Maturation of villus and crypt cell functions in rat small intestine. Role of dietary polyamines

Breastmilk polyamines modify gut gene expression in children at three months of age

BACKGROUND & AIMS

Breastmilk is one of the main sources of exogenous polyamines for newborns and contains higher polyamine content than infant formulas. Polyamines are involved in gut maturation and immune system regulation in animals, although the underlying mechanisms are not fully understood. We quantified polyamines in human mature breastmilk and evaluate their effects on intestinal gene expression in babies at three months of age.

METHODS

Polyamines were quantified in mature milk of 195 women from the prospective Mediterranean NELA birth cohort (Murcia, Spain) at 3 months postpartum. Maternal dietary intake was assessed by food frequency questionnaires. Intestinal gene expression was analysed in babies receiving breastmilk, with high (>p50, n = 25) or low (

RESULTS

Spermidine and spermine were the most prevalent polyamines in breastmilk at 3 months postpartum, while levels of putrescine were lower. Maternal dietary intake of polyamines was not associated with polyamine concentration in breastmilk and there were no differences in the polyamine content between allergic and non-allergic mothers. Microarray analyses of exfoliated gut cells revealed that cell localization and immune system were the most significant biological processes affected by high vs low polyamines in breastmilk. There were 15 differentially expressed genes, 3 up-regulated and 12 down-regulated, in high compared to low polyamine groups. Among the up-regulated genes were tumour necrosis factor alpha-induced protein 6 (TNFAIP6) and interleukin 8; while other immune system-related genes, such as integral membrane protein 2C, lymphocyte antigen 6 complex, transmembrane protein 179B were down-regulated.

CONCLUSIONS

Mature breastmilk presents spermidine and spermine as the most prevalent polyamines. Babies receiving milk with higher polyamine levels showed differences in the expression of genes associated with cell localization and immune system processes.

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Key Words

• Breastmilk
• Exfoliome
• Gene expression
• Intestine
• Polyamines
• Transcriptome

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MESH Headings

• Humans
• Female
• Polyamines/analysis
• Infant
• Milk, Human/chemistry
• Prospective Studies
• Spermidine/analysis
• Adult
• Spain
• Spermine/analysis
• Putrescine/analysis
• Male
• Gene Expression

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Affiliation(s)

María Sánchez-Campillo Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Physiology, University of Murcia, Murcia, Spain
Antonio Gázquez Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Physiology, University of Murcia, Murcia, Spain; Maternal and Child Health and Development Research Network (RICORS-SAMID), Institute of Health Carlos III, Madrid, Spain
María T Pastor-Fajardo Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Pediatrics, Hospital General Universitario de Elche, Alicante, Spain
María J López-Andreo Biology Molecular Section (ACTI), University of Murcia, Murcia, Spain
Adrián Pérez-Andrés Department of Physiology, University of Murcia, Murcia, Spain
Carmen Martínez-Graciá Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Food Science and Technology Department, Faculty of Veterinary, University of Murcia, Murcia, Spain
Jesús Vioque Health and Biomedical Research Institute of Alicante, University Miguel Hernandez (ISABIAL-UMH), Alicante, Spain; CIBER Epidemiology and Public Health (CIBERESP), Madrid, Spain
Virginia Pérez-Fernández Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Sociosanitary Sciences, Faculty of Medicine, University of Murcia, Murcia, Spain
Luís García-Marcos Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Network of Asthma and Adverse and Allergic Reactions (ARADyAL), Madrid, Spain; Pediatric Allergy and Pulmonology Units, Virgen de la Arrixaca University Children's Hospital, University of Murcia, Murcia, Spain
Elvira Larqué Biomedical Research Institute of Murcia (IMIB-Arrixaca), Murcia, Spain; Department of Physiology, University of Murcia, Murcia, Spain; Maternal and Child Health and Development Research Network (RICORS-SAMID), Institute of Health Carlos III, Madrid, Spain.

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Dynamics and Crosstalk between Gut Microbiota, Metabolome, and Fecal Calprotectin in Very Preterm Infants: Insights into Feeding Intolerance

BACKGROUND

Feeding intolerance (FI) is a significant concern in the care of preterm infants, impacting their growth and development. We previously reported that FI is linked to lower fecal calprotectin (FC) levels. This study aims to explore the postnatal dynamics and interplay between microbiota, metabolic profiles, and host immunity in preterm infants with and without FI.

METHODS

Infants with gestational age <32 weeks or birth weight <1500 g were enrolled at the Children's Hospital of Fudan University between January 2018 and October 2020. Weekly fecal samples were analyzed for bacterial profiling, metabolome, and calprotectin levels, exploring their longitudinal development and interrelationships.

RESULTS

Of the 118 very preterm infants studied, 48 showed FI. These infants experienced an interrupted microbial-immune trajectory, particularly at 3-4 weeks of age, marked by a reduced bacterial abundance, alpha diversity, and FC levels. Metabolic changes in FI were pronounced between 3 and 6 weeks. Pantothenic acid and two polyamine metabolites were closely associated with bacterial abundance and FC levels and negatively correlated with the duration to attain full enteral feeding.

CONCLUSIONS

FI infants demonstrated compromised microbiome-immune interactions, potentially influenced by specific metabolites. This research underscored the importance of early microbial and metabolic development in the pathogenesis of FI in very preterm infants.

Metabolite interactions between host and microbiota during health and disease: Which feeds the other?

Metabolites produced by the host and microbiota play a crucial role in how human bodies develop and remain healthy. Most of these metabolites are produced by microbiota and hosts in the digestive tract. Metabolites in the gut have important roles in energy metabolism, cellular communication, and host immunity, among other physiological activities. Although numerous host metabolites, such as free fatty acids, amino acids, and vitamins, are found in the intestine, metabolites generated by gut microbiota are equally vital for intestinal homeostasis. Furthermore, microbiota in the gut is the sole source of some metabolites, including short-chain fatty acids (SCFAs). Metabolites produced by microbiota, such as neurotransmitters and hormones, may modulate and significantly affect host metabolism. The gut microbiota is becoming recognized as a second endocrine system. A variety of chronic inflammatory disorders have been linked to aberrant host-microbiota interplays, but the precise mechanisms underpinning these disturbances and how they might lead to diseases remain to be fully elucidated. Microbiome-modulated metabolites are promising targets for new drug discovery due to their endocrine function in various complex disorders. In humans, metabolotherapy for the prevention or treatment of various disorders will be possible if we better understand the metabolic preferences of bacteria and the host in specific tissues and organs. Better disease treatments may be possible with the help of novel complementary therapies that target host or bacterial metabolism. The metabolites, their physiological consequences, and functional mechanisms of the host-microbiota interplays will be highlighted, summarized, and discussed in this overview.

