Complementary symbiont contributions to plant decomposition in a fungus-farming termite

Termites normally rely on gut symbionts to decompose organic matter but the Macrotermitinae domesticated Termitomyces fungi to produce their own food. This transition was accompanied by a shift in the composition of the gut microbiota, but the complementary roles of these bacteria in the symbiosis have remained enigmatic. We obtained high-quality annotated draft genomes of the termite Macrotermes natalensis, its Termitomyces symbiont, and gut metagenomes from workers, soldiers, and a queen. We show that members from 111 of the 128 known glycoside hydrolase families are represented in the symbiosis, that Termitomyces has the genomic capacity to handle complex carbohydrates, and that worker gut microbes primarily contribute enzymes for final digestion of oligosaccharides. This apparent division of labor is consistent with the Macrotermes gut microbes being most important during the second passage of comb material through the termite gut, after a first gut passage where the crude plant substrate is inoculated with Termitomyces asexual spores so that initial fungal growth and polysaccharide decomposition can proceed with high efficiency. Complex conversion of biomass in termite mounds thus appears to be mainly accomplished by complementary cooperation between a domesticated fungal monoculture and a specialized bacterial community. In sharp contrast, the gut microbiota of the queen had highly reduced plant decomposition potential, suggesting that mature reproductives digest fungal material provided by workers rather than plant substrate.Interspecific mutualism usually allows partner species preferential access to complementary resources. Some hosts internalized microbial symbionts, leading to vertical transmission and varying degrees of genome loss (1), whereas others domesticated external partners that maintained independent reproduction (2). Understanding how such ectosymbioses remain evolutionarily stable is challenging (3) because prokaryote and eukaryote symbionts form interacting communities, which may be difficult for hosts to control when symbionts can achieve higher fitness by pursuing selfish reproductive strategies (4). Digestive symbiotic communities in animal guts provide excellent examples of such ambiguities; recent studies of human microbiotas show that gut communities vary by subject age, geography (5), and diet (6) and that deviating microbiotas can be associated with compromised health (7).Given the continuous flow of food through animal guts, it is intriguing that adaptive microbiotas can normally be maintained (8–10) without invasion by less beneficial or harmful microbes (11). Insect lineages that have relied on nutritional symbioses have existed and adaptively radiated for tens of millions of years, suggesting that the benefits of these symbioses surpass the potential levels-of-selection conflicts that need to be regulated (12). However, beyond examples from humans and some domesticated ungulates, we lack fundamental insight into the genes involved, their expression, and their phenotypic functions. Termites provide a case in point, as they originated >150 Mya and have relied on protist and bacterial gut symbionts for the breakdown of lignocellulose throughout their evolutionary history (13), allowing them to become dominant decomposers in terrestrial ecosystems (13, 14).A single monophyletic subfamily, the Macrotermitinae, realized a major evolutionary transition ca. 30 Mya, when they domesticated the ancestor of the fungal genus Termitomyces (15). They have radiated into 11 termite genera with more than 330 extant species (15, 16) to collectively obtain a massive ecological footprint in the Old World (sub)tropics, matched only by the fungus-growing (attine) ants of the New World (14, 17). Throughout their evolutionary history, the partnership with five major clades of Termitomyces has remained obligate, as no macrotermitine termite is known to have abandoned fungus farming or to rear other fungi than Termitomyces (15) (Fig. 1 A and B). Coinciding with the domestication of Termitomyces, the common ancestor of the Macrotermitinae underwent a major shift in the bacterial gut community (18, 19). The fungus-growing termites thus represent a major metazoan radiation based on a simultaneous tripartite life-history transition: insects becoming farmers, fungi becoming crops, and gut microbiotas adopting largely unknown complementary roles.Open in a separate windowFig. 1.The fungus-growing termite symbiosis and its genomic characteristics. (A) A Macrotermes natalensis colony in South Africa: (i) the underground fungus comb in which Termitomyces is maintained and (ii and iii) the royal chamber with the queen (ii) and the king (iii). (B) Geographic distribution of the Macrotermitinae (gray), with darker areas in southern Africa highlighting the known occurrences of M. natalensis (adapted from ref. 61). (C) The substrate and recurrent Termitomyces inoculation within a colony centered around the termite gut: Asexual Termitomyces spores from fungus comb nodules (i) and plant biomass substrate (ii) are mixed within the termite gut (iii, first gut passage) to become the new fungus comb substrate (iv) within which Termitomyces hyphae grow to maturity so that new nodules with asexual spores are produced (v) until the plant substrate is fully used and the old comb (vi) is consumed by the termites (vii, second gut passage). (D) To characterize the genetic potential of the fungus-growing termite symbiosis, we sequenced M. natalensis and Termitomyces and obtained worker, soldier, and queen gut metagenomes (SI Appendix and GigaScience Database, http://dx.doi.org/10.5524/100055).Fungus-growing termites rely on the external decomposition of plant substrate by their Termitomyces fungus garden symbiont. In Macrotermes species, the fungus comb is managed in a highly structured way, with older workers collecting crude forage material and bringing it back to the nest, where younger workers ingest it together with asexual Termitomyces spores (conidia) provided by fungal nodules from established “fungus-garden combs” to produce primary feces that is deposited as new layers of comb (17, 20) (Fig. 1C). This new substrate quickly develops dense hyphal networks and produces the next cohorts of nodules (2, 20), whereas older termites ultimately consume the old comb (Fig. 1C). This combination of substrate processing and inoculation at first gut passage followed by a second digestive phase makes the termite gut the central operational compartment of the symbiosis. It is here that the entire genetic potential of all members of the symbiosis comes together, presumably shaped by natural selection for optimal collective performance in two sequential digestive phases. To investigate functional complementarity of the three major components of the mutualism, we (i) obtained high-quality draft genome sequences of the fungus-growing termite Macrotermes natalensis, its Termitomyces sp. symbiont, and several caste-specific gut microbiotas; (ii) analyzed the genomic potential for lignocellulolytic enzyme potential to assess functional contributions across partners; and (iii) compared gut microbiotas across sterile and reproductive castes to evaluate functional gut specialization across termite family members.     

