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)

The phosphorylation of D-glucose, as catalyzed by liver postmicrosomal supernatants, prepared from diabetic rats, under conditions aiming at the characterization of gluco-kinase activity, indicates, in addition to the classical fall in enzyme activity, an altered kinetic behaviour, the affinity for D-glucose and the apparent energy of activation being both lower in diabetic than normal rats. These kinetic anomalies persist after separation of cytosolic proteins from low molecular weight metabolites by gel filtration chromatography. They are simulated, to a limited extent, when liver cytosolic proteins from normal rats are glycated in vitro through prolonged exposure to a high concentration of D-glucose. Diabetes causes an increased non-enzymatic glycation of liver cytosolic proteins, including lactate dehydrogenase, as judged by either the ketoamine test, a back-titration procedure or the separation of glycated proteins by affinity chromatography. These findings suggest that chronic hyperglycemia might alter the intrinsic properties of liver glucokinase through a process of non-enzymatic glycation.
Diabetes Res 1990 Jul
PMID:Kinetic behaviour of liver glucokinase in diabetes. II. Possible role of non-enzymatic protein glycation. 213 81

In both starved and diazoxide-treated rats, the rate of D-(U-14C)glucose phosphorylation (10 mM) by liver cytosol, as measured in the presence of D-glucose 6-phosphate, was lower than in fed control rats. Moreover, in these two models of insulinopenia, the sensitivity of glucokinase to a lowering of temperature from 30 degrees C to 10 degrees C and its apparent affinity for D-glucose were both decreased. Such kinetic anomalies could not be attributed to the restricted contribution of N-acetyl-D-glucosamine kinase to the phosphorylation of D-glucose. It is proposed, therefore, that insulin deficiency may lead to a perturbation in either the intrinsic kinetic behaviour of glucokinase or the participation of its regulatory protein, independently of any change in glycemia.
Diabetes Res 1990 Jul
PMID:Kinetic behaviour of liver glucokinase in diabetes. III. Possible role of insulinopenia. 213 82

Tissue culture for one or seven days of pancreatic islets isolated from 21-day old fetal rats was found to be associated with a marked increase in the oxidation of L-(U-14C) glutamine by intact islets and in the activity of both alanine-glutamate and aspartate-glutamate transaminases as well as glutamate dehydrogenase in islet homogenates. This coincided with an increase in the relative amount of mitochondrial DNA. The activities of glucose-phosphorylating enzymes (hexokinase and glucokinase), glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase were less markedly increased during the culture period than those of enzymes involved in amino acid catabolism and located, in part at least, in mitochondria. The combined data suggest that the functional maturation of fetal islets during the culture period is associated with and may be attributable to a preferential maturation of their mitochondria.
Diabetes Res 1990 Apr
PMID:Maturation of fetal rat islet cells in vitro during tissue culture is associated with increased mitochondrial function. 213 6

Substrate cycles (SC) are formed by a 'forward pathway' (FP) and a 'backward pathway' (BP), the difference between FP and BP forming the 'metabolic flux' (MF) through the route of which the cycle is part. SC modulate regulatory effects, i.e. amplify or reduce the % change in MF compared to the % change in FP and BP, thus affecting the sensitivity to regulatory factors, including hormones. A formula is given to calculate (with an approximation of +/- 0.5) the 'flux response index' (FRI), i.e. the factor by which the % change in FP plus the % change in BP must be multiplied to obtain the % change in metabolic flux, when FP and BP undergo opposite, non-unidirectional changes (as is often the case in metabolic regulation). The formula is: FRI = [( FP + BP)/(FP-BP)]/2. By this formula we evaluated the hepatic activities of glucose-6-phosphatase and glucokinase (which roughly reflect hepatic glucose production and uptake, respectively), i.e. the two enzymes that catalyze the cycle between glucose-6-phosphate (glucose-6-P) and glucose. Based on data obtained in normal, nonobese diabetic and obese diabetic subjects as well as in normal, streptozotocin-diabetic, and obese diabetic (ob/ob) mice, we found that FRI was reduced in non-obese diabetic humans and animals whereas it was increased in obese-diabetic humans and mice, compared to normal controls. Thus, diabetes without obesity decreases, and obesity with diabetes increases, the sensitivity of the glucose-6-P/glucose cycle to regulatory agents.
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PMID:A formula for quantifying the effects of substrate cycles (futile cycles) on metabolic regulation. Its application to glucose futile cycle in liver as studied by glucose-6-phosphatase/glucokinase determinations. 215 82

