Chitosan and its derivatives such as low molecular weight chitosans (LMWCs) have been reported to exert many biological activities, such as antioxidant and antitumor effects. However, complex and molecular weight dependent effects of chitosan remain controversial and the mechanisms that mediate these complex effects are still poorly defined. This study was carried out to investigate the immunostimulative effect of different molecular weight chitosan in RAW264.7 macrophages. Our data suggested that two LMWCs (molecular weight of 3 kDa and 50 kDa) both possessed immunostimulative activity, which was dependent on dose and, at the higher doses, also on the molecular weight. LMWCs could significantly enhance the the pinocytic activity, and induce the production of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), interferon-γ (IFN-γ), nitric oxide (NO) and inducible nitric oxide synthase (iNOS) in a molecular weight and concentration-dependent manner. LMWCs were further showed to promote the expression of the genes including iNOS, TNF-α. Taken together, our findings suggested that LMWCs elicited significantly immunomodulatory response through up-regulating mRNA expression of proinflammatory cytokines and activated RAW264.7 macrophage in a molecular weight- and concentration-dependent manner.

This study was conducted to investigate the effect and underlying mechanism of Resveratrol (RES) in regulating skeletal muscle fiber-type switching. We found that RES had no effect on the body weight and food intake of Kunming mice (KM mice) that were orally administered with 400 mg kg⁻¹ d⁻¹ RES for 12 weeks. Notably, the RES administration significantly increased the expression of myosin heavy chain (MyHC) 1, MyHC2a, and MyHC2x in the extensor digitorum longus (EDL) and soleus (SOL) muscles. Furthermore, the muscle immunostaining of the results showed that the RES treatment led to the myofiber type transition from glycolytic to oxidative in muscles. The mRNA and protein levels of the adiponectin receptor (AdipoR), AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) in EDL and SOL were drastically increased after RES treatment. Moreover, the plasma Adiponectin (AdipoQ) protein levels were higher in the RES-treated mice compared to the control mice. Moreover, the in vitro results further demonstrated that the 20 μM RES treatment increased the expression of AdipoR1, AdipoR2, AMPK, PGC-1α and MyHC1, but decreased the expression of MyHC2b in C2C12 myoblasts. Furthermore, mechanistic studies revealed that silencing the AdiopR1, not the AdiopR2, abolished the effect of RES on the expression of AMPK and PGC-1α in the C2C12 cells. These results indicated that RES could regulate skeletal fiber switching through the AdiopR1-AMPK-PGC-1α pathway. This work may provide a new strategy for enhancing endurance and relieving muscle diseases caused by oxidative muscle fiber deficiency.

Research has shown that dendrobium officinale polysaccharide (DOP) can promote follicular development and inhibit the apoptosis of ovarian granular cells in PCOS rats. However, DOP cannot be absorbed directly by the stomach and small intestine but is degraded into short-chain fatty acids by gut microbiota in the large intestine and regulates the composition of gut microbiota. How DOP improved ovarian function in PCOS rats through the blood–brain barrier is unclear. In this study, we generated letrozole-induced PCOS rat models and studied the therapeutic effect and mechanism of DOP. 16S rRNA amplicon sequencing analysis, GC-MS short-chain fatty acid detection, and Gene Expression Omnibus database searching were conducted to screen the significantly changed pathways, and a series of experiments, such as enzyme-linked immunosorbent assay, RT-qPCR, Western blot, and immunohistochemistry, were performed. We found that DOP treatment could improve ovarian morphology and endocrine disorders, restore the normal estrus cycle, increase gut microbiota α diversity, and alter β diversity and enrichment of butyrate-producing bacterium in PCOS rats. In addition, compared with PCOS rats, those treated with DOP exhibited higher butyrate and polypeptide YY levels, possibly due to the regulation of G protein-coupled receptor 41 expression. These results indicated that DOP relieved the symptoms of PCOS rats which may be related to the mechanism of butyrate dependent gut–brain–ovary axis protection.

This study investigated the effects of resveratrol (RES) supplementation on the growth performance, carcass and meat quality, blood lipid levels and ruminal bacterial microbiota of fattening goats. A total of forty castrated Nubian goats (28.25 ± 0.26 kg body weight) were randomly divided into four groups and provided with diets containing different levels of RES (0, 150, 300 and 600 mg/kg) for 120 d. The results showed that RES increased redness and intramuscular fat content, whilst reducing shear force in the longissimus dorsi muscle of goats (p < 0.05). In addition, the final weight, average daily gain, hot carcass weight, net meat weight, carcass lean percentage and eye muscle area of goats were significantly increased in the 150 mg/kg RES group compared with the other three groups, while those in the 600 mg/kg RES group significantly decreased (p < 0.05). RES significantly decreased serum triacylglycerol and LDL-C contents (p < 0.05), and increased HDL-C content and the HDL-C/TC ratio (p < 0.05). Supplementation with 150 mg/kg RES also increased the proportion of Acetitomaculum and Moryella, genera comprising short-chain fatty acid-producing bacteria. The present study indicated that an appropriate supplemental level of RES could improve the growth performance, neat percentage, meat quality, ruminal microbiota and serum lipid levels of fattening goats.

Heat stress (HS) results in health problems in animals. This study was conducted to investigate the effect and the underlying mechanism of HS on the proliferation and differentiation process of 3T3-L1 preadipocytes. 3T3-L1 preadipocytes were treated at 37 °C or 41.5 °C. HS up-regulated the mRNA and protein expression level of heat shock protein 70 (HSP70). Furthermore, the proliferation of 3T3-L1 preadipocytes were significantly inhibited after HS treatment for 2 days. A large number of accumulated lipid droplets were observed under the microscope after HS treatment for 8 days. Notably, the result of oil red O staining showed that the number of lipid droplets increased significantly and the differentiation ability of the cells was enhanced after HS. Moreover, after 2 and 8 d of differentiation, HS increased the transcription levels of fat synthesis genes including peroxisome proliferators activated receptor γ (PPARγ), fatty acid binding protein 2 (AP2), fatty acid synthase (FAS) and CCAAT enhancer binding protein α (CEBPα) genes, while decreasing the transcription levels of lipid decomposition genes including ATGL and HSL genes. In addition, HS reduced the expression of AMPK and PGC-1α, as well as the dephosphorylation of AMPK. 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) can eliminate HS induced lipogenesis by activating AMPK. These results indicated that HS inhibited the proliferation of 3T3-L1 preadipocytes and promoted lipid accumulation by inhibiting the AMPK-PGC-1α signaling pathway in 3T3-L1 preadipocytes. This work lays a theoretical foundation for improving the effect of HS on meat quality of livestock and provides a new direction for the prevention of obesity caused by HS.