Interactive Impacts of Silver and Phosphorus on Autotrophic Biofilm Elemental and Biochemical Quality for a Macroinvertebrate Consumer

Autotrophic biofilms are complex and fundamental biological compartments of many aquatic ecosystems. In particular, these biofilms represent a major resource for many invertebrate consumers and the first ecological barrier against toxic metals. To date, very few studies have investigated the indirect effects of stressors on upper trophic levels through alterations of the quality of biofilms for their consumers. In a laboratory study, we investigated the single and combined effects of phosphorus (P) availability and silver, a re-emerging contaminant, on the elemental [carbon (C):nitrogen (N):P ratios] and biochemical (fatty acid profiles) compositions of a diatom-dominated biofilm initially collected in a shallow lake. We hypothesized that (1) P and silver, through the replacement of diatoms by more tolerant primary producer species, reduce the biochemical quality of biofilms for their consumers while (2) P enhances biofilm elemental quality and (3) silver contamination of biofilm has negative effects on consumers life history traits. The quality of biofilms for consumers was assessed for a common crustacean species, Gammarus fossarum, by measuring organisms’ survival and growth rates during a 42-days feeding experiment. Results mainly showed that species replacement induced by both stressors affected biofilm fatty acid compositions, and that P immobilization permitted to achieve low C:P biofilms, whatever the level of silver contamination. Gammarids growth and survival rates were not significantly impacted by the ingestion of silver-contaminated resource. On the contrary, we found a significant positive relationship between the biofilm P-content and gammarids growth. This study underlines the large indirect consequences stressors could play on the quality of microbial biomass for consumers, and, in turn, on the whole food web

Detrended Fluctuation Analysis in the prediction of type 2 diabetes mellitus in patients at risk: Model optimization and comparison with other metrics

