8-hydroxy-2--deoxyguanosine and Hyperglycemia

Large, prospective, clinical trials have confirmed the efficacy of intensive blood-glucose control to prevent the onset and progression of diabetic complications. However, since it is difficult to maintain blood glucose concentrations close to the normal range, the effect of intensive therapy to prevent diabetic complications may be limited. Other approaches are therefore required to prevent the progression of diabetic complications based on the elucidation of the biological mechanisms. In this review, the impacts of mitochondrial reactive oxygen species (ROS) on diabetes-related complications are described. In endothelial cells, high glucose levels increase mitochondrial ROS, and the normalization of mitochondrial ROS production by inhibitors of mitochondrial metabolism, or by the overexpression of UCP-1 or MnSOD, prevents the glucose-induced accumulation of sorbitol, activation of protein kinase C, and formation of advanced glycation end products, all of which are believed to be major molecular mechanisms of diabetic complications. We also demonstrated that 8-hydroxydeoxyguanosine, which represents mitochondrial oxidative damage, was elevated in patients with either retinopathy, albuminuria, or the increased intima-media thickness of carotid arteries compared to patients without diabetic vascular complications. In addition, to investigate the impact of mitochondrial ROS on diabetic retinopathy in vivo, we established a novel transgenic mouse, which specifically expressed MnSOD in endothelial cells. By the introduction of diabetes, levels of urinary 8-hydroxydeoxyguanosine and expressions of VEGF and fibronectin mRNA in retinas were increased in wild type littermates; however, these observations were ameliorated in transgenic mice. Taking the results together, hyperglycemia could induce mitochondrial ROS production, associating it with the pathogenesis of diabetic vascular complications.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Deoxyguanosine; Diabetes Complications; Endothelial Cells; Fibronectins; Glycation End Products, Advanced; Humans; Hyperglycemia; Mice; Mitochondria; Protein Kinase C; Reactive Oxygen Species; Superoxide Dismutase; Vascular Endothelial Growth Factor A

We previously proposed that hyperglycemia-induced mitochondrial reactive oxygen species (mtROS) generation is a key event in the development of diabetic complications. Interestingly, some common aspects exist between hyperglycemia and hypoxia-induced phenomena. Thus, hyperglycemia may induce cellular hypoxia, and this phenomenon may also be involved in the pathogenesis of diabetic complications. In endothelial cells (ECs), cellular hypoxia increased after incubation with high glucose (HG). A similar phenomenon was observed in glomeruli of diabetic mice. HG-induced cellular hypoxia was suppressed by mitochondria blockades or manganese superoxide dismutase (MnSOD) overexpression, which is a specific SOD for mtROS. Overexpression of MnSOD also increased the expression of aquaporin-1 (AQP1), a water and oxygen channel. AQP1 overexpression in ECs suppressed hyperglycemia-induced cellular hypoxia, endothelin-1 and fibronectin overproduction, and apoptosis. Therefore, hyperglycemia-induced cellular hypoxia and mtROS generation may promote hyperglycemic damage in a coordinated manner.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Apoptosis; Blotting, Western; Cattle; Cell Hypoxia; Cell Line; Deoxyguanosine; Diabetes Mellitus, Experimental; Endothelial Cells; Endothelin-1; Fibronectins; Glucose; Hyperglycemia; Hypoxia; Mice, Inbred C57BL; Mice, Transgenic; Mitochondria; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; Superoxide Dismutase

