Oxidant-mediated repression of mitochondrial transcription in diabetic rats

A correlation between oxidative stress and diabetic retinopathy: An updated review

Oxidative stress (OS) is a cytopathic outcome of excessively generated reactive oxygen species (ROS), down regulated antioxidant defense signaling pathways, and the imbalance between the produced radicals and their clearance. It plays a role in the genesis of several illnesses, especially hyperglycemia and its effects. Diabetic retinal illness, a micro vascular side effect of the condition, is the prime reason of diabetic related blindness. The OS (directly or indirectly) is associated with diabetic retinopathy (DR) and related consequences. The OS is responsible to induce and interfere the metabolic signaling pathways to enhance influx of the polyol cascades and hexosamine pathways, stimulate Protein Kinase-C (PKC) variants, and accumulate advanced glycation end products (AGEs). Additionally, the inequity between the scavenging and generation of ROS is caused by the epigenetic alteration caused by hyperglycemia that suppresses the antioxidant defense system. Induced by an excessive buildup of ROS, retinal changes in structure and function include mitochondrial damage, cellular death, inflammation, and lipid peroxidation. Therefore, it is crucial to comprehend and clarify the mechanisms connected to oxidative stress that underlie the development of DR.

Attenuation of diabetic retinopathy and neuropathy by resveratrol: Review on its molecular mechanisms of action

Resveratrol is an important phenolic phytochemical from the therapeutic perspective. It has therapeutic impacts over wide range of diseases, especially the ones related to oxidative stress. Resveratrol, being primarily a potent anti-oxidant phytochemical, has significant impact against major diseases as inflammatory disorders, diabetes, and cancer. In the current review article, we intend to highlight the molecular aspects of the mechanism of action of resveratrol against major diabetic implications, namely, retinopathy and neuropathy. Both these diabetic implications are among the first fallouts of chronic hyperglycaemia. Resveratrol, via multiple molecular pathways, tend to attenuate and reverse these deformity and other disease-causing implications.

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.

Transcriptomic indices of fast and slow disease progression in two mouse models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is heterogeneous with high variability in the speed of progression even in cases with a defined genetic cause such as superoxide dismutase 1 (SOD1) mutations. We reported that SOD1(G93A) mice on distinct genetic backgrounds (C57 and 129Sv) show consistent phenotypic differences in speed of disease progression and life-span that are not explained by differences in human SOD1 transgene copy number or the burden of mutant SOD1 protein within the nervous system. We aimed to compare the gene expression profiles of motor neurons from these two SOD1(G93A) mouse strains to discover the molecular mechanisms contributing to the distinct phenotypes and to identify factors underlying fast and slow disease progression. Lumbar spinal motor neurons from the two SOD1(G93A) mouse strains were isolated by laser capture microdissection and transcriptome analysis was conducted at four stages of disease. We identified marked differences in the motor neuron transcriptome between the two mice strains at disease onset, with a dramatic reduction of gene expression in the rapidly progressive (129Sv-SOD1(G93A)) compared with the slowly progressing mutant SOD1 mice (C57-SOD1(G93A)) (1276 versus 346; Q-value ≤ 0.01). Gene ontology pathway analysis of the transcriptional profile from 129Sv-SOD1(G93A) mice showed marked downregulation of specific pathways involved in mitochondrial function, as well as predicted deficiencies in protein degradation and axonal transport mechanisms. In contrast, the transcriptional profile from C57-SOD1(G93A) mice with the more benign disease course, revealed strong gene enrichment relating to immune system processes compared with 129Sv-SOD1(G93A) mice. Motor neurons from the more benign mutant strain demonstrated striking complement activation, over-expressing genes normally involved in immune cell function. We validated through immunohistochemistry increased expression of the C3 complement subunit and major histocompatibility complex I within motor neurons. In addition, we demonstrated that motor neurons from the slowly progressing mice activate a series of genes with neuroprotective properties such as angiogenin and the nuclear factor (erythroid-derived 2)-like 2 transcriptional regulator. In contrast, the faster progressing mice show dramatically reduced expression at disease onset of cell pathways involved in neuroprotection. This study highlights a set of key gene and molecular pathway indices of fast or slow disease progression which may prove useful in identifying potential disease modifiers responsible for the heterogeneity of human amyotrophic lateral sclerosis and which may represent valid therapeutic targets for ameliorating the disease course in humans.

Cell Biology Symposium: feed efficiency: mitochondrial function to global gene expression

Understanding the cellular basis of feed efficiency (FE) is instrumental to helping poultry and livestock industries continue to provide high-quality protein for an increasingly crowded world. To understand relationships of FE and gene expression, global RNA transcription was investigated in breast muscle obtained from a male broiler line fed the same diet and individually phenotyped for FE. In these studies, RNA samples obtained from broilers that exhibited either high FE (0.65 ± 0.01) or low FE (0.46 ± 0.01) were analyzed with an Agilent 44K chicken oligoarray. A 1.3-fold cutoff in expression (30% difference between groups) resulted in 782 genes that were differentially expressed (P < 0.05) in muscle between the high- and low-FE phenotypes. Ingenuity Pathway Analysis, an online software program, was used to identify genes, gene networks, and pathways associated with the phenotypic expression of FE. The results indicate that the high-FE phenotype exhibited increased expression of genes associated with 1) signal transduction pathways, 2) anabolic activities, and 3) energy-sensing and energy coordination activities, all of which would likely be favorable to cell growth and development. In contrast, the low-FE broiler phenotype exhibited upregulation of genes 1) associated with actin-myosin filaments, cytoskeletal architecture, and muscle fibers and 2) stress-related or stress-responsive genes. Because the low-FE broiler phenotype exhibits greater oxidative stress, it would appear that the low-FE phenotype is the product of inherent gene expression that is modulated by oxidative stress. The results of these studies begin to provide a comprehensive picture of gene expression in muscle, a major organ of energy demand in an animal, associated with phenotypic expression of FE.

Oxidant-NO dependent gene regulation in dogs with type I diabetes: impact on cardiac function and metabolism

Background

The mechanisms responsible for the cardiovascular mortality in type I diabetes (DM) have not been defined completely. We have shown in conscious dogs with DM that: 1) baseline coronary blood flow (CBF) was significantly decreased, 2) endothelium-dependent (ACh) coronary vasodilation was impaired, and 3) reflex cholinergic NO-dependent coronary vasodilation was selectively depressed. The most likely mechanism responsible for the depressed reflex cholinergic NO-dependent coronary vasodilation was the decreased bioactivity of NO from the vascular endothelium. The goal of this study was to investigate changes in cardiac gene expression in a canine model of alloxan-induced type 1 diabetes.

Methods

Mongrel dogs were chronically instrumented and the dogs were divided into two groups: one normal and the other diabetic. In the diabetic group, the dogs were injected with alloxan monohydrate (40-60 mg/kg iv) over 1 min. The global changes in cardiac gene expression in dogs with alloxan-induced diabetes were studied using Affymetrix Canine Array. Cardiac RNA was extracted from the control and DM (n = 4).

