Transcriptome analysis reveals the synergistic involvement of MGLL and LPIN1 in fatty acid synthesis in broiler pectoral muscles.

Fatty acids (FAs) are one of the most important bioactive compounds affecting the quality of meat. In this study, we compared the expression profiles of genes involved in FA production in the breast muscle of Jingxing Yellow chickens at different days of age determined by transcriptomic analysis to identify key genes and pathways regulating the FA composition of the breast muscle. Through clustering analysis of gene expression data, the growth process of broiler chickens can be divided into two stages, namely the growth and development stage at the 35th and 63rd days of age (D35, D63), and the mature stage at the 119th day of age (D119). The content of some important unsaturated fatty acids (UFAs), such as C18:2n6c, C20:4n6, and C22:6n3, in the pectoral muscles, differed significantly between these two stages (p < 0.05). Therefore, we compared the gene expression profiles at D35 and D63 with those at D119, and identified differentially expressed genes (DEGs). The gene modules related to the five UFAs with significant changes were identified by weighted gene co-expression network analysis (WGCNA), and then 150 crossover genes were identified by crossover analysis of the detected DEGs and WGCNA. The results of the pathway enrichment analysis revealed the glycerolipid metabolism pathway related to lipid metabolism, in which the MGLL and LPIN1 genes were particularly enriched. In this study, the expression levels of MGLL and LPIN1 showed an increasing trend during the growth process of broilers, with a negative regulatory effect on the significantly reduced content of C18:2n6c in the pectoral muscle, and a positive regulatory effect on the significantly increased content of C20:4n6. These findings indicated that MGLL and LPIN1 synergistically promote the deposition of FAs, which may further promote the conversion of linoleic acid (C18:2n6c) to arachidonic acid (C20:4n6). Therefore, screening and identifying FA production-related functional genes are key to elucidate the regulatory molecular mechanism of production of FAs in chicken muscle, aiming to provide a theoretical basis for improving chicken meat quality.

Effect of myristic acid supplementation on triglyceride synthesis and related genes in the pectoral muscles of broiler chickens.

Fatty acids (FAs) can serve as energy for poultry, maintain normal cell structure and function, and support a healthy immune system. Although the addition of polyunsaturated fatty acids (PUFAs) to the diet has been extensively studied and reported, the mechanism of action of saturated fatty acids (SFAs) remains to be elucidated. We investigated the effect of 0.04% dietary myristic acid (MA) on slaughter performance, lipid components, tissue FAs, and the transcriptome profile in chickens. The results showed that dietary MA had no effect on slaughter performance (body weight, carcass weight, eviscerated weight, and pectoral muscle weight) (P > 0.05). Dietary MA enrichment increased MA (P < 0.001) and triglycerides (TGs) (P < 0.01) levels in the pectoral muscle. The levels of palmitic acid, linoleic acid (LA), arachidonic acid (AA), SFAs, monounsaturated fatty acids (MUFAs), and PUFAs were significantly higher (P < 0.01) in the MA supplementation group compared to the control group. However, there were no significant differences in the ratios of PUFA/SFA and n6/omega-3 (n3) between the two groups. The MA content was positively correlated with the contents of palmitic acid, LA, linolenic acid (ALA), n3, n6, SFAs, and unsaturated fatty acids (UFA). DHCR24, which is known to be involved in steroid metabolism and cholesterol biosynthesis pathways, was found to be a significantly lower in the MA supplementation group compared to the control group (P < 0.05, log2(fold change) = -0.85). Five overlapping co-expressed genes were identified at the intersection between the differential expressed genes and Weighted Gene Co­expression Network Analysis-derived hub genes associated with MA phenotype, namely BHLHE40, MSL1, PLAGL1, SRSF4, and ENSGALG00000026875. For the TG phenotype, a total of 28 genes were identified, including CHKA, KLF5, TGIF1, etc. Both sets included the gene PLAGL1, which has a negative correlation with the levels of MA and TG. This study provides valuable information to further understand the regulation of gene expression patterns by dietary supplementation with MA and examines at the molecular level the phenotypic changes induced by supplementation with MA.

Tryptophan Promotes the Production of Xanthophyll Compounds in Yellow Abdominal Fat through HAAO.

Abdominal fat, which in the past was often regarded as waste and discarded, has in recent years been used as a fat source to produce meat by-products. Yellow abdominal fat has higher economic value. Therefore, improving the color of abdominal fat plays an important role in improving the appearance of meat products. This study aimed to identify the contributors and the regulatory network involved in the formation of yellow and white color in abdominal fat. We found that four xanthophyll compounds were significantly different in yellow and white abdominal fat chicken, including zeaxanthin, lutein, canthaxanthin, and ß-cryptoxanthin. There were 551 different and 8 common metabolites significantly correlated with these 4 xanthophyll compounds. Similarly, a total of 54 common genes were identified in 4 common related pathways (Complement and coagulation cascades, Metabolic pathways, PPAR signaling pathway, Carbon metabolism) of the 8 common metabolites. The high expression of HAAO in the yellow abdominal fat group leads to the degradation of tryptophan and its intermediate 5-hydroxyindole, and subsequently to the formation of the four xanthophyll compounds. This process is also regulated by tyrosine, kynurenine 3-monooxygenase (KMO), homogentisate 1, 2-dioxygenase (HGD), etc. Together, these findings show the effect of tryptophan on abdominal fat color, as well as a negative regulatory effect of HAAO and 5-hydroxyindole on the production of xanthophyll compounds involved in abdominal fat coloration.

Identification of characteristic aroma compounds in chicken meat and their metabolic mechanisms using gas chromatography-olfactometry, odor activity values, and metabolomics.

Aroma has an important influence on the aroma quality of chicken meat. This study aimed to identify the characteristic aroma substances in chicken meat and elucidate their metabolic mechanisms. Using gas chromatography-olfactometry and odor activity values, we identified nonanal, octanal, and dimethyl tetrasulfide as the basic characteristic aroma compounds in chicken meat, present in several breeds. Hexanal, 1-octen-3-ol, (E)-2-nonenal, heptanal, and (E,E)-2,4-decadienal were breed-specific aroma compounds found in native Chinese chickens but not in the meat of white-feathered broilers. Metabolomics analysis showed that L-glutamine was an important metabolic marker of nonanal, hexanal, heptanal, octanal, and 1-octen-3-ol. Exogenous supplementation experiments found that L-glutamine increased the content of D-glucosamine-6-P and induced the degradation of L-proline, L-arginine, and L-lysine to enhance the Maillard reaction and promote the formation of nonanal, hexanal, heptanal, octanal, and 1-octen-3-ol, thus improving the aroma profile of chicken meat.