A Single-Scan Ultraselective Heteronuclear Polarization Transfer Method for Unambiguous Complex Structure Assignment.

Complex nuclear magnetic resonance (NMR) signals of organic compounds containing multiple analogous substructures or mixtures pose a significant challenge to structural identification, thus resulting in frequent misassignment of structures. The GEMSTONE method, a single-scan technique that selectively excites a specific proton signal among the crowded NMR signals, was recently proposed as a solution. However, its extension to the polarization transfer method for heteronuclear spin systems was unsuccessful. Herein, we present an extension method that addresses the altered heteronuclear polarization transfer efficiency and enables the acquisition of ultraselective 13 C and 1 H-13 C correlation NMR subspectra with hertz-level signal selectivity in both dimensions. We demonstrate the effectiveness of this technique in the structural analysis of a chromopeptide pharmaceutical and a diastereomeric mixture of a fungicide.

Volume Doubling Times of Pulmonary Metastases in Patients With Bone and Soft-Tissue Sarcomas: Associations With Subsequent New Metastases and Survival After Metastasectomy.

BACKGROUND. Pulmonary metastases of bone and soft-tissue sarcoma are common and have a high recurrence rate after metastasectomy. Factors associated with postmetastasectomy recurrence are not well studied. OBJECTIVE. The purpose of this study was to investigate the association of the volume doubling time (VDT) of pulmonary metastases with the subsequent development of new pulmonary nodules and survival after metastasectomy in patients with bone or soft-tissue sarcoma. METHODS. This retrospective study included patients with bone or soft-tissue sarcoma who, between January 2010 and December 2020, underwent first complete metastasectomy of pulmonary nodules visualized on two sequential preoperative CT scans. Semiautomatic volumetric segmentation of the pulmonary metastases was performed on the two CT scans, and VDTs were calculated. VDT was compared between patients with and without subsequent new metastases after metastasectomy. Cox proportional hazards regression analyses were performed to determine risk factors for recurrence-free survival (RFS) after metastasectomy and for postmetastasectomy overall survival (OS). RESULTS. Forty patients (21 women, 19 men; mean age, 51.1 ± 14.3 [SD] years) were included. Of these patients, 23 (57.5%) developed new metastatic nodules after metastasectomy, and 10 (25.0%) died during follow-up. Median VDT was shorter in patients with, versus those without, new metastases after metastasectomy (56 vs 140 days, p = .002). Only four of 23 patients with new metastases had VDT of 140 days or more. In multivariable analysis, older age (hazard ratio [HR], 1.06; p = .004), female sex (HR, 2.80; p = .03), and VDT less than 140 days (HR, 4.22; p = .01) were independent predictors of worse RFS. Also in multivariable analysis, only older age (HR, 1.17; p = .005) and VDT less than 50 days (HR, 8.60; p = .02) were independent predictors of worse OS. OS was significantly worse in patients with VDT less than 140 days (10 deaths among 27 patients) than in patients with VDT of 140 days or more (no deaths in 13 patients) (p = .01). CONCLUSION. In patients with bone and soft-tissue sarcoma, shorter VDT of pulmonary metastases is independently associated with subsequent new metastases after metastasectomy and worse OS. CLINICAL IMPACT. VDT of pulmonary nodules may be considered in patient selection for pulmonary metastasectomy and in postoperative patient management.

Effective Model Update for Adaptive Classification of Text Streams in a Distributed Learning Environment.

