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Background:The spontaneously hypertensive rat (SHR) is extensively used to study hypertension. Gut microbiota dysbiosis is a notable feature in SHR for reasons unknown. Immunoglobulin A (IgA) is a major host factor required for gut microbiota homeostasis. We hypothesized that inadequate IgA contributes to gut microbiota dysbiosis in SHR.methods:IgA was measured in feces, cecum, serum, liver, gut-associated lymphoid tissue, and milk from SHR and Wistar Kyoto rats. IgA regulatory factors like IgM, IgG, andpIgR(polymeric immunoglobulin receptor) were analyzed. IgA and IgG antibodies and blood pressure (BP) were measured before and after administrating a bacterial antigen (ie, flagellin).Results:Compared with Wistar Kyoto rats, SHR displayed remarkably near-deficient IgA levels accompanied by compensatory increases in serum IgM and IgG and gut-liverpIgRexpression. Inadequate milk IgA in SHR emphasized this immune defect stemmed from the neonatal stage. Reduced IgA+B cells in circulation and Peyer patches indicated a possible reason for the lower IgA in SHR. Noteworthy, a genetic insufficiency was unlikely because administering flagellin to SHR induced anti-flagellin IgA antibodies. This immune response surprisingly accelerated hypertension development in SHR, suggesting IgA quiescence may help maintain lower BP.Conclusions:This study is the first to reveal IgA deficiency in SHR as one host factor associated with gut microbiota dysbiosis and invigorates future research to determine the pathophysiological role of IgA in hypertension.

The relationship between dietary factors and liver disease remains poorly understood. This study evaluated the associations of whole grain and dietary fiber intake with liver cancer risk and chronic liver disease mortality. The National Institutes of Health–American Association of Retired Persons Diet and Health Study cohort recruited 485, 717 retired U.S. participants in 1995–1996. Follow-up through 2011 identified 940 incident liver cancer cases and 993 deaths from chronic liver disease. Compared with the lowest, the highest quintile of whole grain intake was associated with lower liver cancer risk (Hazard ratio [HR]Q5 vs. Q1 = 0.78, 95% confidence interval [CI]: 0.63–0.96) and chronic liver disease mortality (HRQ5 vs. Q1 = 0.44, 95% CI: 0.35–0.55) in multivariable Cox models. Dietary fiber was also associated with lower liver cancer risk (HRQ5 vs. Q1 = 0.69, 95% CI: 0.53–0.90) and chronic liver disease mortality (HRQ5 vs. Q1 = 0.37, 95% CI: 0.29–0.48). Fiber from vegetables, beans and grains showed potential protective effect. Here, we show that higher intake of whole grain and dietary fiber are associated with lower risk of liver cancer and liver disease mortality., Higher intake of dietary fiber and whole grains are associated with reduced risk of various diseases including some cancers. Here, the authors estimate reductions in liver cancer of 22% and 31% and chronic liver disease mortality of 56% and 63% associated with increased whole grain and dietary fiber intake, respectively.

Bile acids (BA) are classically viewed as emulsifiers produced by the liver for aiding the absorption of fats in the gut. Accumulating evidence now recognizes BA as vasoactive agents capable of lowering blood pressure (BP). However, it remains unclear whether the ensuing hypotension can be associated with end-organ damage. To delineate the pathogenic role of BA in the gut-liver-kidney axis, we leveraged our prior finding that a subset of C57BL/6 mice developed cholemia ( i.e. , high circulating BA) when fed a diet supplemented with 7.5% inulin. Briefly, we challenged 4-week-old male mice (n=50) with the inulin diet for one week and identified the subset that developed cholemia (B6 BA ; n=6). Non-cholemic mice (B6; n=6) were maintained as control. Assessment on BP at 6 months of inulin feeding indicated that B6 BA mice (systolic BP: 107.6 ± 2.2 mmHg; diastolic BP: 78.6 ± 3.1 mmHg) are hypotensive relative to non-cholemic B6 mice (systolic BP: 139.8 ± 5.6 mmHg; diastolic BP: 109.0 ± 3.8 mmHg), which was accompanied by polydipsia (7.0 ± 0.4 ml/day in B6 BA vs 4.3 ± 0.2 ml/day water intake in B6), polyuria (2.5 ± 0.1 ml/day in B6 BA vs 1.2 ± 0.1 ml/day urine output in B6), and elevated urinary BA (28.5 ± 1.7 μM in B6 BA vs 3.3 ± 0.6 μM in B6) in B6 BA mice. B6 BA mice also excreted more urinary creatinine (50.4 ± 3.4 mg/dl in B6 BA vs 25.6 ± 1.3 mg/dl in B6), sodium (271.8 ± 20.1 μmol/day in B6 BA vs 103.0 ± 11.0 μmol/day in B6) and potassium (349.2 ± 16.7 μmol/day in B6 BA vs 128.7 ± 7.7 μmol/day in B6), which could be, in part, explained by their higher glomerular filtration rate (1209.0 ± 121.0 in B6 BA vs 681.2 ± 148.7 μl/min/100 g body weight in B6). Of note, B6 BA mice displayed renomegaly, interstitial nephritis, and bile casts in urine, as well as elevated renal transcripts (>2-fold increase relative to B6) for lipocalin 2, kidney injury molecule-1, tumor necrosis factor alpha, collagen type I α1 and endothelin-1. Taken together, these findings demonstrate that our mouse model of diet-induced cholemia presents with low BP and renal pathology. We envision that this model has notable advantages ( e.g. , ease in inducing cholemia, no early morbidity and tractable for long-term study), in lieu of the conventional bile duct ligation approach, for studying how BA regulate BP.

