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)

Two broad-specifically protein phosphatases, termed protein phosphatase-1 (PrP-1) and protein phosphatase-2A (PrP-2A), accounting for all the hepatic activity regulating glycogen phosphorylase, were measured in spontaneously diabetic Chinese hamsters exhibiting persistent glycosuria. When compared with genetically related inbred sublines free of glycosuria, diabetic animals demonstrated approximately 25% increase in PrP-1 activity measured either in crude tissue extracts or in cytosols fractionated by ion-exchange chromatography. No significant alteration in total PrP-2A activity was observed in the diabetic animals. These findings indicate that a specific change in hepatic PrP-1 is associated with genetically acquired diabetes in Chinese hamsters. In contrast to reported data using animals with experimentally induced diabetes mellitus, hepatic PrP-1 was increased in the spontaneously diabetic Chinese hamsters. The data suggests that distinct alterations in PrP-1 and associated metabolic consequences are exhibited by different types of diabetes.
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PMID:Increase in liver protein phosphatase-1 in spontaneously diabetic Chinese hamsters. 303 94

Kinetic studies were carried out on liver glycogen synthase and phosphorylase isolated from genetically diabetic db/db mice. Glycogen synthase a and b enzymes from diabetic mice had Vmax values 30% and 20% lower, respectively, than the enzymes from normal mice. Glycogen synthase b from diabetic mice also had a 30% lower I0.5 for Pi and ATP at physiologic concentrations of UDP-glucose (0.25 mM) compared with the normal enzyme. Kinetic studies of phosphorylase a showed that, at low glycogen concentrations (0.25 mg/ml), the Vmax of the diabetic enzyme was twofold greater than that of the normal enzyme. This was probably related to the diabetic phosphorylase a having a lower apparent Km for glycogen. This enzyme also had a slightly higher I0.5 for ATP compared with the enzyme from normal mice. Structural studies of liver glycogen isolated from these diabetic mice showed differences from normal mouse glycogen. Both the alpha- and beta-amylase limits were lower in the diabetic glycogen, and the average chain lengths, exterior chain lengths, and interior chain lengths calculated from these limits were all shorter in the glycogen from diabetic mice. Although both normal and diabetic glycogen absorbed light maximally at 430 nm when complexed with iodine, the absolute absorbance value was significantly lower for the diabetic glycogen. These data suggest an altered branching pattern of liver glycogen from the diabetic mice and it is suggested that this altered structure may ultimately influence the activities of glycogen-metabolizing enzymes. These results provide further characterization of the db/db mouse and show heretofore undescribed changes in phosphorylase a kinetics and glycogen structure that occur in diabetes.
Diabetes 1986 Feb
PMID:Kinetic properties of glycogen synthase and phosphorylase and structural aspects of glycogen in the db/db mouse liver. 308 Mar 50

Fructose has been considered as an alternative sweetener to sucrose because it results in less glycemia when given to normal subjects or to those with mild noninsulin-dependent diabetes mellitus. Oral fructose also results in efficient glycogen synthesis. However, multiple hepatotoxic effects have been reported following parenteral fructose administration. We have examined the effects of large oral fructose and glucose loads (4 g/kg) and of graded intravenous fructose doses (50-500 mg/kg) on hepatic metabolism and glycogen synthesis in normal, fasted rats. Fructose was absorbed more slowly than glucose when given by gavage (59% vs 91% absorbed in 120 min). Oral fructose administration resulted in greater liver and muscle glycogen synthesis, despite smaller increases in plasma glucose and insulin concentrations, than was found after oral glucose administration. Increases in percent glycogen synthase I (active form) occurred after both oral fructose and glucose loads (67% vs 115% increase). There was no evidence of hepatotoxicity even after a very large oral fructose load. When small (less than or equal to 125 mg/kg) iv doses of fructose were given, the portal vein fructose concentration remained less than or equal to that found after oral fructose administration (1.1 mM). The percent synthase I increased up to threefold, and there was no evidence of hepatotoxicity. Larger iv doses resulted in a fall in percent synthase I, an increase in percent phosphorylase a, and inorganic phosphate and nucleotide depletion. We conclude that the slow absorption of an oral fructose load prevents hepatotoxic effects and permits efficient glycogen synthesis.
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PMID:Metabolic effects of dietary versus parenteral fructose. 309 1

