Biomedical subjects

G Dallner

Publications and source records attributed to G Dallner.

At least 19 recordsLinked to original sources

PubMed2000

Quinone-responsive multiple respiratory-chain dysfunction due to widespread coenzyme Q10 deficiency.

BACKGROUND: The respiratory-chain deficiencies are a broad group of largely untreatable diseases. Among them, coenzyme Q10 (ubiquinone) deficiency constitutes a subclass that deserves early and accurate diagnosis. METHODS: We assessed respiratory-chain function in two siblings with severe encephalomyopathy and renal failure. We used high-performance liquid chromatography analyses, combined with radiolabelling experiments, to quantify cellular coenzyme Q10 content. Clinical follow-up and detailed biochemical investigations of respiratory chain activity were carried out over the 3 years of oral quinone administration. FINDINGS: Deficiency of coenzyme Q10-dependent respiratory-chain activities was identified in muscle biopsy, circulating lymphocytes, and cultured skin fibroblasts. Undetectable coenzyme Q10 and results of radiolabelling experiments in cultured fibroblasts supported the diagnosis of widespread coenzyme Q10 deficiency. Stimulation of respiration and fibroblast enzyme activities by exogenous quinones in vitro prompted us to treat the patients with oral ubidecarenone (5 mg/kg daily), which resulted in a substantial improvement of their condition over 3 years of therapy. INTERPRETATION: Particular attention should be paid to multiple quinone-responsive respiratory-chain enzyme deficiency because this rare disorder can be successfully treated by oral ubidecarenone.

Administration, Oral↗

PubMed2000

Half-life of ubiquinone and plastoquinone in spinach cells.

The half-life of plastoquinone (PQ), ubiquinone-9 (UQ-9) and ubiquinone-10 (UQ-10) in spinach tissue was determined. This was achieved by monitoring the decay of radioactivity incorporated into these lipids from a labeled precursor. The half-life of PQ was 15 h while for UQ-9 and UQ-10 it was longer, i.e. 30 h. The values of half-lives of PQ and UQ suggest a high rate of turnover of these lipids in spinach cells.

Journal Article↗

PubMed2000

Effect of long term fluoride exposure on lipid composition in rat liver.

Chronic fluorosis can severely damage many systems of human body, but its pathogenesis is unclear. Normal composition and structure of cellular membrane lipids are a basic factor to maintain cell function. In this investigation, cellular membrane lipids of the liver were analysed after a long term fluoride treatment for rats and the results are discussed in order to give an explanation for the pathogenesis of this disease. Wistar rats were supplied with drinking water containing either 30 or 100 ppm fluoride (NaF) for seven months. Contents of phospholipid and neutral lipid in rat liver were analyzed by high-performance liquid chromatography, and fatty acid composition from individual phospholipids was measured by gas chromatography. Results showed that the total liver phospholipid content decreased in the rats treated with high dose of fluoride due to a lower content of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and phosphatidylserine (PS). Among the fatty acid compositions of PE and PC in the livers of fluoride poisoned animals, the proportion of polyunsaturated fatty acids (20:4 and 22:6) decreased, whereas saturated fatty acids (16:0 and 18:0) increased. No changes could be detected in the amounts of liver cholesterol and dolichol. Total ubiquinone contents in rat liver were reduced by 11% in the group treated with 30 ppm fluoride and by 42% in the group treated with 100 ppm fluoride. In the subclasses of ubiquinone, both ubiquinone-9 and ubiquinoine-10 amounts decreased after fluoride treatment. These modifications of membrane lipids might be induced by oxidative stress, which might be an important factor in the pathogenesis of chronic fluorosis.

Animals↗

PubMed2000

Influence of peroxisome proliferator-activated receptor alpha on ubiquinone biosynthesis.

The control of ubiquinone biosynthesis by peroxisome proliferators was investigated using peroxisome proliferator activated receptor alpha (PPARalpha)-null mice. Administration of 2-(diethylhexyl)phthalate to control mice resulted in elevated ubiquinone levels in the liver, while dolichol, dolichyl-P and cholesterol concentrations remained unchanged. In PPARalpha-null mice, the level of these lipids were similar to control levels and administration of the peroxisome proliferator did not increase the levels of ubiquinone. The increase in ubiquinone levels was the result of increased synthesis. Induction was most pronounced in liver, kidney and heart, which have relatively high levels of PPARalpha. When the tissue concentration of hydrogen peroxide was elevated by inhibition of catalase activity with aminotriazole, the amount of ubiquinone was not increased, suggesting that the induction of ubiquinone synthesis occured through a direct mechanism. The activities of branch-point enzymes FPP-synthase, squalene synthase, cis-prenyltransferase, trans-prenyltransferase and NPHB-transferase were substantially increased in control but not in PPARalpha-null mice after treatment with peroxisome proliferators. These data suggest that the induction of ubiquinone biosynthesis after administration of peroxisome proliferators is dependent on the PPARalpha through regulation of some of the mevalonate pathway enzymes.

