Daiwen Chen

Oxidative stress-induced diseases and tea polyphenols

Reactive oxide species are the middle products of normal metabolism, and play a crucial role in cell signaling transduction. On the contrary, accumulation of excess reactive oxide species results in oxidative stress that often brings multifarious impairment to cells, including decrease of ATP level in cells, elevation of cytosolic Ca2+, DNA damage, dysfunction of biological function in lipid bilayer and so on. These effects will finally lead to all kinds of diseases. Tea polyphenols are widely considered as a kind of excellent antioxidant agents. It can be antioxidants by directly scavenging reactive oxide species or chelating transition metals, and indirectly upregulating the activity of antioxidant enzymes. In addition, tea polyphenols have also been observed a potent pro-oxidant capacity, which directly leads to the generation of reactive oxide species, and indirectly induces apoptosis and death of cancer cells. The underlying characters of its pro-oxidant activity in some diseases is not well understood. The present review we will discuss the dual character of tea polyphenols, both antioxidant and pro-oxidant properties, in some human diseases induced by oxidative stress.

FoxO1: a novel insight into its molecular mechanisms in the regulation of skeletal muscle differentiation and fiber type specification

FoxO1, a member of the forkhead transcription factor forkhead box protein O (FoxO) family, is predominantly expressed in most muscle types. FoxO1 is a key regulator of muscle growth, metabolism, cell proliferation and differentiation. In the past two decades, many researches have indicated that FoxO1 is a negative regulator of skeletal muscle differentiation while contrasting opinions consider that FoxO1 is crucial for myoblast fusion. FoxO1 is expressed much higher in fast twitch fiber enriched muscles than in slow muscles and is also closely related to muscle fiber type specification. In this review, we summarize the molecular mechanisms of FoxO1 in the regulation of skeletal muscle differentiation and fiber type specification.

Tissue Deposition and Residue Depletion in Broiler Exposed to Melamine-Contaminated Diets

Abstract To investigate the tissue deposition and elimination of melamine (MEL) in broilers, a total of 1 920 commercial 1-d-old male Cobb broilers were randomly allotted to 6 treatments with diets contaminated by MEL at 0, 2, 10, 30, 50, 100 mg kg-1 of diet for 42 d, and followed MEL withdrawal from diet at 50 or 100 mg kg-1 of diet for 96 h. The MEL was found in residue of plasma, liver, kidney, breast, and leg muscle with the highest level in kidney and in dose response manner (except in kidney), but no time response (except in plasma). The MEL residue in organ tissue was below the safe level of 50 ?g mL-1 in blood or 50 ?g kg-1 in tissues proposed by the US FSIS when MEL in diet was lower (2 mg kg-1). The MEL in tissues was eliminated by withdrawal MEL from diets. The elimination half-life of MEL was from 3.2 to 6.6 h, and the clearance time, when MEL residue concentration under limit detection, was from 18.0 to 31.4 h.

Dietary apple pectic oligosaccharide improves gut barrier function of rotavirus-challenged weaned pigs by increasing antioxidant capacity of enterocytes

Rotavirus can lead to decreasing gut barrier function and diarrhea of children and young animals. Apple pectic oligosaccharide treatment reduced diarrhea in rotavirus-infected piglets. This study was conducted to explore whether apple pectic oligosaccharide administration could protect gut barrier function of piglets against rotavirus infection. A total of 28 crossbred weaned barrows were allotted into 2 treatments fed the diets supplementing 0 and 200 mg/kg apple pectic oligosaccharide. Half of pigs in each diet treatment were challenged by rotavirus on d 15. The whole duration of this experiment is 18 days. Rotavirus challenge increased average diarrhea index, and impaired microbiota in cecal digesta, and histology, expressions of tight-junction proteins, mucins and glucagon like peptide-2 concentrations, antioxidant capacity, endoplasmic reticulum stress, autophagy and apoptosis in jejunal mucosa of piglets. However, dietary apple pectic oligosaccharide supplementation relieved effects of rotavirus challenge on diarrhea, gut health, and antioxidant capacity, endoplasmic reticulum stress, autophagy and apoptosis of jejunal mucosa in piglets. These results suggest that apple pectic oligosaccharide administration can prevent diarrhea and damage of gut barrier function via improving antioxidant capacity that might reduce endoplasmic reticulum stress, autophagy and apoptosis of intestinal epithelial cells in rotavirus-infected piglets.

