Stress induced obesity: lessons from rodent models of stress

Growth Hormone Secretagogue Receptor (GHSR) Signaling in the Ventral Tegmental Area (VTA) Mediates Feeding Produced by Chronic Social Defeat Stress in Male Mice

Ghrelin, a hormone secreted by the stomach, binds to the growth hormone secretagogue receptor (GHSR) in various brain regions to produce a number of behavioral effects that include increased feeding motivation. During social defeat stress, ghrelin levels rise in correlation with increased feeding and potentially play a role in attenuating the anxiogenic effects of social defeat. One region implicated in the feeding effects of ghrelin is the ventral tegmental area (VTA), a region implicated in reward seeking behaviors, and linked to social defeat in mice. Here we examined the role of GHSR signaling in the VTA in feeding behavior in mice exposed to social defeat stress. Male C57BL/J6 mice that were socially defeated once daily for 3 weeks ate more, had higher plasma ghrelin level and increased GHSR expression in the VTA compared to non-stressed mice. Socially defeated GHSR KO mice failed to increase their caloric intake in response to this stressor but rescue of GHSR expression in the VTA restored feeding responses. Finally, we pharmacologically blocked VTA GHSR signalling with JMV2959 infused via an indwelling VTA cannula connected to a minipump. Vehicle-treated mice increased their caloric intake during social defeat, but JMV2959-infusions attenuated feeding responses and increased anxiety-like behaviors. The data suggest that GHSR signalling in the VTA is critical for the increases in appetite observed during chronic social defeat stress. Furthermore, these data support the idea that GHSR signaling in the VTA may also have anxiolytic effects, and blocking GHSR in this region may result in an anxiety-like phenotype.

A multi-modal approach to investigate Desmodium gangeticum's influence on stress-induced male infertility: In vivo, in vitro, and in silico assessments

Physical and psychological stress has an inverse relation with male libido and sperm quality. The present study investigates the potential fertility-enhancing properties of Desmodium gangeticum (DG) root extracts in male Wister rats subjected to immobilization-induced stress (SIMB). DG roots were extracted using n-hexane (HEDG), chloroform (CEDG), and water (AEDG). In the pilot study, aphrodisiac protentional was investigated at two doses (125 and 250 mg kg-1) of each extract. In the main study, the HEDG and AEDG at 125 and 250 mg kg-1 were challenged for the stress by immobilization (SIMB), for 6 h daily over 28 days. Parameters assessed included aphrodisiac effects, gonadosomatic index (GSI), semen quality, sperm quantity, fructose content, serum hormonal levels, testicular oxidative stress, and testicular histopathology. Additional in silico studies, including the lipid solubility index, molecular docking, molecular dynamics, and SymMap studies were conducted for validation. HEDG demonstrated significant aphrodisiac activity, improved - GSI, sperm quality and quantity, and fructose content, serum testosterone levels, histological changes induced by SIMB in the testes. Swiss ADME studies indicated Gangetin (a pterocarpan) had a high brain permeation index (4.81), a superior docking score (-8.22), and higher glide energy (-42.60), compared with tadalafil (-7.17). The 'Lig fit Prot' plot in molecular dynamics simulations revealed a strong alignment between Gangetin and phosphodiesterase type 5 (PDE5). HEDG exerts aphrodisiac effects by increasing blood testosterone levels and affecting PDE5 activity. The protective effects on spermatozoa-related parameters and testicular histological changes are attributed to the antioxidant and anti-inflammatory properties, of pterocarpan (gangetin).

The Level of Sex Hormones and Corticosterone in Female Rats during Modeling of Visceral Obesity, Subsequent Physical Activity, and Normalization of the Diet

The effects of diet-induced visceral obesity and non-drug options of its correction on the level of sex hormones and corticosterone were evaluated in 84 female Wistar rats. During stage I, the rats received either a standard diet (STD) or a high-calorie diet (HCD) for 8 weeks. During stage II, the animals were divided into subgroups depending on obesity correction: without correction (STD control and HCD), transition from HCD to STD (HCD/STD) and/or physical activity (treadmill exercise) for the next 8 weeks (HCD/STD+exercise, STD+exercise, and HCD+exercise). Diet-induced visceral obesity resulted in hyperandrogenization and increased blood corticosterone levels in females. Transition from HCD to STD regardless of physical activity led to normalization of testosterone level and, accordingly, to return to the functional norm of estrogen-androgen balance. The positive effect of moderate physical activity on hormonal status is realized only against the background of a balanced diet or during the transition from HCD to STD.

Chronic stress from adolescence to adulthood increases adiposity and anxiety in rats with decreased expression of Krtcap3

We previously identified Keratinocyte-associated protein 3, Krtcap3, as a novel adiposity gene, but subsequently found that its impact on adiposity may depend on environmental stress. To more thoroughly understand the connection between Krtcap3, adiposity, and stress, we exposed wild-type (WT) and Krtcap3 knock-out (KO) rats to chronic stress then measured adiposity and behavioral outcomes. We found that KO rats displayed lower basal stress than WT rats under control conditions and exhibited metabolic and behavioral responses to chronic stress exposure. Specifically, stress-exposed KO rats gained more weight, consumed more food when socially isolated, and displayed more anxiety-like behaviors relative to control KO rats. Meanwhile, there were minimal differences between control and stressed WT rats. At study conclusion stress-exposed KO rats had increased corticosterone (CORT) relative to control KO rats with no differences between WT rats. In addition, KO rats, independent of prior stress exposure, had an increased CORT response to removal of their cage-mate (psychosocial stress), which was only seen in WT rats when exposed to chronic stress. Finally, we found differences in expression of the glucocorticoid receptor, Nr3c1, in the pituitary and colon between control and stress-exposed KO rats that were not present in WT rats. These data support that Krtcap3 expression affects stress response, potentially via interactions with Nr3c1, with downstream effects on adiposity and behavior. Future work is necessary to more thoroughly understand the role of Krtcap3 in the stress response.

Exposure to early-life stress impairs weight-loss maintenance success in mice

OBJECTIVE

The impact of early-life stress on weight-loss maintenance is unknown.

METHODS

Mice underwent neonatal maternal separation (NMS) from 0 to 3 weeks and were weaned onto a high-fat sucrose diet (HFSD) from 3 to 20 weeks. Calorie-restricted weight loss on a low-fat sucrose diet (LFSD) occurred over 2 weeks to induce a 20% loss in body weight, which was maintained for 6 weeks. After weight loss, half of the mice received running wheels, and the other half remained sedentary. Mice were then fed ad libitum on an HFSD or LFSD for 10 weeks and were allowed to regain body weight.

RESULTS

NMS mice had greater weight regain, total body weight, and adiposity compared with naïve mice. During the first week of refeeding, NMS mice had increased food intake and were in a greater positive energy balance than naïve mice. Female mice were more susceptible to NMS-induced effects, including increases in adiposity. NMS and naïve females were more susceptible to HFSD-induced weight regain. Exercise was beneficial in the first week of regain in male mice, but, long-term, only those on the LFSD benefited from exercise. As expected, HFSD led to greater weight regain than LFSD.

CONCLUSIONS

Early-life stress increases weight regain in mice.

The Association of Insomnia and Stress on Cardiovascular Risk Factors during COVID-19 Confinement in the Mexican Population

During the pandemic confinement, the WHO changed the term "social distancing" to "physical distancing", to help people deal with the lack of social contact. As a result, there was an increase in mental health problems, including insomnia and stress, with a negative impact on cardiovascular health. The objective of this research was to identify the association between insomnia and stress and cardiovascular risk (CVR) during the pandemic in a sample of the general population in Mexico; the participants were chosen using the non-probabilistic method. The data were obtained from an online questionnaire about medical histories focused on cardiovascular risk, according to the Official Mexican Standards and Regulations for patients' clinical records, NOM-004-SSA3-2012, along with an index for the severity of insomnia, measured with a seven-item guide, and an instrument to measure stress. The data were analyzed with descriptive statistics for several different variables: sociodemographics, stress, insomnia, and cardiovascular risk. Cardiovascular risk was compared to insomnia and stress variables, which led to statistically significant differences and correlations between the variables. Participants were divided into four groups with respect to CVR, from low to very high CVR. This research demonstrated that women were more susceptible to stress and cardiovascular risk. However, stress was a more major indicator of CVR than insomnia, but in the high and very high CVR groups, insomnia contributed along with stress; coping strategies reduced the risk in the high CVR group but did not function as expected with respect to reducing risk in the very high CVR group. These findings suggest that sleep patterns and mental health alterations present during the pandemic may persist even when the pandemic was declared as having ended and may contribute to increases in cardiovascular risk in the long-term.

