Inverse association of high-fat diet preference and anxiety-like behavior: a putative role for urocortin 2

Cafeteria diet and caloric restriction affect metabolic but not behavioral characteristics in male Wistar rats

This study aimed to evaluate the effects of a cafeteria diet and caloric restriction on behavioral and metabolic profiles of adult male Wistar rats. The rats were randomly divided into three groups (n = 12/group) and from 10 weeks of age fed either ad libitum standard rat chow (control group), ad libitum cafeteria diet in addition to standard chow (diet-induced obesity (DIO) group) or kept on caloric restriction (at 85% weight of controls; restricted group) for a period of 12 weeks. Body weight was assessed twice per week and glucose levels were measured at three times during the 12-week period. At week 11 the animals were behaviorally profiled using the multivariate concentric square field™ (MCSF) test. After 12 weeks of diet the animals were euthanized, blood collected, relative organ weights were assessed and plasma or serum levels of insulin, glucose, and lipid profile were measured. The DIO group gained 23% more weight than the control group (p < 0.001) and increased adipose tissue weight in comparison to the control (p < 0.001) and restricted (p < 0.001) groups. Glucose was significantly increased (p < 0.001) only during the second measurement at week 7 and insulin levels were elevated in the DIO group compared to controls and restricted groups (p < 0.01; p < 0.001, respectively). Plasma cholesterol levels were reduced for both DIO (p < 0.01) and restricted (p < 0.001) groups relative to controls. Adiponectin and leptin levels were higher for the DIO group in comparison to both the control (p < 0.001; p < 0.05) and restricted (p < 0.001; p < 0.001) groups. Thus, the two diets led to significant changes in body weight gain, adiposity, and metabolism. However, they did not alter the behavioral profiles in the MCSF test, suggesting that activity, exploration, risk assessment, risk taking or shelter seeking remained unaffected by the dietary interventions. The current findings suggest that an increase or reduction in energy intake resulted in no behavioral effects, despite the accompanying glycemic alterations potentially related to diabetes development.

Acute caffeine differently affects risk-taking and the expression of BDNF and of adenosine and opioid receptors in rats with high or low anxiety-like behavior

Anxiety disorders are common psychiatric conditions with a partially elucidated neurobiology. Caffeine, an unspecific adenosine receptor antagonist, is a common psychostimulant with anxiogenic effects in sensitive individuals. High doses of caffeine produce anxiety-like behavior in rats but it is not known if this is specific for rats with high baseline anxiety-like behavior. Thus, the aim of this study was to investigate general behavior, risk-taking, and anxiety-like behavior, as well as mRNA expression (adenosine A2A and A1, dopamine D2, and, μ, κ, δ opioid, receptors, BDNF, c-fos, IGF-1) in amygdala, caudate putamen, frontal cortex, hippocampus, hypothalamus, after an acute dose of caffeine. Untreated rats were screened using the elevated plus maze (EPM), giving each rat a score on anxiety-like behavior based on their time spent in the open arms, and categorized into a high or low anxiety-like behavior group accordingly. Three weeks after categorization, the rats were treated with 50 mg/kg caffeine and their behavior profile was studied in the multivariate concentric square field (MCSF) test, and one week later in the EPM. qPCR was performed on selected genes and corticosterone plasma levels were measured using ELISA. The results demonstrated that the high anxiety-like behavior rats treated with caffeine spent less time in risk areas of the MCSF and resituated towards the sheltered areas, a behavior accompanied by lower mRNA expression of adenosine A2A receptors in caudate putamen and increased BDNF expression in hippocampus. These results support the hypothesis that caffeine affects individuals differently depending on their baseline anxiety-like behavior, possibly involving adenosine receptors. This highlights the importance of adenosine receptors as a possible drug target for anxiety disorders, although further research is needed to fully elucidate the neurobiological mechanisms of caffeine on anxiety disorders.

