Short-term exposure to a diet high in fat and sugar, or liquid sugar, selectively impairs hippocampal-dependent memory, with differential impacts on inflammation

Association between a body shape index and cognitive impairment among us older adults from a cross-sectional survey of the NHANES 2011-2014

PURPOSE

This study aimed to assess the relationship between A Body Shape Index (ABSI) and cognitive impairment among older adults in the United States.

METHODS

This cross-sectional study analyzed cognitive function in 2,752 individuals aged 60 and older using data from the 2011-2014 National Health and Nutrition Examination Survey (NHANES). Cognitive assessments were conducted using the Immediate Recall Test (IRT), Delayed Recall Test (DRT), Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST). A Body Shape Index (ABSI) was calculated from waist circumference (WC), weight, and height. The relationship between ABSI and cognitive outcomes was examined through multifactorial linear regression, smooth curve fitting, and subgroup and interaction analyses.

RESULTS

With complete data, 2752 persons 60 and older participated in the study. After adjusting for covariables, these results showed statistically significant negative relationships between ABSI, IRT, and DSST scores. The negative correlation between DSST and ABSI is more substantial in males than females. There is less of a negative link between ABSI, AFT, and DSST among drinkers who consume 12 or more drinks annually compared to those who consume less. Furthermore, compared to individuals without high blood pressure(HBP), those who suffered HBP showed a more significant negative connection between ABSI and AFT.

CONCLUSION

Lower cognitive function was linked to higher ABSI.

Modulation of Gut Microbiota Through Dietary Intervention in Neuroinflammation and Alzheimer's and Parkinson's Diseases

PURPOSE OF REVIEW

The gut microbiota plays a crucial role in the pathogenesis of neuroinflammation and Alzheimer's and Parkinson's diseases. One of the main modulators of the gut microbiota is the diet, which directly influences host homeostasis and biological processes. Some dietary patterns can affect neurodegenerative diseases' progression through gut microbiota composition, gut permeability, and the synthesis and secretion of microbial-derived neurotrophic factors and neurotransmitters. This comprehensive review critically assesses existing studies investigating the impact of dietary interventions on the modulation of the microbiota in relation to neurodegenerative diseases and neuroinflammation.

RECENT FINDINGS

There are limited studies on the effects of specific diets, such as the ketogenic diet, Mediterranean diet, vegetarian diet, and Western diet, on the progression of neuroinflammation and Alzheimer's and Parkinson's diseases through the gut-brain axis. The ketogenic diet displays promising potential in ameliorating the clinical trajectory of mild cognitive impairment and Alzheimer's disease. However, conflicting outcomes were observed among various studies, highlighting the need to consider diverse types of ketogenic diets and their respective effects on clinical outcomes and gut microbiota composition. Vegetarian and Mediterranean diets, known for their anti-inflammatory properties, can be effective against Parkinson's disease, which is related to inflammation in the gut environment. On the other hand, the westernization of dietary patterns was associated with reduced gut microbial diversity and metabolites, which ultimately contributed to the development of neuroinflammation and cognitive impairment. Various studies examining the impact of dietary interventions on the gut-brain axis with regard to neuroinflammation and Alzheimer's and Parkinson's diseases are thoroughly reviewed in this article. A strong mechanistic explanation is required to fully understand the complex interactions between various dietary patterns, gut microbiota, and microbial metabolites and the effects these interactions have on cognitive function and the progression of these diseases.

High-Caloric Diets in Adolescence Impair Specific GABAergic Subpopulations, Neurogenesis, and Alter Astrocyte Morphology

We compared the effects of two different high-caloric diets administered to 4-week-old rats for 12 weeks: a diet rich in sugar (30% sucrose) and a cafeteria diet rich in sugar and high-fat foods. We focused on the hippocampus, particularly on the gamma-aminobutyric acid (GABA)ergic system, including the Ca2+-binding proteins parvalbumin (PV), calretinin (CR), calbindin (CB), and the neuropeptides somatostatin (SST) and neuropeptide Y (NPY). We also analyzed the density of cholinergic varicosities, brain-derived neurotrophic factor (BDNF), reelin (RELN), and cyclin-dependent kinase-5 (CDK-5) mRNA levels, and glial fibrillary acidic protein (GFAP) expression. The cafeteria diet reduced PV-positive neurons in the granular layer, hilus, and CA1, as well as NPY-positive neurons in the hilus, without altering other GABAergic populations or overall GABA levels. The high-sugar diet induced a decrease in the number of PV-positive cells in CA3 and an increase in CB-positive cells in the hilus and CA1. No alterations were observed in the cholinergic varicosities. The cafeteria diet also reduced the relative mRNA expression of RELN without significant changes in BDNF and CDK5 levels. The cafeteria diet increased the number but reduced the length of the astrocyte processes. These data highlight the significance of determining the mechanisms mediating the observed effects of these diets and imply that the cognitive impairments previously found might be related to both the neuroinflammation process and the reduction in PV, NPY, and RELN expression in the hippocampal formation.

Western diet increases brain metabolism and adaptive immune responses in a mouse model of amyloidosis

Diet-induced increase in body weight is a growing health concern worldwide. Often accompanied by a low-grade metabolic inflammation that changes systemic functions, diet-induced alterations may contribute to neurodegenerative disorder progression as well. This study aims to non-invasively investigate diet-induced metabolic and inflammatory effects in the brain of an APPPS1 mouse model of Alzheimer's disease. [18F]FDG, [18F]FTHA, and [18F]GE-180 were used for in vivo PET imaging in wild-type and APPPS1 mice. Ex vivo flow cytometry and histology in brains complemented the in vivo findings. 1H- magnetic resonance spectroscopy in the liver, plasma metabolomics and flow cytometry of the white adipose tissue were used to confirm metaflammatory condition in the periphery. We found disrupted glucose and fatty acid metabolism after Western diet consumption, with only small regional changes in glial-dependent neuroinflammation in the brains of APPPS1 mice. Further ex vivo investigations revealed cytotoxic T cell involvement in the brains of Western diet-fed mice and a disrupted plasma metabolome. 1H-magentic resonance spectroscopy and immunological results revealed diet-dependent inflammatory-like misbalance in livers and fatty tissue. Our multimodal imaging study highlights the role of the brain-liver-fat axis and the adaptive immune system in the disruption of brain homeostasis in amyloid models of Alzheimer's disease.

Neuronal ablation of GHSR mitigates diet-induced depression and memory impairment via AMPK-autophagy signaling-mediated inflammation

Obesity is associated with chronic inflammation in the central nervous system (CNS), and neuroinflammation has been shown to have detrimental effects on mood and cognition. The growth hormone secretagogue receptor (GHSR), the biologically relevant receptor of the orexigenic hormone ghrelin, is primarily expressed in the brain. Our previous study showed that neuronal GHSR deletion prevents high-fat diet-induced obesity (DIO). Here, we investigated the effect of neuronal GHSR deletion on emotional and cognitive functions in DIO. The neuron-specific GHSR-deficient mice exhibited reduced depression and improved spatial memory compared to littermate controls under DIO. We further examined the cortex and hippocampus, the major regions regulating cognitive and emotional behaviors, and found that the neuronal deletion of GHSR reduced DIO-induced neuroinflammation by suppressing proinflammatory chemokines/cytokines and decreasing microglial activation. Furthermore, our data showed that neuronal GHSR deletion suppresses neuroinflammation by downregulating AMPK-autophagy signaling in neurons. In conclusion, our data reveal that neuronal GHSR inhibition protects against DIO-induced depressive-like behavior and spatial cognitive dysfunction, at least in part, through AMPK-autophagy signaling-mediated neuroinflammation.

