Effect of streptozotocin-induced diabetes on oxidative energy metabolism in rat liver mitochondria-A comparative study of early and late effects

Integrative bioinformatic and experimental analysis of benzoylbenzodioxol derivatives: hypoglycemic potential in diabetic mice

We investigated the hypoglycemic activity and pharmacokinetic study of two synthesized benzoyl benzodioxol derivatives, compound I (methyl 2-(6-(2-bromobenzoyl)benzo[d][1,3]dioxol-5-yl)acetate), and compound II, 2-(6-benzoylbenzo[d][1,3]dioxol-5-yl)acetic acid, which showed very strong α-amylase inhibiting activity in our previous study. Then, diabetes was induced by the injection of streptozotocin to mice. The molecular docking simulations and analyses of density functional theory analyses were conducted to study the binding interactions with human pancreatic alpha-amylase, and their pharmacokinetic properties were further evaluated by ADMET profiling. Compound I showed the most important hypoglycemic effect, decreasing the blood glucose by 32.4%, higher than that of compound II by 14.8% and even the positive control acarbose by 22.9%. Histopathological examination revealed that diabetic livers showed portal inflammation with some apoptotic hepatocytes due to streptozotocin treatment, whereas controls without any treatment maintained normal liver architecture. Molecular docking studies gave results for the best binding affinity of the compound I, through its strong water bridges and π-π interactions, and also through analysis with density functional theory, was more stable and reactive when compared to compound II. Further ADMET analysis showed that both compounds shared a promising pharmacokinetic profile, and compound I had the potential for CNS penetration. Thus, compound I was selected as the best candidate for developing new hypoglycemic agents with potent efficacy, good binding interactions, and excellent pharmacokinetic properties.

Myocardial salvage by succinate dehydrogenase inhibition in ischemia-reperfusion injury depends on diabetes stage in rats

Inhibition of succinate dehydrogenase (SDH) by Dimethyl Malonate (DiMal) reduces cardiac ischemia-reperfusion (IR) injury. We investigated the cardioprotective effect of DiMal in a rat model during advancing type 2 diabetes. Zucker Diabetic Fatty rats and lean controls were investigated corresponding to prediabetes, onset and mature diabetes. Hearts were mounted in an isolated perfused model, and subjected to IR for investigation of infarct size (IS) and mitochondrial respiratory control ratio (RCR). DiMal was administered for 10 min before ischemia. Compared with age-matched non-diabetic rats, prediabetic rats had larger IS (49 ± 4% vs. 36 ± 2%, p = 0.007), rats with onset diabetes smaller IS (51 ± 3% vs. 62 ± 3%, p = 0.05) and rats with mature diabetes had larger IS (79 ± 3% vs. 69 ± 2%, p = 0.06). At the prediabetic stage DiMal did not alter IS. At onset of diabetes DiMal 0.6 mM increased IS in diabetic but not in non-diabetic control rats (72 ± 4% vs. 51 ± 3%, p = 0.003). At mature diabetes DiMal 0.1 and 0.6 mM reduced IS (68 ± 3% vs. 79 ± 3% and 64 ± 5% vs. 79 ± 3%, p  = 0.1 and p = 0.01), respectively. DiMal 0.1 mM alone reduced IS in age-matched non-diabetic animals (55 ± 3% vs. 69 ± 2% p = 0.01). RCR was reduced at mature diabetes but not modulated by DiMal. Modulation of SDH activity results in variable infarct size reduction depending on presence and the stage of diabetes. Modulation of SDH activity may be an unpredictable cardioprotective approach.

