title: Testicular injury to rats fed on soybean protein-based vitamin B12-deficient diet can be reduced by methionine supplementation.
abstract: We have previously reported that rats fed on a vitamin B12 (B12)-deficient diet containing 180 g soybean protein per kg diet showed marked histologic damage in their testes. In this paper, we report the effect of B12-deficiency on B12-dependent methionine synthase in the rats' testes and the effect of methionine supplementation of the diet on testicular damage. Rats were fed the soybean protein-based B12-deficient diet for 120 d. We confirmed that those rats were in serious B12-deficiency by measuring urinary methylmalonic acid excretion and B12 content in tissues. Methionine synthase activity in the testis of the B12-deficient rats was less than 2% of that in B12-supplemented (control) rats. To complement disrupted methionine biosynthesis, methionine was supplied in the diet. A supplement of 5 g D,L-methionine per kg diet to the B12-deficient diet did not affect urinary methylmalonic acid excretion of B12-deficient rats. The testicular histology of rats fed the methionine-supplemented B12-deficient diet was almost indistinguishable from that of control rats. Thus, we conclude that the lowered testicular methionine synthase activity is the primary cause of the histologic damage due to B12-deficiency and that methionine supplementation to the diet can reduce the damage. These findings would indicate the importance of the methionine synthase activity, especially for testicular function.
authors.affiliation: Faculty of Engineering, Okayama University, Okayama 700-8530, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamada
authors.forename: Tetsunori
authors.initials: T
authors.lastname: Kawata
authors.forename: Masahiro
authors.initials: M
authors.lastname: Wada
authors.forename: Kazumi
authors.initials: K
authors.lastname: Mori
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tamai
authors.forename: Nobuo
authors.initials: N
authors.lastname: Tanaka
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Tadokoro
authors.forename: Takamasa
authors.initials: T
authors.lastname: Tobimatsu
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Toraya
authors.forename: Akio
authors.initials: A
authors.lastname: Maekawa
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000096:biosynthesis / Q000187:drug effects; D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004032:Diet / Q000379:methods; D019587:Dietary Supplements; D004195:Disease Models, Animal; D005260:Female; D008297:Male; D008715:Methionine / Q000627:therapeutic use*; D008764:Methylmalonic Acid / Q000652:urine; D009929:Organ Size / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D030262:Soybean Proteins / Q000008:administration & dosage*; D013733:Testicular Diseases / Q000150:complications / Q000473:pathology / Q000517:prevention & control*; D013737:Testis / Q000187:drug effects* / Q000503:physiopathology / Q000648:ultrastructure; D014806:Vitamin B 12 Deficiency / Q000150:complications / Q000178:diet therapy* / Q000652:urine
chemical_list: D030262:Soybean Proteins; D008764:Methylmalonic Acid; D008715:Methionine; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase