A sensitive period for environmental regulation of eating behavior and leptin sensitivity

Environmental enrichment accentuates glucose-induced feeding suppression and glial cell line-derived neurotrophic factor gene expression in the hypothalamus of mice

The hypothalamus controls food intake by integrating nutrient signals, of which one of the most important is glucose. Consequently, impairments in hypothalamic glucose-sensing mechanisms are associated with hyperphagia and obesity. Environmental enrichment (EE) is an animal housing protocol that provides complex sensory, motor, and social stimulations and has been proven to reduce adiposity in laboratory mice. However, the mechanism by which EE promotes adiposity-suppressing effect remains incompletely understood. Neurotrophic factors play an important role in the development and maintenance of the nervous system, but they are also involved in the hypothalamic regulation of feeding. Brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) are expressed in the hypothalamus and their expression is stimulated by glucose. EE is associated with increased expression of Bdnf mRNA in the hypothalamus. Therefore, we hypothesized that EE potentiates the anorectic action of glucose by altering the expression of neurotrophic factor genes in the hypothalamus. Male C57BL/6 mice were maintained under standard or EE conditions to investigate the feeding response to glucose and the associated expression of feeding-related neurotrophic factor genes in the hypothalamus. Intraperitoneal glucose injection reduced food intake in both control and EE mice with a significantly greater reduction in the EE group compared to the control group. EE caused a significantly enhanced response of Gdnf mRNA expression to glucose without altering basal Gdnf mRNA expression and Bdnf mRNA response to glucose. These findings suggest that EE enhances glucose-induced feeding suppression, at least partly, by enhancing hypothalamic glucose-sensing ability that involves GDNF.

Glucose metabolism, hippocampal subfields and cognition in first-episode and never-treated schizophrenia

Background

Previous studies have indicated that glucose metabolism and altered hippocampal structure and function play a pivotal role in cognitive deficits in schizophrenia (SZ). This study was designed to explore the inter-relationship between glucose metabolism, hippocampal subfield volume, and cognitive function in the antipsychotics-naive first episode (ANFE) SZ patients.

Methods

We chose the fasting insulin, glucose, and insulin resistance (HOMA-IR) index as biomarkers of glucose metabolism. Cognitive function was assessed by the MATRICS Consensus Cognitive Battery (MCCB). The hippocampal subfield volume, glucose metabolism biomarkers, and cognitive function were evaluated in 43 ANFE SZ and 29 healthy controls (HCs).

Results

Compared with HCs, SZ patients had higher fasting blood glucose and insulin levels and HOMA-IR (all p < 0.05). Correlation analysis revealed that category fluency performance was positively associated with fasting glucose level. Fasting insulin or HOMA-IR was positively associated with the hippocampal subfield volume in patients (all p<0.05). Moreover, the spatial span index score was associated with the volume of the right presubiculum, subiculum, and right hippocampal tail. In addition, multiple regression analysis found that the interaction effects of insulin × right fimbria or insulin × left fimbria were independent predictors of the MCCB total score.

Conclusions

Our findings suggest that abnormal glucose metabolism and cognitive decline occur in the early stage of SZ. The interaction between abnormal glucose metabolism and hippocampal subfields was associated with cognitive functions in SZ.

High-fat/high-sucrose diet worsens metabolic outcomes and widespread hypersensitivity following early-life stress exposure in female mice

Exposure to stress early in life has been associated with adult-onset comorbidities such as chronic pain, metabolic dysregulation, obesity, and inactivity. We have established an early-life stress model using neonatal maternal separation (NMS) in mice, which displays evidence of increased body weight and adiposity, widespread mechanical allodynia, and hypothalamic-pituitary-adrenal axis dysregulation in male mice. Early-life stress and consumption of a Western-style diet contribute to the development of obesity; however, relatively few preclinical studies have been performed in female rodents, which are known to be protected against diet-induced obesity and metabolic dysfunction. In this study, we gave naïve and NMS female mice access to a high-fat/high-sucrose (HFS) diet beginning at 4 wk of age. Robust increases in body weight and fat were observed in HFS-fed NMS mice during the first 10 wk on the diet, driven partly by increased food intake. Female NMS mice on an HFS diet showed widespread mechanical hypersensitivity compared with either naïve mice on an HFS diet or NMS mice on a control diet. HFS diet-fed NMS mice also had impaired glucose tolerance and fasting hyperinsulinemia. Strikingly, female NMS mice on an HFS diet showed evidence of hepatic steatosis with increased triglyceride levels and altered glucocorticoid receptor levels and phosphorylation state. They also exhibited increased energy expenditure as observed via indirect calorimetry and expression of proinflammatory markers in perigonadal adipose. Altogether, our data suggest that early-life stress exposure increased the susceptibility of female mice to develop diet-induced metabolic dysfunction and pain-like behaviors.

Hypothalamic TTF-1 orchestrates the sensitivity of leptin

OBJECTIVE

Thyroid transcription factor-1 (TTF-1), a homeodomain-containing transcription factor, is predominantly expressed in discrete areas of the hypothalamus, which acts as the central unit for the regulation of whole-body energy homeostasis. Current study designed to identify the roles of TTF-1 on the responsiveness of the hypothalamic circuit activity to circulating leptin and the development of obesity linked to the insensitivity of leptin.

METHODS

We generated conditional knock-out mice by crossing TTF-1^flox/flox mice with leptin receptor (ObRb)^Cre or proopiomelanocortin (POMC)^Cre transgenic mice to interrogate the contributions of TTF-1 in leptin signaling and activity. Changes of food intake, body weight and energy expenditure were evaluated in standard or high fat diet-treated transgenic mice by using an indirect calorimetry instrument. Molecular mechanism was elucidated with immunohistochemistry, immunoblotting, quantitative PCR, and promoter assays.

