Alcoholism and obesity: overlapping neuropeptide pathways?

Lateral hypothalamus-projecting noradrenergic locus coeruleus pathway modulates binge-like ethanol drinking in male and female TH-ires-cre mice

A growing body of literature implicates noradrenergic (NE) signaling in the modulation of ethanol consumption. However, relatively few studies have detailed specific brain pathways that mediate NE-associated binge-like ethanol consumption. To begin to fill this gap in the literature, male and female C57BL6/J and TH-ires-cre mice underwent pharmacological and chemogenetic testing, respectively, in combination with "drinking in the dark" procedures to model binge-like consumption of ethanol or sucrose solutions. First, we showed that intraperitoneal administration of the NE reuptake inhibitor, reboxetine, blunted binge-like ethanol intake in C57BL6/J mice. Chemogenetic activation of locus coeruleus (LC) tyrosine hydroxylase (TH)-expressing neurons blunted binge-like ethanol intake regardless of sex. Chemogenetic activation of LC projections to the lateral hypothalamus (LH), a region implicated in ethanol consumption, blunted binge-like ethanol drinking without altering sucrose intake in ethanol-experienced or ethanol-naïve mice. In C57BL/6 J mice, LH-targeted microinfusion of an α1-adrenergic receptor (AR) agonist blunted binge-like ethanol intake across both sexes, while LH infusion of a β-AR agonist blunted binge-like ethanol intake in females exclusively. Finally, in mice with high baseline ethanol intake both an α1- AR agonist and an α-2 AR antagonist blunted binge-like ethanol intake. The present results provide novel evidence that increased NE tone in a circuit arising from the LC and projecting to the LH reduces binge-like ethanol drinking in mice, and may represent a novel approach to treating binge or heavy drinking prior to the development of dependence. This article is part of the special Issue on "Neurocircuitry Modulating Drug and Alcohol Abuse".

Alcohol Withdrawal and Proopiomelanocortin Neuropeptides in an Animal Model of Alcohol Dependence

BACKGROUND

Alcohol is one of the leading threats to health worldwide. Craving for alcohol makes abstinence a difficult challenge by maintaining alcohol dependence. Many studies suppose the hypothalamic-pituitary-adrenal axis, especially the proopiomelanocortin (POMC)-derived neuropeptides, to mediate craving during withdrawal in alcohol dependence. Evidence is available that the two POMC proteins, α-melanocyte-stimulating hormone (α-MSH) and β-endorphin (β-END) are altered by alcohol consumption and influence alcohol consumption, respectively.

OBJECTIVES

We investigated the dynamics of α-MSH and β-END during alcohol withdrawal and the influence of intraperitoneal administration of either α-MSH or β-END in an established rodent model (Wistar rats) for alcohol dependence.

RESULTS

After long-term alcohol self-administration over 12 months and repeated deprivation periods for 3 days, we found a significant decrease in α-MSH levels during withdrawal in rodents (p = 0.006) compared to controls, while β-END levels remained unchanged. Treatment with intraperitoneally administered α-MSH and β-END did not affect alcohol drinking behavior after deprivation.

CONCLUSION

We demonstrate the effects of alcohol deprivation on α-MSH in alcohol-dependent rodents, which appear to mimic α-MSH alteration found after fasting periods during appetite regulation. Therefore, low α-MSH levels are a possible indicator for craving in alcohol-dependent individuals and hence would be a potential target for anti-craving treatment.

Weighted gene co-expression network analysis of expression data of monozygotic twins identifies specific modules and hub genes related to BMI

BACKGROUND

The therapeutic management of obesity is challenging, hence further elucidating the underlying mechanisms of obesity development and identifying new diagnostic biomarkers and therapeutic targets are urgent and necessary. Here, we performed differential gene expression analysis and weighted gene co-expression network analysis (WGCNA) to identify significant genes and specific modules related to BMI based on gene expression profile data of 7 discordant monozygotic twins.

RESULTS

In the differential gene expression analysis, it appeared that 32 differentially expressed genes (DEGs) were with a trend of up-regulation in twins with higher BMI when compared to their siblings. Categories of positive regulation of nitric-oxide synthase biosynthetic process, positive regulation of NF-kappa B import into nucleus, and peroxidase activity were significantly enriched within GO database and NF-kappa B signaling pathway within KEGG database. DEGs of NAMPT, TLR9, PTGS2, HBD, and PCSK1N might be associated with obesity. In the WGCNA, among the total 20 distinct co-expression modules identified, coral1 module (68 genes) had the strongest positive correlation with BMI (r = 0.56, P = 0.04) and disease status (r = 0.56, P = 0.04). Categories of positive regulation of phospholipase activity, high-density lipoprotein particle clearance, chylomicron remnant clearance, reverse cholesterol transport, intermediate-density lipoprotein particle, chylomicron, low-density lipoprotein particle, very-low-density lipoprotein particle, voltage-gated potassium channel complex, cholesterol transporter activity, and neuropeptide hormone activity were significantly enriched within GO database for this module. And alcoholism and cell adhesion molecules pathways were significantly enriched within KEGG database. Several hub genes, such as GAL, ASB9, NPPB, TBX2, IL17C, APOE, ABCG4, and APOC2 were also identified. The module eigengene of saddlebrown module (212 genes) was also significantly correlated with BMI (r = 0.56, P = 0.04), and hub genes of KCNN1 and AQP10 were differentially expressed.

CONCLUSION

We identified significant genes and specific modules potentially related to BMI based on the gene expression profile data of monozygotic twins. The findings may help further elucidate the underlying mechanisms of obesity development and provide novel insights to research potential gene biomarkers and signaling pathways for obesity treatment. Further analysis and validation of the findings reported here are important and necessary when more sample size is acquired.

Lateral hypothalamic melanocortin receptor signaling modulates binge-like ethanol drinking in C57BL/6J mice

Binge ethanol drinking is a highly pervasive and destructive behavior yet the underlying neurobiological mechanisms remain poorly understood. Recent work suggests that overlapping neurobiological mechanisms modulate feeding disorders and excessive ethanol intake, and converging evidence indicates that the melanocortin (MC) system may be a promising candidate. The aims of the present work were to examine how repeated binge-like ethanol drinking, using the 'drinking in the dark' (DID) protocol, impacts key peptides within the MC system and if site-specific manipulation of MC receptor (MCR) signaling modulates binge-like ethanol drinking. Male C57BL/6J mice were exposed to one, three or six cycles of binge-like ethanol, sucrose or water drinking, after which brain tissue was processed via immunohistochemistry (IHC) for analysis of key MC peptides, including alpha-melanocyte stimulating hormone (α-MSH) and agouti-related protein (AgRP). Results indicated that α-MSH expression was selectively decreased, while AgRP expression was selectively increased, within specific hypothalamic subregions following repeated binge-like ethanol drinking. To further explore this relationship, we used site-directed drug delivery techniques to agonize or antagonize MCRs within the lateral hypothalamus (LH). We found that the nonselective MCR agonist melanotan-II (MTII) blunted, while the nonselective MCR antagonist AgRP augmented, binge-like ethanol consumption when delivered into the LH. As these effects were region-specific, the present results suggest that a more thorough understanding of the MC neurocircuitry within the hypothalamus will help provide novel insight into the mechanisms that modulate excessive binge-like ethanol intake and may help uncover new therapeutic targets aimed at treating alcohol abuse disorders.

