p.Q223R leptin receptor polymorphism associated with obesity in Brazilian multiethnic subjects

Meta-analysis investigating the impact of the LEPR rs1137101 (A>G) polymorphism on obesity risk in Asian and Caucasian ethnicities

Obesity is a chronic condition which is identified by the buildup of excess body fat caused by a combination of various factors, including genetic predisposition and lifestyle choices. rs1137101 (A > G) polymorphism in the CHR1 domain of LEPR protein linked to different diseases including obesity. Nevertheless, the connection between this polymorphism and the likelihood of developing obesity has not been determined definitively. Therefore, a meta-analysis was conducted to assess the relationship between rs1137101 and the risk of obesity. The meta-analysis included all studies meeting pre-defined criteria, found through searching databases up until February 2023. A combined odds ratio with a 95% confidence interval was estimated as overall and in continent subgroups for homozygous, heterozygous, recessive, dominant and allelic models using the fixed or the random-effects model. The meta-analysis identified 39 eligible studies with cases and controls (6099 cases/6711 controls) in 38 articles under different ethnic backgrounds. The results indicated a significant relationship between rs1137101 and the likelihood of developing obesity in each of the genetic models [the homozygous model (GG vs. AA: 95% Confidence Interval = 1.12-1.73, Odds Ratio = 1.39, P value = 0.003); the heterozygous model (AG vs. AA: 95% Confidence Interval = 1.07-1.42, Odds Ratio = 1.23, P value = 0.005); the dominant model (AG/GG vs AA: 95% Confidence Interval = 1.10-1.49, Odds Ratio = 1.28, P value = 0.001); the recessive model (GG vs AA/AG: 95% Confidence Interval = 1.02-1.45, Odds Ratio = 1.21, P value = 0.03); and the allelic model (G vs A; 95% Confidence Interval = 1.07-1.33, Odds Ratio = 1.19, P value = 0.002)] tested. Additionally, with an FDR <0.05, all genotypic models demonstrated statistical significance. The association remained significant among subgroups of Asian and Caucasian populations, although analysis in some genetic models did not show a significant association. Begg's and Egger's tests did not show publication biases. In sensitivity analysis, one particular study was found to have an impact on the Recessive model's significance, but other models remained unaffected. The current meta-analysis found significant indications supporting the association between rs1137101 and obesity. To avail a deeper understanding of this association, future research should include large-scale studies conducted in diverse ethnic populations.

Association of TNF-α 308G/A and LEPR Gln223Arg Polymorphisms with the Risk of Type 2 Diabetes Mellitus

The objective of the present study was to identify the association of the TNF-α- 308G/A and leptin receptor (LEPR) Gln223Arg polymorphisms with the risk of development of type 2 diabetes mellitus (T2DM). Methods: A total of 160 volunteers were studied: 108 with T2DM and 52 participants as control, who served as the control group. Polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) for the genomic region of TNF-α- 308G/A and LEPR Gln223Arg were carried out. Results: The frequency of LEPR Gln223Arg genotypes in T2DM and control groups showed significant differences in the distribution of genotypes (p < 0.05). The frequency also of TNF-α- 308G/A genotypes in T2DM and control subjects showed significant differences in the distribution of genotypes (p < 0.05). Conclusion: Our results indicate that there are significant differences in the distribution of genotypes and alleles between the individuals with T2DM and control subjects (p < 0.05).

Comparison of Q223R leptin receptor polymorphism to the leptin gene expression in Greek young volunteers

<abstract><sec> <title>Objective</title> <p>The objective of the present study was to identify the leptin gene expression and the leptin receptor polymorphisms in blood samples and to correlate gene expression values with anthropometric characteristics.</p> </sec><sec> <title>Methods</title> <p>Blood from 140 Greek young volunteers was subjected to polymerase chain reaction–restricted fragment length polymorphism (PCR–RFLP), for the genomic region of Q223R polymorphism at codon 223 in the leptin receptor gene (<italic>LEPR</italic>) coding region. RNA extraction, cDNA synthesis and Quantitative Real-Time PCR was performed for assessing the expression of the leptin gene (<italic>LEP</italic>).</p> </sec><sec> <title>Results</title> <p>Leptin gene was identified in all tested specimens and the gene was expressed in 88.9% of all volunteers with BMI &lt; 25. In addition, it was observed that gene expression is affected by various external factors, such as Body Mass Index (BMI), eating behavior, gender and age. It was also shown that as for the Q223R polymorphism (A to G) allele G occurs with a frequency of 100% in men with BMI &gt; 30 and 75.9% in men and 88.9% in women with BMI 25–30. Volunteers with BMI 25–30 who were homozygous on the G allele were 50% and 77.8% in men and women respectively. All subjects with a BMI &gt; 30 were homozygous on the G allele at 100%.</p> </sec><sec> <title>Conclusions</title> <p>In this small-scale study, results have shown that the leptin gene expression correlates with BMI and that the allele G in Q223R polymorphism is linked to overweight individuals.</p> </sec></abstract>

Leptin Gene G2548A Polymorphism among Mongolians with Metabolic Syndrome

Metabolic syndrome (MetS) corresponds with multiple risk factors. Many studies have indicated that MetS significantly increases the risk of cardiovascular diseases and type 2 diabetes (T2D). The prevalence of MetS was estimated to be one third of the general Mongolian population in 2015. The purpose of our study was to determine polymorphisms of the LEP (Leptin) and LEPR (Leptin receptor) genes that show susceptibility to MetS and to predict the genetic risk of MetS. We selected 160 cases with MetS and 144 with healthy controls. The G2548A polymorphism of the LEP gene and the A668G (Q223R) polymorphism of the LEPR gene were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results of the regression analysis showed that the 2548 amino acids (AA) of LEP gene carriers had increased incidences of MetS (OR = 3.23; p = 0.035). Patients with MetS who were 2548A allele carriers had an increased concentration of serum leptin (p = 0.011). Moreover, G2548A of LEP polymorphism was associated with elevated body mass index (BMI) and fasting blood glucose (FBG) in the case group. Our results confirm that the LEP G2548A loci is the independent risk factor of MetS.

