Adipocyte Progenitor Pools Composition and Cellular Niches Affect Adipogenesis Divergence in Porcine Subcutaneous and Intramuscular Fat.

Intramuscular fat (IMF) contributed positively to pork quality, whereas subcutaneous fat (SCF) was often considered to be a detrimental factor impacting growth and carcass traits. Reducing SCF while maintaining optimal IMF levels requires a thorough understanding of the adipogenic differences between these two adipose depots. Our study explored the differences in adipogenesis between porcine IMF and SCF, and the results showed that subcutaneous adipocytes (SCAs) demonstrate a greater potential for adipogenic differentiation, both in vivo and in vitro. Lipidomic and transcriptomic analyses suggested that intramuscular adipocytes (IMAs) are more inclined to biosynthesize unsaturated fatty acids. Furthermore, single-cell RNA sequencing (scRNA-seq) was employed to dissect the intrinsic and microenvironmental discrepancies in adipogenesis between porcine IMF and SCF. Comparative analysis indicated that SCF was enriched with preadipocytes, exhibiting an enhanced adipogenic potential, while IMF was characterized by a higher abundance of stem cells. Furthermore, coculture analyses of porcine intramuscular adipogenic cells and myogenetic cells indicated that the niche of IMAs inhibited its adipogenic differentiation. Cell communication analysis identified 160 ligand-receptor pairs and channels between adipogenic and myogenetic cells in IMF. Collectively, our study elucidated two intrinsic and microenvironmental novel mechanisms underpinning the divergence in adipogenesis between porcine SCF and IMF.

Tricaprylin, a medium-chain triglyceride, aggravates high-fat diet-induced fat deposition but improves intestinal health.

Medium-chain triglycerides (MCTs) are absorbed and metabolized more rapidly than long-chain triglycerides (LCTs) and therefore are considered to have obesity-prevention potential in foods. The effect of adding tricaprylin, an MCT, to food on fat deposition and intestinal health is uncharted. In this study, mice were randomly divided into four groups and fed a normal diet (ND), ND with tricaprylin, a high-fat diet (HFD), or HFD with tricaprylin. Supplementation of 2% tricaprylin in HFD significantly increased the body weight, fat mass, liver weight, adipocyte size in adipose tissue and liver, and upregulated genes related to fat deposition. Metabolomic analysis of serum and adipose tissue revealed that tricaprylin significantly increased the contents of metabolites related to lipid metabolism, triglyceride storage, and fat deposition related signaling pathways. In vitro experiments and molecular docking analysis suggest that octanoic acid, a primary decomposition product of tricaprylin, may promote adipogenic differentiation of preadipocytes by acting as a PPARγ ligand to activate the expression of lipogenesis-related genes. Although supplementation with 2% tricaprylin in HFD cannot reduce fat deposition, it has a beneficial effect on intestinal health. Tricaprylin improved intestinal morphology, digestive enzyme activity, short-chain fatty acid concentration, and intestinal barrier function-related protein expression, while reducing inflammatory factor levels and the abundance of harmful intestinal microorganisms.

Melatonin promotes gut anti-oxidative status in perinatal rat by remodeling the gut microbiome.

Gut health is important for nutrition absorption, reproduction, and lactation in perinatal and early weaned mammals. Although melatonin functions in maintaining circadian rhythms and preventing obesity, neurodegenerative diseases, and viral infections, its impact on the gut microbiome and its function in mediating gut health through gut microbiota remain largely unexplored. In the present study, the microbiome of rats was monitoring after fecal microbiota transplantation (FMT) and foster care (FC). The results showed that FMT and FC increased intestinal villus height/crypt depth in perinatal rats. Mechanistically, the melatonin-mediated remodeling of gut microbiota inhibited oxidative stress, which led to attenuation of autophagy and inflammation. In addition, FMT and FC encouraged the growth of more beneficial intestinal bacteria, such as Allobaculum, Bifidobacterium, and Faecalibaculum, which produce more short-chain fatty acids to strengthen intestinal anti-oxidation. These findings suggest that melatonin-treated gut microbiota increase the production of SCFAs, which improve gut health by reducing oxidative stress, autophagy and inflammation. The transfer of melatonin-treated gut microbiota may be a new and effective method by which to ameliorate gut health in perinatal and weaned mammals.

LncIMF2 promotes adipogenesis in porcine intramuscular preadipocyte through sponging MiR-217.