[EN] Complexity analysis of glucose time series with Detrended Fluctuation Analysis (DFA) has been proved to be useful for the prediction of type 2 diabetes mellitus (T2DM) development. We propose a modified DFA algorithm, review some of its characteristics and compare it with other metrics derived from continuous glucose monitorization in this setting. Several issues of the DFA algorithm were evaluated: (1) Time windowing: the best predictive value was obtained including all time-windows from 15 minutes to 24 hours. (2) Influence of circadian rhythms: for 48-hour glucometries, DFA alpha scaling exponent was calculated on 24hour sliding segments (1-hour gap, 23-hour overlap), with a median coefficient of variation of 3.2%, which suggests that analysing time series of at least 24-hour length avoids the influence of circadian rhythms. (3) Influence of pretreatment of the time series through integration: DFA without integration was more sensitive to the introduction of white noise and it showed significant predictive power to forecast the development of T2DM, while the pretreated time series did not. (4) Robustness of an interpolation algorithm for missing values: The modified DFA algorithm evaluates the percentage of missing values in a time series. Establishing a 2% error threshold, we estimated the number and length of missing segments that could be admitted to consider a time series as suitable for DFA analysis. For comparison with other metrics, a Principal Component Analysis was performed and the results neatly tease out four different components. The first vector carries information concerned with variability, the second represents mainly DFA alpha exponent, while the third and fourth vectors carry essentially information related to the two "pre-diabetic behaviours" (impaired fasting glucose and impaired glucose tolerance). The scaling exponent obtained with the modified DFA algorithm proposed has significant predictive power for the development of T2DM in a high-risk population compared with other variability metrics or with the standard DFA algorithm.This study has been funded by Instituto de Salud Carlos III through the project PI17/00856 (Co-funded by the European Regional Development Fund, A way to make Europe). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Colás, A.; Vigil, L.; Vargas, B.; Cuesta Frau, D.; Varela, M. (2019). Detrended Fluctuation Analysis in the prediction of type 2 diabetes mellitus in patients at risk: Model optimization and comparison with other metrics. PLoS ONE. 14(12):1-15. https://doi.org/10.1371/journal.pone.0225817S1151412Goldstein, B., Fiser, D. H., Kelly, M. M., Mickelsen, D., Ruttimann, U., & Pollack, M. M. (1998). Decomplexification in critical illness and injury: Relationship between heart rate variability, severity of illness, and outcome. Critical Care Medicine, 26(2), 352-357. doi:10.1097/00003246-199802000-00040Varela, M. (2008). The route to diabetes: Loss of complexity in the glycemic profile from health through the metabolic syndrome to type 2 diabetes. Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy, Volume 1, 3-11. doi:10.2147/dmso.s3812Vikman, S., Mäkikallio, T. H., Yli-Mäyry, S., Pikkujämsä, S., Koivisto, A.-M., Reinikainen, P., … Huikuri, H. V. (1999). Altered Complexity and Correlation Properties of R-R Interval Dynamics Before the Spontaneous Onset of Paroxysmal Atrial Fibrillation. Circulation, 100(20), 2079-2084. doi:10.1161/01.cir.100.20.2079Wang, H., Naghavi, M., Allen, C., Barber, R. M., Bhutta, Z. A., Carter, A., … Coates, M. M. (2016). Global, regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980–2015: a systematic analysis for the Global Burden of Disease Study 2015. The Lancet, 388(10053), 1459-1544. doi:10.1016/s0140-6736(16)31012-1Saudek, C. D., Derr, R. L., & Kalyani, R. R. (2006). Assessing Glycemia in Diabetes Using Self-monitoring Blood Glucose and Hemoglobin A1c. JAMA, 295(14), 1688. doi:10.1001/jama.295.14.1688Monnier, L., Colette, C., & Owens, D. R. (2008). Glycemic Variability: The Third Component of the Dysglycemia in Diabetes. Is it Important? How to Measure it? Journal of Diabetes Science and Technology, 2(6), 1094-1100. doi:10.1177/193229680800200618Abdul-Ghani, M. A., Tripathy, D., & DeFronzo, R. A. (2006). Contributions of  -Cell Dysfunction and Insulin Resistance to the Pathogenesis of Impaired Glucose Tolerance and Impaired Fasting Glucose. Diabetes Care, 29(5), 1130-1139. doi:10.2337/dc05-2179(2017). 2. Classification and Diagnosis of Diabetes:Standards of Medical Care in Diabetes—2018. Diabetes Care, 41(Supplement 1), S13-S27. doi:10.2337/dc18-s002Tabák, A. G., Herder, C., Rathmann, W., Brunner, E. J., & Kivimäki, M. (2012). Prediabetes: a high-risk state for diabetes development. The Lancet, 379(9833), 2279-2290. doi:10.1016/s0140-6736(12)60283-9DeFronzo, R. A., Banerji, M. A., Bray, G. A., Buchanan, T. A., Clement, S., … Tripathy, D. (2009). Determinants of glucose tolerance in impaired glucose tolerance at baseline in the Actos Now for Prevention of Diabetes (ACT NOW) study. Diabetologia, 53(3), 435-445. doi:10.1007/s00125-009-1614-2Nathan, D. M., Davidson, M. B., DeFronzo, R. A., Heine, R. J., Henry, R. R., Pratley, R., & Zinman, B. (2007). Impaired Fasting Glucose and Impaired Glucose Tolerance: Implications for care. Diabetes Care, 30(3), 753-759. doi:10.2337/dc07-9920Ogata, H., Tokuyama, K., Nagasaka, S., Tsuchita, T., Kusaka, I., Ishibashi, S., … Yamamoto, Y. (2012). The lack of long-range negative correlations in glucose dynamics is associated with worse glucose control in patients with diabetes mellitus. Metabolism, 61(7), 1041-1050. doi:10.1016/j.metabol.2011.12.007Kohnert, K.