The ontogeny of leptin mRNA expression in growing broilers and its relationship to metabolic body weight

The polypeptide hormone leptin is produced by both adipose tissue and the l iver and has been shown to induce satiety in chickens. In this study we hav e investigated the developmental regulation of leptin mRNA expression in gr owing broiler chickens. Leptin expression generally increases in all tissue s from 1-12 weeks of age. In the subcutaneous fat depot there is an apparen t pattern of increased leptin mRNA expression occurring at 2, 6, and 10 wee ks post-hatch. This pattern was not evident in the other tissues surveyed a nd may relate to the cycle of loading and unloading of adipocytes with lipi d. No consistent gender differences in leptin expression patterns were dete cted in the tissues surveyed, as is often observed in mammals. Positive cor relations between metabolic body weight and adipose leptin expression level s were observed. Leptin expression by the liver was highly correlated with metabolic body weight from 1-6 weeks of age, and uncorrelated from 6-12 wee ks of age. This pattern of increasing liver leptin expression with increasi ng body weight during the early rapid growth phase of the bird may be due t o limited fat storage during this period, which is followed by rapid body f at accumulation from 6-12 weeks. The characterization and tissue specific d istribution of leptin mRNA expression in the growing broiler indicate simil ar patterns of leptin production to that of growing mammals. Leptin may be involved in lipid flux through the adipocyte as well as the shift in lipid metabolism to increased storage during pre-puberty. (C) 2001 Elsevier Scien ce Inc. All rights reserved.