AMINO ACID METABOLISM IN OSTEOPOROSIS

A bstract : To evaluate amino acid metabolism in osteoporosis, the effects of oral loading with an amino acid mixture were studied in 11 aged patients with advanced osteoporosis, 5 aged patients with mild osteoporosis, and 7 healthy aged subjects (controls). The osteoporotic patients were free of other major diseases. In all three groups the physical examination, blood chemical determinations, urinalysis and fluoroscopy of the upper gastrointestinal tract gave normal findings; in particular, no liver or kidney disease was indicated by the results of function tests. A diagnosis of vertebral osteoporosis was made when the ratio of vertebral to disc density in the lateral tomogram of the lumbar spine was 1.0 or higher; in the normal subjects, the ratio was always less than 1.0. The presence of compression fracture(s) was considered to indicate severe osteoporosis, whereas the absence of such fractures graded the disease as mild. Gaschromatographic analysis of the serum for certain free amino acids was made on the blood specimens drawn immediately before, and at one, two, three and four hours after oral ingestion of the test amino acid mixture. The serum valine level for the severely osteoporotic group was significantly higher at one hour (215 + 21 μg/ml versus 151 + 9 for the controls) and at four hours (178 + 16 μg/ml versus 139 + 8.7 for the controls) after ingestion of the mixture. The peak height of the serum valine level was also significantly higher in the severely osteoporotic patients (263 + 25 μg/ml) than in the controls (192 + 5.5 μg/ml). In the mildly osteoporotic patients the values were intermediate. For leucine and phenylalanine, the tolerance curves for the osteoporotic patients were similar to those for the controls. The findings are consistent with the hypothesis that possibly there is a deficiency or defect of valine transaminase in osteoporosis.