Exonic and intronic sequence variation in the human leptin receptor gene (LEPR)

An integrative framework to prioritize genes in more than 500 loci associated with body mass index

Obesity is a major risk factor for a myriad of diseases, affecting >600 million people worldwide. Genome-wide association studies (GWASs) have identified hundreds of genetic variants that influence body mass index (BMI), a commonly used metric to assess obesity risk. Most variants are non-coding and likely act through regulating genes nearby. Here, we apply multiple computational methods to prioritize the likely causal gene(s) within each of the 536 previously reported GWAS-identified BMI-associated loci. We performed summary-data-based Mendelian randomization (SMR), FINEMAP, DEPICT, MAGMA, transcriptome-wide association studies (TWASs), mutation significance cutoff (MSC), polygenic priority score (PoPS), and the nearest gene strategy. Results of each method were weighted based on their success in identifying genes known to be implicated in obesity, ranking all prioritized genes according to a confidence score (minimum: 0; max: 28). We identified 292 high-scoring genes (≥11) in 264 loci, including genes known to play a role in body weight regulation (e.g., DGKI, ANKRD26, MC4R, LEPR, BDNF, GIPR, AKT3, KAT8, MTOR) and genes related to comorbidities (e.g., FGFR1, ISL1, TFAP2B, PARK2, TCF7L2, GSK3B). For most of the high-scoring genes, however, we found limited or no evidence for a role in obesity, including the top-scoring gene BPTF. Many of the top-scoring genes seem to act through a neuronal regulation of body weight, whereas others affect peripheral pathways, including circadian rhythm, insulin secretion, and glucose and carbohydrate homeostasis. The characterization of these likely causal genes can increase our understanding of the underlying biology and offer avenues to develop therapeutics for weight loss.

Effect of Acupoint Embedding on Serum Leptin and Hypothalamus Leptin Receptor Expression in Rats with Simple Obesity

Background

Acupoint embedding treatment on obesity has been applied in clinical practice for many years and has achieved obvious efficacy. However, animal experimental studies on acupoint embedding are relatively few, and its mechanism remains unclear.

Methods

We established a simple obese rat model using a high-fat diet for 8 weeks. Acupoint embedding therapy was performed once a week for 4 weeks. After the treatment, serum leptin, triglyceride (TG), cholesterol (TC), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) levels were detected by radioimmunoassay, HE staining was used for fat morphology analysis, and immunohistochemical method was used to detect the expression of leptin receptor in hypothalamus.

Results

Compared with model group, acupoint embedding treatment can reduce body weight and Lee's index, reduce serum leptin, TG, TC, and LDL level, increase HDL level, change the morphology and number of adipocytes, and increase the expression of leptin receptor in hypothalamus.

Conclusion

Acupoint embedding therapy can reduce the level of leptin in blood, increase the number of leptin receptors in hypothalamus, enhance the biological effect of leptin, alleviate the leptin resistance in obese body, change the shape of fat, and regulate the level of blood lipid, so as to achieve the goal of weight loss.

Combined donor-recipient genotypes of leptin receptor and adiponectin gene polymorphisms affect the incidence of complications after renal transplantation

BACKGROUND

We aimed to examine whether combined donor/recipient variants in the leptin receptor (LEPR) and adiponectin (ADIPOQ) genes may affect outcomes in renal transplantation.

METHODS

A total of 233 donors and their corresponding 307 recipients were genotyped for LEPR rs1805094, rs1137100 and rs1137101, and ADIPOQ rs1501299 and rs224176. Combined donor/recipient genetic scores were created to investigate associations with delayed graft function (DGF), graft loss and estimated glomerular filtration rate (eGFR).

RESULTS

Recipients whose donors carried variant alleles of LEPR rs1137100 and rs1137101 had lower risk of DGF [OR = 0.48 (0.24-0.97), p = 0.040] and [OR = 0.47 (0.23-0.95), p = 0.035], respectively. In addition, rs1137101 also showed an inverse association with lower incidence of graft loss [OR = 0.44 (0.31-0.97), p = 0.040]. The analysis of genetic scores of donor/recipients showed that again rs1137101 was inversely associated with both outcomes: OR = 0.46 (0.23-0.92), p = 0.029 and OR = 0.45 (0.11-0.81), p = 0.009, respectively. With regard to graft function, the T-allele of ADIPOQ rs1501299 in the donor was related to higher eGFR values (75.26 ± 29.01 vs. 67.34 ± 25.39 ml/min for wild-type grafts, p = 0.012). Higher combined genetic scores in this same polymorphism were also associated with better function (78.33 ± 31.87 vs. 68.25 ± 24.32 ml/min, p = 0.018). Finally, eGFR values were similar between paired kidneys but they were different when comparing grafts with or without the rs1501299 T-variant (77.87 ± 26.50 vs. 69.27 ± 26.73 ml/min, p = 0.016).

CONCLUSIONS

Our study has shown for the first time to our knowledge that variants in LEPR and ADIPOQ genes of the donors and/or their combination with those in the recipients may affect the outcome of renal transplantation.

Leptin in Tumor Microenvironment

Leptin is a hormone that plays a major role as mediator of long-term regulation of energy balance, suppressing food intake, and stimulating weight loss. More recently, important physiological roles other than controlling appetite and energy expenditure have been suggested for leptin, including neuroendocrine, reparative, reproductive, and immune functions. These emerging peripheral roles let hypothesize that leptin can modulate also cancer progression. Indeed, many studies have demonstrated that elevated chronic serum concentrations of leptin, frequently seen in obese subjects, represent a stimulatory signal for tumor growth. Current knowledge indicates that also different non-tumoral cells resident in tumor microenvironment may respond to leptin creating a favorable soil for cancer cells. In addition, leptin is produced also within the tumor microenvironment creating the possibility for paracrine and autocrine action. In this review, we describe the main mechanisms that regulate peripheral leptin availability and how leptin can shape tumor microenvironment.

Association of polymorphisms in leptin and adiponectin genes with long-term outcomes in renal transplant recipients

The effect of polymorphims in leptin and adiponectin genes on long-term outcomes of renal transplantation is unknown. In 349 renal transplant recipients (RTR), we aimed to determine associations between five SNPs in the leptin receptor (LEPR) and adiponectin (ADIPOQ) genes and these outcomes. Follow-up time ranged from 2 to 25 years (mean 10.29 ± 5.16 years). Two SNPs showed associations with long-term outcomes and their statistical significance greatly increased after 39 RTR with a history of cardiovascular events prior to transplantation were removed from the analysis. Adjusted odds ratios (OR) for LEPR rs1805094 and ADIPOQ rs1501299 and risk of graft loss were 0.35 (0.16-0.74) p = 0.006 and 2.37 (1.28-4.37) p = 0.006, respectively. The assessment of risk for global mortality revealed OR values of 0.20 (0.06-0.62), p = 0.005, and 2.43 (1.08-5.44), p = 0.031 for LEPR rs1805094 and ADIPOQ rs1501299, respectively. Our results show that polymorphism in genes involved in leptin and adiponectin function modify long-term outcomes in renal transplantation.

LEPR polymorphisms and haplotypes in Mexican patients with colorectal cancer

INTRODUCTION

Obesity and colorectal cancer could be linked by adipocytokines, which are proteins associated with cell proliferation. High levels of the adipocytokine leptin promote the development of colorectal cancer through its receptor.

OBJECTIVE

To determine the association between c.326A>G and c.668A>G LEPR gene polymorphisms and colorectal cancer.

MATERIALS AND METHODS

DNA was extracted from the peripheral blood of 147 patients with sporadic colorectal cancer and 134 healthy people. Genotypes were obtained by PCRRFLP and the association was determined by the odds ratio (OR) test using the SPSS™, version 10.0, program. Haplotype frequencies and linkage disequilibrium were estimated by the Arlequin, version 3.5, software.

RESULTS

Both polymorphisms were in Hardy-Weinberg equilibrium. Only the c.326A>G heterozygous genotype revealed an increased risk for colorectal cancer development (OR=1.81, 95% CI=1.04-3.16, p=0.04). The AG haplotype showed a significant association with colorectal cancer (OR=0.58, 95% CI=0.35-0.96, p<0.03). Linkage disequilibrium between the variants was only evident for the patients group (r2=0.36).

CONCLUSION

Our results suggest that AG individuals heterozygous for the c.326A>G LEPR variant have a higher risk of colorectal cancer development whereas the AG haplotype (c.326A/c.668G) has a protective effect in the Mexican population.

