Effect of Exercise and Quercetin in Rats with Metabolic Syndrome Induced with Fructose.

Background: Metabolic syndrome (MetS), one of the most researched topics in recent years, is a metabolic disorder that presents with increased inactivity and has increasing prevalence in the developing world where many ready-made foods are consumed. This research aimed to investigate the protective effect of exercise and quercetin administration in a rat model of MetS induced by fructose. Methods: Forty-two male rats were divided into seven groups (n = 6): control (C), fructose (F), exercise (E), quercetin (Q), fructose+exercise (F+E), fructose+quercetin (F+Q), and fructose+quercetin+exercise (F+Q+E). Fructose was given as 20% solution in drinking water, and quercetin (15 mg/kg/day) was administered by oral gavage. Treadmill running exercises were applied 30 min a day for 5 days a week. After the experiments, biochemical assays, Lee index, and body fat mass analyses were measured. Result: Fructose administration caused a statistically significant increase in systolic blood pressures (SBP), triglycerides (TG), VLDL-cholesterol, glucose, insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) compared with the control group, and the MetS model was successfully demonstrated (P < 0.05). It was determined that SBP, serum TG, serum insulin, HOMA-IR, and Lee indexes, and body fat mass, were decreased in the F + E group (P < 0.05). In addition, it was found that the MetS-related parameters improved, except lipid profile in the F + Q group (P < 0.05). Conclusion: These results show that high fructose consumption leads to elevated SBP, TG, cholesterol, body fat mass, glucose, insulin, and HOMA-IR levels, and aerobic exercise training treatment has beneficial effects on these biochemical parameters in rats. Although quercetin has positive effects on SBP and insulin levels, it was observed to cause a significant increase especially in TG and body fat mass. Therefore, more detailed dose studies and pathways of quercetin are needed to elucidate its mechanism of action in body fat mass.

Positive Effects of Melatonin on Renal Nitric Oxide-Asymmetric Dimethylarginine Metabolism in Fructose-Fed Rats.

Background: The incidence of metabolic syndrome is increasing worldwide and this is mainly attributed to high carbohydrate intake, especially of fructose, and sedentary lifestyles. Nitric oxide (NO), which is synthesized by nitric oxide synthase (NOS) enzymes, is a crucial molecule for endothelial and renal health. Asymmetric dimethylarginine (ADMA) is the most potent inhibitor of NOS and it is degraded by dimethylarginine dimethylaminohydrolase (DDAH). The aim of this study was to investigate the effects of melatonin on renal NO-ADMA metabolism using a metabolic syndrome model achieved by fructose administration. Methods: Thirty-two rats were randomly divided into four groups (n = 8): (1) control group, (2) fructose group, (3) melatonin group, and (4) fructose + melatonin group. Fructose (20%) was given in drinking water. Melatonin [20 mg/(kg·day)] was administered in 0.1% ethanol solution. After 8 weeks, kidney tissues were collected to measure tissue levels of nitrite/nitrate (NOx), ADMA, arginine, symmetric dimethylarginine, DDAH activity, and endothelial NOS (eNOS) and inducible NOS (iNOS) protein levels. Results: Fructose led to low arginine/ADMA ratios (AARs) (P < 0.008). Tissue NOx levels of the fructose + melatonin group were significantly higher than those of the fructose group (P < 0.008). ADMA and arginine were significantly higher in the fructose + melatonin group than the control group (P < 0.008). The DDAH activity of the fructose and fructose + melatonin groups was significantly higher than that of the control group (P < 0.008). eNOS protein levels showed no difference and iNOS protein was not detected in any of the groups. Conclusions: A diminished AAR indicates the toxicity of fructose in the kidneys. Melatonin has beneficial effects on the NO-ADMA pathway as it restores NOx levels and increases DDAH activity, possibly as a result of a compensatory mechanism to metabolize increased ADMA.

Beneficial effects of melatonin on serum nitric oxide, homocysteine, and ADMA levels in fructose-fed rats.

