Leptin, a peptide hormone secreted by adipocytes in proportion of the amount of energy stored in fat, plays a central role in regulating human energy homeostasis. In addition, leptin plays a significant permissive role in the physiological regulation of several neuroendocrine axes, including the hypothalamic-pituitary-gonadal, -thyroid, -growth hormone, and -adrenal axes. Decreased levels of leptin, also known as hypoleptinemia, signal to the brain a state of energy deprivation. Hypoleptinemia can be a congenital or acquired condition, and is associated with alterations of the aforementioned axes aimed at promoting survival. More specifically, gonadotropin levels decrease and become less pulsatile under conditions of energy deprivation, and these changes can be at least partially reversed through leptin administration in physiological replacement doses. Similarly, leptin deficiency is associated with thyroid axis abnormalities including abnormal levels of thyrotropin-releasing hormone, and leptin administration may at least partially attenuate this effect. Leptin deficiency results in decreased insulin-like growth factor 1 levels which can be partially ameliorated through leptin administration, and leptin appears to have a much more pronounced effect on the growth of rodents than that of humans. Similarly, adrenal axis function is regulated more tightly by low leptin in rodents than in humans. In addition to congenital leptin deficiency, conditions that may be associated with decreased leptin levels include hypothalamic amenorrhea, anorexia nervosa, and congenital or acquired lipodystrophy syndromes. Accumulating evidence from proof of concept studies suggests that leptin administration, in replacement doses, may ameliorate neuroendocrine abnormalities in individuals who suffer from these conditions.
Amenorrhea/metabolism ; Animals ; Female ; Humans ; Leptin/blood/deficiency/genetics/*metabolism ; Male ; Neurosecretory Systems/*metabolism

OBJECTIVETo assess the association between leptin gene promoter methylation and serum leptin concentrations in patients with impaired glucose regulation (IGR) and type 2 diabetes mellitus (T2DM).

METHODSMethylation status of leptin gene promoter was determined with methylation-specific polymerase chain reaction. Serum leptin concentrations were determined using enzyme-linked immunosorbent assay.

RESULTSAmong three groups of individuals with different levels of glucose, the methylation rates of leptin gene in IGR and T2DM groups were 43.6 % and 31.5 %, respectively, which were significantly lower than that of healthy subjects (59.2%; Chi-square=22.499 and 5.109, respectively, P<0.05). A lower methylation rate was also observed in T2DM group compared with IGR group (Chi-square=3.962, P<0.05). Leptin levels in both T2DM and IGR groups were elevated compared with normoglycemic subjects, but only T2DM group was significantly higher (q=6.81, P<0.01). Linear regression analysis indicated that serum leptin concentrations has increased along with declining of DNA methylation rate (r=-0.95, P<0.01).

CONCLUSIONLower levels of leptin gene promoter DNA methylation and serum leptin concentrations are associated with the development of diabetes. Measurement of the methylation status of leptin gene promoter and expression can facilitate early intervention of the disease.

DNA Methylation ; Diabetes Mellitus, Type 2 ; genetics ; metabolism ; Female ; Genetic Predisposition to Disease ; Glucose ; genetics ; metabolism ; Humans ; Leptin ; blood ; genetics ; metabolism ; Male ; Middle Aged ; Promoter Regions, Genetic

Because of their physiological similarity to humans, pigs provide an excellent model for the study of obesity. This study evaluated diet-induced adiposity in genetically lean pigs and found that body weight and energy intake did not differ between controls and pigs fed the high-fat (HF) diet for three months. However, fat mass percentage, adipocyte size, concentrations of total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C), insulin, and leptin in plasma were significantly higher in HF pigs than in controls. The HF diet increased the expression in backfat tissue of genes responsible for cholesterol synthesis such as Insig-1 and Insig-2. Lipid metabolism-related genes including sterol regulatory element binding protein 1c (SREBP-1c), fatty acid synthase 1 (FASN1), diacylglycerol O-acyltransferase 2 (DGAT2), and fatty acid binding protein 4 (FABP4) were significantly up-regulated in backfat tissue, while the expression of proliferator-activated receptor-α (PPAR-α) and carnitine palmitoyl transferase 2 (CPT2), both involved in fatty acid oxidation, was reduced. In liver tissue, HF feeding significantly elevated the expression of SREBP-1c, FASN1, DGAT2, and hepatocyte nuclear factor-4α (HNF-4α) mRNAs. Microarray analysis further showed that the HF diet had a significant effect on the expression of 576 genes. Among these, 108 genes were related to 21 pathways, with 20 genes involved in adiposity deposition and 26 related to immune response. Our results suggest that an HF diet can induce genetically lean pigs into obesity with body fat mass expansion and adipose-related inflammation.
Adipocytes/cytology* ; Adipogenesis/genetics* ; Adipose Tissue/metabolism* ; Adiposity ; Animals ; Body Weight ; Cholesterol/blood* ; Cholesterol, HDL/blood* ; Cholesterol, LDL/blood* ; Diet, High-Fat ; Inflammation/genetics* ; Insulin/blood* ; Leptin/blood* ; Lipid Metabolism ; Male ; Obesity/genetics* ; Random Allocation ; Swine ; Triglycerides/blood*