Variability in the leptin receptor gene and other risk factors for post-transplant diabetes mellitus in renal transplant recipients

Aim: Post-transplant diabetes mellitus (PTDM) is one of the main complications after kidney transplantation. It is known that leptin plays an important role in glucose metabolism and mutations in the leptin receptor gene (LEPR) are responsible for different complications in renal transplant recipients. We aimed to analyse the association of polymorphisms in LEPR with the development of PTDM in these patients. Methods: A total of 315 renal transplant recipients were genotyped for the Lys109Arg, Gln223Arg and Lys656Asn polymorphisms. The impact of these genetic variables together with other clinical and demographic parameters on PTDM risk was evaluated in a multivariate regression analysis. Results: The 223Arg variant showed a significant association with PTDM risk [OR = 3.26 (1.35-7.85), p = 0.009] after correcting for multiple testing. Carriers of this variant also showed higher BMI values (26.95 ± 4.23) than non-carriers (25.67 ± 4.43, p = 0.025). In addition, it was BMI at transplant and not the BMI increment in the first year after grafting that was associated with PTDM (p > 0.00001). Haplotype analyses did not reveal significant associations. Conclusions: Our result show, for the first time to our knowledge, that genetic variability in the LEPR may contribute significantly to the risk for PTDM in renal transplant recipients. KEY MESSAGES The LEPR Gln223Arg polymorphism significantly contributes to the development of PTDM in renal transplant recipients. The effect of the 223Arg variant on PTDM is strongly modulated by the age of the recipient. The 223Arg variant in the leptin receptor is related to higher BMI in renal transplant recipients.

Complementary Effects of Genetic Variations in LEPR on Body Composition and Soluble Leptin Receptor Concentration after 3-Month Lifestyle Intervention in Prepubertal Obese Children

In obese individuals, weight loss might be affected by variants of the adipokine-encoding genes. We verified whether selected functional single nucleotide polymorphisms in LEP, LEPR and ADIPOQ are associated with changes in serum levels of the respective adipokines and weight loss in 100 prepubertal obese (SDS-BMI > 2) Caucasian children undergoing lifestyle intervention. Frequencies of the -2548G > A LEP, Q223R LEPR, K656N LEPR, -11377C > G and -11426A > G ADIPOQ polymorphisms were analyzed by restriction fragment length polymorphism. Serum adipokine and soluble leptin receptor (sOB-R) concentrations were measured using the ELISA method. Among the analyzed polymorphisms, only LEPR polymorphisms were associated with changes of SDS-BMI or sOB-R concentrations in children after therapy. Carriers of the wild-type K665N and at least one minor Q223R allele had the greatest likelihood of losing weight (OR = 5.09, p = 0.006), an increase in sOB-R (ptrend = 0.022) and decrease in SDS-BMI correlated with the decrease of fat mass (p < 0.001). In contrast, carrying of the wild-type Q223R and at least one minor K665N allele were associated with a decrease in sOB-R concentrations and a decrease in SDS-BMI correlated with a decrease in fat-free mass (p = 0.002). We suggest that the combination of different LEPR variants, not a single variant, might determine predisposition to weight loss in the prepubertal period.

Prevalence, Risk Factors, and Genetic Traits in Metabolically Healthy and Unhealthy Obese Individuals

Objective. To assess prevalence of metabolically healthy individuals among patients with abdominal obesity (AO) and to determine phenotype and potential genetic traits associated with a benign metabolic status. Methods. 503 AO patients without cardiovascular diseases were examined. Waist circumference (WC), BMI, blood pressure, plasma glucose and serum insulin levels, HOMA-IR, lipid profile, and adiponectin (AN) and leptin (LEP) concentrations in serum were measured. Polymorphisms A19G and Q223R of the LEP and LEP receptor gene, and G276T and T45G of the AN gene were investigated. Results. 91.3% of patients were metabolically unhealthy obese (MUO), and 8.7% metabolically healthy obese (MHO). MHO patients were younger, and had lesser BMI and WC, while duration of obesity, frequency, and duration of physical training were greater than MUO patients (p < 0.05). In MHO and MUO patients distribution of the G19G, G19A, and A19A genotypes of the LEP gene and G276G, G276T, and T276T genotypes of AN gene did not differ. The Т45Т genotype was associated with increase of metabolic disorders' risk for patients with АО (OR = 2.331; 95%  CI = 1.121 ÷ 5.132). Conclusions. Prevalence of MHO individuals among patients with AO is low. Benign metabolic status was associated with younger age, lower waist circumference, and higher physical activity, shorter duration of obesity, and G45G adiponectin genotype carriage.

Association of Leptin Receptor Gene Polymorphisms with Genetic Susceptibility to Ischemic Stroke

BACKGROUND

Ischemic stroke is a multifactorial disease that is influenced by both genetic and environmental factors. Identification of the genetic factors that are underlining this disease is important. Leptin receptor (LEPR) mediates the leptin-regulated human energy homeostasis, and mutations of LEPR can increase cardiovascular risks and may predispose an individual to ischemic stroke.

METHODS

We analyzed distribution of 3 single nucleotide polymorphisms (SNPs) of LEPR gene (Lys109Arg, Gln223Arg, and Lys656Asn) in 101 patients with ischemic stroke and 105 controls by polymerase chain reaction-restriction fragment length polymorphism strategy.

RESULTS

Our results showed that there were significant differences in the genotype and allele distribution of Lys109Arg and Gln223Arg polymorphisms of the LEPR gene between case and control. The 109GG and 223GG genotype were associated with a significantly increased risk of ischemic stroke (odds ratio [OR], 3.23; P = .001 and OR, 2.87; P = .008, respectively). The 109G and 223G alleles carriers were correlated with an increased incidence of ischemic stroke (OR, 2.72; P = .001; OR, 2.94; P = .004). By haplotype analyses, we found that 109A/223G/656G haplotype was associated with an increased risk of ischemic stroke although this was not observed in the control group (OR, 3.86; P = .029).

CONCLUSIONS

LEPR 109GG and 223GG genotypes and the 109G and 223G alleles are associated with the risk of ischemic stroke. Our data suggest that LEPR Lys109Arg and Gln223Arg polymorphisms could be used as genetic predictive factor for ischemic stroke.

Polymorphisms of Leptin (-2548 G/A) and Leptin Receptor (Q223R) Genes in Iranian Women with Breast Cancer

Recent studies have shown that polymorphisms in leptin and leptin receptor genes are associated with increased risk for breast cancer. This study aimed at investigating -2548 G/A polymorphism in leptin gene and Q223R polymorphism in leptin receptor gene in patients with breast cancer. The study included 45 women with breast cancer and 41 healthy women. PCR-RFLP was used to determine the genotype of the subjects in terms of -2548 G/A polymorphism in leptin gene and Q223R polymorphism in leptin receptor gene. Serum levels of leptin were also measured by ELISA. For -2548 G/A polymorphism, the genotypes were homozygous AA (OR = 1.13; p = 0.8) and heterozygous GA (OR = 0.41; p = 0.2) and for Q223R polymorphism, the genotypes were homozygous RR (OR = 6.7; p = 0.09) and heterozygous QR (OR = 8.3; p = 0.06). The mean serum level of leptin was 33.22 ± 21.35 ng/mL in patients and 29.49 ± 23.27 ng/mL in the normal participants (p = 0.3). Although, despite the magnitude of the associations, the results suggested no statistically significant contribution of -2548 G/A polymorphism (in leptin gene), Q223R polymorphism (in leptin receptor gene), and serum leptin levels in predicting the risk of breast cancer, further studies with larger sample size are suggested.

Chronic stress aggravates glucose intolerance in leptin receptor-deficient (db/db) mice

Genetic predisposition and environmental challenges interact to determine individual vulnerability to obesity and type 2 diabetes. We previously established a mouse model of chronic subordination stress-induced hyperphagia, obesity, metabolic like-syndrome and insulin resistance in the presence of a high-fat diet. However, it remains to be established if social stress could also aggravate glucose intolerance in subjects genetically predisposed to develop obesity and type 2 diabetes. To answer this question, we subjected genetically obese mice due to deficiency of the leptin receptor (db/db strain) to chronic subordination stress. Over five weeks, subordination stress in db/db mice led to persistent hyperphagia, hyperglycemia and exacerbated glucose intolerance altogether suggestive of an aggravated disorder when compared to controls. On the contrary, body weight and fat mass were similarly affected in stressed and control mice likely due to the hyperactivity shown by subordinate mice. Stressed db/db mice also showed increased plasma inflammatory markers. Altogether our results suggest that chronic stress can aggravate glucose intolerance but not obesity in genetically predisposed subjects on the basis of a disrupted leptin circuitry.

