Glycogen content and activities of key glycolytic enzymes in muscle biopsies from control subjects and patients with chronic alcoholic skeletal myopathy

The capacity for glycolysis in muscle biopsies obtained from long-term heavy alcohol drinking patients has been compared with tissue from control subjects by assay in vitro of the total activities of glycogen phosphorylase, phosphofructokinase and fructose 1,6-bisphosphatase, key regulatory enzymes in the anaerobic glycolytic pathway. Biopsies from 13 of 22 patients had type II fibre atrophy, and the activities of all three enzymes were reduced in these biopsies, when expressed in terms of DNA content, the most striking reduction being in phosphofructokinase activity. The amount of glycogen in the tissue correlated closely with these enzyme activities and was slightly lower in the most atrophic tissue, when expressed in terms of DNA content. The activities of acid and neutral alpha-glucosidases were similar in biopsies from control subjects and patients with various severities of alcohol myopathy. The reduced activities are consistent with a reduced proportion of type II fibre muscle mass in these patients, and suggest that there may be a reduced capacity for glycolysis with resultant reduced lactate production. Whether the changes in enzyme activities are primary to the selective atrophy remains to be established.     

Effects of physical training on the metabolism of skeletal muscle.

With moderate training (30-60 min daily at 70-80% of VO2 max, 3-5 times weekly), the trained muscles display a 40-50% increase in the content of mitochondrial oxidative enzymes. Concomitantly, the total number of muscle capillaries may increase by 50%, whereas the content of glycolytic enzymes is not, or only marginally, affected. The oxidative enzyme increase, which occurs over 6-8 wk, is lost in 4-6 wk if training is stopped. This loss occurs faster than the decrease in muscle capillarization and in the whole-body VO2 max. Trained muscles of athletes have 3-4 times higher oxidative enzyme levels and two- to threefold more capillaries per muscle fiber than untrained muscle. Extensive endurance training results in an enhanced percentage of slow-twitch fibers, but the time course of this change is not known. More extensive changes are observed in chronically stimulated rabbit muscle. In this case, enzymes of oxidation display large increases (6- to 12-fold), whereas there is a decrease of 70-90% in enzymes of glycolysis, glycogenolysis, gluconeogenesis, and high-energy phosphate transfer. There is a normal training response in mitochondrial enzyme activities in individuals with insulin-dependent and non-insulin-dependent diabetes, but the ability to form new skeletal muscle capillaries in response to physical training may be deficient in insulin-dependent diabetes. Training-induced changes in the metabolic character of skeletal muscle leads to an increased reliance on fat metabolism during exercise, with a lowered blood lactate concentration and a sparing of muscle glycogen.     

Serum carnosinase activities in patients with alcoholic chronic skeletal muscle myopathy

1. Serum carnosinase activity was assayed in a group of alcoholic patients with and without histologically proven atrophy of type II skeletal muscle fibres, and in control subjects. No significant activity was detected in muscle biopsy samples or washed erythrocytes. 2. Serum carnosinase activity was significantly lower in chronic alcoholic patients compared with a group of age-matched controls. Alcoholics with abnormal muscle biopsies had significantly lower enzyme activities than either those patients with normal muscle biopsies or the controls. Serum enzyme activities in patients with normal muscle biopsies were not significantly different from controls. 3. Serum carnosinase activity was inversely correlated with the degree of muscle atrophy as measured by the type II fibre atrophy factor. There was a positive correlation between the enzyme activity and skeletal muscle mass as reflected by the creatinine-height index. Furthermore, the enzyme activity significantly increased, with resolution or improvement in the myopathy, in patients who abstained from alcohol. 4. Kinetic studies showed that the reduced carnosinase activity was due mainly to a decrease in the apparent Vmax. The apparent Km was significantly higher in the myopathic compared with non-myopathic alcoholics. Mixing serum from controls and patients with myopathy gave the expected values, indicating the absence of a serum enzyme inhibitory factor. Acute alcohol loading had no effect on the serum carnosinase activity. 5. The decrease in serum carnosinase activity in alcoholics was not related to the severity of their liver disease. Assays of serum carnosinase in chronic alcoholics, can thus be used as a marker of their associated myopathy.     