OBJECTIVE: To investigate the effect of high-fat (HF) diet on the body weight and the mRNA expression of melanin concentrating hormone receptor 1 (MCHR1) and leptin receptor (OB-Rb) in the adipose tissue in rats, the two important and opposite factors in regulating the body weight. METHODS: Post-weaning rats were divided into 3 groups: the NC group were fed a normal-chow diet (NC) (13% calories from fat), the HF group with a HF-diet (47% calories from fat) and the PHF group pair-fed a HF-diet (47% calories from fat). At the end of 8th week, the gained bodyweight, the plasma melanin concentrating hormone (MCH) and leptin, and the expression levels of MCHR1 and OB-Rb in the adipose tissue were measured. RESULTS: Both the HF-diet and pair-fed HF-diet enhanced the body weight (P<0.01), plasma MCH (P<0.01) and leptin concentrations (P<0.05). In the adipose tissue, HF-diet resulted in significant increase in MCHR1 (PHF group,P<0.05) and decrease in OB-Rb mRNA levels (HF group,P<0.01; PHF group,P<0.05). No statistical difference was found between the HF group and the PHF group in terms of the aforementioned data (P>0.05). CONCLUSION Chronic intake of iso-caloric HF-diet and ad libitum HF-diet obviously results in increase in the body weight, serum leptin, and MCH concentration. Diet-induced obesity and related metabolic disorders are possibly correlated with up-regulated expression of MCHR1 and down-regulated expression of OB-Rb in the adipose tissue.
Adipose Tissue ; metabolism ; Animals ; Animals, Newborn ; Diet, High-Fat ; adverse effects ; Dietary Fats ; administration & dosage ; Hypothalamic Hormones ; blood ; Leptin ; blood ; Male ; Melanins ; blood ; Obesity ; etiology ; metabolism ; Pituitary Hormones ; blood ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Leptin ; genetics ; metabolism ; Receptors, Somatostatin ; genetics ; metabolism

AIMTo explore the effect of acute intra-peritoneal infection on leptin expression levels in peripheral blood and vital organs, and find out the role leptin plays in acute inflammation.

METHODSA cecal ligation and perforation model of rats was established, setting groups of sham-operation, intralipid injection, injury, estradiol injection and insulin injection. A rat leptin radioimmunoassay was used to check serum leptin concentrations at 12 h after the injury, and RT-PCR was also used to detect leptin mRNA expressions in adipose tissue, lung and liver.

RESULTSCompared with serum leptin level of sham-operation group after injury, that of all the other four groups showed no significant difference, while the level of intralipid group was significantly higher than that of injury group and estradiol group. Compared with leptin mRNA expression level of sham-operation group after injury, that of the other four groups had different changes. Leptin mRNA expression of intralipid group was significantly increased in adipose tissue but decreased in lung and liver.

CONCLUSIONLeptin expression levels may be affected by the changes of energy metabolism and neuroendocrine function after injury, which suggests a possible protective role for leptin in the recovery of body homeostasis.

Animals ; Female ; Inflammation ; metabolism ; Intestinal Perforation ; Leptin ; blood ; physiology ; Ligation ; Male ; Peritonitis ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Rabbits ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo study the gene expression profile of liver of young apoE(-/-)/LDLR(-/-)/Lepr(db/db) treble genes mutant mice and disclose its relationship to hyperlipidemia and the following atherosclerotic lesion.

METHODSThe gene expression profile was investigated using cDNA microarray technique; the plasma total cholesterol(TC) and triglyceride(TG) levels were analyzed by COD-PAP and GPO-PAP method. And morphological observations of the aorta were made.