Treadmill exercise training improves the high-fat diet-induced behavioral changes in the male rats

The purpose of this study was to investigate the effects of treadmill exercise training on obesity-induced behavioral changes in high-fat diet (HFD)-induced male rats. In this study, 40 male Sprague-Dawley rats were divided into 4 groups after they were weaned: Control (C), Exercise (E), Obese (O) and Obese + Exercise (O + E). For the obesity model % 60 high-fat diet were applied. After obesity was induced, rats were either moderate aerobic exercise (treadmill running) trained or left untrained. Different tasks to assess spatial learning and memory (Morris water maze test (MWMT)), depressive-like behavior (forced swimming test(FST), tail suspension test (TST) and anxiety-like behavior (light-dark test (LDT) and open field test (OFT)) were conducted. Exercise caused a significant reduction in duration of immobility in the O group in FST and the decrease in immobility in the O + E rats in TST. The O + E rats demonstrated a significant increase in the time spent in the light box as compared to the O group in the LDT. The O + E rats did not show any behavioral alterations as compared to all the other groups in the OFT. In the O + E group, there was a significant increase in the time spent in the target quadrant compared to the O group in the MWMT. Our results support that treadmill exercise could improve cognitive, depressive-like, anxiety-like behavioral changes in the HFD-induced obese rats.

Urocortin Neuropeptide Levels Are Impaired in the PBMCs of Overweight Children

The corticotropin-releasing hormone (CRH) and urocortins (UCNs) have been implicated in energy homeostasis and the cellular stress response. However, the expression of these neuropeptides in children remains unclear. Therefore, we determined the impact of obesity on their expression in 40 children who were normal weight, overweight, and had obesity. Peripheral blood mononuclear cells (PBMCs) and plasma were used to assess the expression of neuropeptides. THP1 cells were treated with 25 mM glucose and 200 µM palmitate, and gene expression was measured by real-time polymerase chain reaction (RT-PCR). Transcript levels of neuropeptides were decreased in PBMCs from children with increased body mass index as indicated by a significant decrease in UCN1, UCN3, and CRH mRNA in overweight and obese children. UCN3 mRNA expression was strongly correlated with UCN1, UCN2, and CRH. Exposure of THP1 cells to palmitate or a combination of high glucose and palmitate for 24 h increased CRH, UCN2, and UCN3 mRNA expression with concomitant increased levels of inflammatory and endoplasmic reticulum stress markers, suggesting a crosstalk between these neuropeptides and the cellular stress response. The differential impairment of the transcript levels of CRH and UCNs in PBMCs from overweight and obese children highlights their involvement in obesity-related metabolic and cellular stress.

Growth, behavioural, serum biochemical and morphological changes in female rabbits fed high-fat diet

This study aimed to determine whether high-fat diet (HFD) could cause growth, behavioural, biochemical and morphological changes in young female rabbits. Thirty-six female rabbits were randomly divided into two groups fed with either a high-fat diet (HFD) or a standard normal diet (SND) for 5 weeks. Growth and behavioural changes were recorded during the 5-week feeding period. Tissue samples, including blood and adipose tissue, were obtained after slaughter. HFD rabbits weighed more by the end of the feeding period, had a higher percent body weight and adipose tissue weight change and had longer body and bust lengths than SND rabbits. HFD rabbits significantly reduced their feed intake and feeding frequency during the fourth and fifth weeks. HFD rabbits also showed lower frequency of drinking and resting and increased stereotypical behaviour. Besides, HFD rabbits showed significant physiological abnormalities. HFD rabbits had higher serum cholesterol (TC) and triglycerides (TG) levels than SND rabbits at the end of the feeding period, and higher free fatty acid (FFA) levels than rabbits in the SND group after the third week of feeding. Serum thyroxine (T4) increased significantly in week 2 and week 5 and triiodothyronine (T3) increased significantly in week four. However, there was no significant change in serum glucose (GLU) and insulin (INS) levels. Additionally, HFD reduced the area and diameter of perirenal and subcutaneous fat cells and increased their density. Our findings suggest that HFD rabbits had higher weight gains, accumulation of fat, and more behavioural changes than SND rabbits. Although high levels of fat in the diet had a low impact on hyperglycaemia, it could lead to hyperlipidemia and hyperthyroidism. Our results also suggest that sustained HFD may cause the proliferation of adipocytes in young female rabbits.

