The Orphan G Protein-Coupled Receptor Gene GPR178 Is Evolutionary Conserved and Altered in Response to Acute Changes in Food Intake.

G protein-coupled receptors (GPCRs) are a class of integral membrane proteins mediating physiological functions fundamental for survival, including energy homeostasis. A few years ago, an amino acid sequence of a novel GPCR gene was identified and named GPR178. In this study, we provide new insights regarding the biological significance of Gpr178 protein, investigating its evolutionary history and tissue distribution as well as examining the relationship between its expression level and feeding status. Our phylogenetic analysis indicated that GPR178 is highly conserved among all animal species investigated, and that GPR178 is not a member of a protein family. Real-time PCR and in situ hybridization revealed wide expression of Gpr178 mRNA in both the brain and periphery, with high expression density in the hypothalamus and brainstem, areas involved in the regulation of food intake. Hence, changes in receptor expression were assessed following several feeding paradigms including starvation and overfeeding. Short-term starvation (12-48h) or food restriction resulted in upregulation of Gpr178 mRNA expression in the brainstem, hypothalamus and prefrontal cortex. Conversely, short-term (48h) exposure to sucrose or Intralipid solutions downregulated Gpr178 mRNA in the brainstem; long-term exposure (10 days) to a palatable high-fat and high-sugar diet resulted in a downregulation of Gpr178 in the amygdala but not in the hypothalamus. Our results indicate that hypothalamic Gpr178 gene expression is altered during acute exposure to starvation or acute exposure to palatable food. Changes in gene expression following palatable diet consumption suggest a possible involvement of Gpr178 in the complex mechanisms of feeding reward.

Watching TV and food intake: the role of content.

Obesity is a serious and growing health concern worldwide. Watching television (TV) represents a condition during which many habitually eat, irrespective of hunger level. However, as of yet, little is known about how the content of television programs being watched differentially impacts concurrent eating behavior. In this study, eighteen normal-weight female students participated in three counter-balanced experimental conditions, including a 'Boring' TV condition (art lecture), an 'Engaging' TV condition (Swedish TV comedy series), and a no TV control condition during which participants read (a text on insects living in Sweden). Throughout each condition participants had access to both high-calorie (M&Ms) and low-calorie (grapes) snacks. We found that, relative to the Engaging TV condition, Boring TV encouraged excessive eating (+52% g, P = 0.009). Additionally, the Engaging TV condition actually resulted in significantly less concurrent intake relative to the control 'Text' condition (-35% g, P = 0.05). This intake was driven almost entirely by the healthy snack, grapes; however, this interaction did not reach significance (P = 0.07). Finally, there was a significant correlation between how bored participants were across all conditions, and their concurrent food intake (beta = 0.317, P = 0.02). Intake as measured by kcals was similarly patterned but did not reach significance. These results suggest that, for women, different TV programs elicit different levels of concurrent food intake, and that the degree to which a program is engaging (or alternately, boring) is related to that intake. Additionally, they suggest that emotional content (e.g. boring vs. engaging) may be more associated than modality (e.g. TV vs. text) with concurrent intake.

Association between physical activity and brain health in older adults.

In the present cross-sectional study, we examined physical activity (PA) and its possible association with cognitive skills and brain structure in 331 cognitively healthy elderly. Based on the number of self-reported light and hard activities for at least 30 minutes per week, participants were assigned to 4 groups representing different levels of PA. The cognitive skills were assessed by the Mini Mental State Examination score, a verbal fluency task, and the Trail-making test as a measure of visuospatial orientation ability. Participants also underwent a magnetic resonance imaging of the brain. Multiple regression analysis revealed that greater PA was associated with a shorter time to complete the Trail-making test, and higher levels of verbal fluency. Further, the level of self-reported PA was positively correlated with brain volume, white matter, as well as a parietal lobe gray matter volume, situated bilaterally at the precuneus. These present cross-sectional results indicate that PA is a lifestyle factor that is linked to brain structure and function in late life.

