Arginine metabolism and its protective effects on intestinal health and functions in weaned piglets under oxidative stress induced by diquat

In vivo and in vitro protective effect of arginine against intestinal inflammatory response induced by Clostridium perfringens in broiler chickens

Background

Necrotic enteritis is a widespread disease in poultry caused by Clostridium perfringens. We previously reported that dietary arginine supplementation protected the intestinal mucosa of broiler chickens with necrotic enteritis, but the related protective mechanisms remain unclear. The in vivo trial was designed as a 2 × 2 factorial arrangement to evaluated the effects of arginine supplementation on inflammatory responses, arginine transporters, arginine catabolism and JAK-STAT signalling pathway in broiler chickens challenged with C. perfringens or without C. perfringens. Furthermore, we validated the in vivo results using intestinal epithelial cells of chicken embryos.

Results

C. perfringens infection markedly increased gut gross pathological and histopathological lesion scores, promoted liver C. perfringens invasion, reduced serum arginine levels, and elevated jejunal mucosal lysozyme activities (P < 0.05), but these effects were significantly reversed by arginine supplementation in vivo (P < 0.05). The challenge significantly increased serum procalcitonin levels, jejunal mucosal iNOS activities and jejunal IL-6, TGF-β3, cationic amino acid transporter (CAT)-1, and CAT-3 mRNA expression (P < 0.05), whereas arginine supplementation significantly reduced jejunal IFN-γ, IL-1β, IL-6, IL-10, TGF-β3, and CAT-3 mRNA expression (P < 0.05). Arginine supplementation significantly attenuated the C. perfringens challenge-induced increases in jejunal iNOS, arginase 2, arginine decarboxylase, arginine:glycine amidinotransferase, JAK1, JAK3, STAT1, and STAT6 mRNA expression (P < 0.05). The in vitro experiment showed that C. perfringens challenge markedly increased cellular cytotoxicity and the mRNA expression of IL-1β, IL-8, IL-10, CAT-1 and CAT-3 (P < 0.05), which were significantly reversed by 50 μmol/L and/or 400 μmol/L arginine pre-treatment (P < 0.05).

Conclusions

Arginine prevented C. perfringens challenge-induced circulated arginine deficiency, normalized intestinal arginine transport and catabolism, down-regulated JAK-STAT signalling pathway and attenuated the inflammatory response, which exerted protective effects on the intestine of broiler chickens.

Dietary Tributyrin Attenuates Intestinal Inflammation, Enhances Mitochondrial Function, and Induces Mitophagy in Piglets Challenged with Diquat

The study evaluated the effects of butyric acid, in the form of tributyrin on the oxidative stress, inflammation, and mitochondrial function in diquat-challenged pigs. Twenty-four weaned pigs were allocated to four treatments in a 2 × 2 factorial arrangement with the main effects of tributyrin supplementation and diquat challenge. The results showed that supplemental tributyrin increased ( P < 0.05) average daily gain and average daily feed intake of diquat-challenged pigs. Tributyrin elevated ( P < 0.05) the activities of total antioxidant capacity and superoxide dismutase, reduced ( P < 0.05) malondialdehyde content, and increased ( P < 0.05) mRNA levels of copper and zinc superoxide dismutase and manganese-containing superoxide dismutase of diquat-challenged pigs. Tributyrin relieved ( P < 0.05) intestinal inflammation reflected by decreased mRNA abundances of tumor necrosis factor-α, interferon-γ, and interleukin-6 in the intestine. Tributyrin reduced ( P < 0.05) serum diamine oxidase activity and d-lactate content, increased ( P < 0.05) transepithelial electrical resistance, decreased paracellular flux of dextran (4 kDa), and prevented the diquat-induced decrease ( P < 0.05) in the expressions of claudin-1, occludin, and zonula occludens-1. Tributyrin alleviated ( P < 0.05) diquat-induced mitochondrial dysfunction shown by lowered reactive oxygen species, increased mitochondrial membrane potential, and increased adenosine triphosphate content. Furthermore, tributyrin increased ( P < 0.05) expressions of mitophagy proteins (PTEN-induced putative kinase 1 and Parkin), and ratio of light chain 3-II to light chain 3-I in intestine. Collectively, tributyrin attenuated oxidative stress and intestinal inflammation, improved mitochondrial function, and induced mitophagy in diquat-challenged pigs.

