Hypoglycaemic, antioxidative and nephroprotective effects of taurine in alloxan diabetic rabbits

The therapeutic potential of taurine was investigated under diabetic conditions. Alloxan diabetic rabbits were treated daily for three weeks with 1% taurine in drinking water. The following parameters were measured: 1) serum glucose, urea, creatinine and hydroxyl free radical (HFR) levels; 2) blood glutathione redox state; 3) urine albumin concentration; 4) hepatic and renal HFR levels, GSH/GSSG ratios and the activities of catalase, superoxide dismutase and the enzymes of glutathione metabolism; 5) renal NADPH oxidase activity; 6) the rates of renal and hepatic gluconeogenesis. Histological studies of kidneys were also performed. Taurine administration to diabetic rabbits resulted in 30% decrease in serum glucose level and the normalisation of diabetes-elevated rate of renal gluconeogenesis. It also decreased serum urea and creatinine concentrations, attenuated diabetes-evoked decline in GSH/GSSG ratio and abolished hydroxyl free radicals accumulation in serum, liver and kidney cortex. Animals treated with taurine exhibited elevated activities of hepatic gamma-glutamylcysteine syntetase and renal glutathione reductase and catalase. Moreover, taurine treatment evoked the normalisation of diabetes-stimulated activity of renal NADPH oxidase and attenuated both albuminuria and glomerulopathy characteristic of diabetes. In view of these data, it is concluded that: 1) diminished rate of renal gluconeogenesis seems to contribute to hypoglycaemic effect of taurine; 2) taurine-induced increase in the activities of catalase and the enzymes of glutathione metabolism is of importance for antioxidative action of this amino acid and 3) taurine nephroprotective properties might result from diminished renal NADPH oxidase activity. Thus, taurine seems to be beneficial for the therapy of both diabetes and diabetic nephropathy.     

Identification of an atypical form of 30 kDa SOD—a possible virulence factor in clinical isolates of Shigella spp.

Diabetes-induced changes in glucose formation, intracellular and mitochondrial glutathione redox states as well as hydroxyl free radicals (HFR) generation have been investigated in rabbit kidney-cortex tubules. In contrast to renal tubules of control animals, diabetes-evoked increase in glucose formation in the presence of either aspartate+glycerol+octanoate or malate as gluconeogenic precursors (for about 50%) was accompanied by a diminished intracellular glutathione reduced form (GSH)/glutathione oxidised one (GSSG) ratio by about 30-40%, while the mitochondrial GSH/GSSG ratio was not altered. However, a relationship between the rate of gluconeogenesis and the intracellular glutathione redox state was maintained in renal tubules of both control and diabetic rabbits, as concluded from measurements in the presence of various gluconeogenic precursors. Moreover, diabetes resulted in both elevation of the glutathione reductase activity in rabbit kidney-cortex and acceleration of renal HFR generation (by about 2-fold). On the addition of melatonin, the hormone exhibiting antioxidative properties, the control values of HFR production were restored, suggesting that this compound might be beneficial during diabetes therapy. In view of the data, it seems likely that diabetes-induced increase in HFR formation in renal tubules might be responsible for a diminished intracellular glutathione redox state despite elevated glutathione reductase activity and accelerated rate of gluconeogenesis, providing glucose-6-phosphate for NADPH generation via pentose phosphate pathway.     

Diabetes-induced changes in glucose synthesis,intracellular glutathione status and hydroxyl free radical generation in rabbit kidney-cortex tubules

