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Cell Reports Dec 2023Mismatch between CO production (Vco) and respiration underlies the pathogenesis of obesity hypoventilation. Leptin-mediated CNS pathways stimulate both metabolism and...
Mismatch between CO production (Vco) and respiration underlies the pathogenesis of obesity hypoventilation. Leptin-mediated CNS pathways stimulate both metabolism and breathing, but interactions between these functions remain elusive. We hypothesized that LEPR+ neurons of the dorsomedial hypothalamus (DMH) regulate metabolism and breathing in obesity. In diet-induced obese LeprCre mice, chemogenetic activation of LEPR+ DMH neurons increases minute ventilation (Ve) during sleep, the hypercapnic ventilatory response, Vco, and Ve/Vco, indicating that breathing is stimulated out of proportion to metabolism. The effects of chemogenetic activation are abolished by a serotonin blocker. Optogenetic stimulation of the LEPR+ DMH neurons evokes excitatory postsynaptic currents in downstream serotonergic neurons of the dorsal raphe (DR). Administration of retrograde AAV harboring Cre-dependent caspase to the DR deletes LEPR+ DMH neurons and abolishes metabolic and respiratory responses to leptin. These findings indicate that LEPR+ DMH neurons match breathing to metabolism through serotonergic pathways to prevent obesity-induced hypoventilation.
Topics: Mice; Animals; Leptin; Hypoventilation; Obesity; Respiration; Hypothalamus; Receptors, Leptin
PubMed: 38039129
DOI: 10.1016/j.celrep.2023.113512 -
Cell Metabolism Jul 2021Knowledge of how leptin receptor (LepR) neurons of the mediobasal hypothalamus (MBH) access circulating leptin is still rudimentary. Employing intravital microscopy, we...
Knowledge of how leptin receptor (LepR) neurons of the mediobasal hypothalamus (MBH) access circulating leptin is still rudimentary. Employing intravital microscopy, we found that almost half of the blood-vessel-enwrapping pericytes in the MBH express LepR. Selective disruption of pericytic LepR led to increased food intake, increased fat mass, and loss of leptin-dependent signaling in nearby LepR neurons. When delivered intravenously, fluorescently tagged leptin accumulated at hypothalamic LepR pericytes, which was attenuated upon pericyte-specific LepR loss. Because a paracellular tracer was also preferentially retained at LepR pericytes, we pharmacologically targeted regulators of inter-endothelial junction tightness and found that they affect LepR neuronal signaling and food intake. Optical imaging in MBH slices revealed a long-lasting, tonic calcium increase in LepR pericytes in response to leptin, suggesting pericytic contraction and vessel constriction. Together, our data indicate that LepR pericytes facilitate localized, paracellular blood-brain barrier leaks, enabling MBH LepR neurons to access circulating leptin.
Topics: Animals; Appetite Regulation; Feeding Behavior; Female; Hypothalamus; Leptin; Male; Mice; Mice, Transgenic; Neurons; Pericytes; Receptors, Leptin; Signal Transduction
PubMed: 34129812
DOI: 10.1016/j.cmet.2021.05.017 -
PloS One 2022Abnormally high serum homocysteine levels have been associated with several disorders, including obesity, cardiovascular diseases or neurological diseases. Leptin is an...
Abnormally high serum homocysteine levels have been associated with several disorders, including obesity, cardiovascular diseases or neurological diseases. Leptin is an anti-obesity protein and its action is mainly mediated by the activation of its Ob-R receptor in neuronal cells. The inability of leptin to induce activation of its specific signaling pathways, especially under endoplasmic reticulum stress, leads to the leptin resistance observed in obesity. The present study examined the effect of homocysteine on leptin signaling in SH-SY5Y neuroblastoma cells expressing the leptin receptor Ob-Rb. Phosphorylation of the signal transducer and activator of transcription (STAT3) and leptin-induced STAT3 transcriptional activity were significantly inhibited by homocysteine treatment. These effects may be specific to homocysteine and to the leptin pathway, as other homocysteine-related compounds, namely methionine and cysteine, have weak effect on leptin-induced inhibition of STAT3 phosphorylation, and homocysteine has no impact on IL-6-induced activation of STAT3. The direct effect of homocysteine on leptin-induced Ob-R activation, analyzed by Ob-R BRET biosensor to monitor Ob-R oligomerization and conformational change, suggested that homocysteine treatment does not affect early events of leptin-induced Ob-R activation. Instead, we found that, unlike methionine or cysteine, homocysteine increases the expression of the endoplasmic reticulum (ER) stress response gene, a homocysteine-sensitive ER resident protein. These results suggest that homocysteine may induce neuronal resistance to leptin by suppressing STAT3 phosphorylation downstream of the leptin receptor via ER stress.
