This research project is inspired by yet unpublished observations implying the protein diazepam binding protein (DBI)/acyl CoA-binding protein (ACBP) in the control of autophagy, peripheral metabolism, and appetite. This notion is based on the observations that DBI serum levels correlate with human corpulence (low in anorexia, high in obesity) and that injecting DBI into mice causes hyperphagy (and activation of orexigenic neurons) and weight gain with increased fat deposition, while its neutralization reduces feeding (and activates anorexigenic neurons) and entails weight loss with lipolysis. Incidentally, the secretion of DBI from cells in vitro and in vivo is unconventional and depends on autophagy genes (ATGs). DBI also controls autophagy, meaning that injection of DBI into mice inhibits autophagy, while its neutralization induces autophagic flux. Moreover, DBI has major effects on metabolism affecting glycaemia, fatty acid oxidation, as well as anabolic and catabolic metabolism in adipose tissues and the liver. Based on these results, we propose the in-depth characterization of the DBI system. We will explore the mechanism governing DBI expression in various tissues, the mechanisms explaining its ATG-dependent release from cells, its pharmacology (pharmacokinetics of DBI and its fragments, effects of DBI on its receptors and signalling pathways), elaborate strategies to elevate its expression (by transgenes or by supply of recombinant DBI protein) or neutralization (by inducible knockout, induction of DBI-autoantibodies, or external supply of in-house monoclonal antibodies), and characterize the effects of DBI on metabolism using a battery of distinct methods, while attempting to establish a hierarchy among autophagy-regulatory and diverse metabolic effects. Special attention will be devoted to the question how the peripheral (intraperitoneal or intravenous) administration of DBI or anti-DBI antibodies can affect central appetite control.

The regulation of feeding behavior relies on the integration of both metabolic and reward signals, which collectively ensure adaptive strategies to maintain body homeostasis. However, our modern food environment and the overconsumption of palatable energy-dense food constantly challenges such strategies and can lead to obesity. Indeed, the latest alarming estimations of the World Health Organization (WHO) reveal that in Europe over half of all men and women are overweight, and roughly one-third are obese. While some genetic traits (monogenic causes) have been identified and extensively studied, it is widely recognized that the metabolic syndrome is in essence a multifactorial and multidimensional disorder that encompass complex networks of, yet unclear, feed-forward physiopathological maladaptations. Emerging evidence indicates that obesity may result from a maladapted communication between peripheral organs and the brain. Here, supported by studies and current results, we tackle the hypothesis that the interoceptive gut-brain vagal axis, a rapid relay of viscerotopic information toward the brain, may represent a key site of such maladaptive distortion and may scale obesity-associated metabolic and reward dysfunctions. This project is built upon three main aims: (1) Establishing the role of gut-brain vagal afferents in scaling the adaptive responses of the reward circuit in obesity: from feeding to nutrients-sensing (2) Interrogating the gut-brain vagal axis to restore hedonic and metabolic functions (3) Leveraging the molecular signature of vagal neurons to identify new targets for obesity Using multi-scale in vivo approaches (from networks to targeted pharmacology to molecular cartography), HERO promotes a novel conceptual framework that sees in the vagal axis a functional element to (i) explore new integrative mechanisms underlying obesity and (ii) establish innovative therapeutic strategies for obesity-induced homeostatic and reward dysfunctions.