RESULTS

The selective deletion of TTF-1 gene expression in cells expressing the ObRb or POMC enhanced the anorexigenic effects of leptin as well as the leptin-induced phosphorylation of STAT3. We further determined that TTF-1 inhibited the transcriptional activity of the ObRb gene. In line with these findings, the selective deletion of the TTF-1 gene in ObRb-positive cells led to protective effects against diet-induced obesity via the amelioration of leptin resistance.

CONCLUSIONS

Collectively, these results suggest that hypothalamic TTF-1 participates in the development of obesity as a molecular component involved in the regulation of cellular leptin signaling and activity. Thus, TTF-1 may represent a therapeutic target for the treatment, prevention, and control of obesity.

Digital Economy, Environmental Regulation and Corporate Green Technology Innovation: Evidence from China

Background: As human beings enter the digital age, the impact of the digital economy on environmental regulation and corporate green technology innovation (CGTI) is expanding. In order to effectively strengthen the efficacy of environmental regulation and improve the green technology innovation ability of corporate, this paper conducts in-depth research on the influence process of the digital economy and environmental regulation on the CGTI. Methods: Based on the mediating variable environmental regulation, this paper explores the influence process of the digital economy on CGTI. Combined with empirical analysis methods such as the fixed-effect model, mediating effect model, spatial model and regression analysis, the authors reveal the influence process of the digital economy on CGTI. Results: The digital economy can directly promote the improvement of the green technology innovation level of CGTI. The digital economy can indirectly affect the CGTI through the mediating variable of environmental regulation, marginal effect and spatial spillover effect. Conclusions: The digital economy and CGTI had a significant spatial correlation among different regions in China. In different regions of China, there are significant differences in the relationship between the digital economy, environmental regulation and CGTI.

The role of enriched environment in neural development and repair

In addition to genetic information, environmental factors play an important role in the structure and function of nervous system and the occurrence and development of some nervous system diseases. Enriched environment (EE) can not only promote normal neural development through enhancing neuroplasticity but also play a nerve repair role in restoring functional activities during CNS injury by morphological and cellular and molecular adaptations in the brain. Different stages of development after birth respond to the environment to varying degrees. Therefore, we systematically review the pro-developmental and anti-stress value of EE during pregnancy, pre-weaning, and “adolescence” and analyze the difference in the effects of EE and its sub-components, especially with physical exercise. In our exploration of potential mechanisms that promote neurodevelopment, we have found that not all sub-components exert maximum value throughout the developmental phase, such as animals that do not respond to physical activity before weaning, and that EE is not superior to its sub-components in all respects. EE affects the developing and adult brain, resulting in some neuroplastic changes in the microscopic and macroscopic anatomy, finally contributing to enhanced learning and memory capacity. These positive promoting influences are particularly prominent regarding neural repair after neurobiological disorders. Taking cerebral ischemia as an example, we analyzed the molecular mediators of EE promoting repair from various dimensions. We found that EE does not always lead to positive effects on nerve repair, such as infarct size. In view of the classic issues such as standardization and relativity of EE have been thoroughly discussed, we finally focus on analyzing the essentiality of the time window of EE action and clinical translation in order to devote to the future research direction of EE and rapid and reasonable clinical application.

An enriched environment reestablishes metabolic homeostasis by reducing obesity-induced inflammation

Obesity can lead to chronic inflammation in different tissues, generating insulin and leptin resistance and alterations in glucose and lipid metabolism, favoring the development of degenerative diseases, including type II diabetes. Congruently, the inflammatory signaling inhibition prevents the development of obesity and restores insulin sensitivity. Via the enhancement of central nervous system activity, an enriched environment (EE) has beneficial effects on learning and memory as well as on immune cell functions and inflammation in different disease models. Here, we explored whether an EE can restore energy balance in obese mice that previously presented metabolic alterations. We discovered that an EE improved glucose metabolism, increased insulin signaling in liver, and reduced hepatic steatosis and inflammation, and increased lipolysis and browning in the white adipose tissue of high-fat diet (HFD)-fed mice. Finally, we found reduced inflammatory signaling and increased anorexigenic signaling in the hypothalamus of HFD-fed mice exposed to an EE. These data indicate that an EE is able to restore the metabolic imbalance caused by HFD feeding. Thus, we propose EE as a novel therapeutic approach for treating obesity-related metabolic alterations.

This article has an associated First Person interview with the first author of the paper.

Summary: A series of physiological, histochemical and molecular analyses reveal that enriched environment decreases inflammation in adipose tissue and in hypothalamus, re-establishing glucose metabolism in metabolically compromised mice.

Leptin, the brain and energy homeostasis: From an apparently simple to a highly complex neuronal system

Leptin, produced and secreted by white adipose tissue in tight relationship with adipose mass, informs the brain about the status of the energy stores serving as the main peripheral signal for energy balance regulation through interaction with a multitude of highly interconnected neuronal populations. Most obese patients display resistance to the anorectic effect of the hormone. The present review unravels the multiple levels of complexity that trigger hypothalamic response to leptin with the objective of highlighting those critical hubs that, mainly in the hypothalamic arcuate nucleus, may undergo obesity-induced alterations and create an obstacle to leptin action. Several mechanisms underlying leptin resistance have been proposed, possibly representing useful targets to empower leptin effects. Among these, a special focus is herein dedicated to detail how leptin gains access into the brain and how neuronal plasticity may interfere with leptin function.