Evaluation of the therapeutic potential of Epigallocatechin-3-gallate (EGCG) via oral gavage in young adult Down syndrome mice

Epigallocatechin-3-gallate (EGCG) is a candidate therapeutic for Down syndrome (DS) phenotypes based on in vitro inhibition of DYRK1A, a triplicated gene product of Trisomy 21 (Ts21). Consumption of green tea extracts containing EGCG improved some cognitive and behavioral outcomes in DS mouse models and in humans with Ts21. In contrast, treatment with pure EGCG in DS mouse models did not improve neurobehavioral phenotypes. This study tested the hypothesis that 200 mg/kg/day of pure EGCG, given via oral gavage, would improve neurobehavioral and skeletal phenotypes in the Ts65Dn DS mouse model. Serum EGCG levels post-gavage were significantly higher in trisomic mice than in euploid mice. Daily EGCG gavage treatments over three weeks resulted in growth deficits in both euploid and trisomic mice. Compared to vehicle treatment, EGCG did not significantly improve behavioral performance of Ts65Dn mice in the multivariate concentric square field, balance beam, or Morris water maze tasks, but reduced swimming speed. Furthermore, EGCG resulted in reduced cortical bone structure and strength in Ts65Dn mice. These outcomes failed to support the therapeutic potential of EGCG, and the deleterious effects on growth and skeletal phenotypes underscore the need for caution in high-dose EGCG supplements as an intervention in DS.

Impact of Free-Choice Diets High in Fat and Different Sugars on Metabolic Outcome and Anxiety-Like Behavior in Rats

OBJECTIVE

Rats were exposed to free-choice diets (fat plus one of two different sugar solutions, glucose or sucrose), and the metabolic consequences and impact on locomotor activity and anxiety-like behavior were explored.

METHODS

For 3 weeks, 7-week-old male rats were offered either chow only or free-choice high-fat diets differing in their added sugar: no sugar, sucrose, or glucose. In a second experiment, after 2 weeks on the diets, rats were switched from high sucrose to high glucose for two additional weeks. Metabolic end points included body weight, food intake, food choice, glycemic control, metabolic hormones, fat pad weight, brown adipose tissue weight, and gene expression. Behavioral analysis included locomotor and anxiety-like activity in the open field and elevated plus maze.

RESULTS

Both sugar diets enhanced adiposity and induced hyperphagia, favoring unhealthier dietary selection above that of the control diets (chow or free-choice high-fat with no sugar). Despite isocaloric intake in the sugar-containing diets, offering glucose instead of sucrose was associated with improved insulin sensitivity. The sugar-containing diets reduced activity (but with movements of increased velocity) and induced an anxiety-like phenotype.

CONCLUSIONS

Although free-choice diets negatively impacted on metabolism and anxiety-like behavior, replacing sucrose with glucose improved insulin sensitivity and may therefore be better for health.

Palatable Food Dampens the Long-Term Behavioral and Endocrine Effects of Juvenile Stressor Exposure but May Also Provoke Metabolic Syndrome in Rats

The juvenile period is marked by a reorganization and growth of important brain regions including structures associating with reward seeking behaviors such as the nucleus accumbens (NA) and prefrontal cortex (PFC). These changes are impacted by stressors during the juvenile period and may lead to a predisposition to stress induced psychopathology and abnormal development of brain reward systems. Like in humans, adult rodents engage certain coping mechanisms such as increases in the consumption of calorie-rich palatable foods to reduce stress, but this behavior can lead to obesity and metabolic disorders. In this study, we examined whether stressors during the juvenile period led to increased caloric intake when a palatable diet was accessible, and whether this diet attenuated adult stress responses. In addition, we examined if the stress buffering effects produced by the palatable diet were also accompanied by an offset propensity towards obesity, and by alterations in mRNA expression of dopamine (DA) receptors in the NA and PFC in adulthood. To this end, juvenile male Wistar rats underwent episodic stressor exposure (forced swim, elevated platform stress and restraint) on postnatal days (PD) 27-29 and received access to regular chow or daily limited access to a palatable diet until adulthood. At the age of 2 months, rats were tested on a social interaction test that screens for anxiety-like behaviors and their endocrine responses to an acute stressor. Animals were sacrificed, and their brains processed to detect differences in DA receptor subtype expression in the PFC and NA using qPCR. Results showed that rats that were stressed during the juvenile period displayed higher social anxiety and a sensitized corticosterone response as adults and these effects were attenuated by access to the palatable diet. Nevertheless, rats that experienced juvenile stress and consumed a palatable diet showed greater adiposity in adulthood. Interestingly, the same group displayed greater mRNA expression of DA receptors at the NA. This suggests that access to a palatable diet mitigates the behavioral and endocrine effects of juvenile stressor exposure in adulthood, but at the cost of metabolic imbalances and a sensitized dopaminergic system.

