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)

Seven middle-aged men with manifest type II diabetes mellitus underwent an endurance training programme for 10-15 weeks. The maximal aerobic capacity, as well as the endurance capacity, was improved by 10% (p less than 0.05). The intramuscular glycogen store increased by more than 80% (p less than 0.05) from 350 mumol/g dw (dry weight), and the activities of citrate synthase and 3-hydroxy-acyl-CoA dehydrogenase increased by more than 50% (p less than 0.05) and 30% (p less than 0.05). The activity of glycogen synthase was decreased by approximately 20% (p less than 0.05), whereas lactate dehydrogenase remained unchanged. Capillaries/fibre and fibre area increased by more than 50% (p less than 0.05) and 30% (p less than 0.05) leaving the area of supply constant. Training did not influence fasting blood lipids and glucose, glycosylated hemoglobin, oral glucose tolerance, and insulin response to an oral glucose load measured 72 hours post-exercise. It is concluded that patients with manifest type II diabetes, as normoglycaemic individuals, adapt to physical training. However, no persistent effect on glucohomeostasis and lipaemia is produced by short-term training in the diabetic patients.
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PMID:Skeletal muscle adaptations to physical training in type II (non-insulin-dependent) diabetes mellitus. 336 17

Individual muscle fibers from patients with Duchenne muscular dystrophy at an early stage in their disease, and from apparently normal boys of similar age, were analyzed for 13 enzymes of energy metabolism. This approach avoided the serious problems with muscle homogenate assays from increases in nonparenchymal components and permitted assessment of disease changes in different fiber types. Some enzymes of glycogenolysis (phosphorylase, phosphoglucomutase, and pyruvate kinase) were decreased in dystrophic fibers of all types. Phosphofructokinase was decreased in presumptive type II fibers. Lactate dehydrogenase was increased in type I fibers and essentially unchanged in type II. Phosphoglucoisomerase was near normal. Two enzymes of glucose metabolism not involved in glycogenolysis, hexokinase and glycogen synthase, were near normal, but a third, fructose bisphosphatase, was sharply reduced. Two enzymes of oxidative metabolism, citrate synthase, and beta-hydroxyacyl CoA dehydrogenase, were unchanged or increased. Two enzymes of high energy phosphate transfer, creatine kinase and adenylokinase, were only marginally affected. The net result is to leave the type II fibers, which normally exert the greatest force, with a severe deficit in the glycogenolytic enzyme machinery to maintain that force.
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PMID:Effect of Duchenne muscular dystrophy on enzymes of energy metabolism in individual muscle fibers. 360 Feb 88

Biopsies from 15 human gliomas, five meningiomas, four Schwannomas, one medulloblastoma, and four normal brain areas were analyzed for 12 enzymes of energy metabolism and 12 related metabolites and cofactors. Samples, 0.01-0.25 microgram dry weight, were dissected from freeze-dried microtome sections to permit all the assays on a given specimen to be made, as far as possible, on nonnecrotic pure tumor tissue from the same region. Great diversity was found with regard to both enzyme activities and metabolite levels among individual tumors, but the following generalities can be made. Activities of hexokinase, phosphorylase, phosphofructokinase, glycerophosphate dehydrogenase, citrate synthase, and malate dehydrogenase levels were usually lower than in brain; glycogen synthase and glucose-6-phosphate dehydrogenase were usually higher; and the averages for pyruvate kinase, lactate dehydrogenase, 6-phosphogluconate dehydrogenase, and beta-hydroxyacyl coenzyme A dehydrogenase were not greatly different from brain. Levels of eight of the 12 enzymes were distinctly lower among the Schwannomas than in the other two groups. Average levels of glucose-6-phosphate, lactate, pyruvate, and uridine diphosphoglucose were more than twice those of brain; 6-phosphogluconate and citrate were about 70% higher than in brain; glucose, glycogen, glycerol-1-phosphate, and malate averages ranged from 104% to 127% of brain; and fructose-1,6-bisphosphate and glucose-1,6-bisphosphate levels were on the average 50% and 70% those of brain, respectively.
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PMID:Diversity of metabolic patterns in human brain tumors: enzymes of energy metabolism and related metabolites and cofactors. 661 61

