Glutamate induces oxidative stress not mediated by glutamate receptors or cystine transporters: protective effect of melatonin and other antioxidants

Glutamate is responsible for most of the excitatory synaptic activity and oxidative stress induction in the mammalian brain. This amino acid is increased in the substantia nigra in parkinsonism due to the lack of dopamine restraint to the subthalamic nucleus. Parkinson's disease also shows an increase of iron levels in the substantia nigra and a decrease of glutathione, the antioxidant responsible for the ascorbate radical recycling. Considered together, these facts could make the antioxidant ascorbate behave as a pro-oxidant in parkinsonism. Since both glutamate and ascorbate are present in the synaptosomes and neurons of substantia nigra, we tested 1) if glutamate is able to induce oxidative stress independently of its excitatory activity, and 2) if ascorbate may have synergistic effects with glutamate when these two molecules co-exist. Brains were homogenized in order to disrupt membranes and render membrane receptors and intracellular signaling pathways non-functional. In these homogenates glutamate induced lipid peroxidation, indicating that this amino acid also may cause oxidative stress not mediated by its binding to glutamate receptors or cystine transporters. Ascorbate also induced lipid peroxidation thus behaving as a pro-oxidant. Both substances together produced an additive effect but they did not synergize. Given that melatonin is a potent physiological antioxidant with protective effects in models of neurotoxicity, we tested the role of this secretory product on the pro-oxidant effect of both compounds given separately or in combination. We also checked the protective ability of several other antioxidants. Pharmacological doses of melatonin (millimolar), estrogens, pinoline and trolox (micromolar) prevented the oxidant effect of glutamate, ascorbate, and the combination of both substances. Potential therapeutic application of these results is discussed.     

Metformin protects the ischemic heart by the Akt-mediated inhibition of mitochondrial permeability transition pore opening

Background In the majority of studies, metformin has been demonstrated to cardioprotect diabetic patients, the mechanism of which is unclear. We hypothesized that metformin cardioprotects the ischemic heart through the Akt-mediated inhibition of mitochondrial permeability transition pore (mPTP) opening. Materials and methods Isolated perfused hearts from normoglycemic Wistar or from diabetic Goto-Kakizaki (GK) rats (N ≥ 6/group) were subjected to 35 min ischemia and 120 min of reperfusion. Metformin (50 μmol/l) was added for 15 min at reperfusion, alone or with LY294002 (15 μmol/l), a PI3K inhibitor. Infarct size and Akt phosphorylation were measured. Furthermore, the effect of metformin on mPTP opening in adult cardiomyocytes isolated from both strains was determined. Results Metformin reduced infarct size in both Wistar (35 ± 2.7% metformin vs. 62 ± 3.0% control: P < 0.05) and GK hearts (43 ± 4.7% metformin vs. 60 ± 3.8% control: P < 0.05). This protection was accompanied by a significant increase in Akt phosphorylation. LY294002 abolished the metformin-induced Akt phosphorylation and the infarct-limiting effect of metformin in Wistar (61 ± 6.7% metformin + LY294002 vs. 35 ± 2.7% metformin: P < 0.05) and GK rats (56 ± 5.7% metformin + LY294002 vs. 43 ± 4.7% metformin: P < 0.05). In addition, metformin significantly inhibited mPTP opening and subsequent rigor contracture in both Wistar and GK cardiomyocytes subjected to oxidative stress, in a LY-sensitive manner. Conclusions We report that metformin given at the time of reperfusion reduces myocardial infarct size in both the non-diabetic and diabetic heart and this protective effect is mediated through PI3K and is associated with Akt phosphorylation. Furthermore, cardioprotection appears to be executed through a PI3K-mediated inhibition of mPTP opening. These findings may explain in part the cardioprotective properties of metformin observed in clinical studies of diabetic patients. Returned for 1. Revision: 14 May 2007 1. Revision received: 18 May 2007 Returned for 2. Revision: 4 June 2007 2. Revision received: 23 October 2007     

Effect of vitamin E on oxidative stress status in small intestine of diabetic rat

