Central Regulation Of Energy Homeostasis Research Articles

SUN-012 Role of Leptin-Receptor Expressing Cells in the Pathogenesis of Polycystic Ovary Syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age, and is characterized by hyperandrogenism, oligo/anovulation, and/or polycystic ovaries. Many women with PCOS also suffer from adverse metabolic phenotypes, including central adiposity, insulin resistance, and glucose intolerance, which can exacerbate reproductive dysfunction. Androgens can act upon androgen receptors (AR), which are expressed in many reproductive and metabolic tissues, and contribute to the pathogenesis of PCOS. AR are highly expressed in the neuroendocrine hypothalamus in areas which regulate the hypothalamic-pituitary-gonadal axis and contribute to the central regulation of metabolism. Many phenotypes of PCOS can be modelled in rodents by administration of the non-aromatizable androgen dihydrotestosterone (DHT) during critical periods of development. Neuronal AR is key in the development of PCOS, as female mice with neuronal AR deletion who are exposed to androgen excess are protected against development of anovulation, polycystic ovaries, and metabolic abnormalities. Yet it is not known which populations of neurons confers this protection. We hypothesize that leptin-receptor (LepR) neurons participate in the pathogenesis of PCOS, as sub-populations of LepR neurons co-express AR in the hypothalamus, and LepR neurons are critical in the central regulation of energy homeostasis, and exert permissive actions on puberty and fertility. We have pre-natally androgenized (PNA) a mouse model of AR deletion specifically in LepR cells (LepRΔAR) and are conducting reproductive and metabolic phenotyping. As previously demonstrated, control PNA females show long periods of acyclicity, whereas LepRΔAR PNA female mice show a similar number of days in each stage of the estrous cycle, number of cycles, and cycle length as vehicle treated LepRΔAR females. Our findings indicate that a subpopulation of AR/LepR cells mediate the effects of prenatal androgen excess on female estrous cycles in a mouse model of PCOS-like phenotype.

Integration of energy homeostasis and stress by parvocellular neurons in rat hypothalamic paraventricular nucleus.

Central regulation of energy homeostasis and stress are believed to be reciprocally regulated, i.e. excessive food intake suppresses, while prolonged hunger exacerbates, stress responses in vivo. This relationship may be mediated by neuroendocrine parvocellular corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus that receive both stress- and feeding-related input. We find that hunger strongly and selectively potentiates, while re-feeding suppresses, a cellular analogue of a stress response induced by acute glucopenia in CRH neurons in rat hypothalamic slices. Neuronal activation in response to glucopenia was mediated synaptically, via the relative enhancement of glutamate over GABA input. These results illustrate how acute stress responses may be initiated in vivo and show that it is reciprocally integrated with energy balance via local hypothalamic mechanisms acting at the level of CRH neurons and their afferent terminals. Increased food intake is a common response to help cope with stress, implying the existence of a previously postulated but imperfectly understood, inverse relationship between the regulation of feeding and stress. We have identified components of the neural circuitry that can integrate these homeostatic responses. Prior fasting (∼24h) potentiates, and re-feeding suppresses, excitatory responses to acute glucopenia in about half of the corticotropin releasing hormone (CRH)-expressing, putatively neurosecretory, stress-related neurons in the paraventricular nucleus of the hypothalamus studied. Glucoprivation stress ex vivo resulted from a preferential relative increase in excitatory (glutamatergic) over inhibitory (GABAergic) inputs. Putative preautonomic cells were less sensitive to fasting, and showed a predominant inhibition to acute glucopenia. We conclude that hunger may sensitize hypothalamic stress responses by acting via local mechanisms, at the level of CRH neurons and their presynaptic inputs. Those mechanisms involve neither presynaptic ATP-sensitive potassium channels nor postsynaptic ATP levels.