CONTEXT: Melatonin, a pineal hormone and a potent antioxidant, has important roles in metabolic regulation. OBJECTIVE: This study investigated serum asymmetric dimethylarginine (ADMA), homocysteine (Hcy), nitric oxide (NO) levels, known to be reliable markers of cardiovascular diseases, and determined possible protective effects of melatonin in fructose-fed rats. MATERIALS AND METHODS: Sprague-Dawley rats were divided into four groups: control, fructose, melatonin, and fructose plus melatonin. Metabolic syndrome was induced in rats by 20% (w/v) fructose solution in tap water, and melatonin was administered at the dose of 20 mg/kg bw per day by oral gavage. After 8 weeks, serum lipids, glucose, insulin, ADMA, Hcy, and NOx (the stable end products of NO) levels were quantified. RESULTS: Fructose administration caused a statistically significant increase in systolic blood pressure (SBP), serum insulin, triglycerides, and very low-density lipoprotein (VLDL)-cholesterol levels compared with the control group and the metabolic syndrome model was successfully demonstrated. In comparison with the control group, fructose caused a significant increase in serum ADMA, Hcy, and NOx levels. Melatonin counteracted the changes in SBP, serum ADMA, and Hcy levels found in rats both alone and administered with fructose. DISCUSSION AND CONCLUSION: These results show that high fructose consumption leads to elevated SBP, atherogenic lipid profile, increased serum ADMA, and Hcy levels and melatonin treatment has beneficial effects on these biochemical parameters in rats. Melatonin might be beneficial for the prevention and/or treatment of the cardiovascular complications of metabolic syndrome not only by reducing the well-known risk factors of the disease but also by diminishing blood ADMA and Hcy levels.

The effect of taurine on the relationship between NO, ADMA and homocysteine in endotoxin-mediated inflammation in HUVEC cultures.

The aim of our study was to investigate the effect of taurine on the relationship between nitric oxide (NO), asymmetric dimethylarginine (ADMA) and homocysteine (Hcy) in endotoxin-induced human umblical vein endothelial cell (HUVEC) cultures. For this reason, four groups were formed (n=12). Control group consists of HUVEC cultures without any treatment. Lipopolysaccharide (LPS) and LPS+taurine groups were treated with 10 µg/mL endotoxin, 5 µg/mL taurine and endotoxin+taurine (same doses), respectively. Nitrite/nitrate (NOx), ADMA and Hcy levels were measured. There was a significant increase of NOx, ADMA and Hcy in endotoxemia (p<0.05). Taurine treatment elevated NOx levels significantly (p<0.01) in taurine and LPS + taurine group compared to control group, while it reduced NOx levels compared to LPS group. In contrast, taurine decreased ADMA levels to the control level both in taurine and taurine+LPS group compared to LPS. Hcy levels increased significantly compared to taurine group (p<0.05) and did not change compared to LPS group. Taurine was effective on ADMA-NO relationship whereas no beneficial effect was observed in Hcy levels (p<0.05).

Effect of taurine on brain 8-hydroxydeoxyguanosine and 3-nitrotyrosine levels in endotoxemia.

Taurine is a sulfur-containing ß-amino acid that is found in milimolar concentrations in most mammalian tissues and plasma. It was shown to have cytoprotective effects in many in vitro and in vivo studies and these actions are often attributed to an antioxidant mechanism. In this study, we aimed to investigate the effect of acute taurine administration on endotoxin-induced oxidative and nitrosative stress in brain. Fourty adult male guinea pigs were divided into four groups: control, taurine, endotoxemia, and endotoxemia + taurine. Taurine (300 mg/kg), lipopolysaccharide (LPS, 4 mg/kg), or taurine plus LPS was administered intraperitoneally. After 6 h of incubation, when highest blood levels of taurine and endotoxin were attained, the animals were killed and brain tissue samples were collected. 3-Nitrotyrosine (3-NT), 8-hydroxydeoxyguanosine (8-OHdG) and taurine levels were measured using high-performance liquid chromatography methods. LPS administration significantly increased 3-NT, 8-OHdG levels, and dramatically reduced taurine concentrations in brain tissue compared to control group. The groups in which taurine was administered alone or with LPS, contradiction to well-known antioxidant effect, taurine caused elevated concentrations of 3-NT and 8-OHdG compared to both control and endotoxemia groups. In conclusion, endotoxemia leads to tyrosine nitration and DNA base modification that can be assessed by 3-NT and 8-OHdG, respectively. Taurine did not exhibit any antioxidant effect; moreover, it may contribute to neuronal damage at this dose. Thus, we can suggest that lower dose of taurine administration may be benefial for neuronal protection or adversely taurine administration may have toxic effect at all doses.

