Effects Of Leptin Research Articles

Postnatal surge of adipose-secreted leptin is a robust predictor of fat mass trajectory in mice.

The transient postnatal increase in circulating leptin levels, known as leptin surge, may increase later susceptibility to diet-induced obesity in rodents. However, the source of leptin during the surge needs to be better characterized, and the long-term effects of leptin are contradictory. Characterization of the interaction of leptin with the genetic background, sex, and other factors is required. Here, we focused on the impact of circulating leptin levels and several related variables, measured in 2- and 4-week-old (i) obesity-prone C57BL/6 (B6) and (ii) obesity-resistant A/J mice. In total, 264 mice of both sexes were used. Posttranscriptionally controlled leptin secretion from subcutaneous white adipose tissue, the largest adipose tissue depot in mice pups, was the primary determinant of plasma leptin levels. When the animals were randomly assigned standard chow or high-fat diet (HFD) between 12 - 24 weeks of age, the obesogenic effect of HFD-feeding was observed in B6 but not A/J mice. Only leptin levels at 2 weeks, i.e., close to the maximum in the postnatal leptin surge, correlated with both body weight (BW) trajectory throughout the life and adiposity of the 24-week-old mice. Leptin surge explained 13 and 7 % of the variance in BW and adiposity of B6 mice and 9 and 35 % of the variance in these parameters in A/J mice, with a minor role of sex. Our results prove the positive correlation between the leptin surge and adiposity in adulthood, reflecting the fundamental biological role of leptin. This role could be compromised in obese subjects.

Effect of leptin and adiponectin on the expression of cytokine genes IL-1β, IL-6 AND TNFα in lymphocytes

Metabolic syndrome (MS) is one of the world’s topical health problems. Large-scale epidemiological studies on the prevalence of MS in the world have not been conducted, but according to different authors, depending on the region of residence, the composition of the study population and the diagnostic criteria used, the incidence of MS is at least 10%, and according to estimates of the International Diabetes Federation IDF – up to 25% of the adult population. The metabolic changes in MS are explained by a disturbance in the balance of mediators synthesized by adipose tissue (adiponectin, leptin, resistin, visfatin, vaspin and others); MS is also considered as a subclinical chronic inflammatory process characterized by excessive synthesis of proinflammatory and deficiency of anti-inflammatory cytokines. According to modern ideas, changes in the cellular and humoral immunity in MS are largely due to the imbalance of adipokines: leptin and adiponectin. Increased functional activity of immune cells, including lymphocytes, leads to changes in cytokine gene expression. In the present work, we studied in vitro the expression of IL-1â, IL-6 and TNFá genes in peripheral blood lymphocytes under the influence of adipokines at concentrations characteristic of MS. As a result, differential effects of adipokines on lymphocytes of MS patients and conditionally healthy individuals were found. In conditionally healthy individuals, incubation of lymphocytes with adipokines leptin, adiponectin and their combination, as well as in the presence of physiological solution causes an increase in IL-6 gene expression. The most noticeable effect was observed when cultured with adiponectin. Thus, in norm, with a decrease in the physiological concentration of adiponectin, the expression of IL-6 in lymphocytes increases, indicating insufficient realization of the anti-inflammatory effect of adiponectin. In MS, IL-6 gene expression increases in lymphocytes isolated from peripheral blood in vitro after incubation with adiponectin, a combination of adiponectin and leptin, as well as in the presence of physiological solution. No changes in IL-6 gene expression under the effect of high concentration of leptin were detected. Probably, our results reflect the phenomenon of lymphocyte resistance to leptin action in MS, as under its influence there is not activation of lymphocytes characteristic in vivo, but on the contrary, decrease of activated subpopulations, also there is no change in IL-6 gene expression. Thus, adipokines in concentrations characteristic of metabolic syndrome influence the functional activity of peripheral blood lymphocytes.