Expression levels of genes encoding melanin concentrating hormone (MCH) and MCH receptor change in taste aversion, but MCH injections do not alleviate aversive responses.

Melanin concentrating hormone (MCH) stimulates feeding driven by energy needs and reward and modifies anxiety behavior. Orexigenic peptides of similar characteristics, including nociceptin/orphanin FQ, Agouti-related protein and opioids, increase consumption also by reducing avoidance of potentially tainted food in animals displaying a conditioned taste aversion (CTA). Herein, using real-time PCR, we assessed whether expression levels of genes encoding MCH and its receptor, MCHR1, were affected in CTA in the rat. We also investigated whether injecting MCH intracerebroventricularly (ICV) during the acquisition and retrieval of LiCl-induced CTA, would alleviate aversive responses. MCHR1 gene was upregulated in the hypothalamus and brain stem of aversive animals, MCH mRNA was significantly higher in the hypothalamus, whereas a strong trend suggesting upregulation of MCH and MCHR1 genes was detected in the amygdala. Despite these expression changes associated with aversion, MCH injected prior to the induction of CTA with LiCl as well as later, during the CTA retrieval upon subsequent presentations of the aversive tastant, did not reduce the magnitude of CTA. We conclude that MCH and its receptor form an orexigenic system whose expression is affected in CTA. This altered MCH expression may contribute to tastant-targeted hypophagia in CTA. However, changing the MCH tone in the brain by exogenous peptide was insufficient to prevent the onset or facilitate extinction of LiCl-induced CTA. This designates MCH as one of many accessory molecules associated with shaping an aversive response, but not a critical one for LiCl-dependent CTA to occur.

Central nociceptin/orphanin FQ system elevates food consumption by both increasing energy intake and reducing aversive responsiveness.

Nociceptin/orphanin FQ (N/OFQ), the nociceptin opioid peptide (NOP) receptor ligand, increases feeding when injected centrally. Initial data suggest that N/OFQ blocks the development of a conditioned taste aversion (CTA). The current project further characterized the involvement of N/OFQ in the regulation of hunger vs. aversive responses in rats by employing behavioral, immunohistochemical, and real-time PCR methodology. We determined that the same low dose of the NOP antagonist [Nphe(1)]N/OFQ(1-13)NH(2) delivered via the lateral ventricle diminishes both N/OFQ- and deprivation-induced feeding. This anorexigenic effect did not stem from aversive consequences, as the antagonist did not cause the development of a CTA. When [Nphe(1)]N/OFQ(1-13)NH(2) was administered with LiCl, it moderately delayed extinction of the LiCl-induced CTA. Injection of LiCl + antagonist compared with LiCl alone generated an increase in c-Fos immunoreactivity in the central nucleus of the amygdala. The antagonist alone elevated Fos immunoreactivity in the paraventricular nucleus of the hypothalamus, nucleus of the solitary tract, and central nucleus of the amygdala. Hypothalamic NOP mRNA levels were decreased during energy intake restriction induced by aversion, as well as in non-CTA rats food-restricted to match CTA-reduced consumption. Brain stem NOP was upregulated only in aversion. Prepro-N/OFQ mRNA showed a trend toward upregulation in restricted rats (P = 0.068). We conclude that the N/OFQ system promotes feeding by affecting the need to replenish lacking calories and by reducing aversive responsiveness. It may belong to mechanisms that shift a balance between the drive to ingest energy and avoidance of potentially tainted food.

Acute 19-nortestosterone transiently suppresses hippocampal MAPK pathway and the phosphorylation of the NMDA receptor.