-D. (2015). Utility of different glycemic control metrics for optimizing management of diabetes. World Journal of Diabetes, 6(1), 17. doi:10.4239/wjd.v6.i1.17García Maset, L., González, L. B., Furquet, G. L., Suay, F. M., & Marco, R. H. (2016). Study of Glycemic Variability Through Time Series Analyses (Detrended Fluctuation Analysis and Poincaré Plot) in Children and Adolescents with Type 1 Diabetes. Diabetes Technology & Therapeutics, 18(11), 719-724. doi:10.1089/dia.2016.0208Service, F. J., O’Brien, P. C., & Rizza, R. A. (1987). Measurements of Glucose Control. Diabetes Care, 10(2), 225-237. doi:10.2337/diacare.10.2.225Goldberger, A. L., Amaral, L. A. N., Hausdorff, J. M., Ivanov, P. C., Peng, C.-K., & Stanley, H. E. (2002). Fractal dynamics in physiology: Alterations with disease and aging. Proceedings of the National Academy of Sciences, 99(Supplement 1), 2466-2472. doi:10.1073/pnas.012579499Crenier, L., Lytrivi, M., Van Dalem, A., Keymeulen, B., & Corvilain, B. (2016). Glucose Complexity Estimates Insulin Resistance in Either Nondiabetic Individuals or in Type 1 Diabetes. The Journal of Clinical Endocrinology & Metabolism, 101(4), 1490-1497. doi:10.1210/jc.2015-4035Rodríguez de Castro, C., Vigil, L., Vargas, B., García Delgado, E., García Carretero, R., Ruiz-Galiana, J., & Varela, M. (2016). Glucose time series complexity as a predictor of type 2 diabetes. Diabetes/Metabolism Research and Reviews, 33(2), e2831. doi:10.1002/dmrr.2831Weber, C., & Schnell, O. (2009). The Assessment of Glycemic Variability and Its Impact on Diabetes-Related Complications: An Overview. Diabetes Technology & Therapeutics, 11(10), 623-633. doi:10.1089/dia.2009.0043Pincus, S. M., Gladstone, I. M., & Ehrenkranz, R. A. (1991). A regularity statistic for medical data analysis. Journal of Clinical Monitoring, 7(4), 335-345. doi:10.1007/bf01619355Richman, J. S. (2007). Sample Entropy Statistics and Testing for Order in Complex Physiological Signals. Communications in Statistics - Theory and Methods, 36(5), 1005-1019. doi:10.1080/03610920601036481Platiša, M. M., Bojić, T., Pavlović, S. U., Radovanović, N. N., & Kalauzi, A. (2016). Generalized Poincaré Plots-A New Method for Evaluation of Regimes in Cardiac Neural Control in Atrial Fibrillation and Healthy Subjects. Frontiers in Neuroscience, 10. doi:10.3389/fnins.2016.00038García-Puig, J., Ruilope, L. M., Luque, M., Fernández, J., Ortega, R., & Dal-Ré, R. (2006). Glucose Metabolism in Patients with Essential Hypertension. The American Journal of Medicine, 119(4), 318-326. doi:10.1016/j.amjmed.2005.09.010Lepot, M., Aubin, J.-B., & Clemens, F. (2017). Interpolation in Time Series: An Introductive Overview of Existing Methods, Their Performance Criteria and Uncertainty Assessment. Water, 9(10), 796. doi:10.3390/w9100796Eke, A., Hermán, P., Bassingthwaighte, J., Raymond, G., Percival, D., Cannon, M., … Ikrényi, C. (2000). Physiological time series: distinguishing fractal noises from motions. Pflügers Archiv - European Journal of Physiology, 439(4), 403-415. doi:10.1007/s004249900135Eke, A., Herman, P., Kocsis, L., & Kozak, L. R. (2002). Fractal characterization of complexity in temporal physiological signals. Physiological Measurement, 23(1), R1-R38. doi:10.1088/0967-3334/23/1/201King, A. B., Philis-Tsimikas, A., Kilpatrick, E. S., Langbakke, I. H., Begtrup, K., & Vilsbøll, T. (2017). A Fixed Ratio Combination of Insulin Degludec and Liraglutide (IDegLira) Reduces Glycemic Fluctuation and Brings More Patients with Type 2 Diabetes Within Blood Glucose Target Ranges. Diabetes Technology & Therapeutics, 19(4), 255-264. doi:10.1089/dia.2016.0405Colas, A., Vigil, L., Rodríguez de Castro, C., Vargas, B., & Varela, M. (2018). New insights from continuous glucose monitoring into the route to diabetes. Diabetes/Metabolism Research and Reviews, 34(5), e3002. doi:10.1002/dmrr.3002Henriques, T., Munshi, M. N., Segal, A. R., Costa, M. D., & Goldberger, A. L. (2014). «Glucose-at-a-Glance». Journal of Diabetes Science and Technology, 8(2), 299-306. doi:10.1177/1932296814524095Hinton, P. R. (2004). Statistics Explained. doi:10.4324/9780203496787Van Cauter, E., Blackman, J. D., Roland, D., Spire, J. P., Refetoff, S., & Polonsky, K. S. (1991). Modulation of glucose regulation and insulin secretion by circadian rhythmicity and sleep. Journal of Clinical Investigation, 88(3), 934-942. doi:10.1172/jci115396Qian, J., & Scheer, F. A. J. L. (2016). Circadian System and Glucose Metabolism: Implications for Physiology and Disease. Trends in Endocrinology & Metabolism, 27(5), 282-293. doi:10.1016/j.tem.2016.03.00

