4.6 Article

Associations between amino acids and bone mineral density in men with idiopathic osteoporosis

期刊

BONE
卷 47, 期 5, 页码 959-965

出版社

ELSEVIER SCIENCE INC
DOI: 10.1016/j.bone.2010.08.017

关键词

Amino acids; Male osteoporosis; Bone mineral density; Insulin-like growth factor; Bone histomorphometry

资金

  1. Karolinska Institute
  2. Magn. Bergvall Foundation

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Idiopathic osteoporosis in middle-aged men is characterized by low-level bone formation. Inhibited anabolism may be involved in the pathogenesis of the disease and amino acids may be of importance. In the present study fasting amino acid profiles in plasma and erythrocytes were determined in 22 male idiopathic osteoporosis (MIO) patients and in 20 age-matched healthy men and associated with bone mineral density, bone histomorphometry and hormones. The osteoporotic patients had normal plasma essential amino acids but increased non-essential amino acids (p = 0.001), particularly glutamine and glycine. The ratio essential/non-essential amino acids, an index of protein nutritional status, was decreased in the MIO patients (0.59 (0.04) mu mol/1, mean (SD)), compared to controls (0.66 (0.05), p = 0.001). In the MIO patients, the ratio essential/non-essential plasma amino acids (r = 0.60, p = 0.003) was positively correlated with lumbar spine bone mineral density. The erythrocyte amino acids represent a large proportion of the free amino acids in blood. A novel finding was the lower levels of erythrocyte tryptophan in MIO (12 (2) mu mo1/1) compared to controls (16 (3), p = 0.001) and decreased erythrocyte/plasma ratio (0.28 (0.07) vs. 0.33, (0.06), p<0.01), suggesting an altered amino acid transport of tryptophan between plasma and erythrocytes. In the combined group of MIO and control men (n = 42), bone mineral density was positively correlated with erythrocyte tryptophan in both the lumbar spine (r = 0.45, p = 0.003) and femoral neck (r = 0.56, p<0.001). The bone histomorphometric variables wall thickness, trabecular thickness and mineral apposition rate were all positively associated with erythrocyte tryptophan levels in the MIO patients. In the combined group of MIO and controls, a multiple regression analysis showed that erythrocyte tryptophan could explain 22% of the variation of lumbar spine and 30% of the variation in femoral neck bone mineral density. We conclude that men with idiopathic osteoporosis have changes in free amino acid profiles which indicate their altered utilization. The correlations between tryptophan and bone mineral density and bone histomorphometry suggest a link between tryptophan and osteoblast function which may be important for bone health. (C) 2010 Published by Elsevier Inc.

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