Junk food diet-induced obesity increases D2 receptor autoinhibition in the ventral tegmental area and reduces ethanol drinking

Changes in reward-induced neural activity upon Cafeteria Diet consumption

Excessive consumption of highly palatable foods rich in sugar and fat, often referred to as "junk" or "fast" foods, plays a central role in the development of obesity. The highly palatable characteristics of these foods activate hedonic and motivational mechanisms to promote food-seeking behavior and overeating, which is largely regulated by the brain reward system. Excessive junk food consumption can alter the functioning of this reward system, but exact mechanisms of these changes are still largely unknown. This study investigated whether long-term junk food consumption, in the form of Cafeteria (CAF) diet, can alter the reward system in adult, female Long-Evans rats, and whether different regimes of CAF diet influence the extent of these changes. To this end, rats were exposed to a 6-week diet with either standard chow, or ad libitum daily access to CAF diet, 30 % restricted but daily access to CAF diet, or one-day-a-week (intermittent) ad libitum access to CAF diet, after which c-Fos expression in the Nucleus Accumbens (NAc), Prefrontal Cortex (PFC), and Ventral Tegmental Area (VTA) following consumption of a CAF reward of choice was examined. We found that all CAF diet regimes decreased c-Fos expression in the NAc-shell when presented with a CAF reward, while no changes in c-Fos expression upon the different diet regimes were found in the PFC, and possibly the VTA. Our data suggests that long-term junk food exposure can affect the brain reward system, resulting in an attenuated activity of the NAc-shell.

Patterned Feeding of a Hyper-Palatable Food (Oreo Cookies) Reduces Alcohol Drinking in Rats

While a bidirectional positive link between palatable food intake and alcohol drinking has been suggested, several rodents studies report reduced alcohol drinking following palatable diets exposure. These studies utilized purified rodents’ diets high in sugar/fat; however, the effects of hyper-palatable food (HPF) rich in fat and sugar on alcohol drinking remain unclear. Furthermore, neural substrates involved in HPF-mediated changes in alcohol consumption are poorly understood. Therefore, the present study evaluated the effects of patterned feeding of a hyper-palatable food (Oreo cookies) on alcohol drinking as well as dopamine (DA) and serotonin (5-HT) content in rat’s mesocorticolimbic (medial-prefrontal cortex, orbitofrontal cortex, amygdala, and nucleus accumbens) circuitry. Male Long Evans rats received 8-weeks of intermittent (Mon, Tue, Wed) Oreo cookies access, which induced a patterned feeding, in which rats in the Oreo group overconsumed calories on HPF days whereas underconsumption was observed on chow only (Thu, Fri) days. Following HPF exposure, alcohol consumption was evaluated while patterned feeding continued. Alcohol intake in the Oreo group was significantly lower as compared to the chow controls. However, alcohol intake in the Oreo group increased to the levels seen in the group receiving chow following the suspension of patterned HPF feeding. Finally, DA levels in the nucleus accumbens were significantly greater, whereas its metabolite (DOPAC) levels were lower in the Oreo group compared to the chow controls. Surprisingly, 5-HT levels remained unaltered in all tested brain areas. Together, these data suggest that HPF-associated increased DA availability and reduced DA turnover within mesocorticolimbic circuitry may regulate alcohol drinking following patterned HPF feeding.

Daily associations between alcohol and sweets craving and consumption in early AUD recovery: Results from an ecological momentary assessment study

INTRODUCTION

Alcohol cravings can predict relapse in persons with alcohol use disorder (AUD). Consuming sweets is a commonly recommend strategy to quell alcohol cravings in early recovery from AUD, yet research is equivocal on whether consuming sweets mitigates alcohol cravings or relapse risk. The current study used ecological momentary assessment (EMA) data to examine real-time alcohol cravings, sweet cravings, and consumption of sweets among adults in early recovery from AUD.

METHODS

We used EMA methods to follow 25 adults (n = 14 women, 56%; M. age 40, S.D. 10.68) recently discharged from a partial hospitalization program for AUD for 21 days. Prompts were sent to the participants for completion four times per day via a mobile app. EMA data were disaggregated prior to analysis to examine between- and within-person effects. A series of three mixed linear models tested: 1) the contemporaneous effect of sweet and alcohol cravings, 2) alcohol cravings predicting sweet consumption later in the day, and 3) sweet consumption predicting alcohol craving later in the day.

RESULTS

The results of the first model revealed alcohol cravings were associated with sweet cravings early in recovery. In the second model, no effect occurred between alcohol cravings earlier in the day predicting sweet consumption later in the day. The third model suggested consuming sweets earlier in the day predicted higher alcohol cravings later in the day.

DISCUSSION

Sweet craving and consumption are associated with alcohol cravings among adults in early recovery from AUD. These findings suggest consuming sweets may increase alcohol cravings. If future studies can replicate this result, consuming sweets in early recovery may emerge as a potential risk for relapse in this population.