Leptin receptor polymorphism Gln223Arg (rs1137101) in oral squamous cell carcinoma and potentially malignant oral lesions

The purpose of this study was to assess the LEPR gene Gln223Arg polymorphism (rs1137101) in oral squamous cell carcinoma (OSCC) and in potentially malignant oral lesions (PMOL) in comparison to normal oral mucosa in a Brazilian population. Smokers (n = 89) were selected from a representative sample of 471 individuals from the general population of Montes Claros, Brazil. Participants were age and gender matched to patients with OSCC (n = 25) and oral epithelial dysplasia (n = 25). We investigated the LEPR Gln223Arg polymorphism (A>G; rs1137101) in these groups. Genotype variants were assessed by RFLP-PCR, using MspI (HPAII) restriction endonuclease. The institutional review board of the Universidade Estadual de Montes Claros approved the study (process number 2667/2011). Written informed consent for this study was obtained from all participants. The GG genotype (Arg223Arg) appears to be the more relevant polymorphic variant in OSCC. It occurred, approximately, twice as frequently in OSCC patients than in the general population. In contrast, the A allele in its homozygosis form (Gln223Gln) is significantly associated with the development of PMOL; 80% of the samples from the PMOL group exhibit AA genotype. Our findings suggest new insights regarding LEPR gene variations in the development of OSCC and PMOL.

The Q223R polymorphism in the leptin receptor associates with objectively measured light physical activity in free-living Japanese

Physical activity (PA) is associated with reductions in the risk of all-cause mortality and in the prevalence of cardiovascular disease and stroke. Nevertheless, a large proportion of the general population may not be sufficiently active. PA level has been reported to be influenced by genetic factors, and we investigated whether Q223R polymorphism in the leptin receptor (LEPR) gene was associated with PA level. A total of 556 Japanese adults aged 24-65years old participated in this cross-sectional study. The duration and intensity of PA were objectively evaluated by triaxial accelerometry. Q223R polymorphism was determined by the TaqMan method. The distribution of Q223R polymorphism was: QQ 0.7%, QR 22.6%, and RR 76.6%. The relation between the LEPR genotype and PA level was analyzed by ANCOVA with age and sex as covariates in the Q dominant genetic model. There were significant differences between LEPR genotypes and the time spent in light PA or inactive time. The subjects with RR genotype showed significantly shorter time spent in light PA (RR genotype: 559.4±102.9min/day, QQ/QR genotype: 579.9±103.1min/day) and longer inactive time (RR genotype: 815.5±107.5min/day, QQ/QR genotype: 792.3±107.7min/day) than the subjects with QQ/QR genotype (P<0.05). There were no such differences in the time spent in moderate or vigorous PA. These results suggest that the variety of PA level, especially spontaneous PA in humans, is partly caused by diversity in the LEPR gene.

Analysis of the relationship between three coding polymorphisms in LEPR gene and obesity in northern Chinese

SUMMARY

To determine the effect of variants in LEPR gene on obesity in northern Chinese, three coding polymorphisms Arg109Lys (A/G), Asn656Lys (C/G) and Pro1019Pro (C/T) were investigated for association with overweight and obesity. By a case control design, 248 overweight or obese subjects and 351 lean normal controls were recruited in Harbin region in north China. All three polymorphisms were genotyped by Sequenom single nucleotide polymorphism (SNP) detection system in both cases and controls. Genotypes for all three polymorphisms were in Hardy-Weinberg equilibrium in control subjects. Both groups had similar distribution of alleles and genotypes created by the three coding polymorphisms of LEPR gene. No differences in frequencies of genotypes or alleles between cases and controls for any polymorphism individually were found by χ(2) analysis (p = 0.444, p = 0.507 and p = 0.662, respectively). Further, when the haplotypes of three polymorphisms were assessed, no association for any haplotype of three polymorphisms was revealed. In the present study, the three coding polymorphisms in LEPR gene were firstly investigated in a population of northern Chinese. It was suggested that the three coding polymorphisms in LEPR gene were unlikely to have major effects on susceptibility to obesity in northern Chinese.:

Evaluation of leptin and leptin receptor gene 3' UTR polymorphisms in essential hypertension

INTRODUCTION

Leptin and leptin receptor gene polymorphisms have been associated with obesity; however, their association with blood pressure has not been fully elucidated. The aim of this study was to examine the effect of tetranucleotide repeat polymorphism in the 3' flanking region of the leptin and leptin receptor gene on blood pressure in hypertensives with obesity.

METHODS

Two hundred and eighty hypertensives and 200 healthy controls were analyzed for a tetranucleotide repeat polymorphism of leptin and leptin receptor genes. Genotyping was done by amplifying DNA and determining the allele sizes using gel documentation system. Odds ratios were computed to predict the risk for hypertension caused by specific genotypes of leptin and leptin receptor genes and the effect of interaction between them on the development of hypertension was determined by MDR test.

RESULTS

Significant preponderance in the incidence of male sex, obese individuals and those with positive family history was observed with significant elevation in the mean levels of SBP, DBP, BMI and reduction of HDL levels in hypertensives as compared to controls. Class I/I genotypes of leptin showed significantly high risk for developing hypertension irrespective of obesity. Genotypes of leptin receptor did not confer any risk for hypertension and cohorts studied.

CONCLUSION

Homozygotes I/I were at greater risk for developing hypertension irrespective of obesity. When leptin and leptin receptor genes were considered together, synergistic interaction was observed between the two genes leading to hypertension, while the polymorphism at leptin gene and obesity was correlated.

Role of leptin receptor (LEPR) gene polymorphisms and haplotypes in susceptibility to hepatocellular carcinoma in subjects with chronic hepatitis B virus infection

AIM

The reported association of the leptin receptor (LEPR) protein with hepatocellular carcinoma (HCC) carcinogenesis prompted us to evaluate whether genetic polymorphisms of the LEPR gene affect susceptibility to HCC and its clinicopathologic characteristics.

METHODS

A total of 417 subjects who were diagnosed with HCC and 551 age- and sex-matched subjects without HCC were enrolled in this study. All subjects had chronic hepatitis B virus (HBV) infection. Three single nucleotide polymorphisms (SNPs) of the LEPR gene were determined.

RESULTS

The genotype frequencies of Lys109Arg and Gln223Arg differed significantly between HCC and non-HCC subjects (both p < 0.001). For the Lys109Arg polymorphism, HCC subjects had a higher prevalence of 109Arg/Arg than non-HCC subjects. The 109Arg/Arg carriers had a significantly higher adjusted risk of HCC than the 109Lys/Lys carriers. For the Gln223Arg polymorphism, subjects with the 223Arg/Arg genotype had a significantly higher risk of HCC than those with the 223Gln/Gln genotype. The Lys656Asn SNP did not affect the HCC risk. Haplotype analyses showed that subjects with 109Lys-656Lys-223Arg and 109Arg-656Asn-223Arg haplotypes had an increased HCC risk, while the 109Lys-656Lys-223Gln and 109Lys-656Asn-223Gln haplotypes had protective effects against HCC development. None of these polymorphisms were related to the clinicopathologic features of HCC.

CONCLUSION

The Lys109Arg and Gln223Arg polymorphisms of the LEPR gene are associated with susceptibility to HCC but not with its clinicopathologic features. These polymorphisms may represent genetic markers for the risk of HCC in the context of chronic HBV infection.

Nutrition and physical activity programs for obesity treatment (PRONAF study): methodological approach of the project

BACKGROUND

At present, scientific consensus exists on the multifactorial etiopatogenia of obesity. Both professionals and researchers agree that treatment must also have a multifactorial approach, including diet, physical activity, pharmacology and/or surgical treatment. These two last ones should be reserved for those cases of morbid obesities or in case of failure of the previous ones. The aim of the PRONAF study is to determine what type of exercise combined with caloric restriction is the most appropriate to be included in overweigth and obesity intervention programs, and the aim of this paper is to describe the design and the evaluation methods used to carry out the PRONAF study.

METHODS/DESIGN

One-hundred nineteen overweight (46 males) and 120 obese (61 males) subjects aged 18-50 years were randomly assigned to a strength training group, an endurance training group, a combined strength + endurance training group or a diet and physical activity recommendations group. The intervention period was 22 weeks (in all cases 3 times/wk of training for 22 weeks and 2 weeks for pre and post evaluation). All subjects followed a hypocaloric diet (25-30% less energy intake than the daily energy expenditure estimated by accelerometry). 29-34% of the total energy intake came from fat, 14-20% from protein, and 50-55% from carbohydrates. The mayor outcome variables assesed were, biochemical and inflamatory markers, body composition, energy balance, physical fitness, nutritional habits, genetic profile and quality of life. 180 (75.3%) subjects finished the study, with a dropout rate of 24.7%. Dropout reasons included: personal reasons 17 (28.8%), low adherence to exercise 3 (5.1%), low adherence to diet 6 (10.2%), job change 6 (10.2%), and lost interest 27 (45.8%).