Leptin and Leptin Receptor Genes Are Associated With Obesity-Related Traits Changes in Response to Aerobic Training Program

Leońska-Duniec, A, Jastrzębski, Z, Jażdżewska, A, Krzysztof, F, and Cięszczyk, P. Leptin and leptin receptor genes are associated with obesity-related traits changes in response to aerobic training program. J Strength Cond Res 32(4): 1036-1044, 2018-Leptin (LEP) and leptin receptor (LEPR) genes have been studied for their potential association with development of human obesity and its related complications. Therefore, we have decided to check whether selected body mass, body composition, and metabolic variables observed in physically active participants will be modulated by the polymorphisms. The genotype distribution was examined in a group of 201 women measured for chosen traits before and after the completion of a 12-week aerobic training program. Our results revealed a significant interaction between training and LEP genotype for glucose level. A training-related decrease in plasma glucose concentration in the LEP AG heterozygotes differed significantly from the change in the homozygotes. The polymorphism was also associated with fat-free mass (FFM), total body water (TBW), total cholesterol, triglycerides, and low-density lipoprotein cholesterol (LDL-C) levels. Another finding was a significant interaction between training and LEPR for LDL-C level. As opposed to AG and GG, AA homozygotes demonstrated a training-related decrease in LDL-C level. Our findings also showed that the LEPR G allele is connected with obesity-related traits. The participants with the GG genotype had higher body mass, body mass index (BMI), FFM, and TBW during the entire study period. This study provides evidence that polymorphisms in the LEP and LEPR genes are associated with the magnitude of the effects of regular physical activity on glucose and LDL-C levels, respectively. In addition, we found the association of the G allele of the LEPR polymorphism with body mass and BMI.

Cleavage of the leptin receptor by matrix metalloproteinase-2 promotes leptin resistance and obesity in mice

Obesity and related morbidities pose a major health threat. Obesity is associated with increased blood concentrations of the anorexigenic hormone leptin; however, obese individuals are resistant to its anorexigenic effects. We examined the phenomenon of reduced leptin signaling in a high-fat diet-induced obesity model in mice. Obesity promoted matrix metalloproteinase-2 (Mmp-2) activation in the hypothalamus, which cleaved the leptin receptor's extracellular domain and impaired leptin-mediated signaling. Deletion of Mmp-2 restored leptin receptor expression and reduced circulating leptin concentrations in obese mice. Lentiviral delivery of short hairpin RNA to silence Mmp-2 in the hypothalamus of wild-type mice prevented leptin receptor cleavage and reduced fat accumulation. In contrast, lentiviral delivery of Mmp-2 in the hypothalamus of Mmp-2-/- mice promoted leptin receptor cleavage and higher body weight. In a genetic mouse model of obesity, transduction of cleavage-resistant leptin receptor in the hypothalamus reduced the rate of weight gain compared to uninfected mice or mice infected with the wild-type receptor. Immunofluorescence analysis showed that astrocytes and agouti-related peptide neurons were responsible for Mmp-2 secretion in mice fed a high-fat diet. These results suggest a mechanism for leptin resistance through activation of Mmp-2 and subsequent cleavage of the extracellular domain of the leptin receptor.

Leptin receptor gene (A/G) polymorphism rs1137101 and renal cell carcinoma

Leptin plays an important role in carcinogenesis as leptin/leptin receptor signaling promotes the angiogenesis, proliferation, and inhibits epithelial cell apoptosis. Variants in the leptin receptor gene have potential associations with renal cell carcinoma (RCC). We aimed to investigate association of rs1137101 (A/G) polymorphism at LEPR gene with risk of RCC and patients survival. 123 individuals were classified into group I: 73 RCC patients and group II: 50 healthy controls. Genotyping of the Gln223Arg (A/G) polymorphism rs1137101 at LEPR gene was analyzed using allelic discrimination assay by Real-Time PCR technique. GG genotype was the most frequent among RCC patients (67.1%), while AA genotype was the most frequent in controls (60%); (p < 0.001). By univariate cox regression: gene polymorphism (GG versus GA +AA), stage, histopathologic subtype, and grade were found to affect survival significantly; however, the multivariate analysis showed that only gene polymorphism (GG versus GA +AA) and tumor stage significantly affect survival. LEPR gene variants rs1137101 might be a candidate risk factor for RCC in Egypt. GG genotype is associated with more aggressive tumor behavior and shorter survival compared with GA & AA genotypes so, genotyping of Gln223Arg (A/G) rs1137101 could also predict RCC outcome.

LEPR polymorphism may affect energy balance during weight loss among Brazilians obese adolescents

OBJECTIVE

Leptin is an adipokine released mainly by adipose tissue, with many functions including regulation of energy balance. However, little is known about the effect of LEPR polymorphism on orexigenic and anorexigenic neuropeptides. Thus, the aim of the present study is to verify the influence of LEPR polymorphism (rs2767485) on serum orexigenic (NPY, MCH and AgRP) and anorexigenic (Leptin and α-MSH) neuropeptides levels among obese adolescents submitted to 1year of multicomponent weight loss therapy.

METHODS

Seventy-six adolescents with obesity were enrolled in 1year of weight loss therapy including clinical, nutritional, psychological and exercise-related. Blood samples were collected to analyze neuropeptides (NPY, MCH, AgRP and leptin) and LEPR genotyping. Visceral fat was measured by ultrasound and body composition was measured by plethysmography. The parameters were measured at baseline and after one year. Adolescents were grouped according to genotype (TT or CT+CC group). Effect of the weight loss therapy was analyzed through ANOVA and Wilcox, according to normality. Statistic value was set at <0.05.

