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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Placental glycogen metabolism was investigated in rat pregnancies complicated by streptozotocin-induced diabetes mellitus. Both diabetic and control placentas had increasing glycogen concentration from day 14 to day 16, after which glycogen concentration declined rapidly. The diabetic placentas had significantly elevated glycogen concentration when compared to controls from day 16 through term (day 22). Near term, when control glycogen content fell close to zero, the diabetic placentas still had appreciable glycogen levels. Total phosphorylase activity in the diabetic placentas was significantly higher than control values from day 16-22. Phosphorylase A activity, however, was lower in the diabetic placentas late in gestation, corresponding to the increased glycogen concentration seen at that time. Diabetic placentas had increased total synthase activity on the final 3 days of gestation, although synthase A activity was lower than corresponding control values. The placentas in this model are markedly increased in size late in gestation. No difference in protein concentration or protein/DNA ratio was noted. Total DNA content per placenta was significantly increased in the diabetic placentas after day 16 when compared to controls. Placental DNA in the diabetics continued to increase until day 18-19 of gestation, whereas DNA content in control placentas remained constant after day 16. Thus, the diabetic placentas apparently continue the process of DNA replication after DNA synthesis is complete in the controls.
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PMID:Placental growth and glycogen metabolism in streptozotocin diabetic rats. 641 43

The mechanism of liver glycogen synthesis after refeeding has been investigated in diabetic rats, diabetic insulin-treated rats, and in control rats fasted for 48 h. The accumulation of liver glycogen was the same in diabetic rats and in control rats after 2 h of feeding, but did not proceed any further in the diabetic group during the next 2 h. Insulin-treated diabetic rats synthesized five times more hepatic glycogen than the control rats after 1 h of refeeding, but the amount accumulated at the end of the refeeding period was the same. Feeding resulted in a transient activation of glycogen synthase in untreated as well as in treated diabetic rats. In control rats, however, glycogen synthase was already partially in the active form before access to food, and the onset of glycogen synthesis occurred without further activation of the enzyme. A transient inactivation of phosphorylase was observed in all groups during the meal, but was very slight in the untreated diabetic rats in which phosphorylase a values were already reduced before the access to food. Peripheral glycemia was markedly increased upon refeeding in treated and untreated diabetic rats, but remained normal in control rats. Peripheral insulinemia was increased by feeding in the control rats and remained low in the diabetic rats and high in the insulin-treated diabetic rats. The results indicate that, in normal controls in contrast to diabetic rats, synthase activation is not a prerequisite for the initiation of glycogen synthesis after a meal; phosphorylase inactivation may be of major importance in normal controls, but also appears to play a role in the diabetic animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1984 Oct
PMID:The onset of liver glycogen synthesis in fasted-refed rats. Effects of streptozocin diabetes and of peripheral insulin replacement. 643 61

The effects of variations of glycemia from 1.7 to 35 mM on the activity of glycogen synthase and phosphorylase, on glycogen content, and on U-14C-glucose incorporation into glycogen in the liver of the near-term rat fetus were investigated. Hypoglycemia did not affect the activities of phosphorylase and synthase; total glycogen content was not modified, but incorporation of labeled glucose was markedly decreased. This is consistent with a decreased glycogen synthesis. A slight hyperglycemia (about 5.5 mM) sharply decreased phosphorylase a (active) activity but increased slightly glycogen synthase a activity; liver glycogen content and labeled glucose incorporation were both enhanced. Higher levels of glycemia induced a decrease of phosphorylase a activity of the same order, but by contrast, glycogen synthase a activity increased progressively with increasing glycemia. Sequential study showed that hyperglycemia first induced the decrease of phosphorylase activity, then increased synthase activity. Marked hyperglycemia strongly enhanced liver glycogen content and labeled glucose incorporation. The fetal liver appears very responsive to acute variations of glycemia. The mechanisms seem to be oriented toward maximal glycogen accumulation.
Diabetes 1980 Apr
PMID:Effects of acute variation of fetal glycemia on glycogen storage and on glycogen synthase and phosphorylase activities in the liver of the rat fetus. 676 90

