Environmental Enrichment During Adulthood Reduces Sucrose Binge-Like Intake in a High Drinking in the Dark Phenotype (HD) in C57BL/6J Mice

Behavioural and physiological effects of binge eating: A systematic review and meta-analysis of animal models

Binge eating is defined as eating abnormally large amounts in a brief period of time. Many animal studies have examined the behavioural and physiological effects of binge eating of high-fat, high-sugar foods to model the consequences of human binge eating. The present systematic review of 199 rodent studies sought to identify the behavioural and physiological consequences of binge eating and determine whether changes were specific to binge eating or to general effects of exposure to a palatable diet. A meta-analysis of 18 rodent studies revealed that binge eating produces greater anxiety-like behaviour on the Elevated Plus-Maze with a small effect size and significant funnel plot asymmetry, suggesting that the true effect size is overestimated. A history of binge-like access generally increases progressive ratio breakpoint for the binged food, without altering 'liking' as measured by lick microstructure, suggesting that dissociable effects on 'wanting' but not 'liking' accompany binge eating behaviour and contribute to its persistence. Binge eating appears to enhance compulsive food-seeking behaviour and prevent stress-induced reductions in intake but does not appear to alter depression-like behaviour or locomotor activity. Notably, binge eating may produce comparable metabolic impairments to those observed after extended continuous exposure to a palatable diet despite no overall effects on body weight outcomes in most studies.

Pituitary adenylate cyclase-activating polypeptide (PACAP)+ cells in the paraventricular nucleus of the thalamus: relationship with binge-type eating in male and female mice

RATIONALE

Both the paraventricular nucleus of the thalamus (PVT) and the neuropeptide, pituitary adenylate cyclase-activating polypeptide (PACAP), are thought to be involved in food intake. Importantly, PACAP is expressed in cells of the PVT.

OBJECTIVES

To determine if PACAP in cells of the PVT might mediate some of the involvement of the PVT with palatable food intake.

METHODS

In male and female C57BL/6 J mice and PACAP-Cre transgenic mice on a C57BL/6 J background, limited access to Milk Chocolate Ensure Plus® was used to establish a model of binge-type eating. Next, using quantitative real-time PCR, gene expression of PACAP in the PVT was measured in relation to this binge-type eating. Finally, using chemogenetics in PACAP-Cre transgenic mice, the effect of activation of PVT PACAP+ cells on binge-type eating was determined.

RESULTS

Males and females both engaged in binge-type eating with Ensure, although females engaged in this behavior to a greater degree than males. While females also had a higher baseline level of PVT PACAP mRNA than males, only males showed an increase in levels of PACAP after a history of exposure to Ensure, and only males showed a reduction in levels of PACAP immediately prior to a binge session. Conversely, activation of PACAP+ cells in the PVT reduced binge-type eating of Ensure, specifically in male mice.

CONCLUSIONS

The present findings indicate that PVT PACAP+ cells influence and are influenced by binge-type eating. Thus, PACAP in the PVT might mediate some of the known involvement of the PVT with palatable food intake.

Evaluating the efficacy of the selective orexin 1 receptor antagonist nivasorexant in an animal model of binge-eating disorder

OBJECTIVE

Test the efficacy of the selective orexin 1 receptor (OX1R) antagonist (SO1RA) nivasorexant in an animal model of binge-eating disorder (BED) and study its dose-response relationship considering free brain concentrations and calculated OX1R occupancy. Compare nivasorexant's profile to that of other, structurally diverse SO1RAs. Gain understanding of potential changes in orexin-A (OXA) neuropeptide and deltaFosB (ΔFosB) protein expression possibly underlying the development of the binge-eating phenotype in the rat model used.

METHOD

Binge-like eating of highly palatable food (HPF) in rats was induced through priming by intermittent, repeated periods of dieting and access to HPF, followed by an additional challenge with acute stress. Effects of nivasorexant were compared to the SO1RAs ACT-335827 and IDOR-1104-2408. OXA expression in neurons and neuronal fibers as well as ΔFosB and OXA-ΔFosB co-expression was studied in relevant brain regions using immuno- or immunofluorescent histochemistry.

RESULTS

All SO1RAs dose-dependently reduced binge-like eating with effect sizes comparable to the positive control topiramate, at unbound drug concentrations selectively blocking brain OX1Rs. Nivasorexant's efficacy was maintained upon chronic dosing and under conditions involving more frequent stress exposure. Priming for binge-like eating or nivasorexant treatment resulted in only minor changes in OXA or ΔFosB expression in few brain areas.

DISCUSSION

Selective OX1R blockade reduced binge-like eating in rats. Neither ΔFosB nor OXA expression proved to be a useful classifier for their binge-eating phenotype. The current results formed the basis for a clinical phase II trial in BED, in which nivasorexant was unfortunately not efficacious compared with placebo.

