Tissue distribution of lipase genes related to triglyceride metabolism in laying hens (Gallus gallus)

The triglyceride lipase gene family, including lipoprotein lipase (LPL), hepatic triglyceride lipase (HTGL), carboxyl ester lipase (CEL), endothelial lipase (EL), Lipase H, hormone sensitive lipase (HSL) and adipose triglyceride lipase (ATGL), plays a critical role in lipid metabolism in mammals. In this study, we have identified and characterized the expression profile of these genes in the chicken, Gallus gallus. Chicken LPL and ATGL have been cloned, and HTGL, EL, Lipase H, and CEL sequences were found in the chicken genome database. The deduced amino acid sequences of HTGL, EL, Lipase H, and CEL were 66, 75, 63, and 65% identical with their respective human genes, suggesting conservation of important enzymatic functions. In contrast, a homologue of the HSL gene was not identified in the chicken genome. We performed RT-PCR using chicken liver, muscle, abdominal adipose tissue, or pancreas mRNA as the template, and all partial products were completely matched to the corresponding predicted sequences of triglyceride lipase gene members. Quantitation by qPCR of the transcript levels of these genes in 13 tissues indicates that the expression patterns diverge greatly between species. A particularly interesting pattern was observed in the distribution of EL and HTGL mRNA, which were highly expressed in kidney and ovary. This is the first report of HTGL, EL, Lipase H, and CEL in a pre-mammalian species and reveals novel details about specific features of the expression of these important molecules in lipid metabolism.