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

Tests were carried out on the influence of alloxan-induced diabetes mellitus on the metabolism and the ultrastructure of ovaries of juvenile rats. The diabetes mellitus caused the following changes in the metabolism: reduction in the concentration of ATP and NADPH, increase in the lactate/pyruvate quotient to above 40, reduction in the ATP/ADP quotient to below 1, reduction in the level of activity of the hydrogen-conveying enzymes G-6-P-dehydrogenase, isocitrate dehydrogenase and malate dehydrogenase, increase in the level of activity of the alkaline phosphatase, reduction of the protein content. Ultrastructure: almost complete disappearance of the rough endoplasmic reticulum, shrinkage of the mitochondria, reduction of the cristae and condensation of the matrix. The smooth endoplasmic reticulum remains unchanged, the extent of the Golgi-complex is reduced. Easy removal of the lipid deposits.
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PMID:Metabolism and ultrastructure in ovaries of alloxan-diabetic juvenile rats. 0 67

Inhibition of glucose-stimulated insulin release by exogenous insulin has been demonstrated in pancreatic islets to be associated with a decrease of the NADPH/NADP ratio and the pentose-phosphate cycle activity. Batches of five islets were incubated for 15 and 90 minutes in 1 ml. of KRB buffer with 2 per cent albumin containing 3 mg./ml. glucose and 0, 200, 400, or 800 microU./ml. of rat insulin, and the glucose-6-phosphate (G6P) and 6-phosphogluconate (6PG) contents were determined by enzymatic cycling. In response to a rise in the concentration of insulin, the 6PG/G6P ratio decreased. A close relationship was observed between this decrease of 6PG/G6P ratio and the net insulin release, the absolute rate of glucose oxidation via the pentose phosphate cycle, and the NADPH/NADP ratios measured under similar conditions. The results suggest that exogenous insulin, directly or indirectly, regulates the pentose cycle activity in the pancreatic islets at the G6P dehydrogenase step.
Diabetes 1977 Sep
PMID:6-Phosphogluconate/glucose-6-phosphate ratio in rat pancreatic islets during inhibition of insulin release by exogenous insulin. 1 30

The content of NAD+, NADH, NADP+, NADPH in the liver of normal, fasting rats, those on the low-carbohydrate diet and suffering from alloxan diabetes was studied as affected by nictotinamide. Changes in the NAD+ content, sum of nicotinamide coenzymes, the [NAD+] + [NADP+]/[NADH] +/- [NADPH] and [NAD+] + [NADH] (sum of nicotinamide coenzymes) ratios are mainly due to nicotinamide administration. Changes in the content of reduced forms of both nucleotides depend equally on nicotinamide administration and the physiological state of animals. Response of the rat organism to nicotinamide administration consists in a sharp intensification of NAD+ synthesis and in a less pronounced intensification of NADH, NADP+ and NADPH synthesis.
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PMID:[Content of nicotinamide coenzymes in rat liver under conditions of nicotinamide administration]. 2 48

In the presence of glucose (2 mg/ml), leucine (10 mM) noticeably increased islets' NADPH contents as well as the NADPH:NADP ratio; the changes occurred as soon as 1 min after its addition. NADH concentrations were also increased by leucine. The NADPH:NADP ratio as well as insulin release stimulated by glucose plus leucine were markedly decreased by methylene blue. The thiol oxidants diamide and tert-butyl hydroperoxide also inhibited insulin secretion in response to glucose plus leucine. Employing the perfused pancreas technique, the insulin-releasing action of p-chloromercuribenzoate was further enhanced by leucine. The combined effects were inhibited by tert-butyl hydroperoxide, however. Our data suggest that the insulin-releasing action of leucine depends on the islets' NADPH and reduced glutathione (GSH); in addition, leucine may contribute to insulin secretion by increasing the islet NADPH:NADP ratio and the NADH:NAD ratio. From the data, we assume that the observed increase of NADPH may lead via GSH to an increase in the number of such thiol groups in the beta-cell membrane, which are believed to be related to stimulation of insulin release and, thus, to increase the sensitivity of the beta-cell to stimulation by glucose and/or leucine.
Diabetes 1979 Jun
PMID:Effect of leucine on the pyridine nucleotide contents of islets and on the insulin released--interactions in vitro with methylene blue, thiol oxidants, and p-chloromercuribenzoate. 3 18

