Ciliary neurotrophic factor activates leptin-like pathways and reduces body fat, without cachexia or rebound weight gain, even in leptin-resistant obesity

The Anti-Obesogenic Effects of Muscadine Grapes through Ciliary Neurotrophic Factor Receptor (Cntfr) and Histamine Receptor H1 (Hrh1) Genes in 3T3-L1 Differentiated Mouse Cells

Obesity and type 2 diabetes are prevalent metabolic diseases that have significant links to several chronic diseases, including cancer, diabetes, hypertension, and cardiovascular disease. Muscadine grape extracts have shown the potential to reduce adiposity and improve insulin sensitivity and glucose control. Thus, this study was designed to determine the potential of muscadine grape berries extract (Pineapple and Southern Home) for its antiobesity properties in 3T3-L1 cells as a model for obesity research. The current study's data indicated the total phenolic content (TPC) and 2,2-diphenyl-1-picrylhydraziyl (DPPH) activity were higher in cultivar (CV) Southern Home, meanwhile, elevated the total flavonoid content (TFC) in Pineapple. Both extracts were safe across the tested range (0-5 mg/mL). A noticeable reduction in lipid accumulation was also found in extract-treated cells. In preadipocytes and adipocytes, the tested extracts showed significant alterations in various genes involved in glucose homeostasis and obesity. The most remarkable findings of the current study are the upregulation of two genes, Cntfr (+712.715-fold) and Hrh1 (+270.11-fold) in CV Pineapple extract-treated adipocytes 3T3-L1 and the high fold increase in Ramp3 induced by both Pineapple and Southern Home in pre-adipose cells. Furthermore, the tested extracts showed a potential to alter the mRNA of various genes, including Zfp91, B2m, Nr3c1, Insr, Atrn, Il6ra, Hsp90ab1, Sort1, and Npy1r. In conclusion, the data generated from the current study suggested that the two extracts under investigation are considered potential candidates for controlling insulin levels and managing obesity.

Exploring the landscape of synthetic IL-6-type cytokines

Interleukin-6 (IL-6)-type cytokines not only have key immunomodulatory functions that affect the pathogenesis of diseases such as autoimmune diseases, chronic inflammatory conditions, and cancer, but also fulfill important homeostatic tasks. Even though the pro-inflammatory arm has hindered the development of therapeutics based on natural-like IL-6-type cytokines to date, current synthetic trends might pave the way to overcome these limitations and eventually lead to immune-inert designer cytokines to aid type 2 diabetes and brain injuries. Those synthetic biology approaches include mutations, fusion proteins, and inter-cytokine swapping, and resulted in IL-6-type cytokines with altered receptor affinities, extended target cell profiles, and targeting of non-natural cytokine receptor complexes. Here, we survey synthetic cytokine developments within the IL-6-type cytokine family and discuss potential clinical applications.

CLCF1 inhibits energy expenditure via suppressing brown fat thermogenesis

Brown adipose tissue (BAT) is the main site of nonshivering thermogenesis which plays an important role in thermogenesis and energy metabolism. However, the regulatory factors that inhibit BAT activity remain largely unknown. Here, cardiotrophin-like cytokine factor 1 (CLCF1) is identified as a negative regulator of thermogenesis in BAT. Adenovirus-mediated overexpression of CLCF1 in BAT greatly impairs the thermogenic capacity of BAT and reduces the metabolic rate. Consistently, BAT-specific ablation of CLCF1 enhances the BAT function and energy expenditure under both thermoneutral and cold conditions. Mechanistically, adenylate cyclase 3 (ADCY3) is identified as a downstream target of CLCF1 to mediate its role in regulating thermogenesis. Furthermore, CLCF1 is identified to negatively regulate the PERK-ATF4 signaling axis to modulate the transcriptional activity of ADCY3, which activates the PKA substrate phosphorylation. Moreover, CLCF1 deletion in BAT protects the mice against diet-induced obesity by promoting BAT activation and further attenuating impaired glucose and lipid metabolism. Therefore, our results reveal the essential role of CLCF1 in regulating BAT thermogenesis and suggest that inhibiting CLCF1 signaling might be a potential therapeutic strategy for improving obesity-related metabolic disorders.

CLCF1 signaling restrains thermogenesis and disrupts metabolic homeostasis by inhibiting mitochondrial biogenesis in brown adipocytes

Great progress has been made in identifying positive regulators that activate adipocyte thermogenesis, but negative regulatory signaling of thermogenesis remains poorly understood. Here, we found that cardiotrophin-like cytokine factor 1 (CLCF1) signaling led to loss of brown fat identity, which impaired thermogenic capacity. CLCF1 levels decreased during thermogenic stimulation but were considerably increased in obesity. Adipocyte-specific CLCF1 transgenic (CLCF1-ATG) mice showed impaired energy expenditure and severe cold intolerance. Elevated CLCF1 triggered whitening of brown adipose tissue by suppressing mitochondrial biogenesis. Mechanistically, CLCF1 bound and activated ciliary neurotrophic factor receptor (CNTFR) and augmented signal transducer and activator of transcription 3 (STAT3) signaling. STAT3 transcriptionally inhibited both peroxisome proliferator-activated receptor-γ coactivator (PGC) 1α and 1β, which thereafter restrained mitochondrial biogenesis in adipocytes. Inhibition of CNTFR or STAT3 could diminish the inhibitory effects of CLCF1 on mitochondrial biogenesis and thermogenesis. As a result, CLCF1-TG mice were predisposed to develop metabolic dysfunction even without external metabolic stress. Our findings revealed a brake signal on nonshivering thermogenesis and suggested that targeting this pathway could be used to restore brown fat activity and systemic metabolic homeostasis in obesity.

Ciliary neurotrophic factor is increased in the plasma of patients with obesity and its levels correlate with diabetes and inflammation indices

To establish whether obesity involves activation of endogenous ciliary neurotrophic factor (CNTF) signalling, we evaluated its plasma levels in patients with obesity and correlated its values with the major clinical and haematological indices of obesity, insulin resistance and systemic inflammation. This study involved 118 subjects: 39 healthy controls (19 men), 39 subjects with obesity (19 men) and 40 subjects with obesity and diabetes (20 men). Plasma CNTF and CNTF receptor α (CNTFRα) were measured using commercial ELISA kits. The results showed that plasma CNTF was significantly higher in males and females with obesity with and without diabetes than in healthy subjects. Women consistently exhibited higher levels of circulating CNTF. In both genders, CNTF levels correlated significantly and positively with obesity (BMI, WHR, leptin), diabetes (fasting insulin, HOMA index and HbA1c) and inflammation (IL-6 and hsCRP) indices. Circulating CNTFRα and the CNTF/CNTFRα molar ratio tended to be higher in the patient groups than in controls. In conclusion, endogenous CNTF signalling is activated in human obesity and may help counteract some adverse effects of obesity. Studies involving a higher number of selected patients may reveal circulating CNTF and/or CNTFRα as potential novel diagnostic and/or prognostic markers of obesity, diabetes and associated diseases.