Results

The array data revealed that 797 genes were differentially expressed (P < 0.01; fold change of at least ±2). 150 genes were expressed at significantly greater levels in diabetic dogs and 647 were significantly reduced. There was no change in eNOS mRNA. There was up regulation of some components of the NADPH oxidase subunits (gp91 by 2.2 fold, P < 0.03), and down-regulation of SOD1 (3 fold, P < 0.001) and decrease (4 - 40 fold) in a large number of genes encoding mitochondrial enzymes. In addition, there was down-regulation of Ca²⁺ cycling genes (ryanodine receptor; SERCA2 Calcium ATPase), structural proteins (actin alpha). Of particular interests are genes involved in glutathione metabolism (glutathione peroxidase 1, glutathione reductase and glutathione S-transferase), which were markedly down regulated.

Conclusion

our findings suggest that type I diabetes might have a direct effect on the heart by impairing NO bioavailability through oxidative stress and perhaps lipid peroxidases.

Serum aminotransferase changes with significant weight loss: sex and age effects

In obese subjects, the liver may be differentially affected by significant weight loss depending on as yet unknown factors. We explored clinical factors associated with serum alanine aminotransferase (ALT) changes during significant weight loss in a residential weight loss program. Clinical data from 362 adults who received a comprehensive weight loss intervention (ie, diets, physical fitness, and behavioral modification) in the program were analyzed. Serum ALT was used as a surrogate marker of liver injury. The ALT changes during the program were calculated to create study outcome categories (improvement, no change, or deterioration of ALT during significant weight loss). Variables of demography, lifestyle, and comorbidities at baseline, and total/rate of weight change during the program were explored for associations with the ALT change categories using multiple logistic regression models. Variation by sex was apparent among predictors of ALT deterioration; men with rapid weight loss and women with higher initial body mass index were more likely to experience ALT deterioration, whereas men with prior alcohol consumption were less likely to experience ALT deterioration even after adjusting for baseline ALT (Ps < .03). Variation by age was apparent among predictors of ALT improvement; younger patients with current smoking and older patients with rapid weight loss, diabetes or impaired fasting glucose, or sleep apnea or who followed a reduced-carbohydrate diet were less likely to experience ALT improvement (Ps < .05). A number of clinical factors influence ALT changes during weight loss in sex- and age-specific manners. The patterns that we detected may have pathophysiologic significance beyond the practical implications of our findings in clinical practice related to underlying changes in fat metabolism.

Lutein and docosahexaenoic acid prevent cortex lipid peroxidation in streptozotocin-induced diabetic rat cerebral cortex

The mechanisms underlying diabetic encephalopathy, are largely unknown. Here, we examined whether docosahexaenoic acid (DHA) and lutein could attenuate the oxidative changes of the diabetic cerebral cortex. The levels of malondialdehyde (MDA) were significantly increased and glutathione (GSH) and glutathione peroxidase activity (GPx) were decreased in diabetic rats. The number of 4-hydroxynonenal (4-HNE) positive cells was increased. Treatment with insulin, lutein or DHA and the combination of each antioxidant with insulin, significantly restored all markers concentrations mentioned above, and the increase in 4-HNE inmunofluorescence. We combined 4-HNE immunofluorescence with NeuN (Neuronal Nuclei) staining. The latter demonstrated extensive overlap with the 4-HNE staining in the cortex from diabetic rats. Our findings demonstrate a clear participation of glucose-induced oxidative stress in the diabetic encephalopathy, and that the cells suffering oxidative stress are neurons. Lowering oxidative stress through the administration of different antioxidants may be beneficial for the central nervous tissue in diabetes.

Gases in the mitochondria

Gasomodulators - nitric oxide, carbon monoxide and hydrogen sulphide - are important physiological mediators that have been implicated in disorders such as neurodegeneration and sepsis. Some of their biological functions involve the mitochondria. In particular, their inhibition of cytochrome c oxidase has received much attention as this can cause energy depletion and cytotoxicity. However, reports that cellular energy production and cell survival are maintained even in the presence of gasomodulators are not uncommon. In both cases, modulation of mitochondrial targets by the gasomodulators appears to be an important event. We provide an overview of the effects of the gasomodulators on the mitochondria.

Pygeum africanum: effect on oxidative stress in early diabetes-induced bladder

OBJECTIVE

To evaluate the effect of Pygeum africanum on oxidative stress and functional changes of the bladder after diabetes induction.

MATERIALS AND METHODS

Thirty-two adult Wistar male rats were treated daily for 8 weeks and grouped as follows: Control group (n = 6), Streptozotocin-induced diabetic group (n = 10), diabetes plus P. africanum group (n = 10), and control plus P. africanum group (n = 6). After diabetes induction for 4 weeks, the diabetes plus P. africanum and control plus P. africanum groups were fed with P. africanum (100 mg/kg, orally) in peanut oil for another 4 weeks. The catalase, superoxide dismutase activity, and malondialdehyde levels were measured as a marker of lipid peroxidation. The levels of inducible nitric oxide synthase were also evaluated. Urodynamic studies were performed to evaluate the functional changes of diabetic bladders after P. africanum treatment.

RESULTS

The catalase and superoxide dismutase activities significantly increased (P < 0.05) and maleic dialdehyde levels significantly decreased from diabetic plus P. africanum group compared with diabetic group (P < 0.05). Immunohistochemical studies showed a significantly decreased number of inducible nitric oxide synthase-positive cells in diabetic plus P. africanum group compared with diabetic group (P < 0.05). In diabetic plus P. africanum group, maximal bladder volume significantly decreased, while bladder pressure and maximal bladder pressure significantly increased compared with diabetic group (P < 0.05).

CONCLUSIONS

Early treatment with P. africanum could effectively suppress the oxidative stress status in diabetic bladder and may slow down the process of diabetic cystopathy.

Neuroprotective effect of N-acetylcysteine in the development of diabetic encephalopathy in streptozotocin-induced diabetes

Diabetic encephalopathy is characterized by impaired cognitive functions that involve neuronal damage triggered by glucose driven oxidative stress. The objective of the present study was to determine whether N-acetylcysteine (NAC) supplementation ameliorates learning and memory deficits caused by hyperglycemia-induced oxidative stress in experimental diabetes. Male Wistar rats (200-250 g) were rendered diabetic by a single intraperitoneal injection of streptozotocin (50 mg/kg). Cognitive deficits were observed in diabetic animals assessed using elevated plus maze test after 8 weeks of induction of diabetes. Acetylcholinesterase activity, a marker of cholinergic function, was decreased by 15.6% in the cerebral cortex, 20.9% in cerebellum and 14.9% in brain stem of diabetic rats compared to control rats. There was an increase in lipid peroxidation in cerebral cortex (21.97%), cerebellum (20.4%) and brain stem (25.5%) of diabetic rats. This was accompanied by decrease in glutathione and total thiol content along with decrease in the activities of superoxide dismutase, catalase and glutathione reductase. However, glutathione peroxidase activity increased by 11.2%, 13.6% and 23.1% in cerebral cortex, cerebellum and brain stem respectively, while the activity of glutathione-s-transferase decreased only in cerebral cortex (21.7%). Supplementation with NAC (1.4 g/kg/day in drinking water) significantly attenuated cognitive deficits and oxidative stress in diabetic rats. Our results emphasize the involvement of increased oxidative stress in cognitive impairment in diabetic animals and point towards the potential beneficial role of NAC as an adjuvant therapy to conventional anti-hyperglycemic regimens for the prevention and treatment of diabetic encephalopathy.