Different Types of Dietary Fibers Trigger Specific Alterations in Composition and Predicted Functions of Colonic Bacterial Communities in BALB/c Mice

Soluble dietary fibers (SDF) are fermented more than insoluble dietary fibers (IDF), but their effect on colonic bacterial community structure and function remains unclear. Thus, bacterial community composition and function in the colon of BALB/c mice (n = 7) fed with a high level (approximately 20%) of typical SDF, oat-derived β-glucan (G), microcrystalline cellulose (M) as IDF, or their mixture (GM), were compared. Mice in group G showed a lowest average feed intake (p < 0.05) but no change on the average body weight gain (p > 0.05) compared to other groups, which may be associated with the highest concentration of colonic propionate (p < 0.05) in these mice. The bacterial α-diversity of group G was significantly lower than other groups (p < 0.01). In group G, the relative abundance of bacteria belonging to the phylum Bacteroidetes was significantly increased, whereas bacteria from the phylum Firmicutes were significantly decreased (p < 0.01). The core bacteria for different treatments showed distinct differences. Bacteroides, Dehalobacterium, and Prevotella, including known acetogens and carbohydrate fermenting organisms, were significantly increased in relative abundance in group G. In contrast, Adlercreutzia, Odoribacter, and Coprococcus were significantly more abundant in group M, whereas Oscillospira, Desulfovibrio, and Ruminoccaceae, typical hydrogenotrophs equipped with multiple carbohydrate active enzymes, were remarkably enriched in group GM (p < 0.05). The relative abundance of bacteria from the three classes of Proteobacteria, Betaproteobacteria, Gammaproteobacteria (including Enterobacteriaceae) and Deltaproteobacteria, were significantly more abundant in group G, indicating a higher ratio of conditional pathogenic bacteria in mice fed dietary β-glucan in current study. The predicted colonic microbial function showed an enrichment of “Energy metabolism” and “Carbohydrate metabolism” pathways in mice from group G and M, suggesting that the altered bacterial community in the colon of mice with the two dietary fibers probably resulted in a more efficient degradation of dietary polysaccharides. Our result suggests that the influence of dietary β-glucan (SDF) on colonic bacterial community of mice was more extensively than MCC (IDF). Co-supplementation of the two fibers may help to increase the bacterial diversity and reduce the conditional pathogens in the colon of mice.

Fungi in Gastrointestinal Tracts of Human and Mice: from Community to Functions

Fungi are often ignored in studies on gut microbes because of their low level of presence (making up only 0.1% of the total microorganisms) in the gastrointestinal tract (GIT) of monogastric animals. Recent studies using novel technologies such as next generation sequencing have expanded our understanding on the importance of intestinal fungi in humans and animals. Here, we provide a comprehensive review on the fungal community, the so-called mycobiome, and their functions from recent studies in humans and mice. In the GIT of humans, fungi belonging to the phyla Ascomycota, Basidiomycota and Chytridiomycota are predominant. The murine intestines harbor a more diverse assemblage of fungi. Diet is one of the major factors influencing colonization of fungi in the GIT. Presence of the genus Candida is positively associated with dietary carbohydrates, but are negatively correlated with dietary amino acids, proteins, and fatty acids. However, the relationship between diet and the fungal community (and functions), as well as the underlying mechanisms remains unclear. Dysbiosis of intestinal fungi can cause invasive infections and inflammatory bowel diseases (IBD). However, it is not clear whether dysbiosis of the mycobiome is a cause, or a result of IBD. Compared to non-inflamed intestinal mucosa, the abundance and diversity of fungi is significantly increased in the inflamed mucosa. The commonly observed commensal fungal species Candida albicans might contribute to occurrence and development of IBD. Limited studies show that Candida albicans might interact with immune cells of the host intestines through the pathways associated with Dectin-1, Toll-like receptor 2 (TLR2), and TLR4. This review is expected to provide new thoughts for future studies on intestinal fungi and for new therapies to fungal infections in the GIT of human and animals.

Effects of MicroRNA-27a on Myogenin Expression and Akt/FoxO1 Signal Pathway during Porcine Myoblast Differentiation

ABSTRACT Skeletal myoblast differentiation is controlled by a multitude of transcription factors and signal pathways. Myogenin is a critical transcriptional regulator in the initiation and maintenance of myoblast differentiation. The Akt/FoxO1 signal pathway plays an important role in myoblast differentiation. MicroRNAs are a kind of small noncoding RNAs that have been regarded as important regulators in skeletal muscle cell proliferation and differentiation. The objective of this study was to investigate the effects of microRNA-27a (miR-27a) on myogenin expression and Akt/FoxO1 signal pathway during porcine myoblast differentiation. Here, we found that the expression of miR-27a was gradually diminished at the early differentiation stage and then rebounded. Overexpression of miR-27a suppressed the mRNA and protein expression levels of myogenin during porcine myoblast differentiation, whereas inhibition of miR-27a promoted the mRNA and protein expression levels of myogenin. In addition, overexpression of miR-27a decreased the level of P-Akt/Akt and increased the protein level of FoxO1; however, inhibition of miR-27a increased the level of P-Akt/Akt and decreased the protein level of FoxO1. The present study demonstrated that miR-27a could inhibit myogenin expression and Akt/FoxO1 signal pathway during porcine myoblast differentiation.

