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

Muscle ultrastructure and biochemistry in vastus lateralis muscle biopsies and the response to exercise of 8 lowland Tibetans (T) were compared with those of 8 Nepalese lowlanders (N). Blood hemoglobin was lower in T than in N (119 +/- 3 vs. 131 +/- 2 g/l; P < 0.05). Peak O2 consumption per kilogram of body mass was similar [37.9 +/- 2.2 (T) vs. 40.1 +/- 1.36 ml.min-1.kg body mass-1 (N)]. Maximum exercise blood lactate was the same [11.4 (T) +/- 0.5 vs. 11.3 +/- 0.6 mM (N)]. Muscle fiber type distribution was similar [type I, 58.6 +/- 3.4 (N) vs. 57.0 +/- 3.4% (T); type IIa, 24.1 +/- 3.5 vs. 27.1 +/- 1.6%; type IIb, 17.4 +/- 1.4 vs. 15.9 +/- 2.9%]. T had smaller fiber cross-sectional areas [3,413 +/- 677 (T) vs. 3,895 +/- 447 microns 2 (N); P < 0.05] but had similar number of capillaries per muscle fiber [1.35 +/- 0.23 (T) vs. 1.46 +/- 0.08 (N)] and muscle fiber area supplied per capillary [399 +/- 29 (T) vs. 382 +/- 65 mm2 (N)]. Total mitochondrial volume density was much lower in T (3.99 +/- 0.17%) than in N (5.51 +/- 0.19%) (P < 0.025). Mirroring mitochondrial volume density, citrate synthase and 3-hydroxyacyl-CoA dehydrogenase activities were lower in T than in N (P < 0.05). The activities of L-lactate dehydrogenase and hexokinase were the same in both groups. T had significantly less muscle fiber lipid droplets than did N, which correlated with the low activity of 3-hydroxyacyl-CoA dehydrogenase (r = 0.57, P = 0.02). In conclusion, lowland-born T have a low mitochondrial volume-to-specific peak O2 consumption ratio, which, based on previous measurements on altitude-born Sherpas (B. Kayser, H. Hoppeler, H. Claassen and P. Cerretelli. J. Appl. Physiol. 70: 1938-1942, 1991), appears to be an inborn feature.
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PMID:Muscle ultrastructure and biochemistry of lowland Tibetans. 882 94

Our purpose was to examine the effects of sprint interval training on muscle glycolytic and oxidative enzyme activity and exercise performance. Twelve healthy men (22 +/- 2 yr of age) underwent intense interval training on a cycle ergometer for 7 wk. Training consisted of 30-s maximum sprint efforts (Wingate protocol) interspersed by 2-4 min of recovery, performed three times per week. The program began with four intervals with 4 min of recovery per session in week 1 and progressed to 10 intervals with 2.5 min of recovery per session by week 7. Peak power output and total work over repeated maximal 30-s efforts and maximal oxygen consumption (VO2 max) were measured before and after the training program. Needle biopsies were taken from vastus lateralis of nine subjects before and after the program and assayed for the maximal activity of hexokinase, total glycogen phosphorylase, phosphofructokinase, lactate dehydrogenase, citrate synthase, succinate dehydrogenase, malate dehydrogenase, and 3-hydroxyacyl-CoA dehydrogenase. The training program resulted in significant increases in peak power output, total work over 30 s, and VO2 max. Maximal enzyme activity of hexokinase, phosphofructokinase, citrate synthase, succinate dehydrogenase, and malate dehydrogenase was also significantly (P < 0.05) higher after training. It was concluded that relatively brief but intense sprint training can result in an increase in both glycolytic and oxidative enzyme activity, maximum short-term power output, and VO2 max.
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PMID:Muscle performance and enzymatic adaptations to sprint interval training. 960 10

