Cognitive and neuronal systems underlying obesity

Isomalto-Oligosaccharide Potentiates Alleviating Effects of Intermittent Fasting on Obesity-Related Cognitive Impairment during Weight Loss and the Rebound Weight Gain

Obesity-related cognitive dysfunction poses a significant threat to public health. The present study demonstrated mitigating effects of intermittent fasting (IF) and its combination with isomalto-oligosaccharides and IF (IF + IMO) on cognitive impairments induced by a high-fat-high-fructose (HFHF) diet in mice, with IF + IMO exhibiting superior effects. Transcriptomic analysis of the hippocampus revealed that the protective effects on cognition might be attributed to the suppression of toll-like receptor 4 (TLR4)/NFκB signaling, oxidative phosphorylation, and neuroinflammation. Moreover, both IF and IF + IMO modulated the gut microbiome and promoted the production of short-chain fatty acids, with IF + IMO displaying more pronounced effects. IF + IMO-modulated gut microbiota, metabolites, and molecular targets associated with cognitive impairments were further corroborated using human data from public databases Gmrepo and gutMgene. Furthermore, the fecal microbiome transplantation confirmed the direct impacts of IF + IMO-derived microbiota on improving cognition functions by suppressing TLR4/NFκB signaling and increasing BDNF levels. Notably, prior exposure to IF + IMO prevented weight-regain-induced cognitive decline, suppressed TLR4/NFκB signaling and inflammatory cytokines in the hippocampus, and mitigated weight regain-caused gut dysbacteriosis without altering body weight. Our study underscores that IMO-augmented alleviating effects of IF on obesity-related cognitive impairment particularly during weight-loss and weight-regain periods, presenting a novel nutritional strategy to tackle obesity-related neurodegenerative disorders.

Western diet consumption impairs memory function via dysregulated hippocampus acetylcholine signaling

Western diet (WD) consumption during early life developmental periods is associated with impaired memory function, particularly for hippocampus (HPC)-dependent processes. We developed an early life WD rodent model associated with long-lasting HPC dysfunction to investigate the neurobiological mechanisms mediating these effects. Rats received either a cafeteria-style WD (ad libitum access to various high-fat/high-sugar foods; CAF) or standard healthy chow (CTL) during the juvenile and adolescent stages (postnatal days 26-56). Behavioral and metabolic assessments were performed both before and after a healthy diet intervention period beginning at early adulthood. Results revealed HPC-dependent contextual episodic memory impairments in CAF rats that persisted despite the healthy diet intervention. Given that dysregulated HPC acetylcholine (ACh) signaling is associated with memory impairments in humans and animal models, we examined protein markers of ACh tone in the dorsal HPC (HPCd) in CAF and CTL rats. Results revealed significantly lower protein levels of vesicular ACh transporter in the HPCd of CAF vs. CTL rats, indicating chronically reduced ACh tone. Using intensity-based ACh sensing fluorescent reporter (iAChSnFr) in vivo fiber photometry targeting the HPCd, we next revealed that ACh release during object-contextual novelty recognition was highly predictive of memory performance and was disrupted in CAF vs. CTL rats. Neuropharmacological results showed that alpha 7 nicotinic ACh receptor agonist infusion in the HPCd during training rescued memory deficits in CAF rats. Overall, these findings reveal a functional connection linking early life WD intake with long-lasting dysregulation of HPC ACh signaling, thereby identifying an underlying mechanism for WD-associated memory impairments.

Integrated bioinformatics and statistical approach to identify the common molecular mechanisms of obesity that are linked to the development of two psychiatric disorders: Schizophrenia and major depressive disorder

Obesity is a chronic multifactorial disease characterized by the accumulation of body fat and serves as a gateway to a number of metabolic-related diseases. Epidemiologic data indicate that Obesity is acting as a risk factor for neuro-psychiatric disorders such as schizophrenia, major depression disorder and vice versa. However, how obesity may biologically interact with neurodevelopmental or neurological psychiatric conditions influenced by hereditary, environmental, and other factors is entirely unknown. To address this issue, we have developed a pipeline that integrates bioinformatics and statistical approaches such as transcriptomic analysis to identify differentially expressed genes (DEGs) and molecular mechanisms in patients with psychiatric disorders that are also common in obese patients. Biomarker genes expressed in schizophrenia, major depression, and obesity have been used to demonstrate such relationships depending on the previous research studies. The highly expressed genes identify commonly altered signalling pathways, gene ontology pathways, and gene-disease associations across disorders. The proposed method identified 163 significant genes and 134 significant pathways shared between obesity and schizophrenia. Similarly, there are 247 significant genes and 65 significant pathways that are shared by obesity and major depressive disorder. These genes and pathways increase the likelihood that psychiatric disorders and obesity are pathogenic. Thus, this study may help in the development of a restorative approach that will ameliorate the bidirectional relation between obesity and psychiatric disorder. Finally, we also validated our findings using genome-wide association study (GWAS) and whole-genome sequence (WGS) data from SCZ, MDD, and OBE. We confirmed the likely involvement of four significant genes both in transcriptomic and GWAS/WGS data. Moreover, we have performed co-expression cluster analysis of the transcriptomic data and compared it with the results of transcriptomic differential expression analysis and GWAS/WGS.

Western diet consumption impairs memory function via dysregulated hippocampus acetylcholine signaling

Western diet (WD) consumption during development yields long-lasting memory impairments, yet the underlying neurobiological mechanisms remain elusive. Here we developed an early life WD rodent model to evaluate whether dysregulated hippocampus (HPC) acetylcholine (ACh) signaling, a pathology associated with memory impairment in human dementia, is causally-related to WD-induced cognitive impairment. Rats received a cafeteria-style WD (access to various high-fat/high-sugar foods; CAF) or healthy chow (CTL) during the juvenile and adolescent periods (postnatal days 26-56). Behavioral, metabolic, and microbiome assessments were performed both before and after a 30-day healthy diet intervention beginning at early adulthood. Results revealed CAF-induced HPC-dependent contextual episodic memory impairments that persisted despite healthy diet intervention, whereas CAF was not associated with long-term changes in body weight, body composition, glucose tolerance, anxiety-like behavior, or gut microbiome. HPC immunoblot analyses after the healthy diet intervention identified reduced levels of vesicular ACh transporter in CAF vs. CTL rats, indicative of chronically reduced HPC ACh tone. To determine whether these changes were functionally related to memory impairments, we evaluated temporal HPC ACh binding via ACh-sensing fluorescent reporter in vivo fiber photometry during memory testing, as well as whether the memory impairments could be rescued pharmacologically. Results revealed dynamic HPC ACh binding during object-contextual novelty recognition was highly predictive of memory performance and was disrupted in CAF vs. CTL rats. Further, HPC alpha-7 nicotinic receptor agonist infusion during consolidation rescued memory deficits in CAF rats. Overall, these findings identify dysregulated HPC ACh signaling as a mechanism underlying early life WD-associated memory impairments.

