Mitochondrial Function In Rats Research Articles

Protective effects of physical exercise on MDMA-induced cognitive and mitochondrial impairment

Debate continues about the effect of 3, 4-methylenedioxymethamphetamine (MDMA) on cognitive and mitochondrial function through the CNS. It has been shown that physical exercise has an important protective effect on cellular damage and death. Therefore, we investigated the effect of physical exercise on MDMA-induced impairments of spatial learning and memory as well as MDMA effects on brain mitochondrial function in rats. Male wistar rats underwent short-term (2 weeks) or long-term (4 weeks) treadmill exercise. After completion of exercise duration, acquisition and retention of spatial memory were evaluated by Morris water maze (MWM) test. Rats were intraperitoneally (I.P) injected with MDMA (5, 10, and 15mg/kg) 30min before the first training trial in 4 training days of MWM. Different parameters of brain mitochondrial function were measured including the level of ROS production, mitochondrial membrane potential (MMP), mitochondrial swelling, mitochondrial outermembrane damage, the amount of cytochrome c release from the mitochondria, and ADP/ATP ratio. MDMA damaged the spatial learning and memory in a dose-dependent manner. Brain mitochondria isolated from the rats treated with MDMA showed significant increase in ROS formation, collapse of MMP, mitochondrial swelling, and outer membrane damage, cytochrome c release from the mitochondria, and finally increased ADP/ATP ratio. This study also found that physical exercise significantly decreased the MDMA-induced impairments of spatial learning and memory and also mitochondrial dysfunction. The results indicated that MDMA-induced neurotoxicity leads to brain mitochondrial dysfunction and subsequent oxidative stress is followed by cognitive impairments. However, physical exercise could reduce these deleterious effects of MDMA through protective effects on brain mitochondrial function.

P66 Shc Contributes to Susceptibility to Cerebrovascular Injury and Intracerebral Hemorrhages

BackgroundBreakdown of the blood brain barrier (BBB) and loss of cerebral vessels autoregulation in response to elevated systemic pressure are closely linked to intracerebral hemorrhage and micro bleeds. Presently no established models to study the causes of intracerebral hemorrhage exist that does not rely on surgical interventions and existing models have failed to improve clinical understanding of this condition. Overproduction of reactive oxygen species (ROS) following ischaemia/reperfusion (I/R) is considered a key mechanism leading to BBB damage. It has been shown that the adaptor protein p66(Shc) is crucial regulator for ROS production in several disease states including I/R injury of the brain. p66shc when activated translocates to the mitochondria where it sequesters cytochrome C and generates hydrogen peroxide. The contribution of mitochondria to myogenic tone and autoregulation of the cerebral vasculature is not well defined.We have found previously that rats expressing constitutively active form of p66 Shc (Shc‐CA) have decreased long term survival and increased incidences of stoke despite no significant difference in systemic blood pressure.HypothesisWe hypothesis that p66Shc signaling via mitochondrial translocation contribute to vascular dysfunction of cerebral arteries and intracerebral hemorrhage in hypertensive rats by decreasing mitochondrial ATP while elevating mitochondrial ROS.ResultsVessels from WT rats, lacking p66 Shc protein (Shc‐KO), or expressing Shc‐CA were used for video microscopy. Endothelial dependent dilation to flow was assessed in vessels from Shc‐KO animals compared to their littermate controls (%Max Dilation 100 cm H2O: WT = 1.3±3 vs. Shc‐KO=39±3*; N≥3 P<0.05 one way ANOVA). Shc‐CA failed to develop tone spontaneously or to pharmacological stimuli (as a result no dilator function could be studied) suggesting a defect in vascular smooth muscle function. No difference in tone were observed in WT vs. Shc‐KO. Further evaluation revealed loss of myogenic tone in MCAs of Shc‐CA (% Tone at 150 cm H2O relative to Ca2+ free: WT = 19±6; Shc‐KO = 28±12; Shc‐CA =3±2, n≥2). In vivo cerebral vascular flow was evaluated using Doppler laser probe and revealed an inability of cerebral vessels to respond to altered systemic pressure in vivo. Shc‐CA showed decreased levels of ATP (pmol/mg Protein WT=1±0.2; Shc‐KO=0.7±0.2; Shc‐CA=0.1±0.1*; N≥3 P<0.05 one way ANOVA) and mitochondrial respiration, confirming decreased mitochondrial function in rats that express Shc‐CA.To investigate an underling physiological relevance, rats were perfused with methylene blue (MB). A substantial increase in MB staining in the brain of Shc‐CA was observed, suggesting an increase in permeability of the BBB.