The contribution of respiratory microbiome analysis to a treatable traits model of care

The composition of the airway microbiome in patients with chronic airway diseases, such as severe asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis and cystic fibrosis (CF), has the potential to inform a precision model of clinical care. Patients with these conditions share overlapping disease characteristics, including airway inflammation and airflow limitation. The clinical management of chronic respiratory conditions is increasingly moving away from a one‐size‐fits‐all model based on primary diagnosis, towards care targeting individual disease traits, and is particularly useful for subgroups of patients who respond poorly to conventional therapies. Respiratory microbiome analysis is an important potential contributor to such a ‘treatable traits’ approach, providing insight into both microbial drivers of airways disease, and the selective characteristics of the changing lower airway environment. We explore the potential to integrate respiratory microbiome analysis into a treatable traits model of clinical care and provide a practical guide to the application and clinical interpretation of respiratory microbiome analysis.     

Lactobacillus rhamnosus probiotic prevents airway function deterioration and promotes gut microbiome resilience in a murine asthma model

ABSTRACT

Allergic asthma is a highly prevalent inflammatory disease of the lower airways, clinically characterized by airway hyperreactivity and deterioration of airway function. Immunomodulatory probiotic bacteria are increasingly being explored to prevent asthma development, alone or in combination with other treatments.

