Induction of brain-derived neurotrophic factor by leptin in the ventromedial hypothalamus

Early adversity and the comorbidity between metabolic disease and psychopathology

Although the co-existence of metabolic and psychiatric disorders in the same individual (comorbidity) is very prevalent, the mechanisms by which these disorders co-occur are poorly understood, but a history of early-life adversity is a common developmental risk factor. Exposure to adverse environments during critical periods of development (e.g. fetal life and infancy) modifies the metabolism and the function of the brain persistently, influencing behaviours that contribute to both metabolic and mental health disarrangements over the life course. We will review molecular and clinical evidence supporting the notion that early adversity is an important risk factor for the comorbidity between metabolic and psychiatric conditions. We will also discuss the possible mechanisms involved: neurometabolic programming, epigenetic alterations and the cumulative effects of altered inflammatory and oxidative pathways linked to early adversity.

The Role of BDNF and TrkB in the Central Control of Energy and Glucose Balance: An Update

The global rise in obesity and related health issues, such as type 2 diabetes and cardiovascular disease, is alarming. Gaining a deeper insight into the central neural pathways and mechanisms that regulate energy and glucose homeostasis is crucial for developing effective interventions to combat this debilitating condition. A significant body of evidence from studies in humans and rodents indicates that brain-derived neurotrophic factor (BDNF) signaling plays a key role in regulating feeding, energy expenditure, and glycemic control. BDNF is a highly conserved neurotrophin that signals via the tropomyosin-related kinase B (TrkB) receptor to facilitate neuronal survival, differentiation, and synaptic plasticity and function. Recent studies have shed light on the mechanisms through which BDNF influences energy and glucose balance. This review will cover our current understanding of the brain regions, neural circuits, and cellular and molecular mechanisms underlying the metabolic actions of BDNF and TrkB.

Adipo-oncology: adipocyte-derived factors govern engraftment, survival, and progression of metastatic cancers

Conventional therapies for metastatic cancers have limited efficacy. Recently, cancer therapies targeting noncancerous cells in tumor microenvironments have shown improved clinical outcomes in patients. However, further advances in our understanding of the metastatic tumor microenvironment are required to improve treatment outcomes. Adipocytes are distributed throughout the body, and as a part of the metastatic tumor microenvironment, they interact with cancer cells in almost all organs. Adipocytes secrete various factors that are reported to exert clinical effects on cancer progression, including engraftment, survival, and expansion at the metastatic sites. However, only a few studies have comprehensively examined their impact on cancer cells. In this review, we examined the impact of adipocytes on cancer by describing the adipocyte-secreted factors that are involved in controlling metastatic cancer, focusing on adipokines, such as adiponectin, leptin, visfatin, chemerin, resistin, apelin, and omentin. Adipocyte-secreted factors promote cancer metastasis and contribute to various biological functions of cancer cells, including migration, invasion, proliferation, immune evasion, and drug resistance at the metastatic sites. We propose the establishment and expansion of "adipo-oncology" as a research field to enhance the comprehensive understanding of the role of adipocytes in metastatic cancers and the development of more robust metastatic cancer treatments.

A primary study on rat fetal development and brain-derived neurotrophic factor levels under the control of electromagnetic fields

Background

In previous researches, electromagnetic fields have been shown to adversely affect the behavior and biology of humans and animals; however, body growth and brain-derived neurotrophic factor levels were not evaluated.

Objective

The original investigation aimed to examine whether Electromagnetic Fields (EMF) exposure had adverse effects on spatial learning and motor function in rats and if physical activity could diminish the damaging effects of EMF exposure. In this study, we measured anthropometric measurements and brain-derived neurotrophic factor (BDNF) levels in pregnant rats' offspring to determine if Wi-Fi EMF also affected their growth. These data we report for the first time in this publication.

Methods

Twenty Albino-Wistar pregnant rats were divided randomly into EMF and control (CON) groups, and after delivery, 12 male fetuses were randomly selected. For assessing the body growth change of offspring beginning at delivery, then at 21 postnatal days, and finally at 56 post-natal days, the crown-rump length of the body was assessed using a digital caliper. Examining BDNF factor levels, an Enzyme-linked immunosorbent assay ELISA kit was taken. Bodyweight was recorded by digital scale.

Results

Outcomes of the anthropometric measurements demonstrated that EMF blocked body growth in rats exposed to EMF. The results of the BDNF test illustrated that the BDNF in the EMF liter group was remarkably decreased compared to the CON group. The results indicate that EMF exposure could affect BDNF levels and harm body growth in pregnant rats' offspring.

Conclusions

The results suggest that EMF exposure could affect BDNF levels and impair body growth in pregnant rats' offspring.

Interactive Effects of Serum Leptin Levels and Physical Comorbidity on the Pharmacotherapeutic Response of Depressive Disorders

OBJECTIVE

To investigate individual and interactive associations of baseline serum leptin levels and physical comorbidity with short- and long-term treatment outcomes in outpatients with depressive disorders who received stepwise antidepressant treatment in a naturalistic prospective study design.

METHODS

Baseline serum leptin levels were measured, and the number of concurrent physical disorders ascertained from 1,094 patients. These patients received initial antidepressant monotherapy; then, for patients with an insufficient response or who experienced uncomfortable side effects, treatment was administered using alternative strategies every 3 weeks in the acute treatment phase (at 3, 6, 9, and 12 weeks) and every 3 months in the continuation treatment phase (at 6, 9, and 12 months). Then, 12-week and 12-month remission, defined as a Hamilton Depression Rating Scale score of ≤7, was estimated.

RESULTS

In multivariable logistic regression analyses, individual effects were found only between higher baseline serum leptin levels and 12-week non-remission. Significant interactive effects between higher leptin levels and fewer physical disorders (< 2 physical disorders) on 12-week non-remission were observed. However, neither individual nor interactive effects between leptin levels and physical comorbidity were associated with 12-month remission.

CONCLUSION

The combination of serum leptin level and number of physical disorders may be a useful predictor of short-term treatment responses in patients with depressive disorders receiving pharmacotherapy.

Astrocytic BDNF signaling within the ventromedial hypothalamus regulates energy homeostasis

Brain-derived neurotrophic factor (BDNF) is essential for maintaining energy and glucose balance within the central nervous system. Because the study of its metabolic actions has been limited to effects in neuronal cells, its role in other cell types within the brain remains poorly understood. Here we show that astrocytic BDNF signaling within the ventromedial hypothalamus (VMH) modulates neuronal activity in response to changes in energy status. This occurs via the truncated TrkB.T1 receptor. Accordingly, either fasting or central BDNF depletion enhances astrocytic synaptic glutamate clearance, thereby decreasing neuronal activity in mice. Notably, selective depletion of TrkB.T1 in VMH astrocytes blunts the effects of energy status on excitatory transmission, as well as on responses to leptin, glucose and lipids. These effects are driven by increased astrocytic invasion of excitatory synapses, enhanced glutamate reuptake and decreased neuronal activity. We thus identify BDNF/TrkB.T1 signaling in VMH astrocytes as an essential mechanism that participates in energy and glucose homeostasis.

