Serum creatine kinase isoenzymes in Duchenne muscular dystrophy

Bone Mineral Density Assessment by Quantitative Computed Tomography in Glucocorticoid-Treated Boys With Duchenne Muscular Dystrophy: A Linear Mixed-Effects Modeling Approach

OBJECTIVE

Boys with Duchenne muscular dystrophy (DMD) are at risk of bone damage and low bone mineral density (BMD). The aim of the study is to examine lumbar BMD values measured by QCT and identify the factors associated with BMD loss using a multilevel mixed-effects model.

METHODS

Lumbar BMD was evaluated by quantitative computed tomography (QCT) at diagnosis, 1 and 2 years follow up in patients with DMD who were treated with GC. Demographic data, functional activity scores (FMSs), laboratory parameters and steroid use were recorded. A multilevel mixed-effects model was used to analyze BMD loss.

RESULTS

Nineteen patients with DMD who had a total of sixty complete records between January 2018 and October 2021 were retrospectively analyzed. At baseline, 15.8% of patients (3/19) had low lumbar BMD (Z score ≤ -2), and the mean BMD Z score on QCT was -0.85 (SD 1.32). The mean BMD Z score at 1 and 2 years postbaseline decreased to -1.56 (SD 1.62) and -2.02 (SD 1.36), respectively. In our model, BMD Z score loss was associated with age (β=-0.358, p=0.0003) and FMS (β=-0.454, p=0.031). Cumulative GC exposure and serum levels of calcium, phosphorus, 25(OH)-vitamin D and creatinine kinase did not independently predict BMD loss.

CONCLUSIONS

This study demonstrates that in DMD patients, lumbar BMD decreased gradually and progressively. Age and FMS are the main contributors to BMD loss in boys with DMD. Early recognition of risk factors associated with BMD loss may facilitate the development of strategies to optimize bone health.

Creatine kinase isoenzyme patterns upon chronic exposure to cigarette smoke: protective effect of Bacoside A

Cigarette smoking is implicated as a major risk factor in the development of cardiovascular and cerebrovascular diseases. Creatine kinase (CK) and its isoforms (CK-MM, MB, BB) have been advocated as sensitive markers in the assessment of cardiac and cerebral damage. Therefore, in the present study, we report the isoenzyme patterns of CK in rats upon exposure to cigarette smoke and the protective effect of Bacoside A against chronic smoking induced toxicity. Adult male albino rats were exposed to cigarette smoke and simultaneously administered with Bacoside A, the active constituent from the plant Bacopa monniera, for a period of 12 weeks. The activity of CK was assayed in serum, heart and brain, and its isoenzymes in serum were separated electrophoretically. Rats exposed to cigarette smoke showed significant increase in serum CK activity with concomitant decrease in heart and brain. Also cigarette smoke exposure resulted in a marked increase in all the three isoforms in serum. Administration of Bacoside A prevented these alterations induced by cigarette smoking. Cigarette smoking is known to cause free radical mediated lipid peroxidation leading to increased membrane permeability and cellular damage in the heart and brain resulting in the release of CK into the circulation. The protective effect of Bacoside A on the structural and functional integrity of the membrane prevented the leakage of CK from the respective tissues, which could be attributed to its free radical scavenging and anti-lipid peroxidative effect.

Creatine kinase isoenzymes

Analytical methods for and the clinical significance of ATP:creatine-N-phosphotransferase (EC 2.7.3.2, CK) isoenzymes have been described. The main assay methods for the isoenzymes are electrophoresis, ion-exchange chromatography and immunoinhibition. Electrophoresis is a time-consuming technique, but it is essential for the identification of CK isoenzymes. Ion-exchange chromatography is reliable for the determination of CK-MB and useful for the isolation and purification of CK isoenzymes. The disadvantages of this method are overlapping of isoenzymes with neighbouring fractions and the inevitable dilution of enzyme activity by the elution buffer. Immunoinhibition is a rapid, sensitive, specific and quantitative technique. However, mitochondrial CK and CK-immunoglobulin complex remain after the inhibition of the M subunit with the antibodies. Thus, when assessing the experimental results, it is necessary to be certain that a false positive for CK-MB has not been obtained. Since each technique has both merits and demerits, the technique most suited to the particular laboratory should be selected.

