Large-scale preparation of rat liver mitochondria in high yield

Purification and characterization of aldose reductase from jerboa (Jaculus orientalis) and evaluation of its inhibitory activity by Euphorbia regis-jubae (Webb & Berth) extracts

This study aimed, for the first time, to assess the purification of aldose reductase (AR) in Jaculus orientalis (Dipodidae family) kidney and to evaluate the in vitro aldose reductase inhibitory (ARI) effects of Euphorbia regis-jubae (Euphorbiaceae family) aqueous and hydroethanolic extracts. Initial screening assay of the enzymatic AR activity in different jerboa states (euthermic, prehibernating and hibernating) and tissues (brain, brown adipose tissue, liver and kidneys) was assessed. Then, AR has been purified to homogeneity from the kidneys of prehibernating jerboas by a series of chromatographic technics. Furthermore, the in vitro and in silico ARI effects of E. regis-jubae (Webb & Berth) extracts, characterized by hight performance liquid chromatography (HPLC) on the purified enzyme were evaluated. Our results showed that the highest enzyme activity was detected in the kidneys, followed by white adipose tissue and the lungs of pre-hibernating jerboa. The enzyme was purified to homogeneity from jerboa kidneys during prehibernating state with a purification factor of 53.4-fold and a yield of about 6%. AR is monomeric, active in D(+)-glyceraldehyde substrate and in disodium phosphate buffer. The pH and temperature for AR were determined to be 6.5-7.5 and 35 °C, respectively. Results of the in vitro ARI activity was strongest with both the hydroethanolic extract (IC₅₀ = 96.45 μg/mL) and aqueous extract (IC₅₀ = 140 μg/mL). Molecular docking study indicated that catechin might be the main component in both aqueous and hydroethanolic extracts to inhibited AR. This study provides new evidence on the ARI effect of E. regis-jubae (Webb & Berth), which may be related to its phenolic constituents.

Effects of Multiple Doses of Dichloroacetate on GSTZ1 Expression and Activity in Liver and Extrahepatic Tissues of Young and Adult Rats

Glutathione transferase zeta 1 (GSTZ1), expressed in liver and several extrahepatic tissues, catalyzes dechlorination of dichloroacetate (DCA) to glyoxylate. DCA inactivates GSTZ1, leading to autoinhibition of its metabolism. DCA is an investigational drug for treating several congenital and acquired disorders of mitochondrial energy metabolism, including cancer. The main adverse effect of DCA, reversible peripheral neuropathy, is more common in adults treated long-term than in children, who metabolize DCA more quickly after multiple doses. One dose of DCA to Sprague Dawley rats reduced GSTZ1 expression and activity more in liver than in extrahepatic tissues; however, the effects of multiple doses of DCA that mimic its therapeutic use have not been studied. Here, we examined the expression and activity of GSTZ1 in cytosol and mitochondria of liver, kidney, heart, and brain 24 hours after completion of 8-day oral dosing of 100 mg/kg per day sodium DCA to juvenile and adult Sprague Dawley rats. Activity was measured with DCA and with 1,2-epoxy-3-(4-nitrophenoxy)propane (EPNPP), reported to be a GSTZ1-selective substrate. In DCA-treated rats, liver retained higher expression and activity of GSTZ1 with DCA than other tissues, irrespective of rodent age. DCA-treated juvenile rats retained more GSTZ1 activity with DCA than adults. Consistent with this finding, there was less measurable DCA in tissues of juvenile than adult rats. DCA-treated rats retained activity with EPNPP, despite losing over 98% of GSTZ1 protein. These data provide insight into the differences between children and adults in DCA elimination under a therapeutic regimen and confirm that the liver contributes more to DCA metabolism than other tissues. SIGNIFICANCE STATEMENT: Dichloroacetate (DCA) is one of few drugs exhibiting higher clearance from children than adults, after repeated doses, for reasons that are unclear. We hypothesized that juveniles retain more glutathione transferase zeta 1 (GSTZ1) than adults in tissues after multiple DCA doses and found this was the case for liver and kidney, with rat as a model to assess GSTZ1 protein expression and activity with DCA. Although 1,2-epoxy-3-(4-nitrophenoxy)propane was reported to be a selective GSTZ1 substrate, its activity was not reduced in concert with GSTZ1 protein.

Heart Histopathology and Mitochondrial Ultrastructure in Aged Rats Fed for 24 Months on Different Unsaturated Fats (Virgin Olive Oil, Sunflower Oil or Fish Oil) and Affected by Different Longevity

Diet plays a decisive role in heart physiology, with lipids having especial importance in pathology prevention and development. This study aimed to investigate how dietary lipids varying in lipid profile (virgin olive oil, sunflower oil or fish oil) affected the heart of rats during aging. Heart histopathology, mitochondrial morphometry, and oxidative status were assessed. Typical histopathological features associated with aging, such as valvular lesions, endomyocardical hyperplasia, or papillary muscle calcification, were found at a low extent in all the experimental groups. The most relevant finding was that inflammation registered by fish oil group was lower compared to the other treatments. At the ultrastructural level, heart mitochondrial area, perimeter, and aspect ratio were higher in fish oil-fed rats than in those fed on sunflower oil. Concerning oxidative stress markers, there were differences only in coenzyme Q levels and catalase activity, lower in sunflower oil-fed animals compared with those fed on fish oil. In summary, dietary intake for a long period on dietary fats with different fatty acids profile led to differences in some aspects associated with the aging process at the heart. Fish oil seems to be the fat most protective of heart during aging.

Gene pathways associated with mitochondrial function, oxidative stress and telomere length are differentially expressed in the liver of rats fed lifelong on virgin olive, sunflower or fish oils

This study investigates the effect of lifelong intake of different fat sources rich in monounsaturated (virgin olive oil), n6 polyunsaturated (sunflower oil) or n3 polyunsaturated (fish oil) fatty acids in the aged liver. Male Wistar rats fed lifelong on diets differing in the fat source were killed at 6 and at 24 months of age. Liver histopathology, mitochondrial ultrastructure, biogenesis, oxidative stress, mitochondrial electron transport chain, relative telomere length and gene expression profiles were studied. Aging led to lipid accumulation in the liver. Virgin olive oil led to the lowest oxidation and ultrastructural alterations. Sunflower oil induced fibrosis, ultrastructural alterations and high oxidation. Fish oil intensified oxidation associated with age, lowered electron transport chain activity and enhanced the relative telomere length. Gene expression changes associated with age in animals fed virgin olive oil and fish oil were related mostly to mitochondrial function and oxidative stress pathways, followed by cell cycle and telomere length control. Sunflower oil avoided gene expression changes related to age. According to the results, virgin olive oil might be considered the dietary fat source that best preserves the liver during the aging process.

