The body weight-related differences of leptin and neuropeptide Y (NPY) gene expression in pigs

To determine if body weight change is directly related to altered leptin and neuropeptide Y (NPY) gene expression, we assessed adipose tissue weight, percent body fat, leptin and NPY mRNA levels and serum leptin concentration in pigs at weights of 1, 20, 40, 60, and 90 kg. The results indicated that the weight of adipose tissues and the percent body, fat of pigs significantly increased and correlated with body weight (BW) from 1 to 90 kg (p < 0.01). Serum leptin concentrations and leptin mRNA levels in omental adipose tissue (OAT) increased from I to 60 kg, and then decreased from 60 to 90 kg. At 60 kg, the serum leptin concentration and leptin mRNA level significantly increased by 33.5% (p < 0.01) and 98.2% (p < 0.01), respectively, as compared with the levels at 1 kg. At 60 kg, the amount of leptin mRNA in subcutaneous adipose tissue (SAT) was significantly higher than that of I and 40 kg animals (p < 0.05). NPY gene expression in the hypothalamus also changed with BW and at 60 kg the NPY mRNA level significantly decreased by 54.0% (p < 0.05) as compared with that in I kg. Leptin mRNA in OAT was correlated with serum leptin concentrations (r = 0.98, p < 0.01), body weight (r = 0.82, p < 0.05) and percent body fat (r = 0.81, p < 0.05). This is the first report of the developmental expression of leptin in porcine OAT, peritoneal adipose tissue (PAT) and SAT, and proves that the expression of leptin in OAT could reflect the levels of circulating leptin. These results provide some information for nutritional manipulation of leptin secretion which could lead to practical methods of controlling appetite and growth in farm animals, thereby regulating and improving efficiency of lean meat production and meat production quality.