The role of neurotrophin genes involved in the vulnerability to gambling disorder

Evidence about the involvement of genetic factors in the development of gambling disorder (GD) has been assessed. Among studies assessing heritability and biological vulnerability for GD, neurotrophin (NTF) genes have emerged as promising targets, since a growing literature showed a possible link between NTF and addiction-related disorders. Thus, we aimed to explore the role of NTF genes and GD with the hypothesis that some NTF gene polymorphisms could constitute biological risk factors. The sample included 166 patients with GD and 191 healthy controls. 36 single nucleotide polymorphisms (SNPs) from NTFs (NGF, NGFR, NTRK1, BDNF, NTRK2, NTF3, NTRK3, NTF4, CNTF and CNTFR) were selected and genotyped. Linkage disequilibrium (LD) and haplotype constructions were analyzed, in relationship with the presence of GD. Finally, regulatory elements overlapping the identified SNPs variants associated with GD were searched. The between groups comparisons of allele frequencies indicated that 6 SNPs were potentially associated with GD. Single and multiple-marker analyses showed a strong association between both NTF3 and NTRK2 genes, and GD. The present study supports the involvement of the NTF family in the aetiopathogenesis of GD. An altered cross-regulation of different NTF members signalling pathways might be considered as a biological vulnerability factor for GD.

Efficacy of PEGylated ciliary neurotrophic factor superagonist variant in diet-induced obesity mice

Ciliary neurotrophic factor (CNTF) is a neurotrophic cytokine able to induce appetite reduction, weight loss and antidiabetic effects. However, its susceptibility to neutralizing anti-CNTF antibodies in patients hampered its use for treatment of human obesity and diabetes. In addition, CNTF has a very short plasma half-life, which limits its use as a therapeutic agent. Solutions, directed to prolong its in vivo effects, vary from the implantation of encapsulated secreting cells to identification of more active variants or chemical modification of the protein itself. PEGylation is a widely used modification for shielding proteins from circulating antibodies and for increasing their plasma half-life. Here, we have selected DH-CNTF, a CNTF variant which has a 40-fold higher affinity for the CNTF receptor α accompanied by an increased activity in cellular assays. The PEGylated DH-CNTF retained the biological activity of native protein in vitro and showed a significant improvement of pharmacokinetic parameters. In an acute model of glucose tolerance, the PEG-DH-CNTF was able to reduce the glycemia in diet-induced obese animals, with a performance equaled by a 10-fold higher dose of DH-CNTF. In addition, the PEGylated DH-CNTF analog demonstrated a more potent weight loss effect than the unmodified protein, opening to the use of CNTF as weight reducing agent with treatment regimens that can better meet patient compliance thanks to reduced dosing schedules.

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

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

Controlled release of ciliary neurotrophic factor from bioactive nerve grafts promotes nerve regeneration in rats with facial nerve injuries

It is critical to repair severed facial nerves, as lack of treatment may cause long-term motor and sensory impairments. Ciliary neurotrophic factor (CNTF) plays an important role in terms of enhancing nerve axon regrowth and maturation during peripheral nerve regeneration after injury. However, simple application of CNTF to the transected nerve site does not afford functional recovery, because it is rapidly flushed away by bodily fluids. The aim of the present study was the construction of a new, bioactive composite nerve graft facilitating persistent CNTF delivery to aid the reconstruction of facial nerve defects. The in vitro study showed that the bioactive nerve graft generated sustainable CNTF release for more than 25 days. The bioactive nerve graft was then transplanted into the injury sites of rat facial nerves. At 6 and 12 weeks post-transplantation, functional and histological analyses showed that the bioactive nerve graft featuring immobilized CNTF significantly enhanced nerve regeneration in terms of both axonal outgrowth and Schwann cell proliferation in the rat facial nerve gap model, compared to a collagen tube with adsorbed CNTF that initially released high levels of CNTF. The bioactive nerve graft may serve as novel, controlled bioactive release therapy for facial nerve regeneration.

IL-6 family cytokines as potential therapeutic strategies to treat metabolic diseases

Metabolic disease is highly prevalent. Here we discuss the therapeutic utility of using gp130 receptor ligands as a therapeutic strategy to treat metabolic disease.

STAT3 phosphorylation in central leptin resistance

Mechanism exploitation of energy homeostasis is urgently required because of the worldwide prevailing of obesity-related metabolic disorders in human being. Although it is well known that leptin plays a central role in regulating energy balance by suppressing food intake and promoting energy expenditure, the existence of leptin resistance in majority of obese individuals hampers the utilization of leptin therapy against these disorders. However, the mechanism of leptin resistance is largely unknown in spite of the globally enormous endeavors. Current theories to interpret leptin resistance include the impairment of leptin transport, attenuation of leptin signaling, chronic inflammation, ER tress, deficiency of autophagy, as well as leptin itself. Leptin-activated leptin receptor (LepRb) signals in hypothalamus via several pathways, in which JAK2-STAT3 pathway, the most extensively investigated one, is considered to mediate the major action of leptin in energy regulation. Upon leptin stimulation the phosphorylation of STAT3 is one of the key events in JAK2-STAT3 pathway, followed by the dimerization and nuclear translocation of this molecule. Phosphorylated STAT3 (p-STAT3), as a transcription factor, binds to and regulates its target gene such as POMC gene, playing the physiological function of leptin. Regarding POMC gene in hypothalamus however little is known about the detail of its interaction with STAT3. Moreover the status of p-STAT3 and its significance in hypothalamus of DIO mice needs to be well elucidated. This review comprehends literatures on leptin and leptin resistance and especially discusses what STAT3 phosphorylation would contribute to central leptin resistance.

Ciliary neurotrophic factor (CNTF) and its receptor (CNTFRα) signal through MAPK/ERK pathway in human prostate tissues: a morphological and biomolecular study

Ciliary neurotrophic factor (CNTF) is a member of interleukin-6 type cytokine family. The CNTF receptor complex is a heterodimer including gp130 and CNTF receptor α (CNTFRα) proteins triggering the activation of multiple intracellular signaling pathways including AKT/PI3K, MAPK/ERK and Jak/STAT pathways. At present no data are available on the localization of CNTF and CNTFRα in prostate as well as on the role of CNTF in this organ. In this study we have analyzed the localization of CNTF and CNTFRα by immunohistochemistry and we have used PWR-1E cell line as a model for normal glandular cell to investigate the role of this cytokine. Our results show that CNTF and CNTFRa are expressed in the staminal compart of the prostate and that CNTF selectively inhibits ERK pathway. In conclusion, we suggest that CNTF could be considered as key molecule to maintenance epithelium homeostasis via pERK downregulation by an autocrine mechanism. Further CNTF studies in prostate cancer could be useful to verify the potential role of this cytokine in carcinogenesis.