Increased reactive oxygen species (ROS) levels produced by hyperglycemia and angiotensin-II (AT-II) are considered among the pathogenic factors in the malignant transformation of diabetic renal cells. We aimed to investigate the potential role of AT-II in the increased cancer risk seen in diabetes; measuring oxidative damage to renal DNA and protective antioxidant defenses, including adiponectin (Adp) and plasma antioxidant capacity by the Ferric Reducing Ability of Plasma (FRAP) method. In the kidney of streptozotocin (STZ)-induced (55 mg/kg) diabetic rats either treated or not treated for 3 weeks with losartan, an AT-II type 1 receptor antagonist (20 mg/kg/day); we measured 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) levels, as an index of oxidative DNA damage, circulating Adp and FRAP. Diabetic rats showed significantly higher 8-oxodGuo levels in renal DNA (8.48 ± 0.98 × 10(-6) dG, mean ± SEM n = 11) than normoglycemic ones (1.18 ± 0.04 × 10(-6) dG, mean ± SEM, n=7) and lower plasma Adp and FRAP levels in comparison to normoglycemics. The treatment of diabetic rats with losartan significantly (P < 0.01) reduced 8-oxodGuo levels (5.4 ± 0.58 × 10(-6) dG, mean ± SEM n=9) in renal DNA and conserved FRAP values. Moreover, an inverse correlation was found between 8-oxodGuo in kidney DNA and circulating Adp levels in normoglycemic and diabetic rats. Losartan treatment preserves FRAP levels, reduces DNA oxidative injury and thus the carcinogenesis risk. Furthermore, our results indicate that Adp plasma levels are a further marker of oxidative injury to the kidney and confirm that it is an important part of the plasma antioxidant defense.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adiponectin; Angiotensin II Type 1 Receptor Blockers; Animals; Antioxidants; Deoxyguanosine; Diabetes Mellitus, Experimental; DNA; DNA Damage; Enzyme-Linked Immunosorbent Assay; Hyperglycemia; Kidney; Lipids; Losartan; Malondialdehyde; Oxidative Stress; Oxygen; Random Allocation; Rats; Rats, Wistar; Reactive Oxygen Species

The overproduction of mitochondrial reactive oxygen species (ROS) plays a key role in the pathogenesis of diabetic nephropathy (DN). However, the underlying molecular mechanism remains unclear. Our aim was to investigate the role of PGC-1α in the pathogenesis of DN. Rat glomerular mesangial cells (RMCs) were incubated in normal or high glucose medium with or without the PGC-1α-overexpressing plasmid (pcDNA3-PGC-1α) for 48 h. In the diabetic rats, decreased PGC-1α expression was associated with increased mitochondrial ROS generation in the renal cortex, increased proteinuria, glomerular hypertrophy, and higher glomerular 8-OHdG (a biomarker for oxidative stress). In vitro, hyperglycemia induced the downregulation of PGC-1α, which led to increased DRP1 expression, increased mitochondrial fragmentation and damaged network structure. This was associated with an increase in ROS generation and mesangial cell hypertrophy. These pathological changes were reversed in vitro by the transfection of pcDNA3-PGC-1α. These data suggest that PGC-1α may protect DN via the inhibition of DRP1-mediated mitochondrial dynamic remodeling and ROS production. These findings may assist the development of novel therapeutic strategies for patients with DN.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Biomarkers; Deoxyguanosine; Diabetic Nephropathies; Dynamins; Gene Expression Regulation; Glucose; Humans; Hyperglycemia; Male; Mesangial Cells; Mitochondria; Mitochondrial Dynamics; Oxidative Stress; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Plasmids; Primary Cell Culture; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Signal Transduction; Transcription Factors; Transfection

Oxidative stress is increased in the retina in diabetes, and it is considered to play an important role in the development of retinopathy. Findings indicate that obtusifolin has antioxidant properties. The purpose of this study was to examine the effect of obtusifolin on retinal capillary cell apoptosis and the development of pathology in diabetes. Retina was used from streptozotocin-induced diabetic rats receiving diets supplemented with or without obtusifolin (100, 200, and 400 mg/kg) for 11 months of diabetes. Capillary cell apoptosis (by terminal transferase-mediated dUTP nick-end labeling) and formation of acellular capillaries were investigated in the trypsin-digested retinal microvessels. The effect of obtusifolin administration on retinal 8-hydroxy-2'deoxyguanosine (8-OHdG) and nitrotyrosine levels was determined by enzyme-linked immunosorbent assay. Obtusifolin administration for the entire duration of diabetes inhibited capillary cell apoptosis and the number of acellular capillaries in the retina, despite similar severity of hyperglycemia in the four diabetic groups (with and without obtusifolin). Retinal 8-OHdG and nitrotyrosine levels were significantly increased, respectively, in diabetes, and obtusifolin administration inhibited these increases. Our results demonstrate that the long-term administration of obtusifolin has beneficial effects on the development of diabetic retinopathy via inhibition of accumulation of oxidatively modified DNA and nitrotyrosine in the retina. Obtusifolin represents an achievable adjunct therapy to help prevent vision loss in diabetic patients.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Administration, Oral; Animals; Anthraquinones; Antioxidants; Apoptosis; Capillaries; Deoxyguanosine; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Hyperglycemia; Male; NF-kappa B; Oxidative Stress; Rats; Rats, Wistar; Retina; Tyrosine