Diabetes-induced changes in glucose formation, intracellular and mitochondrial glutathione redox states as well as hydroxyl free radicals (HFR) generation have been investigated in rabbit kidney-cortex tubules. In contrast to renal tubules of control animals, diabetes-evoked increase in glucose formation in the presence of either aspartate + glycerol + octanoate or malate as gluconeogenic precursors (for about 50%) was accompanied by a diminished intracellular glutathione reduced form (GSH)/glutathione oxidised one (GSSG) ratio by about 30–40%, while the mitochondrial GSH/GSSG ratio was not altered. However, a relationship between the rate of gluconeogenesis and the intracellular glutathione redox state was maintained in renal tubules of both control and diabetic rabbits, as concluded from measurements in the presence of various gluconeogenic precursors. Moreover, diabetes resulted in both elevation of the glutathione reductase activity in rabbit kidney-cortex and acceleration of renal HFR generation (by about 2-fold). On the addition of melatonin, the hormone exhibiting antioxidative properties, the control values of HFR production were restored, suggesting that this compound might be beneficial during diabetes therapy. In view of the data, it seems likely that diabetes-induced increase in HFR formation in renal tubules might be responsible for a diminished intracellular glutathione redox state despite elevated glutathione reductase activity and accelerated rate of gluconeogenesis, providing glucose-6-phosphate for NADPH generation via pentose phosphate pathway. (Mol Cell Biochem 261: 91–98, 2004)     

Differential action of methylselenocysteine in control and alloxan-diabetic rabbits

Antidiabetic action of inorganic selenium compounds is commonly accepted. Since in diet selenium mainly exists as selenoamino acids, potential hypoglycemic properties of methylselenocysteine (MSC) were investigated in four groups of rabbits: untreated and MSC-treated control animals as well as alloxan-diabetic and MSC-treated diabetic rabbits. MSC (at a dose of 1 mg/kg body weight) was administered daily for 3 weeks via intraperitoneal injection. The data show, that in MSC-treated control animals plasma glucose concentration was diminished, while plasma urea and creatinine levels as well as urine albumin content were elevated and necrotic changes occurred in kidney-cortex. Decreased GSH/GSSG ratios in blood, liver and kidney-cortex were accompanied by increased glutathione peroxidase and glutathione reductase activities and a diminished renal γ-glutamylcysteine synthetase activity. Death of 50% of control animals was preceded by a dramatic decline in blood glucose concentration. Surprisingly, in MSC-treated diabetic rabbits, plasma glucose levels were either normalized or significantly decreased. Blood and liver GSH/GSSG ratios were increased and renal functions were markedly improved, as indicated by a diminished albuminuria and attenuated histological changes characteristic of diabetes. However, after administration of MSC to diabetic rabbits plasma urea and creatinine levels as well as renal GSH/GSSG ratios were not altered. In view of MSC-induced marked accumulation of selenium in kidneys and liver of control rabbits, accompanied by a decline in blood glucose level, disturbance of glutathione homeostasis and kidney-injury, application of MSC in chemotherapy needs a careful evaluation. On the contrary, MSC supplementation might be beneficial for diabetes therapy due to an improvement of both glycemia and renal function.     

Differential effects of vanadium, tungsten and molybdenum on inhibition of glucose formation in renal tubules and hepatocytes of control and diabetic rabbits: beneficial action of melatonin and N-acetylcysteine

Effect of vanadyl acetylacetonate (VAc), tungstate and molybdate on gluconeogenesis has been studied in isolated hepatocytes and kidney-cortex tubules. In renal tubules of control and alloxan-diabetic animals, the rank order of the metal-compounds-induced (i) inhibition of glucose formation from alanine+glycerol+octanoate or aspartate+glycerol+octanoate, (ii) decrease in the mitochondrial membrane potential (delta psim), (iii) increase in the hydroxyl free radicals (HFR) generation and (iv) decline in glucose-6-phosphatase activity was the following: VAc > tungstate > molybdate. Moreover, in contrast to VAc, both tungstate and molybdate at 100 microM concentration did not practically decrease glucose production in hepatocytes isolated from diabetic rabbits, and significantly increased the rate of lactate formation in renal tubules. N-acetylcysteine at 2 mM concentration partially attenuated vanadium-induced alterations in glucose formation, delta psim and the cellular glutathione redox state, whereas 0.1 mM melatonin did not abolish vanadium-induced changes in gluconeogenesis despite attenuation of vanadium effects on HFR formation and delta psim decline. However, similarly to control rabbits, following 6 days of intraperitoneal administration of both VAc (1.275 mg V/kg body weight daily) and melatonin (1 mg/kg body weight daily) to alloxan-diabetic animals, vanadium-induced elevated serum creatinine and urea levels were decreased, indicating the beneficial effect of melatonin on diabetes- and vanadium-induced nephrotoxicity in rabbits. As serum glucose levels were also significantly diminished by vanadium+melatonin treatment of diabetic animals, the combination therapy of vanadium compounds and melatonin needs a careful evaluation.     