Ciliary Neurotrophic Factor Acts on Distinctive Hypothalamic Arcuate Neurons and Promotes Leptin Entry Into and Action on the Mouse Hypothalamus

In humans and experimental animals, the administration of ciliary neurotrophic factor (CNTF) reduces food intake and body weight. To gain further insights into the mechanism(s) underlying its satiety effect, we: (i) evaluated the CNTF-dependent activation of the Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) pathway in mouse models where neuropeptide Y (NPY) and pro-opiomelanocortin (POMC) neurons can be identified by green fluorescent protein (GFP); and (ii) assessed whether CNTF promotes leptin signaling in hypothalamic feeding centers. Immunohistochemical experiments enabled us to establish that intraperitoneal injection of mouse recombinant CNTF activated the JAK2-STAT3 pathway in a substantial proportion of arcuate nucleus (ARC) NPY neurons (18.68% ± 0.60 in 24-h fasted mice and 25.50% ± 1.17 in fed mice) but exerted a limited effect on POMC neurons (4.15% ± 0.33 in 24-h fasted mice and 2.84% ± 0.45 in fed mice). CNTF-responsive NPY neurons resided in the ventromedial ARC, facing the median eminence (ME), and were surrounded by albumin immunoreactivity, suggesting that they are located outside the blood-brain barrier (BBB). In both normally fed and high-fat diet (HFD) obese animals, CNTF activated extracellular signal-regulated kinase signaling in ME β1- and β2-tanycytes, an effect that has been linked to the promotion of leptin entry into the brain. Accordingly, compared to the animals treated with leptin, mice treated with leptin/CNTF showed: (i) a significantly greater leptin content in hypothalamic protein extracts; (ii) a significant increase in phospho-STAT3 (P-STAT3)-positive neurons in the ARC and the ventromedial hypothalamic nucleus of normally fed mice; and (iii) a significantly increased number of P-STAT3-positive neurons in the ARC and dorsomedial hypothalamic nucleus of HFD obese mice. Collectively, these data suggest that exogenously administered CNTF reduces food intake by exerting a leptin-like action on distinctive NPY ARC neurons and by promoting leptin signaling in hypothalamic feeding centers.

Therapeutic Approaches with Intravitreal Injections in Geographic Atrophy Secondary to Age-Related Macular Degeneration: Current Drugs and Potential Molecules

The present review focuses on recent clinical trials that analyze the efficacy of intravitreal therapeutic agents for the treatment of dry age-related macular degeneration (AMD), such as neuroprotective drugs, and complement inhibitors, also called immunomodulatory or anti-inflammatory agents. A systematic literature search was performed to identify randomized controlled trials published prior to January 2019. Patients affected by dry AMD treated with intravitreal therapeutic agents were included. Changes in the correct visual acuity and reduction in geographic atrophy progression were evaluated. Several new drugs have shown promising results, including those targeting the complement cascade and neuroprotective agents. The potential action of the two groups of drugs is to block complement cascade upregulation of immunomodulating agents, and to prevent the degeneration and apoptosis of ganglion cells for the neuroprotectors, respectively. Our analysis indicates that finding treatments for dry AMD will require continued collaboration among researchers to identify additional molecular targets and to fully interrogate the utility of pluripotent stem cells for personalized therapy.

Biological Effects of Ciliary Neurotrophic Factor on hMADS Adipocytes

Administration of ciliary neurotrophic factor (CNTF) to experimental animals exerts anti-obesity effects by acting on multiple targets. In white adipose tissue CNTF reduces lipid content, promotes fatty acid (FA) oxidation and improves insulin sensitivity. This study was performed to establish whether CNTF exerts similar effects on human white adipocytes. To this end, adipose differentiation was induced in vitro in human multipotent adipose-derived stem (hMADS) cells. CNTF receptor α (CNTFRα) expression was assessed in hMADS cells and adipocytes by qRT-PCR, Western blotting, and immunocytochemistry. After administration of human recombinant CNTF, signaling pathways and gene expression were evaluated by Western blotting and qRT-PCR. Glucose uptake was assessed by measuring 2-nitrobenzodeoxyglucose uptake with a fluorescence plate reader. Lastly, CNTF-induced anti-inflammatory responses were evaluated in hMADS adipocytes stressed with tumor necrosis factor α (TNFα) for 24 h. Results showed that CNTFRα protein expression was higher in undifferentiated hMADS cells than in hMADS adipocytes, where it was however clearly detectable. In hMADS adipocytes, 1 nM CNTF strongly activated the JAK-STAT3 (Janus kinase-signaling transducer and activator of transcription 3) pathway and acutely and transiently activated the AMPK (AMP-activated protein kinase) and AKT (protein kinase B) pathways. Acute CNTF treatment for 20 min significantly increased basal glucose uptake and was associated with increased AKT phosphorylation. Longer-term (24 and 48 h) treatment reduced the expression of lipogenic markers (FA synthase and sterol regulatory element-binding protein-1) and increased the expression of lipolytic [hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL)] and mitochondrial (peroxisome proliferator-activated receptor γ coactivator-1α and carnitine palmitoyltransferase 1) markers. In TNFα-treated hMADS adipocytes, CNTF significantly reduced the expression of monocyte chemoattractant protein 1 and TNFα-induced AKT inhibition. Collectively, these findings demonstrate for the first time that CNTF plays a role also in human adipocytes, driving their metabolism toward a less lipid-storing and more energy-consuming phenotype.

Tanycyte Gene Expression Dynamics in the Regulation of Energy Homeostasis

Animal survival relies on a constant balance between energy supply and energy expenditure, which is controlled by several neuroendocrine functions that integrate metabolic information and adapt the response of the organism to physiological demands. Polarized ependymoglial cells lining the floor of the third ventricle and sending a single process within metabolic hypothalamic parenchyma, tanycytes are henceforth described as key components of the hypothalamic neural network controlling energy balance. Their strategic position and peculiar properties convey them diverse physiological functions ranging from blood/brain traffic controllers, metabolic modulators, and neural stem/progenitor cells. At the molecular level, these functions rely on an accurate regulation of gene expression. Indeed, tanycytes are characterized by their own molecular signature which is mostly associated to their diverse physiological functions, and the detection of variations in nutrient/hormone levels leads to an adequate modulation of genetic profile in order to ensure energy homeostasis. The aim of this review is to summarize recent knowledge on the nutritional control of tanycyte gene expression.

DNA-binding activity of STAT3 increased in hypothalamus of DIO mice; the reduction of STAT3 phosphorylation may facilitate leptin signaling

Leptin-mediated DNA-binding activity of STAT3 in hypothalamus plays crucial roles in the maintenance of energy homeostasis in lean mice; however its effects still remains unclear in case of leptin resistance in mice with diet induced obesity (DIO). In this study significant elevation of both basal and exogenously leptin-treated DNA-binding activity of STAT3 was detected using EMSA in the hypothalamus of male C57BL/6J mice fed high-fat diet for 10 wks, in concomitant with hyperleptinemia, high body weight, high fat mass, and hyperphagia as well as decreased POMC expression. The studies in vitro showed that both DNA binding activity and the proximal SBE of POMC promoter was essential to leptin-mediated POMC expression. However, the diminution of STAT3 phosphorylation, achieved by S3I-201 or a FoxO1 mutant, facilitated leptin-mediated POMC expression. The findings here demonstrated excess STAT3 activity negatively regulated POMC expression in hypothalamus of DIO mice, and suggested the limitation of STAT3 activity may promote leptin signaling.

The Gravitostat Regulates Fat Mass in Obese Male Mice While Leptin Regulates Fat Mass in Lean Male Mice

Leptin has been the only known homeostatic regulator of fat mass, but we recently found evidence for a second one, named the gravitostat. In the current study, we compared the effects of leptin and increased loading (gravitostat stimulation) on fat mass in mice with different levels of body weight (lean, overweight, and obese). Leptin infusion suppressed body weight and fat mass in lean mice given normal chow but not in overweight or obese mice given a high-fat diet for 4 and 8 weeks, respectively. The maximum effect of leptin on body weight and fat mass was obtained already at <44 ng/mL of serum leptin. Increased loading using intraperitoneal capsules with different weights decreased body weight in overweight and obese mice. Although the implantation of an empty capsule reduced the body weight in lean mice, only a nonsignificant tendency of a specific effect of increased loading was observed in the lean mice. These findings demonstrate that the gravitostat regulates fat mass in obese mice, whereas leptin regulates fat mass only in lean mice with low endogenous serum leptin levels. We propose that activation of the gravitostat primarily protects against obesity, whereas low levels of leptin protect against undernutrition.

