Leptin signaling in the hypothalamus: emphasis on energy homeostasis and leptin resistance

Hypothalamic PDE3B deficiency alters body weight and glucose homeostasis in mouse

Pharmacological studies have suggested hypothalamic phosphodiesterase-3B to mediate leptin and insulin action in regulation of energy homeostasis. Whereas Pde3b-null mice show altered energy homeostasis, it is unknown whether this is due to ablation of Pde3b in the hypothalamus. Thus, to address the functional significance of hypothalamic phosphodiesterase-3B, we used Pde3bflox/flox and Nkx2.1-Cre mice to generate Pde3b Nkx2.1KD mice that showed 50% reduction of phosphodiesterase-3B in the hypothalamus. To determine the effect of partial ablation of phosphodiesterase-3B in the hypothalamus on energy and glucose homeostasis, males and females were subjected to either a low- or high-fat diet for 19–21 weeks. Only female but not male Pde3b Nkx2.1KD mice on the low-fat diet showed increased body weight from 13 weeks onward with increased food intake, decreased fat pad weights and hypoleptinemia. Glucose tolerance was improved in high-fat diet-fed male Pde3b Nkx2.1KD mice in association with decreased phosphoenolpyruvate carboxykinase-1 and glucose-6-phosphatase mRNA levels in the liver. Also, insulin sensitivity was increased in male Pde3b Nkx2.1KD mice on the low-fat diet. Changes in body weight or in glucose homeostasis were not associated with any alteration in hypothalamic proopiomelanocortin, neuropepide Y and agouti-related peptide mRNA levels. These results suggest that partial loss of phosphodiesterase-3B in the hypothalamus produces a sex-specific response in body weight and glucose homeostasis, and support a role, at least in part, for hypothalamic phosphodiesterase-3B in regulation of energy and glucose homeostasis in mice.

Gestational Hypoxia and Developmental Plasticity

Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.

Leptin alters somatosensory thalamic networks by decreasing gaba release from reticular thalamic nucleus and action potential frequency at ventrobasal neurons

Leptin is an adipose-derived hormone that controls appetite and energy expenditure. Leptin receptors are expressed on extra-hypothalamic ventrobasal (VB) and reticular thalamic (RTN) nuclei from embryonic stages. Here, we studied the effects of pressure-puff, local application of leptin on both synaptic transmission and action potential properties of thalamic neurons in thalamocortical slices. We used whole-cell patch-clamp recordings of thalamocortical VB neurons from wild-type (WT) and leptin-deficient obese (ob/ob) mice. We observed differences in VB neurons action potentials and synaptic currents kinetics when comparing WT vs. ob/ob. Leptin reduced GABA release onto VB neurons throughout the activation of a JAK2-dependent pathway, without affecting excitatory glutamate transmission. We observed a rapid and reversible reduction by leptin of the number of action potentials of VB neurons via the activation of large conductance Ca²⁺-dependent potassium channels. These leptin effects were observed in thalamocortical slices from up to 5-week-old WT but not in leptin-deficient obese mice. Results described here suggest the existence of a leptin-mediated trophic modulation of thalamocortical excitability during postnatal development. These findings could contribute to a better understanding of leptin within the thalamocortical system and sleep deficits in obesity.

Yoga as an Integrative Approach for Prevention and Treatment of Oral Cancer

Despite tremendous advancements in medicine, the number of oral cancer cases continues to increase, and the need for integrating alternate medicine or adopting an integrative approach has become a compelling cost-effective requirement for the management and treatment of diseases. Conventional treatment of oral cancer involves surgery followed by radiotherapy with or without chemotherapy which causes several complications including poor quality of life and high chances of recurrence of cancer. Oral cancer is often linked with obesity which is major risk factors in other cancers. Apart from obesity, oral cancer is thought to have an inverse relation with neurodegenerative disorders presumably because cell death decreases in the former case and increases in the latter. Ancient mind-body techniques such as yoga have not been adequately tested as a tool to synergize the cellular equilibrium pertaining to the treatment of oral cancer. Nerve growth factor (NGF), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) are among the early experimental cellular biomarkers that may be used to probe the modulation of oral cancer, obesity, and neurodegenerative disorders. Yoga has been reported to influence these molecules in healthy individuals but whether their expression can be altered in patients of oral cancer by yoga intervention is the subject of this research being discussed in this review article. Therefore, the present article not only reviews the current status of research studies in oral cancer, obesity, and neurodegenerative disorders but also how these are linked to each other and why the investigations of the putative NGF pathway, involving TNF-α and IL-6, could provide useful clues to understand the molecular effects brought about by yoga intervention in such patients.

The effects of prenatal undernutrition and a high-fat postnatal diet on central and peripheral orexigenic and anorexigenic factors in female rats

Prenatal undernutrition and postnatal overnutrition increase the risk of some peripheral and central metabolic disorders in adulthood. We speculated that disturbances of appetite/metabolic regulatory factors might already have been established in the early stages of life and contribute to obesity later in life. The effects of a high-fat diet on the levels of peripheral and central appetite/metabolic regulatory factors were compared between the offspring of normally nourished dams and those of undernourished dams in the peri-pubertal period. In the offspring of the normally nourished dams (control), the consumption of the high-fat diet resulted in lower hypothalamic mRNA levels of orexigenic factors (neuropeptide Y (NPY) and prepro-orexin (pporexin)), whereas no such changes were seen in the offspring of the undernourished dams (subjected to intrauterine growth restriction). These results indicate that in high-energy conditions either the adaptive response does not function properly or has not been established in the offspring of undernourished dams. Because NPY and pporexin are negatively regulated by leptin, these findings suggest that in the intrauterine growth restriction group, the leptin resistance of hypothalamic functions, which is usually caused by diet-induced obesity in adulthood, had already been established in the peri-pubertal period.

Adipokines in Liver Cirrhosis

Liver fibrosis can progress to cirrhosis, which is considered a serious disease. The Child-Pugh score and the model of end-stage liver disease score have been established to assess residual liver function in patients with liver cirrhosis. The development of portal hypertension contributes to ascites, variceal bleeding and further complications in these patients. A transjugular intrahepatic portosystemic shunt (TIPS) is used to lower portal pressure, which represents a major improvement in the treatment of patients. Adipokines are proteins released from adipose tissue and modulate hepatic fibrogenesis. These proteins affect various biological processes that are involved in liver function, including angiogenesis, vasodilation, inflammation and deposition of extracellular matrix proteins. The best studied adipokines are adiponectin and leptin. Adiponectin protects against hepatic inflammation and fibrogenesis, and leptin functions as a profibrogenic factor. These and other adipokines are supposed to modulate disease severity in patients with liver cirrhosis. Consequently, circulating levels of these proteins have been analyzed to identify associations with parameters of hepatic function, portal hypertension and its associated complications in patients with liver cirrhosis. This review article briefly addresses the role of adipokines in hepatitis and liver fibrosis. Here, studies having analyzed these proteins in systemic blood in cirrhotic patients are listed to identify adipokines that are comparably changed in the different cohorts of patients with liver cirrhosis. Some studies measured these proteins in systemic, hepatic and portal vein blood or after TIPS to specify the tissues contributing to circulating levels of these proteins and the effect of portal hypertension, respectively.

