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)

The purpose of the present study was to determine the effects of low-frequency electrical stimulation (LFES) on the skeletal muscle metabolic profile of men and women. The knee extensor muscles of sedentary men (N = 16) and women (N = 10) were submitted to 3 h.d-1 of 8-Hz neuromuscular electrical stimulation with the use of a portable stimulator (Respond II, Medtronic), 6 d.wk-1 for 6 wk. Enzyme activity levels of creatine kinase (CK), hexokinase (HK), glyceraldehydephosphate dehydrogenase (GAPDH), 3-hydroxyacyl CoA dehydrogenase (HADH), citrate synthase (CS), phosphofructokinase (PFK), and cytochrome c oxidase (COX) were determined in vastus lateralis muscle samples taken before and after the LFES protocol. The analyses of variance revealed no change in CK and in GAPDH. However, a small decrease in PFK activity, the rate-limiting enzyme of glycolysis, was observed in female (8%) and in male subjects (10%), but it reached significance in males only (P < 0.05). The activity level of HK, a regulatory enzyme of the skeletal muscle glucose phosphorylation (HK), increased significantly in female subjects only (36%; P < 0.01) in response to the stimulation protocol. Activity level of marker enzymes of the Krebs cycle (CS) and of the electron-transfert chain (COX) significantly increased in males (18% and 16%; P < 0.05) as well as in females (31% and 19%; P < 0.05). Increment in the marker enzyme activity of the fatty acid oxidation (HADH) was significant in female subjects (30%; P < 0.01) and, although significant, rather modest in male subjects (12%; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Electrical stimulation-induced changes in skeletal muscle enzymes of men and women. 133 93

The purpose of this study was to compare the effects of two programs of endurance training, of equal duration and intensity, on bone development in female rats. Thirty-eight female Wistar rats were randomly assigned to one of three groups: run-trained (RUN), swim-trained (SWIM) or control (CON). The RUN group ran at a speed of 27 m/min up an 8 degrees incline. Swim trained animals swam with 2% of body weight attached to their tails. Training sessions were 2 h/day, 5 days/week and were conducted over a 10-week period. Hindlimb and forelimb muscles were removed upon sacrifice and analyzed for citrate synthase (CS) activity, liver (LG) and muscle (MG) glycogen. The parametrial fat pads were removed, digested with collagenase, and 2-deoxy-D-[3H]glucose uptake measured in isolated cells. Bone weight, length, diameter, ponderal index and bone mineral content (BMC) were measured in the femur and humerus of each animal. The LG, MG, fat cell volume, glucose uptake of the adipocyte and adrenal weight data indicate that the training response was identical. The CS activity of the muscles indicated that mechanical and recruitment patterns of the upper and lower body differ and could be responsible for bone development patterns found in this study. Exercise had a minimal effect on bone growth in the run-trained animals but did stimulate development in the swim-trained animals. The humerus of the SWIM was significantly (P < 0.05) heavier, wider and had a greater BMC when compared with those of the RUN and CON rats. The results of this study indicate that the muscular forces applied by the swim training protocol produced greater bone adaptations than the forces applied by a running protocol of equal duration and intensity.
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PMID:The effects of exercise mode, swimming vs. running, upon bone growth in the rapidly growing female rat. 134 May 16