Isolation of the high polyamine-producing bacterium Staphylococcus epidermidis FB146 from fermented foods and identification of polyamine-related genes

It has been reported that the intake of polyamines contributes to the extension of healthy life span in animals. Fermented foods contain high concentrations of polyamines thought to be derived from fermentation bacteria. This suggests that bacteria that produce high levels of polyamines could be isolated from fermented foods and utilized as a source of polyamines for human nutrition. In this study, Staphylococcus epidermidis FB146 was isolated from miso, a Japanese fermented bean paste, and found to have a high concentration of putrescine in its culture supernatant (452 μM). We analyzed the presence of polyamines in the culture supernatants and cells of the type strains of 21 representative Staphylococcus species in addition to S. epidermidis FB146, and only S. epidermidis FB146 showed high putrescine productivity. Furthermore, whole-genome sequencing of S. epidermidis FB146 was performed, and the ornithine decarboxylase gene (odc), which is involved in putrescine synthesis, and the putrescine:ornithine antiporter gene (potE), which is thought to contribute to the release of putrescine into the culture supernatant, were present on plasmid DNA harbored by S. epidermidis FB146.

The Role of the Gallbladder, the Intestinal Barrier and the Gut Microbiota in the Development of Food Allergies and Other Disorders

The microbiota present in the gastrointestinal tract is involved in the development or prevention of food allergies and autoimmune disorders; these bacteria can enter the gallbladder and, depending on the species involved, can either be benign or cause significant diseases. Occlusion of the gallbladder, usually due to the presence of calculi blocking the bile duct, facilitates microbial infection and inflammation, which can be serious enough to require life-saving surgery. In addition, the biliary salts are secreted into the intestine and can affect the gut microbiota. The interaction between the gut microbiota, pathogenic organisms, and the human immune system can create intestinal dysbiosis, generating a variety of syndromes including the development of food allergies and autoimmune disorders. The intestinal microbiota can aggravate certain food allergies, which become severe when the integrity of the intestinal barrier is affected, allowing bacteria, or their metabolites, to cross the intestinal barrier and invade the bloodstream, affecting distal body organs. This article deals with health conditions and severe diseases that are either influenced by the gut flora or caused by gallbladder obstruction and inflammation, as well as putative treatments for those illnesses.

Gut-microbiota derived bioactive metabolites and their functions in host physiology

Every individual harbours a complex, diverse and mutualistic microbial flora in their intestine and over the time it became an integral part of the body, affecting a plethora of activities of the host. Interaction between host and gut-microbiota affects several aspects of host physiology. Gut-microbiota affects host metabolism by fermenting unabsorbed/undigested carbohydrates in the large intestine. Not only the metabolic functions, any disturbances in the composition of the gut-microbiota during first 2-3 years of life may impact on the brain development and later affects cognition and behaviour. Thus, gut-dysbiosis causes certain serious pathological conditions in the host including metabolic disorders, inflammatory bowel disease and mood alterations, etc. Microbial-metabolites in recent times have emerged as key mediators and are responsible for microbiota induced beneficial effects on host. This review provides an overview of the mechanism of microbial-metabolite production, their respective physiological functions and the impact of gut-microbiome in health and diseases. Metabolites from dietary fibres, aromatic amino acids such as tryptophan, primary bile acids and others are the potential substances and link microbiota to host physiology. Many of these metabolites act as signalling molecules to a number of cells types and also help in the secretion of hormones. Moreover, interaction of microbiota derived metabolites with their host, immunity boosting mechanisms, protection against pathogens and modulation of metabolism is also highlighted here. Understanding all these functional attributes of metabolites produced from gut-microbiota may lead to the opening of a new avenue for preventing and developing potent therapies against several diseases.

Oral Spermine Supplementation in Gestated Rabbit: A Study on Villi Height of Immature Intestines

Introduction: Immature intestines are the major problem in prematurity. Postnatal oral spermine has been shown in studies to improve intestinal maturation in rats and piglets. This study aimed to find out the efficacy of spermine in rabbits during gestation. Method: An experimental study was done in an unblinded, randomized manner on those treated with and without spermine administration. A morphological examination of hematoxylin-eosin-stained villi was performed under a light microscope with a focus on villi height. Data were subjected to analysis. Results: The median of the spermine-treated group was found to be higher at 24, 26, and 28 days than the non-spermine group, but was not significantly different. Conclusion: Oral spermine supplementation during gestation might improve intestinal villi height in immature rabbit intestines.

Intestinal Microbial Metabolites in Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease characterized by inflammation of axial joints and the pelvis. It is known that intestinal dysbiosis may exert direct pathogenic effects on gut homeostasis and may act as a triggering factor for the host innate immune system to activate and cause inflammation in extraintestinal sites in the so-called "gut-joint axis", contributing to AS pathogenesis. However, although the intestinal microbiota's influence on the clinical manifestation of AS is widely accepted, the mechanisms mediating the cross-talk between the intestinal lumen and the immune system are still not completely defined. Recent evidence suggests that the metabolism of microbial species may be a source of metabolites and small molecules participating in the complex network existing between bacteria and host cells. These findings may give inputs for further research of novel pharmacological targets and pave the way to applying dietary interventions to prevent the onset and ameliorate the clinical presentation of the disease. In this review, we discuss the role of some of the biological mediators of microbial origin, with a particular focus on short-chain fatty acids, tryptophan and vitamin B derivatives, and their role in barrier integrity and type 3 immunity in the context of AS.

Immunometabolism: an overview and therapeutic prospects in autoimmune diseases

Metabolism is a critical immune regulator under physiologic and pathologic conditions. Culminating evidence has disentangled the contribution of distinct metabolic pathways, namely glucolysis, pentose phosphate, fatty acid oxidation, glutaminolysis, Krebs cycle and oxidative phosphorylation, in modulating innate and adaptive immune cells based on their activation/differentiation state. Metabolic aberrations and changes in the intracellular levels of specific metabolites are linked to the inflammatory phenotype of immune cells implicated in autoimmune disorders such as systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis and diabetes. Notably, targeting metabolism such as the mTOR by rapamycin, hexokinase by 2-deoxy-D-glucose, AMP-activated protein kinase by metformin, may be used to ameliorate autoimmune inflammation. Accordingly, research in immunometabolism is expected to offer novel opportunities for monitoring and treating immune-mediated diseases.

The Application of Metabolomics to Probiotic and Prebiotic Interventions in Human Clinical Studies

There is an ever-increasing appreciation for our gut microbiota that plays a crucial role in the maintenance of health, as well as the development of disease. Probiotics are live bacteria that are consumed to increase the population of beneficial bacteria and prebiotics are dietary substrates intended to promote the propagation of beneficial bacteria. In order to optimize the use of probiotics and prebiotics, a more complete biochemical understanding of the impact that these treatments have on the community and functioning of the gut microbiota is required. Nucleic acid sequencing methods can provide highly detailed information on the composition of the microbial communities but provide less information on the actual function. As bacteria impart much of their influence on the host through the production of metabolites, there is much to be learned by the application of metabolomics. The focus of this review is on the use of metabolomics in the study of probiotic and prebiotic treatments in the context of human clinical trials. Assessment of the current state of this research will help guide the design of future studies to further elucidate the biochemical mechanism by which probiotics and prebiotics function and pave the way toward more personalized applications.

