Association between the Gln223Arg polymorphism of the leptin receptor and metabolic syndrome in free-living community elderly

Association of the Human Leptin Receptor Gene (rs1137101; Gln223Arg) Polymorphism and Circulating Leptin in Patients with Metabolic Syndrome in the Indian Population

Phenotypic expression of metabolic syndrome is precipitated by environmental variables along with the individual genetic susceptibility to the obesogenic environment and growing body of evidence suggest a paramount role of adipocytokines. Therefore, identifying the genetic influence on circulation leptin levels and clarifying genotype-phenotype correlation of rs1137101 {Leptin receptor gene (LEPR) Gln223Arg (Q223R; A668G)} in metabolic syndrome were the primary objective of this study. A total of 447 adult participants, including 214 metabolic syndrome patients and 233 healthy controls, were genotyped using polymerase chain reaction-restriction fragment length polymorphism method to unravel the effects of genetic risk loci {Leptin receptor gene; Gln223Arg (Q223R; A668G); rs1137101} on the occurrence of metabolic syndrome in consort with circulation leptin levels. Suitable descriptive statistics was used for different variables. The genotype frequencies were found to be in Hardy-Weinberg equilibrium for both cases (p > 0.2722) as well as in controls (p > 0.2331). However, genotype (x2: 11.26, 2 d.f. p = 0.0036) and allele distribution (x2: 10.51, 2 d.f. p: 0.0012) of the LEPR Gln223Arg (Q223R; A668G) differed significantly between cases and controls. Gln/Arg genotype (OR = 1.6099; 95% CI = 1.0847-2.3893; p value = 0.0181), Arg/Arg genotype (OR = 2.8121; 95% CI = 1.4103-5.6074; p value = 0.0033) and R allele (OR = 1.5875; 95% CI = 1.1996-2.1008; p value = 0.0012) were significantly associated with increased risk of metabolic syndrome in univariate analysis. Further a multivariate logistic regression adjusted for potential confounders showed that Arg/Arg genotype (OR = 1.9; 95% CI = 1.271-2.639; p-value < 0.05) and Gln/Arg (OR: 1.3; 95% CI = 0.873-2.034; p value < 0.05) have a significant risk for the occurrence of the metabolic syndrome. A progressive increase in the serum leptin levels from major homozygous alleles to minor homozygous alleles were observed indicating that rs1137101 modify the serum leptin concentrations in patients with metabolic syndrome. These findings provide enough evidence of a significant association of LEPR Gln223Arg (Q223R; A668G) polymorphism in the LepR gene in Indian patients with increased risk of metabolic syndrome for R allele and Arg/Arg homozygote. Thus, rs1137101 might be a pleiotropic locus for metabolic syndrome and its components in studied population.

Influence of K656N Polymorphism of the Leptin Receptor Gene on Obesity-Related Traits in Nondiabetic Afro-Caribbean Individuals

Background: Ethnic variations have been reported in allelic frequencies of the leptin receptor gene (LEPR) with population-specific effects. We aimed to explore the association of LEPR polymorphisms with obesity, metabolic syndrome (MetS), and leptin levels in Afro-Caribbean nondiabetic subjects. Methods: Genotypic analysis of three LEPR polymorphisms (K109R, Q223R, and K656N) was performed using TaqMan allelic discrimination assays. Associations were measured with phenotypic variables, including body mass index (BMI), waist circumference (WC), and leptin levels. Linear and logistic regressions were performed to evaluate the effects of single-nucleotide polymorphisms (SNPs). Results: Mean age was 46 ± 12 years. Among the 375 participants, 29.3% were obese, 36.3% had abdominal obesity, and 18.1% had MetS. Significant association between BMI (P < 0.002) and WC (P < 0.005) was observed for K656N, whereas the associations were not statistically significant for the other two SNPs. No association was found with leptin levels for the three SNPs. The variant allele frequencies for LEPR 109R, 223R, and 656N were 0.16, 0.46, and 0.20, respectively. In dominant models, the variant allele 656N (GC/CC vs. GG) was associated with prevalence of obesity [odds ratio (OR) 1.82; P = 0.012] and abdominal obesity (OR 2.00; P = 0.007), but not significantly with prevalence of MetS (OR 1.72; P = 0.029). Individuals carrying four variant alleles of the three SNPs had a significantly higher risk of obesity (OR 2.86; P = 0.032) than those carrying none variant allele. Conclusion: Our results suggest an influence of K656N polymorphism in the LEPR gene on obesity and abdominal obesity in this Afro-Caribbean population.

