Genetic variations in the leptin and leptin receptor genes are associated with type 2 diabetes mellitus and metabolic traits in the Korean female population

The milk study protocol: A longitudinal, prospective cohort study of the relationship between human milk metabolic hormone concentration, maternal body composition, and early growth and satiety development in Samoan infants aged 1-4 months

BACKGROUND

Current research suggests that energy transfer through human milk influences infant nutritional development and initiates metabolic programming, influencing eating patterns into adulthood. To date, this research has predominantly been conducted among women in high income settings and/or among undernourished women. We will investigate the relationship between maternal body composition, metabolic hormones in human milk, and infant satiety to explore mechanisms of developmental satiety programming and implications for early infant growth and body composition in Samoans; a population at high risk and prevalence for overweight and obesity. Our aims are (1) to examine how maternal body composition influences metabolic hormone transfer from mother to infant through human milk, and (2) to examine the influences of maternal metabolic hormone transfer and infant feeding patterns on early infant growth and satiety.

METHODS

We will examine temporal changes in hormone transfers to infants through human milk in a prospective longitudinal cohort of n = 80 Samoan mother-infant dyads. Data will be collected at three time points (1, 3, & 4 months postpartum). At each study visit we will collect human milk and fingerpick blood samples from breastfeeding mother-infant dyads to measure the hormones leptin, ghrelin, and adiponectin. Additionally, we will obtain body composition measurements from the dyad, observe breastfeeding behavior, conduct semi-structured interviews, and use questionnaires to document infant hunger and feeding cues and satiety responsiveness. Descriptive statistics, univariate and multivariate analyses will be conducted to address each aim.

DISCUSSION

This research is designed to advance our understanding of variation in the developmental programming of satiety and implications for early infant growth and body composition. The use of a prospective longitudinal cohort alongside data collection that utilizes a mixed methods approach will allow us to capture a more accurate representation on both biological and cultural variables at play in a population at high risk of overweight and obesity.

-2548G>A LEP Polymorphism Is Positively Associated with Increased Leptin and Glucose Levels in Obese Saudi Patients Irrespective of Blood Pressure Status

Background and Objectives: In this study, we aimed to investigate the link between common -2548G>A (rs7799039) promoter variant of the human leptin gene (LEP) with leptin and serum glucose leptin levels in obese Saudi patients. Materials and Methods: A total of 206 Saudi adults (80 obese normotensive nondiabetics, 76 obese hypertensive with Type 2 Diabetes and 50 normotensive nondiabetic controls) were genotyped for -2548G>A LEP polymorphism using the polymerase chain reaction-restriction fragment-length polymorphism technique. Results: Participants with minor AA genotype had significantly higher blood glucose levels (6.8 ± 0.55 mmol/L vs. 5.8 ± 0.30 mmol/L; p < 0.04) and HOMA-IR (4.1 ± 0.84 vs. 2.6 ± 0.67; p = 0.03) against those carrying major GG genotype. Participants with heterozygous GA genotype had significantly higher serum leptin levels against those carrying major GG genotype (40.0 ± 2.6 ng/mL vs. 29.6 ± 2.6 ng/mL; p = 0.04). Further investigation showed that individuals with AA, GA, GA + AA genotypes are at greater risk of developing hyperglycemia compared to those with GG genotype [OR 3.7(1.6–8.4), p = 0.001; 3.2 (1.2–8.6), p = 0.03; 3.5 (1.6–7.7), p = 0.001, respectively]. Additionally, the -2548AA allele was shown to be a risk factor for hyperglycemia [OR 1.9 (1.2–3.0), p = 0.006]. Our data revealed no relationship between this variant of the LEP gene with systolic and diastolic BP, signifying that this genetic variant is not a significant marker of obesity and hypertension in the Saudi population. Conclusions: AA and GA genotypes and LEP gene -2548AA alleles may signify potent risk factors predisposing healthy individuals to develop T2DM regardless of blood-pressure profile.