Commensal gut microbiota are strongly correlated with host hemodynamic homeostasis, but only broadly associated with cardiovascular health. This includes a general correspondence of quantitative and qualitative shifts in intestinal microbial communities found in hypertensive rat models and human patients. However, the mechanisms by which gut microbes contribute to the function of organs important for blood pressure control remain unanswered. To examine the direct effects of microbiota on blood pressure, we conventionalized germ-free (GF) rats with specific pathogen free rats for a short-term period of 10 days, which served as a model system to observe the dynamic responses when reconstituting the holobiome. The absence of microbiota in GF rats resulted with relative hypotension compared to their conventionalized counterparts, suggesting an obligatory role of microbiota in blood pressure homeostasis. Hypotension observed in GF rats was accompanied by a marked reduction in vascular contractility. Both blood pressure and vascular contractility were restored by the introduction of microbiota to GF rats, indicating that microbiota could be impacting blood pressure through a vascular-dependent mechanism. This is further supported by the decrease in actin polymerization in arteries from GF rats. Improved vascular contractility in conventionalized GF rats, as indicated through stabilized actin filaments, was associated with an increase in cofilin phosphorylation. These data indicate that the vascular system senses the presence (or lack of) microbiota to maintain vascular tone via actin polymerization. Taken together, these results constitute a fundamental discovery of the essential nature of microbiota in blood pressure regulation.

Integration of microbiota in a host begins at birth and progresses during adolescence, forming a multidirectional system of physiological interactions. Here, we present an instantaneous effect of natural, bacterial gut colonization on the acceleration of longitudinal and radial bone growth in germ-free born, 7-wk-old male rats. Changes in bone mass and structure were analyzed after 10 days following the onset of colonization through cohousing with conventional rats and revealed unprecedented acceleration of bone accrual in cortical and trabecular compartments, increased bone tissue mineral density, improved proliferation and hypertrophy of growth plate chondrocytes, bone lengthening, and preferential deposition of periosteal bone in the tibia diaphysis. In addition, the number of small in size adipocytes increased, whereas the number of megakaryocytes decreased, in the bone marrow of conventionalized germ-free rats indicating that not only bone mass but also bone marrow environment is under control of gut microbiota signaling. The changes in bone status paralleled with a positive shift in microbiota composition toward short-chain fatty acids (SCFA)-producing microbes and a considerable increase in cecal SCFA concentrations, specifically butyrate. Furthermore, reconstitution of the host holobiont increased hepatic expression of IGF-1 and its circulating levels. Elevated serum levels of 25-hydroxy vitamin D and alkaline phosphatase pointed toward an active process of bone formation. The acute stimulatory effect on bone growth occurred independently of body mass increase. Overall, the presented model of conventionalized germ-free rats could be used to study microbiota-based therapeutics for combatting dysbiosis-related bone disorders.

Mucosal surfaces in the gastrointestinal tract are continually exposed to native, commensal antigens and susceptible to foreign, infectious antigens. Immunoglobulin A (IgA) provides dual humoral responses that create a symbiotic environment for the resident gut microbiota and prevent the invasion of enteric pathogens. This review features recent immunological and microbial studies that elucidate the underlying IgA and microbiota-dependent mechanisms for mutualism at physiological conditions. IgA derailment and concurrent microbiota instability in pathological diseases are also discussed in detail. Highlights of this review underscore that the source of IgA and its structural form can dictate microbiota reactivity to sustain a diverse niche where both host and bacteria benefit. Other important studies emphasize IgA insufficiency can result in the bloom of opportunistic pathogens that encroach the intestinal epithelia and disseminate into circulation. The continual growth of knowledge in these subjects can lead to the development of therapeutics targeting IgA and/or the microbiota to treat life threatening diseases.