Changes in the female arcuate nucleus morphology and neurochemistry after chronic ethanol consumption and long-term withdrawal

Ethanol is a macronutrient whose intake is a form of ingestive behavior, sharing physiological mechanisms with food intake. Chronic ethanol consumption is detrimental to the brain, inducing gender-dependent neuronal damage. The hypothalamic arcuate nucleus (ARN) is a modulator of food intake that expresses feeding-regulatory neuropeptides, such as alpha melanocyte-stimulating hormone (α-MSH) and neuropeptide Y (NPY). Despite its involvement in pathways associated with eating disorders and ethanol abuse, the impact of ethanol consumption and withdrawal in the ARN structure and neurochemistry in females is unknown. We used female rat models of 20% ethanol consumption for six months and of subsequent ethanol withdrawal for two months. Food intake and body weights were measured. ARN morphology was stereologically analyzed to estimate its volume, total number of neurons and total number of neurons expressing NPY, α-MSH, tyrosine hydroxylase (TH) and estrogen receptor alpha (ERα). Ethanol decreased energy intake and body weights. However, it did not change the ARN morphology or the expression of NPY, α-MSH and TH, while increasing ERα expression. Withdrawal induced a significant volume and neuron loss that was accompanied by an increase in NPY expression without affecting α-MSH and TH expression. These findings indicate that the female ARN is more vulnerable to withdrawal than to excess alcohol. The data also support the hypothesis that the same pathways that regulate the expression of NPY and α-MSH in long-term ethanol intake may regulate food intake. The present model of long-term ethanol intake and withdrawal induces new physiological conditions with adaptive responses.

Genetic variants in the CPNE5 gene are associated with alcohol dependence and obesity in Caucasian populations

Alcohol addiction may increase the risk of obesity due to shared genetic components. The Copine V (CPNE5) gene is involved in Ca(2+) binding and may play an important role in the development of the central nervous system. This study tested the genetic associations of 77 single-nucleotide polymorphisms (SNPs) within the CPNE5 gene with alcohol dependence (AD) and obesity using a Caucasian sample - The Study of Addiction - Genetics and Environment (SAGE) sample (1066 AD cases and 1278 non-AD controls, 422 obese cases and 1395 non-obese controls). The Marshfield sample (1442 obese cases and 2122 non-obese controls) was used for replication of obesity. Multiple logistic regression analysis was performed using the PLINK software. In the SAGE sample, we identified 10 SNPs associated with AD and 17 SNPs associated with obesity (p < 0.05). Interestingly, 6 SNPs (rs9986517, rs9470387, rs3213534, rs10456444, rs3752482, and rs9470386) were associated with both AD (OR = 0.77, 0.77, 0.83, 0.84, 0.79 and 1.14, respectively; p = 9.72 × 10(-5), 1.1 × 10(-4), 4.09 × 10(-3), 5.26 × 10(-3), 1.59 × 10(-2), and 3.81 × 10(-2), respectively) and obesity (OR = 0.77, 0.77, 0.78, 0.77, 0.68 and 1.18, respectively; p = 2.74 × 10(-3), 2.69 × 10(-3), 2.45 × 10(-3), 1.01 × 10(-3), 5.18 × 10(-3) and 3.85 × 10(-2), respectively). In the Marshfield sample, rs3752480 was associated with obesity (p = 0.0379). In addition, four SNPs (rs9986517, rs10456444, rs7763347 and rs4714010) showed associations with obesity in the meta-analysis using both samples (p = 0.00493, 0.0274, 0.00346, and 0.0141, respectively). These findings provide the first evidence of common genetic variants in the CPNE5 gene influencing both the AD and obesity; and will serve as a resource for replication in other populations.

Assessment of the Effects of 6 Standard Rodent Diets on Binge-Like and Voluntary Ethanol Consumption in Male C57BL/6J Mice

BACKGROUND

In recent years, much attention has been given to the lack of reproducibility in biomedical research, particularly in preclinical animal studies. This is a problem that also plagues the alcohol research field, particularly in consistent consumption in animal models of alcohol use disorders. One often overlooked factor that could affect reproducibility is the maintenance diet used in preclinical studies.

METHODS

Herein, 2 well-established models of alcohol consumption, the "drinking in the dark" (DID) procedure and the continuous 2-bottle choice (C2BC) paradigm, were employed to determine the effects of diet on ethanol (EtOH) consumption. Male C57BL/6J mice were given 1 of 6 standard rodent chow diets obtained from Purina LabDiet(®) , Inc. (Prolab(®) RMH 3000) or Harlan(®) Laboratories, Inc. (Teklad Diets T.2916, T.2918, T.2920X, T.7912, or T.8940). A separate group of animals were used to test dietary effects on EtOH pharmacokinetics and behavioral measures following intraperitoneal (IP) injections of various doses of EtOH.

RESULTS

Mice eating Harlan diets T.2916 (H2916) and T.2920X (H2920) consumed significantly less EtOH and exhibited lower blood EtOH concentrations (BECs) during DID; however, during C2BC, animals maintained on Harlan T.7912 (H7912) consumed more EtOH and had a higher EtOH preference than the other diet groups. EtOH consumption levels did not stem from changes in alcohol pharmacokinetics, as a separate group of animals administered EtOH IP showed no difference in BECs. However, animals on Harlan diet T.2920X (H2920) were more sensitive to alcohol-induced locomotor activity in an open-field task. No diet-dependent differences were seen in alcohol-induced sedation as measured with loss of righting reflex.

CONCLUSIONS

Although these data do not identify a specific mechanism, together, they clearly show that the maintenance diet impacts EtOH consumption. It is incumbent upon the research community to consider the importance of describing nutritional information in methods, which may help decrease interlaboratory reproducibility issues.

Targeting central melanocortin receptors: a promising novel approach for treating alcohol abuse disorders

The melanocortin (MC) peptides are produced centrally by propiomelanocortin (POMC) neurons within the arcuate nucleus of the hypothalamus and act through five seven-transmembrane G-protein coupled melanocortin receptor (MCR) subtypes. The MC3R and MC4R subtypes, the most abundant central MCRs, are widely expressed in brain regions known to modulate neurobiological responses to ethanol, including regions of the hypothalamus and extended amygdala. Agouti-related protein (AgRP), also produced in the arcuate nucleus, is secreted in terminals expressing MCRs and functions as an endogenous MCR antagonist. This review highlights recent genetic and pharmacological findings that have implicated roles for the MC and AgRP systems in modulating ethanol consumption. Ethanol consumption is associated with significant alterations in the expression levels of various MC peptides/protein, which suggests that ethanol-induced perturbations of MC/AgRP signaling may modulate excessive ethanol intake. Consistently, MCR agonists decrease, and AgRP increases, ethanol consumption in mice. MCR agonists fail to blunt ethanol intake in mutant mice lacking the MC4R, suggesting that the protective effects of MCR agonists are modulated by the MC4R. Interestingly, recent evidence reveals that MCR agonists are more effective at blunting binge-like ethanol intake in mutant mice lacking the MC3R, suggesting that the MC3R has opposing effects on the MC4R. Finally, mutant mice lacking AgRP exhibit blunted voluntary and binge-like ethanol drinking, consistent with pharmacological studies. Collectively, these preclinical observations provide compelling evidence that compounds that target the MC system may provide therapeutic value for treating alcohol abuse disorders and that the utilization of currently available MC-targeting compounds- such as those being used to treat eating disorders- may be used as effective treatments to this end.