Differential effects of selenium compounds on glucose synthesis in rabbit kidney-cortex tubules and hepatocytes. In vitro and in vivo studies

Although selenium is taken with diet mainly as selenoamino acids, its hypoglycaemic action on hepatic gluconeogenesis has been studied with the use of inorganic selenium derivatives. The aim of the present investigation was to compare relative efficacies of inorganic and organic selenium compounds in reducing glucose synthesis in hepatocytes and renal tubules, significantly contributing to the glucose homeostasis. In contrast to hepatocytes, both selenite and methylselenocysteine inhibited renal gluconeogenesis by about 40-45% in control rabbits. Selenate did not affect this process, whereas selenomethionine inhibited gluconeogenesis by about 20% in both hepatocytes and renal tubules. In contrast to methylselenocysteine, selenite decreased intracellular ATP content, glutathione reduced/glutathione oxidized (GSH/GSSG) ratio and pyruvate carboxylase, PEPCK and FBPase activities, while methylselenocysteine diminished PEPCK activity due to elevation of intracellular 2-oxoglutarate and GSSG, inhibitors of this enzyme. Experiments in vivo indicate that in 3 of 9 alloxan-diabetic rabbits treated for 14 days with methylselenocysteine (0.182mg/kg body weight) blood glucose level was normalized, whereas in all diabetic rabbits plasma creatinine and urea levels decreased from 2.52+/-0.18 and 87.4+/-9.7 down to 1.63+/-0.11 and 39.0+/-2.8, respectively. In view of these data selenium supplementation might be beneficial for protection against diabetes-induced nephrotoxicity despite selenium accumulation in kidneys and liver.     

Early oxidative stress in the diabetic kidney: effect of DL-alpha-lipoic acid

Oxidative stress is implicated in the pathogenesis of diabetic nephropathy. The attempts to identify early markers of diabetes-induced renal oxidative injury resulted in contradictory findings. We characterized early oxidative stress in renal cortex of diabetic rats, and evaluated whether it can be prevented by the potent antioxidant, DL-alpha-lipoic acid. The experiments were performed on control rats and streptozotocin-diabetic rats treated with/without DL-alpha-lipoic acid (100 mg/kg i.p., for 3 weeks from induction of diabetes). Malondialdehyde plus 4-hydroxyalkenal concentration was increased in diabetic rats vs. controls (p <.01) and this increase was partially prevented by DL-alpha-lipoic acid. F(2) isoprostane concentrations (measured by GCMS) expressed per either mg protein or arachidonic acid content were not different in control and diabetic rats but were decreased several-fold with DL-alpha-lipoic acid treatment. Both GSH and ascorbate (AA) levels were decreased and GSSG/GSH and dehydroascorbate/AA ratios increased in diabetic rats vs. controls (p <.01 for all comparisons), and these changes were completely or partially (AA) prevented by DL-alpha-lipoic acid. Superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione transferase, and NADH oxidase, but not catalase, were upregulated in diabetic rats vs. controls, and these activities, except glutathione peroxidase, were decreased by DL-alpha-lipoic acid. In conclusion, enhanced oxidative stress is present in rat renal cortex in early diabetes, and is prevented by DL-alpha-lipoic acid.     

