AMP-activated protein kinase (AMPK) has a major role in the modulation of energy balance. AMPK is activated in conditions of low energy, increasing energy production and reducing energy consumption. ...The AMPK pathway is a canonical route regulating energy homeostasis by integrating peripheral signals, such as hormones and metabolites, with neuronal networks. Current evidence has implicated AMPK in the hypothalamus and hindbrain with feeding, brown adipose tissue thermogenesis and browning of white adipose tissue, through modulation of the sympathetic nervous system, as well as glucose homeostasis. Interestingly, several potential antiobesity and/or antidiabetic agents, some of which are currently in clinical use such as metformin and liraglutide, exert some of their actions by acting on AMPK. Furthermore, the orexigenic and weight-gain effects of commonly used antipsychotic drugs are also mediated by hypothalamic AMPK. Overall, this evidence suggests that hypothalamic AMPK signalling is an interesting target for drug development, but is this approach feasible? In this Review we discuss the current understanding of hypothalamic AMPK and its role in the central regulation of energy balance and metabolism.
Energy balance involves the adjustment of food intake, energy expenditure and body fat reserves through homeostatic pathways. These pathways include a multitude of biochemical reactions, as well as ...hormonal cues. Dysfunction of this homeostatic control system results in common metabolism-related pathologies, which include obesity and type 2 diabetes mellitus. Metabolism-disrupting chemicals (MDCs) are a particular class of endocrine-disrupting chemicals that affect energy homeostasis. MDCs affect multiple endocrine mechanisms and thus different cell types that are implicated in metabolic control. MDCs affect gene expression and the biosynthesis of key enzymes, hormones and adipokines that are essential for controlling energy homeostasis. This multifaceted spectrum of actions precludes compensatory responses and favours metabolic disorders. Herein, we review the main mechanisms used by MDCs to alter energy balance. This work should help to identify new MDCs, as well as novel targets of their action.
GLP-1 receptor (GLP-1R) is widely located throughout the brain, but the precise molecular mechanisms mediating the actions of GLP-1 and its long-acting analogs on adipose tissue as well as the brain ...areas responsible for these interactions remain largely unknown. We found that central injection of a clinically used GLP-1R agonist, liraglutide, in mice stimulates brown adipose tissue (BAT) thermogenesis and adipocyte browning independent of nutrient intake. The mechanism controlling these actions is located in the hypothalamic ventromedial nucleus (VMH), and the activation of AMPK in this area is sufficient to blunt both central liraglutide-induced thermogenesis and adipocyte browning. The decreased body weight caused by the central injection of liraglutide in other hypothalamic sites was sufficiently explained by the suppression of food intake. In a longitudinal study involving obese type 2 diabetic patients treated for 1 year with GLP-1R agonists, both exenatide and liraglutide increased energy expenditure. Although the results do not exclude the possibility that extrahypothalamic areas are also modulating the effects of GLP-1R agonists, the data indicate that long-acting GLP-1R agonists influence body weight by regulating either food intake or energy expenditure through various hypothalamic sites and that these mechanisms might be clinically relevant.
Ghrelin is a multifaceted regulator of metabolism. Ghrelin regulates energy balance in the short term via induction of appetite and in the long term via increased body weight and adiposity. Recently, ...several central pathways modulating the metabolic actions of ghrelin were unmasked, and it was shown to act through different hypothalamic nuclei to induce feeding. Ghrelin also modulates glucose homeostasis, but the central mechanisms responsible for this action have not been studied in detail. Although ghrelin also acts through extrahypothalamic areas to promote feeding, this review specifically dissects hypothalamic control of ghrelin’s orexigenic and adipogenic actions and presents current understanding of the intracellular ghrelin orexigenic pathways, including their dependence on other relevant systems implicated in energy balance.
Melanin-concentrating hormone (MCH) is a small cyclic peptide expressed in all mammals, mainly in the hypothalamus. MCH acts as a robust integrator of several physiological functions and has crucial ...roles in the regulation of sleep-wake rhythms, feeding behaviour and metabolism. MCH signalling has a very broad endocrine context and is involved in physiological functions and emotional states associated with metabolism, such as reproduction, anxiety, depression, sleep and circadian rhythms. MCH mediates its functions through two receptors (MCHR1 and MCHR2), of which only MCHR1 is common to all mammals. Owing to the wide variety of MCH downstream signalling pathways, MCHR1 agonists and antagonists have great potential as tools for the directed management of energy balance disorders and associated metabolic complications, and translational strategies using these compounds hold promise for the development of novel treatments for obesity. This Review provides an overview of the numerous roles of MCH in energy and glucose homeostasis, as well as in regulation of the mesolimbic dopaminergic circuits that encode the hedonic component of food intake.
Highlights • Thyroid hormones regulate energy balance and metabolism by acting at the central level. • Thyroid hormones modulate the autonomous nervous system. • Thyroid hormones modulate ...hypothalamic UCP2 and mTOR to regulate feeding. • Thyroid hormones modulate hypothalamic AMPK to regulate thermogenesis in brown adipose tissue. • Thyroid hormones act on the hypothalamus to regulate hepatic glucose metabolism.
