Germ-free Rats Research Articles

Investigation of the metabolites of five major constituents from Berberis amurensis in normal and pseudo germ-free rats.

Berberis amurensis (Berberidaceae) is a traditional Chinese medicine, which is often used to treat hypertension, inflammation, dysentery and enteritis. It contains alkaloids, mainly including berberine, berbamine, magnoflorine, jatrorrhizine and palmatine. Berberis amurensis extracts (BAEs) is often orally taken. Oral herbs might be metabolized by intestinal bacteria in the small intestine. However, the interaction between the herb and the gut microbiota is still unknown. In the current study, UPLC/Q-TOF-MS/MS combined with Metabolitepilot and Peakview software was used to identify the metabolites of BAEs in anti-biotic cocktail induced pseudo germ-free rats and normal rats. As a result, a total of 46 metabolites in normal rats were detected and its main metabolic pathways include demethylation, dehydrogenation, methylation, hydroxylation, sulfation and glucuronidation. Only 29 metabolites existed in pseudo germ-free rats. Dehydrogenated metabolites (M29, M30, M34 and M36), methylated metabolites (M33, M41 and M46) and other metabolites were not detected in pseudo germ-free rats. The result implied that the intestinal bacteria have an influence on the metabolism of BAEs. Furthermore, this investigation might contribute to the understanding of the metabolism of BAEs, and further promote its clinical application.

265 BERBERINE AMELIORATES OVARIECTOMY-INDUCED ANXIETY-LIKE BEHAVIORS BY ENRICHMENT IN EQUOL GENERATING GUT MICROBIOTA

Background Decline in circulating ovarian hormone levels is associated with increment in anxiety and alteration in intestinal microbiota. As a kind of gut microbiota modulator, berberine (BBR) has shown efficacy in treating diseases such as menopausal osteoporosis and type 2 diabetes through regulating bacteria. However, the effects of BBR on ovariectomy-induced anxiety are still unclear and whether or not gut microbiota modifies the possible effect of BBR remain to be fully elucidated. Aim To demonstrate that BBR is able to alleviate anxiety through modulating intestinal microbiota under estrogen-deficient conditions. Methods Female specific pathogen-free (SPF) SD rats were ovariectomized (OVX) or shamoperated (sham). BBR (100mg/kg) or control vehicle was administered via oral gavage every day for four weeks. Open field test (OFT) and elevated plus maze test (EPM) were used to detect the anxiety-like behaviors. Moreover, the 16S rRNA sequencing and liquid chromatography/mass spectrometry (LC/MS) analysis were utilized to validate the changes in intestinal microbes and microbiota isoflavone metabolites, respectively. The concentration of serum estradiol (E2) was measured using ELISA. Further, female germ-free (GF) SD rats were operated and treated with BBR or vehicle under sterile conditions. Fecal microbiota transplantation (FMT) was conducted using fecal samples from SPF rats to colonize GF-OVX rats. Results Compared with SPF-sham rats, OFT and EPM showed increased anxiety in SPFOVX rats, and BBR treatment significantly ameliorated anxiety-like behaviors compared with SPF-OVX rats. The serum level of isoflavone metabolite equol and the ratio of equol to daidzein were decreased by ovariectomy and elevated by BBR treatment. Furthermore, BBR treatment altered the microbiota diversity and taxa richness of the gut microbiome. The alpha diversity revealed a significant reduction in richness and diversity after BBR administration compared with SPF-OVX group. The beta diversity showed dissimilarity in composition among each group. At the genus level, BBR-treated rats harbored a higher abundance of beneficial gut microbes, such as Bacteroides, Bifidobacterium, Lactobacillus, and Akkermansia, among which many species are involved in isoflavone bioconversion (Fig.1). Notably, estrogen deficiency in GF rats also resulted in anxiety-like behaviors, however gavage feeding of BBR to GF-OVX rats had no significant effects on behavior improvement and equol metabolism. FMT of SPF-BBR rats to GF-OVX rats improved anxiety-like behaviors and increased the serum concentration of isoflavone metabolite equol (Fig.2). Conclusions Gut microbiota is critical in BBR treatment of ovariectomy-aggravated anxiety, indicating a promising therapeutic strategy for postmenopausal anxiety. Download : Download high-res image (316KB) Download : Download full-size image Fig. 1 . BBR ameliorates the anxiety-like behaviors and gut dysbiosis of SPF-OVX rats. (A) Elevated plus-maze test results. (B) Open field test results. (C) Ovarian hormone levels. (D) Isoflavone levels. (E) α-diversity indices. (F) β-diversity measured by PCoA. (G) LEfSe analysis from phylum to genus. Data are expressed as the mean ± SEM. *P Download : Download high-res image (217KB) Download : Download full-size image Fig. 2 . GF condition eliminates the anti-anxiety effects of BBR, while fecal microbes from SPF-BBR rats ameliorates anxiety of GF-OVX rats. (A) Elevated plus-maze test results of GF rats. (B) Open field test results of GF rats. (C) Ovarian hormone levels of GF rats. (D) Isoflavone levels of GF rats. (E) Elevated plus-maze test results of FMT rats. (F) Open field test results of FMT rats. (G) Ovarian hormone levels of FMT rats. (H) Isoflavone levels of FMT rats. Data are expressed as the mean ± SEM. *P

