Selection of Leptin Surrogates by a General Phenotypic Screening Method for Receptor Agonists.

There is a high demand for agonist biomolecules such as cytokine surrogates in both biological and medicinal research fields. These are typically sourced through natural ligand engineering or affinity-based screening, followed by individual functional validation. However, efficient screening methods for identifying rare hits within immense libraries are very limited. In this research article, we introduce a phenotypic screening method utilizing biological receptor activation-dependent cell survival (BRADS). This method offers a high-throughput, low-background, and cost-effective approach that can be implemented in virtually any biochemical laboratory setting. As a proof-of-concept, we successfully identified a surrogate for human leptin following a two-week cell culture process, without the need for specialized high-throughput equipment or reagents. This surrogate effectively emulates the activity of native human leptin in cell validation assays. Our findings not only underscore the effectiveness of BRADS but also suggest its potential applicability to a broad range of biological receptors, including Notch and GPCRs.

Effect of Leptin in Human Sertoli Cells Mitochondrial Physiology.

Leptin is an adipose tissue hormone that acts as energy sensor and reproductive function regulator. Recent reports suggest that leptin is involved in mitochondrial biogenesis in different tissue cells. Herein, we hypothesized that leptin could also affect Sertoli cells mitochondrial dynamics and biogenesis. Human Sertoli cells (hSCs) were cultured in the presence of different leptin concentrations (5, 25 and 50 ng/mL) or vehicle for 24 h. The three different leptin concentrations were selected to mimic the circulating levels found either in normal weight, obese, and morbidly obese individuals, respectively. Leptin receptor (LEPR) expression was evaluated as well as mitochondrial membrane potential, complexes levels, complex II activity and basal respiration. Moreover, mitochondrial DNA copy number and expression of mitochondrial biogenesis markers were assessed. In hSCs, leptin concentrations similar to those found both in lean men decreased mitochondrial complex II protein levels, but no changes in its activity were observed. This is in agreement with basal respiration and mitochondrial membrane potential assessments, which indicate no alterations in mitochondrial fitness. Furthermore, no changes in mitochondrial biogenesis markers were observed upon leptin exposure, although SIRT1/3 levels were increased after exposure to the highest leptin concentration. Overall, the increase in SIRT1/3 levels suggests a role for leptin in glycolysis, which given the relevance of SCs glycolytic flux for germ cells nutritional support further reinforces that this mechanism can be linked to obesity-related subfertility/infertility.

Leptin receptor stimulation in late pregnant mouse uterine tissue inhibits spontaneous contractions by increasing NO and cGMP.

The adipokine, leptin exerts inhibitory effect on both spontaneous and oxytocin-induced contractions in myometrium. However, the mechanisms involved in leptin-induced effect are not clear. In the present study, we studied the altered characteristics of uterine contractions in the presence of leptin and the possible mechanisms of its effect in late pregnant (18.5 day) mouse uterus. We conducted functional, biochemical and molecular biology studies to demonstrate the mechanism of leptin-induced response. Leptin exerted an inhibitory response (Emax 40.5 ± 3.99%) on basal uterine contractions. The extent of inhibition was less than that obtained with known uterine relaxants, salbutamol (Emax103 ± 8.66%) and BRL-37344 (Emax 84.79 ± 8.12%). Leptin-induced uterine response was inhibited by leptin receptor antagonist SHLA and JAK-STAT pathway inhibitor, AG-490. The relaxant response was also subdued by NO-cGMP-PK-G pathway blockers L-NAME, 1400W, ODQ and KT-5823. Further, leptin enhanced the levels of NO and cGMP in uterine tissues. Also, SHLA, AG-490 and a combination of 1400 W and L-NAME prevented leptin-induced increase in NO. Similar effect was observed on cGMP levels in presence of leptin and SHLA. However, leptin did not influence CaCl2-induced response in potassium-depolarized tissues. We also detected leptin receptor protein in late pregnant mouse uterus located in endometrial luminal epithelium and myometrial layers. Real-time PCR studies revealed significantly higher expression of short forms of the receptor (ObRa and ObRc) in comparison to the long form (ObRb). In conclusion, the results of the present study suggest that leptin inhibits mouse uterine contraction by stimulating short forms of the leptin receptors and activating NO pathway in a JAK-STAT-dependent manner.

Leptin Receptor as a Potential Target to Inhibit Human Testicular Seminoma Growth.