Physiological Effects of Dietary Amino Acids on Gut Health and Functions of Swine

Gut health has significant implications for swine overall health status and nutrient utilization, due to its various functions including digestion and absorption of nutrients, secretion of mucins and immunoglobulins, and selective barrier protection against harmful antigens and pathogens. Both the basic anatomical structure of the gut (such as epithelial cells) and its luminal microbiota play important roles for maintaining gut health and functions. The interactions between epithelial cells and luminal microbiota have significant impact on host nutrition and health through the metabolism of dietary components. Amino acids, which are major nutrients for pigs, are not only obligatory for maintaining the intestinal mucosal mass and integrity, but also for supporting the growth of microorganisms in the gut. Dietary amino acids are the major fuel of the small intestinal mucosa. Particularly, glutamate, glutamine, and aspartate are the major oxidative fuel of the intestine. Emerging evidence shows that arginine activates the mTOR signaling pathway in the small intestine. Utilization of glycine by the small intestinal mucosa to synthesize glutathione is a very important physiological pathway, and the role of glycine as a powerful cytoprotectant has also been recognized. The major end products of methionine and cysteine metabolism are glutathione, homocysteine and taurine, which play important roles in the intestinal immune and anti-oxidative responses. Threonine is highly utilized by the gut and is particularly important for mucin synthesis and maintenance of gut barrier integrity. Moreover, either a deficiency or an excess of dietary threonine can reduce the synthesis of intestinal mucosal proteins and mucins in young pigs. Various new functions of amino acids on gut health and functions have been discovered in recent years. Thus, this review is to provide some up-to-date knowledge for industry application of dietary amino acids in order to enhance swine gut health and functions, and also it is to provide a comprehensive reference for further scientific research in this regard.

Dietary Arginine Supplementation Affects Intestinal Function by Enhancing Antioxidant Capacity of a Nitric Oxide-Independent Pathway in Low-Birth-Weight Piglets

Background

Low-birth-weight (LBW) neonates are susceptible to intestinal dysfunction. Furthermore, the antioxidant capacity of LBW neonates is significantly lower compared with that of normal-birth-weight (NBW) neonates both at birth and at weaning. In LBW neonates, dietary supplementation with arginine has shown beneficial effects on intestinal function.

Objective

The present study explored the potential mechanisms of arginine-induced protective effects against intestinal dysfunction in LBW piglets.

Methods

Forty 4-d-old LBW piglets [body weight (BW): 1.05 ± 0.04 kg] (Large White × Landrace) were assigned to 4 treatments and artificially fed a whole-milk powder- and whey protein concentrate-based diet (containing 0.65% arginine) either not supplemented with arginine (LBWC) or supplemented with 0.5%, 1.0%, or 1.5% l-arginine for 21 d. In addition, 10 NBW siblings (BW: 1.96 ± 0.03 kg) were selected and fed the basal diet. Growth performance, intestinal morphology, mRNA expression of tight junction protein, redox-sensitive genes and nitric oxide (NO) synthase, cytokines, and redox indexes were determined. Data were subjected to 1-factor ANOVA.