Impact of prolonged chronic social isolation stress on behavior and multifractal complexity of metabolic rate in Octodon degus

Social interaction can improve animal performance through the prevention of stress-related events, the provision of security, and the enhancement of reproductive output and survival. We investigated the effects of prolonged chronic social isolation stress on behavioral, cognitive, and physiological performance in the social, long-lived rodent Octodon degus. Degu pups were separated into two social stress treatments: control (CTRL) and chronically isolated (CI) individuals from post-natal and post-weaning until adulthood. We quantified anxiety-like behavior and cognitive performance with a battery of behavioral tests. Additionally, we measured their basal metabolic rate (BMR) and analyzed the multifractal properties of the oxygen consumption time series using Multifractal Detrended Fluctuation Analysis, a well-known method for assessing the fractal characteristics of biological signals. Our results showed that CI induced a significant increase in anxiety-like behaviors and led to a reduction in social and working memory in male degus. In addition, CI-treated degus reduced the multifractal complexity of BMR compared to CTRL, which implies a decrease in the ability to respond to environmental stressors and, as a result, an unhealthy state. In contrast, we did not observe significant effects of social stress on BMR. Multivariate analyses showed a clear separation of behavior and physiological variables into two clusters, corresponding to CI and CTRL degus. This study provides novel insights into the effects of prolonged chronic social isolation stress on behavior, cognitive performance, and metabolic complexity in this rodent animal model. To the best of our knowledge, it is the first study to integrate cognitive-behavioral performance and multifractal dynamics of a physiological signal in response to prolonged social isolation. These findings highlight the importance of social interactions for the well-being and overall performance of social animals.

Neural crest cells as a source of microevolutionary variation

Vertebrates have some of the most complex and diverse features in animals, from varied craniofacial morphologies to colorful pigmentation patterns and elaborate social behaviors. All of these traits have their developmental origins in a multipotent embryonic lineage of neural crest cells. This "fourth germ layer" is a vertebrate innovation and the source of a wide range of adult cell types. While others have discussed the role of neural crest cells in human disease and animal domestication, less is known about their role in contributing to adaptive changes in wild populations. Here, we review how variation in the development of neural crest cells and their derivatives generates considerable phenotypic diversity in nature. We focus on the broad span of traits under natural and sexual selection whose variation may originate in the neural crest, with emphasis on behavioral factors such as intraspecies communication that are often overlooked. In all, we encourage the integration of evolutionary ecology with developmental biology and molecular genetics to gain a more complete understanding of the role of this single cell type in trait covariation, evolutionary trajectories, and vertebrate diversity.

Circle(s) of Life: The Circadian Clock from Birth to Death

Most lifeforms on earth use endogenous, so-called circadian clocks to adapt to 24-h cycles in environmental demands driven by the planet’s rotation around its axis. Interactions with the environment change over the course of a lifetime, and so does regulation of the circadian clock system. In this review, we summarize how circadian clocks develop in humans and experimental rodents during embryonic development, how they mature after birth and what changes occur during puberty, adolescence and with increasing age. Special emphasis is laid on the circadian regulation of reproductive systems as major organizers of life segments and life span. We discuss differences in sexes and outline potential areas for future research. Finally, potential options for medical applications of lifespan chronobiology are discussed.

Association of long-term air pollution exposure with the risk of prediabetes and diabetes: Systematic perspective from inflammatory mechanisms, glucose homeostasis pathway to preventive strategies

BACKGROUND

Limited evidence suggests the association of air pollutants with a series of diabetic cascades including inflammatory pathways, glucose homeostasis disorder, and prediabetes and diabetes. Subclinical strategies for preventing such pollutants-induced effects remain unknown.

METHODS

We conducted a cross-sectional study in two typically air-polluted Chinese cities in 2018-2020. One-year average PM₁, PM_2.5, PM₁₀, SO₂, NO₂, and O₃ were calculated according to participants' residence. GAM multinomial logistic regression was performed to investigate the association of air pollutants with diabetes status. GAM and quantile g-computation were respectively performed to investigate individual and joint effects of air pollutants on glucose homeostasis markers (glucose, insulin, HbA1c, HOMA-IR, HOMA-B and HOMA-S). Complement C3 and hsCRP were analyzed as potential mediators. The ABCS criteria and hemoglobin glycation index (HGI) were examined for their potential in preventive strategy.

RESULTS

Long-term air pollutants exposure was associated with the risk of prediabetes [Prevalence ratio for O₃ (PR_O₃) = 1.96 (95% CI: 1.24, 3.03)] and diabetes [PR_PM₁ = 1.18 (95% CI: 1.05, 1.32); PR_PM_2.5 = 1.08 (95% CI: 1.00, 1.16); PR_O₃ = 1.35 (95% CI: 1.03, 1.74)]. PM₁, PM₁₀, SO₂ or O₃ exposure was associated with glucose-homeostasis disorder. For example, O₃ exposure was associated with increased levels of glucose [7.67% (95% CI: 1.75, 13.92)], insulin [19.98% (95% CI: 4.53, 37.72)], HOMA-IR [34.88% (95% CI: 13.81, 59.84)], and decreased levels of HOMA-S [-25.88% (95% CI: -37.46, -12.16)]. Complement C3 and hsCRP played mediating roles in these relationships with proportion mediated ranging from 6.95% to 60.64%. Participants with HGI ≤ -0.53 were protected from the adverse effects of air pollutants.

CONCLUSION

Our study provides comprehensive insights into air pollutant-associated diabetic cascade and suggests subclinical preventive strategies.

The effect of chronic stress and its preconditioning on spatial memory as well as hippocampal LRP1 and RAGE expression in a streptozotocin-induced rat model of Alzheimer's disease

According to available evidence, prolonged or chronic exposure to stress is detrimental to various brain structures, including the hippocampus. The current study examined the expression of two critical blood-brain barrier receptors required for amyloid-beta clearance to understand better the mechanism by which chronic stress impairs learning and memory in patients with Alzheimer's disease (AD). Rats were randomly assigned to one of two groups in this study: experiment 1 and experiment 2. Each main group was then divided into four subgroups. Rats were bilaterally injected with streptozotocin (STZ, 3 mg/kg, twice) using the intracerebroventricular (ICV) technique to induce the Alzheimer's model. Additionally, they were subjected to foot shock (1 mA, 1 Hz) for 10 s every 60 s (1 h/day) for ten consecutive days prior to and following STZ injection. The Morris Water Maze (MWM) test was used to assess spatial learning and memory. Real-time PCR was used to determine Low-density lipoprotein receptor-related protein-1 (LRP1) and receptor for advanced glycation end-products (RAGE) mRNA levels in the hippocampus. Moreover, the animals' body weights were determined as physiological parameters in all groups. The results indicated that 10-day chronic electric foot shock stress reduced body weight, impaired spatial learning and memory, decreased hippocampal LRP1 mRNA expression, and increased hippocampal RAGE mRNA expression in a rat AD model. It can be concluded that chronic stress in conjunction with AD alters the expression of LRP1 and RAGE in the hippocampus. The findings pave the way for scientists to develop novel treatment strategies for AD.