Glutathione redox potential in response to differentiation and enzyme inducers

The reduced glutathione (GSH)/oxidized glutathione (GSSG) redox state is thought to function in signaling of detoxification gene expression, but also appears to be tightly regulated in cells under normal conditions. Thus it is not clear that the magnitude of change in response to physiologic stimuli is sufficient for a role in redox signaling under nontoxicologic conditions. The purpose of this study was to determine the change in 2GSH/GSSG redox during signaling of differentiation and increased detoxification enzyme activity in HT29 cells. We measured GSH, GSSG, cell volume, and cell pH, and we used the Nernst equation to determine the changes in redox potential Eh of the 2GSH/GSSG pool in response to the differentiating agent, sodium butyrate, and the detoxification enzyme inducer, benzyl isothiocyanate. Sodium butyrate caused a 60-mV oxidation (from -260 to -200 mV), an oxidation sufficient for a 100-fold change in protein dithiols:disulfide ratio. Benzyl isothiocyanate caused a 16-mV oxidation in control cells but a 40-mV oxidation (to -160 mV) in differentiated cells. Changes in GSH and mRNA for glutamate:cysteine ligase did not correlate with Eh; however, correlations were seen between Eh and glutathione S-transferase (GST) and nicotinamide adenine dinucleotide phosphate (NADPH):quinone reductase activities (N:QR). These results show that 2GSH/GSSG redox changes in response to physiologic stimuli such as differentiation and enzyme inducers are of a sufficient magnitude to control the activity of redox-sensitive proteins. This suggests that physiologic modulation of the 2GSH/GSSG redox poise could provide a fundamental parameter for the control of cell phenotype.     

Red wine prevents brain oxidative stress and nephropathy in streptozotocin-induced diabetic rats

We have studied the effects of red wine on brain oxidative stress and nephropathy in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in Wistar rats with a single intraperitonally injection of STZ (50 mg/kg). Two weeks before and four weeks after injection, red wine was given orally in both normal and diabetic rats. Blood samples were taken from the neck vascular trunk in order to determine the glucose, triglycerides, total cholesterol, HDL-cholesterol (HDL-c), atherogenic index (AI), total protein, blood urea nitrogen (BUN), creatinine, insulin, lipid peroxidation products, reduced glutathione (GSH) and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities. As well, we estimated the lipid peroxidtion, GSH and SOD, GSH-Px and catalase activities in brain and renal homogenates, and the excretion of albumin, proteins and glucose in urine over 24 h period. The administration of STZ caused significant increases in levels of glycosuria, proteinuria, albuminuria, glycemia, total cholesterol and AI, as well as in lipid peroxidation products in the brain, plasma and kidney, whereas it decreased the GSH content and SOD, GSH-Px and catalase activities. Treatment with red wine significantly prevented the changes induced by STZ. These data suggested that red wine has a protective effect against brain oxidative stress, diabetic nephropathy and diabetes induced by STZ, as well as it protects against hypercholesterolemia and atherogenic risk.     

Effects of piperine on antioxidant pathways in tissues from normal and streptozotocin-induced diabetic rats

Using diabetes mellitus as a model of oxidative damage, this study investigated whether subacute treatment (10 mg/kg/day, intraperitoneally for 14 days) with the compound piperine would protect against diabetes-induced oxidative stress in 30-day streptozotocin-induced diabetic Sprague-Dawley rats. Liver, kidney, brain, and heart were assayed for degree of lipid peroxidation, reduced and oxidized glutathione (GSH and GSSG, respectively) content, and activities of the free-radical detoxifying enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. Piperine treatment of normal rats enhanced hepatic GSSG concentration by 100% and decreased renal GSH concentration by 35% and renal glutathione reductase activity by 25% when compared to normal controls. All tissues from diabetic animals exhibited disturbances in antioxidant defense when compared with normal controls. Treatment with piperine reversed the diabetic effects on GSSG concentration in brain, on renal glutathione peroxidase and superoxide dismutase activities, and on cardiac glutathione reductase activity and lipid peroxidation. Piperine treatment did not reverse the effects of diabetes on hepatic GSH concentrations, lipid peroxidation, or glutathione peroxidase or catalase activities; on renal superoxide dismutase activity; or on cardiac glutathione peroxidase or catalase activities. These data indicate that subacute treatment with piperine for 14 days is only partially effective as an antioxidant therapy in diabetes.     

