Endocrine development最新文献

Hypothalamic obesity (HO) is a rare and serious disease of various origins: tumor, traumatism, radiotherapy, vascular, genetic, or even psychotropic drug use. HO usually begins in childhood with eating disorders and progresses with an aggregate of severe comorbidities. Transition from pediatric to adult health care is a critical period to assure weight stability and a good management of comorbidities. In case of loss to follow-up, there is an increased risk of major weight gain and long-term complications with severe obesity. To minimize this risk, pediatric and adult specialists must work together to prepare, supervise, and monitor transition. Transition ideally involves the patient, parents, and care providers with a good communication between pediatric and adult teams from expert centers. Maintaining a diet and physical activity management plan, acquisition of autonomy for hormone replacement therapy and management of psychosocial consequences of obesity are fundamental issues in patients with HO. Patient associations and specialized diet center weight loss programs can help as well as group approaches.

Ghrelin is a pleiotropic hormone, whose effect on growth hormone secretion, through the growth hormone secretagogue (GHS) receptor, is one of its many actions. Relationships between GHS receptor gene variants and human height, both in healthy individuals and in patients with growth disorders have been identified. These include constitutional delay in growth and puberty, idiopathic short stature, and isolated growth hormone deficiency. In this review, we provide an overview of the role of ghrelin in growth.

Despite greater health education, obesity remains one of the greatest health challenges currently facing the world. The prevalence of obesity among children and adolescents and the rising rates of prediabetes and diabetes are of particular concern. A deep understanding of regulatory pathways and development of new anti-obesity drugs with increased efficacy and safety are of utmost necessity. The 2 major biological players in the regulation of food intake are the gut and the brain as peptides released from the gut in response to meals convey information about the energy needs to brain centers of energy homeostasis. There is evidence that gut hormones not only pass the blood-brain barrier and bind to receptors located in different brain areas relevant for body weight regulation, but some are also expressed in the brain as part of hedonic and homeostatic pathways. Regarding obesity interventions, the only truly effective treatment for obesity is bariatric surgery, the long-term benefits of which may actually involve increased activity of gut hormones including peptide YY3-36 and glucagon-like peptide 1. This review discusses critical gut-hormones involved in the regulation of food intake and energy homeostasis and their effects on peripheral tissues versus central nervous system actions.

Gut bacteria exert a variety of metabolic functions unavailable to the host and are increasingly seen as a virtual organ located inside our gastrointestinal tract. Scattered in our intestinal epithelium, enteroendocrine cells (EECs) regulate several aspects of the host's physiology and translate signals coming from the gut microbiota through their hormonal secretions. In this chapter, we will assess the interplay between the gut microbiota and EEC and its consequences for the physiology of the host. We will first describe alterations of different populations of EEC in germ-free animals. The role of mediators of this interaction, such as microbial metabolites and their receptors will also be discussed. Finally, different strategies harnessing host-microbe crosstalk for therapeutic purposes will be presented with an emphasis on obesity and related disorders.

Obesity and its comorbidities such as type 2 diabetes constitute major worldwide health threats, and the identification of an effective medical intervention has emerged as a global priority. The limited effectiveness of historical, anti-obesity treatments is commonly attributed to the complexity of the disease and the redundancy of metabolic regulatory mechanisms that sustain body weight. At the forefront of obesity research is the development of combinational drug therapies that simultaneously target multiple regulatory pathways, which promote dysfunctional metabolism. Recently, molecularly crafted unimolecular "multi-agonism" of balanced activity at 3 key receptors involved in metabolism and specifically the glucagon-like peptide (GLP)-1 receptor, glucose-dependent insulinotropic polypeptide (GIP) receptor and glucagon receptor was reported as superior to conventional monoagonist therapy. These mixed peptide agonists are designed to pharmacologically integrate the insulinotropic and anorexigenic effects of GLP-1, the thermogenic and lipolytic activities of glucagon, and the insulinotropic and insulin sensitizing properties of GIP. The molecular mechanism of these purposefully promiscuous ligands is not completely understood, however, recent studies in pancreatic beta cells point to the prospect of a complex signaling network that can magnify the signaling of multi-agonist ligands. The activation of this signalosome might explain the additional therapeutic benefit inherent to simultaneous cellular activation through multiple metabolic receptors.