Effects of metformin on behavioral alterations produced by chronic sucrose consumption in male rats

Excessive consumption of sugary drinks negatively impacts the developing brain, producing long-lasting behavioral and metabolic disorders. Here, we study whether treatment with the antihyperglycemic agent metformin prevents some of the anxiety and memory alterations produced by chronic sucrose consumption. Male Sprague-Dawley rats had unrestricted access to water (control group) and a bottle containing a 10% sucrose solution (sucrose group, SUC) for 35 days. In parallel, a group of animals from SUC received metformin (25 mg/kg or 50 mg/kg, orally; MET 25 and MET 50 groups, respectively). After 2 weeks of metformin treatment, the animals weighed less than controls. SUC and MET 50 groups compensated for the caloric intake from the sugary solution by consuming less chow. In contrast, total energy intake in MET 25 was higher than the rest of the groups, but they still weighed less than control and SUC groups, suggesting that at this concentration, metformin delays body growth. The animals were then tested for the open field (OF), elevated plus maze (EPM) and novel object location (NOL) tests. In the OF, SUC animals spent more time in the central zone of the arena, evidenced by an increased number of entries and the distance traveled there. In the EPM, SUC animals spent more time in the open arms and less time in the central square. Metformin treatment prevented the decreased anxiety observed in SUC animals in the OF and EPM. In the NOL test, SUC animals showed less interest in novelty and metformin treatment did not improve this alteration. The preference for open spaces in the OF and EPM were associated with increased serum triglycerides (TG) and malondialdehyde levels in the medial prefrontal cortex (mPFC) and the hippocampus (HIP), while poor memory performance was associated with high basal blood glucose levels. In conclusion, the decreased anxiety-like behavior produced by chronic sucrose consumption was prevented by metformin treatment, through a mechanism that probably involves normalization of TG levels and decreased oxidative stress in mPFC and HIP.

Chronic Variable Stress and Cafeteria Diet Combination Exacerbate Microglia and c-fos Activation but Not Experimental Anxiety or Depression in a Menopause Model

The menopause transition is a vulnerable period for developing both psychiatric and metabolic disorders, and both can be enhanced by stressful events worsening their effects. The present study aimed to evaluate whether a cafeteria diet (CAF) combined with chronic variable stress (CVS) exacerbates anxious- or depressive-like behavior and neuronal activation, cell proliferation and survival, and microglia activation in middle-aged ovariectomized (OVX) rats. In addition, body weight, lipid profile, insulin resistance, and corticosterone as an index of metabolic changes or hypothalamus-pituitary-adrenal (HPA) axis activation, and the serum pro-inflammatory cytokines IL-6, IL-β, and TNFα were measured. A CAF diet increased body weight, lipid profile, and insulin resistance. CVS increased corticosterone and reduced HDL. A CAF produced anxiety-like behaviors, whereas CVS induced depressive-like behaviors. CVS increased serum TNFα independently of diet. A CAF and CVS separately enhanced the percentage of Iba-positive cells in the hippocampus; the combination of factors further increased Iba-positive cells in the ventral hippocampus. A CAF and CVS increased the c-fos-positive cells in the hippocampus; the combination of factors increased the number of positive cells expressing c-fos in the ventral hippocampus even more. The combination of a CAF and CVS generates a slight neuroinflammation process and neuronal activation in a hippocampal region-specific manner and differentially affects the behavior.

The Impact of Free and Added Sugars on Cognitive Function: A Systematic Review and Meta-Analysis

A relationship between excessive sugar consumption and cognitive function has been described in animal models, but the specific effects of sugars in humans remains unclear. This systematic review and meta-analysis aimed to evaluate the current knowledge, research characteristics, and quality of evidence of studies investigating the impacts of free and added sugars on human cognition in healthy participants. The review identified 77 studies (65 experimental trials, n = 3831; 9 cross-sectional studies, n = 11,456; and 3 cohort studies, n = 2059). All cohort studies and eight of the nine cross-sectional studies found significant positive correlations between added sugar consumption and risk of cognitive impairment. Four studies identified reduced risk of cognitive impairment associated with natural fructose-containing foods. The majority of randomised control trials assessed short-term glucose facilitation effects on cognitive outcomes. The results from these studies suggest the need for a tightly regulated blood glucose level, dependent on individualised physiological factors, for optimal cognitive function. A meta-analysis of a subset of studies that assessed the impact of glucose on recall found improvements in immediate free recall compared to controls (p = 0.002). The findings highlight the potentially detrimental effect of excessive, long-term, or prenatal added sugar consumption on cognitive function. Further research is needed to examine the specific effects of free and added sugars on cognitive function.

The influence of ultra-processed food consumption on reward processing and energy intake: Background, design, and methods of a controlled feeding trial in adolescents and young adults

BACKGROUND

The greatest age-related weight gain occurs in the early/mid-20s. Overall dietary quality among adolescents and emerging adults (age 18-25) is poor, with ultra-processed foods (UPF) representing more than two-thirds of adolescents' total energy intake (i.e., 68%). UPF consumption may impact cognitive and neurobiological factors that influence dietary decision-making and energy intake (EI). To date, no research has addressed this in this population.

METHODS

Participants aged 18-25 will undergo two 14-day controlled feeding periods (81% UPF, 0% UPF) using a randomly assigned crossover design, with a 4-week washout between conditions. Brain response to a UPF-rich milkshake, as well as behavioral measures of executive function, will be evaluated before and after each diet. Following each diet, measurements include ad libitum buffet meal EI, food selection, eating rate, and eating in the absence of hunger (EAH). Prior to initiating recruitment, controlled diet menus, buffet, and EAH snacks were developed and evaluated for palatability. Sensory and texture attributes of buffet and EAH snack foods were also evaluated.

RESULTS

Overall diet palatability was rated "like very much" (8)/"like moderately"(7) (UPF: 7.6 ± 1.0; Non-UPF: 6.8 ± 1.5). Subjective hardness rating (range = 1-9 [1 = soft, 9 = hard] was similar between UPF and Non-UPF buffet and snack items (UPF:4.22 ± 2.19, Non-UPF: 4.70 ± 2.03), as was the objective measure of hardness (UPF: 2874.33 ± 2497.06 g, Non-UPF: 2243.32 ± 1700.51 g).

CONCLUSIONS

Findings could contribute to an emerging neurobiological understanding of the effects of UPF consumption including energy overconsumption and weight gain among individuals at a critical developmental stage.

The Effect of Fat Intake with Increased Omega-6-to-Omega-3 Polyunsaturated Fatty Acid Ratio in Animal Models of Early and Late Alzheimer's Disease-like Pathogenesis

This work aims to clarify the effect of dietary polyunsaturated fatty acid (PUFA) intake on the adult brain affected by amyloid pathology. McGill-R-Thy1-APP transgenic (Tg) rat and 5xFAD Tg mouse models that represent earlier or later disease stages were employed. The animals were exposed to a control diet (CD) or an HFD based on corn oil, from young (rats) or adult (mice) ages for 24 or 10 weeks, respectively. In rats and mice, the HFD impaired reference memory in wild-type (WT) animals but did not worsen it in Tg, did not cause obesity, and did not increase triglycerides or glucose levels. Conversely, the HFD promoted stronger microglial activation in Tg vs. WT rats but had no effect on cerebral amyloid deposition. IFN-γ, IL-1β, and IL-6 plasma levels were increased in Tg rats, regardless of diet, while CXCL1 chemokine levels were increased in HFD-fed mice, regardless of genotype. Hippocampal 3-nitrotyrosine levels tended to increase in HFD-fed Tg rats but not in mice. Overall, an HFD with an elevated omega-6-to-omega-3 ratio as compared to the CD (25:1 vs. 8.4:1) did not aggravate the outcome of AD regardless of the stage of amyloid pathology, suggesting that many neurobiological processes relevant to AD are not directly dependent on PUFA intake.

High-fat diet negatively affects brain markers, cognitive behaviors, and noncognitive behaviors in the rTg4510 tau mouse model

Alzheimer's disease (AD) drastically impacts cognitive and noncognitive behaviors in both humans and animal models. Two hallmark proteins in AD, amyloid-β plaques and tau neurofibrillary tangles, accumulate in regions of the brain critical for learning and memory, including the hippocampus. Poor dietary choices have been shown to exacerbate cognitive deficits seen in AD. In this study, we assessed the effects of a high-fat diet (HFD - 60 kcal% fat) on cognitive & noncognitive behaviors as well as on brain markers in the rTg4510 tau mouse model. While all mice learned the Morris Water Maze (MWM) task, it was noted that on the last day of acquisition female tau mice had a significantly higher latency to find the platform than male tau mice (p < 0.01). Mice given the HFD spent significantly less time in the target quadrant than those given a control diet (CD) (p < 0.05). Tau mice showed impaired burrowing (p < 0.05) and nesting behaviors (p < 0.001) compared to WT mice and HFD administration worsened burrowing in tau mice. Tau mice exhibited greater levels of glial fibrillary acidic protein (GFAP) (p < 0.05) and significantly less hippocampal cell density than WT mice (p < 0.001). We observed trends of HFD mice having greater levels of GFAP and greater average tangle size than CD mice. These results highlight the importance of dietary choices, especially in older populations more susceptible to AD and its effects.