The protective effects of the melanocortin receptor (MCR) agonist, melanotan-II (MTII), against binge-like ethanol drinking are facilitated by deletion of the MC3 receptor in mice

Recent data have implicated the melanocortin (MC) system in modulating voluntary ethanol consumption. Administration of melanotan-II (MTII), a nonselective melanocortin receptor (MCR) agonist, reduces voluntary ethanol consumption in C57BL/6J mice. Previous studies have demonstrated that central infusion of MTII effectively reduced voluntary ethanol drinking in mutant mice lacking normal expression of MC3R (MC3R-/- mice) but failed to alter ethanol drinking in mice lacking expression of MC4R, demonstrating that central MTII administration reduces voluntary ethanol drinking by signaling through the MC4R. However, evidence shows that the neurocircuitry recruited during excessive binge-like ethanol drinking versus moderate ethanol drinking are not identical. Thus the present study sought to investigate the potential role of the MC3R in binge-like ethanol intake. To this end, the "drinking in the dark" (DID) procedure, a commonly used animal model of binge-like ethanol drinking, was employed. Wild-type MC3R+/+ and MC3R-/- mice were given intracerebroventricular (i.c.v.) infusion of MTII (0.0, 0.25, 0.50, or 1.0 μg) prior to the onset of a 4-h testing period in which mice were given access to 20% (v/v) ethanol. Immediately after the 4-h testing period, tail blood samples were collected from each animal in order to assess blood ethanol concentrations (BECs). Consistent with previous findings, central administration of MTII blunted binge-like ethanol drinking in both MC3R+/+ and MC3R-/- mice. Interestingly, all doses of MTII blunted binge-like ethanol drinking in MC3R-/- mice during the first hour of testing, while only the 1.0 μg dose reduced binge-like drinking in MC3R+/+ mice. Thus, MC3R-/- mice were more sensitive to the protective effects of MTII. These data suggest that MC3Rs oppose the protective effects of MTII against binge-like ethanol drinking, and thus selective MC3R antagonists may have potential therapeutic roles in treating excessive ethanol drinking.

Role of appetite-regulating peptides in the pathophysiology of addiction: implications for pharmacotherapy

Food intake and appetite are regulated by various circulating hormones including ghrelin and glucagon-like-peptide 1 (GLP-1). Ghrelin, mainly released from the stomach, increases food intake, induces appetite, enhances adiposity as well as releases growth hormone. Hypothalamic "ghrelin receptors" (GHS-R1A) have a critical role in food intake regulation, but GHS-R1A are also expressed in reward related areas. GLP-1 is produced in the intestinal mucosa as well as in the hindbrain in response to nutrient ingestion. This gut-brain hormone reduces food intake as well as regulates glucose homeostasis, foremost via GLP-1 receptors in hypothalamus and brain stem. However, GLP-1 receptors are expressed in areas intimately associated with reward regulation. Given that regulation of food and drug intake share common neurobiological substrates, the possibility that ghrelin and GLP-1 play an important role in reward regulation should be considered. Indeed, this leading article describes that the orexigenic peptide ghrelin activates the cholinergic-dopaminergic reward link, an important part of the reward systems in the brain associated with reinforcement and thereby increases the incentive salience for motivated behaviors via this system. We also review the role of ghrelin signaling for reward induced by alcohol and addictive drugs from a preclinical, clinical and human genetic perspective. In addition, the recent findings showing that GLP-1 controls reward induced by alcohol, amphetamine, cocaine and nicotine in rodents are overviewed herein. Finally, the role of several other appetite regulatory hormones for reward and addiction is briefly discussed. Collectively, these data suggest that ghrelin and GLP-1 receptors may be novel targets for development of pharmacological treatments of alcohol and drug dependence.

Ethanol affects acylated and total ghrelin levels in peripheral blood of alcohol-dependent rats

There is a hypothesis that ghrelin could take part in the central effects of alcohol as well as function as a peripheral indicator of the changes which occur during long-term alcohol consumption. The aim of this study was to determine a correlation between alcohol concentration and acylated and total form of ghrelin after a single administration of alcohol (intraperitoneal, i.p.) (experiment 1) and prolonged ethanol consumption (experiment 2). The study was performed using Wistar alcohol preferring (PR) and non-preferring (NP) rats and rats from inbred line (Warsaw High Preferring, WHP; Warsaw Low Preferring, WLP). It was found that ghrelin in ethanol-naive WHP animals showed a significantly lower level when compared with the ethanol-naive WLP or Wistar rats. After acute ethanol administration in doses of 1.0; 2.0 and 4.0 g/kg, i.p., the simple (WHP) or inverse (WLP and Wistar) relationship between alcohol concentration and both form of ghrelin levels in plasma were found. Chronic alcohol intake in all groups of rats led to decrease of acylated ghrelin concentration. PR and WHP rats, after chronic alcohol drinking, had lower levels of both form of ghrelin in comparison with NP and WLP rats, respectively, and the observed differences in ghrelin levels were in inverse relationship with their alcohol intake. In conclusion, it is suggested that there is a strong relationship between alcohol administration or intake, ethanol concentration in blood and both active and total ghrelin level in the experimental animals, and that ghrelin plasma concentration can be a marker of alcohol drinking predisposition.

Genetic variation of the ghrelin signalling system in individuals with amphetamine dependence

The development of amphetamine dependence largely depends on the effects of amphetamine in the brain reward systems. Ghrelin, an orexigenic peptide, activates the reward systems and is required for reward induced by alcohol, nicotine, cocaine and amphetamine in mice. Human genetic studies have shown that polymorphisms in the pre-proghrelin (GHRL) as well as GHS-R1A (GHSR) genes are associated with high alcohol consumption, increased weight and smoking in males. Since the heritability factor underlying drug dependence is shared between different drugs of abuse, we here examine the association between single nucleotide polymorphisms (SNPs) and haplotypes in the GHRL and GHSR, and amphetamine dependence. GHRL and GHSR SNPs were genotyped in Swedish amphetamine dependent individuals (n = 104) and controls from the general population (n = 310). A case-control analysis was performed and SNPs and haplotypes were additionally tested for association against Addiction Severity Interview (ASI) composite score of drug use. The minor G-allele of the GHSR SNP rs2948694, was more common among amphetamine dependent individuals when compared to controls (p_c = 0.02). A significant association between the GHRL SNP rs4684677 and ASI composite score of drug use was also reported (p_c = 0.03). The haplotype analysis did not add to the information given by the individual polymorphisms. Although genetic variability of the ghrelin signalling system is not a diagnostic marker for amphetamine dependence and problem severity of drug use, the present results strengthen the notion that ghrelin and its receptor may be involved in the development of addictive behaviours and may thus serve as suitable targets for new treatments of such disorders.

Ghrelin increases GABAergic transmission and interacts with ethanol actions in the rat central nucleus of the amygdala

The neural circuitry that processes natural rewards converges with that engaged by addictive drugs. Because of this common neurocircuitry, drugs of abuse have been able to engage the hedonic mechanisms normally associated with the processing of natural rewards. Ghrelin is an orexigenic peptide that stimulates food intake by activating GHS-R1A receptors in the hypothalamus. However, ghrelin also activates GHS-R1A receptors on extrahypothalamic targets that mediate alcohol reward. The central nucleus of the amygdala (CeA) has a critical role in regulating ethanol consumption and the response to ethanol withdrawal. We previously demonstrated that rat CeA GABAergic transmission is enhanced by acute and chronic ethanol treatment. Here, we used quantitative RT-PCR (qRT-PCR) to detect Ghsr mRNA in the CeA and performed electrophysiological recordings to measure ghrelin effects on GABA transmission in this brain region. Furthermore, we examined whether acute or chronic ethanol treatment would alter these electrophysiological effects. Our qRT-PCR studies show the presence of Ghsr mRNA in the CeA. In naive animals, superfusion of ghrelin increased the amplitude of evoked inhibitory postsynaptic potentials (IPSPs) and the frequency of miniature inhibitory postsynaptic currents (mIPSCs). Coapplication of ethanol further increased the ghrelin-induced enhancement of IPSP amplitude, but to a lesser extent than ethanol alone. When applied alone, ethanol significantly increased IPSP amplitude, but this effect was attenuated by the application of ghrelin. In neurons from chronic ethanol-treated (CET) animals, the magnitude of ghrelin-induced increases in IPSP amplitude was not significantly different from that in naive animals, but the ethanol-induced increase in amplitude was abolished. Superfusion of the GHS-R1A antagonists D-Lys3-GHRP-6 and JMV 3002 decreased evoked IPSP and mIPSC frequency, revealing tonic ghrelin activity in the CeA. D-Lys3-GHRP-6 and JMV 3002 also blocked ghrelin-induced increases in GABAergic responses. Furthermore, D-Lys3-GHRP-6 did not affect ethanol-induced increases in IPSP amplitude. These studies implicate a potential role for the ghrelin system in regulating GABAergic transmission and a complex interaction with ethanol at CeA GABAergic synapses.

