Abstract
Long noncoding RNA (lncRNA) plays an important regulatory role in mammalian adipogenesis and lipid metabolism. However, their function in the longissimus thoracis (LT) muscle of fatty acid metabolism of Tibetan sheep remains undefined. In this study, fatty acid and fat content in LT muscle of Tibetan sheep were determined, and RNA sequencing was performed to reveal the temporal regularity of lncRNA expression and the effect of lncRNA-miRNA-mRNA ceRNA regulatory network on lipid metabolism of LT muscle in Tibetan sheep at four growth stages (4-month-old, 4 m; 1.5-year-old, 1.5 y; 3.5-year-old, 3.5 y; 6-year-old, 6 y). The results indicated that the intramuscular fat (IMF) content was highest at 1.5 y. Moreover, the monounsaturated fatty acid (MUFA) content in 1.5 y of Tibetan sheep is significantly higher than those of the other groups (P < 0.05), and it was also rich in a variety of polyunsaturated fatty acids (PUFA). A total of 360 differentially expressed lncRNAs (DE lncRNAs) were identified from contiguous period transcriptome comparative groups of 4 m vs. 1.5 y, 1.5 y vs. 3.5 y, 3.5 y vs. 6 y, and 4 m vs. 6 y, respectively. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis found that the target genes in lncRNA trans-mRNA were significantly related to the protein digestion, absorption, and fatty acid biosynthesis pathways (P < 0.05), which demonstrated that DE lncRNA trans-regulated the target genes, and further regulated the growth and development of the LT muscle and intramuscular fatty acid metabolism in Tibetan sheep. We further analyzed the role of the lncRNA-miRNA-mRNA regulatory network in the lipid metabolism of Tibetan sheep. Additionally, GPD2, LIPE (lipase E hormone-sensitive enzyme), TFDP2, CPT1A, ACACB, ADIPOQ, and other mRNA related to fatty acid and lipid metabolism and the corresponding lncRNA-miRNA regulatory pairs were identified. The enrichment analysis of mRNA in the regulatory network found that the AMPK signaling pathway was the most significantly enriched (P = 0.0000112361). Comprehensive transcriptome analysis found that the LIPE, ADIPOQ, ACACB, and CPT1A that were regulated by lncRNA might change the formation of energy metabolism in Tibetan sheep muscle through the AMPK signaling pathway, and oxidized muscle fibers are transformed into glycolytic muscle fibers, reduced IMF content, and the fatty acid profile also changed.
Highlights
Tibetan sheep is the dominant livestock resource in the QinghaiTibet Plateau, living at an altitude above 3,000 m on the QinghaiTibet Plateau with high altitude, low temperature, thinner oxygen, and strong UV radiation
The results of this study indicated that the higher monounsaturated fatty acid (MUFA) and PUFA content were observed in 1.5 y of Tibetan sheep, which demonstrated that 1.5 y was a more suitable slaughter age of Tibetan sheep for a healthy human diet
The results showed that DE lncRNA trans-regulated FASN, to regulate fatty acid metabolism during the growth and development of Tibetan sheep
Summary
Tibetan sheep is the dominant livestock resource in the QinghaiTibet Plateau, living at an altitude above 3,000 m on the QinghaiTibet Plateau with high altitude, low temperature, thinner oxygen, and strong UV radiation. Mammalian skeletal muscle is a heterogeneous tissue, which is composed of various muscle fibers that exhibit different physiological and metabolic properties, such as glycolysis, oxidative metabolism, and contraction. Skeletal muscle growth and development directly influence muscle quality and meat production. Different muscle fiber types of skeletal muscle have an influence on intramuscular fat (IMF), meat tenderness, water retention, juiciness, and fatty acid composition [5, 6]. The IMF determines the meat tenderness and fatty acid profiles in the skeletal muscle [7]. Fatty acids are an important part of cells and are involved in the energy metabolism of human and animals as signaling molecules [8]. Exploring the mechanism of skeletal muscle growth and development is very important to improve lipid and fatty acid metabolism in Tibetan sheep meat
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