Cannabinoid CB1 Receptor Deletion from Catecholaminergic Neurons Protects from Diet-Induced Obesity

High-calorie diets and chronic stress are major contributors to the development of obesity and metabolic disorders. These two risk factors regulate the activity of the sympathetic nervous system (SNS). The present study showed a key role of the cannabinoid type 1 receptor (CB1) in dopamine β-hydroxylase (dbh)-expressing cells in the regulation of SNS activity. In a diet-induced obesity model, CB1 deletion from these cells protected mice from diet-induced weight gain by increasing sympathetic drive, resulting in reduced adipogenesis in white adipose tissue and enhanced thermogenesis in brown adipose tissue. The deletion of CB1 from catecholaminergic neurons increased the plasma norepinephrine levels, norepinephrine turnover, and sympathetic activity in the visceral fat, which coincided with lowered neuropeptide Y (NPY) levels in the visceral fat of the mutant mice compared with the controls. Furthermore, the mutant mice showed decreased plasma corticosterone levels. Our study provided new insight into the mechanisms underlying the roles of the endocannabinoid system in regulating energy balance, where the CB1 deletion in dbh-positive cells protected from diet-induced weight gain via multiple mechanisms, such as increased SNS activity, reduced NPY activity, and decreased basal hypothalamic-pituitary-adrenal (HPA) axis activity.

Corticotropin-releasing factor system in the lateral septum: Implications in the pathophysiology of obesity

Obesity is a pandemic associated with lifestyles changes. These include excess intake of obesogenic foods and decreased physical activity. Brain areas, like the lateral hypothalamus (LH), ventral tegmental area (VTA), and nucleus accumbens (NAcc) have been linked in both homeostatic and hedonic control of feeding in experimental models of diet-induced obesity. Interestingly, these control systems are regulated by the lateral septum (LS), a relay of γ-aminobutyric (GABA) acid neurons (GABAergic neurons) that inhibit the LH and GABAergic interneurons of the VTA. Furthermore, the LS has a diverse receptor population for neurotransmitters and neuropeptides such as dopamine, glutamate, GABA and corticotropin-releasing factor (CRF), among others. Particularly, CRF a key player in the stress response, has been related to the development of overweight and obesity. Moreover, evidence shows that LS neurons neurophysiologically regulate reward and stress, although there is little evidence of LS taking part in homeostatic and hedonic feeding. In this review, we discuss the evidence that supports the role of LS and CRF on feeding, and how alterations in this system contribute to weight gain obesity.

Sexual dimorphism modulates metabolic and cognitive alterations under HFD nutrition and chronic stress exposure in mice. Correlation between spatial memory impairment and BDNF mRNA expression in hippocampus and spleen

AIMS

The accumulated evidence suggests that lifestyle - specifically dietary habits and stress exposure - plays a detrimental role in health. The purpose of the present study was to analyze the interplay of stress, diet, and sex in metabolic and cognitive alterations.

MAIN METHODS

For this purpose, one-month-old C57Bl/6J mice were fed with a standard diet or high-fat diet (HFD). After eight weeks, one subgroup of mice from each respective diet was exposed to 20 weeks of chronic mild stress (CMS), whilst the others were left undisturbed.

KEY FINDINGS

After 28 weeks of HFD feeding, mice from both sexes were overweight, with an increase in caloric intake and abdominal and subcutaneous fat pads. Stress exposure induced a decrease in body weight, related to a decrease in caloric efficiency in both males and females. Results indicate that males are more susceptible than the females in modulating metabolic and cognitive functions under HFD and CMS. Although both sexes demonstrated HFD-induced weight gain, fat accumulation, insulin resistance, high cholesterol, only males exposed to CMS but not females have (i) impaired glucose tolerance with higher glucose level; (ii) significant prolonged latency in Barnes test, suggesting cognitive impairment; (iii) increased IFN-gamma expression in hippocampus, suggesting greater neuroinflammatory response; (iv) poorer cognitive performance related to a decrease in hippocampal and spleen BDNF mRNA expression.

SIGNIFICANCE

The main finding in this study is the presence of a sexual dimorphism in modulating metabolic and cognitive functions under HFD and CMS, showing males are more susceptible than females. In addition, poorer cognitive performance was related to a decrease in hippocampal BDNF mRNA expression. Interestingly, these changes were observed in the spleen as well.

The association between childhood sexual abuse and historical intimate partner violence with body mass index and diabetes: Evidence from the Australian Longitudinal Study on Women's Health

The purpose of this study was to investigate the associations of childhood sexual abuse and historical intimate partner violence with body mass index and diabetes among mid-age women. Data from 5782 participants in the 1946-51 cohort of the Australian Longitudinal Study on Women's Health were used. The association of abuse reported to have occurred before 1996 with body mass index and incident diabetes during 20 years of follow-up were examined using longitudinal logistic regression. Women who experienced childhood sexual abuse only, historical intimate partner violence only, or both forms of abuse had higher risk of obesity compared to women who did not experience either form of abuse. The associations between experiencing childhood sexual abuse only, historical intimate partner violence only, or both forms of abuse and incident diabetes (adjusted odds ratios, AOR = 1.28, 95%CI = 1.00, 1.65, AOR = 1.27 (1.02, 1.58) and AOR = 1.74 (1.27, 2.38) respectively) were attenuated by adding body mass index and other variables in the model (AOR = 1.16, 95%CI = 0.90, AOR = 1.49, 1.17 (0.94, 1.46) and AOR = 1.41 (1.03, 1.95) respectively) compared with women who did not experience abuse. The clinical implication is that awareness of a woman's early life experience of abuse may provide insight into managing her weight and risk of diabetes.

Stress Buffering and Longevity Effects of Amber Extract on Caenorhabditis elegans (C. elegans)

Amber is a fossilized tree resin historically used in wound healing and stress relief. Unfortunately, there is no concrete scientific evidence supporting such efficacy. Here, the stress buffering and longevity effect of Amber extract (AE) in Caenorhabditis elegans (C. elegans) was investigated. Survival assays, health span assays, Enzyme-Linked Immunosorbent Assay (ELISA), Stress biomarker detection assays, Green Fluorescence Proteins (GFP), Real Time quantitative PCR (RT-qPCR) and C. elegans mutants were employed to investigate the stress buffering and longevity effect of AE. In the study, it was observed that AE supplementation improved health span and survival in both normal and stressed worms. Additionally, AE positively regulated stress hormones (cortisol, oxytocin, and dopamine) and decreased fat and reactive oxygen species (ROS) accumulation. Through the Insulin/IGF-1 signaling (IIS) pathway, AE enhanced the nuclear localization of DAF-16 and the expression of heat shock proteins and antioxidant genes in GFP-tagged worms and at messenger RNA levels. Finally, AE failed to increase the survival of daf-16, daf-2, skn-1 and hsf-1 loss-of-function mutants, confirming the involvement of the IIS pathway. Evidently, AE supplementation relieves stress and enhances longevity. Thus, amber may be a potent nutraceutical for stress relief.

Reactivity of the Thyroid System to Short-Term Stress in Wistar Rats with Visceral Obesity and Restricted Social Activity

The obesity problem requires a study of its pathophysiological consequences affecting hormonal regulation and organism’s reactivity to extreme exposures. The study was aimed first to examine the effect of a high-calorie diet and social isolation, as well as their combination for 4 months, on the development of obesity, its metabolic and behavioral sequelae, features of the thyroid status, while at the second stage, to assess the reaction of hormonal indices of the thyroid status to short-term stress in rats. The experiments were carried out on male Wistar rats and at the first stage focused on the effects of a high-calorie diet and social isolation, as well as their combinations for 4 months. At the end of the experiment, behavioral reactions, metabolic syndrome indices, thyroid status, and cortisol levels were evaluated. At the second stage, the animals were exposed to short-term acute stress, and the shifts in the hormonal indices were recorded one hour later versus the initial background. A high-calorie diet led to the development of metabolic syndrome, signs of depression, increased thyroid-stimulating hormone (TSH), thyroxine and triiodothyronine serum levels, as well as iodothyronine deiodinase type 1 (D1) activity, in the rat liver. At the same time, there was a decrease in thyroperoxidase activity and an increase in thyroid levels of triglycerides and malondialdehyde. The physiological response to stress in the control rat group included an increase in cortisol and TSH serum levels, however, against the background of a high-calorie diet, no cortisol release into the bloodstream was recorded. Social isolation did not alter normal reactivity of the adrenal cortex, but reduced TSH release in response to acute stress, since the initial level of this hormone was slightly elevated against the background of chronic social isolation stress. Thus, excessive nutrition and the deficit of social activities in male Wistar rats led to significant changes in the organism’s reactivity to acute stress.

eNAMPT actions through nucleus accumbens NAD+/SIRT1 link increased adiposity with sociability deficits programmed by peripuberty stress

Obesity is frequently associated with impairments in the social domain, and stress at puberty can lead to long-lasting changes in visceral fat deposition and in social behaviors. However, whether stress-induced changes in adipose tissue can affect fat-to-brain signaling, thereby orchestrating behavioral changes, remains unknown. We found that peripubertally stressed male-but not female-mice exhibit concomitant increased adiposity and sociability deficits. We show that reduced levels of the adipokine nicotinamide phosphoribosyltransferase (NAMPT) in fat and its extracellular form eNAMPT in blood contribute to lifelong reductions in sociability induced by peripubertal stress. By using a series of adipose tissue and brain region-specific loss- and gain-of-function approaches, we implicate impaired nicotinamide adenine dinucleotide (NAD+)/SIRT1 pathway in the nucleus accumbens. Impairments in sociability and accumbal neuronal excitability are prevented by normalization of eNAMPT levels or treatment with nicotinamide mononucleotide (NMN), a NAD+-boosting compound. We propose NAD+ boosters to treat social deficits of early life stress origin.