Results

LBW piglets exhibited poorer growth performance (29.9%), lower Claudin1 mRNA level (63.6%), lower antioxidant capacity (22.9 ∼ 24.3%), and higher jejunum interleukin 1 (IL-1) concentration (18.8%) compared with NBW piglets. Dietary supplementation with 0.5% and 1.0% l-arginine significantly enhanced daily BW gain of LBW piglets by 13.6% and 18.2%, respectively. Compared with LBWC, dietary supplementation with 1.0% l-arginine increased the serum insulin concentration (32.2%) and villus height in the jejunum (12.2%) and ileum (20.5%). In the jejunum, the mRNA levels for Claudin1 (105%) and glutathione peroxidase (36%) were higher, and the concentrations of IL-1 (31.7%) and tumor necrosis factor α (TNF-α) (30%) were lower in arginine-treated piglets than in the LBWC group. However, NO synthase activity and NO concentration in the jejunum of LBW piglets were not influenced by l-arginine supplementation.

Conclusion

The results suggested that supplementation with 1.0% l-arginine not only promoted growth performance and improved intestinal functions in LBW piglets but also improved intestinal barrier functions and enhanced antioxidant capacity by an NO-independent pathway.

Diquat-induced oxidative stress increases intestinal permeability, impairs mitochondrial function, and triggers mitophagy in piglets

In the present study, we investigated the influence of diquat-induced oxidative stress on intestinal barrier, mitochondrial function, and the level of mitophagy in piglets. Twelve male Duroc × Landrace × Yorkshire 35-d-old pigs (weaned at 21 d of age), with an average body of 9.6 kg, were allotted to two treatments of six piglets each including the challenged group and the control group. The challenged pigs were injected with 100 mg/kg bodyweight diquat and control pigs injected with 0.9% (w/v) NaCl solution. The results showed that diquat injection decreased ADFI and ADG. Diquat decreased (P < 0.05) the activities of superoxide dismutase and glutathione peroxidase and increased (P < 0.05) the malondialdehyde concentrations. The lower (P < 0.05) transepithelial electrical resistance and higher (P < 0.05) paracellular permeability of fluorescein isothiocyanatedextran 4 kDa were found in diquat challenged piglets. Meanwhile, diquat decreased (P < 0.05) the protein abundance of claudin-1, occluding, and zonula occludens-1 in jejunum compared with the control group. Diquat-induced mitochondrial dysfunction, as demonstrated by increased (P < 0.05) reactive oxygen species production and decreased (P < 0.05) membrane potential of intestinal mitochondria. Diquat-injected pigs revealed a decrease (P < 0.05) of mRNA abundance of genes related to mitochondrial biogenesis and functions, PPARg coactivator-1α, mammalian-silencing information regulator-1, nuclear respiratory factor-1, mt transcription factor A, mt single-strand DNA-binding protein, mt polymerase r, glucokinase, citrate synthase, ATP synthase, and cytochrome coxidase subunit I and V in the jejunum. Diquat induced an increase (P < 0.05) in expression of mitophagy-related proteins, phosphatase and tensin homologue deleted on chromosome 10-induced putative kinase, and Parkin in the intestinal mitochondria, as well as an enhancement of the ratio of light chain 3-II (LC3-II) to LC3-I content in the jejunal mucosa. These results suggest that oxidative stress disrupted the intestinal barrier, caused mitochondrial dysfunction, and triggered mitophagy.

The dynamics of the piglet gut microbiome during the weaning transition in association with health and nutrition

Background

Understanding the composition of the microbial community and its functional capacity during weaning is important for pig production as bacteria play important roles in the pig’s health and growth performance. However, limited information is available regarding the composition and function of the gut microbiome of piglets in early-life. Therefore, we performed 16S rRNA gene and whole metagenome shotgun sequencing of DNA from fecal samples from healthy piglets during weaning to measure microbiome shifts, and to identify the potential contribution of the early-life microbiota in shaping piglet health with a focus on microbial stress responses, carbohydrate and amino acid metabolism.

