Exploring the Mechanisms of Recovery in Anorexia Nervosa through a Translational Approach: From Original Ecological Measurements in Human to Brain Tissue Analyses in Mice.

Anorexia nervosa (AN) is a severe eating disorder where caloric restriction, excessive physical activity and metabolic alterations lead to life-threatening situations. Despite weight restoration after treatment, a significant part of patients experience relapses. In this translational study, we combined clinical and preclinical approaches. We describe preliminary data about the effect of weight gain on the symptomatology of patients suffering from acute AN (n = 225) and partially recovered (n = 41). We measured more precisely physical activity with continuous cardiac monitoring in a sub-group (n = 68). Using a mouse model, we investigated whether a long-term food restriction followed by nutritional recovery associated or not with physical activity may differentially impact peripheral and central homeostatic regulation. We assessed the plasma concentration of acyl ghrelin, desacyl ghrelin and leptin and the mRNA expression of hypothalamic neuropeptides and their receptors. Our data show an effect of undernutrition history on the level of physical activity in AN. The preclinical model supports an important role of physical activity in the recovery process and points out the leptin system as one factor that can drive a reliable restoration of metabolic variables through the hypothalamic regulation of neuropeptides involved in feeding behavior.

Long-Term Energy Deficit in Mice Causes Long-Lasting Hypothalamic Alterations after Recovery.

Although the short-term effects of fasting or energy deficit on hypothalamic neuropeptide circuitries are now better understood, the effects of long-term energy deficit and refeeding remain to be elucidated. We showed that after a long-term energy deficit, mice exhibited persistent hypoleptinemia following the refeeding period despite restoration of fat mass, ovarian activity, and feeding behavior. We aimed to examine the hypothalamic adaptations after 10 weeks of energy deficit and after 10 further weeks of nutritional recovery. To do so, we assessed the mRNA levels of the leptin receptor and the main orexigenic and anorexigenic peptides, and their receptors regulated by leptin. Markers of hypothalamic inflammation were assessed as leptin can also participate in this phenomenon. Long-term time-restricted feeding and separation induced significant increase in mRNA levels of hypothalamic orexigenic peptides, while both Y1 and Y5 receptor mRNAs were downregulated. No changes occurred in the mRNA levels of orexin (OX), melanin-concentrating hormone, pro-opiomelanocortin, 26RFa (26-amino acid RF-amide peptide), and their receptors despite an increase in the expression of melanocortin receptors (MC3-R and MC4-R) and OXR1 (OX receptor 1). The refeeding period induced an overexpression of leptin receptor mRNA in the hypothalamus. The other assessed mRNA levels were normalized except for Y2, Y5, MC3-R, and MC4-R, which remained upregulated. No convincing changes were observed in neuroinflammatory markers, even if interleukin-1ß mRNA levels were increased in parallel with those of Iba1 (ionized calcium-binding adaptor molecule 1), a marker of microglial activation. Normalization of leptin-regulated functions and hypothalamic gene expressions in refed mice with low plasma leptin levels could be sustained by recalibration of hypothalamic sensitivity to leptin.

Interleukin-7, a new cytokine targeting the mouse hypothalamic arcuate nucleus: role in body weight and food intake regulation.

Body weight is controlled through peripheral (white adipose tissue) and central (mainly hypothalamus) mechanisms. We have recently obtained evidence that overexpression of interleukin (IL)-7, a critical cytokine involved in lymphopoiesis, can protect against the development of diet-induced obesity in mice. Here we assessed whether IL-7 mediated its effects by modulating hypothalamic function. Acute subcutaneous injection of IL-7 prevented monosodium glutamate-induced obesity, this being correlated with partial protection against cell death in the hypothalamic arcuate nucleus (ARC). Moreover, we showed that IL-7 activated hypothalamic areas involved in regulation of feeding behavior, as indicated by induction of the activation marker c-Fos in neural cells located in the ventromedial part of the ARC and by inhibition of food intake after fasting. Both chains of the IL-7 receptor (IL-7Ralpha and gamma(c)) were expressed in the ARC and IL-7 injection induced STAT-3 phosphorylation in this area. Finally, we established that IL-7 modulated the expression of neuropeptides that tune food intake, with a stimulatory effect on the expression of pro-opiomelanocortin and an inhibitory effect on agouti-related peptide expression in accordance with IL-7 promoting anorectic effects. These results suggest that the immunomodulatory cytokine IL-7 plays an important and unappreciated role in hypothalamic body weight regulation.

Neurobiological correlates of high (HAB) versus low anxiety-related behavior (LAB): differential Fos expression in HAB and LAB rats.

BACKGROUND: Two Wistar rat lines selectively bred for either high (HAB) or low (LAB) anxiety-related behavior were used to identify neurobiological correlates of trait anxiety. METHODS: We used Fos expression for mapping of neuronal activation patterns in response to mild anxiety-provoking challenges. RESULTS: In both lines, exposure to an open field (OF) or the open arm (OA) of an elevated plus-maze induced Fos expression in several brain areas of the anxiety/fear circuitry. Rats of the HAB type, which showed signs of a hyperanxious phenotype and a hyperreactive hypothalamic-pituitary-adrenal axis compared with LAB rats, exhibited a higher number of Fos-positive cells in the paraventricular nucleus of the hypothalamus, the lateral and anterior hypothalamic area, and the medial preoptic area in response to both OA and OF. Less Fos expression was induced in the cingulate cortex in HAB than in LAB rats. Differential Fos expression in response to either OA or OF was observed in few brain regions, including the thalamus and hippocampus. CONCLUSIONS: The present data indicate that the divergent anxiety-related behavioral response of HAB versus LAB rats to OF and OA exposures is associated with differential neuronal activation in restricted parts of the anxiety/fear circuitry. Distinct hypothalamic regions displayed hyperexcitability, and the cingulate cortex showed hypoexcitability, which suggests that they are main candidate mediators of dysfunctional brain activation in pathologic anxiety.