Alkyl and Aryl Transferases↗

PubMed2000

Subcellular localization of plastoquinone and ubiquinone synthesis in spinach cells.

In vivo labeling of spinach etiolated leaves with [(3)H]mevalonate followed by rapid cell fractionation procedure showed that ER-Golgi membranes are involved in transport of plastoquinone (PQ) and ubiquinone (UQ) to plastids and mitochondria, respectively. Translocation of these lipids was inhibited by agents which affect protein and lipid intracellular transport causing structural and functional disintegration of the ER-Golgi system (monensin, brefeldin) and interfere with mitochondrial energy conservation (carbonyl cyanide m-chlorophenylhydrazone), but was not affected by colchicine which influences the organization of the cytoskeletal network. Colchicine treatment resulted in marked stimulation of PQ and UQ synthesis. Results of experiments with pre-exposure of etiolated seedlings to light suggest that translocation processes are dependent on the plastid developmental state and their capacity as acceptors of PQ. Thus, the experiments indicate that biosynthesis and transport of PQ and UQ involve multiple cellular compartments and that kinetics of the transport process is dependent on the actual physiological conditions.

Biological Transport, Active↗

PubMed1999

Protein prenylation in spinach chloroplasts.

Protein prenylation in plants was studied by in vivo metabolic (3)H-mevalonate labeling in combination with a range of protein synthesis inhibitors. In spinach cotyledons, this posttranslational protein modification was found to be divided into two categories, one representing the conventional prenylation involving farnesyl and geranylgeranyl groups bound to cysteine residues via thioether linkages. This category revealed a similar pattern of prenylated proteins to that observed in mammalian cells and depends on nuclear gene expression. The other category was shown to represent a type of prenylation confined to chloroplasts. It depends on plastid gene expression and does not involve a thioether bond. The modifying isoprenoid could be released from the chloroplastic polypeptides by alkaline treatment and was identified as phytol upon GC-MS analysis. The phytol could readily be derived from all-trans-[(3)H]farnesol, which, like all-trans-[(3)H]geranylgeraniol, was taken up by the cotyledons, resulting in incorporation of radiolabel into proteins.

Animals↗

PubMed1999

In vivo prenylation of rat proteins: modification of proteins with penta- and hexaprenyl groups.

In vivo protein prenylation was studied in newborn rats by repeated injections of [3H]mevalonate. The highest level of protein-bound mevalonate metabolites was found in the kidney, but incorporation was observed in all organs studied. After fluorography of SDS-polyacrylamide gel electrophoresis-separated polypeptides, labeling was found in the 21- to 28-kDa molecular mass region and, after prolonged exposure of the film, additional bands at both higher and lower molecular masses could be detected. Protein prenylation in the kidney increased during the first 5 days after birth, whereas that in the liver reached a maximum on the fourth day. After methyliodide treatment of the prenylated proteins, farnesol, geranylgeraniol, and two larger isoprenoids, pentaprenol and hexaprenol, were released. In the liver, the ratio of protein-bound geranylgeraniol to farnesol increased from 2 to 4.5 during the first 5 days after birth. Upon subfractionation of the kidney, the highest level of labeling was found in mitochondria and microsomes. When the mitochondria were subfractionated into outer membranes, intermembrane space and an inner membrane/matrix fraction, the labeling pattern of prenylated polypeptides differed in all fractions. The results demonstrate that in vivo labeling of rats can be performed to study the extent, type, and distribution of protein prenylation.

Animals↗

PubMed1999

Induction of endogenous coenzyme Q biosynthesis by administration of peroxisomal inducers.

A large number of chemical compounds have been identified which cause peroxisomal proliferation and induce a number of enzymes, mainly those participating in lipid metabolism. Administration of these drugs/chemicals to rats increased coenzyme Q levels in the blood and most of the organs. Levels were raised in all cellular membranes of such organs. The extent of induction of this lipid was 8-fold in young animals but decreased during aging and was absent at 1.5 year of age. One of the regulating factors of the mevalonate pathway is farnesol, which is produced by dephosphorylation of farnesyl-PP and eliminated by phosphorylation including two kinases. Future research will involve a search for modified intermediary metabolites, which increase coenzyme Q synthesis and thereby efficiently elevate the level of this lipid in conditions of deficiency.