Intermittent Hypoxic Conditioning Alleviates Post-Traumatic Stress Disorder-Induced Damage and Dysfunction of Rat Visceral Organs and Brain

Posttraumatic stress disorder (PTSD) causes mental and somatic diseases. Intermittent hypoxic conditioning (IHC) has cardio-, vaso-, and neuroprotective effects and alleviates experimental PTSD. IHC’s ability to alleviate harmful PTSD effects on rat heart, liver, and brain was examined. PTSD was induced by 10-day exposure to cat urine scent (PTSD rats). Some rats were then adapted to 14-day IHC (PTSD+IHC rats), while PTSD and untreated control rats were cage rested. PTSD rats had a higher anxiety index (AI, X-maze test), than control or PTSD+IHC rats. This higher AI was associated with reduced glycogen content and histological signs of metabolic and hypoxic damage and of impaired contractility. The livers of PTSD rats had reduced glycogen content. Liver and blood alanine and aspartate aminotransferase activities of PTSD rats were significantly increased. PTSD rats had increased norepinephrine concentration and decreased monoamine oxidase A activity in cerebral cortex. The PTSD-induced elevation of carbonylated proteins and lipid peroxidation products in these organs reflects oxidative stress, a known cause of organ pathology. IHC alleviated PTSD-induced metabolic and structural injury and reduced oxidative stress. Therefore, IHC is a promising preventive treatment for PTSD-related morphological and functional damage to organs, due, in part, to IHC’s reduction of oxidative stress.

Type 2 diabetes differentially affects the substrate saturation kinetic attributes of erythrocyte hexokinase and phosphofructokinase

The substrate kinetic parameters of hexokinase (HK) and phosphofructokinase (PFK)-the key irreversible enzymes of glycolysis-in erythrocytes from type 2 diabetic subjects were examined in comparison with control subjects. It was observed that the kinetic parameters such as K_m , V_max , Apparent K_cat , K_cat /K_m , and substrate (ATP) inhibition kinetic and substrate binding characteristics are significantly altered in the diabetic group. The observed changes are suggestive of compositional changes in the subunit makeup of HK and PFK. The implication of these findings in relation to energy status of the diabetic erythrocyte and its interrelationship with loss of cell deformability are discussed here.

Predicting anxiety responses to halogenated glucocorticoid drugs using the hexobarbital sleep time test

Glucocorticoids (GCs) are used to treat numerous diseases, but their use in limited by adverse side effects. One such effect is occasional increased anxiety. Since the intensity of hepatic microsomal oxidation has been shown to alter responses to GC, we examined the possibility that rats with lower rates of hepatic GC metabolism would have increased anxiety. We hypothesized that the resulting, excessive GC would stimulate brain monoamine oxidase A (MAO-A), which would reduce brain serotonin, and thereby increase anxiety. Hepatic microsomal oxidative intensity was evaluated by the hexobarbital sleep time (HST) test. Results showed that rats with lower rates of hepatic GC metabolism had elevated brain MAO-A activity, reduced brain serotonin, and more anxiety than rats with higher rates of hepatic GC metabolism. We suggest that the HST test, as an integrative test of microsomal oxidation status, should be useful for predicting individual sensitivity to GC and to other drugs metabolized by the hepatic microsomal oxidation system.

Protective effects of dietary avocado oil on impaired electron transport chain function and exacerbated oxidative stress in liver mitochondria from diabetic rats

Electron transport chain (ETC) dysfunction, excessive ROS generation and lipid peroxidation are hallmarks of mitochondrial injury in the diabetic liver, with these alterations also playing a role in the development of non-alcoholic fatty liver disease (NAFLD). Enhanced mitochondrial sensitivity to lipid peroxidation during diabetes has been also associated to augmented content of C22:6 in membrane phospholipids. Thus, we aimed to test whether avocado oil, a rich source of C18:1 and antioxidants, attenuates the deleterious effects of diabetes on oxidative status of liver mitochondria by decreasing unsaturation of acyl chains of membrane lipids and/or by improving ETC functionality and decreasing ROS generation. Streptozocin-induced diabetes elicited a noticeable increase in the content of C22:6, leading to augmented mitochondrial peroxidizability index and higher levels of lipid peroxidation. Mitochondrial respiration and complex I activity were impaired in diabetic rats with a concomitant increase in ROS generation using a complex I substrate. This was associated to a more oxidized state of glutathione, All these alterations were prevented by avocado oil except by the changes in mitochondrial fatty acid composition. Avocado oil did not prevented hyperglycemia and polyphagia although did normalized hyperlipidemia. Neither diabetes nor avocado oil induced steatosis. These results suggest that avocado oil improves mitochondrial ETC function by attenuating the deleterious effects of oxidative stress in the liver of diabetic rats independently of a hypoglycemic effect or by modifying the fatty acid composition of mitochondrial membranes. These findings might have also significant implications in the progression of NAFLD in experimental models of steatosis.

