High fat diet intake during pre and periadolescence impairs learning of a conditioned place preference in adulthood

A one month high fat diet disrupts the gut microbiome and integrity of the colon inducing adiposity and behavioral despair in male Sprague Dawley rats

High-fat diet (HFD) is associated with gut microbiome dysfunction and mental disorders. However, the time-dependence as to when this occurs is unclear. We hypothesized that a short-term HFD causes colonic tissue integrity changes resulting in behavioral changes. Rats were fed HFD or low-fat diet (LFD) for a month and gut microbiome, colon, and behavior were evaluated. Behavioral despair was found in the HFD group. Although obesity was absent, the HFD group showed increased percent weight gain, epididymal fat tissue, and leptin expression. Moreover, the HFD group had increased colonic damage, decreased expression of the tight junction proteins, and higher lipopolysaccharides (LPS) in serum. Metagenomic analysis revealed that the HFD group had more Bacteroides and less S24-7 which correlated with the decreased claudin-5. Finally, HFD group showed an increase of microglia percent area, increased astrocytic projections, and decreased phospho-mTOR. In conclusion, HFD consumption in a short period is still sufficient to disrupt gut integrity resulting in LPS infiltration, alterations in the brain, and behavioral despair even in the absence of obesity.

The role of dopamine and endocannabinoid systems in prefrontal cortex development: Adolescence as a critical period

The prefrontal cortex plays a central role in the control of complex cognitive processes including action control and decision making. It also shows a specific pattern of delayed maturation related to unique behavioral changes during adolescence and allows the development of adult cognitive processes. The adolescent brain is extremely plastic and critically vulnerable to external insults. Related to this vulnerability, adolescence is also associated with the emergence of numerous neuropsychiatric disorders involving alterations of prefrontal functions. Within prefrontal microcircuits, the dopamine and the endocannabinoid systems have widespread effects on adolescent-specific ontogenetic processes. In this review, we highlight recent advances in our understanding of the maturation of the dopamine system and the endocannabinoid system in the prefrontal cortex during adolescence. We discuss how they interact with GABA and glutamate neurons to modulate prefrontal circuits and how they can be altered by different environmental events leading to long-term neurobiological and behavioral changes at adulthood. Finally, we aim to identify several future research directions to help highlight gaps in our current knowledge on the maturation of these microcircuits.

High-fat diet and fructose drink introduced after weaning rats, induces a better human obesity model than very high-fat diet

In the present study, we associated a high-fat diet (HF group: 45% kcal from lipids) or very high-fat (VHF group: 60% kcal from lipids) diet with a fructose drink (10% fructose) for hydration. Normal rat chow that received the control diet (content 16.3% kcal from lipid-AIN93G) and water. The treatments were introduced soon after weaning and were administered for 70 days. We aimed to compare HF and VHF groups and find which acts as a better model mimicking human obesity. Body mass gain, final body weight, adipocyte area in inguinal depots, visceral and subcutaneous adipose depots, serum triacylglycerol, and VLDL-c were all higher in the HF group, followed by the VHF group, compared to the C group. Only the HF group showed hyperinsulinemia and hyperleptinemia and higher total caloric intake, Lee index, HOMA2-IR, and total cholesterol. Serum TNF-α and IL-6 levels were lower in the HF and VHF groups than in the C group at the end for 70 days. In Summary, the HF (45%) diet administered with fructose induced a higher similarity of metabolic and hormonal alterations associated with human obesity. PRACTICAL APPLICATIONS: High intake of lipids with sugary drinks has been associated with obesity and its comorbidities. Although a diet with 45% or 60% of lipids is considered hyperlipidic, they are different in their effects on eating behavior and also probably from a metabolic point of view. Common sense is that the reduction in intake of lipids is favorable to health. Our study shows that this is not wholly true, and this information contributes to the guidelines for the treatment of obesity. In addition, the scientific literature on the subject has shown the most diverse results and also the use of experimental models with few similarities with human obesity. Our findings can contribute as a good model of obesity initiated during childhood to investigate possible using nutritional strategies, or the adoption of ergogenic nutritional resources in future studies, for example.

Western Diet Consumption During Development: Setting the Stage for Neurocognitive Dysfunction

The dietary pattern in industrialized countries has changed substantially over the past century due to technological advances in agriculture, food processing, storage, marketing, and distribution practices. The availability of highly palatable, calorically dense foods that are shelf-stable has facilitated a food environment where overconsumption of foods that have a high percentage of calories derived from fat (particularly saturated fat) and sugar is extremely common in modern Westernized societies. In addition to being a predictor of obesity and metabolic dysfunction, consumption of a Western diet (WD) is related to poorer cognitive performance across the lifespan. In particular, WD consumption during critical early life stages of development has negative consequences on various cognitive abilities later in adulthood. This review highlights rodent model research identifying dietary, metabolic, and neurobiological mechanisms linking consumption of a WD during early life periods of development (gestation, lactation, juvenile and adolescence) with behavioral impairments in multiple cognitive domains, including anxiety-like behavior, learning and memory function, reward-motivated behavior, and social behavior. The literature supports a model in which early life WD consumption leads to long-lasting neurocognitive impairments that are largely dissociable from WD effects on obesity and metabolic dysfunction.