AIM:To investigate the effect of vitamin E on oxidative stress status in the small intestine of diabetic rats. METHODS:Twenty-four male Wistar rats were randomly divided into three groups:Control (C),non-treated diabetic (NTD) and vitamin E-treated diabetic (VETD) groups. The increases in lipid peroxidation,protein oxidation and superoxide dismutase (SOD) in these three groups was compared after 6 wk. RESULTS:There was no significant difference in catalase activity between NTD and control rats. Compared to NTD rats,the treatment with vitamin E significantly decreased lipid peroxidation and protein oxidation,and also increased catalase activity and SOD. CONCLUSION:The results revealed the occurrence of oxidative stress in the small intestine of diabetic rats. Vitamin E,as an antioxidant,attenuates lipid peroxidation and protein oxidation,and increases antioxidant defense mechanism.     

Alterations of liver mitochondrial bioenergetics in diabetic Goto-Kakizaki rats.

Respiratory indexes and the transmembrane electrical potential (delta psi) were evaluated in mitochondrial preparations from 6-month-old Goto-Kakizaki (GK) and Wistar rats in the presence of glutamate + malate and succinate. We found that in diabetic GK mitochondria, flavin adenine dinucleotide (FAD)-linked respiratory indexes (respiratory control ratio [RCR] and adenosine diphosphate [ADP] to oxygen ratio [ADP/O]) are increased and uncoupled respiration is largely enhanced, indicating increased respiratory chain activity in GK rats. Delta psi development in GK mitochondrial preparations, energized using glutamate + malate or succinate as substrates, and the repolarization rate upon phosphorylation of the added ADP were significantly higher in GK mitochondrial preparations. These results indicate an enhanced activity of the phosphorylation system, confirmed by evaluating delta psi development when the mitochondria are energized by adenosine triphosphate (ATP). Moreover, recovery of the potential upon a phosphorylative cycle is increased in GK mitochondria, reflecting a more efficient coupling between the phosphorylative and oxidative system. Contrasting with results obtained for alloxan- or streptozotocin-induced diabetic rats, this study clearly demonstrates no impairment of mitochondrial bioenergetics in diabetic GK rats. On the contrary, at this age, we observed a higher efficiency of the phosphorylation system as compared with Wistar rats.     

Endothelial dysfunction in type 2 diabetes: effect of antioxidants.

Individuals with insulin resistance and diabetes mellitus have increased cardiovascular morbidity and mortality, caused in part by vascular complications. Endothelial dysfunction has been implicated in the pathogenesis of vascular diabetic disease. This abnormal function of the vasculature precedes cardiovascular disease and is associated with impaired endothelium-dependent vasorelaxation. The main etiology of the increased mortality and morbidity of type 2 diabetic patients is atherosclerosis. Increased production of free radicals is associated with the pathophysiology of diabetes, resulting in oxidative damage to lipids and proteins. Reduction of oxidative stress in diabetic patients may delay the onset of atherogenesis and the appearance of micro- and macrovascular complications. Alpha-lipoic acid (LA) is a multifunctional antioxidant that has been shown to have beneficial effects on polyneuropathy and on markers of oxidative stress in various tissues. This study was conducted to investigate the effects of LA on endothelial function in diabetic and hyperlipidemic animal models. Carbohydrate and lipid metabolism, endothelial function, plasma malondialdehyde (MDA) and urinary 8-hydroxydeoxyguanosine (8-OHdG) were assessed in non-diabetic controls (Wistar rats), untreated diabetic Goto-Kakizaki (GK) rats and, atherogenic diet (AD)-fed GK rats (fed with atherogenic diet only, treated with alpha-lipoic acid and treated with vehicle, for 3 months). AD resulted in a 3-fold increase in both total and non-HDL serum cholesterol levels and in a 2-fold increase triglyceride levels while endothelial function was significantly reduce MDA and 8-OHdG levels were higher in the GK and GK hyperlipidemic groups and were completely reversed by the antioxidant. Hyperlipidemic GK diabetic rats showed significantly reduced endothelial function that was partially improved with LA. Furthermore, lipoic acid significantly reduced serum cholesterol levels, without lowering HDL cholesterol. Alpha-lipoic acid supplementation represents an achievable adjunct therapy to improve endothelial function and reduce oxidative stress, factors that are implicated in the pathogenesis of atherosclerosis in diabetes.     