In this study, we propose dynamic model update methods for the adaptive classification model of text streams in a distributed learning environment. In particular, we present two model update strategies: (1) the entire model update and (2) the partial model update. The former aims to maximize the model accuracy by periodically rebuilding the model based on the accumulated datasets including recent datasets. Its learning time incrementally increases as the datasets increase, but we alleviate the learning overhead by the distributed learning of the model. The latter fine-tunes the model only with a limited number of recent datasets, noting that the data streams are dependent on a recent event. Therefore, it accelerates the learning speed while maintaining a certain level of accuracy. To verify the proposed update strategies, we extensively apply them to not only fully trainable language models based on CNN, RNN, and Bi-LSTM, but also a pre-trained embedding model based on BERT. Through extensive experiments using two real tweet streaming datasets, we show that the entire model update improves the classification accuracy of the pre-trained offline model; the partial model update also improves it, which shows comparable accuracy with the entire model update, while significantly increasing the learning speed. We also validate the scalability of the proposed distributed learning architecture by showing that the model learning and inference time decrease as the number of worker nodes increases.

Prunetin 4'-O-Phosphate, a Novel Compound, in RAW 264.7 Macrophages Exerts Anti-Inflammatory Activity via Suppression of MAP Kinases and the NFκB Pathway.

Biorenovation, a microbial enzyme-assisted degradation process of precursor compounds, is an effective approach to unraveling the potential bioactive properties of the derived compounds. In this study, we obtained a new compound, prunetin 4'-O-phosphate (P4P), through the biorenovation of prunetin (PRN), and investigated its anti-inflammatory effects in lipopolysaccharide (LPS)-treated RAW 264.7 macrophage cells. The anti-inflammatory effect of P4P was evaluated by measuring the production of prostaglandin-E2 (PGE2), nitric oxide (NO), which is an inflammation-inducing factor, and related cytokines such as tumor necrosis factor-α (TNFα), interleukin-1ß (IL1ß), and interleukin-6 (IL6). The findings demonstrated that P4P was non-toxic to cells, and its inhibition of the secretion of NO-as well as pro-inflammatory cytokines-was concentration-dependent. A simultaneous reduction in the protein expression level of pro-inflammatory proteins such as cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) was observed. Moreover, the phosphorylation of mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinase (JNK), p38 MAPK (p38), and nuclear factor kappa B (NFκB) was downregulated. To conclude, we report that biorenovation-based phosphorylation of PRN improved its anti-inflammatory activity. Cell-based in vitro assays further confirmed that P4P could be applied in the development of anti-inflammatory therapeutics.

Luteolin-3'-O-Phosphate Inhibits Lipopolysaccharide-Induced Inflammatory Responses by Regulating NF-κB/MAPK Cascade Signaling in RAW 264.7 Cells.

Luteolin (LT), present in most plants, has potent anti-inflammatory properties both in vitro and in vivo. Furthermore, some of its derivatives, such as luteolin-7-O-glucoside, also exhibit anti-inflammatory activity. However, the molecular mechanisms underlying luteolin-3'-O-phosphate (LTP)-mediated immune regulation are not fully understood. In this paper, we compared the anti-inflammatory properties of LT and LTP and analyzed their molecular mechanisms of action; we obtained LTP via the biorenovation of LT. We investigated the anti-inflammatory activities of LT and LTP in macrophage RAW 264.7 cells. We confirmed from previously reported literature that LT inhibits the production of nitric oxide and prostaglandin E2, as well as the expression of inducible NO synthetase and cyclooxygenase-2. In addition, expressions of inflammatory genes and mediators, such as tumor necrosis factor-α, interleukin-6, and interleukin-1ß, were suppressed. LTP showed anti-inflammatory activity similar to LT, but better anti-inflammatory activity in all the experiments, while also inhibiting mitogen-activated protein kinase and nuclear factor-kappa B more effectively than LT. At a concentration of 10 µM, LTP showed differences of 2.1 to 44.5% in the activity compared to LT; it also showed higher anti-inflammatory activity. Our findings suggest that LTP has stronger anti-inflammatory activity than LT.

Cellular source of hypothalamic macrophage accumulation in diet-induced obesity.