Leptin reduces LPS‐induced A1 reactive astrocyte activation and inflammation via inhibiting p38‐MAPK signaling pathway

AbstractNeurotoxic A1 reactive astrocytes are induced by inflammatory stimuli. Leptin has been confirmed to have neuroprotective properties. However, its effect on the activation of A1 astrocytes in infectious inflammation is unclear. In the current study, astrocytes cultured from postnatal day 1 Sprague–Dawley rats were stimulated with lipopolysaccharide (LPS) to induce an acute in vitro inflammatory response. Leptin was applied 6 h later to observe its protective effects. The viability of the astrocytes was assessed. A1 astrocyte activation was determined by analyzing the gene expression of C3, H2‐D1, H2‐T23, and Serping 1 and secretion of pro‐inflammatory cytokines IL‐6 and TNF‐α. The levels of phospho‐p38 (pp38) and nuclear factor‐κB (NF‐κB) phosphor‐p65 (pp65) were measured to explore the possible signaling pathways. Additionally, an LPS‐induced inflammatory animal model was established to investigate the in vivo effects of leptin on A1 astrocytic activation. Results showed that in the in vitro culture system, LPS stimulation caused elevated expression of A1 astrocyte‐specific genes and the secretion of pro‐inflammatory cytokines, indicating the activation of A1 astrocytes. Leptin treatment significantly reversed the LPS induced upregulation in a dose‐dependent manner. Similarly, LPS upregulated pp38, NF‐κB pp65 protein and inflammatory cytokines were successfully reduced by leptin. In the LPS‐induced animal model, the amelioratory effect of leptin on A1 astrocyte activation and inflammation was further confirmed, showed by the reduced sickness behaviors, A1 astrocyte genesis and inflammatory cytokines in vivo. Our results demonstrate that leptin efficiently inhibits LPS‐induced neurotoxic activation of A1 astrocytes and neuroinflammation by suppressing p38‐MAPK signaling pathway.

Adiponectin and Leptin during Pregnancy: A Systematic Review of Their Association with Pregnancy Disorders, Fetal Growth and Placental Function

During pregnancy, the adipokines leptin and adiponectin can affect placental nutrient transport and inflammatory pathways, potentially leading to altered fetal growth and pregnancy complications including gestational diabetes mellitus (GDM) and preeclampsia (PE). The aim of this systematic review is to gather and analyze research on maternal circulating leptin and adiponectin levels and their relationship to adverse pregnancy and birth outcomes. Additionally, it seeks to determine whether these hormones are linked to alterations in placental transporters and cell signaling pathways. PubMed and MEDLINE were systematically searched to include studies published between 2012 and 2022. All primary data studies reporting serum adiponectin and/or leptin, placental mRNA and protein levels of related transporters, and adverse birth outcomes were eligible. The current systematic review encompasses a total of 14 articles. Abnormal serum maternal leptin and adiponectin levels were associated with changes in fetal growth and placental cellular signaling and nutrient transporters. A majority of studies associated elevated maternal leptin and reduced adiponectin with fetal overgrowth, although this relationship was not consistent and may be complicated when other pathologies are present. The effects of maternal leptin and adiponectin on fetal growth may be driven by placental adaptation in nutrient transporters and mitochondria. Future studies should determine if the placental effects of leptin and adiponectin that have been found in models have mechanistic roles in human pregnancy.

Abstract 10: Adrenal Zona Glomerulosa Long Form Leptin Receptor (LepRb) Protects from Leptin-Mediated Vascular Disorders in Female Mice

Introduction: Previous work from our group demonstrated that leptin is a major contributor to obesity-associated cardiovascular disease, in females, by acting on the adrenal gland to promote aldosterone production. Hypothesis: This leptin-mediated aldosterone secretion is dependent on the presence of the long form leptin receptor (LepRb) in adrenal aldosterone synthase (AS) expressing cells. Methods: We generated AS LepRb deficient mice, ASKO and WT control (ASWT), by crossing LepRb flox/flox mice with AS-Cre mice to investigate the role of LepRb in AS expressing cells in leptin-mediated cardiovascular alteration in females and also generated db/AS + mice that have LepRb only in AS expressing cells by crossing LepR TBflox/flox (db/db) with AS-Cre mice to compare their phenotype. Results: Under baseline conditions, ASKO female mice exhibited no alteration in adrenal AS, plasma aldosterone, systolic blood pressure, and aortic endothelium-dependent relaxation. To mimic obese conditions, we submitted ASWT and ASKO to chronic leptin infusion for a week. Leptin increased adrenal AS expression, aldosterone levels, and blood pressure and impaired endothelial function, which were further elevated in ASKO compared to ASWT, suggesting protective effects of AS LeRb. Both mineralocorticoid receptor (MR) antagonist. eplerenone, or AS antagonist, fadrazole, rescued endothelial function in ASWT and ASKO mice treated with leptin, indicating that leptin-mediated endothelial dysfunction is still aldosterone-dependent in ASKO mice. Restoration of LepRb in AS expressing cells in db/db decreased adrenal AS and plasma aldosterone and improved endothelial function further indicating that AS LepRb blunts leptin-mediated aldosterone production. On a molecular level, leptin treatment elevated aorta NOX1 expression in ASWT, which was further increased in ASKO. Aldosterone treatment increased NOX1 expression in cultured microvascular endothelial cells. Incubation of aortic rings with a selective NOX1 inhibitor restored endothelial function in both ASWT and ASKO treated with leptin, suggesting leptin-mediated aldosterone increased NOX1 expression in the aorta, which causes endothelial dysfunction. Conclusion: These data indicate that AS LepRb protects from leptin-mediated aldosterone production and vascular dysfunction by mitigating the effects of leptin on aldosterone production and suggests that other isoforms of LepR are involved in stimulating aldosterone production.

