Search results for "homéostasie"

The neuropeptide 26RFa in the human gut and pancreas: potential involvement in glucose homeostasis

2019

Objective Recent studies performed in mice revealed that the neuropeptide 26RFa regulates glucose homeostasis by acting as an incretin and by increasing insulin sensitivity. However, in humans, an association between 26RFa and the regulation of glucose homeostasis is poorly documented. In this study, we have thus investigated in detail the distribution of 26RFa and its receptor, GPR103, in the gut and the pancreas, and determined the response of this peptidergic system to an oral glucose challenge in obese patients. Design and methods Distribution of 26RFa and GPR103 was examined by immunohistochemistry using gut and pancreas tissue sections. Circulating 26RFa was determined using a specif…

The neuropeptide 26RFa (QRFP) is a key regulator of glucose homeostasis and its activity is markedly altered in obese/hyperglycemic mice

2019

International audience; Recent studies have shown that the hypothalamic neuropeptide 26RFa regulates glucose homeostasis by acting as an incretin, and increasing insulin sensitivity. In this study, we further characterized the role of the 26RFa/GPR103 peptidergic system in the global regulation of glucose homeostasis using a 26RFa receptor antagonist, and also assessed whether a dysfunction of the 26RFa/GPR103 system occurs in obese hyperglycemic mice. Firstly, we demonstrate that administration of the GPR103 antagonist reduces the global glucose-induced incretin effect and insulin sensitivity whereas, conversely, administration of exogenous 26RFa attenuates glucose-induced hyperglycemia. U…

Hypothalamic glucose sensing : mitochondrial dynamic involument in reactive oxygen species signaling

2011

Energetic homeostasis results in the balance between energy intake and expenditure. The hypothalamus plays an important role in the regulation of both energetic metabolism and food intake in sensing hormonal and metabolic signals. For instance, changes in hypothalamic glucose level modulate food intake and insulin secretion. We have previously found that 1) increased hypothalamic glucose level triggers production of mitochondrial reactive oxygen species (mROS) from the electron transport chain; 2) hypothalamic mROS production is involved in glucose homeostasis and food intake control. The molecular mechanisms involved in glucose-induced hypothalamic mROS production are still unknown. Mitoch…

Role of polysialic acid (PSA) in the control of food intake and body weight

2013

Hypothalamus plays a major role in the regulation of energy homeostasis by the presence of neural circuits controlling food intake. These circuits are plastic and can be rewired during adulthood. We hypothesized that synaptic plasticity can occur during physiological conditions. We have shown that synaptic contact on hypothalamic anorexigen POMC neurons are rewired in mouse upon high fat diet (HFD). This synaptic process is mandatory to adjust energy intake and requires the glycan PSA (polysialic acid). PSA promotes synaptic plasticity in the brain by the weakening of cell-to-cell interaction by addition on NCAM (neural cell adhesion molecule). We hypothesized that a defect in brain synapti…

A new actor involved in hypothalamic glucose detection : the Transient Receptor Potential Canonical (TRPC) channels

2015

Hyperglycemia is detected and integrated by the mediobasal hypothalamus (MBH) which, in turn, inhibits food intake and triggers insulin secretion. The MBH houses specialized glucose-sensitive (GS) neurons, which directly or indirectly modulate their electrical activity in response to changes in glucose level. In a first study, we hypothesized that indirect detection of glucose by MBH GS neurons involves the secretion of endozepine by astrocytes, a gliotransmitter known to inhibit food intake in response to hyperglycemia. The present work shows that endozepines selectively activate anorexigenic MBH pro-opiomelanotortine (POMC) neurons. In the second study, we show that the direct detection o…

Obesogen effects after perinatal exposure of 4,4′-sulfonyldiphenol (Bisphenol S) in C57BL/6 mice

2016

International audience; Bisphenol A were removed from consumer products and replaced by chemical substitutes such as Bisphenol S (BPS). Based on their structural similarity, BPS may be obesogen like Bisphenol A in mice. Our objective was to determine the impact of BPS on lipid homeostasis in C57B1/6 mice after perinatal and chronic exposure. Pregnant mice were exposed to BPS via the drinking water (0.2; 1.5; 50 mu g/kg bw/d). Treatment began at gestational day 0 and continued in offspring up to 23-weeks old. Then, offspring mice were fed with a standard or high fat diet. The body weight, food consumption, fat mass and energy expenditure were measured. A lipid load test was performed to chec…

Role of polysialic acid (PSA) in the control of food intake and body weight

2013

Hypothalamus plays a major role in the regulation of energy homeostasis by the presence of neural circuits controlling food intake. These circuits are plastic and can be rewired during adulthood. We hypothesized that synaptic plasticity can occur during physiological conditions. We have shown that synaptic contact on hypothalamic anorexigen POMC neurons are rewired in mouse upon high fat diet (HFD). This synaptic process is mandatory to adjust energy intake and requires the glycan PSA (polysialic acid). PSA promotes synaptic plasticity in the brain by the weakening of cell-to-cell interaction by addition on NCAM (neural cell adhesion molecule). We hypothesized that a defect in brain synapti…

Détection hypothalamique de l’hyperglycémie : rôle de la dynamique mitochondriale dans la signalisation par les espèces actives de l’oxygène

2011

Xenohormones and oral homeostasis : impact on taste preferences and salivary glands

2012

Oral homeostasis strongly influences taste perceptions. It depends on a healthy oral epithelium and salivary gland secretions, which are both regulated by sex hormones. The aim of this thesis was to identify the effect of an oral exposure to Bisphenol A, a food packaging and dental sealer component, and of a soy-diet containing phytoestrogens on oral homeostasisTwo experiments were conducted in adult rats: a dose-response study of BPA (5μg 12.5 mg / kj / day), and a study about the impact of a soy-diet on the BPA disrupting effects. By using gustation choice tests, and histological and qPCR-TR molecular approach, we identify for the first time an action of BPA on dry mouth. We found that BP…

Astrocytes and hypothalamic glucose sensing: metabolic role and involvement of astroglial connexins

2012

The hypothalamus plays a pivotal role in the nervous control of glucose homeostasis. This area contains gluco-sensitive neurons. Some of them detect increases in glucose levels and regulate glucose homeostasis by stimulating insulin secretion or inhibiting food intake. It is widely accepted that astrocytes are metabolically coupled to neurons. Lactate, resulting from the metabolism of glucose by astrocytes, is transported via the monocarboxylate transporters (MCTs). In addition, gap junctions (GJ), that form networks within astrocytes, are essential to transfer glucose from the bloodstream to the active neurons. These astroglial GJ mainly consist of connexins 43 and 30 (Cxs).The aims of my …