Consequences of early life adverse events on the development of non-communicable diseases in mouse models

The concept of Developmental Origins of Health and Disease (DOHaD) highlights the importance of early life period and raises the hypothesis that Non Communicable Diseases (NCD) could find their origins in perinatal environment. Neonatal maternal separation (MS) is a stress model widely used in rodents as a paradigm of early life adverse events. In my PhD project, I aimed to investigate in aging male and female wild-type mice under normal diet the long-term effects of neonatal MS on intestinal barrier function, metabolism, immunity, auto-immunity, as well as on microbiota. My work aimed to provide experimental data to support a link between early life stress and development of metabolic or autoimmune disorders with aging. In our first study, MS led to glucose intolerance and loss of insulin sensitivity associated with fecal dysbiosis in Post Natal Day (PND) 350 wild-type C3H/HeN male mice fed a standard diet. Fecal IgG concentrations were decreased in MS mice compared to control mice, whereas anti-E. coli IgG, representing humoral response toward commensal microbiota, were significantly increased in plasma of MS mice. MS significantly decreased IL-17 and IL-22 secretion in response to TcR stimulation in small intestine lamina propria (siLP) culture. Besides, TNF secretion in response to LPS-stimulation was slightly increased. The same results were obtained at systemic level (spleen). For the first time, we demonstrated that early life stress alone is a risk factor for metabolic disorders development in aging wild type mice under normal diet. The result of this project gave us the opportunity to question the role of microbiota in MS-induced glucose intolerance. Fecal microbiota transfer of MS mice microbiota was not sufficient to induce glucose intolerance. In our second study in PND350 female, MS increased IL-17 and IL-22 by siLP cells in response to TcR stimulation. TNF secretion with and without LPS stimulation was also increased by MS. Additionally, we observed systemic low-grade inflammation. MS mice developed glucose intolerance associated with decreased insulin secretion in response to glucose stimulus. Ratio of -cell surface to pancreas surface was slightly decreased in MS mice compared to control. This ratio positively correlated with insulin secretion induced by glucose. Taken together, the results of our study showed that MS in wild type female mice under normal diet leaves a long-lasting imprinting on immune-metabolism and pancreas homeostasis. We compared in vivo and ex vivo intestinal permeability measurements in a model of type 1 diabetes (NOD – non-obese diabetic mice). Intestinal permeability was assessed in vivo by gavage and ex vivo in Ussing chambers with the marker FITC-Dextran 4 kDa. Surprisingly, the results of both methods were divergent. The difference between in vivo and ex vivo measurements could not be explained by altered renal excretion. Curiously, diabetic NOD mice had significantly longer small intestine than non-diabetic NOD mice and small intestine length positively correlated with intestinal permeability in vivo. However, there were no difference in intestinal transit time, feces humidity and histological appearance. Altogether, our results highlighted the importance to distinguish intestinal permeability, which is expressed as cm/s, and the notion of systemic exposition to luminal antigen. My PhD project shows that early life adverse events are a risk factor for NCD. Interestingly, our observations in aging mice are similar to epidemiological observations. Indeed, preliminary results suggested that female MS mice develop metabolic disorders with autoimmune characteristics but male MS mice develop classical metabolic disorders with insulin resistance. My work in MS model highlights the importance of early life in the establishment of homeostasis and comforts the concept of DOHaD