RESULTS

C-allele carriers have the orexigenic neuropeptides (NPY, AgRP and MCH) levels statistically higher when compared with TT group, at baseline. Furthermore, TT group seems to respond better to the therapy by a greater delta on BMI. Indeed, the data suggest a concomitant increased of AgRP levels in CT+CC genotypes, after weight loss therapy.

CONCLUSION

Both groups responded to the weight loss intervention, however wildtypes (TT) appear to respond to the intervention most optimally with C carries, where post intervention reduction in BMI was significantly greater in wildtypes. The leptin receptor polymorphism seems to affect neuroendocrine regulation of energy balance among adolescents with obesity.

The Leptin Receptor Complex: Heavier Than Expected?

Under normal physiological conditions, leptin and the leptin receptor (ObR) regulate the body weight by balancing food intake and energy expenditure. However, this adipocyte-derived hormone also directs peripheral processes, including immunity, reproduction, and bone metabolism. Leptin, therefore, can act as a metabolic switch connecting the body's nutritional status to high energy consuming processes. We provide an extensive overview of current structural insights on the leptin-ObR interface and ObR activation, coupling to signaling pathways and their negative regulation, and leptin functioning under normal and pathophysiological conditions (obesity, autoimmunity, cancer, … ). We also discuss possible cross-talk with other receptor systems on the receptor (extracellular) and signaling cascade (intracellular) levels.

Brain derived neurotrophic factor in newly diagnosed diabetes and prediabetes

Brain derived neurotrophic factor (BDNF) is thought to play an important role in glucose metabolism, but the exact mechanism has not been elucidated. The aim was to assess differences in serum BDNF levels across individuals with varying levels of glucose tolerance, and the association of serum BDNF levels with genetic variants and DNA methylation. Participants were selected from an ongoing population-based cohort study in rural China. In a randomly selected subsample of healthy participants (n = 33 males, n = 52 female), we assessed serum BDNF and in n = 50 of these, also DNA methylation. In a second subsample (all women; n = 28 with diabetes, n = 104 with prediabetes, and n = 105 age- and body mass index (BMI)-matched controls), we assessed serum BDNF and genetic variants. In a third subsample (all with diabetes; n = 7 normal BMI + low insulin level, n = 9 normal BMI + high insulin level, n = 9 obese + high insulin level), we assessed DNA methylation. Compared to age- and BMI-matched controls (24.71 (IQR, 20.44, 29.80) ng/ml), serum BDNF was higher in participants with prediabetes (27.38 (IQR, 20.64, 34.29) ng/ml), but lower in those with diabetes (23.40 (IQR, 18.12, 30.34) ng/ml) (P < 0.05). Two genetic variants near BDNF (rs4074134 and rs6265) were confirmed to be associated with BMI. BDNF CpG-6 methylation was positively associated with waist-to-hip ratio (P < 0.05). Furthermore, hyper-methylation in this site was found in participants with diabetes and high fasting insulin levels compared to those with diabetes and low fasting insulin levels, regardless of BMI status (P < 0.001 and P = 0.001, respectively). Observed differences in serum BDNF levels, genetic variants, and DNA methylation patterns across different glucose metabolic state suggest that BDNF may be involved in the pathophysiological process of insulin resistance and type 2 diabetes.

Leptin: From structural insights to the design of antagonists

After its discovery in 1994, it soon became clear that leptin acts as an adipocyte-derived hormone with a central role in the control of body weight and energy homeostasis. However, a growing body of evidence has revealed that leptin is a pleiotropic cytokine with activities on many peripheral cell types. Inappropriate leptin signaling can promote autoimmunity, certain cardiovascular diseases, elevated blood pressure and cancer, which makes leptin and the leptin receptor interesting targets for antagonism. Profound insights in the leptin receptor (LR) activation mechanisms are a prerequisite for the rational design of these antagonists. In this review, we focus on the molecular mechanisms underlying leptin receptor activation and signaling. We also discuss the current strategies to interfere with leptin signaling and their therapeutic potential.

Lack of association between leptin G-2548A polymorphisms and obesity risk: Evidence based on a meta-analysis

BACKGROUND

The prevalence of obesity is increasing in most industrialized and developing countries. We aimed to investigate the association between leptin (LEP) G-2548A polymorphisms and the risk of obesity.

METHODS

We searched the PubMed, Web of Science, and China National Knowledge Infrastructure databases for studies that evaluated the association between LEP G-2548A polymorphisms and obesity risk prior to March 2014. The odds ratio (OR) and its 95% confidence interval (95% CI) were calculated to estimate the risk of obesity. Meta-analysis of subgroup populations and different control sources was conducted using homozygote (AA vs. GG), allelic (A vs. G), dominant (AA+GA vs. GG), recessive (AA vs. GG+GA), and heterozygote (AG vs. GG) models. The heterogeneity of the studies was assessed using χ(2)-tests based on Q-statistics. The pooled ORs were calculated using a random-effects model if there was no heterogeneity; otherwise, a random-effects model was used. Two authors extracted the data independently. The funnel plots, Begg's and Egger's test were used to assess publication bias. All statistical analyses were performed using STATA 12.0 software.

RESULTS

Nine case-controlled publications that evaluated the association between LEP G-2548A polymorphisms and obesity risk, which included 2594 subjects (1235 obesity cases and 1359 controls), were included in our meta-analysis. No significant association between this polymorphism and obesity risk was observed (P>0.05). Significant heterogeneity was detected among the studies. The results of subgroup analysis according to ethnicity and different control groups suggested that LEP G-2548A polymorphisms might increase the obesity risk in African populations in the homozygote (AA vs. GG: OR=2.38, 95% CI=1.15-4.93, P=0.020) and recessive (AA vs. GG+GA: OR=2.03, 95% CI=1.34-3.06, P=0.001) models.

CONCLUSIONS

Overall, this meta-analysis indicated that LEP G-2548A polymorphisms are not associated with obesity risk, although significant associations were observed in the homozygote model (AA vs. GG) and the recessive model (AA vs. GG+GA) in Africa populations. Further studies are still needed to validate and confirm this association.