In this study, wild-type and recombinant probiotic Lactobacillus rhamnosus GR-1 were tested as preventive treatment of experimental allergic asthma in mice. Recombinant L. rhamnosus GR-1 was designed to produce the major birch pollen allergen Bet v 1, to promote allergen-specific immunomodulation. Administration of wild-type and recombinant L. rhamnosus GR-1 prevented the development of airway hyperreactivity. Recombinant L. rhamnosus GR-1 also prevented elevation of airway total cell counts, lymphocyte counts and lung IL-1β levels, while wild-type L. rhamnosus GR-1 inhibited airway eosinophilia. Of note, a shift in gut microbiome composition was observed after asthma development, which correlated with the severity of airway inflammation and airway hyperreactivity. In the groups that received L. rhamnosus GR-1, this asthma-associated shift in gut microbiome composition was not observed, indicating microbiome-modulating effects of this probiotic.

These data demonstrate that L. rhamnosus GR-1 can prevent airway function deterioration in allergic asthma. Bet v 1 expression by L. rhamnosus GR-1 further contributed to lower airway inflammation, although not solely through the expected reduction in T helper 2-associated responses, suggesting involvement of additional mechanisms. The beneficial effects of L. rhamnosus GR-1 correlate with increased gut microbiome resilience, which in turn is linked to protection of airway function, and thus further adds support to the existence of a gut-lung axis.     

A bidirectional association between the gut microbiota and CNS disease in a biphasic murine model of multiple sclerosis

The gut microbiome plays an important role in the development of inflammatory disease as shown using experimental models of central nervous system (CNS) demyelination. Gut microbes influence the response of regulatory immune cell populations in the gut-associated lymphoid tissue (GALT), which drive protection in acute and chronic experimental autoimmune encephalomyelitis (EAE). Recent observations suggest that communication between the host and the gut microbiome is bidirectional. We hypothesized that the gut microbiota differs between the acute inflammatory and chronic progressive stages of a murine model of secondary-progressive multiple sclerosis (SP-MS). This non-obese diabetic (NOD) model of EAE develops a biphasic pattern of disease that more closely resembles the human condition when transitioning from relapsing-remitting (RR)-MS to SP-MS. We compared the gut microbiome of NOD mice with either mild or severe disease to that of non-immunized control mice. We found that the mice which developed a severe secondary form of EAE harbored a dysbiotic gut microbiome when compared with the healthy control mice. Furthermore, we evaluated whether treatment with a cocktail of broad-spectrum antibiotics would modify the outcome of the progressive stage of EAE in the NOD model. Our results indicated reduced mortality and clinical disease severity in mice treated with antibiotics compared with untreated mice. Our findings support the hypothesis that there are reciprocal effects between experimental CNS inflammatory demyelination and modification of the microbiome providing a foundation for the establishment of early therapeutic interventions targeting the gut microbiome that could potentially limit disease progression.     

Structural and functional alterations in the colonic microbiome of the rat in a model of stress induced irritable bowel syndrome

Stress is known to perturb the microbiome and exacerbate irritable bowel syndrome (IBS) associated symptoms. Characterizing structural and functional changes in the microbiome is necessary to understand how alterations affect the biomolecular environment of the gut in IBS. Repeated water avoidance (WA) stress was used to induce IBS-like symptoms in rats. The colon-mucosa associated microbiome was characterized in 13 stressed and control animals by 16S sequencing. In silico analysis of the functional domains of microbial communities was done by inferring metagenomic profiles from 16S data. Microbial communities and functional profiles were compared between conditions. WA animals exhibited higher α-diversity and moderate divergence in community structure (β-diversity) compared with controls. Specific clades and taxa were consistently and significantly modified in the WA animals. The WA microbiome was particularly enriched in Proteobacteria and depleted in several beneficial taxa. A decreased capacity in metabolic domains, including energy- and lipid-metabolism, and an increased capacity for fatty acid and sulfur metabolism was inferred for the WA microbiome. The stressed condition favored the proliferation of a greater diversity of microbes that appear to be functionally similar, resulting in a functionally poorer microbiome with implications for epithelial health. Taxa, with known beneficial effects, were found to be depleted, which supports their relevance as therapeutic agents to restore microbial health. Microbial sulfur metabolism may form a key component of visceral nerve sensitization pathways and is therefore of interest as a target metabolic domain in microbial ecological restoration.     