Most Effective Combination of Nutraceuticals for Improved Memory and Cognitive Performance in the House Cricket, Acheta domesticus

Background: Dietary intake of multivitamins, zinc, polyphenols, omega fatty acids, and probiotics have all shown benefits in learning, spatial memory, and cognitive function. It is important to determine the most effective combination of antioxidants and/or probiotics because regular ingestion of all nutraceuticals may not be practical. This study examined various combinations of nutrients to determine which may best enhance spatial memory and cognitive performance in the house cricket (Acheta domesticus (L.)). Methods: Based on the 31 possible combinations of multivitamins, zinc, polyphenols, omega-3 polyunsaturated fatty acids (PUFAs), and probiotics, 128 house crickets were divided into one control group and 31 experimental groups with four house crickets in each group. Over eight weeks, crickets were fed their respective nutrients, and an Alternation Test and Recognition Memory Test were conducted every week using a Y-maze to test spatial working memory. Results: The highest-scoring diets shared by both tests were the combination of multivitamins, zinc, and omega-3 fatty acids (VitZncPuf; Alternation: slope = 0.07226, Recognition Memory: slope = 0.07001), the combination of probiotics, polyphenols, multivitamins, zinc, and omega-3 PUFAs (ProPolVitZncPuf; Alternation: slope = 0.07182, Recognition Memory: slope = 0.07001), the combination of probiotics, multivitamins, zinc, and omega-3 PUFAs (ProVitZncPuf; Alternation: slope = 0.06999, Recognition Memory: slope = 0.07001), and the combination of polyphenols, multivitamins, zinc, and omega-3 PUFAs (PolVitZncPuf; Alternation: slope = 0.06873, Recognition Memory: slope = 0.06956). Conclusion: All of the nutrient combinations demonstrated a benefit over the control diet, but the most significant improvement compared to the control was found in the VitZncPuf, ProVitZncPuf, PolVitZncPuf, and ProPolVitZncPuf. Since this study found no significant difference between the performance and improvement of subjects within these four groups, the combination of multivitamins, zinc, and omega-3 fatty acids (VitZncPuf) was concluded to be the most effective option for improving memory and cognitive performance.

Added sugar and dietary fiber consumption are associated with creativity in preadolescent children

Objectives: Creativity requires the ability to combine existing mental representations in new ways and depends, in part, on the hippocampus. Hippocampal function is, in turn, affected by a number of health factors, including aerobic fitness, excess adiposity, and diet. Specifically, in rodent studies, diets high in saturated fatty acids and sugar - hallmarks of a western diet- have been shown to negatively impact hippocampal function and thereby impair performance on cognitive tasks that require the hippocampus. Yet relatively few studies have examined the relationship between diet and hippocampal-dependent cognition in children. Methods: The current study therefore sought to explore the relationship of several diet quality markers including dietary lipids (saturated fatty acids and omega-3 fatty acids), simple carbohydrates (added sugars), and dietary fiber with creativity in preadolescent children. Participants (N = 57; mean age = 9.1 years) completed the Verbal Form of the Torrance Test of Creative Thinking (TTCT), a standardized test of creativity known to require the hippocampus. Additionally, participants completed a 3-day food intake record with the assistance of a parent, underwent dual energy x-ray absorptiometry (DXA) to assess central adiposity, and VO2max testing to assess aerobic fitness. Results: Added sugar intake was negatively associated, and dietary fiber was positively associated with overall TTCT performance. These relationships were sustained even after controlling for key covariates. Discussion: These findings are among the first to report an association between added sugar consumption and hippocampal-dependent cognition during childhood and, given the key role of the hippocampus in learning and memory, as well as creative thinking, have potential educational and public health implications.

High fat diet consumption restricted to adolescence has minimal effects on adult executive function that vary by sex

Early life environment can have a lasting effect on brain development and behavior. Diet is a potent environmental factor that can positively or negatively affect neurodevelopment, and unfortunately, the likelihood of a poor diet is high during adolescence. Adverse effects of adolescent high fat diet have been observed on reward-related behaviors, reversal learning, and hippocampal-dependent learning tasks in rodents when tested in adulthood. The prefrontal cortex (PFC) continues to develop throughout adolescence and is thus vulnerable to environmental insults such as poor diet. Therefore, we sought to examine the effects of a high fat diet (HFD) consumed only during adolescence on later life adult PFC-dependent executive function. Male and female mice were fed a HFD (60% energy from fat) during either early or late adolescence then switched to standard chow and tested in a battery of touchscreen-based operant tests of executive function in adulthood. Contrary to our prediction of an adverse effect of HFD, there was no effect of adolescent HFD in males, and females showed faster learning and decreased inattention in adulthood. We conclude that the effects of adolescent-limited HFD on adult executive function are mild, positive, and vary by sex.