Switching from high-fat diet to foods containing resveratrol as a calorie restriction mimetic changes the architecture of arcuate nucleus to produce more newborn anorexigenic neurons

PURPOSE

These days, obesity threatens the health for which one of the main interventions is calorie restriction (CR). Due to the difficulty of compliance with this treatment, CR mimetics such as resveratrol (RSV) have been considered. The present study compared the effects of RSV and CR on hypothalamic remodeling in a diet-switching experiment.

METHODS

C57BL/6 male mice received high-fat diet (HFD) for 4 weeks, subsequently their diet switched to chow diet, HFD + RSV, chow diet + RSV or CR diet for a further 6 weeks. Body weight, fat accumulation, hypothalamic apoptosis and expression of trophic factors as well as generation and fate specification of newborn cells in arcuate nucleus (ARC) were evaluated.

RESULTS

Switching diet to RSV-containing foods leading to weight and fat loss after 6 weeks. In addition, not only a significant reduction in apoptosis but also a considerable increase in production of newborn cells in ARC occurred following consumption of RSV-enriched diets. These were in line with augmentation of hypothalamic ciliary neurotrophic factor and leukemia inhibitory factor expression. Interestingly, RSV-containing diets changed the fate of newborn neurons toward generation of more proopiomelanocortin than neuropeptide Y neurons. The CR had effects similar to those of RSV-containing diets in the all-evaluated aspects besides neurogenesis in ARC.

CONCLUSIONS

Although both RSV-containing and CR diets changed the fate of newborn neurons to create an anorexigenic architecture for ARC, newborn neurons were more available after switching to RSV-enriched diets. It can be consider as a promising mechanism for future investigations.

mTORC1 pathway disruption abrogates the effects of the ciliary neurotrophic factor on energy balance and hypothalamic neuroinflammation

Ciliary neurotrophic factor (CNTF) potently decreases food intake and body weight in diet-induced obese mice by acting through neuronal circuits and pathways located in the arcuate nucleus (ARC) of the hypothalamus. CNTF also exerts pro-inflammatory actions within the brain. Here we tested whether CNTF modifies energy balance by inducing inflammatory responses in the ARC and whether these effects depend upon the mechanistic target of rapamycin complex 1 (mTORC1) pathway, which regulates both energy metabolism and inflammation. To this purpose, chow- and high fat diet (HFD)- fed mice lacking the S6 kinase 1 (S6K1^-/-), a downstream target of mTORC1, and their wild-type (WT) littermates received 12 days continuous intracerebroventricular (icv) infusion of the CNTF analogue axokine (CNTF_Ax15). Behavioral, metabolic and molecular effects were evaluated. Central chronic administration of CNTF_Ax15 decreased body weight and feed efficiency in WT mice only, when fed HFD, but not chow. These metabolic effects correlated with increased number of iba-1 positive microglia specifically in the ARC and were accompanied by significant increases of IL-1β and TNF-α mRNA expression in the hypothalamus. Hypothalamic iNOS and SOCS3 mRNA, molecular markers of pro-inflammatory response, were also increased by CNTF_Ax15. All these changes were absent in S6K1^-/- mice. This study reveals that CNTF_Ax15 requires a functional S6K1 to modulate energy balance and hypothalamic inflammation in a diet-dependent fashion. Further investigations should determine whether S6K1 is a suitable target for the treatment of pathologies characterized by a high neuroinflammatory state.

Effect of human very low-density lipoproteins on cardiotrophin-like cytokine factor 1 (CLCF1) activity

The cytokines CLCF1 and CNTF are ligands for the CNTF receptor and the apolipoprotein E (ApoE) receptor sortilin. Both share structural similarities with the N-terminal domain of ApoE, known to bind CNTF. We therefore evaluated whether ApoE or ApoE-containing lipoproteins interact with CLCF1 and regulate its activity. We observed that CLCF1 forms complexes with the three major isoforms of ApoE in co-immunoprecipitation and proximity assays. FPLC analysis of mouse and human sera mixed with CLCF1 revealed that CLCF1 co-purifies with plasma lipoproteins. Studies with sera from ApoE^-/- mice indicate that ApoE is not required for CLCF1-lipoprotein interactions. VLDL- and LDL-CLCF1 binding was confirmed using proximity and ligand blots assays. CLCF1-induced STAT3 phosphorylation was significantly reduced when the cytokine was complexed with VLDL. Physiological relevance of our findings was asserted in a mouse model of oxygen-induced retinopathy, where the beneficial anti-angiogenic properties of CLCF1 were abrogated when co-administrated with VLDL, indicating, that CLCF1 binds purified lipoproteins or lipoproteins in physiological fluids such as serum and behave as a "lipocytokine". Albeit it is clear that lipoproteins modulate CLCF1 activity, it remains to be determined whether lipoprotein binding directly contributes to its neurotrophic function and its roles in metabolic regulation.

Alleviative effect of ciliary neurotrophic factor analogue on high fat-induced hepatic steatosis is partially independent of the central regulation

Ciliary neurotrophic factor (CNTF) analogues were reported to ameliorate fatty liver in db/db or high-fat diet-fed mice. It is generally thought that CNTF exerts its actions centrally. The aim of this study was to investigate whether peripheral effects of CNTF analogues are involved in the therapeutic effect on high fat-induced hepatic steatosis. The rat model of fatty liver was induced by a high-fat diet (HFD) for 12 weeks. In the next 2 weeks, rats were fed the HFD along with subcutaneous injection of vehicle or mutant recombinant human CNTF (rhmCNTF 0.05-0.2 mg/kg per day). Steatotic HepG2 cells were induced by 50% fetal bovine serum (FBS) for 48 hours, and then treated with rhmCNTF for 24 hours. The results showed that after rhmCNTF treatment, hepatic triglyceride (TG) accumulation was attenuated both in vivo and in vitro. RhmCNTF increased protein expression of CPT-1 and PPARα, and decreased SREBP-1c, FAS and SCD-1 in steatotic HepG2 cells. But the production of nitric oxide and 8-isoPGF_2α in steatotic HepG2 cells was not affected by rhmCNTF. These results suggest that rhmCNTF has a peripheral effect that alleviates fat-induced hepatic steatosis.

In vitro and in vivo characterization of a novel long-acting GLP-1 receptor agonist, exendin-4–Fc fusion protein

Exendin-4 (Ex-4), one of the important glucagon-like peptide-1 receptor (GLP-1R) agonists, has proven to be an effective antidiabetic agent for type 2 diabetes (T2D).

Ciliary neurotrophic factor analogue aggravates CCl4-induced acute hepatic injury in rats

Ciliary neurotrophic factor (CNTF) and CNTF analogs were reported to have hepatoprotective effect and ameliorate hepatic steatosis in db/db or high-fat-diet-fed mice. Because hepatic steatosis and injury are also commonly induced by hepatotoxin, the aim of the present study is to clarify whether CNTF could alleviate hepatic steatosis and injury induced by carbon tetrachloride (CCl₄). Unexpectedly, when combined with CCl₄, CNTF aggravated hepatic steatosis and liver injury. The mechanism is associated with effects of CNTF that inhibited lipoprotein secretion and drastically impaired the ability of lipoproteins to act as transport vehicles for lipids from the liver to the circulation. While injected after CCl₄ cessation, CNTF could improve liver function. These data suggest that CNTF could be a potential hepatoprotective agent against CCl₄-induced hepatic injury after the cessation of CCl₄ exposure. However, it is forbidden to combine recombinant mutant of human CNTF treatment with CCl₄.