Effects of taurine on nitric oxide and 3-nitrotyrosine levels in spleen during endotoxemia.

Taurine (2-aminoethanesulfonic acid) is a free sulfur-containing ß-amino acid which has antioxidant, antiinflammatory and detoxificant properties. In the present study, the role of endotoxemia on peroxynitrite formation via 3-nitrotyrosine (3-NT) detection, and the possible antioxidant effect of taurine in lipopolysaccharide (LPS)-treated guinea pigs were aimed. 40 adult male guinea pigs were divided into four groups; control, endotoxemia, taurine and taurine+endotoxemia. Animals were administered taurine (300 mg/kg), LPS (4 mg/kg) or taurine plus LPS intraperitoneally. After 6 h of incubation, when highest blood levels of taurine and endotoxin were attained, the animals were sacrificed and spleen samples were collected. The amounts of 3-nitrotyrosine and taurine were measured by HPLC, and reactive nitrogen oxide species (NOx) which are stable end products of nitric oxide was measured spectrophotometrically in spleen tissues. LPS administration significantly decreased the concentration of taurine whilst increased levels of 3-NT and NOx compared with control group. It was determined that taurine treatment decreased the levels of 3-nitrotyrosine and NOx in taurine+endotoxemia group. The group in which taurine was administered alone, contradiction to well-known antioxidant effect, taurine caused elevated concentration of 3-NT and NOx. This data suggest that taurine protects spleen against oxidative damage in endotoxemic conditions. However, the effect of taurine is different when it is administered alone. In conclusion, taurine may act as an antioxidant during endotoxemia, and as a prooxidant in healthy subjects at this dose.

High-dose vitamin C supplementation accelerates the Achilles tendon healing in healthy rats.

INTRODUCTION: This experimental study was performed to assess, whether or not, vitamin C, required during the collagen synthesis, would influence the Achilles tendon healing in a healthy rat model. MATERIALS AND METHODS: The right Achilles tendons of 42 healthy female Wistar Albino rats were completely ruptured. The rats were randomly divided into the vitamin C and control groups and both groups included third, tenth and twenty-first day subgroups. One hundred and fifty milligrams (1.5 cc) of vitamin C and 1.5 cc % 0.9 NaCl were injected once for every 2 days for the vitamin C and control groups, respectively. Qualitative and quantitative microscopic comparisons of the repair tissues of both groups were made on the mentioned days. RESULTS: Angiogenesis was more evident on the third day in the vitamin C group. There was a significant difference between the control and vitamin C groups regarding the type I collagen production on the tenth day. The structure of the repair tissue was almost in the form of regular dense connective tissue at the end of twenty-first day in the vitamin C group. Mean collagen fiber diameter was considerably higher, and the number of active fibroblasts in the repair tissue was slightly elevated in the vitamin C group during the entire healing process. CONCLUSION: High-dose vitamin C supplementation once for every 2 days has stimulating effects on the Achilles tendon healing because of early angiogenesis and increased collagen synthesis in a healthy rat model. Further studies are needed to make clear the mentioned encouraging effects of the vitamin C on the Achilles tendon healing.

Effects of hyperbaric oxygen on energy production and xanthine oxidase levels in striated muscle tissue of healthy rats.