Gut Microbiome Modulates Response to Cancer Immunotherapy

With the advent of next-generation sequencing approaches, there has been a renaissance in the microbiome field. Microbial taxonomy and function can now be characterized relatively easily and rapidly-no longer mandating complex culturing approaches. With this renaissance, there is now a strong and growing appreciation for the role of the microbiome (referring to microbes and their genomes) in modulating many facets of physiology-including overall immunity. This is particularly true of the gut microbiome, and there is now an evolving body of the literature demonstrating a role for gut microbes in modulating responses to cancer treatment-particularly immunotherapy. Gut microbes can modulate immunity and anti-tumor responses via a number of different interactions, and these will be discussed herein. Additionally, data regarding the impact of gut microbes on cancer immunotherapy response will be discussed, as will strategies to manipulate the microbiome to enhance therapeutic responses. These efforts to date are not completely optimized; however, there is evidence of efficacy though much additional work is needed in this space. Nonetheless, it is clear that the microbiome plays a central role in health and disease, and strategies to manipulate it in cancer and overall precision health are being explored.

Macronutrient metabolism by the human gut microbiome: major fermentation by-products and their impact on host health

The human gut microbiome is a critical component of digestion, breaking down complex carbohydrates, proteins, and to a lesser extent fats that reach the lower gastrointestinal tract. This process results in a multitude of microbial metabolites that can act both locally and systemically (after being absorbed into the bloodstream). The impact of these biochemicals on human health is complex, as both potentially beneficial and potentially toxic metabolites can be yielded from such microbial pathways, and in some cases, these effects are dependent upon the metabolite concentration or organ locality. The aim of this review is to summarize our current knowledge of how macronutrient metabolism by the gut microbiome influences human health. Metabolites to be discussed include short-chain fatty acids and alcohols (mainly yielded from monosaccharides); ammonia, branched-chain fatty acids, amines, sulfur compounds, phenols, and indoles (derived from amino acids); glycerol and choline derivatives (obtained from the breakdown of lipids); and tertiary cycling of carbon dioxide and hydrogen. Key microbial taxa and related disease states will be referred to in each case, and knowledge gaps that could contribute to our understanding of overall human wellness will be identified.

Intestinal Metabolites Are Profoundly Altered in the Context of HLA-B27 Expression and Functionally Modulate Disease in a Rat Model of Spondyloarthritis

OBJECTIVE

HLA-B27-associated spondyloarthritides are associated with an altered intestinal microbiota and bowel inflammation. We undertook this study to identify HLA-B27-dependent changes in both host and microbial metabolites in the HLA-B27/β2 -microglobulin (β2 m)-transgenic rat and to determine whether microbiota-derived metabolites could impact disease in this major model of spondyloarthritis.

METHODS

Cecal contents were collected from Fischer 344 33-3 HLA-B27/β2 m-transgenic rats and wild-type controls at 6 weeks (before disease) and 16 weeks (with active bowel inflammation). Metabolomic profiling was performed by high-throughput gas and liquid chromatography-based mass spectrometry. HLA-B27/β2 m-transgenic rats were treated with the microbial metabolites propionate or butyrate in drinking water for 10 weeks, and disease activity was subsequently assessed.

RESULTS

Our screen identified 582 metabolites, of which more than half were significantly altered by HLA-B27 expression at 16 weeks. Both microbial and host metabolites were altered, with multiple pathways affected, including those for amino acid, carbohydrate, xenobiotic, and medium-chain fatty acid metabolism. Differences were even observed at 6 weeks, with up-regulation of histidine, tyrosine, spermidine, N-acetylmuramate, and glycerate in HLA-B27/β2 m-transgenic rats. Administration of the short-chain fatty acid propionate significantly attenuated HLA-B27-associated inflammatory disease, although this was not associated with increased FoxP3+ T cell induction or with altered expression of the immunomodulatory cytokines interleukin-10 (IL-10) or IL-33 or of the tight junction protein zonula occludens 1. HLA-B27 expression was also associated with altered host expression of messenger RNA for the microbial metabolite receptors free fatty acid receptor 2 (FFAR2), FFAR3, and niacin receptor 1.

CONCLUSION

HLA-B27 expression profoundly impacts the intestinal metabolome, with changes evident in rats even at age 6 weeks. Critically, we demonstrate that a microbial metabolite, propionate, attenuates development of HLA-B27-associated inflammatory disease. These and other microbiota-derived bioactive mediators may provide novel treatment modalities in HLA-B27-associated spondyloarthritides.

Understanding the Holobiont: How Microbial Metabolites Affect Human Health and Shape the Immune System

The human gastrointestinal tract is populated by a diverse, highly mutualistic microbial flora, which is known as the microbiome. Disruptions to the microbiome have been shown to be associated with severe pathologies of the host, including metabolic disease, cancer, and inflammatory bowel disease. Mood and behavior are also susceptible to alterations in the gut microbiota. A particularly striking example of the symbiotic effects of the microbiome is the immune system, whose cells depend critically on a diverse array of microbial metabolites for normal development and behavior. This includes metabolites that are produced by bacteria from dietary components, metabolites that are produced by the host and biochemically modified by gut bacteria, and metabolites that are synthesized de novo by gut microbes. In this review, we highlight the role of the intestinal microbiome in human metabolic and inflammatory diseases and focus in particular on the molecular mechanisms that govern the gut-immune axis.

Gut microbiota, metabolites and host immunity

The microbiota - the collection of microorganisms that live within and on all mammals - provides crucial signals for the development and function of the immune system. Increased availability of technologies that profile microbial communities is facilitating the entry of many immunologists into the evolving field of host-microbiota studies. The microbial communities, their metabolites and components are not only necessary for immune homeostasis, they also influence the susceptibility of the host to many immune-mediated diseases and disorders. In this Review, we discuss technological and computational approaches for investigating the microbiome, as well as recent advances in our understanding of host immunity and microbial mutualism with a focus on specific microbial metabolites, bacterial components and the immune system.