Concomitant release of ventral tegmental acetylcholine and accumbal dopamine by ghrelin in rats

Ghrelin, an orexigenic peptide, regulates energy balance specifically via hypothalamic circuits. Growing evidence suggest that ghrelin increases the incentive value of motivated behaviours via activation of the cholinergic-dopaminergic reward link. It encompasses the cholinergic afferent projection from the laterodorsal tegmental area (LDTg) to the dopaminergic cells of the ventral tegmental area (VTA) and the mesolimbic dopamine system projecting from the VTA to nucleus accumbens (N.Acc.). Ghrelin receptors (GHS-R1A) are expressed in these reward nodes and ghrelin administration into the LDTg increases accumbal dopamine, an effect involving nicotinic acetylcholine receptors in the VTA. The present series of experiments were undertaken directly to test this hypothesis. Here we show that ghrelin, administered peripherally or locally into the LDTg concomitantly increases ventral tegmental acetylcholine as well as accumbal dopamine release. A GHS-R1A antagonist blocks this synchronous neurotransmitter release induced by peripheral ghrelin. In addition, local perfusion of the unselective nicotinic antagonist mecamylamine into the VTA blocks the ability of ghrelin (administered into the LDTg) to increase N.Acc.-dopamine, but not VTA-acetylcholine. Collectively our data indicate that ghrelin activates the LDTg causing a release of acetylcholine in the VTA, which in turn activates local nicotinic acetylcholine receptors causing a release of accumbal dopamine. Given that a dysfunction in the cholinergic-dopaminergic reward system is involved in addictive behaviours, including compulsive overeating and alcohol use disorder, and that hyperghrelinemia is associated with such addictive behaviours, ghrelin-responsive circuits may serve as a novel pharmacological target for treatment of alcohol use disorder as well as binge eating.

Control of food intake by MC4-R signaling in the lateral hypothalamus, nucleus accumbens shell and ventral tegmental area: interactions with ethanol

The melanocortin system is involved in animal models of obesity and anorexia-cachexia and MC4 receptors (MC4-R) are currently a target system for the development of drugs aimed to treat obesity and eating disorders in humans. Previous evidence suggest that feeding peptides might lack their orexigenic activity while stimulate ethanol intake. The present study comparatively evaluated food intake (4-h interval) in Sprague-Dawley (SD) rats drinking ethanol (6% w/v, 2 bottle choice paradigm) (EE group) and ethanol-naïve (EN) rats in response to bilateral infusion of the selective MC4-R antagonist HS014 (0, 0.02 or 0.05 μg/0.5 μl/site) or the selective MC4-R agonist cyclo(NH-CH(2)-CH(2)-CO-His-d-Phe-Arg-Trp-Glu)-NH(2) (0, 0.75 or 1.5 μg/0.5 μl/site), into the lateral hypothalamus (LH), the nucleus accumbens (NAc), or the ventral tegmental area (VTA). The main findings in the study are: (1) LH-infusions of the MC4-R antagonist increased and the agonist reduced feeding and total calories consumed, while ethanol intake remained unaltered. (2) NAc- and VTA-infusions of the selective agonist reduced food, ethanol and total calories intake. (3) NAc- and VTA-infusions of the MC4-R antagonist increased feeding in EN rats, but not in EE animals which showed a mild increase in ethanol intake, while total calories consumed remained unaltered. Present data show that having ethanol available reduces feeding elicited by NAc and VTA-MC4-R blockade. Additionally, while MC4-R signaling in the LH appears to modulate homeostatic aspects of feeding, it may contribute to non-homeostatic aspects of ingestive behaviors in the VTA and the NAc.

Acute ethanol disrupts photic and serotonergic circadian clock phase-resetting in the mouse

BACKGROUND

Alcohol dependence is associated with impaired circadian rhythms and sleep. Ethanol administration disrupts circadian clock phase-resetting, suggesting a mode for the disruptive effect of alcohol dependence on the circadian timing system. In this study, we extend previous work in C57BL/6J mice to: (i) characterize the suprachiasmatic nucleus (SCN) pharmacokinetics of acute systemic ethanol administration, (ii) explore the effects of acute ethanol on photic and nonphotic phase-resetting, and (iii) determine if the SCN is a direct target for photic effects.

METHODS

First, microdialysis was used to characterize the pharmacokinetics of acute intraperitoneal (i.p.) injections of 3 doses of ethanol (0.5, 1.0, and 2.0 g/kg) in the mouse SCN circadian clock. Second, the effects of acute i.p. ethanol administration on photic phase delays and serotonergic ([+]8-OH-DPAT-induced) phase advances of the circadian activity rhythm were assessed. Third, the effects of reverse-microdialysis ethanol perfusion of the SCN on photic phase-resetting were characterized.

RESULTS

Peak ethanol levels from the 3 doses of ethanol in the SCN occurred within 20 to 40 minutes postinjection with half-lives for clearance ranging from 0.6 to 1.8 hours. Systemic ethanol treatment dose-dependently attenuated photic and serotonergic phase-resetting. This treatment also did not affect basal SCN neuronal activity as assessed by Fos expression. Intra-SCN perfusion with ethanol markedly reduced photic phase delays.

CONCLUSIONS

These results confirm that acute ethanol attenuates photic phase-delay shifts and serotonergic phase-advance shifts in the mouse. This dual effect could disrupt photic and nonphotic entrainment mechanisms governing circadian clock timing. It is also significant that the SCN clock is a direct target for disruptive effects of ethanol on photic shifting. Such actions by ethanol could underlie the disruptive effects of alcohol abuse on behavioral, physiological, and endocrine rhythms associated with alcoholism.

Assessment of voluntary ethanol consumption and the effects of a melanocortin (MC) receptor agonist on ethanol intake in mutant C57BL/6J mice lacking the MC-4 receptor

BACKGROUND

The melanocortin (MC) system is composed of peptides that are cleaved from the polypeptide precursor proopiomelanocortin (POMC). Recent evidence shows that chronic exposure to ethanol significantly blunts central MC peptide immunoreactivity and MC receptor (MCR) agonists protect against high ethanol intake characteristic of C57BL/6J mice. Here, we assessed the role of the MC-4 receptor (MC4R) in voluntary ethanol intake and in modulating the effects of the nonselective MCR agonist melanotan-II (MTII) on ethanol consumption.

METHODS

To assess the role of the MC4R, MC4R knockout (Mc4r(-/-) ) and littermate wild-type (Mc4r(+/+) ) mice on a C57BL/6J background were used. Voluntary ethanol (3, 5, 8, 10, 15, and 20%, v/v) and water intake were assessed using standard two-bottle procedures. In separate experiments, Mc4r(-/-) and Mc4r(+/+) mice were given intracerebroventricular (i.c.v.) infusion of MTII (0, 0.5, or 1.0 μg/1 μl) or intraperitoneal (i.p.) injection of MTII (0 or 5 mg/kg/5 ml). The effects of MTII (0 or 0.5 μg/1 μl, i.c.v.) on 10% sucrose and 0.15% saccharin intake were assessed in C57BL/6J mice.

RESULTS

Mc4r(-/-) mice showed normal consumption of ethanol over all concentrations tested. I.c.v. infusion of MTII significantly reduced ethanol drinking in Mc4r(+/+) mice, but failed to influence ethanol intake in Mc4r(-/-) mice. When administered in an i.p. injection, MTII significantly reduced ethanol drinking in both Mc4r(-/-) and Mc4r(+/+) mice. MTII attenuated consumption of caloric (ethanol, sucrose, and food) and noncaloric (saccharin) reinforcers.