A systematic review of genetic variants associated with metabolic syndrome in patients with schizophrenia

Metabolic syndrome (MetS) is a cluster of factors that increases the risk of cardiovascular disease (CVD), one of the leading causes of mortality in patients with schizophrenia. Incidence rates of MetS are significantly higher in patients with schizophrenia compared to the general population. Several factors contribute to this high comorbidity. This systematic review focuses on genetic factors and interrogates data from association studies of genes implicated in the development of MetS in patients with schizophrenia. We aimed to identify variants that potentially contribute to the high comorbidity between these disorders. PubMed, Web of Science and Scopus databases were accessed and a systematic review of published studies was conducted. Several genes showed strong evidence for an association with MetS in patients with schizophrenia, including the fat mass and obesity associated gene (FTO), leptin and leptin receptor genes (LEP, LEPR), methylenetetrahydrofolate reductase (MTHFR) gene and the serotonin receptor 2C gene (HTR2C). Genetic association studies in complex disorders are convoluted by the multifactorial nature of these disorders, further complicating investigations of comorbidity. Recommendations for future studies include assessment of larger samples, inclusion of healthy controls, longitudinal rather than cross-sectional study designs, detailed capturing of data on confounding variables for both disorders and verification of significant findings in other populations. In future, big genomic datasets may allow for the calculation of polygenic risk scores in risk prediction of MetS in patients with schizophrenia. This could ultimately facilitate early, precise, and patient-specific pharmacological and non-pharmacological interventions to minimise CVD associated morbidity and mortality.

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.

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.

Association of four insulin resistance genes with type 2 diabetes mellitus and hypertension in the Chinese Han population

Insulin resistance plays an important role in the development of type 2 diabetes mellitus (T2DM) and hypertension. The purpose of the present study was to evaluate the association between four insulin resistance genes (ADIPOQ, LEPR, RETN, and TRIB3) and both T2DM and hypertension. A total of 768 Han Chinese subjects were recruited into this study, including 188 cases who had T2DM alone, 223 cases who had hypertension alone, 181 cases with both T2DM and hypertension, and 176 control subjects with neither T2DM nor hypertension. Twenty-three tag SNPs in four insulin resistance genes were genotyped and analyzed for association with T2DM and hypertension. One intron SNP (rs13306519) in LEPR and one 3′UTR SNP (rs1063537) in ADIPOQ demonstrated a significant association with T2DM (P = 0.024 and 0.014 respectively). Another intron SNP (rs12037879) in LEPR and a promoter region SNP (rs266729) in ADIPOQ were significantly associated with hypertension (P = 0.041 and 0.042, respectively). These associations survived the permutation test (P = 0.023, 0.018, 0.026, and 0.035, respectively). These associations were still found to be significant in the additive model after adjusting for potential confounding factors including age, sex, BMI, HDL, LDL, total cholesterol, and triglyceride levels (P = 0.024, 0.016, 0.04, and 0.043, respectively). No other gene variants were found to be significantly associated with T2DM or hypertension (P > 0.05). None of the studied gene variants were found to be significantly associated with T2DM+ hypertension (P > 0.05). A significant interaction was observed between two SNPs rs13306519 in LEPR and rs266729 in ADIPOQ for T2DM (P_int = 0.012, OR_int = 2.67) and hypertension (P_int = 0.0041, OR_int = 2.23). These findings suggest that variants in ADIPOQ and LEPR are risk factors for T2DM and hypertension in the Chinese population and that variants in RETN and TRIB3 are not major risk factors for these diseases.

Association of leptin receptor gene polymorphisms and essential hypertension in a Chinese population

BACKGROUND

The leptin receptor (LEPR) is an important regulator of leptin activity and resistance. Several single nucleotide polymorphisms (SNP) of LEPR have been linked to diseases accompanying obesity and/or obesity-related diseases in different populations. However, the results from published studies remain inconsistent rather than conclusive.

AIM

To investigate whether LEPR SNP are associated with essential hypertension and related metabolic traits in Chinese subjects.

MATERIALS AND METHODS

A total of 544 Chinese patients with hypertension and 357 non-hypertensive subjects were screened. The genotypes of LEPR polymorphisms were determined by PCR-restriction fragment length polymorphism methods. Demographic and biochemical characteristics including waist circumference, waist-to-hip ratio, body mass index (BMI), lipids profiles, glucose metabolism, and leptin levels were obtained for analysis.