Molecular mechanism of DRP1 assembly studied in vitro by cryo-electron microscopy

Mitochondria are dynamic organelles that continually adapt their morphology by fusion and fission events. An imbalance between fusion and fission has been linked to major neurodegenerative diseases, including Huntington's, Alzheimer's, and Parkinson's diseases. A member of the Dynamin superfamily, dynamin-related protein 1 (DRP1), a dynamin-related GTPase, is required for mitochondrial membrane fission. Self-assembly of DRP1 into oligomers in a GTP-dependent manner likely drives the division process. We show here that DRP1 self-assembles in two ways: i) in the presence of the non-hydrolysable GTP analog GMP-PNP into spiral-like structures of ~36 nm diameter; and ii) in the presence of GTP into rings composed of 13-18 monomers. The most abundant rings were composed of 16 monomers and had an outer and inner ring diameter of ~30 nm and ~20 nm, respectively. Three-dimensional analysis was performed with rings containing 16 monomers. The single-particle cryo-electron microscopy map of the 16 monomer DRP1 rings suggests a side-by-side assembly of the monomer with the membrane in a parallel fashion. The inner ring diameter of 20 nm is insufficient to allow four membranes to exist as separate entities. Furthermore, we observed that mitochondria were tubulated upon incubation with DRP1 protein in vitro. The tubes had a diameter of ~ 30nm and were decorated with protein densities. These findings suggest DRP1 tubulates mitochondria, and that additional steps may be required for final mitochondrial fission.

Age-related changes in brain mitochondrial DNA deletion and oxidative stress are differentially modulated by dietary fat type and coenzyme Q₁₀

Mitochondria-related oxidative damage is a primary event in aging and age-related neurodegenerative disorders. Some dietary treatments, such as antioxidant supplementation or the enrichment of mitochondrial membranes with less oxidizable fatty acids, reduce lipid peroxidation and lengthen life span in rodents. This study compares life-long feeding on monounsaturated fatty acids (MUFAs), such as virgin olive oil, and n-6 polyunsaturated fatty acids, such as sunflower oil, with or without coenzyme Q₁₀ supplementation, with respect to age-related molecular changes in rat brain mitochondria. The MUFA diet led to diminished age-related phenotypic changes, with lipoxidation-derived protein markers being higher among the older animals, whereas protein carbonyl compounds were lower. It is noteworthy that the MUFA diet prevented the age-related increase in levels of mitochondrial DNA deletions in the brain mitochondria from aged animals. The findings of this study suggest that age-related oxidative stress is related, at the mitochondrial level, to other age-related features such as mitochondrial electron transport and mtDNA alterations, and it can be modulated by selecting an appropriate dietary fat type and/or by suitable supplementation with low levels of the antioxidant/electron carrier molecule coenzyme Q.

Mitochondrion as a novel site of dichloroacetate biotransformation by glutathione transferase zeta 1

Dichloroacetate (DCA) is a potential environmental hazard and an investigational drug. Repeated doses of DCA result in reduced drug clearance, probably through inhibition of glutathione transferase ζ1 (GSTZ1), a cytosolic enzyme that converts DCA to glyoxylate. DCA is known to be taken up by mitochondria, where it inhibits pyruvate dehydrogenase kinase, its major pharmacodynamic target. We tested the hypothesis that the mitochondrion was also a site of DCA biotransformation. Immunoreactive GSTZ1 was detected in liver mitochondria from humans and rats, and its identity was confirmed by liquid chromatography/tandem mass spectrometry analysis of the tryptic peptides. Study of rat submitochondrial fractions revealed GSTZ1 to be localized in the mitochondrial matrix. The specific activity of GSTZ1-catalyzed dechlorination of DCA was 2.5- to 3-fold higher in cytosol than in whole mitochondria and was directly proportional to GSTZ1 protein expression in the two compartments. Rat mitochondrial GSTZ1 had a 2.5-fold higher (App)K(m) for glutathione than cytosolic GSTZ1, whereas the (App)K(m) values for DCA were identical. Rats administered DCA at a dose of 500 mg/kg/day for 8 weeks showed reduced hepatic GSTZ1 activity and expression of ∼10% of control levels in both cytosol and mitochondria. We conclude that the mitochondrion is a novel site of DCA biotransformation catalyzed by GSTZ1, an enzyme colocalized in cytosol and mitochondrial matrix.

Immunoaffinity purification and characterization of mitochondrial membrane-bound D-3-hydroxybutyrate dehydrogenase from Jaculus orientalis

BACKGROUND

The interconversion of two important energy metabolites, 3-hydroxybutyrate and acetoacetate (the major ketone bodies), is catalyzed by D-3-hydroxybutyrate dehydrogenase (BDH1: EC 1.1.1.30), a NAD+-dependent enzyme. The eukaryotic enzyme is bound to the mitochondrial inner membrane and harbors a unique lecithin-dependent activity. Here, we report an advanced purification method of the mammalian BDH applied to the liver enzyme from jerboa (Jaculus orientalis), a hibernating rodent adapted to extreme diet and environmental conditions.

RESULTS

Purifying BDH from jerboa liver overcomes its low specific activity in mitochondria for further biochemical characterization of the enzyme. This new procedure is based on the use of polyclonal antibodies raised against BDH from bacterial Pseudomonas aeruginosa. This study improves the procedure for purification of both soluble microbial and mammalian membrane-bound BDH. Even though the Jaculus orientalis genome has not yet been sequenced, for the first time a D-3-hydroxybutyrate dehydrogenase cDNA from jerboa was cloned and sequenced.

CONCLUSION

This study applies immunoaffinity chromatography to purify BDH, the membrane-bound and lipid-dependent enzyme, as a 31 kDa single polypeptide chain. In addition, bacterial BDH isolation was achieved in a two-step purification procedure, improving the knowledge of an enzyme involved in the lipid metabolism of a unique hibernating mammal. Sequence alignment revealed conserved putative amino acids for possible NAD+ interaction.

Effect of CV159-Ca(2+)/calmodulin blockade on redox status hepatic ischemia-reperfusion injury in mice evaluated by a newly developed in vivo EPR imaging technique

1,4-Dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid methyl 6-(5-phenyl-3-pyrazolyloxy)hexyl ester (CV159) exhibits selective blocking of Ca(2+)/calmodulin and inhibits Ca(2+) overloading in living organisms. The effects of this antagonist in mice with hepatic ischemia-reperfusion injury were investigated using electron paramagnetic resonance imaging (EPRI) and ex vivo EPR (x-band EPR) techniques. The EPRI determined that the 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl half-life in CV159-treated mice was significantly shorter than that in untreated mice and was almost equal to that in the sham group. Both the cytosolic and the mitochondrial superoxide scavenging activities in CV-treated mice were significantly higher than that in untreated mice. Faint staining of the anti-superoxide dismutase antibody and strong staining of anti-inducible nitric oxide synthase antibody were observed in the liver of control group. In contrast to these findings, immunostaining of these antibodies in the liver of CV159-treated mice were reversed compared to control group. Western blotting showed that CV159 contributed to the high superoxide dismutase expression and low expression of inducible nitric oxide synthase. The alanine aminotransferase level in CV159-treated mice significantly decreased in comparison to that observed in the untreated mice. We conclude that CV159 retains its organ-reducing activity against radicals in hepatic reperfusion injury, which is mediated by the inhibition of Ca(2+) overloading.

Prehibernation and hibernation effects on the D-3-hydroxybutyrate dehydrogenase of the heavy and light mitochondria from liver jerboa (Jaculus orientalis) and related metabolism

The D-3-hydroxybutyrate dehydrogenase (BDH) (EC 1.1.1.30) from liver jerboa (Jaculus orientalis), a ketone body converting enzyme in mitochondria, in two populations of mitochondria (heavy and light) has been studied in different jerboa states (euthermic, prehibernating and hibernating). The results reveal: (1) important variations between states in terms of ketones bodies, glucose and lipid levels; (2) significant differences between the BDH of the two mitochondrial populations in term of protein expression and kinetic properties. These results suggest that BDH leads an important conformational change depending on the physiological state of jerboa. This BDH structural change could be the consequence of the lipid composition modifications in inner mitochondrial membrane leading to changes in BDH catalytic properties.