Reduced ccl11/eotaxin mediates the beneficial effects of environmental stimulation on the aged hippocampus

A deterioration in cognitive performance accompanies brain aging, even in the absence of neurodegenerative pathologies. However, the rate of cognitive decline can be slowed down by enhanced cognitive and sensorimotor stimulation protocols, such as environmental enrichment (EE). Understanding how EE exerts its beneficial effects on the aged brain pathophysiology can help in identifying new therapeutic targets. In this regard, the inflammatory chemokine ccl11/eotaxin-1 is a marker of aging with a strong relevance for neurodegenerative processes. Here, we demonstrate that EE in both elderly humans and aged mice decreases circulating levels of ccl11. Interfering, in mice, with the ccl11 decrease induced by EE ablated the beneficial effects on long-term memory retention, hippocampal neurogenesis, activation of local microglia and of ribosomal protein S6. On the other hand, treatment of standard-reared aged mice with an anti-ccl11 antibody resulted in EE-like improvements in spatial memory, hippocampal neurogenesis, and microglial activation. Taken together, our findings point to a decrease in circulating ccl11 concentration as a key mediator of the enhanced hippocampal function resulting from exposure to EE.

A new action of peptide hormones for survival in a low-nutrient environment

Malnutrition occurs when nutrient intake is too low for any reason and occurs regardless of gender or age. Therefore, besides loss of eating or digestive functionality due to illness, malnutrition can occur when a healthy individual undergoes an extreme diet and biases their nutrition, or when athletes exerts more energy than they can replenish through food. It has recently been reported that in Japan, the mortality rate of leaner individuals is equal to or higher than that of obese people. It is important to understand what homeostatic maintenance mechanism is behind this when the body is under hypotrophic conditions. Such mechanisms are generally endocranially controlled. We address this fundamental concern in this paper by focusing on peptide hormones. We introduce a mechanism for survival in a malnourished state via the regulation of food intake and temperature. Additionally, we will discuss the latest findings and future prospects for research on changes in the endocrine environment associated with malnutrition associated with exercise. We also review changes in next-generation endocrine environments when caused by malnutrition brought on by dieting.

A triheptanoin-supplemented diet rescues hippocampal hyperexcitability and seizure susceptibility in FoxG1+/- mice

The Forkhead Box G1 (FOXG1) gene encodes a transcription factor with an essential role in mammalian telencephalon development. FOXG1-related disorders, caused by deletions, intragenic mutations or duplications, are usually associated with severe intellectual disability, autistic features, and, in 87% of subjects, epileptiform manifestations. In a subset of patients with FoxG1 mutations, seizures remain intractable, prompting the need for novel therapeutic options. To address this issue, we took advantage of a haploinsufficient animal model, the FoxG1+/- mouse. In vivo electrophysiological analyses of FoxG1+/- mice detected hippocampal hyperexcitability, which turned into overt seizures upon delivery of the proconvulsant kainic acid, as confirmed by behavioral observations. These alterations were associated with decreased expression of the chloride transporter KCC2. Next, we tested whether a triheptanoin-based anaplerotic diet could have an impact on the pathological phenotype of FoxG1+/- mice. This manipulation abated altered neural activity and normalized enhanced susceptibility to proconvulsant-induced seizures, in addition to rescuing altered expression of KCC2 and increasing the levels of the GABA transporter vGAT. In conclusion, our data show that FoxG1 haploinsufficiency causes dysfunction of hippocampal circuits and increases the susceptibility to a proconvulsant insult, and that these alterations are rescued by triheptanoin dietary treatment.

Changes in the Brain-Derived Neurotrophic Factor Are Associated with Improvements in Diabetes Risk Factors after Exercise Training in Adolescents with Obesity: The HEARTY Randomized Controlled Trial

Obesity in youth increases the risk of type 2 diabetes (T2D), and both are risk factors for neurocognitive deficits. Exercise attenuates the risk of obesity and T2D while improving cognitive function. In adults, these benefits are associated with the actions of the brain-derived neurotrophic factor (BDNF), a protein critical in modulating neuroplasticity, glucose regulation, fat oxidation, and appetite regulation in adults. However, little research exists in youth. This study examined the associations between changes in diabetes risk factors and changes in BDNF levels after 6 months of exercise training in adolescents with obesity. The sample consisted of 202 postpubertal adolescents with obesity (70% females) aged 14-18 years who were randomized to 6 months of aerobic and/or resistance training or nonexercise control. All participants received a healthy eating plan designed to induce a 250/kcal deficit per day. Resting serum BDNF levels and diabetes risk factors, such as fasting glucose, insulin, homeostasis model assessment (HOMA-B-beta cell insulin secretory capacity) and (HOMA-IS-insulin sensitivity), and hemoglobin A1c (HbA1c), were measured after an overnight fast at baseline and 6 months. There were no significant intergroup differences on changes in BDNF or diabetes risk factors. In the exercise group, increases in BDNF were associated with reductions in fasting glucose (β = -6.57, SE = 3.37, p = 0.05) and increases in HOMA-B (β = 0.093, SE = 0.03, p = 0.004) after controlling for confounders. No associations were found between changes in diabetes risk factors and BDNF in controls. In conclusion, exercise-induced reductions in some diabetes risk factors were associated with increases in BDNF in adolescents with obesity, suggesting that exercise training may be an effective strategy to promote metabolic health and increases in BDNF, a protein favoring neuroplasticity. This trial is registered with ClinicalTrials.gov NCT00195858, September 12, 2005 (funded by the Canadian Institutes of Health Research).