Intraventricular administration of Tenebrio molitor larvae extract regulates food intake and body weight in mice with high-fat diet-induced obesity

We recently reported the in vitro and in vivo antiobesity effects of Tenebrio molitor larvae, a traditional food in many countries, but it remains unknown how the larvae affect appetite regulation in mice with diet-induced obesity. We hypothesized that the extract of T molitor larvae mediates appetite by regulating neuropeptide expression. We investigated T molitor larvae extract's (TME's) effects on anorexigenesis and endoplasmic reticulum (ER) stress-induced orexigenic neuropeptide expression in the hypothalami of obese mice. Intracerebroventricular TME administration suppressed feeding by down-regulating the expression of the orexigenic neuropeptides neuropeptide Y and agouti-related protein. T molitor larvae extract significantly reduced the expression of ER stress response genes. These results suggest that TME and its bioactive components are potential therapeutics for obesity and ER stress-driven disease states.

Perspective: A Historical and Scientific Perspective of Sugar and Its Relation with Obesity and Diabetes

Fructose-containing added sugars, such as sucrose and high-fructose corn syrup, have been experimentally, epidemiologically, and clinically shown to be involved in the current epidemics of obesity and diabetes. Here we track this history of intake of sugar as it relates to these epidemics. Key experimental studies that have identified mechanisms by which fructose causes obesity and diabetes are reviewed, as well as the evidence that the uricase mutation that occurred in the mid-Miocene in ancestral humans acted as a "thrifty gene" that increases our susceptibility for fructose-associated obesity today. We briefly review recent evidence that obesity can also be induced by nondietary sources of fructose, such as from the metabolism of glucose (from high-glycemic carbohydrates) through the polyol pathway. These studies suggest that fructose-induced obesity is driven by engagement of a "fat switch" and provide novel insights into new approaches for the prevention and treatment of these important diseases.

Early life stress experience may blunt hypothalamic leptin signalling

The aim of this study was to investigate whether neonatal maternal separation (MS) - chronic stress experience in early life - affects the anorectic efficacy of leptin in the offspring at adolescence. Sprague-Dawley pups were separated from the dam daily for 3 h during postnatal day 1-14 or left undisturbed as non-handled controls (NH). NH and MS male pups received an intraperitoneal leptin (100 μg/kg) or saline on postnatal day (PND) 28, and then food intake and body weight gain were recorded. The hypothalamic levels of leptin-signalling-related genes, phosphorylated signal transducer and activator of transcription-3 (pSTAT3) and protein-tyrosine phosphatase 1B (PTP1B) were examined at 40 min after a single injection of leptin on PND 39 by immunohistochemistry and Western blot analysis. Leptin-induced suppressions in food intake and weight gain was observed in NH pups, but not in MS. Leptin increased pSTAT3 in the hypothalamic arcuate nucleus of NH pups, but not of MS. Interestingly, basal levels of the hypothalamic PTP1B and pSTAT3 were increased in MS pups compared with NH controls. The results suggest that neonatal MS experience may blunt the anorectic efficacy of leptin later in life, possibly in relation with increased expressions of PTP1B and/or pSTAT3 in the hypothalamus.

Epidemiological bases and molecular mechanisms linking obesity, diabetes, and cancer

The association between diabetes and cancer was hypothesized almost one century ago. Today, a vast number of epidemiological studies support that obese and diabetic populations are more likely to experience tissue-specific cancers, but the underlying molecular mechanisms remain unknown. Obesity, diabetes, and cancer share many hormonal, immune, and metabolic changes that may account for the relationship between diabetes and cancer. In addition, antidiabetic treatments may have an impact on the occurrence and course of some cancers. Moreover, some anticancer treatments may induce diabetes. These observations aroused a great controversy because of the ethical implications and the associated commercial interests. We report an epidemiological update from a mechanistic perspective that suggests the existence of many common and differential individual mechanisms linking obesity and type 1 and 2 diabetes mellitus to certain cancers. The challenge today is to identify the molecular links responsible for this association. Classification of cancers by their molecular signatures may facilitate future mechanistic and epidemiological studies.

Plasma levels of leptin and ghrelin and their correlation with BMI, and circulating lipids and glucose in obese Tunisian women

Background

A National Survey on the Effect of Nutrition conducted in 1996−1997 showed a 14% overall prevalence of obesity in Tunisia with a female predominance. Leptin and ghrelin play crucial roles in regulating body weight and energy balance. Leptin, an anorectic hormone, and ghrelin, an orexigenic hormone, appear to interact with glucose and lipid metabolism.

Objectives

To determine the circulating levels of ghrelin and leptin in obese Tunisian women and to investigate the correlations of these hormones with body mass index (BMI), and circulating lipids and glucose.

Methods

Forty obese women were recruited from patients in the “C” Unit of the National Institute of Nutrition and Food Technology. Twenty normal women were recruited as controls. Plasma levels of the studied variables were measured in patients from both groups and findings were analyzed.

Results

Circulating levels of leptin were significantly higher, while high-density lipoprotein (HDL)-cholesterol and ghrelin levels were significantly lower in the obese women. In the obese women, significant positive correlations were found between circulating levels of leptin and low-density lipoprotein (LDL)-cholesterol, BMI, and glucose; and ghrelin and HDL-cholesterol. Significant negative correlations were found between circulating levels of leptin and HDL-cholesterol and ghrelin; and ghrelin and leptin, LDL-cholesterol, BMI, and glucose. Multivariate analysis revealed that ghrelin was significantly associated with HDL-cholesterol, LDL-cholesterol, and blood glucose.

Conclusions

The significant negative correlation between leptin and ghrelin suggests that these two hormones may be antagonistic. Increased levels of ghrelin are correlated with decreased circulating levels of HDL-cholesterol and increased levels of LDL-cholesterol.