Oxidative stress and diabetic retinopathy

Oxygen metabolism is essential for sustaining aerobic life, and normal cellular homeostasis works on a fine balance between the formation and elimination of reactive oxygen species (ROS). Oxidative stress, a cytopathic consequence of excessive production of ROS and the suppression of ROS removal by antioxidant defense system, is implicated in the development of many diseases, including Alzheimer's disease, and diabetes and its complications. Retinopathy, a debilitating microvascular complication of diabetes, is the leading cause of acquired blindness in developed countries. Many diabetes-induced metabolic abnormalities are implicated in its development, and appear to be influenced by elevated oxidative stress; however the exact mechanism of its development remains elusive. Increased superoxide concentration is considered as a causal link between elevated glucose and the other metabolic abnormalities important in the pathogenesis of diabetic complications. Animal studies have shown that antioxidants have beneficial effects on the development of retinopathy, but the results from very limited clinical trials are somewhat ambiguous. Although antioxidants are being used for other chronic diseases, controlled clinical trials are warranted to investigate potential beneficial effects of antioxidants in the development of retinopathy in diabetic patients.

Responses of mitochondrial biogenesis and function to maternal diabetes in rat embryo during the placentation period

Mitochondria are cellular organelles that have been reported to be altered in diabetes, being closely related to its associated complications. Moreover, mitochondrial biogenesis and function are essential for proper embryo development throughout the placentation period, occurring during organogenesis, when a great rate of congenital malformations have been associated with diabetic pregnancy. Thus, the aim of the current work was to investigate the effect of the diabetic environment on mitochondrial function and biogenesis during the placentation period. For this purpose, we studied the oxidative phosphorylation system (OXPHOS) enzymatic activities as well as the expression of genes involved in the coordinated regulation of both mitochondrial and nuclear genome (PGC-1alpha, NRF-1, NRF-2alpha, mtSSB, and TFAM) and mitochondrial function (COX-IV, COX-I, and beta-ATPase) in rat embryos from control and streptozotocin-induced diabetic mothers. Our results reflected that diabetic pregnancy retarded and altered embryo growth. The embryos from diabetic mothers showing normal morphology presented a reduced content of proteins regulated through the PGC-1alpha mitochondriogenic pathway on gestational day 12. This fact was accompanied by several responses that entailed the activation of OXPHOS activities on the same day and the recovery of the content of the studied proteins to control levels on day 13. As a result, the mitochondria of these embryos would reach a situation close to control on day 13 that could allow them to follow the normal mitochondriogenic schedule throughout a gestational period in which the mitochondrial differentiation process is critical. Nevertheless, malformed embryos from diabetic mothers seemed to show a lower adaptation capability, which could exacerbate their maldevelopment.

Central nervous system protection by resveratrol in streptozotocin-induced diabetic rats

The objective of the present study was to investigate the possible neuroprotective effect of resveratrol against streptozotocin-induced hyperglycaemia in the rat brain and medulla spinalis. Thirty adult male Wistar rats were divided into three groups as follows: control group, streptozotocin-induced diabetic-untreated group, and streptozotocin-induced diabetic resveratrol-treated group. Diabetes was induced by a single injection of streptozotocin (STZ) (60 mg/kg body weight). Three days after streptozotocin injection, resveratrol (10 mg/kg) was injected intraperiteonally daily over 6 weeks to the rats in the treatment group. Six weeks later, seven rats from each group were killed and the brain stem and cervical spinal cord were removed. The hippocampus, cortex, cerebellum, brain stem and spinal cord were dissected for biochemical studies (lipid peroxidation measuring malondialdehyde [MDA], xanthine oxidase [XO], nitric oxide [NO] and glutathione). MDA, XO and NO levels in hippocampus, cortex, cerebellum, brain stem and spinal cord in the streptozotocin-induced diabetic-untreated group increased significantly. Treatment with resveratrol significantly reduced MDA, XO and NO production and increased glutathione levels when compared to the streptozotocin-induced diabetic-untreated group. This study demonstrates that resveratrol is a potent neuroprotective agent against diabetic oxidative damage.

Protective effect of ursodeoxycholic acid on liver mitochondrial function in rats with alloxan-induced diabetes: link with oxidative stress

We investigated the effects of ursodeoxycholic acid (UDCA) on mitochondrial functions and oxidative stress and evaluated their relationships in the livers of rats with alloxan-induced diabetes. Diabetes was induced in male Wistar rats by a single alloxan injection (150 mg kg(-1) b.w., i.p.). UDCA (40 mg kg(-1) b.w., i.g., 30 days) was administered from the 5th day after the alloxan treatment. Mitochondrial functions were evaluated by oxygen consumption with Clark oxygen electrode using succinate, pyruvate+malate or palmitoyl carnitine as substrates and by determination of succinate dehydrogenase and NADH dehydrogenase activities. Liver mitochondria were used to measure chemiluminiscence enhanced by luminol and lucigenin, reduced liver glutathione and the end-products of lipid peroxidation. The activities of both NADH dehydrogenase and succinate dehydrogenase as well as the respiratory control (RC) value with all the substrates and the ADP/O ratio with pyruvate+malate and succinate as substrates were significantly decreased in diabetic rats. UDCA developed the beneficial effect on the mitochondrial respiration and oxidative phosphorylation parameters in alloxan-treated rats, whereas the activities of mitochondrial enzymes were increased insignificantly after the administration of UDCA. The contents of polar carbonyls and MDA as well as the chemiluminescence with luminol were elevated in liver mitochondria of diabetic rats. The treatment with UDCA normalized all the above parameters measured except the MDA content. UDCA administration prevents mitochondrial dysfunction in rats treated with alloxan and this process is closely connected with inhibition of oxidative stress by this compound.