Voluntary wheel running induces an increase in the concentration of the regulatable glucose transporter (GLUT4) in rat plantaris muscle but not in soleus muscle (K. J. Rodnick, J. O. Holloszy, C. E. Mondon, and D. E. James. Diabetes 39: 1425-1429, 1990). Wheel running also causes hypertrophy of the soleus in rats. This study was undertaken to ascertain whether endurance training that induces enzymatic adaptations but no hypertrophy results in an increase in the concentration of GLUT4 protein in rat soleus (slow-twitch red) muscle and, if it does, to determine whether there is a concomitant increase in maximal glucose transport activity. Female rats were trained by treadmill running at 25 m/min up a 15% grade, 90 min/day, 6 days/wk for 3 wk. This training program induced increases of 52% in citrate synthase activity, 66% in hexokinase activity, and 47% in immunoreactive GLUT4 protein concentration in soleus muscles without causing hypertrophy. Glucose transport activity stimulated maximally with insulin plus contractile activity was increased to roughly the same extent (44%) as GLUT4 protein content in soleus muscle by the treadmill exercise training. In a second set of experiments, we examined whether a swim-training program increases glucose transport activity in the soleus in the presence of a maximally effective concentration of insulin. The swimming program induced a 44% increase in immunoreactive GLUT4 protein concentration. Glucose transport activity maximally stimulated with insulin was 62% greater in soleus muscle of the swimmers than in untrained controls. Training did not alter the basal rate of 2-deoxyglucose uptake.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Glucose transporters and maximal transport are increased in endurance-trained rat soleus. 139 70

The effects of epinephrine on glucose metabolism and hydrogen peroxide content were examined in incubated rat macrophages. An increase in the activities of hexokinase and citrate synthase and a reduction in that of glucose-6-phosphate dehydrogenase was found in resident, inflammatory and activated macrophages incubated for 1 hr in the presence of epinephrine. Glucose utilization by incubated resident, inflammatory and activated macrophages was augmented markedly by the addition of epinephrine, whereas lactate formation was depressed. Under the same conditions, there was a 2.6-fold increment of hydrogen peroxide content and of [U-14C]glucose decarboxylation in activated macrophages incubated for 40 min. Similar results were obtained when pyruvate and oxoglutarate was substituted for glucose. These findings suggest that epinephrine may increase hydrogen peroxide production in activated macrophages possibly through a mitochondrial mechanism other than the pentose-phosphate pathway. Between 40 and 90 min of incubation, the content of hydrogen peroxide decreased markedly, and there was no detectable glucose utilization in the presence of epinephrine. These observations are consistent with the idea that this catecholamine stimulates both hydrogen peroxide production and metabolism, the first process being dependent on mitochondrial fuels.
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PMID:Effect of epinephrine on glucose metabolism and hydrogen peroxide content in incubated rat macrophages. 147 89

The purpose of this study was to test the hypothesis that the rate of plasma glucose oxidation during exercise is inversely related to muscle respiratory capacity. To this end, 14 subjects were studied: in 7 of these subjects, the blood lactate threshold (LT) occurred at a relatively high intensity [i.e., at 65 +/- 2% of peak cycle ergometer oxygen uptake (VO2 peak)], whereas in the other 7 subjects, LT occurred at a relatively low intensity (i.e., at 45 +/- 2% of VO2 peak). VO2peak did not differ between the two groups, but citrate synthase activity in the vastus lateralis muscle was 53% higher (P < 0.05) in the high LT group. A primed continuous infusion of [U-13C]glucose was used to quantify rates of glucose appearance (Ra), disappearance (Rd), and oxidation (R(ox)) during 90 min of exercise at 55% VO2peak. Although both absolute and relative rates of oxygen uptake during exercise were similar in the two groups, mean Ra and Rd were 17% lower (P < 0.001) in the high LT group, and mean R(ox) was 25% lower (21.0 +/- 2.6 vs. 27.9 +/- 2.6 mumol.min-1.kg-1; P < 0.001). The percentage of total energy derived from glucose oxidation was inversely related to muscle citrate synthase activity (r = -0.85; P < 0.01). These data support the concept that skeletal muscle respiratory capacity has a major role in determining the metabolic response to submaximal exercise.
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PMID:Plasma glucose kinetics during exercise in subjects with high and low lactate thresholds. 838 22