Perspectives of application of intranasally administered insulin for correction of metabolic and hormonal disorders in diabetes mellitus and metabolic syndrome

In recent years, the possibility of using intranasally administered insulin to treat Alzheimers disease and other cognitive disorders has been widely studied. At the same time, the possibility of its use in the treatment of diabetes mellitus is practically not investigated, which is due to the insufficient study of the molecular mechanisms of its action on the hormonal and metabolic status of the organism. The review discusses literature data and the results of our own research on the role of insulin in the central regulation of energy homeostasis, as well as on the experience of using intranasally administered insulin to correct eating disorders and metabolic and hormonal dysfunctions developing under conditions of experimental diabetes mellitus and metabolic syndrome. In studies involving healthy volunteers, various effects of intranasally administered insulin were shown, including effects on cognitive function, eating behavior and weight loss, and the gender specificity of its action was found. In the course of numerous studies of intranasally administered insulin in animal models of diabetes mellitus, not only stabilization of carbohydrate homeostasis was shown, but also a positive effect in the form of restoration of the functional activity of insulin signaling pathways in the hypothalamus and other parts of the brain. We have presented and analyzed data on the systemic effects of intranasally administered insulin in rodents with experimental models of diabetes mellitus, as well as in healthy individuals.

AMPK promotes induction of the tumor suppressor FLCN through activation of TFEB independently of mTOR.

AMPK is a central regulator of energy homeostasis. AMPK not only elicits acute metabolic responses but also promotes metabolic reprogramming and adaptations in the long-term through regulation of specific transcription factors and coactivators. We performed a whole-genome transcriptome profiling in wild-type (WT) and AMPK-deficient mouse embryonic fibroblasts (MEFs) and primary hepatocytes that had been treated with 2 distinct classes of small-molecule AMPK activators. We identified unique compound-dependent gene expression signatures and several AMPK-regulated genes, including folliculin (Flcn), which encodes the tumor suppressor FLCN. Bioinformatics analysis highlighted the lysosomal pathway and the associated transcription factor EB (TFEB) as a key transcriptional mediator responsible for AMPK responses. AMPK-induced Flcn expression was abolished in MEFs lacking TFEB and transcription factor E3, 2 transcription factors with partially redundant function; additionally, the promoter activity of Flcn was profoundly reduced when its putative TFEB-binding site was mutated. The AMPK-TFEB-FLCN axis is conserved across species; swimming exercise in WT zebrafish induced Flcn expression in muscle, which was significantly reduced in AMPK-deficient zebrafish. Mechanistically, we have found that AMPK promotes dephosphorylation and nuclear localization of TFEB independently of mammalian target of rapamycin activity. Collectively, we identified the novel AMPK-TFEB-FLCN axis, which may function as a key cascade for cellular and metabolic adaptations.—Collodet, C., Foretz, M., Deak, M., Bultot, L., Metairon, S., Viollet, B., Lefebvre, G., Raymond, F., Parisi, A., Civiletto, G., Gut, P., Descombes, P., Sakamoto, K. AMPK promotes induction of the tumor suppressor FLCN through activation of TFEB independently of mTOR.

AMP-activated protein kinase: the current landscape for drug development

Since the discovery of AMP-activated protein kinase (AMPK) as a central regulator of energy homeostasis, many exciting insights into its structure, regulation and physiological roles have been revealed. While exercise, caloric restriction, metformin and many natural products increase AMPK activity and exert a multitude of health benefits, developing direct activators of AMPK to elicit beneficial effects has been challenging. However, in recent years, direct AMPK activators have been identified and tested in preclinical models, and a small number have entered clinical trials. Despite these advances, which disease(s) represent the best indications for therapeutic AMPK activation and the long-term safety of such approaches remain to be established.

MANF: A New Player in the Control of Energy Homeostasis, and Beyond.

All human behaviors, including the control of energy homeostasis, are ultimately mediated by neuronal activities in the brain. Neurotrophic factors represent a protein family that plays important roles in regulating neuronal development, function, and survival. It has been well established that canonical neurotrophic factors, such as brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), play important roles in the central regulation of energy homeostasis. Recently, a class of non-canonical neurotrophic factors, represented by mesencephalic astrocyte-derived neurotrophic factor (MANF), has been discovered. MANF is structurally and functionally distinct from those canonical neurotrophic factors, hence raising the issue of MANF being non-canonical. Nonetheless, emerging evidence suggests that MANF is critically involved in many neuronal activities. Here, we review our current understanding about the functions of MANF in the brain, with a primary focus on the control of energy homeostasis.

Structure and Physiological Regulation of AMPK.

Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a heterotrimeric αβγ complex that functions as a central regulator of energy homeostasis. Energy stress manifests as a drop in the ratio of adenosine triphosphate (ATP) to AMP/ADP, which activates AMPK’s kinase activity, allowing it to upregulate ATP-generating catabolic pathways and to reduce energy-consuming catabolic pathways and cellular programs. AMPK senses the cellular energy state by competitive binding of the three adenine nucleotides AMP, ADP, and ATP to three sites in its γ subunit, each, which in turn modulates the activity of AMPK’s kinase domain in its α subunit. Our current understanding of adenine nucleotide binding and the mechanisms by which differential adenine nucleotide occupancies activate or inhibit AMPK activity has been largely informed by crystal structures of AMPK in different activity states. Here we provide an overview of AMPK structures, and how these structures, in combination with biochemical, biophysical, and mutational analyses provide insights into the mechanisms of adenine nucleotide binding and AMPK activity modulation.

CPT1C in the ventromedial nucleus of the hypothalamus is necessary for brown fat thermogenesis activation in obesity

ObjectiveCarnitine palmitoyltransferase 1C (CPT1C) is implicated in central regulation of energy homeostasis. Our aim was to investigate whether CPT1C in the ventromedial nucleus of the hypothalamus (VMH) is involved in the activation of brown adipose tissue (BAT) thermogenesis in the early stages of diet-induced obesity. MethodsCPT1C KO and wild type (WT) mice were exposed to short-term high-fat (HF) diet feeding or to intracerebroventricular leptin administration and BAT thermogenesis activation was evaluated. Body weight, adiposity, food intake, and leptinemia were also assayed. ResultsUnder 7 days of HF diet, WT mice showed a maximum activation peak of BAT thermogenesis that counteracted obesity development, whereas this activation was impaired in CPT1C KO mice. KO animals evidenced higher body weight, adiposity, hyperleptinemia, ER stress, and disrupted hypothalamic leptin signaling. Leptin-induced BAT thermogenesis was abolished in KO mice. These results indicate an earlier onset leptin resistance in CPT1C KO mice. Since AMPK in the VMH is crucial in the regulation of BAT thermogenesis, we analyzed if CPT1C was a downstream factor of this pathway. Genetic inactivation of AMPK within the VMH was unable to induce BAT thermogenesis and body weight loss in KO mice, indicating that CPT1C is likely downstream AMPK in the central mechanism modulating thermogenesis within the VMH. Quite opposite, the expression of CPT1C in the VMH restored the phenotype. ConclusionCPT1C is necessary for the activation of BAT thermogenesis driven by leptin, HF diet exposure, and AMPK inhibition within the VMH. This study underscores the importance of CPT1C in the activation of BAT thermogenesis to counteract diet-induced obesity.

A Mouse Model of Creatine Transporter Deficiency Reveals Impaired Motor Function and Muscle Energy Metabolism.

Creatine serves as fast energy buffer in organs of high-energy demand such as brain and skeletal muscle. L-Arginine:glycine amidinotransferase (AGAT) and guanidinoacetate N-methyltransferase are responsible for endogenous creatine synthesis. Subsequent uptake into target organs like skeletal muscle, heart and brain is mediated by the creatine transporter (CT1, SLC6A8). Creatine deficiency syndromes are caused by defects of endogenous creatine synthesis or transport and are mainly characterized by intellectual disability, behavioral abnormalities, poorly developed muscle mass, and in some cases also muscle weakness. CT1-deficiency is estimated to be among the most common causes of X-linked intellectual disability and therefore the brain phenotype was the main focus of recent research. Unfortunately, very limited data concerning muscle creatine levels and functions are available from patients with CT1 deficiency. Furthermore, different CT1-deficient mouse models yielded conflicting results and detailed analyses of their muscular phenotype are lacking. Here, we report the generation of a novel CT1-deficient mouse model and characterized the effects of creatine depletion in skeletal muscle. HPLC-analysis showed strongly reduced total creatine levels in skeletal muscle and heart. MR-spectroscopy revealed an almost complete absence of phosphocreatine in skeletal muscle. Increased AGAT expression in skeletal muscle was not sufficient to compensate for insufficient creatine transport. CT1-deficient mice displayed profound impairment of skeletal muscle function and morphology (i.e., reduced strength, reduced endurance, and muscle atrophy). Furthermore, severely altered energy homeostasis was evident on magnetic resonance spectroscopy. Strongly reduced phosphocreatine resulted in decreased ATP/Pi levels despite an increased inorganic phosphate to ATP flux. Concerning glucose metabolism, we show increased glucose transporter type 4 expression in muscle and improved glucose clearance in CT1-deficient mice. These metabolic changes were associated with activation of AMP-activated protein kinase – a central regulator of energy homeostasis. In summary, creatine transporter deficiency resulted in a severe muscle weakness and atrophy despite different compensatory mechanisms.