The intake of fried virgin olive or sunflower oils differentially induces oxidative stress in rat liver microsomes

The effects of non-fried and fried virgin olive and sunflower oils on rat liver microsomal compositional features have been investigated. In addition, plasma antioxidants (α-tocopherol and ubiquinone 9) were investigated as well as the possible oxidative modifications suffered by virgin olive and sunflower oils during the frying process. The frying process decreased the content of α-tocopherol and phenolics in the oils and increased total polar materials. Sunflower oil was affected to a greater extent than olive oil. In rats, the intake of fried oil led to higher levels of lipid peroxidation and a lower concentration of plasma antioxidants. Microsomal fatty acid and antioxidant profiles were also altered. It seems that a strong relationship exists between the loss of antioxidants and the production of toxic compounds in the oils after frying and the extent of the peroxidative events in microsomes, which were also different depending on the fat source. The highly unsaturated sunflower oil was less resistant to the oxidative stress produced by frying and led to a higher degree of lipid peroxidation in liver microsomesin vivothan virgin olive oil.

Age-related mitochondrial DNA deletion in rat liver depends on dietary fat unsaturation

We fed male Wistar rats lifelong on virgin olive (rich in the monounsaturated oleic acid) or sunflower (rich in the polyunsaturated linoleic acid) oil-based diets. At 6 and 24 months, liver mitochondria were analyzed for a mitochondrial DNA (mtDNA) deletion, reactive oxygen species, antioxidants, and ultrastructural alterations. An aging-related increase in the relative amount of the deletion was observed for both dietary groups, being higher in animals fed sunflower oil. Oxidative stress was lower in virgin olive oil-fed animals. Aging led to higher superoxide dismutase, catalase, and glutathione peroxidase activities and increased alpha-tocopherol and coenzyme Q. Mitochondria from aged animals fed sunflower oil exhibited a lower number of cristae and a higher circularity. Results suggest that the age-related increase of the relative amount of deleted mtDNA depends on fat unsaturation. Moreover, the studied mtDNA deletion was correlated with mitochondrial oxidative stress and ultrastructural alterations.

Characterization of two D-beta-hydroxybutyrate dehydrogenase populations in heavy and light mitochondria from jerboa (Jaculus orientalis) liver

Mitochondrial membrane-bound and phospholipid-dependent D-beta-hydroxybutyrate dehydrogenase (BDH) (EC 1.1.1.30), a ketone body converting enzyme in mitochondria, has been studied in two populations of mitochondria (heavy and light) of jerboa (Jaculus orientalis) liver. The results reveal significant differences between the BDH of the two mitochondrial populations in terms of protein expression, kinetic parameters and physico-chemical properties. These results suggest that the beta-hydroxybutyrate dehydrogenases from heavy and light mitochondria are isoform variants. These differences in BDH distribution could be the consequence of cell changes in the lipid composition of the inner mitochondrial membrane of heavy and light mitochondria. These changes could modify both BDH insertion and BDH lipid-dependent catalytic properties.

Acetate generation in rat liver mitochondria; acetyl-CoA hydrolase activity is demonstrated by 3-ketoacyl-CoA thiolase

Acetate has been found as an endogenous metabolite of beta-oxidation of fatty acids in liver. In order to investigate the regulation of acetate generation in liver mitochondria, we attempted to purify a mitochondrial acetyl-CoA hydrolase in rat liver. This acetyl-CoA-hydrolyzing activity in isolated mitochondria was induced by the treatment of rats with di(2-ehtylhexyl)phthalate (DEHP), a peroxisome proliferator which induces expression of several peroxisomal and mitochondrial enzymes involved in beta-oxidation of fatty acids. The purified enzyme was 43-kDa in molecular mass by SDS/PAGE. Internal amino acid sequencing of this enzyme revealed that it was identical with mitochondrial 3-ketoacyl-CoA thiolase, suggesting that this enzyme has two kinds of activities, 3-ketoacyl-CoA thiolase and acetyl-CoA hydrolase activities. Kinetic studies clearly indicated that this enzyme had the both activities and each activity was inhibited by the substrates of the other activity, that is, 3-ketoacyl-CoA thiolase activity was inhibited by acetyl-CoA, on the other hand, acetyl-CoA hydrolase activity was inhibited by acetoacetyl-CoA in a competitive manner. These findings suggested that acetate generation in liver mitochondria is a side reaction of this known enzyme, 3-ketoacyl-CoA thiolase, and this enzyme may regulate its activities depending on each substrate level.

Monounsaturated and omega-3 but not omega-6 polyunsaturated fatty acids improve hepatic fibrosis in hypercholesterolemic rabbits

OBJECTIVE

Although the influence of saturated fatty acids, monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), lipids, cholesterol levels, and other blood lipids has been established, few studies have examined the influence of these dietary lipids on the composition and histologic damage of organs in situations of hypercholesterolemia. Biliary lipids come from the liver, and this organ is essential in cholesterol homeostasis; thus, it may be helpful to evaluate the inter-relations among biliary, hepatic lipids, and hepatotoxic effects in situations of hypercholesterolemia with different dietary lipids. This study investigated whether administration of diets differing in fatty acid profiles (omega-3 PUFA, omega-6 PUFA, or MUFA) influence the content of biliary lipids, the lithogenic index of gallbladder bile, and the development of hepatic fibrosis in hypercholesterolemic rabbits.

METHODS

Thirty rabbits were randomized to one of five groups. A control group received rabbit chow for 80 d. The remaining four groups received a 50-d diet that contained 3% lard and 13% cholesterol to provoke hypercholesterolemia. After this period, three groups were fed for another 30 d on a diet enriched with omega-6 PUFAs, MUFAs, and omega-3 PUFAs, respectively. Liver, bile, and plasma lipid compositions, lipid peroxidation in hepatic mitochondria, and histologic hepatic lesions were analyzed.

RESULTS AND CONCLUSIONS

There was a beneficial effect of MUFA and omega-3 PUFA on hepatic fibrosis in hypercholesterolemic rabbits because both dietary fats led to recovery from hepatic lesions. However, because intake of omega-3 PUFA provoked lithogenic bile in rabbits, MUFA intake would be more advisable.

Coenzyme Q10 Protects From Aging-Related Oxidative Stress and Improves Mitochondrial Function in Heart of Rats Fed a Polyunsaturated Fatty Acid (PUFA)-Rich Diet

Coenzyme Q(10) supplementation on age-related changes in oxidative stress and function of heart mitochondria in rats fed a polyunsaturated fatty acid (PUFA)-rich diet was investigated. Two groups of rats were fed for 24 months on a PUFA-rich diet, differing in supplementation or not with coenzyme Q(10). Animals were killed at 6, 12, or 24 months. Fatty-acid profile, hydroperoxides, alpha-tocopherol, coenzyme Q, catalase and glutathione peroxidase activities, and cytochromes a+a(3), b, c+c(1) and cytochrome c oxidase activity were measured. Coenzyme Q(10)-supplemented animals showed lower hydroperoxide levels; higher content and/or activity of alpha-tocopherol, coenzyme Q, and catalase; and a slightly lower decrease in mitochondrial function. According to that, previously reported positive effects of coenzyme Q supplementation on the life span of rats fed a PUFA-rich diet might be a consequence, at least in part, of a lower oxidative stress level and perhaps, to a minor extent, of a smaller decrease in mitochondrial function.