Gut Microbiota Accelerates Bone Growth and Marrow Adiposity of the Adolescent Gnotobiotic Rat

Skeletal growth and bone homeostasis are significant holobiome components strongly tied to the gut microbiota. We aimed to explore the requirement of gut microbiome for skeletal maturation in an adolescent organism. For our approach, we co-housed young (7-week-old) germ-free (GF) rats with conventional rats of the same age, sex (male), and strain (Sprague Dawley) for 10 days to naturally conventionalize GF (GFC) rats with the gut microbiota by coprophagy. Bone morphometry by micro-CT scanning and histological staining revealed accelerated longitudinal and radial bone growth in GFC rats when compared to GF rats. Changes in bone mass and structure for GFC rats encompassed an increase of bone accrual in cortical and trabecular compartments, greater tissue mineral density, improved proliferation and hypertrophy of growth plate chondrocytes, bone lengthening, and preferential deposition of periosteal bone in the tibia diaphysis. Analysis of bone marrow at the tibia midshaft depicted more adipocyte number, greater adipocyte density, and altered cell size distribution to favor small adipocytes, but reduced megakaryocytes, in GFC rats. Interestingly, putative effector genes responsible for bone mass accumulation were found to be comparable between GF and GFC rats, which shifted our focus onto systemic host and microbial regulatory factors. Assessment of serum markers indicated that the active bone formation could be due to elevated levels of 25-hydroxy vitamin D and alkaline phosphatase. Importantly, 16S ribosomal RNA gene sequencing demonstrated that the prominent bacterial colonizers were Clostridiaceae and Clostridium members, which are potent short chain fatty acid (SCFA) producers. 1H-NMR metabolomics in the cecal contents showed a dramatic increase of SCFA, specifically butyrate, following bacterial colonization. In relation with the literature, our observation of increased hepatic insulin-like growth factor-1 (IGF-1) expression and systemic IGF-1 levels suggest that butyrate promotes bone growth through the somatotropic axis. Collectively, our study demonstrates that gut microbiota can deliver signals to the skeleton for accelerating bone expansion and accumulating marrow fat.