Spontaneously hypertensive rats (SHR) demonstrate elevated blood pressure, cardiac hypertrophy, glucose intolerance, and insulin resistance compared with age-matched Wistar-Kyoto rats (WKY). We investigated concurrent effects of captopril on blood pressure, cardiac mass, myocardial enzyme activities, glucose tolerance, and insulin action in young male SHR. At 10 weeks of age, SHR were randomized into two groups, one receiving distilled water, the other a captopril solution (50 mg/kg body weight/day). We also examined age-matched WKY receiving distilled water. Blood pressure was measured by tail-cuff during the 4-week treatment period and oral glucose tolerance was tested at the end of treatment. Hearts were weighed and ventricular tissue was assayed for activities of 3-hydroxyacyl-CoA dehydrogenase, citrate synthase, and hexokinase. Growth rates were similar between captopril-treated and control SHR, but less than those of WKY. Captopril reduced blood pressure (134 +/- 8 v 177 +/- 8 mm Hg, P < .05) and left ventricular mass (-18%, P < .05) in SHR. Cardiac enzyme activities also changed with captopril treatment, reflecting an increased capacity for beta-oxidation of fatty acids and reduced potential for glucose phosphorylation in the left ventricle of SHR. Serum concentrations of glucose, insulin, and free fatty acids after a brief fast and in response to oral glucose were not different after captopril treatment, suggesting no improvement in insulin action or glucose tolerance. In summary, treatment of young male SHR with captopril reduces blood pressure and cardiac mass, and promotes a small but significant increase in cardiac capacity for oxidation of fatty acids and reduction of glucose phosphorylation. In contrast, metabolic effects of captopril on oral glucose tolerance and insulin action were not evident.
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PMID:Metabolic, hemodynamic, and cardiac effects of captopril in young, spontaneously hypertensive rats. 1037 67

The aim of this study was to determine if there is a relationship among skeletal muscle fiber composition, capillarization, blood pressure (BP) and/or the components of the metabolic syndrome. Two groups were compared: 8 recently diagnosed, untreated, hypertensive men (BP > or = 140/90) and 7 normotensive men as controls. Muscle biopsies were taken from the vastus lateralis part of quadriceps femoris muscle in order to assess: fiber type proportion, capillarization, hexokinase, citrate synthase, beta-hydroxyacyl CoA dehydrogenase activities; lipoprotein lipase mass and activity, free fatty acids and triglycerides. Serum levels of insulin, glucose, cholesterol, uric acid and triglycerides were also assayed. Hypertensive patients had higher insulin levels and insulin resistance [homeostasis model assessment (HOMA)], a decreased hexokinase activity and an increase of muscle lipoprotein lipase mass as compared to controls. Interestingly, correlations among values differ in each group. The percentage of type IIB fibers was related to diastolic BP (blood pressure) in control and to mean BP in hypertensive subjects. Serum cholesterol and glucose were inversely related to the percentage of type I fibers in the control subjects. Negative correlations between capillarization and glucose, cholesterol and uric acid levels were found in control subjects. In all subjects, a strong correlation was found between SBP (systolic BP) and DBP (diastolic BP), and insulin resistance (IR) and uric acid levels. Muscle fiber type proportion and capillarization were related to blood pressure and components of the metabolic syndrome.
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PMID:Muscle fiber composition and capillarization in relation to metabolic alterations in hypertensive men. 1132 89

The activity of muscle metabolic enzymes depends on the amount and type of physical training. We examined muscle enzyme adaptation to prolonged training followed by a period of lowered activity in spinal-cord-injured individuals (SCI). Ten SCI [mean age 35 (SEM 2) years, mean body mass 78 (SEM 4) kg, mean time post-injury 12 (SEM 2) years and range of lesion C5-T4] were given 12 months of functional electrical stimulation of an upright cycling motion for 30 min a day, three times a week, followed by 6 months of training once a week. Activities of glycolytic (hexokinase HK, lactate dehydrogenase LDH) and oxidative (citrate synthase CS, 3-hydroxyacyl-CoA dehydrogenase HAD) enzymes were determined in biopsies of the vastus lateralis muscle taken at 0, 3, 6, 12, and 18 months of training. The degree of sympathoadrenergic activity was evaluated from arterial concentrations of catecholamines in response to acute exercise. Training three times a week induced increases (P < 0.05) in HK (150%), LDH (40%), CS (100%), and HAD (70%) activities that reached a plateau after 3 months. Peak oxygen uptake and power output during exercise by electrical stimulation rose continuously over the first 12 months. After reducing the amount of training by two-thirds, HK, LDH and CS activities remained elevated above basal levels (P < 0.05), whereas HAD, power output and maximal oxygen uptake returned to pretraining levels (P > 0.05). It is concluded that most improvements in glycolytic and mitochondrial oxidative enzyme activities induced by long-term training can be maintained in spinal-cord-injured individuals despite a marked reduction in training frequency unrelated to performance or to the degree of sympathoadrenergic impairment.
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PMID:Muscle enzyme adaptation to training and tapering-off in spinal-cord-injured humans. 1141 39