Aging-related oxidative stress depends on dietary lipid source in rat postmitotic tissues

We investigate mitochondrial-lipid peroxidation of mitotic (liver) and postmitotic (heart and skeletal muscle) tissues of rats fed lifelong on two different lipid sources: virgin olive oil (monounsaturated fatty acids) and sunflower oil (n - 6 polyunsaturated fatty acids). Two groups of 80 rats each were fed over 24 months on a diet differing in the lipid source (virgin olive oil or sunflower oil). Twenty rats per group were killed at 6, 12, 18, and 24 months; liver, heart, and skeletal muscle mitochondria were isolated and the lipid profile, hydroperoxides, vitamin E, and ubiquinone as well as catalase activity measured. Lipid peroxidation was higher in postmitotic tissues, and sunflower oil led to a higher degree of polyunsaturation and peroxidation. The levels of alpha-tocopherol adapted to oxidative stress and preferentially accumulated during aging in heart and skeletal muscle. In conclusion, the type of dietary fat should be considered in studies on aging, since oxidative stress is directly modulated by this factor. This study confirms that postmitotic tissues are more prone to oxidative stress during aging and proposes a hypothesis to explain this phenomenon.

Coenzyme Q supplementation protects from age-related DNA double-strand breaks and increases lifespan in rats fed on a PUFA-rich diet

This study investigates the usefulness of a long-term supplementation with coenzyme Q(10) in rats from the point of view of lifespan, DNA double-strand breaks and to assess whether this supplementation might attenuate oxidative alterations related to PUFA-rich diets, which would allow to preserve beneficial aspects of PUFA on health avoiding their deleterious aspects. Supplemented animals showed higher concentration of coenzyme Q(10) in liver mitochondria, lower levels of DNA double-strand breaks in peripheral blood lymphocytes. Animals supplemented on coenzyme Q reached a significantly higher mean life span (11,7% higher, i.e. 2,5 months) and a significantly higher maximum life span (24% higher, i.e. 6 months) than non-supplemented animals. These results suggest that a long-term supplementation with a small dosage of coenzyme Q(10) might represent a good anti-aging therapy in rats fed on a PUFA-based diet.

Hibernation impact on the catalytic activities of the mitochondrial D-3-hydroxybutyrate dehydrogenase in liver and brain tissues of jerboa (Jaculus orientalis)

BACKGROUND

Jerboa (Jaculus orientalis) is a deep hibernating rodent native to subdesert highlands. During hibernation, a high level of ketone bodies i.e. acetoacetate (AcAc) and D-3-hydroxybutyrate (BOH) are produced in liver, which are used in brain as energetic fuel. These compounds are bioconverted by mitochondrial D-3-hydroxybutyrate dehydrogenase (BDH) E.C. 1.1.1.30. Here we report, the function and the expression of BDH in terms of catalytic activities, kinetic parameters, levels of protein and mRNA in both tissues i.e brain and liver, in relation to the hibernating process.

RESULTS

We found that: 1/ In euthemic jerboa the specific activity in liver is 2.4- and 6.4- fold higher than in brain, respectively for AcAc reduction and for BOH oxidation. The same differences were found in the hibernation state. 2/ In euthermic jerboa, the Michaelis constants, KM BOH and KM NAD+ are different in liver and in brain while KM AcAc, KM NADH and the dissociation constants, KD NAD+and KD NADH are similar. 3/ During prehibernating state, as compared to euthermic state, the liver BDH activity is reduced by half, while kinetic constants are strongly increased except KD NAD+. 4/ During hibernating state, BDH activity is significantly enhanced, moreover, kinetic constants (KM and KD) are strongly modified as compared to the euthermic state; i.e. KD NAD+ in liver and KM AcAc in brain decrease 5 and 3 times respectively, while KD NADH in brain strongly increases up to 5.6 fold. 5/ Both protein content and mRNA level of BDH remain unchanged during the cold adaptation process.

CONCLUSIONS

These results cumulatively explained and are consistent with the existence of two BDH enzymatic forms in the liver and the brain. The apoenzyme would be subjected to differential conformational folding depending on the hibernation state. This regulation could be a result of either post-translational modifications and/or a modification of the mitochondrial membrane state, taking into account that BDH activity is phospholipid-dependent.

Changed energy state and increased mitochondrial beta-oxidation rate in liver of rats associated with lowered proton electrochemical potential and stimulated uncoupling protein 2 (UCP-2) expression: evidence for peroxisome proliferator-activated receptor-alpha independent induction of UCP-2 expression

Lowering of plasma triglyceride levels by hypolipidemic agents is caused by a shift in the liver cellular metabolism, which become poised toward peroxisome proliferator-activated receptor (PPAR) alpha-regulated fatty acid catabolism in mitochondria. After dietary treatment of rats with the hypolipidemic, modified fatty acid, tetradecylthioacetic acid (TTA), the energy state parameters of the liver were altered at the tissue, cell, and mitochondrial levels. Thus, the hepatic phosphate potential, energy charge, and respiratory control coefficients were lowered, whereas rates of oxygen uptake, oxidation of pyridine nucleotide redox pairs, beta-oxidation, and ketogenesis were elevated. Moderate uncoupling of mitochondria from TTA-treated rats was confirmed, as the proton electrochemical potential (Delta(p)) was 15% lower than controls. The change affected the Delta(Psi) component only, leaving the (Delta)pH component unaltered, suggesting that TTA causes induction of electrogenic ion transport rather than electrophoretic fatty acid activity. TTA treatment induced expression of hepatic uncoupling protein 2 (UCP-2) in rats as well as in wild type and PPARalpha-deficient mice, accompanied by a decreased double bond index of the mitochondrial membrane lipids. However, changes of mitochondrial fatty acid composition did not seem to be related to the effects on mitochondrial energy conductance. As TTA activates PPARdelta, we discuss how this subtype might compensate for deficiency of PPARalpha. The overall changes recorded were moderate, making it likely that liver metabolism can maintain its function within the confines of its physiological regulatory framework where challenged by a hypolipemic agent such as TTA, as well as others.

Virgin olive and fish oils enhance the hepatic antioxidant defence system in atherosclerotic rabbits

BACKGROUND & AIMS

In this study we report the effects of sunflower, virgin olive and fish oils on the lipid profile and antioxidant defence system in liver mitochondria from rabbits with experimental atherosclerosis.

METHOD

An atherogenic control group were fed for 50 days on a diet containing 3% lard and 1.3% cholesterol. Four groups were fed for an additional period of 30 days with a diet enriched in different oils: sunflower oil, virgin olive oil, refined olive oil and fish oil. A control group was fed with a standard chow.

RESULTS

The atherogenic diet caused important changes in the hepatic mitochondria lipid profile and in the enzymatic and non-enzymatic antioxidant defence system accompanied with an increase in the content of hydroperoxides in liver mitochondria. The administration of virgin olive and fish oils showed a better profile in the antioxidant system as well as decrease in the content of hydroperoxides.

CONCLUSIONS

The intake of cholesterol- and lard-enriched diet leads to a high impairment in the hepatic antioxidant defence system. However, the replacement of that diet by other unsaturated fat-enriched diets using virgin olive, sunflower and fish oil enhances hepatic antioxidant defence system, virgin olive and fish oil diet provide the best results.