Exogenous leptin alleviates glutamate-excitotoxic injury caused by cerebral ischemia–reperfusion in mice by affecting the expression of glutamate transporters

Ischemic stroke is characterized by high morbidity and mortality and a lack of effective therapeutic interventions. Leptin plays an important role in regulating oxidative stress, angiogenesis, hematopoiesis, etc. Although recent studies have found a neuroprotective effect of leptin, little is known about its role in cerebral ischemia. This study explores the possible roles and potential preventative mechanisms of leptin in cerebral ischemia–reperfusion injury (CIRI). An in vivo middle cerebral artery occlusion/reperfusion (MCAO/R) mouse model was used to replicate the CIRI model, low (0.5 mg/kg), medium (1 mg/kg) and high (2 mg/kg) concentrations of leptin were injected intraperitoneally immediately after inserting the embolic line. After 1.5 h of ischemia and 24 h of reperfusion, we examined the neural function of the mice, collected brain tissue for histological examination, and screened for the optimal concentrations of leptin intervention. On this basis, we observed the changes of cortical apoptosis injury, intracellular calcium fluorescence intensity and astrocyte glial fibrillary acidic protein (GFAP) expression and morphological changes. In addition, we also tested the expression of transporters and metabolism-related enzymes (VGLUT-1, VGLUT-2, GLAST, GLT-1, GS, ATP1α1), the expression of inflammatory factors and the content of glutamate (Glu). Compared with the I/R group, we found that leptin improved neurological deficits, reduced the area of infarcts, maintained the normal morphology of astrocytes (AST), downregulated the expression of VGLUT-1, and upregulates the expression of GLT-1 and GLAST, thereby reducing the content of Glu in the synaptic cleft. Our studies suggest that leptin may have a neuroprotective effect by decreasing the excitotoxicity of glutamate.

Leptin limits hepatic lipid accumulation and inflammation via vagal activation of the JAK2-STAT3/AMPK pathway

Non-Alcoholic Fatty Liver Disease (NAFLD) begins with hepatic lipid accumulation, and leptin has antisteatosis properties. In this study, we investigated the effects of leptin on hepatic steatosis and inflammation through the vagal pathway independently of the inhibitory effect of food intake. Male Sprague-Dawley rats were matched for food intake after the high-fat diet (HFD)-induced obesity model and were injected intraperitoneally with leptin or leptin + lidocaine for 6 weeks. Control rats received equal volumes of saline. Adipose tissue mass, NAFLD activity scores (NAS), hepatic inflammatory factors, hepatic triglyceride content and hepatic lipid metabolism-related protein levels were evaluated. Leptin ameliorated HFD-induced hepatic lipid accumulation, improved NAS, and decreased tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and monocyte chemotactic protein-1 (MCP-1) levels in the presence of matched intake. Lidocaine decreased the phosphorylation of signal transducer and activator of transcription 3 (p-STAT3) expression in the nucleus tractus solitarius (NTS) and abrogated the leptin-mediated improvement. Leptin increased hypothalamic phosphorylated Janus kinase 2 (p-JAK2) and p-STAT3 expression, as well as the expression of mitochondrial respiratory chain-related genes. Leptin also increased hepatic phosphorylated adenosine 5′-monophosphate-activated protein kinase (p-AMPK) expression and phosphorylation of its downstream target acetyl Co A carboxylase 1 (ACC1), reducing de novo lipogenesis. Our results suggest that leptin ameliorated hepatic lipid accumulation and inflammation by activating the JAK2-STAT3/AMPK pathway through the vagal pathway independently of the inhibitory effect of ingestion. Leptin has the potential to be a drug for early NAFLD treatment.