BACKGROUND: Obese mice on a high-fat diet (HFD) display signs of inflammation in the hypothalamic arcuate nucleus (ARC), a critical area for controlling systemic energy metabolism. This has been suggested as a key mechanism of obesity-associated hypothalamic dysfunction. We reported earlier that bone marrow-derived macrophages accumulate in the ARC to sustain hypothalamic inflammation upon chronic exposure to an HFD. However, the mechanism underlying hypothalamic macrophage accumulation has remained unclear. METHODS: We investigated whether circulating monocytes or myeloid precursors contribute to hypothalamic macrophage expansion during chronic HFD feeding. To trace circulating myeloid cells, we generated mice that express green fluorescent protein (GFP) in their lysozyme M-expressing myeloid cells (LysMGFP mice). We conducted parabiosis and bone marrow transplantation experiments using these animals. Mice received an HFD for 12 or 30 weeks and were then sacrificed to analyze LysMGFP cells in the hypothalamus. Hypothalamic vascular permeability in the HFD-fed obese mice was also tested by examining the extravascular leakage of Evans blue and fluorescence-labeled albumin. The timing of LysMGFP cell entry to the hypothalamus during development was also evaluated. RESULTS: Our parabiosis and bone marrow transplantation experiments revealed a significant infiltration of circulating LysMGFP cells into the liver, skeletal muscle, choroid plexus, and leptomeninges but not in the hypothalamic ARC during chronic HFD feeding, despite increased hypothalamic vascular permeability. These results suggested that the recruitment of circulating monocytes is not a major mechanism for maintaining and expanding the hypothalamic macrophage population in diet-induced obesity. We demonstrated instead that LysMGFP cells infiltrate the hypothalamus during its development. LysMGFP cells appeared in the hypothalamic area from the late embryonic period. This cellular pool suddenly increased immediately after birth, peaked at the postnatal second week, and adopted an adult pattern of distribution after weaning. CONCLUSIONS: Bone marrow-derived macrophages mostly populate the hypothalamus in early postnatal life and may maintain their pool without significant recruitment of circulating monocytes throughout life, even under conditions of chronic HFD feeding.

Fibroblast growth factor 21 deficiency aggravates obesity-induced hypothalamic inflammation and impairs thermogenic response.

OBJECTIVE AND DESIGN: Hypothalamic inflammation is closely associated with metabolic dysregulation. Fibroblast growth factor 21 (FGF21) is known to be an important metabolic regulator with anti-inflammatory properties. In this study, we investigated the effects of FGF21 deficiency on obesity-induced hypothalamic inflammation and thermogenic responses. MATERIALS AND METHODS: FGF21-deficient mice and/or wild-type (WT) mice were fed a high-fat diet (HFD) for 12 weeks. RESULTS: FGF21-deficient mice fed an HFD showed increased levels of inflammatory cytokines compared with WT obese control, and this was accompanied by upregulation of gliosis markers in the hypothalamus. Expression of heat-shock protein 72, a marker of neuronal damage, was increased in the FGF21-deficient obese mice, and the expression of hypothalamic neuronal markers involved in anti-thermogenic or thermogenic responses was altered. Moreover, the protein level of uncoupling protein 1 and other thermogenic genes were markedly reduced in the brown adipose tissue of the FGF21-deficient obese mice. CONCLUSIONS: These findings suggest that FGF21 deficiency aggravates obesity-induced hypothalamic inflammation and neuronal injury, leading to alterations in hypothalamic neural circuits accompanied by a reduction of the thermogenic response.

A Novel Thiophene-Based Fluorescent Chemosensor for the Detection of Zn2+ and CN-: Imaging Applications in Live Cells and Zebrafish.

A novel fluorescent turn-on chemosensor DHADC ((E)-3-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2,3-dihydrothiophene-2-carboxamide) has been developed and used to detect Zn2+ and CN-. Compound DHADC displayed a notable fluorescence increase with Zn2+. The limit of detection (2.55 ± 0.05 µM) for zinc ion was far below the standard (76 µM) of the WHO (World Health Organization). In particular, compound DHADC could be applied to determine Zn2+ in real samples, and to image Zn2+ in both HeLa cells and zebrafish. Additionally, DHADC could detect CN- through a fluorescence enhancement with little inhibition with the existence of other types of anions. The detection processes of compound DHADC for Zn2+ and CN- were demonstrated with various analytical methods like Job plots, 1H NMR titrations, and ESI-Mass analyses.

