Controlling plasma leptin level improves quality and productivity of beef

(1)研究了日本黑牛和小母牛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屠体性状的关系。育肥期肉牛和小母牛血浆瘦素浓度升高。虽然小母牛和公牛在皮下脂肪厚度和牛肉大理石纹厚度上没有太大差异，但小母牛的血浆瘦素浓度高于公牛。结果表明，屠宰前的血浆瘦素水平与皮下脂肪或牛肉大理石花纹的厚度之间存在显着的相关性，这可能反映了体脂含量。这些结果表明，血浆瘦素水平可能可作为肉牛育肥程度的指标。另一方面，血浆瘦素水平与小母牛的这些屠体性状无关。(2)我们研究了f…母牛几种脂肪组织中瘦素基因的表达、脂肪细胞大小及其相互关系更吸引人的方向盘。肌内脂肪组织的瘦素基因表达水平低于肌肉间和肾周脂肪组织。皮下储备区的瘦素基因表达水平低于肌间储存区。肌间脂肪组织的脂肪细胞直径大于皮下脂肪组织和肌内脂肪组织。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。雌激素和金雀异黄素作用2小时和8小时后刺激牛脂肪细胞分泌瘦素。雌激素和金雀异黄素作用6h和2 4h后，细胞内瘦素基因表达水平明显升高，但作用2 h对瘦素基因表达无明显影响。低浓度的钒促进瘦素基因的合成，高浓度的钒显著降低瘦素的表达。较少

(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