Human microbiota-associated swine: current progress and future opportunities

Interactions between human microbiome, diet, enteric viruses and immune system: Novel insights from gnotobiotic pig research

Studies over the past few decades demonstrated that gnotobiotic (Gn) pigs provide an unprecedented translational model to study human intestinal health and diseases. Due to the high degree of anatomical, physiological, metabolic, immunological, and developmental similarity, the domestic pig closely mimics the human intestinal microenvironment. Also, Gn piglets can be efficiently transplanted with human microbiota from infants, children and adults with resultant microbial profiles remarkably similar to the original human samples, a feat consistently not achievable in rodent models. Finally, Gn and human microbiota-associated (HMA) piglets are susceptible to human enteric viral pathogens (including human rotavirus, HRV) and can be fed authentic human diets, which further increases the translational potential of these models. In this review, we will focus on recent studies that evaluated the pathophysiology of protein malnutrition and the associated dysbiosis and immunological dysfunction in neonatal HMA piglets. Additionally, we will discuss studies of potential dietary interventions that moderate the effects of malnutrition and dysbiosis on antiviral immunity and HRV vaccines in HMA pigs. Such studies provide novel models and novel mechanistic insights critical for development of drug interventions.

Microbial Ecology along the Gastrointestinal Tract

The ecosystem of the human gastrointestinal (GI) tract traverses a number of environmental, chemical, and physical conditions because it runs from the oral cavity to the anus. These differences in conditions along with food or other ingested substrates affect the composition and density of the microbiota as well as their functional roles by selecting those that are the most suitable for that environment. Previous studies have mostly focused on Bacteria, with the number of studies conducted on Archaea, Eukarya, and Viruses being limited despite their important roles in this ecosystem. Furthermore, due to the challenges associated with collecting samples directly from the inside of humans, many studies are still exploratory, with a primary focus on the composition of microbiomes. Thus, mechanistic studies to investigate functions are conducted using animal models. However, differences in physiology and microbiomes need to be clarified in order to aid in the translation of animal model findings into the context of humans. This review will highlight Bacteria, Archaea, Fungi, and Viruses, discuss differences along the GI tract of healthy humans, and perform comparisons with three common animal models: rats, mice, and pigs.

Dietary changes in nutritional studies shape the structural and functional composition of the pigs' fecal microbiome-from days to weeks

BACKGROUND

The possible impact of changes in diet composition on the intestinal microbiome is mostly studied after some days of adaptation to the diet of interest. The question arises if a few days are enough to reflect the microbial response to the diet by changing the community composition and function. The present study investigated the fecal microbiome of pigs during a time span of 4 weeks after a dietary change to obtain insights regarding the time required for adaptation. Four different diets were used differing in either protein source (field peas meal vs. soybean meal) or the concentration of calcium and phosphorus (CaP).

RESULTS

Twelve pigs were sampled at seven time points within 4 weeks after the dietary change. Fecal samples were used to sequence the 16S rRNA gene amplicons to analyse microbial proteins via LC-MS/MS and to determine the SCFA production. The analysis of OTU abundances and quantification values of proteins showed a significant separation of three periods of time (p = 0.001). Samples from the first day are used to define the 'zero period'; samples of weeks 1 and 2 are combined as 'metabolic period' and an 'equilibrium period was defined based on samples from weeks 3 and 4. Only in this last period, a separation according to the supplementation of CaP was significantly detectable (p = 0.001). No changes were found based on the corn-soybean meal or corn-field peas administration. The analysis of possible factors causing this significant separation showed only an overall change of bacterial members and functional properties. The metaproteomic approach yielded a total of about 9700 proteins, which were used to deduce possible metabolic functions of the bacterial community.

CONCLUSIONS

A gradual taxonomic and functional rearrangement of the bacterial community has been depicted after a change of diet composition. The adaptation lasts several weeks despite the usually assumed time span of several days. The obtained knowledge is of a great importance for the design of future nutritional studies. Moreover, considering the high similarities between the porcine and human gastrointestinal tract anatomy and physiology, the findings of the current study might imply in the design of human-related nutritional studies.

