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

Free radicals have recently been proposed to play a role in the development of diabetic retinopathy. Ischaemia and hyperglycaemia followed by recirculation have been suggested to initiate free radical production in other tissues and the aim of the present study was to examine whether this could also be the case in the retina. The present study showed retinal cell damage, as measured by pycnotic cells, to be more pronounced when ischaemia was combined with hyperglycaemia than when combined with normoglycaemia. As an indication of free radical production, catalase activity was measured, reflecting the production of hydrogen peroxide (H2O2). Small amounts of H2O2 were found to be generated in the normal retina, but did not increase during ischaemia and hyperglycaemia followed by recirculation. It thus seems, as if hyperglycaemia aggravates the harmful effects of ischaemia, but with the methods used, there does not seem to be any increase in free radical production (as measured by H2O2 production) in normal rat retina during ischaemic and hyperglycaemic conditions.
Diabetes Res 1991 Jan
PMID:Hydrogen peroxide production in ischaemic retina: influence of hyperglycaemia and postischaemic oxygen tension. 181 95

Hyperglycemia is increasingly regarded as the cause of the diabetic complications, in particular via the ability of glucose to glycate proteins and generate Maillard browning products which cross-link proteins and render them brown and fluorescent in vitro. Similar changes occur in vivo to long-lived proteins in diabetes mellitus as well as in ageing. The evidence supporting this route of glucose toxicity is discussed in the context of the ability of glucose to oxidize in vitro (catalyzed by trace amounts of transition metal) generating hydrogen peroxide, highly reactive oxidants, and protein-reactive ketoaldehyde compounds. It is suggested that protein browning in vivo may not result from the reactions of glucose with protein but from the transition metal-catalyzed reactions of other small autoxidisable substrates, such as ascorbate, with protein. Overall, studies of glycation and protein browning suggest a critical role for oxidative processes perhaps involving decompartmentalized transition metals and a variety of low molecular weight reducing agents in diabetes mellitus and ageing.
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PMID:Protein glycation and oxidative stress in diabetes mellitus and ageing. 185 74

A reduction in nerve blood flow in chronic experimental diabetes has been linked to impaired conduction. Recently, there have been reports that this is preceded by a period of functional hyperemia. The present investigation explored early changes in sciatic nerve endoneurial blood flow and function in streptozocin-treated rats with durations of diabetes from 1 wk to 4 mo. Blood flow was monitored by microelectrode polarography and hydrogen clearance in thiobutabarbital (Inactin)-anesthetized animals. It was reduced by 41% as early as 1 wk after diabetes induction. There was no evidence of an early functional hyperemia, flow remaining 44% depressed up to 4 mo. In another investigation, similar reductions in blood flow were acutely induced in normal rats rendered hyperglycemic by glucose infusion. In diabetic animals, conduction velocity in sciatic branches supplying gastrocnemius and tibialis anterior muscles was correlated with blood flow. The link was further tested using a group of 2-mo diabetic rats treated with guanethidine. Treatment caused a functional adrenergic sympathectomy, and blood flow increased to within the normal range. Conduction velocity, depressed by 26% with diabetes, was normalized by treatment. These observations support the hypothesis that hyperglycemia-induced blood flow reductions and resultant endoneurial hypoxia are important factors underlying nerve conduction deficits early in the development of diabetic neuropathy.
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PMID:Nerve blood flow in early experimental diabetes in rats: relation to conduction deficits. 185 64

Incubation of corneal collagen type I with glucose in the presence of transition metal ions (copper, iron) results in the formation of collagen aggregates insoluble in 6 M urea, and in 2% sodium dodecyl sulfate + 5% beta-mercaptoethanol. The reaction is mediated by hydrogen peroxide and transition metals since it is inhibited by catalase and by the chelating agent diethylenetriaminepentaacetic acid. Comparative studies showed that copper is more efficient than iron and that the reaction proceeds more rapidly with ribose than with glucose. The data support a mechanism involving transition metal ion catalyzed autoxidation of glucose (and possibly of Amadori products) with generation of superoxide radical. Superoxide dismutation produces hydrogen peroxide, which then generates hydroxyl radicals in the presence of transition metal ions (Fenton reaction). Hydroxyl radical attack is known to lead to cross-linking, which is enhanced in glycated proteins. The experimental data presented are consistent with in vivo alteration of collagen properties during normal aging and with the acceleration of similar changes in diabetes mellitus.
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PMID:The role of nonenzymatic glycosylation, transition metals, and free radicals in the formation of collagen aggregates. 189 43