Review of Plant Extracts and Active Components: Mechanisms of Action for the Treatment of Obesity-Induced Cognitive Impairment

Obesity has been shown to negatively impact cognitive functions, but effective treatments for obesity-induced cognitive impairment are lacking. Natural dietary and plant products, functional foods, and plant-derived compounds have gained attention as potential remedies in part due to the nootropic properties of plants and certain plant-derived agents. This review discusses plant extracts and plant-derived substances that have been shown to ameliorate obesity-induced cognitive impairment in animal models. Mechanistic evaluations of their therapeutic effects are also summarized. A literature search was conducted using PubMed and Google Scholar databases, resulting in the review of 27 English language articles meeting the inclusion criteria. The nine plants (e.g., Ashwagandha, Adzuki bean, and olive) and 18 plant-derived substances (e.g., curcumin, Huperzine A, and Roxburgh's jewel orchid polysaccharides) included in this review improved obesity-induced cognitive impairment through several mechanisms, including attenuation of neuroinflammation, improvement in both central and peripheral insulin resistance, enhancement of neuroprotection and neurogenesis, and modulation of the synthesis and release of cognition-associated neurotransmitters. Based on these findings, plants and plant-derived substances may hold promise for the prevention and treatment of obesity-induced cognitive impairment. Further research is warranted to explore the clinical potential of these plant-derived treatments and to elucidate their underlying molecular mechanisms.

Identification of a Stress-Sensitive Anorexigenic Neurocircuit From Medial Prefrontal Cortex to Lateral Hypothalamus

BACKGROUND

A greater understanding of how the brain controls appetite is fundamental to developing new approaches for treating diseases characterized by dysfunctional feeding behavior, such as obesity and anorexia nervosa.

METHODS

By modeling neural network dynamics related to homeostatic state and body mass index, we identified a novel pathway projecting from the medial prefrontal cortex (mPFC) to the lateral hypothalamus (LH) in humans (n = 53). We then assessed the physiological role and dissected the function of this mPFC-LH circuit in mice.

RESULTS

In vivo recordings of population calcium activity revealed that this glutamatergic mPFC-LH pathway is activated in response to acute stressors and inhibited during food consumption, suggesting a role in stress-related control over food intake. Consistent with this role, inhibition of this circuit increased feeding and sucrose seeking during mild stressors, but not under nonstressful conditions. Finally, chemogenetic or optogenetic activation of the mPFC-LH pathway is sufficient to suppress food intake and sucrose seeking in mice.

CONCLUSIONS

These studies identify a glutamatergic mPFC-LH circuit as a novel stress-sensitive anorexigenic neural pathway involved in the cortical control of food intake.

Prefrontal cortical protease TACE/ADAM17 is involved in neuroinflammation and stress-related eating alterations

Childhood traumatic stress profoundly affects prefrontal cortical networks regulating top-down control of eating and body weight. However, the neurobiological mechanisms contributing to trauma-induced aberrant eating behaviors remain largely unknown. Traumatic stress influences brain immune responses, which may, in turn, disrupt prefrontal cortical networks and behaviors. The tumor necrosis factor alpha-converting enzyme / a disintegrin and metalloproteinase 17 (TACE/ADAM17) is a sheddase with essential functions in brain maturation, behavior, and neuroinflammation. This study aimed to determine the role of TACE/ADAM17 on traumatic stress-induced disruption of eating patterns. We demonstrate a novel mechanistic connection between prefrontal cortical TACE/ADAM17 and trauma-induced eating behaviors. Fifty-two (52) adolescent Lewis rats (postnatal day, PND, 15) were injected intracerebrally either with a novel Accell™ SMARTpool ADAM17 siRNA or a corresponding siRNA vehicle. The RNAscope Multiplex Fluorescent v2 Assay was used to visualize mRNA expression. Observation cages were used to monitor ethological behaviors in a more naturalistic environment over long periods. We found that traumatic stress blunts startle reactivity and alter eating behaviors (increased intake and disrupted eating patterns). We also found that the rats that received prefrontal cortical TACE/ADAM17 siRNA administration exhibited decreased eating and increased grooming behaviors compared to controls. These changes were associated with decreased AIF-1 expression (a typical marker of microglia and neuroinflammation). This study demonstrates that prefrontal cortical TACE/ADAM17 is involved in neuroinflammation and may play essential roles in regulating feeding patterns under stress conditions. TACE/ADAM17 represents a promising target to ameliorate inflammation-induced brain and behavior alterations.

The physiological control of eating: signals, neurons, and networks

During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.

B Vitamins Supplementation Can Improve Cognitive Functions and May Relate to the Enhancement of Transketolase Activity in A Rat Model of Cognitive Impairment Associated with High-fat Diets

OBJECTIVE

To determine whether B vitamin treatment was sufficient to reduce cognitive impairment associated with high-fat diets in rats and to modulate transketolase (TK) expression and activity.

METHODS

To test this, we separated 50 rats into five groups that were either fed a standard chow diet (controls) or a high-fat diet (experimental groups H0, H1, H2, and H3). H0 group animals received no additional dietary supplementation, while H1 group animals were administered 100 mg/kg body weight (BW) thiamine, 100 mg/kg BW riboflavin, and 250 mg/kg BW niacin each day, and group H2 animals received daily doses of 100 mg/kg BW pyridoxine, 100 mg/kg BW cobalamin, and 5 mg/kg BW folate. Animals in the H3 group received the B vitamin regimens administered to both H1 and H2 each day.

RESULTS

Over time, group H0 exhibited greater increases in BW and fat mass relative to other groups. When spatial and memory capabilities in these animals were evaluated via conditioned taste aversion (CTA) and Morris Water Maze (MWM), we found B vitamin treatment was associated with significant improvements relative to untreated H0 controls. Similarly, B vitamin supplementation was associated with elevated TK expression in erythrocytes and hypothalamus of treated animals relative to those in H0 (P<0.05).

CONCLUSION

Together, these findings suggest B vitamin can modulate hypothalamic TK activity to reduce the severity of cognitive deficits in a rat model of obesity. As such, B vitamin supplementation may be a beneficial method for reducing cognitive dysfunction in clinical settings associated with high-fat diets.

Hippocampal neural cell loss in high-fat diet-induced obese rats-exploring the protein networks, ultrastructure, biochemical and bioinformatical markers

OBJECTIVE

Obesity, which has become one of the main health problems, results from irregular and unhealthy nutrition. In particular, an increase in the intake of high-fat foods leads to obesity and associated disorders. It is noteworthy to specify that obese individuals have memory problems. This study aims to examine the effects of high-fat diet on hippocampus, with stereological, histopathological methods and STRING bioinformatic tool.

METHODS

Female Adult Sprague Dawley rats (n = 20) were equally divided into control (CONT) and high-fat diet (HFD) groups. The control group was given standard rat pellet feed, while the high-fat diet group was fed with a 40 % fat content for 2 months. Following the feeding program, rats were sacrificed. The collected blood samples were analyzed biochemically to determine the level of oxidative stress while performing a stereological and histopathological examination of the brain tissues. Functional protein-protein networks for BDNF, C-Fos, CAT, LPO, SOD and MPO by gene ontology (GO) enrichment analysis were evaluated.