-2548G>A LEP Polymorphism Is Positively Associated with Increased Leptin and Glucose Levels in Obese Saudi Patients Irrespective of Blood Pressure Status

Background and Objectives: In this study, we aimed to investigate the link between common -2548G>A (rs7799039) promoter variant of the human leptin gene (LEP) with leptin and serum glucose leptin levels in obese Saudi patients. Materials and Methods: A total of 206 Saudi adults (80 obese normotensive nondiabetics, 76 obese hypertensive with Type 2 Diabetes and 50 normotensive nondiabetic controls) were genotyped for -2548G>A LEP polymorphism using the polymerase chain reaction-restriction fragment-length polymorphism technique. Results: Participants with minor AA genotype had significantly higher blood glucose levels (6.8 ± 0.55 mmol/L vs. 5.8 ± 0.30 mmol/L; p < 0.04) and HOMA-IR (4.1 ± 0.84 vs. 2.6 ± 0.67; p = 0.03) against those carrying major GG genotype. Participants with heterozygous GA genotype had significantly higher serum leptin levels against those carrying major GG genotype (40.0 ± 2.6 ng/mL vs. 29.6 ± 2.6 ng/mL; p = 0.04). Further investigation showed that individuals with AA, GA, GA + AA genotypes are at greater risk of developing hyperglycemia compared to those with GG genotype [OR 3.7(1.6−8.4), p = 0.001; 3.2 (1.2−8.6), p = 0.03; 3.5 (1.6−7.7), p = 0.001, respectively]. Additionally, the -2548AA allele was shown to be a risk factor for hyperglycemia [OR 1.9 (1.2−3.0), p = 0.006]. Our data revealed no relationship between this variant of the LEP gene with systolic and diastolic BP, signifying that this genetic variant is not a significant marker of obesity and hypertension in the Saudi population. Conclusions: AA and GA genotypes and LEP gene -2548AA alleles may signify potent risk factors predisposing healthy individuals to develop T2DM regardless of blood-pressure profile.

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).

Association of polymorphisms in LEPR with type 2 diabetes and related metabolic traits in a Chinese population

Background

Leptin acts as a mediator of inflammation and energy homeostasis by activating leptin receptor (LEPR). We conducted this study to explore the association of polymorphisms in LEPR with type 2 diabetes mellitus (T2DM) and its related metabolic traits.

Methods

We performed a case–control study to investigate the association of polymorphisms in LEPR with T2DM and related metabolic traits in a Chinese population, with a total of 922 T2DM patients and 1031 nondiabetic subjects. Polymorphisms were genotyped using MassARRAY assay.

Results

The G allele of rs1327118 was associated with a decreased risk of T2DM in men (P = 0.044, odds ratio = 0.707, 95% confidence interval = 0.504–0.991) and the G allele of rs3806318 was associated with increased systolic blood pressure (SBP) in men with T2DM. Besides, the women patients carrying the G allele of rs1327118 showed increased SBP and diastolic blood pressure (DBP) levels, but decreased high density lipoprotein cholesterol (HDL-C) level.

Conclusion

Our results suggest that rs1327118 may be associated with SBP, DBP and HDL-C levels in women with T2DM, and rs3806318 may be associated with T2DM and SBP level in men with T2DM. Further studies with larger sample size or functional experiments focused on exact mechanism are required to verify our observations.

A meta-analysis of associations of LEPR Q223R and K109R polymorphisms with Type 2 diabetes risk

Background

Leptin receptor (LEPR) plays a pivotal role in the control of body weight, energy metabolism, and insulin sensitivity. Various genetic association studies were performed to evaluate associations of LEPR genetic variants with type 2 diabetes (T2D) susceptibility.

Methods

A comprehensive search was conducted to identify all eligible case-control studies for examining the associations of LEPR single nucleotide polymorphisms (SNPs) Q223R (rs1137101) and K109R (rs1137100) with T2D risk. Odds ratios (OR) and corresponding 95% confidence intervals (CIs) were used to measure the magnitudes of association.