Eat and Death: Chronic Over-Eating

Obesity-related co-morbidities decrease life quality, reduce working ability and lead to early death. The total amount of dietary fat consumption may be the most potent food-related risk factor for weight gain. In this respect, dietary intake of high-caloric, high-fat diets due to chronic over-eating and sedentary lifestyle lead to increased storage of triglycerides not only in adipose tissue but also ectopically in other tissues . Increased plasma concentrations of non-esterified free fatty acids and lipid-overloaded hypertrophic adipocytes may cause insulin resistance in an inflammation-independent manner. Even in the absence of metabolic disorders, mismatch between fatty acid uptake and utilization leads to the accumulation of toxic lipid species resulting in organ dysfunction. Lipid-induced apoptosis, ceramide accumulation, reactive oxygen species overproduction, endoplasmic reticulum stress, and mitochondrial dysfunction may play role in the pathogenesis of lipotoxicity. The hypothalamus senses availability of circulating levels of glucose, lipids and amino acids, thereby modifies feeding according to the levels of those molecules. However, the hypothalamus is also similarly vulnerable to lipotoxicity as the other ectopic lipid accumulated tissues. Chronic overnutrition most likely provides repetitive and persistent signals that up-regulate inhibitor of nuclear factor kappa B kinase beta subunit/nuclear factor kappa B (IKKβ/NF-κB) in the hypothalamus before the onset of obesity. However, the mechanisms by which high-fat diet induced peripheral signals affect the hypothalamic arcuate nucleus remain largely unknown. In this chapter, besides lipids and leptin, the role of glucose and insulin on specialized fuel-sensing neurons of hypothalamic neuronal circuits has been debated.

The effect of combined inositol hexakisphosphate and inositol supplement in streptozotocin-induced type 2 diabetic rats

Inositol hexakisphosphate (IP6) and inositol both regulate insulin secretion, but their combined use in the management of diabetes deserves investigation. The combined effects of IP6 and inositol supplementation were investigated in streptozotocin-induced type 2 diabetic rats. The following groups of rats were studied for 8 weeks: non-diabetic control, non-diabetic high-fat diet control, diabetic untreated, diabetic rats treated with the combination of IP6 and inositol (650 mg/kg bw) and diabetic rats treated with glibenclamide (10 mg/kg bw). High-fat diet and streptozotocin were used to induce type 2 diabetes mellitus in Sprague-Dawley rats. Body weight, blood glucose, glycated haemoglobin, insulin, serum leptin, HOMA-insulin resistance scores, intestinal amylase activity, serum and faecal lipids and food and fluid consumption were measured. Treatment with the combination significantly reduced blood glucose (306 ± 53 mg/dl) and insulin resistance score (1.93 ± 0.45) compared with diabetic controls (522 ± 24 mg/dl and 5.1 ± 0.69 respectively). Serum leptin (2.8 ± 0.6 ng/dl) and faecal triglycerides (108 ± 8 mg/dl) were significantly increased in rats treated with the combination compared with the diabetic control (1.8 ± 0.06 ng/dl and 86 ± 4 mg/dl). Serum triglyceride (47 ± 5.1 mg/dl), total cholesterol (98 ± 3.2 mg/dl) and food intake (26 ± 0.3 g) were significantly reduced by 45%, 25% and 25%, respectively, in rats treated with the combination compared with the diabetic control. Inositol and IP6 combined supplementation may be effective in the management of type 2 diabetes mellitus and related metabolic disorders by regulating some aspects of lipid and carbohydrate metabolism.

Adipose tissue in control of metabolism

Adipose tissue plays a central role in regulating whole-body energy and glucose homeostasis through its subtle functions at both organ and systemic levels. On one hand, adipose tissue stores energy in the form of lipid and controls the lipid mobilization and distribution in the body. On the other hand, adipose tissue acts as an endocrine organ and produces numerous bioactive factors such as adipokines that communicate with other organs and modulate a range of metabolic pathways. Moreover, brown and beige adipose tissue burn lipid by dissipating energy in the form of heat to maintain euthermia, and have been considered as a new way to counteract obesity. Therefore, adipose tissue dysfunction plays a prominent role in the development of obesity and its related disorders such as insulin resistance, cardiovascular disease, diabetes, depression and cancer. In this review, we will summarize the recent findings of adipose tissue in the control of metabolism, focusing on its endocrine and thermogenic function.

Physiology, pathophysiology and therapeutic implications of enteroendocrine control of food intake

With the increasing prevalence of obesity and its associated comorbidities, strides to improve treatment strategies have enhanced our understanding of the function of the gut in the regulation of food intake. The most successful intervention for obesity to date, bariatric surgery effectively manipulates enteroendocrine physiology to enhance satiety and reduce hunger. Areas covered: In the present article, we provide a detailed overview of the physiology of enteroendocrine control of food intake, and discuss its pathophysiologic correlates and therapeutic implications in both obesity and gastrointestinal disease. Expert commentary: Ongoing research in the field of nutrient sensing by L-cells, as well as understanding the role of the microbiome and bile acid signaling may facilitate the development of novel strategies to combat the rising population health threat associated with obesity. Further refinement of post-prandial satiety gut hormone based therapies, including the development of chimeric peptides exploiting the pleiotropic nature of the gut hormone response, and identification of novel methods of delivery may hold the key to optimization of therapeutic modulation of gut hormone physiology in obesity.

Adult Neurogenesis in the Female Mouse Hypothalamus: Estradiol and High-Fat Diet Alter the Generation of Newborn Neurons Expressing Estrogen Receptor α

Estrogens and leptins act in the hypothalamus to maintain reproduction and energy homeostasis. Neurogenesis in the adult mammalian hypothalamus has been implicated in the regulation of energy homeostasis. Recently, high-fat diet (HFD) and estradiol (E2) have been shown to alter cell proliferation and the number of newborn leptin-responsive neurons in the hypothalamus of adult female mice. The current study tested the hypothesis that new cells expressing estrogen receptor α (ERα) are generated in the arcuate nucleus (ARC) and the ventromedial nucleus of the hypothalamus (VMH) of the adult female mouse, hypothalamic regions that are critical in energy homeostasis. Adult mice were ovariectomized and implanted with capsules containing E2 or oil. Within each hormone group, mice were fed an HFD or standard chow for 6 weeks and treated with BrdU to label new cells. Newborn cells that respond to estrogens were identified in the ARC and VMH, of which a subpopulation was leptin sensitive, indicating that the subpopulation consists of neurons. Moreover, there was an interaction between diet and hormone with an effect on the number of these newborn ERα-expressing neurons that respond to leptin. Regardless of hormone treatment, HFD increased the number of ERα-expressing cells in the ARC and VMH. E2 decreased hypothalamic fibroblast growth factor 10 (Fgf10) gene expression in HFD mice, suggesting a role for Fgf10 in E2 effects on neurogenesis. These findings of newly created estrogen-responsive neurons in the adult brain provide a novel mechanism by which estrogens can act in the hypothalamus to regulate energy homeostasis in females.