Relationship between coumarin-induced hepatocellular toxicity and mitochondrial function in rats

The manifestation of coumarin-induced hepatocellular toxicity may differ and depends on the frequency of administration to rats. A single coumarin dose induces hepatocellular necrosis while repeated doses induce only hepatocyte degeneration. However, the mechanism underlying these effects remains unclear. Therefore, we investigated the mechanism of coumarin-induced hepatotoxicity in rats. Coumarin was administered to male rats as a single dose or for 4 consecutive days, and samples were obtained 4 or 24 h after a single dose or 24 h after the repeated doses. A single coumarin dose significantly induced hepatocellular necrosis in rats; however, toxicity was attenuated after repeated dosing. With a single dose, hepatocellular necrosis was preceded by increased mitochondrial number and size and decreased mitochondrial function. An increased expression of granular cytochrome P450 (CYP) 2E1 protein was observed in the cytoplasm and mitochondria of coumarin-treated rats compared to the expression in the untreated controls. Nevertheless, repeated dosing showed mitochondrial function that was equivalent to that of the control while enlarged CYP2E1 protein droplets were distributed outside the mitochondria. These results suggest that mitochondrial function and CYP2E1 expression might be involved in coumarin-induced hepatocellular toxicity in rats. A reduction in mitochondrial CYP2E1 might be implicated in the acquisition of coumarin resistance after repeated doses.

Effects of a high fat diet and taurine supplementation on metabolic parameters and skeletal muscle mitochondrial function in rats.

Obesity and consumption of a high fat diet are risk factors for the metabolic syndrome and is thought to confer changes in skeletal muscle mitochondrial function. Taurine supplementation has been shown to be able to counteract at least part of the metabolic changes induced by consumption of a high fat diet, yet little is known about the effect of taurine supplementation upon mitochondrial function. Here we assessed the effect of taurine supplementation on glucose and lipid parameters as well as skeletal muscle mitochondrial function in a high fat diet rat model.

Hydrogen-rich saline attenuates neuronal ischemia–reperfusion injury by protecting mitochondrial function in rats

BackgroundHydrogen, a popular antioxidant gas, can selectively reduce cytotoxic oxygen radicals and has been found to protect against ischemia–reperfusion (I/R) injury of multiple organs. Acute neuronal death during I/R has been attributed to loss of mitochondrial permeability transition coupled with mitochondrial dysfunction. This study was designed to investigate the potential therapeutic effect of hydrogen-rich saline on neuronal mitochondrial injury from global cerebral I/R in rats. Materials and methodsWe used a four-vessel occlusion model of global cerebral ischemia and reperfusion, with Sprague–Dawley rats. The rats were divided randomly into six groups (n = 90): sham (group S), I/R (group I/R), normal saline (group NS), atractyloside (group A), hydrogen-rich saline (group H), and hydrogen-rich saline + atractyloside (group HA). In groups H and HA, intraperitoneal hydrogen-rich saline (5 mL/kg) was injected immediately after reperfusion, whereas the equal volume of NS was injected in the other four groups. In groups A and HA, atractyloside (15 μL) was intracerebroventricularly injected 10 min before reperfusion, whereas groups NS and H received equal NS. The mitochondrial permeability transition pore opening and mitochondrial membrane potential were measured by spectrophotometry. Cytochrome c protein expression in the mitochondria and cytoplasm was detected by western blot. The hippocampus mitochondria ultrastructure was examined with transmission electron microscope. The histologic damage in hippocampus was assessed by hematoxylin and eosin staining. ResultsHydrogen-rich saline treatment significantly improved the amount of surviving cells (P < 0.05). Furthermore, hydrogen-rich saline not only reduced tissue damage, the degree of mitochondrial swelling, and the loss of mitochondrial membrane potential but also preserved the mitochondrial cytochrome c content (P < 0.05). ConclusionsOur study showed that hydrogen-rich saline was able to attenuate neuronal I/R injury, probably by protecting mitochondrial function in rats.