Central Actions of Leptin Induce an Atrophic Pattern and Improves Heart Function in Lean Normoleptinemic Rats via PPARβ/δ Activation.

Leptin, acting centrally or peripherally, has complex effects on cardiac remodeling and heart function. We previously reported that central leptin exerts an anti-hypertrophic effect in the heart via cardiac PPARβ/δ activation. Here, we assessed the impact of central leptin administration and PPARβ/δ inhibition on cardiac function. Various cardiac properties, including QRS duration, R wave amplitude, heart rate (HR), ejection fraction (EF), end-diastolic left ventricular mass (EDLVM), end-diastolic volume (EDV), and cardiac output (CO) were analyzed. Central leptin infusion increased cardiac PPARβ/δ protein content and decreased HR, QRS duration, and R wave amplitude. These changes induced by central leptin suggested a decrease in the ventricular wall growth, which was confirmed by MRI. In fact, the EDLVM was reduced by central leptin while increased in rats co-treated with leptin and GSK0660, a selective antagonist of PPARβ/δ activity. In summary, central leptin plays a dual role in cardiac health, potentially leading to ventricular atrophy and improving heart function when PPARβ/δ signaling is intact. The protective effects of leptin are lost by PPARβ/δ inhibition, underscoring the importance of this pathway. These findings highlight the therapeutic potential of targeting leptin and PPARβ/δ pathways to combat cardiac alterations and heart failure, particularly in the context of obesity.

Low Testosterone and High Leptin Activate PPAR Signaling to Induce Adipogenesis and Promote Fat Deposition in Caponized Ganders.

Low or insufficient testosterone levels caused by caponization promote fat deposition in animals. However, the molecular mechanism of fat deposition in caponized animals remains unclear. This study aimed to investigate the metabolomics and transcriptomic profiles of adipose tissues and study the effect of testosterone and leptin on the proliferation of adipocytes. We observed a significant enlargement in the areas of adipocytes in the abdominal fat tissues in capon, as well as increased luciferase activity of the serum leptin and a sharp decrease in the serum testosterone in caponized gander. Metabolomics and transcriptomic results revealed differentially expressed genes and differentially expressed metabolites with enhanced PARR signal pathway. The mRNA levels of peroxisome proliferators-activated receptor γ, fatty acid synthase, and suppressor of cytokine signaling 3 in goose primary pre-adipocytes were significantly upregulated with high leptin treatment and decreased significantly with increasing testosterone dose. Hence, reduced testosterone and increased leptin levels after caponization possibly promoted adipocytes proliferation and abdominal fat deposition by altering the expression of PPAR pathway related genes in caponized ganders. This study provides a new direction for the mechanism through which testosterone regulates the biological function of leptin and fat deposition in male animals.

Interleukin-1β Signaling Contributes to Cell Cycle Arrest and Apoptotic Cell Death by Leptin via Modulation of AKT and p38MAPK in Hepatocytes.

Leptin, an adipose tissue-derived hormone, has exhibited the potent hepatotoxic effects. However, the underlying molecular mechanisms are not fully understood. In this study, we have elucidated the mechanisms by which leptin exerts cytotoxic effects in hepatocytes, particularly focusing on the role of interleukin-1β (IL-1β) signaling. Leptin significantly induced maturation and secretion of IL-1β in cultured rat hepatocytes. Interestingly, inhibition of IL-1β signaling by pretreatment with an IL-1 receptor antagonist (IL-1Ra) or gene silencing of type I IL-1 receptor (IL-1R1) markedly abrogated leptin-induced cell cycle arrest. The critical role of IL-1β signaling in leptin-induced cell cycle arrest is mediated via upregulation of p16, which acts as an inhibitor of cyclin-dependent kinase. In addition, leptin-induced apoptotic cell death was relieved by inhibition of IL-1β signaling, as determined by annexin V/7-AAD binding assay. Mechanistically, IL-1β signaling contributes to apoptotic cell death and cell cycle arrest by suppressing AKT and activation of p38 mitogen-activated protein kinase (p38MAPK) signaling pathways. Involvement of IL-1β signaling in cytotoxic effect of leptin was further confirmed in vivo using hepatocyte specific IL-1R1 knock out (IL-1R1 KO) mice. Essentially similar results were obtained in vivo, where leptin administration caused the upregulation of apoptotic markers, dephosphorylation of AKT, and p38MAPK activation were observed in wild type mice liver without significant effects in the livers of IL-1R1 KO mice. Taken together, these results demonstrate that IL-1β signaling critically contributes to leptin-induced cell cycle arrest and apoptosis, at least in part, by modulating p38MAPK and AKT signaling pathways.