The Pleiotropic Potential of BDNF beyond Neurons: Implication for a Healthy Mind in a Healthy Body

Brain-derived neurotrophic factor (BDNF) represents one of the most widely studied neurotrophins because of the many mechanisms in which it is involved. Among these, a growing body of evidence indicates BDNF as a pleiotropic signaling molecule and unveils non-negligible implications in the regulation of energy balance. BDNF and its receptor are extensively expressed in the hypothalamus, regions where peripheral signals, associated with feeding control and metabolism activation, and are integrated to elaborate anorexigenic and orexigenic effects. Thus, BDNF coordinates adaptive responses to fluctuations in energy intake and expenditure, connecting the central nervous system with peripheral tissues, including muscle, liver, and the adipose tissue in a complex operational network. This review discusses the latest literature dealing with the involvement of BDNF in the maintenance of energy balance. We have focused on the physiological and molecular mechanisms by which BDNF: (I) controls the mitochondrial function and dynamics; (II) influences thermogenesis and tissue differentiation; (III) mediates the effects of exercise on cognitive functions; and (IV) modulates insulin sensitivity and glucose transport at the cellular level. Deepening the understanding of the mechanisms exploited to maintain energy homeostasis will lay the groundwork for the development of novel therapeutical approaches to help people to maintain a healthy mind in a healthy body.

Metabolic homeostasis via BDNF and its receptors

Metabolic disorders result from dysregulation of central nervous system and peripheral metabolic energy homeostatic pathways. To maintain normal energy balance, neural circuits must integrate feedforward and feedback signals from the internal metabolic environment to orchestrate proper food intake and energy expenditure. These signals include conserved meal and adipocyte cues such as glucose and leptin, respectively, in addition to more novel players including brain-derived neurotrophic factor (BDNF). In particular, BDNF's two receptors, tropomyosin related kinase B (TrkB) and p75 neurotrophin receptor (p75NTR), are increasingly appreciated to be involved in whole body energy homeostasis. At times, these two receptors even seem to functionally oppose one another's actions, providing the framework for a potential neurotrophin mediated energy regulatory axis, which we explore further here.

Childhood trauma, the stress response and metabolic syndrome: A focus on DNA methylation

Childhood trauma (CT) is well established as a potent risk factor for the development of mental disorders. However, the potential of adverse early experiences to exert chronic and profound effects on physical health, including aberrant metabolic phenotypes, has only been more recently explored. Among these consequences is metabolic syndrome (MetS), which is characterised by at least three of five related cardiometabolic traits: hypertension, insulin resistance/hyperglycaemia, raised triglycerides, low high-density lipoprotein and central obesity. The deleterious effects of CT on health outcomes may be partially attributable to dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, which coordinates the response to stress, and the consequent fostering of a pro-inflammatory environment. Epigenetic tags, such as DNA methylation, which are sensitive to environmental influences provide a means whereby the effects of CT can be biologically embedded and persist into adulthood to affect health and well-being. The methylome regulates the transcription of genes involved in the stress response, metabolism and inflammation. This narrative review examines the evidence for DNA methylation in CT and MetS in order to identify shared neuroendocrine and immune correlates that may mediate the increased risk of MetS following CT exposure. Our review specifically highlights differential methylation of FKBP5, the gene that encodes FK506-binding protein 51 and has pleiotropic effects on stress responding, inflammation and energy metabolism, as a central candidate to understand the molecular aetiology underlying CT-associated MetS risk.

Gut microbiota: An intermediary between metabolic syndrome and cognitive deficits in schizophrenia

Gut microbiome interacts with the central nervous system tract through the gut-brain axis. Such communication involves neuronal, endocrine, and immunological mechanisms, which allows for the microbiota to affect and respond to various behaviors and psychiatric conditions. In addition, the use of atypical antipsychotic drugs (AAPDs) may interact with and even change the abundance of microbiome to potentially cause adverse effects or aggravate the disorders inherent in the disease. The regulate effects of gut microbiome has been described in several psychiatric disorders including anxiety and depression, but only a few reports have discussed the role of microbiota in AAPDs-induced Metabolic syndrome (MetS) and cognitive disorders. The following review systematically summarizes current knowledge about the gut microbiota in behavior and psychiatric illness, with the emphasis of an important role of the microbiome in the metabolism of schizophrenia and the potential for AAPDs to change the gut microbiota to promote adverse events. Prebiotics and probiotics are microbiota-management tools with documented efficacy for metabolic disturbances and cognitive deficits. Novel therapies for targeting microbiota for alleviating AAPDs-induced adverse effects are also under fast development.

Alpha-Melanocyte-Stimulating Hormone is Elevated in Hypothalamic Obesity Associated with Childhood Craniopharyngioma

OBJECTIVE

The purpose of this study was to investigate the peripheral concentrations of leptin and neuropeptides taking part in the melanocortin pathway in hypothalamic obesity (HO) associated with craniopharyngioma (CP) and to find a peripheral marker for diagnosis.

METHODS

Thirty-one patients (52% girls; median age 16 years) with CP were enrolled in the study group. They were grouped as CP with obesity (CP^obesity , n = 17) and CP without obesity (CP^nonobesity , n = 14). Two control groups without CP consisted of 27 children with obesity (OC) (55% girls; median age 13.8 years) and 25 children without obesity (normal control [NC]) (72% girls; median age 14.5 years). Obesity was defined as BMI percentile ≥ 95%. Fasting serum concentrations of leptin, brain-derived neurotrophic factor (BDNF), and alpha-melanocyte-stimulating hormone (α-MSH) were measured in the groups.

RESULTS

Leptin and BDNF concentrations were correlated with BMI SD score (SDS) in controls (OC + NC) and CP. However, there was no correlation between α-MSH and BMI-SDS in CP or control groups. After adjusting for age, sex, and BMI-SDS, α-MSH was found to be significantly higher in CP^obesity than in other groups, whereas leptin and BDNF were comparable among the four groups.

CONCLUSIONS

Serum BDNF, just like leptin, increased with BMI, regardless of hypothalamic damage. On the contrary, α-MSH concentration was significantly high in HO, designating a potential biomarker for HO in CP.

Plasma brain-derived neurotrophic factor and dynamic cerebral autoregulation in acute response to glycemic control following breakfast in young men

We examined the acute impact of both low- and high-glycemic index (GI) breakfasts on plasma brain-derived neurotrophic factor (BDNF) and dynamic cerebral autoregulation (dCA) compared with breakfast omission. Ten healthy men (age 24 ± 1 yr) performed three trials in a randomized crossover order; omission and Low-GI (GI = 40) and High-GI (GI = 71) breakfast conditions. Middle cerebral artery velocity (transcranial Doppler ultrasonography) and arterial pressure (finger photoplethysmography) were continuously measured for 5 min before and 120 min following breakfast consumption to determine dCA using transfer function analysis. After these measurements of dCA, venous blood samples for the assessment of plasma BDNF were obtained. Moreover, blood glucose was measured before breakfast and every 30 min thereafter. The area under the curve of 2 h postprandial blood glucose in the High-GI trial was higher than the Low-GI trial (P < 0.01). The GI of the breakfast did not affect BDNF. In addition, both very-low (VLF) and low-frequency (LF) transfer function phase or gains were not changed during the omission trial. In contrast, LF gain (High-GI P < 0.05) and normalized gain (Low-GI P < 0.05) were decreased by both GI trials, while a decrease in VLF phase was observed in only the High-GI trial (P < 0.05). These findings indicate that breakfast consumption augmented dCA in the LF range but High-GI breakfast attenuated cerebral blood flow regulation against slow change (i.e., the VLF range) in arterial pressure. Thus we propose that breakfast and glycemic control may be an important strategy to optimize cerebrovascular health.