Aging↗

PubMed1999

The protective role of plasmalogens in iron-induced lipid peroxidation.

The role of plasmalogens in iron-induced lipid peroxidation was investigated in two liposomal systems. The first consisted of total brain phospholipids with and without plasmalogens, and the second of phosphatidylethanolamine/phosphatidylcholine liposomes with either diacyl- or alkenylacyl-phosphatidylethanolamine. By measuring thiobarbituric acid reactive substances, oxygen consumption, fatty acids and aldehydes, we show that plasmalogens effectively protect polyunsaturated fatty acids from oxidative damage, and that the vinyl ether function of plasmalogens is consumed simultaneously. Furthermore, the lack of lag phase, the increased antioxidant efficiency with time, and the experiments with lipid- and water-soluble azo compounds, indicate that plasmalogens probably interfere with the propagation rather than the initiation of lipid peroxidation, and that the antioxidative effect cannot be related to iron chelation.

Azo Compounds↗

PubMed1999

Blood concentration of coenzyme Q(10) increases in rats when esterified forms are administered.

Coenzyme Q levels decrease during aging in most tissues and in the target organs of a number of diseases. The uptake of this lipid into the blood and other tissues was investigated in 6-wk-old male Sprague-Dawley rats after 3 wk of dietary supplementation. In addition to the natural form of coenzyme Q(10), acetylated and succinylated forms were also administered. Coenzyme Q(10) was taken up into the blood, but uptake was significantly greater in rats given the succinylated ( approximately 40%), and particularly, the acetylated forms ( approximately 70%). All three forms increased significantly the total coenzyme Q concentration in both the liver ( approximately 100%) and spleen ( approximately 130%). Coenzyme Q(10) and its esterified forms were not taken up into kidney, heart, muscle or brain. Intraportal and intraperitoneal administration of succinylated coenzyme Q(10) gave results similar to those obtained in the dietary experiments. Uptake of the dietary coenzyme Q(10) into the liver and spleen did not down-regulate the endogenous synthesis, i.e., the amounts of isolated coenzyme Q(9) did not change in these tissues. Thus, esterification of coenzyme Q increases the uptake of dietary lipid into the blood; however, the derivatization does not contribute to the elevation of coenzyme Q levels in various organs.

Acetylation↗

PubMed1999

Decrease and structural modifications of phosphatidylethanolamine plasmalogen in the brain with Alzheimer disease.

Several lipid modifications, some of which were attributed to oxidative stress, have been reported in the brains of patients with Alzheimer disease (AD). To evaluate this possibility, all phospholipids and their ether subclasses from the frontal cortex, hippocampus, and the white matter of AD brain were analyzed by high performance liquid chromatography and gas chromatography. The total phospholipid in the frontal cortex and hippocampus decreased on a DNA basis by about 20% and this change was essentially explained by a selective decrease in phosphatidylethanolamine and phosphatidylcholine. The lower content of phosphatidylethanolamine was due to a specific decrease in the plasmalogen subclass. Phosphatidylethanolamine plasmalogen was also the only lipid exhibiting major structural modifications: a significant decrease in polyunsaturated fatty acids and oleic acid as well as a shift of the aldehyde pattern from 18:1 to 18:0. The only modification observed in the other phospholipids was a decrease in oleic acid in diacyl-phosphatidylethanolamine and diacyl-phosphatidylcholine. None of these changes were observed in the white matter. Both the vinyl ether bond of phosphatidylethanolamine plasmalogen and polyunsaturated fatty acids are major targets in oxidative stress; thus, these specific lipid modifications strongly support the involvement of free radicals in the pathogenesis of AD.

Aged↗

PubMed1999

Synthesis of mevalonate pathway lipids in fibroblasts from Zellweger and X-linked ALD patients.

Fibroblasts were cultured to determine the involvement of peroxisomes in cholesterol and dolichol synthesis. For this purpose, the behavior of cells from patients with Zellweger syndrome, with X-linked adrenoleukodystrophy, and from nondiseased control subjects was studied. Cells both after pretreatment with mevinolin and without pretreatment were incubated in a medium containing [3H]-mevalonate. In fibroblasts from patients with peroxisomal defects, the cholesterol content and mevalonate incorporation into cholesterol were decreased by 10-20% in comparison with control cells. Mevinolin pretreatment decreased the incorporation rate of [3H]-mevalonate into cholesterol but increased the labeling of ubiquinone and dolichol both in diseased and control cells. Squalene synthase activity was unchanged, whereas the activity of farnesyl-pyrophosphate synthase was increased in the diseased states. The results show that in patients with peroxisomal deficiency neither the amount nor the rate of synthesis of cholesterol and dolichol is reduced to any greater extent.

