Changes in gut microbiota induced by oral pathobiont deteriorate the pathology of non-alcoholic fatty liver disease
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ABSTRACT: Periodontitis increases the risk of non-alcoholic fatty liver disease (NAFLD). However, the precise mechanisms are unclear. Here, gut dysbiosis induced by orally administered Porphyromonas gingivalis, a representative periodontopathic bacterium, was implicated in the deterioration of NAFLD pathology. C57BL/6 mice were administered with the vehicle, P. gingivalis or Prevotella intermedia, with weaker periodontal pathogenicity, followed by feeding on a choline-deficient, high fat diet (CDAHFD60). CDAHFD60 feeding induced hepatic steatosis, and combined bacterial administration further aggravated NAFLD pathology with increased fibrosis. Liver gene expression analyses revealed that genes involved in the NAFLD pathology were perturbed with distinctive expression profiles induced by different bacteria. These differences may be due to quantitative and qualitative differences in the influx of gut bacterial products because the serum endotoxin level, gut microbiota composition, and serum metabolite profile caused by ingested P. intermedia and P. gingivalis were different. These findings provide insights into mechanisms linking periodontitis and NAFLD.
Project description:The effect of oral microbiota on the intestinal microbiota has garnered growing attention as a mechanism linking periodontal diseases to systemic diseases. However, the salivary microbiota is diverse and comprises numerous bacteria with a largely similar composition in healthy individuals and periodontitis patients. Thus, the systemic effects of small differences in the oral microbiota are unclear. In this study, we explored how health-associated and periodontitis-associated salivary microbiota differently colonized the intestine and their subsequent systemic effects by analyzing the hepatic gene expression and serum metabolomic profiles. The salivary microbiota was collected from a healthy individual and a periodontitis patient and gavaged into C57BL/6NJcl[GF] mice. Samples were collected five weeks after administration. Gut microbial communities were analyzed by 16S ribosomal RNA gene sequencing. Hepatic gene expression profiles were analyzed using a DNA microarray and quantitative polymerase chain reaction. Serum metabolites were analyzed by capillary electrophoresis time-of-flight mass spectrometry. The gut microbial composition at the genus level was significantly different between periodontitis-associated microbiota-administered (PAO) and health-associated oral microbiota-administered (HAO) mice. The hepatic gene expression profile demonstrated a distinct pattern between the two groups, with higher expression of Neat1, Mt1, Mt2, and Spindlin1, which are involved in lipid and glucose metabolism. Disease-associated metabolites such as 2-hydroxyisobutyric acid and hydroxybenzoic acid were elevated in PAO mice. These metabolites were significantly correlated with Bifidobacterium, Atomobium, Campylobacter, and Haemophilus, which are characteristic taxa in PAO mice. Conversely, health-associated oral microbiota were associated with higher levels of beneficial serum metabolites in HAO mice. The multi-omics approach used in this study revealed that periodontitis-associated oral microbiota is associated with the induction of disease phenotype when they colonized the gut of germ-free mice.
Project description:Periodontitis and infections with periodontal bacteria have been highlighted as risk factors for dementia. In recent years attention has been drawn to the role of microglia cells in neurodegenerative diseases. However, there is limited knowledge of the influence of periodontal bacteria on microglia cells. The aim of the present study was to investigate the interactions between the periodontal bacteria P. gingivalis and microglia cells, and to unravel if these interactions could contribute to Alzheimer’s pathology. Periodontitis and infections with periodontal bacteria have been highlighted as risk factors for dementia. In recent years attention has been drawn to the role of microglia cells in neurodegenerative diseases. However, there is limited knowledge of the influence of periodontal bacteria on microglia cells. The aim of the present study was to investigate the interactions between the periodontal bacteria P. gingivalis and microglia cells, and to unravel if these interactions could contribute to Alzheimer’s pathology. We found, through microarray analysis, that stimulation of microglia cells with P. gingivalis resulted in upregulation of several Alzheimer´s disease associated genes, including NOX4. We also showed that P. gingivalis LPS mediated ROS production and IL-6 and IL-8 induction via NOX4 in microglia. The viability of neurons was shown to be reduced by conditioned media from microglia cells stimulated with P. gingivalis LPS, and that the reduction was NOX4 dependent. The levels of total and phosphorylated Tau in neurons were increased by conditioned media from microglia cells stimulated with P. gingivalis or LPS. This increase was NOX4 dependent. In summary our findings give us a potential mechanistic explanation of how the periodontal pathogen P. gingivalis could trigger or exacerbate AD pathogenesis.