Hypomethylated leptin receptor reduces cerebral ischaemia-reperfusion injury by activating the JAK2/STAT3 signalling pathway.

To investigate the cerebroprotective effects of leptin in vitro and in vivo via the Janus kinase-2 (JAK2)/transcription factor signal transducer and activators of transcription-3 (STAT3) pathway and leptin receptors (LEPR). The study used the cellular oxygen-glucose deprivation (OGD) model in PC12 cells and the middle cerebral artery occlusion (MCAO) rat model of cerebral ischaemia-reperfusion injury (CIRI) to assess changes in gene expression and protein levels following leptin pretreatment. The methylated DNA immunoprecipitation (MeDIP) assay measured DNA methylation levels. The optimal leptin concentration for exerting neuroprotective effects against ischaemia-reperfusion injury in PC12 cells was 200 ng/ml in vitro, but excessive leptin diminished this effect. Leptin pretreatment in the MCAO rat model demonstrated a similar effect to previously reported leptin administration post-CIRI. In addition to regulating the expression of inflammation-related cytokines, Western blot analysis showed that leptin pretreatment upregulated BCL-2 and downregulated caspase 3 levels. The MeDIP analysis demonstrated that DNA methylation regulated LEPR gene expression in the MCAO rat model when leptin pretreatment was used. Exogenous leptin might bind to extra-activated LEPR by reducing the methylation level of the LEPR gene promoter region, which leads to an increase in phosphorylated JAK2/STAT3 and apoptotic signalling pathways.

Trends and characteristics of the metabolically healthy obese phenotype in an Arab population.

The metabolically healthy obesity (MHO) phenotype represents a complex and distinctive trait, the trends and characteristics of which remain unknown in the Saudi Arabian adult population. The present study aims to fill that gap. A combined total of 10,220 Saudi adults from 2 independent cohorts [2008-2019, N = 7,896 (2,903 males and 4,993 females), and 2021-2023, N = 2,324 (830 males and 1,494 females)] aged 19-70 years old was screened, of whom 9,631 (3,428 males and 6,203 females) were included. Anthropometric data were measured, and fasting blood samples were collected to assess glucose, lipids, adipocytokines and inflammatory markers using routine methods and commercially available assays. Obesity was defined as a body mass index (BMI) ≥30 kg/m2. Screening for MHO was done using the empiric definition proposed by Zembic and colleagues and the by the National Cholesterol Education Program's Adult Treatment Panel III (NCEP ATPIII). Of the 3,949 (41.0%) participants with obesity, 33.4% (95% confidence interval, CI, 32-35) were considered MHO using the empiric definition, and 32.8% (95% CI, 31-34) using NCEP-ATPIII. The overall age and gender adjusted prevalence of MHO in the Saudi adult population was 31.6% (95% CI, 30-33) and 30.1% (29-31) by the two definitions, respectively. Females had a higher age-adjusted prevalence of MHO than males (OR = 1.22, 95% CI 1.1-1.4, p = 0.009) as per the ATPIII criteria. MHO prevalence substantially increased over time from 2008 to 2023 (p < 0.001) for both definitions. Circulating leptin levels and insulin resistance were significantly higher in the MUO group than the MHO group independent of the definition used, suggesting the presence of a more severe form of leptin resistance in the MUO group which may explain the worse cardiometabolic profile as compared to the MHO group. In summary, the study highlights the first time the characteristics and trends of the MHO phenotype among Saudi Arabian adults. The pluripotent effects of leptin and its resistance may be central to MHO's progression, or lack thereof, to the MUO phenotype, and this needs further investigation.