Polymorphism in LEP and LEPR May Modify Leptin Levels and Represent Risk Factors for Thyroid Cancer

Purpose. To understand the role of polymorphisms in the LEP (rs7799039 and rs2167270) and LEPR (rs1137101 and rs1137100) genes in DTC susceptibility and their effect on leptin levels. Methods. We studied 153 patients with DTC and 234 controls through TaqMan SNP Genotyping and ELISA, comparing these data to the clinicopathological data of patients with DTC. Results. Patients with AA genotype of rs7799039 had higher levels of serum leptin (9.22 ± 0.98 ng/mL) than those with AG genotype (10.07 ± 0.60 ng/mL; P = 0.005). Individuals with AG genotype of rs2167270 also produced higher serum leptin levels (10.05 ± 0.59 ng/mL) than the subjects with GG genotype (9.52 ± 0.79 ng/mL; P < 0.05). A multivariate logistic regression adjusted for gender, age, and BMI showed that the AG genotype of rs7799039 was an independent risk for DTC (OR, 11.689; P = 0.0183; 95% CI, 1.516-90.119). Similarly, AG and GG genotypes of rs1137101 increased the susceptibility to DTC (OR, 3.747; P = 0.027; 95% CI, 1.161-12.092 and OR, 5.437; P = 0.013; 95% CI, 1.426-20.729). Conclusions. We demonstrated that rs7799039 and rs2167270 polymorphisms modify the serum leptin concentrations in patients with DTC. Furthermore, polymorphisms rs7799039 and rs1137101 increase the risk of DTC development, although they do not correlate with tumor aggressiveness.

20 years of leptin: insights into signaling assemblies of the leptin receptor

Leptin plays a central role in the control of body weight and energy homeostasis, but is a pleiotropic cytokine with activities on many peripheral cell types. In this review, we discuss the interaction of leptin with its receptor, and focus on the structural and mechanistic aspects of the extracellular aspects of leptin receptor (LR) activation. We provide an extensive overview of all structural information that has been obtained for leptin and its receptor via X-ray crystallography, electron microscopy, small-angle X-ray scattering, homology modeling, and mutagenesis studies. The available knowledge is integrated into putative models toward a recapitulation of the LR activation mechanism.

Association of Gln223 Arg polymorphism of the leptin receptor gene with indicators of energy expenditure in obese children

OBJECTIVE

Gln223 Arg polymorphism of the leptin receptor (LEPR) gene is one of the most frequently examined polymorphisms of this gene and has been suggested to be associated with energy expenditure (EE). The aim of the present study was to investigate the association of this variant on indicators of EE-resting metabolic rate (RMR), postabsorptive and postprandial respiratory quotient (RQ), and food-induced thermogenesis (FIT)-in obese children.

METHODS

The study included 486 genotyped children (obese, n = 355). RMR was measured by indirect calorimetry for 45 min. Subsequent to test-food consumption, FIT was measured in a subsample of obese children (n = 121, body mass index 31.9 kg/m(2) (mean ± SD 5.1).

RESULTS

Obese children with the Gln223 Gln genotype showed a significantly lower post-absorptive and postprandial RQ (P = 0.0055 versus P = 0.0002, adjusted for age, sex, and lean body mass) than did groups of children with Gln223 Arg and Arg223 Arg genotypes. No significant differences were observed in FIT and RMR among the carriers and non-carriers of the 223 Arg allele.

CONCLUSION

The significantly lower post-absorptive and postprandial RQ in the group of Gln223 Gln genotype children indicates that the fat oxidation of these children maybe increased before and subsequent to food consumption, which can be important in the planning of diet of these children.

Advances in understanding the interrelations between leptin resistance and obesity

Obesity, which has developed into a global epidemic, is a risk factor in most chronic diseases and some forms of malignancy. The discovery of leptin in 1994 has opened a new field in obesity research. Currently, we know that leptin is the primary signal from energy stores and exerts negative feedback effects on energy intake. However, most individuals with diet-induced obesity (DIO) develop leptin resistance, which is characterized by elevated circulating leptin levels and decreased leptin sensitivity. To date, though various mechanisms have been proposed to explain leptin resistance, the exact mechanisms of leptin resistance in obesity are poorly understood. Consequently, it's an important issue worth discussing regarding what the exact interrelations between leptin resistance and obesity are. Here, we review the latest advancements in the molecular mechanisms of leptin resistance and the exact interrelations between leptin resistance, obesity, and obesity-related diseases, in order to supply new ideas for the study of obesity.

Measurement of the levels of leptin, BDNF associated with polymorphisms LEP G2548A, LEPR Gln223Arg and BDNF Val66Met in Thai with metabolic syndrome

BACKGROUND

Metabolic syndrome is a cluster of metabolic risk factors including dyslipidemia, impaired glucose tolerance, hypertension and central obesity. BDNF (Brain-derived neurotrophic factor) and leptin have been implied in the energy homeostasis. The purposes of this study were to examine concentrations of leptin, BDNF and biochemical parameters in metabolic-syndrome subjects and healthy controls, and also to search for associations of leptin gene (LEP) G2548A, leptin receptor gene (LEPR) Gln223Arg, and BDNF gene (BDNF) Val66Met polymorphisms with leptin levels, BDNF levels and metabolic syndrome among Thais.

METHODS

The case-controlled design was performed using 322 Thai volunteers (160 metabolic-syndrome subjects; 162 controls) during the health screening program. Metabolic syndrome was assessed by using the modified National Cholesterol Education Program, Adult Treatment Panel III criteria. The levels of leptin, BDNF, insulin, glucose and lipids were measured in samples. Genotyping of LEP G2548A, LEPR Gln223Arg and BDNF Val66Met was carried out using polymerase chain reaction-restriction fragment length polymorphism technique.

