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

Particularly rich in polyunsaturated fatty acids, the retina constitutes an excellent model for testing the functional consequences of membrane lipoperoxidation. The effects could be quantified by measuring the amplitude of the electroretinogram which represents the characteristic response of the retina to its physiological stimulus (light photons). The authors report results obtained on isolated rat retina maintained in survival by perfusion. The membrane lipid peroxidation is induced by the non enzymatic catalytic system (Fe2+ + ascorbate). In the presence of such a system, the amplitude of the b-wave of the electroretinogram rapidly decreases and the survival time is notably shortened. These results are discussed with regards to the mechanism generating the electroretinogram and the specific role played by the disk membrane and plasmic membrane of the rod outer segment. Finally, the authors test the radical scavenger properties of a Ginkgo biloba extract. The results indicate that such an extract develops an antiperoxidative effect probably connected with its flavonoid composition. With this extract the survival time of the isolated retina is significantly increased and this result could be related to the retinal cell membrane disorders observed in diabetes.
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PMID:[Effects of oxygenated free radicals on the electrophysiological activity of the isolated retina of the rat]. 405 20

An hypothesis is proposed relating the possible role of vitamin deficiency as an etiologic factor contributing to periodontal disease in diabetes. The hypothesis is based upon the following: (1) transport of ascorbate across cell membranes may be impaired by glucose, but facilitated by insulin; (2) glucose utilization is significantly accelerated by sublethal concentrations of endotoxin; (3) endotoxin-induced histamine sensitivity of tissue is enhanced by ascorbic deficiency; and (4) ascorbic acid deficiency alters mucosal barrier function. The interrelationship of these factors is discussed.
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PMID:Diabetes and periodontal diseases. Possible role of vitamin c deficiency: an hypothesis. 616 18

The composition and nutritional adequacy of subject-selected high carbohydrate, low fat diets were investigated in six women with insulin-dependent diabetes mellitus. Subjects were randomly assigned to begin either the experimental diet with 65% carbohydrate, 20% fat, and 15% protein for 6 wk, or a control diet with 45% carbohydrate, 40% fat, and 15% protein for 4 wk. All subjects completed both dietary periods in a cross-over experimental design. Subjects were allowed free selection in their choice of carbohydrate-rich foods. The resulting selections produced diets with 51% simple and 49% complex carbohydrates and 50 g of dietary fiber during the experimental diet. Similar proportions were also selected during the control diet. Blood chemistries revealed no significant changes in thiamin, riboflavin, vitamin B6, pyridoxal 5'-phosphate, ascorbate, vitamin E, calcium, selenium, or zinc concentrations between the two dietary periods. With the exception of vitamin B6, all vitamin and mineral values were within normal respective ranges. Vitamin B6 status, as assessed by pyridoxal 5'-phosphate, were below or just above the levels of marginal deficiency (2.2 nmol/100 ml) in four of the six individuals, but the lower level observed occurred independent of the dietary treatments. The present study demonstrates that subject-selected high carbohydrate, low fat diets were much lower in complex carbohydrates and fiber than diets previously tested. In addition, the concentration of several nutrients did not appear to be adversely affected by these diets.
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PMID:The composition and nutritional adequacy of subject-selected high carbohydrate, low fat diets in insulin-dependent diabetes mellitus. 634 10

Rates of dehydroascorbate uptake by blood granulocytes and mononuclear cells are slower, and plasma ascorbate concentrations are lower, among persons with diabetes mellitus than in nondiabetic subjects. These measurements do not correlate with one another or with simultaneously measured plasma glucose or glycosylated hemoglobin; they do not differ with type of diabetes or mode of treatment. In those diabetic granulocytes that exhibit slow dehydroascorbate uptake, maximal velocity (Vmax) transport rates for dehydroascorbate, 2-deoxyglucose, and 3-O-methylglucose are decreased, each to the same degree, while Km values for transport of these ligands are not different from those observed in nondiabetic cells. Since diffusion of these ligands is facilitated by a common transporter, these observations may reflect decreased numbers of glucose transporters in the plasma membranes of some diabetic leukocytes.
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PMID:Plasma ascorbate concentrations and blood cell dehydroascorbate transport in patients with diabetes mellitus. 670 18

