Variation in the Conservation of Species-Specific Gene Sets for HMO Degradation and Its Effects on HMO Utilization in Bifidobacteria.

Human milk provides essential nutrients for infants but also consists of human milk oligosaccharides (HMOs), which are resistant to digestion by the infant. Bifidobacteria are among the first colonizers, providing various health benefits for the host. This is largely facilitated by their ability to efficiently metabolize HMOs in a species-specific way. Nevertheless, these abilities can vary significantly by strain, and our understanding of the mechanisms applied by different strains from the same species remains incomplete. Therefore, we assessed the effects of strain-level genomic variation in HMO utilization genes on growth on HMOs in 130 strains from 10 species of human associated bifidobacteria. Our findings highlight the extent of genetic diversity between strains of the same species and demonstrate the effects on species-specific HMO utilization, which in most species is largely retained through the conservation of a core set of genes or the presence of redundant pathways. These data will help to refine our understanding of the genetic factors that contribute to the persistence of individual strains and will provide a better mechanistic rationale for the development and optimization of new early-life microbiota-modulating products to improve infant health.

Preanalytical impact on the accuracy of measurements of glucagon, GLP-1 and GIP in clinical trials.

BACKGROUND: Plasma concentrations of glucagon, GLP-1 and GIP are reported in numerous clinical trials as outcome measures but preanalytical guidelines are lacking. We addressed the impact of commonly used blood containers in metabolic research on measurements of glucagon, GLP-1 and GIP in humans. METHODS: Seventeen overweight individuals were subjected to an overnight fast followed by an intravenous infusion of amino acids to stimulate hormonal secretion. Blood was sampled into five containers: EDTA-coated tubes supplemented with DMSO (control), a neprilysin inhibitor, aprotinin (a kallikrein inhibitor) or a DPP-4 inhibitor, and P800 tubes. Plasma was kept on ice before and after centrifugation and stored at -80 Celsius until batch analysis using validated sandwich ELISAs or radioimmunoassays (RIA). RESULTS: Measures of fasting plasma glucagon did not depend on sampling containers, whether measured by ELISA or RIA. Amino acid-induced hyperglucagonemia was numerically higher when blood was collected into P800 tubes or tubes with aprotinin. The use of p800 tubes resulted in higher concentrations of GLP-1 by RIA compared to control tubes but not for measurements with sandwich ELISA. Plasma concentrations of GIP measured by ELISA were higher in control tubes and negatively affected by P800 and the addition of aprotinin. CONCLUSIONS: The choice of blood containers impacts on measurements of plasma concentrations of glucagon, GLP-1 and GIP, and based on this study, we recommend using EDTA-coated tubes without protease inhibitors or P800 tubes for measurements of glucagon, GLP-1 and GIP in clinical trials.

Cord Blood FGF-21 and GDF-15 Levels Are Affected by Maternal Exposure to Moderate to Severe Anemia and Malaria.

Context: Anemia and malaria are global health problems affecting >50% of pregnant women in sub-Saharan Africa and are associated with intrauterine growth restriction. The hormones fibroblast growth factor 21 (FGF-21) and growth differentiation factor 15 (GDF-15) are involved in metabolic regulation and are expressed in the placenta. No studies exist on FGF-21 and GDF-15 responses to exposures of malaria and anemia in pregnancy. Objective and Methods: Using a prospective, longitudinal pregnancy and birth cohort of women with an average age of 26 years from a rural region in northeastern Tanzania, we examined if FGF-21 and GDF-15 levels in maternal blood at week 33 ± 2 (n = 301) and in cord blood at birth (n = 353), were associated with anemia and malaria exposure at different time points in pregnancy and with neonatal anthropometry. Results: Among mothers at gestation week 33 ± 2, lower FGF-21 levels were observed after exposure to malaria in the first trimester, but not anemia, whereas GDF-15 levels at week 33 ± 2 were not associated with malaria nor anemia. In cord blood, moderate to severe anemia at any time point in pregnancy was associated with higher levels of FGF-21, whereas malaria exposure in the third trimester was associated with lower FGF-21 levels in cord blood. Negative associations were observed between cord blood FGF-21 and GDF-15 levels and neonatal skinfold thicknesses and birthweight. Conclusion: Our results suggest that moderate to severe anemia throughout pregnancy associates with higher FGF-21 levels, and malaria in last trimester associates with lower FGF-21 levels, in the neonates, thereby potentially affecting the future cardiometabolic health of the child.

Arginine-induced glucagon secretion and glucagon-induced enhancement of amino acid catabolism are not influenced by ambient glucose levels in mice.