Topics: Humans; Leptin; Receptors, Leptin; Homocysteine; Cysteine; Neuroblastoma; Endoplasmic Reticulum Stress; STAT3 Transcription Factor; Obesity; Methionine
PubMed: 36512575
DOI: 10.1371/journal.pone.0278965 -
Brain Research Bulletin Sep 2023The nucleus tractus solitarii (NTS) is the primary central station that integrates visceral afferent information and regulates respiratory, gastrointestinal,...
The nucleus tractus solitarii (NTS) is the primary central station that integrates visceral afferent information and regulates respiratory, gastrointestinal, cardiovascular, and other physiological functions. Leptin receptor b (LepRb)-expressing neurons of the NTS (NTS neurons) are implicated in central respiration regulation, respiratory facilitation, and respiratory drive enhancement. Furthermore, LepRb dysfunction is involved in obesity, insulin resistance, and sleep-disordered breathing. However, the monosynaptic inputs and outputs of NTS neurons in whole-brain mapping remain to be elucidated. Therefore, the exploration of its whole-brain connection system may provide strong support for comprehensively understanding the physiological and pathological functions of NTS neurons. In the present study, we used a cell type-specific, modified rabies virus and adeno-associated virus with the Cre-loxp system to map monosynaptic inputs and outputs of NTS neurons in LepRb-Cre mice. The results showed that NTS neurons received inputs from 48 nuclei in the whole brain from five brain regions, including especially the medulla. We found that NTS neurons received inputs from nuclei associated with respiration, such as the pre-Bötzinger complex, ambiguus nucleus, and parabrachial nucleus. Interestingly, some brain areas related to cardiovascular regulation-i.e., the ventrolateral periaqueductal gray and locus coeruleus-also sent a small number of inputs to NTS neurons. In addition, anterograde tracing results demonstrated that NTS neurons sent efferent projections to 15 nuclei, including the dorsomedial hypothalamic nucleus and arcuate hypothalamic nucleus, which are involved in regulation of energy metabolism and feeding behaviors. Quantitative statistical analysis revealed that the inputs of the whole brain to NTS neurons were significantly greater than the outputs. Our study comprehensively revealed neuronal connections of NTS neurons in the whole brain and provided a neuroanatomical basis for further research on physiological and pathological functions of NTS neurons.
Topics: Mice; Animals; Solitary Nucleus; Receptors, Leptin; Neurons; Brain Mapping; Obesity
PubMed: 37348822
DOI: 10.1016/j.brainresbull.2023.110693 -
Endocrinology Jan 2020Glucagon (GCG) is an essential regulator of glucose and lipid metabolism that also promotes weight loss. We have shown that glucagon-receptor (GCGR) signaling increases...
Glucagon (GCG) is an essential regulator of glucose and lipid metabolism that also promotes weight loss. We have shown that glucagon-receptor (GCGR) signaling increases fatty acid oxidation (FAOx) in primary hepatocytes and reduces liver triglycerides in diet-induced obese (DIO) mice; however, the mechanisms underlying this aspect of GCG biology remains unclear. Investigation of hepatic GCGR targets elucidated a potent and previously unknown induction of leptin receptor (Lepr) expression. Liver leptin signaling is known to increase FAOx and decrease liver triglycerides, similar to glucagon action. Therefore, we hypothesized that glucagon increases hepatic LEPR, which is necessary for glucagon-mediated reversal of hepatic steatosis. Eight-week-old control and liver-specific LEPR-deficient mice (LeprΔliver) were placed on a high-fat diet for 12 weeks and then treated with a selective GCGR agonist (IUB288) for 14 days. Liver triglycerides and gene expression were assessed in liver tissue homogenates. Administration of IUB288 in both lean and DIO mice increased hepatic Lepr isoforms a-e in acute (4 hours) and chronic (72 hours,16 days) (P < 0.05) settings. LeprΔliver mice displayed increased hepatic triglycerides on a chow diet alone (P < 0.05), which persisted in a DIO state (P < 0.001), with no differences in body weight or composition. Surprisingly, chronic administration of IUB288 in DIO control and LeprΔliver mice reduced liver triglycerides regardless of genotype (P < 0.05). Together, these data suggest that GCGR activation induces hepatic Lepr expression and, although hepatic glucagon and leptin signaling have similar liver lipid targets, these appear to be 2 distinct pathways.