Obesity-mediated Lipoinflammation Modulates Food Reward Responses

Accumulation of white adipose tissue (WAT) during obesity is associated with the development of chronic low-grade inflammation, a biological process known as lipoinflammation. Systemic and central lipoinflammation accumulates pro-inflammatory cytokines including IL-6, IL-1β and TNF-α in plasma and also in brain, disrupting neurometabolism and cognitive behavior. Obesity-mediated lipoinflammation has been reported in brain regions of the mesocorticolimbic reward circuit leading to alterations in the perception and consumption of ultra-processed foods. While still under investigation, lipoinflammation targets two major outcomes of the mesocorticolimbic circuit during food reward: perception and motivation ("Wanting") and the pleasurable feeling of feeding ("Liking"). This review will provide experimental and clinical evidence supporting the contribution of obesity- or overnutrition-related lipoinflammation affecting the mesocorticolimbic reward circuit and enhancing food reward responses. We will also address neuroanatomical targets of inflammatory profiles that modulate food reward responses during obesity and describe potential cellular and molecular mechanisms of overnutrition linked to addiction-like behavior favored by brain lipoinflammation.

Free-choice high-fat diet consumption reduces lateral hypothalamic GABAergic activity, without disturbing neural response to sucrose drinking in mice

Nutrition can influence the brain and affect its regulation of food intake, especially that of high-palatable foods. We hypothesize that fat and sugar have interacting effects on the brain, and the lateral hypothalamus (LH) is a prime candidate to be involved in this interaction. The LH is a heterogeneous area, crucial for regulating consummatory behaviors, and integrating homeostatic and hedonic needs. GABAergic LH neurons stimulate feeding when activated, and are responsive to consummatory behavior while encoding sucrose palatability. Previously, we have shown that glutamatergic LH neurons reduce their activity in response to sugar drinking and that this response is disturbed by a free-choice high-fat diet (fcHFD). Whether GABAergic LH neurons, and their response to sugar, is affected by a fcHFD is yet unknown. Using head-fixed two-photon microscopy, we analyzed activity changes in LHVgat neuronal activity in chow or fcHFD-fed mice in response to water or sucrose drinking. A fcHFD decreased overall LHVgat neuronal activity, without disrupting the sucrose-induced increase. When focusing on the response per unique neuron, a vast majority of neurons respond inconsistently over time. Thus, a fcHFD dampens overall LH GABAergic activity, while it does not disturb the response to sucrose. The inconsistent responding over time suggests that it is not one specific subpopulation of LH GABAergic neurons that is driving these behaviors, but rather a result of the integrative properties of a complex neural network. Further research should focus on determining how this dampening of LH GABAergic activity contributes to hyperphagia and the development of obesity.

Obesogenic Diet Cycling Produces Graded Effects on Cognition and Microbiota Composition in Rats

SCOPE

The effects of diet cycling on cognition and fecal microbiota are not well understood.

METHOD AND RESULTS

Adult male Sprague-Dawley rats were cycled between a high-fat, high-sugar "cafeteria" diet (Caf) and regular chow. The impairment in place recognition memory produced by 16 days of Caf diet was reduced by switching to chow for 11 but not 4 days. Next, rats received 16 days of Caf diet in 2, 4, 8, or 16-day cycles, each separated by 4-day chow cycles. Place recognition memory declined from baseline in all groups and was impaired in the 16- versus 2-day group. Finally, rats received 24 days of Caf diet continuously or in 3-day cycles separated by 2- or 4-day chow cycles. Any Caf diet access impaired cognition and increased adiposity relative to controls, without altering hippocampal gene expression. Place recognition and adiposity were the strongest predictors of global microbiota composition. Overall, diets with higher Caf > chow ratios produced greater spatial memory impairments and larger shifts in gut microbiota species richness and beta diversity.

CONCLUSION

Results suggest that diet-induced cognitive deficits worsen in proportion to unhealthy diet exposure, and that shifting to a healthy chow for at least a week is required for recovery under the conditions tested here.

Elateriospermum tapos Yoghurt as a Therapeutic Intervention for Obesity-Associated Cognitive Impairments and Anxiety-like Behaviour in a High Fat Diet Maternal Obese Rat Model

Maternal obesity can be considered an intergenerational cycle and is also an important indicator of cognitive impairments. It is thought that using natural products is the best and safest way to combat maternal obesity and associated complications. Recent studies have shown that Elateriospermum tapos (E. tapos) contains bioactive compounds with anti-obesity effects, and yoghurt is a convenient medium for supplementing obese maternal rats with E. tapos extract. Thus, the aim of this study is to investigate the impact of E. tapos in yoghurt on maternally obese rats' cognitive function supplemented with a high-fat diet (HFD). In this study, 48 female Sprague-Dawley rats were used. The rats were fed HFD for a period of 16 weeks to induce obesity, after which they were allowed to mate. Upon confirmation of pregnancy, obese rats were given varying doses of E. tapos (5, 50, and 500 mg/kg) in yoghurt until postnatal (PND) day 21. On PND 21, the dams' body mass index (BMI), Lee index, abdominal circumference, oxidative status, and metabolic profile were measured. The behavioral tests (open field, place, and object recognition) were conducted on PND 21 to access memory. The results show that the 50 and 500 mg/kg E. tapos in yoghurt supplemented groups had similar BMI, Lee index, abdominal circumference, lipid profile, FBG, insulin, FRAP, and GSH levels, as well as a similar recognition index, in comparison with the control group supplemented with saline. In conclusion, the results of this study indicate that the newly formulated E. tapos in yogurt can act as an anti-obesity agent in maternal obesity, alleviate anxiety, and enhance hippocampal-dependent memory.

Childhood obesity is linked to putative neuroinflammation in brain white matter, hypothalamus, and striatum

Neuroinflammation is both a consequence and driver of overfeeding and weight gain in rodent obesity models. Advances in magnetic resonance imaging (MRI) enable investigations of brain microstructure that suggests neuroinflammation in human obesity. To assess the convergent validity across MRI techniques and extend previous findings, we used diffusion basis spectrum imaging (DBSI) to characterize obesity-associated alterations in brain microstructure in 601 children (age 9-11 years) from the Adolescent Brain Cognitive DevelopmentSM Study. Compared with children with normal-weight, greater DBSI restricted fraction (RF), reflecting neuroinflammation-related cellularity, was seen in widespread white matter in children with overweight and obesity. Greater DBSI-RF in hypothalamus, caudate nucleus, putamen, and, in particular, nucleus accumbens, correlated with higher baseline body mass index and related anthropometrics. Comparable findings were seen in the striatum with a previously reported restriction spectrum imaging (RSI) model. Gain in waist circumference over 1 and 2 years related, at nominal significance, to greater baseline RSI-assessed restricted diffusion in nucleus accumbens and caudate nucleus, and DBSI-RF in hypothalamus, respectively. Here we demonstrate that childhood obesity is associated with microstructural alterations in white matter, hypothalamus, and striatum. Our results also support the reproducibility, across MRI methods, of findings of obesity-related putative neuroinflammation in children.

Remodulation Effect of Elateriospermum tapos Yoghurt on Metabolic Profile of Maternal Obesity Induced Cognitive Dysfunction and Anxiety-like Behavior in Female Offspring-An In Vivo Trial on Sprague Dawley Rats

Pre-pregnancy weight gain induces dysregulation in the metabolic profile of the offspring, thereby serving as a key factor for cognitive decline and anxiety status in the offspring. However, early probiotic supplementation during the gestational period is linked with improved metabolic health. At the same time, a natural plant known as Elateriospermum tapos (E. tapos) is proven to improve cognition and modulate the stress hormone due to its high concentration of flavonoids. However, the effects of medicinal plant integrated probiotics in F1 generations warrants further investigation. Thus, this study aimed to study the effect of E. tapos yoghurt on the maternal obesity induced cognitive dysfunction and anxiety in female offspring. In this study, female Sprague Dawley rats were fed with normal chow (n = 8) or high fat diet (n = 40) across pre-pregnancy, gestation, and weaning. The treatment with different concentrations of E. tapos yoghurt (5, 50, and 500 mg/kg/day) were initiated in the obese dams upon post coitum day 0 up to postnatal day 21 (PND 21). Female offspring were weaned on PND 21 and body mass index, waist circumference, lee index, behavior, metabolic parameter, and antioxidant status were analyzed. The result shows that the female offspring of the 500 mg/kg E. tapos yoghurt supplemented group shows a decreased level of insulin, fasting blood glucose, cholesterol, triglycerides, LDL, low fat tissue mass with a high level of HDL, and an increased level of antioxidant status in the hypothalamus. The behavioral assessment proves that the female offspring of the 500 mg/kg E. tapos yoghurt supplemented group exhibits a high recognition index on novel object/place with low anxiety-like behavior in an open field test. In conclusion, our data signify the beneficial effect of early intervention in obese dams on the transgenerational impact on female offspring's metabolic profile, cognitive performance, and anxiety-like behavior.

