Vitamin K1 (Phylloquinone) or Vitamin K2 (Menaquinone-4) Induces Intestinal Alkaline Phosphatase Gene Expression

Effect of Menaquinone-4 on Receptor Activator of Nuclear Factor κB Ligand-Induced Osteoclast Differentiation and Ovariectomy-Induced Bone Loss

Osteoporosis is a progressive metabolic disease characterized by decreased bone mineral density and increased fracture risk. Previous studies have shown that higher intake of vitamin K (VK) correlates with a reduced risk of osteoporosis. However, the effect of menaquinone-4 (MK-4), a specific form of VK, still remains obscure. Therefore, in this study, we investigated the effects of MK-4 on osteoclast differentiation by differentiating RAW 264.7 cells into osteoclasts with the help of receptor activator of nuclear factor-kappa B ligand (RANKL), assessed the mRNA expression of osteoclast-specific genes, and studied the effects of MK-4 in vivo in ovariectomized mice, a postmenopausal osteoporosis murine model. MK-4 inhibited osteoclast differentiation, decreased the mRNA expression of nuclear factor of activated T cells c1 (NFATc1), osteoclast-associated receptor (OSCAR), and cathepsin K (CTSK), and inhibited bone loss in ovariectomized mice. The findings strongly suggest that MK-4 is a therapeutic alternative for postmenopausal osteoporosis.

Characterization and Structure of Alternatively Spliced Transcript Variant of Human Intestinal Alkaline Phosphatase (ALPI) Gene

Intestinal-type alkaline phosphatase (IAP) is expressed at a high concentration in the brush border membrane of intestinal epithelial cells and is known to be a gut mucosal defense factor. In humans, a single gene (ALPI) for IAP has been isolated, and its transcription produces two kinds of alternatively spliced mRNAs (aAug10 and bAug10). Recently, we discovered that vitamin D up-regulated the expression of both types of human IAP alternative splicing variants in Caco-2 cells. However, the functional difference of protein encoded by the mRNA variants has remained elusive. In the present study, we aimed to provide further insight into the characterization and structure of IAP isoforms. To analyze the protein translated from the ALPI gene, we constructed two kinds of cDNA expression plasmids (aAug10 and bAug10), and the transfected cells were homogenized and assayed for alkaline phosphatase (ALP) activity. We also designed the homology-modeled 3D structures of the protein encoded by the mRNA variants (ALPI-aAug10 and ALPI-bAug10). The levels of ALP activity of COS-1 cells transfected with the aAug10 plasmid were increased significantly, while cells transfected with the bAug10 plasmid had undetectable ALP activity. The homology-modeled 3D structures revealed that the variant bAug10 lacks the central N-terminal α-helix and residue corresponding to Asp-42 of ALPI-aAug10 near the active site. This is the first report on the characterization and structure of alternatively spliced transcript variants of the human ALPI gene. Further studies on the regulation of aAug10 and/or bAug10 mRNA expression may identify novel physiological functions of IAP.

Dietary vitamin K3 activates mitophagy, improves antioxidant capacity, immunity and affects glucose metabolism in Litopenaeus vannamei

An 8-week feeding experiment was conducted to appraise the influence of dietary vitamin K₃ on the growth performance, antioxidant capacities, immune responses, mitophagy and glucose metabolism in Litopenaeus vannamei. Six diets containing graded dietary vitamin K₃ (0.40(control), 9.97, 20.29, 39.06, 79.81 and 156.02 mg kg^-1 of vitamin K₃, respectively) levels were formulated. A total of 900 shrimp with 0.90 g initial weight were randomly assigned to six diets with three replications. Our results revealed that diets supplemented with 9.97-156.02 mg kg^-1 vitamin K₃ didn't affect the growth performance in L. vannamei. In general, compared with the control group, 39.06 mg kg^-1 vitamin K₃ group significantly increased (P < 0.05) the total antioxidative capacity, and the activities of catalase, glutathione, nitric oxide synthase, alkaline phosphatase and acid phosphatase in serum and hepatopancreas. 39.06 mg kg^-1 vitamin K₃ group significantly decreased (P < 0.05) the malondialdehyde in serum and hepatopancreas. The mRNA levels of antioxidant and immune related genes were increased synchronously (P < 0.05). In addition, 39.06 mg kg^-1 vitamin K₃ group increased glycogen content and levels of mitophagy (pink1, ampkα, parkin, lc3, atg13, atg12) genes. Expression levels of glucose transport related gene (glut1), glycolysis related genes (hk, pfk), glycogen synthesis related genes (gsk-3β, gys), insulin-like peptides (ILPs)/AKT/PI3K pathway related genes (insr, irsl, akt, pi3k, pdpk1) were increased in the hepatopancreas of 39.06 mg kg^-1 vitamin K₃ group. In conclusion, the present results indicated that although dietary supplementing vitamin K₃ had no influence on the growth performance, 39.06 mg kg^-1 vitamin K₃ could activate ampkα/pink1/parkin mediated mitophagy, improve antioxidant capacity and immune response. Moreover, vitamin K₃ could trigger ILPs/AKT/PI3K signaling pathways and influence glucose metabolism in L. vannamei. This finding would help to advance the field of vitamin K₃ nutrition and guide the development of future crustacean feeds.

