Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.3.3.1 (citrate synthase)
4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Idiopathic dilated cardiomyopathy is associated with derangement of myocardial sarcoplasmic Ca-homeostasis and energy production. The molecular mechanism for these changes is unknown. Accordingly, we used genetic and experimentally-induced models of canine dilated cardiomyopathy and tested the hypothesis that these metabolic changes resulted from altered gene expression, as indicated by mRNA content. We studied dilated cardiomyopathy occurring naturally (n = 9) in Doberman pinschers, and in dogs subjected to rapid ventricular pacing (n = 5), in comparison with normal dogs (n = 9). We determined content and integrity of mRNA's using Northern and slot blotting, and measured activities of their translated product for the Ca-release channel and Ca-ATPase of sarcoplasmic reticulum, lactate dehydrogenase of glycolysis, citrate synthase of the tricarboxylic acid cycle, and for myoglobin, ATP-synthetase and the adenine nucleotide transporter, which are integral in oxidative phosphorylation. We found that, whereas both mRNA content and enzyme activity for markers of Ca-cycling, glycolysis, and oxidative phosphorylation were downregulated (20-80%) in dilated cardiomyopathy, they were upregulated (10-15%) for tricarboxylic acid cycling and for ribosomal RNA. RNA from cardiomyopathic tissue was up to 50% more degraded than for normal hearts in association with a 150% increase in ribonuclease activity. Downregulation of the Ca-cycle was asymmetric, with the Ca-channel being 65% more affected than the Ca-ATPase. This work supports the general paradigm that transcriptional and translational responses to pathophysiology are major determinants of the metabolic response seen in cardiac failure.
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PMID:Myocardial mRNA content and stability, and enzyme activities of Ca-cycling and aerobic metabolism in canine dilated cardiomyopathies. 777 66

It is not known precisely how marine mammals are able to maintain muscle function during active swimming in breath-hold dives, when ventilation stops and heart rate falls. Examination of muscle biochemistry and histochemistry can provide information on the relative importance of different metabolic pathways, the contractile potential of the muscle fibres, the oxygen storage capacity of the muscle and the capillary distribution in these animals. In this study, samples of locomotory muscle were taken from wild grey seals (Halichoerus grypus), harbour seals (Phoca vitulina) and Antarctic fur seals (Arctocephalus gazella); Wistar rat muscle was analysed for comparative purposes. Activities of citrate synthase and beta-hydroxyacyl CoA dehydrogenase were higher in the harbour seal muscle than in the grey seal muscle, suggesting that harbour seals have a greater aerobic capacity. Both phocid muscles had a greater reliance on fatty acid oxidation than the fur seal or rat muscles. The myoglobin data demonstrate that the grey seals have the highest oxygen storage capacity of the three pinniped species, which correlates with their greater diving ability. Myoglobin levels were higher in all three pinniped species than in the Wistar rat. The fibre type compositions suggest that the muscles from the fur seals have higher glycolytic capacities than those of the phocid seals [fur seal pectoralis, 7% slow-twitch oxidative fibres (SO), 25% fast-twitch oxidative glycolytic fibres (FOG), 68% fast-twitch glycolytic fibres (FG); grey seal 57% SO, 5% FOG, 38% FG; area per cents]. However, the pectoralis muscle of the fur seal, although the most glycolytic of the pinniped muscles studied, has the highest capillary density, which indicates a high capacity for fuel distribution. These results show that, while pinniped muscle has an increased oxygen storage potential compared with the muscle of a typical terrestrial mammal, there are no distinct adaptations for diving in the enzyme pathways or fibre type distributions of the pinniped muscle. However, the muscle characteristics of each species can be related to its diving behaviour and foraging strategy.
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PMID:The metabolic characteristics of the locomotory muscles of grey seals (Halichoerus grypus), harbour seals (Phoca vitulina) and Antarctic fur seals (Arctocephalus gazella). 796 4