Alloxan generates hydrogen peroxide in the body, and a small amount of alloxan administered to acatalasemic mice results in diabetes. D-α-Tocopherol (vitamin E) is an antioxidant which helps prevent excess oxidation in the body. In this study, we examined the effect of vitamin E on diabetes caused by alloxan administration in mice.. Mice were maintained on a vitamin E-deprived diet and supplemented diet, respectively, for 14 weeks. Alloxan was then intraperitoneally administered, and blood glucose, glucose tolerance and the insulin level in mouse blood were examined.. Hyperglycemia was observed in the mice maintained on the vitamin E-deprived diet. The incidence of hyperglycemia in the mice maintained on the vitamin E-deprived diet was significantly higher than that in the mice maintained on the supplemented diet. The abnormal glucose metabolism caused by alloxan administration was ameliorated by the vitamin E-supplemented diet.. It is deduced that vitamin E can prevent a decrease of insulin concentration in the blood in this mouse model.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Administration, Oral; Alloxan; alpha-Tocopherol; Animals; Antioxidants; Biomarkers; Blood Glucose; C-Peptide; Catalase; Deoxyguanosine; Diabetes Mellitus, Experimental; Glucose Tolerance Test; Hyperglycemia; Insulin; Insulin Resistance; Male; Mice; Mice, Inbred C3H; Oxidative Stress; Pancreas

Diabetes is characterized by hyperglycemia and development of vascular pathology. Endothelial cell dysfunction is a starting point for pathogenesis of vascular complications in diabetes. We previously showed the polyol erythritol to be a hydroxyl radical scavenger preventing endothelial cell dysfunction onset in diabetic rats. To unravel mechanisms, other than scavenging of radicals, by which erythritol mediates this protective effect, we evaluated effects of erythritol in endothelial cells exposed to normal (7 mM) and high glucose (30 mM) or diabetic stressors (e.g. SIN-1) using targeted and transcriptomic approaches. This study demonstrates that erythritol (i.e. under non-diabetic conditions) has minimal effects on endothelial cells. However, under hyperglycemic conditions erythritol protected endothelial cells against cell death induced by diabetic stressors (i.e. high glucose and peroxynitrite). Also a number of harmful effects caused by high glucose, e.g. increased nitric oxide release, are reversed. Additionally, total transcriptome analysis indicated that biological processes which are differentially regulated due to high glucose are corrected by erythritol. We conclude that erythritol protects endothelial cells during high glucose conditions via effects on multiple targets. Overall, these data indicate a therapeutically important endothelial protective effect of erythritol under hyperglycemic conditions.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Cell Death; Cell Survival; Cells, Cultured; Cytoprotection; Deoxyguanosine; Drug Evaluation, Preclinical; Eicosanoids; Erythritol; Glucose; Human Umbilical Vein Endothelial Cells; Humans; Hyperglycemia; Oxidative Stress; Sweetening Agents; Transcriptome

Chronic high glucose levels lead to the formation of advanced glycation end-products (AGEs) as well as AGE precursors, such as methylglyoxal (MG) and glyoxal, via non-enzymatic glycation reactions in patients with diabetic mellitus. Glyoxalase 1 (GLO-1) detoxifies reactive dicarbonyls that form AGEs. To investigate the interaction between AGEs and GLO-1 in mesangial cells (MCs) under diabetic conditions, AGE levels and markers of oxidative stress were measured in GLO-1-overexpressing MCs (GLO-1-MCs) cultured in high glucose. Furthermore, we also examined levels of high glucose-induced apoptosis in GLO-1-MCs. In glomerular MCs, high glucose levels increased the formation of both MG and argpyrimidine (an MG-derived adduct) as well as GLO-1 expression. GLO-1-MCs had lower intracellular levels of MG accumulation, 8-hydroxy-deoxyguanosine (an oxidative DNA damage marker), 4-hydroxyl-2-nonenal (a lipid peroxidation product), and nitrosylated protein (a marker of oxidative-nitrosative stress) compared to control cells. Expression of mitochondrial oxidative phosphorylation complexes I, II, and III was also decreased in GLO-1-MCs. Furthermore, fewer GLO-1-MCs showed evidence of apoptosis as determined by terminal deoxynucleotidyl transferase-mediated dUTP nick labeling assay, and activation of both poly (ADP-ribose) polymerase 1 cleavage and caspase-3 was lower in GLO-1-MCs than in control cells cultured in high glucose. These results suggest that GLO-1 plays a role in high glucose-mediated signaling by reducing MG accumulation and oxidative stress in diabetes mellitus.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aldehydes; Animals; Apoptosis; Caspase 3; Cell Line; Cells, Cultured; Deoxyguanosine; Diabetes Mellitus; Glycation End Products, Advanced; Hyperglycemia; Lactoylglutathione Lyase; Lipid Peroxidation; Mesangial Cells; Mice; Mitochondria; Ornithine; Oxidative Stress; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerases; Pyrimidines; Pyruvaldehyde