Although in past decades the adipokine leptin and its own receptor have been considered as significant cancer biomarkers, their potential involvement in human testicular seminoma growth and progression remains unexplored. Here, we showed that the expression of leptin and its receptor was significantly higher in human testicular seminoma compared with normal adult testis. Human seminoma cell line TCam-2 also expressed leptin along with the long and short isoforms of leptin receptor, and in response to leptin treatment showed enhanced activation of its downstream effectors. In line with these results, leptin stimulation significantly increased the proliferation and migration of TCam-2 cells. Treatment of TCam-2 cells with the peptide Leu-Asp-Phe-Ile (LDFI), a full leptin-receptor antagonist, completely reversed the leptin-mediated effects on cell growth and motility as well as reduced the expression of several leptin-induced target genes. More importantly, the in vivo xenograft experiments showed that LDFI treatment markedly decreased seminoma tumor growth. Interestingly, LDFI-treated tumors showed reduced levels of the proliferation marker Ki-67 as well as decreased expression of leptin-regulated genes. Taken together, these data identify, for the first time, leptin as a key factor able to affect testicular seminoma behavior, highlighting leptin receptor as a potential target for novel potential treatments in this type of cancer.

Defining the Transcriptional Targets of Leptin Reveals a Role for Atf3 in Leptin Action.

Leptin acts via its receptor (LepRb) to modulate gene expression in hypothalamic LepRb-expressing neurons, thereby controlling energy balance and glucose homeostasis. Despite the importance of the control of gene expression in hypothalamic LepRb neurons for leptin action, the transcriptional targets of LepRb signaling have remained undefined because LepRb cells contribute a small fraction to the aggregate transcriptome of the brain regions in which they reside. We thus employed translating ribosome affinity purification followed by RNA sequencing to isolate and analyze mRNA from the hypothalamic LepRb neurons of wild-type or leptin-deficient (Lepob/ob) mice treated with vehicle or exogenous leptin. Although the expression of most of the genes encoding the neuropeptides commonly considered to represent the main targets of leptin action were altered only following chronic leptin deprivation, our analysis revealed other transcripts that were coordinately regulated by leptin under multiple treatment conditions. Among these, acute leptin treatment increased expression of the transcription factor Atf3 in LepRb neurons. Furthermore, ablation of Atf3 from LepRb neurons (Atf3LepRbKO mice) decreased leptin efficacy and promoted positive energy balance in mice. Thus, this analysis revealed the gene targets of leptin action, including Atf3, which represents a cellular mediator of leptin action.

Modeling the impact of growth and leptin deficits on the neuronal regulation of blood pressure.

The risk of hypertension is increased by intrauterine growth restriction (IUGR) and preterm birth. In the search for modifiable etiologies for this life-threatening cardiovascular morbidity, a number of pathways have been investigated, including excessive glucocorticoid exposure, nutritional deficiency and aberration in sex hormone levels. As a neurotrophic hormone that is intimately involved in the cardiovascular regulation and whose levels are influenced by glucocorticoids, nutritional status and sex hormones, leptin has emerged as a putative etiologic and thus a therapeutic agent. As a product of maternal and late fetal adipocytes and the placenta, circulating leptin typically surges late in gestation and declines after delivery until the infant consumes sufficient leptin-containing breast milk or accrues sufficient leptin-secreting adipose tissue to reestablish the circulating levels. The leptin deficiency seen in IUGR infants is a multifactorial manifestation of placental insufficiency, exaggerated glucocorticoid exposure and fetal adipose deficit. The preterm infant suffers from the same cascade of events, including separation from the placenta, antenatal steroid exposure and persistently underdeveloped adipose depots. Preterm infants remain leptin deficient beyond term gestation, rendering them susceptible to neurodevelopmental impairment and subsequent cardiovascular dysregulation. This pathologic pathway is efficiently modeled by placing neonatal mice into atypically large litters, thereby recapitulating the perinatal growth restriction-adult hypertension phenotype. In this model, neonatal leptin supplementation restores the physiologic leptin surge, attenuates the leptin-triggered sympathetic activation in adulthood and prevents leptin- or stress-evoked hypertension. Further pathway interrogation and clinical translation are needed to fully test the therapeutic potential of perinatal leptin supplementation.