Treadmill Intervention Attenuates the Cafeteria Diet-Induced Impairment of Stress-Coping Strategies in Young Adult Female Rats

The current prevalence of diet-induced overweight and obesity in adolescents and adults is continuously growing. Although the detrimental biochemical and metabolic consequences of obesity are widely studied, its impact on stress-coping behavior and its interaction with specific exercise doses (in terms of intensity, duration and frequency) need further investigation. To this aim, we fed adolescent rats either an obesogenic diet (cafeteria diet, CAF) or standard chow (ST). Each group was subdivided into four subgroups according to the type of treadmill intervention as follows: a sedentary group receiving no manipulation; a control group exposed to a stationary treadmill; a low-intensity treadmill group trained at 12 m/min; and a higher intensity treadmill group trained at 17 m/min. Both the diet and treadmill interventions started at weaning and lasted for 8 weeks. Subjects were tested for anxiety-like behavior in the open field test and for coping strategies in the two-way active avoidance paradigm at week 7 and were sacrificed at week 8 for biometric and metabolic characterization. CAF feeding increased the weight gain, relative retroperitoneal white adipose tissue (RWAT %), and plasma levels of glucose, insulin, triglycerides and leptin and decreased the insulin sensitivity. Treadmill intervention partially reversed the RWAT% and triglyceride alterations; at higher intensity, it decreased the leptin levels of CAF-fed animals. CAF feeding decreased the motor activity and impaired the performance in a two-way active avoidance assessment. Treadmill intervention reduced defecation in the shuttle box, suggesting diminished anxiety. CAF feeding combined with treadmill training at 17 m/min increased the time spent in the center of the open field and more importantly, partially reversed the two-way active avoidance deficit. In conclusion, this study demonstrates that at doses that decreased anxiety-like behavior, treadmill exercise partially improved the coping strategy in terms of active avoidance behavior in the CAF-fed animals. This effect was not observed at lower doses of treadmill training.

Time-dependent behavioral, neurochemical, and metabolic dysregulation in female C57BL/6 mice caused by chronic high-fat diet intake

High-fat diet (HFD) induced obesity is associated not only with metabolic dysregulation, e.g., impaired glucose homeostasis and insulin sensitivity, but also with neurological dysfunction manifested with aberrant behavior and/or neurotransmitter imbalance. Most studies have examined HFD's effects predominantly in male subjects, either in the periphery or on the brain, in isolation and after a finite feeding period. In this study, we evaluated the time-course of selected metabolic, behavioral, and neurochemical effects of HFD intake in parallel and at multiple time points in female (C57BL/6) mice. Peripheral effects were evaluated at three feeding intervals (short: 5-6 weeks, long: 20-22 weeks, and prolonged: 33-36 weeks). Central effects were evaluated only after long and prolonged feeding durations; we have previously reported those effects after the short (5-6 weeks) feeding duration. Ongoing HFD feeding resulted in an obese phenotype characterized by increased visceral adiposity and, after prolonged HFD intake, an increase in liver and kidney weights. Peripherally, 5 weeks of HFD intake was sufficient to impair glucose tolerance significantly, with the deleterious effects of HFD being greater with prolonged intake. Similarly, 5 weeks of HFD consumption was sufficient to impair insulin sensitivity. However, sensitivity to insulin after prolonged HFD intake was not different between control, low-fat diet (LFD) and HFD-fed mice, most likely due to age-dependent decrease in insulin sensitivity in the LFD-fed mice. HFD intake also induced bi-phasic hepatic inflammation and it increased gut permeability. Behaviorally, prolonged intake of HFD caused mice to be hypoactive and bury fewer marbles in a marble burying task; the latter was associated with significantly impaired hippocampal serotonin homeostasis. Cognitive (short-term recognition memory) function of mice was unaffected by chronic HFD feeding. Considering our prior findings of short-term (5-6 weeks) HFD-induced central (hyperactivity/anxiety and altered ventral hippocampal neurochemistry) effects and our current results, it seems that in female mice some metabolic/inflammatory dysregulations caused by HFD, such as gut permeability, appear early and persist, whereas others, such as glucose intolerance, are exaggerated with continuous HFD feeding; behaviorally, prolonged HFD consumption mainly affects locomotor activity and anxiety-like responses, likely due to the advanced obesity phenotype; neurochemically, the serotonergic system appears to be most sensitive to continued HFD feeding.