New insights into the role of spermine in enhancing the antioxidant capacity of rat spleen and liver under oxidative stress

Oxidative stress can damage cellular antioxidant defense and reduce livestock production efficiency. Spermine is a ubiquitous cellular component that plays important roles in stabilizing nucleic acids, modulating cell growth and differentiation, and regulating ion channel activities. Spermine has the potential to alleviate the effects of oxidative stress. However, to date no information is available about the effect of spermine administration on antioxidant property of the liver and spleen in any mammalian in vivo system. This study aims to investigate the protective effect of spermine on rat liver and spleen under oxidative stress. Rats received intragastric administration of either 0.4 μmol/g body weight of spermine or saline once a day for 3 days. The rats in each treatment were then injected with either diquat or sterile saline at 12 mg/kg body weight. Liver and spleen samples were collected 48 h after the last spermine ingestion. Results showed that regardless of diquat treatment, spermine administration significantly reduced the malondialdehyde (MDA) content by 23.78% in the liver and by 5.75% in the spleen, respectively (P < 0.05). Spermine administration also enhanced the catalase (CAT) activity, anti-hydroxyl radical (AHR) capacity and glutathione (GSH) content by 38.68%, 15.53% and 1.32% in the spleen, respectively (P < 0.05). There were interactions between spermine administration and diquat injection about anti-superoxide anion (ASA), AHR capacity, CAT activity, GSH content, and total antioxidant capacity (T-AOC) in the liver and about ASA capacity and T-AOC in the spleen of weaned rats (P < 0.05). Compared with the control group, spermine administration significantly increased the AHR capacity, CAT activity, GSH content, and T-AOC by 40.23%, 31.15%, 30.25%, 35.37% in the liver, respectively (P < 0.05) and increased the T-AOC by 8% in the spleen of weaned rats (P < 0.05). Compared with the diquat group, spermine + diquat group significantly increased ASA capacity by 15.63% in the liver and by 73.41% in the spleen of weaned rats, respectively (P < 0.05). Results demonstrate that spermine administration can increase the antioxidant capacity in the liver and spleen and can enhance the antioxidant status in the spleen and liver under oxidative stress.

The Extracellular Calcium-Sensing Receptor in the Intestine: Evidence for Regulation of Colonic Absorption, Secretion, Motility, and Immunity

Different from other epithelia, the intestinal epithelium has the complex task of providing a barrier impeding the entry of toxins, food antigens, and microbes, while at the same time allowing for the transfer of nutrients, electrolytes, water, and microbial metabolites. These molecules/organisms are transported either transcellularly, crossing the apical and basolateral membranes of enterocytes, or paracellularly, passing through the space between enterocytes. Accordingly, the intestinal epithelium can affect energy metabolism, fluid balance, as well as immune response and tolerance. To help accomplish these complex tasks, the intestinal epithelium has evolved many sensing receptor mechanisms. Yet, their roles and functions are only now beginning to be elucidated. This article explores one such sensing receptor mechanism, carried out by the extracellular calcium-sensing receptor (CaSR). In addition to its established function as a nutrient sensor, coordinating food digestion, nutrient absorption, and regulating energy metabolism, we present evidence for the emerging role of CaSR in the control of intestinal fluid homeostasis and immune balance. An additional role in the modulation of the enteric nerve activity and motility is also discussed. Clearly, CaSR has profound effects on many aspects of intestinal function. Nevertheless, more work is needed to fully understand all functions of CaSR in the intestine, including detailed mechanisms of action and specific pathways involved. Considering the essential roles CaSR plays in gastrointestinal physiology and immunology, research may lead to a translational opportunity for the development of novel therapies that are based on CaSR's unique property of using simple nutrients such as calcium, polyamines, and certain amino acids/oligopeptides as activators. It is possible that, through targeting of intestinal CaSR with a combination of specific nutrients, oral solutions that are both inexpensive and practical may be developed to help in conditioning the gut microenvironment and in maintaining digestive health.

Spermine: new insights into the intestinal development and serum antioxidant status of suckling piglets

The present work aimed at investigating the effects of spermine supplementation and extended spermine administration on the intestinal morphology, enzyme activity, and serum antioxidant capacity of suckling piglets.

The role of the calcium-sensing receptor in gastrointestinal inflammation

The gastrointestinal (GI) tract must balance the extraction of energy and metabolic end-products from ingested nutrition and resident gut microbes and the maintenance of a symbiotic relationship with this microbiota, with the ability to mount functional immune responses to pathogenic organisms to maintain GI health. The gut epithelium is equipped with bacteria-sensing mechanisms that discriminate between pathogenic and commensal microorganisms and regulate host responses between immunity and tolerance. The epithelium also expresses numerous nutrient-sensing receptors, but their importance in the preservation of the gut microbiota and immune homeostasis remains largely unexplored. Observations that a deficiency in the extracellular calcium-sensing receptor (CaSR) using intestinal epithelium-specific receptor knockout mice resulted in diminished intestinal barrier integrity, altered composition of the gut microbiota, modified expression of intestinal pattern recognition receptors, and a skewing of local and systemic innate responses from regulatory to stimulatory, may change the way that this receptor is considered as a potential immunotherapeutic target in gut homeostasis. These findings suggest that pharmacologic CaSR activators and CaSR-based nutrients such as calcium, polyamines, phenylalanine, tryptophan, and oligo-peptides might be useful in conditioning the gut microenvironment, and thus, in the prevention and treatment of disorders such as inflammatory bowel disease (IBD), infectious enterocolitis, and other inflammatory and secretory diarrheal diseases. Here, we review the emerging roles of the CaSR in intestinal homeostasis and its therapeutic potential for gut pathology.

Arginine deprivation and immune suppression in a mouse model of Alzheimer's disease

The pathogenesis of Alzheimer's disease (AD) is a critical unsolved question; and although recent studies have demonstrated a strong association between altered brain immune responses and disease progression, the mechanistic cause of neuronal dysfunction and death is unknown. We have previously described the unique CVN-AD mouse model of AD, in which immune-mediated nitric oxide is lowered to mimic human levels, resulting in a mouse model that demonstrates the cardinal features of AD, including amyloid deposition, hyperphosphorylated and aggregated tau, behavioral changes, and age-dependent hippocampal neuronal loss. Using this mouse model, we studied longitudinal changes in brain immunity in relation to neuronal loss and, contrary to the predominant view that AD pathology is driven by proinflammatory factors, we find that the pathology in CVN-AD mice is driven by local immune suppression. Areas of hippocampal neuronal death are associated with the presence of immunosuppressive CD11c(+) microglia and extracellular arginase, resulting in arginine catabolism and reduced levels of total brain arginine. Pharmacologic disruption of the arginine utilization pathway by an inhibitor of arginase and ornithine decarboxylase protected the mice from AD-like pathology and significantly decreased CD11c expression. Our findings strongly implicate local immune-mediated amino acid catabolism as a novel and potentially critical mechanism mediating the age-dependent and regional loss of neurons in humans with AD.