Gastrointestinal hormones are released from enteroendocrine cells in the digestive tract. More than 30 hormone genes are expressed, which make the gut the largest endocrine organ in the body. At present, it is feasible to conceive the hormones under 5 headings: the structural homology groups most hormones into 9 families, each of which is assumed to originate from a single gene. Today's hormone gene often has multiple phenotypes due to alternative splicing, tandem organization or differentiated maturation of the prohormone. By these mechanisms, more than 100 different hormonal peptides are released from the gut. Gut hormones are also widely expressed in extraintestinal cells. These cells may release different fragments of the same prohormone due to cell-specific processing pathways. Moreover, endocrine cells, immune cells, neurons, myocytes, kidney cells, sperm cells and cancer cells secrete gut peptides in different ways, so the same peptide may act for instance as a hormone, a neurotransmitter, a cytokine, a growth factor or a fertility factor. The targets of gastrointestinal hormones are specific G-protein coupled receptors that are expressed in the cell membrane all over the body. Thus, each gut hormone constitutes a regulatory system operating in the whole organism.

Incretins are hormones secreted into the blood stream from the gut mucosa in response to nutrient intake. They have been characterized based on their capacity to lower blood glucose levels. The more potent reduction of blood glucose coupled to a more intensive stimulation of insulin secretion, in response to oral glucose uptake, as compared to intravenous glucose infusion has further been termed the "incretin effect." As a prototype incretin hormone, the biology of glucagon-like peptide 1 (GLP-1) has been intensively studied. GLP-1 actions are mediated through cyclic adenosine monophosphate-coupled membrane receptors. Classical physiological effects involve stimulation of insulin secretion from pancreatic beta cells and reduction of glucagon secretion from pancreatic alpha cells, inhibition of gastric motility, and increase of satiety with reduced food uptake. The understanding of these metabolic functions has led to the notion that incretin hormones, and specifically GLP-1, would represent ideal antidiabetic treatment options. As native GLP-1 is degraded by dipeptidyl peptidase type 4 (DPP-4) within minutes, other pharmacological approaches to exploit GLP-1 actions for the treatment of type 2 diabetes have been developed. These include DPP-4 inhibitors as oral medications and GLP-1 receptor agonists (incretin mimetics) as peptide compounds to be injected.

The gastrointestinal (GI) tract exhibits an enormous surface area that consists mostly of absorptive enterocytes. Enteroendocrine cells (EECs) are found scattered along the GI tract between absorptive enterocytes and other secretory cells, and comprise around 1% of the epithelial cell population. Interestingly, they develop from the same crypt stem cell as the other absorptive or secretory cells of the gut. EECs differentiate along the crypt villus axis and are renewed every 4-6 days, and hence possess a high plasticity. They constitute the largest endocrine system in the human body by secreting multiple peptide hormones to control, for example, postprandial digestion, insulin homeostasis, food intake, and gut motility. For this purpose, most EECs exhibit luminal sensors that detect the GI tract content. Thereafter, they may act either in a classical endocrine fashion, or by paracrine effects on nearby neural and immune cells. This creates a pivotal role for EECs to influence the GI immune system and the enteric nervous system. In this chapter, the anatomical characteristics, development, differentiation and maturation of EECs are described, and their important biological potential illustrated as part of the gut interacting sensory system.

Enteroendocrine cells (EEC) have been studied extensively for their ability to regulate gastrointestinal motility and insulin release by secretion of peptide hormones. In particular, the L cell-derived incretin glucagon-like peptide 1 has gained enormous attention due to its insulinotropic action and relevance in the treatment of type 2 diabetes. Yet, accumulating data indicates a critical role for EEC and incretins in metabolic adaptation and in orchestrating immune responses beyond blood glucose control. EEC actively sense the lamina propria and luminal environment including the microbiota via receptors and transporters, subsequently mediating signals by secreting hormones and cytokines. Data indicate that immune cells and cytokine-mediated signaling impacts EEC numbers and function during infection and chronic inflammation of the gut, suggesting EEC not only to play a role in these pathologies but also being a target of inflammatory processes. This review presents data on the interrelation of incretins and inflammatory signaling. It focuses on the impact of intestinal inflammation, in particular inflammatory bowel disease, on EEC and the potential role of EEC and incretins in these pathologies. Furthermore, it highlights endoplasmic reticulum unfolded protein response, cytokines and the intestinal microbiota as possible targets of inflammatory and EEC signaling.