Ghrelin and LEAP-2: Rivals in Energy Metabolism Al-Massadi, Omar; Müller, Timo; Tschöp, Matthias ...
Trends in pharmacological sciences (Regular ed.),
August 2018, 2018-08-00, 20180801, Letnik:
39, Številka:
8
Journal Article
Recenzirano
Liver-expressed antimicrobial peptide 2 (LEAP-2), the endogenous noncompetitive allosteric antagonist of the growth hormone secretagogue receptor 1a (GHSR1a), was recently identified as a key ...endocrine factor regulating systemic energy metabolism. This antagonist impairs the ability of ghrelin to activate GHSR1a and diminishes ghrelin-induced Ca2+ release in vitro. The physiological relevance of the molecular LEAP-2-GHSR1a interaction was subsequently demonstrated in vivo. LEAP-2 is therefore a promising therapeutic target in the treatment of obesity and other metabolic diseases. Here, we discuss not only the current understanding of LEAP-2 in metabolic regulation, but also the potential of this peptide in the treatment of obesity and other diseases that involve dysregulation of the ghrelin system.
Ghrelin is a gastric hormone that stimulates food intake, adiposity, and growth hormone (GH) secretion and maintains glucose levels during caloric restriction. It binds to its receptor, the growth hormone secretagogue receptor 1a (GHSR1a).
LEAP-2 is a noncompetitive antagonist of the GHSR1a and can be considered as the first endogenous peptide able to antagonize metabolic actions of ghrelin in vitro and in vivo.
LEAP-2 overexpression impairs the ability of ghrelin to maintain the body weight and blood glucose levels in a period of extreme food shortage.
The characterization of LEAP-2 will provide novel insights in the pursuit of new therapies to tackle metabolic disorders such as obesity and other nutritional or eating disorders.
The sirtuins are a family of highly conserved NAD(+)-dependent deacetylases that act as cellular sensors to detect energy availability and modulate metabolic processes. Two sirtuins that are central ...to the control of metabolic processes are mammalian sirtuin 1 (SIRT1) and sirtuin 3 (SIRT3), which are localized to the nucleus and mitochondria, respectively. Both are activated by high NAD(+) levels, a condition caused by low cellular energy status. By deacetylating a variety of proteins that induce catabolic processes while inhibiting anabolic processes, SIRT1 and SIRT3 coordinately increase cellular energy stores and ultimately maintain cellular energy homeostasis. Defects in the pathways controlled by SIRT1 and SIRT3 are known to result in various metabolic disorders. Consequently, activation of sirtuins by genetic or pharmacological means can elicit multiple metabolic benefits that protect mice from diet-induced obesity, type 2 diabetes, and nonalcoholic fatty liver disease.
Regulation of energy homeostasis is tightly controlled by the central nervous system (CNS). Several key areas such as the hypothalamus and brainstem receive and integrate signals conveying energy ...status from the periphery, such as leptin, thyroid hormones, and insulin, ultimately leading to modulation of food intake, energy expenditure (EE), and peripheral metabolism. The autonomic nervous system (ANS) plays a key role in the response to such signals, innervating peripheral metabolic tissues, including brown and white adipose tissue (BAT and WAT), liver, pancreas, and skeletal muscle. The ANS consists of two parts, the sympathetic and parasympathetic nervous systems (SNS and PSNS). The SNS regulates BAT thermogenesis and EE, controlled by central areas such as the preoptic area (POA) and the ventromedial, dorsomedial, and arcuate hypothalamic nuclei (VMH, DMH, and ARC). The SNS also regulates lipid metabolism in WAT, controlled by the lateral hypothalamic area (LHA), VMH, and ARC. Control of hepatic glucose production and pancreatic insulin secretion also involves the LHA, VMH, and ARC as well as the dorsal vagal complex (DVC), via splanchnic sympathetic and the vagal parasympathetic nerves. Muscle glucose uptake is also controlled by the SNS via hypothalamic nuclei such as the VMH. There is recent evidence of novel pathways connecting the CNS and ANS. These include the hypothalamic AMP-activated protein kinase–SNS–BAT axis which has been demonstrated to be a key modulator of thermogenesis. In this review, we summarize current knowledge of the role of the ANS in the modulation of energy balance.
Glucagon exerts pleiotropic actions on energy balance and has emerged as an attractive target for the treatment of diabetes and obesity in the last few years. Glucagon reduces body weight and ...adiposity by suppression of appetite and by modulation of lipid metabolism. Moreover, this hormone promotes weight loss by activation of energy expenditure and thermogenesis. In this review, we cover these metabolic actions elicited by glucagon beyond its canonical regulation of glucose metabolism. In addition, we discuss recent developments of therapeutic approaches in the treatment of obesity and diabetes by dual- and tri-agonist molecules based on combinations of glucagon with other peptides. New strategies using these unimolecular polyagonists targeting the glucagon receptor (GCGR), have become successful approaches to evaluate the multifaceted nature of glucagon signaling in energy balance and metabolic syndrome.
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