Phosphorus nuclear magnetic resonance evidence of abnormal skeletal muscle metabolism in chronic alcoholics

Toxic Myopathies

Muscle tissue is highly sensitive to drugs and toxins because ot its high metabolic activity and potential sites for disruption of energy-producing pathways. Early recognition of toxic myopathies is important, as they potentially are reversible on removal of the offending toxin, with greater likelihood of complete resolution the sooner this is achieved. Clinical features range from mild muscle pain and cramps to severe weakness with rhabdomyolysis, renal failure, and even death. The pathogenic bases can be multifactorial. This article reviews drugs responsible for common types of toxic myopathy and their clinical and histopathologic features and illustrates possible underlying cellular mechanisms.

Alcohol usage in sport and exercise

In this review we consider some of the acute and chronic effects of alcohol on human exercise and sport performance. The 1982 position stand of the American College of Sport Medicine on the use of alcohol in sport emphasized that there was little benefit for an athlete. Subsequent literature continues to demonstrate that there are adverse effects on performance. However, the literature is often confusing and disparate. We will attempt to explain the effects and speculate on the possible mechanisms. We divide the review into acute and chronic metabolic and physiological effects of alcohol on exercise performance, primarily in humans. We also review the epidemiological evidence of the associations between alcohol use and problem alcohol behaviors in various athletic groups. Finally, we review the limited data on the effectiveness of exercise therapy in the treatment of alcohol dependent patients. In spite of scientific evidence that alcohol use is, in general, detrimental (or of no benefit) to sport (exercise) performance, alcohol continues to be used by athletes both on a chronic basis and even immediately prior to sports participation. There is some encouraging but limited evidence that student-athlete alcohol use is decreasing and exercise can be effective as part of alcohol rehabilitation.

Recovery of muscular energy status in chronic alcoholics after 2 weeks of abstinence

Repeated and excessive consumption of alcohol leads to pathophysiological disorders in skeletal muscles. A successful management of this syndrome requires a strict abstinence and a nutritionally adequate diet. We propose here a simple and noninvasive investigation using 31P magnetic resonance spectroscopy (MRS) to monitor the recovery of the basal energy status of eminence thenar muscles from documented chronic alcoholic patients during a controlled 15-day period of abstinence. Cessation of alcohol abuse induced a significant recovery of the PCr/(PCr+P(i)) ratio otherwise depressed before the abstinence. On the contrary, the relative level of free inorganic phosphate decreased, whereas intracellular pH was not affected. These results demonstrate (a) the rapid improvement of basal muscular energy metabolism during abstinence for patients with a chronic and heavy alcohol consumption, and (b) the feasibility of a follow-up of this recovery by serial examinations using 31P MRS.

Effect of hypothyroidism on phosphorus metabolism in muscle and liver: in vivo P-31 MR spectroscopy study

Hypothyroidism is known to affect nearly every organ and organ system of the human body. The goal of the present study was to gain insight into the phosphorus metabolism and bioenergetic function of striated (calf) muscle and liver in patients with hypothyroidism before and after thyroid hormone treatment. With an ISIS (image-selected in vivo spectroscopy) magnetic resonance (MR) technique for volume selection, phosphorus-31 metabolism of the calf muscle in 10 patients and of the liver in seven patients with severe hypothyroidism was studied before and after treatment. In addition, spectra from the calf muscle and liver were obtained in 10 healthy volunteers. Relative to those from the healthy subjects, the P-31 MR spectra from patients with hypothyroidism showed a significantly diminished phosphocreatine/inorganic phosphate ratio (P less than .01). After thyroid hormone substitution therapy, this ratio returned to normal values within several weeks. No statistically significant changes in the spectra of liver tissue could be detected. The results support the theory that hypothyroidism induces a hormone-dependent, fully reversible impairment of the energy metabolism of striated muscle. Changes in liver metabolism observed with biochemical methods are apparently not detectable with state-of-the-art P-31 MR spectroscopy.

Phosphorus magnetic resonance spectroscopy (31P MRS) in neuromuscular disorders

Phosphorus magnetic resonance spectroscopy monitors muscle energy metabolism by recording the ratio of phosphocreatine to inorganic phosphate at rest, during exercise, and during recovery from exercise. In mitochondrial diseases, abnormalities may appear during some or all these phases. Low phosphocreatine-inorganic phosphate ratios at rest are not disease-specific, but can be increased by drug therapy in several myopathies. Phosphorus magnetic resonance spectroscopy can also record intracellular pH and thus identify disorders of glycogen metabolism in which the production of lactic acid is blocked during ischemic exercise. The measurements of accumulated sugar phosphate intermediates further delineate glycolytic muscle defects. Myophosphorylase deficiency responds to intravenous glucose administration with improved exercise bioenergetics, but no such response is seen in phosphofructokinase deficiency. The muscular dystrophies show no specific bioenergetic abnormality; however, elevation of phospholipids metabolites and phosphodiesters was detected in some cases. While phosphorus magnetic resonance spectroscopy remains primarily a research tool in metabolic myopathies, it will be clinically useful in identifying new therapies and monitoring their effects in a variety of neuromuscular disorders.

[Spectroscopy of phosphorus in nuclear magnetic resonance. General review of clinical applications to the study of human skeletal muscle]

Phosphorus nuclear magnetic resonance spectroscopy enables the energy metabolism of skeletal muscles to be studied non-invasively in vivo. Relative concentrations of phosphocreatine (PCr), inorganic phosphate (iP), monophosphoric sugars (mP) and ATP, as well as intracellular pH values, are directly accessible through the spectra. The striated muscle is continuously studied at rest, during exercise and during recovery. Exercise-induced changes in pH and mP provide indirect information on glycogenolysis and glycolysis. The speed of PCr resynthesis during post-exercise recovery and the PCr/iP ratio values at rest excellently reflect mitochondrial oxidative phosphorylations. Phosphorus NMR spectroscopy therefore is of interest not only to study the impact, through hypoxia, on muscle energy metabolism of such pathologies as cardiac or respiratory failure, or to study various acquired metabolic muscular diseases, but also and above all, to detect and locate muscular enzyme deficiencies involving glycogenolysis, glycolysis or mitochondrial metabolism, thereby pointing to the diagnosis of congenital, and mainly metabolic, myopathies.