RESULTSAmong the 4000 target genes, 92 genes were up-regulated and 105 genes were down-regulated in the treble genes mutants, compared with wild type control. Among the differentially expressed lipid metabolism related genes, cholesterol synthesis gene coding for farnesyl diphosphate farnesyl transferase was down-regulated, while triglyceride metabolism gene e.g. pancreatic lipase related protein 1 gene (Pnliprp1) was up-regulated. Expression profile of carbohydrate, cell skeleton and immune related genes were also altered. On the other hand, in the plasma from the treble genes mutant mice at 5 weeks of age, hyperlipidemia was found to be combined with atheroslerotic lesion. All these biochemical and pathological changes were aggravated following aging.

CONCLUSIONThe data suggested that the multiple genes mutations, especially those involved in lipid metabolism, were contributing to the alteration of liver gene expression profile that might lead to hyperlipidemia and atherosclerotic lesion in the young apoE(-/-)/LDLR(-/-)/Lepr(db/db) mutants.

Animals ; Apolipoproteins E ; genetics ; Cholesterol ; blood ; Farnesyl-Diphosphate Farnesyltransferase ; genetics ; metabolism ; Female ; Gene Expression Profiling ; methods ; Hyperlipidemias ; blood ; genetics ; metabolism ; Lipase ; genetics ; metabolism ; Lipid Metabolism ; Male ; Mice ; Mice, Knockout ; Oligonucleotide Array Sequence Analysis ; methods ; Receptors, LDL ; genetics ; Receptors, Leptin ; genetics ; Triglycerides ; blood

OBJECTIVETo explore the effect of intestinal ischemia/reperfusion (I/R) injury on leptin and orexin-A levels in peripheral blood and central secretory tissues, and investigate the roles of leptin and orexin-A in acute inflammatory responses.

METHODSAn intestinal I/R injury rat model was established, and the rats were grouped according to duration of the reperfusion time following a 60-min ischemia. Radioimmunoassay was used to examine the protein levels of leptin in the serum and adipose tissue, and the protein levels of orexin-A in the plasma and hypothalamus. Reverse transcriptase-polymerase chain reaction was also performed to detect the mRNA expressions of adipose leptin and hypothalamus orexin-A.

RESULTSCompared with that before injury, serum leptin level of 60-min ischemia with 30-min reperfusion (I60'R30') group decreased significantly and that of I60'R360' increased significantly. Compared with the sham-operation group (sham) after injury, serum leptin level of I60'R360' group increased significantly, and adipose leptin protein levels of I60'R30' and I60'R90' groups decreased significantly, whereas that of I60'R360' group increased obviously. Compared with sham group after injury, adipose leptin mRNA expressions of I60'R30', I60'R240' and I60'R360' groups all increased significantly, while that of I60'R150' showed significant decrease. No significant changes were noted in the protein levels of orexin-A either in the plasma or hypothalamus after I/R injury. In comparison with sham group after injury, hypothalamus orexin-A mRNA expressions of I60'R30' and I60'R90' groups showed gradual but significant decrease, and till 150 min of reperfusion, the expression reached its lowest, followed then by slow recovery at 240 and 360 min, though still remaining significantly lower than that of sham group.

CONCLUSIONLeptin and orexin-A have a time-dependent response to intestinal I/R injury, but the former appears to exhibit a faster response, and they may play a certain role in the metabolic disorders of acute inflammation.

Animals ; Female ; Inflammation ; blood ; genetics ; physiopathology ; Intestine, Small ; blood supply ; metabolism ; Intracellular Signaling Peptides and Proteins ; blood ; genetics ; Leptin ; blood ; genetics ; Male ; Neuropeptides ; blood ; genetics ; Orexins ; RNA, Messenger ; biosynthesis ; genetics ; Rabbits ; Radioimmunoassay ; Rats ; Rats, Sprague-Dawley ; Reperfusion Injury ; blood ; genetics ; physiopathology ; Reverse Transcriptase Polymerase Chain Reaction

