Leptin in ruminants. Nutritional and physiological factors of variation

Abstract

Leptin is a hormone secreted mainly by adipose tissue. One of its essential roles is to inform the organism about the level of fat reserves. The leptin gene is expressed in bovine and ovine adipose tissues. Recent results on variations in plasma leptin and/or levels of leptin mRNA in adipose tissues show positive effects of body fatness and feeding level, and an inhibitory ßadrenergic effect in cattle. In sheep, similar effects of body fatness and feeding level are observed, as well as a positive effect of day length. In other respects, in vitro leptin production is stimulated by glucocorticoids and insulin, whose effects are inhibited by growth hormone. Progress in knowlegde about leptin will allow to better understand and control the adaptations of energy metabolism and reproductive activity of ruminants to seasonal variations in daylength and food supply, as well as variations in carcass fatness of growing ruminants.