The senescence-accelerated mouse prone-8 (SAM-P8) oxidative stress is associated with upregulation of renal NADPH oxidase system

Herein, we investigate whether the NADPH oxidase might be playing a key role in the degree of oxidative stress in the senescence-accelerated mouse prone-8 (SAM-P8). To this end, the activity and expression of the NADPH oxidase, the ratio of glutathione and glutathione disulfides (GSH/GSSG), and the levels of malonyl dialdehyde (MDA) and nitrotyrosine (NT) were determined in renal tissue from SAM-P8 mice at the age of 1 and 6 months. The senescence-accelerated-resistant mouse (SAM-R1) was used as control. At the age of 1 month, NADPH oxidase activity and Nox2 protein expression were higher in SAM-P8 than in SAM-R1 mice. However, we found no differences in the GSH/GSSG ratio, MDA, NT, and Nox4 levels between both groups of animals. At the age of 6 months, SAM-R1 mice in comparison to SAM-P8 mice showed an increase in NADPH oxidase activity, which is associated with higher levels of NT and increased Nox4 and Nox2 expression levels. Furthermore, we found oxidative stress hallmarks including depletion in GSH/GSSG ratio and increase in MDA levels in the kidney of SAM-P8 mice. Finally, NADPH oxidase activity positively correlated with Nox2 expression in all the animals (r?=?0.382, P?<?0.05). Taken together, our data allow us to suggest that an increase in NADPH oxidase activity might be an early hallmark to predict future oxidative stress in renal tissue during the aging process that takes place in SAM-P8 mice.     

Curcumin reverses diabetic nephropathy in streptozotocin-induced diabetes in rats by inhibition of PKCβ/p66Shc axis and activation of FOXO-3a

This study investigated if the nephroprotective effect of Curcumin in streptozotocin-induced type 1 diabetes mellitus (DM) in rats involves downregulation/inhibition of p⁶⁶Shc and examined the underlying mechanisms. Rats were divided into 4 groups (n = 12/group) as control, control + Curcumin (100 mg/kg), T1DM, and T1DM + Curcumin. Curcumin was administered orally to control or diabetic rats for 12 weeks daily. As compared to diabetic rats, Curcumin didn't affect either plasma glucose or insulin levels but significantly reduced serum levels of urea, blood urea nitrogen, and creatinine, and concurrently reduced albumin/protein urea and increased creatinine clearance. It also prevented the damage in renal tubules and mitochondria, mesangial cell expansion, the thickness of the basement membrane. Mechanistically, Curcumin reduced mRNA and protein levels of collagen I/III and transforming growth factor- β-1 (TGF-β1), reduced inflammatory cytokines levels, improved markers of mitochondrial function, and suppressed the release of cytochrome-c and the activation of caspase-3. In the kidneys of both control and diabetic rats, Curcumin reduced the levels of reactive oxygen species (ROS), increased mRNA levels of manganese superoxide dismutase (MnSOD) and gamma-glutamyl ligase, increased glutathione (GSH) and protein levels of Bcl-2 and MnSOD, and increased the nuclear levels of nuclear factor2 (Nrf2) and FOXO-3a. Besides, Curcumin reduced the nuclear activity of the nuclear factor-kappa B (NF-κB), downregulated protein kinase CβII (PKCβII), NADPH oxidase, and p⁶⁶Shc, and decreased the activation of p⁶⁶Shc. In conclusion, Curcumin prevents kidney damage in diabetic rats by activating Nrf2, inhibiting Nf-κB, suppressing NADPH oxidase, and downregulating/inhibiting PKCβII/p⁶⁶Shc axis.     

