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Leptin Secretion (leptin + secretion)
Selected AbstractsEffects of ,-aminoisobutyric acid on leptin production and lipid homeostasis: mechanisms and possible relevance for the prevention of obesityFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 3 2010Karima Begriche Abstract ,-Aminoisobutyric acid (BAIBA) is a catabolite of thymine and antiretroviral thymine analogues AZT and d4T. We recently discovered that this ,-amino acid is able to enhance fatty acid oxidation and reduce body weight in mice through an increased production of leptin by the white adipose tissue (WAT). Furthermore, BAIBA could have favourable effects on nonalcoholic steatohepatitis in a leptin-independent manner. In the present review, we shall recall the circumstances that led us to discover the effects of BAIBA on body fat mass and lipid homeostasis. In addition, we put forward several hypothetical mechanisms whereby BAIBA could enhance leptin secretion by WAT and present some anti-inflammatory effects in the liver. We also discuss in this review (i) the deleterious impacts caused by the absence of, or low leptin expression on lipid homeostasis and body weight in humans and animals and (ii) recent data from other investigators suggesting that increasing leptin levels and/or responsiveness may be indeed an attractive pharmacological strategy in order to prevent (and/or treat) obesity, at least in some individuals. [source] Intralobular ducts of human major salivary glands contain leptin and its receptorJOURNAL OF ANATOMY, Issue 5 2002R. De Matteis Abstract Leptin, a 16-kDa hormone, plays an important role in the control of food intake and in energy homeostasis both in rodents and in man. Leptin is mainly produced and secreted by adipocytes, but other tissues and gastric glands have also recently been shown to produce it in a dual (endocrine and exocrine) mode. In addition, a leptin receptor has been detected in taste cells of mouse circumvallate papillae and in rat intestinal epithelium. These data prompted us to carry out a detailed study of human salivary glands as potential leptin-producing organs. Biopsies of salivary glands (submandibular and parotid) obtained from male and female patients during surgery for different clinical indications were subjected to immunohistochemical study for the presence of leptin, its functional receptor, insulin and glucagon. The presence and cellular distribution of glucocorticoid receptor in leptin-secreting cells were also investigated. Double immunohistochemical staining (silver,gold intensification and avidin,biotin,peroxidase) was used for the visualization of glucocorticoid receptor and leptin labelling, respectively. The results show that intralobular duct cells of submandibular and parotid glands are immunoreactive for leptin, leptin receptor and glucagon but not for insulin. Leptin was also detected in some microglobules in whole saliva obtained from four healthy volunteers. Co-localization for leptin, leptin receptor and glucocorticoid receptor in the same cell type suggested a functional relationship between glucocorticoid hormone and leptin secretion also at the level of the salivary glands. [source] In vivo metabolic effects of naringenin in the ethanol consuming rat and the effect of naringenin on adipocytes in vitroJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 3-4 2007K. Szkudelska Summary Naringenin is a bioactive flavanone involved in the inhibition of drug metabolism which exhibits antioxidant, anti-inflammatory and anticancerogenic properties and which recently appeared to be a factor mitigating the hyperlipidaemic effects in rats and rabbits. In the performed experiment, the effect of naringenin, administered intragastrically (50 mg/kg) for 2 weeks to normal and ethanol drinking rats, on insulin and leptin levels and on some metabolic parameters was investigated. Naringenin did not change the hormone levels in any group of rats. Blood glucose, triglyceride, total, esterified and free cholesterol and high-density lipoprotein-cholesterol concentrations were also unaffected by this compound. Only free fatty acids were elevated after the naringenin treatment in the water-drinking rats. In spite of unchanged glucose and insulin concentrations in blood, the tested flavanone reduced the glucose/insulin ratio in ethanol-receiving rats. Liver triglycerides, elevated due to ethanol ingestion, were partially normalized by naringenin. Other tested parameters like liver glycogen and cholesterol, muscle triglycerides and glycogen were not altered in any group of rats. The influence of naringenin (62.5, 125, 250 and 500 ,m) on basal and insulin-stimulated glucose conversion to lipids (lipogenesis) as well as on basal and epinephrine-stimulated glycerol release (lipolysis) in the isolated rat adipocytes was also tested. The basal and the stimulated lipogenesis tended to be decreased in the presence of the flavanone (250 ,m). This inhibitory effect intensified and was statistically significant at the highest concentration of naringenin. The tested compound did not evoke any effect on basal lipolysis while the epinephrine-stimulated process was limited at the highest concentration of the flavanone. Naringenin (62.5, 125, 250 and 500 ,m) had no effect on leptin secretion from the isolated rat adipocytes. Results obtained in our studies demonstrate that naringenin exerts a very weak influence on carbohydrate and lipid metabolism of normal and ethanol-consuming rats and on metabolism of isolated rat adipocytes. [source] Interferon-, Inhibits Metalloproteinase Activity and Cytotrophoblast Cell MigrationAMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 1 2010Vanina Andrea Fontana Citation Fontana VA, Sanchez