Role of appetite-regulating peptides in adipose physiology in broiler chicks

Peptides that regulate feeding behavior via the brain may also regulate energy storage and expenditure in the adipose tissue, a system collectively known as the "brain-fat axis". Neuropeptide Y (NPY) is orexigenic and promotes adipogenesis in both birds and mammals, although mechanisms in adipose tissue are unclear. The first objective was thus to evaluate effects of NPY on chick preadipocyte proliferation and differentiation. Preadipocytes were treated with NPY and gene expression and cellular proliferation were evaluated. Cells were also treated with NPY during differentiation and harvested during the later stages. With increased gene expression of proliferation markers in preadipocytes, and during differentiation increased expression of adipogenesis-associated factors, increased lipid accumulation, and increased activity of an adipogenic enzyme, glycerol-3-phosphate dehydrogenase, results suggest that NPY may enhance preadipocyte activity and adipogenesis and promotes lipid accumulation throughout chicken adipocyte differentiation. Another appetite-regulatory peptide, alpha-melanocyte stimulating hormone (α-MSH), is anorexigenic and mediates lipolysis in adipose tissue, but effects on fat in avians are unreported. The second objective was thus to determine the effects of exogenous α-MSH on adipose tissue physiology in broiler chicks. Chicks were intraperitoneally injected with α-MSH and adipose tissue and plasma collected. Cells isolated from abdominal fat of a different set of chicks were treated with α-MSH. Results suggest that α-MSH increases lipolysis and reduces adipogenesis in chick adipose tissue. Collectively, results of this research provide insights on how appetite-regulatory peptides like NPY and α-MSH affect adipose tissue physiology, thereby playing important roles in regulating whole-body energy balance.