The activity of enzymes with a regulatory function in the pathways of glycolysis, gluconeogenesis, NADPH generation and fatty acid synthesis was measured in the placenta and liver of rats. Compared with the liver, a high activity of pyruvate kinase was found in the placenta, indicating a high glycolytic potential; a small capacity for gluconeogenesis was also present and a moderate to low activity of enzymes associated with lipogenesis. The activity of all placental enzymes fell from day 15 to 20 of gestation irrespective of the pathway they represented. The pattern of decline continued when the gestation was prolonged up to day 26 by the administration of chorionic gonadotropin. The rates of activity disappearance over 11 days of gestation differed for each enzyme, with half-lives ranging from 2.7 days for NADP-malate dehydrogenase to 7 days for glucose-6-phosphate dehydrogenase. In contrast, the activity of hepatic enzymes either remained unchanged or showed individual adaptation to the advancing pregnancy. The regression in placental metabolic capacity after day 15 of gestation was also evident by the decrease in glucose uptake and its channelling to lactate, CO2, glycerol and fatty acids. In addition, placental ageing was associated with triglyceride accumulation, mainly due to the decrease in free fatty acid oxidation. Treatment of pregnant rats with several hormones, while markedly affecting the hepatic enzyme activities, failed to induce appreciable changes in the corresponding placental enzymes. This was illustrated in the case of triiodothyronine treatment. Similarly, insulin deficiency induced by streptozotocin failed to elicit adaptive changes in placental enzyme activities typical of diabetes like those occurring in the maternal liver; some converse responses in the placenta were attributed to hyperglycaemia. On the other hand, responses in some fetal liver enzymes were suggestive of fetal hyperinsulinaemia. These observations indicate that placental enzymes are not susceptible to endocrine regulation and imply that placental metabolism is largely independent of the physiopathological alterations affecting the maternal organism. The gradual activity decreases with gestation suggest that the enzyme complement of the placenta, once developed, is designed to last through its limited lifespan without continuous replenishment. Within this context, no mechanism seems to operate to ind1ce the adaptive synthesis of individual enzymes, and the age of the placenta appears to be the primary factor determining its enzyme activity and metabolic performance.
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PMID:Regulation of placental enzymes of the carbohydrate and lipid metabolic pathways. 3 55

In the paper the author is concerned with the histochemical estimation of the metabolic adaptation of the heart muscle of albino rats during an early experimental alloxan diabetes. It has been found that the state of experimentally produced insulin deficiency directly influences metabolism of the heart muscle and the changes observed in the histochemical reactions prove this. An increase in the intensity of histochemical reactions concerns the PAS-positive reaction and the reactions to the NADH and NADPH tetrazole reductase activities. Alkaline phosphatase shows a decrease in the enzymatic activity, whose nature is transitional and reversible with regard to cytochrome oxidase and ATP-ase. The histochemical picture of metabolic changes depends on the duration time of experimental diabetes.
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PMID:Some histochemical observations on the myocardial metabolism in experimental conditions. Part I. 21 83

Hyperinsulinemia was produced in fetal rhesus monkeys for 21 days in the last third of gestation by subcutaneous pork insulin injected at 19 U a day. Plasma insulin concentrations in treated fetuses (N = 4) were 3525 microU/ml. There was no difference in paired pre- and post-treatment fetal plasma glucose concentration. Activity of the hepatic enzymes that promote glucose utilization (glucokinase and hexokinase) and glycolysis (phosphofructokinase, pyruvate kinase, and pyruvate dehydrogenase) was unaffected. Similarly, glycogen metabolism enzymes (active and inactive synthase and phosphorylase) were unaltered. Two gluconeogenic enzymes (PEPCK and glucose-6-phosphatase) were diminished in the treated group compared with controls. Fetal hyperinsulinemia enhanced lipogenic and NADPH-producing enzyme activities, as evidenced by a twofold increase in fatty acid synthase and in citrate cleavage enzyme activity. Malic enzyme was absent. Hyperinsulinemia with euglycemia (1) increases the activity of enzymes that participate in lipogenesis, (2) decreases some of those controlling gluconeogenesis, and (3) has no effect on the enzymes of glycolysis.
Diabetes 1979 Dec
PMID:Chronic hyperinsulinemia in the fetal rhesus monkey: effects on hepatic enzymes active in lipogenesis and carbohydrate metabolism. 22 50

