Muscle glycogen metabolism in steroid-induced myopathy of rabbits

Effects of treadmill exercise on muscle fibers in mice with steroid myopathy

We studied the effect of treadmill exercise on muscle fibers in mice with experimental steroid myopathy. Frozen sections of the extensor digitorum longus (EDL) and soleus (SOL) muscles were stained with hematoxylin-eosin, and the muscle fiber diameters measured. In the EDL, muscle fiber diameters in the steroid groups decreased significantly compared with those in the control groups; moreover, muscle fiber diameters in the exercise groups increased significantly compared with those in the non-exercise groups, whereas the diameters in the SOL did not differ. We speculate that treadmill exercise may prevent corticosteroid-induced muscle fiber atrophy.

Steroid myopathy: pathogenesis and effects of growth hormone and insulin-like growth factor-I administration

Glucocorticoids have been widely used in the treatment of autoimmune and other diseases. Chronic steroid use, however, could cause proximal muscle weakness and atrophy, termed steroid myopathy. The onset of steroid myopathy is usually insidious and there are no specific laboratory findings except for elevated urinary creatine excretion. Muscle biopsy reveals non-specific type II fiber atrophy. There are many reports showing preventive effects of either growth hormone (GH) or insulin-like growth factor (IGF)-I on steroid myopathy. The pathogenesis of steroid myopathy is not fully understood. Recently, glutamine synthetase has been reported to play a key role in steroid myopathy. GH as well as IGF-I decreased the steroid-induced glutamine synthetase activity in skeletal muscle.

Extrapulmonary effects of chronic obstructive pulmonary disease

Although airflow obstruction is the most obvious and most studied manifestation of chronic obstructive pulmonary disease (COPD), it should not be overlooked that COPD, particularly in its later stages, is associated with many extrapulmonary features that contribute to the morbidity, reduced quality of life, and, possibly, mortality of this disease. We review here the literature on skeletal muscle dysfunction, osteoporosis, and weight loss in COPD, with particular attention to possible approaches to their management. Patients with COPD may also have other extrapulmonary effects such as hormonal abnormalities that could probably be corrected, but less is known about them. COPD, therefore, should be regarded as a systemic disorder. Its systemic manifestations should not be overlooked in the overall care of the patient, because there are important ways in which they can be addressed.

Elevated inosine monophosphate levels in resting muscle of patients with stable chronic obstructive pulmonary disease

In order to investigate disturbances in energy metabolism in resting muscle of patients with stable chronic obstructive pulmonary disease (COPD), concentrations of adenine nucleotides and related compounds were examined comparing 34 COPD patients with eight age-matched healthy control subjects. Biopsies were taken from the anterior tibialis muscle. Special attention was paid to the muscle content of inosine monophosphate (IMP), a deamination product of adenosine monophosphate (AMP), because IMP formation is thought to reflect an imbalance between resynthesis and utilization of adenosine triphosphate (ATP). The absolute concentrations of high-energy phosphate compounds did not differ between patients and control subjects, but the ATP/ADP and the phosphocreatine/creatine ratio were significantly lower in the patients. IMP (detection level = 0.06 mmol/kg dry weight) was detected in 25 of 34 patients versus one of eight control subjects (p = 0.001). Mean (SD) IMP level in these patients was 0.18 (0.14) versus 0.06 mmol/kg dry weight in the one control subject. Based on the presence of detectable levels of muscle IMP, the patient group was divided into two subgroups. In IMP-positive patients, ATP/ADP and phosphocreatine/creatine ratios were significantly lower than in IMP-negative patients. IMP-positive patients were furthermore characterized by a significantly lower DL(CO). The results of this study indicate an imbalance between the utilization and resynthesis of ATP in resting muscle of patients with stable COPD.

Effects of long-term low-dose methylprednisolone on rat diaphragm function and structure

In animal studies, high dosages of corticosteroids cause changes in diaphragm structure and function. The present study was designed to investigate the effects of long-term low-dose methylprednisolone (MP) administration on rat diaphragm contractile properties and morphology. Thirty adult rats were treated with saline or MP (0.2 mg/kg/day s.c.) during 6 months. Contractile properties of isolated diaphragm strips, immunohistochemical characteristics analyzed by means of antibodies reactive with myosin heavy chain isoforms, and enzyme activities were determined in the diaphragm muscle. MP significantly reduced diaphragm force generation by -15% over a wide range of stimulation frequencies. The number of type IIb fibers was reduced by MP. There was a mild but significant decrease in type I and IIa fiber cross-sectional area (CSA), whereas type IIx and IIb CSA did not change. These changes resulted in a reduction in the relative contribution of type IIb fibers to total diaphragm muscle area. Biochemically, MP decreased glycogenolytic activity, while fatty acid oxidation and oxidative capacity were increased. In conclusion, long-term low-dose MP administration caused a marked impairment in diaphragm function. This is accompanied by changes in diaphragm muscle morphology and enzyme capacity.