Role of Hypothalamic TRPV1‐Expressing Neurons in the Regulation of Energy Homeostasis

Transient Receptor Potential Vanilloid type 1 (TRPV1), also known as the capsaicin receptor, is a ligand‐gated nonselective cation channel that has been associated with the regulation of energy homeostasis. Acute stimulation of TRPV1 by a single injection of capsaicin decreased food intake and lowered blood glucose by increasing insulin secretion in wild type mice. Moreover, addition of capsaicin to a high fat diet prevented the development of obesity and improved insulin sensitivity in rodents. TRPV1 is expressed in the hypothalamus, a brain area involved in the regulation of energy intake and energy expenditure. Our previous findings demonstrated that liver‐related hypothalamic neurons express TRPV1 and insulin receptor substrate 2, suggesting the involvement of TRPV1 in the regulation of glucose metabolism. However, the role of TRPV1 in the central control of energy homeostasis in vivo remained to be determined. Transgenic TRPV1‐Cre mice were used throughout the study. First, we investigated the monosynaptic inputs to hypothalamic TRPV1 neurons, using pseudo‐typed rabies virus coupled with helper viruses expressed in Cre‐dependent manner (AAV‐EF1a‐Flex‐TVA‐mCherry + AAV‐CA‐Flex‐RG.ape + EnvA‐RVdG‐GFP). Starter TRPV1 neurons were mainly found in the posterior hypothalamus (PH) and lateral hypothalamus (LH). We observed that these TRPV1‐expressing starter neurons receive monosynaptic inputs from the preoptic area (POA), the dorsomedial hypothalamus (DMH) and the LH, brain areas known for their implication in the regulation of food intake, glucose metabolism and thermogenesis. This finding corroborates the potential involvement of TRPV1 in central regulation of energy homeostasis. Then, we studied the role of hypothalamic TRPV1‐expressing neurons in vivo, using the designer receptor exclusively activated by designer drugs (DREADD) approach. DREADD was expressed in Cre‐dependent manner and located mainly in the PH and LH. Thereby, a single injection of clozapine‐N‐oxide (CNO; 1 mg/kg of body weight) triggered the stimulation (AAV‐hSyn‐DIO‐hM3D( Gq)‐mCherry) or inhibition (AAV‐hSyn‐DIO‐hM4D(Gi)‐mCherry) of TRPV1/DREADD‐expressing neurons, while food intake and glucose tolerance were evaluated. Our data showed that activation of TRPV1‐expressing neurons in the PH/LH did not affect food intake during 6h of a refeeding test, whether hypothalamic TRPV1 expressing neurons were stimulated or inhibited. Similarly, the activation of TRPV1/DREADD‐expressing neurons did not modulate glucose tolerance after an intraperitoneal injection of glucose (2 g/kg of body weight), whether hypothalamic TRPV1 expressing neurons were stimulated or inhibited. In conclusion, despite the previous evidence that TRPV1 is involved in the regulation of the whole‐body energy homeostasis, TRPV1 expressing neurons located in the PH/LH area are likely not involved in the central regulation of food intake or glucose tolerance. Further studies need to be conducted to reveal the physiological role of hypothalamic TRPV1 expressing neurons in vivo.Support or Funding InformationNational Institutes of Health R01 DK099598Core Facilities (Tulane University, School of Medicine)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Porous Nanohydroxyapatite/Collagen Scaffolds Loading Insulin PLGA Particles for Restoration of Critical Size Bone Defect.