Evolution of an increased performance under acute challenge does not exacerbate vulnerability to chronic stress

An adequate stress response plays a vital role in coping with challenges. However, if selection for improved coping with an acute challenge affects the entire stress response system, susceptibility to adverse effects of chronic stressors can be deepened. Here, we used bank voles from lines selected for high swim-induced aerobic metabolism (A) and unselected control (C), and asked if the selection affected sensitivity to chronic mild stress (CMS). The voles were first habituated to daily weighing and feces collection for three weeks, and then for two weeks were exposed to CMS or remained undisturbed. The habituation itself resulted in an increased swim-induced oxygen consumption in both line types, and a decreased body mass. The CMS treatment caused reduction of food consumption in the second week of the experiment, and, in males, a decline in the metabolic rate. Paradoxically, fecal corticosterone metabolites decreased in the CMS-treated group. The response to CMS did not differ between the line types. Thus, the selection for increased performance was not traded off by increased vulnerability to chronic stress. The counter-intuitive results may even lead to a speculation that bank voles—and perhaps also other animals—prefer experiencing unpredictable, unpleasant stressors over the monotony of standard laboratory housing.

Ghrelin and the Control of Energy Balance in Females

Ghrelin is considered one of the most potent orexigenic peptide hormones and one that promotes homeostatic and hedonic food intake. Research on ghrelin, however, has been conducted predominantly in males and particularly in male rodents. In female mammals the control of energy metabolism is complex and it involves the interaction between ovarian hormones like estrogen and progesterone, and metabolic hormones. In females, the role that ghrelin plays in promoting feeding and how this is impacted by ovarian hormones is not well understood. Basal ghrelin levels are higher in females than in males, and ghrelin sensitivity changes across the estrus cycle. Yet, responses to ghrelin are lower in female and seem dependent on circulating levels of ovarian hormones. In this review we discuss the role that ghrelin plays in regulating homeostatic and hedonic food intake in females, and how the effects of ghrelin interact with those of ovarian hormones to regulate feeding and energy balance.

Stress-induced body weight loss and improvements in cardiometabolic risk factors do not translate to improved myocardial ischemic tolerance in western diet-fed mice

Although both diet-induced obesity and psychological stress are recognized as significant independent contributors to cardiometabolic and behavioral disorders, our understanding of how these two disorders interact and influence cardiometabolic risk and myocardial ischemic tolerance is limited. The aim of this study was to assess the combined effects of an obesogenic diet and psychological stress on cardiometabolic risk factors (body weight, dyslipidemia, insulin sensitivity) and postischemic cardiovascular outcomes. C57Bl/6J mice (n = 48) were subject to a combination of 22 weeks of western diet (WD) feeding and chronic restraint stress (CRS) for the last 4 weeks. Metabolic and behavioral changes were assessed using glucose tolerance tests and open field tests (OFTs), respectively. After 22 weeks, cardiac function and ischemic tolerance were assessed in Langendorff perfused hearts. WD feeding increased body weight and worsened blood lipids and insulin sensitivity. WD-fed mice also exhibited reduced exploratory behavior within the OFT. CRS reduced body weight and increased locomotion in both dietary groups and had differential effects on fasting glucose metabolism in the two dietary groups while not impacting non-fasting insulin. Although the WD only marginally reduced reperfusion left ventricular developed pressure recovery, CRS worsened reperfusion diastolic dysfunction in both dietary groups. Interestingly, despite WD+CRS animals exhibiting improved cardiometabolic parameters compared to the WD group, these changes did not translate to marked improvements to postischemic cardiac outcomes. In conclusion, in this study, combined WD feeding and CRS did not act synergistically to worsen cardiometabolic risk factors but instead improved them. Despite these cardiometabolic improvements, WD+CRS increased reperfusion end diastolic pressure which may be indicative of worsened ischemia/reperfusion injury.

Virgin coconut oil abrogates depression-associated cognitive deficits by modulating hippocampal antioxidant balance, GABAergic and glutamatergic receptors in mice

OBJECTIVES

GABA and glutamate neurotransmission play critical roles in both the neurobiology of depression and cognition; and Virgin coconut oil (VCO) is reported to support brain health. The present study investigated the effect of VCO on depression-associated cognitive deficits in mice.

METHODS

Thirty male mice divided into five groups were either exposed to chronic unpredicted mild stress (CUMS) protocol for 28 days or pre-treated with 3 mL/kg b. wt. of VCO for 21 days or post-treated with 3 mL/kg b. wt. of VCO for 21 days following 28 days of CUMS exposure. Mice were subjected to behavioural assessments for depressive-like behaviours and short-term memory, and thereafter euthanised. Hippocampal tissue was dissected from the harvested whole brain for biochemical and immunohistochemical evaluations.

RESULTS

Our results showed that CUMS exposure produced depressive-like behaviours, cognitive deficits and altered hippocampal redox balance. However, treatment with VCO abrogated depression-associated cognitive impairment, and enhanced hippocampal antioxidant concentration. Furthermore, immunohistochemical evaluation revealed significant improvement in GABA_A and mGluR1a immunoreactivity following treatment with VCO in the depressed mice.

CONCLUSIONS

Therefore, findings from this study support the dietary application of VCO to enhance neural resilience in patients with depression and related disorders.

Does serum TSH level act as a surrogate marker for psychological stress and cardio-metabolic risk among adolescent and young people?

OBJECTIVES

The incidence of metabolic syndrome is increasing even at younger ages. Metabolic syndrome constitutes a group of cardiovascular risk factors that include high cholesterol, triacylglycerol, hyperglycemia, central obesity, etc., which increases the risk of cardiovascular disease, diabetes mellitus, may be even cancer. Indian students enter colleges just after crossing their adolescent age and will be exposed to greater academic stress. Psychological stress or depression is associated with transient change in thyroid hormones level or dysfunction. To explore an association among serum Thyroid Stimulating Hormone (TSH) levels, fT3:fT4 ratio, psychological stress scores, and selected known cardio-metabolic risk markers.

METHODS

Forty first year MBBS students were included. Their demographic, anthropometric variables, and the blood pressure were documented. Serum TSH, fT3, fT4, and salivary cortisol level was quantified. The stress level was assessed using Cohen Perceived Stress Scale Scoring. Data were expressed in mean ± standard deviation. Data (parametric/non-parametric) were compared by Independent unpaired ANOVA or Kruskal Wallis test whichever is appropriate. Spearmen correlation analysis was performed.

RESULTS

Serum TSH and Cohen stress score are negatively correlated (r=-0.152), but serum cortisol showed (r=0.763) a positive correlation. TSH levels and the marks obtained in the summative assessments were negatively correlated and the correlation was not statistically significant.

CONCLUSIONS

The psychological stress is associated with low serum TSH, high cortisol, and poor academic performance in first year MBBS students. Blood pressure, plasma glucose, and anthropometric measures were not associated with the psychological stress.