[Steroid-induced myopathy in left-sided ulcerative colitis. Successful treatment and continued therapy with the topical steroid budesonide]

BACKGROUND

Glucocorticoids are an effective treatment of ulcerative colitis. The occurrence of steroid side effects depends on dosage and duration of steroid treatment. It may be a high as 80%. A rare side effect of glucocorticoid therapy is steroid induced myopathia. There exists an acute and a chronic form of steroid induced myopathia. Chronic steroid myopathia affects mainly the proximal musculature of the lower and upper extremities and leads to proximal muscle weakness. Histologically, an atrophy of type IIb-muscle fibers can be found. Chronic steroid myopathia occurs after prolonged treatment with higher doses of glucocorticoids.

CASE REPORT

The case report describes a 25 year old male patient with left-sided ulcerative colitis who developed chronic steroid myopathia after several months of glucocorticoid treatment. After switching from systemic steroids to budesonide the symptoms of myopathia disappeared. Left-sided ulcerative colitis remained in remission.

CONCLUSION

The case documents the disappearance of a severe steroid side effect after switching from a systemic steroid to budesonide.

[Present status of cortisone myopathy]

Steroid myopathy is one of the various side effects of prolonged treatments, particularly with the 9 alpha fluorinated steroids. The receptor protein probably plays a major role with a decrease in protein synthesis. There is no mean to detect this myopathy before clinical signs appear. Neither muscular testing nor enzymes nor electromyography give arguments and muscular biopsy is aggressive. Low density scanner and MNR could help diagnosis. Frequency of disease is not known. A total cumulative maintenance steroid dosage of 400 mg can be sufficient. Proximal muscles are usually involved, quadriceps and other pelvic girdle muscles being more severely affected. Fast twitch glycolytic type IIB fibers are particularly susceptible. Physical exercise is effective in preventing myopathy. Nevertheless, no special rehabilitation program has been tested for the moment in human beings.

Interaction of glucocorticoids and activity patterns affect muscle function

The purpose of this study was to determine the effects of glucocorticoids on muscle mass and contractile properties of muscles of similar fiber composition but differing in activity patterns. Rats were divided into two groups and administered prednisolone (5 mg/kg per day) (P; N = 9) or served as controls (C; N = 10) for 10 days. Contractile properties were then determined in the left gastrocnemius-plantaris-soleus (GPS) muscle complex and a strip of costal diaphragm (D). An index of fatigue was also determined in both muscle preparations. Whole-body, GPS, and D weights decreased (P < 0.05) in the P animals (22%, 17%, and 15%, respectively) when compared to C. Specific tension (PO) increased (P < 0.05) in the GPS complex (21%) and decreased in the D (26%). Maximal shortening velocity (Vmax) was not different (P > 0.05) between groups in either the GPS or the D. While the index of fatigue was not different (P > 0.05) between groups in the D, there was a 30% increase (P < 0.05) in the rate of fatigue in the GPS. These data indicate that, although glucocorticoids cause decreased muscle mass in both D and GPS, a change in muscle architecture may prevent a decrease in force-generating ability in some limb muscles. However, glucocorticoids do not increase D fatigability as seen in the GPS.

Patients with chronic glucocorticoid treatment develop changes in muscle glycogen metabolism

High dose glucocorticoid may induce a significant myopathy with loss of thick myofilament from muscle, particularly if administered in conjunction with depolarizing drugs. Remarkably, the effect of chronic low dose glucocorticoid in muscle is vastly different, although it may induce changes in muscle glycogen metabolism as evidenced in animal experimental trials. However, there is no clear confirmation that these changes could develop similarly in patients. We evaluate clinical, functional, histological and metabolic muscle changes during chronic low-dose glucocorticoid treatment in 11 asthmatic patients. Remarkably, these patients did not develop clinical symptoms of myopathy nor significant muscle weakness or morphological changes in muscle histology. However, glycogen concentration and the activity of the main regulatory enzymes of glycogen metabolism, aldolase and creatine kinase were modified in comparison with controls. An increase in the synthesis and muscle cell deposition of glycogen and a decrease in the muscle glycogen degradation process have been suggested. These changes were not related with malnutrition. There was not correlation between histological and biochemical changes. We conclude that chronic treatment with glucocorticoid causes clear changes in glycogen metabolism in the skeletal muscle, resulting in glycogen muscle storage. The significance of these biochemical changes is unknown, but it can be well an associated phenomenon with glucocorticoid treatment.

Effects of triamcinolone acetonide on plasma amino acids and urinary urea output in rabbits

1. The effect of administering triamcinolone acetonide (10 mg/kg/day), 6 consecutive s.c. injections given daily, on plasma free amino acids and urinary urea output was studied in rabbits. 2. The total free amino acids in plasma decreased significantly from day 2 while ammonia increased significantly only on day 2, glutamine, lysine and branched amino acids increased significantly from day 3 or 5. 3. The output of urinary urea increased significantly from day 3. 4. These findings suggest the inhibition of protein synthesis observed in steroid myopathy may result from a decrease in the amino acid pool in skeletal muscle.