Hypothalamic hormone deficiency enables physiological anorexia in ground squirrels during hibernation

Mammalian hibernators survive prolonged periods of cold and resource scarcity by temporarily modulating normal physiological functions, but the mechanisms underlying these adaptations are poorly understood. The hibernation cycle of thirteen-lined ground squirrels (Ictidomys tridecemlineatus) lasts for 5–7 months and comprises weeks of hypometabolic, hypothermic torpor interspersed with 24–48-h periods of an active-like interbout arousal (IBA) state. We show that ground squirrels, who endure the entire hibernation season without food, have negligible hunger during IBAs. These squirrels exhibit reversible inhibition of the hypothalamic feeding center, such that hypothalamic arcuate nucleus neurons exhibit reduced sensitivity to the orexigenic and anorexigenic effects of ghrelin and leptin, respectively. However, hypothalamic infusion of thyroid hormone during an IBA is sufficient to rescue hibernation anorexia. Our results reveal that thyroid hormone deficiency underlies hibernation anorexia and demonstrate the functional flexibility of the hypothalamic feeding center.

Sleep quality in patients with chronic spontaneous urticaria and relation with Orexin-A, leptin, and ghrelin.

Background: Sleep can be affected in patients with chronic spontaneous urticaria (CSU). The mechanisms of sleep regulation remain poorly understood. Orexin-A, a neuroexcitatory peptide, plays a role in coordinating sleep-wake states. Ghrelin and leptin are involved in sleep regulation through the orexin system. Objective: The effects of orexin-A, ghrelin, and leptin on sleep quality in patients with CSU have not been investigated. We aimed to determine the effects of CSU on sleep quality and the association between serum orexin-A, ghrelin, and leptin levels, and sleep quality in patients with CSU. Methods: Thirty-three patients with CSU and 34 sex- and age-matched controls were included in the study. Serum orexin-A, leptin, and ghrelin levels, and the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS) scores were measured in patients with CSU and in the controls; also used were the chronic urticaria quality-of-life questionnaire score and the urticaria activity score used for 7 consecutive days. Results: Median (minimum-maximum) orexin-A, leptin, and ghrelin levels in patients were 385 pg/mL (90-495 pg/mL), 3.1 ng/mL (0-21.2 ng/mL), and 701.8 pg/mL (101.9-827.7 pg/mL), respectively. Median serum orexin-A and leptin levels were higher in the patients compared with the controls (p < 0.001 and p = 0.012, respectively), whereas the median serum ghrelin levels were similar to the controls (p = 0.616). The serum orexin-A level was positively correlated with ghrelin (r = 0.298, p = 0.014), PSQI sleep quality (r = 0.356, p = 0.003), and ESS (r = 0.357, p = 0.003). Conclusion: Serum orexin-A is associated with sleep quality in patients with CSU. Further studies are needed to elucidate the role of ghrelin and leptin on sleep quality in patients with CSU.

Comment on Lai et al. Dipeptidyl Peptidase 4 Stimulation Induces Adipogenesis-Related Gene Expression of Adipose Stromal Cells. Int. J. Mol. Sci. 2023, 24, 16101.

Adiponectin is a circulating hormone secreted by adipose tissue that exerts, unlike other adipokines such as leptin, anti-inflammatory, anti-atherosclerotic and other protective effects on health. Adiponectin receptor agonists are being tested in clinical trials and are expected to show benefits in many diseases. In a recent article, LW Chen's group used monocyte chemoattractant protein-1 (MCP-1/CCL2) to improve plasma levels of adiponectin, suggesting the involvement of dipeptidyl peptidase 4 (DPP4/CD26) in the mechanism. Here, we discuss the significance of the role of DPP4, favoring the increase in DPP4-positive interstitial progenitor cells, a finding that fits with the greater stemness and persistence of other DPP4/CD26-positive cells.