Examining the role of extacellular vesicles in blood pressure regulation

Extracellular vesicles (EVs) are membrane-enclosed structures that aid in intercellular communication and other biological processes. Recent studies implicate EVs in various acute and chronic disease states, including hypertension. We have previously demonstrated that the gut microbiota plays a causal role in the pathogenesis of hypertension. However, the mechanisms by which the microbiota influences host blood pressure are largely unknown. We hypothesized that EVs act as mediators between the gut microbiota and host, exerting bidirectional effects to regulate blood pressure. For our experiments, we used the spontaneously hypertensive stroke prone rat (SHRSP), a well-known animal model of essential hypertension, and its corresponding normotensive control, the Wistar-Kyoto rat (WKY). To demonstrate the impact of EVs on host blood pressure, we transplanted plasma EVs from SHRSP and WKY donors into SHRSP and WKY recipients via intravenous injection. Treatment duration was 4 weeks, during which systolic blood pressure (SBP) measurements were taken. In SHRSP, WKY-EVs had a statistically significant SBP lowering effect over time compared with SHRSP-EVs (p=0.03), with a reduction of SBP of 23 mmHg at 4 weeks (166 ± 1 vs. 189 ± 3 mmHg; p=0.05). In WKYs, EV type had a significant main effect on SBP (p=0.05), with those receiving SHRSP-EVs exhibiting elevated SBP. We then performed flow cytometry analysis on various tissues from the treatment groups to investigate if immune and inflammatory processes could underlie EV action. We found that SHRSP that received SHRSP-EVs (SHRSP control) had increased Th17 cells (p<0.0001) and decreased regulatory T (Treg) cells (p<0.05) in ileum compared to WKY that received WKY-EVs (WKY control). These results are consistent with previous reports citing Th17/Treg imbalance toward Th17 dominance as a critical factor in hypertension. Interestingly, WKY-EV treatment in SHR restored Th17/Treg balance, decreasing Th17 numbers in brain (p<0.0001), ileum (p<0.0001) and cecum (p<0.01) and increasing Treg numbers in ileum (p<0.001) compared to SHRSP control. Conversely, WKY that received SHR-EVs had fewer Tregs in ileum (p<0.05) compared to WKY control, demonstrating that SHRSP-EV treatment in WKY resulted in deleterious inflammatory effects on gut. Finally, to examine if the effects of EVs on SBP may be mediated through alteration of the gut microbiota, we administered SHRSP-EVs or WKY-EVs to germ free rats lacking a gut microbiota. Germ free rats receiving SHRSP-EVs exhibited significantly elevated SBP as compared to those receiving WKY-EVs (150 ± 5 vs. 129 ± 4 mmHg; p=0.01). This finding further demonstrates the SBP elevating effect of SHRSP-EVs, and suggests EV alteration of the gut microbiota is not required to influence host blood pressure. Future studies will seek to establish how microbiota may alter circulating EV profile and function to promote the pathogenesis of hypertension. Overall, our data suggest that EVs play an important role in regulation of host blood pressure and gut inflammation, in part by alteration of the Th17/Treg balance.

Restructuring the Gut Microbiota by Intermittent Fasting Lowers Blood Pressure

Studies have demonstrated that disruption of the gut microbiota, termed gut dysbiosis, plays a causal role in the development of hypertension (HT) in animal models and patients. Prevention of this dysbiosis can attenuate or abolish HT. Translational mechanisms to prevent gut dysbiosis as well as an understanding of the mechanisms linking gut dysbiosis to HT are lacking. Recent studies revealed that intermittent fasting alters the gut microbiota and the production of microbial metabolites. Thus, we hypothesized that every-other-day-fasting (EODF) would prevent elevations of blood pressure (BP) in the spontaneously hypertensive stroke prone rat (SHRSP) by maintaining a healthy gut microbiota. Five-week old SHRSP rats and normotensive Wistar Kyoto (WKY) rats were randomized to be fed ad lib or on EODF for 10 weeks. BP was measured weekly, and cecal content and plasma were collected at the end of the study. To examine the roles of gut microbiota and microbial metabolites in HT, we performed whole-genome shotgun sequencing on cecal samples and non-targeted metabolomics on cecal contents and plasma. We found that ten-weeks EODF was able to prevent elevations of systolic BP (SBP) in SHRSP compared to ad lib fed SHRSP (~220 vs. ~170 mmHg; n=6-8, p<0.05). Principle coordinate analysis showed that EODF significantly altered the overall composition of both WKY and SHRSP microbiota (WKY p<0.01, SHRSP p<0.009). Multi-omics analysis indicates distinct microbiome and metabolome in SHRSP compared to WKY, and significant alterations to each induced by EODF. To examine the direct effects of the EODF altered microbiota on BP regulation and eliminate the confounding variable of fasting, pooled cecal contents of SHRSP and WKY animals fed ad lib or EODF were given to germ-free (GF) rats by oral gavage. GF rats transplanted with SHRSP ad lib microbiota had a significantly higher SBP as compared to those transplanted with SHRSP EODF microbiota (~152 vs. ~140 mmHg; n=6-7, p<0.01), indicating that microbiota and their metabolites are accountable for the effects of EODF. These findings suggest that EODF is able to prevent HT in SHRSP, and this involves altering the gut microbiota and metabolome.