High doses of anabolic androgenic steroid are associated with changes in personality, e.g. increased aggression and irritability, behavioural changes that may be linked to structural changes in the hippocampus. In this in vivo study we demonstrate acute effects of a single injection of 19-nortestosterone on proteins that play a major role in molecular plasticity at synaptic connections. The steroid rapidly and transiently decreased total and phosphorylated NMDA receptor GluN2B subunit levels and phosphorylated extracellular signal-regulated kinase 1 in rat hippocampal synaptoneurosomes. Pretreatment with the androgen receptor antagonist flutamide prevented these effects suggesting an androgen receptor mediated mode of action. However, flutamide alone stimulated the phosphorylation of both extracellular signal-regulated kinase 1 and 2. EphrinB2 and phosphorylated translation initiation factor 4E, two proteins that act on synaptic plasticity through NMDA receptor and/or mitogen-activated protein kinase pathways, were not affected by any of the treatment regimens. This study demonstrates rapid in vivo effects of an anabolic androgenic steroid on two key elements in hippocampal synaptic plasticity.

VGLUT2 in dopamine neurons is required for psychostimulant-induced behavioral activation.

The "One neuron-one neurotransmitter" concept has been challenged frequently during the last three decades, and the coexistence of neurotransmitters in individual neurons is now regarded as a common phenomenon. The functional significance of neurotransmitter coexistence is, however, less well understood. Several studies have shown that a subpopulation of dopamine (DA) neurons in the ventral tegmental area (VTA) expresses the vesicular glutamate transporter 2 (VGLUT2) and has been suggested to use glutamate as a cotransmitter. The VTA dopamine neurons project to limbic structures including the nucleus accumbens, and are involved in mediating the motivational and locomotor activating effects of psychostimulants. To determine the functional role of glutamate cotransmission by these neurons, we deleted VGLUT2 in DA neurons by using a conditional gene-targeting approach in mice. A DAT-Cre/Vglut2Lox mouse line (Vglut2(f/f;DAT-Cre) mice) was produced and analyzed by in vivo amperometry as well as by several behavioral paradigms. Although basal motor function was normal in the Vglut2(f/f;DAT-Cre) mice, their risk-taking behavior was altered. Interestingly, in both home-cage and novel environments, the gene targeted mice showed a greatly blunted locomotor response to the psychostimulant amphetamine, which acts via the midbrain DA system. Our results show that VGLUT2 expression in DA neurons is required for normal emotional reactivity as well as for psychostimulant-mediated behavioral activation.

Growth hormone replacement in hypophysectomized rats affects spatial performance and hippocampal levels of NMDA receptor subunit and PSD-95 gene transcript levels.

Clinical studies have demonstrated that growth hormone (GH) promotes learning and memory processes in GH-deficient (GHD) patients. In animal studies, GH also influences the N-methyl-D-aspartate (NMDA) receptor system in the hippocampus, an essential component of long-term potentiation (LTP), which is highly involved in memory acquisition. This study was designed to examine the beneficial effects of recombinant human GH (rhGH) on cognitive function in male rats with multiple hormone deficiencies resulting from hypophysectomy (Hx). The performance of an rhGH-treated group and an untreated control group was appraised in the Morris water maze (MWM). The rhGH-treated group performed significantly better in the spatial memory task than the control animals on the second and third trial days. Further training eliminated this difference between the groups. Hippocampal mRNA expression of the NMDA subunits NR1, NR2A and NR2B, insulin-like growth factor type 1 receptor (IGF-1R), and postsynaptic density protein-95 (PSD-95) was then measured in the animals by Northern blot analysis. The results suggest that there may be a relationship between the NMDA receptor subunit mRNA expression levels and learning ability, and that learning is improved by rhGH in Hx rats. Furthermore, a link between MWM performance and PSD-95 was also suggested by this study.

Age-related effects of IGF-1 on the NMDA-, GH- and IGF-1-receptor mRNA transcripts in the rat hippocampus.