CONCLUSIONS

When given centrally, the MCR agonist MTII reduced ethanol drinking by signaling through the MC4R. On the other hand, MTII-induced reduction of ethanol drinking did not require the MC4R when administered peripherally. Together, the present observations show that the MC4R is necessary for the central actions of MCR agonists on ethanol drinking and that MTII blunts the consumption natural reinforcers, regardless of caloric content, in addition to ethanol.

Glutamatergic regulation of ghrelin-induced activation of the mesolimbic dopamine system

Recently, we demonstrated that the central ghrelin signalling system, involving the ghrelin receptor (GHS-R1A), is important for alcohol reinforcement. Ghrelin targets a key mesolimbic circuit involved in natural as well as drug-induced reinforcement, that includes a dopamine projection from the ventral tegmental area (VTA) to the nucleus accumbens. The aim of the present study was to determine whether it is possible to suppress ghrelin's effects on this mesolimbic dopaminergic pathway can be suppressed, by interrupting afferent inputs to the VTA dopaminergic cells, as shown previously for cholinergic afferents. Thus, the effects of pharmacological suppression of glutamatergic, orexin A and opioid neurotransmitter systems on ghrelin-induced activation of the mesolimbic dopamine system were investigated. We found in the present study that ghrelin-induced locomotor stimulation was attenuated by VTA administration of the N-methyl-D-aspartic acid receptor antagonist (AP5) but not by VTA administration of an orexin A receptor antagonist (SB334867) or by peripheral administration of an opioid receptor antagonist (naltrexone). Intra-VTA administration of AP5 also suppressed the ghrelin-induced dopamine release in the nucleus accumbens. Finally the effects of peripheral ghrelin on locomotor stimulation and accumbal dopamine release were blocked by intra-VTA administration of a GHS-R1A antagonist (BIM28163), indicating that GHS-R1A signalling within the VTA is required for the ghrelin-induced activation of the mesolimbic dopamine system. Given the clinical knowledge that hyperghrelinemia is associated with addictive behaviours (such as compulsive overeating and alcohol use disorder) our finding highlights a potential therapeutic strategy involving glutamatergic control of ghrelin action at the level of the mesolimbic dopamine system.

Mood disorders and obesity: understanding inflammation as a pathophysiological nexus

The aim of this review is to evaluate the evidentiary base supporting the hypothesis that the increased hazard for obesity in mood disorder populations (and vice versa) is a consequence of shared pathophysiological pathways. We conducted a PubMed search of all English-language articles with the following search terms: obesity, inflammation, hypothalamic-pituitary-adrenal axis, insulin, cognition, CNS, and neurotransmitters, cross-referenced with major depressive disorder and bipolar disorder. The frequent co-occurrence of mood disorders and obesity may be characterized by interconnected pathophysiology. Both conditions are marked by structural and functional abnormalities in multiple cortical and subcortical brain regions that subserve cognitive and/or affective processing. Abnormalities in several interacting biological networks (e.g. immuno-inflammatory, insulin signaling, and counterregulatory hormones) contribute to the co-occurence of mood disorders and obesity. Unequivocal evidence now indicates that obesity and mood disorders are chronic low-grade pro-inflammatory states that result in a gradual accumulation of allostatic load. Abnormalities in key effector proteins of the pro-inflammatory cascade include, but are not limited to, cytokines/adipokines such as adiponectin, leptin, and resistin as well as tumor necrosis factor alpha and interleukin-6. Taken together, the bidirectional relationship between obesity and mood disorders may represent an exophenotypic manifestation of aberrant neural and inflammatory networks. The clinical implications of these observations are that, practitioners should screen individuals with obesity for the presence of clinically significant depressive symptoms (and vice versa). This clinical recommendation is amplified in individuals presenting with biochemical indicators of insulin resistance and other concurrent conditions associated with abnormal inflammatory signaling (e.g. cardiovascular disease).

Role of melanin-concentrating hormone in the control of ethanol consumption: Region-specific effects revealed by expression and injection studies

The peptide melanin-concentrating hormone (MCH), produced mainly by cells in the lateral hypothalamus (LH), perifornical area (PF) and zona incerta (ZI), is suggested to have a role in the consumption of rewarding substances, such as ethanol, sucrose and palatable food. However, there is limited information on the specific brain sites where MCH acts to stimulate intake of these rewarding substances and on the feedback effects that their consumption has on the expression of endogenous MCH. The current study investigated MCH in relation to ethanol consumption, in Sprague-Dawley rats. In Experiment 1, chronic consumption of ethanol (from 0.70 to 2.7 g/kg/day) dose-dependently reduced MCH gene expression in the LH. In Experiments 2-4, the opposite effect was observed with acute oral ethanol, which stimulated MCH expression specifically in the LH but not the ZI. In Experiment 5, the effect of MCH injection in brain-cannulated rats on ethanol consumption was examined. Compared to saline, MCH injected in the paraventricular nucleus (PVN) and nucleus accumbens (NAc) selectively stimulated ethanol consumption without affecting food or water intake. In contrast, it reduced ethanol intake when administered into the LH, while having no effect in the ZI. These results demonstrate that voluntary, chronic consumption of ethanol leads to local negative feedback control of MCH expression in the LH. However, with a brief exposure, ethanol stimulates MCH-expressing neurons in this region, which through projections to the feeding-related PVN and reward-related NAc can promote further drinking behavior.

Ghrelin receptor antagonism decreases alcohol consumption and activation of perioculomotor urocortin-containing neurons

BACKGROUND

The current therapies for alcohol abuse disorders are not effective in all patients, and continued development of pharmacotherapies is needed. One approach that has generated recent interest is the antagonism of ghrelin receptors. Ghrelin is a gut-derived peptide important in energy homeostasis and regulation of hunger. Recent studies have implicated ghrelin in alcoholism, showing altered plasma ghrelin levels in alcoholic patients as well as reduced intakes of alcohol in ghrelin receptor knockout mice and in mice treated with ghrelin receptor antagonists. The aim of this study was to determine the neuroanatomical locus/loci of the effect of ghrelin receptor antagonism on alcohol consumption using the ghrelin receptor antagonist, D-Lys3-GHRP-6.

METHODS

In Experiment 1, male C57BL/6J mice were injected with saline 3 hours into the dark cycle and allowed access to 15% (v/v) ethanol or water for 2 hours in a 2-bottle choice experiment. On test day, the mice were injected with either saline or 400 nmol of the ghrelin receptor antagonist, D-Lys3-GHRP-6, and allowed to drink 15% ethanol or water for 4 hours. The preference for alcohol and alcohol intake were determined. In Experiment 2, the same procedure was followed as in Experiment 1 but mice were only allowed access to a single bottle of 20% ethanol (v/v), and alcohol intake was determined. Blood ethanol levels were analyzed, and immunohistochemistry for c-Fos was carried out to investigate changes in neural activity. To further elucidate the mechanism by which D-Lys3-GHRP-6 affects alcohol intake, in Experiment 3, the effect of D-Lys3-GHRP-6 on the neural activation induced by intraperitoneal ethanol was investigated. For the c-Fos studies, brain regions containing ghrelin receptors were analyzed, i.e. the perioculomotor urocortin population of neurons (pIIIu), the ventral tegmental area (VTA), and the arcuate nucleus (Arc). In Experiment 4, to test if blood ethanol concentrations were affected by D-Lys3-GHRP-6, blood samples were taken at 2 time-points after D-Lys3-GHRP-6 pretreatment and systemic ethanol administration.