Short-term Cafeteria Diet Is Associated with Fat Mass Accumulation, Systemic and Amygdala Inflammation, and Anxiety-like Behavior in Adult Male Wistar Rats

Obesity is linked to metabolic, hormonal and biochemical alterations, and is also a risk factor for behavioral disorders. Evidence suggests that these disorders may be related to the consumption of hypercaloric diets, fat mass accumulation and changes in inflammation and redox status. Although much is known about the chronic effects of hypercaloric diets on mental health, few studies have evaluated the consequences of short-term exposure of these diets on behavior. The aim of this study was to evaluate nutritional, behavioral (anxiety-like), inflammatory and redox status parameters in adult male Wistar rats exposed to short-term cafeteria diet. Adult Wistar male rats (90 days-old; n = 12/group) received, during 14 days, the diets: Control- standard diet; Simple Cafeteria Diet (SCD)- homogeneous cafeteria diet. Varied Cafeteria Diet (VCD)- cafeteria diet with rotation and variation. Nutritional analyzes and tests for anxiety-like behaviors were performed, in addition to inflammatory and redox status measurements in blood and amygdala. The SCD group showed higher fat energy intake, while the VCD group consumed more energy from carbohydrates. SCD and VCD showed higher fat mass accumulation, in addition to higher levels of TNFα, INFγ, TBARS and FRAP in the blood. Also, SCD and VCD groups reported high levels of TNFα in the amygdala. Regarding behavioral evaluations, SCD and VCD groups showed anxiogenesis in the elevated plus maze, light-dark box, and open field tests. Therefore, the two cafeteria diets induced obesity and systemic inflammation, which in turn, resulted in an increase in amygdala TNFα levels and anxiety-like behaviors in Wistar rats.

Early Intervention of Elateriospermum tapos Yoghurt in Obese Dams Mitigates Intergenerational Cognitive Deficits and Thigmotactic Behaviour in Male Offspring via the Modulation of Metabolic Profile

Maternal obesity is an intergenerational vicious cycle and one of the primary causes of cognitive deficits and high anxiety levels in offspring, which often manifest independently of sex. It is proven that curbing the intergenerational inheritance of obesity through early intervention during the gestation period has a positive outcome on the body composition, cognitive function, and anxiety level of the offspring. A recent discovery shows that the consumption of Elateriospermum tapos (E. tapos) seed extract modulates body mass and ameliorates stress hormones in obese dams, while a probiotic bacterial strain can cross the placenta and boost a child's memory. Thus, we speculate that probiotics are the best medium to integrate plant extract (E. tapos extract) to access the effect on the child's cognition. Thus, this study aimed to investigate the early intervention of E. tapos yoghurt in obese dams in the cognition and anxiety levels of male offspring. In this study, 40 female rats were fed with a high-fat diet (HFD) to induce obesity before pregnancy, while another 8 rats were fed with standard rat pellets for 16 weeks. Upon successful copulation, treatment was initiated for the obese dams up to the postnatal day (PND) 21. The groups included normal chow and saline (NS), HFD and saline (HS), HFD and yoghurt (HY), HFD and 5 mg/kg E. tapos yoghurt (HYT5), HFD and 50 mg/kg E. tapos yoghurt (HYT50), and HFD and 500 mg/kg E. tapos yoghurt (HYT500). All rats were euthanised on PND 21, and the body mass index (BMI), Lee index, and waist circumference were measured for the male offspring. Hippocampal-dependent memory tests and open field tests were conducted to access for cognition and anxiety status. Fasting blood glucose (FBG), total fat (%), insulin, leptin, lipid profile, and antioxidant parameter on serum and hypothalamus (FRAP and GSH) were accessed on PND 21. The result shows male offspring of 50 mg/kg-supplemented obese dams have comparable total fat (%), lipid profile, insulin level, FBG level, plasma insulin level, recognition index, low anxiety level, and improved hypothalamic FRAP and GSH levels to the normal group. In conclusion, this study highlights that the effect of early intervention of our novel formulation of E. tapos yoghurt in obese dams alleviates cognitive deficits and anxiety in male offspring by modulating metabolic profiles at the dose of 50 mg/kg.

Something to Snack on: Can Dietary Modulators Boost Mind and Body?

The last decades have shown that maintaining a healthy and balanced diet can support brain integrity and functionality, while an inadequate diet can compromise it. However, still little is known about the effects and utility of so-called healthy snacks or drinks and their immediate short-term effects on cognition and physical performance. Here, we prepared dietary modulators comprising the essential macronutrients at different ratios and a controlled balanced dietary modulator. We assessed, in healthy adult mice, the short-term effects of these modulators when consumed shortly prior to tests with different cognitive and physical demands. A high-fat dietary modulator sustained increased motivation compared to a carbohydrate-rich dietary modulator (p = 0.041) which had a diminishing effect on motivation (p = 0.018). In contrast, a high-carbohydrate modulator had an initial beneficial effect on cognitive flexibility (p = 0.031). No apparent effects of any of the dietary modulators were observed on physical exercise. There is increasing public demand for acute cognitive and motor function enhancers that can improve mental and intellectual performance in daily life, such as in the workplace, studies, or sports activities. Our findings suggest such enhancers should be tailored to the cognitive demand of the task undertaken, as different dietary modulators will have distinct effects when consumed shortly prior to the task.

Body fat and components of sarcopenia relate to inflammation, brain volume and neurometabolism in older adults

Obesity and sarcopenia are associated with cognitive impairments at older age. Current research suggests that blood biomarkers may mediate this body-brain crosstalk, altering neurometabolism and brain structure eventually resulting in cognitive performance changes. Seventy-four older adults (60-85 years old) underwent bio-impedance body composition analysis, handgrip strength measurements, 8-Foot Up-and-Go (8UG) test, Montreal Cognitive Assessment (MoCA), blood analysis of interleukin-6 (IL-6), kynurenine, and insulin-like growth factor-1 (IGF-1), as well as brain magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (¹H-MRS), estimating neurodegeneration and neuroinflammation. Normal fat% or overweight was associated with larger total gray matter volume compared to underweight or obesity in older adults and obesity was associated with higher N-acetylaspartate/Creatine levels in the sensorimotor and dorsolateral prefrontal cortex. Muscle strength, not muscle mass/physical performance, corresponded to lower kynurenine and higher N-acetylaspartate/Creatine levels in the dorsal posterior cingulate and dorsolateral prefrontal cortex. The inflammatory and neurotrophic blood biomarkers did not significantly mediate these body-brain associations. This study used a multimodal approach to comprehensively assess the proposed mechanism of body-brain crosstalk.

Inflammation, depression, and anxiety related to recognition memory in young adults

Previous research suggests that common modifiable health risk factors (e.g., depression, anxiety, metabolic illness, inflammation) may have an impact on memory. In the present study, we sought to investigate relationships between a number of these health risk factors and two components of recognition memory (recollection and familiarity). Data were analyzed for 96 healthy young adults between 17 and 25 years old. Recollection and familiarity were measured using an associative recognition procedure involving unitized and unrelated word pairs, and regression analyses were used to relate recognition memory performance to physical health (inflammation via plasma IL-6 levels, central obesity via waste-to-hip ratio, and heart rate variability) and mental health (depression via CESD-R, stress via PSS, and state and personality trait anxiety via STAI) measures of modifiable risk factors. Together, these health variables predicted an additional 19% of the variance in recollection beyond what was accounted for by familiarity, and 15% of the variance in familiarity beyond what was accounted for by recollection. These effects were primarily driven by inflammation, depression, and trait anxiety, which were each significant (p < .05) independent predictors of recognition. Higher levels of depression and inflammation were related to worse recollection yet better familiarity. Higher levels of trait anxiety were related to better recollection but were not related to familiarity. These findings demonstrate complex relationships between these modifiable health risk factors and recognition memory. Future longitudinal and cross-sectional research is needed to further explore these relationships and determine whether or not poor health causes these changes in recognition.