Butyrylcholinesterase Deficiency Promotes Adipose Tissue Growth and Hepatic Lipid Accumulation in Male Mice on High-Fat Diet

Despite numerous reports of relationships between weight gain and butyrylcholinesterase (BChE), this enzyme's role in the genesis of obesity remains unclear, but recent research points to strong links with ghrelin, the "hunger hormone." The availability of BChE knockout (KO) mice provides an opportunity to clarify the causal relationship between BChE and obesity onset. We now find that young KO mice have abnormally high plasma ghrelin levels that slowly decline during long-term high-fat feeding and ultimately drop below those in wild-type mice. On such a diet, the KO mice gained notably more weight, more white fat, and more hepatic fat than wild-type animals. In addition to a greater burden of hepatic triglycerides, the livers of these KO mice show distinctly higher levels of inflammatory markers. Finally, their energy expenditure proved to be lower than in wild-type mice despite similar activity levels and increased caloric intake. A gene transfer of mouse BChE with adeno-associated virus vector restored nearly all aspects of the normal phenotype. Our results indicate that BChE strongly affects fat metabolism, has an important impact on fat accumulation, and may be a promising tool for combating obesity.

Sex-dependent regulation of hypothalamic neuropeptide Y-Y1 receptor gene expression in leptin treated obese (ob/ob) or lean mice

Pharmacological and genetic studies have shown that the Y₁ receptor (Y₁R) for Neuropeptide Y (NPY) plays a crucial role in the control of feeding behavior under metabolic conditions of low leptin levels or leptin deficiency. In this study, we investigated the effect of leptin deficiency and leptin replacement on Y₁R gene expression in the hypothalamus of lean and obese Y₁R/LacZ transgenic mice (TgY₁R/LacZ) carrying the murine Y1R promoter linked to the LacZ gene that induces the expression of β-galactosidase. Two daily intraperitoneal injections with leptin (1μg/g of body weight for one week) of male and female lean (TgY₁R/LacZ^+/+) and obese (TgY₁R/LacZ^ob/ob) mice induced a significant decrease of body weight in both sexes and genotypes. In males, leptin administration decreased β-galactosidase activity in the PVN and DMH of lean mice, and increased transgene expression in the same hypothalamic nuclei of obese mice. Sex-related differences were also observed in both genotypes, since leptin treatment failed to affect transgene expression in hypothalamus of lean and obese female mice. These results provide further evidence for a sexual dimorphism of the hypothalamic NPY-Y₁R-mediated pathway in response to changes in leptin circulating levels.

Novel Mechanisms of Compromised Lymphatic Endothelial Cell Homeostasis in Obesity: The Role of Leptin in Lymphatic Endothelial Cell Tube Formation and Proliferation

Leptin is a hormone produced by adipose tissue that regulates various physiological processes. Recent studies have shown that the level of circulating leptin is elevated in obese patients and have suggested a relationship between obesity and postoperative lymphedema. However, the mechanisms by which postoperative lymphedema develops in obese patients and the mechanisms by which leptin regulates lymphatic endothelial cell homeostasis such as tube formation and cell proliferation remain unknown. Here we report that leptin regulates tube formation and cell proliferation in human dermal lymphatic endothelial cells (HDLECs) by activation of the signal transducer and activator of transcription 3 pathway, which is downstream signaling of the leptin receptor. Additionally, we found that upregulation of suppressor of cytokine signaling 3 underlies the mechanisms by which a high dose of leptin inhibits cell proliferation and tube formation. Leptin also enhanced expression of the proinflammatory cytokine IL-6 in HDLECs. Interestingly, IL-6 rescues the compromised cell proliferation and tube formation caused by treatment with a high dose of leptin in an autocrine or paracrine manner. Taken together, our findings reveal a novel mechanism by which compromised HDLECs maintain their homeostasis during inflammation mediated by leptin and IL-6. Thus, regulating the level of leptin or IL-6 may be a viable strategy to reduce the incidence of postoperative lymphedema.

Inhibition of Leptin-ObR Interaction Does not Prevent Leptin Translocation Across a Human Blood-Brain Barrier Model

The adipocyte-derived hormone leptin regulates appetite and energy homeostasis through the activation of leptin receptors (ObR) on hypothalamic neurones; hence, leptin must be transported through the blood-brain barrier (BBB) to reach its target sites in the central nervous system. During obesity, however, leptin BBB transport is decreased, in part precluding leptin as a viable clinical therapy against obesity. Although the short isoform of the ObR (ObRa) has been implicated in the transport of leptin across the BBB as a result of its elevated expression in cerebral microvessels, accumulating evidence indicates that leptin BBB transport is independent of ObRa. In the present study, we employed an ObR-neutralising antibody (9F8) to directly examine the involvement of endothelial ObR in leptin transport across an in vitro human BBB model composed of the human endothelial cell line hCMEC/D3. Our results indicate that, although leptin transport across the endothelial monolayer was nonparacellular, and energy- and endocytosis-dependent, it was not inhibited by pre-treatment with 9F8, despite the ability of the latter to recognise hCMEC/D3-expressed ObR, prevent leptin-ObR binding and inhibit leptin-induced signal transducer and activator of transcription 3 (STAT-3) phosphorylation in hCMEC/D3 cells. Furthermore, hCMEC/D3 cells expressed the transporter protein low-density lipoprotein receptor-related protein-2 (LRP-2), which is capable of binding and endocytosing leptin. In conclusion, our results demonstrate that leptin binding to and signalling through ObR is not required for efficient transport across human endothelial monolayers, indicating that ObR is not the primary leptin transporter at the human BBB, a role which may fall upon LRP-2. A deeper understanding of leptin BBB transport will help clarify the exact causes for leptin resistance seen in obesity and aid in the development of more efficient BBB-penetrating leptin analogues.

Hypothalamic Phosphodiesterase 3B Pathway Mediates Anorectic and Body Weight-Reducing Effects of Insulin in Male Mice

BACKGROUND

Insulin action in the hypothalamus plays a critical role in the regulation of energy homeostasis, yet the intracellular signaling mechanisms mediating insulin action are incompletely understood. Although phosphodiesterase 3B (PDE3B) mediates insulin action in the adipose tissue and it is highly expressed in the hypothalamic areas implicated in energy homeostasis, its role, if any, in mediating insulin action in the hypothalamus is unknown. We tested the hypothesis that insulin action in the hypothalamus is mediated by PDE3B.

METHODS

Using enzymatic assay, we examined the effects of peripheral or central administration of insulin on hypothalamic PDE3B activity in adult mice. Western blotting and immunohistochemistry also examined p-Akt and p-STAT3 levels in the hypothalamus. Effects of leptin on these parameters were also compared. We injected cilostamide, a PDE3 inhibitor, prior to central injection of insulin and examined the 12- to 24-hour food intake and 24-hour body weight. Finally, we examined the effect of cilostamide on insulin-induced proopiomelanocortin (Pomc), neurotensin (Nt), neuropeptide Y (Npy) and agouti-related peptide (Agrp) gene expression in the hypothalamus by qPCR.