Anti-Inflammatory Effects of Formononetin 7-O-phosphate, a Novel Biorenovation Product, on LPS-Stimulated RAW 264.7 Macrophage Cells.

Biorenovation is a microbial enzyme-catalyzed structural modification of organic compounds with the potential benefits of reduced toxicity and improved biological properties relative to their precursor compounds. In this study, we synthesized a novel compound verified as formononetin 7-O-phosphate (FMP) from formononetin (FM) using microbial biotransformation. We further compared the anti-inflammatory properties of FMP to FM in lipopolysaccharide (LPS)-treated RAW264.7 macrophage cells. We observed that cell viabilities and inhibitory effects on LPS-induced nitric oxide (NO) production were greater in FMP-treated RAW 264.7 cells than in their FM-treated counterparts. In addition, FMP treatment suppressed the production of proinflammatory cytokines such as prostaglandin-E2 (PGE2), interleukin-6 (IL-6), and interleukin-1ß (IL-1ß) in a dose-dependent manner and concomitantly decreased the mRNA expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2). We also found that FMP exerted its anti-inflammatory effects through the downregulation of the extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and nuclear factor kappa B (NF-κB) signaling pathways. In conclusion, we generated a novel anti-inflammatory compound using biorenovation and demonstrated its efficacy in cell-based in vitro assays.

The lipopolysaccharide core oligosaccharide of Burkholderia plays a critical role in maintaining a proper gut symbiosis with the bean bug Riptortus pedestris.

Lipopolysaccharide, the outer cell-wall component of Gram-negative bacteria, has been shown to be important for symbiotic associations. We recently reported that the lipopolysaccharide O-antigen of Burkholderia enhances the initial colonization of the midgut of the bean bug, Riptortus pedestris However, the midgut-colonizing Burkholderia symbionts lack the O-antigen but display the core oligosaccharide on the cell surface. In this study, we investigated the role of the core oligosaccharide, which directly interacts with the host midgut, in the Riptortus-Burkholderia symbiosis. To this end, we generated the core oligosaccharide mutant strains, ΔwabS, ΔwabO, ΔwaaF, and ΔwaaC, and determined the chemical structures of their oligosaccharides, which exhibited different compositions. The symbiotic properties of these mutant strains were compared with those of the wild-type and O-antigen-deficient ΔwbiG strains. Upon introduction into Riptortus via the oral route, the core oligosaccharide mutant strains exhibited different rates of colonization of the insect midgut. The symbiont titers in fifth-instar insects revealed significantly reduced population sizes of the inner core oligosaccharide mutant strains ΔwaaF and ΔwaaC These two strains also negatively affected host growth rate and fitness. Furthermore, R. pedestris individuals colonized with the ΔwaaF and ΔwaaC strains were vulnerable to septic bacterial challenge, similar to insects without a Burkholderia symbiont. Taken together, these results suggest that the core oligosaccharide from Burkholderia symbionts plays a critical role in maintaining a proper symbiont population and in supporting the beneficial effects of the symbiont on its host in the Riptortus-Burkholderia symbiosis.

Meal-related oscillations in the serum serotonin levels in healthy young men.