Differential Expression of Mitochondrial and Extramitochondrial Proteins in Lymphocytes of Male Broilers with Low and High Feed Efficiency

Studies were conducted to investigate relationships between mitochondrial and extramitochondrial protein expression, and protein oxidation in lymphocytes obtained from broilers in which individual feed efficiencies were obtained. Lymphocytes were isolated from male broilers from a single line that were shown to exhibit either low (0.48 +/- 0.02, n = 8) or high (0.68 +/- 0.01, n = 7) feed efficiency (FE). Western blot analysis showed that, compared with lymphocytes from high FE broilers, lymphocytes from low FE broilers exhibited a) higher amounts of oxidized proteins (protein carbonyls), b) lower amounts of 3 mitochondrial proteins [core I, cyt c 1 (complex III), and ATP synthase (complex V)], and c) higher amounts of 2 proteins [30 S (complex II) and COX II (complex IV)]. Two-dimensional gel electrophoresis revealed that the intensities of 25 protein spots from pooled samples of lymphocytes from high and low FE broilers differed by 5-fold or more. Three of these protein spots were picked from the gel and subjected to matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry analysis. One protein spot of ~33 kDa was tentatively identified by MALDI-TOF as a fragment of collapsin-2, a component of semaphorin 3D. The results of this study provide further evidence of increased oxidation associated with low FE and further evidence of differential protein expression associated with the phenotypic expression of feed efficiency.

Effects of resveratrol and methylprednisolone on biochemical, neurobehavioral and histopathological recovery after experimental spinal cord injury

AIM

To investigate the neuroprotective effect of resveratrol in an experimental spinal cord injury (SCI) model in rats.

METHODS

Male Wistar albino rats weighing 200-250 g were randomized into six groups. Weight-drop trauma was performed for SCI. Group 1 underwent laminectomy alone. Group 2 underwent laminectomy followed by SCI. Groups 3, 4, 5, and 6 underwent laminectomy followed by SCI and received resveratrol (100 mg/kg), methylprednisolone (MP) (30 mg/kg), resveratrol (100 mg/kg) plus MP (30 mg/kg), and ethanol (2%), respectively. The rats were divided into two subgroups for biochemical analysis (killed at 24 h after surgery) and for neurobehavioral and histopathological evaluation (killed at 6 weeks after surgery). Posttraumatic neurological recovery after surgery was recorded weekly.

RESULTS

Groups 3 and 5 revealed significantly lower malon-dialdehyde, nitric oxide, xanthine oxidase, and higher glutathione levels than group 4 (P<0.05). Neurological recovery rates were significantly better in groups 3 and 5 than group 4 (P<0.05). When spinal trauma size ratios were compared, there was no significant difference between treatment groups.

CONCLUSION

Resveratrol treatment revealed better biochemical recovery in the acute stage of trauma than MP treatment. Although resveratrol and combined treatment revealed better neurobehavioral recovery than MP treatment; resveratrol, MP, and combined treatment modalities improved histopathological recovery at the same level in the final stage of the experiment. Future studies involving different doses of resveratrol and different doses combinations with MP could promise better results as each drug has a different anti-oxidative mechanism of action.

Neuroprotective effect of etomidate in the central nervous system of streptozotocin-induced diabetic rats

It is well known that hyperglycaemia due to diabetes mellitus leads to oxidative stress in the central nervous system. Oxidative stress plays important role in the pathogenesis of neurodegenerative changes. In the present study we investigated the possible neuroprotective effect of etomidate against streptozotocin-induced (STZ-induced) hyperglycaemia in the rat brain and spinal cord. A total of 40 rats were used in this study. Rats were divided into four groups: sham-control, diabetic, diabetic-etomidate treated and vehicle for etomidate treatment group. Diabetes mellitus was induced by a single injection of streptozotocin (60 mg/kg body weight). Three days after streptozotocin injection, etomidate (2 mg/kg) was injected intraperitoneally for etomidate group and lipid emulsion (10%) for vehicle group was injected with corresponding amount intraperitoneally every day for 6 weeks. Six weeks after streptozotocin injection, seven rats from each group were killed and brain, brain stem and cervical spinal cord were removed. The hippocampus, cortex, cerebellum, brain stem and spinal cord were dissected for the biochemical analysis (the level of malondialdehyde [MDA], total nitrite, reduced glutathione [GSH], and xanthine oxidase [XO] activity). STZ-induced diabetes resulted in significantly elevation of MDA, XO and nitrite levels in the hippocampus, cortex, cerebellum, brain stem and spinal cord of the rats (P < 0.05) while etomidate treatment provided significantly lower values (P < 0.05). This study demonstrated that etomidate have neuroprotective effect on the neuronal tissue against the diabetic oxidative damage.

Feed efficiency and mitochondrial function

Studies have been conducted in our laboratory to assess differences in mitochondrial function and biochemistry in male broilers with high and low feed efficiency (FE) from the same genetic line and fed the same diet. Mitochondria obtained from broilers with low FE exhibited greater uncoupling of the electron transport chain (ETC) that was apparently due to site-specific defects in electron transport resulting in higher amounts of reactive oxygen species (ROS) compared with high FE mitochondria. Higher amounts of ROS production in Low FE mitochondria were likely responsible for higher protein carbonyl levels, indicative of higher protein oxidation compared with High FE mitochondria and tissue. In turn, higher protein damage in Low FE mitochondria may have contributed to lower activity of electron transport chain complexes relative to values observed in high FE mitochondria. Low FE mitochondria did not exhibit a compromised ability to carryout oxidative phosphorylation, and although there were differences in expression of certain electron transport chain proteins, there was nothing that would indicate that differences in coupling and respiratory chain activity could be due to a general decrease in protein expression between low and high FE mitochondria. The results of these studies provide insight into understanding cellular mechanisms associated with the phenotypic expression of feed efficiency in broilers.

Neuroprotective effect of mexiletine in the central nervous system of diabetic rats

Both experimental and clinical studies suggests that oxidative stress plays an important role in the pathogenesis of diabetes mellitus type 1 and type 2. Hyperglycaemia leads to free radical generation and causes neural degeneration. In the present study we investigated the possible neuroprotective effect of mexiletine against streptozotocin-induced hyperglycaemia in the rat brain and spinal cord. 30 adult male Wistar rats were divided into three groups: control, diabetic, and diabetic-mexiletine treated group. Diabetes mellitus was induced by a single injection of streptozotocin (60 mg/kg body weight). Mexiletine (50 mg/kg) was injected intraperitoneally every day for six weeks. After 6 weeks the brain, brain stem and cervical spinal cord of the rats were removed and the hippocampus, cortex, cerebellum, brain stem and spinal cord were dissected for biochemical analysis (the level of Malondialdehide [MDA], Nitric Oxide [NO], Reduced Glutathione [GSH], and Xanthine Oxidase [XO] activity). MDA, XO and NO levels in the hippocampus, cortex, cerebellum, brain stem and spinal cord of the diabetic group increased significantly, when compared with control and mexiletine groups (P < 0.05). GSH levels in the hippocampus, cortex, cerebellum, brain stem and spinal cord of the diabetic group decreased significantly when compared with control and mexiletine groups (P < 0.05). This study demonstrates that mexiletine protects the neuronal tissue against the diabetic oxidative damage.