Leptin enhances adult neurogenesis and reduces pathological features in a transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) is the most common dementia worldwide and is characterized by the presence of senile plaques by amyloid-beta (Aβ) and neurofibrillary tangles of hyperphosphorylated Tau protein. These changes lead to progressive neuronal degeneration and dysfunction, resulting in severe brain atrophy and cognitive deficits. With the discovery that neurogenesis persists in the adult mammalian brain, including brain regions affected by AD, studies of the use of neural stem cells (NSCs) for the treatment of neurodegenerative diseases to repair or prevent neuronal cell loss have increased. Here we demonstrate that leptin administration increases the neurogenic process in the dentate gyrus of the hippocampus as well as in the subventricular zone of lateral ventricles of adult and aged mice. Chronic treatment with leptin increased NSCs proliferation with significant effects on proliferation and differentiation of newborn cells. The expression of the long form of the leptin receptor, LepRb, was detected in the neurogenic niches by reverse qPCR and immunohistochemistry. Moreover, leptin modulated astrogliosis, microglial cell number and the formation of senile plaques. Additionally, leptin led to attenuation of Aβ-induced neurodegeneration and superoxide anion production as revealed by Fluoro-Jade B and dihydroethidium staining. Our study contributes to the understanding of the effects of leptin in the brain that may lead to the development of new therapies to treat Alzheimer's disease.

Leptin predicts cortical and subcortical gray matter volume recovery in alcohol dependent patients: A longitudinal structural magnetic resonance imaging study

The neuroprotective effects of leptin and its role in addictive disorders has been highlighted by several recent studies. However, its potential effects on morphological alterations in alcohol dependence are yet to be investigated. Associations between leptin and the longitudinal courses of gray matter volume (GMV) and cortical thickness (CT) were investigated in N = 62 alcohol-dependent patients that underwent structural magnetic resonance imaging after a mean abstinence of 12 (baseline) and 27 days (follow-up) respectively. Blood samples were collected at baseline to determine leptin levels. A cohort of N = 74 healthy individuals served as a reference sample. At baseline, alcohol-dependent patients compared to healthy controls displayed smaller GMV in the insula, parts of the superior, middle and inferior frontal gyri and hippocampal regions and thinner CT in the insula, parts of the superior and middle frontal cortices, the lateral orbitofrontal cortex and parts of the occipital and lingual cortices that partially recovered during abstinence (p_FWE < 0.05). In alcohol-dependent patients, leptin was a significant predictor of GMV and CT recovery in the areas that showed the strongest whole-brain effects, specifically GMV in the right insula (R² = 0.070, p_FDR = 0.040) and left inferior frontal triangular gyrus (R² = 0.076, p_FDR = 0.040), as well as CT in the left insula (R² = 0.158, p_FDR = 0.004) and right superior frontal cortex (R² = 0.180, p_FDR = 0.004). Present results support the role of leptin in predicting GMV and CT recovery during the first month of abstinence in alcohol-dependent patients.

BDNF Val66Met polymorphism alters food intake and hypothalamic BDNF expression in mice

Obesity, a rising public health burden, is a multifactorial disease with an increased risk for patients to develop several pathological conditions including type 2 diabetes mellitus, hypertension, and cardiovascular disease. Increasing evidence suggests a relationship between the human brain-derived neurotrophic factor (BDNF) Val66Met single-nucleotide polymorphism (SNP) and obesity, although the underlying mechanisms of this connection are still not completely understood. In the present study, we found that homozygous knock-in BDNF^Met/Met mice were overweight and hyperphagic compared to wildtype BDNF^Val/Val mice. Increased food intake was associated with reduction of total BDNF and BDNF1, BDNF4 and BDNF6 transcripts in the hypothalamus of BDNF^Met/Met mice. In contrast, in the white adipose tissue total BDNF and Glut4 expression levels were augmented, while sirtuin 1 and leptin receptor (Ob-R) expression levels were reduced in BDNF^Met/Met mice. Moreover, plasmatic leptin levels were decreased in BDNF^Met/Met mice. However, BDNF^Val/Val and BDNF^Met/Met mice showed a similar response to the insulin tolerance test and glucose tolerance test. Altogether, these results suggest that BDNF Val66Met SNP strongly contributes to adipose tissue pathophysiology, resulting in reduced circulating leptin levels and hypothalamic expression of BDNF, which, in turn, promote increased food intake and overweight in BDNF^Met/Met mice.

Role of Somatostatin in the Regulation of Central and Peripheral Factors of Satiety and Obesity

Obesity is one of the major social and health problems globally and often associated with various other pathological conditions. In addition to unregulated eating behaviour, circulating peptide-mediated hormonal secretion and signaling pathways play a critical role in food intake induced obesity. Amongst the many peptides involved in the regulation of food-seeking behaviour, somatostatin (SST) is the one which plays a determinant role in the complex process of appetite. SST is involved in the regulation of release and secretion of other peptides, neuronal integrity, and hormonal regulation. Based on past and recent studies, SST might serve as a bridge between central and peripheral tissues with a significant impact on obesity-associated with food intake behaviour and energy expenditure. Here, we present a comprehensive review describing the role of SST in the modulation of multiple central and peripheral signaling molecules. In addition, we highlight recent progress and contribution of SST and its receptors in food-seeking behaviour, obesity (orexigenic), and satiety (anorexigenic) associated pathways and mechanism.

Brain-Derived Neurotrophic Factor and Diabetes

Diabetes and its chronic complications still represent a great clinical problem, despite improvements made in the diagnosis and treatment of the disease. People with diabetes have a much higher risk of impaired brain function and psychiatric disorders. Neurotrophins are factors that protect neuronal tissue and improve the function of the central nervous system, and among them is brain-derived neurotrophic factor (BDNF). The level and function of BDNF in diabetes seems to be disturbed by and connected with the presence of insulin resistance. On the other hand, there is evidence for the highly beneficial impact of physical activity on brain function and BDNF level. However, it is not clear if this protective phenomenon works in the presence of diabetes. In this review, we summarize the current available research on this topic and find that the results of published studies are ambiguous.

Role of Leptin in Mood Disorder and Neurodegenerative Disease

The critical regulatory role of leptin in the neuroendocrine system has been widely reported. Significantly, leptin can improve learning and memory, affect hippocampal synaptic plasticity, exert neuroprotective efficacy and reduce the risk of several neuropsychiatric diseases. In terms of depression, leptin could modulate the levels of neurotransmitters, neurotrophic factors and reverse the dysfunction in the hypothalamic-pituitary-adrenal axis (HPA). At the same time, leptin affects neurological diseases during the regulation of metabolic homeostasis. With regards to neurodegenerative diseases, leptin can affect them via neuroprotection, mainly including Alzheimer's disease and Parkinson's disease. This review will summarize the mechanisms of leptin signaling within the neuroendocrine system with respect to these diseases and discuss the therapeutic potential of leptin.