Iron is essential for many biological functions, including being a cofactor for enzymes involved in cell proliferation. In line, it has been shown that cancer cells can perturb their iron metabolism towards retaining an abundant iron supply for growth and survival. Accordingly, it has been suggested that iron deprivation through the use of iron chelators could attenuate cancer progression. While they have exhibited anti-tumor properties in vitro, the current therapeutic iron chelators are inadequate due to their low efficacy. Therefore, we investigated whether the bacterial catecholate-type siderophore, enterobactin (Ent), could be used as a potent anti-cancer agent given its strong iron chelation property. We demonstrated that iron-free Ent can exert cytotoxic effects specifically towards monocyte-related tumor cell lines (RAW264.7 and J774A.1), but not primary cells, i.e. bone marrow-derived macrophages (BMDMs), through two mechanisms. First, we observed that RAW264.7 and J774A.1 cells preserve a bountiful intracellular labile iron pool (LIP), whose homeostasis can be disrupted by Ent. This may be due, in part, to the lower levels of lipocalin 2 (Lcn2; an Ent-binding protein) in these cell lines, whereas the higher levels of Lcn2 in BMDMs could prevent Ent from hindering their LIP. Secondly, we observed that Ent could dose-dependently impede reactive oxygen species (ROS) generation in the mitochondria. Such disruption in LIP balance and mitochondrial function may in turn promote cancer cell apoptosis. Collectively, our study highlights Ent as an anti-cancer siderophore, which can be exploited as an unique agent for cancer therapy.

The supplementation of dietary additives into processed foods has exponentially increased in the past few decades. Similarly, the incidence rates of various diseases, including metabolic syndrome, gut dysbiosis, and hepatocarcinogenesis, have been elevating. Current research reveals that there is a positive association between food additives and these pathophysiological diseases. This review highlights the research published within the past 5 years that elucidate and update the effects of dietary supplements on liver and intestinal health. Some of the key findings include: enterocyte dysfunction of fructose clearance causes non-alcoholic fatty liver disease (NAFLD); non-caloric sweeteners are hepatotoxic; dietary emulsifiers instigate gut dysbiosis and hepatocarcinogenesis; and certain prebiotics can induce cholestatic hepatocellular carcinoma (HCC) in gut dysbiotic mice. Overall, multiple reports suggest that the administration of purified, dietary supplements could cause functional damage to both the liver and gut. The extraction of bioactive components from natural resources was considered a brilliant method to modulate human health. However, current research highlights that such purified components may negatively affect individuals with microbiotal dysbiosis, resulting in a deeper break of the symbiotic relationship between the host and gut microbiota, which can lead to repercussions on gut and liver health. Therefore, ingestion of these dietary additives should not go without some caution!

Purpose of Review To review the current knowledge on interactions between dietary factors and microRNAs (miRNAs) in essential hypertension (EH) pathogenesis. Recent Findings There exists an integration of maintenance signals generated by genetic, epigenetic, immune, and environmental (e.g., dietary) factors that work to sustain balance in the gut-liver axis. It is well established that an imbalance in this complex, intertwined system substantially increases the risk for EH. As such, pertinent research has been taken to decipher how each signal operates in isolation and together in EH progression. Recent literature indicates that both macro- and micronutrients interrupt regulatory miRNA expressions and thus, alter multiple cellular processes that contribute to EH and its comorbidities. We highlight how carbohydrates, lipids, proteins, salt, and potassium modify miRNA signatures during EH. The disruption in miRNA expression can negatively impact communication systems such as over activating the renin-angiotensin-aldosterone system, modulating the vascular smooth muscle cell phenotype, and promoting angiogenesis to favor EH. We also delineate the prognostic value of miRNAs in EH and discuss the pros and cons of surgical vs dietary prophylactic approaches in EH prevention. Summary We propose that dietary-dependent perturbation of the miRNA profile is one mechanism within the gut-liver axis that dictates EH development.

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related mortality worldwide. Much recent research has delved into understanding the underlying molecular mechanisms of HCC pathogenesis, which has revealed to be heterogenous and complex. Two major hallmarks of HCC include: (i) a hijacked immunometabolism and (ii) a reprogramming in metabolic processes. We posit that the gut microbiota is a third component in an entanglement triangle contributing to HCC progression. Besides metagenomic studies highlighting the diagnostic potential in the gut microbiota profile, recent research is pinpointing the gut microbiota as an instigator, not just a mere bystander, in HCC. In this chapter, we discuss mechanistic insights on atypical immunometabolism and metabolic reprogramming in HCC, including the examination of tumor-associated macrophages and neutrophils, tumor-infiltrating lymphocytes (e.g., T-cell exhaustion, regulatory T-cells, natural killer T-cells), the Warburg effect, rewiring of the tricarboxylic acid cycle, and glutamine addiction. We further discuss the potential involvement of the gut microbiota in these characteristics of hepatocarcinogenesis. An immediate highlight is that microbiota metabolites (e.g., short chain fatty acids, secondary bile acids) can impair anti-tumor responses, which aggravates HCC. Lastly, we describe the rising 'new era' of immunotherapies (e.g., immune checkpoint inhibitors, adoptive T-cell transfer) and discuss for the potential incorporation of gut microbiota targeted therapeutics (e.g., probiotics, fecal microbiota transplantation) to alleviate HCC. Altogether, this chapter invigorates for continuous research to decipher the role of gut microbiome in HCC from its influence on immunometabolism and metabolic reprogramming.