We investigated the effects of hyperbaric oxygen (HBO) treatment on striated muscle tissue in healthy rats. The treatment group of rats (n=16) was given HBO daily on weekdays for 2 h over a 4-week period while a control group (n=8) was not treated. Tissue samples were taken from the left and right vastus lateralis before and after the HBO treatment period, respectively, for all rats in both groups. Levels of adenosine monophosphate (AMP), adenosine diphosphate, andenosine triphosphate (ATP) and xanthine oxidase in the muscle tissue were determined. HBO treatment caused a statistically significant increase in ATP (p=0.001) and decrease in AMP (p=0.02) in the HBO-treated group, while there were no significant differences in metabolites in the control group. These results suggest that HBO treatment induces an increase in the ATP levels of muscle tissue with normal mitochondria. Thus, HBO might have some beneficial effects in the treatment of heteroplasmic mitochondrial disease, where normal and defective mitochondria coexist.

The relationship between taurine and 3-nitrotyrosine level of hepatocytes in experimental endotoxemia.

It has been proposed that taurine may function as an oxidant in a dose-dependent manner in vivo and in vitro. The present study was carried out to investigate the relationship between taurine concentration and 3-nitrotyrosine level, a stable marker of peroxynitrite action, in hepatocytes of guinea pig in endotoxemia before and after taurine administration. The levels of taurine and 3-nitrotyrosine were measured by HPLC method. In the present study, taurine was low concentration in hepatocytes exposed to endotoxemia. In taurine plus endotoxin treated animals, HPLC analysis showed higher taurine level compared with animals only supplemented with taurine. But 3-nitrotyrosine levels were same in both taurine alone and taurine plus endotoxin groups. In conclusion, taurine is able to prevent the damaging effect of peroxynitrite, at concentration measured in hepatocytes, in our experimental conditions.

Effect of taurine on endotoxin-induced alterations in plasma asymmetric dimethylarginine, L-arginine and nitric oxide in guinea pigs.

The effect of taurine on the plasma levels of L-arginine, asymmetrical dimethylarginine (ADMA) and L-arginine/ADMA ratio and nitric oxide was investigated in experimental endotoxemia. L-arginine and ADMA levels were quantified by high performance liquid chromatography with fluorescence detector. Nitric oxide level was measured with spectrophotometric method. All experiments were performed with four groups (control, taurine, endotoxemia, taurine plus endotoxin) of 10 guinea pigs. After the endotoxin was administrated (4 mg/kg) ADMA level increased, nitric oxide level did not change but L-arginine level and L-arginine/ADMA ratio decreased. When taurine was administrated (300 mg/kg) no effect on ADMA and nitric oxide levels was observed compared to the endotoxemia group. But it was increased the L-arginine/ADMA ratio. Taurine may offer an advantage in because of it increases the reduced L-arginine/ADMA ratio.

Ischemic preconditioning improves liver regeneration by sustaining energy metabolism after partial hepatectomy under ischemia in rats.

BACKGROUND: The protective effect of ischemic preconditioning (IPC) has been reported on improvement of survival, reduction of liver necrosis and enhancement of the regenerative capacity of hepatocytes after partial hepatectomy. This study was undertaken to confirm that IPC has a significant impact on regeneration of hepatocytes after partial hepatectomy in ischemically damaged liver. In addition, we sought to examine the role of adenine nucleotides in this process. METHODS: Wistar rats were subjected to 60 min of total hepatic ischemia, followed by 70% hepatectomy. The animals were subdivided into an IPC (10/15 min) group and a non-IPC (control) group. Liver function tests and arginase activity were analyzed. Hepatic adenosine triphosphate (ATP), adenosine diphosphate and adenosine monophosphate were measured using gradient high-performance liquid chromatography. The liver regeneration was identified using relative liver weight and proliferating cell nuclear antigen (PCNA) labeling index. RESULTS: IPC treatment improved serum liver enzymes and tissue arginase activity (P<0.05) when compared with the control group. The preconditioned livers were associated with upregulation of ATP expression and also increased tissue energy charge. Regenerated liver weight in the IPC group was significantly higher than in the control group (P<0.05). The PCNA labeling index in the remnant livers in the IPC group was also significantly increased at 24 and 48 h after partial hepatectomy (P<0.05). CONCLUSION: These results suggest that IPC-augmented liver regeneration after hepatectomy, probably due to the stabilization of energy metabolism in rats.