Results

For Q223R, 13 studies (11 articles) consisting of a total of 4030 cases and 2844 controls, and for K109R 7 studies (7 articles) consisting of 3319 cases and 2465 controls were available. Under an allele model, Q223R was not significantly associated with T2D risk (OR = 1.09, 95% CI: 0.80–1.48, P-value = 0.5989), which was consistent with results obtained under four genotypic models (ranges: ORs 1.08–1.20, 95% CIs: 0.58–2.02 to 0.64–2.26; P-values, 0.3650–0.8177, which all exceeded multiplicity-adjusted α = 0.05/5 = 0.01). In addition, no significant association was found between K109R and T2D risk based on either an allele model (OR = 0.93, 95% CI: 0.85–1.03, P-value = 0.1868) or four genotypic models (ranges: ORs 0.81–0.99, 95% CIs: 0.67–0.86 to 0.97–1.26, P-values, 0.0207–0.8804 which all exceeded multiplicity-adjusted α of 0.01). The magnitudes of association for these two SNPs were not dramatically changed in subgroup analyses by ethnicity or sensitivity analyses. Funnel plot inspections as well as Begg and Mazumdar adjusted rank correlation test and Egger linear regression test did not reveal significant publication biases in main and subgroup analyses. Bioinformatics analysis predicted that both missense SNPs were functionally neutral and benign.

Conclusions

The present meta-analysis did not detect significant genetic associations between LEPR Q223R and K109R polymorphisms and T2D risk.

Effects of maternal and fetal LEP common variants on maternal glycemic traits in pregnancy

Previous studies suggest that leptin (LEP) has an important role in glucose metabolism in the nonpregnant state. During pregnancy, circulating maternal concentrations of leptin rise significantly, mainly due to increased secretion of leptin from maternal adipose tissue and placenta. This study aimed to analyze the impact of maternal and fetal common LEP variants on glucose homeostasis in the pregnant state. Several glycemic traits, including fasting plasma glucose, fasting plasma insulin (FPI), and plasma glucose 1 hour after a 50-g oral glucose load, were measured in 1,112 unrelated Chinese Han pregnant women at 24–28 weeks gestation. Homeostatic model assessment (HOMA) was used to assess beta cell function (HOMA1-β and HOMA2-β) and insulin resistance (HOMA1-IR and HOMA2-IR).The relationships between glycemic traits and 12 LEP variants were determined. After applying the Bonferroni correction, we detected that (1) maternal rs10954173 and fetal rs10244329 were associated with maternal FPI although the effect of fetal rs10244329 may be not independent of maternal rs10244329, and (2) maternal rs12537573 was associated with maternal FPI and HOMA2-IR. This study provides genetic evidence that both maternal and fetal LEP polymorphisms may affect maternal glucose metabolism in pregnancy.

Investigation of TCF7L2, LEP and LEPR polymorphisms with esophageal squamous cell carcinomas

