The effect of the PLIN1 gene on the metabolism and mitochondria of porcine skeletal muscle satellite cells

Different levels of autophagy induced by transient serum starvation regulate metabolism and differentiation of porcine skeletal muscle satellite cells

This study aimed to investigate the effects of different levels of autophagy induced by transient serum starvation on the metabolism, lipid metabolism, and differentiation of porcine skeletal muscle satellite cells (SMSCs) to preliminary elucidate the role and function of autophagy in the regulatory network of skeletal muscle development. Different levels of autophagy were induced by controlling the serum concentration in the culture system for 24 h. Apoptosis, membrane potential, reactive oxygen species (ROS), ATP, and myogenic and lipogenic differentiation markers were monitored to determine if autophagy affected the metabolism and differentiation of SMSCs. Autophagy was induced in SMSCs via serum starvation (5%, 15%), as evidenced by decreased p62 and mTOR phosphorylation levels and increased LC3B lipidation and AMPK phosphorylation levels. Transmission electron microscopy revealed the presence of autophagosomes, and the rates of morphologically abnormal nuclei and mitochondria gradually increased with the decrease in serum concentration, the number of autophagic lysosomes also increased, indicating that 5% serum starvation induced severe autophagy, while 15% serum starvation induced mild autophagy. Compared with the control group and 15% serum-starved SMSCs, SMSCs undergoing 5% serum starvation had the highest intracellular ATP and ROS levels, the highest percentage of apoptotic cells, and the lowest membrane potential. The 15% serum-starved SMSCs had the highest membrane potential, but the percentage of apoptotic cells did not change significantly compared with the control group. The levels of the myogenic markers MyoD1 and MHC were significantly higher in 15% serum-starved SMSCs than in serum-sufficient SMSCs and the lowest in the 5% serum-starved SMSCs. The lipid contents (measured by Oil Red O staining and quantification of triglycerides) and lipogenic markers Peroxisome Proliferators-activated Receptors γ and Lipoprotein Lipase were also significantly higher in SMSCs undergoing 15% serum starvation than in the control group, and the lowest in the 5% serum-starved SMSCs. Different levels of starvation stress induce different levels of autophagy. Mild autophagy induced by moderate serum starvation promotes the metabolism and differentiation of SMSCs, while severe autophagy renders SMSCs more apoptotic, abnormal metabolism and suppresses SMSC differentiation into adipocytes or myocytes, and reduces lipid metabolisms. Our study suggests that autophagy plays a role in skeletal muscle development and may help design strategies for improving meat production traits in domestic pigs.

Identification of Candidate Genes and Regulatory Competitive Endogenous RNA (ceRNA) Networks Underlying Intramuscular Fat Content in Yorkshire Pigs with Extreme Fat Deposition Phenotypes

Intramuscular fat (IMF) content is vital for pork quality, serving an important role in economic performance in pig industry. Non-coding RNAs, with mRNAs, are involved in IMF deposition; however, their functions and regulatory mechanisms in porcine IMF remain elusive. This study assessed the whole transcriptome expression profiles of the Longissimus dorsi muscle of pigs with high (H) and low (L) IMF content to identify genes implicated in porcine IMF adipogenesis and their regulatory functions. Hundreds of differentially expressed RNAs were found to be involved in fatty acid metabolic processes, lipid metabolism, and fat cell differentiation. Furthermore, combing co-differential expression analyses, we constructed competing endogenous RNAs (ceRNA) regulatory networks, showing crosstalk among 30 lncRNAs and 61 mRNAs through 20 miRNAs, five circRNAs and 11 mRNAs through four miRNAs, and potential IMF deposition-related ceRNA subnetworks. Functional lncRNAs and circRNAs (such as MSTRG.12440.1, ENSSSCT00000066779, novel_circ_011355, novel_circ_011355) were found to act as ceRNAs of important lipid metabolism-related mRNAs (LEP, IP6K1, FFAR4, CEBPA, etc.) by sponging functional miRNAs (such as ssc-miR-196a, ssc-miR-200b, ssc-miR10391, miR486-y). These findings provide potential regulators and molecular regulatory networks that can be utilized for research on IMF traits in pigs, which would aid in marker-assisted selection to improve pork quality.