Metabolomics reveal dynamic host responses in lipid, amino acid, and energy metabolism after acute exposure of gut microbiota in germ‐free rats

Background Integrating germ-free and gnotobiotic models have advanced the understanding of how gut microbiome impacts host physiology. High-throughput omics technologies further provide microbial and metabolite targets for translational purposes. Yet, limited knowledge is known about the immediate effects of natural microbial colonization on host lipid, amino acid, and energy metabolism. Methods To address this, germ-free Sprague Dawley rats were acclimated with the gut microbiota by cohousing them with microbiota-intact rats (1:1 ratio) for 10 days. Characterization of the microbiota composition in the feces was quantified by 16S ribosomal RNA gene sequencing. Cecal metabolites related to primary microbial and secondary host-bacterial co-metabolisms (e.g., tricarboxylic acid cycle, anaerobic fermentation, amino acids) were analyzed by H1-NMR based metabolomics. Targeted metabolomic analysis of serum eicosanoids and leukotrienes were examined by liquid chromatography-mass spectrometry. Gas chromatography was used for analysis of hepatic total fatty acids. Results Natural colonization of the gut microbiota by coprophagy was sufficient to reconstitute the gut microbiota in conventionalized germ-free (GFC) rats. Among the colonizing bacteria, Akkermansia spp. was one of the top abundant genera in GFC rats and thus, could be one of the main contributors to the elevation of inosine and its metabolites, hypoxanthine and xanthine, in the cecal contents. Additionally, catabolism of choline to trimethylamine and dimethylamine was diminished, but there were no changes in creatine levels. GFC rats also exhibited more aromatic (e.g., tyrosine) and acidic (e.g., glutamate) amino acids, but less carboxamide-chained (e.g., glutamine, asparagine) amino acids. Increase of lactate levels suggested a favorability for anaerobic fermentation even though elevated succinate and fumarate indicated functional tricarboxylic acid cycle activity. These changes in energy and amino acid metabolism were paralleled in the serum of GFC rats. Analyzing hepatic lipid fractions revealed an increase of both ω6 and ω3 fatty acids in GFC rats, including their eicosanoid and leukotriene derivatives in circulation (e.g., leukotriene 4; 15S-hydroxy-5Z,8Z,11Z13E,17X-eicosapentaneoic acid). Conclusion This study demonstrates that acute exposure to the gut microbiota causes dynamic metabolic changes in the gut-liver axis.

Dietary switch to Western diet induces hypothalamic adaptation associated with gut microbiota dysbiosis in rats.

Early hyperphagia and hypothalamic inflammation encountered after Western diet (WD) are linked to rodent propensity to obesity. Inflammation in several brain structures has been associated with gut dysbiosis. Since gut microbiota is highly sensitive to dietary changes, we hypothesised that immediate gut microbiota adaptation to WD in rats is involved in inflammation-related hypothalamic modifications. We evaluated short-term impact of WD consumption (2 h, 1, 2 and 4 days) on hypothalamic metabolome and caecal microbiota composition and metabolome. Data integration analyses were performed to uncover potential relationships among these three datasets. Finally, changes in hypothalamic gene expression in absence of gut microbiota were evaluated in germ-free rats fed WD for 2 days. WD quickly and profoundly affected the levels of several hypothalamic metabolites, especially oxidative stress markers. In parallel, WD consumption reduced caecal microbiota diversity, modified its composition towards pro-inflammatory profile and changed caecal metabolome. Data integration identified strong correlations between gut microbiota sub-networks, unidentified caecal metabolites and hypothalamic oxidative stress metabolites. Germ-free rats displayed reduced energy intake and no changes in redox homoeostasis machinery expression or pro-inflammatory cytokines after 2 days of WD, in contrast to conventional rats, which exhibited increased SOD2, GLRX and IL-6 mRNA levels. A potentially pro-inflammatory gut microbiota and an early hypothalamic oxidative stress appear shortly after WD introduction. Tripartite data integration highlighted putative links between gut microbiota sub-networks and hypothalamic oxidative stress. Together with the absence of hypothalamic modifications in germ-free rats, this strongly suggests the involvement of the microbiota-hypothalamus axis in rat adaptation to WD introduction and in energy homoeostasis regulation.

Restructuring the Gut Microbiota by Intermittent Fasting Lowers Blood Pressure.

[Figure: see text].

Berberine alleviates visceral hypersensitivity in rats by altering gut microbiome and suppressing spinal microglial activation