DISCUSSION

Feasibility of the study has been proven, with a low dropout rate which corresponds to the estimated sample size. Transfer of knowledge is foreseen as a spin-off, in order that overweight and obese subjects can benefit from the results. The aim is to transfer it to sports centres. Effectiveness on individual health-related parameter in order to determine the most effective training programme will be analysed in forthcoming publications.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01116856.

Leptin Receptor Gene Variation Predicts Weight Change in Subjects with Impaired Glucose Tolerance

The leptin receptor (OB-R) gene is a promising candidate gene for type 2 diabetes, because leptin and its receptor play an important role in insulin secretion and the development of obesity. Therefore, we studied whether the pentanucleotide insertion polymorphism of the 3'-untranslated region (3'UTR) of the OB-R gene has an influence on the conversion from impaired glucose tolerance (IGT) to type 2 diabetes in the STOP-Noninsulin-Dependent Diabetes Mellitus trial. The STOP trial was a longitudinal, double-blind, placebo-controlled randomized trial that included 1429 subjects with IGT from high-risk populations. Using the restriction fragment length polymorphism method, we genotyped 770 subjects whose DNA was available for the insertion/deletion polymorphism of the 3'UTR of the OB-R gene. We did not find a relationship between the OB-R polymorphism and the conversion from IGT to type 2 diabetes (p = 0.747). However, the insertion allele was associated with a significant reduction in weight (p = 0.016), BMI (p = 0.009), and waist circumference (p = 0.006) in all subjects. Women carrying the I allele had a larger waist circumference change (p = 0.036), whereas men lost more weight and had a greater decrease in BMI. The pentanucleotide insertion/deletion polymorphism in the 3'UTR of the OB-R gene did not influence the conversion to type 2 diabetes in obese patients with IGT. However, this polymorphism was associated with a significant weight change, suggesting that it may potentially modulate the risk for type 2 diabetes.

Leptin Responsiveness to Energy Restriction: Genetic Variation in the Leptin Receptor Gene

Serum leptin concentrations are an important afferent signal in energy balance homeostasis. It has been speculated that the leptin responsiveness to energy restriction is affected by the functionality of the leptin receptor. The purpose of this analysis was to explore the effect of polymorphisms in the LEPR gene on the acute decline in leptin after 4 days of 65% energy restriction. Leptin concentrations of the study group (n = 44; all men) declined by 2.3 +/- 1.5 micro g/L [-39.4% (95% confidence interval: -43.6 to -34.9)]. Leptin responses did not statistically differ between noncarriers and carriers of three mutant variants of the polymorphisms: Lys109/Lys109 (-41.4%) vs. Arg109/+ (-37.0%) (p = 0.33); Gln223/Gln223 (-41.5%) vs. Arg223/+ (-37.8%) (p = 0.40); Lys656/Lys656 (-39.5%) vs. Asn656/+ (-39.3%) (p = 0.96). No effect of the assessed polymorphisms in the LEPR gene on the acute decline in leptin after energy restriction was observed. Power calculations are provided for future studies on the leptin responsiveness to energy restriction.

Relationship between leptin G2548A and leptin receptor Q223R gene polymorphisms and obesity and metabolic syndrome risk in Tunisian volunteers

Leptin is a key hormone of weight regulation that modulates food intake. Since the elaboration of the leptin action mechanism, several studies tried to establish the relationship between obesity and the common polymorphisms of leptin (LEP) and leptin receptor (LEPR) genes, but results were controversial. We studied the association of G2548A of the LEP gene and Q223R of LEPR gene polymorphisms with obesity and metabolic syndrome (MetS). We recruited 169 nonobese volunteers (body mass index [BMI] < 30 kg/m(2)) and 160 obese ones (BMI ≥ 30 kg/m(2)). Glucose, insulin, and lipids were measured. BMI, homeostasis model assessment-insulin resistance (HOMA-IR), and daily energy intake were calculated. After adjustment to confounders parameters, 2548AA was found to increase the MetS (p=0.043) and obesity risk (p=0.019) in the studied population. After stratification according to the degree of obesity, the odds ratio [OR] of 2548AA was associated with moderate obesity (p=0.048) and morbid obesity (p=0.048). The LEPR 223RR genotype was associated with obesity in the studied population (OR=1.74, p=0.037) and only in the overweight (OR=1.8, p=0.049). Subjects with 2548AA had significantly higher BMI, daily energy intake, total cholesterol (TC), waist circumference (WC), insulinemia, and low high-density lipoprotein-cholesterol (HDL-C) levels. With regard to 223RR, we noted a significantly higher daily energy intake, BMI, TC, glycemia, insulinemia, HOMA-IR index, and low HDL-C levels. Haplotype model AR (2548A+223R) and AQ (2548A+223Q) increased the risk of obesity (OR=3.36, p<0.001; OR=2.56, p=0.010, respectively). When we added daily energy intake in adjustment, these significant associations disappeared. In addition, the AR and AQ increased the MetS risk. This significant association persisted after we had added daily energy intake in adjustment. This study showed that LEP G2548A and LEPR Q223R polymorphisms and haplotype combination were associated with MetS and obesity risk in Tunisian volunteers.

Susceptibility of gastric cancer according to leptin and leptin receptor gene polymorphisms in Korea

Purpose

Leptin plays an important role in the control of body weight and also has a growth-factor-like function in epithelial cells. Abnormal expression of leptin and leptin receptor may be associated with cancer development and progression. We evaluated the relationship among leptin and leptin receptors polymorphisms, body mass index (BMI), serum leptin concentrations, and clinicopathologic features with gastric cancer and determined whether they could be the risk factor of gastric cancer.

Methods

We measured the serum leptin concentrations of 48 Korean patients with gastric cancer and 48 age- and sex-matched controls. By polymerase chain reaction-restriction fragment length polymorphism, we investigated one leptin gene promoter G-2548A genotype and four leptin receptor gene polymorphisms at codons 223, 109, 343, and 656.

Results

There was no significant difference between the mean leptin concentrations of the patient and control groups, while BMI was significantly lower in gastric cancer cases (22.9 ± 3.6 vs. 24.5 ± 2.8 kg/m², P = 0.021). There was significant association between the LEPR Lys109Arg genotype and gastric cancer risk, heterozygotes for GA genotype had been proved to increased the risk of gastric cancer, and its corresponding odds ratio was 2.926 (95% confidence interval, 1.248 to 6.861).

Conclusion

Our results suggested that LEPR gene Lys109Arg polymorphism is associated with gastric cancer in Korean patients.

Association of polymorphisms in leptin receptor gene with obesity and type 2 diabetes in the local population of Coimbatore

BACKGROUND:

Candidate gene association studies are very relevant to the area of clinical pharmacology. As information on candidate genes and candidate single nucleotide polymorphisms increases, a number of such candidates can be studied in a population to explore their association with their susceptible disease. One such attractive and popular Single Nucleotide Polymorphism (SNP) candidate for obesity is the gene coding for leptin receptor. The leptin receptor gene (LEPR) polymorphism plays an important role in obesity and type 2 diabetes. But the role of this polymorphism is not yet studied in Indian population. Hence, the study focused to explore the association of leptin receptor polymorphisms (K109R, Q223R and K656N) with obesity and type 2 diabetes in both diabetic and non-diabetic subjects recruited from the local population of Coimbatore.

MATERIALS AND METHODS:

Genotypic analysis for the three polymorphisms has been made for 300 subjects (150 diabetic and 150 non-diabetic) with the age range of 40–60 years using conventional Polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) techniques in a case–control fashion. Allele frequencies were estimated based on the gene count method. Correlation was made with phenotypic variables including body mass index (BMI), waist-to-hip ratio (WHR), insulin and leptin levels for those polymorphisms.

RESULTS AND CONCLUSION:

Among the polymorphisms tested in this study, significant association with BMI (P < 0.05), WHR (P < 0.05) leptin (P < 0.001) and insulin (P < 0.0001) was observed for the SNP Q223R, whereas in the case of the other two polymorphisms the association was not statistically significant. The significance value was calculated based on the χ² test. The controls are also found to have a higher frequency of homozygous mutants for Q223R and are significantly associated with obesity. These findings support the hypothesis that Q223R polymorphism is associated with obesity. It can be speculated that the controls showing the same allele may develop Type 2 diabetes at a later stage and Q223R can act as a strong marker.