The restoration of kidney mitochondria function by inhibition of angiotensin-II production in rats with acute adriamycin-induced nephrotoxicity

Adriamycin (ADR) is commonly used for many solid tumor treatments. Its clinical utility is, however, largely limited by the adverse reactions, are known to be nephrotoxic. The mechanism by which it induces kidney damage is still not completely understood, but its nephrotoxicity might relate to increase reactive oxidant status (ROS), mitochondrial dysfunction. Until now, neurohormonal activation of it is unclear. ADR might activate the renin angiotensin system. Angiotensin-II also induced ROS and mitochondrial dysfunction. The aim of this study was to investigate whether angiotensin-II production inhibition has the protective effect on attenuation of mitochondrial function in rats with acute ADR-nephrotoxicity or not. Rats were divided into five groups as a control, ADR, co-treated ADR with captopril (CAP), co-treated ADR with Aliskren, co-treated ADR with both CAP and Aliskren groups. Creatinine kinase (CK) levels were measured at the end of treatment period. The kidneys were homogenized and biochemical measurements were made in mitochondria, cytosol. Mitochondria membrane potential (MMP) and ATP levels were determined. ADR increased CK levels and oxidative stress in mitochondria too (p < 0.05). ADR significantly decreased MMP and ATP level in kidney mitochondria (p < 0.05). Co-administration with ADR and Aliskren and CAP improved the dissipation of MMP (p < 0.05). The decrease in ATP level was restored by treatment with inhibitors of ACE and renin. We concluded that inhibitors of angiotensin-II are effective against acute ADR induced nephrotoxicity via the restoration of MMP and ATP production and prevention of mitochondrial damage in vivo.

Restorative role of Deprenyl on Mitochondrial function of aging rat cerebellum

Mitochondria are known to be a rich source for the production of free radicals and, consequently, mitochondrial components are susceptible to lipid peroxidation that decreases respiratory activity. The present investigation was designed to evaluate the neuroprotective effect of Deprenyl on mitochondrial function in rats with respect to changes in the mitochondrial energy status. Intraperitoneal administration of liquid deprenyl (2 mg/kg body weight/day for a period of 15 days i.p, significantly P< 0.05) to the experimental rats of three age groups (6, 12 &18 months old) prevented the age related reduction in Tricarboxylic acid cycle enzymes (isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, succinate dehydrogenase and malate dehydrogenase) and respiratory marker enzymes (NADH dehydrogenase and cytochrome-c-oxidase) in the cerebellar mitochondria. The results of the present study indicate that the overall neuroprotective effect of deprenyl is probably related to its ability to retain the energy status of cerebellum by preserving the activities of Tricarboxylic acid cycle enzymes and respiratory marker enzymes at near normalcy and/or to its free radical- scavenging capability against age related aberrations in lipid peroxidation, which is responsible for unalterable changes in neuronal membrane.

Dietary macronutrients modulate the fatty acyl composition of rat liver mitochondrial cardiolipins

The interaction of dietary fats and carbohydrates on liver mitochondria were examined in male FBNF1 rats fed 20 different low-fat isocaloric diets. Animal growth rates and mitochondrial respiratory parameters were essentially unaffected, but mass spectrometry-based mitochondrial lipidomics profiling revealed increased levels of cardiolipins (CLs), a family of phospholipids essential for mitochondrial structure and function, in rats fed saturated or trans fat-based diets with a high glycemic index. These mitochondria showed elevated monolysocardiolipins (a CL precursor/product of CL degradation), elevated ratio of trans-phosphocholine (PC) (18:1/18:1) to cis-PC (18:1/18:1) (a marker of thiyl radical stress), and decreased ubiquinone Q9; the latter two of which imply a low-grade mitochondrial redox abnormality. Extended analysis demonstrated: i) dietary fats and, to a lesser extent, carbohydrates induce changes in the relative abundance of specific CL species; ii) fatty acid (FA) incorporation into mature CLs undergoes both positive (>400-fold) and negative (2.5-fold) regulation; and iii) dietary lipid abundance and incorporation of FAs into both the CL pool and specific mature tetra-acyl CLs are inversely related, suggesting previously unobserved compensatory regulation. This study reveals previously unobserved complexity/regulation of the central lipid in mitochondrial metabolism.