Promotion of Early Gut Colonization by Probiotic Intervention on Microbiota Diversity in Pregnant Sows

The aim of this work was to design a novel mixed probiotic culture for piglets and to evaluate its beneficial effect on the piglets' gut health. The possible mechanisms of probiotic activity, such as adhesion, competitive pathogen exclusion and influence on gut microbiota diversity were determined. Mixed probiotic starter culture is composed of three thermophilic lactic acid bacteria (LAB) strains: Lactobacillus helveticus BGRA43, Lactobacillus fermentum BGHI14 and Streptococcus thermophilus BGVLJ1-44. The strains BGVLJ1-44 and BGRA43 showed good technological properties (fast milk curdling, strong proteolytic activity). In addition, the strain BGVLJ1-44 produces exopolysaccharide (EPS), BGHI14 is heterofermentative LAB strain with significant immunomodulatory effect, while the strain BGRA43 showed strong antimicrobial activity against different pathogens and exhibited significantly higher level of adhesion to Caco-2 cells comparing to other two strains. Both lactobacilli strains BGRA43 and BGHI14 (p < 0.05), as well as probiotic combination (p < 0.01) significantly reduced the adhesion of Escherichia coli ATCC25922 to Caco-2 cells, while the strains BGVLJ1-44 (p < 0.01) and BGRA43 (p < 0.05) significantly reduced adhesion of Salmonella 654/7E (veterinary isolate). The results of farm trial revealed that treatment of sows with new fermented dairy probiotic influenced the piglets' gut colonization with beneficial bacteria and reduced the number of enterobacteriaceae in litters from some treated sows (no significant due to high variability among animals). Finally, this is the first study reporting that the treatment of sows with probiotic combination resulted in the improved microbiota diversity in neonatal piglets.

Effect of antibiotic, probiotic, and human rotavirus infection on colonisation dynamics of defined commensal microbiota in a gnotobiotic pig model

We developed a gnotobiotic (Gn) pig model colonised with defined commensal microbiota (DMF) to provide a simplified and controlled system to study the interactions between intestinal commensals, antibiotics (ciprofloxacin, CIP), probiotics (Escherichia coli Nissle 1917, EcN) and virulent human rotavirus (VirHRV). The DMF included seven gut commensal species of porcine origin that mimic the predominant species in the infant gut. Gn piglets were divided into four groups: DMF control (non-treated), DMF+CIP (CIP treated), DMF+CIP+EcN (CIP/EcN treated), DMF+EcN (EcN treated) and inoculated orally with 10⁵ cfu of each DMF strain. The pig gut was successfully colonised by all DMF species and established a simplified bacterial community by post-bacteria colonisation day (PBCD) 14/post-VirHRV challenge day (PCD) 0. Overall, Bifidobacterium adolescentis was commonly observed in faeces in all groups and time points. At PCD0, after six days of CIP treatment (DMF+CIP), we observed significantly decreased aerobic and anaerobic bacteria counts especially in jejunum (P<0.001), where no DMF species were detected in jejunum by T-RFLP. Following HRV challenge, 100% of pigs in DMF+CIP group developed diarrhoea with higher diarrhoea scores and duration as compared to all other groups. However, only 33% of pigs treated with EcN plus CIP developed diarrhoea. EcN treatment also enhanced the bacterial diversity and all seven DMF species were detected with a higher proportion of Bifidobacterium longum in jejunum in the DMF+CIP+EcN group on PBCD14/PCD0. Our results suggest that EcN increased the proportion of B. longum especially in jejunum and mitigated adverse impacts of antibiotic use during acute-infectious diarrhoea. The DMF model with a simplified gut commensal community can further our knowledge of how commensals and probiotics promote intestinal homeostasis and contribute to host health.