Uncontrolled immune system activation amplifies end-organ injury in hypertension. Nonetheless, the exact mechanisms initiating this exacerbated inflammatory response, thereby contributing to further increases in blood pressure (BP), are still being revealed. While participation of lymphoid-derived immune cells has been well described in the hypertension literature, the mechanisms by which myeloid-derived innate immune cells contribute to T cell activation, and subsequent BP elevation, remains an active area of investigation. In this article, we critically analyze the literature to understand how monocytes, macrophages, dendritic cells, and polymorphonuclear leukocytes, including mast cells, eosinophils, basophils, and neutrophils, contribute to hypertension and hypertension-associated end-organ injury. The most abundant leukocytes, neutrophils, are indisputably increased in hypertension. However, it is unknown how (and why) they switch from critical first responders of the innate immune system, and homeostatic regulators of BP, to tissue-damaging, pro-hypertensive mediators. We propose that myeloperoxidase-derived pro-oxidants, neutrophil elastase, neutrophil extracellular traps (NETs), and interactions with other innate and adaptive immune cells are novel mechanisms that could contribute to the inflammatory cascade in hypertension. We further posit that the gut microbiota serves as a set point for neutropoiesis and their function. Finally, given that hypertension appears to be a key risk factor for morbidity and mortality in COVID-19 patients, we put forth evidence that neutrophils and NETs cause cardiovascular injury post-coronavirus infection, and thus may be proposed as an intriguing therapeutic target for high-risk individuals. © 2021 American Physiological Society. Compr Physiol 11:1575-1589, 2021.

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related mortality worldwide. Much recent research has delved into understanding the underlying molecular mechanisms of HCC pathogenesis, which has revealed to be heterogenous and complex. Two major hallmarks of HCC include: (i) a hijacked immunometabolism and (ii) a reprogramming in metabolic processes. We posit that the gut microbiota is a third component in an entanglement triangle contributing to HCC progression. Besides metagenomic studies highlighting the diagnostic potential in the gut microbiota profile, recent research is pinpointing the gut microbiota as an instigator, not just a mere bystander, in HCC. In this chapter, we discuss mechanistic insights on atypical immunometabolism and metabolic reprogramming in HCC, including the examination of tumor-associated macrophages and neutrophils, tumor-infiltrating lymphocytes (e.g., T-cell exhaustion, regulatory T-cells, natural killer T-cells), the Warburg effect, rewiring of the tricarboxylic acid cycle, and glutamine addiction. We further discuss the potential involvement of the gut microbiota in these characteristics of hepatocarcinogenesis. An immediate highlight is that microbiota metabolites (e.g., short chain fatty acids, secondary bile acids) can impair anti-tumor responses, which aggravates HCC. Lastly, we describe the rising 'new era' of immunotherapies (e.g., immune checkpoint inhibitors, adoptive T-cell transfer) and discuss for the potential incorporation of gut microbiota targeted therapeutics (e.g., probiotics, fecal microbiota transplantation) to alleviate HCC. Altogether, this chapter invigorates for continuous research to decipher the role of gut microbiome in HCC from its influence on immunometabolism and metabolic reprogramming.

Elevated blood pressure or hypertension is the single largest risk factor for cardiovascular diseases which are the leading cause of human deaths. Current clinical management of blood pressure is focused on restoring homeostasis of the host alone, without accounting for commensal gut microbiota. Recent evidence from the CARDIA study in humans and multiple studies using animal models suggest that development of hypertension in the host is associated with alterations in microbiotal communities. Here we examined whether microbiota is necessary for blood pressure and vascular homeostasis by functional evaluation of the gut homeostasis, hemodynamic, and vascular function of gnotobiotic rats reconstituted with microbiota to represent the complete holobiont. Gnotobiotic rats were used to represent incomplete holobionts. To reconstitute complete holobionts, gnotobiotic rats were co-housed with conventionally-raised rats. Acquisition of microbiota was evaluated through monitoring of gross ceca and fecal samples by metagenomic 16S sequencing. BP was recorded and vascular, renal, hepatic, cardiac and gut features were assessed using histology and ex vivo myography. Markers of innate immune effectors (Immune cell population, level of Lcn2, Gut permeability) were used to examine the nature and extent of host immune cell processes concomitantly occurring along with observations of host hemodynamics. Compared to the reconstituted holobiont represented by the animals exposed to microbiota, the incomplete-holobiont represented by gnotobiotic rats, had significantly lower BP (SBP of germ free:109±8 mmHg, SBP of conventionalized:138±10mmHg * ) and vascular contractility responses to phenylephrine (Emax (mN): germ-free: 6.9±1.3, GFC: 11.7±0.7*). Acute exposure of the host to microbiota reconstituted gut microbiotal communities, significantly boosted their gut epithelial cell proliferation, innate immune function and restored vascular contractility. These data indicate that in addition to the dependency of the host on microbiota for essential bodily functions such as digestion of plant-derived complex carbohydrates, the host is also dependent on microbiota for maintaining blood pressure and vascular function