Distribution of glutathione peroxidase 1 in liver tissues of healthy and diabetic rats treated with capsaisin

We investigated the immunohistochemical localization of glutathione peroxidase 1 (GPx 1) and the structural changes that occur in the livers of healthy and diabetic rats that were treated with capsaisin (CAP). Fifty female rats were divided into five groups: group 1, sham; group 2, untreated control; group 3, CAP-treated; group 4, streptozotocin (STZ) diabetic; group 5, STZ diabetic + CAP-treated. STZ was administered to groups 4 and 5; after verifying diabetes, CAP was administered daily for 2 weeks to groups 3 and 5. Diffuse, microvesicular and some macrovesicular fatty degeneration were observed in the cytoplasms of hepatocytes in the livers of the diabetic group. In the CAP-treated diabetic group, fat degeneration in the livers decreased slightly by day 7. Irregularity of the external contours of nuclei of the hepatocytes, swelling of the nuclei, and slight anisocytosis and anisokaryosis were observed in the hepatocytes of the diabetic group. In the CAP-treated diabetic groups, the severity of anisocytosis and anisokaryosis decreased slightly by day 7. In all groups, GPx 1 showed similar immunolocalization, but in the diabetic and diabetic + CAP groups, GPx 1 immunoreactivity was less than in the other groups. GPx 1 immunoreactivity in the CAP-treated diabetic group was weaker than in the diabetic group. In all groups, GPx 1 immunoreactivity was diffusely cytoplasmic in some of the hepatocytes, and diffusely cytoplasmic and diffusely nuclear in other hepatocytes. Also, GPx 1 immunoreactivity in the liver was more intense in the hepatocytes around Kiernan's space. We found that CAP caused a decrease in GPx 1.

Rhinacanthus nasutus Ameliorates Cytosolic and Mitochondrial Enzyme Levels in Streptozotocin-Induced Diabetic Rats

The present study was conducted to evaluate the therapeutic efficacy of Rhinacanthus nasutus (R. nasutus) on mitochondrial and cytosolic enzymes in streptozotocin-induced diabetic rats. The rats were divided into five groups with 6 rats in each group. The methanolic extract of R. nasutus was orally administered at a dose of 200 mg/kg/day, and glibenclamide was administered at a dose of 50 mg/kg/day. All animals were treated for 30 days and were sacrificed. The activities of both intra- and extramitochondrial enzymes including glucose-6-phosphate dehydrogenase (G6PDH), succinate dehydrogenase (SDH), glutamate dehydrogenase (GDH), and lactate dehydrogenase (LDH) were measured in the livers of the animals. The levels of G6PDH, SDH, and GDH were significantly reduced in the diabetic rats but were significantly increased after 30 days of R. nasutus treatment. The increased LDH level in diabetic rats exhibited a significant reduction after treatment with R. nasutus. These results indicate that the administration of R. nasutus altered the activities of oxidative enzymes in a positive manner, indicating that R. nasutus improves mitochondrial energy production. Our data suggest that R. nasutus should be further explored for its role in the treatment of diabetes mellitus.

Effect of lead and cadmium co-exposure on testicular steroid metabolism and antioxidant system of adult male rats

The mechanism of testicular toxicity of lead (Pb) and cadmium (Cd) is poorly understood. Previous studies focused on single metal-related changes in testicular toxicity. This study points towards the possible involvement of Pb- and Cd-induced oxidative stress in the suppression of steroidogenesis. The oxidative status of testis of adult male rats exposed to Pb acetate and cadmium acetate either alone or in combination at a dose of 0.025 mg kg(-1) body weight of metal intraperitoneally for 15 days was studied. Pb and Cd caused an increase in reactive oxygen species (ROS) by elevating testicular malondialdehydes (MDA) and decrease in activities of testicular antioxidant enzymes superoxide dismutase (SOD), catalase, glucose 6 phosphate dehydrogenase (G6PDH) and glutathione-S-transferase (GST) in mitochondrial and/or post-mitochondrial fraction. Activities of steroidogenic enzymes 3β and 17β-hydroxysteroid dehydrogenase also decreased significantly leading to altered testosterone production. Metal-exposed groups showed significantly decreased testicular and epididymal sperm count. Epididymal sperm motility and viability was also decreased on Pb and Cd exposure. Cd exposure showed more toxic effect than lead exposure, while combined exposure demonstrated least toxicity. In vitro experiments showed that vitamin C restores steroidogenic enzyme activities, suggesting that Pb- and Cd-induced ROS inhibits the testicular steroidogenesis.

