Role Of Intestinal Alkaline Phosphatase Research Articles

Necrotizing enterocolitis: a potential protective role for intestinal alkaline phosphatase as lipopolysaccharide detoxifying enzyme.

Necrotizing enterocolitis (NEC) is a life-threatening inflammatory disease. Its onset might be triggered by Toll-Like Receptor 4 (TLR4) activation via bacterial lipopolysaccharide (LPS). We hypothesize that a deficiency of intestinal alkaline phosphatase (IAP), an enzyme secreted by enterocytes that dephosphorylates LPS, may contribute to NEC development. In this prospective pilot study, we analyzed intestinal resection specimens from surgical NEC patients, and from patients undergoing Roux-Y reconstruction for hepatobiliary disease as controls. We assessed IAP activity via enzymatic stainings and assays and explored IAP and TLR4 co-localization through immunofluorescence. The study population consisted of five NEC patients (two Bell's stage IIb and three-stage IIIb, median (IQR) gestational age 25 (24-28) weeks, postmenstrual age at diagnosis 28 (26-31) weeks) and 11 controls (unknown age). There was significantly lower IAP staining in NEC resection specimens [49 (41-50) U/g of protein] compared to controls [115 (76-144), P = 0.03]. LPS-dephosphorylating activity was also lower in NEC patients [0.06 (0-0.1)] than in controls [0.3 (0.2-0.5), P = 0.003]. Furthermore, we observed colocalization of IAP and TLR4 in NEC resection specimens. This study suggests a significantly lower IAP level in resection specimens of NEC patients compared to controls. This lower IAP activity suggests a potential role of IAP as a protective agent in the gut, which needs further confirmation in larger cohorts.

The role of intestinal alkaline phosphatase in the development of obesity. Modulation of enzyme activity by high fat diet and dietary fiber

Interest to the tissue-specific intestinal isoenzyme of alkaline phosphatase (IAP) has increased in recent years due to eating disorders that have led to widespread obesity and diet-related diseases. Obesity is considered as an inflammation of low intensity, which is accompanied by the manifestation of various metabolic complications and a disturbance of intestinal homeostasis. IAP is one of the participants in the mechanism of the macroorganism protection against inflammatory and infectious processes, carrying out enzymatic detoxification of bacterial lipopolysaccharide (the trigger of the inflammatory process). Deficiency of IAP activity contributes to the risk of obesity, inflammatory diseases. The objective of the research was to summarize the current understanding of the role of IAP involved in the molecular mechanism of diet-induced obesity and to evaluate the impact of dietary components - fats and dietary fiber on IAP activity. Material and methods. A literature search on the role of IAP in the development of obesity was carried out using PubMed, Scopus, Web of Science, Google Scholar, ResearchGate, RSCI databases. Results. IAP prevents the development of the inflammatory process by participating in the detoxification of toxic bacterial products, limiting the translocation of pathogenic bacteria from the intestine to various tissues and organs of the macroorganism. The enzyme maintains the integrity of the intestinal barrier, influencing the synthesis and proper localization of tight junction's proteins between intestinal epithelial cells, promotes changes in the composition of the microbiota, decreasing pathogenic bacteria and increasing the population of the community of beneficial microorganisms. IAP is involved in the regulation of fatty acid absorption and influences on the adipogenesis. Monitoring the activity of IAP present in human stool can predict the early development of such complications associated with obesity as metabolic syndrome and diabetes mellitus, Some nutrients modulate IAP activity. Depending on the amount, type, composition of fats and the duration of their consumption, either an increase or decrease in the IAP activity are observed, while dietary fibers stimulate the activity of the enzyme. Conclusion. IAP activity can be considered as an early predictor of the risk of obesity. Deficiency of IAP activity contributes to the development of obesity caused by high-fat diet. The high activity of the enzyme contributes to the support of intestinal homeostasis and limits transepithelial movement of bacteria, weakening the inflammatory process induced by lipopolysaccharides, the excess concentration of which is detected in obesity. Stimulating enzyme activity through dietary intervention reduces the risk of obesity and metabolic complications.

Role of Intestinal Alkaline Phosphatase in Innate Immunity.

