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      Chronic calcitriol supplementation improves the inflammatory profiles of circulating monocytes and the associated intestinal/adipose tissue alteration in a diet-induced steatohepatitis rat model

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          Abstract

          Vitamin D deficiency and up-regulated TNFα-related signals are reported to be involved in abnormalities including intestinal hyper-permeability, bacterial translocation, systemic/portal endotoxemia, intestinal/adipose tissue/hepatic inflammation, and hepatic steatosis in nonalcoholic steatohepatitis (NASH). This study aims to explore the molecular mechanisms and effects of chronic calcitriol [1,25-(OH) 2D 3, hormonal form of vitamin D] on gut-adipose tissue-liver axis abnormalities using a high-fat diet (HFD)-fed rat model of NASH. In HFD-fed obese rats on a 10-week calcitriol (0.3 μg/kg/TIW) or vehicle treatment (NASH-vit. D and NASH-V rats) reigme, various in vivo and in vitro experiments were undertaken. Through anti-TNFα-TNFR1-NFκB signaling effects, chronic calcitriol treatment significantly restored plasma calcitriol levels and significantly improved vitamin D receptor (VDR) expression in monocytes and the small intestine of NASH-vit. D rats. Significantly, plasma and portal endotoxin/TNFα levels, bacterial translocation to mesenteric lymph nodes, plasma DX-4000-FITC, fecal albumin-assessed intestinal hyper-permeability, over-expression of TNFα-related immune profiles in monocytes, inflammation of intestinal/mesenteric adipose tissue (MAT)/liver and hepatic steatosis were improved by chronic calcitriol treatment of NASH rats. Additionally, in vitro experiments with acute calcitriol co-incubation reversed NASH-V rat monocyte supernatant/TNFα-induced monolayer barrier dysfunction in caco-2 cells, cytokine release from MAT-derived adipocytes, and triglyceride synthesis by lean-V rat hepatocytes. Using in vivo and in vitro experiments, our study reported calcitriol signaling in the gut as well as in adipose tissue. Meanwhile, our study suggests that restoration of systemic and intestinal vitamin D deficiency using by chronic vitamin D treatment effectively reduces TNFα-mediated immunological abnormalities associated with the gut-adipose tissue-liver axis and hepatic steatosis in NASH rats.

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          Most cited references36

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          Increased Gut Permeability and Microbiota Change Associate with Mesenteric Fat Inflammation and Metabolic Dysfunction in Diet-Induced Obese Mice

          We investigated the relationship between gut health, visceral fat dysfunction and metabolic disorders in diet-induced obesity. C57BL/6J mice were fed control or high saturated fat diet (HFD). Circulating glucose, insulin and inflammatory markers were measured. Proximal colon barrier function was assessed by measuring transepithelial resistance and mRNA expression of tight-junction proteins. Gut microbiota profile was determined by 16S rDNA pyrosequencing. Tumor necrosis factor (TNF)-α and interleukin (IL)-6 mRNA levels were measured in proximal colon, adipose tissue and liver using RT-qPCR. Adipose macrophage infiltration (F4/80+) was assessed using immunohistochemical staining. HFD mice had a higher insulin/glucose ratio (P = 0.020) and serum levels of serum amyloid A3 (131%; P = 0.008) but reduced circulating adiponectin (64%; P = 0.011). In proximal colon of HFD mice compared to mice fed the control diet, transepithelial resistance and mRNA expression of zona occludens 1 were reduced by 38% (P<0.001) and 40% (P = 0.025) respectively and TNF-α mRNA level was 6.6-fold higher (P = 0.037). HFD reduced Lactobacillus (75%; P<0.001) but increased Oscillibacter (279%; P = 0.004) in fecal microbiota. Correlations were found between abundances of Lactobacillus (r = 0.52; P = 0.013) and Oscillibacter (r = −0.55; P = 0.007) with transepithelial resistance of the proximal colon. HFD increased macrophage infiltration (58%; P = 0.020), TNF-α (2.5-fold, P<0.001) and IL-6 mRNA levels (2.5-fold; P = 0.008) in mesenteric fat. Increased macrophage infiltration in epididymal fat was also observed with HFD feeding (71%; P = 0.006) but neither TNF-α nor IL-6 was altered. Perirenal and subcutaneous adipose tissue showed no signs of inflammation in HFD mice. The current results implicate gut dysfunction, and attendant inflammation of contiguous adipose, as salient features of the metabolic dysregulation of diet-induced obesity.
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            Dysbiosis gut microbiota associated with inflammation and impaired mucosal immune function in intestine of humans with non-alcoholic fatty liver disease