FINDINGS

The number of neurons decreased in the HFD group compared to the CONT group. Damage to the histological structure of the hippocampus region; such as degenerate neurons, damaged mitochondria and extended cisterns of the endoplasmic reticulum was observed. Although C-Fos level and oxidative stress parameters increased in HFD group, BDNF level decreased. While BDNF and C-Fos were observed in pathways related to neuron death, oxidative stress and memory, BDNF was pronounced in the mitochondria, and C-Fos in the endoplasmic reticulum.

DISCUSSION

This study shows that changes in both BDNF and C-Fos levels in obesity due to high-fat diet increase oxidative stress and cause neuron damage in the hippocampus.

The effect of body mass index on hippocampal morphology and memory performance in late childhood and adolescence

Childhood obesity is associated with negative physiological and cognitive health outcomes. The hippocampus is a diverse subcortical structure involved in learned feeding behaviors and energy regulation, and research has shown that the hippocampus is vulnerable to the effects of excess adiposity. Previous studies have demonstrated reduced hippocampal volume in overweight and obese children; however, it is unclear if certain subregions are selectively affected. The purpose of this study was to determine how excess body weight influences regional hippocampal surface morphology and memory performance in a large cross-sectional cohort of 588 children and adolescents between 8.33 and 19.92 years of age using body mass index expressed as a percentage of the 95th percentile cutoff (%BMIp95). We demonstrate %BMIp95 is associated with reduced radial thickness in the superior anterior region of the left hippocampus, and this relationship is predominantly driven by children younger than 14 years. We also found %BMIp95 was associated with worse performance on a spatial episodic memory task and this relationship was partially mediated by the radial thickness of the significant shape cluster. These results demonstrate the differential influence of excess body weight on regional hippocampal structure and hippocampal-dependent behavior in children and adolescents.

Diet, inflammation and the gut microbiome: Mechanisms for obesity-associated cognitive impairment

Poor diet and obesity are associated with cognitive impairment throughout adulthood, and increased dementia risk in aging. Here we review the current literature interrogating the mechanisms by which diets high in fat, or fat and sugar lead to cognitive impairment, focusing on changes to gut microbiome composition, inflammatory signalling and blood-brain barrier integrity. Preclinical studies indicate weight gain is not necessary for diet-induced cognitive impairment. Rather, gut microbiome composition, and systemic and central inflammatory processes appear to contribute to diet-induced cognitive impairment. While both obese humans and rodents exhibit reduced blood-brain barrier integrity, cognitive impairments precede these changes, suggesting other mechanisms may underly diet-induced cognitive changes. Other potential candidates include hormone, glucoregulatory and cardiovascular changes. Poor diet and obesity act through multiple mechanisms to affect cognitive health and the challenge for future research is to identify key processes that can be reversed to improve cognition and quality of life.

Wanting to eat matters: Negative affect and emotional eating were associated with impaired memory suppression of food cues

OBJECTIVE

Previous studies have linked emotional eating with negative affect and decreased inhibitory control. However, studies on inhibitory control have generally focused on motor inhibition. How to stop higher-level cognitive processes, such as food-related memory retrieval or voluntary thoughts, received few direct investigation in field of food intake or food-related decision making. The current study, adopting Anderson and Green's Think/No-Think paradigm, aimed to investigate the relationship between emotional eating, negative affect and food-related memory suppression.

METHOD

Sixty-one young females participated in the current study, during which they finished food specific Think/No-Think task. Their positive and negative affect and eating style were measured using Positive Affect and Negative Affect Schedule and Dutch Eating Behavior Question. The reward value of the food item used in the Think/No-Think task was measured using liking and wanting ratings.

RESULTS

As hypothesized, negative affect and emotional eating were associated with decreased memory suppression of palatable food cues. Further analysis showed that higher emotional eating was associated with greater wanting only among the food items which were previously suppressed however remembered later.

DISCUSSION

The current study presents the first evidence that negative affect and emotional eating were associated with impaired memory suppression of palatable food cues, and it provided insight into the interaction between reward valuation for the food cues and hippocampal memory mechanisms during retrieval suppression.

Cerebral hunger maps in rodents and humans by diffusion weighted MRI

We design, implement and validate a novel image processing strategy to obtain in vivo maps of hunger stimulation in the brain of mice, rats and humans, combining Diffusion Weighted Magnetic Resonance Imaging (DWI) datasets from fed and fasted subjects. Hunger maps were obtained from axial/coronal (rodents/humans) brain sections containing the hypothalamus and coplanar cortico-limbic structures using Fisher's Discriminant Analysis of the combined voxel ensembles from both feeding situations. These maps were validated against those provided by the classical mono-exponential diffusion model as applied over the same subjects and conditions. Mono-exponential fittings revealed significant Apparent Diffusion Coefficient (ADC) decreases through the brain regions stimulated by hunger, but rigorous parameter estimations imposed the rejection of considerable number of pixels. The proposed approach avoided pixel rejections and provided a representation of the combined DWI dataset as a pixel map of the "Hunger Index" (HI), a parameter revealing the hunger score of every pixel. The new methodology proved to be robust both, by yielding consistent results with classical ADC maps and, by reproducing very similar HI maps when applied to newly acquired rodent datasets. ADC and HI maps demonstrated similar patterns of activation by hunger in hypothalamic and cortico-limbic structures of the brain of rodents and humans, albeit with different relative intensities, rodents showing more intense activations by hunger than humans, for similar fasting periods. The proposed methodology may be easily extended to other feeding paradigms or even to alternative imaging methods.

The Cognitive Control of Eating and Body Weight: It's More Than What You "Think"

Over the past decade, a great deal of research has established the importance of cognitive processes in the control of energy intake and body weight. The present paper begins by identifying several of these cognitive processes. We then summarize evidence from human and nonhuman animal models, which shows how excess intake of obesity-promoting Western diet (WD) may have deleterious effects on these cognitive control processes. Findings that these effects may be manifested as early-life deficits in cognitive functioning and may also be associated with the emergence of serious late-life cognitive impairment are described. Consistent with these possibilities, we review evidence, obtained primarily from rodent models, that consuming a WD is associated with the emergence of pathophysiologies in the hippocampus, an important brain substrate for learning, memory, and cognition. The implications of this research for mechanism are discussed within the context of a “vicious-cycle model,” which describes how eating a WD could impair hippocampal function, producing cognitive deficits that promote increased WD intake and body weight gain, which could contribute to further hippocampal dysfunction, cognitive decline, and excess eating and weight gain.