Intestinal alkaline phosphatase (IAP) is a multi-functional protein that has been demonstrated to primarily protect the gut. The role of IAP in maintaining intestinal homeostasis is underscored by the observation that IAP expression is defective in many gastrointestinal-related disorders such as inflammatory bowel disease IBD, necrotizing enterocolitis, and metabolic syndrome and that exogenous IAP supplementation improves the outcomes associated with these disorders. Additionally, studies using transgenic IAP-knock out (IAP-KO) mouse models further support the importance of the defensive role of IAP in the intestine. Supplementation of exogenous IAP and cellular overexpression of IAP have also been used in vitro to dissect out the downstream mechanisms of this protein in mammalian cell lines. Some of the innate immune functions of IAP include lipopolysaccharide (LPS) detoxification, protection of gut barrier integrity, regulation of gut microbial communities and its anti-inflammatory roles. A novel function of IAP recently identified is the induction of autophagy. Due to its critical role in the gut physiology and its excellent safety profile, IAP has been used in phase 2a clinical trials for treating conditions such as sepsis-associated acute kidney injury. Many excellent reviews discuss the role of IAP in physiology and pathophysiology and here we extend these to include recent updates on this important host defense protein and discuss its role in innate immunity via its effects on bacteria as well as on host cells. We will also discuss the relationship between IAP and autophagy and how these two pathways may act in concert to protect the gut.

A role for intestinal alkaline phosphatase in preventing liver fibrosis.

Rationale: Liver fibrosis is frequently associated with gut barrier dysfunction, and the lipopolysaccharides (LPS) -TLR4 pathway is common to the development of both. Intestinal alkaline phosphatase (IAP) has the ability to detoxify LPS, as well as maintain intestinal tight junction proteins and gut barrier integrity. Therefore, we hypothesized that IAP may function as a novel therapy to prevent liver fibrosis.Methods: Stool IAP activity from cirrhotic patients were determined. Common bile duct ligation (CBDL) and Carbon Tetrachloride-4 (CCl4)-induced liver fibrosis models were used in WT, IAP knockout (KO), and TLR4 KO mice supplemented with or without exogenous IAP in their drinking water. The gut barrier function and liver fibrosis markers were tested.Results: Human stool IAP activity was decreased in the setting of liver cirrhosis. In mice, IAP activity and genes expression decreased after CBDL and CCl4 exposure. Intestinal tight junction related genes and gut barrier function were impaired in both models of liver fibrosis. Oral IAP supplementation attenuated the decrease in small intestine tight junction protein gene expression and gut barrier function. Liver fibrosis markers were significantly higher in IAP KO compared to WT mice in both models, while oral IAP rescued liver fibrosis in both WT and IAP KO mice. In contrast, IAP supplementation did not attenuate fibrosis in TLR4 KO mice in either model.Conclusions: Endogenous IAP is decreased during liver fibrosis, perhaps contributing to the gut barrier dysfunction and worsening fibrosis. Oral IAP protects the gut barrier and further prevents the development of liver fibrosis via a TLR4-mediated mechanism.

Role of intestinal alkaline phosphatase in intestinal mucosal barrier

Role of intestinal alkaline phosphatase in intestinal mucosal barrier

The effect of the branched-chain amino acids on the in-vitro activity of bovine intestinal alkaline phosphatase.

Branched-chain amino acids (BCAA) are used as nutritional support for patients with a range of conditions including liver cirrhosis and in-born errors of amino acid metabolism, and they are commonly used "sports" or exercise supplements. The effects of the BCAA on the in-vitro activity of calf intestinal alkaline phosphatase (EC. 3.1.3.1) were studied. All three BCAA were found to be uncompetitive inhibitors of the enzyme with L-leucine being the most potent ( = 24.9 mmol/L) and L-valine, the least potent ( = 37 mmol/L). Mixed BCAA are able to act in combination to inhibit the enzyme. Given the important role of intestinal alkaline phosphatase in gut homeostasis, these findings have potential implications for those taking high levels of BCAA as supplements.