Studies in rats indicated that the major physiologic stimulus for synthesis of liver glycogen is a rise in the portal glucose concentration after ingestion of a meal. Conversely, glycogen degradation in the liver is stimulated by a rise in portal glucagon concentration. In humans, ingestion of carbohydrate lowers the concentration of circulating glucagon, whereas protein stimulates an increase in peripheral glucagon concentration. Little is known about the effects of these nutrients on glucagon concentrations in the rat. Therefore, we studied the effects of oral protein administration to 24-h-fasted rats pretreated with glucose for 2 h to test the effect of two potent but potentially opposite signals for glycogen metabolism. An increase in liver glycogen concentration was observed in fasted rats given oral glucose, as expected. Removal of glucose by the liver could not account for the glycogen synthesized, indicating that most glycogen formed was derived from gluconeogenesis. In addition, the apparent intracellular and extracellular glucose concentrations were not in equilibrium. A small amount of glucose may have been taken up against a concentration gradient. The portal glucagon was not significantly decreased. Oral protein administration to the rats pretreated with glucose resulted in a rapid and dramatic decrease in liver glycogen concentration. This was associated with an increase in the portal glucagon concentration, no change in insulin concentration, a slight increase in liver cAMP concentration, an increase in the active form of phosphorylase, and a decrease in the active form of synthase. Glycogenolysis could account for the glucose released into the circulation from the liver after protein administration.
Diabetes 1987 Jan
PMID:Oral protein hydrolysate causes liver glycogen depletion in fasted rats pretreated with glucose. 309 9

Glyburide, a second-generation sulfonylurea, is used in the treatment of NIDDM because of its hypoglycemic action. However, the site and mechanism of action of this sulfonylurea remain unclear. We examined the ability of glyburide to enhance insulin's inhibitory effect on glucagon-stimulated hepatic glucose production. The livers of fed male rats were perfused with a Krebs-Henseleit buffer containing washed human red blood cells. After a 60-min control period during which the liver was exposed to both insulin and glucagon (10 microU/ml and 11 pg/ml, respectively), the glucagon concentration was increased to 88 pg/ml in the presence of 0, 10, 40, and 240 microU/ml of insulin. Hepatic glucose output and phosphorylase a activity were monitored during the control and elevated-glucagon periods. The glyburide-infused group received glyburide (1.6 microgram/ml) during both the control and elevated-glucagon periods. As expected, high levels of insulin suppressed glucagon-stimulated glucose production and phosphorylase activation. Insulin at a concentration of 10 microU/ml was unable to suppress glucagon's stimulation of glucose production or its activation of phosphorylase. However, in the presence of glyburide it was able to decrease stimulated hepatic glucose production and phosphorylase activation by 40 and 50% respectively. In the absence of insulin, glyburide was unable to suppress glucagon's glycogenolytic action, suggesting that the drug potentiates insulin's action on the liver rather than exerting an inhibitory effect directly. Insulin at a concentration of 240 microU/ml completely suppressed glucagon action, and glyburide had no additional effect. Therefore, glyburide is able to enhance the sensitivity of the perfused rat liver to insulin without altering maximal insulin responsiveness.
Diabetes 1987 Apr
PMID:Glyburide sensitizes perfused rat liver to insulin-induced suppression of glucose output. 310 99

The effects of daily oxytetracycline treatment on the activities of hepatic glycogen synthase, glycogen phosphorylase, plasma glucose, and insulin, and on liver glycogen, free fatty acid, and triglyceride levels were examined in 8- to 15-week-old genetically diabetic and lean mice. Oxytetracycline administration resulted in substantial reductions in the plasma glucose and immunoreactive-insulin levels in both diabetic and lean mice. The drug had no significant effect on the liver glycogen content in either phenotype, regardless of age, but it increased hepatic lipids and depressed body weights in lean animals. The most prominent effect of the drug was in markedly altering the activities of both glycogen synthase and phosphorylase in the liver of older diabetic mice. Oxytetracycline treatment produced a three-fold increase in the percentage of glycogen synthase I activity and reduced by one-third the percentage of glycogen phosphorylase a activity in 15-week-old diabetic mice. In age-matched lean mice treated with oxytetracycline, the percentage of glycogen synthase I activity increased significantly, but the percentage of phosphorylase a activity was unchanged. These data suggest that the drug may alter an aspect of hepatic glycogen metabolism which might lead to an inhibition of glycogenolysis and subsequent diminution of blood sugar levels in the diabetic. The present results show that, while oxytetracycline may be effective in reducing the severity of some of the diabetic symptoms associated with carbohydrate metabolism in this animal model of maturity-onset diabetes, the drug may have adverse effects on aspects of protein and lipid metabolism in these animals.
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PMID:Effects of oxytetracycline treatment on enzymes of hepatic glycogen metabolism in genetically diabetic (db/db) mice. 310 60