Single nucleotide polymorphisms (SNPs) in energy metabolism related gene may be key agents in the development of human malignancies. In this study, we aimed to examine the association of transcription factor 7-like 2, Leptin (LEP) and LEP receptor (LEPR) polymorphisms with esophageal squamous cell carcinoma (ESCC). A total of 507 ESCC cases and 1,496 controls were enrolled. We found that LEPR rs6588147 AA genotype was associated with ESCC risk (AA vs. GG/GA: adjusted OR=1.90, 95%CI=1.00-3.61, P=0.049). In the stratified analyses, LEPR rs6588147 G>A polymorphism increased the risk of ESCC (<63 years subgroup: AA vs. GG: adjusted OR=2.58, 95%CI=1.00-6.62, P=0.049 and AA vs. GA/GG: adjusted OR=2.71, 95%CI=1.06-6.91, P=0.038; male subgroup: AA vs. GG: adjusted OR=2.19, 95%CI=1.02-4.67, P=0.044 and AA vs. GA/GG: adjusted OR=2.26, 95%CI=1.06-4.80, P=0.035). However, LEP rs7799039 A>G decreased the risk of ESCC (≥63 years subgroup: GG vs. AA: adjusted OR=0.47, 95%CI=0.23-0.95, P=0.035 and GG vs. AA/AG: adjusted OR=0.48, 95%CI=0.24-0.96, P=0.038; BMI≥24 kg/m² subgroup: AG vs. AA: adjusted OR=0.66, 95%CI=0.45-0.99, P=0.044). In addition, LEPR rs1137101 G>A polymorphism decreased ESCC risk in some subgroups (ever smoking subgroup: GA vs. GG: adjusted OR=0.66, 95%CI=0.44-1.00, P=0.049; ever drinking subgroup: GA vs. GG: adjusted OR=0.54, 95%CI=0.31-0.95, P=0.031 and GA/AA vs. GG: adjusted OR=0.54, 95%CI=0.31-0.93, P=0.027). Our findings suggest that LEPR rs6588147 G>A polymorphism is associated with the increased risk of ESCC; however, LEP rs7799039 A>G and LEPR rs1137101 G>A polymorphisms may be protective factors for ESCC.

Association of maternal and fetal LEPR common variants with maternal glycemic traits during pregnancy

Recent studies suggested that maternal and placental leptin receptor (LEPR) may be involved in maternal glucose metabolism in pregnancy. To identify maternal and fetal LEPR common variants influencing gestational glycemic traits, we performed association study of 24-28-week maternal fasting glucose, glucose 1 hour after the consumption of a 50-g oral glucose load, fasting insulin and indices of beta-cell function (HOMA-β) and insulin resistance (HOMA-IR) in 1,112 unrelated women and their children. Follow-up of 36 LEPR loci identified 3 maternal loci (rs10889567, rs1137101 and rs3762274) associated with fasting glucose, these 3 fetal loci associated with fasting insulin and HOMA1-IR, as well as these 3 maternal-fetal loci combinations associated with HOMA2-β. We also demonstrated association of maternal locus rs7554485 with HOMA2-β and HOMA2-IR, maternal locus rs10749754 with fasting glucose, fetal locus rs10749754 with HOMA2-IR. However, these associations were no longer statistically significant after Bonferroni correction. In conclusion, our results first revealed multiple associations between maternal and fetal LEPR common variants and gestational glycemic traits. These associations did not survive Bonferroni correction. These corrections are overly conservative for association studies. We therefore believe the influence of these nominally significant variants on gestational glycometabolism will be confirmed by additional studies.

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.

Variations in the Obesity Gene "LEPR" Contribute to Risk of Type 2 Diabetes Mellitus: Evidence from a Meta-Analysis

Leptin is a hormone protein regulating food intake and energy expenditure. A number of studies have evaluated the genetic effect of leptin (LEP) and leptin receptor (LEPR) genes on T2DM. This study aimed to investigate the association between these gene polymorphisms and T2DM by a systematic review and meta-analysis. Published studies were identified through extensive search in PubMed and EMBASE. A total of 5143 T2DM cases and 5021 controls from 14 articles were included in this study. Five functional variants in LEPR were well evaluated. Meta-analysis showed that rs1137101 (p.R223Q) was significantly associated with T2DM in all genetic models: allele model (OR = 1.27, 95% confidence interval (CI) = 1.13-1.42), dominant model (OR = 1.19, 95% CI = 1.05-1.35), homozygote model (OR = 1.82, 95% CI = 1.38-2.39), and recessive model (OR = 1.75, 95% CI = 1.35-2.28), with minimal heterogeneity and no indication of publication bias. Similar associations with T2DM were also found for rs62589000 (p.P1019P) and 3'UTR ins/del, although the data was obtained from a small number of studies. For the other two polymorphisms rs1137100 (p.R109K) and rs8179183 (p.K656N), they were not significantly associated with T2DM. Our results provide robust evidences for the genetic association of rs1137101 (p.R223Q) in LEPR with T2DM susceptibility.