Results

The analysis of 16S rRNA genes and whole metagenome shotgun sequencing revealed significant compositional and functional differences between the fecal microbiome in nursing and weaned piglets. The fecal microbiome of the nursing piglets showed higher relative abundance of bacteria in the genus Bacteroides with abundant gene families related to the utilization of lactose and galactose. Prevotella and Lactobacillus were enriched in weaned piglets with an enrichment for the gene families associated with carbohydrate and amino acid metabolism. In addition, an analysis of the functional capacity of the fecal microbiome showed higher abundances of genes associated with heat shock and oxidative stress in the metagenome of weaned piglets compared to nursing piglets.

Conclusions

Overall, our data show that microbial shifts and changes in functional capacities of the piglet fecal microbiome resulted in potential reductions in the effects of stress, including dietary changes that occur during weaning. These results provide us with new insights into the piglet gut microbiome that contributes to the growth of the animal.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0269-6) contains supplementary material, which is available to authorized users.

l-Citrulline Supplementation: Impact on Cardiometabolic Health

Diminished bioavailability of nitric oxide (NO), the gaseous signaling molecule involved in the regulation of numerous vital biological functions, contributes to the development and progression of multiple age- and lifestyle-related diseases. While l-arginine is the precursor for the synthesis of NO by endothelial-nitric oxide synthase (eNOS), oral l-arginine supplementation is largely ineffective at increasing NO synthesis and/or bioavailability for a variety of reasons. l-citrulline, found in high concentrations in watermelon, is a neutral alpha-amino acid formed by enzymes in the mitochondria that also serves as a substrate for recycling l-arginine. Unlike l-arginine, l-citrulline is not quantitatively extracted from the gastrointestinal tract (i.e., enterocytes) or liver and its supplementation is therefore more effective at increasing l-arginine levels and NO synthesis. Supplementation with l-citrulline has shown promise as a blood pressure lowering intervention (both resting and stress-induced) in adults with pre-/hypertension, with pre-clinical (animal) evidence for atherogenic-endothelial protection. Preliminary evidence is also available for l-citrulline-induced benefits to muscle and metabolic health (via vascular and non-vascular pathways) in susceptible/older populations. In this review, we examine the impact of supplementing this important urea cycle intermediate on cardiovascular and metabolic health outcomes and identify future directions for investigating its therapeutic impact on cardiometabolic health.

Chlorogenic acid improves intestinal barrier functions by suppressing mucosa inflammation and improving antioxidant capacity in weaned pigs

Intestinal barrier plays key roles in maintaining intestinal homeostasis. Inflammation and oxidative damage can severely destroy the intestinal integrity of mammals. Chlorogenic acid (CGA) is a natural polyphenol present in human diet and plants, possessing potent antioxidant and anti-inflammatory activities. This study was conducted to investigate the protective effects of CGA and its molecular mechanisms on intestinal barrier function in a porcine model. Twenty-four weaned pigs were allotted to two groups and fed with a basal diet or a basal diet containing 1000 mg/kg CGA. The results showed that CGA decreased serum D-lactate and diamine oxidase levels, and enhanced the expression and localization of claudin-1 protein in apical intercellular region of small intestinal epithelium. Interestingly, CGA significantly decreased the mucosa histamine and tryptase contents, as well as the tryptase-positive mast cell counts. Moreover, the expression levels of critical inflammation molecules (interleukin-1β, interleukin-6, tumor necrosis factor-α, and nuclear factor-κB) were down-regulated by CGA in jejunal and ileal mucosa. However, the expression levels of inflammation repressors (suppressor of cytokine signaling 1 and toll-interacting protein) were up-regulated by CGA. Importantly, CGA decreased the malondialdehyde content but elevated glutathione peroxidase and catalase content in duodenal and jejunal mucosa. The expression levels of critical molecules in antioxidant signaling (nuclear factor erythroid-derived 2-related factor 2 and heme oxygenase-1) were elevated by CGA in duodenal and jejunal mucosa. These results suggested that CGA could ameliorate intestinal barrier disruption in weaned pigs, which might be mediated by suppressing the TLR4/NF-κB signaling pathway and activating the Nrf2/HO-1 signaling pathway.