The presence of catalase in heart mitochondria may prevent excessive H2O2 from reaching the cytosol, eventually reacting with myoglobin (R. Radi et al., 1991, J. Biol. Chem. 266, 22028-22034). In this report we investigated whether catalase was also present in the mitochondrial matrix of skeletal muscle as it also contains myoglobin which could react with H2O2 produced by mitochondria. Catalase content of skeletal muscle tissue was about 1.4% of that in liver. Simultaneous determinations of citrate synthase (a mitochondrial marker) and catalase in intact mitochondria and mitoplasts indicated that catalase is not associated with muscle mitochondria. The lack of catalase in muscle mitochondria is not due to a limited H2O2 production by these organelles. Rat skeletal muscle mitochondria generated H2O2 (0.64 +/- 0.04 nmol/(min.mg protein), approximately 40% the rate in heart mitochondria. Other groups have shown that training causes an increase in the concentration of mitochondrial electron carriers as well as an increase in the activity of mitochondrial glutathione peroxidase and mitochondrial electron carriers. The increased concentration of mitochondrial electron carriers and the sudden changes in oxygen supply may lead to increased intracellular H2O2 during exercise.
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PMID:Hydrogen peroxide metabolism in skeletal muscle mitochondria. 798 95

It has been suggested that propionyl-L-carnitine administration to ischaemic hearts facilitates the restoration of cardiac function upon reperfusion, but it is still a matter of dispute whether its effect is conveyed via the metabolic effect of the propionyl moiety, the carnitine moiety or other mechanisms involving membrane receptor interactions. The metabolism of propionylcarnitine involves the formation of succinyl-CoA, which causes an increase in the total amount of tricarboxylic acid cycle intermediates. According to the current paradigm, anaplerosis ensures rapid restoration of tricarboxylic acid cycle activity during reperfusion. To evaluate the contribution of anaplerosis to the protective effect of propionylcarnitine during ischaemia and reperfusion, isolated rat hearts were perfused with Krebs-Henseleit bicarbonate buffer containing 5 mM glucose+insulin (12 IU per litre), to which 1 mM propionate, 0.8 mM hexanoate or 1 mM propionylcarnitine were added. Global 20 or 24 min no-flow ischaemia was followed by 10 min reperfusion. The flavoprotein redox state, myoglobin oxygenation, oxygen consumption and mechanical functioning of the heart were recorded and metabolites determined in freeze-trapped tissue. In parallel experiments, the cellular energy state was studied with phosphorus nuclear magnetic resonance spectrometry. The addition of 1 mM propionylcarnitine failed to cause an anaplerotic effect, but did bring about an oxidation of flavins, probably due to citrate synthase inhibition. Propionate showed similar but stronger effects and a marked anaplerosis, but still failed to improve the recovery of the heart upon reperfusion. The addition of hexanoate caused marked anaplerosis upon reperfusion and flavin reduction. The results failed to demonstrate that propionylcarnitine had any beneficial effect on the ischaemic myocardium.
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PMID:Metabolic effects of propionate, hexanoate and propionylcarnitine in normoxia, ischaemia and reperfusion. Does an anaplerotic substrate protect the ischaemic myocardium? 807 Apr 85

Structural and biochemical characteristics of the primary muscles used for swimming (pectoralis, PEC and supracoracoideus, SC) were compared to those of leg muscles in emperor penguins (Aptenodytes forsteri). The mass of PEC-SC was four times that of the leg musculature, and mitochondrial volume density in PEC and SC (4%) was two-thirds that in sartorius (S) and gastrocnemius. The differences in muscle mass and mitochondrial density yielded a 2.2-fold greater total mitochondrial content in PEC-SC than leg muscles, which appears to account for the 1.8-fold greater whole-body highest oxygen consumption previously recorded in emperor penguins during swimming compared to walking. Calculation of maximal mitochondrial O2 consumption in PEC-SC and leg muscle yielded value of 5.8-6.9 ml O2 ml-1 min-1, which are similar to those in locomotory muscles of most mammals and birds. A distinct feature of emperor penguin muscle was its myoglobin content, with concentrations in PEC-SC (6.4 g 100 g-1 among the highest measured in any species. This resulted in a PEC-SC O2 store greater than that of the entire blood. In addition, ratios of myoglobin content to mitochondrial volume density and to citrate synthase activity were 4.4 and 2.5 times greater in PEC than in S, indicative of the significant role of myoglobin in the adaptation of muscle to cardiovascular adjustments during diving.
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PMID:Structural and biochemical characteristics of locomotory muscles of emperor penguins, Aptenodytes forsteri. 927 9

