Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study compared the exercise catecholamine and metabolic responses to a caffeine challenge in trained subjects before and after a 6-wk period of increased caffeine ingestion. Trained subjects (n = 6) were challenged with 500 mg of caffeine followed by prolonged exercise before and after 6 wk of increased caffeine ingestion (500 mg ingested before each daily run). A control group (n = 6) of trained subjects followed the same protocol except for caffeine ingestion. Acute caffeine ingestion resulted in increased plasma epinephrine and decreased respiratory exchange ratio (RER) during exercise. After 6 wk of caffeine supplementation, the epinephrine response to exercise or caffeine plus exercise was decreased, although the latter still resulted in a lower RER value compared with exercise without caffeine ingestion. Activity of key metabolic enzymes (hexokinase, citrate synthase, phosphorylase, and 3-hydroxyacyl-coenzyme A dehydrogenase) from biopsies of the gastrocnemius showed no response to 6 wk of this increased adrenergic receptor stimulation and, on the basis of the lower RER, enhanced fat metabolism. This study suggests that caffeine ingestion by trained subjects causes increases in plasma epinephrine and reduces the RER during exercise. However, habitual stimulation results in a general dampening of the epinephrine response to caffeine or exercise. There was no indication that increased adrenergic stimulation and fat oxidation caused any adaptation in the activity of metabolic enzymes.
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PMID:Acute and habitual caffeine ingestion and metabolic responses to steady-state exercise. 159 18

Previous reports from our laboratory showed that rats fed a polyunsaturated fatty acid-rich diet (UC), during an acute intervals, present important changes in macrophage metabolism and function, while a saturated fatty acid diet (SC) did not induce significant changes (10). In this study, two important questions were addressed: 1. the persistence of the changes induced by the UC and 2. the effect of a SC offered during ageing. The maximal activities of hexokinase, glucose-6-phosphate dehydrogenase, glutaminase, citrate synthase and glutathione peroxidase and the total content of lipid peroxides were measured in resident and inflammatory macrophages of rats fed control chow (CC), UC or SC during 14 months. Intraperitoneal cell migration by thioglycollate injection and the phagocytosis capacity were also evaluated. The results indicate that: 1) the changes caused by UC are exacerbated during ageing, and 2) the SC, given during a prolonged period of time, also caused important alterations of macrophage metabolism and function.
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PMID:Metabolic and functional changes in macrophages of rats fed polyunsaturated or saturated fatty acid rich-diets during ageing. 162 81

The activities of enzymes related to energy metabolism in the gastrocnemius and soleus muscles in young-adult (4 months), mature (12 months), and senescent (24 months) rats were compared after continuous (72 consecutive h) exposure to normobaric hypoxia or normoxia after the vasodilator naftidrofuryl or saline solution had been given intraperitoneally for 30 consecutive days. The maximum rats (Vmax) of the following enzyme activities in the crude extract and/or the crude mitochondrial fraction of each muscle specimen were evaluated for: the anaerobic glycolytic pathway (hexokinase, phosphofructokinase, pyruvate kinase, and lactate dehydrogenase), the tricarboxylic acid cycle (citrate synthase, and malate dehydrogenase), the electron transfer chain (cytochrome oxidase), and the NAD+/NADH redox state (total NADH cytochrome c reductase). The significance of differences between the enzyme activities at different ages or under different experimental conditions in the two tissue preparations of the two muscles were determined by ANOVA. MCA and ETA2 were used to evaluate the net effects of the experimental conditions. First, aging did not seem to affect the soleus and gastrocnemius muscles in the same way. In the gastrocnemius muscle, the major changes were seen in enzymes of the glycolytic pathway, in the crude extracts. In the soleus muscle, the more striking changes in enzyme activities as a function of aging were found in the crude mitochondrial fraction. We also found that hypoxia caused more important changes in 12-month-old rats than in those of other ages (especially the enzyme activities of the gastrocnemius muscle). Naftidrofuryl modified the effects of hypoxia only sometimes and further investigations are necessary before we can draw any conclusions about the pharmacological activity of naftidrofuryl in hypoxia.
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PMID:Effects of hypoxia and pharmacological treatment on enzyme activities in skeletal muscle of rats of different ages. 164 27