Effect of aminoguanidine on lipid peroxidation in streptozotocin-induced diabetic rats.

Diabetes mellitus is postulated to be associated with increased lipid peroxidation, which may contribute to vascular complications. One potential mechanism of the increased lipid peroxidation in diabetes is lipid-linked advanced glycosylation and oxidation. Aminoguanidine (AMGN), the prototype inhibitor of advanced glycosylation end product (AGE) formation, has been recently shown to prevent oxidative modification of low-density lipoprotein (LDL) in vitro at a moderate concentration. It is unknown whether AMGN may act as an antioxidant against lipid peroxidation under hyperglycemia in vivo. To investigate the in vivo effect of AMGN on lipid peroxidation in diabetes, we administered AMGN (1 g/L in drinking water) or vitamin E (400 mg/d for 5 d/wk) to streptozotocin (STZ)-induced diabetic rats for 9 weeks and measured plasma lipid hydroperoxides by ferrous oxidation with xylenol orange II (FOX method) and red blood cell (RBC) membrane malondialdehyde (MDA) and related aldehydes as thiobarbituric acid-reactive substances (TBARS). Plasma lipid hydroperoxide was higher in STZ-induced diabetic rats versus control rats (mean +/- SD, 7.53 +/- 2.03 v 5.62 +/- 0.44 micromol/L, P < .05; n = 8 to 14). RBC membrane TBARS were also higher in STZ-induced diabetic rats than in control rats (2.67 +/- 0.46 v 1.81 +/- 0.19 nmol/mL, P < .05). Plasma lipid hydroperoxide was lower in AMGN-treated (6.23 +/- 0.59 micromol/L, P < .05) and vitamin E-treated (5.29 +/- 0.27 micromol/L, P < .05) diabetic rats than in untreated diabetic rats. RBC membrane TBARS were also lower in AMGN-treated (1.93 +/- 0.12 nmol/mL, P < .05) diabetic rats than in untreated diabetic rats. There was no significant difference in plasma glucose, cholesterol, and triglyceride levels among diabetic groups. Although the mechanism(s) of action of AMGN on lipid peroxidation in vivo should be studied further, these results suggest that AMGN may have an additional beneficial effect as an antioxidant against lipid peroxidation in a prevention trial for diabetic vascular complications.     

Effects of aminoguanidine on lipid and protein oxidation in diabetic rat kidneys

Nonenzymatic glycation of tissue and plasma proteins may stimulate the production of oxidant and carbonyl stress in diabetes. The aim of this study was to evaluate the effects of aminoguanidine (AG) on lipid peroxidation, protein oxidation and nitric oxide (NO) release in diabetic rat kidneys. After induction of diabetes with streptozotocin, female Wistar rats were divided into 2 groups. Group DAG (n=9) rats were given AG hydrogen carbonate (1 g/L) in drinking water and group D (n=8) was diabetic control rats given only tap water. Group H (n=8) was followed as healthy controls. At the end of an 8 week period, NO release, lipid and protein oxidation were determined in kidney tissues. NO release was significantly lower in diabetic rats compared with healthy controls (p<0.05). Lipid peroxidation was significantly high in group D (3.9 +/- 0.3 nmol MDA/g tissue) compared with the group DAG (2.6 0.1 nmol MDA/g tissue, p<0.01) and group H (2.4 +/- 0.2 nmol MDA/g tissue). Protein oxidation was significantly higher in diabetics than healthy controls (563.8 +/- 23.9, 655.8 +/- 7.2, 431.5 +/- 8.8 mmol carbonyl / g tissue for group DAG, D and H, respectively, p< 0.05). A positive correlation between albuminuria and thiobarbituric acid reactive substance (TBARS) levels (r= 0.54,p<0.005) and carbonyl content (r=0.70, p<0.0005) in kidney homogenate were observed. Although AG treatment had no effect on NO release, it significantly decreased lipid peroxidation in diabetic rat cortices. Consequently increased lipid peroxidation -as well as- protein oxidation could be involved in the pathogenesis of diabetic albuminuria.     

Elevated atrial natriuretic peptides and early renal failure in type 2 diabetic Goto-Kakizaki rats.