Methylglyoxal (MGO) is a cytotoxic metabolite produced by in-vivo glycolysis that may result in diabetic complications. The aim of this study was to determine whether MGO and oxidative stress caused apoptosis of renal podocytes in the Zucker diabetic fatty (ZDF) rat, an animal model of type 2 diabetes mellitus. Male ZDF rats aged 21 weeks developed marked hyperglycaemia with proteinuria and albuminuria. Immunohistochemical evaluation of sections of kidney demonstrated expression of MGO and 8-hydroxydeoxyguanosine (8-OHdG) in the podocytes of both normoglycaemic and diabetic rats. Podocyte apoptosis was shown through application of the TUNEL method. These findings suggest that expression of MGO and 8-OHdG is caused by hyperglycaemia, and that this expression is associated with the observed apoptosis of podocytes and is related to diabetic nephropathy.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Apoptosis; Deoxyguanosine; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diabetic Nephropathies; DNA Damage; Hyperglycemia; In Situ Nick-End Labeling; Kidney; Male; Oxidative Stress; Podocytes; Pyruvaldehyde; Rats; Rats, Zucker

The effect of glucose excursions on oxidative stress is an important topic in diabetes research. We investigated this relationship by analyzing markers of oxidative stress and glycemic data from a continuous glucose monitoring system (CGMS) in 30 individuals with normal glucose regulation (NGR), 27 subjects with impaired glucose regulation (IGR), and 27 patients with newly diagnosed type 2 diabetes (T2DM). We compared the mean amplitude of glycemic excursion (MAGE), mean postprandial glucose excursion (MPPGE), and mean postprandial incremental area under the curve (IAUC) with plasma levels of oxidative stress markers 8-iso-PGF2α, 8-OH-dG, and protein carbonyl content in the study subjects. Patients with T2DM or IGR had significantly higher glucose excursions and plasma levels of oxidative stress markers compared to normal controls (P < 0.01 or 0.05). Multiple linear regression analyses showed significant relationships between MAGE and plasma 8-iso-PGF2α, and between MPPGE and plasma 8-OH-dG in patients with IGR or T2DM (P < 0.01 or 0.05). Furthermore, 2h-postprandial glucose level and IAUC were related to plasma protein carbonyl content in the study cohort including T2DM and IGR (P < 0.01). We demonstrate that glucose excursions in subjects with IGR and T2DM trigger the activation of oxidative stress.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adult; Aged; Biomarkers; Blood Glucose; Cohort Studies; Deoxyguanosine; Diabetes Complications; Diabetes Mellitus, Type 2; Dinoprost; Female; Glucose Intolerance; Humans; Hyperglycemia; Hypoglycemia; Male; Middle Aged; Monitoring, Ambulatory; Oxidative Stress; Postprandial Period; Protein Carbonylation