Serum creatine kinase isoenzymes in Duchenne muscular dystrophy determined by sensitive enzyme immunoassay methods

Serum levels of creatine kinase (CK) isoenzymes (MM, MB, and BB) were measured by sensitive enzyme immunoassay (EIA) methods in 50 patients with Duchenne muscular dystrophy (DMD) and in 39 controls. MM, MB, and BB levels in DMD patients were higher than in controls, and these three levels decreased with advancing age of DMD patients. Serum MB levels showed a good correlation with serum levels of carbonic anhydrase III (CA-III), but correlated poorly with electrocardiographic findings, suggesting that the main origin of serum MB in DMD is skeletal muscle rather than cardiac muscle.

Changes in serum enzymes, lactate, and haptoglobin following acute physical stress in international-class athletes

Skeletal muscle is rich in creatine kinase (CK), lactate dehydrogenase (LD), and other enzymes. Many reports describe changes in serum CK and LD following exercise. In our study, 11 male international-class medium-distance runners were followed over a 10-month period prior to the 1984 US Olympic Trials. Cardiorespiratory fitness, evaluated through repetitive treadmill testing, was unchanged in our athletes. Total CK increased significantly during the course of training, and the CK-MB activity was higher than that of sedentary individuals; CK-MB never rose to more than 3% of the total CK. Total LD also rose following acute exercise; however, the proportions of the five isoenzymes were unaltered. There was no change in the LD-1/LD-2 ratio from normal. The origin of the increased serum enzymes was believed to be primarily skeletal muscle. A decrease of serum haptoglobin following acute stress was attributed to intravascular hemolysis and binding of hemoglobin. As expected, serum lactate was dramatically increased immediately postexercise.

Serum CK-MB activity in progressive muscular dystrophy: is it of nosologic value?

Serum creatine-kinase (CK) isoenzyme MB was measured in 53 patients affected by different types of myopathies (20 with Duchenne muscular dystrophy (DMD), eight with the Becker form (BMD), ten with the limb-girdle form (LGMD), six with the facioscapulohumeral form (FSH), and nine affected by polymyositis and in 21 normal control subjects). The aim of this study was to compare each group with the control individuals and to assess the nosologic value of CK-MB activity among some clinically similar dystrophies, which may have an important application for genetic counseling. A statistically significant increased CK-MB activity was found only in the Duchenne and Becker patients when compared with control persons (p less than 0.05). When the different groups of patients were compared among themselves, no significant difference was found between DMD and BMD or LGMD and polymyositis. However, a significant difference was found between BMD and LGMD. Based on these data, it is possible, through discriminant analysis, to estimate the relative biochemical probability of an isolated male patient belonging to either group.

Alterations in creatine kinase, ornithine decarboxylase, and transglutaminase during muscle regeneration

Creatine kinase (CK), transglutaminase (TGase) and ornithine decarboxylase (ODC), enzymes implicated in the regulation of growth processes, were studied during muscle regeneration subsequent to the injection of bupivacaine into rat tibialis anterior. Within 2 days, the percent BB isozyme of CK detected in the muscle was elevated 70-fold coincident with a marked decrease in total CK activity. The MB isozyme also increased and was 15-fold of control at 4-5 days postinjection. TGase activity was increased significantly to greater than 2-fold of control within 2 days of injection and significantly decreased at days 3 through 7 compared to controls. ODC activity was elevated significantly to 2- to 3-fold of control from 2-7 days after injection. These results suggest an early alteration in the expression of a coordinated battery of genes in this model of muscle degeneration-regeneration. The increased expression of MB and BB isozymes of CK in various human neuromuscular diseases may be a manifestation of an ongoing process of degeneration-regeneration.