Contributions of microbiome and mechanical deformation to intestinal bacterial overgrowth and inflammation in a human gut-on-a-chip

A human gut-on-a-chip microdevice was used to coculture multiple commensal microbes in contact with living human intestinal epithelial cells for more than a week in vitro and to analyze how gut microbiome, inflammatory cells, and peristalsis-associated mechanical deformations independently contribute to intestinal bacterial overgrowth and inflammation. This in vitro model replicated results from past animal and human studies, including demonstration that probiotic and antibiotic therapies can suppress villus injury induced by pathogenic bacteria. By ceasing peristalsis-like motions while maintaining luminal flow, lack of epithelial deformation was shown to trigger bacterial overgrowth similar to that observed in patients with ileus and inflammatory bowel disease. Analysis of intestinal inflammation on-chip revealed that immune cells and lipopolysaccharide endotoxin together stimulate epithelial cells to produce four proinflammatory cytokines (IL-8, IL-6, IL-1β, and TNF-α) that are necessary and sufficient to induce villus injury and compromise intestinal barrier function. Thus, this human gut-on-a-chip can be used to analyze contributions of microbiome to intestinal pathophysiology and dissect disease mechanisms in a controlled manner that is not possible using existing in vitro systems or animal models.Various types of inflammatory bowel disease (IBD), such as Crohn’s disease and ulcerative colitis, involve chronic inflammation of human intestine with mucosal injury and villus destruction (1), which is believed to be caused by complex interactions between gut microbiome (including commensal and pathogenic microbes) (2), intestinal mucosa, and immune components (3). Suppression of peristalsis also has been strongly associated with intestinal pathology, inflammation (4, 5), and small intestinal bacterial overgrowth (5, 6) in patients with Crohn’s disease (7) and ileus (8). However, it has not been possible to study the relative contributions of these different potential contributing factors to human intestinal inflammatory diseases, because it is not possible to independently control these parameters in animal studies or in vitro models. In particular, given the recent recognition of the central role of the intestinal microbiome in human health and disease, including intestinal disorders (2), it is critical to incorporate commensal microbes into experimental models; however, this has not been possible using conventional culture systems.Most models of human intestinal inflammatory diseases rely either on culturing an intestinal epithelial cell monolayer in static Transwell culture (9) or maintaining intact explanted human intestinal mucosa ex vivo (10) and then adding live microbes and immune cells to the apical (luminal) or basolateral (mucosal) sides of the cultures, respectively. These static in vitro methods, however, do not effectively recapitulate the pathophysiology of human IBD. For example, intestinal epithelial cells cultured in Transwell plates completely fail to undergo villus differentiation, produce mucus, or form the various specialized cell types of normal intestine. Although higher levels of intestinal differentiation can be obtained using recently developed 3D organoid cultures (11), it is not possible to expose these cells to physiological peristalsis-like motions or living microbiome in long-term culture, because bacterial overgrowth occurs rapidly (within ∼1 d) compromising the epithelium (12). This is a major limitation because establishment of stable symbiosis between the epithelium and resident gut microbiome as observed in the normal intestine is crucial for studying inflammatory disease initiation and progression (13), and rhythmical mechanical deformations driven by peristalsis are required to both maintain normal epithelial differentiation (14) and restrain microbial overgrowth in the intestine in vivo (15).Thus, we set out to develop an experimental model that would overcome these limitations. To do this, we adapted a recently described human gut-on-a-chip microfluidic device that enables human intestinal epithelial cells (Caco-2) to be cultured in the presence of physiologically relevant luminal flow and peristalsis-like mechanical deformations, which promotes formation of intestinal villi lined by all four epithelial cell lineages of the small intestine (absorptive, goblet, enteroendocrine, and Paneth) (12, 16). These villi also have enhanced barrier function, drug-metabolizing cytochrome P450 activity, and apical mucus secretion compared with the same cells grown in conventional Transwell cultures, which made it possible to coculture a probiotic gut microbe (Lactobacillus rhamnosus GG) in direct contact with the intestinal epithelium for more than 2 wk (12), in contrast to static Transwell cultures (17) or organoid cultures (11) that lose viability within hours under similar conditions. In the present study, we leveraged this human gut-on-a-chip to develop a disease model of small intestinal bacterial overgrowth (SIBO) and inflammation. We analyzed how probiotic and pathogenic bacteria, lipopolysaccharide (LPS), immune cells, inflammatory cytokines, vascular endothelial cells and mechanical forces contribute individually, and in combination, to intestinal inflammation, villus injury, and compromise of epithelial barrier function. We also explored whether we could replicate the protective effects of clinical probiotic and antibiotic therapies on-chip to demonstrate its potential use as an in vitro tool for drug development, as well as for dissecting fundamental disease mechanisms.     