The effects of neuropeptide urocortin 2 on the spontaneous discharge and glutamatergic neurotransmission of striatum neurons

The primary cause of the neurodegenerative process that underlies Parkinson's disease (PD) is still unknown. Different mechanisms probably contribute to triggering neuronal death in the nigro-striatum pathway. The neuropeptide urocortin 2 (UCN2) plays an important role in the regulation of striatum (STR) neurons projection. We investigated the effects of UCN2 on spontaneous discharge and glutamatergic responses in STR for a better understanding of the pathogenesis of PD. The experiment used microiontophoresis method to observe the effects of UCN2 on STR neurons' firing rates in vivo. Corticotrophin releasing factor receptor 2 (CRF-R2) selective inhibitor, astressin-2B (AST-2B), was administered simultaneously with UCN2 to investigate the effects of UCN2 on CRF-R2. Moreover, we further explored the effects of UCN2 on glutamatergic responses in STR neurons. We found that UCN2 could significantly inhibit the firing rate of 84% of the tested STR neurons, and its inhibitory effect followed a concentration-dependent manner. During the microiontophoresis of GLU, the excitatory firing of glutamatergic neurons could be attenuated by the addition of UCN2, but enhanced by the application of AST-2B. The results suggest that UCN2 could regulate the effects of STR neurotransmitters (GLU) via CRF-R2 and may thereby contribute to the improvement of PD.

Association between mood and diet quality in subjects with metabolic syndrome participating in a behavioural weight-loss programme: a cross-sectional assessment

BACKGROUND/OBJECTIVE

The interplay between individual's mood fluctuations and nutrition has important health implications. However, little information is available on the relationship between dietary intake and mood state in a population with metabolic syndrome (MetS). The aim of the present study was to evaluate the association between dietary intake and mood state in subjects with MetS.

METHODS

This cross-sectional study was based on the baseline data of 84 volunteers (mean age 49 ± 1 years) recruited into the Metabolic Syndrome Reduction in Navarra-Spain (RESMENA-S) study. Mood state was determined using a mood thermometer visual analogue scale. The dietary intake was assessed with a 48-hours weighted food record, from which a Healthy Eating Index (HEI) score was obtained. Anthropometrical measurements and biochemical parameters were also analysed.

RESULTS

At baseline, a positive association between mood thermometer and HEI was observed. Among the 10 HEI components, vegetables, fruits, calories from lipids, saturated fatty acids, and dietary variety were related with higher mood. Moreover, those participants who consumed more water, fibre, vitamin B6, ascorbic acid, tryptophan, magnesium, and selenium have higher mood.

DISCUSSION

In conclusion, an association between both the overall dietary pattern and isolated nutrients with mood state was observed. The analyses of both dietary patterns and specific nutrients are important to determine the association between mental disorders and dietary intake.

Effects of a post-weaning cafeteria diet in young rats: metabolic syndrome, reduced activity and low anxiety-like behaviour

Among adolescents, overweight, obesity and metabolic syndrome are rapidly increasing in recent years as a consequence of unhealthy palatable diets. Animal models of diet-induced obesity have been developed, but little is known about the behavioural patterns produced by the consumption of such diets. The aim of the present study was to determine the behavioural and biochemical effects of a cafeteria diet fed to juvenile male and female rats, as well as to evaluate the possible recovery from these effects by administering standard feeding during the last week of the study. Two groups of male and female rats were fed with either a standard chow diet (ST) or a cafeteria (CAF) diet from weaning and for 8 weeks. A third group of males (CAF withdrawal) was fed with the CAF diet for 7 weeks and the ST in the 8th week. Both males and females developed metabolic syndrome as a consequence of the CAF feeding, showing overweight, higher adiposity and liver weight, increased plasma levels of glucose, insulin and triglycerides, as well as insulin resistance, in comparison with their respective controls. The CAF diet reduced motor activity in all behavioural tests, enhanced exploration, reduced anxiety-like behaviour and increased social interaction; this last effect was more pronounced in females than in males. When compared to animals only fed with a CAF diet, CAF withdrawal increased anxiety in the open field, slightly decreased body weight, and completely recovered the liver weight, insulin sensitivity and the standard levels of glucose, insulin and triglycerides in plasma. In conclusion, a CAF diet fed to young animals for 8 weeks induced obesity and metabolic syndrome, and produced robust behavioural changes in young adult rats, whereas CAF withdrawal in the last week modestly increased anxiety, reversed the metabolic alterations and partially reduced overweight.