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.

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.

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.

Gene polymorphisms of adiponectin and leptin receptor are associated with early onset of type 2 diabetes mellitus in the Taiwanese population

OBJECTIVE

Adipocytokine genes encoding adiponectin (ADIPOQ) and the leptin receptor (LEPR) affect glucose and fatty acid metabolism. The purpose of this study was to examine the association between early-onset type 2 diabetes mellitus (T2DM) and variability within these two genes in the Han Chinese population of Taiwan.

SUBJECTS

A cross-sectional study of 999 patients from the Han Chinese population of Taiwan with early-onset T2DM (n=264; age at diagnosis, 20 to <45 years) and late-onset T2DM (n=735; age at diagnosis, ~45 years) was performed. Blood samples from T2DM patients were taken for DNA extraction, and levels of serological markers were measured at enrollment. Seven single-nucleotide polymorphisms (SNPs) were selected for genotyping (three SNPs in AIDPOQ and four SNPs in LEPR) by polymerase chain reaction in each patient.

RESULTS

Polymorphisms at the position rs10937273 in ADIPOQ and at the positions rs1892534 and rs2211651 in LEPR were statistically associated with early-onset T2DM (P=0.0246, 0.0014 and 0.0012, respectively). C-reactive protein levels were significantly different among the early-onset T2DM patients with different genotypes at the SNPs rs1892534 and rs2211651 in LEPR (P=0.003 and P=0.004, respectively). In addition, fasting glucose levels were also significantly different among different genotypes at the SNP rs1892534 in LEPR (P=0.038).

CONCLUSION

We conclude that the polymorphisms in the adipocytokine genes ADIPOQ and LEPR are significantly associated with the age at diagnosis of T2DM in the Han Chinese population of Taiwan.

Multivariate linkage scan for metabolic syndrome traits in families with type 2 diabetes

The purpose of this study was to evaluate evidence for linkage to interrelated quantitative features of the metabolic syndrome (MetS). Data on eight quantitative MetS traits (body weight, waist circumference, systolic and diastolic blood pressure, high-density lipoprotein (HDL) cholesterol, triglycerides (TGs), and fasting glucose and insulin measurements) and a 10 cM genome scan were available for 78 white families (n = 532 subjects). These data were used to conduct multipoint, multivariate linkage analyses, including tests for coincident linkage and complete pleiotropy. The strongest evidence for linkage from the bivariate analyses was observed on chromosome 1 (1p22.2) (HDL-TG; univariate lod score equivalent (lod(eq) = 3.99)) with stronger results from the trivariate analysis at the same location (HDL-TG-Insulin; lod(eq) = 4.32). Seven additional susceptibility regions (lod(eq) scores >1.9) were observed (1p36, 1q23, 2q21.2, 8q23.3, 14q23.2, 14q32.11, and 20p11.21). The results from this study indicate that several correlated traits of the MetS are influenced by the same gene(s) that account for some of the clustering of the MetS features.

Candidate gene association study conditioning on individual ancestry in patients with type 2 diabetes and metabolic syndrome from Mexico City

BACKGROUND

Type 2 diabetes (T2D) is influenced by diverse environmental and genetic risk factors. Metabolic syndrome (MS) increases the risk of cardiovascular disease and diabetes. We analysed 14 cases of polymorphisms located in 10 candidate loci, in a sample of patients with T2D and controls from Mexico City.

