進行性筋ジストロフィー症の血清遊離アミノ酸およびtaurine負荷試験の検討

SERUM AMINO ACID STUDIES AND TAURINE LOAD TESTS IN DUCHENNE MUSCULAR DYSTROPHY

　我々は先に進行性筋ジストロフィー症（以下DMPと略）の遊離アミノ酸の尿中排泄様式がtaurineとglycineの比較的増加を有するpartial aminoaciduriaの傾向を示し，飢餓状態のそれと類似している点があることを指摘したが^1），今回はそれに関連して血中の遊離アミノ酸を定量した。また，taurineは筋組織に高濃度に存在し^2），さらに外因性のtaurineの一部は筋に取り込まれることが知られているので^3），DMPのごとく筋組織が徐々に変性，崩壊して行く病態において，経口負荷後のtaurineの血中濃度の推移あるいは尿中排泄率などに変化が見られるかどうかを検討した。

Serum concentrations of 24 free amino acids were determined by using an automatic amino acid analyzer in 23 patients with progressive muscular dystrophy of Duchenne type and 11 control boys. The patients were classified into three groups based on their disability stages. The "walk" group consists of 6 patients who are able to go up and down stairs. The "crawl" group consists of 8 able to crawl on hands and knees. The "unmovable" group consists of 9 unable to move around at all.

1) The sum of the free amino acids was slightly decreased in the "walk" and the "unmovable" groups. Also that of the essential amino acids was decreased in all the three dystrophic groups. But these changes were not statistically significant. However, the sum of the branched-chain amino acids (valine, isoleucine and leucine) was signi-ficanty decreased in the "crawl" and the "un-movable" groups, and was also decreased but not significantly in the "walk" group.

2) With respect to each amino acid, statistically significant changes were noted only in the con-centrations of 8 amino acids. Namely, decreases were in alanine, valine, isoleucine, leucine, pheny-lalanine and tyrosine, and increases were in serine and lysine. In the "walk" group the decrease in alanine was the only significant change. In the "crawl" group, isoleucine, leucine and phenylal-anine were decreased. The changes were the most remarkable in the "unmovable" group, showing obvious changes in all the 8 amino acids mentioned above.

3) It is proposed that there is some similarity in the amino acid pattern between the Duchenne muscular dystrophy and the starvation.

4) Taurine load tests did not reveal any particular differences between the Duchenne patients and controls in the serum taurine level as well asurinary excretion in time course after oral administ-ration. . However, the negative results may support the possibility that the starvation-like pattern of the amino acids is not due to disturbances in the absorption and excretion of amino acids, but pro- bably reflects unknown metabolic derangements in muscle itself of or some alterations in free amino acid pools caused by muscular degeneration.