Effect of LEPR Gln223Arg polymorphism on breast cancer risk in different ethnic populations: a meta-analysis

Leptin and leptin receptor have been implicated in processes leading to breast cancer initiation and progression. An A to G transition mutation in codon 223, in exon 6 of the leptin receptor gene (LEPR) can result in glutamine to arginine substitution (Gln223Arg). A variety of case-control studies have been published evaluating the association between LEPR Gln223Arg polymorphism and breast cancer. However, published studies have yielded contradictory conclusions. This meta-analysis enrolled eight studies to estimate the overall risk of LEPR Gln223Arg polymorphism associated with breast cancer. The pooled ORs were performed for codominant model (Arg/Arg versus Gln/Gln; Arg/Gln versus Gln/Gln), dominant model (Arg/Arg + Arg/Gln versus Gln/Gln), recessive model (Arg/Arg versus Arg/Gln + Gln/Gln). Overall significantly elevated breast cancer risk was found for recessive model (OR 1.32, 95% CI 1.03-1.69) and for genotype Arg/Gln versus Gln/Gln (OR 1.16, 95% CI 1.01-1.34). In the stratified analysis by ethnicity, significantly increased risks were also found among Africans for genotype Arg/Arg versus Gln/Gln: OR 1.86, 95% CI 1.28-2.71, Arg/Gln versus Gln/Gln: OR 1.48, 95% CI 1.10-1.99, dominant model: OR 1.60, 95% CI 1.21-2.11 and recessive model: OR 1.48, 95% CI 1.07-2.05; for Asians, Arg/Arg versus Gln/Gln: OR 6.79, 95% CI 3.42-13.47 and dominant model: OR 2.03, 95% CI 1.42-2.90. However, no significantly increased risk was found among Europeans for all genetic models. In conclusion, the LEPR 223Arg is a low-penetrant risk for developing breast cancer, especially for black African women.

Leptin, leptin gene and leptin receptor gene polymorphism in heart failure with preserved ejection fraction

Heart failure with a normal ejection fraction (HFNEF) is common in obesity and coronary artery disease (CAD). Both ischemia and reperfusion induce leptin (LEP) and leptin receptor (LEPR) gene expression. We aimed to investigate the possible associations of serum leptin, leptin gene and leptin receptor gene polymorphism with HFNEF in patients with CAD. 100 Egyptian CAD patients with HFNEF and 100 healthy subjects (the control group) were genotyped for LEP and LEPR polymorphism. Leptin levels were measured. Serum leptin levels were significantly increased in patients compared to the control group. There was a significant increase in the leptin gene (AA genotype) and the leptin receptor gene (RR genotype) in HFNEF patients compared to the control group. Leptin levels, leptin gene (AA genotype) and LEPR (RR genotype) were more associated with NYHA III than with NYHA I and II. We thus concluded that HFNEF is associated with increased serum leptin levels, and the LEP AA genotype or LEPR RR genotype carries at least a threefold increased risk of developing HFNEF.

Addictive genes and the relationship to obesity and inflammation

There is increasing evidence that the same brain reward circuits involved in perpetuating drug abuse are involved in the hedonic urges and food cravings observed clinically in overweight and obese subjects. A polymorphism of the D2 dopamine receptor which renders it less sensitive to dopamine stimulation has been proposed to promote self-stimulatory behavior such as consuming alcohol, abusing drugs, or binging on foods. It is important to determine how this polymorphism may interact with other well-known candidate genes for obesity including polymorphisms of the leptin receptor gene and the opiomelanocortin gene. Leptin is a proinflammatory cytokine as well as a long-term signal maintaining body fat. Upper-body obesity stimulates systemic inflammation through the action of multiple cytokines including leptin throughout many organs including the brain. The association of numerous diseases including diabetes mellitus, heart disease, as well as depression with chronic low-grade inflammation due to abdominal obesity has raised the possibility that obesity-associated inflammation affecting the brain may promote addictive behaviors leading to a self-perpetuating cycle that may affect not only foods but addictions to drugs, alcohol, and gambling. This new area of interdisciplinary research holds the promise of developing new approaches to treating drug abuse and obesity.

Sex-specific association between leptin receptor polymorphisms and leptin levels and BMI in healthy adolescents

AIM

To examine the relationship of three common polymorphisms in the leptin receptor (LEPR) gene, implicated in the regulation of body weight, with leptin levels and obesity-related phenotypes in a population-based sample of healthy pubertal children in Spain.

METHODS

The study included 806 boys and girls aged 12-16 whose anthropometrical data and body composition were recorded. Serum leptin levels were determined by ELISA. The LEPR Q223R, K109R and K656N polymorphisms were determined by TaqMan® allelic discrimination assays.

RESULTS

When analysing the Q223R polymorphism, we observed that female carriers of the RR genotype had significantly higher plasma leptin levels (18.2 vs. 15.1 ng/mL p = 0.016) and significantly higher mean BMI values (22.5 vs. 21.3 Kg/m² p = 0.032) than QR carriers. Furthermore, the frequency of the RR genotype in overweight-obese girls was significantly higher than that found in normal-weight girls. No significant differences were observed in boys. Neither boys nor girls showed significant differences when comparing leptin levels, anthropometric variables or body composition by K109R or K656N genotype.

CONCLUSION

The fact, that the Q223R polymorphism in the LEPR gene is significantly associated with leptin levels and BMI only in girls, suggests a sex-specific influence of this polymorphism on these variables.

No association of LEPR Gln223Arg polymorphism with leptin, obesity or metabolic disturbances in children

Objective

The aim of the study was to investigate whether the Gln223Arg in the leptin receptor may influence body weight, leptin concentration, and metabolic parameters in children.

Materials and methods

The examined group included 101 obese children (58 girls and 43 boys) with BMI 31.41 ± 5.03 kg/m² (BMI ≥ 2 SDS) and the control group consisted of 41 children with BMI 20.0 ± 0.80 kg/m² (BMI < 1.0 SDS). Polymorphism identification was performed in total genomic DNA using PCRRFLP method.

Results

The distribution of genotypes LEPR was the following: in the obese group: AA - 20.8%, AG-55.4%, GG-23.8%; in the control group AA-31.7%, AG-53.65%, GG-14.65%. Comparative analyses between AA homozygous children and carriers of G alleles did not confirm any relation between the analyzed polymorphism and BMI, leptin concentrations, and metabolic disturbances in children with obesity.

Conclusion

In children with obesity we did not observe association of the LEPR Gln223Arg gene polymorphism with obesity, leptin, insulin resistance, and metabolic abnormalities.

Leptin receptor modulation of adiposity and fertility

The leptin receptor was discovered as a leptin binding protein, which is highly expressed in the choroid plexus. Mapping of the gene's chromosomal locations in rodents revealed that mutations in Lepr were the basis of obesity/diabetes mutations in rodents and humans. Genetic manipulations that target Lepr expression in specific neurons or hypothalamic areas have generated insights into the modes by which body composition and reproductive function are modulated by the leptin receptor. These animal models have also been instrumental in identifying diabetes susceptibility genes. In this review we discuss the evidence that supports the concept of networked functions of leptin receptor as it pertains to feeding, substrate utilization and reproduction.

Leptin levels and leptin receptor polymorphism frequency in healthy populations

BACKGROUND

The leptin receptor gene (LEPR) polymorphism Q223R is one of the most common in the general population, and is thought to be associated with an impaired signaling capacity of the leptin receptor and with higher mean circulating levels of leptin. Leptin is a hormone primarily produced in adipose tissue. Increased levels of leptin have been positively correlated with obesity. We have determined the frequency of the leptin receptor polymorphism (LEPR Q223R) in healthy populations from various ethnic groups, and compared plasma leptin levels across the LEPR Q223R polymorphism in healthy African-Caribbean and Caucasian women.