Pseudomonas aeruginosa pyocyanin directly oxidizes glutathione and decreases its levels in airway epithelial cells

Production of pyocyanin enhances Pseudomonas aeruginosa virulence. Many of pyocyanin's in vitro and in vivo cytotoxic effects on human cells appear to result from its ability to redox cycle. Pyocyanin directly accepts electrons from NADH or NADPH with subsequent electron transfer to oxygen, generating reactive oxygen species. Reduced glutathione (GSH) is an important cellular antioxidant, and it contributes to the regulation of redox-sensitive signaling systems. Using the human bronchial epithelial (HBE) and the A549 human type II alveolar epithelial cell lines, we tested the hypothesis that pyocyanin can deplete airway epithelial cells of GSH. Incubation of both cell types with pyocyanin led to a concentration-dependent loss of cellular GSH (up to 50%) and an increase in oxidized GSH (GSSG) in the HBE, but not A549 cells, at 24 h. An increase in total GSH, mostly as GSSG, was detected in the culture media, suggesting export of GSH or GSSG from the pyocyanin-exposed cells. Loss of GSH could be due to pyocyanin-induced H(2)O(2) formation. However, overexpression of catalase only partially prevented the pyocyanin-mediated decline in cellular GSH. Cell-free electron paramagnetic resonance studies revealed that pyocyanin directly oxidizes GSH, forming pyocyanin free radical and O(2)(-). Pyocyanin oxidized other thiol-containing compounds, cysteine and N-acetyl-cysteine, but not methionine. Thus GSH may enhance pyocyanin-induced cytotoxicity by functioning as an alternative source of reducing equivalents for pyocyanin redox cycling. Pyocyanin-mediated alterations in cellular GSH may alter epithelial cell functions by modulating redox sensitive signaling events.     

Reversible inactivation of Saccharomyces cerevisiae glutathione reductase under reducing conditions

Glutathione reductase from Saccharomyces cerevisiae was rapidly inactivated following aerobic incubation with NADPH, NADH, and several other reductants, in a time- and temperature-dependent process. The inactivation had already reached 50% when the NADPH concentration reached that of the glutathione reductase subunit. The inactivation was very marked at pH values below 5.5 and over 7, while only a slight activity decrease was noticed at pH values between these two values. After elimination of excess NADPH the enzyme remained inactive for at least 4 h. The enzyme was protected against redox inactivation by low concentrations of GSSG, ferricyanide, GSH, or dithiothreitol, and high concentrations of NAD(P)+; oxidized glutathione effectively protected the enzyme at concentrations even lower than GSH. The inactive enzyme was efficiently reactivated after incubation with GSSG, ferricyanide, GSH, or dithiothreitol, whether NADPH was present or not. The reactivation with GSH was rapid even at 0 degree C, whereas the optimum temperature for reactivation with GSSG was 30 degrees C. A tentative model for the redox interconversion, involving an erroneous intramolecular disulfide bridge, is put forward.     

Turnover and functions of glutathione studied with isolated hepatic and renal cells

Suspensions of freshly isolated rat hepatocytes and renal tubular cells contain high levels of reduced glutathione (GSH), which exhibits half-lives of 3-5 and 0.7-1 h, respectively. In both cells types the availability of intracellular cysteine is rate limiting for GSH biosynthesis. In hepatocytes, methionine is actively converted to cysteine via the cystathionine pathway, and hepatic glutathione biosynthesis is stimulated by the presence of methionine in the medium. In contrast, extracellular cystine can support renal glutathione synthesis; several disulfides, including cystine, are rapidly taken up by renal cells (but not by hepatocytes) and are reduced to the corresponding thiols via a GSH-linked reaction sequence catalyzed by thiol transferase and glutathione reductase (NAD(P)H). During incubation, hepatocytes release both GSH and glutathione disulfide (GSSG) into the medium; the rate of GSSG efflux is markedly enhanced during hydroperoxide metabolism by glutathione peroxidase. This may lead to GSH depletion and cell injury; the latter seems to be initiated by a perturbation of cellular calcium homeostasis occurring in the glutathione-depleted state. In contrast to hepatocytes, renal cells metabolize extracellular glutathione and glutathione S-conjugates formed during drug biotransformation to the component amino acids and N-acetyl-cysteine S-conjugates, respectively. In addition, renal cells contain a thiol oxidase acting on extracellular GSH and several other thiols. In conclusion, our findings with isolated cells mimic the physiological situation characterized by hepatic synthesis and renal degradation of plasma glutathione and glutathione S-conjugates, and elucidate some of the underlying biochemical mechanisms.     