The present investigation was designed to determine if atrial natriuretic peptides (ANPs) are increased in a spontaneous model of non-obese type 2 diabetes, the Goto-Kakizaki (GK) rat. Four peptide hormones originating from the ANP prohormone were increased twofold (P < .05) to sixfold (P < .01) in the circulation of GK rats compared with nondiabetic Wistar rats from which the GK colony was originally derived. Thus, ANP, long-acting natriuretic peptide (LANP), vessel dilator, and kaliuretic peptide were (mean +/- SE) 497 +/- 78, 1,285 +/- 105, 457 +/- 45, and 385 +/- 87 pg/mL in GK rats, versus 78 +/- 23, 542 +/- 77, 137 +/- 26, and 134 +/- 33 pg/mL, respectively, in Wistar rats. In evaluating the cause of the increased ANPs, the blood volume of GK rats (16.2 +/- 0.4 mL) was significantly (P < .01) increased compared with Wistar rats (9.5 +/- 0.3 mL). The ventricles of GK rats were not dilated when examined by transthoracic echocardiography, but the venous system was markedly distended. GK rats had a 48% to 79% decrease in renal function (ie, increased serum creatinine and blood urea nitrogen [BUN]) compared with Wistar rats. These results indicate that circulating ANPs are increased in the GK spontaneously diabetic rat secondary to (1) increased blood volume, which leads to increased synthesis and release of ANPs, and (2) renal failure, which results in a delayed metabolic processing of these peptides. The early combined increases of the four atrial peptides collectively may contribute to the hyperfiltration that occurs in early diabetes mellitus.     

Sources of endogenous glucose production in the Goto-Kakizaki diabetic rat

Plasma glucose, insulin and glucose tolerance were quantified in diabetic Goto-Kakizaki (GK) rats (342+/-45 g, n = 5) and compared with weight-matched non-diabetic Wistars (307+/-30 g, n = 8). Compared to Wistars, GK rats had higher fasting plasma insulin (219+/-50 versus 44+/-14 pmol/l, P<0.002) and glucose (9.2+/-2.3 versus 5.5+/-0.5 mmol/l, P<0.025). GK rats showed impaired glucose tolerance (IPGTT 2 h plasma glucose=14+/-1.5 versus 6.4+/-0.1 mmol/l, P<0.001). Endogenous glucose production (EGP) from glycogenolysis, phosphoenolpyruvate (PEP) and glycerol after 6 hours of fasting was quantified by a primed infusion of [U-(13)C]glucose and (2)H(2)O tracers and (2)H/(13)C NMR analysis of plasma glucose. EGP was higher in GK compared to Wistar rats (191+/-16 versus 104+/-27 mumol/kg per min, P<0.005). This was sustained by increased gluconeogenesis from PEP (85+/-12 versus 35+/-4 mumol/kg per min, P<0.02). Gluconeogenesis from glycerol was not different (20+/-3 in Wistar versus 30+/-6 mumol/kg per min for GK), and glycogenolysis fluxes were also not significantly different (76+/-23 mumol/kg per min for GK versus 52+/-19 mumol/kg per min for Wistar). The Cori cycle accounted for most of PEP gluconeogenesis in both Wistar and GK rats (85+/-15% and 77+/-10%, respectively). Therefore, increased gluconeogenesis in GK rats is largely sustained by increased Cori cycling while the maintenance of glycogenolysis indicates a failure in hepatic autoregulation of EGP.     

What are Arrhythmogenic Substrates in Diabetic Rat Atria?

INTRODUCTION: Diabetes mellitus is one of the significant independent risk factors for the development of atrial fibrillation (AF). However, the pathophysiological mechanisms of the relationship have not been fully elucidated. METHODS AND RESULTS: The genetic type II diabetes (GK) rats and their original (Wistar) ones were subjected to electrophysiological (n = 8 per group) and histological (n = 7 per group) studies. At 40 weeks old, when GK rats had significantly (P < 0.01) more increased plasma glucose and HbA(1c) values than Wistar rats, atrial electrical stimuli in the isolated-perfused hearts induced significantly greater number of repetitive atrial responses in GK rats than in Wistar rats (47.9 +/- 17.5 vs 3.1 +/- 1.3 beats, respectively, P < 0.01). GK rats showed significantly longer intra-atrial activation time than Wistar rats (18.3 +/- 0.4 ms vs 15.9 +/- 0.5 ms, P < 0.01) without any significant difference in the atrial refractoriness. The histological examination revealed significantly increased diffuse fibrotic deposition in GK rats atria compared with Wistar ones (P < 0.01). CONCLUSION: The present diabetic GK rat showed increased atrial arrhythmogenicity with intra-atrial conduction disturbance, and thus indicated that the structural remodeling of atrium characterized by diffuse interstitial fibrosis would be a major substrate for diabetes-related AF.     