RESULTS

The study population consists of 1,418 healthy subjects from various ethnic groups. The LEPR Q223R homozygous variant was observed overall in 19% of subjects (n = 1,418), with significant differences based on self reported ethnicity: the proportion of subjects with the homozygous variant was lower in Caucasians (14%, n = 883) than in African-Caribbean (n = 194), African-American (n = 36) and Asian/other ethnic groups (n = 26), (35%, 33% and 34.6% respectively); the frequency in Africans (20%), was similar to the overall study population. The mean +/- standard deviation (SD), circulating leptin levels for African-Caribbean women was 44.7 +/- 31.4 ng/ml, while for Caucasian women the mean was 42.4 +/- 34.8 ng/ml. Adjusted circulating leptin levels in post-menopausal Caucasian women who were LEPR Q223R homozygous variant were marginally statistically significantly higher than in women with the wild-type genotype (p = 0.098). No significant differences in leptin levels by genotype were observed for African-Caribbean women, (heterozygous: p = 0.765, homozygous variant: p = 0.485).

CONCLUSION

These findings suggest an association between mean circulating leptin levels and the LEPR Q223R genotype among post-menopausal Caucasian women.

Functional consequences of the human leptin receptor (LEPR) Q223R transversion

Perturbations in the functional integrity of the leptin axis are obvious candidates for mediation of altered adiposity. In a large number of genetic association studies in humans, the nonconservative LEPR Q223R allele has been inconsistently associated with adiposity. Subtle, long-term effects of such genetic variants can be obscured by effects of the environment and other confounders that render definitive inferences difficult to reach. We directly assessed the biological effects of this variant in 129P3/J mice segregating for the humanized Lepr allele at codon 223. No effects of this allele were detected on body weight, composition, or energy expenditure in animals fed diets of varying fat content over periods as long as 235 days. In vitro, Q223R did not affect leptin signaling as reflected by activation of STAT3. We conclude that Q223R is unlikely to play a significant role in regulation of human adiposity. This approach to vetting of human allelic variation might be more widely used.

Leptin receptor Gln223Arg polymorphism and breast cancer risk in Nigerian women: a case control study

Background

Leptin, a 16 kDa polypeptide hormone, implicated in various physiological processes, exerts its action through the leptin receptor, a member of the class I cytokine receptor family. Both leptin and leptin receptor have recently been implicated in processes leading to breast cancer initiation and progression in animal models and humans. An A to G transition mutation in codon 223 in exon 6 of the leptin receptor gene, resulting in glutamine to arginine substitution (Gln223Arg), lies within the first of two putative leptin-binding regions and may be associated with impaired signaling capacity of the leptin receptor. This study was designed to assess the role of this polymorphism in breast cancer susceptibility in Nigerian women.

Methods

We utilized a polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) assay to evaluate the association between the Gln223Arg polymorphism of the leptin receptor gene and breast risk in Nigeria in a case control study involving 209 women with breast cancer and 209 controls without the disease. Study participants were recruited from surgical outpatient clinics and surgical wards of four University Teaching Hospitals located in Midwestern and southeastern Nigeria between September 2002 and April 2004.

Results

Premenopausal women carrying at least one LEPR 223Arg allele were at a modestly increased risk of breast cancer after adjusting for confounders (OR = 1.8, 95% confidence interval [CI] 1.0–3.2, p = 0.07). There was no association with postmenopausal breast cancer risk (OR = 0.9, 95% CI 0.4–1.8, p = 0.68).

Conclusion

Our results suggest that the LEPR Gln223Arg polymorphism in the extracellular domain of the LEPR receptor gene is associated with a modestly increased risk of premenopausal breast cancer in Nigerian women.

Leptin and its metabolic interactions: an update

Obesity results from an abnormal accumulation of fat in the white adipose tissue. Recent research utilizing genetic models of obesity in rodents has implicated a major role of leptin as a controller of obesity. Leptin is a 167-amino acid peptide hormone encoded by the obesity gene (ob), which is secreted by adipocytes and plays an important role in regulating food intake, energy expenditure and adiposity. Leptin receptors (OB-R) are expressed in the central nervous system mainly in afferent satiety centres of hypothalamus and in peripheral organs such as adipose tissues, skeletal muscles, pancreatic beta-cells and liver, thus indicating the autocrine and paracrine role of leptin in energy regulation. In human beings, a highly organized circadian pattern of leptin secretion is observed with peak levels in the midnight probably resulting from cumulative hyperinsulinemia of entire day. Leptin has a dual role in weight maintenance. Leptin reflects total body adipose tissue mass whereas in conditions of negative and positive energy balance, the dynamic changes in plasma leptin concentration function as a sensor of energy balance and influence the efferent energy regulation pathways. Many effects of leptin on metabolism are mediated by interaction with Insulin and also by synergistic action with cholecystokinin. Besides physiological roles, leptin may influence pathological conditions like obesity-associated atherosclerosis, oxidative stress and cancers. The purpose of the present review is to summarize the important aspects of the biology, actions, and regulation of leptin and to serve as an update of new information.

Positional cloning of "Lisch-Like", a candidate modifier of susceptibility to type 2 diabetes in mice

In 404 Lep^ob/ob F2 progeny of a C57BL/6J (B6) x DBA/2J (DBA) intercross, we mapped a DBA-related quantitative trait locus (QTL) to distal Chr1 at 169.6 Mb, centered about D1Mit110, for diabetes-related phenotypes that included blood glucose, HbA1c, and pancreatic islet histology. The interval was refined to 1.8 Mb in a series of B6.DBA congenic/subcongenic lines also segregating for Lep^ob. The phenotypes of B6.DBA congenic mice include reduced β-cell replication rates accompanied by reduced β-cell mass, reduced insulin/glucose ratio in blood, reduced glucose tolerance, and persistent mild hypoinsulinemic hyperglycemia. Nucleotide sequence and expression analysis of 14 genes in this interval identified a predicted gene that we have designated “Lisch-like” (Ll) as the most likely candidate. The gene spans 62.7 kb on Chr1qH2.3, encoding a 10-exon, 646–amino acid polypeptide, homologous to Lsr on Chr7qB1 and to Ildr1 on Chr16qB3. The largest isoform of Ll is predicted to be a transmembrane molecule with an immunoglobulin-like extracellular domain and a serine/threonine-rich intracellular domain that contains a 14-3-3 binding domain. Morpholino knockdown of the zebrafish paralog of Ll resulted in a generalized delay in endodermal development in the gut region and dispersion of insulin-positive cells. Mice segregating for an ENU-induced null allele of Ll have phenotypes comparable to the B.D congenic lines. The human ortholog, C1orf32, is in the middle of a 30-Mb region of Chr1q23-25 that has been repeatedly associated with type 2 diabetes.

Type 2 diabetes (T2D) accounts for over 90% of instances of diabetes and is a leading cause of medical morbidity and mortality. Twin studies indicate a strong polygenic contribution to susceptibility within the context of obesity. Although approximately ten genes making important contributions to individual risk have been identified, it is clear that others remain to be identified. In this study, we intercrossed obese, diabetes-resistant and diabetes-prone mouse strains to implicate a genetic interval on mouse Chr1 associated with reduced β-cell numbers and elevated blood glucose. We narrowed the region using molecular genetics and computational approaches to identify a novel gene we designated “Lisch-like” (Ll). The orthologous human genetic interval has been repeatedly implicated in T2D. Mice with an induced mutation that reduces Ll expression are impaired in both β-cell development and glucose metabolism, and reduced expression of the homologous gene in zebrafish disrupts islet development. Ll is expressed in organs implicated in the pathophysiology of T2D (hypothalamus, islets, liver, and skeletal muscle) and is predicted to encode a transmembrane protein that could mediate cholesterol transport and/or convey signals related to cell division. Either mechanism could mediate effects on β-cell mass that would predispose to T2D.

The haplotype identified in LEPR gene is associated with type 2 diabetes mellitus in Northern Chinese

Leptin receptor (LEPR) plays an important physiological role in energy metabolism. The study addressed the relationship between leptin receptor gene variations and type 2 diabetes mellitus (T2DM). Three single nucleotide polymorphisms (SNPs) of LEPR gene, Arg109Lys (A/G), Asn656Lys (C/G) and Pro1019Pro (C/T) were detected in a northern population in China. Totally, 317 patients with T2DM and 282 healthy controls were recruited randomly from urban communities in Harbin area in the Northeast of China. All polymorphisms were genotyped by Sequenom SNP detection system in both case and control groups. Linkage disequilibria analysis showed moderate linkage disequilibria between the pair-wise SNPs for all three SNPs. Then, we identified the haplotype covering the three SNPs (AGC) with higher risk of T2DM (OR=1.69 (1.09-2.61)), and showed that there existed significant difference between cases and controls (9.8% vs. 6.0%, P=0.02). We also observed significant difference in frequencies of the heterozygous haplotype combination (GGT/AGC), that is 17.0% vs. 8.2% in cases and controls, respectively (P=0.001). It further supported the evidence that the haplotype (AGC) was associated with T2DM. So, AGC haplotype in LEPR gene could be a risk factor associated with T2DM in Northern Chinese.

