Expression patterns of insulin-like growth factor system members and their correlations with growth and carcass traits in Landrace and Lantang pigs during postnatal development.

The IGF system plays important roles in growth. Nevertheless, few data have been reported so far on the expression of IGF system members and their relationship with growth in domestic animals, especially pigs. In this study, hepatic transcript level of IGF1, IGF2, IGF binding protein 2 (IGFBP2), IGFBP3 and IGF 1 receptor (IGF1R), plasma protein level of IGF1 and IGFBP3, and eight growth or carcass traits, including chest circumference, body length, body height (BH), body weight, carcass weight, loin muscle area (LMA), back fat thickness and average daily gain, were measured in fast-growing Landrace and slow-growing Lantang pigs at the age of 1, 27, 90, 150 and 180 days. The results showed that liver mRNA level of IGF1, IGF2 and IGF1R, and blood protein level of IGF1 have a similar developmental profile in both Landrace and Lantang pigs. Their levels were higher at the early age than that at other older ages. Hepatic transcript abundances of the two growth inhibitors, IGFBP2 and IGFBP3, were mostly higher in Lantang pigs than that in Landrace pigs, at 5 examined postnatal stages. The IGF system members' liver mRNA level and/or serum protein level have significant correlation with each other in different age of Landrace or Lantang pigs. Hepatic mRNA level or serum protein level of IGF system members also has significant correlation with investigated traits, especially with BH and LMA, in different age of Lantang or Landrace pigs. Our results revealed the change profiles of porcine IGF system members' liver transcript level and plasma protein level between different pig breeds and different postnatal developmental ages. Moreover, the correlation analysis results suggest that the IGF system members act coordinately to regulate the growth performance and carcass composition in pigs. The information obtained from the present study is important for elucidation of the regulatory mechanism of IGF system underlying growth, and for genetic improvement in pigs.