Decreased complex II respiration and HNE-modified SDH subunit in diabetic heart

Several lines of research suggest that mitochondria play a role in the etiopathogenesis of diabetic cardiomyopathy, although the mechanisms involved are still debated. In the present study, we report that State 3 oxygen consumption decreases by approximately 35% with glutamate and by approximately 30% with succinate in mitochondria from diabetic rat hearts compared to controls. In these mitochondria the enzymatic activities of complex I and complex II are also decreased to a comparable extent. Western blot analysis of mitochondrial protein pattern using antibodies recognizing proteins modified by the lipid peroxidation product 4-hydroxynonenal indicates the FAD-containing subunit of succinate dehydrogenase as one of the targets of this highly reactive aldehyde. In rats diabetic for 6 or 12 weeks, insulin supplementation for 2 weeks decreases the level of protein modified by 4-hydroxynonenal and restores mitochondrial respiration and enzyme activity to control level. Taken together, these results: (1) indicate that 4-hydroxynonenal is endogenously produced within diabetic mitochondria and forms an adduct with selective mitochondrial proteins, (2) identify one of these proteins as a subunit of succinate dehydrogenase, and (3) provide strong evidence that insulin treatment can reverse and ameliorate free radical damage and mitochondrial function under diabetic conditions.

Biochemical evaluation of mitochondrial respiratory chain in duodenum of low and high feed efficient broilers

Increased H2O2 production, indicating higher oxidative stress, and lower mitochondrial function was previously observed in duodenal mitochondria isolated from broilers with low feed efficiency (FE, gain:feed). Thus, experiments were conducted to 1) evaluate the activity of the respiratory chain complexes (complexes I to V) and 2) assess protein oxidation and mitochondrial protein expression in broilers with low and high FE. Duodenal mitochondria were isolated from broiler breeders with low (0.52 +/- 0.01) and high (0.68 +/- 0.01) FE (n = 8/group). Respiratory chain complex activities were measured spectrophotometrically, whereas mitochondrial protein expression and protein oxidation (carbonyls) were assessed with Western blots. The activities of all complexes, except complex IV, were lower in the low FE compared with high FE mitochondria, whereas protein carbonyl levels were higher in low FE mitochondria. Steady-state levels of 6 out of 7 nuclear-encoded respiratory chain subunits [70S(FP), core I, core II, cytochrome c (cyt c)1, iron-sulfur protein (ISP), and ATPase-alpha] were higher, whereas 3 out of 6 mitochondrial-encoded subunits (ND4, ND6-C, and COX II) were lower in the low FE group, suggesting that sensitivity of mitochondrial proteins to H2O2 or oxidation varies. The general reduction in complex activity and differential protein expression concomitant with higher oxidized proteins in low FE mitochondria suggest that oxidative stress could be contributing to the lower mitochondrial function observed in low FE duodenal mitochondria.

Oxidative stress plays a role in diabetes-induced bladder dysfunction in a rat model

OBJECTIVES

To evaluate the oxidative status of the bladder 8 weeks after diabetes induction. Oxidative stress has recently been implicated in the pathogenesis of diabetes complications, but its role in diabetic cystopathy has not been studied.

METHODS

Sprague-Dawley rats were divided into three groups: control (n = 11), diuretic control (5% sucrose drink; n = 6), and streptozotocin-induced diabetic group (n = 14). Eight weeks later, the bladders were dissected. We measured the antioxidant scavenging enzymes (catalase and superoxide dismutase)-like activity and the levels of the thiobarbituric acid reactive substances, as a marker of lipid peroxidation. We also examined the levels of inducible nitric oxide synthase and apoptosis in the bladders.

RESULTS

We found a statistically significant reduction in the catalase-like activity in the bladders from the diabetic group compared with the other groups (P = 0.017, diabetic versus control); the difference in the superoxide dismutase-like activity was not statistically significant among the groups. The thiobarbituric acid reactive substances levels were significantly greater in the diabetic compared with other groups (131.9 +/- 47.5, 46.7 +/- 17.9, and 60.9 +/- 25.4 nmol/mg protein in the diabetic, control, and diuretic group, respectively, P = 0.006, diabetic versus control). Immunohistochemical and apoptosis studies showed a statistically significant increased number of inducible nitric oxide synthase-positive cells and apoptotic cells in the diabetic bladder smooth muscle cells (P <0.001).

CONCLUSIONS

Our findings showed that oxidative stress occurred in the bladders of the STZ-diabetic rats and was not mediated by diuresis. The oxidative damage of the smooth muscle cells may be a contributory factor in diabetic cystopathy.

Diabetic retinopathy: mitochondrial dysfunction and retinal capillary cell death

Oxidative stress is increased in the retina in diabetes; the levels of oxidatively modified DNA and nitrosylated proteins are elevated, and antioxidant defense enzymes are impaired. The levels of superoxides are elevated in the retina, and the mitochondria become dysfunctional with proapoptotic protein, Bax, translocating from the cytosol into the mitochondria, and cytochrome c leaking out from the mitochondria. This is accompanied by increased retinal capillary cell apoptosis, and the formation of acellular capillaries and pericyte ghosts, the early signs of retinopathy in animal models of diabetic retinopathy. Inhibition of superoxides inhibits glucose -induced mitochondrial dysfunction, activation of caspase-3, and cell death in retinal capillary cells. In animal models, long-term administration of lipoic acid or other antioxidants inhibits the development of diabetic retinopathy via inhibition of accumulation of oxidatively modified DNA and nitrotyrosine and capillary cell apoptosis in the retina. Understanding the role of mitochondria in the development of retinopathy in diabetes should help identify therapies that can neutralize superoxides and inhibit their dysfunction and, ultimately, the development of retinopathy.

Compromised liver mitochondrial function and complex activity in low feed efficient broilers are associated with higher oxidative stress and differential protein expression

Variations in broiler growth and efficiency have been explained in part by differences in mitochondrial function and biochemistry in broilers. To further our knowledge in this regard, 2 experiments were carried out to determine the relationships of a) mitochondrial function and activities of various electron transport chain (ETC) complexes; b) production of H2O2, a reactive oxygen species (ROS), and its association with protein oxidation; and c) mitochondrial protein expression in liver of a single line male broilers with low or high feed efficiency (FE, n = 5 to 8 per group). Mitochondrial function and complex activities were measured polarographically and spectrophotometrically, respectively. H2O2 was measured fluorimetrically, whereas oxidized protein (carbonyls) and specific mitochondrial proteins were analyzed using Western blots. Mitochondrial function (ETC coupling) and activities of ETC complexes (I, II, III, and IV) were higher in high FE compared with low FE broilers. H2O2 and protein carbonyls were higher in the livers of low FE broilers than in high FE broilers. Whereas the expression of 4 immunoreactive proteins [NAD3 (complex I), subunit VII (complex III), cytochrome c oxidase subunits (COX) II, and COX IVb (complex IV)] were higher in low FE liver mitochondria and 2 proteins [subunit 70 (complex II) and a-ATP synthase (complex V)] were higher in high FE birds, there were no differences between groups in the expression of 18 other mitochondrial proteins. In conclusion, increases in oxidative stress in low FE broilers were caused by or may contribute to differences in mitochondrial function (ETC coupling and complex activities) or the differential expression of steady-state levels of some mitochondrial proteins in the liver. Understanding the role of oxidative stress in Low FE broilers will provide clues in understanding the cellular basis of feed efficiency.