Hippocampus ghrelin receptor signaling promotes socially-mediated learned food preference

Social cues are potent regulators of feeding behavior, yet the neurobiological mechanisms through which social cues influence food intake are poorly understood. Here we investigate the hypothesis that the appetite-promoting gut-derived hormone, ghrelin, signals in the hippocampus to promote learned social aspects of feeding behavior. We utilized a procedure known as 'social transmission of food preference' (STFP) in which rats ('Observers') experience a social interaction with another rat ('Demonstrators') that recently consumed flavored/scented chow. STFP learning in Observer rats is indicated by a significant preference for the Demonstrator paired flavor of chow vs. a novel unpaired flavor of chow in a subsequent consumption choice test. Our results show that relative to vehicle treatment, ghrelin targeted to the ventral CA1 subregion of the hippocampus (vHP) enhanced STFP learning in rats. Additionally, STFP was impaired following peripheral injections of l-cysteine that reduce circulating ghrelin levels, suggesting that vHP ghrelin-mediated effects on STFP require peripheral ghrelin release. Finally, the endogenous relevance of vHP ghrelin receptor (GHSR-1A) signaling in STFP is supported by our data showing that STFP learning was eliminated following targeted viral vector RNA interference-mediated knockdown of vHP GHSR-1A mRNA. Control experiments indicate that vHP ghrelin-mediated STFP effects are not secondary to altered social exploration and food intake, nor to altered food preference learning based on nonsocial olfactory cues. Overall these data reveal a novel neurobiological system that promotes conditioned, social aspects of feeding behavior.

Hippocampal atrophy and altered brain responses to pleasant tastes among obese compared with healthy weight children

OBJECTIVE

The hippocampus is a key structure implicated in food motivation and intake. Research has shown that the hippocampus is vulnerable to the consumption of a western diet (i.e., high saturated fat and simple carbohydrates). Studies of patients with obesity (OB), compared with healthy weight (HW), show changes in hippocampal volume and response to food cues. Moreover, evidence suggests that OB children, relative to HW, have greater hippocampal response to taste. However, no study has examined the association of hippocampal volume with taste functioning in children. We hypothesized that OB children, relative to HW, would show a significant reduction in hippocampal volume and that decreased volume would be significantly associated with greater activation to taste. Finally, we explored whether hippocampal activation would be associated with measures on eating and eating habits.

SUBJECTS

Twenty-five 8-12-year-old children (i.e., 13 HW, 12 OB) completed a magnetic resonance imaging scan while participating in a taste paradigm (i.e., 1 ml of 10% sucrose or ionic water delivered pseudorandomly every 20 s).

RESULTS

Children with OB, relative to HW, showed reduced left hippocampal volume (t=1.994, P=0.03, 95% confidence interval (CI)=-40.23,  755.42), and greater response to taste in three clusters within the left hippocampus (z=3.3, P=0.001, 95% CI=-0.241, -0.041; z=3.3, P=0.001, 95% CI=-0.2711, -0.0469; z=2.7, P=0.007, 95% CI=-0.6032, -0.0268). Activation within the hippocampus was associated with eating in the absence of hunger (EAH%; t=2.408, P=0.025, 95% CI= 1.751708, 23.94109) and two subscales on a measure of eating behaviors (Food responsiveness, t=2.572, P=0.017, 95% CI= 0.9565195, 9.043440; Food enjoyment, t=2.298, P=0.032, 95% CI=0.2256749, 4.531298).

CONCLUSION

As hypothesized, OB children, relative to HW, had significantly reduced hippocampal volume, and greater hippocampal activation to taste. Moreover, hippocampal activation was associated with measures of eating. These results contribute to research on the relationship between OB, overeating and cognitive impairment.

Deficits in episodic memory are related to uncontrolled eating in a sample of healthy adults

Despite a substantial amount of animal data linking deficits in memory inhibition to the development of overeating and obesity, few studies have investigated the relevance of memory inhibition to uncontrolled eating in humans. Further, although memory for recent eating has been implicated as an important contributor to satiety and energy intake, the possibility that variations in episodic memory relate to individual differences in food intake control has been largely neglected. To examine these relationships, we recruited ninety-three adult subjects to attend a single lab session where we assessed body composition, dietary intake, memory performance, and eating behaviors (Three Factor Eating Questionnaire). Episodic recall and memory inhibition were assessed using a well-established measure of memory interference (Retrieval Practice Paradigm). Hierarchical regression analyses indicated that memory inhibition was largely unrelated to participants' eating behaviors; however, episodic recall was reliably predicted by restrained vs. uncontrolled eating: recall was positively associated with strategic dieting (β = 2.45, p = 0.02), avoidance of fatty foods (β = 3.41, p = 0.004), and cognitive restraint (β = 1.55, p = 0.04). In contrast, recall was negatively associated with uncontrolled eating (β = -1.15, p = 0.03) and emotional eating (β = -2.46, p = 0.04). These findings suggest that episodic memory processing is related to uncontrolled eating in humans. The possibility that deficits in episodic memory may contribute to uncontrolled eating by disrupting memory for recent eating is discussed.

Hippocampus Contributions to Food Intake Control: Mnemonic, Neuroanatomical, and Endocrine Mechanisms

Food intake is a complex behavior that can occur or cease to occur for a multitude of reasons. Decisions about where, when, what, and how much to eat are not merely reflexive responses to food-relevant stimuli or to changes in energy status. Rather, feeding behavior is modulated by various contextual factors and by previous experiences. The data reviewed here support the perspective that neurons in multiple hippocampal subregions constitute an important neural substrate linking the external context, the internal context, and mnemonic and cognitive information to control both appetitive and ingestive behavior. Feeding behavior is heavily influenced by hippocampal-dependent mnemonic functions, including episodic meal-related memories and conditional learned associations between food-related stimuli and postingestive consequences. These mnemonic processes are undoubtedly influenced by both external and internal factors relating to food availability, location, and physiological energy status. The afferent and efferent neuroanatomical connectivity of the subregions of the hippocampus is reviewed with regard to the integration of visuospatial and olfactory sensory information (the external context) with endocrine and gastrointestinal interoceptive stimuli (the internal context). Also discussed are recent findings demonstrating that peripherally derived endocrine signals act on receptors in hippocampal neurons to reduce (leptin, glucagon-like peptide-1) or increase (ghrelin) food intake and learned food reward-driven responding, thereby highlighting endocrine and neuropeptidergic signaling in hippocampal neurons as a novel substrate of importance in the higher-order regulation of feeding behavior.

Palatable Hyper-Caloric Foods Impact on Neuronal Plasticity

Neural plasticity is an intrinsic and essential characteristic of the nervous system that allows animals “self-tuning” to adapt to their environment over their lifetime. Activity-dependent synaptic plasticity in the central nervous system is a form of neural plasticity that underlies learning and memory formation, as well as long-lasting, environmentally-induced maladaptive behaviors, such as drug addiction and overeating of palatable hyper-caloric (PHc) food. In western societies, the abundance of PHc foods has caused a dramatic increase in the incidence of overweight/obesity and related disorders. To this regard, it has been suggested that increased adiposity may be caused at least in part by behavioral changes in the affected individuals that are induced by the chronic consumption of PHc foods; some authors have even drawn attention to the similarity that exists between over-indulgent eating and drug addiction. Long-term misuse of certain dietary components has also been linked to chronic neuroimmune maladaptation that may predispose individuals to neurodegenerative conditions such as Alzheimer’s disease. In this review article, we discuss recent evidence that shows how consumption of PHc food can cause maladaptive neural plasticity that converts short-term ingestive drives into compulsive behaviors. We also discuss the neural mechanisms of how chronic consumption of PHc foods may alter brain function and lead to cognitive impairments, focusing on prenatal, childhood and adolescence as vulnerable neurodevelopmental stages to dietary environmental insults. Finally, we outline a societal agenda for harnessing permissive obesogenic environments.

