Effects of PUFA on adipoconversion of piglet's preadipocytes in primary culture

GERLI : Groupe d'étude et de recherche en lipidomiqueNational audienc

Epidemic potential of Rift Valley fever in a Sahelian setting

International audienc

A mechanistic model of tsetse fly population dynamics in space and time calibrated on observed data in Senegal

A mechanistic model of tsetse fly population dynamics in space and time calibrated on observed data in Senegal. 8. Workshop Dynamical Systems Applied to Biology and Natural Sciences (DSABNS

Fatty acid acylation of proteins: Emerging cellular functions for saturated fatty acids

Fatty acid acylation of proteins corresponds to the co- or post-translational covalent linkage of a fatty acid, activated in the form of acyl-CoA, to an amino acid residue of the substrate protein. The cellular fatty acids which are involved in protein acylation are mainly saturated fatty acids. Palmitoylation (S-acylation) corresponds to the reversible attachment of palmitic acid (C16:0) to the side chain of a cysteine residue via a thioester bond. N-terminal myristoylation refers to the covalent attachment of myristic acid (C14:0) by an amide bond to the N-terminal glycine of many eukaryotic and viral proteins. Octanoylation (O-acylation) typically concerns the formation of an ester bond between octanoic acid (caprylic acid, C8:0) and the side chain of a serine residue of the gut and brain peptide ghrelin. An increasing number of proteins (enzymes, receptors, oncogenes, tumor suppressors, proteins involved in signal transduction, eukaryotic and viral structural proteins) have been shown to undergo fatty acid acylation. The acyl moiety can mediate protein subcellular localization, protein-protein interaction or protein-membrane interaction. Therefore, through the covalent modification of proteins, saturated fatty acids exhibit emerging specific and important roles in modulating protein functions. This review provides an overview of the recent findings on the various classes of protein acylation leading to the biological ability of saturated fatty acids to regulate many pathways. Finally, the links between these elucidated biochemical mechanisms and the physiological roles of dietary saturated fatty acids are discussed. (c) 2012 Elsevier Masson SAS. All rights reserved

Mechanistic models of Rift Valley fever virus transmission: A systematic review

International audienceRift Valley fever (RVF) is a zoonotic arbovirosis which has been reported across Africa including the northernmost edge, South West Indian Ocean islands, and the Arabian Peninsula. The virus is responsible for high abortion rates and mortality in young ruminants, with economic impacts in affected countries. To date, RVF epidemiological mechanisms are not fully understood, due to the multiplicity of implicated vertebrate hosts, vectors, and ecosystems. In this context, mathematical models are useful tools to develop our understanding of complex systems, and mechanistic models are particularly suited to data-scarce settings. Here, we performed a systematic review of mechanistic models studying RVF, to explore their diversity and their contribution to the understanding of this disease epidemiology. Researching Pubmed and Scopus databases (October 2021), we eventually selected 48 papers, presenting overall 49 different models with numerical application to RVF. We categorized models as theoretical, applied, or grey, depending on whether they represented a specific geographical context or not, and whether they relied on an extensive use of data. We discussed their contributions to the understanding of RVF epidemiology, and highlighted that theoretical and applied models are used differently yet meet common objectives. Through the examination of model features, we identified research questions left unexplored across scales, such as the role of animal mobility, as well as the relative contributions of host and vector species to transmission. Importantly, we noted a substantial lack of justification when choosing a functional form for the force of infection. Overall, we showed a great diversity in RVF models, leading to important progress in our comprehension of epidemiological mechanisms. To go further, data gaps must be filled, and modelers need to improve their code accessibility

Controlling the spatio-temporal dynamics of tsetse flies in a cattle breeding region of senegal

The tsetse fly complex (Glossina spp.) transmits the parasite responsible for African Animal Trypanosomiasis (AAT), or nagana, which is the most economically important livestock disease in Africa. The challenge of the last decades was to design programs that could sustainably control fly populations in different regions of the continent. Given the contrasted outcomes of these programs, there is still a need for a better understanding of the spatio-temporal dynamics of this vector.Mathematical models and computer-based simulations are relevant to assess which control measures should be used and when, accounting for the ecological complexity of the target pest and territorial specificities of the controlled area. They provide a useful tool, complementary to field observations and experiments, to suggest efficient vector management strategies.We developed a deterministic and mechanistic spatio-temporal model of the population dynamics of tsetse flies, structured by sex and age (pupae, teneral and non teneral adults). Temperature and fly density influenced the life-cycle, while spatial diffusion depended on density and relative quality of neighbouring locations. We applied the model on populations of Glossina palpalis gambiensis in the Niayes area of Senegal, for which biological and landscape data were available. The landscape was divided into 250m x 250m cells of heterogeneous carrying capacity, estimated by habitat suitability models. We transformed observed temperatures into “perceived” ones, to account for micro-environments where flies live. Dispersal, mortality, and development rates were calibrated on laboratory data, experts’ opinions and literature.The sensitivity analysis of the model identified the biological and environmental parameters influencing the most population dynamics. We showed that the mortality and development of adult females, along with temperature, were the key drivers of population persistence. Our predictions suggested that combining techniques to both increase mortality and decrease fecundity would be optimal to eradicate tsetse flies in targeted zones. Sequential aerosol technique (SAT), traps and targets (TT) and insecticide-treated livestock (ITL) increase daily mortality rates, whereas the sterile insect technique (SIT), by preventing egg-laying, slows down the development rate of the population. Furthermore, our results highlighted the need for more biological insights to achieve accurate model predictions. Additional field work and experiments are necessary to better infer the relationship between adult mortality and temperature, as well as differences between temperatures from weather stations and temperatures in tsetse fly resting places

It’s risky to wander in September: Modelling the epidemic potential of Rift Valley fever in a Sahelian setting

International audienceEstimating the epidemic potential of vector-borne diseases, along with the relative contribution of underlying mechanisms, is crucial for animal and human health worldwide. In West African Sahel, several outbreaks of Rift Valley fever (RVF) have occurred over the last decades, but uncertainty remains about the conditions necessary to trigger these outbreaks. We use the basic reproduction number (R0) as a measure of RVF epidemic potential in northern Senegal, and map its value in two distinct ecosystems, namely the Ferlo and the Senegal River delta and valley. We consider three consecutive rainy seasons (July-November 2014, 2015 and 2016) and account for several vector and animal species. We parametrize our model with estimates of Aedes vexans arabiensis, Culex poicilipes, Culex tritaeniorhynchus, cattle, sheep and goat abundances. The impact of RVF virus introduction is assessed every week over northern Senegal. We highlight September as the period of highest epidemic potential in northern Senegal, resulting from distinct dynamics in the two study areas. Spatially, in the seasonal environment of the Ferlo, we observe that high-risk locations vary between years. We show that decreased vector densities do not greatly reduce R0 and that cattle immunity has a greater impact on reducing transmission than small ruminant immunity. The host preferences of vectors and the temperature-dependent time interval between their blood meals are crucial parameters needing further biological investigations

Influence of the cis-9, cis-12 and cis-15 double bond position in octadecenoic acid (18:1) isomers on the rat FADS2-catalyzed Delta 6-desaturation

International audienceOleic (cis9-18:1), linoleic (cis9,cis12-18:2) and alpha-linolenic (cis9,cis12,cis15-18:3) acids are well described substrates of the Delta 6-desaturase encoded by the mammalian fatty acid desaturase 2 (FADS2) gene. In addition, at least 9 other very structurally different fatty acids have been shown to be Delta 6- or even Delta 8-desaturated by the FADS2 protein. A better characterization of the substrate specificity of this enzyme is therefore needed. By using commercial cis9-18:1 and chemically synthesized cis12- and cis15-18:1 (sharing the n-6 double bond with 18:2 n-6 and the n-3 double bond with 18:3 n-3, respectively), we tried to decrypt the fatty acid structure driving the FADS2 substrate affinity. We first showed that both recombinant and native rat FADS2 were able to Delta 6-desaturate not only the cis9- but also the cis12- and cis15-18:1 isomers. Next, the inhibitory effect of increasing concentrations of each 18:1 isomer was investigated in vitro on the Delta 6-desaturation of a-linolenic acid. At equimolar inhibitor/substrate ratio (60 mu M), the cis9-18:1 exhibited a significantly higher inhibition (25%) than the cis12- (8%) and cis15-18:1 (5%). This study shows that a single cis double bond in 12- or 15-position in 18:1 is enough to make them low Delta 6-desaturable substrates. If a preexisting cis9-double bond is not absolutely required for the Delta 6-desaturation of octadecenoic acids, its presence is however crucial to explain the higher enzyme affinity. Compared with oleic acid, the additional presence of a cis12-double bond in linoleic acid increased its inhibitory effect on the Delta 6-desaturation of alpha-linolenic acid at low concentration (30 mu M) but not at higher concentrations (60 and 120 mu M). In this classification of the decreasing impact of the double bond when it comes closer to the methyl end of octadecenoic acids, the cis11-18:1 (cis-vaccenic acid) should be considered apart since it is itself not Delta 6-desaturated but still a good competitive inhibitor of the a-linolenic acid 6-desaturation. (C) 2015 Elsevier Ireland Ltd. All rights reserved

