Analysis Of Developmental Differences Of Duck Subcutaneous Adipose Tissues

The subcutaneous adipose tissue is the main organ for lipid deposition and plays an important role in stabilizing metabolic balance. However, the developmental patterns of subcutaneous adipose tissue during Peking duck (Anas platyrhynchos) early development, as well as the reasons for regional differences were not well known. Therefore, we employed Peking duck as materials to investigate the characteristics of subcutaneous adipose tissue formation, and analysis the growing pattern of subcutaneous adipose tissue during duck early growing stages from week1to8, comparing the morphological characteristics and lipid contents in five regions of subcutaneous adipose tissue including neck area (NSF), chest area (CSF), lower abdomen area (ASF), back area (BSF) and leg area (LSF). The mRNA expressions of three molecular maker genes including47-kDa tail interacting protein (TIP47), adipose differentiation-related protein (ADRP) and Perilipin were also detected using quantitative real-time (qRT)-PCR method. In order to investigate the reasons for regional differences of subcutaneous adipose tissue, we analysis the lipid metabolic disorder by using fasting and LPS injection technique. We use RT-PCR method to clone partial cDNA of duck ANGPTL3and ANGPTL4, as well as to analysis the expressions of these genes during duck growth, to investigate correlations between the gene expressions and regional differences of subcutaneous adipose development. The main results of this study are as follows:(1) A combination of adipocyte hyperplasia and hypertrophy is mainly responsible for the development of duck adipose tissue before4weeks of age, after which adipose expansion is accomplished by adipocyte hypertrophy only.(2) There are many regional differences in adipocyte hyperplastic capacity, as well as fat storage capacities (capacities from adipocyte hypertrophy, lipid synthesis and lipid deposition). Adipocytes in NSF have a higher hyperplastic and lipogenic activity compared with these from other regions. Adipocytes in CSF also have a higher lipogenic activity than that in other regions during the early stage of development. Adipocytes in ASF have a higher hypertrophy capacity at week4to8. The greater fat storage capacity in NSF, CSF, ASF are observed compared with these in BSF, LSF at week1to8. In contrast, adipocytes in BSF region have a higher lipogenic activity than other regions during the early stage of development. Adipocytes in LSF region have a higher hyperplastic capacity at week3to4, a higher hypertrophy capacity at week4to8, and a higher metabolic activity at week3to5, whereas the lower performance in fat storage capacity.(3)12hours fasting could induce lipid metabolic disorder. The duck serum total TG, total TC, NEFA, VLDL, HDL-C, LDL-C levels and post-heparin plasma LPL activity showed significant change.(4) Intravenous injection of LPS may have an adverse effect on the duck growth performance and lipid metabolism and could induce regional differences of subcutaneous adipose tissue in fat storage capacity, adipocyte hyperplasia and hypertrophy activity, as well as lipid metabolic activity. TG hydrolases may take part in this metabolic process. Compared with control groups, NSF region in LPS injection groups had a higher LPL activity and lower LPL mRNA levels. CSF region had a higher LPL activity and lower LPL, ATGL, ADRP and PLIN mRNA levels. CSF region had a lower LPL, ATGL and PLIN mRNA levels. BSF region had a lower LPL, ATGL, ADRP and PLIN mRNA levels. However, LSF had a higher LPL, ATGL, ADRP and PLIN mRNA levels.(5) We have got partial cDNA sequences. Results showed that duck ANGPTL3contained1372bp nucleotide and ANGPTL4contained726bp nucleotide. There are significant differences in developmental expression patterns of ANGPTL3and ANGPTL4. The ANGPTL3mRNA levels were negatively correlated with adipocyte diameter in CSF and were positively correlated with the lipid content in NSF. The ANGPTL4mRNA levels were positively correlated with the lipid content in LSF. Results suggested that both ANGPTL3and ANGPTL4coule be related to the development of subcutaneous adipose tissue and contribute to regional differences during duck growth.