Upregulation of colonic luminal polyamines produced by intestinal microbiota delays senescence in mice

Prevention of quality of life (QOL) deterioration is associated with the inhibition of geriatric diseases and the regulation of brain function. However, no substance is known that prevents the aging of both body and brain. It is known that polyamine concentrations in somatic tissues (including the brain) decrease with increasing age, and polyamine-rich foods enhance longevity in yeast, worms, flies, and mice, and protect flies from age-induced memory impairment. A main source of exogenous polyamines is the intestinal lumen, where they are produced by intestinal bacteria. We found that arginine intake increased the concentration of putrescine in the colon and increased levels of spermidine and spermine in the blood. Mice orally administered with arginine in combination with the probiotic bifidobacteria LKM512 long-term showed suppressed inflammation, improved longevity, and protection from age-induced memory impairment. This study shows that intake of arginine and LKM512 may prevent aging-dependent declines in QOL via the upregulation of polyamines.

Increased bacterial putrescine has no impact on gut morphology and physiology in gnotobiotic adolescent mice

Gut bacteria influence host anatomy and physiology. It has been proposed that bacterial metabolites including polyamines are responsible for intestinal maturation and mucosal growth. We have hypothesised that bacterially produced polyamines act as trophic factors and thereby influence large intestinal crypt depth and thickness of the different gut layers. For that purpose, germ-free mice were associated with two different microbial consortia. One group was colonised with a simplified human microbiota (SIHUMI). The second group was associated with SIHUMI + Fusobacterium varium (SIHUMI + Fv), which is known to produce high amounts of polyamines. Polyamine concentrations were measured by HPLC and morphological parameters were determined microscopically. Germ-free and conventional mice served as controls. The caecal putrescine concentration of the SIHUMI + Fv was 61.8 μM (47.6-75.5 μM), whereas that of conventional and SIHUMI mice was 28.8 μM (1.3-41.7 μM) and 24.5 μM (16.8-29.1 μM), respectively. The caecal putrescine concentration of germ-free mice was only 0.6 μM (0-1.0 μM). Caecal crypt depth and thickness of the different caecal layers revealed no significant differences between SIHUMI and SIHUMI + Fv mice. However, the crypt depth in the caeca of conventional, SIHUMI and SIHUMI + Fv mice was increased by 48.6% (P<0.001), 39.7% (P<0.001) and 28.5% (P<0.05), respectively, compared to germ-free mice. These findings indicate that increased intestinal putrescine concentrations do not influence gut morphology in our gnotobiotic adolescent mice.

Polyamine levels in breast milk are associated with mothers' dietary intake and are higher in preterm than full-term human milk and formulas

BACKGROUND

Polyamine intake from milk is considered essential for post-natal maturation of the immune system and small intestine. The present study aimed to determine polyamine content in human milk after preterm delivery and the association with mothers' dietary intake. In comparison, the polyamine levels were compared with those in term breast milk and some corresponding formulas.

METHODS

Transitional breast milk was collected from 40 mothers delivering after 24-36 weeks of gestation, and from 12 mothers delivering after full term. Food intake was assessed in mothers delivering preterm babies using a 3-day diary. Polyamines were analysed by high-performance liquid chromatography.

RESULTS

The dietary intake of polyamines was significantly associated with breast milk content but weaker for spermine than for spermidine and putrescine. Total polyamine level was higher in preterm than term milk and lower in the corresponding formulas. Putrescine, spermidine and spermine contents [mean (SEM)] in preterm milk were 165.6 (25), 615.5 (80) and 167.7 (16) nmol dL⁻¹, respectively, with the levels of putrescine and spermidine being 50% and 25% higher than in term milk. The content of spermine did not differ.

CONCLUSIONS

Dietary intake of polyamines has an impact on the content in breast milk. The difference between human milk after preterm and term delivery might be considered when using donor human milk for preterm infants. The corresponding formulas had lower contents. Further studies are important for determining the relationship between tissue growth and maturation and optimal intake.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Probiotics-induced increase of large intestinal luminal polyamine concentration may promote longevity

Many mechanisms contribute to senescence, such as telomere shortening in replicative cells, cumulative damage to DNA leading to genomic instability, and oxidative damage to molecules by reactive oxygen species (ROS). These include chronic low-grade inflammation (inflammageing), a major risk factor for ageing and age-related diseases, such as Alzheimer's disease and type II diabetes. Furthermore, the prevention of inflammageing seems to be one of the most effective approaches to increase longevity. Here, I discuss the rationale and recent evidence for probiotic-induced upregulation of intestinal luminal polyamine (PA) production in the extension of lifespan by preventing inflammageing.

Influence of breast milk polyamines on suckling rat immune system maturation

The aim of this study was to ascertain whether the supplementation of polyamines present in breast milk, i.e. spermine (SPM) and spermidine (SPD), influenced the post-natal maturation of the systemic and intestinal immune system in rats. From birth, pups daily received SPM or SPD. At 5, 11 and 18 days old, small intestine intraepithelial lymphocytes (IEL), lamina propria lymphocytes (LPL) and splenocytes were phenotypically characterized. SPM and, less evidently, SPD accelerated the maturation of CD8+ IEL, and enhanced the presence of intraepithelial NK cells and IEL related with specific immune responses on the proximal and distal small intestine, respectively. Polyamines increased the percentage of more mature CD4+ LPL and enhanced the early presence of splenic B cells and, later, that of NK cells. However, no effect on Ig-secretory function was detected. These results suggest that breast milk polyamines improve the maturation of the rat intestinal and systemic immune system.

Novel regulatory aspects of the extracellular Ca2+-sensing receptor, CaR

The capacity to sense and adapt to changes in environmental cues is of paramount importance for every living organism. From yeast to man, cells must be able to match cellular activities to growth environment and nutrient availability. Key to this process is the development of membrane-bound systems that can detect modifications in the extracellular environment and to translate these into biological responses. Evidence gathered over the last 15 years has demonstrated that many of these cell surface "sensors" belong to the G protein-coupled receptor superfamily. Crucial to our understanding of nutrient sensing in mammalian species has been the identification of the extracellular Ca(2+)/cation-sensing receptor, CaR. CaR was the first ion-sensing molecule identified in man and genetic studies in humans have revealed the importance of the CaR in mineral ion metabolism. Latter, it has become apparent that the CaR also plays an important role outside the Ca(2+) homeostatic system, as an integrator of multiple environmental signals for the regulation of many vital cellular processes, from cell-to-cell communication to secretion and cell survival/cell death. Recently, novel aspects of receptor function reveal an unexpected role for the CaR in the regulation of growth and development in utero.

Effects of dietary polyamines at physiologic doses in early-weaned piglets

OBJECTIVE

Polyamines are essential for many cell functions, and they form part of the composition of maternal milk; despite this, their addition to infant formulas is currently under evaluation. The aim of the present study was to evaluate the effects of milk formulas designed to resemble sow milk supplemented with polyamines at maternal physiologic milk doses on the gut maturation of early-weaned piglets.