RESULTS

Peripheral or central injection of insulin significantly increased PDE3B activity in the hypothalamus in association with increased p-Akt levels but without any change in p-STAT3 levels. However, leptin-induced increase in PDE3B activity was associated with an increase in both p-Akt and p-STAT3 levels in the hypothalamus. Prior administration of cilostamide reversed the anorectic and body weight-reducing effects as well as stimulatory effect of insulin on hypothalamic Pomc mRNA levels. Insulin did not alter Nt, Npy and Agrp mRNA levels.

CONCLUSION

Insulin induction of hypothalamic PDE3B activity and the reversal of the anorectic and body weight-reducing effects and stimulatory effect of insulin on hypothalamic Pomc gene expression by cilostamide suggest that activation of PDE3B is a novel mechanism of insulin signaling in the hypothalamus.

Allomyrina Dichotoma Larvae Regulate Food Intake and Body Weight in High Fat Diet-Induced Obese Mice Through mTOR and Mapk Signaling Pathways

Recent evidence has suggested that the Korean horn beetle (Allomyrina dichotoma) has anti-hepatofibrotic, anti-neoplastic, and antibiotic effects and is recognized as a traditional medicine. In our previous works, Allomyrina dichotoma larvae (ADL) inhibited differentiation of adipocytes both in vitro and in vivo. However, the anorexigenic and endoplasmic reticulum(ER) stress-reducing effects of ADL in obesity has not been examined. In this study, we investigated the anorexigenic and ER stress-reducing effects of ADL in the hypothalamus of diet-induced obese (DIO) mice. Intracerebroventricular (ICV) administration of ethanol extract of ADL (ADE) suggested that an antagonizing effect on ghrelin-induced feeding behavior through the mTOR and MAPK signaling pathways. Especially, ADE resulted in strong reduction of ER stress both in vitro and in vivo. These findings strongly suggest that ADE and its constituent bioactive compounds are available and valuable to use for treatment of various diseases driven by prolonged ER stress.

A synthetic fragment of leptin increase hematopoietic stem cell population and improve its engraftment ability

Several studies have shown the important actions of cytokine leptin that regulates food intake and energy expenditure. Additionally, the ability to modulate hematopoiesis has also been demonstrated. Previous reports have shown that some synthetic sequences of leptin molecules can activate leptin receptor. Herein, decapeptides encompassing amino acids from positions 98 to 122 of the leptin molecule were constructed to evaluate their effects on hematopoiesis. Among them, the synthetic peptide Lep(110-119)-NH2 (LEP F) was the only peptide that possessed the ability to increase the percentage of hematopoietic stem cells (HSC). Moreover, LEP F also produced an increase of granulocyte/macrophage colony-forming units and activated leptin receptor. Furthermore, LEP F also improves the grafting of HSC in bone marrow, but did not accelerate the recovery of bone marrow after ablation with 5-fluorouracil. These results show that LEP F is a positive modulator of the in vivo expansion of HSC and could be useful in bone marrow transplantation.

Association between urinary 3-phenoxybenzoic acid and body mass index in Korean adults: 1(st) Korean National Environmental Health Survey

BACKGROUND

According to US-EPA report, the use of pyrethrins and pyrethroids has increased during the past decade, and their area of use included not only in agricultural settings, but in commerce, and individual household. It is known that urinary 3-PBA, major metabolite of pyrethroid, have some associations with health effect in nervous and endocrine system, however, there's no known evidence that urinary 3-PBA have associations with obesity.

METHOD

We used data of 3671 participants aged above 19 from the Korean National Environmental Health Survey in 2009-2011. In our analysis, multivariate piece-wise regression and logistic regression analysis were used to investigate the association between urinary 3-PBA (3-Phenoxybenzoic Acid) and BMI.

RESULT

Log-transformed level of urinary 3-PBA had significantly positive association with BMI at the low-level range of exposure (p < 0.0001), and opposite associations were observed at the high level exposure (p = 0.04) after adjusting covariates. In piece-wise regression analysis, the flexion point that changes direction of the associations was at around 4 ug/g creatinine of urinary 3-PBA. As quintiles based on concentration of urinary 3-PBA increased to Q4, the ORs for prevalence of overweight (BMI ≥ 23 kg/m(2)) were increased, and the OR of Q5 was lower than that of Q4 (OR = 1.810 for Q4; OR = 1.483 for Q5). In the analysis using obesity (BMI ≥ 25 kg/m(2)) as outcome variable, significant associations were observed between obesity and quintiles of 3-PBA, however, there were no differences between the OR of Q5 and that of Q4 (OR = 1.659 for Q4; OR = 1.666 for Q5).

CONCLUSION

Our analysis suggested that low-level of pyrethroid exposure has positive association with BMI, however, there is an inverse relationship above the urinary 3-PBA level at 4 ug/g creatinine.

Relationship of high leptin levels with an adverse lipid and insulin profile in 6-8 year-old children in Spain

BACKGROUND AND AIMS

Leptin, an adipokine elevated in obesity, may be related to an adverse cardiovascular risk profile in childhood. However, evidence for this relationship in pre-pubertal children is scarce. We aimed to analyze the relationship between leptin levels and lipid and insulin profiles in Spanish children.

METHODS AND RESULTS

Our population-based sample included 389 males and 369 females aged 6-8 years. Lipid levels were determined by standard methods, insulin by radioimmunoassay and leptin by sandwich ELISA. Leptin levels were higher in girls (8.6 ng/ml) than boys (4.7 ng/ml) (p < 0.001). Leptin increased from ages 6 to 8 in girls, but remained steady in boys. In both sexes, leptin increased significantly (p < 0.001) across weight category from normal weight to obese. Children in the highest tertile of leptin concentration showed significantly (p < 0.01) lower levels of HDL-cholesterol (HDL-C) and apolipoprotein-AI (apo-AI) and significantly higher triglyceride (TG) levels than children in lower tertiles. However, in linear regression analysis, after adjustment for body mass index (BMI), leptin only accounted for 1.5% of the variance of HDL-C in boys, and 2.6% of the variance of apo-AI in girls. Leptin was strongly and positively correlated with insulin and HOMA. Upon regression analysis, leptin contributed to over 20% of the variability in insulin and HOMA, independent of BMI.

CONCLUSION

Leptin levels show sex differences in pre-pubertal children. In this age group, leptin levels are strongly related to insulin, and affect lipid profile -namely HDL-C, apo-AI and TG- particularly when leptin levels are high.