Expression of receptors for insulin and leptin in the ventral tegmental area/substantia nigra (VTA/SN) of the rat: Historical perspective.

UNLABELLED: Since the publication of the observation that dopaminergic neurons in the ventral tegmental area/substantia nigra of the rat express receptors for insulin and leptin, numerous studies have extended and validated these findings. Thus, these major metabolic hormones have effects on synaptic and cell signaling function of the midbrain dopamine neurons, across a range of concentrations that reflect physiologic (fasting vs. fed) and pathophysiologic (diabetes) circumstances. The capacity of metabolic hormones to alter reward behaviors, including palatability-related food intake; motivation for food; and the conditioning of place preference by food, is now appreciated as an integral part of the larger actions of these hormones to regulate caloric homeostasis. Finally, the delineation of metabolic hormone effects on the CNS reward circuitry of normal animals provides the rationale and experimental basis for evaluating dysfunction of reward circuitry in obesity and diabetes. ORIGINAL ARTICLE ABSTRACT: EXPRESSION OF RECEPTORS FOR INSULIN AND LEPTIN IN THE VENTRAL TEGMENTAL AREA/SUBSTANTIA NIGRA (VTA/SN) OF THE RAT: Recent studies have demonstrated that the metabolic hormones insulin and leptin can modulate behavioral performance in reward-related paradigms. However, specific anatomical substrate(s) within the CNS for these effects remain to be identified. We hypothesize that midbrain dopamine neurons, which have been implicated to be critical in the mediation of motivational and reward aspects of stimuli, contribute to these behavioral effects of insulin and leptin. As one approach to evaluate this hypothesis, we used double-labeling fluorescence immunohistochemistry to determine whether the midbrain dopamine neurons express insulin receptors or leptin receptors. Extensive co-expression of tyrosine hydroxylase (a marker for dopamine neurons) with both the insulin receptor and the leptin receptor was observed in the ventral tegmentum and substantia nigra. These findings suggest that midbrain dopamine neurons are direct targets of insulin and leptin, and that they participate in mediating the effects of these hormones on reward-seeking behavior. This article is part of a Special Issue entitled SI:50th Anniversary Issue.

Leptin influences the excitability of area postrema neurons.

The area postrema (AP) is a circumventricular organ with important roles in central autonomic regulation. This medullary structure has been shown to express the leptin receptor and has been suggested to have a role in modulating peripheral signals, indicating energy status. Using RT-PCR, we have confirmed the presence of mRNA for the leptin receptor, ObRb, in AP, and whole cell current-clamp recordings from dissociated AP neurons demonstrated that leptin influenced the excitability of 51% (42/82) of AP neurons. The majority of responsive neurons (62%) exhibited a depolarization (5.3 ± 0.7 mV), while the remaining affected cells (16/42) demonstrated hyperpolarizing effects (-5.96 ± 0.95 mV). Amylin was found to influence the same population of AP neurons. To elucidate the mechanism(s) of leptin and amylin actions in the AP, we used fluorescence resonance energy transfer (FRET) to determine the effect of these peptides on cAMP levels in single AP neurons. Leptin and amylin were found to elevate cAMP levels in the same dissociated AP neurons (leptin: % total FRET response 25.3 ± 4.9, n = 14; amylin: % total FRET response 21.7 ± 3.1, n = 13). When leptin and amylin were coapplied, % total FRET response rose to 53.0 ± 8.3 (n = 6). The demonstration that leptin and amylin influence a subpopulation of AP neurons and that these two signaling molecules have additive effects on single AP neurons to increase cAMP, supports a role for the AP as a central nervous system location at which these circulating signals may act through common intracellular signaling pathways to influence central control of energy balance.

Leptin Matures Aspects of Lung Structure and Function in the Ovine Fetus.