Oxidative stress (OS) has been implicated in the aetiology and progression of diabetic complications including diabetic foot ulcer. In this study, the levels of lipid peroxides (LPO) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) as well as the enzymatic antioxidant activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in type 2 diabetes mellitus and diabetic foot ulcer subjects were assessed and compared with apparently healthy normal subjects to understand the involvement of OS in the subjects.. The above-mentioned OS markers were measured in 50 subjects for each of the following groups: type 2 diabetes mellitus (DM), diabetic foot ulcer (DF) and non-diabetic control (NC).. Significant elevated values of LPO (39.86%) and 8-OHdG (45.53%) were found in DM subjects compared with the NC subjects. This increase in both parameters was greater for DF subjects: 80.23% and 53.91% respectively. SOD activities were significantly reduced in DM (14.82%) and DF (4.09%) subjects in contrast with elevated activities of GPx observed in DM (21.87%) and DF (20.94%) subjects. Glycated haemoglobin/fasting plasma glucose (HbA1c/FPG) correlated positively with LPO, 8-OHdG and GPx, whereas a negative correlation was observed for SOD.. Increased oxidation subsequent to diabetic conditions induces an over-expression of GPx activity suggesting a compensatory mechanism by the body to prevent further tissue damage in the subjects.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adult; Antioxidants; Blood Glucose; Case-Control Studies; Deoxyguanosine; Diabetes Mellitus, Type 2; Diabetic Foot; Disease Progression; Female; Glutathione Peroxidase; Glycated Hemoglobin; Humans; Hyperglycemia; Lipid Peroxides; Male; Middle Aged; Oxidative Stress; Risk Factors; Superoxide Dismutase

The aim of the study was to elucidate the chain of events leading to oxidative damage in endothelial cells exposed to high glucose.. The nitric oxide synthase (NOS) cofactor tetrahydrobiopterin (BH4), the peroxynitrite decomposition catalyst FP15, the inhibitor of mitochondrial complex II thenoyltrifluoroacetone (TTFA) and the antioxidant superoxide dismutase (SOD) mimetic Mn(III)tetrakis(4-benzoic acid) porphyrin chloride (MnTBAP) were individually added to human umbilical vein endothelial cells (HUVEC) cultured in high glucose. This study was designed to establish the possible sequence of action of NOS, peroxynitrite and superoxide anion in the oxidative damage cascade.. We found that in high glucose, nitrotyrosine, 8OHdG, NO (+40%) and O2- (+300%) production, eNOS and caspase-3 expression increased, while Bcl-2 expression decreased. MnTBAP and TTFA were able to normalize all the parameters assayed. FP15 caused an increase in NO production, did not interfere with eNOS expression and O2- generation, but was able to reduce apoptosis and to normalize nitrotyrosine and 8OHdG formation. BH4 enrichment was able to reduce O2- generation, nitrotyrosine and 8OHdG formation and apoptosis. The addition of this cofactor did not affect eNOS expression, but increased NO formation, more than FP15.. These data show the starting role of superoxide anion generated at mitochondrial level in the cascade of events leading to hyperglycemia generated apoptosis.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Apoptosis; Biopterins; Caspase 3; Cells, Cultured; Deoxyguanosine; Endothelial Cells; Glucose; Humans; Hyperglycemia; Metalloporphyrins; Nitric Oxide; Nitric Oxide Synthase Type III; Proto-Oncogene Proteins c-bcl-2; Superoxides; Thenoyltrifluoroacetone; Tyrosine

Keishibukuryogan, one of the traditional herbal formulations, is used clinically to improve blood circulation. It consists of the following five crude drugs: Cinnamomi Cortex, Poria, Moutan Cortex, Persicae Semen and Paeoniae Radix. In this study, the effects of keishibukuryogan against renal damage in spontaneously diabetic WBN/Kob rats were examined. Oral administration of keishibukuryogan significantly attenuated urinary protein excretion and serum creatinine levels. It did not affect body weight loss and blood glucose levels, but it suppressed renal and hepatic weights of WBN/Kob rats. Keishibukuryogan also reduced fibronectin and transforming growth factor beta(1) (TGF-beta(1)) protein expression in the renal cortex. Furthermore, lipid peroxidation levels in both kidney and liver were significantly lower than those of untreated control WBN/Kob rats. Urinary excretion of 8-hydroxy-deoxyguanosine was suppressed by keishibukuryogan treatment. These results suggest that keishibukuryogan reduces oxidative stress by hyperglycemia, and that it protects renal function and suppresses fibronectin deposition induced by TGF-beta(1) production in WBN/Kob rats.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Blood Glucose; Creatinine; Deoxyguanosine; Diabetes Mellitus, Experimental; Drugs, Chinese Herbal; Fibronectins; Hyperglycemia; Kidney; Lipid Peroxidation; Male; Medicine, Traditional; Organ Size; Oxidative Stress; Phytotherapy; Plant Preparations; Protective Agents; Proteinuria; Rats; Rats, Wistar; Transforming Growth Factor beta1; Weight Loss