Background: Recent evidence supports that metabolic dysfunction underlies hypertension. Injection of kynurenate, a metabolite of tryptophan pathway, into the paraventricular nucleus of the hypothalamus (PVN) lowers blood pressure (BP). Intestinal absorption and metabolism of tryptophan are impacted by gut microbiota. Since gut-brain axis contributes to gut dysbiosis-inducd hypertension, we hypothesized that gut microbiota modulates the levels of kynurenic pathway metabolites that have central impact on BP regulation. Methods: We, for the first time, used 7 weeks old male Germ-free (GF) Spague Dawley (SD) rats (n=5) and GF rats co-housed with conventional SD rats for 10 days (GFC) (n=6). BP was measured by tail-cuff. Serum metabolites were quantified by 6495 triple quandrople mass spectrometryand data was normalized using isotoplic labelled compounds. The nucleus of the solitary tract (NTS), the principal sensory nucleus for peripheral changes, and the PVN, a relay center projecting sympathetic output based on the integrated afferent inputs from brain regions including NTS, were analyzed by microarray hybridization for mRNA expression. Results: Compared to the GF rats, GFC rats had significantly higher systolic (139 mmHg vs 115 mmHg, p p p p Cd74, Il1b, Cxcl1, Mmp14 ) in the PVN (gene ontology analysis, p Sox11, Tp53, Cdk6, Hoxb4, Foxo4, Cyr61 ) in the NTS (gene ontology analysis, p Conclusion: Colonization of gut microbiota in GF rats induced increased cell differentiation and synaptic plasticity in the NTS and immune responses in the PVN, indicating the restructured sensory neurons of the NTS and enhanced sympathetic output from the PVN. These are in line with increased levels of kynurenic acid and 3-hydroxy kynurenine, and BP, respectively, suggesting that BP regulation by the gut-brain axis may be mediated by kynurenic pathway.

In recent years there has been growing evidence regarding the effect of microbiota on the skeletal growth and homeostasis. Here we present, for the first time, accelerated longitudinal and radial bone growth in young (7-week-old) germ-free male rats after short-term exposure to a newly established gut microbiota. Changes in bone mass and structure were analyzed after 10 days following the onset of colonization through cohousing with conventional rats and revealed unprecedented acceleration of bone accrual in cortical and trabecular compartments, increased bone tissue mineral density, improved proliferation and hypertrophy of growth plate chondrocytes, bone lengthening, and preferential deposition of periosteal bone in tibia diaphysis. In addition, the number of small-in-size adipocytes increased, while the number of megakaryocytes decreased, in the bone marrow of conventionalized germ-free rats. The observed changes in bone status were paralleled with a positive shift in microbiota composition towards short chain fatty acids (SCFA)-producing microbes, which reflected a dramatic increase in cecal concentration of SCFA, specifically butyrate. Further, reconstitution of the host holobiont increased hepatic expression of IGF-1 and its circulating levels, implicating an involvement of the somatotropic axis. Increased serum levels of 25-hydroxy vitamin D and alkaline phosphatase pointed toward an active process of bone formation. The acute stimulatory effect on bone growth occurred independently of body mass increase and resembled reversal of dysbiosis in adolescence, which is marked by rapid skeletal expansion. These findings may help in developing microbiota-based therapeutics to combat bone related disorders resulting from hormonal defects and/or malnutrition in children and adolescence.