High fat induces acute and chronic inflammation in the hypothalamus: effect of high-fat diet, palmitate and TNF-α on appetite-regulating NPY neurons

BACKGROUND

Consumption of dietary fat is one of the key factors leading to obesity. High-fat diet (HFD)-induced obesity is characterized by induction of inflammation in the hypothalamus; however, the temporal regulation of proinflammatory markers and their impact on hypothalamic appetite-regulating neuropeptide Y/agouti-related peptide (NPY/AgRP) neurons remains undefined.

METHODS

Mice were injected with an acute lipid infusion for 24 h or fed a HFD over 8-20 weeks. Characterized mouse NPY/AgRP hypothalamic cell lines were used for in vitro experimentation. Immunohistochemistry in brain slices or quantitative real-time PCR in cell lines, was performed to determine changes in the expression of key inflammatory markers and neuropeptides.

RESULTS

Hypothalamic inflammation, indicated by tumor necrosis factor (TNF)-α expression and astrocytosis in the arcuate nucleus, was evident following acute lipid infusion. HFD for 8 weeks suppressed TNF-α, while significantly increasing heat-shock protein 70 and ciliary neurotrophic factor, both neuroprotective components. HFD for 20 weeks induced TNF-α expression in NPY/AgRP neurons, suggesting a detrimental temporal regulatory mechanism. Using NPY/AgRP hypothalamic cell lines, we found that palmitate provoked a mixed inflammatory response on a panel of inflammatory and endoplasmic reticulum (ER) stress genes, whereas TNF-α significantly upregulated IκBα, nuclear factor (NF)-κB and interleukin-6 mRNA levels. Palmitate and TNF-α exposure predominantly induced NPY mRNA levels. Utilizing an I kappa B kinase β (IKKβ) inhibitor, we demonstrated that these effects potentially occur via the inflammatory IKKβ/NF-κB pathway.

CONCLUSIONS

These findings indicate that acute lipid and chronic HFD feeding in vivo, as well as acute palmitate and TNF-α exposure in vitro, induce markers of inflammation or ER stress in the hypothalamic appetite-stimulating NPY/AgRP neurons over time, which may contribute to a dramatic alteration in NPY/AgRP content or expression. Acute and chronic HFD feeding in vivo temporally regulates arcuate TNF-α expression with reactive astrocytosis, which suggests a time-dependent neurotrophic or neurotoxic role of lipids.

The role of gp130 receptor cytokines in the regulation of metabolic homeostasis

It is well known that obesity is responsible, at least in part, for the increased incidence of chronic diseases such as type 2 diabetes, cardiovascular disease and certain types of cancer. Despite public education programs emphasizing lifestyle modifications to arrest this global pandemic, it is now estimated that 10-15% of the world's population are overweight or obese. As a result, new therapeutic options for the treatment of obesity-related disorders are clearly warranted. Much of the benefit of physical activity has been attributed to several mechanisms including reduced adiposity, increased cardiorespiratory fitness, reduced circulating lipids and the maintenance of muscle mass. However, the observation that the gp130 receptor cytokine interleukin-6 (IL-6) was released from skeletal muscle during exercise to improve metabolic homeostasis altered our understanding of the health benefits of exercise and opened avenues for research into potential novel therapeutics to treat metabolic disease. One gp130 receptor cytokine in particular, ciliary neurotrophic factor (CNTF), a pluripotent neurocytokine, showed efficacy as a potential anti-obesogenic therapy. This review examines the potential of gp130 receptor ligands, with a focus on IL-6 and CNTF as therapeutic strategies to treat obesity-related disorders.

A combination of cytokines EGF and CNTF protects the functional beta cell mass in mice with short-term hyperglycaemia

AIMS/HYPOTHESIS

When the beta cell mass or function declines beyond a critical point, hyperglycaemia arises. Little is known about the potential pathways involved in beta cell rescue. As two cytokines, epidermal growth factor (EGF) and ciliary neurotrophic factor (CNTF), restored a functional beta cell mass in mice with long-term hyperglycaemia by reprogramming acinar cells that transiently expressed neurogenin 3 (NGN3), the current study assesses the effect of these cytokines on the functional beta cell mass after an acute chemical toxic insult.

METHODS

Glycaemia and insulin levels, pro-endocrine gene expression and beta cell origin, as well as the role of signal transducer and activator of transcription 3 (STAT3) signalling, were assessed in EGF+CNTF-treated mice following acute hyperglycaemia.

RESULTS

The mice were hyperglycaemic 1 day following i.v. injection of the beta cell toxin alloxan, when the two cytokines were applied. One week later, 68.6 ± 4.6% of the mice had responded to the cytokine treatment and increased their insulin(+) cell number to 30% that of normoglycaemic control mice, resulting in restoration of euglycaemia. Although insulin(-) NGN3(+) cells appeared following acute EGF+CNTF treatment, genetic lineage tracing showed that the majority of the insulin(+) cells originated from pre-existing beta cells. Beta cell rescue by EGF+CNTF depends on glycaemia rather than on STAT3-induced NGN3 expression in acinar cells.

CONCLUSIONS/INTERPRETATION

In adult mice, EGF+CNTF allows the rescue of beta cells in distress when treatment is given shortly after the diabetogenic insult. The rescued beta cells restore a functional beta cell mass able to control normal blood glucose levels. These findings may provide new insights into compensatory pathways activated early after beta cell loss.

Action of Administered Ciliary Neurotrophic Factor on the Mouse Dorsal Vagal Complex

Ciliary neurotrophic factor (CNTF) induces weight loss in obese rodents and humans through activation of the hypothalamic Jak-STAT (Janus kinase-signal transducer and activator of transcription) signaling pathway. Here, we tested the hypothesis that CNTF also affects the brainstem centers involved in feeding and energy balance regulation. To this end, wild-type and leptin-deficient (ob/ob and db/db) obese mice were acutely treated with intraperitoneal recombinant CNTF. Coronal brainstem sections were processed for immunohistochemical detection of STAT3, STAT1, STAT5 phosphorylation and c-Fos. In wild-type mice, CNTF treatment for 45 min induced STAT3, STAT1, and STAT5 phosphorylation in neurons as well as glial cells of the area postrema; here, the majority of CNTF-responsive cells activated multiple STAT isoforms, and a significant proportion of CNTF-responsive glial cells bore the immaturity and plasticity markers nestin and vimentin. After 120 min CNTF treatment, c-Fos expression was intense in glial cells and weak in neurons of the area postrema, it was intense in several neurons of the rostral and caudal solitary tract nucleus (NTS), and weak in some cholinergic neurons of the dorsal motor nucleus of the vagus. In the ob/ob and db/db mice, Jak-STAT activation and c-Fos expression were similar to those induced in wild-type mouse brainstem. Treatment with CNTF (120 min, to induce c-Fos expression) and leptin (25 min, to induce STAT3 phosphorylation) demonstrated the co-localization of the two transcription factors in a small neuron population in the caudal NTS portion. Finally, weak immunohistochemical CNTF staining, detected in funiculus separans, and meningeal glial cells, matched the modest amount of CNTF found by RT-qPCR in micropunched area postrema tissue, which in contrast exhibited a very high amount of CNTF receptor. Collectively, the present findings show that the area postrema and the NTS exhibit high, distinctive responsiveness to circulating exogenous and, probably, endogenous CNTF.