Gestational protein restriction induces alterations in placental morphology and mitochondrial function in rats during late pregnancy

The placenta acts a regulator of nutrient composition and supply from mother to fetus and is the source of hormonal signals that affect maternal and fetal metabolism. Thus, appropriate development of the placenta is crucial for normal fetal development. We investigated the effect of gestational protein restriction (GPR) on placental morphology and mitochondrial function on day 19 of gestation. Pregnant dams were divided into two groups: normal (NP 17 % casein) or low-protein diet (LP 6 % casein). The placentas were processed for biochemical, histomorphometric and ultrastructural analysis. The integrity of rat placental mitochondria (RPM) isolated by conventional differential centrifugation was measured by oxygen uptake (Clark-type electrode). LP animals presented an increase in adipose tissue and triacylglycerol and a decrease in serum insulin levels. No alterations were observed in body, liver, fetus, or placenta weight. There was also no change in serum glucose, total protein, or lipid content. Gestational protein restriction had tissue-specific respiratory effects, with the observation of a small change in liver respiration (~13 %) and considerable respiratory inhibition in placenta samples (~37 %). The higher oxygen uptake by RPM in the LP groups suggests uncoupling between respiration and oxidative phosphorylation. In addition, ultrastructural analysis of junctional zone giant cells from LP placenta showed a disorganized cytoplasm, with loss of integrity of most organelles and intense vacuolization. The present results led us to hypothesize that GPR alters placental structure and morphology, induces sensitivity to insulin, mitochondrial abnormalities and suggests premature aging of the placenta. Further studies are needed to test this hypothesis.

Naringin Improves Diet-Induced Cardiovascular Dysfunction and Obesity in High Carbohydrate, High Fat Diet-Fed Rats

Obesity, insulin resistance, hypertension and fatty liver, together termed metabolic syndrome, are key risk factors for cardiovascular disease. Chronic feeding of a diet high in saturated fats and simple sugars, such as fructose and glucose, induces these changes in rats. Naturally occurring compounds could be a cost-effective intervention to reverse these changes. Flavonoids are ubiquitous secondary plant metabolites; naringin gives the bitter taste to grapefruit. This study has evaluated the effect of naringin on diet-induced obesity and cardiovascular dysfunction in high carbohydrate, high fat-fed rats. These rats developed increased body weight, glucose intolerance, increased plasma lipid concentrations, hypertension, left ventricular hypertrophy and fibrosis, liver inflammation and steatosis with compromised mitochondrial respiratory chain activity. Dietary supplementation with naringin (approximately 100 mg/kg/day) improved glucose intolerance and liver mitochondrial dysfunction, lowered plasma lipid concentrations and improved the structure and function of the heart and liver without decreasing total body weight. Naringin normalised systolic blood pressure and improved vascular dysfunction and ventricular diastolic dysfunction in high carbohydrate, high fat-fed rats. These beneficial effects of naringin may be mediated by reduced inflammatory cell infiltration, reduced oxidative stress, lowered plasma lipid concentrations and improved liver mitochondrial function in rats.

Mitochondrial DNA damage and its effect on mitochondrial function in rats with obstructive jaundice

This study investigated mitochondrial DNA (mtDNA) damage in rats with obstructive jaundice (OJ) and to explore its effect on mitochondrial and hepatic function. Forty-eight male Wistar rats were randomly divided into two groups: sham-operated (Sham) and bile duct ligation (BDL). Blood and tissue samples were collected from the two groups on days 1, 4, 7 and 14 following surgery. Hepatic and mitochondrial function were measured. Long and accurate PCR, restriction enzyme digestion and gene sequencing were used to analyze the locations of mtDNA deletions. In addition, quantitative fluorescent PCR was used to measure the relative amounts of total DNA in hepatocytes and mtDNA deletions. Results showed that the hepatic and mitochondrial function was compromised in the BDL group compared to the Sham group. Notably, a novel 11,194-bp mtDNA deletion (nucleotide positions 4101-15294) and fewer mtDNA copies were found compared to the Sham group. With prolonged ligation time, there was a decrease in the copy number, while the ratio of mtDNA deletions to total mtDNA levels increased in the BDL group. These changes were consistent with damage to hepatic and mitochondrial function. A novel 11,194-bp mtDNA deletion and fewer mtDNA copies were detected in hepatocytes of rats with OJ. The mtDNA deletions may therefore be an important factor leading to mitochondrial and hepatic dysfunction.