Metabolism of palmitate in isolated working hearts from spontaneously diabetic "BB" Wistar rats

Myocardial fatty acid metabolism was studied in spontaneously-diabetic "BB" Wistar rats. The study involved 4 groups: control Wistar rats, nondiabetic littermates of "BB" Wistar rats, insulin-treated diabetic "BB" rats, and diabetic "BB" rats in which insulin treatment was removed 24 hours prior to study (uncontrolled diabetes). Hearts were perfused for 30 minutes as isolated working hearts in perfusate containing 1.2 mM (1-14C)-palmitate bound to 3% albumin, and 11 mM glucose. Palmitate oxidative rates, calculated as micromoles palmitate oxidized per gram dry weight per minute, were significantly decreased in both diabetic groups (0.447 +/- 0.043 and 0.528 +/- 0.038 in uncontrolled diabetic and treated diabetic versus 0.584 +/- 0.032 and 0.629 +/- 0.033 in nondiabetic littermate and control rats, respectively). This decrease was accompanied, however, by a significant decrease in the heart rate of these 2 groups when compared with control or nondiabetic animals. If the decreased heart function in the diabetic animals was accounted for, no decrease in palmitate oxidative rates occurred, suggesting that fatty acid oxidative metabolism is not impaired in the diabetic myocardium. In the uncontrolled diabetic rats, an increased rate of palmitate incorporation into myocardial triglycerides was seen compared with treated diabetic, nondiabetic littermates, and control rats (8.5 +/- 0.3 mumol/g dry wt/30 min versus 4.8 +/- 0.3, 5.9 +/- 0.7, and 5.7 +/- 0.3, respectively). Myocardial levels of coenzyme A were elevated in the uncontrolled diabetic rats compared with all other groups (647 +/- 25 nmol/g dry wt versus 484 +/- 27, 508 +/- 56, and 534 +/- 9, in treated diabetic, nondiabetic, and control rats, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

No significant effect of vitamin E deficiency or supplementation on collagen-linked fluorescence in skin of diabetic rats.

It is speculated that oxidative stress in vivo may have some influence on advanced, nonenzymatic, glycosylation end products. However, this has not been demonstrated yet. We assessed changes in collagen-linked fluorescence in the skin of nondiabetic and streptozotocin-induced diabetic rats fed three different diets for 4 weeks that could modify oxidative stress: vitamin E-deficient (D), vitamin E-supplemented (S), and control (C). The serum lipid peroxide level expressed as thiobarbituric acid (TBA) activity in diabetic rats on the S diet (9.6 +/- 1.0 [SE] nmol/L/mL) was significantly (P less than .01) lower than that in rats on the D diet (111.4 +/- 22.4), and similar to that in nondiabetic rats on the C diet (12.4 +/- 2.2). The collagen-linked fluorescence level was significantly (P less than .01) higher in diabetic rats than in nondiabetic rats, which corresponded to the serum glucose and glycosylated hemoglobin levels. However, there were no significant differences in the fluorescence levels among three groups classified by three different diets in both nondiabetic and diabetic rats (21.7 +/- 1.7 arbitrary U/mg collagen for D, 22.3 +/- 2.0 for C, and 22.8 +/- 2.5 for S in nondiabetic rats v 41.2 +/- 4.1 for D, 40.1 +/- 4.7 for C, and 39.3 +/- 3.5 for S in diabetic rats), despite significant changes in serum lipid peroxide levels. Consequently, there were no significant changes found in collagen-linked fluorescence levels in diabetic rats wherein oxidative stress was modified by vitamin E deficiency and supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Active transport of gamma-aminobutyric acid and glycine into synaptic vesicles.

