Central and peripheral interactions between the agouti-related protein and leptin

Charbonneau, Chantal

doi:10.1016/s0006-291x(04)00956-8

Cited by 4 publications

(7 citation statements)

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“…Furthermore, constant light or constant dark (20 days) resulted in differential changes in rat adrenal NPY expression (29). AgRP expression is regulated in the adrenal gland by fasting in a similar fashion to that in the hypothalamus (30). Additionally, peripheral AgRP infiltrates various peripheral organs, including the adrenal gland and adipose tissue, in a fasting‐dependent manner (22), that raises the possibility for autocrine/paracrine actions for AgRP (31).…”

Section: Discussionmentioning

confidence: 99%

Circadian Expression of Genes Regulating Food Intake

Stütz

Staszkiewicz

Ptitsyn

et al. 2007

Obesity

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(MCH), leptin, and its hypothalamic receptor (LR) are key regulators of food intake and energy homeostasis. In the present study, we examined the circadian expression profiles of these genes. Research Methods and Procedures:We used quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to measure mRNA levels, spectral analysis to evaluate periodicity, and correlation analysis to examine for associations with diurnal food intake. Results: No gene in particular stood out as a strong candidate, but the overall circadian expression profiles of leptin and its hypothalamic receptor came close to statistically and graphically resembling the diurnal feeding behavior of mice. In mathematical terms, adrenal AgRP exhibited strong circadian expression and had the highest correlation with food intake, followed by leptin. Yet its highest point of expression occurred 8 hours after nocturnal food intake had peaked, suggesting that adrenal AgRP could not play a direct role in the initiation of nocturnal feeding; neither did hypothalamic AgRP, NPY, POMC, CART, Orexin, or MCH. Discussion: These data show that ad libitum feeding in mice is influenced by complex central and peripheral circuits involving orexigenic and anorectic agents of which leptin and its hypothalamic receptor could play more prevalent roles.

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Section: Discussionmentioning

confidence: 99%

Circadian Expression of Genes Regulating Food Intake

Stütz

Staszkiewicz

Ptitsyn

et al. 2007

Obesity

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“…AGRPergic neurons have been shown to express receptors for leptin (a fatty tissue hormone), which has an inhibitory effect on AGRP expression [10]. The blood leptin level in obesity is known to increase significantly, and this is has been seen to be associated with decreased AGRP expression [1, 2, 10].…”

Section: Discussionmentioning

confidence: 99%

“…[10], providing evidence that various metabolic factors arriving in the peripheral bloodstream from the visceral organs and tissues can have direct effects on the functional activity of AGRPergic neurons. These latter in turn operate as mediators and have modulatory actions on target neurons, particularly dopaminergic neurons.…”

Section: Discussionmentioning

confidence: 99%

“…AGRP mRNA has been shown to be present only in neurons in the arcuate (or infundibular) nucleus of the hypothalamus in various mammals [7,12]. This encodes a propeptide from which a convertasedependent process forms several active protein fragments [11,19].AGRP in the brain has been shown to be an endogenous antagonist of melanocortin receptors types 3 and 4, and its functional significance is assessed in the literature as being related to the control of feeding behavior as an appetite-activating factor [10,11, 23]. However, increases in appetite are not always associated with increases in the AGRP balance in the brain.…”

mentioning

confidence: 99%

“…AGRP in the brain has been shown to be an endogenous antagonist of melanocortin receptors types 3 and 4, and its functional significance is assessed in the literature as being related to the control of feeding behavior as an appetite-activating factor [10,11, 23]. However, increases in appetite are not always associated with increases in the AGRP balance in the brain.…”

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The Role of AGRP in Regulating Dopaminergic Neurons in the Brain

Mikhrina

Романова

2015

Neurosci Behav Physi

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A new protein found in rodent brains has extensive structural similarity with agouti protein, which is expressed in the skin and produces a rusty coloration of the coat in rodents [16]. Because of this, the new protein was named agouti-related protein (AGRP). AGRP mRNA has been shown to be present only in neurons in the arcuate (or infundibular) nucleus of the hypothalamus in various mammals [7,12]. This encodes a propeptide from which a convertasedependent process forms several active protein fragments [11,19].AGRP in the brain has been shown to be an endogenous antagonist of melanocortin receptors types 3 and 4, and its functional significance is assessed in the literature as being related to the control of feeding behavior as an appetite-activating factor [10,11, 23]. However, increases in appetite are not always associated with increases in the AGRP balance in the brain. Thus, for example, obesity developing as a result of increased food intake is accompanied by a decrease in AGRP expression [1, 10], which does not correspond to its functional role as an appetite activator. In addition, the literature contains reports of studies demonstrating the role of AGRP as a melanocortin receptor agonist [22], as well as the suggestion that it acts via other, as yet unknown, types of receptor [20], which widens our understanding of the functional significance of this peptide.Immunohistochemical studies have demonstrated the presence of AGRP-immunoreactive processes in various parts of the brain [7, 13], which seems to provide evidence of the involvement of this peptide in regulating a variety of body functions.Analysis of published data, along with our own observations, provides evidence that AGRP-immunoreactive processes are detected in those areas of the brain containing dopaminergic neurons themselves (the arcuate nucleus of the hypothalamus, the zona incerta, the ventral tegmental area, the paraventricular nucleus of the hypothalamus, the periacqueductal gray matter) and their targets (the preoptic area, the paraventricular and supraoptic nuclei of the hypothalamus, etc.) [7]. However, the literature lacks any data on the possible involvement of AGRP in regulating the functional activity of dopaminergic brain neurons. Thus, the aim of the present work was to determine the possibility and nature of the influences of AGRP on dopaminergic brain neurons. We performed immunohistochemical studies to support the existence of structural interactions of AGRPand dopaminergic neurons, as well as in vitro experiments in which living slices of brain areas containing dopaminerImmunoreactive processes containing agouti-regulated protein (AGRP) were detected in various dopaminergic structures in the brains of rats and mice. Double immunolabeling demonstrated the presence of AGRP-immunoreactive processes around the bodies of dopaminergic neurons. In in vitro experiments, incubation of brain tissue from the ventral tegmental area and hypothalamus with AGRP(83-132) identified significant reductions in the optical density of tyrosine h...

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