Can We Selectively Reduce Appetite for Energy-Dense Foods? An Overview of Pharmacological Strategies for Modification of Food Preference Behavior

Excessive intake of food, especially palatable and energy-dense carbohydrates and fats, is largely responsible for the growing incidence of obesity worldwide. Although there are a number of candidate antiobesity drugs, only a few of them have been proven able to inhibit appetite for palatable foods without the concurrent reduction in regular food consumption. In this review, we discuss the interrelationships between homeostatic and hedonic food intake control mechanisms in promoting overeating with palatable foods and assess the potential usefulness of systemically administered pharmaceuticals that impinge on the endogenous cannabinoid, opioid, aminergic, cholinergic, and peptidergic systems in the modification of food preference behavior. Also, certain dietary supplements with the potency to reduce specifically palatable food intake are presented. Based on human and animal studies, we indicate the most promising therapies and agents that influence the effectiveness of appetite-modifying drugs. It should be stressed, however, that most of the data included in our review come from preclinical studies; therefore, further investigations aimed at confirming the effectiveness and safety of the aforementioned medications in the treatment of obese humans are necessary.

Reorganization of brain connectivity in obesity

Global brain connectivity (GBC) identifies regions of the brain, termed "hubs," which are densely connected and metabolically costly, and have a wide influence on brain function. Since obesity is associated with central and peripheral metabolic dysfunction we sought to determine if GBC is altered in obesity. Two independent fMRI data sets were subjected to GBC analyses. The first data set was acquired while participants (n = 15 healthy weight and 15 obese) tasted milkshake and the second with participants at rest (n = 33 healthy weight and 28 obese). In the resting state and during milkshake consumption GBC is consistently decreased in the ventromedial and ventrolateral prefrontal cortex, insula and caudate nucleus, and increased in brain regions belonging to the dorsal attention network including premotor areas, superior parietal lobule, and visual cortex. During milkshake consumption, but not at rest, additional decreases in GBC are observed in feeding-related circuitry including the insula, amygdala, anterior hippocampus, hypothalamus, midbrain, brainstem and somatomotor cortex. Additionally, GBC differences were not accounted for by age. These results demonstrate that obesity is associated with decreased GBC in prefrontal and feeding circuits and increased GBC in the dorsal attention network. We therefore conclude that global brain organization is altered in obesity to favor networks important for external orientation over those monitoring homeostatic state and guiding feeding decisions. Furthermore, since prefrontal decreases are also observed at rest in obese individuals future work should evaluate whether these changes are associated with neurocognitive impairments frequently observed in obesity and diabetes. Hum Brain Mapp 38:1403-1420, 2017. © 2016 Wiley Periodicals, Inc.

Ghrelin: A link between memory and ingestive behavior

Feeding is a highly complex behavior that is influenced by learned associations between external and internal cues. The type of excessive feeding behavior contributing to obesity onset and metabolic deficit may be based, in part, on conditioned appetitive and ingestive behaviors that occur in response to environmental and/or interoceptive cues associated with palatable food. Therefore, there is a critical need to understand the neurobiology underlying learned aspects of feeding behavior. The stomach-derived "hunger" hormone, ghrelin, stimulates appetite and food intake and may function as an important biological substrate linking mnemonic processes with feeding control. The current review highlights data supporting a role for ghrelin in mediating the cognitive and neurobiological mechanisms that underlie conditioned feeding behavior. We discuss the role of learning and memory on food intake control (with a particular focus on hippocampal-dependent memory processes) and provide an overview of conditioned cephalic endocrine responses. A neurobiological framework is provided through which conditioned cephalic ghrelin secretion signals in neurons in the hippocampus, which then engage orexigenic neural circuitry in the lateral hypothalamus to express learned feeding behavior.

GLP-1 and weight loss: unraveling the diverse neural circuitry

Glucagon-like peptide-1 (GLP-1) is currently one of the most promising biological systems for the development of effective obesity pharmacotherapies. Long-acting GLP-1 analogs potently reduce food intake and body weight, and recent discoveries reveal that peripheral administration of these drugs reduces food intake largely through humoral pathways involving direct action on brain GLP-1 receptors (GLP-1R). Thus, it is of critical importance to understand the neural systems through which GLP-1 and long-acting GLP-1 analogs reduce food intake and body weight. In this review, we discuss several neural, physiological, cellular and molecular, as well as behavioral mechanisms through which peripheral and central GLP-1R signaling reduces feeding. Particular attention is devoted to discussion regarding the numerous neural substrates through which GLP-1 and GLP-1 analogs act to reduce food intake and body weight, including various hypothalamic nuclei (arcuate nucleus of the hypothalamus, periventricular hypothalamus, lateral hypothalamic area), hindbrain nuclei (parabrachial nucleus, medial nucleus tractus solitarius), hippocampus (ventral subregion; vHP), and nuclei embedded within the mesolimbic reward circuitry [ventral tegmental area (VTA) and nucleus accumbens (NAc)]. In some of these nuclei [VTA, NAc, and vHP], GLP-1R activation reduces food intake and body weight without concomitant nausea responses, suggesting that targeting these specific pathways may be of particular interest for future obesity pharmacotherapy. The widely distributed neural systems through which GLP-1 and GLP-1 analogs act to reduce body weight highlight the complexity of the neural systems regulating energy balance, as well as the challenges for developing effective obesity pharmacotherapies that reduce feeding without producing parallel negative side effects.

Trans fatty acid intake and emotion regulation

We examined whether there is a relationship between trans fatty acid intakes and emotion regulation, mediated by positive or negative affect. Archival data on 1699 men and 3293 women were used to measure trans fatty acid intake at baseline, positive, and negative affects and emotion regulation at follow-up. Higher trans fatty acid intake related to subsequent difficulties with emotional awareness (p = 0.045), clarity (p = 0.012), and regulation strategies (p = 0.009). Affect mediated these relationships. Lower trans fatty acid intake associated with increased positive and decreased negative affects which, in turn, associated with improved emotion regulation. Trans fatty acid intakes may be associated with subsequent ability to regulate emotions.

Hippocampus ghrelin signaling mediates appetite through lateral hypothalamic orexin pathways

Feeding behavior rarely occurs in direct response to metabolic deficit, yet the overwhelming majority of research on the biology of food intake control has focused on basic metabolic and homeostatic neurobiological substrates. Most animals, including humans, have habitual feeding patterns in which meals are consumed based on learned and/or environmental factors. Here we illuminate a novel neural system regulating higher-order aspects of feeding through which the gut-derived hormone ghrelin communicates with ventral hippocampus (vHP) neurons to stimulate meal-entrained conditioned appetite. Additional results show that the lateral hypothalamus (LHA) is a critical downstream substrate for vHP ghrelin-mediated hyperphagia and that vHP ghrelin activated neurons communicate directly with neurons in the LHA that express the neuropeptide, orexin. Furthermore, activation of downstream orexin-1 receptors is required for vHP ghrelin-mediated hyperphagia. These findings reveal novel neurobiological circuitry regulating appetite through which ghrelin signaling in hippocampal neurons engages LHA orexin signaling.