From clinical uncertainties to precision medicine: the emerging role of the gut barrier and microbiome in small bowel functional diseases

Introduction: Over the last decade, remarkable progress has been made in the understanding of disease pathophysiology. Many new theories expound on the importance of emerging factors such as microbiome influences, genomics/omics, stem cells, innate intestinal immunity or mucosal barrier complexities. This has introduced a further dimension of uncertainty into clinical decision-making, but equally, may shed some light on less well-understood and difficult to manage conditions.

Areas covered: Comprehensive review of the literature on gut barrier and microbiome relevant to small bowel pathology. A PubMed/Medline search from 1990 to April 2017 was undertaken and papers from this range were included.

Expert commentary: The scenario of clinical uncertainty is well-illustrated by functional gastrointestinal disorders (FGIDs). The movement towards achieving a better understanding of FGIDs is expressed in the Rome IV guidelines. Novel diagnostic and therapeutic protocols focused on the GB and SB microbiome can facilitate diagnosis, management and improve our understanding of the underlying pathological mechanisms in FGIDs.     

Anaerobic 4-hydroxyproline utilization: Discovery of a new glycyl radical enzyme in the human gut microbiome uncovers a widespread microbial metabolic activity

ABSTRACT

The discovery of enzymes responsible for previously unappreciated microbial metabolic pathways furthers our understanding of host-microbe and microbe-microbe interactions. We recently identified and characterized a new gut microbial glycyl radical enzyme (GRE) responsible for anaerobic metabolism of trans-4-hydroxy-l-proline (Hyp). Hyp dehydratase (HypD) catalyzes the removal of water from Hyp to generate Δ¹-pyrroline-5-carboxylate (P5C). This enzyme is encoded in the genomes of a diverse set of gut anaerobes and is prevalent and abundant in healthy human stool metagenomes. Here, we discuss the roles HypD may play in different microbial metabolic pathways as well as the potential implications of this activity for colonization resistance and pathogenesis within the human gut. Finally, we present evidence of anaerobic Hyp metabolism in sediments through enrichment culturing of Hyp-degrading bacteria, highlighting the wide distribution of this pathway in anoxic environments beyond the human gut.     

Antidepressant treatment with fluoxetine during pregnancy and lactation modulates the gut microbiome and metabolome in a rat model relevant to depression

ABSTRACT

Up to 10% of women use selective serotonin reuptake inhibitor (SSRI) antidepressants during pregnancy and postpartum. Recent evidence suggests that SSRIs are capable of altering the gut microbiota. However, the interaction between maternal depression and SSRI use on bacterial community composition and the availability of microbiota-derived metabolites during pregnancy and lactation is not clear.

We studied this using a rat model relevant to depression, where adult females with a genetic vulnerability and stressed as pups show depressive-like behaviors. Throughout pregnancy and lactation, females received the SSRI fluoxetine or vehicle. High-resolution 16S ribosomal RNA marker gene sequencing and targeted metabolomic analysis were used to assess the fecal microbiome and metabolite availability, respectively.