Heterogeneity of Rift Valley fever virus transmission potential across livestock hosts, quantified through a model-based analysis of host viral load and vector infection

International audienceQuantifying the variation of pathogens’ life history traits in multiple host systems is crucial to understand their transmission dynamics. It is particularly important for arthropod-borne viruses (arboviruses), which are prone to infecting several species of vertebrate hosts. Here, we focus on how host-pathogen interactions determine the ability of host species to transmit a virus to susceptible vectors upon a potentially infectious contact. Rift Valley fever (RVF) is a viral, vector-borne, zoonotic disease, chosen as a case study. The relative contributions of livestock species to RVFV transmission has not been previously quantified. To estimate their potential to transmit the virus over the course of their infection, we 1) fitted a within-host model to viral RNA and infectious virus measures, obtained daily from infected lambs, calves, and young goats, 2) estimated the relationship between vertebrate host infectious titers and probability to infect mosquitoes, and 3) estimated the net infectiousness of each host species over the duration of their infectious periods, taking into account different survival outcomes for lambs. Our results indicate that the efficiency of viral replication, along with the lifespan of infectious particles, could be sources of heterogeneity between hosts. Given available data on RVFV competent vectors, we found that, for similar infectious titers, infection rates in the Aedes genus were on average higher than in the Culex genus. Consequently, for Aedes -mediated infections, we estimated the net infectiousness of lambs to be 2.93 (median) and 3.65 times higher than that of calves and goats, respectively. In lambs, we estimated the overall infectiousness to be 1.93 times higher in individuals which eventually died from the infection than in those recovering. Beyond infectiousness, the relative contributions of host species to transmission depend on local ecological factors, including relative abundances and vector host-feeding preferences. Quantifying these contributions will ultimately help design efficient, targeted, surveillance and vaccination strategies

Apport de la modélisation épidémiologique à la santé animale

National audienceAnticipating infection dynamics, at all scales (host, herd, production area), makes it possible to limit the impact of animal epidemics by identifying interventions adapted to the epidemiological situation. This issue, which is crucial for ensuring the sustainability of livestock farming, veterinary public health and animal welfare, is even more important in the context of global changes due to the evolution of system components. Epidemiological modelling provides a relevant analytical framework to address this issue, complementing observational and experimental approaches. In this article, the contributions of epidemiological modelling will be illustrated through four examples of animal diseases: bovine viral diarrhea, which is often studied within a single host and virus framework; African swine fever, which circulates at the interface between wild and domestic fauna; respiratory diseases, whose detection is increasingly based on the use of sensors in a precision farming context; and vector-borne diseases, whose epidemiology is highly driven by ecological processes, as multiple hosts and vector species are involved, with the population dynamics strongly impacted by environmental and climatic characteristics. These examples, encompassing a diversity of situations from the point of view of the pathosystem complexity, the generated epidemiological dynamics and the links with the environment, will allow us to address the methodological challenges still to be met: interconnecting models with observation data, real-time modelling, integrating models into a One Health - Eco Health approach, taking into account interactions between scales, coconstructing models together with animal health managers and public decision-makers, and modelling decision mechanisms