Topics: Animals; Area Under Curve; Diet, High-Fat; Fatty Liver; Gene Expression Regulation; Homeostasis; Lipid Metabolism; Liver; Mice; Mice, Knockout; Obesity; Peptides; Receptors, Glucagon; Receptors, Leptin; Signal Transduction
PubMed: 31673703
DOI: 10.1210/endocr/bqz013 -
Cells Oct 2020Obesity is associated with increased breast cancer risk and poorer cancer outcomes; however, the precise etiology of these observations has not been fully identified....
Obesity is associated with increased breast cancer risk and poorer cancer outcomes; however, the precise etiology of these observations has not been fully identified. Our previous research suggests that adipose tissue-derived fibroblast growth factor-2 (FGF2) promotes the malignant transformation of epithelial cells through the activation of fibroblast growth factor receptor-1 (FGFR1). FGF2 is increased in the context of obesity, and increased sera levels have been associated with endocrine-resistant breast cancer. Leptin is a marker of obesity and promotes breast carcinogenesis through several mechanisms. In this study, we leverage public gene expression datasets to evaluate the associations between FGFR1, leptin, and the leptin receptor (LepR) in breast cancer. We show a positive association between FGFR1 and leptin protein copy number in primary breast tumors. These observations coincided with a positive association between Janus kinase 2 (Jak2) mRNA with both leptin receptor (LepR) mRNA and FGFR1 mRNA. Moreover, two separate Jak2 inhibitors attenuated both leptin+FGF2-stimulated and mouse adipose tissue-stimulated MCF-10A transformation. These results demonstrate how elevated sera FGF2 and leptin in obese patients may promote cancer progression in tumors that express elevated FGFR1 and LepR through Jak2 signaling. Therefore, Jak2 is a potential therapeutic target for FGFR1 amplified breast cancer, especially in the context of obesity.
Topics: Body Mass Index; Breast Neoplasms; Female; Humans; Leptin; Receptor, Fibroblast Growth Factor, Type 1; Receptors, Leptin
PubMed: 33019728
DOI: 10.3390/cells9102224 -
Neuroendocrinology 2019Endospanin 1 (Endo1), a protein encoded in humans by the same gene than the leptin receptor (ObR), and increased by diet-induced obesity, is an important regulator of... (Review)
Review
Endospanin 1 (Endo1), a protein encoded in humans by the same gene than the leptin receptor (ObR), and increased by diet-induced obesity, is an important regulator of ObR trafficking and cell surface exposure, determining leptin signaling strength. Defective intracellular trafficking of the leptin receptor to the neuronal plasma membrane has been proposed as a mechanism underlying the development of leptin resistance observed in human obesity. More recently, Endo1 has emerged as a mediator of "selective leptin resistance." The underlying mechanisms of the latter are not completely understood, but the possibility of differential activation of leptin signaling pathways was suggested among others. In this respect, the expression level of Endo1 is crucial for the appropriate balance between different leptin signaling pathways and leptin functions in the hypothalamus and is likely participating in selective leptin resistance for the control of energy and glucose homeostasis.
Topics: Adaptor Proteins, Signal Transducing; Animals; Hypothalamus; Leptin; Neurons; Receptors, Leptin; Signal Transduction
PubMed: 30326479
DOI: 10.1159/000494557 -
Cell Death & Disease Feb 2023Metformin is the biguanide of hepatic insulin sensitizer for patients with non-alcohol fatty liver disease (NAFLD). Findings regarding its efficacy in restoring blood...
Metformin is the biguanide of hepatic insulin sensitizer for patients with non-alcohol fatty liver disease (NAFLD). Findings regarding its efficacy in restoring blood lipids and liver histology have been contradictory. In this study, we explore metformin's preventive effects on NAFLD in leptin-insensitive individuals. We used liver tissue, serum exosomes and isolated hepatocytes from high-fat diet (HFD)-induced Zucker diabetic fatty (ZDF) rats and leptin receptor (Lepr) knockout rats to investigate the correlation between hepatic Lepr defective and liver damage caused by metformin. Through immunostaining, RT-PCR and glucose uptake monitoring, we showed that metformin treatment activates adenosine monophosphate (AMP)-activated protein kinase (AMPK) and its downstream cytochrome C oxidase (CCO). This leads to overactivation of glucose catabolism-related genes, excessive energy repertoire consumption, and subsequent hepatocyte pyroptosis. Single-cell RNA sequencing further confirmed the hyper-activation of glucose catabolism after metformin treatment. Altogether, we showed that functional Lepr is necessary for metformin treatment to be effective, and that long-term metformin treatment might promote NAFLD progression in leptin-insensitive individuals. This provides important insight into the clinical application of metformin.