Involvement of ObRb receptor, nitric oxide, and BKCa channel signaling pathways in leptin-induced relaxation of pregnant mouse uterus

The purpose of this study was to determine the receptor subtype and the underlying mechanisms involved in the relaxant effect to leptin in mid- and late-pregnant mouse uterus. We determined the relative mRNA expression of receptor subtypes, eNOS, and BKCa channel by quantitative PCR and also the overall receptor expression by immunohistochemistry. Isometric tension studies were conducted to evaluate the effects of leptin and to delineate its mechanisms. A selective siRNA for the ObRb receptor was used to determine the participation of the receptor subtype in biochemical and molecular effects of leptin.The relaxant response to leptin was greater in mid-pregnancy compared to late pregnancy and was mediated by the activation of BKCa channels by eNOS-derived nitric oxide in an ObRb receptor-dependent manner. In comparison to mid-pregnancy, expression of short forms (mainly ObRa receptor) of the receptor was significantly increased in late pregnancy, whereas ObRb receptor expression was similar in both phases.The results of the study suggest that ObRb receptor mediates leptin-induced increase in eNOS expression and NO synthesis. Leptin-induced eNOS expression and activation cause cGMP-independent stimulation of BKCa channels causing uterine relaxation. Increased short forms of the receptors and reduced BKCa channels exert a negative effect on uterine relaxation in late pregnancy. Leptin may have a physiological role in maintaining uterine quiescence in mid-pregnancy and its reduced relaxant response in late gestation may facilitate labor. Further, ObRb receptor agonists may be useful in the management of preterm labor.

Exogenous leptin improves cerebral ischemia-reperfusion-induced glutamate excitotoxic injury in mice by up-regulating GLT-1 and GLAST expression in astrocytes

To investigate the protective effect of exogenous leptin against focal cerebral ischemia-reperfusion (I/R) injury in mice and explore the underlying mechanism. A total of 100 C57BL/6 mice were randomly divided into 5 groups, including a sham-operated group, cerebral I/R model group, and 3 leptin treatment groups with intraperitoneal injections of 0.5, 1.0 or 2.0 leptin immediately after occlusion of the internal carotid artery. At 24 h after reperfusion, neurological function scores of the mice were assessed, and TTC staining was used to determine the area of cerebral infarction. The pathological changes in the cortical brain tissue of the mice were observed using HE staining, and degenerative damage of the cortical neurons were assessed with Fluoro-Jade C staining. The expression of glial fibrillary acidic protein in cortical brain tissues was detected using immunohistochemistry and Western blotting. In another 45 C57BL/6 mice with sham operation, I/R modeling, or leptin (1 mg/kg) treatment, glutamic acid in the cortical brain tissue was detected using glutamate assay, and cortical glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) protein expressions were detected using immunohistochemistry. Compared with the I/R model mice, the leptin-treated mice had significantly lower neurological deficit scores, smaller cerebral infarct area, milder pathologies in the cortical brain tissue, and lessened cortical neuronal damage with normal morphology and less excessive proliferation of the astrocytes. Leptin treatment significantly up-regulated the expressions of GLT-1 and GLAST and lowered the content of glutamic acid in the brain tissue of the I/R mice. Exogenous leptin has obvious neuroprotective effect against cerebral I/R injury in mice, mediated probably by controlling excessive astrocyte proliferation and up-regulating cortical GLT-1 and GLAST expressions to reduce glutamate-mediated excitotoxic injury of the astrocytes.

AgRP neuron cis-regulatory analysis across hunger states reveals that IRF3 mediates leptin’s acute effects

AgRP neurons in the arcuate nucleus of the hypothalamus (ARC) coordinate homeostatic changes in appetite associated with fluctuations in food availability and leptin signaling. Identifying the relevant transcriptional regulatory pathways in these neurons has been a priority, yet such attempts have been stymied due to their low abundance and the rich cellular diversity of the ARC. Here we generated AgRP neuron-specific transcriptomic and chromatin accessibility profiles from male mice during three distinct hunger states of satiety, fasting-induced hunger, and leptin-induced hunger suppression. Cis-regulatory analysis of these integrated datasets enabled the identification of 18 putative hunger-promoting and 29 putative hunger-suppressing transcriptional regulators in AgRP neurons, 16 of which were predicted to be transcriptional effectors of leptin. Within our dataset, Interferon regulatory factor 3 (IRF3) emerged as a leading candidate mediator of leptin-induced hunger-suppression. Measures of IRF3 activation in vitro and in vivo reveal an increase in IRF3 nuclear occupancy following leptin administration. Finally, gain- and loss-of-function experiments in vivo confirm the role of IRF3 in mediating the acute satiety-evoking effects of leptin in AgRP neurons. Thus, our findings identify IRF3 as a key mediator of the acute hunger-suppressing effects of leptin in AgRP neurons.