IMAGING IN ENDOCRINOLOGY: The use of functional MRI to study the endocrinology of appetite

In the present review article, we summarise current thinking about the neuroendocrinology of appetite and feeding behaviour. We discuss how the homeostatic control of energy balance, wherein the hypothalamus orchestrates food intake and energy expenditure in response to peripheral signals about nutritional status, can be easily overridden by the powerful reward value of food. We focus on how functional magnetic resonance imaging has shed light on our understanding of the way hormones can interact with the brain to modulate appetite.

Physiological mechanisms by which non-nutritive sweeteners may impact body weight and metabolism

Evidence linking sugar-sweetened beverage (SSB) consumption to weight gain and other negative health outcomes has prompted many individuals to resort to artificial, non-nutritive sweetener (NNS) substitutes as a means of reducing SSB intake. However, there is a great deal of controversy regarding the biological consequences of NNS use, with accumulating evidence suggesting that NNS consumption may influence feeding and metabolism via a variety of peripheral and central mechanisms. Here we argue that NNSs are not physiologically inert compounds and consider the potential biological mechanisms by which NNS consumption may impact energy balance and metabolic function, including actions on oral and extra-oral sweet taste receptors, and effects on metabolic hormone secretion, cognitive processes (e.g. reward learning, memory, and taste perception), and gut microbiota.

Relationships between diet-related changes in the gut microbiome and cognitive flexibility

Western diets are high in fat and sucrose and can influence behavior and gut microbiota. There is growing evidence that altering the microbiome can influence the brain and behavior. This study was designed to determine whether diet-induced changes in the gut microbiota could contribute to alterations in anxiety, memory or cognitive flexibility. Two-month-old, male C57BL/6 mice were randomly assigned high-fat (42% fat, 43% carbohydrate (CHO), high-sucrose (12% fat, 70% CHO (primarily sucrose) or normal chow (13% kcal fat, 62% CHO) diets. Fecal microbiome analysis, step-down latency, novel object and novel location tasks were performed prior to and 2weeks after diet change. Water maze testing for long- and short-term memory and cognitive flexibility was conducted during weeks 5-6 post-diet change. Some similarities in alterations in the microbiome were seen in both the high-fat and high-sucrose diets (e.g., increased Clostridiales), as compared to the normal diet, but the percentage decreases in Bacteroidales were greater in the high-sucrose diet mice. Lactobacillales was only significantly increased in the high-sucrose diet group and Erysipelotrichales was only significantly affected by the high-fat diet. The high-sucrose diet group was significantly impaired in early development of a spatial bias for long-term memory, short-term memory and reversal training, compared to mice on normal diet. An increased focus on the former platform position was seen in both high-sucrose and high-fat groups during the reversal probe trials. There was no significant effect of diet on step-down, exploration or novel recognitions. Higher percentages of Clostridiales and lower expression of Bacteroidales in high-energy diets were related to the poorer cognitive flexibility in the reversal trials. These results suggest that changes in the microbiome may contribute to cognitive changes associated with eating a Western diet.

Food reward system: current perspectives and future research needs

This article reviews current research and cross-disciplinary perspectives on the neuroscience of food reward in animals and humans, examines the scientific hypothesis of food addiction, discusses methodological and terminology challenges, and identifies knowledge gaps and future research needs. Topics addressed herein include the role of reward and hedonic aspects in the regulation of food intake, neuroanatomy and neurobiology of the reward system in animals and humans, responsivity of the brain reward system to palatable foods and drugs, translation of craving versus addiction, and cognitive control of food reward. The content is based on a workshop held in 2013 by the North American Branch of the International Life Sciences Institute.

Obesity: Cognitive impairment and the failure to 'eat right'

A recent study has found that obese women (but not men) have difficulty inhibiting food-rewarded, but not money-rewarded, appetitive behaviour, suggesting that obesity is associated with cognitive deficits that could selectively promote food intake, perhaps in a sex-dependent manner.

The impact of the Bellagio Report on healthy agriculture, healthy nutrition, healthy people: scientific and policy aspects and the International Network of Centers for Genetics, Nutrition and Fitness for Health

The Bellagio Report on Healthy Agriculture, Healthy Nutrition, Healthy People was the result of a meeting held at the Rockefeller Foundation Bellagio Center in the fall of 2012. The meeting was science based but policy oriented. The Bellagio Report concluded that: (1) sugar consumption, especially in the form of high-energy fructose in soft drinks, poses a major and insidious health threat, particularly for children; (2) current diets in most populations, albeit with regional differences, are deficient in omega-3 fatty acids but too high in omega-6 fatty acid intake, and (3) not all calories are the same since calories from different sources (i.e. glucose or fructose or omega-6 or omega-3 fatty acids) have different metabolic and neurohormonal effects. This paper summarizes the scientific progress and policy actions that have occurred in these three areas. Genetic variation in populations and gene-nutrient interactions are fundamental concepts that need to be taken into consideration in growth and development and in the prevention and management of chronic noncommunicable diseases since there is enormous variation in both the frequency of genetic variants and dietary composition worldwide. Furthermore, this paper updates the Bellagio Report in terms of the scientific and policy aspects, both of which have expanded over the past 2 years, and describes the progress made in establishing an International Network of Centers for Genetics, Nutrition and Fitness for Health.

Hippocampal GLP-1 receptors influence food intake, meal size, and effort-based responding for food through volume transmission

Glucagon-like peptide-1 (GLP-1) is produced in the small intestines and in nucleus tractus solitarius (NTS) neurons. Activation of central GLP-1 receptors (GLP-1Rs) reduces feeding and body weight. The neural circuits mediating these effects are only partially understood. Here we investigate the inhibition of food intake and motivated responding for food in rats following GLP-1R activation in the ventral hippocampal formation (HPFv), a region only recently highlighted in food intake control. Increased HPFv GLP-1R activity following exendin-4 administration potently reduced food intake (both chow and Western diet) and body weight, whereas HPFv GLP-1R blockade increased food intake. These hypophagic effects were based on reduced meal size, and likely do not involve nausea as HPFv exendin-4 did not induce a conditioned flavor avoidance. HPFv GLP-1R activation also reduced effort-based responding for food under an operant progressive ratio reinforcement schedule, but did not affect food conditioned place preference expression. To investigate possible routes of HPFv GLP-1 signaling, immunohistochemical analysis revealed the absence of GLP-1 axon terminals in the HPFv, suggesting volume transmission as a mechanism of action. Consistent with this, the presence of active GLP-1 was detected in both the cerebrospinal fluid (CSF) and the HPFv. The source of CSF GLP-1 may be NTS GLP-1-producing neurons, as, (1) ∼30% of NTS GLP-1 neurons colocalized with the retrograde tracer fluorogold (FG) following lateral ventricle FG injection, and (2) GLP-1-immunoreactive axon terminals were observed adjacent to the ventricular ependymal layer. Collectively these findings illuminate novel neuronal and behavioral mechanisms mediating food intake reduction by GLP-1.

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.