PUBLIC SIGNIFICANCE

Nivasorexant is a new investigational drug for the treatment of binge-eating disorder (BED). It underwent clinical testing in a phase II proof of concept trial in humans but was not efficacious compared with placebo. The current manuscript investigated the drug's efficacy in reducing binge-like eating behavior of a highly palatable sweet and fat diet in a rat model of BED, which initially laid the foundation for the clinical trial.

Alcohol and energy drinks: individual contribution of common ingredients on ethanol-induced behaviour

Since energy drinks (EDs) were sold to the general public as soft drinks and recreational beverages, mixing EDs with ethanol has grown in popularity, particularly among younger people. Given the research that links these drinks with higher risk behaviors and increased ethanol intake, ethanol combined with EDs (AmEDs) is a particularly worrying combination. EDs generally commonly include a variety of ingredients. Sugar, caffeine, taurine, and B-group vitamins are almost always present. Studies on the combined effect of ethanol and sugar and caffeine on ethanol-induced behaviors are extensive. Not so much in regards to taurine and vitamins. This review briefly summarises available information from research on the isolated compounds on EtOH-induced behaviors first, and secondly, the combination of AmEDs on EtOH effects. The conclusion is that additional research is needed to fully comprehend the characteristics and consequences of AmEDs on EtOH-induced behaviors.

Effects of chronic psychosocial stress on 'binge-like' sucrose intake in mice

Binge eating episodes are persistent and are essential features of numerous eating disorders (EDs). Susceptibility to EDs is largely presumed to be associated with early life stress. In fact, converging evidence from preclinical animal studies have implicated stress as a driver of binge eating. Still, literature examination indicates that vulnerability to EDs may depend on factors such as severity, time, and the type of stressor. Therefore, we aimed at exploring the link between chronic psychosocial stress and 'binge-like' sucrose intake in adolescent mice. To this aim, intruders' experimental mice were exposed to the chronic subordinate colony (CSC) housing, in the presence of a resident aggressive mouse for 2 weeks. At the end of the stress period, mice were tested for anxiety-like behavior then assessed for 'binge-like' intake of sucrose using a long-term drinking in the dark (DID) method that successfully replicates binge eating in humans. As expected, and compared to single housed colony controls (SHC), CSC exposure elicited an anxiogenic-like response in the open field (OF) and elevated-plus maze (EPM) tests and reduced weight gain. Most importantly, we report here for the first time, that mice exposed to chronic psychosocial stress displayed a 'binge-like' consumption of sucrose. However, neither quinine (bitter) nor saccharin (sweet) intakes were affected by CSC exposure. Finally, using Pearson's correlation, results showed a strong correlation between anxiety-like behavior parameters and sucrose intake. Overall these findings support the validity of our chronic psychosocial stress to model binge EDs and establish the long-term consequences of stress on 'binge-like' eating in male mice. These data suggest that chronic psychosocial stress is a risk factor for developing anxiety-associated EDs.

Efficacy of choline and DHA supplements or enriched environment exposure during early adult obesity in mitigating its adverse impact through aging in rats

INTRODUCTION

The aim of this study was to assess the efficacy of choline and DHA or exposure to environmental enrichment in obese adult and aging rats on alterations in body mass index, serum lipid profile and arterial wall changes, despite stopping high fat diet consumption and interventions during adulthood.

METHODS

21 day old male Sprague Dawley rats were assigned as Experiment-1 & 2 - PND rats were divided into 4 groups with interventions for 7 months (n = 8/group). NC- Normal control fed normal chow diet; OB- Obese group, fed high fat diet; OB + CHO + DHA- fed high fat diet and oral supplementation of choline, DHA. OB + EE- fed high fat diet along with exposure to enriched environment .Experiment-2 had similar groups and interventions as experiment 1 but for next 5 months were fed normal chow diet without any interventions. Body mass index was assessed and blood was analyzed for serum lipid profile. Common Carotid Artery (CCA) was processed for Haematoxylin and eosin, Verhoff Vangeison stains. Images of tissue sections were analyzed and quantified using image J and tissue quant software.

RESULTS

In experiment.1, mean body mass index (p < 0.001), serum lipid profile (p < 0.01), thickness of tunica intima (p < 0.05), tunica media (p < 0.01) and percentage of collagen fibers (p < 0.01) of CCA were significantly increased in OB compared to NC. These were significantly attenuated in OB + CHO + DHA and OB + EE compared to OB. In experiment.2, mean body mass index (p < 0.01), serum lipid profile (p < 0.05) and thickness of tunica media of CCA (p < 0.01) were significantly increased in OB compared to NC. In OB + CHO + DHA and OB + EE, significant attenuation was observed in mean body mass index and mean thickness of tunica media compared to same in OB.