Accumulating evidence shows that agents targeting gut dysbiosis are effective for improving symptoms of irritable bowel syndrome (IBS). However, the potential mechanisms remain unclear. In this study we investigated the effects of berberine on the microbiota-gut-brain axis in two rat models of visceral hypersensitivity, i.e., specific pathogen-free SD rats subjected to chronic water avoidance stress (WAS) and treated with berberine (200 mg· kg−1 ·d−1, ig, for 10 days) as well as germ-free (GF) rats subjected to fecal microbiota transplantation (FMT) from a patient with IBS (designated IBS-FMT) and treated with berberine (200 mg· kg−1 ·d−1, ig, for 2 weeks). Before the rats were sacrificed, visceral sensation and depressive behaviors were evaluated. Then colonic tryptase was measured and microglial activation in the dorsal lumbar spinal cord was assessed. The fecal microbiota was profiled using 16S rRNA sequencing, and short chain fatty acids (SCFAs) were measured. We showed that berberine treatment significantly alleviated chronic WAS-induced visceral hypersensitivity and activation of colonic mast cells and microglia in the dorsal lumbar spinal cord. Transfer of fecal samples from berberine-treated stressed donors to GF rats protected against acute WAS. FMT from a patient with IBS induced visceral hypersensitivity and pro-inflammatory phenotype in microglia, while berberine treatment reversed the microglial activation and altered microbial composition and function and SCFA profiles in stools of IBS-FMT rats. We demonstrated that berberine did not directly influence LPS-induced microglial activation in vitro. In both models, several SCFA-producing genera were enriched by berberine treatment, and positively correlated to the morphological parameters of microglia. In conclusion, activation of microglia in the dorsal lumbar spinal cord was involved in the pathogenesis of IBS caused by dysregulation of the microbiota–gut–brain axis, and the berberine-altered gut microbiome mediated the modulatory effects of the agent on microglial activation and visceral hypersensitivity, providing a potential option for the treatment of IBS.

Oxyberberine, an absorbed metabolite of berberine, possess superior hypoglycemic effect via regulating the PI3K/Akt and Nrf2 signaling pathways

Berberine (BBR) is a promising anti-diabetic isoquinoline alkaloid from Rhizoma coptidis, while its bioavailability was extremely low. Here, the existing form and pharmacokinetics of BBR were comparatively characterized in conventional and antibiotic-induced pseudo germ-free (PGF) rats. Furthermore, we comparatively investigated the antidiabetic effect and potential mechanism of BBR and its intestinal oxidative metabolite oxyberberine (OBB) in STZ-induced diabetic rats. Results showed that BBR and OBB existed mainly as protein-bound form in blood, while protein-bound OBB was significantly depleted in PGF rats. Treatment with OBB and BBR effectively decreased clinical symptoms of diabetic rats, reduced blood glucose level, ameliorated the pancreatic damage, and mitigated oxidative stress and inflammatory markers. However, the anti-diabetes effect of BBR was obviously compromised by antibiotics. In addition, OBB exerted superior anti-diabetes effect to BBR of the same dose, significantly up-regulated the mRNA expression of Nrf2 signaling pathway and substantially promoted the pancreatic levels of PI3K/Akt signaling pathway. In conclusion, BBR and its absorbed oxidative metabolite OBB were mainly presented and transported in the protein-bound form in vivo. The gut microbiota may play an important role in the anti-diabetes effect of BBR through transforming itself into the superior hypoglycemic metabolite OBB. OBB possessed favorable hypoglycemic and pancreatic β-cells protective effects, which may stand a huge potential to be further developed into a promising anti-diabetes candidate.

Berberine ameliorates ovariectomy-induced anxiety-like behaviors by enrichment in equol generating gut microbiota

The gut microbiota is recognized as a promising therapeutic target for anxiety. Berberine (BBR) has shown efficacy in the treatment of diseases such as postmenopausal osteoporosis, obesity, and type 2 diabetes through regulating the gut microbiota. However, the effects of BBR on postmenopausal anxiety are still unclear. The purpose of the study is to test whether BBR ameliorates anxiety by modulating intestinal microbiota under estrogen-deficient conditions. Experimental anxiety was established in specific pathogen-free (SPF) ovariectomized (OVX) rats, which were then treated with BBR for 4 weeks before undergoing behavioral tests. Open field and elevated plus maze tests demonstrated that BBR treatment significantly ameliorated anxiety-like behaviors of OVX rats compared with vehicle-treated counterparts. Moreover, as demonstrated by 16S rRNA sequencing and liquid chromatography/mass spectrometry (LC/MS) analysis, BBR-treated OVX rats harbored a higher abundance of beneficial gut microbes, such as Bacteroides, Bifidobacterium, Lactobacillus, and Akkermansia, and exhibited increased equol generation. Notably, gavage feeding of BBR had no significant anti-anxiety effects on germ-free (GF) rats that underwent ovariectomy, whereas GF rats transplanted with fecal microbiota from SPF rats substantially phenocopied the donor rats in terms of anxiety-like symptoms and isoflavone levels. This study indicates that the gut microbiota is critical in the treatment of ovariectomy-aggravated anxiety, and that BBR modulation of the gut microbiota is a promising therapeutic strategy for treating postmenopausal symptoms of anxiety.