The activity of several regulatory enzymes representing the pathways of glycolysis, gluconeogenesis, NADPH generation and lipogenesis was measured in rat placenta maternal and foetal livers on the 20th day of gestation. Streptozotocin diabetes, induced on the 12th day of gestation, or 48 h of fasting did not induce adaptive changes in the activity of placental enzymes while producing a typical insulin deficiency pattern in maternal liver. Foetal liver enzyme activities were unaffected by fasting and in diabetes showed changes suggestive of foetal hyperinsulinaemia. A small increase was observed in the activity of placental pyruvate kinase and a small decrease in that of PEP carboxylase in diabetic and in glucocorticoid-treated rats; these changes were reciprocal to those in the maternal liver and were attributed to hyperglycaemia, as was the increase in placental glycogen. Lack of response to insulin deficiency and to other endocrine alterations indicates that placenta is not sensitive to stimuli which induce adaptive alterations in hepatic enzymes. The only consistent change found in placental enzyme activities was a decrease associated with gestational age.
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PMID:Placental enzymes of glycolysis, gluconeogenesis and lipogenesis in the diabetic rat and in starvation. Comparison with maternal and foetal liver. 72 Jul 82

Enzyme activities operative in glucose degradation and citrate cleavage pathway were studied in the adipose tissue of twenty-four patients with adult-onset diabetes and normal body weight, aged 59+/-9 years, and twenty-four matched controls. In normal tissue, type II (heat-inactivated) hexokinase moderately predominated over type I (heat-resistant). 6-Phosphofructokinase had an extremely low activity, which was by far the lowest among the ten glycolytic enzyme activities investigated, and which therefore might greatly limit the glycolytic rate. The level of glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase (decarboxylating) was elevated above that occurring in other tissues. This, especially if considered together with the low 6-phosphofructokinase activity, would suggest a major role of pentose cycle in glucose degradation. Of the citrate cleavage pathway enzymes, ATP citrate-lyase, although having a lower activity than malate dehydrogenase and malate dehydrogenase (decarboxylating) (NADP), was readily measurable, which contrasts with previous data by others. This finding is consistent with the occurrence of lipogenetic capacity in human adipose tissue. In diabetic tissue, there was a decreased activity, both on a protein and on a wet-weight basis, of enzymes concerned with the glucose entry into metabolic pathways, namely hexokinase (both type I and, especially, type II) and pentose cycle dehydrogenases, as well as of pyruvate kinase. This could be connected with the defective glucose utilization by adipose tissue in diabetes. Beside the above-mentioned dehydrogenases, malate dehydrogenase (decarboxylating) (NADP) was also diminished. The reduction of these NADPH-forming enzymes, which supply reducing equivalents for fatty acid synthesis, would suggest a depressed lipogenesis.
Diabetes 1975 Oct
PMID:Enzymes of glucose metabolism and of the citrate cleavage pathway in adipose tissue of normal and diabetic subjects. 118 27

Aldose reductase catalyzes the NADPH-linked reduction of hexoses to their respective sugar-alcohols, which are involved in the pathogenesis of "sugar-cataracts". In the lenses, the reaction catalyzed by G-6-PD is the source of NADPH supply blocking sugar-alcohol formation and consequently prevents or delays the onset of "sugar-cataracts". We have investigated the effect of G-6-PD deficiency, either experimentally induced or genetically transmitted, on the sorbitol accumulation in whole cells incubated in high glucose media and on the "sugar-cataracts" formation in a galactosemic rat model. We also screened 31 Negro male adults with diabetes mellitus for red cell G-6-PD deficiency. G-6-PD deficiency produced a significant inhibition on sorbitol accumulation in rat lenses and human red cells incubated in 50 mM glucose. In the galactosemic rat model G-6-PD deficiency experimentally induced with acetaminophen delayed the development of cataracts. Finally, two diabetic individuals were G-6-PD deficient and did not show cataracts whereas cataracts were identified in six other diabetic patients.
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PMID:Effects of G-6-PD deficiency, experimentally induced or genetically transmitted, on the sorbitol pathway activity. In vitro and in vivo studies. 130 88


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