Effect of porcine glucagon-like peptides-2 on tight junction in GLP-2R + IPEC-J2 cell through the PI3 k/Akt/mTOR/p70S6K signalling pathway.

Because of rare glucagon-like peptide-2 (GLP-2) receptor (+) cells within the gut mucosa, the molecular mechanisms transducing the diverse actions of GLP-2 remain largely obscure. This research identified the naturally occurring intestinal cell lines that endogenously express GLP-2R and determined the molecular mechanisms of the protective effects of GLP-2-mediated tight junctions (TJ) in GLP-2R (+) cell line. (i) Immunohistochemistry results showed that GLP-2R is localised to the epithelia, laminae propriae and muscle layers of the small and large bowels of newborn piglets. (ii) GLP-2R expression was apparent in the cytoplasm of endocrine cells in IPEC-J2 cell lines. (iii) The protein expressions of ZO-1, claudin-1, occludin, p-PI3 K, p-Akt, p-mTOR and p-p70S6K significantly (p < 0.05) increased in GLP-2-treated IPEC-J2 cells, and all of them significantly (p < 0.05) decreased when LY-294002 or rapamycin was added. GLP-2 improves intestinal TJ expression of GLP-2R (+) cells through the PI3 k/Akt/mTOR/p70S6K signalling pathway.

Association Analysis of Myosin Heavy-chain Genes mRNA Transcription with the Corresponding Proteins Expression of Longissimus Muscle in Growing Pigs.

The goal of this work was to investigate the correlations between MyHC mRNA transcription and their corresponding protein expressions in porcine longissimus muscle (LM) during postnatal growth of pigs. Five DLY (Duroc×Landrace×Yorkshire) crossbred pigs were selected, slaughtered and sampled at postnatal 7, 30, 60, 120, and 180 days, respectively. Each muscle was subjected to quantity MyHCs protein contents through an indirect enzyme-linked immunosorbent assay (ELISA), to quantity myosin heavy-chains (MyHCs) mRNA abundances using real-time polymerase chain reaction. We calculated the proportion (%) of each MyHC to total of four MyHC for two levels, respectively. Moreover, the activities of several key energy metabolism enzymes were determined in LM. The result showed that mRNA transcription and protein expression of MyHC I, IIa, IIx and IIb in LM all presented some obvious changes with postnatal aging of pigs, especially at the early stage after birth, and their mRNA transcriptions were easy to be influenced than their protein expressions. The relative proportion of each MyHC mRNA was significantly positively related to that of its corresponding protein (p<0.01), and MyHC I mRNA proportion was positively correlated with creatine kinase (CK), succinate dehydrogenase (SDH), malate dehydrogenase (MDH) activities (p<0.05). These data suggested that MyHC mRNA transcription can be used to reflect MyHC expression, metabolism property and adaptive plasticity of porcine skeletal muscles, and MyHC mRNA composition could be a molecular index reflecting muscle fiber type characteristics.

Effect of dietary omega6/omega3 on growth performance, carcass traits, meat quality and fatty acid profiles of Beijing-you chicken.

The effects of varying the omega6 to omega3 fatty acid ratio (omega6/omega3) of diets on growth performance, carcass traits, meat quality and fatty acid composition of breast muscle were investigated in Beijing-you chickens grown to 92 days. A total of 360 one-day-old female BJY chickens were fed diets containing 0%, 0.12%, 0.42%, 1.00% or 1.97% linseed oil replacing equal weights of maize oil to make dietary omega6/omega3 to be approximately 30:1, 20:1, 10:1, 5:1 and 2.5:1. Subcutaneous fat thickness and intramuscular fat content increased significantly in birds fed up to 10:1 omega6/omega3. a* values (redness of meat, dimension of the CIELAB-system) progressively increased as the diets contained increasing omega3 content, up to the 10:1 omega6/omega3.The changes in b* (yellowness of meat, dimensions of the CIELAB-system) were also significant but the pattern was almost the reverse of changes in a*. Shear force increased significantly as dietary omega6/omega3 was reduced from 30:1 to 5:1. Decreasing the dietary omega6/omega3 clearly decreased the content in breast muscle of C20:1 and C22:1, but increased that of C24:1. C20:4, C20:5 and C22:5, increased significantly by decreasing the dietary omega6/omega3, and the birds fed the 10:1 diet had higher contents of C22:6 than other treatments. This study has clearly demonstrated that decreasing the dietary omega6/omega3, increases the deposition of desirable omega3 and omega6 long chain PUFA in the edible tissue, thereby achieving nutritionally enriched meat.

Porcine glucagon-like peptide-2 microspheres ameliorate inflammation in lipopolysaccharide-challenged weaning piglets.