Day-to-day fasting self-monitored blood glucose variability is associated with risk of hypoglycaemia in insulin-treated patients with type 1 and type 2 diabetes: a post hoc analysis of the SWITCH trials

AIMS: To investigate the association between day-to-day fasting self-monitored blood glucose (SMBG) variability and risk of hypoglycaemia in type 1 (T1D) and type 2 diabetes (T2D), and compare day-to-day fasting SMBG variability between treatments with insulin degludec (degludec) and insulin glargine 100 units/mL (glargine U100). MATERIALS AND METHODS: Data were retrieved from two double-blind, randomised, treat-to-target, two-period (32 weeks each) crossover trials of degludec versus glargine U100 in T1D (SWITCH 1, n=501) and T2D (SWITCH 2, n=720). Available fasting SMBGs were used to determine the standard deviation (SD) of day-to-day fasting SMBG variability for each patient and treatment combination. The association between day-to-day fasting SMBG variability and overall symptomatic, nocturnal symptomatic and severe hypoglycaemia was analysed for the pooled population using linear regression, and with fasting SMBG variability included as a three-level factor defined by population tertiles. Finally, day-to-day fasting SMBG variability was compared between treatments. RESULTS: Linear regression showed that day-to-day fasting SMBG variability was significantly associated with overall symptomatic, nocturnal symptomatic, and severe hypoglycaemia risk in T1D and T2D (p<0.05). Day-to-day fasting SMBG variability was significantly associated (p<0.01) with all categories of hypoglycaemia risk, except for severe hypoglycaemia in T2D when analysed within tertiles. Degludec was associated with 4% lower day-to-day fasting SMBG variability than glargine U100 in T1D (p=0.0082) and 10% lower in T2D (p<0.0001). CONCLUSIONS: Higher day-to-day fasting SMBG variability is associated with an increased risk of overall symptomatic, nocturnal symptomatic and severe hypoglycaemia. Degludec has significantly lower day-to-day fasting SMBG variability versus glargine U100. This article is protected by copyright. All rights reserved

Albiglutide and cardiovascular outcomes in patients with type 2 diabetes and cardiovascular disease (Harmony Outcomes): a double-blind, randomised placebo-controlled trial

Background: Glucagon-like peptide 1 receptor agonists differ in chemical structure, duration of action, and in their effects on clinical outcomes. The cardiovascular effects of once-weekly albiglutide in type 2 diabetes are unknown. We aimed to determine the safety and efficacy of albiglutide in preventing cardiovascular death, myocardial infarction, or stroke. Methods: We did a double-blind, randomised, placebo-controlled trial in 610 sites across 28 countries. We randomly assigned patients aged 40 years and older with type 2 diabetes and cardiovascular disease (at a 1:1 ratio) to groups that either received a subcutaneous injection of albiglutide (30–50 mg, based on glycaemic response and tolerability) or of a matched volume of placebo once a week, in addition to their standard care. Investigators used an interactive voice or web response system to obtain treatment assignment, and patients and all study investigators were masked to their treatment allocation. We hypothesised that albiglutide would be non-inferior to placebo for the primary outcome of the first occurrence of cardiovascular death, myocardial infarction, or stroke, which was assessed in the intention-to-treat population. If non-inferiority was confirmed by an upper limit of the 95% CI for a hazard ratio of less than 1·30, closed testing for superiority was prespecified. This study is registered with ClinicalTrials.gov, number NCT02465515. Findings: Patients were screened between July 1, 2015, and Nov 24, 2016. 10 793 patients were screened and 9463 participants were enrolled and randomly assigned to groups: 4731 patients were assigned to receive albiglutide and 4732 patients to receive placebo. On Nov 8, 2017, it was determined that 611 primary endpoints and a median follow-up of at least 1·5 years had accrued, and participants returned for a final visit and discontinuation from study treatment; the last patient visit was on March 12, 2018. These 9463 patients, the intention-to-treat population, were evaluated for a median duration of 1·6 years and were assessed for the primary outcome. The primary composite outcome occurred in 338 (7%) of 4731 patients at an incidence rate of 4·6 events per 100 person-years in the albiglutide group and in 428 (9%) of 4732 patients at an incidence rate of 5·9 events per 100 person-years in the placebo group (hazard ratio 0·78, 95% CI 0·68–0·90), which indicated that albiglutide was superior to placebo (p&lt;0·0001 for non-inferiority; p=0·0006 for superiority). The incidence of acute pancreatitis (ten patients in the albiglutide group and seven patients in the placebo group), pancreatic cancer (six patients in the albiglutide group and five patients in the placebo group), medullary thyroid carcinoma (zero patients in both groups), and other serious adverse events did not differ between the two groups. There were three (&lt;1%) deaths in the placebo group that were assessed by investigators, who were masked to study drug assignment, to be treatment-related and two (&lt;1%) deaths in the albiglutide group. Interpretation: In patients with type 2 diabetes and cardiovascular disease, albiglutide was superior to placebo with respect to major adverse cardiovascular events. Evidence-based glucagon-like peptide 1 receptor agonists should therefore be considered as part of a comprehensive strategy to reduce the risk of cardiovascular events in patients with type 2 diabetes. Funding: GlaxoSmithKline