Leptin receptor expressing neurons express phosphodiesterase-3B (PDE3B) and leptin induces STAT3 activation in PDE3B neurons in the mouse hypothalamus

Leptin signaling in the hypothalamus is critical for normal food intake and body weight regulation. Cumulative evidence suggests that besides the signal transducer and activator of transcription-3 (STAT3) pathway, several non-STAT3 pathways including the phosphodiesterase-3B (PDE3B) pathway mediate leptin signaling in the hypothalamus. We have shown that PDE3B is localized in various hypothalamic sites implicated in the regulation of energy homeostasis and that the anorectic and body weight reducing effects of leptin are mediated by the activation of PDE3B. It is still unknown if PDE3B is expressed in the long form of the leptin-receptor (ObRb)-expressing neurons in the hypothalamus and whether leptin induces STAT3 activation in PDE3B-expressing neurons. In this study, we examined co-localization of PDE3B with ObRb neurons in various hypothalamic nuclei in ObRb-GFP mice that were treated with leptin (5mg/kg, ip) for 2h. Results showed that most of the ObRb neurons in the arcuate nucleus (ARC, 93%), ventromedial nucleus (VMN, 94%), dorsomedial nucleus (DMN, 95%), ventral premammillary nucleus (PMv, 97%) and lateral hypothalamus (LH, 97%) co-expressed PDE3B. We next examined co-localization of p-STAT3 and PDE3B in the hypothalamus in C57BL6 mice that were treated with leptin (5mg/kg, ip) for 1h. The results showed that almost all p-STAT3 positive neurons in different hypothalamic nuclei including ARC, VMN, DMN, LH and PMv areas expressed PDE3B. These results suggest the possibility for a direct role for the PDE3B pathway in mediating leptin action in the hypothalamus.

Effects of the intragastric balloon MedSil on weight loss, fat tissue, lipid metabolism, and hormones involved in energy balance

Background

The prevalence of obesity continues to increase worldwide. Because obesity is associated with a number health-related problems as well as a shortened life span, treating obesity is an important clinical concern. Although various treatments are currently available, many are not efficacious in the long term. Therefore, additional medical treatment options for morbidly obese individuals must be explored. In this study, we examined the effects of the intragastric balloon MedSil® on anthropometric measures and hormones associated with lipid and energy metabolism.

Methods

Twenty-two obese patients underwent insertion of the intragastric balloon MedSil® following a clinical exam, body composition scan, and collection of blood samples. Six months following implantation of the balloon, additional anthropometric and serological measures were taken.

Results

Six months following insertion of the MedSil® balloon, we observed significant decreases in body weight, body mass index, and fat mass. Compared with baseline levels, ghrelin serum levels were increased significantly, while leptin, FGF21, and glycated hemoglobin levels significantly decreased, 6 months after balloon insertion.

Conclusions

The MedSil® intragastric balloon is a safe and effective treatment for morbid obesity, with positive effects on anthropometric measures and lipid metabolism.

Phosphodiesterase-3B-cAMP pathway of leptin signalling in the hypothalamus is impaired during the development of diet-induced obesity in FVB/N mice

The phosphodiesterase-3B (PDE3B)-cAMP pathway plays an important role in transducing the action of leptin in the hypothalamus. Obesity is usually associated with hyperleptinaemia and resistance to anorectic and body weight-reducing effects of leptin. To determine whether the hypothalamic PDE3B-cAMP pathway of leptin signalling is impaired during the development of diet-induced obesity (DIO), we fed male FVB/N mice a high-fat diet (HFD: 58% kcal as fat) or low-fat diet (LFD: 6% kcal as fat) for 4 weeks. HFD fed mice developed DIO in association with hyperphagia, hyperleptinaemia and hyperinsulinaemia. Leptin (i.p.) significantly increased hypothalamic PDE3B activity and phosphorylated (p)-Akt levels in LFD-fed but not in HFD-fed mice. However, basal p-Akt levels in hypothalamus were increased in DIO mice. Additionally, amongst six-microdissected brain nuclei examined, leptin selectively decreased cAMP levels in the arcuate nucleus (ARC) of LFD-fed mice but failed to do so in HFD-fed mice. We next tested whether both the PBE3B and Akt pathways of leptin signalling remained impaired in DIO mice on the HFD for 12 weeks (long-term). DIO mice were hyperinsulinaemic and hyperleptinaemic in association with impaired glucose and insulin tolerance. Although, in LFD-fed mice, leptin significantly increased PDE3B activity and p-Akt levels in the hypothalamus, it failed to do so in HFD-fed mice. Also, basal p-Akt levels in the hypothalamus were increased in DIO mice and leptin had no further effect. Similarly, immunocytochemistry showed that leptin increased the number of p-Akt-positive cells in the ARC of LFD-fed but not in HFD-fed mice, and there was an increased basal number of p-Akt positive cells in the ARC of DIO mice. These results suggest that the PDE3B-cAMP- and Akt-pathways of leptin signalling in the hypothalamus are impaired during the development of DIO. Thus, a defect in the regulation by leptin of the hypothalamic PDE3B-cAMP pathway and Akt signalling may be one of the mechanisms of central leptin resistance and the development of DIO.

Improved serum leptin and ghrelin following bariatric surgery predict better postoperative cognitive function

BACKGROUND AND PURPOSE

Bariatric surgery is associated with improved cognitive function, but the mechanisms underlying these gains remain poorly understood. Disturbed leptin and ghrelin systems are common in obese individuals and are associated with impaired cognitive function in other samples. Bariatric surgery has been shown to improve serum leptin and ghrelin levels, and these changes may underlie postoperative cognitive improvements.

METHODS

Eighty-four patients completed a computerized cognitive test battery prior to bariatric surgery and at 12 months postoperatively. Participants also submitted to an 8-hour fasting blood draw to quantify serum leptin and ghrelin concentrations at these same time points.

RESULTS

Baseline cognitive impairments and disturbed leptin and ghrelin levels improved at the 12-month follow-up compared to presurgery. Higher leptin levels were associated with worse attention/executive function at baseline; no such findings emerged for ghrelin. Regression analyses controlling for baseline factors and demographic characteristics showed that both decreased leptin and increased ghrelin following surgery was associated with better attention/executive function at the 12-month follow-up. These effects diminished after controlling for the postoperative change in body mass index (BMI); however, BMI change did not predict 12-month cognitive function.

CONCLUSIONS

Improvements in leptin and ghrelin levels following bariatric surgery appear to contribute to postoperative cognitive benefits. These gains may involve multiple mechanisms, such as reduced inflammation and improved glycemic control. Future studies that employ neuroimaging are needed to clarify the underlying mechanisms and determine whether the effects of bariatric surgery on leptin and ghrelin levels can attenuate adverse brain changes and/or risk of dementia in severely obese individuals.

Control of appetite and energy intake by SCFA: what are the potential underlying mechanisms?