Dietary long-chain, but not medium-chain, triglycerides impair exercise performance and uncouple cardiac mitochondria in rats

Short-term consumption of a high-fat diet impairs exercise capacity in both rats and humans, and increases expression of the mitochondrial uncoupling protein, UCP3, in rodent cardiac and skeletal muscle via activation of the transcription factor, peroxisome proliferator-activated receptor α (PPARα). Unlike long-chain fatty acids however, medium-chain fatty acids do not activate PPARα and do not increase muscle UCP3 expression. We therefore investigated exercise performance and cardiac mitochondrial function in rats fed a chow diet (7.5% kcal from fat), a long-chain triglyceride (LCT) rich diet (46% kcal from LCTs) or a medium-chain triglyceride (MCT) rich diet (46% kcal from MCTs). Rats fed the LCT-rich diet for 15 days ran 55% less far than they did at baseline, whereas rats fed the chow or MCT-rich diets neither improved nor worsened in their exercise capacities. Moreover, consumption of an LCT-rich diet increased cardiac UCP3 expression by 35% and decreased oxidative phosphorylation efficiency, whereas consumption of the MCT-rich diet altered neither UCP3 expression nor oxidative phosphorylation efficiency. Our results suggest that the negative effects of short-term high-fat feeding on exercise performance are predominantly mediated by long-chain rather than medium-chain fatty acids, possibly via PPARα-dependent upregulation of UCP3.

Effects of the cannabinoid CB1 antagonist rimonabant on hepatic mitochondrial function in rats fed a high-fat diet

The aim of this study was to investigate the effect of rimonabant treatment on hepatic mitochondrial function in rats fed a high-fat diet. Sprague-Dawley rats fed a high-fat diet (35% lard) for 13 wk were treated with rimonabant (10 mg·kg(-1)·day(-1)) during the last 3 wk and matched with pair-fed controls. Oxygen consumption with various substrates, mitochondrial enzyme activities on isolated liver mitochondria, and mitochondrial DNA quantity were determined. Body weight and fat mass were decreased in rats treated with rimonabant compared with pair-fed controls. Moreover, the serum adiponectin level was increased with rimonabant. Hepatic triglyceride content was increased, while serum triglycerides were decreased. An increase of mitochondrial respiration was observed in rats treated with rimonabant. The increase of mitochondrial respiration with palmitoyl-CoA compared with respiration with palmitoyl-l-carnitine stating that the entry of fatty acids into mitochondria via carnitine palmitoyltransferase I was increased in rats treated with rimonabant. Moreover, rimonabant treatment led to a reduction in the enzymatic activity of ATP synthase, whereas the quantity of mitochondrial DNA and the activity of citrate synthase remained unchanged. To summarize, rimonabant treatment leads to an improvement of hepatic mitochondrial function by increasing substrate oxidation and fatty acid entry into mitochondria for the β-oxidation pathway and by increasing proton leak. However, this increase of mitochondrial oxidation is regulated by a decrease of ATP synthase activity in order to have only ATP required for the cell function.

Threonine-deficient diets induced changes in hepatic bioenergetics

Diets deficient in an indispensable amino acid are known to suppress food intake in rats. Few studies were focused at understanding how amino acid-deficient diets may elicit biochemical changes at the mitochondrial level. The goal of this study was to evaluate mitochondrial function in rats fed diets with 0.00, 0.18, 0.36, and 0.88% threonine (Thr) (set at 0, 30, 60, and 140% of Thr requirement for growth). Here, it is described for the first time that Thr-deficient diets induce a specific uncoupling of mitochondria in liver, especially with NADH-linked substrates, not observed in heart (except for Thr-devoid diet). The advantage of this situation would be to provide ATP to support growth and maintenance when high-quality protein food (or wealth of high-quality food in general) is available, whereas Thr-deficient diets (or deficient-quality protein food) promote the opposite, increasing mitochondrial uncoupling in liver. The uncoupling with NADH substrates would favor the use of nutrients as energy sources with higher FADH-to-NADH ratios, such as fat, minimizing the first irreversible NADH-dependent catabolism of many amino acids, including Thr, thus enhancing the use of the limiting amino acid for protein synthesis when a low quality protein source is available.

