Long non-coding RNAs (lncRNAs) are emerging as powerful regulators of adipocyte differentiation, fat metabolism and gene expression. However, the functional roles and mechanisms of lncRNAs in these processes remain unclear. Here, we identified a novel antisense transcript, named APMAP-AS, transcribed from adipocyte membrane-associated protein (APMAP) in the pig genome. APMAP-AS and APMAP were highly expressed in retroperitoneal adipose of obese pigs, compared with that in control pigs. Using a bone mesenchymal stem cells (BMSCs) adipogenic differentiation model, we found that APMAP-AS positively regulated adipogenic differentiation. APMAP-AS had the potential to form an RNA–RNA duplex with APMAP, and increased the stability of APMAP mRNA. Additionally, APMAP-AS promoted lipid metabolism and inhibited the expression of inflammatory factors. These findings of a natural antisense transcript for a regulatory gene associated with lipid synthesis might further our understanding of lncRNAs in driving adaptive adipose tissue remodeling and preserving metabolic health.

Follistatin (FST) is an important regulator of skeletal muscle growth and adipose deposition through its ability to bind to several members of the transforming growth factor-β (TGF-β) superfamily, and thus may be a good candidate for future animal breeding programs.  However, the molecular mechanisms underlying the phenotypic changes have yet to be clarified in pig.  We generated transgenic (TG) pigs that express human FST specifically in skeletal muscle tissues and characterized the phenotypic changes compared with the same tissues in wild-type pigs.  The TG pigs showed increased skeletal muscle growth, decreased adipose deposition, and improved metabolism status (P<0.05).  Transcriptome analysis detected important roles of the PIK3–AKT signaling pathway, calcium-mediated signaling pathway, and amino acid metabolism pathway in FST-induced skeletal muscle hypertrophy, and depot-specific oxidative metabolism changes in psoas major muscle.  Furthermore, the lipid metabolism-related process was changed in adipose tissue in the TG pigs.  Gene set enrichment analysis revealed that genes related to lipid synthesis, lipid catabolism, and lipid storage were down-regulated (P<0.01) in the TG pigs for subcutaneous fat, whereas genes related to lipid catabolism were significantly up-regulated (P<0.05) in the TG pigs for retroperitoneal fat compared with their expression levels in wild-type pigs.  In liver, genes related to the TGF-β signaling pathway were over-represented in the TG pigs, which is consistent with the inhibitory role of FST in regulating TGF-β signaling.  Together, these results provide new insights into the molecular mechanisms underlying the phenotypic changes in pig.

Chenghua (CH) pig and Qingyu (QY) pig are typical Chinese native fatty breeds.  CH pig is mainly distributed in Chengdu Plain, while QY pig is widely distributed throughout the mountain areas around the Sichuan Basin.  There are significant differences in their phenotypic traits, including body image, growth performance, and meat quality.  This study compared several meat quality traits of CH and QY pigs and conducted a genome-wide DNA methylation analysis using reduced representation bisulfite sequencing (RRBS).  It was observed that the pH at 45 min (pH_45min, P=5.22e–13), lightness at 45 min (L*_45min, P=4.85e–5), and lightness at 24 h (L*_24h, P=3.57e–5) of CH pigs were higher than those of QY pigs.  We detected 10 699 differentially methylated cytosines (DMCs) and 2 760 differentially methylated genes (DMGs) associated with these DMCs.  Functional analysis showed that these DMGs were mainly enriched in the AMPK signaling pathway, Type II diabetes mellitus, Insulin signaling pathway, mTOR signaling pathway, and Insulin resistance.  Furthermore, 15 DMGs were associated with fat metabolism (ACACA, CAB39, CRADD, CRTC2, FASN, and GCK), muscle development (HK2, IKBKB, MTOR, PIK3CD, PPARGC1A, and RPTOR), or meat quality traits (PCK1, PRKAG2, and SLC2A4).  The findings may help to understand further the epigenetic regulation mechanisms of meat quality traits in pigs and provide new basic data for the study of local pigs.

DNA methyltransferases (Dnmts) comprise a family of proteins which involved in the establishment and maintenance of DNA methylation patterns.  In pig, the molecular characterization and tissue expression profile of Dnmt gene family are not clear.  To solve this problem, reverse transcriptase PCR and rapid amplification of cDNA ends were used to clone the sequences of the porcine Dnmt2 and Dnmt3b genes.  Furthermore, the mRNA expression profiles of Dnmt1, Dnmt2, Dnmt3a and Dnmt3b genes from 54 adult tissues and 2 entire fetuses of Rongchang pig were analyzed by quantitative real-time PCR (qRT-PCR).  As a result, the lengths of porcine Dnmt2 and Dnmt3b gene cDNAs were 1 227 and 2 559 bp with cytosine-C5 specific DNA methylase domain, respectively.  The four Dnmt genes were highly expressed in longissimus dorsi muscle (P<0.01).  Dnmt1 is highly expressed in heart (P<0.01) and Dnmt 2 shows its preference in liver and seminal vesicle tissue (P<0.01).  Dnmt3a and Dnmt3b are highly expressed in the two fetus stages (P<0.01).  All these results suggested that each gene has its specific expression profile, and deeper study is required to dig more details between the methylation level and Dnmt family mRNA expressions in different tissues.