CONCLUSION

Adult obesity has negative impact on body mass index, serum lipid profile and arterial wall structure that persists through aging. Supplementation of choline and DHA or exposure to enriched environment during obesity attenuates these negative impacts through aging.

Binge-Like, Naloxone-Sensitive, Voluntary Ethanol Intake at Adolescence Is Greater Than at Adulthood, but Does Not Exacerbate Subsequent Two-Bottle Choice Drinking

The present study assessed the effects of ethanol exposure during adolescence or adulthood. We exposed Wistar rats, males or females, to self-administered 8–10% (v/v) ethanol (BINGE group) during the first 2 h of the dark cycle, three times a week (Monday, Wednesday, and Friday) during postnatal days (PDs) 32–54 or 72–94 (adolescent and adults, respectively). During this period, controls were only handled, and a third (IP) condition was given ethanol intraperitoneal administrations, three times a week (Monday, Wednesday, and Friday), at doses that matched those self-administered by the BINGE group. The rats were tested for ethanol intake and preference in a two-bottle (24 h long) choice test, shortly before (PD 30 or 70) and shortly after (PD 56 or 96) exposure to the binge or intraperitoneal protocol; and then tested for free-choice drinking during late adulthood (PDs 120–139) in intermittent two-bottle intake tests. Binge drinking was significantly greater in adolescents vs. adults, and was blocked by naloxone (5.0 mg/kg) administered immediately before the binge session. Mean blood ethanol levels (mg/dl) at termination of binge session 3 were 60.82 ± 22.39. Ethanol exposure at adolescence, but not at adulthood, significantly reduced exploration of an open field-like chamber and significantly increased shelter-seeking behavior in the multivariate concentric square field. The rats that had been initially exposed to ethanol at adolescence drank, during the intake tests conducted at adulthood, significantly more than those that had their first experience with ethanol at adulthood, an effect that was similar among BINGE, IP and control groups. The study indicates that binge ethanol drinking is greater in adolescent that in adults and is associated with heightened ethanol intake at adulthood. Preventing alcohol access to adolescents should reduce the likelihood of problematic alcohol use or alcohol-related consequences.

Environmental enrichment reduces food seeking and taking in rats: A review

Environmental enrichment (EE) for rodents is generally defined as providing subjects with an environment enhanced with access to conspecifics, novel and tactile stimuli, and in many preparations, more space. EE exposure, in particular as an "intervention" in adult rodents, decreases food and drug seeking and taking. This review focuses on the reduction of sucrose seeking and taking in rats assessed in operant-based procedures. The operant-based model provides a means to evaluate addiction-related behaviors. Findings using the model might translate to clinically-relevant addiction behaviors directed towards both drugs and food. Both overnight (acute) and one month (chronic) EE effects on behavior are described, including a recent evaluation of the persistence of EE effects following its removal. EE effects on neurobiology related to sucrose seeking using the model are outlined, with a special emphasis on meso-cortico-limbic terminals. Overall, our working hypothesis for how EE reduces sucrose seeking and taking is that EE alters processing of incentive valence. This may also be accompanied by changes in learning and affect. Anti-seeking and anti-taking effects of EE have translational implications for the prevention and treatment of both drug addiction and food-focused behaviors ("food addiction").

Protective and therapeutic benefits of environmental enrichment on binge-like sucrose intake in C57BL/6J mice

Binge eating disorder (BED) is characterized, in part, by recurrent episodes of eating large quantities of food in a short period of time. Repetitive binge episodes are a common pattern of consumption during the early stages of substance abuse, and it has been proposed that binge patterns of consumption might favor the transition to BED and "food addiction". Therefore, it is of paramount importance to provide new behavioral strategies that protect vulnerable binge-prone individuals from transitioning to BED and food addiction. Recently, we showed protective and therapeutic benefits of environmental enrichment (EE) on binge-like intake of ethanol in C57BL/6J mice, in agreement with previous evidence showing EE modulation of drug intake, drug relapse and drug reward. In the present study, adolescent mice reared under EE conditions were evaluated for binge-like consumption of sucrose during adulthood in a long-term drinking in the dark (DID) procedure that effectively models binge consumption in humans. Additionally, we tested binge-like intake in adults reared under standard conditions (SE) with long-term exposure to sucrose DID and the effects on sucrose DID of switching from SE to EE conditions. We report here, for the first time, that early EE exposure protects mice from binge-like excessive sucrose intake during adulthood. Ongoing binge-like high sucrose intake in SE-reared mice was also significantly reduced when switched to EE conditions. The present observations suggest that EE exposure might be a promising tool for preventing repetitive binge-like sucrose consumption from transitioning to BED and food addiction.