Activities of hexokinase, phosphofructokinase, fructose bisphosphatase and 2-oxoglutarate dehydrogenase in muscle of normal subjects and very ill surgical patients

1. The activities of hexokinase, phosphofructokinase, fructose bisphosphatase and 2-oxoglutarate dehydrogenase have been measured in the vastus lateralis and rectus abdominus muscle of normal human subjects and in very ill surgical patients. 2. The activities of these enzymes in the muscle of control subjects were similar to the pattern seen in the skeletal muscle of other mammals and lower vertebrates. 3. Fructose bisphosphatase and phosphofructokinase activities were significantly lower in the muscle of ill patients although the depression of the activity of fructose bisphosphatase was much greater than that of phosphofructokinase in both muscle types of ill patients. 4. The maximum rate of cycling in the fructose 6-phosphate--fructose, 1,6-diphosphate cycle may be altered in the ill. 5. This decreased cycling may have a direct influence on the sensitivity of glycolysis to regulators such as the adenine nucleotides and may reduce the ability to maintain body temperature. 6. Increased glycogen synthesis in these muscles may indicate that the role of fructose bisphosphatase is unlikely to be solely in glycogen resynthesis.     

Muscle atrophy in rats following denervation, casting, inflammation, and tenotomy.

One week after unilateral denervation, tenotomy, casting, or joint inflammation, skeletal muscles of adult female Wistar rats were studied to determine the effect of these processes on muscle weights and fiber diameters of the soleus, the red and white regions of the plantaris, plus muscle weights and protein content of the gastrocnemius. All atrophic processes caused greater weight loss of the soleus than of the plantaris or gastrocnemiums. Within the soleus and plantaris muscles, the type-I fiber atrophy was equal to the type-II fiber atrophy except for the white region of the plantaris following tenotomy, where the wasting of the type-I fiber was greater than that of type II. This study also demonstrated that denervation, tenotomy, casting, and inflammation resulted in a greater loss of myofibrillar proteins (content and absolute amounts) than of sarcoplasmic and stromal proteins. Denervation generally was found to have the greatest effect on the parameters evaluated. The findings are consistent with the hypothesis that slow muscle is more dependent than fast muscle on neuronal control, and that nerve controls muscle through the dual role of impulse activity and axoplasmic flow.     

Carnitine concentration in relation to enzyme activities and substrate utilization in human skeletal muscles.

The relationships between the carnitine concentration and enzyme activities representative of different metabolic pathways, glycogenolysis, glycolysis, beta-oxidation of fatty acids, citric acid cycle, and respiratory chain were studied in skeletal muscle tissue from 18 volunteering subjects. In addition, the in vitro incorporation rates of glucose-carbon and palmitate-carbon into different metabolites, and the concentration of glycogen, triglycerides, and phospholipids were determined in the same tissue specimen. The carnitine concentration correlated positively and statistically significantly with the activities of 3-OH-acyl-CoA dehydrogenase and citrate synthase, with the incorporation rate of palmitate-carbon into CO2, and the incorporation rate of glucose-carbon into lactate in the muscle tissue. The results indicate a coupling between the concentration of carnitine and the capacity for long-chained fatty acid oxidation in human skeletal muscles.     

Effect of hyperthyroidism on fibre-type composition,fibre area,glycogen content and enzyme activity in human skeletal muscle

Summary. Seven hyperthyroid patients were studied by repeated muscle biopsies (vastus lateralis) before and after a period of medical treatment which averaged 10 months. The biopsies were analysed with regard to fibre-type composition, fibre area, capillary density, glycogen content and enzyme activities representing the glycolytic capacity (hexokinase, 6-phosphofructokinase), oxidative capacity (oxoglutarate dehydrogenase, citrate synthase) and Ca²⁺- and Mg²⁺-stimulated ATPase in muscle. In the pretreatment biopsy (hyperthyroid state), there was a significantly lower proportion of type I fibres (30% vs. 41%), a higher capillary density (23%), lower glycogen content (33%), and higher hexokinase activity (32%) compared with the post-treatment biopsy. No significant changes in the activity of the remaining enzymes were observed. The present study indicates that hyperthyroidism induces a transformation from type I to type II fibres in human skeletal muscle. The increase in hexokinase activity probably reflects a higher glucose utilization by skeletal muscle in order to compensate partially for the reduced glycogen content.     

