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

Recent reports suggest that excess amounts of sugar alcohol are linked to leukocyte dysfunctions associated with diabetes. As the polyol pathway has not been firmly established in leukocytes, we have investigated NADPH-dependent reductases and sugar alcohol formation in dog leukocytes. NADPH-dependent reductase activity was observed with DL-glyceraldehyde as substrate in both mononuclear and polymorphonuclear leukocytes isolated from dog. By chromatofocusing, this activity corresponded primarily to aldehyde reductase rather than aldose reductase. The enzymatic conversion of glucose to the sugar alcohol sorbitol in leukocytes was confirmed in vitro by 19F nuclear magnetic resonance (NMR) spectroscopy using 3-deoxy-3-fluoro-D-glucose as substrate. The NMR spectrum obtained after incubation with 10 Mm 3-deoxy-3-fluoro-D-glucose at 37 degrees C for 24 h displayed newly formed 3-deoxy-3-fluoro-D-sorbitol and 3-deoxy-3-fluoro-D-fructose peaks with both mononuclear and polymorphonuclear leukocytes. Sugar alcohol production in leukocytes from galactose-fed dogs was also observed in vivo. Galactitol accumulation was consistently observed by gas chromatography to occur in mononuclear cells while only trace amounts of galactitol were observed in polymorphonuclear leukocytes. Activation of NADPH oxidase activity in neutrophils isolated from galactose-fed dogs by zymosan was also significantly reduced compared to that of nongalactosemic control dogs. These results indicate that glucose is converted to fructose through sorbitol in both mononuclear and polymorphonuclear leukocytes despite the observations that these cells primarily contain aldehyde reductase rather than aldose reductase. In vivo, sugar alcohol accumulation in mononuclear cells is greater than in polymorphonuclear leukocytes.
J Diabetes Complications
PMID:Polyol pathway and NADPH-dependent reductases in dog leukocytes. 897 81

Periodontal disease, a frequent complication of diabetes mellitus, is the major cause of tooth loss. However, studies on neutrophil function in patients with this condition have yielded contradictory findings. The NADPH oxidase activity of 40 diabetic patients with periodontosis who were on metabolic control was evaluated and compared with that in 40 healthy subjects. Superoxide anion production was measured by a photometric method, with NBT reduction at 490 nm in a microplate reader and by a microscopic method, with a percentage of positive PMNs with granules of formazan in the cytoplasm. When the PMN respiratory burst was activated by phorbol myristate acetate (PMA), a protein kinase C (PKC) soluble activator, superoxide production of diabetics (4.31 +/- 1.67 A x 10(-3)/min) and normal subjects (4.25 +/- 1.25 A x 10(-3)/min) was comparable by photometric method, whereas a significantly defective response to opsonized zymosan was observed when the microscopic method was used (58 +/- 17% in diabetics and 66 +/- 18% in controls; p = 0.05). Therefore in patients with diabetes the impact on PMN function is of multifactorial origin, and is probably correlated to the glucose level and to glycation of PMN protein, such as NADPH oxidase or myeloperoxidase. Alternatively, glucose in PMN may be reduced by aldose reductase to polyols, and this pathway requires NADPH, the coenzyme for the respiratory burst. Moreover, we found that superoxide production in response to opsonized zymosan was reduced in diabetic patients. The activation of protein tyrosine kinase (PTK) is an important mechanism underlying transmembrane signaling and, moreover, protein tyrosine phosphorylations, stimulated by zymosan receptor-mediated activation, might be caused by the activation of specific PTK, whereas activation by PMA is probably mediated through another PKC type.
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PMID:Respiratory burst of neutrophils in diabetic patients with periodontal disease. 970 64

We examined the levels of reactive oxygen-related enzymes in human umbilical vein endothelial cells cultured with high concentrations of glucose, in vitro. From the results, elevated levels of catalase mRNA and its protein were exhibited in the presence of higher glucose. In addition, the message level of p22-phox as the active center of NADPH oxidase, was slightly increased. Taken together, the endothelial injury induced by diabetes may associated to the elevated level of O2- production. However, the level of catalase as .OH scavenger was mainly increased, cooperatively.
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PMID:[Expression of reactive oxygen-related enzymes in human umbilical vein endothelial cells (HUVEC) cultured with high concentrations of glucose]. 1044 48