A Role of Intestinal Alkaline Phosphatase 3 (Akp3) in Inorganic Phosphate Homeostasis

Background/Aims: Hyperphosphatemia is a serious complication of late-stage chronic kidney disease (CKD). Intestinal inorganic phosphate (Pi) handling plays an important role in Pi homeostasis in CKD. We investigated whether intestinal alkaline phosphatase 3 (Akp3), the enzyme that hydrolyzes dietary Pi compounds, is a target for the treatment of hyperphosphatemia in CKD. Methods: We investigated Pi homeostasis in Akp3 knockout mice (Akp3^-/-). We also studied the progression of renal failure in an Akp3^-/- mouse adenine treated renal failure model. Plasma, fecal, and urinary Pi and Ca concentration were measured with commercially available kit, and plasma fibroblast growth factor 23, parathyroid hormone, and 1,25(OH)₂D₃ concentration were measured with ELISA. Brush border membrane vesicles were prepared from mouse intestine using the Ca²⁺ precipitation method and used for Pi transport activity and alkaline phosphatase activity. In vivo intestinal Pi absorption was measured with oral ³²P administration. Results: Akp3^-/- mice exhibited reduced intestinal type II sodium-dependent Pi transporter (Npt2b) protein levels and Na-dependent Pi co-transport activity. In addition, plasma active vitamin D levels were significantly increased in Akp3^-/- mice compared with wild-type animals. In the adenine-induced renal failure model, Akp3 gene deletion suppressed hyperphosphatemia. Conclusion: The present findings indicate that intestinal Akp3 deletion affects Na⁺-dependent Pi transport in the small intestine. In the adenine-induced renal failure model, Akp3 is predicted to be a factor contributing to suppression of the plasma Pi concentration.

Role of intestinal alkaline phosphatase in calcium absorption

Bamboo vinegar, a natural liquid manufactured from bamboo, has been regarded as a potential antibiotic substitute in animal production. In this study, we evaluated the effects and mechanism of bamboo vinegar powder (BVP) on the antioxidant ability of pigs. A total of 40 Duroc × Landrace × Yorkshire healthy pigs (80.88 ± 0.82 kg) were selected and randomly allocated into 5 different groups: control group (CG, fed with basal diets); antibiotic group (AG, fed with antibiotic-supplemented diets); 0.5% BVP group (0.5% BVG, fed 0.5% BVP-supplemented diets); 1.0% BVP group (1.0% BVG, fed with 1.0% BVP-supplemented diets) and 1.5% BVP group (1.5% BVG, fed with 1.5% BVP-supplemented diets). With the BVP-supplemented diets, the activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in the blood increased (P < 0.05), the activities of GSH-Px and catalase (CAT) in the liver also increased (P < 0.05), the activity of total antioxidant capacity (T-AOC) increased both in the liver and blood (P < 0.05), but the activity of iNOS in the liver and blood decreased (P < 0.05). Moreover, the gene expressions of Nuclear related factor 2 (Nrf2), catalytic subunit of glutamate-cysteine ligase (GCLC), NAD(P)H quinone dehydrogenase 1(NQO1), heme oxygenase 1(HO1), Glutathione peroxidase (GSH-Px) and Catalase (CAT) in the liver were also increased due to the addition of BVP (P < 0.05). In conclusion, BVP supplementation improved the antioxidant ability of the liver in finishing pigs by increasing the activity of some antioxidant enzymes and decreasing the activity of oxidative stress enzymes. These changes may be due to the activation of the Nrf2-Are pathway.

The Role of Intestinal Alkaline Phosphatase in Inflammatory Disorders of Gastrointestinal Tract.

Over the past few years, the role of intestinal alkaline phosphatase (IAP) as a crucial mucosal defence factor essential for maintaining gut homeostasis has been established. IAP is an important apical brush border enzyme expressed throughout the gastrointestinal tract and secreted both into the intestinal lumen and into the bloodstream. IAP exerts its effects through dephosphorylation of proinflammatory molecules including lipopolysaccharide (LPS), flagellin, and adenosine triphosphate (ATP) released from cells during stressful events. Diminished activity of IAP could increase the risk of disease through changes in the microbiome, intestinal inflammation, and intestinal permeability. Exogenous IAP exerts a protective effect against intestinal and systemic inflammation in a variety of diseases and represents a potential therapeutic agent in diseases driven by gut barrier dysfunction such as IBD. The intestinal protective mechanisms are impaired in IBD patients due to lower synthesis and activity of endogenous IAP, but the pathomechanism of this enzyme deficiency remains unclear. IAP has been safely administered to humans and the human recombinant form of IAP has been developed. This review was designed to provide an update in recent research on the involvement of IAP in intestinal inflammatory processes with focus on IBD in experimental animal models and human patients.