Acid hydrolases in normal and diseased human muscle

The activities of acid phosphatase and β-acetylglucosaminidase in muscles from normal persons and from patients with various muscular and neuromuscular diseases have been determined. They are normal in all minimally abnormal muscles irrespective of their different disease etiologies. Increased amounts of these enzymes are only found in the severely deranged muscles obtained from patients with Duchenne muscular dystrophy, other dystrophies, polymyositis, spinal muscular atrophy and in other myopathies. These results suggest that these enzymes are involved in muscle degeneration in humans.     

Glucose tolerance in relation to skeletal muscle enzyme activities in cancer patients.

Glucose metabolism and skeletal muscle enzyme activities were studied in nineteen cancer patients and twelve matched controls. The fasting insulin values were normal but the fasting glucose values and the sum of glucose were increased and the sum of insulin was decreased during intravenous glucose tolerance test in the cancer patients. The elimination rate of glucose (k-value) during glucose challenge was, however, not significantly different in cancer patients as compared with that of appropriate controls. The activities of enzymes representative for glycogen turnover, glycolysis, citric acid cycle and respiratory chain were significantly lower in the muscle tissue of cancer patients, while the activity of 3-hydroxyacyl-CoA dehydrogenase, an enzyme in the beta-oxidation of fatty acids, was unchanged and the activity of glucose-6-phosphate dehydrogenase was significantly higher. Rate limiting enzyme activities in muscle tissue, phosphofructokinase and cytochrome c oxidase correlated signficantly with plasma insulin and glucose during glucose challenge. The results point at the possibility of covariating debilitation of pancreatic beta-cells and skeletal muscle enzymes caused by the malignant tumour.     

Glucocorticosteroid status in chronic alcoholics with and without skeletal muscle myopathy

1. Chronic alcoholism is associated with a selective atrophy of type II skeletal muscle fibres. We studied the glucocorticoid status of chronic alcoholics with and without myopathy to determine if hypercortisolism is responsible for the myopathy. 2. Twenty-four hour urinary cortisol excretion and diurnal serum cortisol measurements were not significantly different in chronic alcoholics, with and without atrophy of type II skeletal muscle fibres. 3. Diurnal serum cortisol variation was normal for both groups of alcoholics studied. None of the patients with myopathy had raised serum cortisol levels. 4. We conclude that chronic alcoholic myopathy is not due to alcohol-related pseudo-Cushing's syndrome.     

骨关节病患者肌纤维萎缩类型及其与日常活动的相关性

背景:骨关节病患者因制动等原因可出现严重的肌纤维萎缩,但目前对这类肌纤维萎缩的微观分类及其与日常活动的研究较少。目的:观察骨关节病患者肌肉萎缩类型以及其与日常活动的相关性。方法:纳入24例老年女性骨关节病患者,应用功能独立性评定量表对患者习惯性的日常运动进行了评价,在进行关节置换过程中对患者肌纤维进行了测定并通过活检进行组织病理学侧量。同时选取同期因骨折需要进行修复的4例女性患者为对照组。观察患者的肌纤维(Ⅰ型、ⅡA型和ⅡB型)发生萎缩类型和比率变化。结果与结论:骨关节病患者根据发生萎缩的肌纤维类型不同,分为1型、2B型何1+2AB型。Ⅰ型的肌纤维肌横截面积明显小于ⅡA型和ⅡB型肌纤维(P<0.05)。大部分骨关节病患者在得病过程中仅发生同一种肌纤维类型的萎缩,而非所有的肌纤维均出现萎缩。功能独立性评定量表评分从1+2AB型,2B型和1型逐渐减少(P<0.05)。结果证实,肌肉萎缩1+2AB型对骨关节病患者日常活动影响最大,而单纯的2B型影响最小。     

