Chronic infection of the cystic fibrosis (CF) airway by the opportunistic pathogen Pseudomonas aeruginosa is the leading cause of morbidity and mortality for adult CF patients. Prolonged infections are accompanied by adaptation of P. aeruginosa to the unique conditions of the CF lung environment, as well as marked diversification of the pathogen into phenotypically and genetically distinct strains that can coexist for years within a patient. Little is known, however, about the causes of this diversification and its impact on patient health. Here, we show experimentally that, consistent with ecological theory of diversification, the nutritional conditions of the CF airway can cause rapid and extensive diversification of P. aeruginosa. Mucin, the substance responsible for the increased viscosity associated with the thick mucus layer in the CF airway, had little impact on within-population diversification but did promote divergence among populations. Furthermore, in vitro evolution recapitulated traits thought to be hallmarks of chronic infection, including reduced motility and increased biofilm formation, and the range of phenotypes observed in a collection of clinical isolates. Our results suggest that nutritional complexity and reduced dispersal can drive evolutionary diversification of P. aeruginosa independent of other features of the CF lung such as an active immune system or the presence of competing microbial species. We suggest that diversification, by generating extensive phenotypic and genetic variation on which selection can act, may be a key first step in the development of chronic infections.

Context Patients with type 1 diabetes (T1D) have lower microbiota diversity and distinct gut microbial profiles that have been linked to changes in intestinal permeability. Prebiotics are nondigestible carbohydrates that alter gut microbiota and could potentially improve glycemic control and reduce intestinal permeability and thereby insulin sensitivity. Objective To determine the effect of prebiotics on glycemic control, gut microbiota, and intestinal permeability in children with T1D. Design A randomized, placebo-controlled trial in children 8 to 17 years of age with T1D using placebo or prebiotic oligofructose-enriched inulin for 12 weeks. Baseline, 3-month, and 6-month assessments included HbA1c, C-peptide, gut microbiota, intestinal permeability, frequency of diabetic ketoacidosis (DKA), and severe hypoglycemia. Results Forty-three subjects were randomized and 38 completed the study. The groups were similar at baseline: prebiotic (N = 17), age 12.5 years (SD of 2.8), HbA1c 8.02% (SD of 0.82); placebo (N = 21), age 12.0 years (SD of 2.6), HbA1c 8.08% (SD of 0.91). No significant differences were found in the frequency of DKA or severe hypoglycemia. At 3-months, C-peptide was significantly higher (P = 0.029) in the group who received prebiotics, which was accompanied by a modest improvement in intestinal permeability (P = 0.076). There was a significant increase in the relative abundance of Bifidobacterium within the prebiotic group at 3 months that was no longer present after the 3-month washout. The placebo group had significantly higher relative abundance of Streptococcus, Roseburia inulinivorans, Terrisporobacter, and Faecalitalea compared with the prebiotic group at 3 months. Conclusion Prebiotics are a potentially novel, inexpensive, low-risk treatment addition for T1D that may improve glycemic control. Further larger-scale trials are needed.

Local adaptation seems to be common in natural systems, but the genetic causes of its evolution remain poorly understood. Here we characterize the genetic causes of trade-offs generating local adaptation in populations of Pseudomonas fluorescens that had previously been evolved for specialization on three different carbon resources. We measured the fitness effects of mutations that arose during selection in that environment and in alternative environments to quantify the degree of specialization. We find that all mutations are beneficial in the environment of selection and that those arising later during adaptation are associated with increasingly antagonistic effects in alternative environments compared with those arising earlier, consistent with a multioptima version of Fisher's geometric model of adaptation. We also find that fitness of pairs of beneficial mutations are consistently less than additive in selection environments, producing a pattern of diminishing returns, but are more variable in alternative environments, being either positive or negative. Finally, we find that mutations in genes associated with loss of motility are beneficial across all environments, whereas mutations involving other functions, such as gene regulation, had more variable effects, being more environment specific. Taken together, these results provide a detailed account of the genetics of specialization and suggest that the evolution of trade-offs associated with local adaptation may often result from the antagonistic effects of beneficial mutations substituted later in adaptation.

Stevia is a natural low-calorie sweetener that is growing in popularity in food and beverage products. Despite its widespread use, little is understood of its impact on the gut microbiota, an important environmental factor that can mediate metabolism and subsequent obesity and disease risk. Furthermore, given previous reports of dysbiosis with some artificial low-calorie sweeteners, we wanted to understand whether prebiotic consumption could rescue potential stevia-mediated changes in gut microbiota. Three-week old male Sprague–Dawley rats were randomized to consume: (1) Water (CTR); (2) Rebaudioside A (STV); (3) prebiotic (PRE); (4) Rebaudioside A + prebiotic (SP) (n = 8/group) for 9 weeks. Rebaudioside was added to drinking water and prebiotic oligofructose-enriched inulin added to control diet (10%). Body weight and feces were collected weekly and food and fluid intake biweekly. Oral glucose and insulin tolerance tests, gut permeability tests, dual X-ray absorptiometry, and tissue harvest were performed at age 12 weeks. Rebaudioside A consumption alone did not alter weight gain or glucose tolerance compared to CTR. Rebaudioside A did, however, alter gut microbiota composition and reduce nucleus accumbens tyrosine hydroxylase and dopamine transporter mRNA levels compared to CTR. Prebiotic animals, alone or with Rebaudioside A, had reduced fat mass, food intake, and gut permeability and cecal SCFA concentration. Adding Rebaudioside A did not interfere with the benefits of the prebiotic except for a significant reduction in cecal weight. Long-term low-dose Rebaudioside A consumption had little effect on glucose metabolism and weight gain; however, its impact on gut microbial taxa should be further examined in populations exhibiting dysbiosis such as obesity.