In human and ovine fetuses, glucocorticoids stimulate leptin secretion, although the extent to which leptin mediates the maturational effects of glucocorticoids on pulmonary development is unclear. This study investigated the effects of leptin administration on indices of lung structure and function before birth. Chronically catheterized singleton sheep fetuses were infused iv for 5 days with either saline or recombinant ovine leptin (0.5 mg/kg · d leptin (LEP), 0.5 LEP or 1.0 mg/kg · d, 1.0 LEP) from 125 days of gestation (term ∼145 d). Over the infusion, leptin administration increased plasma leptin, but not cortisol, concentrations. On the fifth day of infusion, 0.5 LEP reduced alveolar wall thickness and increased the volume at closing pressure of the pressure-volume deflation curve, interalveolar septal elastin content, secondary septal crest density, and the mRNA abundance of the leptin receptor (Ob-R) and surfactant protein (SP) B. Neither treatment influenced static lung compliance, maximal lung volume at 40 cmH2O, lung compartment volumes, alveolar surface area, pulmonary glycogen, protein content of the long form signaling Ob-Rb or phosphorylated signal transducers and activators of transcription-3, or mRNA levels of SP-A, C, or D, elastin, vascular endothelial growth factor-A, the vascular endothelial growth factor receptor 2, angiotensin-converting enzyme, peroxisome proliferator-activated receptor γ, or parathyroid hormone-related peptide. Leptin administration in the ovine fetus during late gestation promotes aspects of lung maturation, including up-regulation of SP-B.

Beyond Lipoprotein Receptors: Learning from Receptor Knockouts Mouse Models about New Targets for Reduction of the Atherosclerotic Plaque.

Atherosclerosis and its complications represent the leading death cause worldwide, despite many therapeutic developments. Atherosclerosis is a complex, multistage disease whereby perturbed lipid metabolism leads to cholesterol accumulation into the vascular walls and plaque formation. Generation of apoE-/- and LDLR-/- atherosclerosis mouse models opened the avenue for investigating the mechanisms of action for specific molecules. We focus herein on the involvement of non-lipoprotein receptors in atherogenesis, as revealed by their total or site-specific ablation in the aforementioned murine models. The receptors reviewed span a broad range, from molecules related to lipid metabolism (adiponectin receptors) to molecules whose connection with atherogenesis is less obvious (cannabinoid receptors). We also outline cross-transplantation studies which allowed uncoupling the lipid modulating effects from the inflammatory ones. For certain receptors, since knockouts were unavailable, pharmacological data are presented instead. We emphasize the contribution of the receptors to the pathology, based on functional criteria, such as oxidative stress, immune response, inflammation, angiogenesis. Controversial aspects regarding the pro- or anti- atherogenic activity of some receptors are highlighted. We assume these discrepancies are due to the experimental setup, animal models used, tissue-specific action, various isoforms analyzed, divergent signaling or cross-talk between metabolic and immune pathways. Understanding the influences of cellular receptors in the progression of atherosclerosis allows their modulation towards an antiatherogenic phenotype. The experimental studies in animal models were in some cases successfully extrapolated to humans leading to atheroma reduction, and we expect this to occur even to a greater extent, based on the newest achievements.

Leptin/LepRb in the Ventral Tegmental Area Mediates Anxiety-Related Behaviors.

BACKGROUND: Leptin, an adipose-derived hormone, has been implicated in emotional regulation. We have previously shown that systemic administration of leptin produces anxiolytic-like effects and deletion of the leptin receptor, LepRb, in midbrain dopamine neurons leads to an anxiogenic phenotype. This study investigated whether activation or deletion of LepRb in the ventral tegmental area of adult mice is capable of inducing anxiolytic and anxiogenic effects, respectively. METHODS: Mice were cannulated in the ventral tegmental area and received bilateral intra-ventral tegmental area infusions of leptin or the JAK2/STAT3 inhibitor AG490. Anxiety-like behaviors were assessed using the elevated plus-maze, light-dark box, and novelty suppressed feeding tests. Deletion of LepRb in the ventral tegmental area was achieved by bilateral injection of AAV-Cre into the ventral tegmental area of adult Lepr(flox/flox) mice. Anxiety-related behaviors were evaluated 3 weeks after viral injection. RESULTS: Intra-ventral tegmental area infusions of leptin reduced anxiety-like behaviors, as indicated by increased percent open-arm time and open-arm entries in the elevated plus-maze test, increased time spent in the light side and decreased latency to enter the light side of the light-dark box, and decreased latency to feed in the novelty suppressed feeding test. Blockade of JAK2/STAT3 signaling in the ventral tegmental area by AG490 attenuated the anxiolytic effect produced by systemic administration of leptin. Lepr(flox/flox) mice injected with AAV-Cre into the ventral tegmental area showed decreased leptin-induced STAT3 phosphorylation and enhanced anxiety-like behaviors in the elevated plus-maze test and the novelty suppressed feeding test. CONCLUSIONS: These findings suggest that leptin-LepRb signaling in the ventral tegmental area plays an important role in the regulation of anxiety-related behaviors.