Regulation of corticotropin-releasing factor and urocortin 2/3 mRNA by leptin in hypothalamic N39 cells

Corticotropin-releasing factor (CRF) activates the pituitary-adrenal axis during stress, and shows anorectic effects via CRF type 1 receptors in the hypothalamus. Both urocortin (Ucn) 2 and Ucn3 also act as anorectic neuropeptides via CRF type 2 receptors. Leptin, a product of the obesity gene secreted mainly from adipose tissue, reduces food intake and increases energy expenditure. A possible interaction between leptin and CRF/Ucns has been suggested, as leptin can regulate expression and activation of CRF and Ucns in the hypothalamus. This study aimed to explore the possible function of leptin in the hypothalamus, and its effects in regulating CRF and Ucns. The study identified mRNA expression of the leptin receptor (Ob-R) and its subtypes, CRF, and Ucn2/3 in mouse hypothalamic N39 cells. Leptin stimulated signal transducer and activators of transcription type 3 (STAT3) phosphorylation, directly increased the mRNA levels of both CRF and Ucn2/3 in hypothalamic cells, and increased Ob-Rb mRNA levels. A Janus kinase inhibitor inhibited the leptin-mediated increase in STAT3 phosphorylation, and then the increases in CRF and Ucn2/3 mRNA levels. Leptin may contribute to a stress response or anorectic effect via the regulation of CRF and Ucn2/3 in the hypothalamus.

Diet-regulated anxiety

A substantial proportion of noncommunicable disease originates in habitual overconsumption of calories, which can lead to weight gain and obesity and attendant comorbidities. At the other end of the spectrum, the consequences of undernutrition in early life and at different stages of adult life can also have major impact on wellbeing and quality of life. To help address some of these issues, greater understanding is required of interactions with food and contemporary diets throughout the life course and at a number of different levels: physiological, metabolic, psychological, and emotional. Here we review the current literature on the effects of dietary manipulation on anxiety-like behaviour. This evidence, assembled from study of preclinical models of diet challenge from gestation to adult life, supports a role for diet in the important connections between psychology, physiology, and behaviour. Analogous processes in the human population in our current obesogenic environment are likely to contribute to individual and societal challenges in this area.

Effects of a high-fat diet and bamboo extract supplement on anxiety- and depression-like neurobehaviours in mice

High-fat diet is a major causative factor of overweight and obesity, which are associated with an increased risk of neuropsychiatric diseases, such as anxiety and depression. In the present study, we investigated the protective effects of bamboo extract (BEX) on anxiety- and depression-like neurobehaviours in mice treated with a high-fat diet. Male mice with CD-1 genetic background were treated for 2 months with either a standard or a high-fat diet (10 or 45 % energy from fat, respectively), with or without the BEX supplement (11 g dry mass per 17 MJ). The anxiety levels of mice were evaluated using open-field and hole-board tests, and depression was measured using the force-swimming test. The anxiety responses of the animals were found significantly increased after the high-fat diet treatment, and this elevation was effectively abolished by the BEX supplement. The high-fat diet seemed to have an anti-depressive effect in mice at the tested time point, but the effect of the BEX supplement on the depression level of the animals was not conclusive. The high-fat diet significantly decreased total glutathione content in the blood while the BEX supplement increased glutathione oxidation. In summary, the present study shows that decreased total glutathione concentration in the blood co-occurred with a high-fat treatment, high anxiety level and low depression level in mice, and when supplemented in a high-fat diet, BEX had an anxiolytic effect in mice.

Association of TMEM18 variants with BMI and waist circumference in children and correlation of mRNA expression in the PFC with body weight in rats

Genome-wide association studies have shown a strong association of single-nucleotide polymorphisms (SNPs) in the near vicinity of the TMEM18 gene. The effects of the TMEM18-associated variants are more readily observed in children. TMEM18 encodes a 3TM protein, which locates to the nuclear membrane. The functional context of TMEM18 and the effects of its associated variants are as of yet undetermined. To further explore the effects of near-TMEM18 variants, we have genotyped two TMEM18-associated SNPs, rs6548238 and rs4854344, in a cohort of 2352 Greek children (Healthy Growth Study). Included in this study are data on anthropomorphic traits body weight, BMI z-score and waist circumference. Also included are dietary energy and macronutrient intake as measured via 24-h recall interviews. Major alleles of rs6548238 and rs4854344 were significantly associated with an increased risk of obesity (odds ratio = 1.489 (1.161-1.910) and 1.494 (1.165-1.917), respectively), and positively correlated to body weight (P = 0.017, P = 0.010) and waist circumference (P = 0.003, P = 0.003). An association to energy and macronutrient intake was not observed in this cohort. We also correlated food intake and body weight in a food choice model in rats to Tmem18 expression in central regions involved in feeding behavior. We observed a strong positive correlation between TMEM18 expression and body weight in the prefrontal cortex (PFC) (r = 0.5694, P = 0.0003) indicating a potential role for TMEM18 in higher functions related to feeding involving the PFC.

