform. Up to 20 to 35% of beta cells, mainly in central regions of the islets, showed poor or no incorporation of label. Peripheral nonbeta, endocrine islet cells and mesenchymal islet cells were all uniformly labeled. Incorporation of either amino acid into nonbeta endocrine and mesenchymal cells was not much affected by the absence of glucose in the incubation buffer. In contrast, incorporation of the amino acids into beta cells was strikingly affected. Incorporation of [3H]leucine into proinsulin and insulin at 0 mM glucose measured by specific immunoprecipitation and by silver grain densities over beta cells was 15 to 20 times less than at 20 mM glucose. Incorporation of [3H]tryptophan, an amino acid absent in proinsulin, into nonhormonal, sedentary beta cell proteins studied by radioautography, similarly, was strikingly affected in the absence of glucose. Thus, radioautography revealed a great sensitivity of both hormonal and nonhormonal protein biosynthesis in the beta cell to the concentration of glucose in the medium.
Diabetes 1980 Oct
PMID:Biosynthesis of proinsulin and other islet cell proteins in pancreatic beta cells of the rat: a radioautographic evaluation of glucose effects in vitro. 700 60

Rats were infused for brief periods with buffer, glucose, or insulin. L-[4,5-3H] leucine (2.5 mCi) or L-[2,3-3H]-tryptophan (0.5 mCi) was quickly injected intravenously 30 min after the onset of the infusion, when marked hyperglycemia or hypoglycemia had been established. Rats remained connected to the infusion system and were killed 30 min after the injection of the labeled amino acid. Pancreatic islets were isolated by enzymatic digestion of the pancreas. They were processed for radioautography or for the measurement of [3H] proinsulin and [3H] insulin by immunoprecipitation and of other islet [3H] proteins by TCA precipitation. Various tissues of the rats were also removed to measure TCA-precipitable-labeled proteins. Incorporation of [3H]-leucine into proinsulin and insulin was 9 to 20 times greater in the hyperglycemic than in the hypoglycemic rats. Incorporation of [3H]-tryptophan into sedentary beta-cell proteins, measured by thea density of silver grain in radioautographs, showed a sixfold difference. The great sensitivity of hormonal and nonhormonal protein biosynthesis of the pancreatic beta cell to plasma glucose was unique among tissues and among other pancreatic islet cells we studied.
Diabetes 1980 Oct
PMID:In vivo incorporation of [3H[ leucine and [3H] tryptophan into proinsulin-insulin and other islet cell proteins in normoglycemic, hyperglycemic, and hypoglycemic rats. 700 61


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