Fluoxetine Modulates the Activity of Hypothalamic POMC Neurons via mTOR Signaling

Hypothalamic proopiomelanocortin (POMC) neurons are important players in the regulation of energy homeostasis; we previously demonstrated that environmental stimulation excites arcuate nucleus circuits to undergo plastic remodeling, leading to altered ratio between excitatory and inhibitory synaptic contacts on these neurons. The widely used selective serotonin reuptake inhibitor fluoxetine (FLX) is known to affect body weight. On the other hand, FLX administration mimics the effects of environmental stimulation on synaptic plasticity in the hippocampus and cortex. The mammalian target of rapamycin (mTOR) pathway is instrumental in these phenomena. Thus, we aimed at investigating whether and how FLX affects POMC neurons activity and hypothalamic mTOR function. Adult mice expressing green fluorescent protein (GFP) under the POMC promoter were treated with FLX for 3 weeks resulting in diminished body weight. Patch clamp recordings performed on POMC neurons indicate that FLX increases their firing rate and the excitatory AMPA-mediated transmission, and reduces the inhibitory GABAergic currents at presynaptic level. Immunofluorescence studies indicate that FLX increases the ratio between excitatory and inhibitory synaptic contacts on POMC neurons. These changes are associated with an increased activity of the hypothalamic mTOR pathway. Use of the mTOR inhibitor rapamycin blunts the effects of FLX on body weight and on functional and structural plasticity of POMC neurons. Our findings indicate that FLX is able to remodel POMC neurons, and that this may be partly mediated by the mTOR signaling pathway.

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.

The Leptin Resistance

Leptin is an adipocyte-derived hormone, which contributes to the homeostatic regulation of energy balance and metabolism through humoral and neural pathways. Leptin acts on the neurons in certain brain areas such as the hypothalamus, hippocampus, and brain stem to regulate food intake, thermogenesis, energy expenditure, and homeostasis of glucose/lipid metabolism. The pathologically increased circulating leptin is a biomarker of leptin resistance, which is common in obese individuals. Leptin resistance is defined by a reduced sensitivity or a failure in response of the brain to leptin, showing a decrease in the ability of leptin to suppress appetite or enhance energy expenditure, which causes an increased food intake and finally leads to overweight, obesity, cardiovascular diseases, and other metabolic disorders. Leptin resistance is a challenge for clinical treatment or drug discovery of obesity. Until recently, emerging evidence has been showing novel mechanisms of the leptin resistance. Here, we summarized the advances and controversy of leptin resistance and associated diseases, for better understanding the physiology and pathophysiology of leptin as well as the new strategies for treating obesity and metabolic disorders.

Loss of Leptin-Induced Modulation of Hippocampal Synaptic Trasmission and Signal Transduction in High-Fat Diet-Fed Mice

Hippocampal plasticity is triggered by a variety of stimuli including sensory inputs, neurotrophins and inflammation. Leptin, whose primary function is to regulate food intake and energy expenditure, has been recently shown to affect hippocampal neurogenesis and plasticity. Interestingly, mice fed a high-fat diet (HFD) exhibit impaired hippocampal function, but the underlying mechanisms are poorly understood. To address this issue, we compared leptin responsiveness of hippocampal neurons in control and HFD-fed mice by combining single-cell electrophysiology and biochemical assays. We found that leptin modulated spontaneous and evoked synaptic transmission in control, but not HFD, mice. This functional impairment was paralleled by blunted activation of STAT-3, one of the key signal transduction pathways controlled by the fully functional isoform of the leptin receptor, ObRb. In addition, SOCS-3 expression was non-responsive to leptin, indicating that modulation of negative feedback impinging on ObRb was also altered. Our results advance the understanding of leptin action on hippocampal plasticity and, more importantly, suggest that leptin resistance is a key determinant of hippocampal dysfunction associated with hypercaloric diet.

The emotional eating and negative food relationship experiences of obese and overweight adults

Overweight and obesity pose serious public health problems, affecting 68.8% of Americans. Previous research indicated that psychological factors played important roles in an individual's motivation to consume food. In particular, emotional eating, defined as overeating in response to negative affect, has received particular attention as a risk factor for obesity. This study explored and addressed the emotional factors involved in the development of emotional eating. A total of 10 Midwestern American male and female adults, previously diagnosed as medically overweight and obese, were recruited via online and print advertisement using maximum variation and snowball sampling methods. Using a semi-structured, face-to-face interview format, participants shared their perspectives about the development and persistence of emotional eating. The interviews were transcribed and Atlas.ti software was used to assist in thematic analysis of emotional eating. Study results yielded themes, such as emotional triggers, food cravings, comfort from foods, mindless eating, and childhood experiences. Findings indicated that participants generally lacked emotional self-care, but desired to decrease their emotional eating behaviors. Implications are discussed to construct creative, evidence-based treatments for the overweight and obese emotional eaters.