Self-Reported Dietary Habits and Intensity of Negative Emotions: From a Population of Moroccan University Students

Emotional disorders are an ever-increasing problem in our society, accounting for a significant portion of the global burden of disease. A healthy and balanced diet is now one of the promising avenues for the prevention and care of psychiatric disorders. The principal objective of this cross-sectional study was to analyze the relationship between eating habits, frequency of consumption of certain foods, and mental well-being in a sample of students. A food frequency questionnaire was developed to describe participants' eating habits. The DAS21 self-questionnaire was used to assess the intensity of negative emotions associated with depression, anxiety, and stress. The age of the participants, who numbered 620, varied from 18 to 25 years (mean age: 22.32 years). The consumption of the different foods studied was varied, with a low consumption of fruits and vegetables. The prevalence of emotional disorders was high among the students. Skipping breakfast had a negative impact on mental well-being. High frequency of consumption of apples, seafood, kiwi, dried fruits, sardines, olive oil, green leafy vegetables, tomatoes, carrots and apricots was beneficial to the mental health of students. This suggests that healthy eating behaviours based on a balanced diet may be an interesting avenue for preventing and treating psychopathological disorders.

Long-Term Memory Function Impairments following Sucrose Exposure in Juvenile versus Adult Rats

We previously described that excessive consumption of sucrose during youth produces fear memory and anxiety-like behavior in adulthood. Here, we evaluated whether high cognitive function is also affected by studying early sucrose consumption in object recognition memory (NOR). Male Sprague Dawley rats were tested for short-term, long-term, and consolidated NOR after 25 days of unlimited sucrose access in juvenile (PD 25–50) or adult age (PD 75–100). All rats spent equal time exploring the two objects during the sample phase T1. When animals were exposed for 2, 24 h or 7 days later to a copy of the objects presented in T1 and a novel object, the sucrose-exposed juvenile group failed to distinguish between the familiar and the novel objects in contrast with the rest of the groups. Sucrose-exposed animals developed hypertriglyceridemia and glucose intolerance, but juvenile animals showed increased fasting glycemia and sustained the glucose intolerance longer. Moreover, sucrose decreased hippocampal proBDNF expression in juveniles while it was increased in adults, and sucrose also increased RAGE expression in adults. The NOR exploration ratio correlated negatively with basal glycemia and positively with proBDNF. Taken together, these data suggest that sucrose-induced alterations in glucose metabolism may contribute to a long-term decline in proBDNF and impaired recognition memory.

IL10/AMPK pathway was associated with the hippocampal anti-inflammatory response to high-sugar and high-fat diet withdrawal

OBJECTIVE

The present experimental study aimed to evaluate the effect of consuming an obesogenic diet (OD) on serum and hippocampal inflammation and proteins related to energy metabolism, alongside, we evaluated how the same parameters responded to an OD withdrawal.

SUBJECTS

Thirty male 60-days-old Wistar rats were used.

METHODS

The control group (n = 10) was fed the control diet across the whole experiment. The remaining animals were fed a high-sugar/high-fat (HSHF) diet for 30 days (n = 20) and half of them were placed on the control diet for 48 h (n = 10) afterwards.

RESULTS

OD intake decreased hippocampal AMPK phosphorylation, although, it did not increase serum inflammation and only increased hippocampal pNFκBp65 levels without any increase in the cytokines assessed. Moreover, OD withdrawal led to higher inflammatory markers in the serum and hippocampus and higher hippocampal AMPK phosphorylation. The mediation models applied suggested that the effect of OD withdrawal on hippocampal inflammation was driven by serum inflammation, which activated the hippocampal IL10/AMPK anti-inflammatory pathway as a response.

CONCLUSION

Our analyses suggest that OD withdrawal increases serum inflammation with hippocampal consequent inflammatory alterations. Despite the general assumption that improving diet improves health, this may not be immediate.

Cognitive Function Is Associated With Multiple Indices of Adiposity in the Canadian Longitudinal Study on Aging: A Cross-Sectional Analysis

OBJECTIVE

Prior studies have suggested reciprocal relationships between cognitive function and adiposity, but this has not been investigated with population representative data sets. The purpose of this study was to examine the association between cognitive function and adiposity in a large population-based sample of middle-aged and older adults. It was hypothesized that better scores on tests of cognitive function would be associated with lower adiposity, and this association would be primarily mediated through life-style behavior and physical health status.

METHODS

Using baseline data from the Canadian Longitudinal Study on Aging ( N = 30,097), we tested our hypotheses using three indicators of cognitive function (animal fluency, Stroop interference, and reaction time) and four indicators of adiposity (body mass index, total fat mass, waist circumference, and waist-hip ratio). Hierarchical multivariable linear regression modeling was conducted followed by tests for moderation by socioeconomic status and mediation through diet, physical activity, hypertension, and diabetes status.

RESULTS

All measures of cognitive indicators were significantly associated with adiposity after adjusting for confounders. In general, superior performance on animal fluency, Stroop, and reaction time tasks were associated with lower adiposity by most metrics. Stroop interference was associated with lower adiposity across all metrics, including body mass index ( b = - 0.04, 95 % confidence interval [CI] = - 0.06  to - 0.01), total fat mass ( b = 19.35, 95 % CI = 8.57  to 30.12), waist circumference ( b = 33.83, 95 % CI = 10.08  to 57.58), and waist-hip ratio ( b = 0.13, 95 % CI = 0.01  to 0.24). These associations were more substantial for moderate- and high-income subpopulations. Mediation analyses suggested that the aforementioned effects were mediated through life-style behavior (e.g., diet and physical activity) and physical health conditions (e.g., diabetes and hypertension).

CONCLUSIONS

Reliable associations exist between cognitive function and adiposity in middle-aged and older adults. The associations seem to be mediated through life-style behavior and physical health conditions.

Appetitive interoception, the hippocampus and western-style diet

Obesity, Type 2 diabetes and other metabolic disorders continue to pose serious challenges to human health and well-being. An important source of these challenges is the overconsumption of saturated fats and sugar, main staples of what has been called the Western-style diet (WD). The current paper describes a theoretical model and supporting evidence that links intake of a WD to interference with a specific brain substrate that underlies processing of interoceptive signals of hunger and satiety. We review findings from rats and humans that the capacity of these signals to modulate the strength of appetitive and eating behavior depends on the functional integrity of the hippocampus and the learning memory operations it performs. Important among these operations is the use of contextual information to retrieve memories that are associated with other events. Within our framework, satiety provides an interoceptive context that informs animals that food cues and appetitive behavior will not be followed by rewarding postingestive outcomes. This serves to prevent those cues and responses from retrieving those reward memories. The findings reviewed provide evidence that consuming a WD and the high amounts of saturated fat and sugar it contains (a) is associated with the emergence of pathophysiologies to which the hippocampus appears selectively vulnerable (b) impairs hippocampal-dependent learning and memory (HDLM) and (c) weakens behavioral control by interoceptive hunger and satiety contextual stimuli. It is hypothesized that these consequences of WD intake may establish the conditions for a vicious cycle of further WD intake, obesity, and potentially cognitive decline.

Neuroinflammatory responses following zinc or branched-chain amino acids supplementation in obese rats

The excessive production of pro-inflammatory mediators, characteristic of obesity, leads to neuroinflammation. Zinc (Zn) and the branched-chain amino acids (BCAA) are supplements known for their immunomodulatory properties. Our goal was to evaluate if Zn or BCAA supplementation can affect long-term recognition memory and neuroinflammatory parameters of obese rats after a high-fat diet (HFD). Three-month-old Wistar rats were divided into six groups: Standard diet (SD) + vehicle; SD + Zn; SD + BCAA; High-fat diet (HFD) + vehicle; HFD + Zn; and HFD + BCAA. Diets were administrated for 19 weeks, Zn (1,2 mg/kg/day) or BCAA (750 mg/kg/day) supplementation was conducted in the last 4 weeks. Long-term recognition memory was evaluated by the novel object recognition test. IL-1β immunoreactivity in the cortex and hippocampus, and IL-6 levels in the cortex tissue were assessed. Astrogliosis were evaluated through GFAP + cell count and morphological analysis (Sholl Method). Zn supplementation improved object recognition memory in HFD-fed rats, which was not observed following BCAA supplementation. The levels of IL-6 in the cerebral cortex were higher after HFD, which was not diminished after neither supplementation. Obesity also led to increased IL-1β immunoreactivity in the cerebral cortex and hippocampus, which was reduced by Zn. BCAA supplementation also diminished IL-1β immunoreactivity, but only in the hippocampus. We also showed that astrocyte reactivity caused by HFD is area-dependent, being the cerebral cortex more susceptible to the diet. Even though BCAA and Zn can affect IL-1β immunoreactivity and astrocyte morphology, only Zn improved memory. Future studies are needed to clarify the pathways by which Zn improves cognition in obesity.