Lifelong enhancement of body mass from adolescent stress in male hamsters

In hamsters, exposure to stress in adulthood causes increased body weight. We addressed how social stress during puberty would impact food intake and body weight. Stressed hamsters started gaining significantly more weight than controls after only two days of stress exposure. Over a two-week period, stressed subjects gained 10% more weight and consumed more food than controls. At the end of the stress period, stressed hamsters collected nearly twice as many palatable sugar pellets from an arena than controls. Stressed subjects presented 15-20% more body fat in mesenteric, inguinal, and retroperitoneal fat pads. In order to assess the duration of these effects, we analyzed data from previous studies keeping hamsters for over two months past the stress period in puberty. Our analysis shows that stressed hamsters stopped gaining more weight after the stress period, but their body weights remained elevated for over two months, consistently weighing 10% more than their non-stressed counterparts. We also analyzed conditioning training data collected after the period of stress in late puberty and early adulthood (P56 to P70) that was part of the original studies. Training consisted of lever pressing for palatable food rewards. At these times, previously stressed hamsters retrieved similar numbers of food pellets from the conditioning chambers, suggesting no difference in appetite after the stress period. These data showing a long-lasting effect of stress on body weight may be relevant to studies on the ontogeny of lifelong obesity.

Effects of early-life exposure to Western diet and voluntary exercise on adult activity levels, exercise physiology, and associated traits in selectively bred High Runner mice

Exercise behavior is under partial genetic control, but it is also affected by numerous environmental factors, potentially including early-life experiences whose effects persist into adulthood. We studied genetic and early-life environmental effects on wheel-running behavior in a mouse model that includes four replicate high runner (HR) lines selectively bred for increased voluntary wheel running as young adults and four non-selected control (C) lines. In a full factorial design, mice from each line were granted wheel access or not and administered either standard or Western diet (WD) from weaning (3 weeks old) to 6 weeks of age (sexual maturity). In addition to acute effects, after a washout period of 8 weeks (∼6 human years) in which all mice had standard diet and no wheel access, we found both beneficial and detrimental effects of these early-life exposures. During the first week of treatments, WD increased distance run by 29% in C mice and 48% in HR mice (significant Diet × Linetype interaction), but diet effects disappeared by the third week. Across the three weeks of juvenile treatment, WD significantly increased fat mass (with lean mass as a covariate). Tested as adults, early-life exercise increased wheel running of C mice but not HR mice in the first week. Early-life exercise also reduced adult anxiety-like behavior and increased adult fasted blood glucose levels, triceps surae mass, subdermal fat pad mass, and brain mass, but decreased heart ventricle mass. Using fat mass as a covariate, early-life exercise treatment increased adult leptin concentration. In contrast, early-life WD increased adult wheel running of HR mice but not C mice. Early-life WD also increased adult lean mass and adult preference for Western diet in all groups. Surprisingly, early-life treatment had no significant effect on adult body fat or maximal aerobic capacity (VO2max). No previous study has tested for combined or interactive effects of early-life WD and exercise. Our results demonstrate that both factors can have long-lasting effects on adult voluntary exercise and related phenotypes, and that these effects are modulated by genetic background. Overall, the long-lasting effects of early-life exercise were more pervasive than those of WD, suggesting critical opportunities for health intervention in childhood habits, as well as possible threats from modern challenges. These results may be relevant for understanding potential effects of activity reductions and dietary changes associated with the obesity epidemic and COVID-19 pandemic.

The effect of ambient ozone on glucose-homoeostasis: A prospective study of non-diabetic older adults in Beijing

OBJECTIVE

To investigate potential effects of short- and medium-term exposure to low levels of ozone (O3) on glucose-homeostasis in non-diabetic older adults.

METHODS

166 non-diabetic, older participants in Beijing were deemed eligible to partake in this longitudinal population-based study. Observations were recorded on three separate occasions from November 2016 up until January 2018. Concentrations of outdoor O3 were monitored throughout the study period. Biomarkers indicative of glucose-homeostasis, including fasting blood glucose, insulin, HbAlc, glycated albumin percentage (glycated albumin/albumin), HOMA-IR and HOMA-B were measured at 3 sessions. A linear mixed effects model with random effects was adopted to quantify the effect of O3 across a comprehensive set of glucose-homeostasis markers.

RESULTS

Short-term O3 exposure positively associated with increased fasting blood glucose, insulin, HOMA-IR and HOMA-B. The effect on glucose occurred at 3-, 5-, 6- and 7-days, although the largest effect manifested on 6-days (5.6%, 95% CI: 1.4, 9.9). Significant associations with both insulin and HOMA-IR were observed on the 3- and 4-days. For HOMA-B, positive associations were identified from 3- to 7-days with estimates ranging from 40.0% (95% CI: 2.3, 91.5) to 83.1% (95% CI: 25.3, 167.5). Stratification suggests that women may be more susceptible to short-term O3 exposure. There does not appear to be a significant association between O3 and glucose-homeostasis in medium-term exposures.

CONCLUSIONS

In this study, we found that O3 exposure is at least partially associated with type II diabetes in older adults with no prior history of this condition. O3 therefore appears to be a potential risk factor, which is a particular concern when we consider the rise in global concentrations. Evidence also suggests that women may be more susceptible to short-term O3 exposure although we are not quite sure why. Future research may look to investigate this phenomenon further.

Collective Housing of Mice of Different Age Groups before Maturity Affects Mouse Behavior

Background

Although population housing is recommended by many animal management and ethical guidelines, the effect of collective housing of mice of different age groups on mouse behavior has not been clarified. Since the development of the central nervous system continues to occur before sexual maturation, the stress of social ranking formation among male individuals in mixed housing conditions can affect postmaturation behavior. To assess these effects, sexually immature mice of different ages were housed in the same cage and a series of behavioral tests were performed after maturation.

Results

The findings for three groups of mice—junior mice housed with older mice, senior mice housed with younger mice, and mice housed with other mice of the same age—were compared. Junior mice showed higher body weight and activity as well as lower grip strength and anxiety-like behaviors than other mice. In contrast, senior mice showed lower body temperature and increased aggression, antinociceptive effect, and home-cage activity in the dark period in comparison with other mice.

Conclusions

Thus, combined housing of immature mice of different age groups affects mouse behavior after maturation. Appropriate prematuration housing conditions are crucial to eliminate the uncontrollable bias caused by age-related social stratification.

Association of generalized and central obesity with serum and salivary cortisol secretion patterns in the elderly: findings from the cross sectional KORA-Age study

The study aimed to examine the sex specific association of obesity with cortisol metabolism in a sample of older community dwelling people. The cross-sectional analysis included 394 men and 375 women (aged 65–90 years) of the population-based KORA-Age study. Multivariable regression analyses were employed to examine the association between cortisol samples (serum and salivary samples of morning after awakening (M1), 30 min later (M2) and at late night (LNSC)). Obesity was calculated as waist-to-hip ratio (WHR) and body mass index (BMI). Cortisol levels were not significantly different between obesity measures except for elevated serum cortisol (P = 0.02) levels in individuals with a low WHR. Higher M1 levels were especially apparent in women with normal BMI. Serum cortisol levels were inversely related to WHR (P = 0.004) and CAR_AUC was inversely associated with BMI (P = 0.007). Sex-stratified analytic models revealed that both obesity measures showed a non-linear association with cortisol diurnal pattern (M1/LNSC) in men. Impaired cortisol patterns emerged at both very ends of the body weight distribution. These findings do not support a cortisol driven obesity etiology in an older population and even point to an inverse association of body weight with cortisol levels. Differences of cortisol secretion patterns in generalized and abdominal fat distribution were marginal.

Effect of intranasal administration of neuropeptide Y and single prolonged stress on food consumption and body weight in male rats

Emerging evidence indicates that intranasal delivery of neuropeptide Y (NPY) to the brain has therapeutic potential for management of stress-triggered neuropsychiatric disorders. Here we aimed to determine how intranasal administration of NPY, either before or immediately after, traumatic stress in single prolonged stress (SPS) rodent model of Post-traumatic stress disorder (PTSD) impacts food consumption and body weight. SPS stressors suppressed food consumption for at least two days in the vehicle-treated animals. When given prior to SPS stressors, intranasal NPY prevented the SPS-elicited reduction in food intake only for several hours afterwards. When given after the SPS stressors, under conditions shown to prevent behavioral and biochemical impairments, intranasal NPY had no effect on food intake. Although all groups showed circadian variation, the SPS-exposed rats ate less than unstressed animals during the dark (active) phase. Seven days after exposure to SPS stressors, there were no differences in food intake, although body weight was still lower than unstressed controls in all the experimental groups. Thus, traumatic stress has pronounced effect on food consumption during the rodent's active phase, and a prolonged effect on body weight. Single intranasal infusion of NPY, which was previously shown to prevent development of several PTSD associated behavioral and neuroendocrine impairments, did not elicit prolonged changes in stress triggered food consumption nor regulation of body weight.