Enriching the Housing Environment for Mice Enhances Their NK Cell Antitumor Immunity via Sympathetic Nerve-Dependent Regulation of NKG2D and CCR5

Mice housed in an enriched environment display a tumor-resistant phenotype due to eustress stimulation. However, the mechanisms underlying enriched environment-induced protection against cancers remain largely unexplained. In this study, we observed a significant antitumor effect induced by enriched environment in murine pancreatic cancer and lung cancer models. This effect remained intact in T/B lymphocyte-deficient Rag1^-/- mice, but was nearly eliminated in natural killer (NK) cell-deficient Beige mice or in antibody-mediated NK-cell-depleted mice, suggesting a predominant role of NK cells in enriched environment-induced tumor inhibition. Exposure to enriched environment enhanced NK-cell activity against tumors and promoted tumoral infiltration of NK cells. Enriched environment increased the expression levels of CCR5 and NKG2D (KLRK1) in NK cells; blocking their function effectively blunted the enriched environment-induced enhancement of tumoral infiltration and cytotoxic activity of NK cells. Moreover, blockade of β-adrenergic signaling or chemical sympathectomy abolished the effects of enriched environment on NK cells and attenuated the antitumor effect of enriched environment. Taken together, our results provide new insight into the mechanism by which eustress exerts a beneficial effect against cancer. Cancer Res; 77(7); 1611-22. ©2017 AACR.

Identification of a novel leptin receptor duplicate in Atlantic salmon: Expression analyses in different life stages and in response to feeding status

In recent years rapidly growing research has led to identification of several fish leptin orthologs and numerous duplicated paralogs possibly arisen from the third and fourth round whole genome duplication (3R and 4R WGD) events. In this study we identify in Atlantic salmon a duplicated LepRA gene, named LepRA2, that further extend possible evolutionary scenarios of the leptin and leptin receptor system. The 1121 amino acid sequence of the novel LepRA2 shares 80% sequence identity with the LepRA1 paralog, and contains the protein motifs typical of the functional (long form) leptin receptor in vertebrates. In silico predictions showed similar electrostatic properties of LepRA1 and LepRA2 and high sequence conservation at the leptin interaction surfaces within the CHR/leptin-binding and FNIII domains, suggesting conserved functional specificity between the two duplicates. Analysis of temporal expression profiles during pre-hatching stages indicate that both transcripts are involved in modulating leptin developmental functions, although the LepRA1 paralog may play a major role as the embryo complexity increases. There is ubiquitous distribution of LepRs underlying pleiotropism of leptin in all tissues investigated. LepRA1 and LepRA2 are differentially expressed with LepRA1 more abundant than LepRA2 in most of the tissues investigated, with the only exception of liver. Analysis of constitutive LepRA1 and LepRA2 expression in brain and liver at parr, post-smolt and adult stages reveal striking spatial divergence between the duplicates at all stages investigated. This suggests that, beside increased metabolic requirements, leptin sensitivity in the salmon brain might be linked to important variables such as habitat, ecology and life cycle. Furthermore, leptins and LepRs mRNAs in the brain showed gene-specific variability in response to long term fasting, suggesting that leptin's roles as modulator of nutritional status in Atlantic salmon might be governed by distinct genetic evolutionary processes and distinct functions between the paralogs.

A dynamic architecture of life

In recent decades, a profound conceptual transformation has occurred comprising different areas of biological research, leading to a novel understanding of life processes as much more dynamic and changeable. Discoveries in plants and animals, as well as novel experimental approaches, have prompted the research community to reconsider established concepts and paradigms. This development was taken as an incentive to organise a workshop in May 2014 at the Academia Nazionale dei Lincei in Rome. There, experts on epigenetics, regeneration, neuroplasticity, and computational biology, using different animal and plant models, presented their insights on important aspects of a dynamic architecture of life, which comprises all organisational levels of the organism. Their work demonstrates that a dynamic nature of life persists during the entire existence of the organism and permits animals and plants not only to fine-tune their response to particular environmental demands during development, but underlies their continuous capacity to do so. Here, a synthesis of the different findings and their relevance for biological thinking is presented.

Modulation of hippocampal neural plasticity by glucose-related signaling

Hormones and peptides involved in glucose homeostasis are emerging as important modulators of neural plasticity. In this regard, increasing evidence shows that molecules such as insulin, insulin-like growth factor-I, glucagon-like peptide-1, and ghrelin impact on the function of the hippocampus, which is a key area for learning and memory. Indeed, all these factors affect fundamental hippocampal properties including synaptic plasticity (i.e., synapse potentiation and depression), structural plasticity (i.e., dynamics of dendritic spines), and adult neurogenesis, thus leading to modifications in cognitive performance. Here, we review the main mechanisms underlying the effects of glucose metabolism on hippocampal physiology. In particular, we discuss the role of these signals in the modulation of cognitive functions and their potential implications in dysmetabolism-related cognitive decline.

Exercise training and calorie restriction influence the metabolic parameters in ovariectomized female rats

The estrogen deficiency after menopause leads to overweight or obesity, and physical exercise is one of the important modulators of this body weight gain. Female Wistar rats underwent ovariectomy surgery (OVX) or sham operation (SO). OVX and SO groups were randomized into new groups based on the voluntary physical activity (with or without running) and the type of diet for 12 weeks. Rats were fed standard chow (CTRL), high triglyceride diet (HT), or restricted diet (CR). The metabolic syndrome was assessed by measuring the body weight gain, the glucose sensitivity, and the levels of insulin, triglyceride, leptin, and aspartate aminotransferase transaminase (AST) and alanine aminotransferase (ALT). The exercise training combined with the CR resulted in improvements in the glucose tolerance and the insulin sensitivity. Plasma TG, AST, and ALT levels were significantly higher in OVX rats fed with HT but these high values were suppressed by exercise and CR. Compared to SO animals, estrogen deprivation with HT caused a significant increase in leptin level. Our data provide evidence that CR combined with voluntary physical exercise can be a very effective strategy to prevent the development of a metabolic syndrome induced by high calorie diet.

Fuel homeostasis and locomotor behavior: role of leptin and melanocortin pathways

BACKGROUND

While it is now accepted that genes and their products affect food intake, the concept that locomotor behavior or the propensity for physical activity is controlled by neuro hum oral regulators is frequently underappreciated. In mammals, complex interactions have developed to allow the cross-talk between fuel homeostasis and physical activity.