In recent years, there has been a renewed interest in the role of dietary fibre in obesity management. Much of this interest stems from animal and human studies which suggest that an increased intake of fermentable fibre can suppress appetite and improve weight management. A growing number of reports have demonstrated that the principal products of colonic fermentation of dietary fibre, SCFA, contribute to energy homeostasis via effects on multiple cellular metabolic pathways and receptor-mediated mechanisms. In particular, over the past decade it has been identified that a widespread receptor system exists for SCFA. These G-protein-coupled receptors, free fatty acid receptor (FFAR) 2 and FFAR3 are expressed in numerous tissue sites, including the gut epithelium and adipose tissue. Investigations using FFAR2- or FFAR3-deficient animal models suggest that SCFA-mediated stimulation of these receptors enhances the release of the anorectic hormones peptide tyrosine tyrosine and glucagon-like peptide-1 from colonic L cells and leptin from adipocytes. In addition, the SCFA acetate has recently been shown to have a direct role in central appetite regulation. Furthermore, the SCFA propionate is a known precursor for hepatic glucose production, which has been reported to suppress feeding behaviour in ruminant studies through the stimulation of hepatic vagal afferents. The present review therefore proposes that an elevated colonic production of SCFA could stimulate numerous hormonal and neural signals at different organ and tissue sites that would cumulatively suppress short-term appetite and energy intake.

Emerging role of leptin in rheumatoid arthritis

Numerous studies have suggested the importance of leptin against autoimmune diseases such as systemic lupus erythematosus (SLE), multiple sclerosis (MS) and psoriasis. To summarize our current understanding of the role of leptin in inflammatory responses and rheumatoid arthritis (RA), a systematic review was conducted to assess the discrepancy of leptin in RA and its effect on immunity according to different studies. Recently, emerging data have indicated that leptin is involved in the pathological function of RA, which is common in autoimmune disorders. This review discusses the possible consequences of leptin levels in RA. Blocking the key signal pathways of leptin and inhibiting the leptin activity-like leptin antagonist may be a promising way for potential therapeutic treatment of RA at risk of detrimental effects. However, leptin was increased in patients with RA and may also regulate joint damage. Thus, more understanding of the mechanism of leptin in RA would be advantageous in the future.

Three months of high-fructose feeding fails to induce excessive weight gain or leptin resistance in mice

High-fructose diets have been implicated in obesity via impairment of leptin signaling in humans and rodents. We investigated whether fructose-induced leptin resistance in mice could be used to study the metabolic consequences of fructose consumption in humans, particularly in children and adolescents. Male C57Bl/6 mice were weaned to a randomly assigned diet: high fructose, high sucrose, high fat, or control (sugar-free, low-fat). Mice were maintained on their diets for at least 14 weeks. While fructose-fed mice regularly consumed more kcal and expended more energy, there was no difference in body weight compared to control by the end of the study. Additionally, after 14 weeks, both fructose-fed and control mice displayed similar leptin sensitivity. Fructose-feeding also did not change circulating glucose, triglycerides, or free fatty acids. Though fructose has been linked to obesity in several animal models, our data fail to support a role for fructose intake through food lasting 3 months in altering of body weight and leptin signaling in mice. The lack of impact of fructose in the food of growing mice on either body weight or leptin sensitivity over this time frame was surprising, and important information for researchers interested in fructose and body weight regulation.

The gut-brain axis in obesity

Currently the only effective treatment for morbid obesity with a proven mortality benefit is surgical intervention. The underlying mechanisms of these surgical techniques are unclear, but alterations in circulating gut hormone levels have been demonstrated to be at least one contributing factor. Gut hormones seem to communicate information from the gastrointestinal tract to the regulatory appetite centres within the central nervous system (CNS) via the so-called 'Gut-Brain-Axis'. Such information may be transferred to the CNS either via vagal or non-vagal afferent nerve signalling or directly via blood circulation. Complex neural networks, distributed throughout the forebrain and brainstem, are in control of feeding and energy homoeostasis. This article aims to review how appetite is potentially regulated by these gastrointestinal hormones. Identification of the underlying mechanisms of appetite and weight control may pave the way to develop better surgical techniques and new therapies in the future.

The Expression of Leptin, Estrogen Receptors, and Vitellogenin mRNAs in Migrating Female Chum Salmon, Oncorhynchus keta: The Effects of Hypo-osmotic Environmental Changes

Leptin plays an important role in energy homeostasis and reproductive function in fish, especially in reproduction. Migrating fish, such as salmonoids, are affected by external environmental factors, and salinity changes are a particularly important influence on spawning migrations. The aim of this study was to test whether changes in salinity affect the expression of leptin, estrogen receptors (ERs), and vitellogenin (VTG) in chum salmon (Oncorhynchus keta). The expression and activity of leptin, the expression of ERs and VTG, and the levels of estradiol-17β and cortisol increased after the fish were transferred to FW, demonstrating that changes in salinity stimulate the HPG axis in migrating female chum salmon. These findings reveal details about the role of elevated leptin levels and sex steroid hormones in stimulating sexual maturation and reproduction in response to salinity changes in chum salmon.

Thyroid hormone and leptin in the testis

Leptin is primarily expressed in white adipose tissue; however, it is expressed in the hypothalamus and reproductive tissues as well. Leptin acts by activating the leptin receptors (Ob-Rs). Additionally, the regulation of several neuroendocrine and reproductive functions, including the inhibition of glucocorticoids and enhancement of thyroxine and sex hormone concentrations in human beings and mice are leptin functions. It has been suggested that thyroid hormones (TH) could directly regulate leptin expression. Additionally, hypothyroidism compromises the intracellular integration of leptin signaling specifically in the arcuate nucleus. Two TH receptor isoforms are expressed in the testis, TRa and TRb, with TRa being the predominant one that is present in all stages of development. The effects of TH involve the proliferation and differentiation of Sertoli and Leydig cells during development, spermatogenesis, and steroidogenesis. In this context, TH disorders are associated with sexual dysfunction. An endocrine and/or direct paracrine effect of leptin on the gonads inhibits testosterone production in Leydig cells. Further studies are necessary to clarify the effects of both hormones in the testis during hypothyroidism. The goal of this review is to highlight the current knowledge regarding leptin and TH in the testis.