Pig models on intestinal development and therapeutics

The gastrointestinal tract plays a vital role in nutrient supply, digestion, and absorption, and has a crucial impact on the entire organism. Much attention is being paid to utilize animal models to study the pathogenesis of gastrointestinal diseases in response to intestinal development and health. The piglet has a body size similar to that of the human and is an omnivorous animal with comparable anatomy, nutritional requirements, and digestive and associated inflammatory processes, and displays similarities to the human intestinal microbial ecosystem, which make piglets more appropriate as an animal model for human than other non-primate animals. Therefore, the objective of this review is to summarize key attributes of the piglet model with which to study human intestinal development and intestinal health through probing into the etiology of several gastrointestinal diseases, thus providing a theoretical and hopefully practical, basis for further studies on mammalian nutrition, health, and disease, and therapeutics. Given the comparable nutritional requirements and strikingly similar brain developmental patterns between young piglets and humans, the piglet has been used as an important translational model for studying neurodevelopmental outcomes influenced by pediatric nutrition. Because of similarities in anatomy and physiology between pigs and mankind, more emphasises are put on how to use the piglet model for human organ transplantation research.

Formula diet driven microbiota shifts tryptophan metabolism from serotonin to tryptamine in neonatal porcine colon

BACKGROUND

The gut microbiota of breast-fed and formula-fed infants differ significantly, as do the risks for allergies, gut dysfunction, and upper respiratory tract infections. The connections between breast milk, various formulas, and the profiles of gut bacteria to these childhood illnesses, as well as the mechanisms underlying the effects, are not well understood.

METHODS

We investigated distal colon microbiota by 16S RNA amplicon sequencing, morphology by histomorphometry, immune response by cytokine expression, and tryptophan metabolism in a pig model in which piglets were sow-fed, or fed soy or dairy milk-based formula from postnatal day (PND) 2 to 21.

RESULTS

Formula feeding significantly (p < 0.05) altered the colon microbiota relative to the sow feeding. A significant reduction in microbial diversity was noted with formula groups in comparison to sow-fed. Streptococcus, Blautia, Citrobacter, Butrycimonas, Parabacteroides, Lactococcus genera were increased with formula feeding relative to sow feeding. In addition, relative to sow feeding, Anaerotruncus, Akkermansia, Enterococcus, Acinetobacter, Christensenella, and Holdemania were increased in milk-fed piglets, and Biliophila, Ruminococcus, Clostridium were increased in soy-fed piglets. No significant gut morphological changes were noted. However, higher cytokine mRNA expression (BMP4, CCL11, CCL21) was observed in the distal colon of formula groups. Formula feeding reduced enterochromaffin cell number and serotonin, but increased tryptamine levels relative to sow feeding.

CONCLUSION

Our data confirm that formula diet alters the colon microbiota and appears to shift tryptophan metabolism from serotonin to tryptamine, which may lead to greater histamine levels and risk of allergies in infants.

Guidance on the risk assessment of substances present in food intended for infants below 16 weeks of age

Following a request from the European Commission to EFSA, the EFSA Scientific Committee (SC) prepared a guidance for the risk assessment of substances present in food intended for infants below 16 weeks of age. In its approach to develop this guidance, the EFSA SC took into account, among others, (i) an exposure assessment based on infant formula as the only source of nutrition; (ii) knowledge of organ development in human infants, including the development of the gut, metabolic and excretory capacities, the brain and brain barriers, the immune system, the endocrine and reproductive systems; (iii) the overall toxicological profile of the substance identified through the standard toxicological tests, including critical effects; (iv) the relevance for the human infant of the neonatal experimental animal models used. The EFSA SC notes that during the period from birth up to 16 weeks, infants are expected to be exclusively fed on breast milk and/or infant formula. The EFSA SC views this period as the time where health-based guidance values for the general population do not apply without further considerations. High infant formula consumption per body weight is derived from 95th percentile consumption. The first weeks of life is the time of the highest relative consumption on a body weight basis. Therefore, when performing an exposure assessment, the EFSA SC proposes to use the high consumption value of 260 mL/kg bw per day. A decision tree approach is proposed that enables a risk assessment of substances present in food intended for infants below 16 weeks of age. The additional information needed when testing substances present in food for infants below 16 weeks of age and the approach to be taken for the risk assessment are on a case-by-case basis, depending on whether the substance is added intentionally to food and is systemically available.