Modulation of the immune response and metabolism in germ-free rats colonized by the probiotic Lactobacillus salivarius LI01.

The gut microbiota plays an important role in multifaceted physiological functions in the host. Previous studies have assessed the probiotic effects of Lactobacillus salivarius LI01. In this study, we aimed to investigate the potential effects and putative mechanism of L. salivarius LI01 in immune modulation and metabolic regulation through the monocolonization of germ-free (GF) Sprague-Dawley (SD) rats with L. salivarius LI01. The GF rats were separated into two groups and administered a gavage of L. salivarius LI01 or an equal amount of phosphate-buffered saline. The levels of serum biomarkers, such as interleukin (IL)-1α, IL-5, and IL-10, were restored by L. salivarius LI01, which indicated the activation of Th0 cell differentiation toward immune homeostasis. L. salivarius LI01 also stimulated the immune response and metabolic process by altering transcriptional expression in the ileum and liver. A Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed significant enrichment of the 5'-adenosine monophosphate-activated protein kinase (AMPK) signaling pathway, which indicated that L. salivarius LI01 exerts an effect on energy accumulation. The LI01 group showed alterations in fecal carbohydrates accompanied by an increased body weight gain. In addition, L. salivarius LI01 produced indole-3-lactic acid (ILA) and enhanced arginine metabolism by rebalancing the interconversion between arginine and proline. These findings provide evidence showing that L. salivarius LI01 can directly impact the host by modulating immunity and metabolism. KEY POINTS : • Lactobacillus salivarius LI01 conventionalizes the cytokine profile and activates the immune response. • LI01 modulates carbohydrate metabolism and arginine transaction. • LI01 generates tryptophan-derived indole-3-lactic acid. • The cytochrome P450 family contributes to the response to altered metabolites.

Region-specific sex modulation of central oxytocin receptor by gut microbiota: An ontogenic study.

Oxytocin (OT) is a developmentally important neuropeptide recognized to play a dominant role in social functioning and stress-related behaviors, in a sex-dependent manner. Nonetheless, the underlining factors driving OT and OT receptor (OTR) early brain development remain unclear. Recent evidence highlight the critical influence of gut microbiota and its bidirectional interaction with the brain on neurodevelopment via the gut microbiota-brain axis. Therefore, we aimed to determine the impact of gut microbiota on the OTR system of the rat brain at different developmental stages in a pilot study. Quantitative OTR [125 I]-OVTA autoradiographic binding was carried out in the forebrain of male and female conventional (CON) and germ-free (GF) rats at postnatal days (PND) 8, 22, and 116-150. OTR binding was also assessed in the eyes of PND 1 and PND 4 GF female rats. Significant "microbiota × sex × region" interaction and age-dependent effects on OTR binding were demonstrated. Microbiota status influenced OTR levels in males but not females with higher levels of OTR observed in GF versus CON rats in the cingulate, prelimbic, and lateral/medial/ventral orbital cortex, and septum across all age groups, while sex differences were observed in GF, but not in CON rats. Interestingly, OTRs present in the eyes of CON rats were abolished in GF rats. This is the first study to uncover a sex-specific role of gut microbiota on the central OTR system, which may have implications in understanding the developmental neuroadaptations critical for behavioral regulation and the etiology of certain neurodevelopmental disorders.

Effects of Pediococcus pentosaceus LI05 on immunity and metabolism in germ-free rats.

Many Pediococcus spp. have health-promoting benefits, and Pediococcus pentosaceus LI05 is one such species that was proved to be beneficial in previous studies. Our research aimed to determine the immune and metabolic effects of P. pentosaceus LI05 on germ-free rats. Germ-free rats were gavaged with P. pentosaceus LI05 suspensions (1 × 109 CFU) for 2 weeks, and 3 weeks later, blood, spleen, intestine and liver samples were gathered for metabolome, intestine morphology, immunity, and transcriptomics analyses. Oral gavage of P. pentosaceus LI05 reduced the bodyweight of rats, which manifested as increased fecal carbohydrate concentrations, decreased intestinal fat intake and the hepatic fat synthesis gene expression, and accelerated fat-to-glycogen conversion. In addition, P. pentosaceus LI05 exhibited an anti-inflammatory ability, reducing serum proinflammatory cytokine levels and increasing intestinal subepidermal CD4+ cell levels. Furthermore, administration of P. pentosaceus LI05 increased the antimicrobial ability and enhanced the liver detoxification function. These results indicate that as a probiotic, P. pentosaceus LI05 ameliorates the hampered immune response of GF animals and improves the metabolism of fat and toxic substances.