Insulin-like growth factor-1 (IGF-1) and growth hormone (GH) have been suggested to promote memory and cognitive capabilities. In a recent publication we observed that GH increase the proportion of the NR2B subunit mRNA transcript of the NMDA receptor in rat hippocampus. NR2B has been suggested to be essential for spatial learning and long-term potentiation (LTP). This effect of GH might be IGF-1-mediated or a result of a co-ordination with IGF-1. To test this hypothesis further, we examined the effects of 10 daily s.c. injections of IGF-1 on NMDA receptor subunits (NR1, NR2A, and NR2B), GH receptor (GHR), GH binding protein (GHBP) and type 1 IGF receptor (IGF-1R) gene transcripts in the hippocampus. The NR2B subunit mRNA increased in young (11 weeks) but not in older (14-16 months) rats and the expression of the NR2A mRNA was decreased in both groups. The ratio of NR2B to NR2A is suggested to mirror the potential for synaptic plasticity. In both age groups, IGF-1 treatment resulted in a significant increase of this ratio at transcription level. The GHR mRNA increased in young rats, mimicking the effect of GH, while the IGF-1R mRNA was decreased in the older group of rats after IGF-1 treatment. These results suggest that IGF-1 in many aspects may mediate the actions earlier shown for GH.

Growth hormone induces age-dependent alteration in the expression of hippocampal growth hormone receptor and N-methyl-D-aspartate receptor subunits gene transcripts in male rats.

Studies were conducted to evaluate the effects of s.c. injected recombinant human growth hormone (GH) on the expression of the gene transcript of N-methyl-D-aspartate receptor subunits type 1 (NR1), type 2A (NR2A), and type 2B (NR2B) in the male rat hippocampus. The GH-induced effects on the expression of hippocampal gene transcripts of GH receptor (GHR) and GH-binding protein were also examined. Male Sprague-Dawley rats, kept in four groups of two different ages, was treated with the hormone or saline during 10 days before decapitation and tissue dissection. Brain tissues collected were analyzed for mRNA content by using the Northern blot technique. The results indicated that in adult young rats (11 weeks of age) the hormone elicited a decrease in the mRNA expression of NR1 but an increase in that of the NR2B subunit. In elderly adult rats (57-67 weeks of age) GH induced an increase in the expression of the hippocampal message for NR1 and NR2A. Meanwhile, the hormone induced a significant up-regulation of the GHR transcript in hippocampus of adult young rats but not in elderly adult rats. It was further found that a significant positive correlation exists between the level of GHR mRNA and the expression of the NR2B subunit transcript in adult young rats. The GH-induced increase in the expression of hippocampal mRNA for the NR2B subunit is compatible with a previously observed memory promoting effect seen for the hormone, because overexpression of this N-methyl-D-aspartate receptor subunit is shown to enhance cognitive capabilities.

Vinyl sulfide cyclized analogues of angiotensin II with high affinity and full agonist activity at the AT(1) receptor.

Vinyl sulfide cyclized analogues of the octapeptide angiotensin II that are structurally related to the cyclic disulfide agonist c[Hcy(3,5)]Ang II have been prepared. The synthesis relies on the reaction of the mercapto group of a cysteine residue in position 3 with the formyl group of allysine incorporated in position 5 of angiotensin II. A mixture of the cis and the trans isomers was formed, and these were separated and isolated by RP-HPLC. Thus, the three-atom CH(2)[bond]S[bond]S element of the AT(1) receptor agonist c[Hcy(3,5)]Ang II has been displaced by a bioisosteric three-atom S[bond]CH[double bond]CH element. A comparative conformational analysis of the 13-membered ring systems of c[Hcy(3,5)]Ang II and the 13-membered cyclic vinyl sulfides with cis and trans configuration, respectively, suggested that all three systems adopted very similar low-energy conformations. This similarity was also reflected in the bioactivity. Both of the compounds that contained the ring systems encompassing the cis or trans vinyl sulfide elements between positions 3 and 5 exhibited K(i) values less than 2 nM and exerted full agonism at the AT(1) receptor. In contrast, vinyl sulfide cyclization involving the amino acid residues 5 and 7 rendered inactive compounds. The cyclic vinyl sulfides that have agonist activity were both shown to possess low-energy conformers compatible with the previously proposed 3D model for the bioactive conformation of Ang II.