Effect of sitagliptin on cardiovascular outcomes in type 2 diabetes

BACKGROUND: Data are lacking on the long-term effect on cardiovascular events of adding sitagliptin, a dipeptidyl peptidase 4 inhibitor, to usual care in patients with type 2 diabetes and cardiovascular disease. METHODS: In this randomized, double-blind study, we assigned 14,671 patients to add either sitagliptin or placebo to their existing therapy. Open-label use of antihyperglycemic therapy was encouraged as required, aimed at reaching individually appropriate glycemic targets in all patients. To determine whether sitagliptin was noninferior to placebo, we used a relative risk of 1.3 as the marginal upper boundary. The primary cardiovascular outcome was a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for unstable angina. RESULTS: During a median follow-up of 3.0 years, there was a small difference in glycated hemoglobin levels (least-squares mean difference for sitagliptin vs. placebo, -0.29 percentage points; 95% confidence interval [CI], -0.32 to -0.27). Overall, the primary outcome occurred in 839 patients in the sitagliptin group (11.4%; 4.06 per 100 person-years) and 851 patients in the placebo group (11.6%; 4.17 per 100 person-years). Sitagliptin was noninferior to placebo for the primary composite cardiovascular outcome (hazard ratio, 0.98; 95% CI, 0.88 to 1.09; P<0.001). Rates of hospitalization for heart failure did not differ between the two groups (hazard ratio, 1.00; 95% CI, 0.83 to 1.20; P = 0.98). There were no significant between-group differences in rates of acute pancreatitis (P = 0.07) or pancreatic cancer (P = 0.32). CONCLUSIONS: Among patients with type 2 diabetes and established cardiovascular disease, adding sitagliptin to usual care did not appear to increase the risk of major adverse cardiovascular events, hospitalization for heart failure, or other adverse events

Poincaré Plot Quantification for Assessing Glucose Variability from Continuous Glucose Monitoring Systems and a New Risk Marker for Hypoglycemia: Application to Type 1 Diabetes Patients Switching to Continuous Subcutaneous Insulin Infusion.

Abstract Background: The Poincaré plot (PCP) is a valuable tool for describing glucose variability (GV) from continuous glucose monitoring (CGM) but remains only visual and qualitative. The aim of this work was to validate metrics for the geometry of the PCP in type 1 diabetes and to apply them to the study of a series of patients switching to continuous subcutaneous insulin infusion (CSII). Patients and Methods: We reviewed the CGM profiles of 44 patients with type 1 diabetes. A subgroup (n=13) used CGM before and after 6 months on CSII. Additionally, we prospectively collected seven recordings from healthy controls. The new PCP metrics were correlated with hypoglycemia and classical GV indices and were compared between groups. Results: SDs related to the PCP fitting ellipse (SD1, SD2) and area and shape of the fitting ellipse (SFE) were all higher in diabetes patients than in the controls and decreased significantly on CSII. SD1 represented short-term GV and was equivalent to continuous overlapping net glycemic action (CONGA). SD2 represented long-term GV and correlated with the SD of glucose levels (r≥0.98), mean of daily differences (r≥0.91), and mean amplitude of glycemic excursions (r≥0.88). SFE correlated positively with CONGA at 1 h but not with the other indices and was inversely correlated with hypoglycemic episodes (Spearman's ρ=-0.42), independently of the coefficient of variation and the Low Blood Glucose Index in a multivariate analysis (partial r=-0.34). Conclusions: PCP metrics are correlated with known GV indices and may be used for the study of CGM recording series in type 1 diabetes. SFE is a new risk marker for hypoglycemia.JOURNAL ARTICLESCOPUS: ar.jinfo:eu-repo/semantics/publishe

Towards a reassessment of factors limiting biological production in headwaters streams : nutrients, fatty acids or detrital carbon quality ?