Project description:The outer membrane vesicles (OMVs) produced by Porphyromonas gingivalis (P. gingivalis) contain a variety of bioactive molecules that may be involved in the progression of periodontitis. However, the participation of P. gingivalis OMVs in the development of periodontitis has not been elucidated. Here we isolated P. gingivalis OMVs and confirmed their participation in periodontitis both in vivo and in vitro. Microcomputed Tomography (micro-CT) and histological analysis showed that under the stimulation of P. gingivalis OMVs, the alveolar bone of rats was significantly resorbed in vivo. We found that P. gingivalis OMVs were taken up by hPDLCs (human Periodontal Ligament Cells, hPDLCs) in vitro, then subsequently resulting in apoptosis and inflammatory cytokines releasing which was accomplished by the microRNA-size small RNAs (msRNAs) sRNA45033 in the P. gingivalis OMVs. Through bioinformatics analysis and screening of target genes, Chromobox 5 (CBX5) was identified as the downstream target of screened-out small RNA s45033. Using dual-luciferase reporter assay, overexpression, and knockdown methods, s45033 was confirmed to target CBX5 to regulate hPDLCs apoptosis. In addition, Cleavage Under Targets and Tagmentation (Cut&Tag) analysis confirmed the mechanism that CBX5 regulates apoptosis through the methylation of p53 DNA. Collectively, these findings indicate that the role of P. gingivalis OMVs is immunologically relevant and related to bacterial virulence in the development of periodontitis.
Project description:Non-alcoholic fatty liver disease (NAFLD) is rapidly becoming the most common liver disease worldwide, yet the pathogenesis of NAFLD is only partially understood. Here, we investigated the role of the gut bacteria in NAFLD by stimulating the gut bacteria via feeding mice the fermentable dietary fiber guar gum and suppressing the gut bacteria via chronic oral administration of antibiotics. Guar gum feeding profoundly altered the gut microbiota composition, in parallel with reduced diet-induced obesity and improved glucose tolerance. Strikingly, despite reducing adipose tissue mass and inflammation, guar gum enhanced hepatic inflammation and fibrosis, concurrent with markedly elevated plasma and hepatic bile acid levels. Consistent with a role of elevated bile acids in the liver phenotype, treatment of mice with taurocholic acid stimulated hepatic inflammation and fibrosis. In contrast to guar gum, chronic oral administration of antibiotics effectively suppressed the gut bacteria, decreased portal secondary bile acid levels, and attenuated hepatic inflammation and fibrosis. Neither guar gum or antibiotics influenced plasma lipopolysaccharide levels. In conclusion, our data indicate a causal link between changes in gut microbiota and hepatic inflammation and fibrosis in a mouse model of NAFLD, possibly via alterations in bile acids.
Project description:Non–alcoholic fatty liver disease (NAFLD) is high prevalent in worldwide and associated with chronic kidney disease (CKD). Infection with Opisthorchis viverrini (Ov) infection and consumption of high fat and high fructose (HFF) exacerbates NAFLD to nonalcoholic steatohepatitis in hamsters. Here, we aimed to investigate the effect a combination of HFF diet and Ov infection on kidney pathology via alteration of gut microbiome and proteome in hamster.
Project description:Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in Western countries. There is growing evidence that dysbiosis of the intestinal microbiota and disruption of microbiota-host interactions contribute to the pathology of NAFLD. We previously demonstrated that gut microbiota derived tryptophan metabolite indole-3-acetate (I3A) was decreased in both cecum and liver of high-fat diet-fed mice and attenuated the expression of inflammatory cytokines in macrophages and TNF-a and fatty acid induced inflammatory responses in an aryl-hydrocarbon receptor (AhR) dependent manner in hepatocytes. In this study, we investigated the effect of orally administered I3A in a mouse model of diet induced NAFLD. Western diet (WD)-fed mice given sugar water (SW) with I3A showed dramatically decreased serum ALT, hepatic TG, liver steatosis, hepatocyte ballooning, lobular inflammation, and hepatic production of inflammatory cytokines, compared to WD-fed mice given only SW. Metagenomic analysis show that I3A administration did not significantly modify the intestinal microbiome, suggesting that I3A’s beneficial effects likely reflect the metabolite’s direct actions on the liver. Administration of I3A partially reversed WD induced alterations of liver metabolome and proteome, notably, decreasing expression of several enzymes in hepatic lipogenesis and β- oxidation. Mechanistically, we also show that AMP-activated protein kinase (AMPK) mediates the anti-inflammatory effects of I3A in macrophages. The potency of I3A in alleviating liver steatosis and inflammation clearly demonstrates its potential as a therapeutic modality for preventing the progression of steatosis to NASH.
Project description:Porphyromonas gingivalis is a gram-negative bacterium that causes destructive chronic periodontitis. In addition, this bacterium is also involved in the development of cardiovascular disease. The aim of this study was to investigate the effects of P. gingivalis infection on gene and protein expression in human aortic smooth muscle cells (AoSMCs) and its relation to cellular function.