CONTEXT: Serotonin acts as a neurotransmitter in the central and enteric nervous systems, modulating psychological, metabolic and gastrointestinal functions. Serotonin is also found in the serum or plasma, indicating its potential role as a hormone. OBJECTIVE: We aimed to assess the 24-hour diurnal profile of serum serotonin in relation to meal ingestion in healthy adult men. METHODS: Ten healthy (5 lean and 5 obese) male subjects were enrolled in this study. Blood samples were drawn every 30-60 minutes throughout a 24-hour period to determine the serotonin levels. Three meals were provided on a fixed schedule. To confirm the effect of meal intake on serum serotonin levels, 4 subjects underwent fasting until 1500 h and were then provided a meal without notice. RESULTS: Serum serotonin levels had distinct diurnal variations, with the highest levels early in the morning and the lowest levels in the midafternoon and during sleep. Notably, these diurnal oscillations were markedly reduced in obese subjects. Fluctuations in serum serotonin levels were associated with meal intake, and the levels peaked 30 minutes before meals and exhibited a trough during the postprandial period. Fasting blunted the meal-related oscillations in serum serotonin levels. Moreover, unexpected meal intake did not lead to a premeal increase in serum serotonin levels. CONCLUSIONS: Serum serotonin levels displayed meal-related diurnal oscillations, which were disrupted by fasting and obesity. These findings suggest the possibility that circulating serotonin modulates metabolic function in humans.

Angiopoietin-like peptide 4 regulates insulin secretion and islet morphology.

Insulin secretion from pancreatic islet ß-cells is primarily regulated by the blood glucose level, and also modulated by a number of biological factors produced inside the islets or released from remote organs. Previous studies have shown that angiopoietin-like protein 4 (Angptl4) controls glucose and lipid metabolism through its actions in the liver, adipose tissue, and skeletal muscles. In this present study, we investigated the possible role of Angptl4 in the regulation of insulin secretion from pancreatic islets. Angptl4 was found to be highly expressed in the α-cells but not ß-cells of rodent islets. Moreover, treatment of rodent islets with Angptl4 peptide potentiated glucose-stimulated insulin secretion through a protein kinase A-dependent mechanism. Consistently, Angptl4 knockout mice showed impaired glucose tolerance. In the cultured islets from Angptl4 knockout mice, glucose-stimulated insulin secretion was significantly lower than in islets from wild type mice. Angptl4 peptide replacement partially reversed this reduction. Moreover, Angptl4 knockout mice had dysmorphic islets with abnormally distributed α-cells. In contrast, the ß-cell mass and distribution were not significantly altered in these knockout mice. Our current data collectively suggest that Angptl4 may play a critical role in the regulation of insulin secretion and islet morphogenesis.

NERP-2 regulates gastric acid secretion and gastric emptying via the orexin pathway.

Neuroendocrine regulatory peptide (NERP)-2 is derived from a distinct region of VGF, a neurosecretory protein originally identified as a product of a nerve growth factor-responsive gene in rat PC12 cells. Colocalization of NERP-2 with orexin-A in the lateral hypothalamus increases orexin-A-induced feeding and energy expenditure in both rats and mice. Orexigenic and anorectic peptides in the hypothalamus modulate gastric function. In this study, we investigated the effect of NERP-2 on gastric function in rats. Intracerebroventricular administration of NERP-2 to rats increased gastric acid secretion and gastric emptying, whereas peripheral administration did not affect gastric function. NERP-2-induced gastric acid secretion and gastric emptying were blocked by an orexin 1 receptor antagonist, SB334867. NERP-2 also induced Fos expression in the lateral hypothalamus and the dorsomotor nucleus of the vagus X, which are key sites in the central nervous system for regulation of gastric function. Atropine, a blocker of vagal efferent signal transduction, completely blocked NERP-2-induced gastric acid secretion. These results demonstrate that central administration of NERP-2 activates the orexin pathway, resulting in elevated gastric acid secretion and gastric emptying.

Impact of diabetes duration and degree of carotid artery stenosis on major adverse cardiovascular events: a single-center, retrospective, observational cohort study.