The cafeteria diet: A standardized protocol and its effects on behavior

Obesity is a major health risk, with junk food consumption playing a central role in weight gain, because of its high palatability and high-energy nutrients. The Cafeteria (CAF) diet model for animal experiments consists of the same tasty but unhealthy food products that people eat (e.g. hot dogs and muffins), and considers variety, novelty and secondary food features, such as smell and texture. This model, therefore, mimics human eating patterns better than other models. In this paper, we systematically review studies that have used a CAF diet in behavioral experiments and propose a standardized CAF diet protocol. The proposed diet is ad libitum and voluntary; combines different textures, nutrients and tastes, including salty and sweet products; and it is rotated and varied. Our summary of the behavioral effects of CAF diet show that it alters meal patterns, reduces the hedonic value of other rewards, and tends to reduce stress and spatial memory. So far, no clear effects of CAF diet were found on locomotor activity, impulsivity, coping and social behavior.

Emotional Eating in Pregnant Women during the COVID-19 Pandemic and Its Association with Dietary Intake and Gestational Weight Gain

Reproductive health is a significant public health issue during pandemics; however, the impacts of the novel 2019 coronavirus disease (COVID-19) on noninfected pregnant women are still unknown. This study intends (1) to examine whether emotional eating (EE) occurred during the pandemic triggered by disease concerns and (2) to explore the associations among EE, dietary changes, and gestational weight gain (GWG). Based on an online survey, 640 new mothers who experienced the lockdown in their third trimester were recruited from seven provinces in China. EE was evaluated with the Chinese version of the Dutch Eating Behavior Questionnaire, EE domain. A self-designed e-questionnaire was used to collect the data of participants on the sociodemographic characteristics, concerns about the COVID-19 pandemic, maternity information, physical activities, and dietary changes during lockdown. The results show that the average EE score was 26.5 ± 8.3, and women living in a severely affected area, who are very worried about the pandemic and who had less physical activity had a higher tendency of EE. Although there is a dietary pattern changed during pandemic, the average GWG in the studied group was in the normal range. However, a higher EE score was associated with a significant excess of GWG in women not from Wuhan (EE score 33–65 vs. 13–22: adjusted Odd Ratio (OR), 95% Confidence Interval (CI) = 1.90, 1.08–3.32). The sensitivity analysis that additionally adjusted for the pregestational body mass index and gestational metabolic disease was consistent with this result. The mediation model was also examined and showed that, after adjusting for living area and exercise, EE was associated with significantly increased consumption of cereals (EE score 33–65 vs. 13–22: adjusted OR, 95% CI = 2.22, 1.29–3.82) and oil (EE score 33–65 vs. 13–22: adjusted OR, 95% CI = 3.03, 1.06–8.69) but decreased consumption of fish and seafood (EE score 33–65 vs. 13–22: adjusted OR, 95% CI = 1.88, 1.14–3.11; 23–32 vs. 13–22: adjusted OR, 95% CI = 1.79, 1.20–2.66). In conclusion, this study indicated that EE occurred in a proportional number of pregnant women during the COVID-19 pandemic and is associated with excess GWG mediated by increased intake of certain foods. The findings suggest the need for psychosocial and nutritional education and interventions during pregnancy checkups. Further studies are needed to determine modifiable psychosocial predictors and potential nutritional concerns in pregnant women during disease outbreaks.

Reduced alcohol drinking following patterned feeding: Role of palatability and acute contingent availability

Recent studies from our lab have demonstrated that intermittent high-fat diet access reduces alcohol drinking in rats. However, it was unclear if caloric overload, palatability, or diet itself triggered reduced alcohol drinking. It is also unknown if a similar paradigm could reduce relapse-like alcohol drinking. The presented study tested the hypothesis that acute intermittent palatable diet (PD) access would rescue relapse-like drinking and palatability, but not diet itself contributes to reduced drinking. Male Long Evans rats received six-weeks intermittent or chronic chow (controls) or PDs (high-fat diet, high-sugar diet) exposure, and alcohol testing occurred following PDs suspension. Alcohol intake was not significantly different among groups in either condition, suggesting that diet itself did not impact alcohol drinking. A subset of these rats received two-weeks intermittent PDs (Int-PDs) exposure and alcohol testing reinitiated while Int-PDs access continued. Alcohol intake significantly escalated (~137% compared to baseline; alcohol deprivation effect) in the chow controls, whereas it remained unchanged in PD groups. These data demonstrate the critical importance of acute intermittent PDs availability and its protective effect in relapse-like drinking. To assess the contribution of palatability in reduced alcohol drinking, a separate group of rats received two-weeks intermittent high-sugar diet (Int-HSD) or saccharin (Int-SAC) access and tested for alcohol drinking while Int-HSD/SAC continued. Alcohol drinking significantly decreased (~30%) in both HSD and SAC groups compared to the controls. These data identify the critical parameters by which acute intermittent PD access reduces alcohol drinking and could have important therapeutic implications in the management of alcoholism.