Not surprisingly, we found that pregnancy and lactation segregate in terms of fecal microbiome diversity and composition, accompanied by changes in metabolite availability. However, we also showed that fluoxetine treatment altered important features of this transition from pregnancy to lactation most clearly in previously stressed dams, with lower fecal amino acid concentrations. Amino acid concentrations, in turn, correlated negatively with the relative abundance of bacterial taxa such as Prevotella and Bacteroides.

Our study demonstrates an important relationship between antidepressant use during the perinatal period and maternal fecal metabolite availability in a rat model relevant to depression, possibly through parallel changes in the gut microbiome. Since microbial metabolites contribute to homeostasis and development, insults to the maternal microbiome by SSRIs might have health consequences for mother and offspring.     

Distinct contributions of the amygdala and parahippocampal gyrus to suspicion in a repeated bargaining game

Humans assess the credibility of information gained from others on a daily basis; this ongoing assessment is especially crucial for avoiding exploitation by others. We used a repeated, two-person bargaining game and a cognitive hierarchy model to test how subjects judge the information sent asymmetrically from one player to the other. The weight that they give to this information is the result of two distinct factors: their baseline suspicion given the situation and the suspicion generated by the other person's behavior. We hypothesized that human brains maintain an ongoing estimate of the credibility of the other player and sought to uncover neural correlates of this process. In the game, sellers were forced to infer the value of an object based on signals sent from a prospective buyer. We found that amygdala activity correlated with baseline suspicion, whereas activations in bilateral parahippocampus correlated with trial-by-trial uncertainty induced by the buyer's sequence of suggestions. In addition, the less credible buyers that appeared, the more sensitive parahippocampal activation was to trial-by-trial uncertainty. Although both of these neural structures have previously been implicated in trustworthiness judgments, these results suggest that they have distinct and separable roles that correspond to their theorized roles in learning and memory.     

Effects of cationic hydroxyethyl cellulose on glucose metabolism and obesity in a diet-induced obesity mouse model

Background: To investigate the effect of a new soluble fiber, namely cationic hydroxyethyl cellulose (cHEC), on weight loss and metabolic disorders associated with obesity using a high‐fat diet‐induced obese mouse model. Methods: Obese male C57BL/6J (B6) mice were fed high‐fat (60% kcal) diets supplemented with cHEC for 5 weeks. Body weight, energy intake, mesenteric adipose and liver weights, plasma cholesterol, plasma insulin, glucose, adiponectin, and leptin were assessed to determine the effects of cHEC. Hepatic and fecal lipids were also analyzed to investigate the effect of cHEC on lipid absorption and metabolism. Results: Supplementation of the high‐fat diet with cHEC resulted in significant weight loss in obese mice. In addition, significant decreases were seen in mesenteric adipose and liver weights, as well as concentrations of plasma cholesterol and hepatic lipids. A significant improvement in glucose homeostasis, insulin sensitivity, and leptin concentrations were observed at 4% cHEC. Moreover, increases in fecal excretion of total bile acids, sterols, and fats indicated altered fat absorption when cHEC was supplemented in the diet. Conclusions: We have shown in the present study that cHEC reduces body weight, improves insulin sensitivity, and prevents the development of metabolic syndrome. Furthermore, the effects of cHEC on glucose and lipid homeostasis in B6 mice are mediated by improvements in leptin sensitivity resulting from reduced fat absorption.     

