• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.535-538
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• 2000

Human leptin is a 16 kDa (146 amino acids) protein secreted from adipocytes and influences body weight homeostasis. In this report, active human leptin was successfully produced in the culture medium of Bacillus subtilis. After simple purification steps consisting of ammonium sulfate precipitation and anion-exchange column chromatography, 2.3 mg of leptin with a purity of greater than 95% was obtained from the 0.5 L culture with the recovery yield of 54.9%. The purified leptin showed the correct folding structure with one disulfide bond.

• Journal of Gastric Cancer
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• v.8 no.4
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• pp.176-181
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• 2008

Purpose: The adipocyte-derived cytokine leptin plays a major role in the control of stable body weight by suppressing food intake and increasing energy metabolism. Leptin regulates the cell proliferation of various epithelial cells and it may be involved in the promotion of cancer. Leptin and its receptor are highly expressed in gastric adenocarcinoma, but the association between the serum leptin level and the tissue expression of leptin is uncertain. We evaluated the serum leptin level and the expressions of leptin and leptin receptor in gastric cancer, and we explore the possible mechanism and role of leptin in the carcinogenesis of gastric cancer. Materials and Methods: 72 carcinomas that were curatively resected at our hospital from October 2005 to March 2007 were included in this study. By immunoassay and immunohistochemical staining, we evaluated the serum leptin level and the expressions of leptin and its receptor, and we analyzed their relationship together with the clinicopathological variables. Results: The serum leptin level was increased as the patient's BMI increased and it was decreased in H. pylori infected patients. The expression of leptin was increased as the TNM stage increased (P=0.014), and the expression of leptin receptor in the intestinal type gastric adenocarcinoma was higher than that in the diffuse type gastric adenocarcinoma (71.4% vs 28.6%, respectively, P=0.033). Conclusion: There was no significant correlation between the serum leptin level and expression of leptin in gastric cancer patients. The expression of leptin was associated with the TNM stage, but its role in the pathogenesis of gastric cancer has to be elucidated.

• Clinical and Experimental Pediatrics
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• v.51 no.3
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• pp.256-261
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• 2008

Purpose : Leptin and adiponectin are two representative adipocytokines. Leptin increases, but adiponectin decreases, with obesity and insulin resistance. We aimed to study the relationship between the leptin/adiponectin ratio and insulin resistance in healthy children. Methods : Seventy-seven healthy children (36 boys and 41 girls) were enrolled in this study. Anthropometric measurements were performed, and the percentage of weight for height (%WFH) was calculated in each subject. Fasting plasma levels of glucose, insulin, leptin, adiponectin, testosterone, estradiol, and sex-hormone binding globulin (SHBG) were measured. The free androgen index (FAI) was used as a representative of testosterone bioactivity. The homeostasis model assessment was used to estimate the degree of insulin resistance (HOMA-IR). Results : In the boys, HOMA-IR was significantly correlated with age, pubertal stage, free androgen index (FAI), leptin, and the leptin/adiponectin ratio. HOMA-IR was also significantly related to age, percentage of weight for height (%WFH), pubertal stage, estradiol, leptin, and the leptin/adiponectin ratio in girls. The leptin/adiponectin ratio was independently related to HOMA-IR after adjusting for age, %WFH, and FAI in the boys (P<0.05). The leptin/adiponectin ratio was not independently related to HOMA-IR after adjusting for age, %WFH, and estradiol in girls. Conclusion : In non-obese healthy children, the leptin/adiponectin ratio was significantly correlated with insulin resistance. The leptin/adiponectin ratio was independently related to insulin resistance even after adjusting for age, degree of obesity, and androgen levels in healthy boys.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.7
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• pp.1039-1048
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• 2007