RESULTS

Serum leptin levels were significantly higher in the metabolic-syndrome group than the control group (p < 0.01), but the BDNF difference between them was not significant. Significant associations of LEPR Gln223Arg polymorphism were found with leptin and glucose levels (p < 0.05), after adjusting for potential covariates. This LEPR polymorphism in the metabolic-syndrome group was also significantly more frequent than in the control group (p < 0.05). However, other gene polymorphisms, LEP G2548A and BDNF Val66Met, showed no significant relationship with leptin levels, BDNF levels or metabolic syndrome.

CONCLUSION

These findings suggest leptin levels are linked with metabolic syndrome. LEPR Gln223Arg polymorphism impacted leptin concentrations, and this gene polymorphism may influence susceptibility to metabolic syndrome among Thais.

Investigation of associations between obesity and LEP G2548A and LEPR 668A/G polymorphisms in a Turkish population

Objective. Obesity is a complex heterogeneous disease that is caused by genes, environmental factors, and the interaction between the two. The leptin (LEP) and leptin receptor (LEPR) genes have been evaluated for polymorphisms that could potentially be related to the pathophysiology of obesity and its complications. The aim of this study was to investigate the role of LEP G2548A and LEPR 668A/G polymorphisms in the pathogenesis of obesity. Subjects. The study included 127 patients with obesity and 105 healthy controls. Polymerase chain reaction and restriction fragment length analysis for LEP G2548A and LEPR 668A/G polymorphisms were applied. Results. There was no statistically significant difference in the genotype frequencies of the LEP gene polymorphism between patients and control groups (P > 0.05). We found a difference in the LEPR genotypes between patients and controls, but this was not statistically significant (P = 0.05). Additionally, we found an increased risk of obesity in the LEP/LEPR GG/GG combined genotype (P < 0.05). Conclusion. Our findings indicate that the LEP G2548A polymorphism is not a relevant obesity marker and that the LEPR 668A/G polymorphism may be related to obesity in a Turkish population. Further researches with larger patient population are necessary to ascertain the implications of LEP and LEPR polymorphisms in obesity.

Association of leptin receptor gene Q223R polymorphism on lipid profiles in comparison study between obese and non-obese subjects

OBJECTIVES

Leptin is a hormone secreted from adipocytes. It regulates metabolism and energy homeostasis through the leptin receptor (LEPR) which is localized centrally in hypothalamus as well as in peripheral tissues. The aim of this study was to investigate the association of leptin receptor gene Q223R polymorphism on obesity in association with body mass index (BMI), lipid parameters, plasma leptin levels and homeostasis model assessment of insulin resistance (HOMA-IR).

DESIGN AND METHODS

The study included 110 obese and 90 non-obese subjects. The LEPR Q223R polymorphism was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Plasma leptin levels, serum lipid and antropometric parameters were measured.

RESULTS

No association was found between LEPR gene Q223R polymorphism and BMI in both study and control groups. Strikingly study group with non-obese subjects and with the RR genotype (homozygous mutant) had significantly higher serum total cholesterol (p<0.001) and low density lipoprotein cholesterol (LDL-cholesterol) levels (p<0.05) than QR (heterozygous) and QQ (wild type) genotypes. In obese group, subjects with the RR genotypes had significantly higher triglycerides (p<0.05) levels, waist (p<0.05) and hip circumferences (p<0.001) than the QQ and QR genotypes.

CONCLUSIONS

Our results suggest that the LEPR gene Q223R polymorphism has an association with waist and hip circumferences in obese group but no direct association with obesity although there is a significant influence on lipid profile both in obese and non-obese subjects.

Association of annexin A5 polymorphisms with obesity

Annexin A5 (ANXA5), which is known as a protein with anticoagulative function, may play a role in triglyceride biosynthesis. Triglycerides are involved in lipid and energy metabolism, which are important in the elucidation of obesity. To investigate the association between single-nucleotide polymorphisms (SNPs) of ANXA5 and obesity in a Korean population, 372 participants (213 overweight/obese individuals and 159 control subjects) were enrolled from the Kyung Hee University Medical Center and Keimyung University Dongsan Medical Center. The genotypes of five SNPs (rs12510548, rs4240260, rs3756281, rs13136094 and rs6534313) were evaluated in ANXA5 using the multiple logistic regression analysis with the codominant 1, codominant 2, dominant, recessive and log-additive models. The genotype and allele frequencies of the five investigated SNPs exhibited significant differences between the control and the overweight/obese groups: rs12510548 (P=0.004 in the codominant 2 model, P=0.0019 in the recessive model, P=0.027 in the log-additive model and P=0.026 in allele frequencies); rs4240260 (P=0.002 and Fisher's exact P=0.0006 in the codominant 2 model, P=0.0007 and Fisher's exact P=0.0007 in the recessive model, P=0.020 and Fisher's exact P=0.0019 in the log-additive model and P=0.020 in allele frequencies); rs3756281 (P=0.016 in the codominant 2 model and P=0.0094 in the recessive model); rs13136094 (P=0.0030 and Fisher's exact P=0.0011 in the codominant 2 model, P=0.0012 and Fisher's exact P=0.0013 in the recessive model, P=0.034 and Fisher's exact P=0.0035 in the log-additive model and P=0.024 in allele frequencies); and rs6534313 (P=0.0010 and Fisher's exact P=0.0003 in the codominant 2 model, P=0.0003 and Fisher's exact P=0.0003 in the recessive model, P=0.0075 and Fisher's exact P=0.0010 in the log-additive model and P=0.005 in allele frequencies). Two haplotypes were weakly associated with obesity (GGATG, P=0.037 and CAGCC, P=0.020). Results of the present study suggested that ANXA5 may be associated with the development of obesity in a Korean population.

Lack of mutations in the leptin receptor gene in severely obese children

OBJECTIVE

To analyze the LEPR gene in obese children and to investigate the associations between molecular findings and anthropometric and metabolic features.