Possible involvement of 15-deoxy-Δ(12,14) -prostaglandin J2 in the development of leptin resistance.

Obesity is a worldwide health problem that urgently needs to be solved. Leptin is an anti-obesity hormone that activates satiety signals to the brain. Evidence to suggest that leptin resistance is involved in the development of obesity is increasing; however, the molecular mechanisms involved remain unclear. We herein demonstrated that 15-deoxy-Δ(12,14) -prostaglandin J2 (15d-PGJ2 ) was involved in the development of leptin resistance. A treatment with 15d-PGJ2 inhibited the leptin-induced activation of signal transducer and activator of transcription 3 (STAT3) in neuronal cells (SH-SY5Y-Ob-Rb cells). Furthermore, the intracerebroventricular administration of 15d-PGJ2 reversed the inhibitory effects of leptin on food intake in rats. The peroxisome proliferator-activated receptor gamma (PPAR-γ) antagonist, GW9662, slightly reversed the inhibitory effects of 15d-PGJ2 on the leptin-induced activation of STAT3 in neuronal cells. The PPAR-γ agonist, rosiglitazone, also inhibited leptin-induced STAT3 phosphorylation. Therefore, the inhibitory effects of 15d-PGJ2 may be mediated through PPAR-γ. On the other hand, 15d-PGJ2 -induced leptin resistance may not be mediated by endoplasmic reticulum stress or suppressor of cytokine signaling 3. The results of the present study suggest that 15d-PGJ2 is a novel factor for the development of leptin resistance in obesity. Leptin resistance, an insensitivity to the actions of leptin, is involved in the development of obesity. Here, we found 15-deoxy-Δ(12,14) -prostaglandin J2 (15d-PGJ2 ) may be involved in the development of leptin resistance. The present results suggest that the 15d-PGJ2 may be a novel factor for the development of leptin resistance in obesity. 15d-PGJ2 , 15-Deoxy-Δ(12,14) -prostaglandin J2; STAT3, signal tranducer and activator of transcription 3.

FoxO1 negatively regulates leptin-induced POMC transcription through its direct interaction with STAT3.

FoxO1, which is up-regulated during early stages of diet-induced leptin resistance, directly interacts with STAT3 and prevents STAT3 from binding to specificity protein 1 (SP1)-pro-opiomelanocortin (POMC) promoter complex, and thereby inhibits STAT3-mediated regulation of POMC transcription. FoxO1 also binds directly to the POMC promoter and negatively regulates its transcription. The present study aims to understand the relative contribution of the two interactions in regulating POMC expression. We studied the structural requirement of FoxO1 for its interaction with STAT3 and POMC promoter, and tested the inhibitory action of FoxO1 mutants by using biochemical assays, molecular biology and computer modelling. FoxO1 mutant with deletion of residues Ala137-Leu160 failed to bind to STAT3 or inhibit STAT3-mediated POMC activation, although its binding to the POMC promoter was unaffected. Further analysis mapped Gly140-Leu160 to be critical for STAT3 binding. The identified region Gly140-Leu160 was conserved among mammalian FoxO1 proteins, and showed a high degree of sequence identity with FoxO3, but not FoxO4. Consistently, FoxO3 could interact with STAT3 and inhibit POMC promoter activity, whereas FoxO4 could not bind to STAT3 or affect POMC promoter activity. We further identified that five residues (Gln145, Arg147, Lys148, Arg153 and Arg154) in FoxO1 were necessary in FoxO1-STAT3 interaction, and mutation of these residues abolished its interaction with STAT3 and inhibition of POMC promoter activity. Finally, a FoxO1-STAT3 interaction interface model generated by computational docking simulations confirmed that the identified residues of FoxO1 were in close proximity to STAT3. These results show that FoxO1 inhibits STAT3-mediated leptin signalling through direct interaction with STAT3.

Rescue of cardiac leptin receptors in db/db mice prevents myocardial triglyceride accumulation.