Methylprednisolone increases dystrophin levels by inhibiting myotube death during myogenesis of normal human muscle in vitro

The glucocorticoid methylprednisolone (Mepd) increased dystrophin and myosin heavy chain levels in differentiated cultures of cloned human myoblasts. Mepd increased the number of myotubes per area by preventing myotube death and detachment during myogenesis in vitro. Myotube death was the result of an endogenous process initiated early during myoblast fusion. It occurred between days 4 and 5 of differentiation (3 days after its initiation) and was inhibited by cycloheximide, indicating that a programmed death mechanism may be involved. Inhibition of myotube death accounted for the increased levels of muscle-specific proteins; the amount of dystrophin per myonucleus was the same with or without Mepd treatment. These effects of glucocorticoids on primary muscle cultures may bear on the recent observation that prednisone transiently enhances muscle function in Duchenne muscular dystrophy.

Steroid myopathy. Insidious cause of muscle weakness

Steroids are so commonly prescribed for so many conditions that physicians tend to become somewhat cavalier in their use. With drug therapy of any type, however, this tendency can lead to trouble. Steroid myopathy, as occurs in Cushing's syndrome. Can develop with steroid therapy and can cause irreversible atrophy if not detected and treated early.

Effects of dexamethasone on fibre subtypes in rat muscle

The extent to which dexamethasone treatment produced atrophy of fast-twitch (EDL) and slow-twitch (SOL) muscles in rat was investigated. The mean weight of steroid-treated EDL muscles was decreased as compared to normal, whereas SOL muscles from normal and dexamethasone-treated animals showed no significant difference. Muscle fibre diameters also showed comparatively minor changes in SOL, which consists of Type 1 (slow oxidative) and Type 2A (fast oxidative/glycolytic) fibres. Rat EDL contains, in addition to Type 1 and Type 2A fibres, two sub-populations of fast glycolytic fibres (Types 2B and 2B'). These fibre types showed the most severe degree of atrophy both after dexamethasone treatment and after denervation. The mean ratio of the weights of denervated to innervated EDL muscles was lower in steroid-treated rats than in normal animals suggesting that the atrophy produced by steroid treatment in conjunction with denervation was more than simply additive. Analysis of the proportions of histochemical fibre types in SOL and EDL showed that dexamethasone treatment produced no major alterations in the fibre type constitution of these muscles. However, further histochemical studies showed that there was relatively severe impairment of myophosphorylase activity in Type 2B' (fast glycolytic) fibres as compared to other fibre types; conversely Type 1 fibres frequently contained increased myophosphorylase. Levels of beta-hydroxybutyrate dehydrogenase were low in both normal and steroid-treated EDL but high in SOL which also showed higher general oxidative activity. It is suggested that the particular susceptibility of fast glycolytic fibres to atrophy as a result of steroid treatment may be linked to: 1 the relatively severe reduction of myophosphorylase activity in these fibres and 2 their comparative inability to utilize alternative energy sources, especially substrates derived from free fatty acids.

Glucocorticoids enhance glucose uptake and affect differentiation and beta-adrenergic responsiveness in muscle cell cultures

The role of glucocorticoids (GLC) in liver glycogen metabolism is well characterized; its role in peripheral tissues is not as well understood (Baxter, 1976). GLC administration in vivo is associated with hyperglycemia, but it is not clear whether decreased glucose uptake in a peripheral tissue like muscle accounts, in part, for the effect. We investigated the relationship of glucose uptake to beta-adrenergic responsiveness in muscle cell cultures exposed to GLC. Under these conditions GLC and other serum factors are present in at least a tenfold dilution relative to in vivo conditions. We observed that the GLC dexamethasone (DEX) induces a significantly enhanced Vmax for deoxyglucose uptake in the rat muscle cell lines L8 (200--400%) and L6E9 (50--100%). DEX inhibits cell fusion and promotes epithelioid morphology within the effective dose range (L8 greater than L6E9). Growth is slightly enhanced (10--20%) at 0.1--1.0 microM. In these cells DEX also inhibits intracellular beta-adrenergic-sensitive cyclic AMP accumulation and reduces basal, catecholamine-sensitive and fluoride-sensitive adenylate cyclase in cell homogenates. The effects of DEX on deoxyglucose uptake and beta-adrenergic responsiveness are both dose (1 nM--0.1 nM) and time (1--3 days) dependent, and reversible. The degree of inhibition of the beta-adrenergic system seems to be directly related to the degree of enhancement of deoxyglucose uptake. These observations suggest that the action of DEX on muscle cell glucose uptake is related to its effect on the beta-adrenergic system.