In rat hepatocytes, the basal glycogen synthase activation state is decreased in the fed and diabetic states, whereas glycogen phosphorylase a activity decreases only in diabetes. Diabetes practically abolishes the time- and dose-dependent activation of glycogen synthase to glucose especially in the fed state. Fructose, however, is still able to activate this enzyme. Glycogen phosphorylase response to both sugars is operative in all cases. Cell incubation with the combination of 20 mM glucose plus 3 mM fructose produces a great activation of glycogen synthase and a potentiated glycogen deposition in both normal and diabetic conditions. Using radiolabeled sugars, we demonstrate that this enhanced glycogen synthesis is achieved from both glucose and fructose even in the diabetic state. Therefore, the presence of fructose plays a permissive role in glycogen synthesis from glucose in diabetic animals. Glucose and fructose increase the intracellular concentration of glucose 6-phosphate and fructose reduces the concentration of ATP. There is a close correlation between the ratio of the intracellular concentrations of glucose 6-phosphate and ATP (G6-P/ATP) and the activation state of glycogen synthase in hepatocytes from both normal and diabetic animals. However, for any given value of the G6-P/ATP ratio, the activation state of glycogen synthase in diabetic animals is always lower than that of normal animals. This suggests that the system that activates glycogen synthase (synthase phosphatase activity) is impaired in the diabetic state. The permissive effect of fructose is probably exerted through its capacity to increase the G6-P/ATP ratio which may partially increase synthase phosphatase activity, rendering glycogen synthase active.
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PMID:Glycogen synthesis from glucose and fructose in hepatocytes from diabetic rats. 314 17

The concentrations of glycogen phosphorylase protein were determined by rocket immunoelectrophoresis in liver extracts from rats that had artificially induced altered hormonal patterns. These levels were compared with measurements of total phosphorylase activity. Minipump-induced chronic hyperglucagonemia and streptozotocin-induced diabetes resulted in 47% and 67% decreases, respectively, in total phosphorylase activity along with corresponding 52% and 68% drop, respectively, in phosphorylase protein levels. Insulin replacement in diabetic rats returned both parameters to control values. Minipump-induced hyperinsulinemia or injection of glucagon antiserum, T3, or propylthiouracil had no effect. The results of this study indicate that conditions which lead to an elevation of the glucagon to insulin molar ratio to values higher than 1.0 cause a significant decrease in the liver phosphorylase protein level.
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PMID:Regulation of rat liver glycogen phosphorylase concentration by in vivo relative levels of glucagon and insulin. 329 37

The effects of enteric galactose alimentation on neonatal glucose turnover and hepatic glycogen synthesis were investigated in a newborn animal model of diabetic pregnancy. Control pups and pups of diabetic dogs were studied in the basal state and after each group of pups was randomly fed equivalent amounts of galactose or glucose by oral-gastric tubes. Basal fasting blood glucose levels were not statistically different between the groups, whereas basal plasma insulin levels were 2-3 times higher in pups born to diabetic mothers. Blood glucose levels at each time point in response to glucose or galactose feeding in pups of diabetic mothers were not statistically different; however, the rise of plasma insulin concentrations was attenuated in pups of diabetic mothers fed galactose. The increase in the systemic rate of appearance of glucose and in glucose clearance were attenuated in pups of diabetic mothers fed galactose compared with those fed glucose. Hepatic glycogen content was augmented above basal levels in pups of diabetic mothers. Although glycogen synthase activity was not different between glucose- or galactose-fed pups of diabetic mothers, the active component of glycogen phosphorylase was reduced by both glucose and galactose feedings. Galactose alimentation had a greater effect on glycogen phosphorylase than did glucose alimentation. The observed increase in glycogen synthesis and reduced systemic glucose appearance after galactose alimentation could not be accounted for by the previously proposed excess of galactokinase over glucokinase activities when the latter enzyme was assayed at saturation. Indeed, neonatal hepatic glucokinase activity appeared to be induced during diabetic pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1987 Nov
PMID:Galactose assimilation in pups of diabetic canine mothers. 331 54

The effect of maternal diabetes on functional and biochemical maturation of the fetal lung was studied in a rabbit model. Pregnancy was initiated only after diabetes had been established. Both the pregnant doe and its fetuses were hyperglycemic. For comparison, the fetal heart and liver were also studied. In the diabetic group, the DNA content was lower in the fetal heart and lung while the protein content was higher in all three tissues. The glycogen levels were higher only in the fetal lung. Glycogen synthase was higher in the fetal lung and heart while phosphorylase activity was higher in all three tissues from the diabetic group. The activities of key enzymes involved in glycolysis were not affected. No difference was observed in the concentration of total phospholipids or in the ability of the airway fluid to reduce surface tension. In contrast, fetal lungs from diabetic does did not expand as well as the controls and retained less air on deflation. These findings suggest that the utilization of glycogen in fetal lungs from the diabetic does was not complete and that the increased incidence of respiratory distress in infants of diabetic mothers may not be due to a lack of surfactant.
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PMID:Maternal diabetes and its effect on biochemical and functional development of rabbit fetal lung. 340 84


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