METHODS

We fed 30 newborn piglets with maternal milk (n=10), a control milk formula (n=10), or a milk formula supplemented with polyamines (5 nmol/mL of spermine and 20 nmol/mL of spermidine, n=10) for 13 d (day 2 after birth through day 15). Several growth and intestinal development parameters were measured.

RESULTS

The piglets fed the formula containing polyamine at physiologic doses showed significantly increased crypt depth in the small intestine compared with those fed with the control formula. Villus length was correlated to crypt depth. Although there were no differences in the disaccharidase activities between the animals fed the two formulas, alkaline phosphatase and gamma-glutamyl transferase activities tended to be higher in the jejunum of those fed the polyamine-supplemented diet. Dietary polyamines did not significantly modify the gut mucosal concentrations of putrescine, spermine, or spermidine.

CONCLUSION

Milk formulas supplemented with polyamines at maternal milk physiologic doses slightly enhanced gut growth and maturation in neonatal piglets.

Characterization of alpha,alpha-trehalase released in the intestinal lumen by the probiotic Saccharomyces boulardii

OBJECTIVE

Trehalose intolerance due to alpha,alpha-trehalase deficiency has scarcely been studied. The purpose of this study was to measure alpha,alpha-trehalase activity in intestinal biopsy samples from 200 consecutive patients over a period of 6 months, and to characterize alpha,alpha-trehalase released by the probiotic Saccharomyces boulardii (S. boulardii).

MATERIAL AND METHODS

Enzyme activities were measured in human and rat intestinal mucosal samples using the micromethod of Messer & Dalqvist. alpha,alpha-trehalase from S. boulardii was immunoprecipitated and Western blotted using an IgG purified antibody raised against a 23 amino acid peptide of alpha,alpha-trehalase of S. cerevisiae.

RESULTS

Among 200 patients, most of whom complained of abdominal symptoms and diarrhoea, 18 (9%) had total alpha,alpha-trehalase deficiency (0-12 U/g mucosa) and 39 had partial deficiency (3-12 U/g mucosa). Only 4 patients (2%) presented selective alpha,alpha-trehalase deficiency with otherwise normal disaccharidases. Expressed per gram of powder, alpha,alpha-trehalase from S. boulardii delivered in vitro an activity 175 times higher than that of human trehalase per gram of intestinal mucosa. V(max) (22+/-0.43 micromol) and K(m) (5 mM) were close to that of the human enzyme, whereas Western blot revealed a signal of two subunits of 82 kDa. Finally, treatment of rats with S. boulardii resulted in increases in alpha,alpha-trehalase activities of 25 to 45% (p<0.01) in endoluminal fluid and intestinal mucosa compared with in controls.

CONCLUSIONS

Our data suggest that alpha,alpha-trehalase deficiency is more common than is believed and that oral administration of S. boulardii could be beneficial in patients with digestive symptoms caused by trehalose intolerance.

Polyamines and the intestinal tract

Owing to their high turnover, the intestinal mucosal cells have a particularly high requirement for polyamines. Therefore, they are an excellent charcol for the study of polyamine function in rapid physiological growth and differentiation. After a cursory introduction to the major aspects of polyamine metabolism, regulation, and mode of action, we discuss the contribution of the polyamines to the maintenance of normal gut function, the maturation of the intestinal mucosa, and its repair after injuries. Repletion of cellular polyamine pools with (D,L)-2-(difluoromethyl)ornithine has considerably improved our understanding of how the polyamines are involved in the regulation of normal and neoplastic growth. Unfortunately, the attempts to exploit polyamine metabolism as a cancer therapeutic target have not yet been successful. However, the selective inactivation of ornithine decarboxylase appears to be a promising chemopreventive method in familial adenomatous polyposis. Presumably, it relies on the fact that ornithine decarboxylase is a critical regulator of the proliferative response of the protooncogene c-myc, but not of its apoptotic response.

LKM512 yogurt consumption improves the intestinal environment and induces the T-helper type 1 cytokine in adult patients with intractable atopic dermatitis

BACKGROUND

In atopic dermatitis (AD) patients, the intestinal mucosal barrier function is weakened, permiting frequent invasion by antigens. Polyamines and short-chain fatty acids (SCFA) produced by intestinal bacteria are involved in the promotion of intestinal mucosal barrier functions.

AIM

Our aim was to investigate the effect of pro-biotic yogurt containing Bifidobacterium animalis subsp. lactis LKM512 (LKM512 yogurt) on subjective symptoms, intestinal microbiota, intestinal bacterial metabolites (polyamines and SCFA), and T-helper type 1 (Th1)/Th2 balance in intractable AD patients.

METHODS

In a double-blind, placebo-controlled, crossover study, LKM512 yogurt was given for 4 weeks to 10 adult AD patients who were diagnosed with moderate AD (four males and six females; average age, 22.1 years). The subjective symptoms were recorded after each intervention. The dynamics of fecal microbiota were analysed by the terminal-restriction fragment length polymorphism method. The effects of LKM512 yogurt on fecal polyamines, SCFA, and serum cytokines were evaluated.

RESULTS

Scores of itch and burning tended to improve to a greater extent by LKM512 yogurt consumption than by placebo consumption. LKM512 yogurt (P<0.005) and placebo consumption (P<0.05) significantly increased the serum IFN-gamma concentration by six- and threefold, respectively. Fecal microbiota was altered dynamically by LKM512 yogurt consumption, in particular, the bacterial species and phylotypes of Bifidobacterium, Clostridium cluster IV and subcluster XIVa were increased in number. In addition, fecal spermidine concentration was significantly (P<0.05) increased, while fecal butyrate also tended to be increased by LKM512 yogurt consumption.

CONCLUSION

We conclude that LKM512 yogurt consumption may be effective against intractable adult-type AD and this effect depends on the recovery of the intestinal mucosal barrier function and the induction of the Th1-type cytokine by polyamines and SCFA, particularly, butyrate, produced by the altered intestinal microbiota.

Comparison of fecal microbiota and polyamine concentration in adult patients with intractable atopic dermatitis and healthy adults

Fecal microbiota and polyamine concentration obtained from eleven intractable adult-type atopic dermatitis (AD) patients and thirteen healthy adults were compared. Fecal microbiota were analyzed using terminal-restriction fragment length polymorphism. The fecal microbiota of volunteers were divided into two clusters, A (n=16) and B (n=8), and the number of AD patients was found to be higher in Cluster B than Cluster A, suggesting that there are relationships between the obstinacy of intractable adult-type AD and intestinal microbiota in Cluster B. Fecal spermidine concentration in Cluster B were lower than that in Cluster A significantly (P<0.05). Fecal putrescine concentration in Cluster B also tended to be lower than that in Cluster A. Terminal-restriction fragment (T-RF) of 122 bp generated by digestion with Hha I, which were predicted as unknown bacteria, were detected characteristically in Cluster A. In contrast, T-RFs of 368/9 bp generated by digestion with Hha I, which were predicted as Enterobacteriaceae, were detected characteristically in Cluster B. These bacteria are closely associated with intestinal polyamine concentration. These findings raise the possibility that a low concentration of intestinal polyamines produced by intestinal microbiota is one of the important factors in the onset of intractable adult-type AD.