RESULTS

This case-control study showed associations between the frequencies of AA genotype and A allele of Gln223Arg and hypertension (p=0.029, p=0.002, respectively). Furthermore, the Gln223Arg polymorphism was significantly associated with plasma leptin levels (p<0.001), while no correlations between Lys109Arg SNP and hypertension were found. Multivariate logistic regression analysis evidenced that A allele carriers of Gln223Arg (AA+AG) showed higher risks of hypertension than GG carriers after adjustment of age and sex (adjusted odds ratio: 1.549, 95% confidence interval: 1.031- 2.036, p=0.035). BMI, fasting serum insulin, oral glucose tolernace test (OGTT)-2h glucose, serum leptin, as well as LDL-cholesterol (LDL-C) levels were also independent risk factors of hypertension in this population. In addition, significant associations were observed between the Gln223Arg and Lys109Arg SNP and serum total cholesterol, LDL-C, and fasting plasma glucose levels in hypertensive patients. Besides, A allele of Gln223Arg had raised diastolic blood pressure, compared with GG carriers (p=0.001). While variance of Lys109Arg was associated with waist-to-hip ratio, OGTT-2h glucose, and homeostasis model assessment of insulin resistance (p<0.05).

CONCLUSIONS

LEPR polymorphisms may be a marker for susceptibility to essential hypertension in Chinese subjects, and be involved in the development of several features including dyslipidemia and impaired glucose regulation in hypertension subjects.

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.

Polymorphisms of INSIG2, MC4R, and LEP are associated with obesity- and metabolic-related traits in schizophrenic patients

BACKGROUND

Schizophrenic patients have a high prevalence of metabolic adversities. Previous studies have suggested some candidate genes for obesity- and metabolic-related traits, including the insulin-induced gene (INSIG2), melanocortin 4 receptor gene (MC4R), and leptin and leptin receptor genes (LEP and LEPR). We aimed to investigate the associations between these genes and metabolic disturbances in patients with schizophrenia in Taiwan.

METHODS

Patients with a diagnosis of schizophrenia or schizoaffective disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, were recruited from 36 community psychiatric rehabilitation centers or hospitals in Taipei. A total of 650 subjects were enrolled, and 577 were included in the genetic analyses. The anthropometric (body mass index, waist circumference [WC], and blood pressure) and biochemical measurements (fasting plasma glucose, insulin, triglyceride, high-density lipoprotein cholesterol, and Homeostasis Model of Assessment - Insulin Resistance index [HOMA-IR]) were assessed. Seven loci in the 4 genes were genotyped using standard TaqMan assays. Genetic association analyses were conducted for binary and quantitative measurements of the previously mentioned traits. Obese patients with schizophrenia exhibited more metabolic disturbances than nonobese patients.

RESULTS AND CONCLUSIONS

Our data showed that INSIG2 was significantly associated with fasting plasma glucose (for rs17587100, P < 0.0001), MC4R was associated with WC (for rs2229616, P = 0.005), and LEP was associated with body mass index and WC (for rs7799039, P < 0.01). In addition, these loci showed suggestive associations with traits including high-density lipoprotein cholesterol and triglyceride, metabolic syndrome, insulin level, and HOMA-IR index (P = 0.05). In addition to the effect from antipsychotic medications and an unhealthy lifestyle, genetic factors also contribute to the high prevalence of obesity and metabolic disturbances in patients with schizophrenia, especially genes involved in metabolic-related pathways.

Genetic variants and the metabolic syndrome: a systematic review

Several candidate gene studies on the metabolic syndrome (MetS) have been conducted. However, for most single nucleotide polymorphisms (SNPs) no systematic review on their association with MetS exists. A systematic electronic literature search was conducted until the 2nd of June 2010, using HuGE Navigator. English language articles were selected. Only genes of which at least one SNP-MetS association was studied in an accumulative total population ≥ 4000 subjects were included. Meta-analyses were conducted on SNPs with three or more studies available in a generally healthy population. In total 88 studies on 25 genes were reviewed. Additionally, for nine SNPs in seven genes (GNB3, PPARG, TCF7L2, APOA5, APOC3, APOE, CETP) a meta-analysis was conducted. The minor allele of rs9939609 (FTO), rs7903146 (TCF7L2), C56G (APOA5), T1131C (APOA5), C482T (APOC3), C455T (APOC3) and 174G>C (IL6) were more prevalent in subjects with MetS, whereas the minor allele of Taq-1B (CETP) was less prevalent in subjects with the MetS. After having systematically reviewed the most studied SNP-MetS associations, we found evidence for an association with the MetS for eight SNPs, mostly located in genes involved in lipid metabolism.