Increased leptin levels have been suggested to contribute to cardiac hypertrophy and attenuate cardiac lipid accumulation in obesity, although it has been difficult to separate leptin's direct effects from those caused by changes in body weight and adiposity. To determine whether leptin attenuates cardiac lipid accumulation in obesity or directly causes left ventricular hypertrophy (LVH), we generated a novel mouse model in which the long form of the leptin receptor (LepR) was "rescued" only in cardiomyocytes of obese db/db mice. Reexpression of cardiomyocyte leptin receptors in db/db mice did not cause LVH but reduced cardiac triglycerides and improved cardiac function. Compared with lean wild-type (WT) or db/db-cardiac LepR rescue mice, db/db mice exhibited significantly lower E/A ratio, a measurement of early to late diastolic filling, which averaged 1.5 ± 0.07 in db/db vs. 1.9 ± 0.08 and 1.8 ± 0.11 in WT and db/db-cardiac LepR rescue mice, respectively. No differences in systolic function were observed. Although db/db and db/db-cardiac LepR rescue mice exhibited similar increases in plasma triglycerides, insulin, glucose, and body weight, cardiac triglycerides were significantly higher in db/db compared with WT and db/db cardiac LepR rescue mice, averaging 13.4 ± 4.2 vs. 3.8 ± 1.6 vs. 3.8 ± 0.7 mg/g, respectively. These results demonstrate that despite significant obesity and increases in plasma glucose and triglycerides, db/db cardiac LepR rescue mice are protected against myocardial lipid accumulation. However, we found no evidence that leptin directly causes LVH.

Molecular dynamics, dynamic site mapping, and highthroughput virtual screening on leptin and the Ob receptor as anti-obesity target.

Body weight control is a mechanism finely regulated by several hormonal, metabolic, and nervous pathways. The leptin receptor (Ob-R) is crucial for energy homeostasis and regulation of food uptake. Leptin is a 16 kDa hormone that is mainly secreted by fat cells into the bloodstream, and under normal circumstances, circulating levels are proportionate to the fat body mass. Sensing of elevated leptin levels by the hypothalamic neurocircutry activates a negative feedback loop resulting in reduced food intake and increased energy expenditure. Decreased concentrations lead to opposite effects. Therefore rational design of leptin agonists constitute an appealing challenge in the battle against obesity. In this study, we performed protein-protein docking among the re-built crystal structure of leptin and leptin binding domain (LBD). The obtained complex was used as a starting point to carry out nanosecond-scale molecular dynamics simulations to characterize the key regions in terms of physical-chemical features involved in the protein-protein interaction (dynamic site mapping filtered by means multivariate analysis) and used to carry out a HTVS. The main goal of this study was to suggest guidelines for the rational drug design of new agonists of leptin. Identified hits could be a consistent starting point to carry out in vitro testing.

The over-expression of miR-200a in the hypothalamus of ob/ob mice is linked to leptin and insulin signaling impairment.

Early in life, leptin plays a crucial role in hypothalamic neural organization. Leptin, most likely, controls neural gene expression conferring then specific phenotype regarding energy homeostasis. MicroRNAs are new regulators for several physiological functions, including the regulation of metabolism. However, the impact of leptin on hypothalamic microRNA patterns remains unknown. Here, we demonstrate that miR-200a, miR-200b and miR-429 are up-regulated in the hypothalamus of genetically obese and leptin deficient ob/ob mice. Leptin treatment down-regulates these miRNAs in ob/ob hypothalamus. The hypothalamic silencing of miR-200a increased the expression level of leptin receptor and insulin receptor substrate 2, reduced body weight gain, and restored liver insulin responsiveness. In addition, the overexpression of pre-miR-200a in a human neuroblastoma cell line impaired insulin and leptin signaling. These findings link the alteration of leptin and insulin signaling to the up-regulation of hypothalamic miR-200a which could be a new target for treatment of obesity.

Increased risk of cardiovascular complications in chronic kidney disease: a possible role of leptin.