AIM

The aim of this review is to provide a synopsis of the influence of the leptin-melanocortin pathway, a well-studied pivotal player in body weight regulation, on locomotor behaviors.

CONCLUSIONS

In rodents, reductions in leptin levels that physiologically occur following acute food deprivation or a reduction of the fat mass consequent to prolonged caloric restrictions are associated with a decrease in total locomotor activity and simultaneous increase in food-anticipatory activity, a locomotor behavior which reflects a foraging attitude. These actions can be prevented by leptin administration and are at least partially mediated by the neurons of the melanocortin pathway. In humans, twin studies have attributed to genetic factors approximately 50% of the variance of physical activity. An elevated number of the genes or loci which may affect physical activity are involved in body weight homeostasis. Polymorphisms of the melanocortin-4 and leptin receptors have repeatedly been associated with the level of physical activity. Unraveling the complexity of the regulation of locomotor behavior and the interconnections with the pathways involved in energy homeostasis may help explain the substantial individual variability in physical activities in humans and disentangle the harmful effects of sedentary lifestyle, which may be distinct from the detrimental effects of obesity.

Leptin: A hormone linking activation of neuroendocrine axes with neuropathology

Leptin, a peptide hormone secreted by adipocytes, plays a central role in controlling appetite and weight in both rodents and humans. Basic science and clinical research suggest that this hormone not only affects the regulation of the neuroendocrine axes, but also exerts effects on the central nervous system with subsequent alterations in psychological functions. For instance, leptin suppresses cortisol secretion during stress-related activation of the adrenal axis. As psychiatric disorders like depression are associated with hypercortisolism, leptin is proposed to exert anti-depressant-like effects due to its inhibition of chronically overactive hypothalamo-pituitary-adrenal axis function. Moreover, leptin status of depressed patients could serve as a prognostic marker for therapy response. Besides its influence on neuroendocrine pathways leptin seems to have direct central effects on brain development and neuroplasticity. Low leptin levels have been shown to be associated with increased risk of developing dementia, supporting the idea of a pro-cognitive effect of leptin. These areas may have direct clinical implications and deserve to be studied further in the future.

The association between childhood sexual and physical abuse with incident adult severe obesity across 13 years of the National Longitudinal Study of Adolescent Health

BACKGROUND

Severe obesity has increased, yet childhood antecedents of adult severe obesity are not well understood.

OBJECTIVE

Estimate adult-onset severe obesity risk in individuals with history of childhood physical and/or sexual abuse compared with those who did not report abuse.

METHODS

Longitudinal analysis of participants from the US National Longitudinal Study of Adolescent Health (n = 10,774) wave II (1996; aged 12-22 years) followed through wave IV (2008-2009; aged 24-34 years). New cases of adult-onset severe obesity (body mass index [BMI] ≥ 40 kg/m2 using measured height and weight) in individuals followed over 13 years who were not severely obese during adolescence (BMI <120% of 95th percentile Centers for Disease Control and Prevention National Center for Health Statistics growth curves).

RESULTS

The combined occurrence of self-reported sexual and physical abuse during childhood was associated with an increased risk of incident severe obesity in adulthood in non-minority females (hazard ratio [HR; 95% Confidence Interval] = 2.5; 1.3, 4.8) and males (HR = 3.6; 1.5, 8.5) compared with individuals with no history of abuse.

CONCLUSION

In addition to other social and emotional risks, exposure to sexual and physical abuse during childhood may increase risk of severe obesity later in life. Consideration of the confluence of childhood abuse might be considered as part of preventive and therapeutic approaches to address severe obesity.

Childhood maltreatment and obesity: systematic review and meta-analysis

Obesity is a prevalent global-health problem associated with substantial morbidity, impairment and economic burden. Because most readily available forms of treatment are ineffective in the long term, it is essential to advance knowledge of obesity prevention by identifying potentially modifiable risk factors. Findings from experimental studies in non-human primates suggest that adverse childhood experiences may influence obesity risk. However, observations from human studies showed heterogeneous results. To address these inconsistencies, we performed Medline, PsycInfo and Embase searches till 1 August 2012 for articles examining the association between childhood maltreatment and obesity. We then conducted a meta-analysis of the identified studies and explored the effects of various possible sources of bias. A meta-analysis of 41 studies (190 285 participants) revealed that childhood maltreatment was associated with elevated risk of developing obesity over the life-course (odds ratio=1.36; 95% confidence interval=1.26-1.47). Results were not explained by publication bias or undue influence of individual studies. Overall, results were not significantly affected by the measures or definitions used for maltreatment or obesity, nor by confounding by childhood or adult socioeconomic status, current smoking, alcohol intake or physical activity. However, the association was not statistically significant in studies of children and adolescents, focusing on emotional neglect, or adjusting for current depression. Furthermore, the association was stronger in samples including more women and whites, but was not influenced by study quality. Child maltreatment is a potentially modifiable risk factor for obesity. Future research should clarify the mechanisms through which child maltreatment affects obesity risk and explore methods to remediate this effect.

