Understanding the dynamics of muscle transcriptome during development and between breeds differing in muscle growth is necessary to uncover the complex mechanism underlying muscle development. Herein, we present the first transcriptome-wide longissimus dorsi muscle development research concerning Lantang (LT, obese) and Landrace (LR, lean) pig breeds during 10 time-points from 35 days-post-coitus (dpc) to 180 days-post-natum (dpn) using Solexa/Illumina's Genome Analyzer. The data demonstrated that myogenesis was almost completed before 77 dpc, but the muscle phenotypes were still changed from 77 dpc to 28 dpn. Comparative analysis of the two breeds suggested that myogenesis started earlier but progressed more slowly in LT than in LR, the stages ranging from 49 dpc to 77 dpc are critical for formation of different muscle phenotypes. 595 differentially expressed myogenesis genes were identified, and their roles in myogenesis were discussed. Furthermore, GSK3B, IKBKB, ACVR1, ITGA and STMN1 might contribute to later myogenesis and more muscle fibers in LR than LT. Some myogenesis inhibitors (ID1, ID2, CABIN1, MSTN, SMAD4, CTNNA1, NOTCH2, GPC3 and HMOX1) were higher expressed in LT than in LR, which might contribute to more slow muscle differentiation in LT than in LR. We also identified several genes which might contribute to intramuscular adipose differentiation. Most important, we further proposed a novel model in which MyoD and MEF2A controls the balance between intramuscular adipogenesis and myogenesis by regulating CEBP family; Myf5 and MEF2C are essential during the whole myogenesis process while MEF2D affects muscle growth and maturation. The MRFs and MEF2 families are also critical for the phenotypic differences between the two pig breeds. Overall, this study contributes to elucidating the mechanism underlying muscle development, which could provide valuable information for pig meat quality improvement. The raw data have been submitted to Gene Expression Omnibus (GEO) under series GSE25406.

Summary: The innate immune response provides the initial defence mechanism against infection by other organisms. However, an excessive immune response will cause damage to host tissues. In an attempt to identify microRNAs (miRNAs) that regulate the innate immune response in inflammation and homeostasis, we examined the differential expression of miRNAs using microarray analysis in the spleens of mice injected intraperitoneally with lipopolysaccharide (LPS) and saline, respectively. Following challenge, we observed 19 miRNAs up‐regulated (1·5‐fold) in response to LPS. Among these miRNAs, miR‐1224, whose expression level increased 5·7‐fold 6 hr after LPS injection and 2·3‐fold after 24 hr, was selected for further study. Tissue expression patterns showed that mouse miR‐1224 is highly expressed in mouse spleen, kidney and lung. Transfection of miR‐1224 mimics resulted in a decrease in basal tumour necrosis factor‐α (TNF‐α) promoter reporter gene activity and a down‐regulation of LPS‐induced TNF‐α mRNA in RAW264.7 cells. With public databases of miRNA target prediction, miR‐1224 was shown to bind to the 3′ untranslated region (UTR) of Sp1 mRNA, whose coding product controls TNF‐α expression at the transcriptional level. Furthermore, we found that in HEK‐293 cells, the activity of the luciferase reporter bearing Sp1 mRNA 3′ UTR was down‐regulated significantly when transfected with miR‐1224 mimics. After transfection of miR‐1224 in RAW264.7 cells, nucleus Sp1 protein level decreased, and when endogenous miR‐1224 was blocked, the decrease was abolished. Therefore, we initially speculated that miR‐1224 was a negative regulator of TNF‐α in an Sp1‐dependent manner, which was confirmed in vivo by chromatin immunoprecipitation assay, and might be involved in regulating the LPS‐mediated inflammatory responses.

Patients with metabolic syndrome have a higher risk of type II diabetes and cardiovascular disease. The metabolic syndrome has become an urgent public health problem. Insulin resistance is the common pathophysiological basis of metabolic syndrome. The higher incidence of insulin resistance in obese groups is due to increased levels of inflammatory factors during obesity. Therefore, developing a therapeutic strategy for insulin resistance has great significance for the treatment of the metabolic syndrome. Dihydromyricetin, as a bioactive polyphenol, has been used for anti‐inflammatory, antitumor, and improving insulin sensitivity. However, the target of DHM and molecular mechanism of DHM for preventing inflammation‐induced insulin resistance is still unclear. In this study, we first confirmed the role of dihydromyricetin in inflammation‐induced insulin resistance in vivo and in vitro. Then, we demonstrated that dihydromyricetin resisted inflammation‐induced insulin resistance by activating Ca²⁺‐CaMKK‐AMPK using signal pathway blockers, Ca²⁺ probes, and immunofluorescence. Finally, we clarified that dihydromyricetin activated Ca²⁺‐CaMKK‐AMPK signaling pathway by interacting with the phospholipase C (PLC), its target protein, using drug affinity responsive target stability (DARTS) assay. Our results not only demonstrated that dihydromyricetin resisted inflammation‐induced insulin resistance via the PLC‐CaMKK‐AMPK signal pathway but also discovered that the target protein of dihydromyricetin is the PLC. Our results provided experimental data for the development of dihydromyricetin as a functional food and new therapeutic strategies for treating or preventing PLC.

The process of transgenesis involves the introduction of a foreign gene, the transgene, into the genome of an animal. Gene transfer by pronuclear mic