Envelhecimento e longevidade no Rio Grande do Sul: um perfil histórico, étnico e de morbi-mortalidade dos idosos

O Estado Rio Grande do Sul apresenta uma grande diversidade étnica e cultural na sua população. Entretanto, pouco se sabe sobre o perfil genético desta população em relação às doenças crônicas não-transmissíveis (DCNT) e o do padrão de herança de acordo com a origem étnica. Fatores como etnia e composição genética, em conjunto com a Reforma Sanitária brasileira e com o estilo de vida, têm possivelmente contribuído de forma substancial para o aumento da expectativa média de vida ao nascer e da longevidade dos gaúchos. A população do Rio Grande do Sul tem apresentado um acelerado processo de envelhecimento populacional e com um padrão diferenciado de morbi-mortalidade para as faixas etárias acima de 60 anos. O aumento da longevidade da população trouxe consigo um aumento não somente da incidência e prevalência, mas também da mortalidade por DCNT, tais como doenças cardiovasculares e neoplasias. Por isso, as políticas públicas de saúde precisam contemplar as peculiaridades étnicas, culturais e biológicas para que a população possa envelhecer com qualidade de vida. É dentro desse contexto que o presente artigo pretende contribuir na discussão do processo de envelhecimento populacional do Rio Grande do Sul.

Associations among metabolic syndrome, ischemia, inflammatory, oxidatives, and lipids biomarkers

CONTEXT

Metabolic syndrome (MS) is described as a cluster of cardiometabolic risk factors. Studies suggest that ischemia-modified albumin (IMA) is a biomarker of cardiovascular diseases. IMA levels could be associated with cardiometabolic risks and represent a possible indication of microvascular dysfunction in MS patients.

OBJECTIVE

To confirm this possible association, we evaluated the association between IMA levels and MS.

DESIGN

We performed a case-control study (32 healthy individuals and 74 subjects with MS) to evaluate the association between MS, IMA, and other biomarkers [high-sensitivity C-reactive protein (hs-CRP), oxidized low-density lipoprotein (OxLDL), oxidized low-density lipoprotein autoantibodies (anti-OxLDL), IL-6, lipid profile, and glucose].

RESULTS

The MS group showed higher levels of IMA (0.618 +/- 0.1355) as well as higher levels of hs-CRP, OxLDL, anti-OxLDL, and IL-6 than did control subjects (IMA = 0.338 +/- 0.0486) (P < 0.01). Multivariate analysis showed that IMA and MS association was independent of sex, age, diabetes mellitus 2, and hypercholesterolemia.

CONCLUSION

We found an association between IMA and MS. Additional studies including prospective genetic variation approaches need to be performed to help elucidate this association between IMA and MS and its potential clinical role.

Leptin receptor polymorphisms interact with polyunsaturated fatty acids to augment risk of insulin resistance and metabolic syndrome in adults

The leptin receptor (LEPR) is associated with insulin resistance, a key feature of metabolic syndrome (MetS). Gene-fatty acid interactions may affect MetS risk. The objective was to investigate the relationship among LEPR polymorphisms, insulin resistance, and MetS risk and whether plasma fatty acids, a biomarker of dietary fatty acids, modulate this. LEPR polymorphisms (rs10493380, rs1137100, rs1137101, rs12067936, rs1805096, rs2025805, rs3790419, rs3790433, rs6673324, and rs8179183), biochemical measurements, and plasma fatty acid profiles were determined in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754). LEPR rs3790433 GG homozygotes had increased MetS risk compared with the minor A allele carriers [odds ratio (OR) = 1.65; 95% CI: 1.05-2.57; P = 0.028], which may be accounted for by their increased risk of elevated insulin concentrations (OR 2.40; 95% CI: 1.28-4.50; P = 0.006) and insulin resistance (OR = 2.15; 95% CI: 1.18-3.90; P = 0.012). Low (less than median) plasma (n-3) and high (n-6) PUFA status exacerbated the genetic risk conferred by GG homozygosity to hyperinsulinemia (OR 2.92-2.94) and insulin resistance (OR 3.40-3.47). Interestingly, these associations were abolished against a high (n-3) or low (n-6) PUFA background. Importantly, we replicated some of these findings in an independent cohort. Homozygosity for the LEPR rs3790433 G allele was associated with insulin resistance, which may predispose to increased MetS risk. Novel gene-nutrient interactions between LEPR rs3790433 and PUFA suggest that these genetic influences were more evident in individuals with low plasma (n-3) or high plasma (n-6) PUFA.