Evaluation of the Probiotic Strain Bifidobacterium longum subsp. Infantis CECT 7210 Capacities to Improve Health Status and Fight Digestive Pathogens in a Piglet Model

Probiotics have been demonstrated to be useful to enhance gut health and prevent gastrointestinal infections. The objective of this study is to demonstrate the potential of the probiotic strain Bifidobacterium longum subsp. infantis CECT 7210 (B. infantis IM1) to prevent and fight intestinal disease by using a Salmonella Typhimurium (Trial 1) or an enterotoxigenic Escherichia coli K88 (Trial 2) oral challenge in a weaning piglet model. Seventy-two piglets were used in each trial. After an adaptation period, animals were orally challenged. One animal per pen was euthanized at Days 4 and 8/9 (Trial 1/Trial 2) post-inoculation (PI). Animal performance, clinical signs, pathogen excretion, fermentation, immune response, and intestinal morphology were evaluated. In Trial 1, most parameters responded to the challenge, whereas, in Trial 2, effects were much milder. Consistent effects of the probiotic were detected in both experiments: Reduction of pathogen excretion (P = 0.043 on Day 3 PI, Trial 1) or ileal colonization (33% reduction of animals with countable coliforms; P = 0.077, Trial 2); increases in intraepithelial lymphocytes (P = 0.002 on Day 8 PI in Trial 1, P = 0.091 on Day 4 PI in Trial 2), and improvement of the fermentation profile by increasing butyric acid in non-challenged animals [P challenge × probiotic (interaction) = 0.092 in Trial 1 and P = 0.056 in Trial 2] concomitant with an enhancement of the villus:crypt ratio on Day 8/9 PI (P interaction = 0.091 for Trial 1 and P = 0.006 for Trial 2). Challenged animals treated with the probiotic showed reduced feed intakes (P interaction = 0.019 in Trial 1 and P = 0.020 in Trial 2) and had lower short-chain fatty acid concentrations in the colon (P interaction = 0.008 in Trial 1 and P = 0.082 in Trial 2). In conclusion, this probiotic demonstrated potential to reduce the intestinal colonization by pathogens and to stimulate local immune response. However, effects on feed intake, microbial fermentation, and intestinal architecture showed a differential pattern between challenged and non-challenged animals. Effects of the probiotic intervention were dependent on the structure of the ecosystem in which it was applied.

Olive oil bioactives protect pigs against experimentally-induced chronic inflammation independently of alterations in gut microbiota

Subclinical chronic inflammation (SCI) is associated with impaired animal growth. Previous work has demonstrated that olive-derived plant bioactives exhibit anti-inflammatory properties that could possibly counteract the growth-depressing effects of SCI. To test this hypothesis and define the underlying mechanism, we conducted a 30-day study in which piglets fed an olive-oil bioactive extract (OBE) and their control counterparts (C+) were injected repeatedly during the last 10 days of the study with increasing doses of Escherichia coli lipopolysaccharides (LPS) to induce SCI. A third group of piglets remained untreated throughout the study and served as a negative control (C-). In C+ pigs, SCI increased the circulating concentration of interleukin 1 beta (p < 0.001) and decreased feed ingestion (p < 0.05) and weight gain (p < 0.05). These responses were not observed in OBE animals. Although intestinal inflammation and colonic microbial ecology was not altered by treatments, OBE enhanced ileal mRNA abundance of tight and adherens junctional proteins (p < 0.05) and plasma recovery of mannitol (p < 0.05) compared with C+ and C-. In line with these findings, OBE improved transepithelial electrical resistance (p < 0.01) in TNF-α-challenged Caco-2/TC-7 cells, and repressed the production of inflammatory cytokines (p < 0.05) in LPS-stimulated macrophages. In summary, this work demonstrates that OBE attenuates the suppressing effect of SCI on animal growth through a mechanism that appears to involve improvements in intestinal integrity unrelated to alterations in gut microbial ecology and function.

Integrative Physiology: At the Crossroads of Nutrition, Microbiota, Animal Physiology, and Human Health

Nutrition is paramount in shaping all aspects of animal biology. In addition, the influence of the intestinal microbiota on physiology is now widely recognized. Given that diet also shapes the intestinal microbiota, this raises the question of how the nutritional environment and microbial assemblages together influence animal physiology. This research field constitutes a new frontier in the field of organismal biology that needs to be addressed. Here we review recent studies using animal models and humans and propose an integrative framework within which to define the study of the diet-physiology-microbiota systems and ultimately link it to human health. Nutritional Geometry sits centrally in the proposed framework and offers means to define diet compositions that are optimal for individuals and populations.