On the basis of the percentage creatine kinase-MM, human skeletal muscle cells cultured on growth and differentiation media containing the serum substitute Ultroser G reach a significantly higher maturation grade after 7 days of differentiation than cells cultured on serum-containing media. They also remain viable for longer periods. The myotubes are much longer, their nuclei are often localized in rows on the periphery, and they show cross-striation more frequently. The activities of creatine kinase, citrate synthase, cytochrome c oxidase, AMP deaminase, and phosphorylase are significantly higher. Extending the differentiation period to 3 weeks increases the maturation grade of the cultures and the activities of all the enzymes mentioned before, except phosphorylase. A correlation exists between the enzyme activities and the maturation grade of the muscle cells. The content of fatty acid-binding protein also increases significantly with the maturation grade in contrast to the palmitate oxidation rate. The AMP deaminase and creatine kinase activity and the percentage MM-type remain lower in cultured cells than in adult muscle and the hexokinase activity remains higher, but the other enzyme activities become comparable after 20 days of differentiation. The myotubes, derived from Ultroser G-containing culture media, show spontaneous contractions after 12 days and cross-striation after 20 days when immunostained for the M-subunit of creatine kinase. These cells possess clusters of acetylcholine receptors, but aggregation of desmin at the site of the clusters was never detectable. The possibility of cultivating muscle cells with a predictable maturation grade allows the study of muscle development and muscular diseases caused by differentiation defects or by deficiency of a maturation-dependent (iso)enzyme.
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PMID:The biochemical and structural maturation of human skeletal muscle cells in culture: the effect of the serum substitute Ultroser G. 164 54

1. The metabolism of glucose and glutamine was studied in the small intestine and the colon of rats after 4-5 weeks of hypothyroidism. 2. Hypothyroidism resulted in increases in the plasma concentrations of ketone bodies (P less than 0.05), cholesterol (P less than 0.001) and urea (P less than 0.001), but decreases in the plasma concentrations of free fatty acids (P less than 0.05) and triacylglycerol (P less than 0.001). These changes were associated with decreases in the plasma concentrations of total tri-iodothyronine, free tri-iodothyronine, total thyroxine and free thyroxine. 3. Hypothyroidism decreased both the DNA content (by 30.5%) and the protein content (by 23.6%) of intestinal mucosa, with the protein/DNA ratio remaining unchanged. The villi in the jejunum were shorter (P less than 0.05) and the crypt depth was decreased by about 26.5% in hypothyroid rats. 4. Portal-drained visceral blood flow showed no marked change in response to hypothyroidism, but was accompanied by decreased rates of extraction of glucose, lactate and glutamine and release of glutamate, alanine and ammonia. 5. Enterocytes and colonocytes isolated from hypothyroid rats showed decreased rates of utilization and metabolism of glucose and glutamine. 6. The maximal activities of hexokinase (EC 2.7.1.1), 6-phosphofructokinase (EC 2.7.1.11), pyruvate kinase (EC 2.7.1.40), citrate synthase (EC 4.1.3.28), oxoglutarate dehydrogenase (EC 1.2.4.2) and phosphate-dependent glutaminase (EC 3.5.1.2) were decreased in intestinal mucosal scrapings from hypothyroid rats. Similar decreases were obtained in colonic mucosal scrapings (except for citrate synthase and oxoglutarate dehydrogenase) from hypothyroid rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of hypothyroidism on glucose and glutamine metabolism by the gut of the rat. 165 36

Na-K ATPase activity in the brain decreased significantly after diabetes was induced with streptozotocin in rats. Largest decreases were observed in the hippocampus (-30%) and the cerebral cortex (-26%). Smaller decreases were observed in the thalamus (-13%), hypothalamus (-11%) and brain stem (-10%). Na-K ATPase activity in the striatum and the cerebellum were not significantly decreased. The varied decreases suggest that the regional variation of the enzyme is enhanced in the diabetic state. The enzymes of glucose metabolic pathway, namely hexokinase, lactate dehydrogenase and citrate synthase in the brain regions largely remained unchanged although increases in lactate dehydrogenase were observed in some regions. Acetylcholinesterase activity, a marker for the cholinergic system, remains unaltered in the brain during diabetes. The results are discussed with respect to the possible metabolic factors which alter the Na-K ATPase in the brain and its comparison with the peripheral nerve.
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PMID:Diabetes induced by streptozotocin causes reduced Na-K ATPase in the brain. 166 46

The effects of training and naftidrofuryl treatment were observed in 21-month-old Long-Evans rats. Rats were injected intraperitoneally twice daily for 8 weeks with 7 mg.kg-1 of naftidrofuryl acid (SN, TN), or with 7 mg.kg-1 fumaric acid (SC and TC) or used as solvent. Training groups (TC, TN) started a progressive 8-week training programme of treadmill exercise. The activities of lactate dehydrogenase (LDH), hexokinase (HK), citrate synthase (CS) and 3-hydroxyacyl-Co-A-dehydrogenase (HAD), were measured in Soleus (SOL), Extensor Digitorum Longus (EDL) and Diaphragm (DIA) muscles. The mean VO2max value was 65 ml.min-1.kg-1 for 21-month-old rats. The training protocol induced increases in the mean VO2max values in the TC and TN groups, 71.8 and 74.4 ml.min-1.kg-1. In sedentary groups (SN), naftidrofuryl increased enzymatic activities (HK, CS, HAD) in the three muscles examined. When the animals underwent 8 weeks of physical training, the enzymatic activities (HK, CS, HAD) increased in SOL, EDL and DIA. When training was combined with naftidrofuryl treatment the increases in enzymatic activities were greater than those induced by training alone. However, the total changes did not differ for the sum of the changes produced by each condition alone.
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PMID:Enzymatic adaptations to treadmill training under the influence of naftidrofuryl acid in diaphragm and limb muscles of old rats. 171 85