Overnutrition Induced Cognitive Impairment: Insulin Resistance, Gut-Brain Axis, and Neuroinflammation

Overnutrition-related obesity has become a worldwide epidemic, and its prevalence is expected to steadily rise in the future. It is widely recognized that obesity exerts negative impacts on metabolic disorders such as type 2 diabetes mellitus (T2DM) and cardiovascular diseases. However, relatively fewer reports exist on the impairment of brain structure and function, in the form of memory and executive dysfunction, as well as neurogenerative diseases. Emerging evidence indicates that besides obesity, overnutrition diets independently induce cognitive impairments via multiple mechanisms. In this study, we reviewed the clinical and preclinical literature about the detrimental effects of obesity or high-nutrition diets on cognitive performance and cerebral structure. We mainly focused on the role of brain insulin resistance (IR), microbiota-gut-brain axis, and neuroinflammation. We concluded that before the onset of obesity, short-term exposure to high-nutrition diets already blunted central responses to insulin, altered gut microbiome composition, and activated inflammatory mediators. Overnutrition is linked with the changes in protein expression in brain insulin signaling, leading to pathological features in the brain. Microbiome alteration, bacterial endotoxin release, and gut barrier hyperpermeability also occur to trigger mental and neuronal diseases. In addition, obesity or high-nutrition diets cause chronic and low-grade systematic inflammation, which eventually spreads from the peripheral tissue to the central nervous system (CNS). Altogether, a large number of unknown but potential routes interact and contribute to obesity or diet-induced cognitive impairment. The challenge for future research is to identify effective interventions involving dietary shifts and personalized therapy targeting the underlying mechanisms to prevent and improve cognition deficits.

Hippocampal Endoplasmic Reticulum Stress Hastens Motor and Cognitive Decline in Adult Male Rats Sustainedly Exposed to High-Sucrose Diet

Metabolic dysfunctions, such as hyperglycemia and insulin resistance, have been associated to cognitive impairment and dementia regardless of advanced age, although the underlying mechanisms are still elusive. Thus, this study investigates the deleterious effects of metabolic syndrome (MetS) induced by long-term exposure to a high-sucrose diet on motor and cognitive functions of male adult rats and its relationship with hippocampal endoplasmic reticulum (ER) stress. Weaned Wistar male rats were fed a high-sucrose diet until adulthood (HSD; 6 months old) and compared to both age-matched (CTR; 6 months old) and middle-aged chow-fed rats (OLD; 20 months old). MetS development, serum redox profile, behavioral, motor, and cognitive functions, and hippocampal gene/protein expressions for ER stress pro-adaptive and pro-apoptotic pathways, as well as senescence markers were assessed. Prolonged exposure to HSD induced MetS hallmarked by body weight gain associated to central obesity, hypertriglyceridemia, insulin resistance, and oxidative stress. Furthermore, HSD rats showed motor and cognitive decline similar to that in OLD animals. Noteworthy, HSD rats presented marked hippocampal ER stress characterized by failure of pro-adaptive signaling and increased expression of Chop, p21, and Parp-1 cleavage, markers of cell death and aging. This panorama resembles that found in OLD rats. In toto, our data showed that early and sustained exposure to a high-sucrose diet induced MetS, which subsequently led to hippocampus homeostasis disruption and premature impairment of motor and cognitive functions in adult rats.

A Short-Term Sucrose Diet Impacts Cell Proliferation of Neural Precursors in the Adult Hypothalamus

Radial glia-like cells in the hypothalamus and dorsal vagal complex are neural precursors (NPs) located near subventricular organs: median eminence and area postrema, respectively. Their strategic position can detect blood-borne nutrients, hormones, and mitogenic signals. Hypothalamic NPs increase their proliferation with a mechanism that involves hemichannel (HC) activity. NPs can originate new neurons in response to a short-term high-fat diet as a compensatory mechanism. The effects of high carbohydrate Western diets on adult neurogenesis are unknown. Although sugars are usually consumed as sucrose, more free fructose is now incorporated into food items. Here, we studied the proliferation of both types of NPs in Sprague Dawley rats exposed to a short-term high sucrose diet (HSD) and a control diet. In tanycyte cultures, we evaluated the effects of glucose and fructose and a mix of both hexoses on HC activity. In rats fed an HSD, we observed an increase in the proliferative state of both precursors. Glucose, either in the presence or absence of fructose, but not fructose alone, induced in vitro HC activity. These results should broaden the understanding of the nutrient monitoring capacity of NPs in reacting to changes in feeding behavior, specifically to high sugar western diets.

Global Proteome Profiling of the Temporal Cortex of Female Rats Exposed to Chronic Stress and the Western Diet

The increasing consumption of highly processed foods with high amounts of saturated fatty acids and simple carbohydrates is a major contributor to the burden of overweight and obesity. Additionally, an unhealthy diet in combination with chronic stress exposure is known to be associated with the increased prevalence of central nervous system diseases. In the present study, the global brain proteome approach was applied to explore protein alterations after exposure to the Western diet and/or stress. Female adult rats were fed with the Western diet with human snacks and/or subjected to chronic stress induced by social instability for 12 weeks. The consumption of the Western diet resulted in an obese phenotype and induced changes in the serum metabolic parameters. Consuming the Western diet resulted in changes in only 5.4% of the proteins, whereas 48% of all detected proteins were affected by chronic stress, of which 86.3% were down-regulated due to this exposure to chronic stress. However, feeding with a particular diet modified stress-induced changes in the brain proteome. The down-regulation of proteins involved in axonogenesis and mediating the synaptic clustering of AMPA glutamate receptors (Nptx1), as well as proteins related to metabolic processes (Atp5i, Mrps36, Ndufb4), were identified, while increased expression was detected for proteins involved in the development and differentiation of the CNS (Basp1, Cend1), response to stress, learning and memory (Prrt2), and modulation of synaptic transmission (Ncam1, Prrt2). In summary, global proteome analysis provides information about the impact of the combination of the Western diet and stress exposure on cerebrocortical protein alterations and yields insight into the underlying mechanisms and pathways involved in functional and morphological brain alterations as well as behavioral disturbances described in the literature.

How to preserve healthy aging through nutritional strategies: The new approach of the Food Social Network (Food NET) project

BACKGROUND: Aging is a process that does not refer only to the accumulation of damage in a human being over time but rather to individual changes determined by genetic, lifestyle, social and environmental factors. Aging is one of the greatest known risk factors for most human diseases. An older person in good health has a good level of independence, weighs less on the national health system and plays a productive and active role in his/her community; thus, the concept of “healthy aging”, reflecting older adult-environment fit should be promoted. The interactions between lifestyle, including nutrition, and health play a fundamental role in the aging process; eating habits and eating behaviours are recognized as important modifiable factors potentially leading to a healthy “phenotype”. OBJECTIVE AND METHODS: A multidisciplinary consortium with three Italian universities (the University of Milano-Bicocca, University of Pavia and University of Calabria) and Italian Small-Medium Enterprises proposed the Food Social Network (Food NET) project. Food NET overall outcome is to achieve target-specific guidelines and exact technologies for accessible functional foods, aimed at improving the quality of life and nutritional status of citizens (aged>65) of the Metropolitan City of Milan (Italy). CONCLUSIONS: This project is part of the “Smart Living” and food-related strategies aimed at responding to the needs of this target population, developing new food products, appropriate to meet the specific requirements and ensuring and promoting sustainable diets for healthy aging by effective food policy approaches.

High sucrose diet does not impact spatial cognition in rats using advanced touchscreen technology

INTRODUCTION

Western diets, including those consisting of saturated fats, simple sugars and processed foods, is rising at an unprecedented rate. These lead to obesity and metabolic diseases, and possibly cognitive deficits. Exploring this, recent studies demonstrate marked impairment in spatial learning in rodents exposed to high-sugar diets. We utilised advanced touchscreen technology to assess several spatial and non-spatial components of cognition in rats chronically exposed to a high sucrose diet.

METHODS

Male Wistar rats received 70 ml of 10% sucrose solution each day, or control tap water, persisting for the experiment duration (total n = 32). After 5 weeks of diet, rats performed Pairwise Discrimination, Location Discrimination, or Progressive Ratio tasks on automated touchscreens, and performance compared between groups.

