INTERACTIONS AMONG ENDOCRINE, NUTRITIONAL AND GENETIC FACTORS CONTROLLING METABOLISM IN THE BROILER

Authors: Rosebrough, Robert; McMurtry, John; Richards, Mark; Mitchell, Alva; Ramsay, Timothy; Ashwell, Christopher

Submitted to: Poultry and Avian Biology Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2004
Publication Date: 5/31/2005
Citation: Rosebrough, R.W., McMurtry, J.P., Richards, M.P., Mitchell, A.D., Ramsay, T.G., Ashwell, C.M. 2005. Interactions among endocrine, nutritional and genetic factors controlling metabolism in the broiler. Avian and Poultry Biology Reviews. 16(2):95-100.

Interpretive Summary: Excess fat production by the modern broiler chicken presents a two-fold problem. The consumer has health concerns about the link between cardiovascular disease and dietary fat. The producer would like to produce more lean meat rather than fat condemned at the processing plant. Historically shifts in metabolism have resulted in dietary fat being merely shunted to replace that synthesized from other feed ingredients. We have found that altering feeding regimens and dietary crude protein in the broiler will cause permanent changes in fat synthesis and storage, such that dietary fat will not be shunted to body fat stores. The present review summarizes the hypotheses that dietary protein elicited changes in intermediary metabolism and if changes resulted from alterations in the expression of genes coding for certain regulatory proteins. Although increasing dietary protein decreased fat synthesis by the broiler, gene expression may not accompany this decrease unless the diet contained a very high level of protein. Modest increases in dietary protein will decrease lipid synthesis without affecting gene expression.

Technical Abstract: The purpose of this work was to summarize possible relationships among certain indices of lipid metabolism and specific gene expression in chickens fed different diets under varying states of endocrine perturbations. Variations in nutrient intake are communicated to the liver and other internal organs by alterations in the levels of hormones that respond to dietary changes. Similarly, the molecular details for the mechanisms by which glucagon, insulin, glucocorticoids, and fatty acids regulate gene expression remain to be determined. The role of fatty acids is particularly interesting because it may provide a model for mechanisms by which genes are regulated by metabolic intermediates. Although well understood in prokaryotic systems, transcriptional regulation via metabolic intermediates is not well known in eukaryotes. We feel that it is important to understand how signals from all of the relevant regulatory pathways are integrated to bring about changes in both the transcription and translation of a message for a particular protein. It should be pointed out; however, that metabolic regulation at the gene level only occurs when feeding very radical diets. In addition to physiological questions, however, there are still many aspects of the molecular mechanisms that have not been clarified.