Maximal in vitro activities of key metabolic enzymes were measured in brain and eye heaters of five species of scombroid fishes. Istiophorid billfishes (blue marlin, striped marlin and Mediterranean spearfish), xiphiid billfishes (Pacific and Mediterranean stocks) and a scombrid fish (butterfly mackerel) were included in the analysis. Our main objectives were (1) to assess the maximum possible substrate flux in heater tissue, and (2) to determine what metabolic substrates could fuel heat production. Heater tissue of all scombroids examined showed extremely high oxidative capacity. Activities of citrate synthase, a commonly measured index of oxidative metabolism, included the highest value ever reported for vertebrate tissue. In most billfishes, citrate synthase activities were similar to or higher than those found for mammalian cardiac and avian flight muscle. Marker enzymes for aerobic carbohydrate metabolism (hexokinase) and fatty acid metabolism (carnitine palmitoyltransferase and 3-hydroxyacyl-CoA dehydrogenase) also displayed extraordinarily high activities. Activities of carnitine palmitoyltransferase measured in heater organs were among the highest reported for vertebrates. These results indicate that heat production could be fueled aerobically by either lipid or carbohydrate metabolism. Inter- and intraspecifically, heater organs of fishes from the colder Mediterranean waters had a higher aerobic capacity and, hence, a greater heat-generating potential, than fishes from the warmer waters of the Pacific. This difference may be attributed to different thermal environments or it may result from allometry, since fishes caught in the Mediterranean were considerably smaller than those caught in the Pacific.
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PMID:Activities of key metabolic enzymes in the heater organs of scombroid fishes. 175 72

The maximum activities of some key enzymes of metabolism were studied in lungs of fed and 48-h-starved rats. The maximum activity of hexokinase in the lung is similar to that of other tissues of the body, but lower than that of phosphorylase and 6-phosphofructokinase. High activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were found in lung tissue, suggesting the importance of the pentose phosphate pathway in the lung. The activities of hexokinase and 6-phosphofructokinase were decreased whereas that of phosphorylase increased in response to starvation. Of the enzymes of the tricarboxylic acid cycle whose activities were measured, that of oxoglutarate dehydrogenase was the lowest, yet its activity (approximately 4.2 nmol/min per mg protein at 37 degrees C) was considerably greater than the flux through the cycle (0.46 nmol/min per mg protein at 37 degrees C; calculated from oxygen consumption by incubated lung slices). The activities of both oxoglutarate dehydrogenase and citrate synthase were decreased by starvation. The activities of 3-oxoacid CoA-transferase and acetoacetyl-CoA thiolase were low in lung tissue compared to those of other tissues (eg kidney, brain) and that of 3-hydroxybutyrate dehydrogenase was very low. The activity of carnitine palmitoyl transferase is higher in the lung, suggesting that fatty acids (and possibly acetoacetate) could provide acetyl-CoA as substrate for the tricarboxylic acid cycle. Very low rates of utilization of 3-hydroxybutyrate were observed during incubation of lung slices, but that of oleate was 1.2 nmol/h per mg of protein.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolism of glucose, glutamine, long-chain fatty acids and ketone bodies by lungs of the rat. 176

1. Cells from the bone marrow and cells from the thymus of the rat were incubated in the presence of glucose and glutamine and phytohaemagglutinin, concanavalin-A or lipopolysaccharide. Cells were harvested at times up to 4 hr, extracted and maximum activities of hexokinase, lactate dehydrogenase, citrate synthase or glutaminase measured. 2. In bone marrow cells, there were little changes in enzyme activities except for an increase in the activity of citrate synthase which was prevented by concanavalin-A. This mitogen also caused a decrease in the activity of hexokinase. 3. In contrast, in thymocytes, the activities of hexokinase and glutaminase were decreased in the control condition but addition of lipopolysaccharide, a B-cell mitogen prevented these decreases in activity and concanavalin-A maintained the activity of glutaminase. Concanavalin-A caused a decrease in hexokinase activity but a marked increase in that of glutaminase. 4. It is suggested that changes in the maximum activities of hexokinase and glutaminase over this 4 hr period may represent the effect of removal of thymus-produced growth factors, whose effects can be replaced, at least in part, by two mitogens.
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PMID:Effect of B- and T-cell mitogens on the maximum activities of hexokinase, lactate dehydrogenase, citrate synthase and glutaminase in bone marrow cells and thymocytes of the rat during four hours of culture. 177 87


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