The multivariate concentric square field test reveals behavioral profiles of risk taking, exploration, and cognitive impairment in mice subjected to traumatic brain injury

There is a need for more efficient tests to evaluate functional outcome following experimental traumatic brain injury (TBI), reflecting deficits in cognitive, sensory, and motor functions that are seen in TBI patients. The Multivariate Concentric Square Field (MCSF) test is a relatively new behavioral model that measures exploration, risk taking, risk assessment, and shelter seeking, all of which are evolutionarily-conserved strategies for survival. The multivariate design enables scoring of different functional domains in a single test situation, with a free choice of optional environmental settings. Furthermore, repeated trials permits cognitive effects to be measured. In the present study, 11 anesthetized C57BL6 mice received controlled cortical injury (CCI) (0.5 mm and 3.3 m/sec) over the right parietal cerebral cortex or sham surgery (n = 12). Naïve mice (n = 12) not subjected to any surgical procedure were also included. The animals were evaluated in the MCSF test at 2 and 7 days post-surgery, and behavioral profiles were analyzed. The results revealed differences in risk taking and explorative behavior between the sham animals and the animals subjected to trauma. Animals subjected to trauma were characterized by taking more risks and had a higher level of exploration activity, but they sought less shelter. Repeated exposure to the MCSF caused a general decrease in activity in the naïve and sham group, while a more specific behavioral impairment was seen in injured mice, suggesting cognitive dysfunction. We submit that the MCSF test is a useful complementary tool for functional outcome evaluation in experimental TBI.

Diet choice, cortisol reactivity, and emotional feeding in socially housed rhesus monkeys

Chronic psychosocial stress produces an array of adverse health consequences that are highly comorbid, including emotional eating, affective disorders, and metabolic syndrome. The consumption of high caloric diets (HCDs) is thought to provide comfort in the face of unrelenting psychosocial stress. Using social subordination in female rhesus monkeys as a model of continual exposure to daily stressors in women, we tested the hypothesis that subordinate females would consume significantly more calories from a HCD compared to dominant females, and this pattern of food intake would be associated with reduced cortisol release and reduced frequency of anxiety-like behaviors. Food intake, parameters of cortisol secretion, and socio-emotional behavior were assessed for 3 weeks during a no choice phase when only a low caloric diet (LCD) was available and during a choice condition when both a LCD and HCD were available. While all animals preferred the HCD, subordinate females consumed significantly more of the HCD than did dominant females. A flattening of the diurnal cortisol rhythm and a greater increase in serum cortisol to an acute social separation occurred during the diet choice condition in all females. Furthermore, the rate of anxiety-like behavior progressively declined during the 3-week choice condition in subordinate but not dominant females. These data provide support for the hypothesis that daily exposure to psychosocial stress increases consumption of calorically dense foods. Furthermore, consumption of HCDs may be a metabolic stressor that synergizes with the psychosocial stress of subordination to further increase the consumption of these diets.

Diet-induced obesity differentially regulates behavioral, biomechanical, and molecular risk factors for osteoarthritis in mice

Introduction

Obesity is a major risk factor for the development of osteoarthritis in both weight-bearing and nonweight-bearing joints. The mechanisms by which obesity influences the structural or symptomatic features of osteoarthritis are not well understood, but may include systemic inflammation associated with increased adiposity. In this study, we examined biomechanical, neurobehavioral, inflammatory, and osteoarthritic changes in C57BL/6J mice fed a high-fat diet.

Methods

Female C57BL/6J mice were fed either a 10% kcal fat or a 45% kcal fat diet from 9 to 54 weeks of age. Longitudinal changes in musculoskeletal function and inflammation were compared with endpoint neurobehavioral and osteoarthritic disease states. Bivariate and multivariate analyses were conducted to determine independent associations with diet, percentage body fat, and knee osteoarthritis severity. We also examined healthy porcine cartilage explants treated with physiologic doses of leptin, alone or in combination with IL-1α and palmitic and oleic fatty acids, to determine the effects of leptin on cartilage extracellular matrix homeostasis.