Increased plasma leptin as a novel predictor for psychopathological depressive symptoms in chronic schizophrenia

BACKGROUND

Depressive symptoms are often seen in schizophrenia. The overlap in presentation makes it difficult to distinguish depressive symptoms from the negative symptoms of schizophrenia. The adipokine leptin was found to be altered in both depression and schizophrenia. There are few studies focusing on the prediction of leptin in diagnosis and evaluation of depressive symptoms in schizophrenia.

OBJECTIVEAIMS

To assess the plasma leptin level in patients with schizophrenia and its relationships with depressive symptoms.

METHODS

Cross-sectional studies were applied to (1) compare the levels of plasma leptin between schizophrenia (n=74) and healthy controls (n=50); and (2) investigate the relationship between plasma leptin levels and depressive subscores.

RESULTS

(1) Plasma leptin levels were significantly higher in patients with schizophrenia than in healthy controls. (2) Correlation analysis revealed a significant negative association between leptin levels and the depressed factor scores on the Positive and Negative Syndrome Scale (PANSS). (3) Stepwise multiple regression analyses identified leptin as an influencing factor for depressed factor score on PANSS.

CONCLUSION

Leptin may serve as a predictor for the depressive symptoms of chronic schizophrenia.

Hormonal and nutritional regulation of postnatal hypothalamic development

The hypothalamus is a key centre for regulation of vital physiological functions, such as appetite, stress responsiveness and reproduction. Development of the different hypothalamic nuclei and its major neuronal populations begins prenatally in both altricial and precocial species, with the fine tuning of neuronal connectivity and attainment of adult function established postnatally and maintained throughout adult life. The perinatal period is highly susceptible to environmental insults that, by disrupting critical developmental processes, can set the tone for the establishment of adult functionality. Here, we review the most recent knowledge regarding the major postnatal milestones in the development of metabolic, stress and reproductive hypothalamic circuitries, in the rodent, with a particular focus on perinatal programming of these circuitries by hormonal and nutritional influences. We also review the evidence for the continuous development of the hypothalamus in the adult brain, through changes in neurogenesis, synaptogenesis and epigenetic modifications. This degree of plasticity has encouraging implications for the ability of the hypothalamus to at least partially reverse the effects of perinatal mal-programming.

Elevated glycemia and brain glucose utilization predict BDNF lowering since early life

Obesity and diabetes associate with neurodegeneration. Brain glucose and BDNF are fundamental in perinatal development. BDNF is related to brain health, food intake and glucose metabolism. We characterized the relationship between glycemia and/or brain glucose utilization (by 18FDG-PET during fasting and glucose loading), obesity and BDNF in 4-weeks old (pre-obese) and 12-weeks old (obese) Zucker fa/fa rats, and their age-matched fa/+ controls. In 75 human infants, we assessed cord blood BDNF and glucose levels, appetite regulating hormones, body weight and maternal factors. Young and adult fa/fa rats showed glucose intolerance and brain hyper-utilization compared to controls. Glycemia and age were positively related to brain glucose utilization, and were negative predictors of BDNF levels. In humans, fetal glycemia was dependent on maternal glycemia at term, and negatively predicted BDNF levels. Leptin levels were associated with higher body weight and lower BDNF levels. Glucose intolerance and elevated brain glucose utilization already occur in young, pre-obese rats, suggesting that they precede obesity onset in Zucker fatty rats. Glycemic elevation and brain glucose overexposure predict circulating BDNF deficiency since perinatal and early life. Future studies should evaluate whether the control of maternal and fetal glycemia during late intrauterine development can prevent these unfavorable interactions.

Long-Term Sex-Dependent Vulnerability to Metabolic challenges in Prenatally Stressed Rats

Prenatal stress (PNS) might affect the developmental programming of adult chronic diseases such as metabolic and mood disorders. The molecular mechanisms underlying such regulations may rely upon long-term changes in stress-responsive effectors such as Brain-Derived Neurotrophic Factor (BDNF) that can affect neuronal plasticity underlying mood disorders and may also play a role in metabolic regulation. Based upon previous data, we hypothesized that PNS might lead to greater vulnerability to an obesogenic challenge experienced at adulthood. In order to investigate our hypothesis, pregnant Sprague-Dawley female rats underwent a chronic procedure of restraint stress during the last week of gestation. The adult offspring were then challenged with a high fat diet (HFD) over 8 weeks and tested for metabolic and emotional endpoints. Moreover, brain specific changes in Bdnf expression levels were also assessed. Overall, HFD resulted in increased caloric intake, insulin resistance, impaired glucose tolerance and higher circulating levels of leptin, while PNS increased the leptin/adiponectin ratio, an index of metabolic risk in adult male subjects. Interestingly, HFD consumption increased anxiety-like behaviors in the Elevated Plus Maze, particularly in males, and this effect was buffered by PNS. Levels of Bdnf were finely modulated by PNS and HFD in a region- and sex-dependent fashion: female offspring overall showed greater plasticity, possibly mediated through increased total Bdnf mRNA expression both in the hippocampus and in the hypothalamus. In conclusion, while the experience of maternal stress during intrauterine life promotes metabolic dysfunction induced by a HFD at adulthood, the interaction between PNS and HFD is positive in male subjects, and in agreement with the match-mismatch hypothesis, resulting in a reduction of anxious behaviors.

Effect of food deprivation or short-term Western diet feeding on BDNF protein expression in the hypothalamic arcuate, paraventricular, and ventromedial nuclei

Mutations in the brain-derived neurotrophic factor (BDNF) gene are associated with human obesity, and BDNF has potent inhibitory effects on eating and body weight. Little is known about the effects of energy balance manipulations on BDNF protein in the hypothalamus, though this brain region is critical for regulation of feeding and body weight and has high levels of BDNF. Here we investigated the effects of negative and positive energy status on BDNF protein levels in the arcuate (ARC), paraventricular, and ventromedial (VMH) hypothalamic nuclei and the ectorhinal cortex. To achieve this, mice were food deprived for 48 h or fed a Western diet (WD), a restricted amount of WD, or chow for 6 h, 48 h, 1 wk, or 3 wk. BDNF protein levels were estimated as the number of neurons in each brain region that exhibited BDNF-like immunoreactivity. Food deprivation decreased BDNF protein (and mRNA) expression in the ARC compared with fed mice (32%). In contrast, 1 wk of WD consumption increased BDNF protein expression in the VMH compared with chow or restricted WD feeding (40%) and, unexpectedly, increased BDNF protein in the ectorhinal cortex (20%). Furthermore, of the diet conditions and durations tested, only 1 wk of WD consumption was associated with both hyperphagia and excess weight, suggesting that effects of one or both contributed to the changes in BDNF levels. The decrease in ARC BDNF may support increased feeding in food-deprived mice, whereas the increase in the VMH may moderate overeating in WD-fed mice.

