Controlling plasma leptin level improves quality and productivity of beef

(1)研究了日本黑阉牛和小母牛在育肥过程中血浆瘦素浓度的变化。我们还研究了血浆瘦素水平与胴体性状的关系。育肥期间，阉牛和母牛血浆瘦素浓度升高。尽管小母牛和阉牛在皮下脂肪厚度或牛肉大理石花纹方面没有很大差异，但血浆瘦素浓度在小母牛中高于阉牛。肉牛屠宰前的血浆瘦素水平与皮下脂肪厚度或牛肉大理石花纹之间存在显著相关性，这可能反映了体内脂肪含量。上述结果提示，血浆瘦素水平可作为肥育程度的指标。另一方面，血浆瘦素水平与这些胴体性状无关。(2)研究了瘦素mRNA的表达与脂肪细胞大小的关系。肌内脂肪组织瘦素mRNA水平低于肌间和肾周脂肪组织。瘦素mRNA水平在皮下库低于肌间库。肌间脂肪组织的脂肪细胞直径大于皮下和肌内脂肪组织。瘦素mRNA水平与脂肪细胞直径呈正相关。(3)研究了雌激素、性类固醇激素和染料木素、大豆异黄酮对牛脂肪细胞瘦素分泌和mRNA表达的影响。我们还检测了钒对瘦素mRNA表达的影响。雌激素和染料木黄酮在处理2和8小时后刺激牛脂肪细胞分泌瘦素。另一方面，在治疗6和24 h后，雌激素和染料木素增加了瘦素mRNA的水平，但治疗2 h对瘦素mRNA的合成没有显著影响。低浓度钒增加瘦素基因合成，高浓度钒显著降低瘦素基因表达。少

(1)We studied the changes of plasma leptin concentration during fattening in Japanese Black steers and heifers. We also examined the relationship between plasma leptin level and carcass traits. Plasma leptin concentration was increased during fattening period in the steers and heifers. Although there is no great difference between heifers and steers in the thickness of subcutaneous fat or beef marbling, plasma leptin concentration was higher in the heifers than in the steers. The steers showed the significant correlation between plasma leptin level just before slaughter and the thickness of subcutaneous fat or beef marbling that probably reflected body fat content. These results suggested that plasma leptin level possibly used as the index for the degree of fattening in the steers. On the other hand, plasma leptin level did not related to these carcass traits in the heifers.(2)We investigated leptin mRNA expression, adipocyte size, and their relationship in several adipose tissues of f … More attening steers. The intramuscular adipose tissues had a lower leptin mRNA level than the intermuscular and perirenal adipose tissues. The leptin mRNA level was lower in the subcutaneous depot than in the intermuscular depot. The adipocyte diameter was larger in the intermuscular adipose tissue than in the subcutaneous and the intramuscular adipose tissues. Leptin mRNA level was positively correlated to adipocyte diameter.(3)We investigated the influence of estrogen, sex steroid hormone, and genistein, soybean isoflavone, on leptin secretion and mRNA expression in bovine adipocytes. We also examined the effect of vanadium on leptin mRNA expression. Estrogen and genistein stimulated in leptin secretion from bovine adipocytes after 2 and 8 h of treatment. On the other hand, mRNA levels for leptin were increased by estrogen and genistein after 6 and 24 h of treatment, though 2 h of treatment did not significantly affect leptin mRNA synthesis. Low concentration of vanadium increased leptin gene synthesis, while high concentration decreased leptin expression prominently. Less