This study aimed to investigate the effects of porcine [gly2] glucagon-like peptide-2 (p[gly2]GLP-2) microspheres on lipopolysaccharide-challenged piglets and to evaluate efficacy of microspheres for administration compared with more conventional administration. Eighteen 21-d-old Duroc female piglets were randomly assigned into 3 groups: the control group (intraperitoneal injection with 3 mL saline solution daily), the glucagon-like peptide-2 (GLP-2) group (intraperitoneal injection with 3 mL p[gly2]GLP-2 at 20 nmol/kg BW daily), and the microsphere (MS) group (intraperitoneal injection with 100 mg p[gly2]GLP-2 microsphere suspension at Day 1). On Day 8, all piglets were injected with 100 µg lipopolysaccharide/kg BW. Results showed that administration of p[gly2]GLP-2 microspheres decreased the -lactic acid and methane dicarboxylic aldehyde content of the serum and increased the villus height and villus crypt ratio in the duodenum and ileum. Inducible nitric oxide synthase activity in the duodenum and ileum decreased, whereas enzyme activity for sucrose and Na-K adenosine triphosphatase in the ileum increased with treatment of p[gly2]GLP-2 microspheres. In the MS group, we observed downregulation of IL-8, TNF-α, IFN-γ, and GLP-2R mRNA expression in the ileum, upregulation of positive cell expression in the duodenum and positive cell expression in the ileum, and downregulation of GLP-2 receptor positive cell expression in the ileum. One injection of p[gly2]GLP-2 microspheres was as effective as p[gly2]GLP-2 administered for 7 d. Results suggested that p[gly2]GLP-2 can be a candidate agent for ameliorating weaning stress in piglets and that the use of microspheres is an ideal delivery system for GLP-2.

PEGylated porcine glucagon-like peptide-2 improved the intestinal digestive function and prevented inflammation of weaning piglets challenged with LPS.

This study was conducted to determine the effects on intestinal function, anti-inflammatory role and possible mechanism of polyethylene glycosylated (PEGylated) porcine glucagon-like peptide-2 (pGLP-2), a long-acting form of pGLP-2, in weaning piglets challenged with Escherichia coli lipopolysaccharide (LPS). We divided 18 weaned piglets on day 21 into three groups (control, LPS and LPS+PEG-pGLP-2; n=6). The piglets from the LPS+PEG-pGLP-2 group were injected with PEG-pGLP-2 at 10 nmol/kg BW from 5 to 7 days of the trials daily. On 8th day, the piglets in the LPS and LPS+PEG-pGLP-2 groups were intraperitoneally administered with 100 µg LPS/kg. The control group was administered with the same volume of saline solution. The piglets were then sacrificed on day 28. Afterwards, serum, duodenum, jejunum and ileum samples were collected for analysis of structural and functional endpoints. LPS+PEG-pGLP-2 treatment increased (P<0.05) lactase activities in the duodenum and the jejunum compared with LPS treatment. LPS+PEG-pGLP-2 treatment also significantly increased sucrase activity in the jejunum compared with LPS treatment. Furthermore, LPS treatment increased (P<0.05) the mRNA expression levels of interleukin (IL)-8, tumour necrosis factor-α (TNF-α) and IL-10 in the ileum compared with the control treatment. By contrast, LPS+PEG-pGLP-2 treatment decreased (P<0.05) the mRNA expression levels of IL-8, IL-10 and TNF-α in the ileum compared with the LPS treatment. LPS treatment also increased (P<0.05) the mRNA expression level of GLP-2 receptor (GLP-2R) and the percentage of GLP-2R-positive cells in the ileum; by comparison, these results were (P<0.05) reduced by LPS+PEG-pGLP-2 treatment. Moreover, LPS+PEG-pGLP-2 treatment increased (P<0.05) the content of serum keratinocyte growth factor compared with the control group and the LPS group. The protective effects of PEG-pGLP-2 on intestinal digestive function were associated with the release of GLP-2R mediator (keratinocyte growth factor) and the decrease in the expressions of intestinal pro-inflammatory cytokines.

Age-related changes and nutritional regulation of myosin heavy-chain composition in longissimus dorsi of commercial pigs.

The objective of this study is to investigate the age-related changes of and the effects of dietary conjugated linoleic acid (CLA) on muscle-fibre types in commercial pigs. We divided 25 crossbred male pigs into five age groups (7, 30, 60, 100 and 180 days) and 30 finishing pigs into two dietary groups (one fed a CLA-enriched diet and the other fed a control diet for 30 days). We analysed the composition (%) of myosin heavy-chain (MyHC) mRNA according to the absolute copies of each MyHC (I, IIa, IIb and IIx) mRNA, and the activities of succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) in the longissimus muscle. From days 7 to 180, the MyHC I mRNA abundance and SDH and MDH activities presented a decreasing trend, the MyHC IIb mRNA abundance presented a steady trend and the MyHC IIa and IIx mRNA abundances presented an increasing trend. On day 30, MyHC I and IIb mRNA abundances were at their lowest (P < 0.05), and the MyHC IIa and IIx mRNA abundances were at their highest (P < 0.05). In the CLA group, the MyHC I mRNA abundance and the activities of SDH and MDH were improved in the longissimus muscle, whereas pressure loss, drip loss and average back fat depth significantly decreased (P < 0.01) and shear force significantly increased (P < 0.01). Loin eye area, feed conversion rate and meat colour showed some tendency to be improved. These results indicated that more oxidative fibres might convert to glycolytic fibres with increasing age or weight, and that the early developmental stage might be a key stage for this conversion. During the finishing stage, the proportion of oxidative fibres might be increased by dietary CLA supplementation, which may contribute to the water-holding capacity of meat. The results would provide an important basis for the application of muscle-fibre types in the improvement of pork quality.