骨关节病患者肌纤维萎缩类型及其与日常活动的相关性

背景：骨关节病患者因制动等原因可出现严重的肌纤维萎缩,但目前对这类肌纤维萎缩的微观分类及其与日常活动的研究较少。目的：观察骨关节病患者肌肉萎缩类型以及其与日常活动的相关性。方法：纳入24例老年女性骨关节病患者,应用功能独立性评定量表对患者习惯性的日常运动进行了评价,在进行关节置换过程中对患者肌纤维进行了测定并通过活检进行组织病理学侧量。同时选取同期因骨折需要进行修复的4例女性患者为对照组。观察患者的肌纤维（Ⅰ型、ⅡA型和ⅡB型）发生萎缩类型和比率变化。结果与结论：骨关节病患者根据发生萎缩的肌纤维类型不同,分为1型、2B型何1＋2AB型。Ⅰ型的肌纤维肌横截面积明显小于ⅡA型和ⅡB型肌纤维（P〈0.05）。大部分骨关节病患者在得病过程中仅发生同一种肌纤维类型的萎缩,而非所有的肌纤维均出现萎缩。功能独立性评定量表评分从1＋2AB型,2B型和1型逐渐减少（P〈0.05）。结果证实,肌肉萎缩1＋2AB型对骨关节病患者日常活动影响最大,而单纯的2B型影响最小。     

Myopathy in CRPS-I: Disuse or neurogenic?

The diagnosis Complex Regional Pain Syndrome type I (CRPS‐I) is based on clinical symptoms, including motor symptoms. Histological changes in muscle tissue may be present in the chronic phase of CRPS‐I. Aim of this study was to analyze skeletal muscle tissue from amputated limbs of patients with CRPS‐I, in order to gain more insight in factors that may play a role in changes in muscles in CRPS‐I. These changes may be helpful in clarifying the pathophysiology of CRPS‐I. Fourteen patients with therapy resistant and longstanding CRPS‐I, underwent an amputation of the affected limb. In all patients histological analysis showed extensive changes in muscle tissue, such as fatty degeneration, fibre atrophy and nuclear clumping, which was not related to duration of CRPS‐I prior to amputation. In all muscles affected, both type 1 and type 2 fibre atrophy was found, without selective type 2 fibre atrophy. In four patients, type grouping was observed, indicating a sequence of denervation and reinnervation of muscle tissue. In two patients even large group atrophy was present, suggesting new denervation after reinnervation. Comparison between subgroups in arms and legs showed no difference in the number of changes in muscle tissue. Intrinsic and extrinsic muscles were affected equally. Our findings show that in the chronic phase of CRPS‐I extensive changes can be seen in muscle tissue, not related to duration of CRPS‐I symptoms. Signs of neurogenic myopathy were present in five patients.     

脂质沉积性肌病2例报告并文献复习

目的：探讨脂质沉积性肌病（LSM）的临床和肌肉病理特点。方法：分析2例脂质沉积性肌病患者的临床特点、实验室检查、肌活检资料,并复习相关文献。结果：LSM的主要临床特点为四肢近端肌无力和对运动不耐受,肌萎缩多不明显,血清肌酶轻中度升高,肌电图多呈肌源性损害;肌肉病理显示肌纤维空泡变性,脂滴明显增多,电镜也证实肌纤维内脂滴堆积。结论：LSM是一种少见的肌病类型,以肢体近端肌无力和对运动不耐受为主要表现,临床上多长期误诊,确诊依靠肌肉病理检查。     

Replacing acid alpha-glucosidase in Pompe disease: recombinant and transgenic enzymes are equipotent, but neither completely clears glycogen from type II muscle fibers.