Lead and cadmium co-exposure mediated toxic insults on hepatic steroid metabolism and antioxidant system of adult male rats

The redox status and steroid metabolism of liver of adult male rat exposed to lead (Pb) and cadmium (Cd) either alone or in co-exposure (0.025 mg/kg body weight intraperitoneally/15 days) was studied. Pb and Cd significantly accumulated in the liver. The activity of steroid metabolizing enzymes 17-betahydroxysteroid oxidoreductase and uridine diphosphate-glucuronyltransferase were decreased in experimental animals. 17-beta-Hydroxysteroid dehydrogenase was reduced to 33%, 38%, and 24% on treatment of Pb, Cd, and co-exposure (Pb + Cd). Furthermore, the activity of uridine diphosphate-glucuronosyltransferase was significantly reduced to 27% (Pb exposure), 36% (Cd exposure), and 25% (co-exposure of Pb + Cd). Cd exposure exhibited more toxic effect than Pb, while co-exposure demonstrated the least. The activities of antioxidant enzymes, superoxide dismutase, catalase, glutathione reductase, and glucose-6-phosphate dehydrogenase decreased and glutathione peroxidase increased in mitochondrial and post-mitochondrial fractions. The level of lipid peroxidation increased, and cellular glutathione concentration decreased. Hepatic DNA was decreased, whereas RNA content and the activity of alanine transaminase remained unchanged. Histological studies revealed that only Cd-exposed groups exhibited cytotoxic effect. These results suggest that when Pb and Cd are present together in similar concentrations, they exhibited relatively decreased toxic effect when compared to lead and cadmium in isolation with regard to decreased steroid metabolizing and antioxidant enzyme activities. This seems that the toxic effect of these metals is antagonized by co-exposure due to possible competition amongst Pb and Cd for hepatic accumulation.

Influences of crude extract of tea leaves, Camellia sinensis, on streptozotocin diabetic male albino mice

Natural remedies from medicinal plants are considered to be effective and safe alternative treatment for diabetes mellitus. The aim of the present study was to investigate the hypoglycemic activity of the crude tea leaves extract on streptozotocin (STZ)-induced diabetic mice. The average body weight of animals with diabetes and their percentage changes of body weight gain after 15 and 30 days were significantly lower than that of the normal control mice. In diabetic mice, supplementation with tea leaves extract decreased the loss of body weight. After 15 and 30 days, significant increases in the levels of serum glucose, triglycerides, cholesterol, creatinine, urea, uric acid, glutamic pyruvic acid transaminase (GPT) and glutamic oxaloacetic acid transaminase (GOT) were noted in STZ-diabetic mice fed with normal diet. Also, the values of total protein in this group were statistically declined after 15 and 30 days. The levels of serum glucose and GPT were significantly elevated after 15 and 30 days in diabetic mice supplemented with tea leaves extract. Moreover, the level of serum GOT was notably increased after 30 days. Insignificant alterations were observed in the levels of serum triglycerides, cholesterol, total protein, creatinine, urea and uric acid in diabetic mice supplemented with tea leaves extract. Thus, the present results have shown that tea leaves extract has the antihyperglycemic, antihyperlipidemic, and antihyperproteinemic effects and consequently may alleviate liver and kidney damage associated with STZ-induced diabetes in mice.