Increased Expression of Colonic Mucosal Melatonin in Patients with Irritable Bowel Syndrome Correlated with Gut Dysbiosis

Dysregulation of the gut microbiota/gut hormone axis contributes to the pathogenesis of irritable bowel syndrome (IBS). Melatonin plays a beneficial role in gut motility and immunity. However, altered expression of local mucosal melatonin in IBS and its relationship with the gut microbiota remain unclear. Therefore, we aimed to detect the colonic melatonin levels and microbiota profiles in patients with diarrhea-predominant IBS (IBS-D) and explore their relationship in germ-free (GF) rats and BON-1 cells. Thirty-two IBS-D patients and twenty-eight healthy controls (HCs) were recruited. Fecal specimens from IBS-D patients and HCs were separately transplanted into GF rats by gavage. The levels of colon mucosal melatonin were assessed by immunohistochemical methods, and fecal microbiota communities were analyzed using 16S rDNA sequencing. The effect of butyrate on melatonin synthesis in BON-1 cells was evaluated by ELISA. Melatonin levels were significantly increased and negatively correlated with visceral hypersensitivity in IBS-D patients. GF rats inoculated with fecal microbiota from IBS-D patients had high colonic melatonin levels. Butyrate-producing Clostridium cluster XIVa species, such as Roseburia species and Lachnospira species, were positively related to colonic mucosal melatonin expression. Butyrate significantly increased melatonin secretion in BON-1 cells. Increased melatonin expression may be an adaptive protective mechanism in the development of IBS-D. Moreover, some Clostridium cluster XIVa species could increase melatonin expression via butyrate production. Modulation of the gut hormone/gut microbiota axis offers a promising target of interest for IBS in the future.

Microbiota Introduced to Germ-Free Rats Restores Vascular Contractility and Blood Pressure.

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 (BP) control remain unanswered. To examine the direct effects of microbiota on BP, 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 with their conventionalized counterparts, suggesting an obligatory role of microbiota in BP homeostasis. Hypotension observed in GF rats was accompanied by a marked reduction in vascular contractility. Both BP and vascular contractility were restored by the introduction of microbiota to GF rats, indicating that microbiota could impact BP 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. Overall, these results constitute a fundamental discovery of the essential nature of microbiota in BP regulation.

Abstract P112: Elevated Blood Pressure In Conventionalized Germ-free Rats Is Coupled With Upregulation Of Kynurenic Pathway Metabolites And Central Immune Responses

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 &lt;0.05), diastolic BP (96 mmHg vs 79 mmHg, p &lt;0.05), and serum levels of kynurenic acid (-9.76 vs -10.21, p &lt;0.05) and 3-hydroxy kynurenine (-6.49 vs -7.34, p &lt;0.01). Coupled with these increases in kynurenic pathway metabolites, microarray analyses demonstrated increased immune responses (e.g. Cd74, Il1b, Cxcl1, Mmp14 ) in the PVN (gene ontology analysis, p &lt;0.001) and increased cell differentiation and synaptic plasticity (e.g. Sox11, Tp53, Cdk6, Hoxb4, Foxo4, Cyr61 ) in the NTS (gene ontology analysis, p &lt;0.01). 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.

Abstract P241: Intermittent Fasting Lowers Blood Pressure In A Rat Model Of Hypertension By Modulating The Gut Microbiota