Differential Responses of Liver and Hypothalamus to the Nutritional Condition During Lactation and Adult Life

It was previously reported that liver glucose metabolism in rats under caloric restriction differs from that of freely-fed rats. This study hypothesized that these changes (1) were related to the expression of hypothalamic neuropeptides involved in metabolic control, and (2) were not a residual effect of litter size. To those purposes, liver glucose metabolism and hypothalamic expression of the orexigenic neuropeptides NPY (neuropeptide Y) and AgRP (agouti gene-related peptide); and of the anorexigenic neuropeptides POMC (pro-opiomelanocortin) and CART (cocaine- and amphetamine-related transcripts) were investigated. Male Wistar rats from two different litter sizes (G6 and G12, with 6 or 12 pups, respectively) were subjected to free feeding (GL, ad libitum), 50% caloric restriction (GR) or caloric restriction+ad libitum refeeding (GRL) until the age of 90 days. Biometric values were lower in GR than in GL, while in GRL they were totally or partially recovered. Blood glucose variation during the pyruvate tolerance test (PTT) was small in GR. During in situ liver perfusion, total, basal, and adrenaline-stimulated liver glucose outputs were high in GR, but additional glucose output in the presence of alanine was negligible. Refeeding (GRL) yielded values close to those of GL. Litter size did not consistently influence any of these variables. The expression of transcripts of the hypothalamic neuropeptides was responsive to feeding regimen, litter size and/or their interaction and differed from G6 to G12, while the metabolic changes of the liver were qualitatively equal in both GR. Therefore, the changes in glucose metabolism in the liver of rats under caloric restriction were not determined by either litter size or hypothalamic neuropeptide expression and were linked only to the prevailing feeding regimen of the adult animal.

Individual housing of male C57BL/6J mice after weaning impairs growth and predisposes for obesity

For (metabolic) research models using mice, singly housing is widely used for practical purposes to study e.g. energy balance regulation and derangements herein. Mouse (social) housing practices could however influence study results by modulating (metabolic) health outcomes. To study the effects of the social housing condition, we assessed parameters for energy balance regulation and proneness to (diet induced) obesity in male C57Bl/6J mice that were housed individually or socially (in pairs) directly after weaning, both at standard ambient temperature of 21°C. During adolescence, individually housed mice had reduced growth rate, while energy intake and energy expenditure were increased compared to socially housed counterparts. At 6 weeks of age, these mice had reduced lean body mass, but significantly higher white adipose tissue mass compared to socially housed mice, and higher UCP-1 mRNA expression in brown adipose tissue. During adulthood, body weight gain of individually housed animals exceeded that of socially housed mice, with elevations in both energy intake and expenditure. At 18 weeks of age, individually housed mice showed higher adiposity and higher mRNA expression of UCP-1 in inguinal white but not in brown adipose tissue. Exposure to an obesogenic diet starting at 6 weeks of age further amplified body weight gain and adipose tissue deposition and caused strong suppression of inguinal white adipose tissue mRNA UCP-1 expression. This study shows that post-weaning individual housing of male mice impairs adolescent growth and results in higher susceptibility to obesity in adulthood with putative roles for thermoregulation and/or affectiveness.

Effects of repetitive gentle handling of male C57BL/6NCrl mice on comparative behavioural test results

Mice are the most commonly used laboratory animals for studying diseases, behaviour, and pharmacology. Behavioural experiment battery aids in evaluating abnormal behaviour in mice. During behavioural experiments, mice frequently experience human contact. However, the effects of repeated handling on mice behaviour remains unclear. To minimise mice stress, methods of moving mice using transparent tunnels or cups have been recommended but are impractical in behavioural tests. To investigate these effects, we used a behavioural test battery to assess differences between mice accustomed to the experimenter’s handling versus control mice. Repeatedly handled mice gained slightly more weight than control mice. In behavioural tests, repeatedly handled mice showed improved spatial cognition in the Y-maze test and reduced anxiety-like behaviour in the elevated plus-maze test. However, there was no change in anxiety-like behaviour in the light/dark transition test or open-field test. Grip strength, rotarod, sociability, tail suspension, Porsolt forced swim, and passive avoidance tests revealed no significant differences between repeatedly handled and control mice. Our findings demonstrated that mice repeatedly handled by the experimenter before behavioural tests showed reduced anxiety about high altitudes and improved spatial cognition, suggesting that repeated contact can affect the results of some behavioural tests.

The adrenal gland in stress - Adaptation on a cellular level

Human individuals are constantly confronted to various kinds of stressors and the body's response and adaptation is essential for human health. The adrenal gland as the main producer of stress hormones plays a major role in the response to physiological challenges and is able to adapt to these physiological needs. Proper adaptation is of particular importance since dysregulation of the stress system is the cause of various human diseases including obesity, depression, Parkinson's disease, and post-traumatic stress disorder. Therefore, it is fundamental to understand the physiological, cellular, and molecular underpinnings of the stress adaptation in humans. Because of ethical reasons it is problematic to study the plasticity of the human gland in stress. Hence, various experimental models have been established for the analysis of the functional and cellular role of the adrenal gland adaptation on a translational approach. Here, we summarize the insights of stress-induced adrenal plasticity gained from these models and discuss their relevance to clinical observations.

β1-adrenergic receptors mediate plasma acyl-ghrelin elevation and depressive-like behavior induced by chronic psychosocial stress

The ghrelin system is a key component of the mood and metabolic responses to chronic psychosocial stress. For example, circulating acyl-ghrelin rises in several rodent and human stress models, administered acyl-ghrelin induces antidepressant-like behavioral responses in mice, and mice with deleted ghrelin receptors (GHSRs) exhibit exaggerated depressive-like behaviors, changed eating behaviors, and altered metabolism in response to chronic stress. However, the mechanisms mediating stress-induced rises in ghrelin are unknown and ghrelin's antidepressant-like efficacy in the setting of chronic stress is incompletely characterized. Here, we used a pharmacological approach in combination with a 10-day chronic social defeat stress (CSDS) model in male mice to investigate whether the sympathoadrenal system is involved in the ghrelin response to stress. We also examined the antidepressant-like efficacy of administered ghrelin and the synthetic GHSR agonist GHRP-2 during and/or after CSDS. We found that administration of the β1-adrenergic receptor (β1AR) blocker atenolol during CSDS blunts the elevation of plasma acyl-ghrelin and exaggerates depressive-like behavior. Neither acute injection of acyl-ghrelin directly following CSDS nor its chronic administration during or after CSDS nor chronic delivery of GHRP-2 during and after CSDS improved stress-induced depressive-like behavior. Thus, β1ARs drive the acyl-ghrelin response to CSDS, but supplementing the natural increases in acyl-ghrelin with exogenous acyl-ghrelin or GHSR agonist does not further enhance the antidepressant-like actions of the endogenous ghrelin system in the setting of CSDS.

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.