The human leukaemic cell line HL60 undergoes differentiation to granulocyte-like cells in response to dimethylsulphoxide (DMSO). The rates of glucose and glutamine utilization were studied in HL60 cells that were either undifferentiated or fully differentiated by 9 days exposure to DMSO. Differentiation did not alter the rate of utilization of exogenous glucose, approximately 75% of which was converted to lactate in each case. The activities of hexokinase, phosphofructokinase, pyruvate kinase and citrate synthase were similarly unaffected. In contrast, the activity of the oxidative segment of the pentose-phosphate pathway was enhanced by differentiation, and no glycogen synthase activity could be detected. These observations are consistent with the significantly lower content of glycogen, the increased activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase and the increased oxidation of [1-14C] glucose relative to [6-14C] glucose in the differentiated cells. Glucose utilization was depressed by exogenous glutamine but, at the same time, glutamine utilization was enhanced by glucose in both cell types; these reciprocal effects were more pronounced in the undifferentiated HL60 cells. Glucose utilization may be depressed in the presence of glutamine as a result of the allosteric inhibition of a rate-limiting step of glycolysis (eg. phosphofructokinase). In spite of having glutaminase activity twice that of their differentiated counterparts, the uptake of glutamine by undifferentiated HL60 cells was low, especially when it was the sole substrate. The stimulation of glutaminolysis by glucose may be due to activation of mitochondrial glutamine transport. A large proportion of the glutamine utilized by both cells contributed to a net accumulation of glutamate, aspartate and alanine, whilst up to 35% was oxidized to CO2. In contrast, almost all of the glucose utilized was converted to lactate and very little was oxidized. The high rates of glycolysis and glutaminolysis observed before and after differentiation may not contribute primarily to energy production but may supply, in undifferentiated cells, substrates for biosynthetic processes that generate nucleic acid precursors or, in the case of differentiated cells which synthesize reactive oxygen intermediates, substrates that maintain NADP in a reduced state.
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PMID:Glycolytic, glutaminolytic and pentose-phosphate pathways in promyelocytic HL60 and DMSO-differentiated HL60 cells. 833 14

Hindlimb weight bearing after a 3-day period of hindlimb suspension (reweighting) of juvenile rats results in a marked transient elevation in soleus glycogen concentration that cannot be explained on the basis of the activities of glycogen synthase and phosphorylase. We have hypothesized that enhanced glucose transport activity could underlie this response. We directly tested this hypothesis by assessing the response of insulin-dependent and insulin-independent glucose transport activity (in vitro 2-[1,2-3H]deoxy-D-glucose uptake) as well as glucose transporter (GLUT-4) protein levels during a 48-h reweighting period. After a net glycogen loss (from 29 +/- 2 to 16 +/- 1 nmol/mg muscle; P < 0.05) during the first 2 h of reweighting, glycogen accumulated at an average rate of 1.4 nmol.mg-1.h-1 up to 18 h, reaching an apex of 38 +/- 1 nmol/mg. During this same reweighting period, insulin-independent, but not insulin-dependent, glucose transport activity was significantly enhanced (P < 0.05 vs. weight-bearing control values) and was associated with an elevated level of GLUT-4 protein and the specific activity of total hexokinase. The specific activity of citrate synthase was also increased. By 24 h of reweighting, although insulin-independent glucose transport activity and GLUT-4 protein remained elevated, glycogen accumulation had ceased, likely due to enhanced phosphorylase activity at this time point. These results are consistent with the interpretation that the glycogen supercompensation seen during reweighting of the rat soleus may be regulated in part by an enhanced glucose flux arising from an increase in insulin-independent glucose transport activity and hexokinase activity.
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PMID:Role of glucose transport in glycogen supercompensation in reweighted rat skeletal muscle. 872 37