Effects of three different conjugated linoleic acid preparations on insulin signalling, fat oxidation and mitochondrial function in rats fed a high-fat diet

To investigate the effects of three different conjugated linoleic acid (CLA) preparations containing different ratios of CLA isomers on insulin signalling, fatty acid oxidation and mitochondrial function, Sprague-Dawley rats were fed a high-fat diet either unsupplemented or supplemented with one of three CLA preparations at 1 % of the diet for 8 weeks. The first CLA preparation contained approximately 30 % cis-9, trans-11 (c9, t11)-CLA isomer and 40 % trans-10, cis-12 (t10, c12)-CLA isomer (CLA-mix). The other two preparations were an 80:20 mix (c9, t11-CLA-mix) or a 10:90 mix of two CLA isomers (t10, c12-CLA-mix). Insulin resistance was decreased in all three supplemented groups based on the results of homeostasis model assessment and the revised quantitative insulin-sensitivity check index. The phosphorylation of insulin receptor substrate-1 on serine decreased in the livers of all three supplemented groups, while subsequent Akt phosphorylation increased only in the t10, c12-CLA-mix group. Both the c9, t11-CLA-mix and the t10, c12-CLA-mix increased the expression of hepatic adiponectin receptors R1 and 2, which are thought to enhance insulin sensitivity and fat oxidation. The c9, t11-CLA-mix increased protein and mRNA levels of PPAR alpha, acyl-CoA oxidase and uncoupling protein, which are involved in fatty acid oxidation and energy dissipation. The c9, t11-CLA-mix enhanced mitochondrial function and protection against oxidative stress by increasing the activities of cytochrome c oxidase, manganese-superoxide dismutase, glutathione peroxidase, and glutathione reductase and the level of GSH. In conclusion, all three CLA preparations reduced insulin resistance. Among them, the c9, t11-CLA-mix was the most effective based on the parameters reflecting insulin resistance and fat oxidation, and mitochondrial antioxidative enzyme activity in the liver.

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.

Mitochondria respiration and susceptibility to ischemia–reperfusion injury in diabetic hearts

Cardiovascular complications are the primary cause of death for diabetic patients. Clinical and experimental observation has showed the development of dysfunctional cardiomyopathy as one of the main complications of diabetes. Whether the cardiomyopathy results from an increased susceptibility of cardiac tissue to ischemic insult or from a specific functional defect of cardiac mitochondria is a controversial issue. The investigation of possible functional defect in cardiac mitochondria from diabetic rats indicates a decline in state 3 respiration only in animals presenting a marked decrease in body weight. Mitochondria from rats presenting a level of hyperglycemia similar to diabetic animals but not the marked weight loss typical of the latter group show no decline in state 3 respiration, the values being indistinguishable from those of control mitochondria. Mitochondria from hyperglycemic rats, however, show a 15–20% increase in state 4 oxygen consumption but only when glutamate is used as energetic substrate, as compared to a 40–50% increase in state 4 respiration in mitochondria from diabetic rats under similar experimental conditions. This phenomenon is unrelated to diabetes duration, as it is observed at 2 as well as 8 weeks after diabetes onset. Taken together, these data argue against hyperglycemia per se being a direct cause of the decline in state 3 oxygen consumption observed in cardiac mitochondria of type-I diabetic rats and indicate that differences exist in cardiac mitochondrial function in rats generically labeled as diabetic. These differences can contribute to explain discrepancies in experimental results reported by various groups in the field and provide an additional parameter to be taken into consideration in evaluating the varying sensitivity of diabetic hearts to ischemia–reperfusion injury.