Obesity and diabetes are characterized by deregulations of endogenous glucose production. Three organs, the liver, kidney and intestine can produce glucose in the blood because they have the key enzyme: glucose-6 phosphatase (G6Pase). While hepatic glucose production is deleterious, intestinal glucose production is beneficial, since it sends a signal to the brain and exerts anti-obesity and anti-diabetes mediated by the hypothalamus. This especially takes place when intestinal glucose production is induced by diets enriched in protein or in soluble fiber fermented by the gut microbiota. We here want to make the proof of concept that intestinal glucose production per se may exert beneficial effects, i.e. regardless of any nutritional regulation. With this aim, we shall characterize new original animal models developed by the laboratory. We shall study the protection of mice constitutively overexpressing intestinal G6Pase against the development of obesity and diabetes induced by a deleterious “westernized” diet (rich in fat and sucrose). Using a procedure of overexpression inducible (by tamoxifen), we shall evaluate the capacity of intestinal glucose production to combat obesity and the deregulation of glucose control under conditions of pre-established obesity/diabetes. As an alternative to mimic intestinal glucose production and its benefits, we shall study the effect of infusions of glucose into the portal vein (via a catheter) in rodent models of obesity, pre-diabetes or diabetes. This will include genetic models of obesity/diabetes, such as Ob/Ob and Db/Db mice, and the Zucker Diabetic Fatty rat. In parallel, we shall deepen the molecular mechanisms involved in the central signal initiated by intestinal glucose production. This will include the identification of the nervous routes of transmission of the portal glucose signal, using an approach of electrophysiology on isolated gastrointestinal nerves and on central nuclei in vivo, and of the molecular mechanisms taking place in the hypothalamus, focusing on the original hypothesis of an interaction between the portal glucose signal and the hypothalamic leptin signalling. This will be studied by comparing the mechanisms taking place in mice deficient in intestinal G6Pase and mice overexpressing intestinal G6Pase. A better knowledge of the mechanisms initiated by intestinal glucose production and its metabolic benefits could pave the way for future approaches of prevention or treatment of metabolic diseases.

Cardiac cell therapy holds a real promise for improving function of the chronically failing myocardium. However, so far, clinical outcomes of patients included in cell therapy trials have not met the expectations raised by the preceding experimental studies. Analysis of the causes for these suboptimal results leads to three major conclusions : (1) repair of scarred myocardium should be best achieved by cells endowed with a cardiomyogenic differentiation potential as cell types used so far clinically (skeletal myoblasts, bone marrow-derived cells, adipose tissue-derived cells) lack the ability to convert into cardiomyocytes; (2) injection-based cell delivery is not satisfactory, primarily because it involves a proteolytic dissociation of the cells which sets the stage for their apoptotic death; and (3) the efficacy of the cell transplant is largely dependent on the engraftment rate which, in turn, requires cells to receive an adequate blood supply to survive. To address these issues, we propose to switch from mere cell therapy to a more composite tissue engineering construct entailing the use of human embryonic stem cell (hESC)-derived cardiac progenitors seeded onto a biocompatible scaffold along with endothelial cells from the same hESC source to provide the necessary trophic support. Although the concept of such a co-seeded patch is not new, a remaining issue is that of the migration of the cells away from the scaffold to colonize the underlying myocardium. The basic objective of this project is to design a patch allowing such a migration with the premise that the patch-derived cells will then improve angiogenesis and heart function, possibly through their coupling with host cardiomyocytes. To achieve this objective, we plan to develop an electrospun nanofibrous collagen-based patch co-seeded with two synergistically cross-talking cell populations originating from the same hESC cell line and differentially pre-committed to yield both cardiac progenitors and endothelial cells. By controlling the porous size and the mechanical and chemical properties of the scaffolds, we will first optimize their suitability for cell loading, cell survival and proliferation before assessing their permissivity with regard to cell migration. We will then optimize the permissivity of this patch with regard to cell migration by physical (pore size), chemical (surface chemistry) and eventually biological (active molecule adjuncts) adjustments. To mimic the future environment of the patch, we will then develop an ex vivo model whereby the patch is put in contact with an epicardial layer obtained during cardiac surgical operations, with the assumption that epicardium-secreted factors may play a key role in driving the patch-bound cells towards the inner layers of the myocardium, keeping the additional intramyocardial delivery of chemoattractants as a back-up solution. The development of this ex vivo model which mimics the cardiac in vivo environment, should allow us to limit unnecessary use of animals and to screen rapidly different parameters to obtain more appropriate cellularized biomaterial for cardiac cell therapy. Following this step, the capacity of the cells to migrate away from this patch and subsequently to enhance function of the chronically infarcted myocardium will ultimately be tested in an in vivo model of permanent coronary artery ligation. To achieve these objectives, we have built a multidisciplinary consortium which involve three laboratories and a company which have expertise in 1) nanotechnology and biomaterial architecture, 2) development of collagen-based biomaterials for clinical use, 3) cardiovascular development and differentiation of hESC towards the cardiac and endothelial lineages, and 4) small and large animal models of myocardial infarction and clinical cell-based trials for cardiovascular repair.