Diabetic modulation of the temperature kinetics properties of cytochrome oxidase activity in rat brain mitochondria

The effects of alloxan-diabetes and subsequent treatment with insulin on temperature kinetics properties of cytochrome oxidase activity from rat brain mitochondria were examined. The enzyme activity decreased only at the late stage of diabetes which was not normalized by insulin treatment; however at early stage of diabetes hyper-stimulation occurred. In the control animals the Arrhenius plot was chair shaped with three energies of (E1, E2 and E3) and two phase transition temperatures (Tt1 and Tt2). At early diabetic stage the Arrhenius plot became biphasic and E1)and E2 decreased; insulin treatment reversed chair-shaped pattern with increase in E2. These changes correlated with transient changes in the phospholipids profiles especially decreased acidic phospholipids. The temperature kinetics parameters were minimally affected at the late stage of diabetes or by insulin treatment. Thus at the late stage the brain tissue seems to have readjusted to its insulin homeostasis.

Effect of alloxan diabetes and subsequent insulin treatment on temperature kinetics properties of succinate oxidase activity in rat kidney mitochondria

Early and late effects of alloxan diabetes and subsequent treatment with insulin on the temperature kinetics properties of succinate oxidase (SO) activity in rat kidney mitochondria were examined. In diabetic animals SO activity increased significantly and the increase was more pronounced at the late stage. Insulin treatment partially restored SO activity. However, the effect was temperature-dependent. In diabetic animals the energy of activation in the low temperature range (E(L)) increased significantly while that in the high temperature range (E(H)) decreased. The latter seems to be responsible for improving catalytic efficiency in the diabetic state. Insulin treatment normalized E(H) only in the 1-month diabetic group. The phase transition temperature (Tt), decreased in diabetic animals. Insulin treatment caused an increase beyond the control value in Tt in 1-month diabetic animals. The results suggest that insulin status-dependent modulation of SO activity is a complex process.

Insulin status-dependent alterations in lipid/phospholipid composition of rat kidney microsomes and mitochondria

Early and late effects of alloxan-diabetes on lipid/phospholipid composition in rat kidney microsomes and mitochondria were examined. In microsomes, early diabetic state resulted in an increase in contents of total phospholipids (TPL), cholesterol (CHL), with an increase in the lysophospholipids (Lyso), phosphatidylcholine (PC), and phosphatidylinositol (PI) components. The sphingomyelin (SPM), phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidic acid (PA) content decreased. Treatment with insulin had no effect on PC but PE increased and the other components decreased. In the 1-month diabetic group PI, PS, PE, and PA components decreased, whereas Lyso and PC increased. Treatment with insulin had restorative effects on PE, PI, and PS; Lyso was further elevated whereas PA decreased. In mitochondria, at an early stage of diabetes marginally increased CHL content was restored by insulin treatment. Long-term diabetes lowered the TPL and elevated the CHL content. Treatment with insulin partially restored the TPL and CHL content. A diabetic state decreased the proportion of PE and diphosphatidylglycerol (DPG) components but increased the Lyso, SPM, PC, PI, and PS components in the mitochondria. Treatment with insulin had a partial restorative effect. The membrane fluidity of both microsomes and mitochondria decreased in general in the diabetic condition and was not corrected by insulin treatment at a late stage. However, at an early stage, treatment with insulin fluidized both membranes.

Insulin-status-dependent modulation of FoF1 ATPase activity in rat kidney mitochondria

The early and late effects of alloxan-diabetes and insulin treatment on kinetic properties of mitochondrial FoF1 ATPase were examined. Diabetic state resulted in significant decrease in the activity while insulin treatment caused hyper-stimulation. In control animals the enzyme activity resolved in three kinetic components. In diabetic condition only component I and II were present. With insulin treatment component III was restored but component II was abolished. Diabetic state and insulin treatment had varied effects on Km values of the three components, whereas the Vmax values were generally on the higher side. Evaluation of the AppKcat/Km values revealed that diabetic state resulted in increased catalytic efficiency; insulin treatment brought back these values to normality. Temperature kinetics studies indicated that the phase transition temperature decreased significantly in the diabetic and insulin-treated diabetic animals. The energy of activation in low temperature range increased in the diabetic animals. Insulin treatment corrected the Arrhenius pattern at early stage of diabetes; at late stage the pattern was reversed. The results are suggestive of subtle insulin-status-dependent alterations in membrane structure - function relationships.