Leptin and the sympathetic connection of fat to bone

Loss of body weight is associated with bone loss, and body weight gain is associated with increased bone formation. The molecular mechanisms linking body weight, body composition, and bone density are now better understood. Lean mass is likely to have a significant, local effect on bone modeling and remodeling through mechanotransduction pathways. In contrast to the local regulation of bone formation and resorption by muscle-derived stimuli, peripheral body fat appears to influence bone mass via secretion of systemic, endocrine factors that link body weight to bone density even in non-weight bearing regions (e.g., the forearm). The cytokine-like hormone leptin, which is secreted by fat cells, is an important candidate molecule linking changes in body composition with bone formation and bone resorption. Increases in body fat increase leptin levels and stimulate periosteal bone formation through its direct anabolic effects on osteoblasts, and through central (CNS) effects including the stimulation of the GH-IGF-1 axis and suppression of neuropeptide Y, a powerful inhibitor of bone formation. Stimulation of beta2-adrenergic receptors through central (hypothalamic) leptin receptors does, however, increase remodeling of trabecular bone, resulting in a lower cancellous bone volume that may be better adapted to a concomitantly larger cortical bone compartment. These findings suggest that body weight and body fat can regulate bone mass and structure through molecular pathways that are independent of load-bearing. Furthermore, pharmacological manipulation of the signaling pathways activated by leptin may have significant potential for the treatment and prevention of bone loss.

Leptin and leptin receptor gene polymorphisms in obstructive sleep apnea syndrome

BACKGROUND

Obstructive sleep apnea is common in obese people. Leptin is an adipocyte-derived signaling factor that has an important role in metabolic control. There is growing evidence that leptin regulation is altered in obstructive sleep apnea syndrome (OSAS). The aim of this study was to investigate the relation between polymorphisms of the leptin and leptin receptor (LEPR) genes and OSAS.

METHODS

The study population consisted of 130 patients with OSAS and 50 healthy control subjects. All the subjects were Japanese. Diagnostic polysomnography was performed in all patients and control subjects. A highly polymorphic tetranucleotide repeat polymorphism in the 3'-flanking region of the leptin gene and three single nucleotide polymorphisms (SNPs) [Lys109Arg (A/G) in exon 4, Gln223Arg (A/G) in exon 6, and Lys656Asn (G/C) in exon 14] in the LEPR gene were examined.

RESULTS

There were no significant differences in allelic frequencies and genotype distributions of the examined polymorphisms of the leptin and LEPR genes between OSAS patients and control subjects. For the LEPR gene, the wild-type alleles of the Gln223Arg and Lys656Asn SNPs had a marginally significant effect on mild OSAS, which was defined as an apnea-hypopnea index from 10 and 20 events/h in the dominant model.

CONCLUSIONS

The tetranucleotide repeat polymorphism of the leptin gene and the Lys109Arg, Gln223Arg, and Lys656Asn SNPs in the LEPR gene were not associated with OSAS in the Japanese population. Further studies are required to confirm the association of the wild types of Gln223Arg and Lys656Asn SNPs with the severity of OSAS.

Bone mass in prepubertal boys is associated with a Gln223Arg amino acid substitution in the leptin receptor

OBJECTIVE

The contribution of leptin to bone mass acquisition in humans remains unclear. We investigated the association of the Gln223Arg polymorphism in the leptin receptor gene (LEPR) with bone mineral content (BMC) and areal bone mineral density (aBMD) in prepubertal boys and LEPR interaction with vitamin D receptor (VDR) genotypes (Bsm1 and Fok1).

DESIGN

In a cross-sectional design with a longitudinal follow-up, dual-energy x-ray absorptiometry measurements at the lumbar spine, hip, femoral diaphysis, and radius were performed at baseline (mean age 7.4 +/- 0.4 yr) and 2 yr later in 222 healthy Caucasian males.

RESULTS

LEPR genotypes were significantly associated with baseline BMC at the hip (P = 0.017), femur diaphysis (P = 0.019), and radius (P = 0.007) and with height (P = 0.041) as well as with physical activity (P = 0.016). Associations with height and BMC at femur diaphysis and radius remained significant after 2 yr. Significant differences in 2-yr bone mass gain at the spine and femur neck were also found among LEPR genotypes. In contrast, adjusting BMC for projected bone area (aBMD) and/or weight, height, and physical activity resulted in a weak association only at the femur (P = 0.014-0.054). VDR polymorphisms were not associated with BMC or aBMD, but significant interactions occurred between VDR Fok1 and LEPR genotypes.

CONCLUSIONS

The LEPR Gln223Arg polymorphism was associated with bone mass in growing boys. The association, however, was markedly dependent on bone area, body size, and physical activity, in addition to VDR genetic variation, suggesting that the leptin system may modulate bone mass in humans mostly through indirect mechanisms.

Genes, fat intake, and cardiovascular disease risk factors in the Quebec Family Study

OBJECTIVE

The aim of this study was to assess gene-diet interaction effects on cardiovascular disease (CVD) risk factors (waist circumference, plasma triacylglycerol, high-density lipoprotein-cholesterol and fasting glucose concentrations, and diastolic and systolic blood pressure) in the Quebec Family Study cohort.

DESIGN

Sixty-four polymorphisms from 45 candidate genes were studied in 645 subjects. Dietary fat intake was obtained from a 3-day weighted food record.

RESULTS

We observed 18 significant interactions at a p value <or= 0.01. Among them, the Pro12Ala polymorphism in peroxisome proliferator-activated receptor gamma, alone or in interaction with fat intake, significantly modulated waist circumference (p = 0.0005 for both effects). Additionally, the apolipoprotein E genotype in interaction with fat intake was significantly associated with diastolic and systolic blood pressure (p = 0.01 and p = 0.001, respectively). The ghrelin Leu72Met polymorphism also interacted with dietary fat in its relation to waist circumference and triacylglycerol concentrations (p = 0.0004 and p = 0.005).

DISCUSSION

These results suggest that several alleles at candidate genes interact with dietary fat intake to modulate well-known CVD risk factors. The identification of gene-diet interaction effects is likely to provide useful information concerning the etiology of CVD.

Genetic susceptibility and body mass in childhood cancer survivors

Childhood cancer survivors are at increased risk of many long-term treatment-related sequel such as second cancers, cardiovascular disease, and pulmonary complications. Certain treatments seem to influence the risk of becoming overweight, obese, or underweight, and abnormal body mass index (BMI) is associated with increased morbidity and mortality. Because BMI is modifiable, it is important to identify treatment and patient-related factors contributing to altered BMI. New research areas include exploring how genetic susceptibility through population polymorphism may contribute to BMI. Illuminating potential gene-environment interactions that influence obesity and underweight might be more readily accomplished in a study of high-risk individuals (i.e., childhood cancer survivors) with well-characterized exposures. The new Childhood Cancer Research Network in the Children's Oncology Group, when fully implemented, should make it less difficult in the future to recruit the large numbers of patients needed for such studies.

Variants of the CFC1 gene in patients with laterality defects associated with congenital cardiac disease

OBJECTIVES

This study was designed to assess the frequency and types of genetic variants in CFC1 in children with laterality disorders associated with cardiovascular involvement.

BACKGROUND

Laterality syndromes are estimated to comprise 3% of neonates with congenital cardiac disease. Genetic predisposition in some cases of laterality defects has been suggested by associated chromosomal anomalies and familial aggregation, often within consanguineous families, suggesting autosomal recessive inheritance. Mice with induced homozygous mutations in cfc1, and heterozygous CFC1 mutations in humans, have been associated with laterality defects.

METHODS

Direct sequence analysis of the coding sequence of CFC1 was performed in 42 subjects with laterality defects and congenital cardiac disease.

RESULTS

We identified 3 synonymous coding variants, 3 non-synonymous coding variants (N21H, R47Q, and R78W), and 2 intronic variants in CFC1. The N21H variant was observed in 3 of 19 affected Caucasians, and the R47Q variant in another 2. Neither polymorphism was observed in Caucasian controls. Furthermore, all subjects with the N21H polymorphism had double outlet right ventricle. Transmission of both the N21H and R47Q polymorphisms from unaffected parents was demonstrated, and all three non-synonymous variants had significant allele frequencies in unaffected African-American subjects, suggesting that other factors must also contribute to laterality defects.