Peptidyl arginine deiminase-4 (PAD4) is indispensable for generation of neutrophil extracellular traps (NETs), which can provide antimicrobial effects during host innate immune response; however, the role of PAD4 against gastrointestinal infection is largely unknown. Herein, we challenged PAD4-deficient (Pad4-/-) mice and wild-type (WT) littermates with Citrobacter rodentium (CR), and investigated bacteria clearance and gut pathology. Luminal colonization of CR in Pad4-/- mice peaked between 11-14 days post-infection, whereas WT mice suppressed the infection by 14 days. We demonstrated that Pad4-/- mice were unable to form NETs, whereas WT mice showed increased NETs formation in the colon during infection. Pad4-/- mice showed aggravated CR-associated inflammation as indicated by elevated systemic and colonic pro-inflammatory markers. Histological analysis revealed that transmissible colonic hyperplasia, goblet cell depletion, and apoptotic cell death were more pronounced in the colon of CR-infected Pad4-/- mice. Treating WT mice with deoxyribonuclease I, which can disrupt NETs generation, recapitulated the exacerbated CR infection and gut pathology associated with the loss of PAD4. Administration of the PAD4 inhibitor, Cl-amidine also aggravated CR infection, but to a lesser extent. Taken together, our findings highlight the importance of PAD4 in the mucosal clearance of CR and in resolving gut-associated inflammation.

Owing to their health benefits, dietary fermentable fibers, such as refined inulin, are increasingly fortified in processed foods to enhance their nutritional value. However, we previously demonstrated that when inulin was fed to Toll-like receptor 5 deficient (T5KO) mice susceptible to dysbiosis, a subset of them developed cholestasis and subsequently liver cancer in a gut microbiota-dependent manner. Therefore, we hypothesized that clearance of bacterial taxa, and thereby gut metabolites, involved in the onset and progression to liver cancer could abate the disease in these mice. Such a reshaping of microbiota by vancomycin treatment was sufficient to halt the development of liver cancer in inulin-fed T5KO mice; however, this intervention did not remedy disease penetrance for cholestatic liver injury and its sequelae, including hyperbilirubinemia, hypolipidemia, cholemia and liver fibrosis. Selective depletion of gut bacterial communities was observed in vancomycin-treated mice, including Gram-positive Lachnospiraceae and Ruminococcaceae belonging to the phylum Firmicutes, Bifidobacteria of the phylum Actinobacteria, which ferment fibers, and Clostridium cluster XIVa, which produce secondary bile acids. Lack of liver cancer in vancomycin-treated mice strongly correlated with the substantial loss of secondary bile acids in circulation. Although cholemia was unabated by vancomycin, the composition of serum bile acids shifted toward an abundance of hydrophilic primary bile acids, denoted by the increase in conjugated-to-unconjugated bile acid ratio. Taken together, the present study suggests that microbiotal regulation of bile acid metabolism is one of the critical mediators of fermentable fiber-induced liver cancer in dysbiotic mice.

Hepatocellular carcinoma (HCC), the most malignant form of primary liver cancer, is the fourth most prevalent cause of cancer mortality globally. It was recently discovered that the dietary fermentable fiber, inulin, can reprogram the murine liver to favor HCC development in a gut microbiota-dependent manner. Determining the molecular pathways that are either over expressed or repressed during inulin-induced HCC would provide a platform of potential therapeutic targets. In the present study, we have combined analysis of the novel inulin-induced HCC murine model and human HCC samples to identify differentially expressed genes (DEGs) in hepatocarcinogenesis. Hepatic transcriptome profiling revealed that there were 674 DEGs in HCC mice compared to mice safeguarded from HCC. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis uncovered enrichment in ECM-receptor interaction, steroid hormone biosynthesis, PPAR signaling pathway, focal adhesion and protein digestion and absorption during inulin-induced HCC. Tandem mass tag based quantitative, multiplexed proteomic analysis delineated 57 differentially expressed proteins, where the over-expressed proteins were associated with cell adhesion molecules, valine, leucine and isoleucine degradation and ECM-receptor interaction. After obtaining the human orthologs of the mouse genes, we did a comparison analysis to level 3 RNA-seq data found in the Cancer Genome Atlas (TCGA) database, corresponding to human HCC (n = 361) and healthy liver (n = 50) samples. Out of the 549 up-regulated and 68 down-regulated human orthologs identified, 142 genes (137 significantly over-expressed and 5 significantly under-expressed) were associated with human HCC. Using univariate survival analysis, we found 27 over-expressed genes involved in cell-cell adhesion and cell division that were associated with poor HCC patient survival. Overall, the genetic and proteomics signatures highlight potential underlying mechanisms in inulin-induced HCC and support that this murine HCC model is human relevant.