The effect of vitamin A pretreatment on radiation induced alteration in neutrophil functions.

The aim of this investigation was to determine whether pre-administration of vitamin A will be effective in preventing the radiation-induced decline in MPO-H2O2 system and the end product of reactive nitrogen species (NOx) in guinea pig. Animals were subjected to 612 cG of radiation and polimorfonuclear leukocytes were isolated and then NOx and myeloperoxidase activity were measured. In irradiated animals, a marked decrease in NOx level and myeloperoxidase activity have been found compared to control (p = 0.001 and p < 0.000 respectively). The application of vitamin A significantly improved the radiation-induced decrease (for both p < 0.00). In conclusion pre-treatment of vitamin A is efficient to protect against radiation induced alteration in polimorfonuclear leukocyte.

Effect of vitamin A pretreatment on Escherichia coli-induced lipid peroxidation and level of 3-nitrotyrosine in kidney of guinea pig.

In the present study, we report the effect of vitamin A (Vit A, retinol palpitate) on kidney lipid peroxidation and 3-nitrotyrosine (3-NT) levels induced after Escherichia coli administration to guinea pigs. Vit A was administrated intraperitoneally (i.p.) to guinea pigs at a dose 15,000 IU/kg per day for 7 days prior to E. coli injection. On day 8, the animals were injected i.p. with E. coli dosed at 12 x10(9) colony forming units per kilogram. Kidneys were collected 6 h after administration of E. coli. Malondialdehyde (MDA) as a lipid peroxidation product, and 3-NT levels were measured by reverse phase high-performance liquid chromatography. There was a significant increase in MDA and 3-NT levels in lipopolysaccaharide-induced group (p<0.001). 3-NT was not detectable in kidney of normal control animals. However, Vit A administration prior to E. coli injection prevented 3-NT formation but did not prevent the rice in MDA level of kidney (p<0.001). Vit A alone did not alter the MDA level in the kidney of the control group.

The effects of nitric oxide synthesis on the Na+ ,K(+)-ATPase activity in guinea pig kidney exposed to lipopolysaccharides.

Endotoxins (lipopolysaccharides; LPS) are known to cause multiple organ failure, including renal dysfunction. LPS triggers the synthesis and release of cytokines and the vasodilator nitric oxide (NO*). A major contributor to the increase in NO* production is LPS-stimulated expression of inducible nitric oxide synthase (iNOS). This occurs in vasculature and most organs including the kidney. During endotoxemia, NO* and superoxide react spontaneously to form the potent and versatile oxidant peroxynitrite (ONOO-) and the formation of 3-nitrotyrosine (nTyr)-protein adducts is a reliable biomarker of ONOO- generation. Therefore, the present study was aimed at investigating the role of endogenous nitric oxide in regulating Na+,K(+)-ATPase activity in the kidney, and at investigating the possible contribution of reactive nitrogen species (RNS) by measuring of iNOS activity. In addition, the present study was aimed at investigating the relationship between nTyr formation with iNOS and Na+,K(+)-ATPase activities. Previously in our study, nTyr was not detectable in kidney of normal control animals but was detected markedly in LPS exposed animals. In this study, kidney Na+,K(+)-ATPase activity were maximally inhibited 6 h after LPS injection (P:0.000) and LPS treatment significantly increased iNOS activity of kidney (P:0.000). The regression analysis revealed a very close correlation between Na+,K(+)-ATPase activity and nTyr levels of LPS treated animals (r = -0.868, P = 0.001). Na+,K(+)-ATPase activity were also negatively correlated with iNOS activity (r = -0.877, P = 0.001) in inflamed kidney. These data suggest that NO* and ONOO- contribute to the development of oxidant injury. Furthermore, the source of NO* may be iNOS. iNOS are expressed by the kidney, and their activity may increase following LPS administration. In addition, NO* and ONOO- formation inhibited Na+,K(+)-ATPase activity. This results also have strongly suggested that bacterial LPS disturbs activity of membrane Na+,K(+)-ATPase that may be an important component leading to the pathological consequences such as renal dysfunction in which the production of RNS are increased as in the case of LPS challenge.