Intramuscular fat is positively related to meat quality including tenderness, flavor, and juiciness. Long noncoding RNA (LncRNA) plays a vital role in regulating adipogenesis. However, it is largely unknown about lncRNAs associated with porcine intramuscular adipocyte adipogenesis. In the present study, we focus on a novel LncRNA, which is named lncIMF2, associated with adipogenesis by our previous RNA-sequence analysis and bioinformatics analysis. We demonstrated LncIMF2 knockdown inhibited the proliferation of porcine intramuscular adipocytes while expression of cell cycle-related genes was decreased. Besides, we found LncIMF2 knockdown inhibited expression of adipogenic differentiation marker genes including PPARγ (Peroxisome proliferator-activated reporter gamma) and ATGL (Adipose triglyceride lipase). Similarly, overexpression of LncIMF2 promotes proliferation and differentiation of porcine intramuscular preadipocytes. Moreover, we proved that IncIMF2 acts as a molecular sponge for MicroRNA-217 (miR-217), which has been found associated with adipogenesis, thereby affecting the expression of the miR-217 target gene. Collectively, our findings will contribute to a deeper understanding of the role of LncRNA in pig IMF deposition for the improvement of meat quality.

COPS3 AS lncRNA enhances myogenic differentiation and maintains fast-type myotube phenotype.

Long non-coding RNAs (lncRNAs) play essential roles in myogenesis. Here, we identified a novel long non-coding RNA, named COPS3 AS lncRNA (COP9 signalosome complex subunit 3 antisense lncRNA), which was transcribed from the mouse COPS3 gene antisense strand and highly expressed in glycolytic muscle fibers. Functionally, COPS3 AS lncRNA knockdown inhibited myogenic differentiation in myoblasts, whereas its overexpression promoted the process. Moreover, COPS3 AS lncRNA maintained the fast-twitch myotubes phenotype. Mechanistically, although COPS3 AS lncRNA did not form AS lncRNA/mRNA dimer with COPS3 mRNA, it as a competing endogenous RNA (ceRNA) to sponge miR-762, promoted myogenic differentiation and Fast-MyHC expression by modulating miR-762 target gene myogenic differentiation 1 (MyoD1). Taken together, COPS3 AS lncRNA is a key candidate regulator of myogenesis and fast-MyHC myotubes specification by miR-762/MyoD signalling axis.

METTL3 promotes proliferation and myogenic differentiation through m6A RNA methylation/YTHDF1/2 signaling axis in myoblasts.

Skeletal muscle development has an important impact on muscle-related diseases and domestic animal meat production. The m6A RNA methylation is a common post-transcriptional modification, affecting the development and metabolism of various organs. However, the effect and regulatory mechanism of methyltransferase like 3 (METTL3) on myogenesis are still unclear. Here, we showed that the mRNA levels of METTL3 was greater in skeletal muscles including extensor digitorum longus (EDL), soleus (SOL), tibialis anterior (TA) and gastrocnemius (GAS). Moreover, METTL3 highly expressed in the early stage of myoblast proliferation at hour 0 and the late stage of myoblast differentiation at day 8, indicating it was involved in myogenesis. Interestingly, METTL3 knockdown inhibited myoblast proliferation and myogenic differentiation, whereas METTL3 overexpression promoted these processes. Mechanically, METTL3 overexpression increased the ratio of mRNA m6A/A and shortened the time of P21 and P27 mRNA half level, causing the mRNAs downregulation via reducing their stability. Meanwhile, the promotion of cell proliferation by METTL3 overexpression was attenuated by YTH N6-methyladenosine RNA binding protein 2 (YTHDF2) knockdown. Furthermore, the promotion of myogenic differentiation by METTL3 overexpression was weakened by YTHDF1 knockdown through reducing the mRNA translation of MRFs including MyHC, MyoD and MyoG. Therefore, METTL3 facilitates myoblast proliferation and myogenic differentiation. Overall, these findings suggest that METTL3/m6A RNA methylation/YTHDF1/2 signaling axis is a novel strategy for the regulation of skeletal muscle development.

[The effect of fat mass and obesity associated proteins mediated mRNA m6A modification on animal fat deposition and its application prospects].

In the process of animal fat deposition, the proliferation and differentiation of pre-adipocytes and the change of lipid droplet content in adipocytes are regulated by a series of transcription factors and signal pathways. Although researchers have conducted in-depth studies on the transcriptional regulation mechanisms of adipogenesis, there are relatively few reports on post-transcriptional modification on mRNA levels. The modification of mRNA m6A regulated by methyltransferase, demethylase and methylation reading protein is a dynamic and reversible process, which is closely related to fat deposition in animals. Fat mass and obesity associated proteins (FTO) act as RNA demethylases that affect the expression of modified genes and play a key role in fat deposition. This article summarized the mechanism of FTO-mediated demethylation of mRNA m6A in the process of animal fat deposition, suggesting that FTO may become a target for effective treatment of obesity. Moreover, this review summarized the development of FTO inhibitors in recent years.