Lipocalin 2 (Lcn2) is a multifunctional innate immune protein that limits microbial overgrowth. Our previous study demonstrated that the gut microbiota directly induces intestinal Lcn2 production, and Lcn2-deficient ( Lcn2−/−) mice exhibit gut dysbiosis. Coincidentally, gut dysbiosis is associated with metabolic syndrome pathogenesis, and elevated Lcn2 levels has been considered a potential clinical biomarker of metabolic syndrome. Yet whether Lcn2 mitigates or exacerbates metabolic syndrome remains inconclusive. Our objective was to determine whether Lcn2 deficiency-induced compositional changes in gut microbiota contribute to gain in adiposity in aged mice. Utilizing Lcn2−/− mice and their wild-type (WT) littermates, we measured metabolic markers, including fasting blood glucose, serum lipids, fat pad weight, and insulin resistance at ages 3, 6, and 9 mo old. Relative to WT mice, aged Lcn2−/− mice exhibited a gain in adiposity associated with numerous features of metabolic syndrome, including insulin resistance and dyslipidemia. Surprisingly, supplementation with a high-fat diet did not further aggravate metabolic syndrome that spontaneously occurs in Lcn2−/− mice by 6 mo of age. Interestingly, chow-fed Lcn2−/− mice displayed marked differences in the bacterial abundance and metabolomic profile of the gut microbiota compared with WT mice. Overall, our results demonstrate that Lcn2 is essential to maintain metabolic and gut microbiotal homeostasis, where deficiency induces spontaneous delayed onset of metabolic syndrome.

The gut microbiota contains tens of trillions of microorganisms, including at least 1000 different bacterial species that contain more than 3 million genes, which is 150 times more than the human genome. Along with ensuring proper digestion of certain foods, the gut microbiota has been labeled as a metabolic-immunoregulatory organ that strongly impacts host nutrient, xenobiotic and drug metabolism, in concordance to maintaining structural integrity of the gut mucosal barrier and providing immunomodulation. Therefore, the gut microbiota is a key factor in shaping the hosts biochemical profiles and influencing health and disease. In this chapter, we will discuss recent research that elucidates how the gut microbiota modulates host lipid metabolism and how this subsequently affects pathophysiology. This includes exploring the gut microbiota on lipogenesis, beiging, metabolic endotoxemia, and circadian rhythm. This chapter will also discuss the emerging discipline of lipidomics, which is advancing the field of personalized medicine.

The metabolism of macro and micronutrients is a complex and highly regulated biological process. An imbalance in the metabolites and their signaling networks can lead to non-resolving inflammation and consequently to the development of chronic inflammatory-associated diseases. Therefore, identifying the accumulated metabolites and altered pathways during inflammatory disorders would not only serve as ‘real time’ markers, but also help in the development of nutritional therapeutics. In this review, we explore recent research that has delved into elucidating the effects of carbohydrate/calorie restriction, protein malnutrition, lipid emulsions and micronutrient deficiencies on metabolic health and inflammation. Moreover, we describe the integrated stress response in terms of amino acid starvation and lipemia, and how this modulates new age diseases such as inflammatory bowel disease and atherosclerosis. Lastly, we explain the latest research on metaflammation and inflammaging. This review focuses on multiple signaling pathways, including, but not limited to, the FGF21-β-hydroxybutryate-NLRP3 axis, the GCN2-eIF2α-ATF4 pathway, the von Hippel-Lindau/Hypoxia-inducible transcription factor pathway and the TMAO-PERK-FoxO1 axis. Additionally, throughout the review, we explain how the gut microbiota responds to altered nutrient status and also how antimicrobial peptides generated from nutrient-based signaling pathways can modulate the gut microbiota. Collectively, it must be emphasized that metabolic starvation and inflammation are strongly regulated by both environmental (i.e. nutrition, gut microbiome) and non-environmental (i.e. genetics) factors, which can influence the susceptibility to inflammatory disorders.

Aberrant immune responses are linked to hypertension; yet, neutrophils remain relatively understudied. Both neutrophilia and elevated neutrophil-to-lymphocyte (N/L) ratio are used as clinical biomarkers of hypertension. Likewise, neutrophilia is reported in spontaneously hypertensive rats. Whether these features are associated with an increase in neutrophil extracellular traps (NETs) generation is unknown. We hypothesized that neutrophilia and NETs directly correlate with hypertension whereby lowering neutrophilia and NETs are therapeutically beneficial to lower blood pressure (BP). Herein, we used various, genetic rat models divergent in BP to study the neutrophil-hypertension axis. These include the Dahl Salt-Sensitive (S) and Resistant (R) rats, and the low (LCR) and high (HCR) exercise capacity runner rats. LCR (2.1±0.3 10 9 /l) and S rats (1.2±0.5 10 9 /l) exhibited neutrophilia compared to HCR (0.98±0.5 10 9 /l) and R rats (1.04±0.5 10 9 /l), p