Interoceptive conditioning with nicotine using extinction and re-extinction to assess stimulus similarity with bupropion

Bupropion is an atypical antidepressant that increases long-term quit rates of tobacco smokers. A better understanding of the relation between nicotine and this first-line medication may provide insight into improving treatment. For all experiments, rats first had nicotine (0.4 mg base/kg) and saline session intermixed; intermittent access to sucrose only occurred on nicotine session. Nicotine in this protocol comes to differentially control "anticipatory" dipper entries. To more closely examine the overlap in the interoceptive stimulus effects of nicotine and bupropion, we assessed whether subsequent prolonged and repeated non-reinforced (extinction) sessions with the bupropion stimulus could weaken responding to nicotine (i.e., transfer of extinction). We also examined whether retraining the discrimination after initial extinction and then conducting extinction again (i.e., re-extinction) with bupropion would affect responding. We found that bupropion (20 and 30 mg/kg) fully substituted for the nicotine stimulus in repeated 20-min extinction sessions. The extent of substitution in extinction did not necessarily predict performance in the transfer test (e.g., nicotine responding unchanged after extinction with 20 mg/kg bupropion). Generalization of extinction back to nicotine was not seen with 20 mg/kg bupropion even after increasing the number of extinction session from 6 to 24. Finally, there was evidence that learning in the initial extinction phase was retained in the re-extinction phase for nicotine and bupropion. These findings indicate that learning involving the nicotine stimuli are complex and that assessment approach for stimulus similarity changes conclusions regarding substitution by bupropion. Further research will be needed to identify whether such differences may be related to different facets of nicotine dependence and/or its treatment.

Physical performance and disability in schizophrenia

Despite 50 years of pharmacological and psychosocial interventions, schizophrenia remains one of the leading causes of disability. Schizophrenia is also a life-shortening illness, caused mainly by poor physical health and its complications. The end result is a considerably reduced lifespan that is marred by reduced levels of independence, with few novel treatment options available.

Disability is a multidimensional construct that results from different, and often interacting, factors associated with specific types and levels of impairment. In schizophrenia, the most poignant and well characterized determinants of disability are symptoms, cognitive and related skills deficits, but there is limited understanding of other relevant factors that contribute to disability. Here we conceptualize how reduced physical performance interacts with aging, neurobiological, treatment-emergent, and cognitive and skills deficits to exacerbate ADL disability and worsen physical health. We argue that clearly defined physical performance components represent underappreciated variables that, as in mentally healthy people, offer accessible targets for exercise interventions to improve ADLs in schizophrenia, alone or in combination with improvements in cognition and health. And, finally, due to the accelerated aging pattern inherent in this disease – lifespans are reduced by 25 years on average – we present a training model based on proven training interventions successfully used in older persons. This model is designed to target the physical and psychological declines associated with decreased independence, coupled with the cardiovascular risk factors and components of the metabolic syndrome seen in schizophrenia due to their excess prevalence of obesity and low fitness levels.

Blood-brain barrier disruption: mechanistic links between Western diet consumption and dementia

Both obesity and Alzheimer's disease (AD) are major health burdens in Western societies. While commonly viewed as having separate etiologies, this review highlights data suggesting that intake of "Western diets", diets high in saturated fatty acids (SFA) and simple carbohydrates, may pose a common environmental risk factor contributing to the development of both of these adverse pathologies. We discuss the effects of Western Diet intake on learning and memory processes that are dependent on the hippocampus, as well as the importance of this brain region in both obesity development and the onset of Alzheimer's and other dementias. A putative mechanism is discussed that mechanistically links Western diet consumption, blood brain barrier (BBB) degradation, and subsequent hippocampal damage and dementia pathology.

Incretins and amylin: neuroendocrine communication between the gut, pancreas, and brain in control of food intake and blood glucose

Arguably the most fundamental physiological systems for all eukaryotic life are those governing energy balance. Without sufficient energy, an individual is unable to survive and reproduce. Thus, an ever-growing appreciation is that mammalian physiology developed a redundant set of neuroendocrine signals that regulate energy intake and expenditure, which maintains sufficient circulating energy, predominantly in the form of glucose, to ensure that energy needs are met throughout the body. This orchestrated control requires cross talk between the gastrointestinal tract, which senses the incoming meal; the pancreas, which produces glycemic counterregulatory hormones; and the brain, which controls autonomic and behavioral processes regulating energy balance. Therefore, this review highlights the physiological, pharmacological, and pathophysiological effects of the incretin hormones glucagon-like peptide-1 and gastric inhibitory polypeptide, as well as the pancreatic hormone amylin, on energy balance and glycemic control.

Human cognitive function and the obesogenic environment

Evidence is accumulating which suggests that, in addition to leading to unprecedented rates of obesity, the current food environment is contributing to the development of cognitive impairment and dementia. Recent experimental research indicates that many of the cognitive deficits associated with obesity involve fundamental inhibitory processes that have important roles in the control of food intake, implicating these cognitive impairments as a risk factor for weight gain. Here, we review experiments that link obesity with deficits in memory, attentional, and behavioral control and contemplate how these deficits may predispose individuals to overeat. Specifically, we discuss how deficits in inhibitory control may reduce one's ability to resist eating when confronted with the variety of foods and food cues that are ubiquitous in today's environment. Special attention is given to the importance of memory inhibition to the control of eating and appetitive behavior, and the role of the hippocampus in this process. We also discuss the potential etiology of both obesity and obesity-related cognitive impairment, highlighting non-human animal research which links both of these effects to the consumption of the modern "Western" diet that is high in saturated fats and simple carbohydrates. We conclude that part of what makes the current food environment "obesogenic" is the increased presence of food cues and the increased consumption of a diet which compromises our ability to resist those cues. Improving control over food-related cognitive processing may be useful not only for combating the obesity epidemic but also for minimizing the risk of serious cognitive disorder later in life.

Sleep extension improves neurocognitive functions in chronically sleep-deprived obese individuals

BACKGROUND

Sleep deprivation and obesity, are associated with neurocognitive impairments. Effects of sleep deprivation and obesity on cognition are unknown, and the cognitive long-term effects of improvement of sleep have not been prospectively assessed in short sleeping, obese individuals.

OBJECTIVE

To characterize neurocognitive functions and assess its reversibility.

DESIGN

Prospective cohort study.

SETTING

Tertiary Referral Research Clinical Center.

PATIENTS

A cohort of 121 short-sleeping (<6.5 h/night) obese (BMI 30-55 kg/m(2)) men and pre-menopausal women.

INTERVENTION

Sleep extension (468±88 days) with life-style modifications.

MEASUREMENTS

Neurocognitive functions, sleep quality and sleep duration.

RESULTS

At baseline, 44% of the individuals had an impaired global deficit score (t-score 0-39). Impaired global deficit score was associated with worse subjective sleep quality (p = 0.02), and lower urinary dopamine levels (p = 0.001). Memory was impaired in 33%; attention in 35%; motor skills in 42%; and executive function in 51% of individuals. At the final evaluation (N = 74), subjective sleep quality improved by 24% (p<0.001), self-reported sleep duration increased by 11% by questionnaires (p<0.001) and by 4% by diaries (p = 0.04), and daytime sleepiness tended to improve (p = 0.10). Global cognitive function and attention improved by 7% and 10%, respectively (both p = 0.001), and memory and executive functions tended to improve (p = 0.07 and p = 0.06). Serum cortisol increased by 17% (p = 0.02). In a multivariate mixed model, subjective sleep quality and sleep efficiency, urinary free cortisol and dopamine and plasma total ghrelin accounted for 1/5 of the variability in global cognitive function.