Dietary pea fiber increases diversity of colonic methanogens of pigs with a shift from Methanobrevibacter to Methanomassiliicoccus-like genus and change in numbers of three hydrogenotrophs

BackgroundPea fiber (PF) is a potential fibrous supplement in swine production. The influence of dietary PF on microbial community in the colon of pigs remains largely unexplored. Methanogens in the hindgut of monogastric animals play important roles in degradation of dietary fibers and efficient removal of microbial metabolic end product H2. Understanding the impact of dietary PF on the structure of colonic methanogens may help understand the mechanisms of microbe-mediated physiological functions of PF. This study investigated the influence of PF on the diversity and quantity and/or activity of colonic methanongens of piglets and finishing pigs. Four archaeal 16S rRNA clone libraries were constructed for piglets and finishers fed with control (Piglet-C and Finisher-C) or PF diet (Piglet-P and Finisher-P).ResultsThere were 195, 190, 194 and 196 clones obtained from the library Piglet-C, Piglet-P, Finisher-C and Finisher-P, respectively, with corresponding 12, 11, 11 and 16 OTUs (operational taxonomic units). Significant differences of Shannon Index among the four libraries were found (Pu2009<u20090.05). Libshuff analysis showed that the archaeal community structure among the four libraries were significantly different (Pu2009<u20090.0001). The predominant methanogens shifted from Methanobrevibacter to Methanobrevibacter and Methanomassiliicoccus-like genus as a result of dietary PF. Supplementation of PF significantly increased the copy numbers of mcrA and dsrA genes (Pu2009<u20090.05).ConclusionsAlteration of methanogenic community structure may lead to functional transition from utilization of H2/CO2 to employment of both H2/CO2 and methanol/CO2. Quantification of three functional genes (mcrA, dsrA and fhs) of methanogens, sulfate-reducing bacteria (SRB) and acetogens revealed that dietary PF also increased the activity of methanogens and SRB,probably associated with increased proportion of Methanomassiliicoccus luminyensis-species. Further study is required to examine the interaction between specific methanogens and SRB during fermentation of dietary PF.

MicroRNA-139-5p suppresses myosin heavy chain I and IIa expression via inhibition of the calcineurin/NFAT signaling pathway

MicroRNAs (miRNAs) are a class of small non-coding RNAs that are widely involved in a variety of biological processes. Different skeletal muscle fiber type composition exhibits characteristic differences in functional properties and energy metabolism of skeletal muscle. However, the molecular mechanism by which miRNAs control the different type of muscle fiber formation is still not fully understood. In the present study, we characterized the role of microRNA-139-5p (miR-139-5p) in the regulation of myosin heavy chain (MyHC) isoform expression and its underlying mechanisms. Here we found that the expression of miR-139-5p was significantly higher in mouse slow-twitch muscle than in fast-twitch muscle. Overexpression of miR-139-5p downregulated the expression of MyHC I and MyHC IIa, whereas inhibition of miR-139-5p upregulated them. We also found that the levels of calcineurin (CaN), NFATc1, MEF2C and MCIP1.4, which are the components of CaN/NFAT signaling pathway that has shown to positively regulate slow fiber-selective gene expression, were notably inhibited by miR-139-5p overexpression. Furthermore, treatment of phenylephrine (PE), a α1-adrenoceptor agonist, abolished the inhibitory effect of miR-139-5p on MyHC I and MyHC IIa expression. Together, our findings indicated that the role of miR-139-5p in regulating the MyHC isoforms, especially MyHC I and MyHC IIa, may be achieved through inhibiting CaN/NFAT signaling pathway.

Effects of active immunization against porcine Sox6 on meat quality and myosin heavy chain isoform expression in growing-finishing pigs

Abstract A feeding trial for 91 days was conducted to investigate effects of active immunization against porcine Sox6 (pSox6) on meat quality and myosin heavy chain (MyHC) isoform expression in growing-finishing pigs. Twenty-four castrated Durocu2009×u2009Landraceu2009×u2009Yarkshire pigs were randomly divided into three groups: (1) Control group; (2) 1u2009mg/head pSox6 active immunity group; (3) 4u2009mg/head pSox6 active immunity group (4u2009mg/head group). The results showed that pigs in 4u2009mg/head group had a greater a* (Redness) and a higher marbling score, while no significant effect was observed in L* (Lightness), b* (Yellowness), intramuscular fat and cooking loss. Muscle succinic dehydrogenase activity in pSox6 active immunization groups was significantly increased, and muscle lactate dehydrogenase activity was significantly reduced. Meanwhile, active immunization against pSox6 upregulated the mRNA expression of MyHC I, while no effect was observed on the mRNA expressions of MyHC IIa, MyHC IIx, MyHC IIb. In addition, pigs in the 4u2009mg/head group exhibited lower Sox6 mRNA level and higher MyHC I protein level, while no significant influence was observed on MyHC IIb protein level. Together, our data imply that active immunization against pSox6 could improve the pork quality and promote the MyHC I expression in growing-finishing pigs.