Although gamma-aminobutyric acid (GABA) and glycine are recognized as major amino acid inhibitory neurotransmitters in the central nervous system, their storage is poorly understood. In this study we have characterized vesicular GABA and glycine uptakes in the cerebrum and spinal cord, respectively. We present evidence that GABA and glycine are each taken up into isolated synaptic vesicles in an ATP-dependent manner and that the uptake is driven by an electrochemical proton gradient. Uptake for both amino acids exhibited kinetics with low affinity (Km in the millimolar range) similar to vesicular glutamate uptake. The ATP-dependent GABA uptake was not inhibited by the putative amino acid neurotransmitters glycine, taurine, glutamate, or aspartate or by GABA analogs, agonists, and antagonists. Similarly, ATP-dependent glycine uptake was hardly affected by GABA, taurine, glutamate, or aspartate or by glycine analogs or antagonists. The GABA uptake was not affected by chloride, which is in contrast to the uptake of the excitatory neurotransmitter glutamate, whereas the glycine uptake was slightly stimulated by low concentrations of chloride. Tissue distribution studies indicate that the vesicular uptake systems for GABA, glycine, and glutamate are distributed in different proportions in the cerebrum and spinal cord. These results suggest that the vesicular uptake systems for GABA, glycine, and glutamate are distinct from each other.     

体外培养高糖、高脂喂养大鼠主动脉平滑肌细胞钙化的研究

目的 检测高糖、高脂喂养Goto-Kakizaki（GK）糖尿病大鼠主动脉平滑肌细胞（SMCs）的血管钙化指标,探讨糖尿病血管钙化的相关机制.方法 高糖、高脂喂养GK及Wistar大鼠2周,同时分离培养两组大鼠的主动脉SMCs,Wistar大鼠SMCs作为对照.通过细胞计数法观察细胞生长状况,以甲基百里香酚蓝比色法测定两组大鼠细胞层及培养上清中钙的含量,实时定量PCR检测两组细胞碱性磷酸酶（ALP）、骨桥蛋白（OPN）、核心结合因子α-1（Cbfα-1）、α-平滑肌肌动蛋白（α-SMA）的基因表达.结果 与Wistar大鼠SMCs相比,GK大鼠SMCs生长速度明显缓慢（F =363.392,P＜0.05）;细胞层钙含量[（0.56±0.22） vs.（0.39±0.09）,t=2.47,P＜0.05]明显增加,培养上清中钙含量[（0.82±0.22）vs.（1.20±0.17）,t=-22.573,P＜0.05]明显减少.GK大鼠SMCs中ALP （t=12.963,P＜0.05）、OPN（t=8.305,P＜0.05）及Cbfα-1（t=10.109,P＜0.05）的基因表达增加,同时α-SMA（t=-8.219,P＜ 0.05）的基因表达减少.结论 高糖、高脂喂养的GK糖尿病大鼠的主动脉平滑肌细胞易发生钙化.     

Glycolaldehyde Induces Oxidative Stress in the Heart: A Clue to Diabetic Cardiomyopathy?

Cardiovascular complications account for 80% of the mortality related to diabetes mellitus. Hyperglycemia is believed to be the major culprit of angiopathy and cardiomyopathy. High glucose levels and oxidative stress cause elevation of Advanced Glycation End-products that are known to contribute to diabetic complications and correlate with many diseases. However, there are few reports describing the effects of glycating agents other than glucose. Here, we aimed to evaluate the effects of glycolaldehyde (GA) on oxidative stress parameters in the heart of Wistar rats. Male Wistar rats received a single injection of GA (10, 50 or 100 mg/Kg) and were sacrificed 6, 12 or 24 h after injection. As indexes of oxidative stress, we quantified protein carbonylation, lipid peroxidation and total reduced thiols. The activities of superoxide dismutase, catalase and glyoxalase I were assayed. Also, the content of N ^ɛ-(carboxymethyl)lysine (CML) was quantified. Glycolaldehyde induced an imbalance in the redox status, with increased protein carbonylation and lipoperoxidation. Catalase and glyoxalase I had a decrease in their activities. Despite the oxidative stress, we observed no increase in CML content. These results suggest that short-chain aldehydes such as GA might have a significant role in the development of diabetic cardiomyopathy.     