RESULTS

In Experiment 1, D-Lys3-GHRP-6 reduced preference to alcohol and in a follow-up experiment (Experiment 2) also dramatically reduced alcohol intake when compared to saline-treated mice. The resulting blood ethanol concentrations were lower in mice treated with the ghrelin receptor antagonist. Immunohistochemistry for c-Fos showed fewer immunopositive cells in the pIIIu of the antagonist-treated mice but no difference was seen in the VTA or Arc. In Experiment 3, D-Lys3-GHRP-6 reduced the induction of c-Fos by intraperitoneal ethanol in the pIIIu but had no effect in the VTA. In the Arc, there was a significant increase in the number of c-Fos immunopositive cells after D-Lys3-GHRP-6 administration, but the antagonist had no effect on ethanol-induced expression of c-Fos. D-Lys3-GHRP-6-pretreatment also did not affect the blood ethanol concentrations observed after a systemic injection of ethanol when compared to saline-pretreated mice (Experiment 4).

CONCLUSIONS

These findings indicate that the action of ghrelin on the regulation of alcohol consumption may occur via the pIIIu.

The melanocortin-4 receptor: physiology, pharmacology, and pathophysiology

The melanocortin-4 receptor (MC4R) was cloned in 1993 by degenerate PCR; however, its function was unknown. Subsequent studies suggest that the MC4R might be involved in regulating energy homeostasis. This hypothesis was confirmed in 1997 by a series of seminal studies in mice. In 1998, human genetic studies demonstrated that mutations in the MC4R gene can cause monogenic obesity. We now know that mutations in the MC4R are the most common monogenic form of obesity, with more than 150 distinct mutations reported thus far. This review will summarize the studies on the MC4R, from its cloning and tissue distribution to its physiological roles in regulating energy homeostasis, cachexia, cardiovascular function, glucose and lipid homeostasis, reproduction and sexual function, drug abuse, pain perception, brain inflammation, and anxiety. I will then review the studies on the pharmacology of the receptor, including ligand binding and receptor activation, signaling pathways, as well as its regulation. Finally, the pathophysiology of the MC4R in obesity pathogenesis will be reviewed. Functional studies of the mutant MC4Rs and the therapeutic implications, including small molecules in correcting binding and signaling defect, and their potential as pharmacological chaperones in rescuing intracellularly retained mutants, will be highlighted.

Modulation of feeding and locomotion through mu and delta opioid receptor signaling in the nucleus accumbens

Opioid signaling has been strongly implicated in driving palatable food consumption. The nucleus accumbens (NAcc) is one important site of this effect; hyperphagia elicited by administration of exogenous mu opioid receptor (MOR) ligands in this brain region has been well documented. However, the role that endogenous opioid ligands in the NAcc play in controlling food intake remains poorly understood. Enkephalins, which signal through both the MOR and delta opioid receptor (DOR), are highly expressed within a subset of NAcc neurons, and have been shown to be sensitive to manipulations of diet and motivation. To investigate a potential role for these signaling molecules in regulating palatability-driven consumption, we measured high fat chow intake in rats following a series of pharmacological manipulations of NAcc opioid signaling. NAcc infusion of the MOR agonist [D-Ala2, N-MePHe4, Gly-ol]-enkephalin (DAMGO) robustly increased palatable food intake, as has previously been demonstrated. In contrast, neither infusion of Met-enkephalin, its synthetic analogue [D-Ala2] Met-enkephalin (DALA) nor the DOR-specific ligand [D-Pen2, Pen5]-enkephalin (DPDPE) had significant effects on food intake. However, when administered in combination with DAMGO, DPDPE significantly suppressed the magnitude of DAMGO-evoked feeding. Further analysis of DPDPE effects revealed that the drug strongly increased locomotor activity. Suppressive effects on feeding, then, may have occurred through competition between feeding and locomotion for behavioral expression.

Associations between substance use and body mass index: moderating effects of sociodemographic characteristics among Taiwanese adolescents

The aim of this study was to analyze the association between substance use and body mass index (BMI) among adolescents in Southern Taiwan. A total of 10,259 adolescent students aged 11-19 years were selected by stratified random sampling for proportional representation of districts, schools and grades in Southern Taiwan, and completed the questionnaires. The body weight, body height, experience of substance use and sociodemographic characteristics including sex, age, residential background and paternal/maternal educational levels were collected. The association between substance use and BMI, and the moderating effects of sociodemographic characteristics were examined. After adjusting for sociodemographic characteristics, BMI was higher for adolescents who smoke cigarettes or drink alcohol than for those who do not regularly smoke or drink. Chewing betel nuts and using illicit drugs were not significantly associated with BMI. Paternal education level had a moderating effect on the association between smoking and BMI. Smoking, alcohol drinking, and low paternal education level were associated with higher BMI among adolescents. Thus, healthcare professionals should pay more attention to the weight-related problems among these adolescents.

Hormones and drinking behaviour: new findings on ghrelin, insulin, leptin and volume-regulating hormones. An ESBRA Symposium report

There is growing evidence for a role of appetite-related peptides and volume-regulating hormones in alcoholism. In particular, recent evidence has suggested that hormones, such as ghrelin, insulin and leptin and volume-regulating hormones, could play a role in alcohol-seeking behaviour. The goal of this review is to discuss the results of recent preclinical and clinical investigations on this topic. The findings indicate that neuroendocrinological mechanisms are potentially involved in the neurobiology of alcohol craving. Accordingly, research on this topic could lead to possible development of new therapeutic approaches in the treatment of patients with alcohol problems.

Medical and substance-related comorbidity in bipolar disorder: translational research and treatment opportunities

It is well established that individuals with bipolar disorder are differentially affected by substance-related as well as medical disorders (ie, cardiometabolic disorders, respiratory disorders, neurological disorders, and infectious diseases). Emerging evidence indicates that some comorbid conditions (eg, diabetes mellitus) in bipolar individuals may be subserved by overlapping neurobiological networks. Disturbances in glucocorticoid/insulin signaling and immunoinflammatory effector systems are points of pathophysiological commonality between bipolar disorder and “stress-sensitive” medical disorders. Subphenotyping bipolar disorder as a function of comorbidity and temporality of onset may provide an opportunity for refining disease pathophysiological models and developing innovative disease-modifying therapies.

Transient up-regulation of cocaine- and amphetamine-regulated transcript peptide (CART) immunoreactivity following ethanol withdrawal in rat hypothalamus

We investigated the profile of CART immunoreactivity in some discrete hypothalamic nuclei following chronic ethanol treatment and withdrawal conditions. Adult, male, Sprague-Dawley rats were fed with liquid diet (pair-fed) or liquid diet containing ethanol (ethanol-fed) for 15 days. Thereafter, all the animals were given access to ethanol free nutritionally balanced liquid diet and killed at 0, 24, 48 and 72 h post-withdrawal, and their brains processed for immunocytochemistry using monoclonal antibodies against CART. CART-immunoreactive fibers, but not the cells, were significantly increased in the paraventricular nucleus (PVN). However, the profile of CART-immunoreactive cells and/or fibers in the periventricular area (PeA), arcuate nucleus (ARC), perifornical area inclusive of lateral hypothalamus (LH) and tuber cinereum (TC), dorsomedial (DMH), and ventromedial (VMH) hypothalamus at the 0 h ethanol withdrawal time point was quite similar to that in the pair-fed control rats. Twenty-four hours following ethanol withdrawal, the immunoreactivity in all these areas was dramatically increased. While significant reduction in CART immunoreactivity was noticed in the PVN, PeA, ARC and VMH at 48 h, immunoreactive profile was restored to normal by 72 h post-ethanol withdrawal. The immunoreactive profile in the LH, TC and DMH resembled that of the pair-fed groups at 48 and 72 h post-withdrawal intervals. However, CART-immunoreactive profile in the supraoptic nucleus did not respond to the chronic ethanol treatment and/or withdrawal. We suggest that transient up-regulation of CART in some discrete hypothalamic nuclei following ethanol withdrawal, at least in part, may contribute to the pathogenesis of ethanol withdrawal-induced symptoms like anxiety and anorexia.