Les cours d’eau de tête de bassin versant, malgré leurs tailles réduites, jouent des rôles importants pour le fonctionnement des milieux situés en aval, et rendent de nombreux services écologiques. Depuis l’émergence du River Continuum Concept, le fonctionnement de ces cours d’eau est considéré comme reposant principalement sur les apports allochtones de matière organique détritique par opposition aux écosystèmes aval de plus grande taille dans lesquels la production primaire autochtone est considérée comme prépondérante. Bien que les détritus soient, par définition, des ressources de moindre qualité pour leurs consommateurs que les végétaux vivants, le rôle des facteurs qui limitent la production biologique et les processus fonctionnels dans ces écosystèmes détritiques reste encore peu exploré. Par exemple la carence en éléments minéraux essentiels (notamment en azote et en phosphore) dans les détritus peut limiter le développement des organismes vivants dans les cours d’eau. De ce fait, la disponibilité en éléments minéraux dans la colonne d’eau, en stimulant la croissance, l’activité des décomposeurs et la qualité élémentaire des ressources par le processus d’immobilisation microbienne, pourrait contrôler pour partie les processus écologiques en jeu dans ces écosystèmes. En étudiant in situ la réponse des communautés microbiennes aux nutriments le long d’un gradient d’occupation des sols, nos travaux ont mis en évidence un effet positif des éléments dissous (N et P) sur la décomposition des litières et les activités enzymatiques des décomposeurs, et ce même pour les niveaux en nutriments les plus élevés du gradient, pour lesquels des effets inverses étaient attendus. Indépendamment, dans des cours d’eau anciennement soumis à de forts dépôts acidifiants, nous avons pu observer une récupération du processus de décomposition des litières. Néanmoins, cette restauration s’accompagnant d’un appauvrissement marqué en N, des perturbations du fonctionnement de ces cours d’eau pourrait se manifester à terme. Le rôle de la production primaire dans les cours d’eau de tête de bassin versant a ensuite été questionné. En effet, bien qu’étant mineur quantitativement, l’apport de carbone de forte qualité pourrait jouer un rôle non négligeable sur le fonctionnement des cours d’eau de tête de bassin versant. En particulier, l’importance et le rôle des apports en acides gras polyinsaturés (AGPI) via les biofilms phototrophes ont été questionnés. En se basant sur un suivi de terrain sur 15 cours d’eau des Vosges le long d’un gradient d’acidification, nos recherches ont tout d’abord pu mettre en évidence la présence de biofilms diatomiques riches en AGPI, malgré le caractère très forestier de ces cours d’eau. Dans un second temps, une expérience en conditions contrôlées a permis d’observer le rôle positif des apports, mêmes faibles, de ressources diatomiques sur la croissance et la survie du crustacé amphipode Gammarus fossarum. Sans cet apport, ces organismes se sont avérés incapables de maintenir leurs niveaux internes d’AGPI, suggérant qu’une consommation de producteurs primaires autochtones était indispensable à ces organismes détritivores. Nos résultats ont ainsi pu mettre en évidence les rôles fondamentaux que peuvent jouer la disponibilité en éléments dissous (N et P) et la qualité du carbone dans les ressources sur la production biologique et sur le processus de décomposition des litières dans les cours d’eau de tête de bassin versant. Ces résultats appellent désormais à investiguer plus profondément les interactions entre ces deux facteurs limitants, et à comprendre dans quels contextes l’un des facteurs pourrait suppléer l’autre. En particulier, il sera intéressant de rechercher comment diverses perturbations anthropiques (xénobiotiques, réchauffement climatique etc…) pourraient affecter l’intensité ou la nature de ces limitationsDespite their reduced sizes, headwater streams play important roles in the functioning of downstream ecosystems and provide numerous ecological services. Since the River Continuum Concept, the functioning of these streams has been considered as mainly relying on allochthonous supplies of detrital organic matter for their functioning, in contrast with downstream ecosystems of larger size where primary production is considered to be predominant. Despite that detritus represent, by definition, a resource of lower quality for its consumers than living plants, the nature of the factors limiting the biological production and functional processes in these detrital ecosystems remains sparsely explored. First, the lack of essential elements (in particular nitrogen and phosphorus) in detritus could be a major constraint for the development of living organisms in streams. As a result, the availability of mineral elements in the water column, by stimulating the growth and activity of decomposers, but also by increasing the elemental quality of resources through microbial immobilization, could control ecological processes in a higher extent than previously believed in these ecosystems. By studying in situ, the response of microorganisms to nutrients availability along a land-use gradient, our results have shown a positive effect of the dissolved elements (N and P) on the decomposition of leaf litters and the enzymatic activities of the decomposers, even for the highest nutrient levels of the gradient, for which adverse effects were expected. Independently, in streams formerly subjected to acidification, we observed a recovery of the process of leaf litter decomposition. Nevertheless, this recovery was accompanied by a marked N reduction in the ecosystem, huge changes in stream functioning might be expected in the medium to long term. The role of autochthonous primary production was then questioned. Indeed, while being quantitatively minor, this contribution of high quality carbon may play a significant role in the functioning of headwater streams. In particular, the importance and role of polyunsaturated fatty acid (PUFA) intakes via phototrophic biofilms was questioned. Based on a field survey of 15 rivers in the Vosges Mountains along an acidification gradient, our results first showed the presence of diatomic biofilms rich in PUFA, despite these streams are clearly in a forested context. In a second step, an experimentation carried out under controlled conditions permitted to observe the positive role of diatomic resources, even in low concentrations, on the growth and survival of the crustacean amphipod Gammarus fossarum. Without this input, these organisms were unable to maintain their internal levels of PUFAs, suggesting that the consumption of autochthonous primary producers might be essential for these detritivore organisms. All our results permit to highlight the fundamental roles that can be played by the availability of dissolved elements (N and P) and the carbon quality of the resources on the biological production and on leaf litter decomposition in headwater streams. These results stress the need for more profound investigation of the interactions between these two limiting factors, and for understanding in which contexts one factor could supplement the other. In particular, it will be interesting to investigate to what extent various anthropogenic disturbances (xenobiotics, global warming, etc...) could affect the intensity or the nature of these limitation

