THE ONTOGENY OF LEPTIN MRNA EXPRESSION IN GROWING BROILERS AND ITS RELATIONSHIP TO METABOLIC BODY WEIGHT

Authors: Ashwell, Christopher; Richards, Mark; McMurtry, John

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2001
Publication Date: 10/1/2001
Citation: Domestic Animal Endocrinology 21:161-168, 2001.

Interpretive Summary: The hormone leptin is produced by both adipose tissue and the liver and has been shown to induce reduce food intake chickens. In this study we have studies how leptin functions in growing broiler chickens. Leptin activity generally increases in fat and liver from 1-12 weeks of age. In the subcutaneous fat depot there is an apparent pattern of increased leptin mRNA expression occurring at 2, 6, and 10 weeks post-hatch. This pattern was not evident in the other tissues surveyed and may relate to patterns of fat storage. No consistent gender differences in leptin expression patterns were detected in the tissues surveyed, as is often observed in growing mammals. Positive correlations between body weight and fat leptin expression levels were observed. Leptin expression in the liver was highly correlated with body weight from 1-6 weeks of age. This pattern of liver leptin expression paired with increasing body weight during the rapid growth phase of the bird may be due to limited fat storage during this period, which is followed by rapid body fat accumulation from 6-12 weeks. The characterization and tissue specific distribution of leptin mRNA expression in the growing broiler indicate similar patterns of leptin production to that of growing mammals. Leptin may function as a signal or reporter of altered lipid metabolism at the end of the rapid growth phase towards increased lipid storage.

Technical Abstract: The polypeptide hormone leptin is produced by both adipose tissue and the liver and has been shown to induce satiety in chickens. In this study we have investigated the developmental regulation of leptin mRNA expression in growing broiler chickens. Leptin expression generally increases in adipose and hepatic tissues from 1-12 weeks of age. In the subcutaneous fat tdepot there is an apparent pattern of increased leptin mRNA expression occurring at 2, 6, and 10 weeks post-hatch. This pattern was not evident in the other tissues surveyed and may relate to the cycle of loading and unloading of adipocytes with lipid. No consistent gender differences in leptin expression patterns were detected in the tissues surveyed, as is often observed in growing mammals. Positive correlations between metabolic body weight and adipose leptin expression levels 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 weeks of age. This pattern of liver leptin expression paired with increasing body weight during the rapid growth phase of the bird may be due to limited fat storage during this period, which is followed by rapid body fat accumulation from 6-12 weeks. The characterization and tissue specific distribution of leptin mRNA expression in the growing broiler indicate similar patterns of leptin production to that of growing mammals. Leptin may function as a signal or reporter of altered lipid metabolism at the end of the rapid growth phase towards increased lipid storage.