Role of intestinal alkaline phosphatase in calcium absorption

Role of intestinal alkaline phosphatase in calcium absorption

Stop chronic kidney disease progression: Time is approaching

Progression of chronic kidney disease (CKD) is inevitable. However, the last decade has witnessed tremendous achievements in this field. Today we are optimistic; the dream of withholding this progression is about to be realistic. The recent discoveries in the field of CKD management involved most of the individual diseases leading the patients to end-stage renal disease. Most of these advances involved patients suffering diabetic kidney disease, chronic glomerulonephritis, polycystic kidney disease, renal amyloidosis and chronic tubulointerstitial disease. The chronic systemic inflammatory status and increased oxidative stress were also investigated. This inflammatory status influences the anti-senescence Klotho gene expression. The role of Klotho in CKD progression together with its therapeutic value are explored. The role of gut as a major source of inflammation, the pathogenesis of intestinal mucosal barrier damage, the role of intestinal alkaline phosphatase and the dietary and therapeutic implications add a novel therapeutic tool to delay CKD progression.

A novel approach to maintain gut mucosal integrity using an oral enzyme supplement.

To determine the role of intestinal alkaline phosphatase (IAP) in enteral starvation-induced gut barrier dysfunction and to study its therapeutic effect as a supplement to prevent gut-derived sepsis. Critically ill patients are at increased risk for systemic sepsis and, in some cases, multiorgan failure leading to death. Years ago, the gut was identified as a major source for this systemic sepsis syndrome. Previously, we have shown that IAP detoxifies bacterial toxins, prevents endotoxemia, and preserves intestinal microbiotal homeostasis. WT and IAP-KO mice were used to examine gut barrier function and tight junction protein levels during 48-hour starvation and fed states. Human ileal fluid samples were collected from 20 patients postileostomy and IAP levels were compared between fasted and fed states. To study the effect of IAP supplementation on starvation-induced gut barrier dysfunction, WT mice were fasted for 48 hours +/- IAP supplementation in the drinking water. The loss of IAP expression is associated with decreased expression of intestinal junctional proteins and impaired barrier function. For the first time, we demonstrate that IAP expression is also decreased in humans who are deprived of enteral feeding. Finally, our data demonstrate that IAP supplementation reverses the gut barrier dysfunction and tight junction protein losses due to a lack of enteral feeding. IAP is a major regulator of gut mucosal permeability and is able to ameliorate starvation-induced gut barrier dysfunction. Enteral IAP supplementation may represent a novel approach to maintain bowel integrity in critically ill patients.

Regulation of intestinal calcium absorption by luminal calcium content: role of intestinal alkaline phosphatase.

Intestinal alkaline phosphatase is a brush border enzyme that is stimulated by calcium. Inhibition of intestinal alkaline phosphatase increases intestinal calcium absorption. We hypothesized that intestinal alkaline phosphatase acts as a minute-to-minute regulatory mechanism of calcium entry. The aim of this study was to evaluate the mechanism by which intestinal luminal calcium controls intestinal calcium absorption. We performed kinetic studies with purified intestinal alkaline phosphatase and everted duodenal sacs and showed that intestinal alkaline phosphatase modifies the luminal pH as a function of enzyme concentration and calcium luminal content. A decrease in pH occurred simultaneously with a decrease in calcium absorption. The inhibition of intestinal alkaline phosphatase by l-phenylalanine caused an increase in calcium absorption. This effect was also confirmed in calcium uptake experiments with isolated duodenal cells. Changes in luminal pH arising from intestinal alkaline phosphatase activity induced by luminal calcium concentration modulate intestinal calcium absorption.

Luminal ATP: the missing link between intestinal alkaline phosphatase, the gut microbiota, and inflammation?

gut dysbiosis is a common feature to many inflammatory diseases but the cause-and-effect relationships between the gut microbiota and host inflammation are poorly understood. For metabolic disorders and obesity, however, bacterial lipopolysaccharide (LPS), an emblematic member of pathogen-associated

The role of intestinal alkaline phosphatase in pediatric inflammatory bowel and celiac diseases

Intestinal alkaline phosphatase enzyme plays a pivotal role in the maintenance of intestinal mucosal barrier integrity with the detoxification capacity of lipopolysaccharide, the ligand of Toll-like receptor 4. The inappropriate immune responses and the damage of the mucosal barrier may contribute to the initiation of inflammatory bowel and celiac diseases. In the inflamed colonic mucosa of children with inflammatory bowel disease and in the duodenal mucosa of newly diagnosed children with celiac disease, the decreased intestinal alkaline phosphatase and increased Toll-like receptor 4 protein expression may generate enhanced lipopolysaccharide activity, which may strengthen tissue damaging processes. The enhancement of intestinal alkaline phosphatase activity in an animal model of colitis and in therapy resistant, adult patients with ulcerative colitis reduced the symptoms of intestinal inflammation. In accordance with these results, the targeted intestinal administration of the enzyme in the two examined disorders may be a supplemental therapeutic option in the future.