Cellular mechanism underlying leptin-induced anion secretion of rat epididymal epithelial cells.

A large number of studies have shown that leptin plays an important role in the regulation of fertility via the hypothalamus-pituitary-gonad axis. However, its peripheral function in epididymis was still elusive. The purpose of this study was to determine the pro-secretion effect of leptin on the rat epididymal epithelium. In the present study, real-time quantitative polymerase chain reaction, western blot, and immunohistochemical analysis were employed to detect the expression pattern of leptin receptors in rat epididymis. The pro-secretion effect of leptin on epididymal epithelial cells was measured by short-circuit current, and the prostaglandin E2 and cyclic adenosine monophosphate level was evaluated by enzyme-linked immunosorbent assay. We verified that the leptin receptor was located on the epididymal epithelium, with a relatively high expression level in corpus and cauda epididymis. Ussing chamber experiments showed that leptin stimulated a significant rise of the short-circuit current in rat epididymal epithelial cells, which could be abolished by the specific leptin receptor antagonist peptide Allo-aca, or by removing the ambient Cl- and HCO3 -. Furthermore, the leptin-stimulated short-circuit current response could be abrogated by blocking the apical cystic fibrosis transmembrane regulator or the basolateral Na+-K+-2Cl- cotransporter. Our pharmacological experiments manifested that interfering with the prostaglandin H synthase-2-prostaglandin E2-EP2/EP4-adenylate cyclase pathways could significantly blunt the cystic fibrosis transmembrane regulator-mediated anion secretion induced by leptin. The enzyme-linked immunosorbent assay demonstrated that leptin could induce a substantial increase in prostaglandin E2 release and cyclic adenosine monophosphate synthesis of primary cultured rat cauda epididymal epithelial cells. Our data also suggested that JAK2, ERK, and PI3K-dependent phosphorylation may be involved in the activation of prostaglandin H synthase-2 and the subsequent prostaglandin E2 production. The present study demonstrated the pro-secretion function of leptin in rat epididymal epithelium via the activation of cystic fibrosis transmembrane regulator and Na+-K+-2Cl- cotransporter, which was dependent on the paracrine/autocrine prostaglandin E2 stimulated EP2/EP4-adenylate cyclase pathways, and thus contributed to the formation of an appropriate microenvironment essential for sperm maturation.

The potential bone regeneration effects of leptin- and osteolectin-coated 3D-printed PCL scaffolds: an in vivo study

This study investigated the effectiveness of bone regeneration upon the application of leptin and osteolectin to a three-dimensional (3D) printed poly(ϵ-caprolactone) (PCL) scaffold. A fused deposition modeling 3D bioprinter was used to fabricate scaffolds with a diameter of 4.5 mm, a height of 0.5 mm, and a pore size of 420–520 nm using PCL (molecular weight: 43 000). After amination of the scaffold surface for leptin and osteolectin adhesion, the experimental groups were divided into the PCL scaffold (control), the aminated PCL (PCL/Amine) scaffold, the leptin-coated PCL (PCL/Leptin) scaffold, and the osteolectin-coated PCL (PCL/Osteo) scaffold. Next, the water-soluble tetrazolium salt-1 (WST-1) assay was used to assess cell viability. All groups exhibited cell viability rates of >100%. Female 7-week-old Sprague–Dawley rats were used for in vivo experiments. Calvarial defects were introduced on the rats’ skulls using a 5.5 mm trephine bur. The rats were divided into the PCL (control), PCL/Leptin, and PCL/Osteo scaffold groups. The scaffolds were then inserted into the calvarial defect areas, and the rats were sacrificed after 8-weeks to analyze the defect area. Micro-CT analysis indicated that the leptin- and osteolectin-coated scaffolds exhibited significantly higher bone regeneration. Histological analysis revealed new bone and blood vessels in the calvarial defect area. These findings indicate that the 3D-printed PCL scaffold allows for patient-customized fabrication as well as the easy application of proteins like leptin and osteolectin. Moreover, leptin and osteolectin did not show cytotoxicity and exhibited higher bone regeneration potential than the existing scaffold.