Environmental enrichment strengthens corticocortical interactions and reduces amyloid-β oligomers in aged mice

Brain aging is characterized by global changes which are thought to underlie age-related cognitive decline. These include variations in brain activity and the progressive increase in the concentration of soluble amyloid-β (Aβ) oligomers, directly impairing synaptic function and plasticity even in the absence of any neurodegenerative disorder. Considering the high social impact of the decline in brain performance associated to aging, there is an urgent need to better understand how it can be prevented or contrasted. Lifestyle components, such as social interaction, motor exercise and cognitive activity, are thought to modulate brain physiology and its susceptibility to age-related pathologies. However, the precise functional and molecular factors that respond to environmental stimuli and might mediate their protective action again pathological aging still need to be clearly identified. To address this issue, we exploited environmental enrichment (EE), a reliable model for studying the effect of experience on the brain based on the enhancement of cognitive, social and motor experience, in aged wild-type mice. We analyzed the functional consequences of EE on aged brain physiology by performing in vivo local field potential (LFP) recordings with chronic implants. In addition, we also investigated changes induced by EE on molecular markers of neural plasticity and on the levels of soluble Aβ oligomers. We report that EE induced profound changes in the activity of the primary visual and auditory cortices and in their functional interaction. At the molecular level, EE enhanced plasticity by an upward shift of the cortical excitation/inhibition balance. In addition, EE reduced brain Aβ oligomers and increased synthesis of the Aβ-degrading enzyme neprilysin. Our findings strengthen the potential of EE procedures as a non-invasive paradigm for counteracting brain aging processes.

Environment and Brain Plasticity: Towards an Endogenous Pharmacotherapy

Brain plasticity refers to the remarkable property of cerebral neurons to change their structure and function in response to experience, a fundamental theoretical theme in the field of basic research and a major focus for neural rehabilitation following brain disease. While much of the early work on this topic was based on deprivation approaches relying on sensory experience reduction procedures, major advances have been recently obtained using the conceptually opposite paradigm of environmental enrichment, whereby an enhanced stimulation is provided at multiple cognitive, sensory, social, and motor levels. In this survey, we aim to review past and recent work concerning the influence exerted by the environment on brain plasticity processes, with special emphasis on the underlying cellular and molecular mechanisms and starting from experimental work on animal models to move to highly relevant work performed in humans. We will initiate introducing the concept of brain plasticity and describing classic paradigmatic examples to illustrate how changes at the level of neuronal properties can ultimately affect and direct key perceptual and behavioral outputs. Then, we describe the remarkable effects elicited by early stressful conditions, maternal care, and preweaning enrichment on central nervous system development, with a separate section focusing on neurodevelopmental disorders. A specific section is dedicated to the striking ability of environmental enrichment and physical exercise to empower adult brain plasticity. Finally, we analyze in the last section the ever-increasing available knowledge on the effects elicited by enriched living conditions on physiological and pathological aging brain processes.

Feed your head: neurodevelopmental control of feeding and metabolism

During critical periods of development early in life, excessive or scarce nutritional environments can disrupt the development of central feeding and metabolic neural circuitry, leading to obesity and metabolic disorders in adulthood. A better understanding of the genetic networks that control the development of feeding and metabolic neural circuits, along with knowledge of how and where dietary signals disrupt this process, can serve as the basis for future therapies aimed at reversing the public health crisis that is now building as a result of the global obesity epidemic. This review of animal and human studies highlights recent insights into the molecular mechanisms that regulate the development of central feeding circuitries, the mechanisms by which gestational and early postnatal nutritional status affects this process, and approaches aimed at counteracting the deleterious effects of early over- and underfeeding.

Perilesional treatment with chondroitinase ABC and motor training promote functional recovery after stroke in rats

Ischemic stroke insults may lead to chronic functional limitations that adversely affect patient movements. Partial motor recovery is thought to be sustained by neuronal plasticity, particularly in areas close to the lesion site. It is still unknown if treatments acting exclusively on cortical plasticity of perilesional areas could result in behavioral amelioration. We tested whether enhancing plasticity in the ipsilesional cortex using local injections of chondroitinase ABC (ChABC) could promote recovery of skilled motor function in a focal cortical ischemia of forelimb motor cortex in rats. Using the skilled reaching test, we found that acute and delayed ChABC treatment induced recovery of impaired motor skills in treated rats. vGLUT1, vGLUT2, and vGAT staining indicated that functional recovery after acute ChABC treatment was associated with local plastic modification of the excitatory cortical circuitry positive for VGLUT2. ChABC effects on vGLUT2 staining were present only in rats undergoing behavioral training. Thus, the combination of treatments targeting the CSPG component of the extracellular matrix in perilesional areas and rehabilitation could be sufficient to enhance functional recovery from a focal stroke.

Environment, leptin sensitivity, and hypothalamic plasticity

Regulation of feeding behavior has been a crucial step in the interplay between leptin and the arcuate nucleus of the hypothalamus (ARC). On one hand, the basic mechanisms regulating central and peripheral action of leptin are becoming increasingly clear. On the other hand, knowledge on how brain sensitivity to leptin can be modulated is only beginning to accumulate. This point is of paramount importance if one considers that pathologically obese subjects have high levels of plasmatic leptin. A possible strategy for exploring neural plasticity in the ARC is to act on environmental stimuli. This can be achieved with various protocols, namely, physical exercise, high-fat diet, caloric restriction, and environmental enrichment. Use of these protocols can, in turn, be exploited to isolate key molecules with translational potential. In the present review, we summarize present knowledge about the mechanisms of plasticity induced by the environment in the ARC. In addition, we also address the role of leptin in extrahypothalamic plasticity, in order to propose an integrated view of how a single diffusible factor can regulate diverse brain functions.