Results

High susceptibility to dietary obesity was associated with increased osteoarthritic changes in the knee and impaired musculoskeletal force generation and motor function compared with controls. A high-fat diet also induced symptomatic characteristics of osteoarthritis, including hyperalgesia and anxiety-like behaviors. Controlling for the effects of diet and percentage body fat with a multivariate model revealed a significant association between knee osteoarthritis severity and serum levels of leptin, adiponectin, and IL-1α. Physiologic doses of leptin, in the presence or absence of IL-1α and fatty acids, did not substantially alter extracellular matrix homeostasis in healthy cartilage explants.

Conclusions

These results indicate that diet-induced obesity increases the risk of symptomatic features of osteoarthritis through changes in musculoskeletal function and pain-related behaviors. Furthermore, the independent association of systemic adipokine levels with knee osteoarthritis severity supports a role for adipose-associated inflammation in the molecular pathogenesis of obesity-induced osteoarthritis. Physiologic levels of leptin do not alter extracellular matrix homeostasis in healthy cartilage, suggesting that leptin may be a secondary mediator of osteoarthritis pathogenesis.

Lower risk taking and exploratory behavior in alcohol-preferring sP rats than in alcohol non-preferring sNP rats in the multivariate concentric square field (MCSF) test

The present investigation continues previous behavioral profiling studies of selectively bred alcohol-drinking and alcohol non-drinking rats. In this study, alcohol-naïve adult Sardinian alcohol-preferring (sP) and non-preferring (sNP) rats were tested in the multivariate concentric square field (MCSF) test. The MCSF test has an ethoexperimental approach and measures general activity, exploration, risk assessment, risk taking, and shelter seeking in laboratory rodents. The multivariate design enables behavioral profiling in one and the same test situation. Age-matched male Wistar rats were included as a control group. Five weeks after the first MCSF trial, a repeated testing was done to explore differences in acquired experience. The results revealed distinct differences in exploratory strategies and behavioral profiles between sP and sNP rats. The sP rats were characterized by lower activity, lower exploratory drive, higher risk assessment, and lower risk taking behavior than in sNP rats. In the repeated trial, risk-taking behavior was almost abolished in sP rats. When comparing the performance of sP and sNP rats with that of Wistar rats, the principal component analysis revealed that the sP rats were the most divergent group. The vigilant behavior observed in sP rats with low exploratory drive and low risk-taking behavior is interpreted here as high innate anxiety-related behaviors and may be related to their propensity for high voluntary alcohol intake and preference. We suggest that the different lines of alcohol-preferring rats with different behavioral characteristics constitute valuable animal models that mimic the heterogeneity in human alcohol dependence.

Impact of nandrolone decanoate on gene expression in endocrine systems related to the adverse effects of anabolic androgenic steroids

Elite athletes, body builders and adolescents misuse anabolic-androgenic steroids (AAS) in order to increase muscle mass or to enhance physical endurance and braveness. The high doses misused are associated with numerous adverse effects. The purpose of this study was to evaluate the impact of chronic supratherapeutic AAS treatment on circulating hormones and gene expression in peripheral tissues related to such adverse effects. Quantitative real-time PCR was used to measure expression levels of in total 37 genes (including peptide hormones, cell membrane receptors, nuclear receptors, steroid synthesising enzymes and other enzymes) in the pituitary, testes, adrenals, adipose tissue, kidneys and liver of male Sprague-Dawley rats after 14-day administration of the AAS nandrolone decanoate, 3 or 15 mg/kg. Plasma glucose and levels of adrenocorticotropic hormone (ACTH), adiponectin, corticosterone, ghrelin, insulin and leptin were also measured. We found several expected effects on the hypothalamic-pituitary-gonadal axis, while the treatment also caused a number of other not previously identified changes in circulating factors and gene transcription levels such as the dose-dependent reduction of the beta(3)-adrenergic receptor in adipose tissue, reduction of both circulating and mRNA levels of adiponectin, up-regulation of both hydroxymethylglutaryl-CoA-reductase, the rate-limiting enzyme in de novo synthesis of cholesterol, and the receptor for ACTH in the adrenals. The results provide evidence for wide ranging effects of AAS on the hypothalamic-pituitary-adrenal axis, adipose tissue and substrates of the renal control of blood pressure.