Glucokinase is expressed in both the liver and the pancreatic beta-cell and plays a key role in the metabolism of glucose by both tissues. Expression of this enzyme is differentially regulated; hepatic glucokinase is stimulated by insulin and repressed by cAMP, whereas beta-cell glucokinase activity is increased by glucose. Recently, the glucokinase gene has been characterized and was found to contain two different transcription control regions. One region regulates transcription of the gene in the liver, whereas the other region, which lies at least 12 kilobases further upstream, controls transcription in the pancreatic beta-cell. The finding of two different transcription control regions in a single glucokinase gene provides a genetic basis for the tissue-specific differential regulation of glucokinase and will serve as the basis for further studies to identify and characterize the different regulatory elements and factors in the liver and beta-cell, which are presumably involved. Comparison of different glucokinase cDNAs isolated from hepatic, insulinoma, and islet cDNA libraries indicates that at least three glucokinase isoforms are generated by differential RNA processing of the glucokinase gene transcripts. Whether any of these glucokinase isoforms are functionally unique remains to be determined.
Diabetes 1990 May
PMID:Glucokinase gene structure. Functional implications of molecular genetic studies. 218 4

This article reviews evidence for a pivotal role of glucokinase as glucose sensor of the pancreatic beta-cells. Glucokinase explains the capacity, hexose specificity, affinities, sigmoidicity, and anomeric preference of pancreatic islet glycolysis, and because stimulation of glucose metabolism is a prerequisite of glucose stimulation of insulin release, glucokinase also explains many characteristics of this beta-cell function. Glucokinase of the beta-cell is induced or activated by glucose in contrast to liver glucokinase, which is regulated by insulin. Tissue-specific regulation corresponds with observations that liver and pancreatic beta-cell glucokinase are structurally distinct. Glucokinase could play a glucose-sensor role in hepatocytes as well, and certain forms of diabetes mellitus might be due to glucokinase deficiencies in pancreatic beta-cells, hepatocytes, or both.
Diabetes 1990 Jun
PMID:Glucokinase as glucose sensor and metabolic signal generator in pancreatic beta-cells and hepatocytes. 218 59

Effects of pioglitazone (5-[4-[2-(5-etyl-2-pyridyl)ethoxy] benzyl]-2,4-thiazolidinedione, AD-4833, also known as U-72, 107E) on peripheral and hepatic insulin resistance were examined using genetically obese-hyperglycemic rats, Wistar fatty. Pioglitazone was administered to fatty rats (3 mg/kg/d) and lean rats (10 mg/kg/d) for 6 days. Pioglitazone decreased hyperglycemia and hypertriglyceridemia without affecting hyperinsulinemia in the fatty rats, and significantly reduced plasma levels of triglyceride and insulin without altering normoglycemia in the lean rats. The same rats were subjected to an isotopic method combined with a euglycemic clamp technique for assessing insulin sensitivity in hepatic glucose production (HGP) and peripheral glucose utilization (PGU). HGP decreased and PGU increased in response to infused insulin in the lean rats but did not in the fatty rats, indicating that insulin resistance was present in the liver and peripheral tissues of the fatty rats. Treatment with pioglitazone restored the responses of HGP and PGU to infused insulin in the fatty rats, but did not produce any changes in the lean rats. When the same levels of glycemia and insulinemia were established by 480 mU/h of insulin in both treated and control fatty groups, PGU was 1.5-fold higher and HGP was 3-fold lower in the pioglitazone treated group. Pioglitazone also corrected the abnormality in hepatic enzyme regulation by insulin of the fatty rats: glucose-6-phosphatase decreased and glucokinase increased, suggesting the increased response of the liver to insulin and the resultant suppression of HGP. Therefore, pioglitazone is expected to be useful for treating abnormal glucose and lipid metabolism in non-insulin-dependent diabetes mellitus through reducing insulin resistance of the peripheral tissues and liver.
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PMID:Effects of pioglitazone on hepatic and peripheral insulin resistance in Wistar fatty rats. 219 15