Neurotrophic factor control of satiety and body weight

Energy balance--that is, the relationship between energy intake and energy expenditure--is regulated by a complex interplay of hormones, brain circuits and peripheral tissues. Leptin is an adipocyte-derived cytokine that suppresses appetite and increases energy expenditure. Ironically, obese individuals have high levels of plasma leptin and are resistant to leptin treatment. Neurotrophic factors, particularly ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF), are also important for the control of body weight. CNTF can overcome leptin resistance in order to reduce body weight, although CNTF and leptin activate similar signalling cascades. Mutations in the gene encoding BDNF lead to insatiable appetite and severe obesity.

n-3 Fatty Acids Induce Neurogenesis of Predominantly POMC-Expressing Cells in the Hypothalamus

Apoptosis of hypothalamic neurons is believed to play an important role in the development and perpetuation of obesity. Similar to the hippocampus, the hypothalamus presents constitutive and stimulated neurogenesis, suggesting that obesity-associated hypothalamic dysfunction can be repaired. Here, we explored the hypothesis that n-3 polyunsaturated fatty acids (PUFAs) induce hypothalamic neurogenesis. Both in the diet and injected directly into the hypothalamus, PUFAs were capable of increasing hypothalamic neurogenesis to levels similar or superior to the effect of brain-derived neurotrophic factor (BDNF). Most of the neurogenic activity induced by PUFAs resulted in increased numbers of proopiomelanocortin but not NPY neurons and was accompanied by increased expression of BDNF and G-protein-coupled receptor 40 (GPR40). The inhibition of GPR40 was capable of reducing the neurogenic effect of a PUFA, while the inhibition of BDNF resulted in the reduction of global hypothalamic cell. Thus, PUFAs emerge as a potential dietary approach to correct obesity-associated hypothalamic neuronal loss.

Central Administration of the Ciliary Neurotrophic Factor Analogue, Axokine, Does Not Play a Role in Long-Term Energy Homeostasis in Adult Mice

BACKGROUND/AIMS

Ciliary neurotrophic factor (CNTF) exerts powerful anorectic effects and has been suggested to regulate long-term energy balance by inducing adult neurogenesis in the arcuate nucleus of the hypothalamus.

METHODS

The CNTF analogue, Axokine, was infused into the lateral ventricle of high-fat-fed mice for 1 week. Food intake, energy expenditure, body mass, glucose metabolism, and neurogenesis in the arcuate nucleus (ARC) of the hypothalamus were assessed 3 weeks after cessation of Axokine treatment.

RESULTS

Short-term administration of Axokine induced an anorexic response but did not promote sustained weight loss. Instead, a rapid rebound in food intake and body mass occurred immediately after cessation of Axokine treatment, and this tended to reduce insulin sensitivity. Immunolabeling of 5-bromo-2'-deoxyuridine revealed limited neurogenesis in the ARC 3 weeks after Axokine treatment.

CONCLUSION

These findings suggest that Axokine/CNTF does not induce substantial or sustained ARC neurogenesis or contribute to the long-term regulation of energy balance in mice.

Genetic basis of interindividual susceptibility to cancer cachexia: selection of potential candidate gene polymorphisms for association studies

Cancer cachexia is a complex and multifactorial disease. Evolving definitions highlight the fact that a diverse range of biological processes contribute to cancer cachexia. Part of the variation in who will and who will not develop cancer cachexia may be genetically determined. As new definitions, classifications and biological targets continue to evolve, there is a need for reappraisal of the literature for future candidate association studies. This review summarizes genes identified or implicated as well as putative candidate genes contributing to cachexia, identified through diverse technology platforms and model systems to further guide association studies. A systematic search covering 1986-2012 was performed for potential candidate genes / genetic polymorphisms relating to cancer cachexia. All candidate genes were reviewed for functional polymorphisms or clinically significant polymorphisms associated with cachexia using the OMIM and GeneRIF databases. Pathway analysis software was used to reveal possible network associations between genes. Functionality of SNPs/genes was explored based on published literature, algorithms for detecting putative deleterious SNPs and interrogating the database for expression of quantitative trait loci (eQTLs). A total of 154 genes associated with cancer cachexia were identified and explored for functional polymorphisms. Of these 154 genes, 119 had a combined total of 281 polymorphisms with functional and/or clinical significance in terms of cachexia associated with them. Of these, 80 polymorphisms (in 51 genes) were replicated in more than one study with 24 polymorphisms found to influence two or more hallmarks of cachexia (i.e., inflammation, loss of fat mass and/or lean mass and reduced survival). Selection of candidate genes and polymorphisms is a key element of multigene study design. The present study provides a contemporary basis to select genes and/or polymorphisms for further association studies in cancer cachexia, and to develop their potential as susceptibility biomarkers of cachexia.

Cardiotrophin-1: A multifaceted cytokine

Cardiotrophin-1 (CT-1) is a member of the gp130 family of cytokines that have pleiotropic functions on different tissues and cell types. Although many effects of CT-1 have been described on the heart, there is an extensive research showing important protective effects in other organs such as liver, kidney or nervous system. Recently, several studies have pointed out that CT-1 might also play a key role in the regulation of body weight and intermediate metabolism. This paper will review many aspects of CT-1 physiological role in several organs and discuss data for consideration in therapeutic approaches.

Ciliary neurotrophic factor (CNTF): New facets of an old molecule for treating neurodegenerative and metabolic syndrome pathologies

Ciliary neurotrophic factor (CNTF) is the most extensively studied member of the cytokine family that signal through intracellular chains of the gp130/LIFRβ receptor. The severe phenotype in patients suffering from mutations inactivating LIFRβ indicates that members of this cytokine family play key, non-redundant roles during development. Accordingly, three decades of research has revealed potent and promising trophic and regulatory activities of CNTF in neurons, oligodendrocytes, muscle cells, bone cells, adipocytes and retinal cells. These findings led to clinical trials to test the therapeutic potential of CNTF and CNTF derivatives for treating neurodegenerative and metabolic diseases. Promising results have encouraged continuation of studies for treating retinal degenerative diseases. Results of some clinical trials showed that side-effects may limit the systemically administrated doses of CNTF. Therefore, therapies being currently tested rely on local delivery of CNTF using encapsulated cytokine-secreting implants. Since the side effects of CNTF might be linked to its ability to activate the alternative IL6Rα-LIFRβ-gp130 receptor, CNTFR-specific mutants of CNTF have been developed that bind to the CNTFRα-LIFRβ-gp130 receptor. These developments may prove to be a breakthrough for therapeutic applications of systemically administered CNTF in pathologies such as multiple sclerosis or Alzheimer's disease. The "designer cytokine approach" offers future opportunities to further enhance specificity by conjugating mutant CNTF with modified soluble CNTFRα to target therapeutically relevant cells that express gp130-LIFRβ and a specific cell surface marker.