Endurance exercise training increases the oxidative capacity of skeletal muscles, reflecting the induction of genes encoding enzymes of intermediary metabolism. To test the hypothesis that changes in gene expression may be triggered specifically during recovery from contractile activity, we quantified c-fos, alpha B-crystallin, 70-kDa heat shock protein (hsp70), myoglobin, and citrate synthase RNA in rabbit tibialis anterior muscle during recovery from intermittent (8 h/day), low-frequency (10 Hz) motor nerve stimulation. Recovery from a single 8-h bout of stimulation was characterized by large (> 10-fold) transient increases in c-fos, alpha B-crystallin, and hsp70 mRNA. Similar changes were noted during recovery after 7 or 14 days of stimulation (8 h/day). Myoglobin and citrate synthase mRNA were also induced during recovery, but the changes were of lesser magnitude (2- to 2.5-fold) and were observed only following repeated bouts of muscle activity (7th or 14th day) that promoted sustained (> 24 h) increases in these transcripts. These findings indicate that recovery from exercise is associated with specific transient changes in the expression of immediate early and stress protein genes, suggesting that the products of these genes may have specific roles in the remodeling process evoked by repeated bouts of contractile activity.
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PMID:Transient regulation of c-fos, alpha B-crystallin, and hsp70 in muscle during recovery from contractile activity. 948 22

To compare the diving capacities of juvenile and adult emperor penguins Aptenodytes forsteri, and to determine the physiological variables underlying the diving ability of juveniles, we monitored diving activity in juvenile penguins fitted with satellite-linked time/depth recorders and examined developmental changes in body mass (Mb), hemoglobin concentration, myoglobin (Mb) content and muscle citrate synthase and lactate dehydrogenase activities. Diving depth, diving duration and time-at-depth histograms were obtained from two fledged juveniles during the first 2.5 months after their depature from the Cape Washingon colony in the Ross Sea, Antarctica. During this period, values of all three diving variables increased progressively. After 8-10 weeks at sea, 24-41 % of transmitted maximum diving depths were between 80 and 200 m. Although most dives lasted less than 2 min during the 2 month period, 8-25 % of transmitted dives in the last 2 weeks lasted 2-4 min. These values are lower than those previously recorded in adults during foraging trips. Of the physiological variables examined during chick and juvenile development, only Mb and Mb content did not approach adult values. In both near-fledge chicks and juveniles, Mb was 50-60 % of adult values and Mb content was 24-31 % of adult values. This suggests that the increase in diving capacity of juveniles at sea will be most dependent on changes in these factors.
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PMID:Development of diving capacity in emperor penguins. 1006 67