Adolescent Stress Disrupts the Maturation of Anxiety-related Behaviors and Alters the Developmental Trajectory of the Prefrontal Cortex in a Sex- and Age-specific Manner

Adolescence is a window of vulnerability to environmental factors such as chronic stress that can disrupt brain development and cause long-lasting behavioral dysfunction, as seen in disorders like depression, anxiety, and schizophrenia. There are also sex differences in the prevalence of these disorders across the lifespan. However, the mechanisms of how adolescent stress contributes to neuropsychiatric phenotypes are not well understood, nor are the mediating effects of sex. We hypothesize that adolescent stress disrupts the γ-aminobutyric acid (GABA) system in the prefrontal cortex (PFC) in a sex-specific manner, as this system matures during adolescence and plays an important role in cognitive and emotional functioning. We exposed male and female mice to unpredictable chronic mild stress (UCMS) during adolescence (post-natal day [PND] 28-42). One cohort underwent testing for PFC-related behavioral and molecular changes 24 h following the cessation of stress (late adolescence); a separate cohort was tested approximately 2.5 weeks after the end of UCMS (adulthood). We observed an age-related decline in anxiety-like behaviors in control mice, while mice stressed in adolescence showed elevated anxiety-like behaviors in both adolescence and adulthood. PFC-dependent cognitive functioning was also impaired in adult males stressed in adolescence. Adolescent stress disrupted expression patterns of parvalbumin (PV) and perineuronal nets (PNNs) in the PFC, as well as NMDA receptor subunit composition, in a sex- and age-specific manner. The findings presented here contribute to understanding how adolescent stress may lead to neuropsychiatric disorders such as anxiety by disrupting the development of the PFC and emotional behaviors.

Refeeding after caloric restriction reverses altered liver glucose release

CONTEXT

Caloric restriction increases liver glucose release (LGR), but it is not known if this is a permanent condition.

OBJECTIVE

To investigate if refeeding after caloric restriction reverses the high LGR.

MATERIALS AND METHODS

Rats were organised in six-pups litters (GC); 12-pups litters with either 50% caloric restriction from 21 to 80 days of age (GR) or fed at will from 50 to 80 days of age (GRL). Liver perfusion was made at the age of 80 days.

RESULTS

LGR was higher in the GR both during basal and adrenaline-stimulated conditions. Refeeding after caloric restriction decreased it to values close to those of GC rats.

DISCUSSION

The altered LGR of GR rats was reversed by refeeding (group GRL). The influence of hypothalamic neuropetides on these hepatic changes is suggested.

CONCLUSIONS

Enhanced LGR under caloric restriction is not programmed by early feeding; instead, it is determined by the current nutritional conditions.

Function-related Drivers of Skull Morphometric Variation and Sexual Size Dimorphism in a Subterranean Rodent, Plateau Zokor (Eospalax baileyi)

Sexual dimorphism is prevalent in most living organisms. The difference in size between sexes of a given species is generally known as sexual size dimorphism (SSD). The magnitude of the SSD is determined by Rensch's rule where size dimorphism increases with increasing body size when the male is the larger sex and decreases with increasing average body size when the female is the larger sex. The unique underground environment that zokors (Eospalax baileyi) live under in the severe habitat of the Qinghai‐Tibetan Plateau (QTP) could create SSD selection pressures that may or may not be supported by Rensch's rule, making this scientific question worthy of investigation. In this study, we investigated the individual variation between sexes in body size and SSD of plateau zokors using measurements of 19 morphological traits. We also investigated the evolutionary mechanisms underlying SSD in plateau zokors. Moreover, we applied Rensch's rule to all extant zokor species. Our results showed male‐biased SSD in plateau zokors: The body‐ and head‐related measurements were greater in males than in females. Linear regression analysis between body length, body weight, and carcass weight showed significant relationships with some traits such as skull length, lower incisor length, and tympanic bulla width, which might support our prediction that males have faster growth rates than females. Further, the SSD pattern corroborated the assumption of Rensch's rule in plateau zokors but not in the other zokor species. Our findings suggest that the natural underground habitat and behavioral differences between sexes can generate selection pressures on male traits and contribute to the evolution of SSD in plateau zokors.

The antidepressant fluoxetine acts on energy balance and leptin sensitivity via BDNF

Leptin and Brain Derived Neurotrophic Factor (BDNF) pathways are critical players in body weight homeostasis. Noninvasive treatments like environmental stimulation are able to increase response to leptin and induce BDNF expression in the brain. Emerging evidences point to the antidepressant selective serotonin reuptake inhibitor Fluoxetine (FLX) as a drug with effects similar to environmental stimulation. FLX is known to impact on body weight, with mechanisms yet to be elucidated. We herein asked whether FLX affects energy balance, the leptin system and BDNF function. Adult lean male mice chronically treated with FLX showed reduced weight gain, higher energy expenditure, increased sensitivity to acute leptin, increased hypothalamic BDNF expression, associated to changes in white adipose tissue expression typical of “brownization”. In the Ntrk2^tm1Ddg/J model, carrying a mutation in the BDNF receptor Tyrosine kinase B (TrkB), these effects are partially or totally reversed. Wild type obese mice treated with FLX showed reduced weight gain, increased energy output, and differently from untreated obese mice, a preserved acute response to leptin in terms of activation of the intracellular leptin transducer STAT3. In conclusion, FLX impacts on energy balance and induces leptin sensitivity and an intact TrkB function is required for these effects to take place.

Effects of high-intensity interval versus mild-intensity endurance training on metabolic phenotype and corticosterone response in rats fed a high-fat or control diet

The aim of the present study was to compare the effects of high-intensity interval training (HI) to mild-intensity endurance training (ME), combined with a high-fat diet (HFD) or control diet (CD) on metabolic phenotype and corticosterone levels in rats. Fifty-three rats were randomized to 6 groups according to diet and training regimen as follows: CD and sedentary (CS, n = 11), CD and ME (CME, n = 8), CD and HI (CHI, n = 8), HFD and sedentary (HS, n = 10), HFD and ME (HME, n = 8), and HFD and HI (HHI, n = 8). All exercise groups were trained for 10 weeks and had matched running distances. Dietary intake, body composition, blood metabolites, and corticosterone levels were measured. Histological lipid droplets were observed in the livers. The HFD led to hyperglycemia, hyperlipidemia and higher body fat (all, P < 0.01, η² > 0.06), as well as higher corticosterone levels (P < 0.01, η² = 0.09) compared with the CD groups. Exercise training improved fat weight, glucose, and lipid profiles, and reduced corticosterone levels (P < 0.01, η² = 0.123). Furthermore, body and fat weight, serum glucose and triglycerides, lipid content in the liver, and corticosterone levels (P < 0.05) were lower with HI training compared to ME training. Reductions in HFD-induced body weight gain, blood glucose and lipid profiles, and corticosterone levels, as well as improvements in QUICKI were better with HHI compared to HME. Correlation analyses revealed that corticosterone levels were significantly associated with phenotype variables (P < 0.01). Corticosterone level was inversely correlated with QUICKI (r = −0.38, P < 0.01). Altogether, these results indicate that HFD may elicit an exacerbated basal serum corticosterone level and thus producing a metabolic imbalance. Compared with ME training, HI training contributes to greater improvements in metabolic and corticosterone responses, leading to a greater reduction in susceptibility to HFD-induced disorders.

Hypothalamic-pituitary-adrenal axis hypersensitivity in female rats on a post-weaning high-fat diet after chronic mild stress

A high-fat diet (HFD) is highly correlated to obesity, metabolic diseases and certain behavioral changes. However, the effects of post-weaning HFD in rats during puberty and the role of the hypothalamic-pituitary-adrenal (HPA) axis in this process have remained elusive. The present study hypothesized that the HPA axis mediates the behavioral alterations induced by a post-weaning HFD. To investigate this, female rats were divided into two groups, one of which was fed a HFD from postnatal weeks (PWs) 4-12, while the other group received standard chow. Rats in each group were then subdivided into two subgroups each, and from PW 9-12, animals from one of the two subgroups were subjected to chronic mild stress (CMS), while the other subgroup received no stress. At PW 12, the body weight of rats receiving a HFD but no DMS was significantly higher than that in the control group. The frequency of crossing and rearing in the open field test and the time in the center of the Y-maze were decreased following CMS. Total time to escape was decreased in rats receiving HFD and after CMS. The serum levels of adrenocorticotropic hormone and corticosterone were increased in rats receiving an HFD and after CMS, and the mRNA levels of corticotropin-releasing hormone and arginine vasopressin in the hypothalamus were increased in the HFD + CMS group compared to that in the control group. The mRNA expression of glucocorticoid receptor (GR) in the hippocampi of rats in the HFD + CMS group was significantly decreased and the mineralocorticoid receptor/GR ratio was increased compared to that in the groups receiving either CMS or a HFD. In conclusion, these results indicated that female rats fed a post-weaning HFD showed HPA axis hypersensitivity under CMS, which may mediate behavioral alterations.