Dietary trans fatty acids alter the compositions of microsomes and mitochondria and the activities of microsome delta6-fatty acid desaturase and glucose-6-phosphatase in livers of pregnant rats

This study was designed to investigate the effects of three diets with different levels of trans fatty acids and the physiologic status on the physicochemical properties and enzymatic activities of liver microsomes and mitochondria. Three groups of 10 female weaning rats each were fed for 10 wk one of three diets differing in their trans fatty acid contents (Control, 0 mol/100 mol total fatty acids; high, 14.5 mol/100 mol; very high, 30 mol/100 mol). At the onset of adult life (10 wk of age), they were mated. Six rats in each group were killed at the end of gestation (Pregnant rat groups). The four remaining pregnant rats continued to receive their experimental diets until weaning of their litters. Six pups from the litters for each group (3 males and 3 females) were selected and fed the same experimental diet as the dams from wk 3 to 10 of age (2nd generation virgin groups) and then killed. Trans fatty acid levels in liver microsomes and mitochondria rose in parallel with the dietary trans fatty acid content, whereas saturated fatty acids dropped in both organelles with increasing trans fatty acids. Pregnant and 2nd generation adult rats fed trans isomers also had lower levels of cholesterol and a lower cholesterol/phosphorus ratio in their liver microsomes compared with controls. A significant interaction between diet and pregnancy was detected in the activities of delta6-desaturase and glucose-6-phosphatase in liver microsomes. Dietary trans fatty acids decreased the activities of both enzymes but only in pregnant rats. No differences in the fluorescence anisotropy of membranes or the enzymatic activities in liver mitochondria were observed. In conclusion, dietary trans fatty acids significantly lowered cholesterol and the cholesterol/phosphorus ratio in liver microsomes. This effect might contribute to low delta6-desaturase and glucose-6-phosphatase activities in liver microsomes of pregnant rats.

Ageing-related tissue-specific alterations in mitochondrial composition and function are modulated by dietary fat type in the rat

This study investigated the way in which feeding rats with two fat sources (olive or sunflower oils) affected electron-transport components and function of mitotic (liver) and postmitotic (heart and skeletal muscle) tissues during ageing. Rats adapted the mitochondrial-membrane-lipid profile to dietary fat throughout the study, suggesting that the benefits to eat either of the two fats might be maintained lifelong. Liver was more resistant to dietary changes and ageing than heart and skeletal muscle, which showed higher levels of coenzyme Q, cytochrome b, and cytochrome a + a3 with ageing and lower cytochrome c oxidase and complex IV turnover. Dietary fat differentially modulated the response of tissues during ageing, with sunflower oil leading to the highest levels of coenzyme Q and cytochromes b and a + a3. Since high levels of cytochrome b have been related to increased age, it could be hypothesized that olive oil could lead to less aged mitochondria.

Feeding fried oil changes antioxidant and fatty acid pattern of rat and affects rat liver mitochondrial respiratory chain components

Fat frying is a popular food preparation method but several components like antioxidant vitamins could be lost due to oxidation and some others with toxic effects could appear. Because of such large consumption of frying oils, the effect of high temperatures on the oils is of major concern both for product quality and nutrition, taking into account that dietary fat source deeply influences several biochemical parameters, especially of mitochondrial membranes. Virgin olive oil possesses specific features for modulating the damages occurred by endogenous and exogenous oxidative stress being particularly rich in antioxidant molecules. We evaluated the extent of modifications suffered by virgin olive oil following a short-time deep fat frying procedure: vitamin E and phenolic compound as well as total antioxidant capacity (measured by ESR) decreased, while polar compounds increased. The intake of such an altered oil mainly affected the hydroperoxide and TBARS contents of mitochondrial membranes which were enhanced after the dietary treatments. Also, several mitochondrial respiratory chain components (Coenzyme Q, cytochrome b, c + c1, and a + a3) were affected.

Mitochondrial glycerol phosphate acyltransferase contains two transmembrane domains with the active site in the N-terminal domain facing the cytosol

The topography of mitochondrial glycerol-3-phosphate acyltransferase (GPAT) was determined using rat liver mitochondria and mutagenized recombinant rat GPAT (828 aa (amino acids)) expressed in CHO cells. Hydrophobicity analysis of GPAT predicts two transmembrane domains (TMDs), residues 472-493 and 576-592. Residues 224-323 correspond to the active site of the enzyme, which is believed to lie on the cytosolic face of the outer mitochondrial membrane. Protease treatment of rat liver mitochondria revealed that GPAT has a membrane-protected segment of 14 kDa that could correspond to the mass of the two predicted TMDs plus a loop between aa 494 and 575. Recombinant GPAT constructs containing tagged epitopes were transiently expressed in Chinese hamster ovary cells and immunolocalized. Both the C and N termini epitope tags could be detected after selective permeabilization of only the plasma membrane, indicating that both termini face the cytosol. A 6-8-fold increase in GPAT-specific activity in the transfected cells confirmed correct protein folding and orientation. When the C terminus and loop-tagged GPAT construct was immunoassayed, the epitope at the C terminus could be detected when the plasma membrane was permeabilized, but loop-epitope accessibility required disruption of the outer mitochondrial membrane. Similar results were observed when GPAT was truncated before the second TMD, again consistent with an orientation in which the loop faces the mitochondrial intermembrane space. Although protease digestion of the HA-tagged loop resulted in preservation of a 14-kDa fragment, consistent with a membrane protected loop domain, neither the truncated nor loop-tagged enzymes conferred GPAT activity when overexpressed, suggesting that the loop plays a critical structural or regulatory role for GPAT function. Based on these data, we propose a GPAT topography model with two transmembrane domains in which both the N (aa 1-471) and C (aa 593-end) termini face the cytosol and a single loop (aa 494-575) faces the intermembrane space.

Acyl-CoA synthetase isoforms 1, 4, and 5 are present in different subcellular membranes in rat liver and can be inhibited independently

Inhibition studies have suggested that acyl-CoA synthetase (ACS, EC ) isoforms might regulate the use of acyl-CoAs by different metabolic pathways. In order to determine whether the subcellular locations differed for each of the three ACSs present in liver and whether these isoforms were regulated independently, non-cross-reacting peptide antibodies were raised against ACS1, ACS4, and ACS5. ACS1 was identified in endoplasmic reticulum, mitochondria-associated membrane (MAM), and cytosol, but not in mitochondria. ACS4 was present primarily in MAM, and the 76-kDa ACS5 protein was located in mitochondrial membrane. Consistent with these locations, N-ethylmaleimide, an inhibitor of ACS4, inhibited ACS activity 47% in MAM and 28% in endoplasmic reticulum. Troglitazone, a second ACS4 inhibitor, inhibited ACS activity <10% in microsomes and mitochondria and 45% in MAM. Triacsin C, a competitive inhibitor of both ACS1 and ACS4, inhibited ACS activity similarly in endoplasmic reticulum, MAM, and mitochondria, suggesting that a hitherto unidentified triacsin-sensitive ACS is present in mitochondria. ACS1, ACS4, and ACS5 were regulated independently by fasting and re-feeding. Fasting rats for 48 h resulted in a decrease in ACS4 protein, and an increase in ACS5. Re-feeding normal chow or a high sucrose diet for 24 h after a 48-h fast increased both ACS1 and ACS4 protein expression 1.5-2.0-fold, consistent with inhibition studies. These results suggest that ACS1 and ACS4 may be linked to triacylglycerol synthesis. Taken together, the data suggest that acyl-CoAs may be functionally channeled to specific metabolic pathways through different ACS isoforms in unique subcellular locations.