Systemic administration of ghrelin induces conditioned place preference and stimulates accumbal dopamine

Ghrelin, preferably via hypothalamic circuits, is known to play a role in the control of energy balance, body weight homeostasis and appetite. In addition, it has recently been found that ghrelin injection into key structures of the mesolimbic dopamine (DA) system increases food intake in rodents and induces locomotor stimulation as well as accumbal DA overflow in mice. Thus, centrally administered ghrelin activates the mesolimbic DA system. However, ghrelin is mainly produced in and secreted from peripheral tissues. The present series of experiments were therefore undertaken to investigate the effects of peripherally injected ghrelin on mesolimbic DA system activity and, herewith, associated behaviours. It was found that intraperitoneal administration of ghrelin (0.33 mg/kg) induces locomotor stimulation, conditioned place preference and accumbal DA-overflow in mice. In conclusion, peripherally produced ghrelin, e.g. in the stomach, may activate the mesolimbic DA system. This suggests that the pre-prandial rise in plasma ghrelin may, via this system, increase the incentive value for motivated behaviours such as food seeking.

Alpha-conotoxin MII-sensitive nicotinic acetylcholine receptors are involved in mediating the ghrelin-induced locomotor stimulation and dopamine overflow in nucleus accumbens

Previously, we have reported that the orexigenic peptide ghrelin activates the cholinergic-dopaminergic reward link, involving nicotinic acetylcholine receptors (nAChR). The alpha(3)-alpha(7) and beta(2)-beta(4) subunits of the nAChR can be combined into pentameric nAChRs, with different functional roles. The present experiments show that the locomotor stimulatory effects of ghrelin, either into laterodorsal tegmental area (LDTg) or ventral tegmental area (VTA), are mediated via ventral tegmental nAChR, but neither the alpha(4)beta(2) (using dihydro-beta-erythroidine) nor the alpha(7) (using methyllycaconitine) subtypes appears to be involved. On the other hand, the alpha(3)beta(2), beta(3) and/or alpha(6) (using alpha-conotoxin MII) subtypes in the VTA mediate the stimulatory and DA-enhancing effects of ghrelin, a pattern that ghrelin shares with ethanol (n=5-8). Radioligand-binding experiments shown that ghrelin does not interfere directly with nAChRs (n=26). We therefore suggest that the alpha(3)beta(2), beta(3) and/or alpha(6) subtypes might be pharmacological targets for treatment of addictive behaviours including compulsive overeating and alcoholism.

Alcoholism, craving, and hormones: the role of leptin, ghrelin, prolactin, and the pro-opiomelanocortin system in modulating ethanol intake

Evidence is growing that appetite regulating peptides such as leptin and ghrelin, but also other hormones including prolactin are altered in alcoholism. The brain pro-opiomelanocortin (POMC) system which has important mediating roles in alcohol intake also has important functions in prolactin regulation and energy homeostasis. Furthermore, it has been demonstrated to be functionally integrated with leptin regulation. The satiety factor leptin seems to be counteracted by the gut-derived peptide ghrelin which increases hunger and food intake. Consequently, the POMC system may have a role in integrating regulation of alcohol effects and these seemingly disparate regulatory systems. The goal of this mini-review is to discuss the results of some recent investigations of the potential interactions of these systems with acute and chronic alcohol responses.

Pediatric obesity: parallels with addiction and treatment recommendations

Rates of pediatric obesity have increased dramatically over the past decade. This trend is especially alarming because obesity is associated with significant medical and psychosocial consequences. It may contribute to cardiovascular, metabolic, and hepatic complications, as well as to psychiatric difficulties. The development of obesity appears to be influenced by a complex array of genetic, metabolic, and neural frameworks, along with behavior, eating habits, and physical activity. Numerous parallels exist between obesity and addictive behaviors, including genetic predisposition, personality, environmental risk factors, and common neurobiological pathways in the brain. Typical treatments for pediatric obesity include behavioral interventions targeting diet or exercise. These treatments have yielded mixed results and typically have been examined in specialty clinic populations, limiting their generalizability. There are limited medication options for overweight children and adolescents, and no approved medical intervention in children younger than 16 years old. Bariatric surgery may be an option for some adolescents, but due to the risks of surgery, it is often seen as a last resort. The parallels between addiction and obesity aid in developing novel interventions for pediatric obesity. Motivational enhancement and cognitive-behavioral strategies used in addiction treatment may prove to be beneficial.

The role of hypothalamic peptide gene expression in alcohol self-administration behavior

Self-administration of ethanol and food share many common features and Richter hypothesized that an increase in ethanol consumption would decrease feeding to balance the excess calories contained in the ethanol. Previously, we have shown that individual alcohol consumption correlates with neurotransmitter gene expression, especially in the prefrontal cortex. To test the hypothesis of Richter, we measured hypothalamic gene expression of receptors or neuropeptides of known relevance for the regulation of food intake using qPCR and correlated this to individual ethanol consumption in Wistar rats. For validation, gene expression was first correlated with body weight. We found a correlation of dynorphin, somatostatin, melanocortin-4 receptor and serotonin 5-HT(2C) with body weight and trends to correlation for CART, thus confirming the established role of the hypothalamus in the regulation of weight. For ethanol consumption, correlations were found for CRH receptors 1 and 2 and vasopressin while strong trends were observed for galanin receptor 1, orexin receptor 1, MCH and adrenoceptor alpha(1B). Therefore, alcohol consumption does seem to involve several hypothalamic systems which also mediate feeding responses and suggests that the hypothalamus, together with the prefrontal cortex, may determine the 'stopping point' of an individual.

Role of cannabinoidergic mechanisms in ethanol self-administration and ethanol seeking in rat adult offspring following perinatal exposure to Delta9-tetrahydrocannabinol

The present study evaluated the consequences of perinatal Delta(9)-tetrahydrocannabinol (Delta(9)-THC) treatment (5 mg/kg/day by gavage), either alone or combined with ethanol (3% v/v as the only fluid available), on ethanol self-administration and alcohol-seeking behavior in rat adult offspring. Furthermore, the effect of the selective cannabinoid CB(1) receptor antagonist, SR-141716A, on ethanol self-administration and on reinstatement of ethanol-seeking behavior induced either by stress or conditioned drug-paired cues was evaluated in adult offspring of rats exposed to the same perinatal treatment. Lastly, microarray experiments were conducted to evaluate if perinatal treatment with Delta(9)-tetrahydrocannabinol, ethanol or their combination causes long-term changes in brain gene expression profile in rats. The results of microarray data analysis showed that 139, 112 and 170 genes were differentially expressed in the EtOH, Delta(9)-THC, or EtOH+Delta(9)-THC group, respectively. No differences in alcohol self-administration and alcohol seeking were observed between rat groups. Intraperitoneal (IP) administration of SR-141716A (0.3-3.0 mg/kg) significantly reduced lever pressing for ethanol and blocked conditioned reinstatement of alcohol seeking. At the same doses SR-141716A failed to block foot-shock stress-induced reinstatement of alcohol seeking. The results reveal that perinatal exposure to Delta(9)-THC ethanol or their combination results in evident changes in gene expression patterns. However, these treatments do not significantly affect vulnerability to ethanol abuse in adult offspring. On the other hand, the results obtained with SR-141716A emphasize that endocannabinoid mechanisms play a major role in ethanol self-administration, as well as in the reinstatement of ethanol-seeking behavior induced by conditioned cues, supporting the idea that cannabinoid CB(1) receptor antagonists may represent interesting agents for the pharmacotherapy of alcoholism.