Background Circulating cell-free DNA (cfDNA) is a proposed latent biomarker for several cancers, including liver cancer. Deoxyribonucleases (DNases) facilitate the timely and efficient degradation of cfDNA, leading us to hypothesize that DNase I and/or II might be a more sensitive early biomarker than cfDNA. To test this hypothesis, a study was conducted in a large, prospective cohort. Methods A nested case-control study (224 liver cancer case patients and 224 matched control subjects) was conducted in a cohort of Finnish male smokers, followed from baseline (1985–1988) to 2014. The associations among DNase I activity, cfDNA, and the risk of liver cancer were assessed using multivariable-adjusted conditional logistic regression. Results DNase I activity, whether measured as radius (mm) or as units per milliliter, was statistically significantly associated with increased risk of liver cancer (Ptrend 2.7 mm, hazard ratio [HR] = 3.03, 95% confidence interval [CI] = 1.59 to 5.77; DNase I activity >2.72 units/mL, HR = 3.30, 95% CI = 1.64 to 6.65). The strength of this association was not substantially altered by exclusion of cases diagnosed within the first five years of follow-up or those with hepatitis C virus (HCV) infection. In contrast, cfDNA and DNase II was not statistically significantly associated with risk of liver cancer. Conclusions DNase I activity was a superior latent biomarker of liver cancer than cfDNA. These findings advance the goal of developing a means to detect liver cancer years well before the development of clinical manifestations.

The original version of this article contained a mistake. The statement “VSL#3 (commercialized as Visbiome®)” is not correct. VSL#3® is not commercialized under the brand Visbiome®. It is currently available in the market with the same brand and is being sold in more than 30 countries.

The inflammasome cytokine IL-1b is an important mediator of the inflammatory responses against invading pathogens. However, it is not clear whether sustained IL-1b signaling following the loss of its endogenous inhibitor, secretory IL-1 receptor antagonist (sIL-1Ra), could improve mucosal immunity against the enteropathogen, Citrobacter rodentium (CR). In light of increased prescription of rec-sIL-1Ra (aka Anakinra) to treat inflammatory bowel disease, we undertook this study. At basal levels, sIL-1Ra-deficient (sIL-1RaKO) mice displayed leukocytosis and elevated inflammatory marker, i.e. serum and fecal lipocalin 2. Furthermore, bone marrow-derived macrophages and neutrophils from sIL-1RaKO mice generated higher levels of iNOS and nitrite, and ROS and NETs, respectively. These results collectively suggest sIL-1RaKO mice have low-grade chronic inflammation. Based on these results, we hypothesized that sIL-1RaKO mice with persistent IL1-b signaling could efficiently clear CR infection than their WT littermates. Oral challenge of CR (1×109 CFU/mouse) resulted in luminal colonization, which peaked at day 7 post-infection, in both groups; however, sIL-1RaKO mice displayed a higher CR burden and an exacerbated infection. The aggravated course of infection was further visualized by inoculating sIL-1RaKO mice with bioluminescent CR. Histologic analysis revealed that transmissible colonic hyperplasia was more pronounced in sIL-1RaKO mice. Interestingly, basal ileal Paneth’s cell-specific antimicrobial proteins (Ang4 and Reg3g) were significantly reduced in sIL-1RaKO mice. Collectively, our results demonstrate that a balanced mucosal IL-1b signaling is required to counter and clear enteropathogen infection.

Dietary fermentable, soluble fibers (e.g. inulin) are known for promoting health; yet, ~40% of Toll-like receptor 5 deficient (T5KO) mice fed inulin-containing diet (ICD) develop icteric hepatocellular carcinoma (HCC) (Cell, 2018). Specifically, the disease progresses starting with hepatic cholestasis and neutrophilic inflammation at one month, followed by HCC at 6 months of ICD feeding. This diet-driven HCC was dependent on the gut microbiota and was mediated, largely in part, via surfeit production of immunosuppressive short-chain fatty acids (SCFA) and secondary bile acids, presumably as compensatory mechanisms against inflammation in the 40% pre-HCC T5KO mice. What was most striking was the upregulation of systemic bilirubin (a host immunosuppressive metabolite) within one week of ICD feeding. The hyperbilirubinemia was accompanied with an increase in IgA by ~50 and ~10-fold in the serum and liver, respectively, compared to the 60% non-HCC T5KO mice. Markers for anti-tumor T cell exhaustion, i.e. hepatic PD-L1 and layilin, were also upregulated, where the former was elevated within a week of feeding and persisted, while the latter was observed at 6 months. Hepatic immune cell phenotyping after the onset of HCC revealed substantial increase in CD4+FOXP3+PD-L1+T cells and IgA+IL10+PD-L1+Bcells, with the latter denoting a recently identified subset of highly immunosuppressive B cells. Our unprecedented findings collectively demonstrate that dietary fibers and SCFA —which are widely-held to be anti-inflammatory— could potentiate immunosuppression and impede anti-tumor immune surveillance in the tumor microenvironment in mice with gut microbiota dysbiosis.