Topics: Rats; Animals; Metformin; AMP-Activated Protein Kinases; Non-alcoholic Fatty Liver Disease; Leptin; Receptors, Leptin; Pyroptosis; Rats, Zucker; Liver; Hepatocytes; Glucose
PubMed: 36737598
DOI: 10.1038/s41419-023-05623-4 -
International Journal of Obesity (2005) Dec 2008The adipocyte-derived hormone, leptin, signals the status of body energy stores to the central nervous system to regulate appetite and energy expenditure. A specific... (Review)
Review
The adipocyte-derived hormone, leptin, signals the status of body energy stores to the central nervous system to regulate appetite and energy expenditure. A specific long-form leptin receptor (LepRb), a type I cytokine receptor, mediates leptin action on LepRb-expressing neurons in the brain. Leptin binding to LepRb activates the associated Janus kinase-2 (Jak2) tyrosine kinase to promote the phosphorylation of Jak2 and three residues on LepRb; each of these sites mediates a distinct aspect of downstream LepRb signaling, with differing physiologic functions. Tyr(1138) --> STAT3 signaling suppresses feeding, but is not required for a number of other leptin actions. Tyr(985) binds SH2-containing tyrosine phosphatase-2 and suppressor of cytokine signaling-3 and primarily mediates the attenuation of LepRb signaling in vivo. The role for Tyr(1077), the major regulator of signal transducer and activator of transcription-5 (STAT5) during leptin signaling, in the physiologic response to leptin remains unclear, although the obese phenotype of animals deleted for STAT5 in the brain suggests the potential importance of this signaling pathway. Leptin also modulates a number of other signaling pathways in the brain, including PI 3-kinase, mammalian target of rapamycin and AMP-dependent protein kinase; the pathways by which leptin controls these signals remain unclear, however, and may involve some indirect mechanisms. Important issues regarding leptin action and LepRb signaling in the future include not only the more thorough analysis of intracellular signaling pathways, but the neural substrate by which leptin acts, as most major populations of LepRb neurons remain poorly studied.
Topics: Animals; Homeostasis; Humans; Hypothalamus; Insulin Resistance; Leptin; Mice; Receptors, Cell Surface; Receptors, Leptin; STAT3 Transcription Factor; STAT5 Transcription Factor; Signal Transduction; Suppressor of Cytokine Signaling 3 Protein; Suppressor of Cytokine Signaling Proteins
PubMed: 19136996
DOI: 10.1038/ijo.2008.232 -
Molecular Medicine Reports May 2018The present study investigated the expression of leptin and its receptor in the left testis and hypothalamus of rats with varicocele and clarified their roles in the...
The present study investigated the expression of leptin and its receptor in the left testis and hypothalamus of rats with varicocele and clarified their roles in the pathogenesis of varicocele‑induced testicular dysfunction. A total of 40 male rats were divided randomly into four groups. Groups 1 (G1) and 3 (G3) underwent a sham operation. Groups 2 (G2) and 4 (G4) underwent operations to form a varicocele created by partial ligation of the left renal vein. G1 and G2 rats were euthanized 4 weeks after the operation while G3 and G4 rats were euthanized at 8 weeks. The expression of leptin and its receptor was analyzed by immunohistochemistry. The mRNA levels of leptin, its receptor, kisspeptin (KiSS‑1), G‑protein coupled receptor 54 (GPR54), gonadotropin releasing hormone (GnRH), luteinizing hormone (LH), and follicle‑stimulating hormone (FSH) were measured by reverse transcription‑quantitative polymerase chain reaction. Testicular spermatogenesis function and gonadal hormone levels were measured. Compared with G1 and G3, the expression of leptin and its receptor in rat testis was significantly higher in G2 and G4, respectively. Leptin expression was inversely associated with the number of sperm in the left epididymis, thickness of the seminiferous epithelium and the diameter of seminiferous tubules. The expression of leptin receptors in the hypothalamus of G2 and G4 was significantly increased compared with that in G1 and G3, respectively. The mRNA levels of KiSS‑1, GPR54, GnRH, LH and FSH in G2 and G4 were significantly increased compared with that in G1 and G3, respectively. Serum testosterone levels in G2 and G4 rats were significantly lower than those in G1 and G3 rats, respectively. There was no significant difference between the serum levels of FSH, LH and leptin. These results suggest that leptin and its receptor may serve significant roles in the pathogenesis of varicocele-induced testicular dysfunction.
Topics: Animals; Gene Expression Regulation; Immunohistochemistry; Leptin; Male; Rats, Sprague-Dawley; Receptors, Leptin; Spermatogenesis; Testis; Varicocele
PubMed: 29568885
DOI: 10.3892/mmr.2018.8753