Microbiota-host interplay at the gut epithelial level, health and nutrition

Growing evidence suggests the implication of the gut microbiota in various facets of health and disease. In this review, the focus is put on microbiota-host molecular cross-talk at the gut epithelial level with special emphasis on two defense systems: intestinal alkaline phosphatase (IAP) and inducible heat shock proteins (iHSPs). Both IAP and iHSPs are induced by various microbial structural components (e.g. lipopolysaccharide, flagellin, CpG DNA motifs), metabolites (e.g. n-butyrate) or secreted signal molecules (e.g., toxins, various peptides, polyphosphate). IAP is produced in the small intestine and secreted into the lumen and in the interior milieu. It detoxifies microbial components by dephosphorylation and, therefore, down-regulates microbe-induced inflammation mainly by inhibiting NF-κB pro-inflammatory pathway in enterocytes. IAP gene expression and enzyme activity are influenced by the gut microbiota. Conversely, IAP controls gut microbiota composition both directly, and indirectly though the detoxification of pro-inflammatory free luminal adenosine triphosphate and inflammation inhibition. Inducible HSPs are expressed by gut epithelial cells in proportion to the microbial load along the gastro-intestinal tract. They are also induced by various microbial components, metabolites and secreted molecules. Whether iHSPs contribute to shape the gut microbiota is presently unknown. Both systems display strong anti-inflammatory and anti-oxidant properties that are protective to the gut and the host. Importantly, epithelial gene expressions and protein concentrations of IAP and iHSPs can be stimulated by probiotics, prebiotics and a large variety of dietary components, including macronutrients (protein and amino acids, especially L-glutamine, fat, fiber), and specific minerals (e.g. calcium) and vitamins (e.g. vitamins K1 and K2). Some food components (e.g. lectins, soybean proteins, various polyphenols) may inhibit or disturb these systems. The general cellular and molecular mechanisms involved in the microbiota-host epithelial crosstalk and subsequent gut protection through IAP and iHSPs are reviewed along with their nutritional modulation. Special emphasis is also given to the pig, an economically important species and valuable biomedical model.

Modeling human enteric dysbiosis and rotavirus immunity in gnotobiotic pigs

Background

Rotavirus vaccines have poor efficacy in infants from low- and middle-income countries. Gut microbiota is thought to influence the immune response to oral vaccines. Thus, we developed a gnotobiotic (Gn) pig model of enteric dysbiosis to study the effects of human gut microbiota (HGM) on immune responses to rotavirus vaccination, and the effects of rotavirus challenge on the HGM by colonizing Gn pigs with healthy HGM (HHGM) or unhealthy HGM (UHGM). The UHGM was from a Nicaraguan infant with a high enteropathy score (ES) and no seroconversion following administration of oral rotavirus vaccine, while the converse was characteristic of the HHGM. Pigs were vaccinated, a subset was challenged, and immune responses and gut microbiota were evaluated.

Results

Significantly more rotavirus-specific IFN-γ producing T cells were in the ileum, spleen, and blood of HHGM than those in UHGM pigs after three vaccine doses, suggesting HHGM induces stronger cell-mediated immunity than UHGM. There were significant correlations between multiple Operational Taxonomic Units (OTUs) and frequencies of IFN-γ producing T cells at the time of challenge. There were significant positive correlations between Collinsella and CD8+ T cells in blood and ileum, as well as CD4+ T cells in blood, whereas significant negative correlations between Clostridium and Anaerococcus, and ileal CD8+ and CD4+ T cells. Differences in alpha diversity and relative abundances of OTUs were detected between the groups both before and after rotavirus challenge.

Conclusion

Alterations in microbiome diversity and composition along with correlations between certain microbial taxa and T cell responses warrant further investigation into the role of the gut microbiota and certain microbial species on enteric immunity. Our results support the use of HGM transplanted Gn pigs as a model of human dysbiosis during enteric infection, and oral vaccine responses.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-016-0136-y) contains supplementary material, which is available to authorized users.