SUBJECTS AND METHODS

Thirty-two patients were evaluated regarding anthropometric characteristics, blood pressure, heart rate, serum glucose, insulin, leptin levels, and lipid profile. The molecular study consisted of the amplification and automatic sequencing of the coding region of LEPR in order to investigate new mutations.

RESULTS

We identified a high prevalence of metabolic disorders: impaired fasting glucose in 12.5% of the patients, elevated HOMA-IR in 85.7%, low HDL-cholesterol levels in 46.9%, high triglyceride levels in 40.6%, and hypertension in 58.6% of the patients. The molecular study identified 6 already described allelic variants: rs1137100 (exon-2), rs1137101 (exon-4), rs1805134 (exon-7), rs8179183 (exon-12), rs1805096 (exon-18), and the deletion/insertion of the pentanucleotide CTTTA at 3'untranslated region.

CONCLUSIONS

The frequency of alleles observed in this cohort is similar to that described in the literature, and was not correlated with any clinical feature. The molecular findings in the analysis of the LEPR did not seem to be implicated in the etiology of obesity in these patients.

Genetic polymorphisms in adipokine genes and the risk of obesity: a systematic review and meta-analysis

Polymorphisms in adipokine genes, such as leptin (LEP), leptin receptor (LEPR), resistin (RETN), adiponectin (ADIPOQ), interleukin-1β (IL-1β), IL-6 (IL-6), and tumor necrosis factor-α (TNF-α) may be involved in the development of obesity. We conducted a systematic review of published evidence on the association between different adipokine genes and the risk of obesity. Librarian-designed searches of PubMed and HuGeNet, review of reference lists from published reviews and content expert advice identified potentially eligible studies. The genotyping information and polymorphisms of different adipokine genes, numbers of genotyped cases and controls and frequencies of genotypes were extracted from 48 eligible studies included in this review. Twenty-one polymorphisms each associated with obesity in at least one study were identified. Polymorphisms in the adipokine genes, LEP, LEPR, and RETN were not associated with obesity susceptibility, whereas ADIPOQ G276T (T vs. G: odds ratio (OR), 1.59; 95% confidence interval (CI), 1.39-1.81), IL-1β C3953T (CC vs. CT+TT: OR, 1.61; 95% CI, 1.18-2.20), and TNF-α G308A (GG vs. GA+AA: OR, 1.19; 95% CI, 1.02-1.39) polymorphisms were associated with an increased risk of obesity. The IL-6 G174C polymorphism was also associated obesity when using allelic comparisons, the recessive genetic model and the dominant genetic model with OR (95% CI) of 1.95 (1.37-2.77), 1.44 (1.15-1.80), and 1.36 (1.16-1.59), respectively. No significant evidence of publication bias was present. However, these "null" results were underpowered due to a small pooled sample size, and analysis of additional case-control studies with larger sample sizes should provide further clarifications.

The G3057A LEPR polymorphism is associated with obesity in Tunisian women

OBJECTIVES

The aim of this study was to evaluate the effect of the G3057A (rs62589000) LEPR polymorphism on obesity risk and plasma leptin, insulin, and lipid levels in a sample of the Tunisian population.

DESIGN AND METHODS

Three hundred and ninety-three obese patients and 317 controls participated in this study. The G3057A genotype was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

In the entire study sample, no significant differences in genotype frequencies were observed between obese patients and controls. However, stratified analysis by gender revealed a quantitative increase in the variant allele (33.3% vs. 25.8%; χ(2)=4.90, p=0.026) in obese women (but not men) compared to controls. When a dominant model of inheritance was assumed, the GA+AA genotypes were more prevalent in these obese female patients than in controls (58.3% vs. 47.8%; χ(2)=4.08, p=0.044). Unconditional logistic regression showed that in women only, obesity risk was significantly higher for homozygotes for the variant allele (OR=2.73, 95% CI 1.03-7.21) and for carriers of GA+AA genotypes (OR=1.53, 95% CI 1.01-2.31) compared with homozygotes for the normal allele. The association between the G3057A LEPR variant and obesity remained statistically significant even after adjustment for age. No relationship was found between the G3057A LEPR polymorphism and leptin and insulin levels. Additionally, this LEPR gene variant had no effect on plasma lipid concentrations.

CONCLUSION

There is evidence in this study that the G3057A LEPR polymorphism is associated with obesity in Tunisian women.

Genetics talks to epigenetics? The interplay between sequence variants and chromatin structure

Transcription is regulated by two major mechanisms. On the one hand, changes in DNA sequence are responsible for genetic gene regulation. On the other hand, chromatin structure regulates gene activity at the epigenetic level. Given the fundamental participation of these mechanisms in transcriptional regulation of virtually any gene, they are likely to co-regulate a significant proportion of the genome. The simple concept behind this idea is that a mutation may have a significant impact on local chromatin structure by modifying DNA methylation patterns or histone type recruitment. Yet, the relevance of these interactions is poorly understood. Elucidating how genetic and epigenetic mechanisms co-participate in regulating transcription may assist in some of the unresolved cases of genetic variant-phenotype association. One example is loci that have biologically predictable functions but genotypes that fail to correlate with phenotype, particularly disease outcome. Conversely, a crosstalk between genetics and epigenetics may provide a mechanistic explanation for cases in which a convincing association between phenotype and a genetic variant has been established, but the latter does not lie in a promoter or protein coding sequence. Here, we review recently published data in the field and discuss their implications for genetic variant-phenotype association studies.

Variations in Adipokine Genes AdipoQ, Lep, and LepR are Associated with Risk for Obesity-Related Metabolic Disease: The Modulatory Role of Gene-Nutrient Interactions

Obesity rates are rapidly increasing worldwide and facilitate the development of many related disease states, such as cardiovascular disease, the metabolic syndrome, type 2 diabetes mellitus, and various types of cancer. Variation in metabolically important genes can have a great impact on a population's susceptibility to becoming obese and/or developing related complications. The adipokines adiponectin and leptin, as well as the leptin receptor, are major players in the regulation of body energy homeostasis and fat storage. This paper summarizes the findings of single nucleotide polymorphisms in these three genes and their effect on obesity and metabolic disease risk. Additionally, studies of gene-nutrient interactions involving adiponectin, leptin, and the leptin receptor are highlighted to emphasize the critical role of diet in susceptible populations.