Bladder function is dependent upon cellular metabolism of substrates and the adequate generation of high-energy phosphate compounds. Partial outlet obstruction induces a marked decrease in bladder function which is associated with a significant decrease in the oxidative metabolism of glucose. The current investigation was designed to determine whether the time course of the decrease in mitochondrial oxidation in the hypertrophied urinary bladder is similar to the time course of the contractile dysfunction observed. In these studies we determined: 1) the rate of 14C-pyruvate metabolism to 14CO2 in control and obstructed tissue (1, 3, 5 and 7 days), and 2) the mitochondrial enzymatic activities of malate dehydrogenase and citrate synthase. The results can be summarized as follows: 1) The rate of pyruvate metabolism decreases by over 50% within one day following partial outlet obstruction, and remains at this level for the seven day period of study. 2) Kinetic analysis demonstrates that the change in enzymatic activity is related to a decrease in Vmax; the Kd for pyruvate is similar for control and after all time periods of obstruction. 3) The enzymatic activity of malate dehydrogenase and citrate synthase is reduced by over 50% within one day following partial obstruction, and remains at this level throughout the 7 day study period. These metabolic results correlate in time and duration with the decreased ability of the bladder to empty following partial outlet obstruction.
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PMID:Effect of outlet obstruction on pyruvate metabolism of the rabbit urinary bladder. 148 49

The biochemical, histochemical, and structural changes induced by endurance training and long-term exposure to high altitude were studied in the diaphragm muscle of rats exposed to simulated altitude (HA: n = 16; Pb = 62 kPa, 463 Torr; 4000 m) and compared to animals maintained at sea-level (SL: n = 16). Half of the animals in each group were trained (T) by swimming for 12 weeks, the other half were kept sedentary (S). Except for a small decrease in type I fibres in the HA-S group (-7%, P < 0.05), in favour of type IIab and type IIb fibres, neither high-altitude exposure nor endurance training had an overall affect on fibre type distribution. The mean fibre cross-sectional area was found to be unaffected by altitude and/or chronic exercise. Capillary density was shown to be increased by both high-altitude exposure (P < 0.02) and training (P < 0.001), whereas capillary growth, estimated by the capillary/fibre ratio, was unaffected in both cases. Following endurance training, a modest increase in citrate synthase was shown to occur to the same extent in the HA-T and SL-T groups (+15% and +16% respectively, NS). Hexokinase increased following training (P < 0.05) and high-altitude exposure (P < 0.001). In normoxic and hypoxic animals, endurance training enhanced the ratio of the heart-specific lactate dehydrogenase isozyme LDH1 to total LDH activity (+59%, P < 0.01; +92%, P < 0.05 respectively). It may be hypothesized that the increased glucose phosphorylation capacity observed in diaphragm muscle contributes to the reduction of glycogen utilization during exercise.
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PMID:Effects of endurance training at high altitude on diaphragm muscle properties. 148 82

This investigation evaluated the hypothesis that the age-related decline in cold-induced thermogenesis observed in male (F344) rats is associated with altered substrate concentrations of glucose, lactate, and/or liver and muscle glycogen. Body mass-independent O2 consumption, core temperature, and serum glucose and lactate concentrations were measured at rest and during 4 h of exposure to 5 degrees C in male F344 rats ages 6, 12, and 26 months. At the end of the 4-h cold exposure, liver, soleus, and gastrocnemius tissues were removed, frozen, and analyzed for glycogen concentration and/or citrate synthase activity. Core temperature decreased during cold exposure and was consistently less in the 26-month versus the 6- and 12-month rats. There were no significant differences between the 6- and 12-month-old rats with respect to cold-induced O2 consumption, but measures were significantly lower in the 26-month-old rats. During cold exposure, serum lactate and glucose concentrations increased in the 26-month-old animals compared to those in the 6- and 12-month-old rats, while liver glycogen concentrations decreased in all groups, and gastrocnemius glycogen contents decreased in the 12- and 26-month-old rats. Citrate synthase specific activity (mumol.[min.microgram.protein] -1) did not differ with age. These data suggest that carbohydrate availability (as measured by serum glucose and muscle glycogen) is not a limiting factor in the attenuated cold-exposed thermogenic response of the 26-month-old male F344 rat. However, it appears that the 26-month-old rat may have a diminished capacity to fully oxidize carbohydrate during cold exposure.
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PMID:Effect of cold on serum substrate and glycogen concentration in young and old Fischer 344 rats. 152 93