Hyperglycemia is a major independent risk factor for diabetic macrovascular disease. The consequences of exposure of endothelial cells to hyperglycemia are well established. However, little is known about how adipocytes respond to both acute as well as chronic exposure to physiological levels of hyperglycemia. Here, we analyze adipocytes exposed to hyperglycemia both in vitro as well as in vivo. Comparing cells differentiated at 4 mm to cells differentiated at 25 mm glucose (the standard differentiation protocol) reveals severe insulin resistance in cells exposed to 25 mm glucose. A global assessment of transcriptional changes shows an up-regulation of a number of mitochondrial proteins. Exposure to hyperglycemia is associated with a significant induction of reactive oxygen species (ROS), both in vitro as well as in vivo in adipocytes isolated from streptozotocin-treated hyperglycemic mice. Furthermore, hyperglycemia for a few hours in a clamped setting will trigger the induction of a pro-inflammatory response in adipose tissue from rats that can effectively be reduced by co-infusion of N-acetylcysteine (NAC). ROS levels in 3T3-L1 adipocytes can be reduced significantly with pharmacological agents that lower the mitochondrial membrane potential, or by overexpression of uncoupling protein 1 or superoxide dismutase. In parallel with ROS, interleukin-6 secretion from adipocytes is significantly reduced. On the other hand, treatments that lead to a hyperpolarization of the mitochondrial membrane, such as overexpression of the mitochondrial dicarboxylate carrier result in increased ROS formation and decreased insulin sensitivity, even under normoglycemic conditions. Combined, these results highlight the importance ROS production in adipocytes and the associated insulin resistance and inflammatory response.

Topics: 3T3-L1 Cells; 8-Hydroxy-2'-Deoxyguanosine; Acetylcysteine; Adenoviridae; Adipocytes; Animals; Blotting, Northern; Cell Differentiation; Deoxyguanosine; Diabetes Mellitus, Experimental; Dicarboxylic Acid Transporters; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Gene Expression Regulation; Glucose; Hyperglycemia; Immunoblotting; Inflammation; Insulin; Interleukin-6; Membrane Potentials; Mice; Mitochondria; Oxidative Stress; Oxygen; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Streptozocin; Time Factors; Transcription, Genetic; Up-Regulation

Considering that increased oxidative stress induced by hyperglycaemia plays a possible role in the pathogenesis of diabetic complications and that mitochondrial DNA (mDNA) is thought to be more vulnerable than nuclear DNA, we investigated what somatic mutations actually occur in the mDNA of diabetic patients. We also studied the relations between those mutations and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) which is known to increase considerably in people with diabetes.. We identified somatic mutations by subcloning and sequencing two segments of mDNA [control region (nt 15996-16401) and the segment encompassing t-RNA(Leu(UUR))(nt 3149-3404)] in the peripheral blood cells of six diabetic women and control subjects matched for age and sex. This was done in 20 colonies each. In each case we also assayed urinary 8-OHdG.. No difference in the aggregate somatic mutational burden of mDNA was found between patients and control subjects. However, the incidence of somatic transversion mutations in mDNA was significantly higher in diabetic patients than in control subjects (13.93+/-4.57 x 10(-5) vs 1.27+/-1.27 x 10(-5) mutations per base pair; p=0.031, according to Mann-Whitney U-test). There was no significant difference in transition mutations. A correlation was found between the transversion mutational burden and HbA(1)c values, but not between it and 8-OHdG content in the urine.. We showed that somatic transversion point mutations of mDNA increase in diabetic patients. Such transversion mutations can become a new biomarker for mDNA damage associated with hyperglycaemia and possibly caused by oxidative stress but not reflected by urinary 8-OHdG.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adult; Base Sequence; Diabetes Mellitus; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; DNA, Mitochondrial; Female; Guanine; Humans; Hyperglycemia; Middle Aged; Mutation; Polymerase Chain Reaction; Reference Values