This study was conducted to determine if an oral squamous cell carcinoma alters mRNA expression of serotonin transporter (5-HTT) in the central nervous system. KB cell line derived from a human oral squamous cell carcinoma was inoculated into nude mice, and mRNA expression level of 5-HTT in the dorsal raphe nucleus (DRN) was examined by in situ hybridization when the tumor mass reached to -10% of total body weight. Plasma leptin levels were determined by radioimmunoassay method using a commercial kit. 5-HTT mRNA level was significantly decreased in the DRN of tumor bearing mice, compared to the age-matching non-tumor control. Plasma leptin level decreased concomitantly in tumor bearing mice. These results suggest that oral carcinoma may suppress 5-HTT gene expression in the central nervous system, perhaps in relation with decreased plasma leptin level.
Animals ; Body Weight ; Carcinoma, Squamous Cell/*metabolism/pathology ; DNA, Complementary ; *Gene Expression Regulation, Neoplastic ; Humans ; Leptin/blood ; Male ; Membrane Glycoproteins/*genetics/metabolism ; Membrane Transport Proteins/*genetics/metabolism ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Mouth Neoplasms/*metabolism/pathology ; Nerve Tissue Proteins/*genetics/metabolism ; RNA, Messenger/*metabolism ; Radioimmunoassay ; Raphe Nuclei/*metabolism ; Research Support, Non-U.S. Gov't ; Serotonin/metabolism

The role of leptin in the control of obesity, insulin resistance and type II diabetes has been reported, however, the regulatory mechanism of leptin in animals affected by hormones is not clearly understood. In this study, the effects of insulin, epinephrine, growth hormone or dexamethasone on the expression of leptin was examined in mouse primary adipocytes. The leptin expression was also studied in the adipose tissue of the mouse treated with insulin or growth hormone (0.3 or 0.6 units/animal). Insulin (100 nM) or dexamethasone (100 nM) stimulated leptin mRNA transcription while epinephrine (100 nM) alleviated its transcription in mouse primary adipocytes. The level of leptin protein in cultured media of adipocytes treated with insulin or dexamethasone was higher than that of the control group but growth hormone or epinephrine treatment had no effect on them. Insulin administration (0.6 units/mouse) enhanced leptin mRNA as well as leptin protein in mouse adipose tissue but growth hormone administration (0.3 or 0.6 units/mouse) had no effect on them. Leptin protein level in sera of mice injected with insulin or growth hormone was not significantly different from that of control group. These results indicate that both insulin and dexamethasone stimulate leptin gene expression and secretion of its product, whereas, growth hormone has no effect on the expression of leptin gene in mouse adipocytes.
Adipocytes/*metabolism ; Animal ; Cells, Cultured ; Culture Media/analysis ; Dexamethasone/pharmacology ; Dose-Response Relationship, Drug ; Epinephrine/pharmacology ; Gene Expression Regulation/*drug effects ; Growth Hormone/blood/*pharmacology ; Hypoglycemic Agents/blood/*pharmacology ; Insulin/blood/*pharmacology ; Leptin/blood/genetics/*metabolism ; Male ; Mice ; Mice, Inbred ICR ; RNA, Messenger/analysis ; Transcription, Genetic/drug effects

The role of leptin in the control of obesity, insulin resistance and type II diabetes has been reported, however, the regulatory mechanism of leptin in animals affected by hormones is not clearly understood. In this study, the effects of insulin, epinephrine, growth hormone or dexamethasone on the expression of leptin was examined in mouse primary adipocytes. The leptin expression was also studied in the adipose tissue of the mouse treated with insulin or growth hormone (0.3 or 0.6 units/animal). Insulin (100 nM) or dexamethasone (100 nM) stimulated leptin mRNA transcription while epinephrine (100 nM) alleviated its transcription in mouse primary adipocytes. The level of leptin protein in cultured media of adipocytes treated with insulin or dexamethasone was higher than that of the control group but growth hormone or epinephrine treatment had no effect on them. Insulin administration (0.6 units/mouse) enhanced leptin mRNA as well as leptin protein in mouse adipose tissue but growth hormone administration (0.3 or 0.6 units/mouse) had no effect on them. Leptin protein level in sera of mice injected with insulin or growth hormone was not significantly different from that of control group. These results indicate that both insulin and dexamethasone stimulate leptin gene expression and secretion of its product, whereas, growth hormone has no effect on the expression of leptin gene in mouse adipocytes.
Adipocytes/*metabolism ; Animal ; Cells, Cultured ; Culture Media/analysis ; Dexamethasone/pharmacology ; Dose-Response Relationship, Drug ; Epinephrine/pharmacology ; Gene Expression Regulation/*drug effects ; Growth Hormone/blood/*pharmacology ; Hypoglycemic Agents/blood/*pharmacology ; Insulin/blood/*pharmacology ; Leptin/blood/genetics/*metabolism ; Male ; Mice ; Mice, Inbred ICR ; RNA, Messenger/analysis ; Transcription, Genetic/drug effects