Peptides and food intake

The mechanisms for controlling food intake involve mainly an interplay between gut, brain, and adipose tissue (AT), among the major organs. Parasympathetic, sympathetic, and other systems are required for communication between the brain satiety center, gut, and AT. These neuronal circuits include a variety of peptides and hormones, being ghrelin the only orexigenic molecule known, whereas the plethora of other factors are inhibitors of appetite, suggesting its physiological relevance in the regulation of food intake and energy homeostasis. Nutrients generated by food digestion have been proposed to activate G-protein-coupled receptors on the luminal side of enteroendocrine cells, e.g., the L-cells. This stimulates the release of gut hormones into the circulation such as glucagon-like peptide-1 (GLP-1), oxyntomodulin, pancreatic polypeptides, peptide tyrosine tyrosine, and cholecystokinin, which inhibit appetite. Ghrelin is a peptide secreted from the stomach and, in contrast to other gut hormones, plasma levels decrease after a meal and potently stimulate food intake. Other circulating factors such as insulin and leptin relay information regarding long-term energy stores. Both hormones circulate at proportional levels to body fat content, enter the CNS proportionally to their plasma levels, and reduce food intake. Circulating hormones can influence the activity of the arcuate nucleus (ARC) neurons of the hypothalamus, after passing across the median eminence. Circulating factors such as gut hormones may also influence the nucleus of the tractus solitarius (NTS) through the adjacent circumventricular organ. On the other hand, gastrointestinal vagal afferents converge in the NTS of the brainstem. Neural projections from the NTS, in turn, carry signals to the hypothalamus. The ARC acts as an integrative center, with two major subpopulations of neurons influencing appetite, one of them coexpressing neuropeptide Y and agouti-related protein (AgRP) that increases food intake, whereas the other subpopulation coexpresses pro-opiomelanocortin (POMC) and cocaine and amphetamine-regulated transcript that inhibits food intake. AgRP antagonizes the effects of the POMC product, α-melanocyte-stimulating hormone (α-MSH). Both populations project to areas important in the regulation of food intake, including the hypothalamic paraventricular nucleus, which also receives important inputs from other hypothalamic nuclei.

Hematopoietic stem cell expansion caused by a synthetic fragment of leptin

Leptin is a cytokine that regulates food intake, energy expenditure and hematopoiesis. Based on the tridimensional structure of the human leptin molecule, six fragments have been synthesized, (Ac-Lep23-47-NH2, [LEP1]; Ac-Lep48-71-NH2, [LEP2]; Ac-Lep72-88-NH2, [LEP3]; Ac-Lep92-115-NH2, [LEP4], Ac-[Ser(117)]-Lep116-140-NH2, [LEP5] and Ac-Lep141-164-NH2, [LEP6]), and their effects on hematopoiesis were evaluated. The mice were treated with 1mg/kg LEP5 for 3 days. The mature and primitive hematopoietic populations were quantified. We observed that the mature populations from the bone marrow and spleen were not affected by LEP5. However, the peptide caused at least a two-fold increase in the number of hematopoietic stem cells, the most primitive population of the bone marrow. Additionally, the number of granulocyte/macrophage colony-forming units produced by bone marrow cells in methylcellulose also increased by 40% after treatment with LEP5, and the leptin receptor was activated. These results show that the leptin fragment LEP5 is a positive modulator of the in vivo expansion of hematopoietic stem cells.

Regulation of corticotropin-releasing factor and urocortin 2/3 mRNA by leptin in hypothalamic N39 cells

Corticotropin-releasing factor (CRF) activates the pituitary-adrenal axis during stress, and shows anorectic effects via CRF type 1 receptors in the hypothalamus. Both urocortin (Ucn) 2 and Ucn3 also act as anorectic neuropeptides via CRF type 2 receptors. Leptin, a product of the obesity gene secreted mainly from adipose tissue, reduces food intake and increases energy expenditure. A possible interaction between leptin and CRF/Ucns has been suggested, as leptin can regulate expression and activation of CRF and Ucns in the hypothalamus. This study aimed to explore the possible function of leptin in the hypothalamus, and its effects in regulating CRF and Ucns. The study identified mRNA expression of the leptin receptor (Ob-R) and its subtypes, CRF, and Ucn2/3 in mouse hypothalamic N39 cells. Leptin stimulated signal transducer and activators of transcription type 3 (STAT3) phosphorylation, directly increased the mRNA levels of both CRF and Ucn2/3 in hypothalamic cells, and increased Ob-Rb mRNA levels. A Janus kinase inhibitor inhibited the leptin-mediated increase in STAT3 phosphorylation, and then the increases in CRF and Ucn2/3 mRNA levels. Leptin may contribute to a stress response or anorectic effect via the regulation of CRF and Ucn2/3 in the hypothalamus.

Role of adipokines signaling in the modulation of T cells function

The field that links immunity and metabolism is rapidly expanding. Apparently non-immunological disorders such as obesity and type 2 diabetes have been linked to immune dysregulation, suggesting that metabolic alterations can be induced by or be consequence of an altered self-immune tolerance. In this context, adipose tissue produces and releases a variety of pro-inflammatory and anti-inflammatory factors, termed "adipokines," which can be considered as the bridge between obesity-related exogenous factors, such as nutrition and lifestyle, and the molecular events leading to metabolic syndrome, inflammatory, and/or autoimmune conditions. In obesity, increased production of most adipokines impacts on multiple functions such as appetite and energy balance, modulation of immune responses, insulin sensitivity, angiogenesis, blood pressure, lipid metabolism, and so on. This report aims to discuss some of the recent topics of adipocytokine research and their related signaling pathways, that may be of particular importance as could lead to effective therapeutic strategies for obesity-associated diseases.

Adult-onset obesity induced by early life overnutrition could be reversed by moderate caloric restriction

Overnutrition during the suckling period (small litter, SL) results in the development of adult-onset obesity. Our aim was to investigate whether two levels of caloric restriction (CR) in the early postweaning period can reverse obese phenotype in SL rats. The normal litter (NL) had 12 pups/dam and SL had 3 male pups/dam from the postnatal day 3 until day 21. After weaning, rats consumed lab chow as indicated: 1) NL and SL groups were on ad libitum regimen up to day 140, 2) another SL group was pair-fed (SL/PF) to NL(∼14% reduction), 3) SL/PF/AL group was pair-fed up to day 94 and then switched to ad libitum feeding, 4) SL/CR group received 24% reduction (moderate CR) in food intake compared with SL, and 5) SL/CR/AL group was on 24% CR up to day 94 and then switched to ad libitum feeding. Pair-feeding reduced body weight gains and serum insulin and leptin levels compared with SL rats, but these parameters were restored to SL levels in the SL/PF/AL rats after switching to ad libitum feeding. Interestingly, the moderate CR normalized these parameters in SL/CR and SL/CR/AL rats compared with NL. The expression of neuropeptide Y, proopiomelanocortin, and leptin receptor returned to control levels in hypothalami from SL/CR and SL/CR/AL rats. These results indicate that appropriate manipulation of energy intake during the early postweaning period could lead to longer-lasting effects on the regulation of body weight homeostasis via reversal of the early preweaning programming effects on the hypothalamic appetite regulation mechanism.