Antidiabetic Effect of Brain-Derived Neurotrophic Factor and Its Association with Inflammation in Type 2 Diabetes Mellitus

Brain-derived neurotrophic factor (BDNF) is a neurotrophin, which plays an important role in the central nervous system, and systemic or peripheral inflammatory conditions, such as acute coronary syndrome and type 2 diabetes mellitus (T2DM). BDNF is also expressed in several nonneuronal tissues, and platelets are the major source of peripheral BDNF. Here, we reviewed the potential role of BDNF in platelet reactivity in T2DM and its association with selected inflammatory and platelet activation mediators. Besides that, we focused on adipocytokines such as leptin, resistin, and adiponectin which are considered to take part in inflammation and both lipid and glucose metabolism in diabetic patients as previous studies showed the relation between adipocytokines and BDNF. We also reviewed the evidences of the antidiabetic effect of BDNF and the association with circulating inflammatory cytokines in T2DM.

Developmental changes in the hypothalamic mRNA expression levels of brain-derived neurotrophic factor and serum leptin levels: Their responses to fasting in male and female rats

The actions and responses of hypothalamic appetite regulatory factors change markedly during the neonatal to pre-pubertal period in order to maintain appropriate metabolic and nutritional conditions. In this study, we examined the developmental changes in the hypothalamic mRNA levels of brain-derived neurotrophic factor (BDNF), which is a potent anorectic factor and the changes in the sensitivity of the hypothalamic expression of this factor to fasting during the neonatal to pre-pubertal period. Under fed conditions, hypothalamic BDNF mRNA expression decreased during development in both male and female rats. Similarly, the serum levels of leptin, which is a positive regulator of hypothalamic BDNF expression, also tended to fall during the developmental period. The serum leptin level and the hypothalamic BDNF mRNA level were found to be positively correlated in both sexes under the fed conditions. Hypothalamic BDNF mRNA expression was decreased by 24h fasting (separating the rats from their mothers) in the early neonatal period (postnatal day 10) in both males and females, but no such changes were seen at postnatal day 20. Twenty-four hours' fasting (food deprivation) did not affect hypothalamic BDNF mRNA expression in the pre-pubertal period (postnatal day 30). On the other hand, the rats' serum leptin levels were decreased by 24h fasting (separating the rats from their mothers at postnatal day 10 and 20, and food deprivation at postnatal day 30) throughout the early neonatal to pre-pubertal period. The correlation between serum leptin and hypothalamic BDNF mRNA levels was not significant under the fasted conditions. It can be speculated that leptin partially regulates hypothalamic BDNF mRNA levels, but only in fed conditions. Such changes in hypothalamic BDNF expression might play a role in maintaining appropriate metabolic and nutritional conditions and promoting normal physical development. In addition, because maternal separation induces a negative energy balance and short- and long-term stress responses, it is also possible that reductions in hypothalamic BDNF mRNA levels in the early neonatal period (postnatal day 10) may be partially induced by stress responses of the maternal deprivation.

Regulation of body fat mass by the gut microbiota: Possible mediation by the brain

New insight suggests gut microbiota as a component in energy balance. However, the underlying mechanisms by which gut microbiota can impact metabolic regulation is unclear. A recent study from our lab shows, for the first time, a link between gut microbiota and energy balance circuitries in the hypothalamus and brainstem. In this article we will review this study further.

The role of pancreatic polypeptide in the regulation of energy homeostasis

Imbalances in normal regulation of food intake can cause obesity and related disorders. Inadequate therapies for such disorders necessitate better understanding of mechanisms that regulate energy homeostasis. Pancreatic polypeptide (PP), a robust anorexigenic hormone, effectively modulates food intake and energy homeostasis, thus potentially aiding anti-obesity therapeutics. Intra-gastric and intra-intestinal infusion of nutrients stimulate PP secretion from the gastrointestinal tract, leading to vagal stimulation that mediates complex actions via the neuropeptide Y4 receptor in arcuate nucleus of the hypothalamus, subsequently activating key hypothalamic nuclei and dorsal vagal complex of the brainstem to influence energy homeostasis and body composition. Novel studies indicate affinity of PP for the relatively underexplored neuropeptide y6 receptor, mediating actions via the suprachiasmatic nucleus and pathways involving vasoactive intestinal polypeptide and insulin like growth factor 1. This review highlights detailed mechanisms by which PP mediates its actions on energy balance through various areas in the brain.

Neonatal Treatment with a Pegylated Leptin Antagonist Induces Sexually Dimorphic Effects on Neurones and Glial Cells, and on Markers of Synaptic Plasticity in the Developing Rat Hippocampal Formation

The present study aimed to better understand the role of the neonatal leptin surge, which peaks on postnatal day (PND)9-10, on the development of the hippocampal formation. Accordingly, male and female rats were administered with a pegylated leptin antagonist on PND9 and the expression of neurones, glial cells and diverse markers of synaptic plasticity was then analysed by immunohistochemistry in the hippocampal formation. Antagonism of the actions of leptin at this specific postnatal stage altered the number of glial fibrillary acidic protein positive cells, and also affected type 1 cannabinoid receptors, synaptophysin and brain-derived neurotrophic factor (BDNF), with the latter effect being sexually dimorphic. The results indicate that the physiological leptin surge occurring around PND 9-10 is critical for hippocampal formation development and that the dynamics of leptin activity might be different in males and females. The data obtained also suggest that some but not all the previously reported effects of maternal deprivation on hippocampal formation development (which markedly reduces leptin levels at PND 9-10) might be mediated by leptin deficiency in these animals.

Leptin attenuates the detrimental effects of β-amyloid on spatial memory and hippocampal later-phase long term potentiation in rats

β-Amyloid (Aβ) is the main component of amyloid plaques developed in the brain of patients with Alzheimer's disease (AD). The increasing burden of Aβ in the cortex and hippocampus is closely correlated with memory loss and cognition deficits in AD. Recently, leptin, a 16kD peptide derived mainly from white adipocyte tissue, has been appreciated for its neuroprotective function, although less is known about the effects of leptin on spatial memory and synaptic plasticity. The present study investigated the neuroprotective effects of leptin against Aβ-induced deficits in spatial memory and in vivo hippocampal late-phase long-term potentiation (L-LTP) in rats. Y maze spontaneous alternation was used to assess short term working memory, and the Morris water maze task was used to assess long term reference memory. Hippocampal field potential recordings were performed to observe changes in L-LTP. We found that chronically intracerebroventricular injection of leptin (1μg) effectively alleviated Aβ1-42 (20μg)-induced spatial memory impairments of Y maze spontaneous alternation and Morris water maze. In addition, chronic administration of leptin also reversed Aβ1-42-induced suppression of in vivo hippocampal L-LTP in rats. Together, these results suggest that chronic leptin treatments reversed Aβ-induced deficits in learning and memory and the maintenance of L-LTP.

