Abstract
The objective of the present review is to discuss the results of published studies that show how nutrition affects the expression of genes involved in lipid metabolism and how diet manipulation might change marbling and composition of fat in beef. Several key points in the synthesis of fat in cattle take place at the molecular level, and the association of nutritional factors with the modulation of this metabolism is one of the recent targets of nutrigenomic research. Within this context, special attention has been paid to the study of nuclear receptors associated with fatty acid metabolism. Among the transcription factors involved in lipid metabolism, the peroxisome proliferator-activated receptors (PPARs) and sterol regulatory element-binding proteins (SREBPs) stand out. The mRNA synthesis of these transcription factors is regulated by nutrients, and their metabolic action might be potentiated by diet components and change lipogenesis in muscle. Among the options for dietary manipulation with the objective to modulate lipogenesis, the use of different sources of polyunsaturated fatty acids, starch concentrations, forage ratios and vitamins stand out. Therefore, special care must be exercised in feedlot feed management, mainly when the goal is to produce high marbling beef.
Highlights
The amount, distribution and composition of fat in beef are some of the factors that exert the greatest impact on the organoleptic and nutritional quality of this food
Before discussing in detail how some nutrients, such as fatty acids, might change the expression of definite genes, the main processes involved in adipogenesis and lipid metabolism will be briefly reviewed, as several of the investigated genes encode enzymes or are transcription factors that modulate the expression of genes involved in lipid metabolism
Adipogenesis is an inclusive term describing the commitment of progenitors (MSC) to pre-adipocytes, proliferation of pre-adipocytes, differentiation of pre-adipocytes into adipocytes, and conversion of cells into lipid-assimilating cells found within fat tissue [3,4]
Summary
The amount, distribution and composition of fat in beef are some of the factors that exert the greatest impact on the organoleptic and nutritional quality of this food. The other pathway is related to the action of fatty acids as metabolic modifiers, either by directly altering the synthesis and deposition of fatty acids in the tissues or by affecting biological processes in the animals, such as the modulation of gene expression in ruminants. In either case, understanding the action of fatty acids in animal metabolism demands adequate knowledge of the molecular processes involved in the synthesis and utilization of fatty acids in the tissues. The studies addressing these subjects usually associate gene expression and nutrition; they are called nutrigenomics or functional genomics. Before discussing in detail how some nutrients, such as fatty acids, might change the expression of definite genes, the main processes involved in adipogenesis and lipid metabolism will be briefly reviewed, as several of the investigated genes encode enzymes or are transcription factors that modulate the expression of genes involved in lipid metabolism
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