Insulin is considered to be a classical central regulator of energy homeostasis. Recently, the effect of insulin on bone has gained a lot of attention, but little attention has been paid to the application in bone tissue engineering. In this study, porous nanohydroxyapatite/collagen (nHAC) scaffolds incorporating poly lactic-co-glycolic acid (PLGA) particles were successfully developed as an insulin delivery platform for bone regeneration. Bioactive insulin was successfully released from the PLGA particles within the scaffold, and the size of the particles as well as the release kinetics of the insulin could be efficiently controlled through Shirasu porous glass premix membrane emulsification technology. It was indicated that the nHAC/PLGA composite scaffolds possessed favorable mechanical and structural properties for cell adhesion and proliferation, as well as the differentiation into osteoblasts. It was also demonstrated that the nHAC/PLGA scaffolds implanted into a rabbit critical-size mandible defect possessed tissue compatibility and higher bone restoration capacity compared with the defects that were filled with or without nHAC scaffolds. Furthermore, the in vivo results showed that the nHAC/PLGA scaffolds which incorporated insulin-loaded microspheres with a size of 1.61 μm significantly accelerated bone healing compared with two other composite scaffolds. Our study indicated that the local insulin released at the optimal time could substantially and reproducibly improve bone repair.

The obesity‐related Adipokinetic hormone controls feeding and expression of neuropeptide regulators of Drosophila metabolism

Homeostasis of circulating and storage energy reserves in mammals is dependent on the antagonistically acting insulin and glucagon signaling. In the model organism Drosophila melanogaster, this function is executed by the insulin‐like peptides and the glucagon‐like Adipokinetic hormone (AKH). Loss of Drosophila AKH results in the adulthood‐specific onset of obesity coupled with hypoglycemia. However, apart from the role of AKH in the lipid mobilization, the physiological and endocrine underpinnings of the AKH deficiency‐triggered obesity are unknown. Here, we investigate the role of AKH in feeding and metabolic rate control, and address the interactions of this hormone with other endocrine regulators of fly metabolism. Via in vivo gain‐ and loss‐of‐function analyses, we show that despite its anti‐obesity effects, AKH is an orexigenic peptide. Moreover, AKH also affects expression of orexigenic factors CCHamide‐2 and neuropeptide F. In addition, AKH regulates metabolic genes like Corazonin, Limostatin, and Insulin‐like peptides (Ilps) 2, 3, 5, and 6. Altogether, our work shows that the Drosophila AKH is a central regulator of energy homeostasis; next to its well‐known role in the control of energy expenditure, this hormone controls also food intake, and expression of other endocrine regulators of fly metabolism.Practical applications: Basic research of the neuroendocrine regulation of metabolism in the fruit fly D. melanogaster has potential applications in both human medicine and insect pest control. The evolutionary conservation of the key metabolic pathways, together with the unprecedented choice of transgenic tools turned the fruit fly into a useful model to study human diseases, including obesity and diabetes. Based on the evolutionary conservation of AKH and glucagon functions, our investigations might provide useful hints regarding the physiological actions, and endocrine interactions of human glucagon, too. In addition, insect neuropeptides are emerging as important targets for the parasite and pest control; understanding of their regulatory networks has thus potential implications also in the development of novel insecticides.Adipokinetic hormone (AKH) is an insect analog of the human hormone glucagon. Our investigations of the roles of this hormone in the model organism Drosophila melanogaster have shown that this anti‐obesity factor is a central regulator of fly metabolism, and controls crucial processes such as feeding, metabolic rate, storage of energy reserves, and expression of regulatory genes from the neuropeptide hormone family, including the fly homologs of human insulin.

AMPK activators: mechanisms of action and physiological activities.

AMP-activated protein kinase (AMPK) is a central regulator of energy homeostasis, which coordinates metabolic pathways and thus balances nutrient supply with energy demand. Because of the favorable physiological outcomes of AMPK activation on metabolism, AMPK has been considered to be an important therapeutic target for controlling human diseases including metabolic syndrome and cancer. Thus, activators of AMPK may have potential as novel therapeutics for these diseases. In this review, we provide a comprehensive summary of both indirect and direct AMPK activators and their modes of action in relation to the structure of AMPK. We discuss the functional differences among isoform-specific AMPK complexes and their significance regarding the development of novel AMPK activators and the potential for combining different AMPK activators in the treatment of human disease.