Examining Adolescence as a Sensitive Period for High-Fat, High-Sugar Diet Exposure: A Systematic Review of the Animal Literature

Animal studies suggest that poor nutrition (e.g., high-fat, high-sugar diets) may lead to impairments in cognitive functioning. Accumulating evidence suggests that the deleterious effects of these diets appear more pronounced in animals maintained on this diet early in life, consistent with the notion that the developing brain may be especially vulnerable to environmental insults. The current paper provides the first systematic review of studies comparing the effects of high-fat, high-sugar diet exposure during adolescence and adulthood on memory performance. The majority of studies (7/8) identified here report diet-induced memory problems when diet exposure began in adolescence but not adulthood. These findings lend support to the hypothesis that adolescence is a sensitive period during which palatable diets may contribute to negative neurocognitive effects. The current review explores putative mechanisms involved in diet-induced cognitive dysfunction and highlights promising areas for further research.

Switching Adolescent High-Fat Diet to Adult Control Diet Restores Neurocognitive Alterations

In addition to metabolic and cardiovascular disorders, obesity is associated with adverse cognitive and emotional outcomes. Its growing prevalence in adolescents is particularly alarming since this is a period of ongoing maturation for brain structures (including the hippocampus and amygdala) and for the hypothalamic-pituitary-adrenal (HPA) stress axis, which is required for cognitive and emotional processing. We recently demonstrated that adolescent, but not adult, high-fat diet (HF) exposure leads to impaired hippocampal function and enhanced amygdala function through HPA axis alteration (Boitard et al., 2012, 2014, 2015). Here, we assessed whether the effects of adolescent HF consumption on brain function are permanent or reversible. After adolescent exposure to HF, switching to a standard control diet restored levels of hippocampal neurogenesis and normalized enhanced HPA axis reactivity, amygdala activity and avoidance memory. Therefore, while the adolescent period is highly vulnerable to the deleterious effects of diet-induced obesity, adult exposure to a standard diet appears sufficient to reverse alterations of brain function.

Adolescent Maturational Transitions in the Prefrontal Cortex and Dopamine Signaling as a Risk Factor for the Development of Obesity and High Fat/High Sugar Diet Induced Cognitive Deficits

Adolescence poses as both a transitional period in neurodevelopment and lifestyle practices. In particular, the developmental trajectory of the prefrontal cortex (PFC), a critical region for behavioral control and self-regulation, is enduring, not reaching functional maturity until the early 20 s in humans. Furthermore, the neurotransmitter dopamine is particularly abundant during adolescence, tuning the brain to rapidly learn about rewards and regulating aspects of neuroplasticity. Thus, adolescence is proposed to represent a period of vulnerability towards reward-driven behaviors such as the consumption of palatable high fat and high sugar diets. This is reflected in the increasing prevalence of obesity in children and adolescents as they are the greatest consumers of “junk foods”. Excessive consumption of diets laden in saturated fat and refined sugars not only leads to weight gain and the development of obesity, but experimental studies with rodents indicate they evoke cognitive deficits in learning and memory process by disrupting neuroplasticity and altering reward processing neurocircuitry. Consumption of these high fat and high sugar diets have been reported to have a particularly pronounced impact on cognition when consumed during adolescence, demonstrating a susceptibility of the adolescent brain to enduring cognitive deficits. The adolescent brain, with heightened reward sensitivity and diminished behavioral control compared to the mature adult brain, appears to be a risk for aberrant eating behaviors that may underpin the development of obesity. This review explores the neurodevelopmental changes in the PFC and mesocortical dopamine signaling that occur during adolescence, and how these potentially underpin the overconsumption of palatable food and development of obesogenic diet-induced cognitive deficits.

Free-choice high-fat diet alters circadian oscillation of energy intake in adolescent mice: role of prefrontal cortex

PURPOSE

Our aim was to characterize the effect of an unfamiliar high-fat diet (HFD) on circadian feeding behaviour, plasma parameters, body weight (BW), and gene expression in the prefrontal cortex (PFC) of adolescent male mice. To this end, mice were allowed to consume a HFD during 48 h, but one group was allowed a free choice of HFD or normal chow (FC-HFD), while the other was restricted to a non-optional unfamiliar HFD feeding (NOP-HFD).

