Performance, intestinal permeability, and gene expression of selected tight junction proteins in broiler chickens fed reduced protein diets supplemented with arginine, glutamine, and glycine subjected to a leaky gut model

Changing dietary protein and amino acids may impact intestinal barrier function. Experiments were conducted in broiler chickens to evaluate supplementation of L-glutamine, glycine, and L-arginine in a reduced protein (RP) diet. Experiment 1 examined the growth performance of broilers fed 5 dietary treatments: 1) a standard diet; 2) an RP diet (193.9 g/kg CP in grower and 176.9 g/kg CP in finisher); 3) RP diet supplemented with 10 g/kg L-Gln; 4) RP diet supplemented with 10 g/kg Gly; 5) RP diet supplemented with 5 g/kg L-Arg. Each experimental diet was replicated 6 times with 10 birds per replicate. In a subset of 96 birds, experiment 2 tested the 4 RP diets with and without dexamethasone (DEX) to induce leaky gut. Each diet was replicated 24 times. Fluorescein isothiocyanate dextran (FITC-d) was used to test intestinal permeability (IP). Gene expression of selected tight junction proteins in ileal and jejunal tissues was assayed by quantitative PCR. From day 7 to 35, the RP diet increased feed intake (FI) (P < 0.05) and body weight gain (BWG) compared with the standard diet while Gln reduced FI and BWG (P < 0.05) compared with RP. Gly had no effect on BWG or FCR. Supplementation of Arg improved FCR from day 21 to 35 and day 7 to 35. In experiment 2, Arg tended to lower FITC-d (P = 0.086). DEX increased passage of FITC-d into the serum (P < 0.001). The villi surface area was increased in birds fed higher Arg (P < 0.05). DEX and diet interacted (P < 0.01) for jejunal claudin-3 mRNA level where DEX upregulated claudin-3 for all diets except the Arg diet. In summary, with a moderate reduction of protein, satisfactory performance can be obtained. Although Gln and Gly had no demonstrable positive effect on IP and performance of broilers, increasing the dietary Arg by approximately 140% improved FCR and showed indications of improved intestinal barrier function of birds fed an RP diet under a stress model.

Genotypic and nutritional regulation of gene expression in two sheep hindlimb muscles with distinct myofibre and metabolic characteristics

This study investigated whether the expression profile of GDF8 (myostatin), myogenic regulatory factors (MRFs: MYF5, MYOD1, MYOG (myogenin), and MYF6), and IGF-system (IGF1, IGF2, IGF1R) genes are correlated with anatomical muscle, nutrition level, and estimated breeding values (EBVs) for muscling, growth, and/or fatness. Real-time PCR was employed to quantitatively measure the mRNA levels of these genes in the semimembranosus (SM) and semitendinosus (ST) muscles of growing lambs. The lambs were sired by Poll Dorset rams with differing EBVs for growth, muscling, and fatness, and were fed either high or low quality and availability pasture from birth to ~8 months of age. With the exception of MYOD1, the mRNA levels of all genes examined in this study showed varying degrees of nutritional regulation. All the MRF mRNA levels were higher in the SM muscle than the ST muscle, whereas myostatin mRNA was higher in the ST muscle than the SM muscle. Interactions between muscle type and nutrition were detected for IGF2, MYF6, and myogenin, while positive correlations between IGF2 and IGF1R and between MYOD1 and myogenin mRNA levels were apparent in both muscles. At the genotypic level, subtle differences in mRNA levels suggested interactions between nutrition and sire EBV. The findings of this study confirm that the MRFs, IGFs, and myostatin genes are differentially affected by a variety of factors that include nutrition, muscle type, and sire EBVs. Together, these data suggest that this suite of genes has important roles during postnatal muscle growth, even at quite late stages of growth and development.

Analysis of the sheep trichohyalin gene: potential structural and calcium-binding roles of trichohyalin in the hair follicle

Trichohyalin is a structural protein that is produced and retained in the cells of the inner root sheath and medulla of the hair follicle. The gene for sheep trichohyalin has been purified and the complete amino acid sequence of trichohyalin determined in an attempt to increase the understanding of the structure and function of this protein in the filamentous network of the hardened inner root sheath cells. Sheep trichohyalin has a molecular weight of 201,172 and is characterized by the presence of a high proportion of glutamate, arginine, glutamine, and leucine residues, together totaling more than 75% of the amino acids. Over 65% of trichohyalin consists of two sets of tandem peptide repeats which are based on two different consensus sequences. Trichohyalin is predicted to form an elongated alpha-helical rod structure but does not contain the sequences required for the formation of intermediate filaments. The amino terminus of trichohyalin contains two EF hand calcium-binding domains indicating that trichohyalin plays more than a structural role within the hair follicle. In situ hybridization studies have shown that trichohyalin is expressed in the epithelia of the tongue, hoof, and rumen as well as in the inner root sheath and medulla of the hair follicle.