Fugui Yin

Digestion rate of dietary starch affects systemic circulation of amino acids in weaned pigs

The present study was conducted to evaluate the in vitro and in vivo digestibility of dietary starch and its digestive behaviour on the systemic circulating amino acids (AA) in weaned pigs. Eighteen weanling pigs surgically fitted with a catheter in the jugular vein were randomly assigned to three dietary treatment groups. Sticky rice starch (SRS) was hydrolysed more quickly in vitro (P < 0.05) than maize starch (MS) and resistant starch (RS), and was almost completely hydrolysed within 4 h. The in vivo digestibility of dietary starch in different segments of the small intestine was significantly different. SRS was digested (81.9 %; P < 0.05) in the anterior jejunum, but not more than half of the MS and RS was digested in the same segment of the small intestine. The digestibilities of isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, valine, alanine, aspartate and serine in the SRS group were higher than in the MS group (P < 0.05), and all nutritionally indispensable and dispensable AA in the SRS group were higher when compared with those in the RS group (P < 0.05). The serum concentrations of nutritionally indispensable AA, proline and serine in the three groups were increased to a peak point within 1.5 h postprandially then decreased gradually; however, the time that serum concentrations of alanine, aspartate, glutamate and glycine in each group increased to a peak point was different. The concentrations of nutritionally indispensable AA, including arginine, cystine, histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, tyrosine and valine at 09.30 hours and arginine, cystine, histidine, isoleucine, methionine, phenylalanine, threonine, tryptophan, tyrosine and valine at 13.30 hours in the SRS group were higher than in the MS group (P < 0.05); all nutritionally indispensable AA in the SRS group were higher than in the RS group at 09.30 and 13.30 hours (P < 0.05), respectively. We conclude that dietary starches digested rapidly in vitro have higher digestibility in the anterior small intestine of pigs. Diets containing rapidly digestible starch ameliorate the digestive and absorptive function and regulate AA metabolism to beneficially increase the entry of dietary AA into the systemic circulation in pigs.

Transcriptome Analysis Reveals Regulation of Gene Expression for Lipid Catabolism in Young Broilers by Butyrate Glycerides

Background & Aims Butyrate has been shown to potently regulate energy expenditure and lipid metabolism in animals, yet the underlying mechanisms remain to be fully understood. The aim of this study was to investigate the molecular mechanisms of butyrate (in the form of butyrate glycerides, BG)-induced lipid metabolism at the level of gene expression in the jejunum and liver of broilers. Methodology/Principal Findings Two animal experiments were included in this study. In Experiment 1, two hundred and forty male broiler chickens were equally allocated into two groups: 1) basal diet (BD), 2) BG diets (BD + BG). Growth performance was compared between treatments for the 41-day trial. In Experiment 2, forty male broiler chickens were equally allocated into two groups. The general experimental design, group and management were the same as described in Experiment 1 except for reduced bird numbers and 21-day duration of the trial. Growth performance, abdominal fat deposition, serum lipid profiles as well as serum and tissue concentrations of key enzymes involved in lipid metabolism were compared between treatments. RNA-seq was employed to identify both differentially expressed genes (DEGs) and treatment specifically expressed genes (TSEGs). Functional clustering of DEGs and TSEGs and signaling pathways associated with lipid metabolism were identified using Ingenuity Pathways Analysis (IPA) and DAVID Bioinformatics Resources 6.7 (DAVID-BR). Quantitative PCR (qPCR) assays were subsequently conducted to further examine the expression of genes in the peroxisome proliferator-activated receptors (PPAR) signaling pathway identified by DAVID-BR. Dietary BG intervention significantly reduced abdominal fat ratio (abdominal fat weight/final body weight) in broilers. The decreased fat deposition in BG-fed chickens was in accordance with serum lipid profiles as well as the level of lipid metabolism-related enzymes in the serum, abdominal adipose, jejunum and liver. RNA-seq analysis indicated that dietary BG intervention induced 79 and 205 characterized DEGs in the jejunum and liver, respectively. In addition, 255 and 165 TSEGs were detected in the liver and jejunum of BG-fed group, while 162 and 211 TSEGs genes were observed in the liver and jejunum of BD-fed birds, respectively. Bioinformatic analysis with both IPA and DAVID-BR further revealed a significant enrichment of DEGs and TSEGs in the biological processes for reducing the synthesis, storage, transportation and secretion of lipids in the jejunum, while those in the liver were for enhancing the oxidation of ingested lipids and fatty acids. In particular, transcriptional regulators of THRSP and EGR-1 as well as several DEGs involved in the PPAR-α signaling pathway were significantly induced by dietary BG intervention for lipid catabolism. Conclusions Our results demonstrate that BG reduces body fat deposition via regulation of gene expression, which is involved in the biological events relating to the reduction of synthesis, storage, transportation and secretion, and improvement of oxidation of lipids and fatty acids.