Adrenoleukodystrophy↗

PubMed1998

Elevation of ubiquinone content by peroxisomal inducers in rat liver during aging.

The effect of di(2-ethylhexyl)phthalate (DEHP) on the induction of peroxisomes and the content of ubiquinone in the liver was studied in rats between 25 and 496 days of age. During this period, peroxisomal beta-oxidation of fatty acids was greatly decreased but it could be induced many-fold in all ages. The ubiquinone (UQ) content was increased upon induction 6-fold in the first weeks of life, but the extent of this elevation continuously narrowed and no induction could be observed in the oldest animals, even after prolonged treatment with the plasticizer. In contrast, the treatment decreased the amount of liver cholesterol in all age groups. Treatment with this peroxisomal inducer increased the biosynthesis of UQ while the breakdown rate was found to be unaffected, as the half-life of this lipid was 103 and 106 h in control and treated rats, respectively. These results indicate that treatment with peroxisomal inducers increases the liver UQ content by increasing the rate of biosynthesis and that this effect is not apparent in aged rats.

Aging↗

PubMed1998

Alterations in the biosynthesis of cholesterol, dolichol and dolichyl-P in the genetic cholesterol homeostasis disorder, Niemann-Pick type C disease.

The biosynthesis of cholesterol, dolichol and dolichyl-P were investigated in a murine model of Niemann-Pick type C disease using both in vitro and in vivo systems. In vivo incorporation of [3H]mevalonate into squalene, dolichol and dolichyl-P decreased. The amount of dolichyl-P was elevated due to a decrease in the rate of degradation. Labeling of squalene and cholesterol of liver homogenates in vitro was decreased in the diseased mice and a lowering of microsomal activities of both HMG-CoA reductase and squalene synthase were also observed. In experiments with brain homogenate, decreased [3H]mevalonate labeling of squalene, cholesterol and dolichol was found in vitro. The decreases in cis-prenyltransferase and squalene synthase activities were observed at a very early phase of the disease. In contrast to the decreased biosynthesis of cholesterol observed in vitro, the labeling of total liver cholesterol was found to be increased in Niemann-Pick type C liver upon in vivo investigation, possibly due to the accumulation of this lipid as a result of a deficient transport process. In the brain, where in vivo labeling reflects only biosynthesis, a decreased rate of cholesterol synthesis was demonstrated.

Animals↗

PubMed1998

Reduced cholesterol accumulation and improved deficient peroxisomal functions in a murine model of Niemann-Pick type C disease upon treatment with peroxisomal proliferators.

Niemann-Pick type C disease is an inherited disorder characterized by lysosomal accumulation of cholesterol and the mutant gene has recently been identified. The predicted gene product is a transmembrane protein showing homology to proteins involved in the regulation of cholesterol homeostasis, such as 3-hydroxy-3-methylglutaryl-coenzyme A and the sterol regulatory element binding protein cleavage-activating protein. Recent investigations have established a peroxisomal deficiency, which raised the question of whether peroxisomal proliferation could affect this cholesterol-processing error. Mutant mice with Niemann-Pick type C disease were treated with the peroxisomal inducer perfluorooctanoic acid, which increased peroxisomal beta-oxidation and catalase activity to the same level as in control mice. Not only the peroxisomal, but also the lysosomal malfunctions were corrected and the cholesterol content was decreased. Clofibrate, another peroxisomal inducer, restored both peroxisomal enzyme activities and ubiquinone content. It appears that in Niemann-Pick type C disease treatment with appropriate peroxisomal inducers restores basic cellular functions, indicating a relationship between peroxisomes and cholesterol homeostasis, and thereby may effectively interfere with the development of the disease.

Animals↗

PubMed1998

Phosphorylation of farnesol in rat liver microsomes: properties of farnesol kinase and farnesyl phosphate kinase.