Ameliorative potential of S-allyl cysteine on oxidative stress in STZ induced diabetic rats

Increased oxidative stress and impaired antioxidant defense mechanism are important factors in the pathogenesis and progression of diabetes mellitus and other oxidant-related diseases. The present study was undertaken to evaluate the possible protective effects of S-allyl cysteine (SAC) against oxidative stress in streptozotocin (STZ) induced diabetic rats. SAC was administered orally for 45 days to control and STZ induced diabetic rats. The effects of SAC on glucose, plasma insulin, thiobarbituric acid reactive substances (TBARS), hydroperoxide, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH), oxidized glutathione (GSSG) and GSH/GSSG ratio were studied. The levels of glucose, TBARS, hydroperoxide, and GSSG were increased significantly whereas the levels of plasma insulin, reduced glutathione, GSH/GSSG ratio, superoxide dismutase, catalase and GPx were decreased in STZ induced diabetic rats. Administration of SAC to diabetic rats showed a decrease in plasma glucose, TBARS, hydroperoxide and GSSG. In addition, the levels of plasma insulin, superoxide dismutase, catalase, GPx and reduced glutathione (GSH) were increased in SAC treated diabetic rats. The above findings were supported by histological observations of the liver and kidney. The antioxidant effect of SAC was compared with glyclazide, a well-known antioxidant and antihyperglycemic drug. The present study indicates that the SAC possesses a significant favorable effect on antioxidant defense system in addition to its antidiabetic effect.     

糖尿病肾病合并非糖尿病肾病的临床病理分析

目的：分析糖尿病肾病合并非糖尿病肾病的临床病理特点。方法：选取我院肾内科收治的临床诊断为糖尿病肾病的患者56 例,肾脏穿刺进行肾脏活体组织检查,通过病理诊断将患者分为两组,分别为糖尿病肾病组和糖尿病肾病合并非糖尿病肾病组, 比较两组患者的糖尿病病程、糖化血红蛋白、血压、血肌酐、血尿素氮、血尿酸、血清白蛋白、尿蛋白定量、血尿、视网膜病变。结果： 经肾脏组织活检,56例患者中NDRD 患者24 例(42.9%),DN患者32 例(57.1%);对24 例NDRD患者进行病理类型分类,其中IgA 肾病33.0%,膜性肾病25.0%、系膜增生性肾小球肾炎20.2%、高血压肾损害8.3%、微小病变4.2%、局灶节段硬化性肾炎4.2%、新 月体性肾小球肾炎4.2%。与DN组比较,NDRD 组糖尿病病程、糖化血红蛋白、血尿、视网膜病变均有差异(P＜0.05);而血肌酐、血 尿素氮、血尿酸、血清白蛋白、尿蛋白定量均无明显差异(P＞0.05)。结论：临床诊断的糖尿病肾病患者中有很大一部分实际上为糖 尿病肾病合并非糖尿病肾病,且以IgA 型肾病比较多见,糖尿病病程、糖化血红蛋白、血尿、视网膜病变对鉴别二者具有一定的指 导意义。     

Redox analysis of human plasma allows separation of pro-oxidant events of aging from decline in antioxidant defenses