Physical exercise in overweight to obese individuals induces metabolic- and neurotrophic-related structural brain plasticity

Previous cross-sectional studies on body-weight-related alterations in brain structure revealed profound changes in the gray matter (GM) and white matter (WM) that resemble findings obtained from individuals with advancing age. This suggests that obesity may lead to structural brain changes that are comparable with brain aging. Here, we asked whether weight-loss-dependent improved metabolic and neurotrophic functioning parallels the reversal of obesity-related alterations in brain structure. To this end we applied magnetic resonance imaging (MRI) together with voxel-based morphometry and diffusion-tensor imaging in overweight to obese individuals who participated in a fitness course with intensive physical training twice a week over a period of 3 months. After the fitness course, participants presented, with inter-individual heterogeneity, a reduced body mass index (BMI), reduced serum leptin concentrations, elevated high-density lipoprotein-cholesterol (HDL-C), and alterations of serum brain-derived neurotrophic factor (BDNF) concentrations suggesting changes of metabolic and neurotrophic function. Exercise-dependent changes in BMI and serum concentration of BDNF, leptin, and HDL-C were related to an increase in GM density in the left hippocampus, the insular cortex, and the left cerebellar lobule. We also observed exercise-dependent changes of diffusivity parameters in surrounding WM structures as well as in the corpus callosum. These findings suggest that weight-loss due to physical exercise in overweight to obese participants induces profound structural brain plasticity, not primarily of sensorimotor brain regions involved in physical exercise, but of regions previously reported to be structurally affected by an increased body weight and functionally implemented in gustation and cognitive processing.

Brain-derived neurotrophic factor modulates angiotensin signaling in the hypothalamus to increase blood pressure in rats

Brain-derived neurotrophic factor (BDNF) expression increases in the paraventricular nucleus of the hypothalamus (PVN) in response to hypertensive stimuli including stress and hyperosmolarity. However, it is unclear whether BDNF in the PVN contributes to increases in blood pressure (BP). We tested the hypothesis that increased BDNF levels within the PVN would elevate baseline BP and heart rate (HR) and cardiovascular stress responses by altering central angiotensin signaling. BP was recorded using radiotelemetry in male Sprague-Dawley rats after bilateral PVN injections of adeno-associated viral vectors expressing green fluorescent protein (GFP) or myc epitope-tagged BDNF fusion protein. Cardiovascular responses to acute stress were evaluated 3 to 4 wk after injections. Additional GFP and BDNF-treated animals were equipped with osmotic pumps for intracerebroventricular infusion of saline or the angiotensin type-1 receptor (AT1R) inhibitor losartan (15 μg·0.5 μl(-1)·h(-1)). BDNF treatment significantly increased baseline BP (121 ± 3 mmHg vs. 99 ± 2 mmHg in GFP), HR (394 ± 9 beats/min vs. 314 ± 4 beats/min in GFP), and sympathetic tone indicated by HR- and BP-variability analysis and adrenomedullary tyrosine hydroxylase protein expression. In contrast, body weight and BP elevations to acute stressors decreased. BDNF upregulated AT1R mRNA by ∼80% and downregulated Mas receptor mRNA by ∼50% in the PVN, and losartan infusion partially inhibited weight loss and increases in BP and HR in BDNF-treated animals without any effect in GFP rats. Our results demonstrate that BDNF overexpression in the PVN results in sympathoexcitation, BP and HR elevations, and weight loss that are mediated, at least in part, by modulating angiotensin signaling in the PVN.

Exercise, nutrition and the brain

Accumulating evidence suggests that diet and lifestyle can play an important role in delaying the onset or halting the progression of age-related health disorders and can improve cognitive function. Exercise has been promoted as a possible prevention for neurodegenerative diseases. Exercise will have a positive influence on cognition and it increases the brain-derived neurotrophic factor, an essential neurotrophin. Several dietary components have been identified as having effects on cognitive abilities. In particular, polyphenols have been reported to exert their neuroprotective actions through the potential to protect neurons against injury induced by neurotoxins, an ability to suppress neuroinflammation, and the potential to promote memory, learning, and cognitive function. Dietary factors can affect multiple brain processes by regulating neurotransmitter pathways, synaptic transmission, membrane fluidity, and signal-transduction pathways. Flavonols are part of the flavonoid family that is found in various fruits, cocoa, wine, tea and beans. Although the antioxidant effects of flavonols are well established in vitro, there is general agreement that flavonols have more complex actions in vivo. Several cross-sectional and longitudinal studies have shown that a higher intake of flavonoids from food may be associated with a better cognitive evolution. Whether this reflects a causal association remains to be elucidated. Several studies have tried to 'manipulate' the brain in order to postpone central fatigue. Most studies have clearly shown that in normal environmental circumstances these interventions are not easy to perform. There is accumulating evidence that rinsing the mouth with a carbohydrate solution will improve endurance performance. There is a need for additional well controlled studies to explore the possible impact of diet and nutrition on brain functioning.

Controversies about a common etiology for eating and mood disorders

Obesity and depression represent a growing health concern worldwide. For many years, basic science and medicine have considered obesity as a metabolic illness, while depression was classified a psychiatric disorder. Despite accumulating evidence suggesting that obesity and depression may share commonalities, the causal link between eating and mood disorders remains to be fully understood. This etiology is highly complex, consisting of multiple environmental and genetic risk factors that interact with each other. In this review, we sought to summarize the preclinical and clinical evidence supporting a common etiology for eating and mood disorders, with a particular emphasis on signaling pathways involved in the maintenance of energy balance and mood stability, among which orexigenic and anorexigenic neuropeptides, metabolic factors, stress responsive hormones, cytokines, and neurotrophic factors.

Can neuropeptides treat obesity? A review of neuropeptides and their potential role in the treatment of obesity

Obesity is a major worldwide public health issue. The physiological systems that regulate body weight are thus of great interest as targets for anti-obesity agents. Peptidergic systems are critical to the regulation of energy homeostasis by key regions in the hypothalamus and brainstem. A number of neuropeptide systems have therefore been investigated as potential treatments for obesity. Blocking orexigenic peptide signals such as neuropeptide Y, melanin-concentrating hormone, orexins, relaxin-3 and galanin-like peptide or stimulating anorectic signalling pathways used by peptides such as the melanocortins, ciliary neurotrophic factor and brain-derived neurotrophic factor, are approaches that have shown some promise, but which have also highlighted possible concerns. Manipulation of central peptidergic systems poses a number of therapeutic problems, including brain access and side effects. Given that the homeostatic defence of body weight may limit the effectiveness of any single-target therapy developed, a combination therapy approach may offer the best hope for the effective prevention and treatment of obesity.

LINKED ARTICLES

This article is part of a themed section on Neuropeptides. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.170.issue-7.

The neuroanatomical function of leptin in the hypothalamus

The anorexigenic hormone leptin plays an important role in the control of food intake and feeding-related behavior, for an important part through its action in the hypothalamus. The adipose-derived hormone modulates a complex network of several intercommunicating orexigenic and anorexigenic neuropeptides in the hypothalamus to reduce food intake and increase energy expenditure. In this review we present an updated overview of the functional role of leptin in respect to feeding and feeding-related behavior per distinct hypothalamic nuclei. In addition to the arcuate nucleus, which is a major leptin sensitive hub, leptin-responsive neurons in other hypothalamic nuclei, including the, dorsomedial-, ventromedial- and paraventricular nucleus and the lateral hypothalamic area, are direct targets of leptin. However, leptin also modulates hypothalamic neurons in an indirect manner, such as via the melanocortin system. The dissection of the complexity of leptin's action on the networks involved in energy balance is subject of recent and future studies. A full understanding of the role of hypothalamic leptin in the regulation of energy balance requires cell-specific manipulation using of conditional deletion and expression of leptin receptors. In addition, optogenetic and pharmacogenetic tools in combination with other pharmacological (such as the recent discovery of a leptin receptor antagonist) and neuronal tracing techniques to map the circuit, will be helpful to understand the role of leptin receptor expressing neurons. Better understanding of these circuits and the involvement of leptin could provide potential sites for therapeutic interventions in obesity and metabolic diseases characterized by dysregulation of energy balance.