Increased risks of cancers and oxidative DNA damage have been observed in diabetic patients. Many endogenous aldehydes such as 3-deoxyglucosone and glyceraldehyde (GA) increase under hyperglycemic conditions. We showed that these aldehydes induced Cu(II)-mediated DNA damage, including 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation. GA had the strongest ability to damage DNA, and addition of low concentrations of H2O2 markedly enhanced the DNA damage. GA significantly increased 8-oxodG formation in human cultured cells (HL-60), and H2O2 enhanced it. We conclude that oxidative DNA damage by hyperglycemia-related aldehydes, especially GA, and marked enhancement of DNA damage by H2O2 may participate in diabetes-associated carcinogenesis.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aldehydes; Copper; Deoxyglucose; Deoxyguanosine; Diabetes Complications; DNA Damage; Drug Synergism; Glyceraldehyde; HL-60 Cells; Humans; Hydrogen Peroxide; Hyperglycemia; Neoplasms; Oxidation-Reduction

To clarify the mechanism of involvement of oxidative stress in hypertensives, we investigated the relationship between the marker of oxidative DNA damage, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), and cardiovascular risk factors, such as hypertension and serum glycosylated hemoglobin (HbA1c), among Tanzanians aged 46-58 years who were not on antihypertensive medication.. Sixty subjects (males/females, 28/ 32) were selected randomly from the subjects who completed a 24h urine collection in our epidemiological study at Dar es Salaam, Tanzania in 1998. The subjects were divided into two groups, hypertensive subjects (systolic blood pressure (SBP) > or = 140 mmHg and/or diastolic blood pressure (DBP) > or =90 mmHg) and normotensive subjects (SBP < 140 mmHg and DBP < 90 mmHg) or hyperglycemic subjects (HbA1c > or = 6.0%) and normoglycemic subjects (HbA1c < 6.0%). Biological markers from urine and blood were analyzed centrally in the WHO Collaborating Center.. The mean levels of HbA1c and 8-OHdG were significantly higher in the hypertensive subjects than in the normotensive subjects (P < 0.05). Urinary 8-OHdG was significantly higher in hyperglycemic subjects than in normoglycemic subjects. HbA1c was positively correlated with the 24-h urinary 8-OHdG excretions (r= 0.698, P < 0.0001).. These findings suggest oxidative DNA damage is increased in hypertensive subjects, and there is a positive correlation between the level of blood glucose estimated as HbA1c and oxidative DNA damage. Hyperglycemia related to insulin resistance in hypertension in Tanzania is associated with increased urinary 8-OHdG.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Cardiovascular Diseases; Circadian Rhythm; Deoxyguanosine; DNA Damage; Female; Glycated Hemoglobin; Humans; Hyperglycemia; Hypertension; Male; Middle Aged; Oxidative Stress; Risk Factors; Tanzania

Reactive oxygen species are involved in a diversity of biological phenomena such as inflammation, carcinogenesis, aging, and atherosclerosis. We and other investigators have shown that the level of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker for oxidative stress, is increased in either the urine or the mononuclear cells of the blood of type 2 diabetic patients. However, the association between type 2 diabetes and oxidative stress in the pancreatic beta-cells has not been previously described. We measured the levels of 8-OHdG and 4-hydroxy-2-nonenal (HNE)-modified proteins in the pancreatic beta-cells of GK rats, a model of nonobese type 2 diabetes. Quantitative immunohistochemical analyses with specific antibodies revealed higher levels of 8-OHdG and HNE-modified proteins in the pancreatic beta-cells of GK rats than in the control Wistar rats, with the levels increasing proportionally with age and fibrosis of the pancreatic islets. We further investigated whether the levels of 8-OHdG and HNE-modified proteins would be modified in the pancreatic beta-cells of GK rats fed with 30% sucrose solution or 50 ppm of voglibose (alpha-glucosidase inhibitor). In the GK rats, the levels of 8-OHdG and HNE-modified proteins, as well as islet fibrosis, were increased by sucrose treatment but reduced by voglibose treatment. These results indicate that the pancreatic beta-cells of GK rats are oxidatively stressed, and that chronic hyperglycemia might be responsible for the oxidative stress observed in the pancreatic beta-cells.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aldehydes; Animals; Blood Glucose; Deoxyguanosine; Diabetes Mellitus, Type 2; Enzyme Inhibitors; Hyperglycemia; Immunohistochemistry; Inositol; Insulin; Islets of Langerhans; Oxidative Stress; Proteins; Rats; Rats, Inbred Strains; Solutions; Sucrose