Pharmacological Management of the Obese Patient

Being obese goes beyond moral failure or a character flaw. Obesity has the defining characteristics of a chronic disease for which there is no cure. Treatment may require lifelong treatment which may include pharmacotherapy. Experience with long term use of obesity drugs is limited but evidence suggests that pharmacotherapy can improve patient outcomes and patient outlook. With current obesity drugs, weight loss is usually modest but clinically significant satisfying the FDA threshold for drug effectiveness. This weight loss is associated with clinically significant improvements in many obesity co morbidities and risk factors and could eliminate some risk factors with continued use. When used in conjunction with a comprehensive program for weight management, obesity drugs can reduce appetite or hunger, increase satiety, provide improved control over aberrant eating behaviors and modify food seeking behaviors. Pharmacotherapy can enhance weight loss and compliance during the periods of weight loss and in maintaining that weight loss, increasing physical activity and may enhance a focus on making life long changes.

This article will discuss mechanisms of action of obesity drugs, theories of altered body defense of body weight, Food and Drug Administration (FDA) approved obesity drugs, and off-label use of FDA approved drugs. The value of over-the counter (OTC) medications and diet supplements, as well as fat substitutes in the treatment of obesity drugs will be explored. Obesity drugs awaiting FDA approval and compounds under development will be reviewed. The section on approaches to drug management will include clinical considerations for; who should receive pharmacotherapy and when, length of treatment and drug discontinuation, weight regain and the role of pharmacotherapy.

Oncostatin m modulation of lipid storage

Oncostatin M (OSM) is a cytokine belonging to the gp130 family, whose members serve pleiotropic functions. However, several actions of OSM are unique from those of other gp130 cytokines, and these actions may have critical roles in inflammatory mechanisms influencing several metabolic and biological functions of insulin-sensitive tissues. In this review, the actions of OSM in adipose tissue and liver are discussed, with an emphasis on lipid metabolism.

Codon optimization and factorial screening for enhanced soluble expression of human ciliary neurotrophic factor in Escherichia coli

BACKGROUND

Neurotrophic factors influence survival, differentiation, proliferation and death of neuronal cells within the central nervous system. Human ciliary neurotrophic factor (hCNTF) has neuroprotective properties and is also known to influence energy balance. Consequently, hCNTF has potential therapeutic applications in neurodegenerative, obesity and diabetes related disorders. Clinical and biological applications of hCNTF necessitate a recombinant expression system to produce large amounts of functional protein in soluble form. Earlier attempts to express hCNTF in Escherichia coli (E. coli) were limited by low amounts and the need to refold from inclusion bodies.

RESULTS

In this report, we describe a strategy to effectively identify constructs and conditions for soluble expression of hCNTF in E. coli. Small-scale expression screening with soluble fusion tags identified many conditions that yielded soluble expression. Codon optimized 6-His-hCNTF construct showed soluble expression in all the conditions tested. Large-scale culture of the 6-His-hCNTF construct yielded high (10 - 20 fold) soluble expression (8 - 9 fold) as compared to earlier published reports. Functional activity of recombinant 6-His-hCNTF produced was confirmed by its binding to hCNTF receptor (hCNTFRα) with an EC50 = 36 nM.

CONCLUSION

Our results highlight the combination of codon optimization and screening soluble fusion tags as a successful strategy for high yielding soluble expression of hCNTF in E. coli. Codon optimization of the hCNTF sequence seems to be sufficient for soluble expression of hCNTF. The combined approach of codon optimization and soluble fusion tag screen can be an effective strategy for soluble expression of pharmaceutical proteins in E. coli.

Tanycytes: a gateway to the metabolic hypothalamus

The central regulation of energy balance relies on the ability of the brain to promptly and efficiently sense variations of metabolic state. To achieve this, circulating hormonal and metabolic signals have to cross the blood-brain interface, where unusual glial cells named tanycytes have been described to play a key role in this process. Tanycytes are specialised polarised ependymoglial cells that line the floor of the third ventricle and send a single process to contact hypothalamic neurones and blood vessels. Although their role in the regulation of energy balance via the modulation of neuronal activity or their chemosensitivity has been already described, recent studies ascribe a new function to tanycytes in the regulation of energy homeostasis as a result of their capacity to regulate the access of metabolic signals to the hypothalamus. This review discusses the peculiar place of tanycytes within the blood-hypothalamus interface, as well as a striking capacity to remodel their own interface to ensure an adaptive metabolic response to energy imbalances.

Oestradiol and diet modulate energy homeostasis and hypothalamic neurogenesis in the adult female mouse

Leptin and oestradiol have overlapping functions in energy homeostasis and fertility, and receptors for these hormones are localised in the same hypothalamic regions. Although, historically, it was assumed that mammalian adult neurogenesis was confined to the olfactory bulbs and the hippocampus, recent research has found new neurones in the male rodent hypothalamus. Furthermore, some of these new neurones are leptin-sensitive and affected by diet. In the present study, we tested the hypothesis that diet and hormonal status modulate hypothalamic neurogenesis in the adult female mouse. Adult mice were ovariectomised and implanted with capsules containing oestradiol (E2 ) or oil. Within each group, mice were fed a high-fat diet (HFD) or maintained on standard chow (STND). All animals were administered i.c.v. 5-bromo-2'-deoxyuridine (BrdU) for 9 days and sacrificed 34 days later after an injection of leptin to induce phosphorylation of signal transducer of activation and transcription 3 (pSTAT3). Brain tissue was immunohistochemically labelled for BrdU (newly born cells), Hu (neuronal marker) and pSTAT3 (leptin sensitive). Although mice on a HFD became obese, oestradiol protected against obesity. There was a strong interaction between diet and hormone on new cells (BrdU+) in the arcuate, ventromedial hypothalamus and dorsomedial hypothalamus. HFD increased the number of new cells, whereas E2 inhibited this effect. Conversely, E2 increased the number of new cells in mice on a STND diet in all hypothalamic regions studied. Although the total number of new leptin-sensitive neurones (BrdU-Hu-pSTAT3) found in the hypothalamus was low, HFD increased these new cells in the arcuate, whereas E2 attenuated this induction. These results suggest that adult neurogenesis in the hypothalamic neurogenic niche is modulated by diet and hormonal status and is related to energy homeostasis in female mice.

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.

JAK-STAT and feeding

The regulation of energy balance requires a complex system to homeostatically maintain the adult body at a precise set point. The central nervous system, particularly the hypothalamus, plays a key role in integrating a variety of signals that can relay information about the body's energy stores. As part of this system, numerous cytokines and hormones contribute to the regulation of food intake and energy homeostasis. Cytokines, and some hormones, are known to act through JAK-STAT intracellular signaling pathways. The hormone leptin, which plays a vital role in appetite regulation, signals through the JAK-STAT pathway, and it is through this involvement that the JAK-STAT pathway has become an established component in the mechanisms regulating food intake within the body. Emerging research, however, is now showing that this involvement of JAK-STAT is not limited to its activation by leptin. Furthermore, while the JAK-STAT pathway may simply act to transmit the anorectic signal of circulating factors, this intracellular signaling pathway may also become impaired when normal regulation of energy balance is disrupted. Thus, altered JAK-STAT signaling may contribute to the breakdown of the normal homeostatic mechanisms maintaining body weight in obesity.