Neuroprotective effects of physical activity on the brain: a closer look at trophic factor signaling

While the relationship between increased physical activity and cognitive ability has been conjectured for centuries, only recently have the mechanisms underlying this relationship began to emerge. Convergent evidence suggests that physical activity offers an affordable and effective method to improve cognitive function in all ages, particularly the elderly who are most vulnerable to neurodegenerative disorders. In addition to improving cardiac and immune function, physical activity alters trophic factor signaling and, in turn, neuronal function and structure in areas critical for cognition. Sustained exercise plays a role in modulating anti-inflammatory effects and may play a role in preserving cognitive function in aging and neuropathological conditions. Moreover, recent evidence suggests that myokines released by exercising muscles affect the expression of brain-derived neurotrophic factor synthesis in the dentate gyrus of the hippocampus, a finding that could lead to the identification of new and therapeutically important mediating factors. Given the growing number of individuals with cognitive impairments worldwide, a better understanding of how these factors contribute to cognition is imperative, and constitutes an important first step toward developing non-pharmacological therapeutic strategies to improve cognition in vulnerable populations.

Effects of energy status and diet on Bdnf expression in the ventromedial hypothalamus of male and female rats

Sex differences exist in the regulation of energy homeostasis in response to calorie scarcity or excess. Brain-derived neurotrophic factor (BDNF) is one of the anorexigenic neuropeptides regulating energy homeostasis. Expression of Bdnf mRNA in the ventromedial nucleus of the hypothalamus (VMH) is closely associated with energy and reproductive status. We hypothesized that Bdnf expression in the VMH was differentially regulated by altered energy balance in male and female rats. Using dietary intervention, including fasting-induced negative energy status and high-fat diet (HFD) feeding-induced positive energy status, along with low-fat diet (LFD) feeding and HFD pair-feeding (HFD-PF), effects of diets and changes in energy status on VMH Bdnf expression were compared between male and female rats. Fasted males but not females had lower VMH Bdnf expression than their fed counterparts following 24-hour fasting, suggesting that fasted males reduced Bdnf expression to drive hyperphagia and body weight gain. Male HFD obese and HFD-PF non-obese rats had similarly reduced expression of Bdnf compared with LFD males, indicating that dampened Bdnf expression was associated with feeding a diet high in fat instead of increased adiposity. Decreased BDNF signaling during HFD feeding would increase a drive to eat and may contribute to diet-induced obesity in males. In contrast, VMH Bdnf expression was stably maintained in females when energy homeostasis was disturbed. These results suggest sex-distinct regulation of central Bdnf expression by diet and energy status.

Measurement of the levels of leptin, BDNF associated with polymorphisms LEP G2548A, LEPR Gln223Arg and BDNF Val66Met in Thai with metabolic syndrome

BACKGROUND

Metabolic syndrome is a cluster of metabolic risk factors including dyslipidemia, impaired glucose tolerance, hypertension and central obesity. BDNF (Brain-derived neurotrophic factor) and leptin have been implied in the energy homeostasis. The purposes of this study were to examine concentrations of leptin, BDNF and biochemical parameters in metabolic-syndrome subjects and healthy controls, and also to search for associations of leptin gene (LEP) G2548A, leptin receptor gene (LEPR) Gln223Arg, and BDNF gene (BDNF) Val66Met polymorphisms with leptin levels, BDNF levels and metabolic syndrome among Thais.

METHODS

The case-controlled design was performed using 322 Thai volunteers (160 metabolic-syndrome subjects; 162 controls) during the health screening program. Metabolic syndrome was assessed by using the modified National Cholesterol Education Program, Adult Treatment Panel III criteria. The levels of leptin, BDNF, insulin, glucose and lipids were measured in samples. Genotyping of LEP G2548A, LEPR Gln223Arg and BDNF Val66Met was carried out using polymerase chain reaction-restriction fragment length polymorphism technique.

RESULTS

Serum leptin levels were significantly higher in the metabolic-syndrome group than the control group (p < 0.01), but the BDNF difference between them was not significant. Significant associations of LEPR Gln223Arg polymorphism were found with leptin and glucose levels (p < 0.05), after adjusting for potential covariates. This LEPR polymorphism in the metabolic-syndrome group was also significantly more frequent than in the control group (p < 0.05). However, other gene polymorphisms, LEP G2548A and BDNF Val66Met, showed no significant relationship with leptin levels, BDNF levels or metabolic syndrome.

CONCLUSION

These findings suggest leptin levels are linked with metabolic syndrome. LEPR Gln223Arg polymorphism impacted leptin concentrations, and this gene polymorphism may influence susceptibility to metabolic syndrome among Thais.

Neurotrophins and the regulation of energy balance and body weight

Complex interactions between the brain and peripheral tissues mediate the effective control of energy balance and body weight. Hypothalamic and hindbrain neural circuits integrate peripheral signals informing the nutritional status of the animal and in response regulate nutrient intake and energy utilization. Obesity and its many medical complications emerge from the dysregulation of energy homeostasis. Excessive weight gain might also arise from alterations in reward systems of the brain that drive consumption of calorie dense, palatable foods in the absence of an energy requirement. Several neurotrophins, most notably brain-derived neurotrophic factor, have been implicated in the molecular and cellular processes underlying body weight regulation. Here, we review investigations interrogating their roles in energy balance and reward centers of the brain impacting feeding behavior and energy expenditure.

Maintained expression of genes associated with metabolism in the ventromedial hypothalamic nucleus despite development of leptin resistance during pregnancy in the rat

Hyperphagia and weight gain to acquire energy stores for development and growth of the fetus and to prepare for the demands of lactation are important adaptations to support a healthy pregnancy. As a consequence, hypothalamic leptin resistance develops to enable maintenance of a positive energy state. During pregnancy there is a decrease in leptin receptor expression and reduced leptin-induced phospho signal transducer and activator of transcription 3 (pSTAT3) in the ventromedial nucleus of the hypothalamus (VMN), suggesting that the VMN is a key site of pregnancy-induced modification in the control of energy homeostasis. The aim of this study was to investigate expression levels of known gene targets, which are involved in metabolic regulation and glucosensing, within the VMN during pregnancy. Using in situ hybridization, pituitary adenylate cyclase-activated polypeptide (Pacap), brain-derived neurotrophic factor (Bdnf), and glucokinase messenger ribonucleic acid (mRNA) expression were localized in the hypothalamus of nonpregnant and day 14 pregnant rats, then expression levels were compared by quantitative polymerase chain reaction (qPCR) using laser capture microdissection of the VMN and arcuate nucleus. Despite significantly elevated plasma leptin and insulin concentrations, and lower blood glucose levels, during pregnancy, no significant changes in gene expression of Pacap, Bdnf, or glucokinase were detected between nonpregnant and day 14 pregnant groups. These data suggest that loss of leptin and insulin sensitivity in the VMN might allow gene expression to be maintained at normal/control levels in this nucleus, despite marked changes in the levels of these important regulatory hormones. These data provide further evidence for development of leptin resistance in the VMN as an adaptive response during pregnancy.