The aim of this study was to determine the effects of 8 weeks of resistance training (RT) on the myoglobin concentration ([Mb]) in human skeletal muscle, and to compare the change in the [Mb] in two different RT protocols. The two types of protocol used were interval RT (IRT) of moderate to low intensity with a high number of repetitions and a short recovery time, and repetition RT (RRT) of high intensity with a low number of repetitions and a long recovery time. A group of 11 healthy male adults voluntarily participated in this study and were divided into IRT (n = 6) and RRT (n = 5) groups. Both training protocols were carried out twice a week for 8 weeks. At the completion of the training period, the one-repetition maximal force values and isometric force were increased significantly in all the subjects, by about 38.8% and 26.0%, respectively (P < 0.01). The muscle fibre composition was unchanged by the 8 weeks of training. The muscle fibre cross-sectional areas were increased significantly by both types of training in all fibre types (I, IIa and IIb, mean + 16.1 %, P < 0.05). The [Mb] showed no significant changes at the completion of the training [IRT from 4.63 (SD 0.63) to 4.48 (SD 0.72), RRT from 4.47 (SD 0.75) to 4.24 (SD 0.80) mg x g(-1) wet tissue] despite a significant decrease in citrate synthase activity [IRT from 5.27 (SD 1.45) to 4.49 (SD 1.48), RRT from 5.33 (SD 2.09) to 4.85 (SD 1.87) micromol x min(-1) x g(-1) wet tissue; P < 0.05] observed after both protocols. These results suggested that myoglobin and mitochondria enzymes were regulated by different mechanisms in response to either type of RT. Moreover, the maintained [Mb] in hypertrophied muscle should preserve oxygen transport from capillaries to mitochondria even when diffusion distance is increased.
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PMID:Maintenance of myoglobin concentration in human skeletal muscle after heavy resistance training. 1009 Jun 35

The objective was to assess the aerobic capacity of skeletal muscles in pinnipeds. Samples of swimming and nonswimming muscles were collected from Steller sea lions (Eumetopias jubatus, n = 27), Northern fur seals (Callorhinus ursinus, n = 5), and harbor seals (Phoca vitulina, n = 37) by using a needle biopsy technique. Samples were either immediately fixed in 2% glutaraldehyde or frozen in liquid nitrogen. The volume density of mitochondria, myoglobin concentration, citrate synthase activity, and beta-hydroxyacyl-CoA dehydrogenase was determined for all samples. The swimming muscles of seals had an average total mitochondrial volume density per volume of fiber of 9.7%. The swimming muscles of sea lions and fur seals had average mitochondrial volume densities of 6.2 and 8.8%, respectively. These values were 1.7- to 2.0-fold greater than in the nonswimming muscles. Myoglobin concentration, citrate synthase activity, and beta-hydroxyacyl-CoA dehydrogenase were 1.1- to 2. 3-fold greater in the swimming vs. nonswimming muscles. The swimming muscles of pinnipeds appear to be adapted for aerobic lipid metabolism under the hypoxic conditions that occur during diving.
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PMID:High aerobic capacities in the skeletal muscles of pinnipeds: adaptations to diving hypoxia. 1019 10

The effects of insulin treatment on skeletal muscle characteristics were studied in 18 patients (62 +/- 11 years) with poorly controlled diabetes mellitus type 2 (mean duration 7.5 +/- 6 years). Skeletal muscle biopsy samples were taken from the lateral portion of the quadriceps muscle before and after a period of insulin treatment of 40 +/- 14 days. Enzyme activities (phosphofructokinase, 3-hydroxyacyl-CoA dehydrogenase, citrate synthase, lactate dehydrogenase and creatine kinase) and myoglobin content were assessed. In a subgroup of 11 patients (60 +/- 11 years), skeletal muscle fibre type composition (type I, IIA, IIB and IIC) and fibre type cross-sectional area were also analysed. Following insulin treatment there were 32 and 38% increases, respectively, in the cross-sectional areas of type IIA and IIB fast-twitch fibres (P<0. 02). The fibre type distribution did not change. The myoglobin content in muscle decreased by 20% (P<0.01). Of the enzymes tested, the 3-hydroxyacyl-CoA dehydrogenase activity decreased by 10% (P<0. 04). Serum glucose, HbA1C and serum triglyceride levels decreased (P<0.001) and body weight and arm muscle circumference increased (P<0.02). In conclusion, insulin treatment of patients with poorly controlled non-insulin-dependent diabetes mellitus increased the fast-twitch fibre area, reduced myoglobin levels and decreased muscle enzyme activity related to fatty acid oxidation.
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PMID:Insulin treatment increases skeletal muscle fibre area in patients with diabetes mellitus type 2. 1097 46


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