Insulin-status-dependent modulation of FoF1-ATPase activity in rat liver mitochondria

Early and late effects of alloxan diabetes and insulin treatment on mitochondrial membrane structure and function were evaluated by studying the kinetic properties of mitochondrial membrane marker enzyme FoF1-ATPase and its modulation by membrane lipid/phospholipid composition and membrane fluidity. Under all experimental conditions the enzyme displayed three kinetically distinguishable components. In 1 wk-old diabetic animals the enzyme activity was unchanged; however, K(m) and V(max) of component I increased and K(m) of component II decreased. Insulin treatment resulted in lowering of K(m) and V(max) of components II and Ill. One-mon diabetic state resulted in decreased enzyme activity, whereas insulin treatment caused hyperstimulation. K(m) of components I and II decreased together with decreased V(max) of all the components. Insulin treatment restored the K(m) and V(max) values. In late-stage diabetes the catalytic efficiency of components I and II increased; insulin treatment had drastic adverse effect. Binding pattern of ATP was unchanged under all experimental conditions. Diabetic state resulted in progressive decrease in energy of activation in the low temperature range (E(L)). Insulin treatment lowered the energy of activation in the high temperature range (E(H)) without correcting the E(L) values. The phase transition temperatures increased in diabetic state and were not corrected by insulin treatment. Long-term diabetes lowered the total phospholipid content and elevated the cholesterol content; insulin treatment had partial restorative effect. The membrane fluidity decreased in general in diabetic condition and was not corrected by insulin treatment at late stage. Regression analysis studies suggest that specific phospholipid classes and/or their ratios may play a role in modulation of the enzyme activity.

Insulin status differentially affects energy transduction in cerebral mitochondria from male and female rats

Effects of STZ diabetes and treatment with insulin on cerebral mitochondrial metabolism in the male and female rats were examined. Diabetic state resulted in generalized decrease in the state 3 respiration rates in the males with practically all the substrates except glutamate where the opposite effect was seen. Diabetic state had no adverse effect on the respiratory activity in the females. Insulin treatment had no restorative effect in the males. By contrast in the females, adverse effects were noted. The cytochromes contents decreased in STZ diabetes with the effect being more pronounced in the males; treatment with 1 unit of insulin restored the cytochromes contents. STZ diabetes also resulted in decreased dehydrogenases activities with the effect being more pronounced in the females: insulin treatment resulted in hyper-stimulation of glutamate dehydrogenase and succinate DCIP reductase activities; restoration of malate dehydrogenase activity was only partial. The results point out that STZ diabetes and insulin treatments differentially affect cerebral mitochondrial energy metabolism in the male and female rats.

Effect of streptozotocin-induced diabetes on oxidative energy metabolism in rat kidney mitochondria. A comparative study of early and late effects

AIM

The effects of streptozotocin (STZ)-induced diabetes on oxidative energy metabolism of rat kidney mitochondria were examined at the end of 1 week and 1 month of STZ treatment.

METHODS

At the end of 1 week of induction of diabetes, respiration rates with pyruvate + malate and succinate as the substrates increased while those with beta-hydroxybutyrate and ascorbate + TMPD decreased. Respiration with glutamate was not affected. Insulin treatment had no alleviating effect. The changes persisted through 1 month of induction of diabetes and were not corrected by insulin treatment even at this stage. beta-hydroxybutyrate dehydrogenase activity registered significant decrease while the succinate dehydrogenase activity increased in diabetic and insulin-treated diabetic animals whereas only marginal changes were evident in the composition of the cytochromes.

RESULTS

The ATPase activity tended to be high in the diabetic groups and was restored by insulin treatment. At both the stages, i.e. early and late stages of diabetes the mitochondria were tightly coupled and the ADP/O ratios were in normal expected ranges.

CONCLUSION

Taken together, the results suggest that kidney is the major target tissue to suffer impairment of mitochondrial function with the onset of the disease which persists throughout and that insulin treatment is ineffective in restoring the normal state.