A mixture of milk and vegetable lipids in infant formula changes gut digestion, mucosal immunity and microbiota composition in neonatal piglets

PURPOSE

Although composition of infant formula has been significantly improved during the last decade, major differences with the composition and structure of breast milk still remain and might affect nutrient digestion and gut biology. We hypothesized that the incorporation of dairy fat in infant formulas could modify their physiological impacts by making their composition closer to that of human milk. The effect of milk fat and milk fat globule membrane (MFGM) fragments in infant formulas on gut digestion, mucosal immunity and microbiota composition was evaluated.

METHODS

Three formulas containing either (1) vegetable lipids stabilized only by proteins (V-P), (2) vegetable lipids stabilized by a mixture of proteins and MFGM fragments (V-M) and (3) a mixture of milk and vegetable lipids stabilized by a mixture of proteins and MFGM fragments (M-M) were automatically distributed to 42 newborn piglets until slaughter at postnatal day (PND) 7 or 28, and compared to a fourth group of sow's suckling piglets (SM) used as a breast-fed reference.

RESULTS

At both PND, casein and β-lactoglobulin digestion was reduced in M-M proximal jejunum and ileum contents compared to V-P and V-M ones leading to more numerous β-Cn peptides in M-M contents. The IFNγ cytokine secretion of ConA-stimulated MLN cells from M-M piglets tended to be higher than in V-P ones at PND 7 and PND 28 and was closer to that of SM piglets. No dietary treatment effect was observed on IL-10 MLN cell secretion. Changes in faecal microbiota in M-M piglets resulted in an increase in Proteobacteria and Bacteroidetes and a decrease in Firmicutes phyla compared to V-P ones. M-M piglets showed higher abundances of Parabacteroides, Escherichia/Shigella and Klebsiella genus.

CONCLUSIONS

The incorporation of both milk fat and MFGM fragments in infant formula modifies protein digestion, the dynamic of the immune system maturation and the faecal microbiota composition.

Growing up in a Bubble: Using Germ-Free Animals to Assess the Influence of the Gut Microbiota on Brain and Behavior

There is a growing recognition of the importance of the commensal intestinal microbiota in the development and later function of the central nervous system. Research using germ-free mice (mice raised without any exposure to microorganisms) has provided some of the most persuasive evidence for a role of these bacteria in gut-brain signalling. Key findings show that the microbiota is necessary for normal stress responsivity, anxiety-like behaviors, sociability, and cognition. Furthermore, the microbiota maintains central nervous system homeostasis by regulating immune function and blood brain barrier integrity. Studies have also found that the gut microbiota influences neurotransmitter, synaptic, and neurotrophic signalling systems and neurogenesis. The principle advantage of the germ-free mouse model is in proof-of-principle studies and that a complete microbiota or defined consortiums of bacteria can be introduced at various developmental time points. However, a germ-free upbringing can induce permanent neurodevelopmental deficits that may deem the model unsuitable for specific scientific queries that do not involve early-life microbial deficiency. As such, alternatives and complementary strategies to the germ-free model are warranted and include antibiotic treatment to create microbiota-deficient animals at distinct time points across the lifespan. Increasing our understanding of the impact of the gut microbiota on brain and behavior has the potential to inform novel management strategies for stress-related gastrointestinal and neuropsychiatric disorders.

The Gut Microbiome and Its Role in Obesity

The human body is host to a vast number of microbes, including bacterial, fungal and protozoal microoganisms, which together constitute our microbiota. Evidence is emerging that the intestinal microbiome is intrinsically linked with overall health, including obesity risk. Obesity and obesity-related metabolic disorders are characterized by specific alterations in the composition and function of the human gut microbiome. Mechanistic studies have indicated that the gastrointestinal microbiota can influence both sides of the energy balance equation; namely, as a factor influencing energy utilization from the diet and as a factor that influences host genes that regulate energy expenditure and storage. Moreover, its composition is not fixed and can be influenced by several dietary components. This fact raises the attractive possibility that manipulating the gut microbiota could facilitate weight loss or prevent obesity in humans. Emerging as possible strategies for obesity prevention and/or treatment are targeting the microbiota, in order to restore or modulate its composition through the consumption of live bacteria (probiotics), nondigestible or limited digestible food constituents such as oligosaccharides (prebiotics), or both (synbiotics), or even fecal transplants.