Oxidative stress is a component of diseases and degenerative processes associated with aging. However, no means are available to assess causative oxidative events separately from decline in function of protective antioxidant systems. Previous studies show that ongoing oxidative processes maintain plasma cysteine/cystine redox at a value that is more oxidized than the antioxidant glutathione/glutathione disulfide (GSH/GSSG) system, suggesting that redox analysis of these plasma thiols could allow separate evaluation of an increase in oxidative events from a decline in antioxidant function. The present study uses measurement of cysteine/cystine and GSH/GSSG redox in plasma of 122 healthy individuals aged 19-85 years to determine whether thiol-disulfide redox changes occur with age. The results show a linear oxidation of cysteine/cystine redox state with age at a rate of 0.16 mV/year over the entire age span. In contrast, GSH/GSSG redox was not oxidized prior to 45 years and subsequently was oxidized at a nearly linear rate of 0.7 mV/year. These data suggest that there is a continuous, linear increase in oxidative events throughout adult life but that the capacity of the GSH antioxidant system is maintained until 45 years and then declines rapidly. The data further suggest that redox states of cysteine/cystine and GSH/GSSG provide an approach to clinically distinguish between increased causative oxidative events and decreased GSH antioxidant function. In principle, such analyses can be used to assess efficacy of intervention strategies against oxidative stress prior to or early after onset of clinical symptoms in aging and age-related disease.     

Glutathione and thioredoxin redox during differentiation in human colon epithelial (Caco-2) cells

Cellular redox, maintained by the glutathione (GSH)- and thioredoxin (Trx)-dependent systems, has been implicated in the regulation of a variety of biological processes. The redox state of the GSH system becomes oxidized when cells are induced to differentiate by chemical agents. The aim of this study was to determine the redox state of cellular GSH/glutathione disulfide (GSH/GSSG) and Trx as a consequence of progression from proliferation to contact inhibition and spontaneous differentiation in colon carcinoma (Caco-2) cells. Results showed a significant decrease in GSH concentration, accompanied by a 40-mV oxidation of the cellular GSH/GSSG redox state and a 28-mV oxidation of the extracellular cysteine/cystine redox state in association with confluency and increase in differentiation markers. The redox state of Trx did not change. Thus the two central cellular antioxidant and redox-regulating systems (GSH and Trx) were independently controlled. According to the Nernst equation, a 30-mV oxidation is associated with a 10-fold change in the reduced/oxidized ratio of a redox-sensitive dithiol motif. Therefore, the measured 40-mV oxidation of the cellular GSH/GSSG couple or the 28-mV oxidation of the extracellular cysteine/cystine couple should be sufficient to function in signaling or regulation of differentiation in Caco-2 cells.     

Genetic analysis of tissue glutathione concentrations and redox balance

Glutathione redox balance—defined as the ratio GSH/GSSG—is a critical regulator of cellular redox state, and declines in this ratio are closely associated with oxidative stress and disease. However, little is known about the impact of genetic variation on this trait. Previous mouse studies suggest that tissue GSH/GSSG is regulated by genetic background and is therefore heritable. In this study, we measured glutathione concentrations and GSH/GSSG in liver and kidney of 30 genetically diverse inbred mouse strains. Genetic background caused an approximately threefold difference in hepatic and renal GSH/GSSG between the most disparate strains. Haplotype association mapping determined the loci associated with hepatic and renal glutathione phenotypes. We narrowed the number of significant loci by focusing on those located within protein-coding genes, which we now consider to be candidate genes for glutathione homeostasis. No candidate genes were associated with both hepatic and renal GSH/GSSG, suggesting that genetic regulation of GSH/GSSG occurs predominantly in a tissue-specific manner. This is the first quantitative trait locus study to examine the genetic regulation of glutathione concentrations and redox balance in mammals. We identified novel candidate genes that have the potential to redefine our knowledge of redox biochemistry and its regulation and inform future therapeutic applications.