Ghrelin administration into tegmental areas stimulates locomotor activity and increases extracellular concentration of dopamine in the nucleus accumbens

Ghrelin stimulates appetite, increases food intake and causes adiposity by mechanisms that include direct actions on the brain. Previously, we showed that intracerebroventricular administration of ghrelin has stimulatory and dopamine-enhancing properties. These effects of ghrelin are mediated via central nicotine receptors, suggesting that ghrelin can activate the acetylcholine-dopamine reward link. This reward link consists of cholinergic input from the laterodorsal tegmental area (LDTg) to the mesolimbic dopamine system that originates in the ventral tegmental area (VTA) and projects to the nucleus accumbens. Given that growth hormone secretagogue receptors (GHSR-1A) are expressed in the VTA and LDTg, brain areas involved in reward, the present series of experiments were undertaken to examine the hypothesis that these regions may mediate the stimulatory and dopamine-enhancing effects of ghrelin, by means of locomotor activity and in vivo microdialysis in freely moving mice. We found that local administration of ghrelin into the VTA (1 microg in 1 microl) induced an increase in locomotor activity and in the extracellular concentration of accumbal dopamine. In addition, local administration of ghrelin into the LDTg (1 microg in 1 microl) caused a locomotor stimulation and an increase in the extracellular levels of accumbal dopamine. Taken together, this indicates that ghrelin might, via activation of GHSR-1A in the VTA and LDTg, stimulate the acetylcholine-dopamine reward link, implicating that ghrelin is a part of the neurochemical overlap between the reward systems and those that regulate energy balance.

Relationship Between Ghrelin Levels, Alcohol Craving, and Nutritional Status in Current Alcoholic Patients

BACKGROUND

Ghrelin is a peptide produced mainly by the gut and hypothalamus. Ghrelin is able to stimulate food-seeking behavior. Alcohol-craving and food-seeking behavior could share common neural circuits. Ghrelin is related to nutritional status, but few data are available in alcoholic patients on the relationship between ghrelin and nutritional disorders.

METHODS

Plasma ghrelin was evaluated in 15 current alcoholic male patients compared with 15 healthy male volunteers. Craving was evaluated by the Obsessive-Compulsive Drinking Scale. Body composition was assessed by dual-energy X-ray absorptiometry. Energy substrate utilization was evaluated by indirect calorimetry.

RESULTS

Ghrelin was significantly reduced in alcohol-dependent patients with respect to healthy subjects (p=0.0278). A significant positive correlation was found between ghrelin and craving (r=0.55; p=0.034). A preferential utilization of lipids as an energy substrate with a reduction of the fat mass (p=0.01) and an increase of the free fat mass (p=0.0091) was found in alcoholic patients.

CONCLUSIONS

Within our sample showing low ghrelin levels probably related to the impaired nutritional status; patients with higher levels of ghrelin showed higher levels of alcohol craving. These preliminary data indicate that ghrelin could be implicated in the neurobiological mechanisms of alcohol craving, other than a hormone influenced by the nutritional status.

Intrauterine ethanol exposure results in hypothalamic oxidative stress and neuroendocrine alterations in adult rat offspring

Prenatal ethanol (EtOH) exposure is associated with low birth weight, followed by increased appetite, catch-up growth, insulin resistance, and impaired glucose tolerance in the rat offspring. Because EtOH can induce oxidative stress, which is a putative mechanism of insulin resistance, and because of the central role of the hypothalamus in the regulation of energy homeostasis and insulin action, we investigated whether prenatal EtOH exposure causes oxidative damage to the hypothalamus, which may alter its function. Female rats were given EtOH by gavage throughout pregnancy. At birth, their offspring were smaller than those of non-EtOH rats. Markers of oxidative stress and expression of neuropeptide Y and proopiomelanocortin (POMC) were determined in hypothalami of postnatal day 7 (PD7) and 3-mo-old (adult) rat offspring. In both PD7 and adult rats, prenatal EtOH exposure was associated with decreased levels of glutathione and increased expression of MnSOD. The concentrations of lipid peroxides and protein carbonyls were normal in PD7 EtOH-exposed offspring, but were increased in adult EtOH-exposed offspring. Both PD7 and adult EtOH-exposed offspring had normal neuropeptide Y and POMC mRNA levels, but the adult offspring had reduced POMC protein concentration. Thus only adult offspring preexposed to EtOH had increased hypothalamic tissue damage and decreased levels of POMC, which could impair melanocortin signaling. We conclude that prenatal EtOH exposure causes hypothalamic oxidative stress, which persists into adult life and alters melanocortin action during adulthood. These neuroendocrine alterations may explain weight gain and insulin resistance in rats exposed to EtOH early in life.

Ghrelin Levels Are Increased in Alcoholism

BACKGROUND

The neuropeptides leptin and ghrelin are involved in the appetite regulating network consisting of distinct orexigenic (ghrelin) and anorexigenic (leptin) circuitries. Recently, it has been shown that elevated leptin levels are associated with alcohol craving in patients suffering from alcoholism. Therefore, the aim of the present pilot study was to determine whether the gut-derived peptide ghrelin which increases hunger and food intake is altered and associated with alcohol craving in alcoholic patients

METHODS

Two types of alcoholic inpatients, group A (active drinker, acutely intoxicated, n=97) and group B (early abstainer, who had stopped drinking 24-72 hrs before, n=21) were consecutively included in a prospective study from the first day of hospitalization. Ghrelin plasma levels and craving data were assessed on days 0, 1, 2 and 7(-10) and compared to those of 24 healthy controls

RESULTS

At each time-point ghrelin plasma levels of alcoholic patients were significantly increased compared to healthy subjects. Furthermore, early abstainers showed significantly higher ghrelin levels than active drinkers. In the group of active drinkers ghrelin plasma levels were significantly increased at each time point compared to baseline. No correlations were found between ghrelin levels and craving data measured by the visual analogue scale or the Obsessive Compulsive Drinking Scale

CONCLUSIONS

Ghrelin levels are elevated in alcoholism and seem to further increase during alcohol withdrawal. However, ghrelin levels do not seem to be associated with alcohol craving.

Increased relative risk of subsequent affective disorders in patients with a hospital diagnosis of obesity

OBJECTIVE

To investigate the risk of clinical affective disorders of patients who were hospitalized because of obesity in the study period 1 January 1977 to 31 December 1999.

METHOD

Using data from Danish hospital registers, three study cohorts were identified by their diagnoses at discharge from hospital: one cohort comprising all patients with a first hospital admission with an index diagnosis of obesity, and two control cohorts comprising all patients with a first hospital admission with an index diagnosis of osteoarthritis or of non-toxic goiter, respectively. Later admissions to psychiatric hospital wards with discharge diagnoses of affective disorders were used as outcome events. Rates of readmission were estimated using competing risks models in survival analyses. Age, sex, abuse, and calendar time were included as covariables in the analyses.

RESULTS

A study sample of 165,425 patients discharged with an index diagnosis was identified. In total, 1081 events occurred in the observation period. An index diagnosis of obesity was associated with an increased risk of affective-disorders hospitalization when compared with patients with osteoarthritis (Rate ratio: 1.35 (95% CI: 1.09-1.67)) and tended to be associated with an increased risk when compared to patients with non-toxic goiter (Rate ratio: 1.23 (95% CI: 0.99-1.53)). Patients with obesity diagnoses who did not have additional hospital diagnoses of substance- or alcohol abuse had a risk of affective disorders that was 1.55 (95% CI: 1.23-1.95) times greater than that of osteoarthritis patients without abuse diagnoses.

CONCLUSIONS

Patients hospitalized with obesity may be prone to developing affective disorders that require in-hospital treatment, but the excess risk is modest. Severe obesity seems to be associated with other risk factors for mood disorders than those related to comorbid alcohol- or substance abuse.