The purpose of the present study was to investigate the relationship between intra-abdominal-obesity susceptibility and the adaptation of skeletal muscle metabolic and histochemical characteristics when fed a high-fat diet (HFD) for a short period of time. Twenty-four male Wistar rats were fed a HFD (39.7% calories of fat) for 5 wk. After the 5-wk dietary period, the rats were sacrificed and divided into intra-abdominal-obesity-prone (OP) or obesity-resistant (OR) groups according to the total intra-abdominal fat pads (epididymal, mesenteric, and perirenal) weights. A superficial portion of the Muscle (M.) gastrocnemius tissue obtained from 2 groups before and after feeding the HFD were analyzed to determine their hexokinase (HK), (beta-hydroxyacyl CoA dehydrogenase (beta-HAD), and citrate synthase (CS) activities. Muscle fiber composition and capillary density were examined in the deep portion of the M. gastrocnemius, soleus, and extensor digitorum longus (EDL) gained after the HFD. While the OP group had more intra-abdominal fat pads and a heavier final body weight than the OR group, there was no significant difference in the energy intake between the two. Due to the HFD, the OP group showed significant increases in beta-HAD and CS activities, while the OR group did not. Change of beta-HAD activity by HFD in the OP group was significantly greater than that in the OR group. The ratio of fat oxidation, expressed as beta-HAD/CS, significantly increased in the OP group, but not in the OR group. No differences were found in either the muscle fiber composition or capillarization. These results suggest that intra-abdominal-obesity-susceptive rats may have a higher adaptation degree in muscle oxidative enzyme activities as characteristic in the early stage of intra-abdominal adipose accumulation.
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PMID:Adaptation of skeletal muscle characteristics to a high-fat diet in rats with different intra-abdominal-obesity susceptibilities. 1459 10

The purpose of the present study was to investigate the relationship among intra-abdominal adipose storage, adaptation in the serum leptin concentration and skeletal muscle enzyme activity after a 4-week energy restriction (ER). Thirty-one male Wistar rats were divided into 40% energy restricted (n=24) or ad libitum-fed control (CL) rats (n=7). The energy-restricted rats were grouped into the most fat (MF, n=7), medium (n 10) and the least fat (LF, n=7) by their intra-abdominal fat pads mass (epididymal, mesenteric, and perirenal) after ER. A superficial portion of M. gastrocnemius tissue obtained before and after the diet period were analyzed to determine the activities of hexokinase (HK), beta-hydroxyacyl CoA dehydrogenase (beta-HAD) and citrate synthase (CS). Blood samples were also collected for a serum leptin assay. At the baseline, no difference was found in either the leptin concentration or the enzyme activities among LF, MF and CL. The serum leptin concentration was positively correlated with the muscle activities of beta-HAD and CS, while it negatively correlated with HK/beta-HAD. After ER, the activities of HK, beta-HAD and CS were all significantly lower in LF than in CL. Among the energy-restricted rats, the intra-abdominal fat pad weight, leptin concentration and the activities of beta-HAD, CS, beta-HAD/CS all significantly correlated with one another. The changes in leptin and the activity of beta-HAD were also positively correlated. These findings indicate that parallel decreases in the serum leptin and skeletal muscle enzyme activities with the energy restriction-induced intra-abdominal adipose reduction, thus may suggest the leptin to have a regulative effect on the muscle enzyme activity during ER.
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PMID:Decreased serum leptin and muscle oxidative enzyme activity with a dietary loss of intra-abdominal fat in rats. 1471 57

The present study examined the effects of chronic activation of 5'-AMP-activated protein kinase (AMPK) on the oxidative capacity and myosin heavy chain (MHC) based fibre phenotype of rodent fast- and slow-twitch muscles. Sprague-Dawley rats received daily injections for 4 weeks of the known AMPK activator 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) or vehicle (control). The AICAR group displayed increases in hexokinase-II (HXK-II) activity, expression, and phosphorylation in fast-twitch muscles (P<0.001) but not in the slow-twitch soleus (SOL). In the AICAR group, citrate synthase (EC 4.1.3.7) and 3-hydroxyacyl-CoA-dehydrogenase (EC 1.1.1.35) were elevated 1.6- and 2.1-fold (P<0.05), respectively, in fast-twitch medial gastrocnemius (MG), and by 1.2- and 1.4-fold (P<0.05) in the slower-twitch plantaris (PLANT). No changes were observed in the slow-twitch SOL. In contrast, the activity of glyceraldehyde phosphate dehydrogenase (EC 1.2.1.12) remained unchanged in all muscles. AICAR treatment did not alter the MHC-based fibre type composition in fast- or slow-twitch muscles, as determined by immunohistochemical and electrophoretic analytical methods or by RT-PCR. We conclude that chronic activation of AMPK mimics the metabolic changes associated with chronic exercise training (increased oxidative capacity) in the fast-twitch MG and PLANT, but does not coordinately alter MHC isoform content or mRNA expression.
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PMID:Effects of chronic AICAR administration on the metabolic and contractile phenotypes of rat slow- and fast-twitch skeletal muscles. 1471 43