Impairment of nitric oxide-dependent vascular relaxation is a characteristic feature of the insulin-resistant state. To understand those mechanisms, we examined imbalance of O2-/NO production in aortic endothelial cells obtained from high fructose-fed, exogenous hyperinsulinemic, and control rats. Aortic segments from both high fructose-fed and insulin-treated rats produced a 4-fold more O2- than control rats evaluated by a chemiluminescence method. The O2- production in the aortas of both high fructose-fed and insulin-treated rats was mediated through activation of NADH/NADPH oxidase. In isometric tension studies, high fructose vessels with endothelium elicited impaired relaxation in response to acetylcholine or a calcium ionophore A23187 when compared with control rats, whereas these impaired vascular responses were not found in insulin-treated rats. Furthermore, endothelial constitutive NO synthase activity was increased in vessels from insulin-treated rats, but decreased in vessels from high fructose-fed rats. These results indicate that relative excess of O2- production through activation of NADH/NADPH oxidase over NO generation in endothelial cells may contribute to impaired endothelial-dependent relaxation in insulin-resistant state.
Diabetes Res Clin Pract 1999 Sep
PMID:Free radical production in endothelial cells as a pathogenetic factor for vascular dysfunction in the insulin resistance state. 1058 73

Superoxide anion plays important roles in vascular disease states. Increased superoxide production contributes to reduced nitric oxide (NO) bioactivity and endothelial dysfunction in experimental models of vascular disease. We measured superoxide production by NAD(P)H oxidase in human blood vessels and examined the relationships between NAD(P)H oxidase activity, NO-mediated endothelial function, and clinical risk factors for atherosclerosis. Endothelium-dependent vasorelaxations and direct measurements of vascular superoxide production were determined in human saphenous veins obtained from 133 patients with coronary artery disease and identified risk factors. The predominant source of vascular superoxide production was an NAD(P)H-dependent oxidase. Increased vascular NAD(P)H oxidase activity was associated with reduced NO-mediated vasorelaxation. Furthermore, reduced endothelial vasorelaxations and increased vascular NAD(P)H oxidase activity were both associated with increased clinical risk factors for atherosclerosis. Diabetes and hypercholesterolemia were independently associated with increased NADH-dependent superoxide production. The association of increased vascular NAD(P)H oxidase activity with endothelial dysfunction and with clinical risk factors suggests an important role for NAD(P)H oxidase-mediated superoxide production in human atherosclerosis. The full text of this article is available at http://www.circresaha.org. Key Words:atherosclerosis endothelium superoxide nitric oxide diabetes Two Distinct Congenital Arrhythmias Evoked by a Multidysfunctional Na(+) Channel Marieke W. Veldkamp, Prakash C. Viswanathan, Connie Bezzina, Antonius Baartscheer, Arthur A.M. Wilde, Jeffrey R. Balser Abstract-The congenital long-QT syndrome (LQT3) and the Brugada syndrome are distinct, life-threatening rhythm disorders linked to autosomal dominant mutations in SCN5A, the gene encoding the human cardiac Na(+) channel. It is believed that these two syndromes result from opposite molecular effects: LQT3 mutations induce a gain of function, whereas Brugada syndrome mutations reduce Na(+) channel function. Paradoxically, an inherited C-terminal SCN5A mutation causes affected individuals to manifest electrocardiographic features of both syndromes: QT-interval prolongation (LQT3) at slow heart rates and distinctive ST-segment elevations (Brugada syndrome) with exercise. In the present study, we show that the insertion of the amino acid 1795insD has opposite effects on two distinct kinetic components of Na(+) channel gating (fast and slow inactivation) that render unique, simultaneous effects on cardiac excitability. The mutation disrupts fast inactivation, causing sustained Na(+) current throughout the action potential plateau and prolonging cardiac repolarization at slow heart rates. At the same time, 1795insD augments slow inactivation, delaying recovery of Na(+) channel availability between stimuli and reducing the Na(+) current at rapid heart rates. Our findings reveal a novel molecular mechanism for the Brugada syndrome and identify a new dual mechanism whereby single SCN5A mutations may evoke multiple cardiac arrhythmia syndromes by influencing diverse components of Na(+) channel gating function. The full text of this article is available at http://www.circresaha.org. Key Words: Na(+) channel inactivation long-QT syndrome Brugada syndrome
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PMID:UltraRapid communications : vascular superoxide production by NAD(P)H OxidaseAssociation with endothelial dysfunction and clinical risk factors 1080 75

Superoxide anion plays important roles in vascular disease states. Increased superoxide production contributes to reduced nitric oxide (NO) bioactivity and endothelial dysfunction in experimental models of vascular disease. We measured superoxide production by NAD(P)H oxidase in human blood vessels and examined the relationships between NAD(P)H oxidase activity, NO-mediated endothelial function, and clinical risk factors for atherosclerosis. Endothelium-dependent vasorelaxations and direct measurements of vascular superoxide production were determined in human saphenous veins obtained from 133 patients with coronary artery disease and identified risk factors. The predominant source of vascular superoxide production was an NAD(P)H-dependent oxidase. Increased vascular NAD(P)H oxidase activity was associated with reduced NO-mediated vasorelaxation. Furthermore, reduced endothelial vasorelaxations and increased vascular NAD(P)H oxidase activity were both associated with increased clinical risk factors for atherosclerosis. Diabetes and hypercholesterolemia were independently associated with increased NADH-dependent superoxide production. The association of increased vascular NAD(P)H oxidase activity with endothelial dysfunction and with clinical risk factors suggests an important role for NAD(P)H oxidase-mediated superoxide production in human atherosclerosis. The full text of this article is available at http://www.circresaha.org.
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PMID:Vascular superoxide production by NAD(P)H oxidase: association with endothelial dysfunction and clinical risk factors. 1080 76