Effects of melatonin on 3-nitrotyrosine formation and energy charge ratio in guinea pig kidney in LPS-induced stress.

The aim of this study was to evaluate the effects of Escherichia coli-derived lipopolysaccharide on guinea pig kidney by measuring the energy charge ratio and 3-nitrotyrosine levels. In addition the possible protective role of melatonin against lipopolysaccharide-mediated peroxynitrite formation and energy depletion of kidney was determined. Guinea pigs were either pretreated with melatonin or saline (for the control) followed by intraperitoneal administration of E. coli. Six hours after the administration of E. coli, guinea pig kidney ATP, ADP, AMP and 3-nitrotyrosine levels were measured by reverse-phase high performance liquid chromatography. There was a significant increase in the formation of 3-nitrotyrosine and decrease in energy charge in the endotoxin-induced group. However melatonin administration prevented 3-nitrotyrosine formation while failing to prevent or restore changes in the energy charge ratio of the kidney.

The effect of desferrioxamine on peroxynitrite-induced oxidative damage in erythrocytes.

The aim of this study was to investigate the effect of desferrioxamine on peroxynitrite-mediated damage in erythrocytes by measuring the 3-nitrotyrosine level and glutathione peroxidase and Na(+)-K(+) ATPase activities in vitro. 3-Nitrotyrosine levels were determined by HPLC; glutathione peroxidase and Na(+)-K(+) ATPase activities were measured by spectrophotometry. Peroxynitrite increased the 3-nitrotyrosine level but decreased both enzyme activities. In the presence of desferrioxamine, glutathione peroxidase activity was increased with a decrease in the 3-nitrotyrosine level. Desferrioxamine was found to possess an important antioxidant activity as assessed in an in vitro system, reducing protein nitration, restoring enzyme activities and maintaining erythrocyte membrane integrity.

Impaired Na+,K+-ATPase activity as a mechanism of reactive nitrogen species-induced cytotoxicity in guinea pig liver exposed to lipopolysaccharides.

In animal models of endotoxin, the excess production of NO and the reactive nitrogen species (RNS), are potent oxidant and nitrating agents, lead to lipid peroxidation, apoptosis, tissue dysfunction and injury and inactivate enzymes in many cell types. Although liver functions are well known to deteriorate following bacterial infection, the underlying specific mechanism(s) remain a matter of considerable debate. Therefore, the aim of the present study was to determine the in vivo effect of bacterial lipopolysaccharides (LPS) on Na+,K+-ATPase activity of guinea pig liver, and to investigate the possible contribution of RNS by measuring of iNOS activity and 3-nitrotyrosine (nTyr) levels. Liver Na+,K+-ATPase activity were maximally inhibited 6 h after LPS injection (p < 0.001 ). nTyr was not detectable in liver of normal control animals, but was detected markedly in LPS exposed animals. LPS treatment significantly increased iNOS activity of liver (p < 0.001). The regression analysis revealed a very close correlation between Na+,K+-ATPase activity and nTyr levels of LPS treated animals (r = -0.863, p < 0.001). Na+, K+-ATPase activity were also negatively correlated with iNOS activity (r = -0.823, p < 0.003) in inflamed tissues. Our results have strongly suggested that bacterial LPS disturbs activity of membrane Na+,K+-ATPase that may be an important component leading to the pathological consequences such as hepatocyte cell loss and dysfunction in which the production of RNS are increased as in the case of LPS challenge.