The relationship between microbiota and polyamine concentration in the human intestine: a pilot study

The fecal microbiota of 10 hospitalized elderly subjects and 14 healthy adults were analyzed by terminal-restriction fragment length polymorphism (T-RFLP) analysis using Hha I, Msp I, Hae III, and Alu I, as well as fecal polyamine (PA) concentration. The T-RFLP profiles of the fecal microbiota of the subjects were roughly divided into 2 clusters-I (9 out of 11 were derived from hospitalized elderly subjects) and II (12 out of 13 were derived from healthy adults). The average concentration of putrescine in Cluster II was 5.8 times higher than that of putrescine in Cluster I (P=0.0015). Using a phylogenetic assignment database for T-RFLP analysis of human colonic microbiota, the terminal-restriction fragments (T-RFs) characteristically detected in the case of subjects with high fecal PA concentration were predicted to be derived from bacterial species and phylotypes belonging to Clostridium subcluster XIVa, particularly including Clostridium xylanolyticum, Clostridium saccharolyticum, the uncultured human intestinal bacterium clone JW1H4 (a relative of Desulfotomaculum guttoideum), Roseburia intestinalis, the uncultured bacterium clone 41F10 (a relative of Eubacterium ramulus), Roseburia cecicola, Ruminococcus obeum and its relatives. From these results, we concluded that fecal microbiota may be linked with fecal PA concentration and that some bacterial species belonging to Clostridium subcluster XIVa may play a major role in the control of intestinal PA concentration in humans.

Oral polyamine administration modifies the ontogeny of hexose transporter gene expression in the postnatal rat intestine

Gastrointestinal mucosal polyamines influence enterocyte proliferation and differentiation during small intestinal maturation in the rat. Studies in postnatal rats have shown that ornithine decarboxylase (ODC) protein and mRNA peak before the maximal expression of brush-border membrane (BBM) sucrase-isomaltase (SI) and the sugar transporters sodium-dependent glucose transporter 1 (SGLT1) and glucose transporter 2 (GLUT2). This study was undertaken to test the hypothesis that the oral administration of spermidine in postnatal rats upregulates the expression of ODC, thereby enhancing the expression of SI and SGLT1 in the brush-border membrane as well as basolateral membrane-facilitative GLUT2 and Na(+)-K(+)-ATPase. Northern and Western blot analyses were performed with antibodies and cDNA probes specific for SI, SGLT1, GLUT2, alpha(1)- and beta(1)-subunits of Na(+)-K(+)-ATPase, and ODC. Postnatal rats fed 6 mumol spermidine daily for 3 days from days 7 to 9 were killed either on postnatal day 10 (Sp10) or day 13 following a 3-day washout period (Sp13). Sp10 rats showed a precocious increase in the abundance of mRNAs for SI, SGLT1, and GLUT2 and Na(+)-K(+)-ATPase activity and alpha(1)- and beta(1)-isoform gene expression compared with controls. ODC activity and protein and mRNA abundance were also increased in Sp10 animals. The increased expression of these genes was not sustained in Sp13 rats, suggesting that these effects were transient. Thus, 3 days of oral polyamine administration induces the precocious maturation of glucose transporters in the postnatal rat small intestine, which may be mediated by alterations in ODC expression.

Oral administration of spermine advances intestinal maturation in sucking piglets

The objective of this study was to investigate the effect of orally administered spermine at various doses on intestinal maturation in sucking piglets. Thirty-six 11-day-old sucking piglets were assigned randomly to one of six treatments to receive via a stomach tube 0, 0·1, 0·2, 0·3, 0·4, or 0·5 mmol spermine per kg live weight (LW) per day for 3 days. At day 14 of age, duodenum, jejunum and ileum were obtained for biochemical and morphological analysis. Increasing the dose of orally administered spermine increased intestinal weight (linear effect, P<0·01), mucosal weight (linear effect, P<0·05), and mucosal protein, DNA and RNA contents of the duodenum (linear effect, P≤0·01) and jejunum (linear effect, P<0·01). Elevating spermine doses also enhanced (linear effect, P≤0·02) the specific activities of maltase and sucrase but decreased (linear effect, P<0·01) lactase specific activity in the jejunum and duodenum. Furthermore, augmenting oral doses of spermine increased crypt depth and villus width but reduced villus height in the jejunum (linear effect, P<0·05) and duodenum (linear effect, P<0·01). For most measurements, the effects were observed at the oral spermine doses of 0·3 to 0·5 mmol/kg LW per day. Collectively, the results show that oral administration of optimal doses of spermine to 11-day-old sucking piglets induces precocious intestinal maturation and promotes intestinal growth.

Inulin, oligofructose and mineral metabolism — experimental data and mechanism

Numerous investigations performed in animal models in the past 10 years have shown repeatedly that non-digestible oligosaccharides (NDO), such as inulin, oligofructose or transgalacto-oligosaccharides (TOS), stimulate mineral absorption, mainly calcium and magnesium. Long-term beneficial effects on bone health have been indicated by accumulation of bone mineral content in growing rats or prevention of bone loss in ovariectomized rats. However, bone mineral content or density are not necessarily associated with bone quality. In recent studies both oligofructose and calcium prevented loss of trabecular bone area induced by oestrogen deficiency, this, however, occurred at different trabecular shapes. The effects of NDO on mineral metabolism may be based on the enhancement of passive and active mineral transport across the intestinal epithelium, mediated by an increase in certain metabolites of the intestinal flora and a reduction of pH. The possible impact of short-chain fatty acids, butyrate in particular, and of polyamines on the stimulation of mineral absorption capacity, and the interaction of oligofructose and antibiotics is discussed.

Effects of Saccharomyces boulardii on intestinal mucosa

Saccharomyces boulardii (S. boulardii) is a non-pathogenic biotherapeutic agent, widely prescribed in a lyophilized form in many countries over the world. S. boulardii acts as a shuttle liberating effective enzymes, proteins and trophic factors during its intestinal transit that improve host immune defenses, digestion, and absorption of nutrients. In addition, S. boulardii secretes during its intestinal transit polyamines, mainly spermine and spermidine that regulate gene expression and protein synthesis. In this review, we will focus on the interactions of the yeast with the host intestinal mucosa.