Two experiments were conducted to determine whether leptin is a metabolic signal for gonadotropin secretion in ewes. In the first experiment, twenty-eight cyclic Chal ewes were assigned randomly to an energy restricted, no leptin group (ERNL) (60% of maintenance; n = 14) and an energy normal, no leptin group (ENNL) (100% of maintenance; n = 14) for 71 days (6 estrous cycles). Estrus was synchronized with seven consecutive injections of $PGF_{2{\alpha}}$ Biweekly, body weight (BW) and body condition score (BCS) were determined and blood samples were collected to measure plasma leptin concentration. Blood samples were also taken to determine plasma progesterone concentration twice weekly. After each PG injection from the second injection to the end of experiment, four ewes were selected and blood samples were collected at 20 minutes and at hourly intervals for 3 h to detect plasma LH and FSH concentration. In the second experiment, after the ceasing of the estrous cycle caused by energy restriction, six acyclic ewes were selected and randomly allotted to two groups (n = 3) and received the following treatment for four days. Ewes in an energy restricted, leptin group (ERL) were fed with a ration which provided 60% of maintenance energy requirements and intravenously injected with $4{\mu}g$ leptin/kg BW daily. Ewes in an energy excess, no leptin group (EENL) were fed with a ration that provided 180% (120%+60%) of maintenance energy requirements and intravenously injected with 1 ml saline daily. In both groups, blood samples were collected at 20 minutes and at hourly intervals for 3 h before feeding on d 0 and d 5, and for 3 h before and after injections as above on d 2 and d 4 to detect plasma LH and FSH concentration. In the first experiment, BW and BCS from the $2^{nd}$ estrous cycle, and leptin from the $3^{rd}$ estrous cycle to the end of the experiment significantly (p<0.05) decreased. In ERNL ewes, mean plasma concentrations of FSH significantly (p<0.01) decreased from the $4^{th}$ estrous cycle to d 71 and LH pulsatile secretion was suppressed on d 71, so that, mean plasma concentrations of LH (p<0.05), LH pulse frequency (p<0.01) and LH pulse amplitude (p<0.05) significantly decreased. In the second experiment, injection of leptin significantly increased mean circulating concentrations of LH (p<0.05), LH pulse frequency (p<0.01), LH pulse amplitude (p<0.05) and mean circulating concentrations of FSH (p<0.01) and leptin (p<0.01). High energy intake significantly (p<0.05) stimulated pulsatile secretion of LH and leptin secretion (p<0.01), but non-significantly increased plasma FSH concentration. The results of this study indicate that leptin is a metabolic signal for the GnRH-LH/FSH axis in feed-restricted fat-tailed ewes.

• Journal of Sasang Constitutional Medicine
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• v.22 no.1
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• pp.34-40
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• 2010

1. Objectives: Leptin is ob-gene originated hormone that is concerned with energy metabolism, obesity and asthma which features are supposed to related with Sasangin's 4 viscera physiological theory of Sasang constitutional medicine(SCM). This study aims to investigate whether serum leptin concentration is associated with Sasangin. 2. Methods: Two Way ANOVA analysis was used on the constitution and serum leptin concentration corresponding with BMI among 1054 cases drawn from the Constitutional Information Bank, which was a database with clinically confirmed constitution cases collected from 21 oriental medical institutes in Korea starting from November 2007 to May 2009. The measurement of serum leptin concentration is implemented through radioimmunoassay by request to SCL. 3. Results: Male subjects showed notable difference(p=0.033) in the comparison between constitution and serum leptin concentration corresponding to BMI levels. Tae-eumins showed the highest serum leptin concentration levels in the normal and overweight groups, followed by Soyangin and Soeumin. As the groups changed from overweight to obese, there was an interaction phenomenon in the order of serum leptin concentration levels(p=0.040). As a result, Soeumins showed the highest serum leptin concentration levels and Tae-eumins and Soyangins followed in place. Female subjects did not show statistically notable differences in comparison between constitution and serum leptin concentration corresponding to BMI levels(p=0.239). Serum leptin concentration levels among overweight and obese groups, resulted in the order of Soeumins, Tae-eumins, and Soyangins. But in the as groups changed from overweight to normal the order resulted in Tae-eumin, Soyangin, and Soeumin(p=0.660). 4. Conclusion: Due to a number of limitations in this study, the examination of the relation between constitution and leptin, a main hormone responsible for the digestion, appetite, and energy metabolism, resulted to be uncertain. But statistically notable differences were confirmed in male Tae-eumins with the consideration of BMI. Further examination of the relation between constitution and leptin is necessary through prospective studies with the restriction of confusion variables in the future.

• BMB Reports
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• v.34 no.2
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• pp.156-165
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• 2001

Leptin is a circulating non-glycosylated protein that is mainly produced in adipocytes. Leptin acts in the brain to regulate food intake and energy expenditure. Previously we reported our success in the isolation of a partial cDNA of the long form of the leptin receptor, OB-Rb, from rat spleen, and showed that leptin might also play a role in peripheral immune organs. In the present study, for the first time, the complete coding region of OB-Rb cDNA was cloned from rat splenocytes, and its nucleotide sequence was determined. The cDNA was then further expressed in E. coli and mammalian cells, thereby confirming the functional integrity of this receptor. Prokaryotically overexpressed OB-R protein was then used as an immunizing antigen in BALE/c mice to produce leptin receptor-specific antibodies. By using them, we confirmed the cell surface expression of OB-Rb in transfected CHO cells. It is our belief that the reagents, as produced in this study, will be of great use in further studies of the biological role of rat leptin.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.9
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• pp.3621-3627
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• 2015