The purpose of this study was to examine the relationship between skeletal muscle GLUT-4 protein and postexercise glycogen storage in human subjects fed adequate carbohydrate. Eleven men completed 2 h of cycling, and a biopsy of the vastus lateralis was performed immediately after exercise cessation for the determination of muscle GLUT-4 protein and glycogen concentrations, glycogen synthase activity, and citrate synthase activity. The subjects ingested meals providing 2.0 g carbohydrate/kg body weight at 0, 2, and 4 h postexercise, and a second biopsy was performed 6 h postexercise. Muscle glycogen concentration increased significantly during the 6-h recovery period (glycogen immediately postexercise, 27.2 +/- 5.4 mmol/kg wet weight; glycogen storage, 52.4 +/- 2.9 mmol x kg wet weight-1 x 6 h-1; P<0.05). Glycogen storage during recovery was directly related to GLUT-4 protein (2.20 +/- 0.33 arbitrary standard units; r = 0.63; P<0.05) and inversely related to glycogen immediately postexercise (r = -0.70; P < 0.05). A direct correlation existed between glycogen storage during recovery and the activity of the I form of glycogen synthase (r = 0.60; P < 0.05). These results suggest that muscle GLUT-4 protein concentration, as well as factors relating to glucose disposal, may affect postexercise glycogen storage in humans fed adequate carbohydrate.
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PMID:Skeletal muscle GLUT-4 and postexercise muscle glycogen storage in humans. 892 77

1. Thinness at birth is associated with insulin resistance in adult life and an apparent delay in activation of glycolysis/glycogenolysis in exercising skeletal muscle. As developmental abnormalities of skeletal muscle histology or metabolism may explain this association we examined muscle histology, biochemistry and blood flow in a group of 27 adult women whose birth details were known. 2. Subjects were examined by near-infrared spectroscopy to determine forearm muscle oxygen supply, and by muscle biopsy and forearm plethysmography. Those with a ponderal index at birth < 23 kg/m3 were insulin resistant (assessed by the short insulin-tolerance test-mean rate constants for glucose disappearance = 4.14 compared with 4.83%/min, P = 0.045) and had significantly more rapid muscle reoxygenation than the remainder of the subjects (13 compared with 22 s, P = 0.004). 3. Thinness at birth did not influence muscle capillary density, muscle glycogen content, glycogen synthase activity, citrate synthase activity or resting forearm blood flow. 4. Insulin resistance seen after fetal malnutrition was not associated with abnormal muscle histology, resting muscle blood flow, mitochondrial volume or glycogen content. 5. The increase in muscle reoxygenation rate in adult subjects who were thin at birth could occur to promote oxidative ATP synthesis in compensation for the delay in activation of glycolysis/glycogenolysis. It suggests altered regulation rather than structure of the muscle microcirculation. These changes appear to antedate the structural and biochemical changes seen in muscle from patients with established diabetes.
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PMID:Fetal growth and insulin resistance in adult life: role of skeletal muscle morphology. 909 10

As muscle tissue constitutes a main target organ for glucose metabolism and is responsible for the development of insulin resistance, it seems plausible to elucidate the relationship between blood pressure and muscle morphology and metabolism. The association between blood pressure and capillarization/morphology of the vastus lateralis muscle and metabolic variables was evaluated in 24 perimenopausal obese women [body mass index (BMI) 34.9 +/- 1.1; waist-hip ratio (WHR) 0.90 +/- 0.02]. The muscle enzyme activity of lipoprotein lipase (LPL), citrate synthase and glycogen synthase was determined. There was a significant negative correlation between the percentage of type I fibres and relative fibre area of type I on the one hand and systolic and diastolic blood pressure on the other. There was a negative correlation between the capillary density (i.e. number of capillaries/muscle fibre) and a positive correlation between the diffusion distance (fibre area supplied by one capillary) and diastolic blood pressure. The activities of LPL and citrate synthase were positively correlated with the percentage of type I and negatively correlated with the percentage of type II muscle fibres. The activity of LPL was also negatively correlated with plasma glucose and the insulin/C-peptide ratio. The insulin/C-peptide ratio was positively correlated with the percentage of type II muscle fibres. In stepwise multiple regression analyses, 20-30% of the variation in systolic and diastolic blood pressure could be explained by the variables of muscle fibre distribution. Excluding muscle morphological variables from the regression model, the insulin/C-peptide ratio accounted for 13% of the variation in systolic and diastolic blood pressure. The results of the study show the close association between muscle morphology and blood pressure. It remains to be elucidated whether this association indicates a causal relationship.
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PMID:High blood pressure and muscle morphology/metabolism--causal relationship or only associated factors? 964 8