M, Cebral E, Calvo JC. Interferon-, inhibits metalloproteinase activity and cytotrophoblast cell migration. Am J Reprod Immunol 2010; 64: 20,26 Problem, Establishment of a successful pregnancy relies on a complex fetal,mother communication that starts with the embryo adhering and invading the endometrium. This requires remodeling of extracellular matrix, performed by metalloproteinases. Cytokines, such as interferon-, (IFN-,), play a role in implantation and could affect the success of pregnancy. Method of study, Using JEG-3 cell line as model, we cultured the cells in the presence or absence of IFN-, and determined the activities of MMP-2 and MMP-9 using zymography and the secretion of leptin using Western blot. Results, Interferon-, inhibits gelatinase activity from MMP-2 and MMP-9 in a dose-dependent manner, reducing the secretion of leptin (not because of a general inhibition on protein synthesis) and impairs cell migration on Matrigel. Conclusion, Our results correlate with previous reports from our laboratory indicating that IFN- , is deleterious for mouse embryo outgrowth, having an effect on metalloproteinases activity as well as leptin secretion. [source] The infrapatellar fat pad in knee osteoarthritis: An important source of interleukin-6 and its soluble receptorARTHRITIS & RHEUMATISM, Issue 11 2009Emilie Distel Objective Obesity is a potent risk factor in knee osteoarthritis (OA). It has been suggested that adipokines, secreted by adipose tissue (AT) and largely found in the synovial fluid of OA patients, derive in part from the infrapatellar fat pad (IFP), also known as Hoffa's fat pad. The goal of this study was to characterize IFP tissue in obese OA patients and to compare its features with thigh subcutaneous AT to determine whether the IFP contributes to local inflammation in knee OA via production of specific cytokines. Methods IFP and subcutaneous AT samples were obtained from 11 obese women (body mass index ,30 kg/m2) with knee femorotibial OA. Gene expression was measured by real-time quantitative polymerase chain reaction. Cytokine concentrations in plasma and in conditioned media of cultured AT explants were determined by enzyme-linked immunosorbent assay or by Luminex xMAP technology. Results In IFP tissue versus subcutaneous AT, there was a decrease in the expression of genes for key enzymes implicated in adipocyte lipid metabolism, whereas the expression levels of genes for AT markers remained similar. A 2-fold increase in the expression of the gene for interleukin-6 (IL-6), a 2-fold increase in the release of IL-6, and a 3.6-fold increase in the release of soluble IL-6 receptor (sIL-6R) were observed in IFP samples, compared with subcutaneous AT, but the rates of secretion of other cytokines in IFP samples were similar to the rates in subcutaneous AT. In addition, leptin secretion was decreased by 40%, whereas adiponectin secretion was increased by 70%, in IFP samples versus subcutaneous AT. Conclusion Our results indicate that the IFP cytokine profile typically found in OA patients could play a role in paracrine inflammation via the local production of IL-6/sIL-6R and that such a profile might contribute to damage in adjacent cartilage. [source] The release of leptin and its effect on hormone release from human pituitary adenomasCLINICAL ENDOCRINOLOGY, Issue 6 2001Márta Korbonits BACKGROUND Leptin is the protein product of the obese gene, known to play an important role in body energy balance. The leptin receptor exists in numerous isoforms, the long isoform being the major form involved in signal transduction. Leptin expression has recently been demonstrated in the human pituitary, both in normal tissue and in pituitary adenomas. The long isoform of the leptin receptor has also been shown to be present in pituitary adenomas; however, contrasting results have been obtained regarding its expression in the normal human pituitary. AIM The aim of this study was (i) to investigate the presence and pattern of distribution of leptin mRNA and the long isoform of its receptor mRNA in the normal pituitary and in different types of pituitary adenomas with RT-PCR; (ii) to study leptin secretion from human pituitary tumours in culture and (iii) to assess in vitro pituitary hormone release following stimulation with human leptin. RESULTS Leptin receptor long isoform expression was detected in 2/4 GH-secreting adenomas, 12/17 non-functioning adenomas, 5/9 ACTH-secreting adenomas, 1/2 prolactinomas, 2/2 FSH-secreting adenomas and 5/5 normal pituitaries. The receptor long isoform did not segregate with any particular tumour type, and varying levels of expression were detected between the tissues studied. Leptin mRNA was detected at a low level of expression in 2/7 GH-secreting adenomas, 9/14 non-functioning adenomas, 2/3 ACTH-secreting adenomas, 1/3 prolactinomas and 1/3 FSH-secreting adenomas. We were unable to detect leptin mRNA in any of the five normal pituitaries removed at autopsy; however, immunostaining of a non-tumorous pituitary adjacent to an adenoma removed at transsphenoidal surgery showed scattered leptin positive cells. Culture of pituitary adenomas showed that 16/47 released leptin into the incubation media. Leptin release did not correlate with tumour type or with any of the other pituitary hormones released. In vitro leptin stimulation of pituitary tumours caused stimulation of FSH and ,-subunit secretion from a non-functioning adenoma and TSH secretion from a somatotroph adenoma. CONCLUSION We conclude that not only is leptin stored within the pituitary, but it may also be released from pituitary cells and modulate other pituitary hormone secretion. Pituitary leptin may therefore be a novel paracrine regulator of pituitary function. [source] | |||||||||||||