Effect of fluoride on oxygen consumption (OC) by rat tissues

Effect of fluoride on oxygen consumption (OC) by rat tissues

Modulating effect of monofluorophosphate (MFP) on zoledronate (Z) action in ovariectomized rats (OVX)

Modulating effect of monofluorophosphate (MFP) on zoledronate (Z) action in ovariectomized rats (OVX)

Role of intestinal alkaline phosphatase (IAP) in calcium (Ca) absorption

Role of intestinal alkaline phosphatase (IAP) in calcium (Ca) absorption

A Role for Intestinal Alkaline Phosphatase in the Maintenance of Local Gut Immunity

Intestinal alkaline phosphatase (IAP) is a gut mucosal defense factor known to dephosphorylate lipopolysaccharide (LPS); however, the role of IAP in the gut response to luminal bacteria remains poorly defined. We investigated immune responses of wild-type (WT) and IAP-knockout (IAP-KO) mice to LPS and Salmonella typhimurium challenges. Cryostat sectioning and standard indirect immunohistochemical staining for major histocompatibility complex (MHC) class II molecules were performed on liver tissue from WT and IAP-KO mice. WT and IAP-KO mice were orally gavaged with S. typhimurium; bacterial translocation to mesenteric nodes, liver, and spleen was determined by tissue homogenization and plating. In other experiments, WT and IAP-KO mice received intraperitoneal injections of LPS, with subsequent quantification of complete blood counts and serum interleukin (IL)-6 by enzyme-linked immunosorbent assay (ELISA). WT and IAP-KO whole blood were plated and stimulated with LPS and Pam-3-Cys, followed by cytokine assays. Immunohistologic liver examinations showed increased expression of MHC class II molecules in IAP-KO mice. Following S. typhimurium challenge, WT mice appeared moribund compared with IAP-KO mice, with increased bacterial translocation. WT mice had >50% decrease (P<.005) in platelets and 1.8-fold (P<.05) increased serum IL-6 compared with IAP-KO mice in response to LPS injections. IAP-KO whole-blood stimulation with LPS and Pam-3-Cys resulted in increased IL-6 and tumor necrosis factor (TNF)-alpha secretion compared with WT. IAP-KO mice exhibit characteristics consistent with local LPS tolerance. Whole-blood response of IAP-KO mice did not reflect systemic tolerance. These data suggest that IAP is a local immunomodulating factor, perhaps regulating LPS-toll-like receptor 4 (TLR4) interaction between commensal microflora and intestinal epithelium.

The Protective Role of Intestinal Alkaline Phosphatase in Necrotizing Enterocolitis

Enterocytes produce intestinal alkaline phosphatase (iAP), which detoxifies lipopolysaccharide (LPS), a mediator in necrotizing enterocolitis (NEC) pathogenesis. We hypothesize that aberrant expression or function of iAP contributes to the pathogenesis of NEC. Newborn Sprague Dawley rat pups were divided into three main groups. Control pups were breast fed, while two groups were exposed to intermittent hypoxia, LPS, and formula feeding for 4 d to induce NEC. Bovine iAP, with and without the presence of LPS, was administered orally to one of the NEC groups. The intestine was harvested and used to detect alkaline phosphatase (AP) activity and protein expression. Terminal ileum sections were used to grade intestinal injury and stained for AP. Comparisons were made with adult rat duodenum. Compared with adult rats, control pups expressed significantly less AP protein but had 2-fold higher AP activity. NEC pup AP activity was significantly decreased compared to controls (P < or = 0.05), which paralleled both the AP protein expression and immunofluorescence assay results. Following iAP administration, immunofluorescence, protein expression, and activity of AP were significantly increased compared with NEC pups without iAP supplementation. All NEC pups had intestinal injury grades > or = 2 on a 4-point scale, while control and iAP-treated pups had grades < 0.25 (P < 0.001). Enteral administration of iAP to rat pups with experimental NEC increased AP activity levels to that of controls, and appears to protect the intestine. This opens up a new area of study in NEC pathophysiology as well as a potential novel treatment strategy to prevent the development of NEC.