A series of synthetic peptides corresponding to the amino-terminal sequence of human growth hormone (hGH) has been studied for insulin-potentiating effects using three different bioassay systems: (1) intravenous insulin tolerance tests, (2) insulin binding to specific receptors of hepatic plasma membranes and isolated hepatocytes, and (3) modulation of insulin-dependent glycogen synthase and glycogen phosphorylase in muscle and adipose tissue. The results establish that the minimum active sequence is the hexapeptide (hGH 8-13) containing H2N-Arg-Leu-Phe-Asp-Asn-Ala-COOH and strongly indicate that the insulin-potentiating action of the active peptides is to increase the binding of insulin to specific receptors and thus modulate the action of glycogen synthase and phosphorylase, producing hypoglycemia as the result of increased glycogen storage in liver, muscle, and adipose tissue.
Diabetes 1980 Oct
PMID:The minimal amino acid sequence of the insulin-potentiating fragments of human growth hormone: its mechanism of action. 677 19

The effects of epinephrine, vasopressin, and A23187 on glycogen synthase and phosphorylase were examined in isolated rat liver parenchymal cells from fed animals. In normal calcium-containing hepatocytes, epinephrine, vasopressin, and A23187 were more potent at inactivating glycogen synthase, previously activated with 30 mM glucose, than at activating phosphorylase. In calcium-depleted hepatocytes (cells washed and incubated with 1 mM EGTA), the effect of epinephrine on both enzyme activities was impaired, while the effects of vasopressin and A23187 were completely abolished. Insulin was more effective at inhibiting the effects of epinephrine in calcium-depleted cells, but it was without effect on vasopressin and A23187 actions. The ability of epinephrine, vasopressin, and A23187 to elicit calcium efflux from cells was not altered by the presence of 30 mM glucose. These findings are consistent with the idea that the alpha-adrenergic inactivation of liver glycogen synthase may be a result of the increased stimulation of a calcium-dependent protein kinase, possibly phosphorylase b kinase.
Diabetes 1980 Aug
PMID:The role of calcium in alpha-adrenergic inactivation of glycogen synthase in rat hepatocytes and its inhibition by insulin. 677 24

Rat liver glycogen synthase shows almost a 2-fold increase in activity 8 days after onset of alloxan diabetes. Immunological and catalytic criteria indicate that the change in activity is associated with an increase in the amount of enzyme in the diabetic. Apparent rates of degradation were determined for isolated glycogen synthase and phosphorylase from the livers of 2-, 5-, and 8-day diabetic, insulin-treated diabetic and normal rats using the double isotope ([3H]leucine and [14C]leucine) labeling method (Arias, I. M., Doyle, D., and Schimke, R. T. (1969) J. Biol. Chem. 244, 3303-3315). Relative rates of enzyme synthesis and degradation were determined by comparing the 3H incorporation and 3H/14C ratios of the isolated enzymes to the isotope labeling of a liver fraction representing the average of liver proteins. Glycogen synthase showed a gradual increase in the rate of degradation through the course of diabetes with an average relative rate of degradation in the 8-day diabetic 1.8 times greater than the normal. The relative rate of synthesis for glycogen synthase in the diabetic was 2.2- to 2.5-fold greater than the normal. Phosphorylase from 5- and 8-day diabetic rats had relative rates of degradation 4.0-5.3 times greater than enzyme from the normal. In the diabetic, the rate of degradation of phosphorylase was greater than for synthase while the opposite was observed in the normal rat. The relative rate of synthesis for phosphorylase from diabetic rats was approximately 4.5-fold greater than normal. The increased concentration of glycogen synthase in the diabetic liver is because of an increased rate of synthesis and not a decreased rate of enzyme degradation.
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PMID:Effects of alloxan diabetes on the turnover of rat liver glycogen synthase. Comparison with liver phosphorylase. 680 82

The administration of the dried leaf powder of Gymnema sylvestre regulates the blood sugar levels in alloxan diabetic rabbits. G. sylvestre therapy not only produced blood glucose homeostasis but also increased the activities of the enzymes affording the utilisation of glucose by insulin dependent pathways: it controlled phosphorylase levels, gluconeogenic enzymes and sorbitol dehydrogenase. The uptake and incorporation of [14C] glucose into the glycogen and protein are increased in the liver, kidney and muscle in G. sylvestre administered diabetic animals when compared to the untreated diabetic animals. Pathological changes initiated in the liver during the hyperglycemic phase are reversed by controlling hyperglycemia by G. sylvestre. G. sylvestre, a herb used for the control of diabetes mellitus in several parts of India, appears to correct the metabolic derangements in diabetic rabbit liver, kidney and muscle.
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PMID:Enzyme changes and glucose utilisation in diabetic rabbits: the effect of Gymnema sylvestre, R.Br. 686 51