Le Rybelsus® (sémaglutide): le traitement du diabète de type 2 par un agoniste du récepteur du GLP-1 par voie orale devient réalité !

Despite recent advances in the management of type 2 diabetes and the development of new therapeutic options, many patients still do not reach their glycemic targets. Until now, the most powerful anti-diabetic treatments were only available in injectables (insulin and GLP-1 receptor agonists, GLP-1 RA) and this may constitute a barrier to the treatment intensification in outpatient follow-up. In this context, the development of Rybelsus®, the first GLP-1 RA (semaglutide), available in tablets, is first and foremost a technological tour de force. But with a clinical efficacy and security comparable to that of its injectable equivalent, this newcomer to our therapeutic arsenal offers us a tremendous opportunity to improve the glycemic control of our type 2 diabetic patients in the first line of care.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Vers une réévaluation des facteurs limitant la production biologique dans les cours d’eau de tête de bassin versant : nutriments, acides gras ou qualité du carbone détritique ?

Despite their reduced sizes, headwater streams play important roles in the functioning of downstream ecosystems and provide numerous ecological services. Since the River Continuum Concept, the functioning of these streams has been considered as mainly relying on allochthonous supplies of detrital organic matter for their functioning, in contrast with downstream ecosystems of larger size where primary production is considered to be predominant. Despite that detritus represent, by definition, a resource of lower quality for its consumers than living plants, the nature of the factors limiting the biological production and functional processes in these detrital ecosystems remains sparsely explored. First, the lack of essential elements (in particular nitrogen and phosphorus) in detritus could be a major constraint for the development of living organisms in streams. As a result, the availability of mineral elements in the water column, by stimulating the growth and activity of decomposers, but also by increasing the elemental quality of resources through microbial immobilization, could control ecological processes in a higher extent than previously believed in these ecosystems. By studying in situ, the response of microorganisms to nutrients availability along a land-use gradient, our results have shown a positive effect of the dissolved elements (N and P) on the decomposition of leaf litters and the enzymatic activities of the decomposers, even for the highest nutrient levels of the gradient, for which adverse effects were expected. Independently, in streams formerly subjected to acidification, we observed a recovery of the process of leaf litter decomposition. Nevertheless, this recovery was accompanied by a marked N reduction in the ecosystem, huge changes in stream functioning might be expected in the medium to long term. The role of autochthonous primary production was then questioned. Indeed, while being quantitatively minor, this contribution of high quality carbon may play a significant role in the functioning of headwater streams. In particular, the importance and role of polyunsaturated fatty acid (PUFA) intakes via phototrophic biofilms was questioned. Based on a field survey of 15 rivers in the Vosges Mountains along an acidification gradient, our results first showed the presence of diatomic biofilms rich in PUFA, despite these streams are clearly in a forested context. In a second step, an experimentation carried out under controlled conditions permitted to observe the positive role of diatomic resources, even in low concentrations, on the growth and survival of the crustacean amphipod Gammarus fossarum. Without this input, these organisms were unable to maintain their internal levels of PUFAs, suggesting that the consumption of autochthonous primary producers might be essential for these detritivore organisms. All our results permit to highlight the fundamental roles that can be played by the availability of dissolved elements (N and P) and the carbon quality of the resources on the biological production and on leaf litter decomposition in headwater