Probiotic supplementation can positively affect anxiety and depressive symptoms: a systematic review of randomized controlled trials

Gastrointestinal microbiota, consisting of microbial communities in the gastrointestinal tract, play an important role in digestive, metabolic, and immune functioning. Preclinical studies on rodents have linked behavioral and neurochemical changes in the central nervous system with deficits or alterations in these bacterial communities. Moreover, probiotic supplementation in rodents has been shown to markedly change behavior, with correlated changes in central neurochemistry. While such studies have documented behavioral and mood-related supplementation effects, the significance of these effects in humans, especially in relation to anxiety and depression symptoms, are relatively unknown. Thus, the purpose of this paper was to systematically evaluate current literature on the impact of probiotic supplementation on anxiety and depression symptoms in humans. To this end, multiple databases, including Medline, PsycINFO, PubMed, Scopus, and Web of Science were searched for randomized controlled trials published between January 1990 and January 2016. Search results led to a total of 10 randomized controlled trials (4 in clinically diagnosed and 6 in non-clinical samples) that provided limited support for the use of some probiotics in reducing human anxiety and depression. Despite methodological limitations of the included trials and the complex nature of gut-brain interactions, results suggest the detection of apparent psychological benefits from probiotic supplementation. Nevertheless a better understanding of developmental, modulatory, and metagenomic influences on the GI microbiota, specifically as they relate to mood and mental health, represent strong priorities for future research in this area.

The Role of Lactoferrin in Gastrointestinal and Immune Development and Function: A Preclinical Perspective

The early postnatal period is a critical time for gastrointestinal (GI) and immune development. Neonates fed mother's milk have more rapid GI and immune development than fed-formula infants. In addition, clinical and epidemiologic data provide strong evidence that breastfeeding reduces the incidence and/or severity of infectious diseases. Lactoferrin is a 77 kDa, iron-binding glycoprotein that is present at high concentration in human milk compared with bovine milk and infant formula. It is a multifunctional protein that mediates many of the physiological processes in which breastfed infants have advantages over their formula-fed peers, including promoting GI and immune development, protection from infections, and improved cognitive development. Feeding bovine lactoferrin or recombinant human lactoferrin was well tolerated and stimulated intestinal cell proliferation and increased villus length and crypt depth in piglets. Lactoferrin also influenced both systemic and GI immune development by stimulating a balanced T-helper-1/T-helper-2 cytokine immune response. Further, there was a tendency for immune cells to secrete more anti-inflammatory cytokines in an unstimulated state, while being primed for a robust pro-inflammatory response when presented with a bacterial trigger in piglets fed lactoferrin. These findings support clinical studies demonstrating benefits of dietary lactoferrin in the prevention of infections, late onset sepsis, and necrotizing enterocolitis.

Intestinal Microbiota and Microbial Metabolites Are Changed in a Pig Model Fed a High-Fat/Low-Fiber or a Low-Fat/High-Fiber Diet