Lipid peroxidation and extracellular matrix in normal and cirrhotic rat livers following 70% hepatectomy

BACKGROUND/AIMS: The aim was to measure the deposition of collagens and proteoglycans and the underlying mechanism leading to lipid peroxidation due to oxidative stress in partially hepatectomized normal and cirrhotic rats. METHODOLOGY: Four groups of adult Wistar rats were used comprising normal livers, regenerated normal livers, cirrhotic livers, and regenerated cirrhotic livers. Cirrhosis was induced by intragastric administration of carbon tetrachloride and phenobarbital in the drinking water of the rats. Hydroxyproline, as a constituent of collagens, uronic acid, as a constituent of proteoglycans, and malondealdehyde, an end-product of lipid peroxides, were measured in normal and cirrhotic rats, and following partial hepatectomy. RESULTS: Hydroxyproline, uronic acid and malondealdehyde levels were 234.2 +/- 41.2, 11.82 +/- 1.92, 46.3 +/- 5.8 and 211.8 +/- 43.6, 9.16 +/- 1.41, 48.5 +/- 7.5 for normal and regenerated normal livers respectively. The values after partial hepatectomy in cirrhotic and regenerated cirrhotic livers were 396.9 +/- 48.5, 17.96 +/- 1.62, 144.5 +/- 25.1 and 309.6 +/- 43.2, 13.35 +/- 1.72, 229.9 +/- 24.4, respectively. When the cirrhotic liver group was compared with the normal liver group, the levels of hydroxyproline, uronic acid and malondealdehyde were significantly higher (p < 0.001). Uronic acid levels of regenerated normal and regenerated cirrhotic livers and hydroxyproline level of regenerated cirrhotic liver were significantly less than those of their non-regenerated states (p < 0.01). Although the malondealdehyde levels of normal and regenerated normal livers did not differ significantly (p > 0.05), the malondealdehyde levels of regenerated cirrhotic liver was significantly higher than cirrhotic liver (p < 0.01). The histopathological examination with light microscopy did not reveal any obvious difference between the groups other than between normal and cirrhotic. CONCLUSIONS: Cirrhotic livers revealed a significantly higher amount of extracellular matrix constituents and lipid peroxidation than normal livers. Although partial hepatectomy in cirrhotic livers caused decreases in the tissue levels of collagens and proteoglycans, it did not actually lower the ongoing oxidative stress, known as physiological lipid peroxidation, in normal and cirrhotic livers following partial hepatectomy.     

SUMO4、NF-κB、IκB在2型糖尿病大鼠肾脏中的表达及意义（英文）

目的：探讨2型糖尿病大鼠肾脏组织小泛素相关修饰蛋白4（SUMO4）、核转录因子（NF）-κB、NF-κB的抑制因子（IκB）的表达及意义。方法：取10只40周龄的无特定病原体（SPF）级雄性自发性糖尿病（GK）大鼠,10只40周龄的SPF级雄性Wistar大鼠,通过HE染色法观察肾组织病变、免疫组化法观察肾组织的SUMO4与IκB、SUMO4与NF-κB表达情况。结果：GK大鼠的肾小球毛细血管球肥大,基底膜轻度增厚,肾小球系膜细胞增生、肥大,肾小管上皮细胞肥大。与正常Wistar大鼠比较,GK大鼠的肾脏NF-κB[（0.232±0.034）比（0.634±0.058）]、IκB[（0.242±0.027）比（0.712±0.078）]及SUMO4[（0.160±0.031）比（0.545±0.045）]的表达水平均明显升高（P均〈0.01）。结论：NF-κB、IκB及SUMO4在GK大鼠肾脏组织表达增多。从而推断在2型糖尿病大鼠肾脏SUMO可能抑制NF-κB转录活性,SUMO化可能成为治疗糖尿病肾脏微血管病变的一个新靶点。     

Antioxidants attenuate early up regulation of retinal vascular endothelial growth factor in streptozotocin-diabetic rats