Tissue samples were taken from the gastrocnemius muscle of 26 randomly selected, glucose-tolerant, 48-yr-old men. Hexokinase, phosphorylase, lactate dehydrogenase (LDH), succinate dehydrogenase, and lipoprotein lipase activity (LPLA), as well as the area per fiber type and capillary density, were determined. Mean fiber area correlated positively with relative body weight (r equals 0.53, P less than 0.01), but capillary density did not. The result is that, in cases of high body weight, each capillary supplies a larger muscle fiber area. Serum insulin concentration in the fasting state correlated positively with body weight (r equals 0.77, P less than 0.001) and with mean fiber area per capillary (r equals 0.87; P less than 0.001). Only during the latter part of an oral glucose tolerance test (OGTT) did blood glucose concentrations correlate with relative body weight and mean fiber area per capillary (r equals 0.42, r equals 0.51, P less than 0.05). A stepwise multiple regression analysis showed that the different muscle morphology measurements could account for 3/4 of the variation in the fasting serum insulin concentration, the fasting insulin/glucose ratio, and the blood glucose concentration at 120 min in the OGTT. Of the intracellular enzymes, only LDH (r equals -0.71, P less than 0.001) correlated with the mean fiber area per capillary. LPLA correlated with capillary density (r equals 0.66, P less than 0.001), and, long with the muscle morphology measurements, could account for 3/4 of the variation in serum triglyceride concentrations. The results show that a large mean muscle fiber area/capillary ratio indicates a morphologic imbalance, which is related to both glucose tolerance and various degrees of insulin sensitivity.
Diabetes 1981 Jan
PMID:Body weight, skeletal muscle morphology, and enzyme activities in relation to fasting serum insulin concentration and glucose tolerance in 48-year-old men. 701 1

The ultrastructure of dog cardiomyocytes was studied one month after reproducing alloxan diabetes, with respect to myocardial extraction from the blood of glucose, nonesterified fatty acids, beta-lipoproteins and ketone bodies as well as to respiration in conjunction with oxidative phosphorylation of mitochondria, hexokinase and phosphorylase activity. Destructive changes in mitochondria, increased glycogen content in cardiomyocytes were revealed in the absence of glucose consumption by the myocardium which absorbed only lipoid metabolites. Lipoid inclusions were rarely seen in cardiomyocytes. The myocardium showed the increased content of lysosomes and hydrolytic phosphorylase. It is suggested that lipoid metabolites transform to glycogen, with lysosomes participating in the process.
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PMID:[Ultrastructural manifestations of early metabolic disorders in the myocardium of dogs with alloxan diabetes]. 739 46

Impaired glycogen synthesis is present in subjects at risk for developing non-insulin-dependent diabetes mellitus (NIDDM), suggesting that it is a primary defect in NIDDM. To examine whether defects in glycogen metabolism are present at birth in an animal model of NIDDM, glycogen synthase (GS), glycogen phosphorylase (GP), and total glycogen content were measured in liver and quadriceps muscle of 1-day- and 20-week-old insulin-resistant New Zealand Obese (NZO) mice and control (NZC) mice. In livers of both neonatal and adult NZO mice, active GS was reduced by 54% and 36%, respectively, as compared with that in NZC mice (P < .03). Total liver GS activity was the same in neonates, but was 65% higher in adult NZO as compared with NZC mice (P < .02). Liver glycogen was 28% lower at birth in NZO mice (P < .03), but was 49% higher at 20 weeks of age. Active and total GP were the same in NZO and NZC animals, despite hyperinsulinemia in 20-week-old NZO mice. In muscle, active GS was reduced by 41% in both 1-day- and 20-week-old NZO mice (P < .02). Total GS was also lower in NZC mice at 1 day of age (P < .01), but not at 20 weeks. No differences were detected in GP activity or in total glycogen content in muscle. Therefore, reduced GS activity is an early defect present at birth in the insulin-resistant NZO mouse in both liver and muscle. However, it is not the sole determinant of the amount of glycogen deposited in tissues.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Defects in liver and muscle glycogen metabolism in neonatal and adult New Zealand obese mice. 747 88


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