RESULTS

Sucrose rats consumed all the sugar solution provided to them, and had significantly increased caloric intake, compared to controls (p < 0.0001). However, in all tests, we found no significant difference in cognitive performance between Sucrose and Control treated rats. This included the number of trials for acquisition, and reversal, in Pairwise Discrimination, and number of trials required to complete Location Discrimination (p > 0.05 for all outcomes). No differences were observed in perseverative behaviour, motivation levels, or processing speed.

CONCLUSION

Our study found no evidence to suggest that chronic consumption of sucrose impairs cognition, including both spatial and non-spatial learning tasks. These findings suggest that not all aspects of spatial cognition are negatively impacted by high sugar diet in rodents, and that particular use of touchscreen technology may probe different aspects of cognition than traditional tasks.

Hypothalamic pregnenolone mediates recognition memory in the context of metabolic disorders

Obesity and type 2 diabetes are associated with cognitive dysfunction. Because the hypothalamus is implicated in energy balance control and memory disorders, we hypothesized that specific neurons in this brain region are at the interface of metabolism and cognition. Acute obesogenic diet administration in mice impaired recognition memory due to defective production of the neurosteroid precursor pregnenolone in the hypothalamus. Genetic interference with pregnenolone synthesis by Star deletion in hypothalamic POMC, but not AgRP neurons, deteriorated recognition memory independently of metabolic disturbances. Our data suggest that pregnenolone's effects on cognitive function were mediated via an autocrine mechanism on POMC neurons, influencing hippocampal long-term potentiation. The relevance of central pregnenolone on cognition was also confirmed in metabolically unhealthy patients with obesity. Our data reveal an unsuspected role for POMC neuron-derived neurosteroids in cognition. These results provide the basis for a framework to investigate new facets of POMC neuron biology with implications for cognitive disorders.

Ten-week high fat and high sugar diets in mice alter gut-brain axis cytokines in a sex-dependent manner

Diets high in fat and sugar induce inflammation throughout the body, particularly along the gut-brain axis; however, the way these changes in immune signaling mediate one another remains unknown. We investigated cytokine changes in the brain and colon following prolonged high fat or sugar diet in female and male adult C57BL/6 mice. Ten weeks of high fat diet increased levels of TNFα, IL-1β, IL-6, IFNγ, and IL-10 in the female hippocampus and altered cytokines in the frontal cortex of both sexes. High sugar diet increased hippocampal cytokines and decreased cytokines in the diencephalon and frontal cortex. In the colon, high fat diet changed cytokine expression in both sexes, while high sugar diet only increased TNFα in males. Causal mediation analysis confirmed that colon IL-10 and IL-6 mediate high fat diet-induced neuroimmune changes in the female hippocampus and male frontal cortex. Additionally, high fat diet increased food consumption and weight gain in both sexes, while high sugar diet decreased male weight gain. These findings reveal a novel causal link between gut and brain inflammation specific to prolonged consumption of high fat, not high sugar, diet. Importantly, this work includes females which have been under-represented in diet research, and demonstrates that diet-induced neuroinflammation varies by brain region between sexes. Furthermore, our data suggest female brains are more vulnerable than males to inflammatory changes following excessive fat and sugar consumption, which may help explain the increased risk of inflammation-associated psychiatric conditions in women who eat a Western Diet rich in both dietary components.

Inflammatory Blood Biomarker Kynurenine Is Linked With Elevated Neuroinflammation and Neurodegeneration in Older Adults: Evidence From Two 1H-MRS Post-Processing Analysis Methods

RATIONALE AND OBJECTIVES

Pro-inflammatory processes have been argued to play a role in conditions associated with cognitive decline and neurodegeneration, like aging and obesity. Only a limited number of studies have tried to measure both peripheral and central biomarkers of inflammation and examined their interrelationship. The primary aim of this study was to examine the hypothesis that chronic peripheral inflammation would be associated with neurometabolic changes that indicate neuroinflammation (the combined elevation of myoinositol and choline), brain gray matter volume decrease, and lower cognitive functioning in older adults.

MATERIALS AND METHODS

Seventy-four older adults underwent bio-impedance body composition analysis, cognitive testing with the Montreal Cognitive Assessment (MoCA), blood serum analysis of inflammatory markers interleukin-6 (IL-6) and kynurenine, magnetic resonance imaging (MRI), and proton magnetic resonance spectroscopy (¹H-MRS) of the brain. Neurometabolic findings from both Tarquin and LCModel ¹H-MRS post-processing software packages were compared. The regions of interest for MRI and ¹H-MRS measurements were dorsal posterior cingulate cortex (DPCC), left hippocampal cortex (HPC), left medial temporal cortex (MTC), left primary sensorimotor cortex (SM1), and right dorsolateral prefrontal cortex (DLPFC).

RESULTS

Elevated serum kynurenine levels were associated with signs of neuroinflammation, specifically in the DPCC, left SM1 and right DLPFC, and signs of neurodegeneration, specifically in the left HPC, left MTC and left SM1, after adjusting for age, sex and fat percentage (fat%). Elevated serum IL-6 levels were associated with increased Glx levels in left HPC, left MTC, and right DLPFC, after processing the ¹H-MRS data with Tarquin. Overall, the agreement between Tarquin and LCModel results was moderate-to-strong for tNAA, tCho, mIns, and tCr, but weak to very weak for Glx. Peripheral inflammatory markers (IL-6 and kynurenine) were not associated with older age, higher fat%, decreased brain gray matter volume loss or decreased cognitive functioning within a cohort of older adults.

CONCLUSION

Our results suggest that serum kynurenine may be used as a peripheral inflammatory marker that is associated with neuroinflammation and neurodegeneration, although not linked to cognition. Future studies should consider longitudinal analysis to assess the causal inferences between chronic peripheral and neuroinflammation, brain structural and neurometabolic changes, and cognitive decline in aging.

Sexually Dimorphic Effects of a Western Diet on Brain Mitochondrial Bioenergetics and Neurocognitive Function

A Western diet (WD), high in sugars and saturated fats, impairs learning and memory function and contributes to weight gain. Mitochondria in the brain provide energy for neurocognitive function and may play a role in body weight regulation. We sought to determine whether a WD alters behavior and metabolic outcomes in male and female rodents through impacting hippocampal and hypothalamic mitochondrial bioenergetics. Results revealed a sexually dimorphic macronutrient preference, where males on the WD consumed a greater percentage of calories from fat/protein and females consumed a greater percentage of calories from a sugar-sweetened beverage. Both males and females on a WD gained body fat and showed impaired glucose tolerance when compared to same-sex controls. Males on a WD demonstrated impaired hippocampal functioning and an elevated tendency toward a high membrane potential in hippocampal mitochondria. Comprehensive bioenergetics analysis of WD effects in the hypothalamus revealed a tissue-specific adaption, where males on the WD oxidized more fat, and females oxidized more fat and carbohydrates at peak energy demand compared to same-sex controls. These results suggest that adult male rats show a susceptibility toward hippocampal dysfunction on a WD, and that hypothalamic mitochondrial bioenergetics are altered by WD in a sex-specific manner.

Short-term high-fat diet favors the appearances of apoptosis and gliosis by activation of ERK1/2/p38MAPK pathways in brain

High-fat diet (HFD) has been associated with neuroinflammation and apoptosis in distinct brain regions. To explore the effect of short-term (7, 14 and 21 days) high-fat overfeeding on apoptosis, inflammatory signaling proteins, APP changes and glial cell activities in cerebral cortex and cerebellum. Mice were fed with HFD for different lengths (up to 21 days) and after each time body weights of mice was tested, then the apoptotic proteins, IL-1β, APP, BACE1and MAPKs, Akt and NF-κB signaling activity were evaluated by western blots. Results demonstrate that short period of high-fat overnutrition significantly promotes apoptosis, APP expression at day 21 of cerebral cortex and at day 7 of cerebellum compared to chow diet. In addition, increased GFAP+astrocytes, Iba-1+microglia and IL-1β 30 were observed in cerebral cortex after 21 days HFD, but no changes for 7 days overfeeding of cerebellum. Serendipitously, ERK1/2 pathway was activated both in cerebral cortex and cerebellum for different time course of HFD. Furthermore, increased phospho-p38 MAPK level was observed in cerebellum only. In consistent with in vivo results, SH-SY5Y cells treatment with cholesterol (50 μM, 100 μM) for 48 h culture in vitro demonstrated that pro-apoptotic proteins were enhanced as well. In brief, short-term HFD consumption increases sensitivity to apoptosis, APP and IL-1β production as well as gliosis in cerebral cortex and cerebellum, which may be related to enhancement of ERK1/2 and p38 MAPK activation.

