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CART in the regulation of appetite and energy homeostasis.

ABSTRACT: The cocaine- and amphetamine-regulated transcript (CART) has been the subject of significant interest for over a decade. Work to decipher the detailed mechanism of CART function has been hampered by the lack of specific pharmacological tools like antagonists and the absence of a specific CART receptor(s). However, extensive research has been devoted to elucidate the role of the CART peptide and it is now evident that CART is a key neurotransmitter and hormone involved in the regulation of diverse biological processes, including food intake, maintenance of body weight, reward and addiction, stress response, psychostimulant effects and endocrine functions (Rogge et al., 2008; Subhedar et al., 2014). In this review, we focus on knowledge gained on CART's role in controlling appetite and energy homeostasis, and also address certain species differences between rodents and humans.

SUBMITTER: Lau J

PROVIDER: S-EPMC4195273 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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CART in the regulation of appetite and energy homeostasis.

Lau Jackie J Herzog Herbert H

Frontiers in neuroscience 20141013

The cocaine- and amphetamine-regulated transcript (CART) has been the subject of significant interest for over a decade. Work to decipher the detailed mechanism of CART function has been hampered by the lack of specific pharmacological tools like antagonists and the absence of a specific CART receptor(s). However, extensive research has been devoted to elucidate the role of the CART peptide and it is now evident that CART is a key neurotransmitter and hormone involved in the regulation of divers ...[more]

PMID: 25352770

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Project description:OBJECTIVE:The cocaine- and amphetamine-regulated transcript (CART) codes for a pivotal neuropeptide important in the control of appetite and energy homeostasis. However, limited understanding exists for the defined effector sites underlying CART function, as discrepant effects of central CART administration have been reported. METHODS:By combining Cart-cre knock-in mice with a Cart adeno-associated viral vector designed using the flip-excision switch (AAV-FLEX) technology, specific reintroduction or overexpression of CART selectively in CART neurons in the arcuate nucleus (Arc) and lateral hypothalamic area (LHA), respectively, was achieved. The effects on energy homeostasis control were investigated. RESULTS:Here we show that CART neuron-specific reintroduction of CART into the Arc and LHA leads to distinct effects on energy homeostasis control. Specifically, CART reintroduction into the Arc of otherwise CART-deficient Cartcre/cre mice markedly decreased fat mass and body weight, whereas CART reintroduction into the LHA caused significant fat mass gain and lean mass loss, but overall unaltered body weight. The reduced adiposity in ArcCART;Cartcre/cre mice was associated with an increase in both energy expenditure and physical activity, along with significantly decreased Npy mRNA levels in the Arc but with no change in food consumption. Distinctively, the elevated fat mass in LHACART;Cartcre/cre mice was accompanied by diminished insulin responsiveness and glucose tolerance, greater spontaneous food intake, and reduced energy expenditure, which is consistent with the observed decrease of brown adipose tissue temperature. This is also in line with significantly reduced tyrosine hydroxylase (Th) and notably increased corticotropin-releasing hormone (Crh) mRNA expressions in the paraventricular nucleus (PVN). CONCLUSIONS:Taken together, these results identify catabolic and anabolic effects of CART in the Arc and LHA, respectively, demonstrating for the first time the distinct and region-specific functions of CART in controlling feeding and energy homeostasis.

Project description:The current study has investigated the hypothalamic gene expressions regulated by glucocorticoid (GC), key hormones in energy homeostasis. Using serial analysis of gene expression (SAGE) method, we have studied the effects of adrenalectomy (ADX) and GC on the transcriptomes of mouse hypothalamus. Approximately, 180 000 SAGE tags, which correspond to 50 000 tag species, were isolated from each group of intact or adrenalectomized mice, as well as 1, 3 and 24 hours after GC injection. ADX has upregulated diazepam binding inhibitor gene expression, while downregulating vomeronasal 1 receptor D4, genes involved in mitochondrial phosphorylation (cytochrome c oxidase 1 and NADH dehydrogenase 3), 3b-hydroxysteroid dehydrogenase-1, and prostaglandin D2 synthase. GC has increased the gene expression levels of dehydrogenase/reductase member 3, prostaglandin D2 synthase, solute carrier family 4 member 4, and five cytoskeletal proteins including myosin light chain phosphorylatable fast and troponin C2 fast. On the other hand, GC has reduced the mRNA levels of calmodilin 1 and expressed sequence tag similar to (EST) calmodilin 2, ATP synthase F0 subunit 6, and solute carrier family 4 member 3. Moreover, seven uncharacterized and 43 novel transcripts were modulated by ADX and GC. The current study has identified genes that may regulate hypothalamic systems governing energy balance in response to ADX and GC. Keywords: Hormone effect analysis Male C57BL6 mice were obtained from Charles River Laboratories (St. Constant, QC, Canada), at 12-14 weeks of age. Mice were housed in an air-conditioned room (19-25 degree) with controlled lighting from 07:15 to 19:15 h and were given free access to food (Lab Rodent Diet No. 5002) and water. One week prior to sampling of hypothalamus, adrenalectomy was performed in mice of all experimental groups (n = 12 per group). ADX mice received sodium chloride (0.9g/dl) in their drinking water after the surgery. GC (corticosterone, 0.1 mg per mouse) was subcutaneously injected to ADX mice and the hypothalamus was harvested at 1 hour (ADX + GC 1 h), 3 hours (ADX + GC 3 h) and 24 hours (ADX + GC 24 h) after the GC injection. ADX received an injection of vehicle solution (5% ethanol with 0.4% methocel A15LV premium) at 24 hours prior to sacrifice. All mice were killed between 08:30 and 12:30 by decapitation under isoflurane anesthesia. Brain was removed from the skull and the hypothalamus was immediately dissected, frozen in liquid nitrogen, pooled together for each group, and stored at -80 degree until RNA extraction.

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CART in the regulation of appetite and energy homeostasis.

Publications

CART in the regulation of appetite and energy homeostasis.

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