The term oxidative stress refers to a situation in which cells are exposed to excessive levels of either molecular oxygen or chemical derivatives of oxygen (ie, reactive oxygen species). Three enzyme systems produce reactive oxygen species in the vascular wall: NADH/NADPH oxidase, xanthine oxidoreductase, and endothelial nitric oxide synthase. Among vascular reactive oxygen species superoxide anion plays a critical role in vascular biology because it is the source for many other reactive oxygen species and various vascular cell functions. It is currently thought that increases in oxidant stress, namely excessive production of superoxide anion, are involved in the pathophysiology of endothelial dysfunction that accompanies a number of cardiovascular risk factors including hypercholesterolemia, hypertension and cigarette smoking. On the other hand, vascular oxidant stress plays a pivotal role in the evolution of clinical conditions such as atherosclerosis, diabetes and heart failure.
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PMID:Vascular oxidant stress: molecular mechanisms and pathophysiological implications. 1087 82

Diabetes mellitus is associated with increased ROS generation, oxidative injury and obesity. To elucidate the relationship between nutrition and ROS generation, we have investigated the effect of glucose challenge on ROS generation by leucocytes, p47phox protein, a key protein in the enzyme NADPH oxidase and alpha-tocopherol levels. Blood samples were drawn from 14 normal subjects prior to, at 1, 2 and 3 h following ingestion of 75 g glucose. ROS generation by polymorphonuclear leucocytes (PMNL) and mononuclear cells (MNC) increased to a peak of 244 +/- 42% and 233 +/- 34% of the basal respectively at 2h. The levels of p47phox in MNC homogenates increased significantly at 2 h and 3 h after glucose intake. alpha-Tocopherol levels decreased significantly at 1 h, 2 h and 3 h. We conclude that glucose intake stimulates ROS generation and p417phox of NADPH oxidase; increases oxidative load and causes a fall in alpha-tocopherol concentration.
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PMID:Glucose challenge stimulates reactive oxygen species (ROS) generation by leucocytes. 1094 14

It is well known that infections in patients with diabetes mellitus are more severe, although there is controversy for increased susceptibility to them. Non-specific immune response mechanisms could be related to defense and/or susceptibility to pathogens. The aim of this study was to investigate the activity of several enzymes involved in the primary host defense mechanisms in non-insulin dependent diabetes mellitus (NIDDM). Twenty NIDDM females with a mean HbA(1c) level of 8.19% were included. No patient had clinical evidence of infection. As controls 20 healthy females were studied. The enzymes tested were dipeptidyl-peptidase I (DPP-I), cathepsin B and D, NADPH oxidase and superoxide dismutase (oxidative burst) and collagenase. Isolated leukocytes were incubated with the specific substrates in pyrogen free conditions. The intracellular enzyme activity was analyzed by flow cytometry. Collagenase enzymatic activity was similar in the three leukocyte subpopulations studied. Oxidative burst induction in monocytes was comparable between both groups. Enzyme activity of cathepsin B and D in all cell subsets, oxidative burst in PMN cells, and DPP-I in lymphocytes and monocytes from patients, was higher than those from healthy females (P<0.05). Overall, our findings demonstrate an enhanced functional status of several intracellular leukocyte enzymes in NIDDM. Furthermore, the increased oxidative burst induction and the consequent production of free radicals, may contribute to vascular complications. Other mechanisms - either from the non-specific or specific immune response - deserve investigation to establish if diabetic patients are more susceptible to infectious diseases.
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PMID:Innate immune response mechanisms in non-insulin dependent diabetes mellitus patients assessed by flow cytoenzymology. 1106 9

Accumulating evidence suggests that oxidant stress alters many functions of the endothelium, including modulation of vasomotor tone. Inactivation of nitric oxide (NO(.)) by superoxide and other reactive oxygen species (ROS) seems to occur in conditions such as hypertension, hypercholesterolemia, diabetes, and cigarette smoking. Loss of NO(.) associated with these traditional risk factors may in part explain why they predispose to atherosclerosis. Among many enzymatic systems that are capable of producing ROS, xanthine oxidase, NADH/NADPH oxidase, and uncoupled endothelial nitric oxide synthase have been extensively studied in vascular cells. As the role of these various enzyme sources of ROS become clear, it will perhaps be possible to use more specific therapies to prevent their production and ultimately correct endothelial dysfunction.
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PMID:Endothelial dysfunction in cardiovascular diseases: the role of oxidant stress. 1107 78


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