Complete spinal cord lesion leads to profound metabolic abnormalities and striking changes in muscle morphology. Here we assess the effects of electrically stimulated leg cycling (ESLC) on whole body insulin sensitivity, skeletal muscle glucose metabolism, and muscle fiber morphology in five tetraplegic subjects with complete C5-C7 lesions. Physical training (seven ESLC sessions/wk for 8 wk) increased whole body insulin-stimulated glucose uptake by 33+/-13%, concomitant with a 2.1-fold increase in insulin-stimulated (100 microU/ml) 3-O-methylglucose transport in isolated vastus lateralis muscle. Physical training led to a marked increase in protein expression of GLUT4 (378+/-85%), glycogen synthase (526+/-146%), and hexokinase II (204+/-47%) in vastus lateralis muscle, whereas phosphofructokinase expression (282+/-97%) was not significantly changed. Hexokinase II activity was significantly increased, whereas activity of phosphofructokinase, glycogen synthase, and citrate synthase was not changed after training. Muscle fiber type distribution and fiber area were markedly altered compared to able-bodied subjects before ESLC training, with no change noted in either parameter after ECSL training. In conclusion, muscle contraction improves insulin action on whole body and cellular glucose uptake in cervical cord-injured persons through a major increase in protein expression of key genes involved in the regulation of glucose metabolism. Furthermore, improvements in insulin action on glucose metabolism are independent of changes in muscle fiber type distribution.
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PMID:Exercise-induced overexpression of key regulatory proteins involved in glucose uptake and metabolism in tetraplegic persons: molecular mechanism for improved glucose homeostasis. 983 60

The maximal activity of a selection of enzymes involved in muscle carbohydrate handling, citric acid cycle and fatty acyl beta-oxidation were studied after treatment with the fluorinated corticosteroid triamcinolone and compared to a similar treatment of the non-fluorinated corticosteroid prednisolone in an equipotent anti-inflammatory dose. Furthermore, because triamcinolone causes loss of body mass and muscle wasting, the effects of triamcinolone were investigated relative to a control group, with the same loss of body mass, due to nutritional deprivation. The study was performed in male Wistar rats in the following treatment groups: TR, triamcinolone treatment (0.25 mg x kg(-1) x day(-1) for 2 weeks), which resulted in a reduction of body mass (24%); ND, nutritional deprivation (30% of normal daily food intake for 2 weeks) resulting in a similar (24%) decrease of body mass as TR; PR, prednisolone treatment (0.31 mg x kg(-1) x day(-1) for 2 weeks), with a 10% increase in body mass; FF, free-fed control group, with a 12% increase in body mass in 2 weeks. Compared to FF, TR induced an increase in phosphofructokinase (PFK) activity (P < 0.01), glycogen synthase [GS(i + d)] activity (P < 0.05) and glycogen content (P < 0.01) in the tibialis anterior muscle. The PR and ND caused no alterations in PFK or citrate synthase (CS) activity compared to FF. Compared to PR, TR induced an increase in PFK (P < 0.01), CS (P < 0.05) and GS(i + d) activity (P < 0.01). Both TR and PR caused an increased muscle glycogen content, being more pronounced in TR (P < 0.05). Compared to ND, TR induced an increased CS (P < 0.05) and GS(i + d) activity (P < 0.01) and glycogen content (P < 0.01). The ND resulted in a decreased glycogen content compared to FF (P < 0.05). None of the treatments affected the activity of glycogen phosphorylase, beta-hydroxyacyl coenzyme A dehydrogenase and lactate dehydrogenase. It was concluded that corticosteroids led to an increased muscle glycogen content; however, the changes in the enzymes of carbohydrate metabolism were corticosteroid type specific and did not relate to undernutrition, which accompanied the triamcinolone treatment.
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PMID:Enzyme activity of rat tibialis anterior muscle differs between treatment with triamcinolone and prednisolone and nutritional deprivation. 1004 33


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