Colorectal cancer (CRC) is one of most common causes of cancer-related death worldwide. Recent studies have suggested that microbial and environmental factors including diet and lifestyle can impact on colon cancer development. Vitamin D deficiency and dysfunction of vitamin D receptor (VDR) also correlate with colon cancer. Moreover, leptin, a 16-kDa polypeptide, participates in the regulation of food intake and is associated with other environmental factors affecting colon cancer through the leptin receptor. Altered levels of serum leptin and patterns of expression of its receptor (LPR) may be observed in human colon tumours. Furthermore, the collected data from in vitro and in vivo studies have indicated that consuming probiotic non-pathogenic lactic acid bacteria have beneficial effects on colon cancer. Probiotics, inflammation and vitamin D/VDR have been correlated with leptin and its receptor and are also with colon cancer. Thus, in this paper, we review recent progress on the roles of probiotic, vitamin D/VDR and leptin/LPR in inflammation and colon cancer.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.7
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• pp.954-959
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• 2004

In a herd of 24 spring-born steers, plasma leptin and performance of selected purebred (n=5) and backcrossed Hereford (n=5) were compared in a year-round summer grazing and winter feedlot fattening. Bimonthly blood collection and body weight measurement were accomplished. The plasma samples were analyzed for leptin, insulin, total cholesterol, triglyceride, NEFA and glucose. The experimental design utilized one-way ANOVA with breed as the treatment. The purebred obtained higher plasma NEFA (p<0.001) compared to backcross, regardless of seasonal feeding systems (SFS). The backcross showed gradual increase and nonresponsiveness of plasma leptin to SFS. During summer grazing, attenuation of plasma leptin and sudden elevation when shifted to winter feedlot fattening were observed in purebred. Plasma leptin obtained linear relationship with body weight of purebred (r=0.53;p<0.001) and backcrossed Hereford (r=0.49; p<0.01). The purebred and backcrossed Hereford, when shifted to summer grazing, resulted to sustained and restricted daily gain, respectively. Therefore, cattle breeds of higher growth potential exhibit significant elevation of plasma leptin after 400 kg BW, when animal starts to deposit significant body fat.

• Korean Journal of Community Nutrition
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• v.7 no.4
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• pp.475-483
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• 2002

The purpose of this study was to investigate the relationship among eating habits, eating behaviors, obesity indices and serum leptin levels of 97 school children in the Daegu and Kyungpuk areas. The subjects consisted of 42 boys and 55 girls from the 4th and 5th grades. The prevalence rate of obesity was 63.6% in the males and 36.4% in the females. The nutritional status of the subjects was assessed using 24-hour dietary recalls and blood analyses. The mean serum leptin levels of the obese group (12.84 $\pm$ 6.97 ng/ml) were significantly higher than those of the non-obese group (2.43 $\pm$ 1.53 ng/ml) (p < 0.001) . The mean eating behavior scores and MAR were significantly different in the two groups. Nutrient intakes were low and fell short of the RDA. Serum leptin levels showed a significant negative correlation with eating habit (r= -0.24) and eating behavior scores (r= -0.40) (p < 0.05, p < 0.001). It was speculated that nutritional intervention and education about the appropriate nutrient intake requirements of developing children might be necessary.

• Journal of the East Asian Society of Dietary Life
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• v.22 no.2
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• pp.219-223
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• 2012

The purpose of this study was to investigate the body composition, biochemical parameters, and consumption of convenience foods according to leptin receptor polymorphism in university students. A survey was conducted on a total of 418 students - 271 males and 147 females. Based on a self-reporting method, questionnaires were administered for over 20 minutes, and leptin receptor and blood samples were analyzed. The genotype frequencies of leptin receptor polymorphism were Gln/Arg heterozygote (64.8%) and Gln/Gln homozygote (35.2%). Leptin polymormphism showed no significant association with biochemical parameters(ALT, cholesterol, triglyceride, HDL-cholesterol, LDL-cholesterol, and hemoglobin) and body composition. GG homozygote was associated with a higher risk of visceral fat obesity compared to those with GA heterozygote (odd ratio 1.758, 95% confidence intervals 0.812~3.803). Leptin polymorphism appeared to be a genetic risk factor for visceral fat obesity. This study suggests that leptin polymorphism has a causative role to body fat distribution in Korean.