Dietary oils high in oleic acid, but with different non-glyceride contents, have different effects on lipid profiles and peroxidation in rabbit hepatic mitochondria

The influence on the lipid profile and lipid peroxidation in rabbit-liver mitochondria exerted by different edible oils high in oleic acid but different non-glyceride phenolic fractions was studied. High-phenolic virgin olive oil from the variety "Picual", the same oil submitted to an exhaustive process of washing to eliminate the phenolic fraction without altering the lipid profile and high-oleic sunflower oil (poor in phenolic compounds) were added to rabbit diets. The results reveal the importance of the different oleic: linoleic ratio of the lipid sources on the lipid profile of mitochondrial membranes. This is highlighted by the greater proportion of saturated fatty acids and the lower content in oleic acid (p < 0.05) shown by the rabbits fed on high-oleic sunflower oil. The group fed on the fat rich in phenolics exhibited the highest level of antioxidants (alpha-tocopherol, ubiquinone 10) and the highest activity of glutathione peroxidase as well as the lowest content in hydroperoxides and TBARS. The study provides evidences in vivo about the considerable antioxidant capacity of the phenolic fraction of virgin olive oil in rabbit-liver mitochondria and the important role that this non-glyceride fraction can play in the overall antioxidant benefits attributed to this oil.

Production of acetate in the liver and its utilization in peripheral tissues

In experimental rat liver perfusion we observed net production of free acetate accompanied by accelerated ketogenesis with long-chain fatty acids. Mitochondrial acetyl-CoA hydrolase, responsible for the production of free acetate, was found to be inhibited by the free form of CoA in a competitive manner and activated by reduced nicotinamide adenine dinucleotide (NADH). The conditions under which the ketogenesis was accelerated favored activation of the hydrolase by dropping free CoA and elevating NADH levels. Free acetate was barely metabolized in the liver because of low affinity, high K(m), of acetyl coenzyme A (acetyl-CoA) synthetase for acetate. Therefore, infused ethanol was oxidized only to acetate, which was entirely excreted into the perfusate. The acetyl-CoA synthetase in the heart mitochondria was much lower in K(m) than it was in the liver, thus the heart mitochondria was capable of oxidizing free acetate as fast as other respiratory substrates, such as succinate. These results indicate that rat liver produces free acetate as a byproduct of ketogenesis and may supply free acetate, as in the case of ketone bodies, to extrahepatic tissues as fuel.

Dietary fat type and regular exercise affect mitochondrial composition and function depending on specific tissue in the rat

Physical exercise and fatty acids have been studied in relation to mitochondrial composition and function in rat liver, heart, and skeletal muscle. Male rats were divided into two groups according to dietary fat type (virgin olive and sunflower oils). One-half of the animals from each group were subjected to a submaximal exercise for 8 weeks; the other half acted as sedentary controls. Coenzyme Q, cytochromes b, c + c1, a + a3 concentrations, and the activity of cytochrome c oxidase were determined. Regular exercise increased (P < 0.05) the concentration of the above-mentioned elements and the activity of the cytochrome c oxidase by roughly 50% in liver and skeletal muscle. In contrast, physical exercise decreased (P < 0.05) cytochrome c oxidase activity in the heart (in micromol/min/g, from 8.4+/-0.1 to 4.9+/-0.1 in virgin olive oil group and from 9.7+/-0.1 to 6.7+/-0.2 in sunflower oil animals). Dietary fat type raised the levels of coenzyme Q, cytochromes, and cytochrome c oxidase activity in skeletal muscle (P < 0.05) among the rats fed sunflower oil. In conclusion, dietary fat type, regular exercise, and the specific tissue modulate composition and function of rat mitochondria.

Virgin olive oil and coenzyme Q10 protect heart mitochondria from peroxidative damage during aging

The mitochondrial theory of aging suggests that this phenomenon is the consequence of random somatic mutations in mitochondrial DNA, induced by long-term exposure to free radical attack. There are two potential dietary means of delaying the effects of free radicals on cellular aging, i.e., enrichment of mitochondrial membranes with monounsaturated fatty acids and supplementation with antioxidants. We have performed a preliminary study on male rats, 6 or 12 month old, fed with diets differing in the nature of the fat (virgin olive oil or sunflower oil) and/or with antioxidant supplementation (coenzyme Q10), analysing hydroperoxide and coenzyme Q9 and Q10 in heart mitochondria. Preliminary results allow us to conclude that the CoQ10 dietetic supplementation as well as the enrichment of the cellular membranes with monounsaturated fatty acids, successfully protect mitochondrial membranes from aged rats against the free radical insult.

Olive oil supplemented with vitamin E affects mitochondrial coenzyme Q levels in liver of rats after an oxidative stress induced by adriamycin

In this study we have evaluated the supplementation of olive oil with vitamin E on coenzyme Q concentration and lipid peroxidation in rat liver mitochondrial membranes. Four groups of rats were fed on virgin olive, olive plus 200 mg/kg of vitamin E or sunflower oils as lipid dietary source. To provoke an oxidative stress rats were administered intraperitoneally 10 mg/kg/day of adriamycin the last two days of the experiment. Animals fed on olive oil plus vitamin E had significantly higher coenzyme Q and vitamin E levels but a lower mitochondrial hydroperoxide concentration than rats fed on olive oil. Retinol levels were not affected, by either different diets or adriamycin treatment. In conclusion, an increase in coenzyme Q and alpha-tocopherol in these membranes can be a basis for protection against oxidation and improvement in antioxidant capacity.

Tissue specific interactions of exercise, dietary fatty acids, and vitamin E in lipid peroxidation

Both physical exercise and ingestion of polyunsaturated fatty acids that play an essential role in free radical-mediated damages cause lipid peroxidation. The intake of specific fatty acids can modulate the membrane susceptibility to lipid peroxidation. Data confirmed that liver, skeletal muscle, and heart have different capabilities to adapt their membrane composition to dietary fatty acids, the heart being the most resistant to changes. Such specificity affects membrane hydroperoxide levels that depend on the type of dietary fats and the rate of fatty acid incorporation into the membrane. Sedentary rats fed a monounsaturated fatty acid-rich diet (virgin olive oil) showed a higher protection of their mitochondrial membranes against peroxidation than sedentary rats fed a polyunsaturated fatty acid-rich diet (sunflower oil). Rats subjected to training showed higher hydroperoxide contents than sedentary animals, and exhaustive effort enhanced the aforementioned results as well as in vitro peroxidation with a free radical inducer. This study suggests that peroxide levels first depend on tissue, then on diet and lastly on exercise, both in liver and muscle but not in heart. Finally, it appears that alpha-tocopherol is a less relevant protective agent against lipid peroxidation than monounsaturated fatty acids.

Plasma antioxidants are strongly affected by iron-induced lipid peroxidation in rats subjected to physical exercise and different dietary fats

Plasma is an important vehicle through which antioxidant molecules are conveyed and in which they may show different behaviors, either acting as a protective factor for oxidative damage to different blood elements or using it as a vehicle through which dietary antioxidant factors would be distributed to the body. The aim of the study was to determine the plasma level of vitamin E, coenzyme Q, uric acid and vitamin A and their relation with the cellular oxidative damage mediated by physical training and the ingestion of different fat (virgin olive and sunflower oils). Male Wistar rats were divided into 8 subgroups based on the dietary fat intake and their physical activity. Results show that both dietary fat and physical training affect susceptibility to iron-induced lipid peroxidation in plasma and the tissues that were studied. The increase of this lipid peroxidation parallels a decrease of the level of all the plasma antioxidants that were studied.