Studies have demonstrated that disruption of the gut microbiota, termed gut dysbiosis, plays a causal role in the development of hypertension (HT) in animal models and patients. Recent studies revealed that intermittent fasting alters the gut microbiota and the production of microbial metabolites. Thus, we hypothesized that every-other-day-fasting (EODF) would prevent elevations of blood pressure (BP) in spontaneously hypertensive stroke prone rat (SHRSP) by maintaining a healthy gut microbiota. Five-week old SHRSP rats and normotensive Wistar Kyoto (WKY) rats were randomized to be fed ad lib or on EODF for 10 weeks. BP was measured weekly, and cecal content and plasma were collected at the end of the study. To examine the roles of gut microbiota and microbial metabolites in hypertension, we performed whole-genome shotgun sequencing on cecal samples and non-targeted metabolomics on cecal contents and plasma. To examine the direct effects of the EODF altered microbiota on BP regulation and eliminate the confounding variable of fasting, pooled cecal contents of SHRSP and WKY animals fed ad lib or EODF were given to germ free (GF) rats by oral gavage. We found that ten-weeks EODF was able to prevent elevations of systolic BP (SBP) in SHRSP compared to ad lib fed SHRSP (~220 vs. ~170mmHg; n=6-8, p&lt;0.05), and that germ free rats transplanted with SHRSP ad lib microbiota had a significantly higher SBP as compared to those transplanted with SHRSP EODF microbiota (~152 vs. ~140 mmHg; n=6-7, p&lt;0.01), indicating that microbiota and their metabolites are accountable for the effects of EODF. Principle coordinate analysis showed that EODF significantly altered the overall composition of both WKY and SHRSP microbiota (WKY p&lt;0.01, SHRSP p&lt;0.009). Multi-omics analysis indicates distinct microbiome and metabolome in SHRSP compared to WKY, and significant alterations to each induced by EODF. These findings suggest that EODF is able to prevent hypertension in SHRSP, and this involves altering the gut microbiota and metabolome.

Abstract P238: Bile Acid Metabolites Modulate Hypertension

Hypertension is the single prominent risk factor of epidemic proportions leading to cardiovascular disease and stroke, which comprise the top two reasons for mortality of humans in the modern age. Much of the attention for the unknown causes of hypertension was focused on genetics and dietary salt, but in recent years, host-microbiotal interaction is gaining importance. Host-microbiotal partnership is key for the generation of many bioactive molecules including bile acid (BA) metabolites. Primary bile acids are synthesized and conjugated by the host but deconjugated and further modified to secondary BA by gut commensal bacteria. BA metabolites serve as important ligands for host nuclear receptors and/or G-protein-coupled receptors. These receptors have pivotal roles in blood pressure regulation. However, the effect of the host-microorganism biliary network on blood pressure (BP) remains poorly characterized. Here we report that both dietary salt and genetic factors rewire the composition of bile acids and BP. Specific reductions in conjugated bile acids were noted in human hypertensives as well as in rats with hypertension. Conjugation of bile acids by the host alone, devoid of the deconjugation step by microbiota, was sufficient to decrease BP of germ-free rats compared to germ-free conventionalized rats. Nutritional restoration of the conjugation of bile acids with Taurine increased the availability of circulating conjugated bile acids as ligands and ameliorated host susceptibility to hypertension via BA nuclear receptors and G-protein-coupled receptors. Thus, hosts and their bacterial symbionts can control host BP homeostasis via the resulting pool of bile acid metabolites. Sources of funding: National Institutes of Health (R01HL143082).

Ascorbic acid deficiency induces hepatic and intestinal expression of inflammation-related genes irrespective of the presence or absence of gut microbiota in ODS rats

We have previously demonstrated that ascorbic acid (AsA) deficiency causes inflammatory changes in the liver and intestine in Osteogenic Disorder Shionogi (ODS) rats, which are unable to synthesize AsA. We have suggested that AsA deficiency increased intestinal interleukine (IL)-6 production, stimulating hepatic acute phase proteins (APPs) expression via the portal vein. In this study, we determined whether these hepatic and intestinal inflammatory changes by AsA deficiency are induced in germ-free (GF) ODS rats. For 18 days, male specific pathogen-free (SPF) ODS rats were fed the basal diet containing 600 mg AsA/kg (control group) or the AsA-free diet (AsA-deficient group) in SPF conditions, while male GF ODS rats were fed the basal diet (control group) or the AsA-free diet (AsA-deficient group) in GF conditions. Firstly, AsA deficiency significantly elevated the hepatic expression of APPs in both SPF and GF rats. In hepatic mRNA levels of some APPs, significant interaction between GF and AsA-deficiency effects was observed. Secondly, AsA deficiency elevated intestinal IL-6 and IL-1β mRNA levels in both SPF and GF rats, and significant interaction between GF and AsA-deficiency effects was observed in these mRNA levels of jejunum and cecum. In SPF and GF rats, AsA deficiency elevated portal IL-6 concentration. These results show that AsA deficiency caused hepatic and intestinal inflammatory changes in both the GF and SPF ODS rats and indicate that AsA deficiency could directly induce intestinal inflammatory changes without the involvement of gut microbiota.