Palatable high-fat diet intake influences mnemonic and emotional aspects in female rats in an estrous cycle-dependent manner

Worldwide, the excessive consumption of fat and/or sugar has increased considerably. Palatable high-fat diets (HFDs) lead to metabolic disturbances and obesity, and impact emotional and cognitive processes. Previous studies in rodent models suggested that HFDs often cause multiple behavioral alterations, such as learning and memory deficits, and anxiety-like behaviors. Different sexes imply different behavioral and cognitive abilities; yet, most of these studies dealt with male or ovariectomized rats. We evaluated HFD effects in female rats submitted to different behavioral tasks, considering the effects of endogenous hormonal variations throughout estrous cycle. Female Wistar rats in each phase of the estrous cycle using commercial chow (CC) or HFD for 32 days. During treatment, behavioral assessments using sucrose preference (SP), elevated plus-maze (EPM), open field (OF) and novel-object recognition (NOR). At the end of the behavioral tests, animals were euthanized, and performed an immunohistochemical analysis of the brains by brain-derived neurotrophic factor (BDNF) and tyrosine hydroxylase (TH). The main results demonstrated that (1) HFD-fed rats had higher body mass gain and food intake, without altering caloric intake, (2) rats in diestrus had lower sucrose intake, (3) females in metestrus and diestrus showed deficits in the novel-object recognition memory. Furthermore, TH-immunoreactivity decreased in the dorsal striatum and BDNF in the hippocampus in HFD-fed females. These results suggest that HFD alters neurochemical and metabolic aspects that may induce phase-dependent behavioral changes in female rats.

Western diet as a trigger of Alzheimer's disease: From metabolic syndrome and systemic inflammation to neuroinflammation and neurodegeneration

An excess of saturated fatty acids and simple sugars in the diet is a known environmental risk factor of Alzheimer's disease (AD) but the holistic view of the interacting processes through which such diet may contribute to AD pathogenesis is missing. We addressed this need through extensive analysis of published studies investigating the effects of western diet (WD) on AD development in humans and laboratory animals. We reviewed WD-induced systemic alterations comprising metabolic changes, induction of obesity and adipose tissue inflammation, gut microbiota dysbiosis and acceleration of systemic low-grade inflammation. Next we provide an overview of the evidence demonstrating that WD-associated systemic alterations drive impairment of the blood-brain barrier (BBB) and development of neuroinflammation paralleled by accumulation of toxic amyloid. Later these changes are followed by dysfunction of synaptic transmission, neurodegeneration and finally memory and cognitive impairment. We conclude that WD can trigger AD by acceleration of inflammaging, and that BBB impairment induced by metabolic and systemic inflammation play the central role in this process. Moreover, the concurrence of neuroinflammation and Aβ dyshomeostasis, which by reciprocal interactions drive the vicious cycle of neurodegeneration, contradicts Aβ as the primary trigger of AD. Given that in 2019 the World Health Organization recommended focusing on modifiable risk factors in AD prevention, this overview of the sequential, complex pathomechanisms initiated by WD, which can lead from peripheral disturbances to neurodegeneration, can support future prevention strategies.

Interactive influences of food, contexts and neurocognitive systems on addictive eating

Compulsive eating is a common symptom of different conditions, including obesity, binge eating disorder and bulimia. One hypothesis is that contemporary food products promote compulsive eating via addiction-like mechanisms. However, what is the addictive substance in food, and what is the phenotypic overlap between obesity / eating disorders and addictions are questions that remain unresolved. In this review, we applied a multilevel framework of addiction, which encompasses the 'drug' (certain foods), the person's mindset, and the context, to improve understanding of compulsive eating. Specifically, we reviewed evidence on the addictive properties of specific foods, the neurocognitive systems that control dietary choices, and their interaction with physical, emotional and social contexts. We focused on different target groups to illustrate distinct aspects of the proposed framework: the impact of food and contextual factors were examined across a continuum, with most studies conducted on healthy participants and subclinical populations, whereas the review of neurocognitive aspects focused on clinical groups in which the alterations linked to addictive and compulsive eating are particularly visible. The reviewed evidence suggest that macronutrient composition and level of processing are associated with the addictive properties of food; there are overlapping neuroadaptations in reward and decision-making circuits across compulsive eating conditions; and there are physical and social contexts that fuel compulsive eating by exploiting reward mechanisms and their interaction with emotions. We conclude that a biopsychosocial model that integrates food, neurobiology and context can provide a better understanding of compulsive eating manifestations in a transdiagnostic framework.

Diseases, Disorders, and Comorbidities of Interoception

Interoception, the sense of the body's internal physiological state, underpins homeostatic reflexes, motivational states, and sensations contributing to emotional experiences. The continuous nature of interoceptive processing, coupled to behavior, is implicated in the neurobiological construction of the sense of self. Aberrant integration and control of interoceptive signals, originating in the brain and/or the periphery, can perturb the whole system. Interoceptive abnormalities are implicated in the pathophysiology of psychiatric disorders and in the symptomatic expression of developmental, neurodegenerative, and neurological disorders. Moreover, interoceptive mechanisms appear central to somatic disorders of brain-body interactions, including functional digestive disorders, chronic pain, and comorbid conditions. The present article provides an overview of disorders of interoception and suggests future directions for better understanding, diagnosis, and management of these disorders.

Of 'junk food' and 'brain food': how parental diet influences offspring neurobiology and behaviour

Unhealthy lifestyles and mental health problems are increasingly prevalent globally. Not only are 'junk food'-induced overweight and obesity risk factors for the development of brain disorders but they are also associated intergenerationally with ill health. Here, we reflect on the current knowledge of how maternal and paternal diet influences offspring brain development and behaviour, potentially predisposing children to mental health problems. Mounting evidence indicates diet-induced maternal and paternal programming of infant metabolism and neurobehavioural function, with potential downstream effects on mental health and resilience. Beyond the central nervous system (CNS), the microbiota-gut-brain axis has emerged as an important mediator of host physiology. We discuss how intergenerational seeding of the gut microbiome via parental lineage can influence offspring gut health and neurobiology.

Age-Related Cognitive Decline May Be Moderated by Frequency of Specific Food Products Consumption

Our study aimed to evaluate whether the type of food products and the frequency of their consumption are associated with cognitive functioning in younger and older adults. The impact of diets that are high in added sugars and saturated fat on cognitive functioning, especially on memory, was at the center of our interest. Participants in the study were 204 healthy adults (aged 20-55) who performed a multitasking cognitive test and completed dietary and psychological questionnaires. Stepwise regression analysis with age and food consumption patterns as predictors, and the cognitive task performance as a dependent variable, revealed that cognitive task performance worsened with age. However, we found that the frequency of consuming different types of foods (healthy versus unhealthy dietary patterns) moderates the effects of age on cognitive functioning. Red meat and animal fat consumption were negatively correlated with cognitive performance, and this relation was dependent on the age of our participants. Conversely, white meat and fish consumption were positively related to memory. Different indices of dietary patterns (both positive and negative) were stronger predictors of cognitive performance in the older adult group. We interpret our results as evidence that diet may be a protective (or worsening) factor in age-related cognitive decline.

Binge eating behavior and incentive motivation with a cafeteria diet

Binge-like eating behavior (BLE) has been characterized as an eating disorder in which subjects have an enhanced intake of food, mainly fats. However, intake of fats and carbohydrates may have differential effects on motivation. Previously it was shown that BLE produces an increase in operant responding for vegetable shortening, but others were unable to replicate the finding using sucrose as the reinforcer. Our aim was to determine if BLE behavior induced with a cafeteria-like diet (CaLD) with several options with fat content would produce an increment in performance. Male Wistar rats were trained under an exponential progressive ratio schedule of sucrose reinforcement; thereafter, the limited access model was used to induce BLE using CaLD options. Finally, subjects were tested for increments in break points (BPs) in the progressive ratio schedule. Rats with intermittent access to CaLD options showed a clear BLE with an escalation in their intake; however they showed compensatory decrements of chow intake that rendered a similar body weight gain to a continuous access group. Although we were unable to observe an increase in BPs after BLE we were able to observe a protection against the decrements of BP previously observed with sugar. Different mechanisms for processing high fat and high carbohydrate reinforcers are variables worth exploring to gain a better understanding of BLE behavior in rodent models.