Amino acids stimulate the secretion of glucagon, and glucagon receptor signaling regulates amino acid catabolism via ureagenesis, together constituting the liver-α cell axis. Impairment of the liver-α cell axis is observed in metabolic diseases such as diabetes. It is, however, unknown whether glucose affects the liver-α cell axis. We investigated the role of glucose on the liver-α cell axis in vivo and ex vivo. The isolated perfused mouse pancreas was used to evaluate the direct effect of low (3.5 mmol/L) and high (15 mmol/L) glucose levels on amino acid (10 mmol/L arginine)-induced glucagon secretion. High glucose levels alone lowered glucagon secretion, but the amino acid-induced glucagon responses were similar in high and low glucose conditions (P = 0.38). The direct effect of glucose on glucagon and amino acid-induced ureagenesis was assessed using isolated perfused mouse livers stimulated with a mixture of amino acids (VaminR, 10 mmol/L) and glucagon (10 nmol/L) during high and low glucose conditions. Urea production increased robustly but was independent of glucose levels (P = 0.95). To investigate the whole body effects of glucose on the liver-α cell axis, four groups of mice received intraperitoneal injections of glucose-Vamin (2 g/kg, + 3.5 µmol/g, respectively, G/V), saline-Vamin (S/V), glucose-saline (G/S), or saline-saline (S/S). Blood glucose did not differ significantly between G/S and G/V groups. Levels of glucagon and amino acids were similar in the G/V and S/V groups (P = 0.28). Amino acids may overrule the inhibitory effect of glucose on glucagon secretion and the liver-α cell axis may operate independently of glucose in mice.NEW & NOTEWORTHY Glucagon is an essential regulator of our metabolism. Recent evidence suggests that the physiological actions of glucagon reside in amino acid catabolism in the so-called liver-α cell axis, in which amino acids stimulate glucagon secretion and glucagon enhances hepatic amino acid catabolism. Here, it is demonstrated that this feedback system is independent of glycemia possibly explaining why hyperglycemia in diabetes may not suppress α cell secretion.

In Vitro Effects of Live and Heat-Inactivated Bifidobacterium animalis Subsp. Lactis, BB-12 and Lactobacillus rhamnosus GG on Caco-2 Cells.

Probiotic-host interaction can be cell-to-cell or through metabolite production. Dead (inactive) organisms could interact with the host, leading to local effects and possible health benefits. This research examined the effects of live and heat-inactivated Bifidobacterium animalis subsp. lactis, BB-12 (BB-12) and Lactobacillus rhamnosus GG (LGG) on cultured Caco-2 cells focusing on epithelial integrity and production of inflammatory mediators. Live organisms increased transepithelial electrical resistance (TEER), a barrier-integrity marker, with LGG having a greater effect than BB-12. When mildly heat-treated, both organisms had a more modest effect on TEER than when alive. When they were heat-inactivated, both organisms had only a limited effect on TEER. Neither live nor heat-inactivated organisms affected production of six inflammatory mediators produced by Caco-2 cells compared to control conditions. Pre-treatment with heat-inactivated LGG or BB-12 did not alter the decline in TEER caused by exposure to an inflammatory cocktail of cytokines. However, pre-treatment of Caco-2 cells with heat-inactivated organisms alone or their combination decreased the production of interleukin (IL)-6, IL-18, and vascular endothelial growth factor. To conclude, while the live organisms improve the epithelial barrier using this model, neither live nor heat-inactivated organisms directly elicit an inflammatory response by the epithelium. Pre-treatment with heat-inactivated BB-12 or LGG can reduce some components of the response induced by an inflammatory stimulus.

Models for total, elastic and diffractive cross sections.

The LHC has brought much new information on total, elastic and diffractive cross sections, which is not always in agreement with extrapolations from lower energies. The default framework in the Pythia event generator is one case in point. In this article we study and implement two recent models, as more realistic alternatives. Both describe total and elastic cross sections, whereas one also includes single diffraction. Noting some issues at high energies, a variant of the latter is proposed, and extended also to double and central diffraction. Further, the experimental definition of diffraction is based on the presence of rapidity gaps, which however also could be caused by colour reconnection in nondiffractive events, a phenomenon that is studied in the context of a specific model. Throughout comparisons with LHC and other data are presented.

Dietary nucleotide supplements in infant formula modify the expression of P-glycoprotein in the intestinal epithelium in vitro.

The effect of dietary nucleotides at concentrations found in supplemented infant formula on P-glycoprotein (P-gp) expression in colon cells was examined. We report that P-gp expression in colon cells was significantly decreased in a time- and concentration-dependent manner. When colon cells were co-cultured with lymphocytes, so as to mimic the involvement of gut-associated lymphoid tissue in normal gut pathophysiology, we observed a reversal of this effect with a demonstrated increase in P-gp expression. These findings have important implications on effects of nucleotide exposure on increasing drug bioavailability, reducing the capacity for xenobiotic efflux, and increasing the risk of inflammatory bowel disease in susceptible infants. Future studies are directed at defining both the mechanisms underlying these findings and effects of dietary nucleotide supplementation in vivo.