Our understanding of the pathophysiological mechanisms underlying chronic pain in inflammatory bowel disease is incomplete. Here we show that microbial manipulation modulates the development of visceral, but not somatic, pain in a mouse model of postinflammatory dextran sodium sulfate colitis. CONCLUSIONS:The microbiome plays a central role in postinflammatory visceral hypersensitivity. Microbial-derived SCFAs can sensitize nociceptive neurons and may contribute to the pathogenesis of postinflammatory visceral pain.

Chronic infection of the cystic fibrosis (CF) airway by the opportunistic pathogenPseudomonas aeruginosa is the leading cause of morbidity and mortality for adult CF patients.Prolonged infections are accompanied by adaptation of P. aeruginosa to the unique conditions of the CF lung environment as well as marked diversification of the pathogen into phenotypically and genetically distinct strains that can coexist for years within a patient. Little is known, however, about the causes of this diversification and its impact on patient health. Here, we show experimentally that, consistent with ecological theory of diversification, the nutritional conditions of the CF airway can cause rapid and extensive diversification of P. aeruginosa. The increased viscosity associated with the thick mucous layer in the CF airway had little impact on within-population diversification but did promote divergence among populations. Notably, in vitro evolution recapitulated patho-adaptive traits thought to be hallmarks of chronic infection, including reduced motility and increased biofilm formation, and the range of phenotypes observed in a collection of clinical isolates. Our results suggest that nutritional complexity and reduced dispersal can drive evolutionary diversification of P. aeruginosa independent of other features of the CF lung such as an active immune system or the presence of competing microbial species. They also underscore the need to obtain diverse samples of P. aeruginosa when developing treatment plans. We suggest that diversification, by generating extensive phenotypic and genetic variation on which selection can act, may be a key first step in the transition from transient to chronic infection. Significance StatementChronic infection with the opportunistic pathogen Pseudomonas aeruginosa is the leading cause of lung transplant or death in cystic fibrosis patients. P. aeruginosa diversifies in the CF lung, although why this happens remains a mystery. We allowed P. aeruginosa to evolve in the laboratory under a range of conditions approximating the CF lung. The diversity of evolved populations was highest, and most closely resembled the range of phenotypes among clinical isolates, in environments resembling the spectrum of nutritional resources available in the CF lung. Our results point to the nutritional complexity of the CF lung as a major driver of diversification and they suggest that diversity could be important in the development of chronic infections.peer-reviewed)

Sex hormone binding globulin (SHBG) is a glycoprotein expressed predominantly in the hepatocytes. It regulates the transport of sex steroid hormones in the blood stream to their target tissues. The expression of the SHBG gene is subject to multifactorial regulation including hormonal, metabolic, and nutritional aspects. Against this background, we investigated the effect of fatty liver and metabolic syndrome, together with other parameters, on serum SHBG concentrations in a population-based cohort in Germany. This cross-sectional study included 870 women and 787 men (average age 42.3±12.8 years), who underwent ultrasound screening for fatty liver in addition to providing a complete medical history and undergoing physical and laboratory examination. Fatty liver was diagnosed on ultrasound criteria in 159 women (18.3%) and 287 men (36.5%). Fatty liver was shown to exert a significant influence on serum SHBG concentrations in men and in premenopausal women. Men with grade 1 fatty liver had a 1.96-fold increased risk (95%-confidence interval=1.28-3.02; p=0.0022) and postmenopausal women with grade 1 fatty liver a 2.4-fold risk (95%-confidence interval=1.11-5.27; p=0.0267) for low SHBG concentrations. Among metabolic parameters, HDL-C represented as affecting factor in men (p=0.0058) and premenopausal women (p=0.0002), while cholesterol only showed an association in premenopausal women (p=0.0439) and triglyceride in postmenopausal women (p=0.0436). No association of concentrations of SHBG and metabolic syndrome was observed. Age, BMI and waist-to-hip ratio also influence the SHBG concentration. Based on these findings, we conclude that fat accumulation in the liver influences SHBG concentrations in men and premenopausal women.

This study assessed the feasibility and benefits of high intensity interval training (HIIT) plus lifestyle education among inactive adults with celiac disease. 41 participants were randomized to receive the intervention (HIIT+) for 12-weeks or waitlist control (WLC). Testing was completed at baseline, immediately post- and 3-months post-intervention. Generalized estimating equations were used to assess changes in the outcome variables over time between the groups. Mean percent of age-predicted maximum heart rate was 97.9% and average rating of perceived exertion (RPE) was 6.33 (out of 10) during HIIT intervals. Following the intervention, the HIIT+ group showed enrichment in relative abundance of Parabacteroides and Defluviitaleaceae_UCG¬_011 while WLC showed enrichment in relative abundance of Roseburia intestinalis, Klebsiella and Adlercreutzia. A unique set of taxa were differentially abundant between the groups at 3-months post-intervention. HIIT+ participants experienced a reduction in resting heart rate (-6.6 bpm) immediately post-intervention compared to WLC. Further research is needed to establish an optimal HIIT protocol that may improve VO2max and metabolic syndrome biomarkers. Findings from this pilot study provide preliminary evidence that a HIIT+ intervention is feasible for inactive adults with celiac disease and leads to favourable changes in resting HR alongside potentially beneficial shifts in gut microbiota. Trial registration number: ClinicalTrials.gov number NCT03520244 Novelty • High intensity interval training leads to potentially beneficial changes in the gut microbiota of adults with celiac disease. • A high intensity interval training exercise intervention is feasible and well tolerated for patients with celiac disease.