Role of Vitamin K in Intestinal Health

Intestinal diseases, such as inflammatory bowel diseases (IBDs) and colorectal cancer (CRC) generally characterized by clinical symptoms, including malabsorption, intestinal dysfunction, injury, and microbiome imbalance, as well as certain secondary intestinal disease complications, continue to be serious public health problems worldwide. The role of vitamin K (VK) on intestinal health has drawn growing interest in recent years. In addition to its role in blood coagulation and bone health, several investigations continue to explore the role of VK as an emerging novel biological compound with the potential function of improving intestinal health. This study aims to present a thorough review on the bacterial sources, intestinal absorption, uptake of VK, and VK deficiency in patients with intestinal diseases, with emphasis on the effect of VK supplementation on immunity, anti-inflammation, intestinal microbes and its metabolites, antioxidation, and coagulation, and promoting epithelial development. Besides, VK-dependent proteins (VKDPs) are another crucial mechanism for VK to exert a gastroprotection role for their functions of anti-inflammation, immunomodulation, and anti-tumorigenesis. In summary, published studies preliminarily show that VK presents a beneficial effect on intestinal health and may be used as a therapeutic drug to prevent/treat intestinal diseases, but the specific mechanism of VK in intestinal health has yet to be elucidated.

Intestinal alkaline phosphatase modulation by food components: predictive, preventive, and personalized strategies for novel treatment options in chronic kidney disease

Alkaline phosphatase (AP) is a ubiquitous membrane-bound glycoprotein that catalyzes phosphate monoesters' hydrolysis from organic compounds, an essential process in cell signaling. Four AP isozymes have been described in humans, placental AP, germ cell AP, tissue nonspecific AP, and intestinal AP (IAP). IAP plays a crucial role in gut microbial homeostasis, nutrient uptake, and local and systemic inflammation, and its dysfunction is associated with persistent inflammatory disorders. AP is a strong predictor of mortality in the general population and patients with cardiovascular and chronic kidney disease (CKD). However, little is known about IAP modulation and its possible consequences in CKD, a disease characterized by gut microbiota imbalance and persistent low-grade inflammation. Mitigating inflammation and dysbiosis can prevent cardiovascular complications in patients with CKD, and monitoring factors such as IAP can be useful for predicting those complications. Here, we review IAP's role and the results of nutritional interventions targeting IAP in experimental models to prevent alterations in the gut microbiota, which could be a possible target of predictive, preventive, personalized medicine (PPPM) to avoid CKD complications. Microbiota and some nutrients may activate IAP, which seems to have a beneficial impact on health; however, data on CKD remains scarce.

Consumption of non-digestible oligosaccharides elevates colonic alkaline phosphatase activity by up-regulating the expression of IAP-I, with increased mucins and microbial fermentation in rats fed a high-fat diet