BACKGROUND: We aimed to investigate the impact of diabetes duration and carotid artery stenosis (CAS) on the occurrence of major adverse cardiovascular events (MACE) in patients with type 2 diabetes mellitus (T2DM) without clinical cardiovascular disease. METHODS: A total of 2006 patients with T2DM, without clinical cardiovascular disease, aged >50 years, and who underwent baseline carotid Doppler ultrasound screening with regular follow-ups at the outpatient clinic of our diabetes center, were stratified into four subgroups according to diabetes duration and CAS degree. The primary outcomes included the occurrence of MACE, defined as fatal or nonfatal stroke and myocardial infarction, and all-cause mortality. RESULTS: The difference in the MACE incidence was significantly greater in patients with a longer diabetes duration (≥10 years) and significant CAS (50-69% luminal narrowing) (p < 0.001). Analysis of individual MACE components indicated a trend towards an increased incidence of stroke (p < 0.001), parallel to a longer diabetes duration and significant CAS. In contrast, the risk of myocardial infarction was significantly higher in patients with a diabetes duration <10 years and significant CAS (p = 0.039). Multivariate regression analysis showed that patients with both a longer diabetes duration and significant CAS demonstrated additive and very high risks of MACE (hazard ratio [HR], 2.07; 95% confidence interval [CI] 1.17-3.66; p = 0.012) and stroke (HR, 3.38; 95% CI 1.54-7.44; p = 0.002). CONCLUSIONS: The risk of MACE is significantly greater in patients with T2DM, without clinical cardiovascular disease, who have both a longer diabetes duration and significant CAS, compared with those who have a shorter duration and/or nonsignificant CAS.

Hypofractionated stereotactic radiosurgery for pituitary metastases.

Pituitary metastases (PMs) are uncommon, representing only 1% of pituitary lesions. The diagnosis of PMs can be challenging and an optimal management remains to be determined. Here, we present a pilot clinical study on the efficacy and safety of hypofractionated stereotactic radiosurgery (SRS) with an optimized dosimetric plan in treating PMs. Between June 2013 and December 2014, seven consecutive patients (4 men and 3 women; median age 62 years) had been diagnosed with PMs based on their characteristic clinical and radiological features and subsequently treated using hypofractionated SRS. Primary cancers originated from the lung (n = 5) or the breast (n = 2). All patients presented with diabetes insipidus (DI). Anterior pituitary and visual dysfunction were combined in 4 and 3 patients, respectively. On magnetic resonance imaging (MRI), PMs involved the pituitary stalk and/or the posterior lobe in all patients. SRS of a cumulative marginal dose 31 Gy with dose-volume constraints for the optic apparatus was delivered in 5 daily fractions. As results, tumor was locally controlled in all patients with substantial responses on MRI (including complete remission in 4 patients). The median survival time was 14 months (range, 6-24 months) after SRS. DI and visual dysfunction improved in all patients, although anterior pituitary dysfunction did not recover. No patients experienced any deterioration in visual, pituitary, or other cranial nerve functions. These results suggest a promising role of hypofractionated SRS in treating PMs in terms of both tumor control and functional outcomes.

A new Schiff-base chemosensor for selective detection of Cu2+ and Co2+ and its copper complex for colorimetric sensing of S2- in aqueous solution.

A new Schiff-base colorimetric chemosensor 1 was developed for the detection of Cu2+, Co2+ and S2-. Sensor 1 could simply monitor Cu2+ and Co2+ by a color change from colorless to yellow. The binding modes of 1 to Cu2+ and Co2+ were determined to be a 2 : 1 complexation stoichiometry through Job's plot and ESI-mass spectrometry analysis. The detection limits (0.02 µM and 0.63 µM) for Cu2+ and Co2+ were lower than the recommended values (31.5 µM and 1.7 µM) by the World Health Organization (WHO) for Cu2+ and the Environmental Protection Agency (EPA) for Co2+, respectively. Importantly, 1 could detect and quantify Cu2+ in real water samples. In addition, the Cu2+-2·1 complex could be used as a highly selective colorimetric sensor for S2- in the presence of other anions without any interference. Moreover, the sensing mechanisms of Cu2+ and Co2+ by 1 were explained by theoretical calculations.