The powerhouse takes control of the cell: is the mitochondrial permeability transition a viable therapeutic target against neuronal dysfunction and death?

Stroke and neurodegenerative disease exert an increasing large toll on human health at the levels both of the individual and of society. As an example of each, in the United States, stroke is the major single cause of overall morbidity and mortality, and the financial costs of Alzheimer's disease alone dwarfs the entire federal medical research budget. It has been long recognized that mitochondrial energy production is essential for the second to second functions of the central nervous system (CNS), and that severe mitochondrial impairment is incompatible with normal cerebral function. The last decade, however, has brought a growing understanding that mitochondria play an even greater role than previously suspected. Increased understanding of the role of mitochondria in antioxidant defense and calcium homeostasis further solidified the importance of mitochondria in CNS function--just as increased understanding of mitochondrial roles in calcium-mediated toxicity and production of reactive species further exemplified the Janus role of mitochondria--as mediators of CNS dysfunction. Perhaps most unexpected, however, was the evidence that mitochondria serve as the dominant integrators, checkpoints, and amplifiers of the cell death signals in the CNS. The mechanism of propagation of cell death cascades by mitochondria remains controversial. In this review, we focus on the evidence that supports the involvement of an event termed the mitochondrial permeability transition that (i) occurs (patho)physiologically; (ii) occurs in the CNS, and; (iii) is a potential target for pharmaceutical intervention against CNS dysfunction, injury, and cell loss resulting from stroke, trauma, and neurodegenerative disease.

Determination of mitochondrial function and site-specific defects in electron transport in duodenal mitochondria in broilers with low and high feed efficiency

Duodenal mitochondria were isolated from broiler breeder males with high (0.79+/-0.01, n = 9) and low (0.63+/-0.02, n = 9) feed efficiency (FE) to assess relationships of FE with duodenal mitochondrial function and site-specific defects in electron transport. Sequential additions of adenosine diphosphate (ADP) resulted in 1) higher respiratory control ratio (RCR; an index of respiratory chain coupling) in high FE mitochondria provided succinate, and 2) higher ADP to oxygen ratio (ADP:O; an index of oxidative phosphorylation) in low FE mitochondria provided NADH-linked substrates (malate, pyruvate, or both). Basal electron leak, measured as H2O2 production, was greater in low FE mitochondria provided succinate (P = 0.08) or NADH-linked substrates. As H2O2 levels were elevated in low FE compared with high FE mitochondria by complex I (P+/-0.07) and complex II inhibition, the higher basal electron leak in low FE mitochondria was apparently due to site-specific defects in electron transport at complexes I and II. Elevations in H2O2 above basal levels indicated that high FE mitochondria may also exhibit electron transport defects at complexes I and III. Despite an ability to produce adenosine triphosphate (ATP) that was equal or superior to that demonstrated in high FE duodenal mitochondria, low FE mitochondria exhibited a greater inherent degree of electron leak. The results provide insight into the role that duodenal mitochondria play in the phenotypic expression of FE in broilers.

The retina: oxidative stress and diabetes

A prominent and early feature of the retinopathy of diabetes mellitus is a diffuse increase in vascular permeability. As the disease develops, the development of frank macular oedema may result in vision loss. That reactive oxygen species production is likely to be elevated in the retina, and that certain regions of the retina are enriched in substrates for lipid peroxidation, may create an environment susceptible to oxidative damage. This may be more so in the diabetic retina, where hyperglycaemia may lead to elevated oxidant production by a number of mechanisms, including the production of oxidants by vascular endothelium and leukocytes. There is substantial evidence from animal and clinical studies for both impaired antioxidant defences and increased oxidative damage in the retinae of diabetic subjects that have been, in the case of animal studies, reversible with antioxidant supplementation. Whether oxidative damage has a causative role in the pathology of diabetic retinopathy, and thus whether antioxidants can prevent or correct any retinal damage, has not been established, nor has the specific nature of any damaging species been characterised.

Brain energy metabolism during hypoglycaemia in healthy and type 1 diabetic subjects

AIMS/HYPOTHESIS

This study aimed to examine brain energy metabolism during moderate insulin-induced hypoglycaemia in Type 1 diabetic patients and healthy volunteers.

METHODS

Type 1 diabetic patients (mean diabetes duration 13 +/- 2.5 years; HbA1c 6.8 +/- 0.3%) and matched controls were studied before, during (0-120 min) and after (120-240 min) hypoglycaemic (approximately 3.0 mmol/l) hyperinsulinaemic (1.5 mU x kg(-1) min(-1)) clamp tests. Brain energy metabolism was assessed by in vivo 31P nuclear magnetic resonance spectroscopy of the occipital lobe (3 Tesla, 10-cm surface coil).

RESULTS

During hypoglycaemia, the diabetic patients showed blunted endocrine counter-regulation. Throughout the study, the phosphocreatine:gamma-ATP ratios were lower in the diabetic patients (baseline: controls 3.08 +/- 0.29 vs diabetic patients 2.65 +/- 0.43, p<0.01; hypoglycaemia: 2.97 +/- 0.38 vs 2.60 +/- 0.35, p<0.05; recovery: 3.01 +/- 0.28 vs 2.60 +/- 0.35, p<0.01). Intracellular pH increased in both groups, being higher in diabetic patients (7.096 +/- 0.010 vs. 7.107 +/- 0.015, p<0.04), whereas intracellular magnesium concentrations decreased in both groups (controls: 377 +/- 33 vs 321 +/- 39; diabetic patients: 388 +/- 47 vs 336 +/- 68 micromol/l; p<0.05).

CONCLUSIONS/INTERPRETATION

Despite a lower cerebral phosphocreatine:gamma-ATP ratio in Type 1 diabetic patients at baseline, this ratio does not change in control or diabetic patients during modest hypoglycaemia. However, both groups exhibit subtle changes in intracellular pH and intracellular magnesium concentrations.

