Alterations in gene expression that affect lean tissue accretion and meat quality in food producing animals

Postnatal skeletal muscle growth is a result of hypertrophy of existing skeletal muscle fibers in
food producing animals. Accumulation of additional nuclei, as a source of DNA, to the
multinucleated skeletal muscle fiber aids in fiber hypertrophy during periods of rapid skeletal
muscle growth. Muscle satellite cells are recognized as the source of nuclei to support muscle
hypertrophy. These changes in both skeletal muscle hypertrophy and muscle satellite cell activity
are due in part, to changes in gene expression of key genes responsible for alterations in
postnatal muscle growth. Accretion of myofibrillar protein is a balance between protein
synthesis and protein degradation. Changes in rate of protein synthesis can be affected by
upregulating different isoforms of myosin heavy chain. These changes in mRNA concentrations
are related to protein synthesis. In addition, up regulation of certain transcription factors, such as
the myogenic regulatory factors, have been shown to positively impact proliferation and
differentiation of muscle satellite cells. Adipose tissue gene expression can be regulated by
specific nutrients and growth promotants as well. Our data has shown that specific fatty acids
such as palmitic acid, oleic acid, and linolenic acid can regulate expression of key adipogenic
genes responsible for both subcutaneous and intramuscular adipose tissue accretion in meat
animals. Increased knowledge of the mechanism by which nutrients and growth promotants
regulate lean tissue deposition and adipogenesis in meat animals will allow for effective
application of these techniques to optimize lean tissue growth and minimize the negative effects
on meat quality.