CONCLUSIONS

Three non-synonymous variants in CFC1 were identified, the N21H variant being associated with laterality defects in Caucasians, but not fully penetrant. One or more of these non-synonymous missense variants may act as a susceptibility allele in conjunction with other genes, and/or environmental factors, to cause laterality defects.

Effect of genetic variation in the leptin gene promoter and the leptin receptor gene on obesity risk in a population-based case-control study in Spain

There are no good genetic markers for incorporating the study of genetic susceptibility to obesity in epidemiological studies. In animal models, the leptin (LEP) and the leptin receptor (LEPR) genes have been shown to be very important in obesity because leptin functions as a negative feedback signal in regulating body-weight through reducing food intake and stimulating energy expenditure. In humans, several polymorphisms in these genes have been described. However, their association with obesity is still very controversial because there are no good case-control studies designed to specifically test this association. Our objective has been to conduct a population-based case-control study to estimate the risk of obesity arising from the -2548G > A and Q223R polymorphisms in the LEP and LEPR genes, respectively. 303 obese cases (101 men and 202 women) and 606 controls (202 men and 404 women) were selected from a Spanish Mediterranean population. Genetic, clinical and life-style characteristics were analyzed. No association was found between the -2548G > A polymorphism and obesity. However, the Q223R variant was significantly associated with obesity in a recessive model, the RR genotype being more prevalent in controls than in obese subjects. The inverse association between the Q223R polymorphism and obesity (OR = 0.62; 95% CI: 0.39-0.99) remained significant even after additional adjustment for education, tobacco smoking, alcohol, physical activity, origin of the obese patient, and the -2548G > A polymorphism in the LEP gene (OR = 0.54; 95% CI: 0.32-0.89). In conclusion, the -2548G > A polymorphism is not a relevant obesity marker in this Mediterranean population, although Q223R does seen to be so.

Relationships among serum leptin, leptin receptor gene polymorphisms, and breast cancer in Korea

Leptin plays an important role in the regulation of body fat homeostasis, and potential associations of leptin receptor gene (LEPR) polymorphisms with obesity have been suggested. Obesity is considered to relate to breast cancer. We assessed the role of leptin in relation to breast cancer. We measured the serum leptin concentrations of 45 Korean pre-treatment patients with breast cancer and 45 age-matched controls. By direct sequencing, we investigated four leptin receptor gene (LEPR) polymorphisms at codons 109, 223, 656, and 1019. There was no significant difference between the mean leptin concentrations of the patient and control groups in both pre- and post-menopausal women. The frequencies of the wild-type for LEPR codons 109, 223, and 1019 were very low. No increased risk estimate was found for the four LEPR polymorphisms. Our results indicate that it is difficult to explain breast cancer on the basis of serum leptin concentrations or polymorphisms in the LEPR gene.

Polymorphisms in the leptin and leptin receptor genes in relation to resting metabolic rate and respiratory quotient in the Québec Family Study

BACKGROUND

Leptin (LEP) is an endocrine hormone that participates in many metabolic pathways, including those associated with the central regulation of energy homeostasis.

OBJECTIVE

We examined the associations between polymorphisms in the LEP and leptin receptor (LEPR) genes and resting metabolic rate (RMR) and respiratory quotient (RQ) in the Quebec Family Study.

METHODS AND SUBJECTS

Three polymorphisms in LEPR (K109R, Q223R and K656N) and one in LEP (19A > G) were genotyped in 678 subjects. RMR, RQ at rest and RQ while sitting, standing and walking at 4.5 km/h (RQ45) were adjusted for age, sex, fat mass and fat-free mass.

RESULTS

RQ45 was associated with the LEPR-K109R (P = 0.004) and Q223R (P = 0.03) polymorphisms, and RMR showed association with the LEPR-K656N polymorphism (P = 0.006). For the LEP-19A > G polymorphism, no significant associations were observed. However, LEP-A19A homozygotes who were carriers of the LEPR N656 allele had a significantly lower RQ45 compared to other genotype combinations (P for interaction=0.003).

CONCLUSION

These findings suggest that DNA sequence variation in the LEPR gene contributes to human variation in RMR and in the relative rates of substrate oxidation during low-intensity exercise in steady state but not in a resting state.

Genetics of leptin and obesity: a HuGE review

Leptin is an important regulator of the mass of adipose tissue and of body weight; it operates by inhibiting food intake and stimulating energy expenditure. Some polymorphic genes involved in the regulation of leptin-the leptin gene (LEP A19G), the leptin receptor gene (LEPR Q223R, K109R, and K656N), and the peroxisome proliferator-activated receptor-gamma gene (PPARG P12A and C161T)--have been investigated as possible factors associated with obesity. Allelic frequencies of these polymorphisms show ethnic variation. The authors performed a meta-analysis of the available data on the association between these polymorphisms and obesity based on case-control studies. Odds ratios and 95% confidence intervals for obesity associated with leptin polymorphisms were calculated by using both fixed- and random-effects models. Results suggest no evidence of association between the genes under study and obesity. The lack of association could be due to the complex pathogenesis of obesity, which involves a number of genetic and environmental factors. Large studies including testing of multiple genes in both obese and lean subjects, with epidemiologic data on dietary habits in different ethnic groups, are necessary to better understand the role of leptin in regulating weight in human populations.

Leptin and soluble leptin receptor levels in obese children in fasting and satiety states

AIM

To investigate the role of soluble leptin receptors in leptin resistance in obese children.

METHODS

Thirty-one obese children (16 boys and 15 girls) with a median age of 12.1 years and 15 age- and sex-matched controls were included in the study. Leptin and soluble leptin receptor levels were measured in fasting and satiety states.

RESULTS

Serum leptin levels were significantly higher and soluble leptin receptor levels were significantly lower in obese children compared to controls in fasting and satiety states. In obese children, there was a high and inverse correlation between leptin levels and soluble leptin receptor levels after fasting. Prepubertal obese children had lower leptin and higher soluble leptin, receptor levels compared to pubertal children in both states.

CONCLUSION

In this study, being the first to consider both fasting and satiety states, obese children were found to have higher leptin, but lower soluble leptin receptor levels, compared to controls. With these findings, it can be postulated that leptin resistance in obese children originates from a defect of soluble leptin receptor production.

Tyrosine phosphatase 1B and leptin receptor genes and their interaction in type 2 diabetes

OBJECTIVES

The association between three tyrosine phosphatase 1B (PTP1B) gene polymorphisms and type 2 diabetes was examined by comparing the prevalence rates of these polymorphisms in type 2 diabetic patients and healthy control subjects. Furthermore, the association of the polymorphisms and PTP1B and leptin receptor (LepR) gene-gene interactions with complications of type 2 diabetes were examined in type 2 diabetic patients.

SUBJECTS AND METHODS

A total of 257 Finnish patients with type 2 diabetes and 285 nondiabetic subjects were screened. Single nucleotide polymorphisms were determined using polymerase chain reaction and restriction enzymes. The diagnosis of coronary heart disease was based on clinical and ECG criteria. The prevalences of cerebrovascular and peripheral vascular diseases were assessed on the basis of clinical criteria. Laboratory analyses were carried out in the hospital laboratory.

RESULTS

We did not find any differences in the genotype distributions or allele frequencies of IVS6 + G82A and Pro387Leu polymorphisms between the type 2 diabetics and controls. There were differences in the genotype frequencies of the Pro303Pro (C981T)-polymorphism between the two studied groups (P = 0,018); there were eight T981T subjects in the control population but none amongst the type 2 diabetics. However, there were no differences in the allele frequencies. In addition, significant associations between the IVS6 + G82A polymorphism and body mass index (BMI), albuminuria, glycohaemoglobin A1 (GHBA1) and hypertension in type 2 diabetic patients (P = 0,026-0,031) were observed. Pro387Leu and Pro303Pro did not associate with risk factors or diabetic complications. We also found a gene-gene interaction effect between PTP1B and the LepR gene with the genotype combination IVS6 + A82A and Arg223Arg having the highest BMI compared with the other genotype combinations (P = 0.0043 for trend). The interaction between these two polymorphisms explained 3% of the variation in BMI in diabetic patients when the other covariates were taken into account.

CONCLUSIONS

We conclude that the PTP1B IVS6 + G82A polymorphism was associated with BMI, albuminuria, GHBA1 and hypertension in type 2 diabetic patients. The 981T/T-genotype of the Pro303Pro- polymorphism might have some protective role against the development of type 2 diabetes. The interaction effects between the PTP1B IVS6 + A82A and LepR Arg223Arg genotypes influenced BMI, explaining 3% of its variation. A synergistic effect of PTP1B and LepR variants on the leptin signalling may be involved.