Leptin is a small peptide hormone (16 kDa), a product of the obesity gene (Ob), and is mainly synthesized and secreted by adipocytes. It is removed from the blood by the kidneys. The kidney is not only a site of leptin clearance, but also a target organ for its action in different pathophysiological states. Several studies have documented a strong relationship between chronic kidney disease (CKD) and accelerated cardiovascular disease (CVD) defined as a cardiorenal syndrome. Patients with stage 3 and 4 CKD develop cardiovascular complications and are at increased risk of death from CVD. Renal dysfunction promotes several mechanisms responsible for exacerbation of cardiovascular disease. These include activation of the renin-angiotensin system, oxidative stress, elevated asymmetric dimethylarginine (ADMA), low-grade inflammation with increased circulating cytokines, and dyslipidemia. Recently, it has been observed that plasma leptin level is elevated in patients with cardiorenal syndrome. In obesity, hyperleptinemia combined with selective leptin resistance appear to have a critical role in the development and progression of kidney disease, CVD and metabolic syndrome. This has clinical implications for the treatment of obesity-related hypertension and kidney disease. In this paper the role of leptin in chronic kidney disease and accelerated cardiovascular disease is out lined. The link between hyperleptinemia and development and progression of morphologic changes that effect kidney in obese patients is also discussed.

Leptin in thrombosis and atherosclerosis.

A world-wide obesity epidemic is threatening to have a major impact on the prevalence of chronic and acute vascular diseases. In addition to weight loss interventions, which have met with modest success to date, it will be important to understand mechanisms by which obesity promotes vascular disease processes. Studies of leptin, a hormone produced by the adipocyte, have supported the concept that adipocyte-specific products may be mediating some of the vascular risk associated with obesity. This mini-review provides an overview of some of the preclinical studies demonstrating causal relationships between leptin and vascular endpoints. Therapeutic strategies designed to block leptin-mediated signaling events in cells contributing to vascular disease may prove beneficial in obese subjects at risk for vascular complications.

What fans the fire: insights into mechanisms of leptin in metabolic syndrome-associated heart diseases.

Obesity and metabolic syndrome are one of the most devastating risk factors for cardiovascular diseases. The obesity gene product leptin plays a central role in the regulation of food intake and energy expenditure. The physiological and pathophysiological roles of leptin in cardiovascular system have been investigated extensively since its discovery in 1994. In addition to its well-established metabolic effects, more recent evidence have depicted a rather pivotal role of leptin in inflammation, oxidative stress, endoplasmic reticulum stress, apoptosis and tissue remodeling en route to the pathogenesis of type 2 diabetes mellitus, hypertension, atherosclerosis, and insulin resistance. Under physiological condition, leptin is known to reduce appetite, promote energy expenditure, increase sympathetic activity, facilitate glucose utilization and improve insulin sensitivity. In addition, leptin may regulate cardiac and vascular function through a nitric oxide-dependent mechanism. However, hyperleptinemia usually occurs with progressively increased body weight and metabolic syndrome development, leading to a state of global or selective leptin resistance. Both central and peripheral leptin resistance may be present under pathophysiological conditions such as inflammation, insulin resistance, hyperlipidemia and a cadre of other cardiovascular diseases including hypertension, atherosclerosis, obesity, ischemic heart disease and heart failure. In this review, we will discuss cardiovascular actions of leptin related to various components of metabolic syndrome. Particular emphasis will be given to insights derived from therapeutic interventions with lifestyle modification, cardiovascular drugs, anti-diabetic and anti-obesity drugs.

Mechanisms linking leptin to arterial and venous thrombosis: potential pharmacological targets.

Epidemiological evidence strongly links excess body weight with an increased risk to develop atherothrombotic complications. Obesity is frequently associated with systemic and local inflammation as well as elevated circulating leptin levels, and clinical studies found hyperleptinemia to correlate not only with measures of adiposity, but also with circulating biomarkers of an increased metabolic and cardiovascular risk or surrogate markers of subclinical atherosclerosis. Moreover, experimental studies in mice with systemic disruption of the leptin-leptin receptor system as well as after administration or neutralization of the adipokine demonstrated that leptin promotes both arterial and venous thrombosis. In addition to directly binding to and activating platelets and thus potentiating their aggregation in response to agonist stimulation, leptin enhances the expression of prothrombotic and anti-fibrinolytic proteins in vascular and inflammatory cells. On the other hand, its ability to mobilize and recruit vascular progenitor cells from the bone marrow to sites of vascular injury was found to be impaired in hyperleptinemic, obese humans and rodents. Thus, leptin promotes thrombus formation and resolution by several different mechanisms involving primary hemostasis, the coagulation cascade as well as the integrity of the vessel wall. Dissection of the molecular mechanisms underlying each of its actions may pave the road for novel therapeutic options in targeting the increased risk of thrombosis associated with obesity, keeping in mind unresolved issues of a cell-specific leptin resistance as well as individual differences in the responsiveness to leptin.