Progression to impaired glucose regulation, diabetes and metabolic syndrome in Chinese women with a past history of gestational diabetes

BACKGROUND: To examine the risk of developing impaired glucose regulation (IGR), diabetes mellitus (DM) and metabolic syndrome (MetS) in Chinese women with history of gestational diabetes. METHODS: 203 Chinese women enrolled in a previous study were followed up at a median of 8 (range 7-10) years of whom 136 had normal glucose tolerance (NGT) and 68 had gestational diabetes mellitus (GDM) and gestational impaired glucose tolerance (GIGT). RESULTS: In women with a history of gestational diabetes (n = 4), GIGT (n = 63) and NGT (n = 136), 2 (50%), 19 (30.2%) and 21 (15.4%) developed IGR while 2 (50%), 4 (6.3%), 3 (2.2%) developed DM respectively. Most women developed IGR (86%, n = 36) or DM (78%, n = 7) were undiagnosed. MetS occurred in 16 (7.9%) women with similar rates between those with and those without a history of gestational diabetes (7.5% vs 8.1%; p = 0.85). History of gestational diabetes [OR: 3.8 (95% CI 1.9-7.8)] and body mass index (BMI) >/= 23 kg/m(2) [OR: 3.4 (95% CI 1.7-6.8)] at first antenatal visit were predictors for IGR or DM. Family history of DM [OR: 5.0 (95% CI 1.5-16.4)] and BMI >/= 23 kg/m(2) [OR: 28.3 (95% CI 3.6-223)] at first antenatal visit were predictors for MetS. CONCLUSIONS: Chinese women with a history of gestational diabetes have a high risk of IGR or DM. Overweight at the first antenatal visit is a common risk factor for IGR, DM and MetS. A prior history of gestational diabetes was predictive of IGR and DM while a positive family history of DM was predictive of MetS.     

The effect of portal and peripheral insulin delivery on carbohydrate and lipid metabolism in a miniature pig model of human IDDM

Summary A pig model of insulin-dependent diabetes was used to examine the importance of the portal-systemic insulin gradient for whole-body metabolic control. Six pigs had jugular vein, portal vein, and carotid artery cannulae implanted before being made diabetic (150 mg kg^{− 1} streptozotocin). Each animal received 4 weeks of portal and 4 weeks of peripheral insulin delivery in random order. The blood glucose target range was 5–10 mmol · l^{− 1}, and serum fructosamine and fasting and postprandial blood glucose concentrations were not different between peripheral and portal insulin infusion. Insulin requirement was not different between the 4 week infusion periods, but fasting peripheral insulin levels after peripheral delivery (124 ± 16 (mean ± SEM) pmol · l^{− 1}) were significantly higher (p < 0.05) than in portally infused (73.8 ± 5.4 pmol · l^{− 1}) or pre-diabetic control animals (68.4 ± 3.6 pmol · l^{− 1}). Basal hepatic glucose output was also higher (p < 0.05) in peripherally (4.2 ± 0.4 mg · kg^{− 1}· min^{− 1}) than in portally infused animals (2.9 ± 0.4 mg · kg^{− 1}· min^{− 1}) or controls (3.0 ± 0.3 mg · kg^{− 1}· min^{− 1}). Clamp glucose metabolic clearance rate was, however, not different between the peripheral and portal insulin delivery routes (8.1 ± 1.0 vs 9.0 ± 0.7 ml · kg^{− 1}· min^{− 1}), although both were significantly lower (p < 0.05) than that measured in prediabetic control animals (11.7 ± 1.0 ml · kg^{− 1}· min^{− 1}). Lipid profiles and subfractions were similar in all three groups. It is concluded that the portal route of delivery is superior to the peripheral in maintaining more appropriate insulin concentrations and control of hepatic glucose output, although in the absence of euglycaemia it is still associated with significant metabolic abnormalities. [Diabetologia (1997) 40: 1125–1134] Received: 25 February 1997 and in revised form: 23 May 1997     

Toward a porcine in vivo model to analyze the pathogenesis of TLR5-dependent enteropathies