We have recently reported that soluble dietary fibre, glucomannan, increased colonic alkaline phosphatase (ALP) activity and the gene expression without affecting the small-intestinal activity and that colonic ALP was correlated with gut mucins (index of intestinal barrier function). We speculated that dietary fermentable carbohydrates including oligosaccharides commonly elevate colonic ALP and gene expression as well as increase mucin secretion and microbial fermentation. To test this hypothesis, male Sprague-Dawley rats were fed a diet containing 30 % lard with or without 4 % fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), raffinose (RAF) and lactulose (LAC), which are non-digestible oligosaccharides or isomalto-oligosaccharides (IMOS; some digestible oligosaccharides) for 2 weeks. Colon ALP activity, the gene expression and gut luminal variables including mucins, organic acids and microbiota were measured. Colonic ALP was significantly elevated in the FOS, RAF and LAC groups, and a similar trend was observed in the GOS group. Colonic expression of intestinal alkaline phosphatase (IAP -I), an ALP gene, was significantly elevated in the FOS, GOS and RAF groups and tended to be increased in the LAC group. Dietary FOS, GOS, RAF and LAC significantly elevated faecal mucins, caecal n-butyrate and faecal ratio of Bifidobacterium spp. Dietary IMOS had no effect on colonic ALP, mucins, organic acids and microbiota. Colon ALP was correlated with mucins, caecal n-butyrate and faecal Bifidobacterium spp. This study demonstrated that non-digestible and fermentable oligosaccharides commonly elevate colonic ALP activity and the expression of IAP-I, with increasing mucins and microbial fermentation, which might be important for protection of gut epithelial homoeostasis.

Intestinal alkaline phosphatase deficiency leads to lipopolysaccharide desensitization and faster weight gain

Animals develop in the presence of complex microbial communities, and early host responses to these microbes can influence key aspects of development, such as maturation of the immune system, in ways that impact adult physiology. We previously showed that the zebrafish intestinal alkaline phosphatase (ALPI) gene alpi.1 was induced by Gram-negative bacterium-derived lipopolysaccharide (LPS), a process dependent on myeloid differentiation primary response gene 88 (MYD88), and functioned to detoxify LPS and prevent excessive host inflammatory responses to commensal microbiota in the newly colonized intestine. In the present study, we examined whether the regulation and function of ALPI were conserved in mammals. We found that among the mouse ALPI genes, Akp3 was specifically upregulated by the microbiota, but through a mechanism independent of LPS or MYD88. We showed that disruption of Akp3 did not significantly affect intestinal inflammatory responses to commensal microbiota or animal susceptibility to Yersinia pseudotuberculosis infection. However, we found that Akp3(-/-) mice acquired LPS tolerance during postweaning development, suggesting that Akp3 plays an important role in immune education. Finally, we demonstrated that inhibiting LPS sensing with a mutation in CD14 abrogated the accelerated weight gain in Akp3(-/-) mice receiving a high-fat diet, suggesting that the weight gain is caused by excessive LPS in Akp3(-/-) mice.

Peyer's patches and mesenteric lymph nodes cooperatively promote enteropathy in a mouse model of food allergy

Background and Objective

To improve the efficacy and safety of tolerance induction for food allergies, identifying the tissues responsible for inducing intestinal inflammation and subsequent oral tolerance is important. We used OVA23-3 mice, which express an ovalbumin-specific T-cell receptor, to elucidate the roles of local and systemic immune tissues in intestinal inflammation.

Methods and Results

OVA23-3 mice developed marked enteropathy after consuming a diet containing egg white (EW diet) for 10 days but overcame the enteropathy (despite continued moderate inflammation) after receiving EW diet for a total of 28 days. Injecting mice with anti-IL-4 antibody or cyclosporine A confirmed the involvement of Th2 cells in the development of the enteropathy. To assess the individual contributions of Peyer’s patches (PPs), mesenteric lymph nodes (MLNs), and the spleen to the generation of effector CD4⁺ T-cells, we analyzed the IL-4 production, proliferation in response to ovalbumin, and CD4⁺ T-cell numbers of these tissues. EW feeding for 10 days induced significant IL-4 production in PPs, the infiltration of numerous CD4⁺ T-cells into MLNs, and a decrease in CD4⁺ T-cell numbers in spleen. On day 28, CD4⁺ T-cells from all tissues had attenuated responses to ovalbumin, suggesting tolerance acquisition, although MLN CD4⁺ T-cells still maintained IL-4 production with proliferation. In addition, removal of MLNs but not the spleen decreased the severity of enteropathy and PP-disrupted mice showed delayed onset of EW-induced inflammatory responses. Disruption of peripheral lymphoid tissues or of both PPs and MLNs almost completely prevented the enteropathy.

Conclusions

PPs and MLNs coordinately promote enteropathy by generating effector T-cells during the initial and exacerbated phases, respectively; the spleen is dispensable for enteropathy and shows tolerogenic responses throughout EW-feeding. The regulation of PPs may suppress the initiation of intestinal inflammation, subsequently restricting MLNs and inhibiting the progression of food-allergic enteropathy.