Pompe disease (type II glycogen storage disease) is an autosomal recessive disorder caused by a deficiency of lysosomal acid alpha-glucosidase (GAA) leading to the accumulation of glycogen in the lysosomes primarily in cardiac and skeletal muscle. The recombinant human GAA (rhGAA) is currently in clinical trials for enzyme replacement therapy of Pompe disease. Both clinical data and the results of preclinical studies in our knockout model of this disease show that rhGAA is much more effective in resolving the cardiomyopathy than the skeletal muscle myopathy. By contrast, another form of human GAA--transgenic enzyme constitutively produced in liver and secreted into the bloodstream of knockout mice (Gaa-/-)--completely prevented both cardiac and skeletal muscle glycogen accumulation. In the experiments reported here, the transgenic enzyme was much less efficient when delivered to skeletal muscle after significant amounts of glycogen had already accumulated. Furthermore, the transgenic enzyme and the rhGAA have similar therapeutic effects, and both efficiently clear glycogen from cardiac muscle and type I muscle fibers, but not type II fibers. Low abundance of proteins involved in endocytosis and trafficking of lysosomal enzymes combined with increased autophagy in type II fibers may explain the resistance to therapy.     

Dichloroacetate inhibits glycolysis and augments insulin-stimulated glycogen synthesis in rat muscle.

The decrease in plasma lactate during dichloroacetate (DCA) treatment is attributed to stimulation of lactate oxidation. To determine whether DCA also inhibits lactate production, we measured glucose metabolism in muscles of fed and fasted rats incubated with DCA and insulin. DCA increased glucose-6-phosphate, an allosteric modifier of glycogen synthase, approximately 50% and increased muscle glycogen synthesis and glycogen content greater than 25%. Lactate release fell; inhibition of glycolysis accounted for greater than 80% of the decrease. This was associated with a decrease in intracellular AMP, but no change in citrate or ATP. When lactate oxidation was increased by raising extracellular lactate, glycolysis decreased (r = - 0.91), suggesting that lactate oxidation regulates glycolysis. When muscle lactate production was greatly stimulated by thermal injury, DCA increased glycogen synthesis, normalized glycogen content, and inhibited glycolysis, thereby reducing lactate release. The major effect of DCA on lactate metabolism in muscle is to inhibit glycolysis.     

Strenuous exercise-induced alterations of muscle fiber cross-sectional area and fiber-type distribution in steroid myopathy rats

OBJECTIVE: To investigate the effect of exercise intensity on the muscle histopathology in steroid myopathy rats. DESIGN: Eight-week-old male Wistar rats (n=40) were divided into four groups: a control group (n=4), steroid-only group (n=12), moderate exercise + steroid group (n=12), and a high-intensity exercise + steroid group (n=12). Five weeks after triamcinolone injection, the soleus muscle (SOL) and extensor digitorum longus muscle (EDL) were removed and stained for adenosine triphosphatase (ATPase). The muscle fiber area and fiber type distribution of each fiber type were measured. RESULTS: In the high-intensity exercise group, the type I fibers in the SOL and the type IIb fibers in the EDL showed significant atrophy. In the fiber distribution of the SOL, type I fibers decreased in the steroid-only group and high-intensity exercise group as compared with the control, whereas there was a significant increase in the moderate exercise group vs. the steroid-only group. In the EDL, type I fibers were significantly greater in the moderate- and high-intensity exercise groups, whereas type IIb fibers significantly decreased in the moderate-exercise group as compared with the steroid-only group. CONCLUSIONS: In rats with steroid myopathy, high-intensity exercise caused changes such as muscle atrophy. The fiber type distribution of the SOL changed from type II fibers to type I fibers in the moderate exercise group. Intensive exercise, however, resulted in transformation from type I to type II in the fiber type distribution. For the EDL, no significant fiber type changes were observed with high-intensity exercise when compared with moderate exercise.     

Excess purine degradation in exercising muscles of patients with glycogen storage disease types V and VII.

