The prevalence of obesity and its comorbidities has reached pandemic proportions and its economic and social burden highlights the need to develop therapeutic strategies beyond traditional lifestyle interventions. It is now well established that the obese brain is stressed, and the hypothesis that endoplasmic reticulum (ER) stress in hypothalamic cells is causally linked to obesity and associated comorbidities has been well supported. We have identified a novel thioredoxin-like protein called SELENOT that regulates redox homeostasis. The genetic invalidation of SELENOT in mice is lethal in utero and the reduction of its expression in POMC neurons or beta-pancreatic cells, major sites of metabolic integration, causes an alteration of hormonal secretions. Conversely, administration of a peptide mimetic of SELENOT, named PSELT, attenuates obesity and hyperglycemia in a pilot study performed in mice. Our goal is to demonstrate that SELENOT is an important regulator of ER stress and POMC production associated with energy homeostasis, and that the SELENOT peptide we developed may represent a valuable therapeutic tool against obesity and type 2 diabetes. In particular, we would like to answer the following questions: 1. What are the molecular mechanisms underlying the regulation of ER stress by SELENOT? 2. What is the role of SELENOT in POMC neuron function? 3. What are the metabolic effects of the PSELT peptide and its mechanism of action. The data obtained will be essential in order to use the PSELT as a therapy against obesity and its comorbidities, which represent a priority issue for the French health system.

Tight regulation of energy homeostasis at multiple levels is instrumental for organisms to cope with changes in food availability. The Central Nervous System (CNS) orchestrates a complex array of processes mediating energy intake and expenditure. Hormonal, neuronal and nutritional signals according to changes in food absorption, energy storage and energy consumption in different organs reach the CNS which in turn triggers corresponding changes in feeding behavior and peripheral cellular metabolism. Orexigenic neuropeptide Y (NPY) and agouti-related peptide (AgRP)-expressing AgRP/NPY neurons and anorexigenic proopiomelancortin (POMC)-expressing neurons in the arcuate nucleus of the hypothalamus are primarily involved in the regulation of energy homeostasis. To control appetite and peripheral metabolism, these neurons are regulated by several hormones. Among others, leptin, ghrelin and insulin emerged as key players in this context. Both leptin and insulin receptors are expressed in these neurons and both insulin and leptin have been found to activate POMC and to inhibit AgRP/NPY neurons. Ghrelin enhances the activity of AgRP/NPY neurons via its receptor, while it decreases the action of POMC neurons through a ghrelin receptor independent mechanism. Dysfunction of these neuronal circuits is known to contribute to overnutrition and obesity that eventually culminates in life-threatening type 2 diabetes (T2D) and/or cardiovascular diseases. Recent genome-wide association studies (GWAS) and GWAS meta-analyses revealed that they represent complex polygenic diseases. In fact more than ~250 genetic loci have been identified for monogenic, syndromic, or common forms of T2D and/or obesity-related traits. Despite this remarkable success, the contribution of most obesity- and T2D-associated single nucleotide polymorphism (SNPs) to the pathogenesis of these diseases remains largely elusive. CDC123 (cell division cycle protein 123)/CaMK1D (calcium/calmodulin-dependent protein kinase ID) represents one such locus on chromosome 10 strongly associated with T2D. Fine mapping identified a predominant SNP within this locus enhancing CaMK1D gene transcription. Thus, CaMK1D expression might be enhanced in and contribute to T2D. Substantial work in the past including our own efforts established a concept in which canonical stress kinase signaling interferes with physiologic metabolic pathways contributing to obesity-related insulin resistance and beta cell dysfunction, two main hallmarks of T2D. Keeping the focus and expertise on kinase-mediated signaling, we recently started to center our efforts on CaMK1D and its role in this disease context. In the last years, we have generated results directing us to hypothesize that CaMK1D primarily acts in AgRP neurons in the hypothalamus to control appetite and energy expenditure in response to ghrelin. The objective will be to explore more fundamentally the role of CaMK1D in AgRP neurons, opening a new avenue going beyond our previous research activity and expertise. To this end, we initiated a national collaborative project with the laboratory of Dr. Serge Luquet at the Functional and Adaptive Biology Unit at University of Paris specialized in central control of feeding behaviour and energy expenditure. Our partner laboratory will provide state-of-the-art neurometabolic tools and the necessary complementary expertise to pinpoint a role of CaMK1D in AgRP neurons. Our comprehensive experimental approach covering basic aspects of cellular signaling, physiology and neuroscience will thus set the stage for a new concept explaining as to how CaMK1D controls body weight and how its deregulation may contribute to obesity and T2D.