Isozyme patterns and protein profiles in neuromuscular disorders

The isozyme patterns of six different enzymes and the polypeptide profiles of soluble proteins have been examined in muscle biopsy specimens from 74 patients with a wide variety of neuromuscular disorders. About half of the samples showed unusual features in at least one, and often several, of the enzymes and proteins tested. The extent of the biochemical abnormalities was roughly proportional to the severity of the disorders. In all cases the unusual isozymes and polypeptide profiles seemed to reflect a reversion to the fetal pattern of gene expression. However, this change appeared to occur in extant muscle and was not dependent on the appearance of new muscle fibres. Among the enzymes, phosphoglycerate mutase followed by creatine kinase appeared to be the most sensitive index of muscle disorder. The extent of the change in the muscle creatine kinase isozyme pattern was not correlated with the levels of serum creatine kinase activity.

Alterations in creatine kinase in fresh muscle and cell cultures in Duchenne dystrophy

Creatine kinase (CK) (total and isoenzymes) was measured in cultures obtained by dissociation and subsequent plating of cells from biopsied quadriceps muscle of 10 patients with Duchenne muscular dystrophy (DMD) and 20 controls. The total cellular CK and CK-MM reached highest values around 21 days in both DMD and control cultures, suggesting that DMD cultures do not show delayed myoblast fusion. There was a significant decrease of total cellular CK in DMD cultures at all stages, but the maximum differences were noted for the peak values. The CK isoenzyme pattern in DMD cultures demonstrated a higher percentage of CK-BB and CK-MB and a lower percentage of CK-MM than was observed in cultures from the controls. Addition of cytosine arabinoside after myoblast fusion to muscle cell cultures did not induce significant changes of CK isoenzyme pattern. There was no difference in the CK levels in culture medium from controls and DMD patients. The alterations of cellular CK were similar in fresh muscle and cell cultures from DMD patients.

Creatine kinase isozyme transition in chicks with hereditary muscular dystrophy

In both normal chicks and chicks with hereditary muscular dystrophy the BB (brain) and MB (hybrid) isozymes were the predominant forms of creatine kinase (CK) activity in embryonic skeletal muscle. As myogenesis progressed, activity due to the MM (muscle) isozyme progressively increased, and by 1 week ex ovo, the MM isozyme accounted for approximately 97% of total muscle activity in both genotypes. During this time, the proportion of the MM isozyme was slightly but significantly lower in dystrophic muscles. After hatching the proportion of the MB isozyme and its total activity decreased in normal muscle, but increased in dystrophic pectoral muscle, and by 5 months ex ovo, the MB isozyme accounted for 10% of total CK activity. Prior to hatching there was no consistent difference in total CK activity between normal and dystrophic tissues, but by 1 week after hatching and thereafter, total CK activity was significantly lower in dystrophic pectoral muscle.

Serum creatine kinase BB and MM concentrations determined by radioimmunoassay in neuromuscular disorders

We measured the MM and BB isoenzymes of serum creatine kinase (CK) by radioimmunoassay in 89 patients with neuromuscular disorders and 44 definite or possible carriers of Duchenne muscular dystrophy (DMD). The CK-MM isoenzyme was closely associated with total CK enzymatic activity. CK-BB was not as closely correlated with total CK but was usually increased in the inflammatory myopathies and DMD and normal in myasthenia gravis, Guillain-Barré syndrome, and amyotrophic lateral sclerosis as well as in neuropathies in which CK is usually normal. In myopathies, CK-BB may be useful for assessing the level of disease activity or the regenerative component. More study is necessary to assess the role of CK-BB in detection of DMD carriers.

Biochemistry of muscle membranes in Duchenne muscular dystrophy

In Duchenne muscular dystrophy, as in other genetic diseases, there must be a biochemical abnormality. This fundamental genetic fault has not been identified, but several indirect lines of evidence suggest that the surface membranes of skeletal muscle are affected. The biochemical evidence implies abnormal egress of soluble enzymes and other proteins from muscle, abnormal permeability, and altered properties of membrane-bound enzymes. As a result of the presumed genetic abnormality, functional properties are altered, and impaired regulation of intracellular calcium content could be responsible for the hallmarks of the disease--progressive weakness and degeneration of muscle. The evidence is by no means conclusive, however, and some of it is contradictory. Technical advances must be made before isolated membranes can be characterized biochemically. Other theories are also being evaluated.