An ethanolic-aqueous extract of Curcuma longa decreases the susceptibility of liver microsomes and mitochondria to lipid peroxidation in atherosclerotic rabbits

Atherosclerosis is characterized by oxidative damage which affects lipoproteins, the walls of blood vessels and subcellular membranes. This study evaluates the antioxidant capacity of a Curcuma longa extract on the lipid peroxidation of liver mitochondria and microsome membranes in atherosclerotic rabbits. Male rabbits fed a 3% (w/w) lard and 1.3% (w/w) cholesterol diet were randomly assigned to three groups. Two groups were treated with different dosages of a turmeric extract (A and B) and the third group (control) with a curcumin-free solution. Basal and in vitro 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced hydroperoxide and TBARS productions in liver mitochondria and microsomes were analyzed. Group A had the lowest concentration of mitochondrial hydroperoxides. In microsomes, the basal hydroperoxide levels were similar in all groups but, after the induction of oxidation, group C registered the highest value; TBARS production followed the same trend in mitochondria. These findings suggest that active compounds in curcuma extract may be protective in preventing lipoperoxidation of subcellular membranes in a dosage-dependent manner.

Catalytic enzyme histochemistry and biochemical analysis of dihydroorotate dehydrogenase/oxidase and succinate dehydrogenase in mammalian tissues, cells and mitochondria

Dihydroorotate dehydrogenase (EC 1.3.3.1 or EC 1.3.99.11) catalyzes the fourth sequential step in the de novo synthesis of uridine monophosphate. In eukaryotes it is located in the inner mitochondrial membrane, with ubiquinone as the proximal and cytochrome oxidase as the ultimate electron transfer system, whereas the rest of pyrimidine biosynthesis takes place in the cytosol. Here, the distribution of dihydroorotate dehydrogenase activity in cryostat sections of various rat tissues, and tissue samples of human skin and kidney, was visualized by light microscopy using the nitroblue tetrazolium technique. In addition, a hydrogen peroxide-producing oxidase side-reactivity of dihydroorotate dehydrogenase could be visualized by trapping the peroxide with cerium-diaminobenzidine. The pattern of activity was similar to that of succinate dehydrogenase, but revealed a less intensive staining. High activities of dihydroorotate dehydrogenase were found in tissues with known proliferative, regenerative, absorptive or excretory activities, e.g., mucosal cells of the ileum and colon crypts in the gastrointestinal tract, cultured Ehrlich ascites tumor cells, and proximal tubules of the kidney cortex, whilst lower activities were present in the periportal area of the liver, testis and spermatozoa, prostate and other glands, and skeletal muscle. Dihydroorotate dehydrogenase and succinate dehydrogenase activity in Ehrlich ascites tumor cells grown in suspension culture were quantified by application of nitroblue tetrazolium or cyanotolyl tetrazolium and subsequent extraction of the insoluble formazans with organic solvents. The ratio of dihydroorotate dehydrogenase to succinate dehydrogenase activity was 1:4. This was in accordance with that of 1:5 obtained from oxygen consumption measurement of isolated mitochondria on addition of dihydroorotate or succinate. The ratio determined with mitochondria from animal tissues was up to 1:15 (rat liver, bovine heart). The application of the enzyme inhibitors brequinar sodium and toltrazuril verified the specificity of the histochemical and biochemical methods applied.

Potential mechanism of cadmium-induced cytotoxicity in rat hepatocytes: inhibitory action of cadmium on mitochondrial respiratory activity

The present study was designed to clarify the mechanism of cadmium (Cd)-induced toxicity in rat hepatocytes. Cd and Mg-ATP induced cellular acidification at concentrations lower than 25 microM. In Mg-ATP-treated cells, maximal acidification occurred within 2.5 min, with a subsequent return to control levels. In Cd-treated cells, maximal acidification (pH 6.76) occurred 10 min after exposure to the metal, then the cytoplasmic pH began to rise but did not return to normal. Cd eliminated the membrane potential of isolated mitochondria in media at both pH 6.5 and 7.4. This effect of Cd on membrane potential was approximately equivalent in both media when the metal concentration was 5 microM, but was more intense in the medium at pH 6.5 than in the medium at pH 7.4 at the metal concentration > 5 microM. Acidic medium alone had no effect on membrane potential. Mitochondrial uptake of Cd increased in a dose-dependent manner in media at both pH 7.4 and 6.5. The uptake of 5 microM Cd was significantly increased by acidic medium, however at Cd concentrations > 5 microM, there were no pH-dependent differences in Cd uptake. The incubation of hepatocytes in the medium at pH 6.0 and 6.5 resulted in 5 and 7.5% inhibition of mitochondrial respiration in intact cells, respectively. The presence of 10 microM Cd in the medium at pH 6.0 enhanced this inhibition. Mitochondrial respiration was inhibited to 60% of the control mitochondria at pH 7.4 when exposed to the medium at pH 6.5 without Cd and this inhibition was extended to 70% by the presence of 5 microM Cd. Cd in the medium at pH 7.4 had no deleterious effect on mitochondrial respiration at all concentrations examined. The results indicate that the respiratory activity of mitochondria is sensitive to the low pH rather than to Cd although the metal strongly inhibits the activity when in the medium at low pH. Therefore, it appears Cd-induced acidification plays an important role in the initiation of deteriorative processes in mitochondria.

Peroxidative extent and coenzyme Q levels in the rat: influence of physical training and dietary fats

Sport practice is widely recognized as capable of producing peroxidative damages, even of severe intensity. Dietary manipulations can also modify membrane susceptibility to peroxidation. In previous experiments we found that, while dietary virgin olive oil successfully protects mitochondrial and microsomal membranes from endogenous, xenobiotics-induced peroxidation, dietary polyunsaturated oils lead to increased peroxidative levels. In the latter conditions, cell machinery tries to counteract the structural and functional changes which have occurred, by modulating enzyme activities and concentrations, by increasing biosynthesis of coenzyme Q and by mobilizing cholesterol. In the present study we hypothesized that combining these two aspects could give useful information on the membrane response to peroxidation phenomena that daily occur throughout the lifespan. Rats fed different dietary oils as only fat source underwent a carefully designed training program and were killed at different times following acute or chronic exercise. Results show that peroxidation related to chronic training and to an acute bout of exercise sum up with peroxidative effects induced by dietary factors. The above mentioned phenomena occurred simultaneously with increased tissue levels of coenzyme Q, possibly triggered within a physiological reactive antioxidant strategy.

Mitochondrial and microsomal cholesterol mobilization after oxidative stress induced by adriamycin in rats fed with dietary olive and corn oil

The influence of three different dietary fats (8%) and of endogenous lipid peroxidation with regard to cholesterol concentrations in liver mitochondria and microsomes and in serum has been investigated in the rat. Although the different diet fat used did not produce any effect on serum cholesterol, it was possible to show that each experimental diet differently influenced the microsomal and mitochondrial levels of cholesterol. The highest mitochondrial and microsomal cholesterol content was found in case of diet supplemented with virgin olive oil and the lowest with rectified olive oil. An endogenous oxidative stress induced by adriamycin was able to produce a clear decrease in microsomal and mitochondrial cholesterol level and a sharp increase in serum concentration in all three groups. However, dietary fats and adriamycin had no effect on the microsomal and mitochondrial membrane viscosity as detected by fluorescence polarization. These results are consistent with the hypothesis that mitochondrial and microsomal cholesterol can exchange with exogenous pools when phospholipid peroxidation occurs.

