HORMONAL REGULATION OF POSTNATAL CHICKEN PREADIPOCYTE DIFFERENTIATION IN VITRO

Authors: Ramsay, Timothy; Rosebrough, Robert

Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2002
Publication Date: 11/27/2002
Citation: Ramsay, T.G., Rosebrough, R.W. 2003. Hormonal regulation of postnatal chicken preadipocyte differentiation in vitro. Comparative Biochemistry and Physiology Part B. 136:245-253.

Interpretive Summary: A cell culture system was developed for chicken adipose tissue that permits analysis of the hormonal regulation of the cells over extended time periods. Cells are isolated from the abdominal fat pad of broilers and put into tissue culture. Through the use of low serum conditions and the hormones, insulin and dexamethasone, one can now produce fat cells in culture that mimic the development of cells grown in a much richer environment. Simplification of the environment of the cells permits careful examination of key events in the development of the cell. Thus, key regulatory steps for fat accumulation may be identified. This culture experiment demonstrated that the hormones IGF-I and Triiodothyronine may not function in chicken fat cell formation, while insulin and glucocorticoids are very important.

Technical Abstract: The present study was designed to develop a culture system from the stromal vascular cells of chicken adipose tissue that can be used to identify hormones that promote adipocyte formation. Abdominal adipose tissue was excised from 2-4 week old male broilers by sterile dissection. The stromal vascular cell fraction from the adipose tissue was isolated by collagenase digestion, filtration, and subsequent centrifugation. These preadipocytes were seeded in 6 well culture plates and proliferated to confluency in 10% fetal bovine serum in DMEM/F12 (50:50) medium. At confluency, experiments were initiated to determine hormonal requirements for differentiation. IBMX (10 mM) in combination with 1mM dexamethasone could not promote differentiation, as determined by the expression of citrate lyase and sn-glycerol-3-phosphate dehydrogenase relative to lactate dehydrogenase. Insulin (100 nM) stimulated expression of CL and GPDH (P<0.05) in the presence of 2.5% chicken serum, but not with 10% chicken serum. T3 (1 nM) and IGF-I (100 ng/ml) had no effect on differentiation. Dexamethasone (1 mM) stimulated differentiation (P<0.05). The combination of insulin and T3 stimulated differentiation (P<0.05) but the effect was no greater than insulin alone. Insulin, dexamethasone and 2.5% chicken serum synergistically stimulated differentiation and thus can replace 10% chicken serum in culture. Heparin (10 U/ml) in combination with insulin and dexamethasone promoted lipid filling of differentiated cells. Development of a culture system that only requires low serum concentrations for stimulating adipocyte formation may permit identification of important regulatory hormones for differentiation.