To investigate purine catabolism in exercising muscles of patients with muscle glycogen storage disease, we performed ischemic forearm exercise tests and quantitated metabolites appearing in cubital venous blood. Two patients with glycogen storage disease type V and three with glycogen storage disease type VII participated in this study. Basal lactate concentrations lowered in every patient with glycogen storage disease type V or type VII. Two patients with glycogen storage disease type VII, who had markedly elevated concentrations of serum uric acid (14.3 and 11.9 mg/dl, respectively), showed high basal concentrations of ammonia (118 and 79 mumol/liter, respectively; 23 +/- 4 mumol/liter in healthy controls) and of hypoxanthine (23.4 and 20.4 mumol/liter, respectively; 2.0 +/- 0.4 mumol/liter in healthy controls). Other patients showed near normal measurements of these metabolites. After forearm exercise, ammonia, inosine, and hypoxanthine levels increased greatly in every patient studied, in contrast with the lack of increase in lactate levels. The incremental area under the concentration curves for venous ammonia was 13-fold greater in the glycogen storage disease group than in controls (1,120 +/- 182 vs. 83 +/- 26 mumol X min/liter). The incremental areas of inosine and hypoxanthine were also greater in the glycogen storage disease group (29.2 +/- 7.2 vs. 0.4 +/- 0.1 and 134.6 +/- 23.1 vs. 14.9 +/- 3.2 mumol X min/liter, respectively). The incremental areas of ammonia in controls and in glycogen storage disease patients strongly correlated with those of hypoxanthine (r = 0.984, n = 11, P less than 0.005). These findings indicated that excess purine degradation occurred in the exercising muscles of patients with glycogen storage disease types V and VII, and suggested that the ATP pool in the exercising muscles may be deranged because of defective glycogenolysis or glycolysis.     

Glycogen synthase and phosphofructokinase protein and mRNA levels in skeletal muscle from insulin-resistant patients with non-insulin-dependent diabetes mellitus.

In patients with non-insulin-dependent diabetes mellitus (NIDDM) and matched control subjects we examined the interrelationships between in vivo nonoxidative glucose metabolism and glucose oxidation and the muscle activities, as well as the immunoreactive protein and mRNA levels of the rate-limiting enzymes in glycogen synthesis and glycolysis, glycogen synthase (GS) and phosphofructokinase (PFK), respectively. Analysis of biopsies of quadriceps muscle from 19 NIDDM patients and 19 control subjects showed in the basal state a 30% decrease (P < 0.005) in total GS activity and a 38% decrease (P < 0.001) in GS mRNA/microgram DNA in NIDDM patients, whereas the GS protein level was normal. The enzymatic activity and protein and mRNA levels of PFK were all normal in diabetic patients. In subgroups of NIDDM patients and control subjects an insulin-glucose clamp in combination with indirect calorimetry was performed. The rate of insulin-stimulated nonoxidative glucose metabolism was decreased by 47% (P < 0.005) in NIDDM patients, whereas the glucose oxidation rate was normal. The PFK activity, protein level, and mRNA/microgram DNA remained unchanged. The relative activation of GS by glucose-6-phosphate was 33% lower (P < 0.02), whereas GS mRNA/micrograms DNA was 37% lower (P < 0.05) in the diabetic patients after 4 h of hyperinsulinemia. Total GS immunoreactive mass remained normal. In conclusion, qualitative but not quantitative posttranslational abnormalities of the GS protein in muscle determine the reduced insulin-stimulated nonoxidative glucose metabolism in NIDDM.     

Alcoholic skeletal myopathy, a clinical and pathological study

One hundred and fifty-one inpatients with a history of chronic heavy alcohol intake were examined for evidence of muscle disease. Ninety-two patients (60 per cent) had histologically abnormal biopsies of the quadriceps muscle. The most common abnormality, which was often severe, was type II muscle fibre atrophy. Seven patients (5 per cent) had histological evidence of acute myopathy, one of whom presented with the full clinical picture of acute rhabdomyolysis. Twenty-three patients had cirrhosis, 36 were significantly malnourished and 98 had evidence of a peripheral neuropathy. None of these features, however, were sufficient to account for the muscle abnormalities. There was no clear relationship between musculo-skeletal symptoms and muscle biopsy histology. Serum creatine kinase activity was elevated in only 23 subjects and was an insensitive indicator of subclinical acute myopathy and of chronic alcoholic myopathy. Follow-up studies after abstinence from alcohol invariably showed both objective and subjective improvement of muscle function - often in the absence of any clinical recovery from the peripheral neuropathy. Continued alcohol consumption was accompanied by persistence and often deterioration of muscle fibre atrophy. It is concluded that chronic skeletal myopathy is a frequent consequence of alcohol abuse and may result from a direct toxic effect of ethanol on muscle fibres.