Dietary butyrate glycerides modulate intestinal microbiota composition and serum metabolites in broilers

Butyrate can modulate the immune response and energy expenditure of animals and enhance intestinal health. The present study investigated changes in the intestinal microbiota composition and serum metabolites of young broilers in response to 3,000 ppm butyrate in the form of butyrate glycerides (BG) via pyrosequencing of bacterial 16S rRNA genes and nuclear magnetic resonance (NMR). The dietary treatment did not affect the alpha diversity of intestinal microbiota, but altered its composition. Thirty-nine key operational taxonomic units (OTUs) in differentiating cecal microbiota community structures between BG treated and untreated chickens were also identified. Bifidobacterium was, in particular, affected by the dietary treatment significantly, showing an increase in not only the abundance (approximately 3 fold, P ≤ 0.05) but also the species diversity. The (NMR)-based analysis revealed an increase in serum concentrations of alanine, low-density and very low-density lipoproteins, and lipids (P ≤ 0.05) by BG. More interestingly, the dietary treatment also boosted (P ≤ 0.05) serum concentrations of bacterial metabolites, including choline, glycerophosphorylcholine, dimethylamine, trimethylamine, trimethylamine-N-oxide, lactate, and succinate. In conclusion, the data suggest the modulation of intestinal microbiota and serum metabolites by BG dietary treatment and potential contribution of intestinal bacteria to lipid metabolism/energy homeostasis in broilers.

Synthesis and Degradation of Proteins in Pigs

Growth of animals is the complex result of competition between anabolic and catabolic process, which implies constant changes and remodeling through synthesis of new proteins and breakdown of existing proteins (Jobgen et al. 2006; Tan et al.,2009). Together, these processes are called protein turnover and produce muscle growth or hypertrophy when synthesis is greater than breakdown and muscle wasting when synthesis is less than breakdown (Norton and Layman 2006). Protein turnover requires large amounts of ATP. However, this costly metabolic cycle fulfills key obligatory functions, including protein homeostasis, cell turnover, removal of aged and damaged proteins, synthesis of new proteins like heat-shock and immunological proteins, gluconeogenesis from amino acids, wound healing, tissue repair, adaptation to nutritional and pathological alterations, and immune responses (Wu 2009). In pigs, although the protein syntheses increase in all tissues, the greatest response occurs in skeletal muscle in response to feeding stimulation. The elevated postprandial protein synthesis in skeletal muscle of pigs therefore increases the protein deposition during the post-absorptive period allowing growth and development. A sharp increase of circulating glucose, insulin, and amino acids, especially some nutritional indispensable amino acids, is observed after meal (Yin et al. 2010, 2011), in accordance with higher protein deposition in pigs (Drew et al. 2012). The mechanism responsible for the stimulation of protein synthesis by feeding was therefore focused on the roles of postprandial circulating glucose, insulin, and amino acids. The protein degradation is a process where proteins are broken into smaller peptides as well as free amino acids, the latter being either reused for new protein synthesis or further degraded into several metabolites, several of them being able to generate ATP for energy use. In addition, the protein degradation plays important roles in animal physiological process, especially in the cellular signal transduction system as well as in the maintenance of the integrity of the proper folded state of protein.

Measurement of Synthesis and Degradation of Proteins

Continuous synthesis and breakdown or remodeling of proteins (also called protein turnover) is a principal characteristic of protein metabolism. During animal production, the net differences between synthesis and breakdown represent the actual marketable muscle foods. Because protein synthesis is highly endergonic and protein breakdown is metabolically energy dependent, the efficiency of production can be markedly enhanced by lower muscle protein breakdown rates. Various methodological approaches to study protein synthesis and breakdown, with particular emphasis toward food-producing animals, are presented. These include whole-animal tracer amino acid infusion in vivo, quantifying marker amino acid release from muscle proteins, and in vitro amino acid release-based methodologies. From such methods, protein synthesis rates and protein breakdown rates (mass units/time) may be obtained (Helene et al. 2002). The paper briefly reviews the methodology developed over the past 30 years to study protein turnover.