Malignant external otitis (MEO) is a rare disease due to a Pseudomonas infection of the external ear occurring in an elderly patient with uncontrolled diabetes mellitus. Its high mortality raises the question of an alteration of the defense mechanisms of the body. A 58-year-old man was affected with MEO, and after several months of unsuccessful treatment, a study of the function of his polymorphonuclear neutrophil leukocytes (PMNs) revealed a defect of the migration capability. Ascorbic acid (vitamin C) was proved in vitro to be able to improve the results of the migration test. The patient was treated for one month with ascorbic acid and, parallel to the normalization of the chemotaxis test results, the ear lesions healed. The mechanism of such an alteration of the PMN function, implying several factors (the active infection, old age, and diabetes mellitus), is still unclear. Nevertheless, it is certainly important to test the PMN function in patients with MEO and treat them with immunomodulators.
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PMID:Malignant external otitis and polymorphonuclear leukocyte migration impairment. Improvement with ascorbic acid. 705 15

Quantitative and qualitative composition of phospholipids as well as lipid peroxidation were studied in outer and inner mitochondrial membranes and microsomal fraction from rat liver tissue under conditions of alloxane diabetes. In the diabetes amount of phospholipids, mainly cardiolipins and phosphatidylethanolamines, was increased in the inner and decreased in the outer mitochondrial membranes. Phosphatidylcholines and phosphatidylserines were increased in microsomal fraction. At the same time, lipid peroxidation was activated both in ascorbate- and NADPH-dependent systems of oxidation. These data suggest that lipid peroxidation affects the composition of mitochondrial membranes either by means of removing of the substances from membranes or via their redistribution between the subcellular fractions.
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PMID:[Phospholipid-phospholipid relations and changes of free radical lipid oxidation in biological membranes during alloxan diabetes]. 717 34

We studied the effect of supplementation with vitamins C, E and beta-carotene (PARABION, produced by Syndipharma) on antioxidative status in kidneys of male Wistar rats with diabetes induced by intravenous application of streptozotocin (45 mg.kg-1 of body weight). The animals received subtherapeutic doses of Insulin Interdep (6 U.kg-1 of body weight). A significant decrease of malondialdehyde (MDA), reduced (GSH) and oxidized (GSSG) glutathione and reduction of the activities of Se-glutathione peroxidase (Se-GSH-PX, EC. 1.11.1.9.) and glutathione S-transferase (GST, EC. 2.5.1.18.) were observed in kidneys of diabetic rats treated with these vitamins. On the contrary, the activity of CuZn-superoxide dismutase (CuZn-SOD, EC. 1.15.1.1) and the level of vitamin C (vit. C) increased significantly. No changes were observed for vitamin E (vit. E), beta-carotene and catalase (CAT, EC. 1.11.1.6). Supplementation with vitamins C, E and beta-carotene resulted in an improvement of antioxidative status of kidneys of rats with streptozotocin-induced diabetes.
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PMID:Effect of intake of exogenous vitamins C, E and beta-carotene on the antioxidative status in kidneys of rats with streptozotocin-induced diabetes. 747 41

Male guinea pigs subjected to prolonged marginal ascorbic acid deficiency developed moon facies and oedema, features of functional adrenal hypercorticism. Compared with age- and sex-matched controls fed an adequate diet for a similar period, ascorbate deficiency had no effect on submandibular gland weight but elicited a significant (p < 0.005) reduction in stimulated whole-saliva flow rate. Plasma cortisol concentration (nmol/L) was significantly increased (p < 0.005) in the deficient animals (998.21 +/- 57.19 compared to 254.66 +/- 15.62 for the controls). Associated with marked hypercortisolaemia in the deficient animals was a significant (p < 0.01) but less prominent increase in the whole-saliva cortisol level, resulting in a mean saliva/plasma cortisol ratio of 46% for this group compared to 72% for the controls. Increased corticosteroid levels suppress immunological and inflammatory responses, particularly neutrophil function, impair production of some cytokines, inhibit collagen synthesis, and impair wound healing and bone matrix formation. Numerous conditions such as ageing, stress, smoking, ionizing radiation, ingestion of drugs, protein malnutrition, diabetes, and several other pathological states, which are among the risk factors for xerostomia and periodontal/oral mucosal lesions, promote tissue depletion of ascorbate. This study suggests that increased salivary and blood levels of glucocorticoids in these conditions may be important in reducing the ability of the host to mount an effective immune response to oral pathogens.
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PMID:Effect of marginal ascorbic acid deficiency on saliva level of cortisol in the guinea pig. 748 75