METHODS

Energy intake was monitored at 6-h intervals during 48 h. Mice cohorts were killed at 6-h intervals after 48-h dietary treatment, and PFC samples dissected for RT-PCR analysis.

RESULTS

Mice on the FC-HFD protocol avoided eating the standard chow, showed lower energy intake and lower BW increase than NOP-HFD mice. All animals with access to HFD exhibited nocturnal overeating, but diurnal hyperphagia was more prominent in the FC-HFD cohort. A robust increase in tyrosine hydroxylase (Th) gene expression was detected specifically during the light period of the circadian cycle in FC-HFD mice. In contrast, both protocols similarly up-regulated the expression of cytosolic malic enzyme (Me1), which is very sensitive to HFD.

CONCLUSION

Our data show that the PFC participates in driving motivational feeding during HFD-evoked hyperphagia and also suggest that sensory neural pathways might be relevant for the onset of eating disorders and overweight. Moreover, we have observed that animals that had the possibility of choosing between standard chow and HFD were more hyperphagic and specifically displayed an overexpression of the tyrosine hydroxylase gene.

Effects of sucrose and high fructose corn syrup consumption on spatial memory function and hippocampal neuroinflammation in adolescent rats

Excessive consumption of added sugars negatively impacts metabolic systems; however, effects on cognitive function are poorly understood. Also unknown is whether negative outcomes associated with consumption of different sugars are exacerbated during critical periods of development (e.g., adolescence). Here we examined the effects of sucrose and high fructose corn syrup-55 (HFCS-55) intake during adolescence or adulthood on cognitive and metabolic outcomes. Adolescent or adult male rats were given 30-day access to chow, water, and either (1) 11% sucrose solution, (2) 11% HFCS-55 solution, or (3) an extra bottle of water (control). In adolescent rats, HFCS-55 intake impaired hippocampal-dependent spatial learning and memory in a Barne's maze, with moderate learning impairment also observed for the sucrose group. The learning and memory impairment is unlikely based on nonspecific behavioral effects as adolescent HFCS-55 consumption did not impact anxiety in the zero maze or performance in a non-spatial response learning task using the same mildly aversive stimuli as the Barne's maze. Protein expression of pro-inflammatory cytokines (interleukin 6, interleukin 1β) was increased in the dorsal hippocampus for the adolescent HFCS-55 group relative to controls with no significant effect in the sucrose group, whereas liver interleukin 1β and plasma insulin levels were elevated for both adolescent-exposed sugar groups. In contrast, intake of HFCS-55 or sucrose in adults did not impact spatial learning, glucose tolerance, anxiety, or neuroinflammatory markers. These data show that consumption of added sugars, particularly HFCS-55, negatively impacts hippocampal function, metabolic outcomes, and neuroinflammation when consumed in excess during the adolescent period of development.

Omega 3 polyunsaturated fatty acid improves spatial learning and hippocampal peroxisome proliferator activated receptors (PPARα and PPARγ) gene expression in rats

Background

This study examined the effects of dietary polyunsaturated fatty acids (PUFA) as different n-6: n-3 ratios on spatial learning and gene expression of peroxisome- proliferator-activated receptors (PPARs) in the hippocampus of rats. Thirty male Sprague–Dawley rats were randomly allotted into 3 groups of ten animals each and received experimental diets with different n-6: n-3 PUFA ratios of either 65:1, 22:1 or 4.5:1. After 10 weeks, the spatial memory of the animals was assessed using the Morris Water Maze test. The expression of PPARα and PPARγ genes were determined using real-time PCR.

Results

Decreasing dietary n-6: n-3 PUFA ratios improved the cognitive performance of animals in the Morris water maze test along with the upregulation of PPARα and PPARγ gene expression. The animals with the lowest dietary n-6: n-3 PUFA ratio presented the highest spatial learning improvement and PPAR gene expression.

Conclusion

It can be concluded that modulation of n-6: n-3 PUFA ratios in the diet may lead to increased hippocampal PPAR gene expression and consequently improved spatial learning and memory in rats.

Validity and reliability of an estimated daily intake scale for fat

The reliability and validity of an Estimated Daily Intake Scale for Fat (EDIS-F) used to measure daily intake of fat in a participant’s diet was tested. A Cronbach’s alpha was used to determine the reliability of the EDIS-F. To determine the validity of this scale, scores on this scale were correlated with known factors related to daily intake of fat (e.g., ratings of liking for a high fat food and the body mass index score of participants). A 13-item EDIS-F was shown to be reliable, and scores on the EDIS-F significantly correlated with ratings of liking for a high fat cream cheese cracker and BMI, but not with gender, consistent with the assertion that this scale measures daily intake of fat. Implications for using this scale are discussed.