streams. These results stress the need for more profound investigation of the interactions between these two limiting factors, and for understanding in which contexts one factor could supplement the other. In particular, it will be interesting to investigate to what extent various anthropogenic disturbances (xenobiotics, global warming, etc...) could affect the intensity or the nature of these limitationsLes cours d’eau de tête de bassin versant, malgré leurs tailles réduites, jouent des rôles importants pour le fonctionnement des milieux situés en aval, et rendent de nombreux services écologiques. Depuis l’émergence du River Continuum Concept, le fonctionnement de ces cours d’eau est considéré comme reposant principalement sur les apports allochtones de matière organique détritique par opposition aux écosystèmes aval de plus grande taille dans lesquels la production primaire autochtone est considérée comme prépondérante. Bien que les détritus soient, par définition, des ressources de moindre qualité pour leurs consommateurs que les végétaux vivants, le rôle des facteurs qui limitent la production biologique et les processus fonctionnels dans ces écosystèmes détritiques reste encore peu exploré. Par exemple la carence en éléments minéraux essentiels (notamment en azote et en phosphore) dans les détritus peut limiter le développement des organismes vivants dans les cours d’eau. De ce fait, la disponibilité en éléments minéraux dans la colonne d’eau, en stimulant la croissance, l’activité des décomposeurs et la qualité élémentaire des ressources par le processus d’immobilisation microbienne, pourrait contrôler pour partie les processus écologiques en jeu dans ces écosystèmes. En étudiant in situ la réponse des communautés microbiennes aux nutriments le long d’un gradient d’occupation des sols, nos travaux ont mis en évidence un effet positif des éléments dissous (N et P) sur la décomposition des litières et les activités enzymatiques des décomposeurs, et ce même pour les niveaux en nutriments les plus élevés du gradient, pour lesquels des effets inverses étaient attendus. Indépendamment, dans des cours d’eau anciennement soumis à de forts dépôts acidifiants, nous avons pu observer une récupération du processus de décomposition des litières. Néanmoins, cette restauration s’accompagnant d’un appauvrissement marqué en N, des perturbations du fonctionnement de ces cours d’eau pourrait se manifester à terme. Le rôle de la production primaire dans les cours d’eau de tête de bassin versant a ensuite été questionné. En effet, bien qu’étant mineur quantitativement, l’apport de carbone de forte qualité pourrait jouer un rôle non négligeable sur le fonctionnement des cours d’eau de tête de bassin versant. En particulier, l’importance et le rôle des apports en acides gras polyinsaturés (AGPI) via les biofilms phototrophes ont été questionnés. En se basant sur un suivi de terrain sur 15 cours d’eau des Vosges le long d’un gradient d’acidification, nos recherches ont tout d’abord pu mettre en évidence la présence de biofilms diatomiques riches en AGPI, malgré le caractère très forestier de ces cours d’eau. Dans un second temps, une expérience en conditions contrôlées a permis d’observer le rôle positif des apports, mêmes faibles, de ressources diatomiques sur la croissance et la survie du crustacé amphipode Gammarus fossarum. Sans cet apport, ces organismes se sont avérés incapables de maintenir leurs niveaux internes d’AGPI, suggérant qu’une consommation de producteurs primaires autochtones était indispensable à ces organismes détritivores. Nos résultats ont ainsi pu mettre en évidence les rôles fondamentaux que peuvent jouer la disponibilité en éléments dissous (N et P) et la qualité du carbone dans les ressources sur la production biologique et sur le processus de décomposition des litières dans les cours d’eau de tête de bassin versant. Ces résultats appellent désormais à investiguer plus profondément les interactions entre ces deux facteurs limitants, et à comprendre dans quels contextes l’un des facteurs pourrait suppléer l’autre. En particulier, il sera intéressant de rechercher comment diverses perturbations anthropiques (xénobiotiques, réchauffement climatique etc…) pourraient affecter l’intensité ou la nature de ces limitation