Aims/hypothesis: A strong positive correlation has been found between lipid peroxidation product and vascular endothelial growth factor concentrations in the vitreous of patients with proliferative diabetic retinopathy. To establish a causal relation between diabetes-associated enhanced oxidative stress and vascular endothelial growth factor production, we evaluated two antioxidants, dl-α-lipoic acid and taurine, on retinal vascular endothelial growth factor protein and mRNA expression and on parameters of oxidative stress in streptozotocin-diabetic rats. Methods: Our experiments were on control rats and streptozotocin-diabetic rats with a 6-week duration of diabetes, treated with or without dl-α-lipoic acid (100 mg · kg^–1· d^–1, i. p.) or taurine (1 % in the diet) starting from induction of diabetes. Vascular endothelial growth factor protein in retinal homogenates was assessed by sandwich ELISA with an affinity-purified polyclonal antibody and vascular endothelial growth factor mRNA by ribonuclease protection assay. Retinal lipid peroxidation products i. e. malondialdehyde plus 4-hydroxyalkenals were quantified with n-methyl-2-phenylindole. Retinal reduced and oxidized glutathione, ascorbate, dehydroascorbate, and sorbitol pathway intermediates were measured spectrofluorometrically, and taurine by reverse-phase HPLC. Results: Vascular endothelial growth factor protein concentration (means ± SD) was increased in diabetic rats compared with control rats (33 ± 7 vs 19 ± 5 pg/mg total protein, p < 0.01) This increase was attenuated by taurine (26 ± 8, p < 0.05) and prevented by dl-α-lipoic acid (21 ± 4, p < 0.01). Vascular endothelial growth factor mRNA abundance was reduced by 1.4-fold in diabetic rats compared with control rats and this decrease was attenuated but not completely prevented by both antioxidants. Malondialdehyde plus 4-hydroxyalkenal concentration was increased in diabetic rats compared with control rats, and both antioxidants arrested accumulation of lipid peroxidation products. Taurine, reduced glutathione, oxidized glutathione, ascorbate, dehydroascorbate and sorbitol pathway intermediate concentrations as well as oxidized glutathione/reduced glutathione and dehydroascorbate/ascorbate ratios were similar in control and diabetic rats treated with or without taurine. Conclusion/interpretation: Oxidative stress is directly involved in up regulation of vascular endothelial growth factor protein in the retina during early diabetes. [Diabetologia (2001) 44: 1102–1110] Received: 29 December 2001 and in revised form: 21 May 2001     

Preoperative feeding does not reverse postoperative insulin resistance in skeletal muscle in the rat

Metabolic studies on injured and postoperative patients have shown impaired glucose disposal in peripheral tissues after trauma. Using small-bowel resection as a model of surgical trauma, we investigated whether substrate availability could ameliorate the changes in muscle glucose uptake induced by trauma. We also studied the effect of preoperative feeding on postoperative insulin-stimulated insulin receptor substrate-1 (IRS-1)-associated phosphatidylinositol (PI) 3-kinase activity in both Wistar rats and genetically non-insulin-dependent diabetic Goto-Kakazaki rats (GK rats). Serum glucose, insulin, plasma epinephrine, lactate, and plasma nonesterified free fatty acids (NEFAs) were measured as indicators of the metabolic state and surgical stress. Insulin-stimulated glucose transport was significantly reduced in fed traumatized Wistar rats compared with fed nontraumatized rats (P < .05). Significant increases in in vivo insulin-stimulated IRS-1-associated PI 3-kinase activity were found in fed traumatized Wistar rats compared with fed nontraumatized Wistar rats and fasted traumatized Wistar rats, as well as fed traumatized GK rats compared with fed nontraumatized GK animals (all P < .017). Serum insulin concentrations were significantly reduced in fed traumatized Wistar and GK rats compared with the respective fed nontraumatized groups (both P < .01). Serum glucose levels were significantly elevated in fed traumatized GK rats compared with fed nontraumatized animals (P < .01). In the present study, preoperative feeding did not prevent a postoperative reduction in insulin-stimulated glucose transport in skeletal muscle. The finding that insulin-stimulated PI 3-kinase activity increased after trauma in both Wistar and GK rats indicates that postoperative insulin resistance is not caused by an impairment in the early steps of the insulin signaling pathway. The postoperative decreases in serum insulin despite high blood glucose suggest that trauma impairs the insulin response to hyperglycemia.