Controlling plasma leptin level improves quality and productivity of beef

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(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