Low Feed Efficient Broilers Within a Single Genetic Line Exhibit Higher Oxidative Stress and Protein Expression in Breast Muscle with Lower Mitochondrial Complex Activity

The objectives of this study were to determine the effects of low or high feed efficiency (FE) on a) protein oxidation, b) the activities of various respiratory chain complexes, and c) expression of various mitochondrial proteins in male broilers within a single genetic line. Tissue homogenate or mitochondria were isolated from breast muscle of broilers with high (0.80 +/- 0.01) and low FE (0.62 +/- 0.02). The complex activities were measured spectrophotometrically, and the levels of oxidized protein (carbonyl) and immunoreactive mitochondrial proteins were analyzed using Western blots. Protein carbonyl levels were higher in low FE compared with high FE broilers breast muscle, which indicated enhanced protein oxidation in low FE mitochondria. Activities of all respiratory chain complexes (I, II, III, IV) were higher in high FE compared with low FE broilers for breast mitochondria. Whereas the expression of immunoreactive proteins was higher in low FE muscle mitochondria for 5 mitochondrial proteins [core I, cyt c1, cyt b (complex III), COX II (cytochrome c oxidase subunit II, complex IV), and adenine nucleotide translocator (ANT1)], there were no differences between groups in the expression of 9 other respiratory chain protein subunits associated with complexex I, II, III, IV, and V. SDS-PAGE revealed a protein band of 47 kDa that was expressed at a higher level in low FE compared with high FE mitochondria. The differential expression of certain mitochondrial proteins and the 47-kDa band might be a compensatory response either to the lower complex activities or increased protein oxidation observed in low FE birds.

Oral administration of orthovanadate and Trigonella foenum graecum seed power restore the activities of mitochondrial enzymes in tissues of alloxan-induced diabetic rats

The effect of oral administration of sodium orthovanadate (SOV) and Trigonella foenum graecum seed powder (TSP), a medicinal plant used extensively in Asia, on the mitochondrial metabolism in the alloxan diabetic rats has been investigated. Rats were injected with alloxan monohydrate (20 mg/100 g body wt) or vehicle (Na-acetate buffer), the former were treated with either 2 IU insulin i.p., 0.6 mg/ml SOV ad libitum, 5% TSP ad libitum, and a combination of 0.2% SOV and 5% TSP ad libitum for 21 days. Selected rate-limiting enzymes of the tricarboxylic acid cycle, hydrogen shuttle system, ketone body metabolism, amino acid metabolism and urea cycle were measured in the mitochondrial and cytosolic fractions of liver, kidney and brain tissues of the experimental rats. Majority of the mitochondrial enzymes in the tissues of the diabetic rats had significantly higher activities compared to the control rats. Similarly, the activities of mitochondrial and cytosolic aminotransferases and arginase were significantly higher in liver and kidney tissues of the diabetic rats. The separate administrations of SOV and TSP to diabetic rats were able to restore the activities of these enzymes to control values. The lower dose of SOV (0.2%) administered in combination with TSP to diabetic rats lowered the enzyme activities more significantly than when given in a higher dose (0.6%) separately. This is the first report of the effective combined action of oral SOV and TSP in ameliorating the altered mitochondrial enzyme activities during experimental type-1 diabetes. Our novel combined oral administration of SOV and TSP to diabetic rats thus conclusively proves as a possible method to minimize potential vanadate toxicity without compromising its positive effects in the therapy of experimental type-1 diabetes.

OxyR regulon controls lipid peroxidation-mediated oxidative stress in Escherichia coli

Membrane lipid peroxidation processes yield products that may react with DNA and proteins to cause oxidative modifications. The oxyR gene product regulates the expression of enzymes and proteins that are needed for cellular protection against oxidative stress. Upon exposure to tert-butylhydroperoxide (t-BOOH) and 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH), which induce lipid peroxidation in membranes, the Escherichia coli oxyR overexpression mutant was much more resistant to lipid peroxidation-mediated cellular damage, when compared to the OxyR deletion mutant in regard to growth kinetics, viability, and DNA damage. The deletion of the OxyR gene in E. coli also resulted in increased susceptibility of superoxide dismutase to lipid peroxidation-mediated inactivation. The results indicate that the peroxidation of lipid is probably one of the important intermediary events in free radical-induced cellular damage. Also, the oxyR regulon plays an important protective role in lipid peroxidation-mediated cellular damage.

Reduced activity of mtTFA decreases the transcription in mitochondria isolated from diabetic rat heart

To evaluate abnormalities in the mitochondrial transcription factor A (mtTFA) function as a cause of mitochondrial dysfunction in diabetes, we measured the mRNA contents of the proteins consisting of the mitochondrial respiratory chain as well as transcriptional and translational activities in the mitochondria isolated from controls and streptozotocin-induced diabetic rat hearts. Using Northern blot analysis, we found 40% reduced mRNA contents of mitochondrial-encoded cytochrome b and ATP synthase subunit 6 in diabetic rat hearts compared with control rats (P < 0.05). These abnormalities were completely recovered by insulin treatment. Furthermore, the mitochondrial activities of transcription and translation were decreased significantly in mitochondria isolated from diabetic rats by 60% (P < 0.01) and 71% (P < 0.01), respectively, compared with control rats. The insulin treatment also completely normalized these abnormalities in diabetic rats. Consistently, gel retardation assay showed a reduced binding of mtTFA to the D-loop of mitochondrial DNA in diabetic rats, although there was no difference in the mtTFA mRNA and protein content between the two groups. On the basis of these findings, a reduced binding activity of mtTFA to the D-loop region in the hearts of diabetic rats may contribute to the decreased mitochondrial protein synthesis.

Association of mitochondrial function with feed efficiency within a single genetic line of male broilers

Studies were conducted to determine relationships between feed efficiency and mitochondrial function and biochemistry. After feed efficiency (FE; gain:feed) was determined in broiler breeder males between 6 and 7 wk of age, mitochondria were isolated from breast and leg muscle from birds with high FE (0.83+/-0.01, n = 6) and low FE (0.64+/-0.01, n = 7). Respiratory chain coupling, assessed by the respiratory control ratio (RCR), was greater in high FE breast, and leg mitochondria provided NADH-linked, but not FADH-linked, energy substrates. There were no differences, however, in the adenosine diphosphate to oxygen (ADP:O) ratio (an index of oxidative phosphorylation) when mitochondria were provided either energy substrate. Electron leak, as determined by generation of H202, was greater in the low FE than in high FE breast mitochondria. Electron leak increased following inhibition of electron transport at Complex I (with rotenone) and Complex III (with antimycin A) in low FE but not in high FE breast mitochondria. There were no differences in basal electron leak in leg mitochondria between groups, but H202 generation was elevated (P < 0.07) compared to basal values in low FE leg mitochondria after Complex I inhibition. The activities of Complexes I and II were greater in high FE breast and leg muscle mitochondria compared to those in low FE mitochondria. The results indicate that lower respiratory chain coupling in low FE muscle mitochondria may be due to lower activities of Complexes I and II and defects in electron leak and provide insight into cellular mechanisms associated with the phenotypic expression of feed efficiency in broilers.