Saccharomyces boulardii produces in rat small intestine a novel protein phosphatase that inhibits Escherichia coli endotoxin by dephosphorylation

Using a polyclonal antibody raised against a highly conserved sequence of 38 amino acids containing the activation site (VTDSAAGAT) common to mammalian and yeast alkaline phosphatases (AP), we identified in decapsidated Saccharomyces boulardii a protein phosphatase detected by autoradiography as a single signal (63 kD). Using an affinity chromatography column, the protein phosphatase could be concentrated 39.1-fold and presented as a doublet of two subunits. Compared with rat and bovine purified intestinal AP, the enzyme from S. boulardii had a greater ability to dephosphorylate the lipopolysaccharide (LPS) of Escherichia coli 055B5. When tested in vivo, intraperitoneal injection of intact LPS to rats produced, after 9 h, 100 ng/mL of circulating tumor necrosis factor-alpha with inflammatory lesions and apoptotic bodies in the liver and the heart, whereas rats injected with partially dephosphorylated LPS produced only 40 ng/mL tumor necrosis factor-alpha without organic lesions. In conclusion, S. boulardii is able to inhibit toxicity of E. coli surface endotoxins by the release of a protein phosphatase exhibiting a great capacity of dephosphorylation.

Role of calcium and other trace elements in the gastrointestinal physiology

Calcium is an essential ion in both marine and terrestrial organisms, where it plays a crucial role in processes ranging from the formation and maintenance of the skeleton to the regulation of neuronal function. The Ca²⁺ balance is maintained by three organ systems, including the gastrointestinal tract, bone and kidney.

Since first being cloned in 1993 the Ca²⁺-sensing receptor has been expressed along the entire gastrointestinal tract, until now the exact function is only partly elucidated. As of this date it still remains to be determined if the Ca²⁺-sensing receptor is involved in calcium handling by the gastrointestinal tract. However, there are few studies showing physiological effects of the Ca²⁺-sensing receptor on gastric acid secretion and fluid transport in the colon. In addition, polyamines and amino acids have been shown to activate the Ca²⁺-sensing receptor and also act as allosteric modifiers to signal nutrient availability to intestinal epithelial cells. Activation of the colonic Ca²⁺-sensing receptor can abrogate cyclic nucleotide-mediated fluid secretion suggesting a role of the receptor in modifying secretory diarrheas like cholera. For many cell types changes in extracellular Ca²⁺ concentration can switch the cellular behavior from proliferation to terminal differentiation or quiescence. As cancer remains predominantly a disease of disordered balance between proliferation, termination and apoptosis, disruption in the function of the Ca²⁺-sensing receptor may contribute to the progression of neoplastic disease. Loss of the growth suppressing effects of elevated extracellular Ca²⁺ have been demonstrated in colon carcinoma, and have been correlated with changes in the level of CaSR expression.

Intestinal effects of long-lasting spermine ingestion by suckling rats

Spermine ingestion induces the precocious maturation of the small intestine in suckling rats. Previous observations suggest that spermine-induced intestinal maturation is a two-step phenomenon. The first step is the elimination of immature enterocytes (4-10 h post spermine ingestion) and the second step is the replacement of previous immature cells by adult-type enterocytes (2-3 days post initial spermine administration). The spermine-induced maturation is reversible when spermine administration is stopped. This work was undertaken in order to check whether the extension of polyamine administration (for 3-7 days) after the appearance of spermine-induced maturation can retain the mature state of the small intestine. Our results indicate that extension of spermine administration does not prevent some parameters (sucrase and maltase specific activities) reverting to a typical 'immature' value while others remain at a typical 'mature' level (mucosal weight and lactase specific activity). Our results show that there are at least two different mechanisms in required for the control of spermine-induced maturation of the small intestine.

Modulation of intestinal urea cycle by dietary spermine in suckling rat

Argininosuccinate synthetase, an ubiquitous enzyme in mammals, catalyses the formation of argininosuccinate, the precursor of arginine. Arginine is recognised as an essential amino acid in foetuses and neonates, but also as a conditionally essential amino acid in adults. Argininosuccinate synthetase is initially expressed in enterocytes during the developmental period, it disappeared from this organ then appeared in the kidneys. Although the importance of both intestinal and renal argininosuccinate synthetases has been recognised for a long time, nutrients have not yet been identified as inducers of the gene expression. In the context of a proteomic screening of intestinal modifications induced by dietary spermine in suckling rats, we showed that argininosuccinate synthetase and carbamoyl phosphate synthase disappeared from enterocytes after this treatment. The disappearance of argininosuccinate synthetase in small intestine was confirmed by immunodetection. Expression of carbamoyl phosphate synthase and argininosuccinate synthetase coding genes decreased also after spermine administration. Expression of other urea cycle enzyme coding genes was modulated by spermine administration: argininosuccinate lyase decreased and arginase increased. Our results fit with the developmental variation of argininosuccinate synthetase and carbamoyl phosphate synthase. Modulation of the gene expression for several urea cycle enzymes suggests a coordination between all the pathway steps and switch toward polyamine (or proline and glutamate) biosynthesis from ornithine.

Enhancement of lysozyme stability and activity by polyamines

Spermine, a low molecular weight polyamine, administered orally to suckling rats induces the maturation of the small intestine. In this organ, lysozyme is an important component of the innate immunity. In this report, we analysed the binding of spermine to lysozyme and its effect on thermal inactivation of the protein by spectroscopy techniques. The activity of the enzyme was analysed in presence of spermine by lysoplate technique. We studied the effects of spermine ingestion by suckling rats on intestinal lysozyme activity and gene expression. We reported that spermine binds to lysozyme and increases in vitro the thermal stability and the activity of the protein. When administered orally to suckling rats, spermine increases the lysozyme activity in jejunum, but not in ileum. This increase is not due to a modification of the gene expression. The observed effects lead us to postulate that spermine could be used in some mammals as a promoter of the innate immunity.

Differential effect of dietary spermine on alkaline phosphatase activity in jejunum and ileum of unweaned rats

Spermine is a low molecular weight polyamine involved in the postnatal maturation of the gut. When it is administered orally to suckling rats it induces the maturation of their spleen, liver, pancreas, and small intestine. We showed that this polyamine modulates differently the activity of alkaline phosphatase in jejunum and ileum in suckling rat. In 14-day-old rat which had received spermine orally for 3 days, once daily, an increase of alkaline phosphatase activity in the jejunum and a decrease of this activity in the ileum was observed. Alkaline phosphatase was located at the bottom of the villus in the control jejunum and in the whole length of the villus in spermine-treated rats. On the contrary, in ileum of controls, this enzyme was present in the whole length of the villus but disappeared in the spermine-treated animals. An enzyme mass shift was observed in the small intestine after spermine administration. Spermine administration did not change the expression of genes coding for alkaline phosphatase, suggesting a post-transcriptional modification.