Brain-derived neurotrophic factor in VMH as the causal factor for and therapeutic tool to treat visceral adiposity and hyperleptinemia in type 2 diabetic Goto-Kakizaki rats

We previously reported that the type 2 diabetic Goto-Kakizaki (GK) rats at young adult ages (6-12 weeks) exhibited increased visceral fat mass and hyperleptinemia, due to hyperphagia caused primarily by neuropeptide Y (NPY) overexpression in the hypothalamic arcuate nucleus. Later, we found that GK rats continued to exhibit mesenteric fat accumulation and hyperleptinemia at least until 26 weeks of age, while hyperphagia and NPY overexpression ceased at 15 weeks of age. Therefore, we hypothesized that the long-lasting fat accumulation and hyperleptinemia are due to unidentified brain dysfunction other than NPY overexpression. In GK rats aged 26 weeks, glucose transporter-2 (GLUT2) mRNA expression in ventromedial hypothalamus (VMH) was markedly reduced in parallel with significant decreases in brain-derived neurotrophic factor (BDNF) mRNA level and BDNF-expressing cell numbers in the VMH. Pharmacologic inhibition of glucose utilization reduced BDNF mRNA expression in VMH in vivo and in vitro. The results suggested that impaired glucose utilization caused the reduction of BDNF. On the other hand, intracerebroventricular injection of BDNF for 6 days ameliorated hyperleptinemia in a long-lasting manner concurrently with feeding suppression in GK rats. Restricted feeding paired to BDNF-treated rats reduced plasma leptin level only transiently. BDNF treatment also reduced mesenteric fat mass in GK rats. These results reveal a novel action mode of BDNF to long-lastingly counteract visceral adiposity and hyperleptinemia in addition to and independently of its anorexigenic action. These results suggest that visceral fat accumulation and hyperleptinemia are at least partly due to the reduction of BDNF in VMH primarily caused by impaired glucose utilization in GK rats. The BDNF supplementation could provide an effective treatment of visceral obesity, hyperleptinemia and leptin resistance in type 2 diabetes.

The gut microbiota reduces leptin sensitivity and the expression of the obesity-suppressing neuropeptides proglucagon (Gcg) and brain-derived neurotrophic factor (Bdnf) in the central nervous system

The gut microbiota contributes to fat mass and the susceptibility to obesity. However, the underlying mechanisms are not completely understood. To investigate whether the gut microbiota affects hypothalamic and brainstem body fat-regulating circuits, we compared gene expression of food intake-regulating neuropeptides between germ-free and conventionally raised (CONV-R) mice. We found that CONV-R mice had decreased expression of the antiobesity neuropeptide glucagon-like peptide-1 (GLP-1) precursor proglucagon (Gcg) in the brainstem. Moreover, in both the hypothalamus and the brainstem, CONV-R mice had decreased expression of the antiobesity neuropeptide brain-derived neurotrophic factor (Bdnf). CONV-R mice had reduced expression of the pro-obesity peptides neuropeptide-Y (Npy) and agouti-related protein (Agrp), and increased expression of the antiobesity peptides proopiomelanocortin (Pomc) and cocaine- and amphetamine-regulated transcript (Cart) in the hypothalamus. The latter changes in neuropeptide expression could be secondary to elevated fat mass in CONV-R mice. Leptin treatment caused less weight reduction and less suppression of orexigenic Npy and Agrp expression in CONV-R mice compared with germ-free mice. The hypothalamic expression of leptin resistance-associated suppressor of cytokine signaling 3 (Socs-3) was increased in CONV-R mice. In conclusion, the gut microbiota reduces the expression of 2 genes coding for body fat-suppressing neuropeptides, Gcg and Bdnf, an alteration that may contribute to fat mass induction by the gut microbiota. Moreover, the presence of body fat-inducing gut microbiota is associated with hypothalamic signs of Socs-3-mediated leptin resistance, which may be linked to failed compensatory body fat reduction.

Important role of ventromedial hypothalamic carnitine palmitoyltransferase-1a in the control of food intake

Carnitine palmitoyltransferase-1 (CPT-1) liver isoform, or CPT-1a, is implicated in CNS control of food intake. However, the exact brain nucleus site(s) in mediating this action of CPT-1a has not been identified. In this report, we assess the role of CPT-1a in hypothalamic ventromedial nucleus (VMN). We stereotaxically injected an adenoviral vector containing CPT-1a coding sequence into the VMN of rats to induce overexpression and activation of CPT-1a. The VMN-selective activation of CPT-1a induced an orexigenic effect, suggesting CPT-1a in the VMN is involved in the central control of feeding. Intracerebroventricular administration of etomoxir, a CPT-1 inhibitor, decreases food intake. Importantly, in the animals with VMN overexpression of a CPT-1a mutant that antagonizes the CPT-1 inhibition by etomoxir, the anorectic response to etomoxir was attenuated. This suggests that VMN is involved in mediating the anorectic effect of central inhibition of CPT-1a. In contrast, arcuate nucleus (Arc) overexpression of the mutant did not alter etomoxir-induced inhibition of food intake, suggesting that Arc CPT-1a does not play significant roles in this anorectic action. Furthermore, in the VMN, CPT-1a appears to act downstream of hypothalamic malonyl-CoA action of feeding. Finally, we show that in the VMN CPT-1 activity was altered in concert with fasting and refeeding states, supporting a physiological role of CPT-1a in mediating the control of feeding. All together, CPT-1a in the hypothalamic VMN appears to play an important role in central control of food intake. VMN-selective modulation of CPT-1a activity may therefore be a promising strategy in controlling food intake and maintaining normal body weight.

Electroconvulsive seizures activate anorexigenic signals in the ventromedial nuclei of the hypothalamus

The ventromedial nucleus of the hypothalamus (VMH) plays an important role in feeding and energy homeostasis. Electroconvulsive seizure (ECS) therapy is highly effective in the treatment of several psychiatric diseases, including depression, but may also have beneficial effects in other neurological diseases. Although it has been reported that the neurons of the VMH are strongly activated by ECS stimulation, the specific effects of ECS in this hypothalamic subnucleus remain unknown. To address this issue, we investigated the changes in gene expression in microdissected-VMH samples in response to ECS in mice, and examined the behavioral effects of ECS on feeding behavior. ECS significantly induced the expression of immediate-early genes such as Fos, Fosb, and Jun, as well as Bdnf, Adcyap1, Hrh1, and Crhr2 in the VMH. Given that signals of these gene products are suggested to have anorexigenic roles in the VMH, we also examined the effect of ECS on food intake and body weight. Repeated ECS had a suppressive effect on food intake and body weight gain under both regular and high-fat diet conditions. Furthermore, gold-thioglucose-induced hypothalamic lesions, including the VMH and the arcuate nucleus, abolished the anorexigenic effects of ECS, indicating the requirement for the activation of the hypothalamus. Our data show an effect of ECS on increased expression of anorexigenic factors in the VMH, and suggest a role in the regulation of energy homeostasis by ECS.