LIMITATIONS

Drop-out rate.

CONCLUSIONS

Chronically sleep-deprived obese individuals exhibit substantial neurocognitive deficits that are partially reversible upon improvement of sleep in a non-pharmacological way. These findings have clinical implications for large segments of the US population.

TRAIL REGISTRATION

www.ClinicalTrials.gov NCT00261898. NIDDK protocol 06-DK-0036.

Healthy Alberta Communities: impact of a three-year community-based obesity and chronic disease prevention intervention

OBJECTIVE

To assess the impact of a 3 year (2006-2009) community-based intervention for obesity and chronic disease prevention in four diverse "Healthy Alberta Communities" (HAC).

METHODS

Targeted intervention development incorporated the ANGELO conceptual framework to help community stakeholders identify environmental determinants of obesity amenable to intervention. Several inter-related initiatives were implemented. To evaluate, we surveyed separate samples of adults in HAC communities before and after the interventions and compared responses to identical survey questions asked of adults living in Alberta in two waves of the Canadian Community Health Survey (CCHS).

RESULTS

The HAC sample included 4761 (2006) and 4733 (2009) people. The comparison sample included 9775 and 9784 respondents in 2005 and 2009-10 respectively. Self-reported body mass index showed no change, and neither were there significant changes in behaviors relative to secular trends. Most significant outcomes were relevant to social conditions, specifically sense of belonging to community in the intervention communities.

CONCLUSION

Health outcome indicators at the community level may not be sufficiently sensitive to capture changes which, over a relatively short term, would only be expected to be incremental, given that interventions were directed primarily to creating environmental conditions supportive of changes in behavioral outcomes rather than toward health outcome change directly.

Treatment of obesity and disability in schizophrenia

Despite 50 years of pharmacological and psychosocial interventions, schizophrenia remains one of the leading causes of disability. The inability to function in everyday settings includes deficits in performance of social, occupational, and independent living activities. Schizophrenia is also a life-shortening illness, caused mainly by poor physical health and its complications. Dysfunctional lifestyles including sedentary behavior and lack of physical activity prevail, while treatment with adipogenic psychotropic medication interacts with poor performance in screening, monitoring, and intervention that result in shortening of life expectancies by 25 to 30 years. Disability interferes with self-care and medical care, further worsening physical health to produce a vicious cycle of disability. Further, the neurobiological impact of obesity on brain functioning is substantial and relevant to schizophrenia. Simultaneous treatment of cognitive deficits and related deficits in functional skills, ubiquitous determinants of everyday functioning in schizophrenia, and targeted interventions aimed at poor physical health, especially obesity and associated comorbidities, may lead to additive or even interactive gains in everyday functioning in patients with schizophrenia not previously realized with other interventions.

Ghrelin signaling in the ventral hippocampus stimulates learned and motivational aspects of feeding via PI3K-Akt signaling

BACKGROUND

The stomach-derived hormone ghrelin drives higher-order feeding processes related to food reward and food seeking via central nervous system signaling at its receptor (GHSR1A). The specific nuclei mediating these effects are only partially understood. Here, we use a rat model to examine whether ghrelin signaling in the ventral subregion of the hippocampus (VHPC), a brain substrate of recent interest in energy balance control, affects learned and motivational aspects of feeding behavior.

METHODS

The effects of VHPC ghrelin administration were examined on feeding-relevant behavioral paradigms, including meal pattern analysis, operant lever pressing for sucrose, and conditioned stimulus-induced feeding. The intracellular signaling and downstream neuronal pathways stimulated by VHPC GHSR1A activation were assessed with immunoblot analysis and behavioral pharmacology.

RESULTS

Ghrelin delivery to the VHPC but not the dorsal hippocampus increased food intake primarily by increasing meal frequency. Intra-VHPC ghrelin delivery also increased willingness to work for sucrose and increased spontaneous meal initiation in nondeprived rats after the presentation of a conditioned stimulus that previously signaled meal access when the rats were food-restricted. The food intake enhancing effects of VHPC ghrelin were blocked by co-administration of a phosphoinositide 3-kinase (PI3K) inhibitor (LY294002). Immunoblot analyses provided complementary support for ghrelin activated PI3K-Akt signaling in the VHPC and revealed that this activation is blunted with high-fat diet consumption. Other immunoblot results show that VHPC GHSR1A signaling activates downstream dopaminergic activity in the nucleus accumbens.

CONCLUSIONS

These findings illuminate novel neuronal and behavioral mechanisms mediating ghrelinergic control of cognitive aspects of feeding control.

Long-term, intermittent, insulin-induced hypoglycemia produces marked obesity without hyperphagia or insulin resistance: a model for weight gain with intensive insulin therapy

A major side effect of insulin treatment of diabetes is weight gain, which limits patient compliance and may pose additional health risks. Although the mechanisms responsible for this weight gain are poorly understood, it has been suggested that there may be a link to the incidence of recurrent episodes of hypoglycemia. Here we present a rodent model of marked weight gain associated with weekly insulin-induced hypoglycemic episodes in the absence of diabetes. Insulin treatment caused a significant increase in both body weight and fat mass, accompanied by reduced motor activity, lowered thermogenesis in response to a cold challenge, and reduced brown fat uncoupling protein mRNA. However, there was no effect of insulin treatment on total food intake nor on hypothalamic neuropeptide Y or proopiomelanocortin mRNA expression, and insulin-treated animals did not become insulin-resistant. Our results suggest that repeated iatrogenic hypoglycemia leads to weight gain, and that such weight gain is associated with a multifaceted deficit in metabolic regulation rather than to a chronic increase in caloric intake.

Cognitive deficits, obesity and disability in schizophrenia

Despite 50 years of pharmacological and psychosocial interventions schizophrenia remains one of the leading causes of disability. The inability to function in everyday settings includes deficits in performance of social, occupational, and independent living activities. Schizophrenia is also a life-shortening illness, caused mainly by poor physical health and its complications. Dysfunctional lifestyles including sedentary behavior and lack of physical activity prevail, while treatment with adipogenic antipsychotic medication interacts with poor performance in screening, monitoring, and intervention that result in shortening of life expectancies by 25–30 years. Disability interferes with self-care and medical care, further worsening physical health to produce a vicious cycle of disability. Further, the neurobiological impact of obesity on brain functioning is substantial and relevant to schizophrenia. Decision making deficits that lead to choices resulting in obesity themselves have neurobiological determinants. Simultaneous treatment of cognitive deficits and related deficits in functional skills, ubiquitous determinants of everyday functioning in schizophrenia, and targeted interventions aimed at poor physical health, especially obesity and associated comorbidities, may lead to additive or even interactive gains in everyday functioning in patients with schizophrenia not previously realized with other interventions.