Genetic variation in the hypothalamic pathways and its role on obesity

Over recent decades, the prevalence of obesity has increased dramatically worldwide. Although this epidemic is mainly attributable to modern (western) lifestyle, multiple twin and adoption studies indicate the significant role of genes in the individual's predisposition to becoming obese. As the hypothalamus plays a central role in controlling body weight, its regulatory circuits may represent a crucial system in the pathogenesis of the disorder. Genetic variations in genes in the hypothalamic pathways may therefore contribute to the susceptibility for obesity in humans and animals. We summarize current knowledge on the physiological role of the hypothalamus in body-weight regulation and review genetic studies on the hypothalamic candidate genes in relation to obesity. Together, data from functional and genetic studies as well as the new, common, obesity loci identified in genome-wide association scans support an important role for the hypothalamic genes in predisposing to obesity. However, findings are still inconclusive for many candidate genes. To improve our understanding of the genetic architecture of common obesity, we suggest that specific obesity phenotypes should be considered and different analytical approaches used. Such studies should consider multiple genes from the same physiological pathways, together with environmental risk factors.

Not all obese subjects of multiethnic origin are at similar risk for developing hypertension and type 2 diabetes

BACKGROUND

Whether insulin resistance and not obesity per se is the major contributor to clinical outcomes associated with obesity has not been fully established. This study evaluated in a group of obese Brazilians of multiethnic origin to what extent the prevalence of hypertension and other cardiometabolic risk factors varies as a function of the degree of insulin sensitivity.

METHODS

The study involved 118 individuals (mean age of 44+/-12 years; BMI=38.6+/-7.9 kg/m(2)) without evidence of diabetes or cardiovascular disease. Insulin resistance was assessed by HOMA-IR index, which was used to stratify patients into tertiles.

RESULTS

The mean HOMA-IR in tertile 1, the most insulin-sensitive group, was 2.7+/-0.8 and in tertile 3, the most insulin-resistant group, 9.1+/-2.4 (P<0.001). Mean arterial pressure showed a linear and significant variation across the HOMA-IR tertiles 1, 2, and 3 (94.3+/-11.7; 98.7+/-11.4; 105.0+/-12.4 mm Hg), as did fasting plasma glucose (93.6+/-12.1; 98.1+/-12.7; 100.0+/-11.0 mg/dL), uric acid (4.7+/-1.4; 5.9+/-1.9; 6.3+/-1.4 mg/dL), HDL-cholesterol (48.1+/-11.6; 46.5+/-10.5; 42.2+/-8.0 mg/dL), and plasma adiponectin (7.8+/-3.3; 7.0+/-2.8; 6.3+/-6.5 microg/mL), respectively. The results indicated that 27.5% of our patients had dysglicemia, 28.2% had hypertriglyceridemia, and 30.7% had arterial hypertension in the most insulin-sensitive tertile, when compared with 51%, 53.8% and 79.4%, respectively, in the most insulin-resistant tertile. A stepwise regression analysis showed that only HOMA-IR and age independently affected the risk for increased systolic blood pressure.

CONCLUSION

In conclusion, our findings have shown that the risk of developing essential hypertension, type 2 diabetes, and cardiovascular disease is accentuated in obese individuals who are also more insulin resistant.

LEPR p.Q223R Polymorphism influences plasma leptin levels and body mass index in Tunisian obese patients

BACKGROUND AND AIMS

The leptin receptor (LEPR) plays a crucial role in the regulation of body weight. Several common polymorphisms have been described in the human LEPR gene including the p.Q223R polymorphism (rs1137101). The association of this polymorphism with obesity or related metabolic phenotypes has been controversial. The aim of this study was to investigate the impact of the LEPR p.Q223R polymorphism on body mass index (BMI), plasma leptin and lipid parameters in a sample of the Tunisian population.

METHODS

The study included 391 obese patients and 302 normal weight subjects. LEPR p.Q223R genotypes were identified by the PCR-RFLP analysis.

RESULTS

Obese patients homozygous for RR genotype showed lower leptin levels than those with other genotypes (p = 0.005) adjusted for age, BMI and gender. Stratified analysis by gender revealed that obese male patients carrying the R allele showed significantly lower BMI (p = 0.007) and leptin levels (p = 0.037) than subjects homozygous for the Q allele. In obese women, the LEPR p.Q223R polymorphism was found associated with lower leptin concentrations (p = 0.05). After adjustment for age and BMI, the association between the LEPR variant and plasma leptin remained significant only within female patients (p = 0.027). A general linear model including leptin as dependant variable and age, BMI, menopausal status and genotype as covariates revealed that the LEPR p.Q223R polymorphism is independently associated with leptin levels in obese women (p = 0.026).

CONCLUSIONS

Our findings suggest that the LEPR p.Q223R polymorphism influences plasma leptin levels and BMI in obese patients.

Common SNPs in LEP and LEPR associated with birth weight and type 2 diabetes-related metabolic risk factors in twins

OBJECTIVE

Children born small for gestational age are at increased risk of developing type 2 diabetes in adulthood. The satiety signal leptin that regulates food intake and energy expenditure might be a possible molecular link, as umbilical cord leptin levels are positively correlated with birth weight. In the present study, we examined whether common single nucleotide polymorphisms (SNPs) in the leptin (LEP; 19G>A) gene and its receptor (LEPR; Q223R and K109R) are associated with birth weight and adult metabolic risk factors for type 2 diabetes in twins.