As farnesol may serve as a nonsterol endogenous regulator of the mevalonate pathway, the possibility that a kinase specific for its phosphorylation is present in the rat liver was investigated. In the 10,000 g supernatant of rat liver, farnesyl monophosphate was synthesized in the presence of ATP. The Km value for farnesol was 2.3 microM. Various detergents inhibited the activity of the enzyme. The farnesol kinase was present in rough and in smooth I microsomes, but not in smooth II microsomes, mitochondria, peroxisomes, Golgi, or plasma membranes. The enzyme was associated with the inner, luminal surface of the vesicles. Further analyses have demonstrated that an enzymatic mechanism exists which catalyzes the phosphorylation of farnesyl-P to farnesyl-PP. Activity of the farnesyl phosphate kinase resulted in the phosphorylation of the monophosphate by CTP but not by ATP, GTP, or UTP. This enzyme is activated by low concentrations of detergents. Treatment with proteases and chemical probes indicate that this second phosphorylation reaction probably takes place on the outer, cytoplasmic surface of microsomal vesicles. These results demonstrate that rat liver microsomes contain two enzymes for the consecutive phosphorylation of farnesol to farnesyl-PP.

Adenosine Triphosphate↗

PubMed1998

Analysis of ubiquinone and tocopherol levels in normal and hyperlipidemic human plasma.

The type and amount of lipophilic antioxidants in plasma of hyperlipidemic patients are of great importance since they play a central role in preventing deleterious oxidation of blood lipids and proteins. Isolation and quantitation of lipophilic antioxidants from hyperlipidemic plasma samples meet great obstacles because of increased levels of various intermediary lipid products. This study was designed to develop a rapid and efficient extraction and separation procedure for simultaneous analysis of ubiquinone-9 and -10 as well as alpha-, delta-, and gamma-tocopherol isomers. The levels of ubiquinone-10, alpha- and gamma-tocopherol were analyzed in human plasma samples using high-performance liquid chromatography. Lipid extraction was performed by petroleum ether/methanol/water. After phase separation, ubiquinone was reduced to ubiquinol by sodium borohydride and the lipids were separated on a C18 column. A binary gradient with solvents containing lithium perchlorate was used, and an electrochemical detector was employed for quantitation. This procedure was also efficient for the analysis of antioxidant lipids in samples containing a large number of accumulated and interfering lipid intermediates. Thus, the procedure described here is useful for efficient and rapid quantitation of ubiquinones and tocopherols in human plasma samples, especially those originating from hyperlipidemic patients.

Chromatography, High Pressure Liquid↗

PubMed1998

Gemfibrozil-induced decrease in serum ubiquinone and alpha- and gamma-tocopherol levels in men with combined hyperlipidaemia.

BACKGROUND: Low blood levels of antioxidants are associated with an increased risk of developing coronary artery disease. Lipophilic antioxidants are transported in lipoproteins, and hypolipidaemic therapy may therefore alter their blood concentrations. METHODS: The present randomized, placebo-controlled cross-over study of 21 men with combined hyperlipidaemia examines whether 10-12 weeks of gemfibrozil treatment affects the serum concentrations of the antioxidants ubiquinone-10 or alpha- or gamma-tocopherol. RESULTS: Gemfibrozil treatment lowered plasma triglycerides and both total and very low-density lipoprotein (VLDL)-cholesterol (P < 0.001 for all by ANOVA), whereas high-density lipoprotein (HDL)-cholesterol increased (P < 0.001). The median serum levels of ubiquinone-10 decreased from 1.30 mumol L-1 (interquartile range 0.87-1.71 mumol L-1) with placebo to 0.76 mumol L-1 (0.66-0.95) with gemfibrozil treatment (P < 0.001). Corresponding levels for alpha- and gamma-tocopherol were: 68.5 mumol L-1 (51.1-84.7) vs. 40.8 mumol L-1 (30.3-55.0) and 8.6 mumol L-1 (5.2-16.7) vs. 4.3 mumol L-1 (3.5-7.0) respectively (P < 0.001 for both). The decrease in serum antioxidants was also evident when standardized for total cholesterol (P < 0.05) or LDL-cholesterol (P < 0.001). Normolipaemic control subjects had significantly lower antioxidant levels than placebo-treated patients: ubiquinone 0.63 mumol L-1 (0.41-1.05), alpha-tocopherol 34.3 mumol L-1 (27.3-45.6) and gamma-tocopherol 3.2 mumol L-1 (2.5-4.2) (P < 0.001 for all). The association of antioxidants with lipoprotein lipids was further established by positive correlations between the levels of antioxidants and those of total cholesterol (r = 0.64, P < 0.001) or total triglycerides (r = 0.71, P < 0.001). CONCLUSION: Gemfibrozil treatment of men with combined hyperlipidaemia reduces serum antioxidant levels to the levels seen in healthy normolipidaemic men. The mechanisms and the relevance of this finding remain unclear and need to be addressed in further studies.

Adult↗