Chronic Corticosterone Treatment During Adolescence Has Significant Effects on Metabolism and Skeletal Development in Male C57BL6/N Mice

Glucocorticoids are potent modulators of metabolic and behavioral function. Their role as mediators in the "stress response" is well known, but arguably their primary physiological function is in the regulation of cellular and organismal metabolism. Disruption of normal glucocorticoid function is linked to metabolic disease, such as Cushing syndrome. Glucocorticoids are also elevated in many forms of obesity, suggesting that there are bidirectional effects of these potent hormones on metabolism and metabolic function. Adolescence is a time of rapid physical growth, and disruptions during this critical time likely have important implications for adult function. The hypothalamic-pituitary-adrenal axis continues to mature during this period, as do tissues that respond to glucocorticoids. In this work, we investigate how chronic noninvasive exposure to corticosterone affects metabolic outcomes (body weight, body composition, insulin, and glucose homeostasis), as well as changes in bone density in both adult and adolescent male mice. Specifically, we report a different pattern of metabolic effects in adolescent mice compared with adults, as well as an altered trajectory of recovery in adolescents and adults. Together, these data indicate the profound influence that adolescent development has on the metabolic outcomes of chronic corticosterone exposure, and describe a tractable model for understanding the short- and long-term impacts of hypercortisolemic states on physiological and neurobehavioral functions.

Altered functionality of the corticotrophin-releasing hormone receptor-2 in the hypothalamic paraventricular nucleus of hyperphagic maternally separated rats

Early-life stress induces endocrine and metabolic alterations that increase food intake and overweight in adulthood. The stress response activates the corticotropin-releasing hormone (CRH) and urocortins' (Ucns) system in the hypothalamic paraventricular nucleus (PVN). These peptides induce anorexic effects through CRH-R2 receptor activation; however, chronic stressed animals develop hyperphagia despite of high PVN CRH expression. We analyzed this paradoxical behavior in adult rats subjected to maternal separation (MS) for 180min/daily during post-natal days 2-14, evaluating their body weight gain, food intake, serum corticosterone and vasopressin concentrations, PVN mRNA expression of CRH-R1, CRH-R2, CRH, Ucn2, Ucn3, vasopressin and CRH-R2 protein levels. MS adults increased their feeding, weight gain as well as circulating corticosterone and vasopressin levels, evincing chronic hyperactivity of the stress system. MS induced higher PVN CRH, Ucn2 and CRH-R2 mRNA expression and protein levels of CRH-R2 showed a tendency to decrease in the cellular membrane fraction. An intra-PVN injection of the CRH-R2 antagonist antisauvagine-30 in control adults increased receptor's mRNA expression, mimicking the observed PVN receptor's up-regulation of early-life MS adults. An injection of Ucn-2 directly into the PVN reduced food intake and increased PVN pCREB/CREB ratio in control animals; in contrast, Ucn-2 was unable to reduce food intake and enhance phosphorylated-CREB levels in PVN of MS rats. In conclusion, the chronic hyperactivity of the stress axis and PVN CRH-R2 resistance to Ucn2 effects, supported impaired receptor functionality in MS animals, probably due to its chronic stimulation by CRH or Ucn2, induced by early-life stress.

Stress, overeating, and obesity: Insights from human studies and preclinical models

Eating disorders and obesity have become predominant in human society. Their association to modern lifestyle, encompassing calorie-rich diets, psychological stress, and comorbidity with major diseases are well documented. Unfortunately the biological basis remains elusive and the pharmacological treatment inadequate, in part due to the limited availability of valid animal models. Human research on binge eating disorder (BED) proves a strong link between stress exposure and bingeing: state-levels of stress and negative affect are linked to binge eating in individuals with BED both in laboratory settings and the natural environment. Similarly, classical animal models of BED reveal an association between acute exposure to stressors and binging but they are often associated with unchanged or decreased body weight, thus reflecting a negative energy balance, which is uncommon in humans where most commonly BED is associated with excessive or unstable body weight gain. Recent mouse models of subordination stress induce spontaneous binging and hyperphagia, altogether more closely mimicking the behavioral and metabolic features of human BED. Therefore the translational relevance of subordination stress models could facilitate the identification of the neurobiological basis of BED and obesity-associated disease and inform on the development of innovative therapies.

Panic Disorder Comorbidity with Medical Conditions and Treatment Implications

Panic disorder (PD) is unique among the anxiety disorders in that panic symptoms are primarily of a physical nature. Consequently, comorbidity with medical illness is significant. This review examines the association between PD and medical illness. We identify shared pathophysiological and psychological correlates and illustrate how physiological activation in panic sufferers underlies their symptom experience in the context of the fight-or-flight response and beyond a situation-specific response pattern. We then review evidence for bodily symptom perception accuracy in PD. Prevalence of comorbidity for PD and medical illness is presented, with a focus on respiratory and cardiovascular illness, irritable bowel syndrome, and diabetes, followed by an outline for potential pathways of a bidirectional association. We conclude by illustrating commonalities in mediating mechanistic pathways and moderating risk factors across medical illnesses, and we discuss implications for diagnosis and treatment of both types of conditions.

A high fat diet-induced decrease in hippocampal newly-born neurons of male mice is exacerbated by mild psychological stress using a Communication Box

BACKGROUND

Obese persons have a higher incidence of depression than healthy-weight persons. Several studies indicated that the exposure to a high fat diet (HFD) results in a decrease in hippocampal neurogenesis, which leads to higher stress response and stress-induced depression. Although stress is a risk factor for obesity and depression, no studies to date have investigated the effect of stress on the hippocampal neurogenesis of HFD-induced obese animals. The aim of this study was to elucidate whether or not obese HFD-fed mice are vulnerable to stress-induced depression by investigating hippocampal neurogenesis.

METHODS

Sixty-four male ICR mice (four weeks of age) were fed a control (N=24) or 45%HFD (N=40) for seven weeks. Of the HFD-fed group, twenty-four mice met the criteria for "diet-induced obesity". The animals were then exposed to three consecutive days of psychological stress using a Communication Box. Half were sacrificed to evaluate the physiological changes, and the other half were perfused to quantify hippocampal neuroblasts/immature neurons by the estimation of doublecortin-immunopositive cells.

RESULTS

In the HFD-fed mice, psychological stress resulted in increases in caloric intake and visceral adipose tissue and a significant decrease in doublecortin-positive cells in the dentate gyrus; however, no such differences were found in the control diet-fed group. Limitations Further study using other neurogenic markers to assess the stage-specific changes in hippocampal neurogenesis will be required CONCLUSIONS: Our findings suggest that an HFD-induced decrease in hippocampal newly-born neurons leads to stress vulnerability, which may contribute to a high risk of stress-induced depression for obese persons.

Determinants of Perceived Stress in Individuals with Obesity: Exploring the Relationship of Potentially Obesity-Related Factors and Perceived Stress

OBJECTIVE

Associations of specific types of stress with increased food intake and subsequent weight gain have been demonstrated in animal models as well as in experimental and epidemiological studies on humans. This study explores the research question of to what extent potentially obesity-related factors determine perceived stress in individuals with obesity.

METHODS

N = 547 individuals with obesity participated in a cross-sectional study assessing perceived stress as the outcome variable and potential determinants of stress related to obesity. Based on the available evidence, a five factorial model of 'obesity-related obesogenic stressors' was hypothesized, including the dimensions, 'drive for thinness', 'impulse regulation', 'ineffectiveness', 'social insecurity', and 'body dissatisfaction'. The model was tested using multiple linear regression analyses.

RESULTS

The five factorial model of 'potentially obesity-related stressors' resulted in a total variance explanation of adjusted R² = 0.616 for males and adjusted R² = 0.595 for females for perceived stress. The relative variance contribution of the five included factors differed substantially for the two sexes.

CONCLUSION

The findings of this cross-sectional study support the hypothesized, potentially obesity-related factors: 'drive for thinness', 'impulse regulation', 'ineffectiveness', 'social insecurity', and 'body dissatisfaction' as relevant determinants of perceived stress in individuals with obesity.