Addition of benzoate to the medium reservoir of glucose-limited chemostat cultures of Saccharomyces cerevisiae CBS 8066 growing at a dilution rate (D) of 0.10 h-1 resulted in a decrease in the biomass yield, and an increase in the specific oxygen uptake rate (qO2) from 2.5 to as high as 19.5 mmol g-1 h-1. Above a critical concentration, the presence of benzoate led to alcoholic fermentation and a reduction in qO2 to 13 mmol g-1 h-1. The stimulatory effect of benzoate on respiration was dependent on the dilution rate: at high dilution rates respiration was not enhanced by benzoate. Cells could only gradually adapt to growth in the presence of benzoate: a pulse of benzoate given directly to the culture resulted in wash-out. As the presence of benzoate in cultures growing at low dilution rates resulted in large changes in the catabolic glucose flux, it was of interest to study the effect of benzoate on the residual glucose concentration in the fermenter as well as on the level of some selected enzymes. At D = 0.10 h-1, the residual glucose concentration increased proportionally with increasing benzoate concentration. This suggests that modulation of the glucose flux mainly occurs via a change in the extracellular glucose concentration rather than by synthesis of an additional amount of carriers. Also various intracellular enzyme levels were not positively correlated with the rate of respiration. A notable exception was citrate synthase: its level increased with increasing respiration rate. Growth of S. cerevisiae in ethanol-limited cultures in the presence of benzoate also led to very high qO2 levels of 19-21 mmol g-1 h-1. During growth on glucose as well as on ethanol, the presence of benzoate coincided with an increase in the mitochondrial volume up to one quarter of the total cellular volume. Also with the Crabtree-negative yeasts Candida utilis, Kluyveromyces marxianus and Hansenula polymorpha, growth in the presence of benzoate resulted in an increase in qO2 and, at high concentrations of benzoate, in aerobic fermentation. In contrast to S. cerevisiae, the highest qO2 of these yeasts when growing at D = 0.10 h-1 in the presence of benzoate was equal to, or lower than the qO2 attainable at mu(max) without benzoate. Enzyme activities that were repressed by glucose in S. cerevisiae also declined in K. marxianus when the glucose flux was increased by the presence of benzoate.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effect of benzoic acid on metabolic fluxes in yeasts: a continuous-culture study on the regulation of respiration and alcoholic fermentation. 152 84

The objective of this study was to determine whether insulin secretion from single pancreatic beta cells is reduced by endurance training. Male Sprague Dawley rats either trained (T, N = 9) for 11 wk on a rodent treadmill, remained sedentary, and were fed ad libitum (S, N = 8) or remained sedentary and were food restricted (pair fed, PF, N = 8) so that final body weights were similar to T. After training, T had significantly higher red gastrocnemius muscle citrate synthase activity compared with S and PF. In vivo insulin secretion was lower in T (4.6 +/- 1.4 ng.ml-1, mean +/- SEM of 70' + 90' concentrations during a hyperglycemic glucose clamp) when compared with S, 8.1 +/- 1.6 and PF, 9.7 +/- 1.7 ng.ml-1. In vitro insulin secretion from single beta cells was measured using the cell blot assay (Kendall and Hymer, Endocrinology, 121:2260-2262, 1987) and T, had lower secretion 2.6 +/- 1.4 pg.cell-1 when compared (P less than 0.05) with S, 6.7 +/- 0.6, but not lower than PF, 4.1 +/- 1.7 pg.cell-1. These data suggest that some of the training-induced reduction in insulin secretory response to glucose may be attributable to changes within the beta cell itself.
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PMID:Effect of training on insulin secretion from single pancreatic beta cells. 156 Jul 38


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