METHODS

We analysed the association of 14 polymorphisms located within 10 genes (TCF7L2, ENPP1, ADRB3, KCNJ11, LEPR, PPARgamma, FTO, CDKAL1, SIRT1 and HHEX) with T2D and MS. The analysis included 519 subjects with T2D defined according to the ADA criteria, 389 with MS defined according to the AHA/NHLBI criteria and 547 controls. Association was tested with the program ADMIXMAP including individual ancestry, age, sex, education and in some cases body mass index (BMI), in a logistic regression model.

RESULTS

The two markers located within the TCF7L2 gene showed strong associations with T2D (rs7903146, T allele, odd ratio (OR) = 1.76, p = 0.001 and rs12255372, T allele, OR = 1.78, p = 0.002), but did not show significant association with MS. The non-synonymous rs4994 polymorphism of the ADRB3 gene was associated with T2D (Trp allele, OR = 0.62, p = 0.001) and MS (Trp allele, OR = 0.74, p = 0.018). Nominally significant associations were also observed between T2D and the SIRT1 rs3758391 SNP and MS and the HHEX rs5015480 polymorphism.

CONCLUSIONS

Variants located within the gene TCF7L2 are strongly associated with T2D but not with MS, providing support to previous evidence indicating that polymorphisms at the TCF7L2 gene increase T2D risk. In contrast, the non-synonymous ADRB3 rs4994 polymorphism is associated with T2D and MS.

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.

Genetic variation in D7S1875 repeat polymorphism of leptin gene is associated with increased risk for depression: a case-control study from India

BACKGROUND

Epidemiologic data suggest an association between obesity and depression, however findings vary considerably across different studies. Both depression and obesity are disabling disorders associated with loss over appetite control, influenced by genetic and environmental factors and are risk factors for diseases like hypertension, cardiovascular disorders, etc. This study attempts to establish a link between the symptoms of depression, metabolic disorders, and obesity, to unravel the underlying association/s.

METHODS

This exploratory case-control study comprises 133 clinically diagnosed depressed individuals and 136 age matched controls. DNA from all 269 subjects was genotyped for D7S1875 repeat polymorphism in the promoter region of Leptin (LEP) gene using polymerase chain reaction.

RESULTS

Frequency of the shorter allele of D7S1875 (<208 bp) was 0.73 in the depressive group versus 0.67 in the control group (P=.01). Cases homozygous for D7S1875> or =208 bp alleles had significantly higher value of systolic (130 versus 122; P<.009) and diastolic (85.4 versus 81; P=.01) blood pressure (SBP and DBP) than the individuals homozygous for<208 bp allele. A similar trend was observed for SBP (127.8 versus 123.6; P=.03) among controls homozygous for the longer or the shorter allele. Thus, the LEP gene appears to be an important genetic determinant for susceptibility to depression in the Indian population (OR=1.4913, 95% CI=1.0334-2.1522; P=.04).

CONCLUSIONS

Our findings suggest that LEP gene variants could be related to depression and associated co-morbidities such as hypertension.

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.

Leptin is associated with blood pressure and hypertension in women from the National Heart, Lung, and Blood Institute Family Heart Study

Leptin is a key neuroendocrine hormone regulating food intake, metabolism, and fat accumulation, and it may also affect blood pressure and contribute to hypertension through sympathetic activation in the vasculature or at the renal level. Although previous studies have shown that the distribution of leptin is significantly different between males and females, as is the risk of hypertension between males and females, results regarding the role of leptin in the gender-specific regulation of blood pressure are controversial. Thus, we performed family-based association analyses in the National Heart, Lung, and Blood Institute Family Heart Study to test the hypothesis that LEPTIN gene variants and the plasma leptin level influence variability in blood pressure and the risk of hypertension differently by gender. We identified significant associations between LEPTIN single nucleotide polymorphisms with blood pressure and hypertension, but in postmenopausal women only. We also identified significant associations between plasma leptin levels and both blood pressure and hypertension in women. The current study supports a role for LEPTIN and plasma leptin levels in blood pressure regulation in women. It also provides insight into the gender differences in hypertension, as well as the differential distribution and activity of leptin in men and women.