Insulin secretion by pancreatic beta-cell plays a key role in the control of glucose homeostasis by stimulating glucose uptake and utilization by liver, fat, and muscles. The balance between insulin secretion and action on peripheral tissues is in dynamic equilibrium and when insulin resistance develops in peripheral tissues, in conditions such as pregnancy, obesity, or aging, the pancreatic beta-cells increase their insulin secretion capacity and their number. Type 2 diabetes (T2D), a hyperglycemic syndrome, appears when the beta-cells are no longer able to compensate for the insulin resistance of peripheral tissues. In healthy conditions, the beta-cell plasticity required to preserve normoglycemia is controlled by many signals, in particular derived from the insulin-target tissues. Under metabolic stress conditions induced by excess consumption of energy-rich diets, insulin resistance in target tissues leads to the secretion of different types of inflammatory molecules, including several classes of lipids and cytokines. These can combine with cytokines secreted by activated inflammatory cells to negatively impact on beta-cell function and viability. Therefore, changes in insulin target tissues under metabolic stress can induce beta-cell dysfunctions through the release in the blood of beta-cell active molecules. The overall objective of this research proposal is to investigate the link between metabolic dysfunctions induced in insulin target tissues by calorie-rich diet feeding and the induction of beta-cell dysfunction. To this end two strains of mice (C57Bl6 and DBA2), known for their differential response to metabolic stresses, will be fed a normal chow or a high fat diet (HFD) for different periods of time and key parameters of beta-cell function and insulin action will be determined and plasma lipidomic and cytokine profile will be analyzed. Islets, liver, adipose tissue (visceral and subcutaneous depot), skeletal muscle (soleus and tibialis anterior) will be isolated for mRNA extraction and profiling by RNASeq analysis. These data will be analyzed in four major steps: 1) identification of gene modules in each tissue that correlate with the measured parameters of beta-cell function and of insulin action; 2) identification of plasma lipid and cytokine modules that correlate with the measured physiological parameters; 3) for those plasma lipids and cytokines that correlate with beta-cell dysfunction, analyze their direct effect on mouse islets and human beta-cell lines; 4) identify which lipid metabolic pathways in insulin target tissues may lead to the production of the plasma lipids that impact on beta-cell function. This systems biology investigation of metabolic stress-induced deregulation of glucose homeostasis will generate a new integrated view of changes in insulin target tissue transcriptome that is associated with, and may cause beta-cell demise through production and release in the plasma of bioactive molecules. This approach may lead to the identification of novel biomarkers for progression to T2D, which could also be new targets for drug or lifestyle intervention in treatment of diabetes. This proposal is based on previous work of this group of investigators performed in the frame of a EU IMI project that ends in September 2015.

Anorexia nervosa (AN) is a serious disease characterized by decreased food intake and body weight, associated with excessive physical activity (PA) and a preference for protein-enriched diet (PED) that is known to decrease hunger. AN patients maintain euglycemia and minimal body weight, despite low energy intake and increased PA, suggesting that adaptations should take place at the level of energy metabolism and of endogenous glucose production (EGP). EGP is activated during fasting, with an increased contribution of renal (RGN) and intestinal gluconeogenesis (IGN). Since food restriction (FR) is featured by partial fasting state, we hypothesize a change in EGP characteristic of fasting in FR, i.e. increased RGN and IGN. Since IGN curbs hunger via a signal to the brain, we hypothesize that this could help to endure food restriction in AN. Since PED induces IGN, this could explain why AN patients adopt this kind of regimen. At last, since the portal glucose signal initiated by IGN induces food preference, we hypothesize that increased IGN could enhance the preference for PED in AN patients or FR mice (aim1). PA is matched with fasting and PED under several aspects. We hypothesize that PA should activate IGN, which could enhance the behaviour of PA via IGN action on the reward system (aim 2.) We will then raise the question of the adaptation of energy expenditure and metabolism in FR associated with physical activity, which might explain the plateauing of body weight in this situation (aim 3). Aims 1 to 3 will be assessed using a mouse model of FR/AN recently developed. In parallel, the hypothesis that food preference for PED and PA could be correlated will be assessed in a cohort of patients suffering from AN using dedicated questionnaires (aim 4). At last, the microbiota composition could have a role in the metabolic/behavioral adaptations in AN, and in food restriction and PA. his hypothesis will be assessed in our AN model of mouse and our cohort of patients (aim 5).

Parkinson's disease (PD) is one of the major degenerative diseases for which there is no cure. There is therefore a pressing need to identify mechanisms implicated in PD pathogenesis that can be targeted for therapy. In this context, LRRK2, one of the major genetic determinants of sporadic and familial forms of MP, has emerged as a promising therapeutic target. Specifically, the importance of LRRK2 phosphorylation for its physiological and pathological functioning has recently become clear. Here, we will study the targeting of LRRK2 phosphorylation in PD models in drosophila, rodent neurons, rodent brains and in human cells. The validation of LRRK2 phosphorylation as a potential therapeutic target will open perspectives to develop modulators of phosphoregulators as candidate therapeutics for PD.