ABSTRACT

Non-communicable diseases, such as the metabolic syndrome and inflammatory bowel disease, constitute serious public health threats in developed countries. Besides environmental factors, genetic predispositions contribute to the onset and progression of the disease. State-of-the-art mouse models recently highlight the involvement of Toll-like receptor 5 (TLR5)–driven microbiota composition in the development of metabolic disorders. Here, we discuss the causes and consequences of an altered enteric microbiota and provide information on a similar mechanism in another species, the pig. We show for the first time that a single nucleotide polymorphism in the porcine TLR5 gene conferring impaired functionality is associated with changes in the intestinal microbiota in adult sows and neonatal piglets. Changes in the developing adaptive cellular immune response support the concept of TLR5-driven changes of the microbe-host interplay also in the pig. Together, these findings suggest that pigs with impaired TLR-functionality might represent a model for TLR5-driven diseases in humans.     

Effects of exposure to bisphenol A and ethinyl estradiol on the gut microbiota of parents and their offspring in a rodent model

Gut dysbiosis may result in various diseases, such as metabolic and neurobehavioral disorders. Exposure to endocrine disrupting chemicals (EDCs), including bisphenol A (BPA) and ethinyl estradiol (EE), especially during development, may also increase the risk for such disorders. An unexplored possibility is that EDC-exposure might alter the gut microbial composition. Gut flora and their products may thus be mediating factors for the disease-causing effects of these chemicals. To examine the effects of EDCs on the gut microbiome, female and male monogamous and biparental California mice (Peromyscus californicus) were exposed to BPA (50 mg/kg feed weight) or EE (0.1 ppb) or control diet from periconception through weaning. 16s rRNA sequencing was performed on bacterial DNA isolated from fecal samples, and analyses performed for P₀ and F₁ males and females. Both BPA and EE induced generational and sex-dependent gut microbiome changes. Many of the bacteria, e.g. Bacteroides, Mollicutes, Prevotellaceae, Erysipelotrichaceae, Akkermansia, Methanobrevibacter, Sutterella, whose proportions increase with exposure to BPA or EE in the P₀ or F₁ generation are associated with different disorders, such as inflammatory bowel disease (IBD), metabolic disorders, and colorectal cancer. However, the proportion of the beneficial bacterium, Bifidobacterium, was also elevated in fecal samples of BPA- and EE-exposed F₁ females. Intestinal flora alterations were also linked to changes in various metabolic and other pathways. Thus, BPA and EE exposure may disrupt the normal gut flora, which may in turn result in systemic effects. Probiotic supplementation might be an effective means to mitigate disease-promoting effects of these chemicals.     

The influence of selenium substitution on microcirculation and glutathione metabolism after warm liver ischemia/reperfusion in a rat model

Ischemia/reperfusion (I/R) injury is a variable yet unavoidable complication in liver surgery and transplantation. Selenium-dependent glutathione-peroxidases (GPx) and selenoproteins function as antioxidant defense systems. One target in preventing I/R injury is enhancing the capacity of endogenous redox defense. It was the aim of this study to analyze the effects of selenium substitution on liver microcirculation, hepatocellular injury and glutathione status in a model of partial warm liver ischemia in the rat.Sodium selenite was administered in three different dosages i.v.: 0.125 μg/g, 0.25 μg/g and 0.375 μg/g body weight and compared to an untreated control group (each n = 10). Intravital microscopy was performed after 70 min of partial warm liver ischemia and 90 min of reperfusion. Liver tissue and plasma samples were taken at the end of the experiment for laboratory analysis.Microcirculation improved significantly in all therapy groups in contrast to control animals. ALT levels decreased significantly whereas malondialdehyde levels remained unchanged. In liver tissue, selenium supplementation caused an increase in the amount of total and reduced glutathione without changes in oxidized glutathione. This effect is likely mediated by selenite itself and selenoprotein P rather than by modulating GPx activity.We were able to show that selenite substitution has an immediate protective effect on I/R injury after warm hepatic ischemia by acting as a radical scavenger and preserving the antioxidative capacity of the liver.