Abstract
Simple SummaryIntramuscular fat is an important factor affecting meat quality and consumer acceptance. Appropriate increases in the intramuscular fat content contribute to the improvement of meat quality, and genetic selection is an effective method to increase the intramuscular fat content in chickens. In this study, chicken lines divergently selected for their intramuscular fat content were used to investigate the mechanisms behind differential intramuscular fat deposition. These results found in this study may contribute to the improvement of meat quality in chickens.Intramuscular fat (IMF)—an important factor affecting meat quality—can be appropriately increased by genetic selection. Chicken lines divergently selected for IMF content were used in this study to investigate the mechanisms behind differential IMF deposition. Sixty 15th generation chickens were genotyped using the IASCHICK 55K single nucleotide polymorphism (SNP) chip. After quality control, 59 chickens and 36,893 SNPs were available for subsequent analysis. Population structure assessment indicated that the lines were genetically differentiated. Based on the top 1% paired fixation index values, three pathways were significantly (p < 0.05) enriched, and nine genes were considered candidate genes for differential IMF deposition. Differences between the lines in the expressions of representative genes involved in the above pathways were detected in 16th generation chickens. This study suggests that genetic selection for increased IMF in the pectoralis major muscle may enhance fatty acid synthesis, transport, and esterification, and reduce triglyceride hydrolysis. The peroxisome proliferator-activated receptor (PPAR) signaling pathway, glycerolipid metabolism, and fatty acid degradation pathway may have contributed to the differences in IMF deposition between the lines. These results contribute to the understanding of the genetic mechanisms behind IMF deposition, and the improvement of chicken meat quality.
Highlights
Meat quality plays an essential role in consumer acceptance, and intramuscular fat (IMF), deposited within the muscle tissue, is a widely acknowledged indicator of meat quality [1]
The results of this study were consistent with this interpretation, as the higher ACSL1 expression in the F line than the C line coincided with the greater IMF deposition found in the former. These results indicated that weaker lipolysis and stronger lipogenesis processes may contribute to the higher IMF content found in the F line than the C
In the peroxisome proliferator-activated receptor (PPAR) signaling pathway, lipolysis related genes were downregulated (PPARα and PPARβ/δ), and lipogenesis related genes were up regulated (ACSL1, AFABP, malic enzyme 1 (ME1), perilipin 1 (PLIN1) and PPARγ) in the F line. These results demonstrated that the F-line chickens exhibited enhanced fatty acid synthesis, transport, and esterification processes, and reduced hydrolysis of triglycerides stored in lipid droplets, which may explain the higher IMF
Summary
Meat quality plays an essential role in consumer acceptance, and intramuscular fat (IMF), deposited within the muscle tissue, is a widely acknowledged indicator of meat quality [1]. Numerous studies have explored the molecular mechanisms behind differential IMF deposition using different chicken breeds with typically different IMF contents [2,3,4]; the different genetic backgrounds of the chickens used makes explaining the inconsistent results of these studies difficult. As they have the same genetic origin, IMF-divergent selection lines are considered a good model for studying the molecular mechanisms behind IMF deposition. The low to moderate heritability (0.12–0.16) of the IMF content in native Chinese chickens [7] increased the difficulty of genetic selection, resulting in few IMF selection lines being developed far
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