Treatment of neurodevelopmental disorders in adulthood

Brain development in neurodevelopmental disorders has been considered to comprise a sequence of critical periods, and abnormalities occurring during early development have been considered irreversible in adulthood. However, findings in mouse models of neurodevelopmental disorders, including fragile X, Rett syndrome, Down syndrome, and neurofibromatosis type I suggest that it is possible to reverse certain molecular, electrophysiological, and behavioral deficits associated with these disorders in adults by genetic or pharmacological manipulations. Furthermore, recent studies have suggested that critical period-like plasticity can be reactivated in the adult brain by environmental manipulations or by pharmacotherapy. These studies open up a tantalizing possibility that targeted pharmacological treatments in combination with regimes of training or rehabilitation might alleviate or reverse the symptoms of neurodevelopmental disorders even after the end of critical developmental periods. Even though translation from animal experimentation to clinical practice is challenging, these results suggest a rational basis for treatment of neurodevelopmental disorders in adulthood.

Exercise training effects on inflammatory gene expression in white adipose tissue of young mice

We aimed to determine the effects of 6 wks of exercise on inflammatory markers in mice concomitantly fed either high-fat (HF) or normal chow (NC) diets in young mice. C57BL/6 mice were randomized into (n = 10/group) an NC/sedentary (NC/SED), NC/exercise (NC/EX), HF/SED, and HF/EX groups. Treadmill exercise was performed 5 d/wk at 12 m/min, with 12% grade for 40 min/d. Liver triglycerides and gene expression of F4/80, MCP-1, TNF-α, leptin, and VEGF in visceral white adipose were determined. NC groups had lower body weights after 6 wks versus the HF groups (22.8 ± 0.2 versus 25.7 ± 0.4 g) (P < 0.0001). F4/80 gene expression (indicator of macrophage infiltration) and liver triglycerides were greatest amongst the HF/SED group, with no differences between the remaining groups. VEGF (indicator of angiogenesis) was greatest in the HF/EX versus the other 3 groups (P < 0.05). Exposure of an HF diet in sedentary young mice increased visceral adipose depots and liver triglycerides versus an NC diet. Exercise training while on the HF diet protected against hepatic steatosis and possibly macrophage infiltration within white adipose tissue. This suggests that moderate exercise while on an HF diet can offer some level of protection early on in the development of obesity.

Influence of the core circadian gene "Clock" on obesity and leptin resistance in mice

Alterations in metabolism could be due to cell-autonomous effects associated with altered expression of Clock in central nervous system feeding centers and/or peripheral tissues involved in metabolism. Clock mutant mice are hyperphagic and obese, which indicates that Clock is related to obesity. In the present study, we used intracerebroventricular injection of recombinant adenoviral vector harboring Clock genes to explore the role of Clock on diet induced obesity and the mechanisms involved in leptin resistance and leptin signaling in mice. The results demonstrated that expression of Clock in the arcuate nucleus of diet induced obesity mice was down-regulated. The recombinant adenoviral vector harboring Clock genes could reduce obesity indexes of diet induced obesity mice including body weight, BMI and total fat mass, attenuate hyperleptinemia, increase leptin sensitivity and decrease accumulated suppressor of cytokine signaling-3 in the arcuate nucleus. These results indicate that Clock plays an important role on obesity, which may be involved in leptin resistance and regulation of suppressor of cytokine signaling-3 in arcuate nucleus.

Environmental enrichment during rearing alters corticosterone levels, thymocyte numbers, and aggression in female BALB/c mice

The goal of environmental enrichment for laboratory animals is to improve welfare, but some enrichment practices may affect research in unintended ways or even be harmful to the animals themselves. We previously found that mice raised at a commercial vendor then given multiple enrichment devices upon arrival at our facilities experienced thymic atrophy and greater variation in measured parameters than did their unenriched counterparts, suggesting that enrichment conditions affected corticosteroid expression in mice. The current study verified and expanded these results, examining 120 female BALB/c mice raised with or without nesting material at a commercial vendor (n = 60 per group) and allocated (n = 20 per group) to receive no enrichment, nesting material, or 'superenrichment' on arrival at our facilities. Nesting material provided prior to weaning was associated with higher levels of urinary corticosteroid, whereas superenrichment and nesting material during the adult period both led to increased thymic atrophy. Paradoxically, mice that never received enrichment, despite having the lowest corticosterone levels and least thymic atrophy, had increased tail wounds resulting from aggressive interactions. Therefore, enrichment devices that are as seemingly innocuous as nesting material, even if only provided in the preweaning period, may lead to significant, lasting changes in behavioral, physical, or immunologic measures with the potential to alter research outcomes.

Post-weaning chronic social isolation produces profound behavioral dysregulation with decreases in prefrontal cortex synaptic-associated protein expression in female rats

Early life stressors in rodents, including maternal separation and social isolation, have been shown to disrupt brain development and profoundly affect a wide-range of behaviors in adult animals. In this study, we focus on the development of female Sprague-Dawley rats in the presence and absence of conspecifics during the critical period of social play. Similar studies in male rodents have shown that this form of social deprivation results in dysregulated dopaminergic and serotonergic functions in the brain with core features of neuropsychiatric disorders including anxiety disorder and schizophrenia. Here we examined the behavioral and biochemical effects of post-weaning social isolation in female rats. Our findings demonstrated that isolation rearing produced marked deficits in social interaction behaviors and increased anxiety in open-field and novelty-suppressed feeding tests. The expression of synaptic-associated proteins PSD95 and synapsin I as well as glutamate receptors subunits GluR1 and NR1 in the prefrontal cortex (PFC) were significantly reduced in isolation-reared female rats. Current findings provide evidence that in female rats, post-weaning environmental disruption can result in profound dysregulation of synapse-related proteins and behavior.