DESIGN

SNPs were genotyped in 396 monozygotic and 232 dizygotic twins (286 men and 342 women, mean age 25 years) recruited from the East Flanders Prospective Twin Survey. Data were analysed using linear mixed models.

RESULTS

The LEPR K109R SNP was associated with birth weight (KK, KR and RR (95% confidence interval, CI): 2511 (2465-2557), 2575 (2516-2635) and 2726 (2606-2845) gram; P(additive)=0.001). Also the LEPR Q223R SNP showed a significant association with weight at birth (QQ, QR and RR (95% CI): 2492 (2431-2554), 2545 (2495-2595) and 2655 (2571-2740) gram; P(additive)=0.003). Furthermore, an interaction between the LEPR K109R and the Q223R SNP on birth weight was observed (P=0.014). G allele carriers of the LEP 19G>A SNP had higher high-density lipoprotein (HDL) cholesterol levels compared to 19A homozygotes (GX vs AA (95% CI): 1.62 (1.58-1.66) vs 1.49 (1.40-1.58) mmol l(-1); P(recessive)=0.013).

CONCLUSIONS

This study indicates that leptin may act as a growth-promoting signal during fetal development, and suggests a possible role for the LEPR in explaining the inverse relationship between birth weight and the development of metabolic diseases in adulthood. Additionally, these results suggest that the LEP 19G>A SNP affect HDL cholesterol levels.

Genome-wide scan revealed genetic loci for energy metabolism in Hispanic children and adolescents

OBJECTIVE

Genome-wide scans were conducted in search for genetic locations linked to energy expenditure and substrate oxidation in children.

DESIGN

Pedigreed data of 1030 Hispanic children and adolescents were from the Viva La Familia Study which was designed to investigate genetic and environmental risk factors for the development of obesity in Hispanic families. A respiratory calorimeter was used to measure 24-h total energy expenditure (TEE), basal metabolic rate (BMR), sleep metabolic rate (SMR), 24-h respiratory quotient (24RQ), basal metabolic respiratory quotient (BMRQ) and sleep respiratory quotient (SRQ). Protein, fat and carbohydrate oxidation (PROOX, FATOX and CHOOX, respectively) were also estimated. All participants were genotyped for 384 single tandem repeat markers spaced an average of 10 cM apart. Computer program SOLAR was used to perform the genetic linkage analyses.

RESULTS

Significant linkage for TEE was detected on chromosome 1 near marker D1S2841, with a logarithm of the odds (LOD) score of 4.0. SMR, BMRQ and PROOX were associated with loci on chromosome 18, 17 and 9, respectively, with LOD scores of 4.88, 3.17 and 4.55, respectively. A genome-wide scan of SMR per kg fat-free mass (SpFFM) peaked in the same region as SMR on chromosome 18 (LOD, 5.24). Suggestive linkage was observed for CHOOX and FATOX. Several candidate genes were found in the above chromosomal regions including leptin receptor (LEPR).

CONCLUSION

Regions on chromosomes 1, 9, 17 and 18 harbor genes affecting variation in energy expenditure and substrate oxidation in Hispanic children and adolescents.

The common genetic variant upstream of INSIG2 gene is not associated with obesity in Indian population

The high incidence of obesity has resulted in increased morbidity and mortality worldwide. Obesity, a common lifestyle disorder, is caused by multiple factors with heredity playing a strong causal role. Recently, a genetic variation upstream of insulin-induced gene 2 (INSIG2) (rs7566605) has been reported to be associated with obesity in four separate cohorts. Because the lifestyle and food preferences of a large proportion of Indian population differ from the rest of the world, we studied the impact of this polymorphism with body mass index (BMI). The study consisted of two cohorts--1577 healthy individuals from three major linguistic lineages in India and 610 coronary artery disease cases and controls. In the two cohorts studied, no significant association was observed between the polymorphism and BMI. However, frequency of homozygous variant genotype was higher in non-obese individuals as compared with obese individuals in both cohorts although the difference was marginally significant only in the case-control cohort under the assumption of a recessive model. Furthermore, regardless of age and sex, mean BMI did not vary with genotype under the assumptions of recessive model. Thus, in contrast to earlier reports, the variant upstream of INSIG2 is not a determinant of BMI in Indian population.

Population variation and differences in serum leptin independent of adiposity: a comparison of Ache Amerindian men of Paraguay and lean American male distance runners

Background

Serum leptin variation is commonly associated with fat percentage (%), body mass index (BMI), and activity. In this investigation, we report population differences in mean leptin levels in healthy men as well as associations with fat % and BMI that are independent of these factors and reflect likely variation resulting from chronic environmental conditions.

Methods

Serum leptin levels, fat %, and BMI were compared between lean American distance runners and healthy Ache Native Americans of Paraguay. Mean levels were compared as were the regressions between fat %, BMI, and leptin. Comparisons were performed between male American distance runners (n = 13, mean age 32.2 ± 9.2 SD) and highly active male New World indigenous population (Ache of Paraguay, n = 20, mean age 32.8 ± 9.2) in order to determine whether significant population variation in leptin is evident in physically active populations living under different ecological circumstances independent of adiposity and BMI.

Results

While the Ache were hypothesized to exhibit higher leptin due to significantly greater adiposity (fat %, Ache 17.9 ± 1.8 SD; runners 9.7 ± 3.2, p < 0.0001), leptin levels were nonetheless significantly higher in American runners (Ache 1.13 ng/ml ± 0.38 SD; runners 2.19 ± 1.15; p < 0.007). Significant differences in the association between leptin and fat % was also evident between Ache and runner men. Although fat % was significantly related with leptin in runners (r = 0.90, p < 0.0001) fat % was negatively related in Ache men (r = -0.50, p < 0.03).

Conclusion

These results illustrate that chronic ecological conditions in addition to activity are likely factors that contribute to population variation in leptin levels and physiology. Population variation independent of adiposity should be considered to be an important source of variation, especially in light of ethnic and population differences in the incidence and etiology of obesity, diabetes, and other metabolic conditions.