Interleukin-1 beta (IL-1 beta) has been implicated in the pathogenesis of insulin-dependent diabetes mellitus. In the present study we have investigated the effects of IL-1 beta on glucose metabolism in clonal HIT-T15 beta cells. In the short-term (1 h), 25 U/ml IL-1 beta significantly increased the rates of insulin release and glucose utilisation, but not glucose oxidation. In contrast, after 48 h, IL-1 beta inhibited insulin release and glucose utilisation and oxidation. By assaying enzymes (hexokinase, glucokinase, pyruvate dehydrogenase, glucose 6-phosphatase) and nucleotides (ATP, ADP) associated with the regulation of glycolysis and glucose oxidation, we conclude that the inhibitory effects of IL-1 beta may be due to impaired glucokinase activity.
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PMID:Interleukin-1 beta inhibits glucokinase activity in clonal HIT-T15 beta-cells. 219 15

We assessed our speculation that 2-cyclohexen-1-one (CHX) impairs glucose-induced insulin secretion through inactivation of glucokinase. Treatment of pancreatic islets with CHX at concentrations (0-5 mM) that caused a dose-dependent inactivation of glucokinase activity similarly inhibited glucose-induced insulin secretion. Another glucose-phosphorylating enzyme (hexokinase) in pancreatic islets was little affected by CHX. CHX-induced inactivation of glucokinase was blocked by the presence of its substrates (glucose and mannose) and an inhibitor (N-acetylglucosamine), all of which also protected against the inhibitory effect of the drug on glucose-induced insulin secretion. CHX also impaired insulin secretion induced by D-glyceraldehyde and dimethyl succinate, which are believed to stimulate the release of the hormone by being directly oxidized by glyceraldehyde-3-phosphate dehydrogenase, by entering the midstream of the glycolytic pathway as glyceraldehyde 3-phosphate, or by entering the tricarboxylic acid cycle in mitochondria after intracellular hydrolysis. The inhibitory effect of CHX on glucose-induced insulin secretion, however, was far more marked than that on insulin secretion evoked by D-glyceraldehyde and dimethyl succinate at any CHX concentrations used. Our study revealed that the inhibitory action of CHX on glucose-induced insulin secretion is exerted mainly, but not solely, through inactivation of glucokinase. This conclusion supports the view that glucokinase is a key enzyme in the recognition of glucose as an insulin secretagogue in pancreatic islets.
Diabetes 1990 Oct
PMID:Participation of glucokinase inactivation in inhibition of glucose-induced insulin secretion by 2-cyclohexen-1-one. 221 70

In mice with streptozotocin-induced diabetes of 3 days' duration, the hexokinase/glucose-6-phosphatase (HK/G6Pase) ratio in the kidney was enhanced by 52% (mean +/- SEM: 0.40 +/- 0.04 vs. 0.26 +/- 0.03; p less than 0.02) compared to control mice as a result of a 25% increase of HK (16.68 +/- 0.93 vs. 13.31 +/- 1.04 nmol/min/mg protein; p = 0.05) and a 17% decrease of G6Pase (42.51 +/- 2.75 vs. 51.25 +/- 1.89; p less than 0.05). In contrast, as expected, the corresponding ratio (HK + glucokinase/G6Pase) was strikingly reduced in the liver. In 9-day diabetic mice, the kidney enzyme changes were much smaller; however, in a chronic disease such as diabetes, even minimal deviations from the normal may lead to significant metabolic changes with time. The enhanced HK/G6Pase ratio in the diabetic kidney suggests an increase in glucose utilization. This may contribute to the increased synthesis of glycogen, glycoproteins (including basement membrane) and RNA (via provision of ribose-phosphate) occurring in the diabetic kidney and supports the view that the kidney (as opposed to other tissues) shows an 'anabolic response' to diabetes.
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PMID:Increased hexokinase/glucose-6-phosphatase ratio in the diabetic kidney as index of glucose overutilization. 255 19


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