The amino acid exchange R28E in ciliary neurotrophic factor (CNTF) abrogates interleukin-6 receptor-dependent but retains CNTF receptor-dependent signaling via glycoprotein 130 (gp130)/leukemia inhibitory factor receptor (LIFR)

Ciliary neurotrophic factor (CNTF) is a neurotrophic factor with therapeutic potential for neurodegenerative diseases. Moreover, therapeutic application of CNTF reduced body weight in mice and humans. CNTF binds to high or low affinity receptor complexes consisting of CNTFR·gp130·LIFR or IL-6R·gp130·LIFR, respectively. Clinical studies of the CNTF derivative Axokine revealed intolerance at higher concentrations, which may rely on the low-affinity binding of CNTF to the IL-6R. Here, we aimed to generate a CNTFR-selective CNTF variant (CV). CV-1 contained the single amino acid exchange R28E. Arg(28) is in close proximity to the CNTFR binding site. Using molecular modeling, we hypothesized that Arg(28) might contribute to IL-6R/CNTFR plasticity of CNTF. CV-2 to CV-5 were generated by transferring parts of the CNTFR-binding site from cardiotrophin-like cytokine to CNTF. Cardiotrophin-like cytokine selectively signals via the CNTFR·gp130·LIFR complex, albeit with a much lower affinity compared with CNTF. As shown by immunoprecipitation, all CNTF variants retained the ability to bind to CNTFR. CV-1, CV-2, and CV-5, however, lost the ability to bind to IL-6R. Although all variants induced cytokine-dependent cellular proliferation and STAT3 phosphorylation via CNTFR·gp130·LIFR, only CV-3 induced STAT3 phosphorylation via IL-6R·gp130·LIFR. Quantification of CNTF-dependent proliferation of CNTFR·gp130·LIFR expressing cells indicated that only CV-1 was as biologically active as CNTF. Thus, the CNTFR-selective CV-1 will allow discriminating between CNTFR- and IL-6R-mediated effects in vivo.

Muscle ciliary neurotrophic factor receptor α promotes axonal regeneration and functional recovery following peripheral nerve lesion

Ciliary neurotrophic factor (CNTF) administration maintains, protects, and promotes the regeneration of both motor neurons (MNs) and skeletal muscle in a wide variety of models. Expression of CNTF receptor α (CNTFRα), an essential CNTF receptor component, is greatly increased in skeletal muscle following neuromuscular insult. Together the data suggest that muscle CNTFRα may contribute to neuromuscular maintenance, protection, and/or regeneration in vivo. To directly address the role of muscle CNTFRα, we selectively-depleted it in vivo by using a "floxed" CNTFRα mouse line and a gene construct (mlc1f-Cre) that drives the expression of Cre specifically in skeletal muscle. The resulting mice were challenged with sciatic nerve crush. Counting of nerve axons and retrograde tracing of MNs indicated that muscle CNTFRα contributes to MN axonal regeneration across the lesion site. Walking track analysis indicated that muscle CNTFRα is also required for normal recovery of motor function. However, the same muscle CNTFRα depletion unexpectedly had no detected effect on the maintenance or regeneration of the muscle itself, even though exogenous CNTF has been shown to affect these functions. Similarly, MN survival and lesion-induced terminal sprouting were unaffected. Therefore, muscle CNTFRα is an interesting new example of a muscle growth factor receptor that, in vivo under physiological conditions, contributes much more to neuronal regeneration than to the maintenance or regeneration of the muscle itself. This novel form of muscle-neuron interaction also has implications in the therapeutic targeting of the neuromuscular system in MN disorders and following nerve injury. J. Comp. Neurol. 521: 2947-2965, 2013. © 2013 Wiley Periodicals, Inc.

Oncostatin m is produced in adipose tissue and is regulated in conditions of obesity and type 2 diabetes

CONTEXT

Adipose tissue is a highly active endocrine organ that secretes many factors that affect other tissues and whole-body metabolism. Adipocytes are responsive to several glycoprotein 130 (gp130) cytokines, some of which have been targeted as potential antiobesity therapeutics.

OBJECTIVE

Oncostatin M (OSM) is a gp130 family member known to inhibit adipocyte differentiation in vitro, but its effects on other adipocyte properties are not characterized. The expression of OSM in white adipose tissue (WAT) has not been evaluated in the context of obesity. Thus, our objective was to examine the expression of adipose tissue OSM in obese animals and humans.

DESIGN

OSM expression was examined in adipose tissues from mice with diet-induced and genetic obesity and in obese humans as well as in fractionated adipose tissue from mice. Murine adipocytes were used to examine OSM receptor expression and the effects of OSM on adipocytes, including the secretion of factors such as plasminogen activator inhibitor 1 and IL-6, which are implicated in metabolic diseases.

RESULTS

OSM expression is increased in rodent and human obesity/type 2 diabetes mellitus. In humans, OSM levels correlate with body weight and insulin and are inversely correlated with glucose disposal rate as measured by hyperinsulinemic-euglycemic clamp. OSM is not produced from the adipocytes in WAT but derives from cells in the stromovascular fraction, including F4/80(+) macrophages. The specific receptor of OSM, OSM receptor-β, is expressed in adipocytes and adipose tissue and increased in both rodent models of obesity examined. OSM acts on adipocytes to induce the expression and secretion of plasminogen activator inhibitor 1 and IL-6.

CONCLUSIONS

These data indicate that WAT macrophages are a source of OSM and that OSM levels are significantly induced in murine and human obesity/type 2 diabetes mellitus. These studies suggest that OSM produced from immune cells in WAT acts in a paracrine manner on adipocytes to promote a proinflammatory phenotype in adipose tissue.

Improved metabolic phenotype of hypothalamic PTP1B-deficiency is dependent upon the leptin receptor

Protein tyrosine phosphatase 1B (PTP1B) is a known regulator of central metabolic signaling, and mice with whole brain-, leptin receptor (LepRb) expressing cell-, or proopiomelanocortin neuron-specific PTP1B-deficiency are lean, leptin hypersensitive, and display improved glucose homeostasis. However, whether the metabolic effects of central PTP1B-deficiency are due to action within the hypothalamus remains unclear. Moreover, whether or not these effects are exclusively due to enhanced leptin signaling is unknown. Here we report that mice with hypothalamic PTP1B-deficiency (Nkx2.1-PTP1B(-/-)) display decreased body weight and adiposity on high-fat diet with no associated improvements in glucose tolerance. Consistent with previous reports, we find that hypothalamic deletion of the LepRb in mice (Nkx2.1-LepRb(-/-)) results in extreme hyperphagia and obesity. Interestingly, deletion of hypothalamic PTP1B and LepRb (Nkx2.1-PTP1B(-/-):LepRb(-/-)) does not rescue the hyperphagia or obesity of Nkx2.1-LepRb(-/-) mice, suggesting that hypothalamic PTP1B contributes to the central control of energy balance through a leptin receptor-dependent pathway.

Transient cytokine treatment induces acinar cell reprogramming and regenerates functional beta cell mass in diabetic mice

Reprogramming of pancreatic exocrine cells into cells resembling beta cells may provide a strategy for treating diabetes. Here we show that transient administration of epidermal growth factor and ciliary neurotrophic factor to adult mice with chronic hyperglycemia efficiently stimulates the conversion of terminally differentiated acinar cells to beta-like cells. Newly generated beta-like cells are epigenetically reprogrammed, functional and glucose responsive, and they reinstate normal glycemic control for up to 248 d. The regenerative process depends on Stat3 signaling and requires a threshold number of Neurogenin 3 (Ngn3)-expressing acinar cells. In contrast to previous work demonstrating in vivo conversion of acinar cells to beta-like cells by viral delivery of exogenous transcription factors, our approach achieves acinar-to-beta-cell reprogramming through transient cytokine exposure rather than genetic modification.