Improved Efficiency of Hepatic Mitochondrial Function in Rats with Cholestasis Induced by an Acute Dose of α-Naphthylisothiocyanate

Cholestasis is a feature of many chronic human liver diseases. Previous studies pointed out an impairment of mitochondrial function as a cause of hepatocyte dysfunction leading to cholestatic liver injury. This study was aimed to evaluate liver mitochondrial bioenergetics of α-naphthylisothiocyanate-treated Wistar rats, an experimental model of cholestasis. Serum markers of liver injury and endogenous adenine nucleotides were measured. Changes in membrane potential, mitochondrial respiration, and alterations in mitochondrial permeability transition pore induction were monitored. In rats injected with α-naphthylisothiocyanate, liver injury with cholestasis developed within 48 h, as indicated by both serum enzyme activities and total bilirubin concentration. Liver mitochondria isolated from α-naphthylisothiocyanate-treated rats had a higher state 3 respiration, respiratory control ratio, ADP/O, and endogenous ATP/ADP ratio compared to controls. No change in state 4 respiration was observed. Associated with these parameters, cholestatic mitochondria exhibited an increased resistance to disruption of mitochondrial calcium homeostasis due to permeability transition pore induction. Hepatic mitochondria isolated from α-naphthylisothiocyanate-treated rats exhibited an improved efficiency. These data indicate that an adaptive response to resist cell death occurs during α-naphthylisothiocyanate-induced acute cholestasis.

Relationship between hepatic mitochondrial functions in vivo and in vitro in rats with carbon tetrachloride-induced liver cirrhosis

Background/Aims: The metabolic capacity of liver mitochondria is impaired in rats with carbon tetrachloride (CCl4)-induced cirrhosis. These studies were performed to find out whether benzoate and/or palmitate are suitable substrates for assessing hepatic mitochondrial function in vivo.Methods:In vivo metabolism of benzoate and 1-14C-palmitate was assessed by monitoring urinary excretion of hippurate and exhalation of 14CO2, respectively, in cirrhotic and control rats (n=8 for each group). Isolation of liver mitochondria, and in vitro benzoate and palmitate metabolism were performed by methods published previously. The hepatic content of mitochondria was assessed by stereological analysis of the volume of hepatocytes and by biochemical determination, using the activity of citrate synthase.Results: Renal excretion of hippurate following i.p. administration of benzoate was reduced in cirrhotic rats (64±15 vs. 85±14% of administered dose over 24 h), and showed a linear correlation with hippurate formation by isolated mitochondria. The activities of benzoyl-CoA synthase and benzoyl-CoA:glycine Nacyltransferase were reduced by approximately 60%, and the coenzyme A content by 50% in hepatic mitochondria from cirrhotic rats, explaining impaired hippurate formation. Peak exhalation of 14CO2 after i.p. administration of 1-14C-palmitate was reduced by 44% and the area under the 14CO2 exhalation-time curve by 34% in cirrhotic rats. Peak 14CO2 exhalation revealed a linear correlation with oxidative metabolism of palmitoylcarnitine in isolated mitochondria. Both in vivo benzoate and palmitate metabolism showed a linear correlation with the volume fraction of hepatocytes. The mitochondrial protein content was reduced in cirrhotic rats per g liver and per liver but equal to control rats per volume of hepatocytes.Conclusions:In vivo metabolism of both palmitate and benzoate reflects hepatic mitochondrial function in rats with CCl4-induced cirrhosis. Hepatic mitochondrial function is impaired in rats with CCl4-induced cirrhosis due to both reduced mitochondrial volume per liver and impaired metabolism of the remaining mitochondria. In contrast to rats with secondary biliary cirrhosis, rats with CCl4-induced cirrhosis showed no hepatic mitochondrial proliferation to counteract reduced mitochondrial function.

HMG CoA reductase inhibitor accelerates aging effect on diaphragm mitochondrial respiratory function in rats.

We examined effects of pravastatin on age-related changes in mitochondrial function in rats. Decline in the activity of complex I of the mitochondrial electron transport chain was observed in diaphragm and psoai major in rats aged 35 and 55 weeks, and that of complex IV in rats aged 55 weeks. Pravastatin accelerated significantly age-related decline in the activity of complex I of diaphragm mitochondria, though pravastatin did not show significant effect on normally observed age-associated decline in the activities of complex IV of psoai major and diaphragm mitochondria. Aging effect on mitochondrial respiratory function was not observed on heart muscle and liver in rats up to 55 weeks old, and pravastatin did not effect significantly heart and liver mitochondrial respiratory function. From these results, careful clinical examination on respiratory muscle function should be necessary in patients treated with pravastatin particularly in elderly patients.