Oxidative biotransformation of xenobiotics and endogenous substances involves glutathione in reduced form as an integral component through two mechanisms: glutathione peroxidase catalysing the reduction of hydrogen peroxide and organic hydroperoxides, and glutathione-S-transferases catalysing the conjugation of oxygenated derivatives with glutathione. We studied glutathione and glutathione-related enzyme activities in haemolysed venous blood samples from 49 healthy children and from 11 children with diabetes mellitus, 10 children with rheumatoid arthritis, seven children with active coeliac disease, and seven children with acute lymphoblastic leukaemia. Among the healthy children glutathione content and the activities of glutathione reductase, glutathione peroxidase, and glutathione-S-transferase were unrelated to sex; age-dependent differences were also minor. The patients with diabetes mellitus had decreased activity of glutathione reductase. The patients with acute lymphoblastic leukaemia had increased activity of both glutathione peroxidase and glutathione-S-transferase, possibly reflecting an adaptive response to free-radicals. The patients with active coeliac disease had control levels of all measured parameters of glutathione-related reactions indicating, since we earlier found decreased activities of glutathione peroxidase in intestinal mucosa of celiacs, that blood may not always reflect tissue-specific changes.
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PMID:Glutathione and glutathione-metabolizing enzymes in the erythrocytes of healthy children and in children with insulin-dependent diabetes mellitus, juvenile rheumatoid arthritis, coeliac disease and acute lymphoblastic leukaemia. 204 16

Emphysematous pyelonephritis is a severe necrotizing infection that usually occurs in patients with diabetes mellitus or obstructive uropathy. Although glucose fermentation has been considered as the main cause of gas production the actual mechanism remains controversial. Compositions of gas samples from 2 patients with emphysematous pyelonephritis recently encountered were analyzed, and showed 15% hydrogen, 4.8% carbon dioxide, 60% nitrogen, 6.7% oxygen and some unknown gases in case 1, and 3.4% hydrogen, 22% carbon dioxide, 66% nitrogen and 9.8% oxygen in case 2. These results tend to implicate mixed acid fermentation of glucose as the pathway by which emphysematous urinary tract infections develop.
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PMID:Mixed acid fermentation of glucose as a mechanism of emphysematous urinary tract infection. 205 76

We investigated the vascular response (blood flow and resting vascular resistance) and the metabolic response (exchange of metabolites and respiratory gases) to local insulin administration in the forearms of healthy young volunteers with the use of the perfused-forearm technique. In the postabsorptive state, the deep tissues of the forearm (mostly skeletal muscle) took up glucose (mean +/- SE 1.09 +/- 0.17 mumol.min-1.dl-1 forearm vol), beta-hydroxybutyrate (0.267 +/- 0.130 mumol.min-1.dl-1), and O2 (9.96 +/- 1.02 mumol.min-1.dl-1) and released lactate (0.284 +/- 0.098 mumol.min-1.dl-1), glycerol (0.029 +/- 0.012 mumol.min-1.dl-1), citrate (0.091 +/- 0.030 mumol.min-1.dl-1), alanine (0.184 +/- 0.044 mumol.min-1.dl-1), CO2 (7.36 +/- 0.97 mumol.min-1.dl-1), and protons (12.1 +/- 1.4 pmol.min-1.dl-1). Forearm blood flow (by venous occlusion plethysmography) was 2.95 +/- 0.18 ml.min-1.dl-1, and intra-arterial systolic/diastolic blood pressure was 116 +/- 3/76 +/- 2 mmHg. Local indirect calorimetry indicated dominance of fat as the oxidative substrate (RQ 0.76 +/- 0.09) and an energy expenditure rate of 1.03 +/- 0.11 cal.min-1.dl-1 forearm vol. One hundred minutes of intra-arterial insulin infusion (deep venous plasma insulin concn of 125 +/- 11 microU/ml) had no detectable effect on forearm blood flow, resting forearm vascular resistance, heart rate, or blood pressure. Local hyperinsulinemia significantly stimulated glucose uptake (to 4.79 +/- 0.61 mumol.min-1.dl-1 forearm vol, P less than 0.001), lactate and pyruvate release (to 0.710 +/- 0.093 and 0.032 +/- 0.016 mumol.min-1.dl-1 forearm vol, respectively; P less than 0.01 for both), potassium uptake (0.76 +/- 0.22 mueq.min-1.dl-1, P less than 0.001), and free fatty acid uptake (0.123 +/- 0.041 mumol.min-1.dl-1 forearm vol, P less than 0.05); glycerol balance switched to a net uptake (P less than 0.001), alanine release was restrained by 33% (P less than 0.05), and beta-hydroxybutyrate and citrate release were unchanged. Despite these metabolic changes, local rates of substrate oxidation and energy expenditure were not altered by insulin. In contrast, forearm proton release was significantly stimulated by insulin (to 14.8 +/- 1.4 pmol.min-1.dl-1, P less than 0.02). Proton release was also found to be directly related to resting forearm vascular resistance independent of the effect of insulin (multiple r = 0.64, P less than 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)
Diabetes 1990 Apr
PMID:Effects of insulin on hemodynamics and metabolism in human forearm. 218 Jul 59

We identified a possible endogenous substrate (pp185) of the insulin-receptor kinase in human adipocytes by treating intact cells with insulin and immunoblotting the cellular extracts with polyclonal antiphosphotyrosine antibody. This 185,000-Mr protein was phosphorylated on tyrosine residues in response to insulin in both rat and human adipocytes. The time course of pp185 phosphorylation at 37 degrees C was rapid and corresponded closely to insulin-receptor autophosphorylation but preceded insulin-stimulated glucose transport. Unlike many growth factor receptors, including the insulin receptor, pp185 was not adsorbed to wheat-germ agglutinin. We found that pp185 phosphorylation occurred at 12 degrees C and that the phosphoprotein was associated with both cytoplasmic and membrane fractions at this temperature. Furthermore, pp185 phosphorylation was induced to the same extent as insulin by vanadate and hydrogen peroxide, compounds previously shown to mimic the biologic effects of insulin. In addition, dose-response analysis of insulin-stimulated glucose transport, receptor autophosphorylation, and pp185 phosphorylation resulted in ED50 values of 0.3, 12, and 12 ng/ml, respectively. These results demonstrate the magnitude of "spare" autophosphorylation and pp185 phosphorylation with respect to glucose transport stimulation in human adipocytes. To determine whether the insulin resistance characteristic of non-insulin-dependent diabetes mellitus (NIDDM) and obesity is associated with a defect in receptor autophosphorylation and/or endogenous substrate phosphorylation, we estimated the extent of beta-subunit and pp185 phosphorylation in adipocytes from NIDDM, obese, and healthy subjects. Although the efficiency of coupling between receptor activation and pp185 phosphorylation was normal in obesity and NIDDM, the capacity for insulin-receptor autophosphorylation was approximately 50% lower in NIDDM subjects compared with nondiabetic obese or lean subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 1990 Feb
PMID:Insulin-receptor autophosphorylation and endogenous substrate phosphorylation in human adipocytes from control, obese, and NIDDM subjects. 222 34

Gastric emptying, mouth-to-cecum transit and whole gut transit of a solid-liquid meal were measured in 43 insulin-treated diabetics and in 30 control subjects by using scintigraphic techniques, the hydrogen breath test and stool markers. In the diabetics various parameters including duration of diabetes, gastrointestinal symptoms and complications such as autonomic neuropathy, peripheral neuropathy and proteinuria were determined and related to gastrointestinal transit times. Gastric emptying was significantly prolonged in diabetics as compared to the control group (p less than 0.05) with 35% of the diabetics disclosing abnormally delayed gastric emptying, whereas no significant overall differences were observed between diabetics and controls concerning mouth-to-cecum transit and whole gut transit time. However, abnormally prolonged mouth-to-cecum transit was detected in 23% and delayed whole gut transit in 26% of the diabetics (p less than 0.02 as compared to the control group). There was a significant correlation of dyspeptic symptoms and diarrhea with prolonged gastric emptying (p less than 0.001). Gastric emptying, but not mouth-to-cecum transit or whole gut transit was significantly related to autonomic nerve dysfunction (p less than 0.001) and peripheral neuropathy (p less than 0.02). Furthermore, gastric emptying and WGT were significantly correlated to proteinuria (p less than 0.03). Using a linear regression model, autonomic neuropathy, diarrhea and dyspeptic symptoms were the major parameters in predicting delayed gastric emptying. It is concluded that in diabetics different compartments of the gut are affected by gastrointestinal motor abnormalities and that these segments are probably regulated by independent or different control mechanisms.
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PMID:Gastrointestinal transit disorders in patients with insulin-treated diabetes mellitus. 230 21

The present study investigated changes of gastrointestinal transit in diabetes mellitus by a variant of the hydrogen exhalation method, which produces reliable estimates of oro-cecal transit times of a lactulose test meal. Relation to metabolic state and small fibre neuropathy was also evaluated. The latter was indexed by Airaksinen's variability score for resting pulse frequency, Ewing's index of respiratory sinus arrhythmia, and warm and cold thresholds at the foot. 15 inpatients with verified type I diabetes (nine female, six male) and eleven healthy controls (nine female, two male) were under investigation. Ages ranged from 19 to 47 and 27 to 49 years, respectively. No clearcut signs of angiopathy or neuropathy were present in patients. HbA1c values were moderately high (means +/- s = 8.2 +/- 1.6). Diabetes patients showed prolonged transit compared to controls (means +/- s = 102.7 +/- 28.2 min, and 79.6 +/- 15.4, resp.; p = 0.02, U-test). Two patients had extremely long transit times, none showed acceleration. However, neither indices of small fibre neuropathy nor metabolic parameters were significantly correlated with transit measures. Prolonged oro-cecal transit, therefore, seems to be due to a specific visceral-autonomic or primary enteric neuropathy, which is still limited to the gastrointestinal system in this stage, and/or metabolic effects.
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PMID:[Studies on orocecal transit in diabetes mellitus]. 235 97


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