The intestinal microbiota and its metabolites appear to be an important factor for gastrointestinal function and health. However, research is still needed to further elaborate potential relationships between nutrition, gut microbiota and host’s health by means of a suitable animal model. The present study examined the effect of two different diets on microbial composition and activity by using the pig as a model for humans. Eight pigs were equally allotted to two treatments, either fed a low-fat/high-fiber (LF), or a high-fat/low-fiber (HF) diet for 7 weeks. Feces were sampled at day 7 of every experimental week. Diet effects on fecal microbiota were assessed using quantitative real-time PCR, DNA fingerprinting and metaproteomics. Furthermore, fecal short-chain fatty acid (SCFA) profiles and ammonia concentrations were determined. Gene copy numbers of lactobacilli, bifidobacteria (P<0.001) and Faecalibacterium prausnitzii (P<0.05) were higher in the LF pigs, while Enterobacteriaceae were more abundant in the HF pigs (P<0.001). Higher numbers of proteins affiliated to Enterobacteriaceae were also present in the HF samples. Proteins for polysaccharide breakdown did almost exclusively originate from Prevotellaceae. Total and individual fecal SCFA concentrations were higher for pigs of the LF treatment (P<0.05), whereas fecal ammonia concentrations did not differ between treatments (P>0.05). Results provide evidence that beginning from the start of the experiment, the LF diet stimulated beneficial bacteria and SCFA production, especially butyrate (P<0.05), while the HF diet fostered those bacterial groups which have been associated with a negative impact on health conditions. These findings correspond to results in humans and might strengthen the hypothesis that the response of the porcine gut microbiota to a specific dietary modulation is in support of using the pig as suitable animal model for humans to assess diet-gut-microbiota interactions.

Data are available via ProteomeXchange with identifier PXD003447.

Gut Microbiome and Kidney Disease in Pediatrics: Does Connection Exist?

Child development is a unique and continuous process that is impacted by genetics and environmental factors. Gut microbiome changes with development and depends on the stage of gut maturation, nutrition, and overall health. In spite of emerging data and active study in adults, the gut-renal axis in pediatrics has not been well considered and investigated. This review will focus on the current knowledge of gut microbiota impacts on kidney disease with extrapolation to the pediatric population.

Effect of Freezing Conditions on Fecal Bacterial Composition in Pigs

Simple Summary

Storage of gut samples may affect the extractability of intact DNA and analyzed bacterial composition. In this study, we compared the DNA yield and the abundance of total bacteria and eight bacterial taxa when DNA was extracted from fresh fecal samples of pigs or from freeze stored samples with or without prior snap-freezing in liquid nitrogen. Results showed that the greatest differences in DNA yield and bacterial abundances were found when DNA was extracted from fresh feces compared to freeze stored fecal samples.

Abstract

Sample preservation and recovery of intact DNA from gut samples may affect the inferred gut microbiota composition in pigs. This study aimed to evaluate the effect of the freezing process and storage temperature prior to DNA extraction on DNA recovery and bacterial community composition in pig feces using quantitative PCR. Fresh fecal samples from six growing pigs were collected and five aliquots of each prepared: (1) total DNA extracted immediately; (2) stored at −20 °C; (3) snap frozen and stored at −20 °C; (4) stored at −80 °C; and (5) snap frozen and stored at −80 °C. Results showed that DNA yields from fresh fecal samples were, on average, 25 to 30 ng higher than those from the various stored samples. The DNA extracted from fresh samples had more gene copies of total bacteria and all targeted bacterial groups per gram feces compared to DNA extraction from frozen samples. Data presentation also modified the observed effect of freeze storage; as results for Lactobacillus group, Enterococcus spp., Streptococcus spp., Clostridium cluster IV, Bacteroides-Prevotella-Porphyromonas and Enterobacteriaceae showed the opposite effect when expressed as relative abundance, by being greater in freeze stored feces than in fresh feces. Snap freezing increased the relative proportion of Clostridium cluster IV by 24%. In conclusion, the freezing process affected DNA yield and bacterial abundances, whereas snap freezing and storage temperature had only little influence on abundances of bacterial populations in pig feces.

Minipigs in Translational Immunosafety Sciences: A Perspective

The porcine immune system has been studied especially with regard to infectious diseases of the domestic pig, highlighting the economic importance of the pig in agriculture. Recently, in particular, minipigs have received attention as alternative species to dogs or nonhuman primates in drug safety evaluations. The increasing number of new drug targets investigated to modulate immunological pathways has triggered renewed interest to further explore the porcine immune system. Comparative immunological studies of minipigs with other species broaden the translational models investigated in drug safety evaluations. The porcine immune system overall seems functionally similar to other mammalian species, but there are some anatomical, immunophenotypical, and functional differences. Here, we briefly review current knowledge of the innate and adaptive immune system in pigs and minipigs. In conclusion, more systematic and cross-species comparisons are needed to assess the significance of immunological findings in minipigs in the context of translational safety sciences.