            Non-alcoholic fatty liver disease (NAFLD) has recently been considered to be under the influence of the gut microbiota, which might exert toxic effects on the human host after intestinal absorption and delivery to the liver via the portal vein. In this study, the composition of the gut microbiota in NAFLD patients and healthy subjects was determined via 16S ribosomal RNA Illumina next-generation sequencing. Among those taxa displaying greater than 0.1% average abundance in all samples, five genera, including Alistipes and Prevotella, were significantly more abundant in the gut microbiota of healthy subjects compared to NAFLD patients. Alternatively, Escherichia, Anaerobacter, Lactobacillus and Streptococcus were increased in the gut microbiota of NAFLD patients compared to healthy subjects. In addition, decreased numbers of CD4+ and CD8+ T lymphocytes and increased levels of TNF-α, IL-6 and IFN-γ were detected in the NAFLD group compared to the healthy group. Furthermore, irregularly arranged microvilli and widened tight junctions were observed in the gut mucosa of the NAFLD patients via transmission electron microscopy. We postulate that aside from dysbiosis of the gut microbiota, gut microbiota-mediated inflammation of the intestinal mucosa and the related impairment in mucosal immune function play an important role in the pathogenesis of NAFLD.
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              Physiological role of adipose tissue: white adipose tissue as an endocrine and secretory organ.

              The traditional role attributed to white adipose tissue is energy storage, fatty acids being released when fuel is required. The metabolic role of white fat is, however, complex. For example, the tissue is needed for normal glucose homeostasis and a role in inflammatory processes has been proposed. A radical change in perspective followed the discovery of leptin; this critical hormone in energy balance is produced principally by white fat, giving the tissue an endocrine function. Leptin is one of a number of proteins secreted from white adipocytes, which include angiotensinogen, adipsin, acylation-stimulating protein, adiponectin, retinol-binding protein, tumour neorosis factor a, interleukin 6, plasminogen activator inhibitor-1 and tissue factor. Some of these proteins are inflammatory cytokines, some play a role in lipid metabolism, while others are involved in vascular haemostasis or the complement system. The effects of specific proteins maybe autocrine or paracrine, or the site of action maybe distant from adipose tissue. The most recently described adipocyte secretory proteins are fasting-induced adipose factor, a fibrinogen-angiopoietin-related protein, metallothionein and resistin. Resistin is an adipose tissue-specific factor which is reported to induce insulin resistance, linking diabetes to obesity. Metallothionein is a metal-binding and stress-response protein which may have an antioxidant role. The key challenges in establishing the secretory functions of white fat are to identify the complement of secreted proteins, to establish the role of each secreted protein, and to assess the pathophysiological consequences of changes in adipocyte protein production with alterations in adiposity (obesity, fasting, cachexia). There is already considerable evidence of links between increased production of some adipocyte factors and the metabolic and cardiovascular complications of obesity. In essence, white adipose tissue is a major secretory and endocrine organ involved in a range of functions beyond simple fat storage.
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                Author and article information

                Contributors
                Role: InvestigationRole: Writing – original draft
                Role: Project administrationRole: SoftwareRole: Validation
                Role: Data curationRole: Formal analysis
                Role: ConceptualizationRole: Methodology
                Role: ConceptualizationRole: Validation
                Role: InvestigationRole: Methodology
                Role: ConceptualizationRole: Funding acquisitionRole: Project administrationRole: ResourcesRole: SupervisionRole: Validation
                Role: ResourcesRole: Supervision
                Role: Project administrationRole: Supervision
                Role: Funding acquisitionRole: Project administrationRole: Supervision
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                23 April 2018
                2018
                : 13
                : 4
                : e0194867
                Affiliations
                [1 ] Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
                [2 ] Department of Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan
                [3 ] Division of Allergy and Immunology, Taipei Veterans General Hospital, Taipei, Taiwan
                [4 ] Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan
                [5 ] Chia-Yi Branch of Taichung Veterans General Hospital, Chiayi, Taiwan
                [6 ] Division of Infection, Taipei Veterans General Hospital, Taipei, Taiwan
                [7 ] Division of Gastroenterology and Hepatology, Taipei Veterans General Hospital, Taipei, Taiwan
                [8 ] Division of General Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
                IDIBAPS Biomedical Research Institute, SPAIN
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Author information
                http://orcid.org/0000-0003-2919-9853
                Article
                PONE-D-17-36888
                10.1371/journal.pone.0194867
                5912737
                29684027
                316a09f3-b37c-4902-af83-d884f4745d73
                © 2018 Su et al

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 28 October 2017
                : 12 March 2018
                Page count
                Figures: 6, Tables: 3, Pages: 17
                Funding
                Funded by: funder-id http://dx.doi.org/10.13039/501100001868, National Science Council;
                Award ID: NSC-102-2314-B-010-036-MY3
                Award Recipient :
                Funded by: Taipei Veteran General Hospital
                Award ID: V106EA-007
                Award Recipient :
                We especially thank Yun-Ru Wang, Fan-Yi Jhan, Che-Jui Chang and Yen-Ling Lin for their excellent technical supports. This work was entirely supported by research grants NSC-102-2314-B-010-036-MY3 and from the National Science Council, and V106EA-007, VGHUST105-GI-2-2 and by the Taipei Veterans General Hospital.
                Categories
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