Project description:Porphyromonas gingivalis (P. gingivalis) is a key pathogen in periodontitis. Our previous study indicated that periodontitis induced by P. gingivalis increases the percentage of CD19+ B cells, Th17, Treg, gMDSCs and mMDSCs but decreases the ratio of B10 cells in CIA mice. It’s unclear which virulence factors of P. gingivalis are involved in these processes. Here, our study first indicated that such effects are mainly resulted from the undenatured proteins other than the DNA, RNA or LPS of P. gingivalis. As gingipains are enzymes and virulence factors which play vital role in the progression in periodontitis through affecting innate and adaptive immune system, we then compared the influence of the wild-type strain of P. gingivalis (ATCC33277) with its isogenic gingipain-null mutant (△K△RAB) on B cells. The results showed that B cells infected with △K△RAB exhibited increased levels of IL-6 and others cytokines (IL-1β,IL-23) involve in Th17 differentiation compared to wild-type strain, also the frequency of IL-10 producing regulatory B cells (B10). Furthermore, the peritonitis induced by △K△RAB enhanced the proportion of B10 and Th17 compared with treated with ATCC33277. Cumulatively, this study preliminarily revealed deletion of gingipains affected the antigen presentation of B cell that promoted B cells express the cytokines which promoted T cells toward Th17 and the secretion immunosuppressive cytokines of B cells that enhanced the frequency of B10 which implicated gingipains are vital in altering B cell function to participated immune response.
Project description:Prevotella intermedia is a Gram-negative bacterium belonging to the Bacteroidetes phylum and is notably linked to periodontitis. Several other species within this phylum have been reported to possess the general O-glycosylation system, and the O-glycoproteome has been well characterized in Tannerella forsythia, Porphyromonas gingivalis, and Flavobacterium johnsoniae. In this study, we used electron cryotomography (cryoET) to view the ultrastructure of P. intermedia for the first time, revealing an electron dense surface layer surrounding both cells and outer membrane vesicles (OMVs). Interestingly, the OMVs were frequently large (>200 nm) and were of two types, with the lumens being either electron dense or translucent. LC-MS/MS analyses of OMVs and various cell fractions of P. intermedia resulted in the identification of 1655 proteins including 62 predicted T9SS cargo proteins. Consistent with the presence of large OMVs with electron dense lumens, periplasmic proteins contributed to nearly half the protein content of OMVs. For the glycoproteome, 445 unique O-glycosylation sites within 226 glycoproteins were identified. The O-glycosylation motif exhibited a much broader range than reported in other species, with O-glycosylation found at D(S/T)(A/I/L/M/T/V/S/C/G/F/N/E/Q/D/P). A single major O-glycan was identified of delta mass 1531.48 Da and its sequence was determined by MS2 and MS3 analyses using a combination of CID and HCD fragmentation modes. Following partial deglycosylation with trifluoromethanesulfonic acid, the O-glycan sequence was confirmed to be dHex-dHex-HexNAc(HPO3-C6H12O5)-dHex-Hex-HexA-Hex(dHex). Bioinformatic analyses of O-glycoprotein localization predicted 73 periplasmic proteins, 53 inner membrane proteins, 52 lipoproteins, 26 outer membrane proteins, and 14 proteins secreted by the T9SS.
Project description:The pathological progression of nonalcoholic fatty liver disease (NAFLD) is driven by multiple factors, and nonalcoholic steatohepatitis (NASH) represents its progressive form. In our previous studies, we found that bicyclol had beneficial effects on NAFLD/NASH. Here we aim to investigate the underlying molecular mechanisms of the bicyclol effect on NAFLD/NASH induced by high-fat diet (HFD) feeding. A mice model of NAFLD/NASH induced by HFD-feeding for 8 weeks was used. As a pretreatment, bicyclol (200 mg/kg) was given to mice by oral gavage twice daily. Hematoxylin and eosin (H&E) stains were processed to evaluate hepatic steatosis, and hepatic fibrous hyperplasia was assessed by Masson staining. Biochemistry analyses were used to measure serum aminotransferase, serum lipids, and lipids in liver tissues. Proteomics and bioinformatics analyses were performed to identify the signaling pathways and target proteins. The real-time RT-PCR and Western blot analyses were performed to verify the proteomics data. As a result, bicyclol had a markedly protective effect against NAFLD/NASH by suppressing the increase of serum aminotransferase, hepatic lipid accumulation and alleviating histopathological changes in liver tissues. Proteomics analyses showed that bicyclol remarkably restored major pathways related to immunological responses and metabolic processes altered by HFD feeding. Consistent with our previous results, bicyclol significantly inhibited inflammation and oxidative stress pathway related indexes (SAA1, GSTM1 and RDH11). Furthermore, the beneficial effects of bicyclol were closely associated with the signaling pathways of bile acid metabolism (NPC1, SLCOLA4 and UGT1A1), cytochrome P450-mediated metabolism (CYP2C54, CYP2C70 and CYP3A25), biological processes such as metal ion metabolism (Ceruloplasmin and Metallothionein-1), angiogenesis (ALDH1A1) and immunological responses (IFI204 and IFIT3). These findings suggested that bicyclol is a potential preventive agent for NAFLD/NASH by targeting multiple mechanisms in future clinical investigations.