Age- and brain region-specific differences in mitochondrial bioenergetics in Brown Norway rats

Mitochondria are central regulators of energy homeostasis and play a pivotal role in mechanisms of cellular senescence. The objective of the present study was to evaluate mitochondrial bioenergetic parameters in 5 brain regions (brain stem [BS], frontal cortex, cerebellum, striatum, hippocampus [HIP]) of 4 diverse age groups (1 month [young], 4 months [adult], 12 months [middle-aged], 24 months [old age]) to understand age-related differences in selected brain regions and their possible contribution to age-related chemical sensitivity. Mitochondrial bioenergetic parameters and enzyme activities were measured under identical conditions across multiple age groups and brain regions in Brown Norway rats (n = 5/group). The results indicate age- and brain region–specific patterns in mitochondrial functional endpoints. For example, an age-specific decline in ATP synthesis (State III respiration) was observed in BS and HIP. Similarly, the maximal respiratory capacities (State V1 and V2) showed age-specific declines in all brain regions examined (young > adult > middle-aged > old age). Amongst all regions, HIP had the greatest change in mitochondrial bioenergetics, showing declines in the 4, 12, and 24-months age groups. Activities of mitochondrial pyruvate dehydrogenase complex and electron transport chain complexes I, II, and IV enzymes were also age and brain region specific. In general, changes associated with age were more pronounced with enzyme activities declining as the animals aged (young > adult > middle-aged > old age). These age- and brain region-specific observations may aid in evaluating brain bioenergetic impact on the age-related susceptibility to environmental chemical stressors.

Insulin Does Not Target CamkIIα Neurones to Critically Regulate the Neuroendocrine Reproductive Axis in Mice.

Insulin signalling in the brain plays an important role in the central regulation of energy homeostasis and fertility, such that mice exhibiting widespread deletion of insulin receptors (InsR) throughout the brain and peripheral nervous system display diet sensitive obesity and hypothalamic hypogonadism. However, the specific cell types mediating the central effects of insulin on fertility remain largely unidentified. To date, the targeted deletion of InsR from individual neuronal populations implicated in the metabolic control of fertility has failed to recapitulate the hypogonadic and subfertile phenotype observed in brain-specific InsR knockout mice. Because insulin and leptin share similar roles as centrally-acting metabolic regulators of fertility, we used the Cre-loxP system to generate mice with a selective inactivation of the Insr gene from the same widespread neuronal population previously shown to mediate the central effects of leptin on fertility by crossing Insr-flox mice with calcium/calmodulin-dependent protein kinase type IIα (CamkIIα)-Cre mice. Multiple reproductive and metabolic parameters were then compared between male and female Insr-flox/Cre-positive (CamK-IRKO) and Insr-flox/Cre-negative control mice. Consistent with brain-specific InsR knockout mice, CamK-IRKO mice exhibited a mild but significant obesogenic phenotype. Unexpectedly, CamK-IRKO mice exhibited normal reproductive maturation and function compared to controls. No differences in the age of puberty onset, oestrous cyclicity or fecundity were observed between CamK-IRKO and control mice. We conclude that the central effects of insulin on the neuroendocrine reproductive axis are not critically mediated via the same neuronal populations targeted by leptin.

Letters to Editor Methodological approach to brain derived neurotrophic factor in children with autism spectrum disorder

Dear Editor, In a recent issue of Annals of Neurosciences, we read with great interest the article by Kasarpalkar and colleagues entitled “Brain-Derived Neurotrophic Factor in children with Autism Spectrum Disorder” in which the investigators reported that the protective effect of brain derived neurotrophic factor (BDNF) due to relatively higher levels in mild phenotypes of autism compared to severe autism and its possible diagnostic role in autism spectrum disorders.1 However, we think that some points should be discussed. BDNF is signaling protein that involved in the central regulation of energy homeostasis. Maffioletti and colleagues reported that serum preparation procedure is quite important issue to present robust methodology while measuring serum BDNF.2 BDNF level is presumably affected from duration of the clotting procedure due to being stored in thrombocytes. They observed progression on serum BDNF concentrations, which reached 38% of the plateau value after 10 min, 91.8% after 30 min, and 100% after 1 hour. Therefore, they recommended the minimum clotting duration for a correct serum BDNF dosage as 1 hour. However, in this study, the authors stated that serum samples were separated immediately after blood was collected. We think that standardization of clotting process is highly important to prevent misinterpretation of serum BDNF levels. Previous studies suggested that certain diseases such as epilepsy, allergic rhinitis and atopic dermatitis could likely affect BDNF levels.3 In addition, medications such as aspirin and corticosteroids, and dietary supplements such as vitamin E, vitamin A, vitamin B12, folic acid, zinc, omega-3 fatty acids, and ginkgo biloba extracts can influence BDNF levels.4-6 In this regard, without defining these contributing factors, interpreting the results is problematic. The authors did not express any of above contributors. In conclusion, clarifying these concerns will certainly provide a clearer picture when interpreting serum BDNF levels among participants.