Cytochrome oxidase induction after oxidative stress induced by adriamycin in liver of rats fed with dietary olive oil

The influence of different kinds of dietary fat (8%) and of endogenous lipid peroxidation with regard to cytochrome c oxidase activity and cytochrome a + a3 concentrations in mitochondria from rat liver has been investigated. It was possible to confirm that the dietary fat induced higher phospholipid degradation in mitochondrial membranes; moreover an endogenous oxidative stress induced by adriamycin was able to increase the peroxidative effects. We have found that the peroxidative effects could sometimes induce an apparent enhancement of cytochrome oxidase activity due to a significant increase of cytochrome a + a3 content. This finding lets us suppose that both changes in the lipid environment and some peroxidation damage could occur in the membrane as a consequence of the fat assumed. Furthermore we should suggest that an induction of the synthesis of cytochrome a + a3 might be related to an enhanced production of peroxides at membrane level.

Changes in mitochondrial and microsomal rat liver coenzyme Q9 and Q10 content induced by dietary fat and endogenous lipid peroxidation

The influence of different kinds of dietary fat (8%) and of endogenous lipid peroxidation with regard to coenzyme Q9 (CoQ9) and coenzyme Q10 (CoQ10) concentrations in mitochondria and microsomes from rat liver has been investigated by means of an HPLC technique. Although the different diet fats used did not produce any effect on microsomes, it was possible to show that each experimental diet differently influenced the mitochondrial levels of CoQ9 and CoQ10. The highest mitochondrial CoQ content was found in case of a diet supplemented with corn oil. An endogenous oxidative stress induced by adriamycin was able to produce a sharp decrease in mitochondrial CoQ9 levels in the rats to which corn oil was administered. The results suggest that dietary fat ought to be considered when studies concerning CoQ mitochondrial levels are carried out.

Interactions of the mitochondrial membrane rat liver D-3-hydroxybutyrate dehydrogenase with glass beads during adsorption chromatography. Relationships with the activation of the enzyme by phospholipids

D-3-Hydroxybutyrate dehydrogenase (BDH) is an NAD(+)-dependent dehydrogenase of the mitochondrial inner membrane involved in the energetic balance between the liver and peripheral organs in mammals. It allows the conversion of ketone bodies (acetoacetate and D-3-hydroxybutyrate) and it is one of the best documented lipid-requiring enzymes with a dependence on lecithins. After release of proteins from the membrane by phospholipase A2 treatment of salt-treated mitochondria, the rat liver enzyme is absorbed on controlled-pore glass beads. After batch washing, the enzyme, devoid of lipids (apoBDH), is specifically eluted at pH 8.05-8.15 with a 0.1 M Tris-1 M LiBr buffer under reducing conditions (5 mM dithiothreitol). It appears that during BDH absorption, the glass beads mimic the phospholipid surface of biomembranes.

Natural distribution and occurrence of coenzyme Q homologues

The knowledge of coenzyme Q levels in tissues, organs, and subcellular compartments is of outstanding interest. A wide amount of data regarding coenzyme Q distribution and occurrence was collected in the last decades; nevertheless the data are often hard to compare because of the different extraction methods and different analytical techniques used. We have undertaken a systematic study for detecting the ubiquinone content in subcellular compartments, cells, and whole-tissue homogenates by a previously standardized HPLC method performed after an extraction procedure identical for all samples. It was confirmed that the major coenzyme Q homologue in rat tissues is coenzyme Q9; however, it was pointed out that all the rodents samples tested contain more than one coenzyme Q homologue. The coenzyme Q homologue distribution is tissue dependent with relatively high coenzyme Q10 content in brain mitochondria, irrespective of the rat strain used. There is no constant relationship of the coenzyme Q content in mitochondria and microsomes fractions. Most organisms tested (including other mammals, bird and fish specimens) have only coenzyme Q10, while the protozoan Tetrahymena pyriformis contains only coenzyme Q8.

Studies on the role of ubiquinone in the control of the mitochondrial respiratory chain

This study examines the possible role of Coenzyme Q (CoQ, ubiquinone) in the control of mitochondrial electron transfer. The CoQ concentration in mitochondria from different tissues was investigated by HPLC. By analyzing the rates of electron transfer as a function of total CoQ concentration, it was calculated that, at physiological CoQ concentration NADH cytochrome c reductase activity is not saturated. Values for theoretical Vmax could not be reached experimentally for NADH oxidation, because of the limited miscibility of CoQ10 with the phospholipids. On the other hand, it was found that CoQ3 could stimulate alpha-glycerophosphate cytochrome c reductase over three-fold. Electron transfer being a diffusion-coupled process, we have investigated the possibility of its being subjected to diffusion control. A reconstruction study of Complex I and Complex III in liposomes showed that NADH cytochrome c reductase was not affected by changing the average distance between complexes by varying the protein: lipid ratios. The results of a broad investigation on ubiquinol cytochrome c reductase in bovine heart submitochondrial particles indicated that the enzymic rate is not diffusion-controlled by ubiquinol, whereas the interaction of cytochrome c with the enzyme is clearly diffusion-limited.

Effects of chromium(VI) and chromium(III) on energy charge and oxygen consumption in rat thymocytes

The cytotoxic effects of chromium compounds in two oxidation states have been studied in rat thymocytes. endogenous nucleotide levels and oxygen consumption were examined as relevant parameters of the physiological state of the cell. Incubation of rat thymocytes with Cr(VI) produced a marked unbalance of endogenous purine nucleotide pool and a parallel decrease in oxygen consumption. A close correlation between the reduction of oxygen consumption and ATP level in rat thymocytes treated with increasing concentrations of Cr(VI) has been found. In rat thymocytes permeabilized with digitonin and in isolated rat liver mitochondria both Cr(VI) and Cr(III) showed, at different range of concentrations, a marked inhibition of maximal oxygen consumption rate (uncoupled respiration). The effects observed were depending on chromium oxidation state and on different mitochondrial sites of substrate oxidation.

Inhibitory effect of glucose on the maturation of rat liver mitochondria at birth. Phospholipid and oxidative metabolism

(1) The rate of ATP synthesis coupled with succinate oxidation in rat liver mitochondria is low at birth and increases rapidly during the first postnatal hours (Nakazawa, T., Asami, K., Suzuki, H. and Yakawa, O. (1973) J. Biochem. 73, 397-406). A glucose injection given to newborn rats immediately after birth seemed to delay this maturation process. (2) Glucose administration specifically diminished the rate of 32Pi incorporation into phosphatidylcholine both in microsomes and in mitochondria while other phospholipids remained unaffected. (3) In newborn rat liver, 32Pi incorporation into phospholipids can be explained by de novo synthesis of phospholipids in microsomes followed by transfer to mitochondria with two exceptions phosphatidylserine and sphingomyelin. Indeed, after a 20-min incorporation of 32Pi into phospholipids, the specific radioactivity of phosphatidylserine and sphingomyelin was higher in mitochondria than in microsomes. (4) As far as phospholipid synthesis is concerned, no precursor-product relationship could be observed between light and heavy mitochondria.