A systematic review on different models of inducing obesity in animals: Advantages and limitations

Several animals have been in the limelight of basic research associated with metabolic diseases like obesity. Obesity can be considered as a significant public health concern in the world. It raises the chances for a variety of disease conditions that includes diabetes, hypertension, liver disease, and cancers, which, in turn, decreases the overall lifespan of adult men and women. The World Health Organization has considered obesity as a global epidemic. Researchers have made several attempts to classify human obesity, but none have been successful. Animal obesity can be classified based on their etiology; however, till now, no animal model of obesity can replicate models of the human condition, they have only provided clues into the causes, aftermaths, and preventive remedy to human adiposity. Over the years, there are varieties of animal models used to induce obesity. Some of them include monogenic, polygenic, surgical, seasonal, and other models of obesity. Apart from the advantages of these models, most of them are accompanied by limitations. The primary purpose of this review is, therefore, to highlight the several models with their advantages and limitations. By knowing the benefits and limitations of animal models of obesity, researchers may be at liberty to select the appropriate one for the study of obesity.

Behavioral and Neurobiological Consequences of Hedonic Feeding on Alcohol Drinking

A complex interplay of peripheral and central signaling mechanisms within the body of an organism maintains energy homeostasis. In addition, energy/food intake is modified by various external factors (e.g., palatability, food availability, social and environmental triggers). Highly palatable foods can provoke maladaptive feeding behavior, which in turn disrupts normal homeostatic regulation resulting in numerous health consequences. Furthermore, neuroendocrine peptides, traditionally considered to regulate appetite and energy homeostasis, also control the intake and reinforcing properties of alcohol and drugs of abuse. Therefore, dysregulated eating as a result of a hedonic/binge-like intake of hyper-palatable food may impact alcohol drinking behavior. Relevant in this case is the fact that eating disorders are highly comorbid with several neuropsychiatric conditions, including alcohol use disorder. The present review is intended to summarize the neurobiological and functional consequences of hedonic feeding on alcohol intake.

Recent Advances in the Neurobiology of Altered Motivation Following Bariatric Surgery

PURPOSE OF REVIEW

There is compelling evidence in the clinical population that long-term weight loss secondary to bariatric surgery is mitigated by the reemergence of maladaptive feeding behaviors and in some cases new onset substance abuse.

RECENT FINDINGS

A review of the current literature suggests that physical restructuring of the GI tract during WLS alters secretion of feeding peptides and nutrient-sensing mechanisms that directly target the brain's endogenous reward system, the mesolimbic dopamine system. Post-surgical changes in GI physiology augment activation of the mesolimbic system. In some patients, this process may contribute to a reduced appetite for palatable food whereas in others it may support maladaptive motivated behavior for food and chemical drugs. It is concluded that future studies are required to detail the timing and duration of surgical-induced changes in GI-mesolimbic communication to more fully understand this phenomenon.

Maternal dyslipidaemic diet induces sex-specific alterations in intestinal function and lipid metabolism in rat offspring

This study investigated the effects of a maternal dyslipidaemic (DLP) diet on lipid metabolism, microbial counts in faeces and hepatic and intestinal morphology in rat offspring with respect to sex during different phases of life. Wistar rats (dams) were fed a control (CTL) or DLP during gestation and lactation. After weaning, CTL and DLP offspring were fed a standard diet. The effects of a maternal DLP on body composition, biochemical parameters, faecal microbiota and intestinal and hepatic histomorphometric characteristics in rat offspring were evaluated at 30 and 90 d of age. The DLP diet during gestation and lactation caused lower birth weight and a greater weight gain percentage at the end of the 90-d period in both male and female offspring. Female pups from DLP dams had higher liver fat levels compared with CTL (P≤0·001) at 90 d of age. Males from DLP dams had greater visceral fat weight and lower Lactobacillus spp. faecal counts at 90 d of age (P≤0·001) as well as lower faecal fat excretion (P≤0·05) and Bacteroides spp. faecal counts (P≤0·001) at 30 d of age when compared with pups from CTL dams. However, both dams and DLP pups showed damage to intestinal villi. A maternal DLP alters intestinal function and lipid metabolism in a sex-specific manner and is a potential predisposing factor for health complications in offspring from the juvenile period to the adult period.

Hungry brains: A meta-analytical review of brain activation imaging studies on food perception and appetite in obese individuals

The dysregulation of food intake in chronic obesity has been explained by different theories. To assess their explanatory power, we meta-analyzed 22 brain-activation imaging studies. We found that obese individuals exhibit hyper-responsivity of the brain regions involved in taste and reward for food-related stimuli. Consistent with a Reward Surfeit Hypothesis, obese individuals exhibit a ventral striatum hyper-responsivity in response to pure tastes, particularly when fasting. Furthermore, we found that obese subjects display more frequent ventral striatal activation for visual food cues when satiated: this continued processing within the reward system, together with the aforementioned evidence, is compatible with the Incentive Sensitization Theory. On the other hand, we did not find univocal evidence in favor of a Reward Deficit Hypothesis nor for a systematic deficit of inhibitory cognitive control. We conclude that the available brain activation data on the dysregulated food intake and food-related behavior in chronic obesity can be best framed within an Incentive Sensitization Theory. Implications of these findings for a brain-based therapy of obesity are briefly discussed.