Diabetes-associated nitration of tyrosine and inactivation of succinyl-CoA:3-oxoacid CoA-transferase

High levels of reactive species of nitrogen and oxygen in diabetes may cause modifications of proteins. Recently, an increase in protein tyrosine nitration was found in several diabetic tissues. To understand whether protein tyrosine nitration is the cause or the result of the associated diabetic complications, it is essential to identify specific proteins vulnerable to nitration with in vivo models of diabetes. In the present study, we have demonstrated that succinyl-CoA:3-oxoacid CoA-transferase (SCOT; EC 2.8.3.5) is susceptible to tyrosine nitration in hearts from streptozotocin-treated rats. After 4 and 8 wk of streptozotocin administration and diabetes progression, SCOT from rat hearts had a 24% and 39% decrease in catalytic activity, respectively. The decrease in SCOT catalytic activity is accompanied by an accumulation of nitrotyrosine in SCOT protein. SCOT is a mitochondrial matrix protein responsible for ketone body utilization. Ketone bodies provide an alternative source of energy during periods of glucose deficiency. Because diabetes results in profound derangements in myocardial substrate utilization, we suggest that SCOT tyrosine nitration is a contributing factor to this impairment in the diabetic heart.

Enhanced mitochondrial testicular antioxidant capacity in Goto-Kakizaki diabetic rats: role of coenzyme Q

Because diabetes mellitus is associated with impairment of testicular function, ultimately leading to reduced fertility, this study was conducted to evaluate the existence of a cause-effect relationship between increased oxidative stress in diabetes and reduced mitochondrial antioxidant capacity. The susceptibility to oxidative stress and antioxidant capacity (in terms of glutathione, coenzyme Q, and vitamin E content) of testis mitochondrial preparations isolated from Goto-Kakizaki (GK) non-insulin-dependent diabetic rats and from Wistar control rats, 1 yr of age, was evaluated. It was found that GK mitochondrial preparations showed a lower susceptibility to lipid peroxidation induced by ADP/Fe(2+), as evaluated by oxygen consumption and reactive oxygen species generation. The decreased susceptibility to oxidative stress in diabetic rats was associated with an increase in mitochondrial glutathione and coenzyme Q9 contents, whereas vitamin E was not changed. These results demonstrate a higher antioxidant capacity in diabetic GK rats. We suggest this is an adaptive response of testis mitochondria to the increased oxidative damage in diabetes mellitus.

High-throughput profiling of the mitochondrial proteome using affinity fractionation and automation

Recent studies have demonstrated the need for complementing cellular genomic information with specific information on expressed proteins, or proteomics, since the correlation between the two is poor. Typically, proteomic information is gathered by analyzing samples on two-dimensional gels with the subsequent identification of specific proteins of interest by using trypsin digestion and mass spectrometry in a process termed peptide mass fingerprinting. These procedures have, as a rule, been labor-intensive and manual, and therefore of low throughput. The development of automated proteomic technology for processing large numbers of samples simultaneously has made the concept of profiling entire proteomes feasible at last. In this study, we report the initiation of the (eventual) complete profile of the rat mitochondrial proteome by using high-throughput automated equipment in combination with a novel fractionation technique using minispin affinity columns. Using these technologies, approximately one hundred proteins could be identified in several days. In addition, separate profiles of calcium binding proteins, glycoproteins, and hydrophobic or membrane proteins could be generated. Because mitochondrial dysfunction has been implicated in numerous diseases, such as cancer, Alzheimer's disease and diabetes, it is probable that the identification of the majority of mitochondrial proteins will be a beneficial tool for developing drug and diagnostic targets for associated diseases.

Strategies for evaluation of signaling pathways and transcription factors altered in aging

Aging is characterized by an accumulation of oxidative injury to DNA, RNA, proteins, lipids, and carbohydrates. In addition to damage, oxidative stress can initiate cell signaling cascades that modulate cell function, growth, and death. Aging and two common age-related diseases, diabetes mellitus and atherosclerosis, may share common oxidant-related signaling pathways that lead to abnormal transcription factor activation and ultimately to cellular dysfunction, degeneration, or death. This review will focus on approaches to evaluate key redox-sensitive signaling pathways and the transcription factors altered by diabetes, atherosclerosis, and aging.

Purine catabolism: links to mitochondrial respiration and antioxidant defenses?

Type I diabetes in rodents is associated with a spectrum of liver mitochondrial abnormalities ranging from evidence of oxidative stress and altered antioxidant defenses to frank defects in respiration rates and respiratory control ratios. To better address the myriad changes in redox metabolism in these mitochondria, we have applied new chromatographic techniques that enable simultaneous analysis of multiple components of pathways of interest (e.g., purine catabolites and oxidation by-products). We report here a portion of these results, which, in conjunction with other reported data, suggest that purine catabolism may contribute to mitochondrial antioxidant defenses by producing the antioxidant urate. In liver mitochondria from diabetic rats, increases in uric acid (threefold) and its direct precursor xanthine (sixfold) were observed in moderate diabetes, but levels fell essentially to normal in severe disease. Failure to maintain elevated xanthine and uric acid occurred contemporaneously with progressive mitochondrial dysfunction. Regression analysis revealed altered precursor-product relationships between xanthine, its precursors, and uric acid. An independent set of studies in isolated rat liver mitochondria showed that mitochondrial respiration was associated with essentially uniform decreases (approximately 30%) in all purine catabolites measured (urate, xanthine, hypoxanthine, guanine, guanosine, and xanthosine). That result suggests the potential for steady production of urate. Taken together, the two studies raise the possibility that purine catabolism may be a previously unappreciated component of the homeostatic response of mitochondria to oxidant stress and may play a critical role in slowing progressive mitochondrial dysfunction in certain disease states.

Decreased susceptibility to lipid peroxidation of Goto-Kakizaki rats: relationship to mitochondrial antioxidant capacity

The respiratory function and the antioxidant capacity of liver mitochondrial preparations isolated from Goto-Kakizaki non-insulin dependent diabetic rats and from Wistar control rats, with the age of 6 months, were compared. It was found that Goto-Kakizaki mitochondrial preparations presented a higher coupling between oxidative and phosphorylative systems, compared to non-diabetic preparations. Goto-Kakizaki mitochondria presented a lower susceptibility to lipid peroxidation induced by ADP/Fe2+, as evaluated by the formation of thiobarbituric acid substances. The decreased susceptibility to peroxidation in diabetic rats was correlated with an increase in mitochondrial vitamin E (alpha-tocopherol) content and GSH/GSSG ratio. Moreover, the glutathione reductase activity was significantly increased, whereas the glutathione peroxidase was decreased. Superoxide dismutase activity was unchanged in diabetic rats. Fatty acid analyses showed that the content in polyunsaturated fatty acids of Goto-Kakizaki mitochondrial membranes was significantly higher compared to controls. These results indicate that the lower susceptibility to lipid peroxidation of mitochondria from diabetic rats was related to their antioxidant defense systems, and may correspond to an adaptative response of the cells against oxidative stress in the early phase of diabetes.