More than 15% dietary protein has reportedly not led to significant muscle hypertrophy in normal growing rats. The aim of this study was to test whether a high protein (HP) diet affects myostatin (Mstn) synthesis in a rat gastrocnemius muscle. Twenty-four male Wistar rats (4-wk-old) were divided into three groups: 1) control diet (15% protein; 15P, n = 8), 2) the 25P group (25% protein, n = 8), and 3) the 35P group (35% protein, n = 8). After 3 wk of isoenergetic feedings, the Mstn level in skeletal muscles was determined using Northern and Western blotting analysis. After the experimental feeding, muscle masses were similar among groups. The 35P showed significant high expressions of Mstn both at mRNA and protein levels. Obtained results suggest that a high-protein diet leads to the high Mstn level to restrict muscle hypertrophy.
Koichi Nakazato, Tatsuro Hirose and Hongsun Song
Naoki Kikuchi, Dai Ueda, Seok-ki Min, Koichi Nakazato and Shoji Igawa
To examine the relationship between ACTN3 polymorphisms and level of athletic performance in Japanese wrestlers.
The control group consisted of 243 healthy Japanese individuals. The authors divided 135 wrestlers into 3 groups based on their results in national or international competitions. They classified as elite 24 wrestlers who had placed in the top 8 in a world championship or participated in Olympic games, 28 wrestlers who had participated in world championships or become champions in Japan’s national championships were classified as subelite, and 83 wrestlers were classified as national (N-W, ie, national-level wrestler). In addition, the authors combined the elite and subelite to form the classification international-level wrestlers (I-W).
The frequency of the null X allele and the XX genotype were significantly lower in the I-W group than in the control group. However, there was no significant difference in ACTN3 genotype or allele frequency between the N-W and control groups. The frequency of the ACTN3 XX genotype in the elite groups was lower than that of all groups, and a linear tendency was observed between ACTN3 XX genotype and athletic status.
In conclusion, the data indicated that ACTN3 polymorphisms were related to athletic performance in Japanese wrestlers.