Ascorbate (vitamin C) degradation products can undergo non-enzymatic glycation (Maillard reaction) with proteins to form highly crosslinked structures with brown pigmentation and characteristic fluorescence. Proteins in the body, especially the long-lived proteins develop similar changes during aging and diabetes. Several studies have shown excessive degradation of ascorbate in plasma in diabetes, and in ocular lens during aging and cataract formation. Recent studies have suggested that ascorbate degradation products-mediated glycation plays a role in lens pigmentation and cataract formation. However, the precise chemical nature of ascorbate-specific advanced glycation end-products are not known. Here, we report the purification and characterization of a glycation end-product derived from one of the major degradation products of ascorbate, L-threose. This compound was characterized to be 2-acetamido-6-(3-(1,2-dihydroxyethyl)-2-formyl-4-hydroxymethyl-1- pyrrolyl)hexanoic acid (formyl threosyl pyrrole or FTP) formed by the condensation of epsilon-amino group of lysine with two molecules of threose. Formation of FTP occurred rapidly in the incubation of threose and lysine and reached plateau level within a day. We have developed a sensitive assay for its quantification in proteins based on enzyme digestion followed by HPLC. Ribonuclease A and human lens crystallins incubated with L-threose showed time- and sugar concentration-dependent increases in FTP, reaching 8.2 and 2.48 nmol per mg protein, respectively after one week of incubation. Human plasma proteins showed a peak with identical retention time as that of purified FTP under two different HPLC conditions. FTP may be used as a sensitive marker to assess ascorbate-mediated protein glycation and modifications in aging and diabetes.
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PMID:Protein modification by the degradation products of ascorbate: formation of a novel pyrrole from the Maillard reaction of L-threose with proteins. 749 3

The prevalence of coronary artery disease (CAD) in the urban population of India is similar to that in developed countries; Indian immigrants in industrialized countries have the highest prevalence of CAD. This is a cross-sectional survey within a random sample of a single urban setting in India. The relation between risk of CAD and plasma levels of vitamins A, C, E, and beta-carotene was examined in 72 of 595 elderly subjects (12.1%) with CAD (aged 50 to 84 years). Plasma levels of vitamins A, C, E, and beta-carotene were significantly related to risk of CAD. Smoking (n = 145) and diabetes (n = 70) were the confounding factors. Lipid peroxides were higher in patients with CAD and diabetes, and in those who smoked. The inverse relation between CAD and low plasma vitamin C was substantially reduced after adjustment for smoking and diabetes. Vitamin A and E levels remained independently and inversely related to the risk of CAD after adjustment for age, smoking, diabetes, blood pressure, blood lipoproteins, and relative weight and body mass index. The adjusted odds ratios for CAD between the lowest and highest quintiles of vitamin E levels were 2.53 (95% confidence interval [CI] 1.11 to 5.31), vitamin C, 2.21 (95% CI 1.12 to 3.15), and beta-carotene, 1.72 (95% CI 0.88 to 3.62). The fatty acid composition of the diet, blood lipid levels, central obesity (waist-hip ratio), smoking habits, blood pressure, and plasma insulin levels do not appear to account for high rates of CAD among elderly Indians.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Dietary intake, plasma levels of antioxidant vitamins, and oxidative stress in relation to coronary artery disease in elderly subjects. 750 2


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