A Colorimetric and Fluorescent Chemosensor for the Selective Detection of Cu2+ and Zn2+ Ions.

A new bi-functional chemosensor 1 based on 3,5-dichlorosalicylaldehyde and 2-(methylthio)aniline has been synthesized. It can detect Cu2+ with a color change from pale yellow to dark yellow in aqueous solution. The selective mechanism of 1 for Cu2+ was proposed to be the enhancement of the intramolecular charge transfer (ICT) band, which was explained by theoretical calculations. The sensor 1 could be used to detect and quantify Cu2+ in water samples. In addition, the sensor 1 displayed "turn-on" fluorescence response only to Zn2+, based on an effect of chelation-enhanced fluorescence (CHEF). Therefore, 1 can serve as a 'single sensor for two different targets' with dual modes.

Leptin signalling pathways in hypothalamic neurons.

Leptin is the most critical hormone in the homeostatic regulation of energy balance among those so far discovered. Leptin primarily acts on the neurons of the mediobasal part of hypothalamus to regulate food intake, thermogenesis, and the blood glucose level. In the hypothalamic neurons, leptin binding to the long form leptin receptors on the plasma membrane initiates multiple signaling cascades. The signaling pathways known to mediate the actions of leptin include JAK-STAT signaling, PI3K-Akt-FoxO1 signaling, SHP2-ERK signaling, AMPK signaling, and mTOR-S6K signaling. Recent evidence suggests that leptin signaling in hypothalamic neurons is also linked to primary cilia function. On the other hand, signaling molecules/pathways mitigating leptin actions in hypothalamic neurons have been extensively investigated in an effort to treat leptin resistance observed in obesity. These include SOCS3, tyrosine phosphatase PTP1B, and inflammatory signaling pathways such as IKK-NFκB and JNK signaling, and ER stress-mitochondrial signaling. In this review, we discuss leptin signaling pathways in the hypothalamus, with a particular focus on the most recently discovered pathways.

Leptin Elongates Hypothalamic Neuronal Cilia via Transcriptional Regulation and Actin Destabilization.

Terminally differentiated neurons have a single, primary cilium. The primary cilia of hypothalamic neurons play a critical role in sensing metabolic signals. We recently showed that mice with leptin deficiency or resistance have shorter cilia in the hypothalamic neurons, and leptin treatment elongates cilia in hypothalamic neurons. Here, we investigated the molecular mechanisms by which leptin controls ciliary length in hypothalamic neurons. In N1 hypothalamic neuronal cells, leptin treatment increased the expression of intraflagellar transport proteins. These effects occurred via phosphatase and tensin homolog/glycogen synthase kinase-3ß-mediated inhibition of the transcriptional factor RFX1. Actin filament dynamics were also involved in leptin-promoted ciliary elongation. Both leptin and cytochalasin-D treatment induced F-actin disruption and cilium elongation in hypothalamic neurons that was completely abrogated by co-treatment with the F-actin polymerizer phalloidin. Our findings suggest that leptin elongates hypothalamic neuronal cilia by stimulating the production of intraflagellar transport proteins and destabilizing actin filaments.

Clusterin/ApoJ enhances central leptin signaling through Lrp2-mediated endocytosis.

Hypothalamic leptin signaling plays a central role in maintaining body weight homeostasis. Here, we show that clusterin/ApoJ, recently identified as an anorexigenic neuropeptide, is an important regulator in the hypothalamic leptin signaling pathway. Coadministration of clusterin potentiates the anorexigenic effect of leptin and boosts leptin-induced hypothalamic Stat3 activation. In cultured neurons, clusterin enhances receptor binding and subsequent endocytosis of leptin. These effects are mainly mediated through the LDL receptor-related protein-2 (Lrp2). Notably, inhibition of hypothalamic clusterin, Lrp2 or endocytosis abrogates anorexia and hypothalamic Stat3 activation caused by leptin. These findings propose a novel regulatory mechanism in central leptin signaling pathways.