A canine gracilis model was used to study muscle energy metabolism and enzyme activities after free vascularized muscle transfer. Fifteen male mongrel dogs underwent orthotopic, free transfer of the left gracilis with microneurovascular anastomosis. After a minimum of 10 months' recovery, muscle biopsy specimens were obtained from the transfers and the contralateral controls and analyzed for relative fiber type areas and maximum activities of phosphorylase, hexokinase, phosphofructokinase, glycerol-3-phosphate dehydrogenase (GPDH), pyruvate kinase, lactate dehydrogenase, citrate synthase, succinate dehydrogenase, 3-hydroxyacyl coenzyme A dehydrogenase (HAD), and creatine phosphokinase. Biopsy specimens obtained before and after a 10 minute, 20-Hz contraction were analyzed for glucose, glycogen, glycolytic intermediates, phosphocreatine, total creatine, and adenine nucleotides (adenosine triphosphate, adenosine diphosphate, adenosine monophosphate, inosine monophosphate, and inosine). There was no significant transfer versus control difference in type I relative fiber area (45 +/- 4 percent versus 44 +/- 3 percent). Total creatine was significantly reduced in the transferred muscles relative to control (83.1 +/- 3.0 mmol/kg versus 100.6 +/- 5.1 mmol/kg dry weight). Maximal activities of phosphorylase, pyruvate kinase, lactate dehydrogenase, citrate synthase, succinate dehydrogenase, HAD, and creatine phosphokinase were diminished in transfers relative to controls, although hexokinase activity was significantly higher in the freely transferred gracilis muscles. During the 20-Hz contraction, muscle transfers produced less force initially, although the force/time integral over the 10-minute stimulation was similar in transfers (277 +/- 25 N/g/second) and controls (272 +/- 24 N/g/second). The contraction was associated with significant glvcogen use and lactate accumulation in both transfers and controls, although this was less pronounced for the transfers. Glycolytic flux appeared muted in the transfers relative to controls. Significant, similar high-energy phosphagen reductions and inosine monophosphate accumulation were noted during the contraction in both groups. Contractile activity is associated with the expected pattern of muscle metabolite changes following free vascularized transfer, indicating the components of cellular energy metabolism are not qualitatively altered after microneurovascular muscle transfer. In contrast, quantitative differences suggest that free vascularized muscle transfer can be associated with a muscle enzyme profile consistent with deconditioning and the presence of denervated muscles fibers in the absence of fiber type profile changes.
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PMID:Metabolic characteristics of experimental free vascularized canine gracilis muscle transfers. 1510 85

Some evidence suggests that resistance training may lower relative muscle mitochondrial content via "dilution" of the organelle in a larger muscle fibre. Such an adaptation would reduce fatigue resistance, as well as compromise oxidative ATP synthesis and the capacity for fatty-acid oxidation. We investigated the effect of resistance training on mitochondrial enzymes of the citric acid cycle (citrate synthase; CS) and beta-oxidation (beta-hydroxyacyl CoA dehydrogenase; beta-HAD), as well as markers of the potential for glucose phosphorylation (hexokinase; HK) and glycolysis (phosphofructokinase; PFK). Twelve untrained men (21.9 +/- 0.5 y; 1.79 +/- 0.03 m; 83.2 +/- 3.2 kg) participated in a 12 week progressive resistance-training program. Muscle biopsies were taken from the vastus lateralis before (PRE) and after (POST) training. Training increased mean muscle fibre cross-sectional area (p < 0.05) and the activities of CS (PRE = 4.53 +/- 0.44 mol.kg protein(-1).h(-1); POST = 5.63 +/- 0.40 mol.kg protein(-1).h(-1); p < 0.001) and beta-HAD (PRE = 2.55 +/- 0.28 mol.kg protein(-1).h(-1); POST = 3.11 +/- 0.21 mol.kg protein(-1).h(-1); p < 0.05). The activity of HK increased 42% (p < 0.05), whereas the activity of PFK remained unchanged. We conclude that resistance training provides a stimulus for improving muscle oxidative potential, as reflected by the increased activities of CS and beta-HAD following resistance training induced hypertrophy.
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PMID:Increased muscle oxidative potential following resistance training induced fibre hypertrophy in young men. 1711 Oct 3


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