Early life origins of metabolic disease: Developmental programming of hypothalamic pathways controlling energy homeostasis.

A wealth of animal and human studies demonstrate that perinatal exposure to adverse metabolic conditions - be it maternal obesity, diabetes or under-nutrition - results in predisposition of offspring to develop obesity later in life. This mechanism is a contributing factor to the exponential rise in obesity rates. Increased weight gain in offspring exposed to maternal obesity is usually associated with hyperphagia, implicating altered central regulation of energy homeostasis as an underlying cause. Perinatal development of the hypothalamus (a brain region key to metabolic regulation) is plastic and sensitive to metabolic signals during this critical time window. Recent research in non-human primate and rodent models has demonstrated that exposure to adverse maternal environments impairs the development of hypothalamic structure and consequently function, potentially underpinning metabolic phenotypes in later life. This review summarizes our current knowledge of how adverse perinatal environments program hypothalamic development and explores the mechanisms that could mediate these effects.

Fertility-regulating Kiss1 neurons arise from hypothalamic POMC-expressing progenitors.

Hypothalamic neuronal populations are central regulators of energy homeostasis and reproductive function. However, the ontogeny of these critical hypothalamic neuronal populations is largely unknown. We developed a novel approach to examine the developmental pathways that link specific subtypes of neurons by combining embryonic and adult ribosome-tagging strategies in mice. This new method shows that Pomc-expressing precursors not only differentiate into discrete neuronal populations that mediate energy balance (POMC and AgRP neurons), but also into neurons critical for puberty onset and the regulation of reproductive function (Kiss1 neurons). These results demonstrate a developmental link between nutrient-sensing and reproductive neuropeptide synthesizing neuronal populations and suggest a potential pathway that could link maternal nutrition to reproductive development in the offspring.

Neuronal redox imbalance results in altered energy homeostasis and early postnatal lethality.

Redox imbalance is believed to contribute to the development and progression of several neurodegenerative disorders. Our aim was to develop an animal model that exhibits neuron-specific oxidative stress in the CNS to study the consequences and eventually find clues regarding the pathomechanisms of oxidative insults in neuronal homeostasis. We therefore generated a novel neuron-specific superoxide dismutase 2 (SOD2)-deficient mouse by deleting exon 3 of the SOD2 gene using CamKIIα promoter-driven Cre expression. These neuron-specific SOD2 knockout (SOD2(nko)) mice, although born at normal frequencies, died at the age of 4 weeks with critical growth retardation, severe energy failure, and several neurologic phenotypes. In addition, SOD2(nko) mice exhibited severe neuronal alterations such as reactive astrogliosis, neuronal cell cycle inhibition, and induction of apoptosis. JNK activation and stabilization of p53, as a result of reactive oxygen species accumulation, are most likely the inducers of neuronal apoptosis in SOD2(nko) mice. It is remarkable that hypothalamic regulation of glucose metabolism was affected, which in turn induced necrotic brain lesions in SOD2(nko) mice. Taken together, our findings suggest that exclusive deficiency of SOD2 in neurons results in an impaired central regulation of energy homeostasis that leads to persistent hypoglycemia, hypoglycemia-related neuropathology, and an early lethality of the mutant mice.

The multiple universes of estrogen-related receptor α and γ in metabolic control and related diseases.

The identification of the estrogen-related receptors (ERRs) as the first orphan nuclear receptors ignited a new era in molecular endocrinology, which led to the discovery of new ligand-dependent response systems. Although ERR subfamily members have yet to be associated with a natural ligand, the characterization of these orphan receptors has demonstrated that they occupy a strategic node in the transcriptional control of cellular energy metabolism. In particular, ERRs are required for the response to various environmental challenges that require high energy levels by the organism. As central regulators of energy homeostasis, ERRs may also be implicated in the etiology of metabolic disorders, such as type 2 diabetes and metabolic syndrome. Here, we review the recent evidence that further highlights the role of ERRs in metabolic control, particularly in liver and skeletal muscle, and their likely involvement in metabolic diseases. Consequently, we also explore the promises and pitfalls of ERRs as potential therapeutic targets.