Heritability of quantitative traits associated with type 2 diabetes mellitus in large multiplex families from South India

Heritability and genetic correlations of obesity indices and cardiometabolic traits in the Northern Chinese families

OBJECTIVE

This study aimed to investigate the heritability of various obesity indices and their shared genetic factors with cardiometabolic traits in the Chinese nuclear family.

METHODS

A total of 1270 individuals from 538 nuclear families were included in this cross-sectional study. Different indices were used to quantify fat mass and distribution, including body index mass (BMI), visceral fat index (VFI), and body fat percent (BFP). Heritability and genetic correlations for all quantitative traits were estimated using variance component models. The susceptibility-threshold model was utilized to estimate the heritability for binary traits.

RESULTS

Heritability estimates for obesity indices were highest for BMI (59%), followed by BFP (49%), and VFI (40%). Heritability estimates for continuous cardiometabolic traits varied from 24% to 50%. All obesity measures exhibited consistently significant positive genetic correlations with blood pressure, fasting blood glucose, and uric acid (rG range: 0.26-0.57). However, diverse genetic correlations between various obesity indices and lipid profiles were observed. Significant genetic correlations were limited to specific pairs: BFP and total cholesterol (rG = 0.24), BFP and low-density lipoprotein cholesterol (rG = 0.25), and VFI and triglyceride (rG = 0.33).

CONCLUSION

The genetic overlap between various obesity indices and cardiometabolic traits underscores the importance of pleiotropic genes. Further studies are warranted to investigate specific shared genetic and environmental factors between obesity and cardiometabolic diseases.

Burden of Type 2 Diabetes and Associated Cardiometabolic Traits and Their Heritability Estimates in Endogamous Ethnic Groups of India: Findings From the INDIGENIUS Consortium

To assess the burden of type 2 diabetes (T2D) and its genetic profile in endogamous populations of India given the paucity of data, we aimed to determine the prevalence of T2D and estimate its heritability using family-based cohorts from three distinct Endogamous Ethnic Groups (EEGs) representing Northern (Rajasthan [Agarwals: AG]) and Southern (Tamil Nadu [Chettiars: CH] and Andhra Pradesh [Reddys: RE]) states of India. For comparison, family-based data collected previously from another North Indian Punjabi Sikh (SI) EEG was used. In addition, we examined various T2D-related cardiometabolic traits and determined their heritabilities. These studies were conducted as part of the Indian Diabetes Genetic Studies in collaboration with US (INDIGENIUS) Consortium. The pedigree, demographic, phenotypic, covariate data and samples were collected from the CH, AG, and RE EEGs. The status of T2D was defined by ADA guidelines (fasting glucose ≥ 126 mg/dl or HbA1c ≥ 6.5% and/or use of diabetes medication/history). The prevalence of T2D in CH (N = 517, families = 21, mean age = 47y, mean BMI = 27), AG (N = 530, Families = 25, mean age = 43y, mean BMI = 27), and RE (N = 500, Families = 22, mean age = 46y, mean BMI = 27) was found to be 33%, 37%, and 36%, respectively, Also, the study participants from these EEGs were found to be at increased cardiometabolic risk (e.g., obesity and prediabetes). Similar characteristics for the SI EEG (N = 1,260, Families = 324, Age = 51y, BMI = 27, T2D = 75%) were obtained previously. We used the variance components approach to carry out genetic analyses after adjusting for covariate effects. The heritability (h2) estimates of T2D in the CH, RE, SI, and AG were found to be 30%, 46%, 54%, and 82% respectively, and statistically significant (P ≤ 0.05). Other T2D related traits (e.g., BMI, lipids, blood pressure) in AG, CH, and RE EEGs exhibited strong additive genetic influences (h2 range: 17% [triglycerides/AG and hs-CRP/RE] - 86% [glucose/non-T2D/AG]). Our findings highlight the high burden of T2D in Indian EEGs with significant and differential additive genetic influences on T2D and related traits.

Genetic association of anthropometric traits with type 2 diabetes in ethnically endogamous Sindhi families

Background

Ethnically endogamous populations can shed light on the genetics of type 2 diabetes. Such studies are lacking in India. We conducted this study to determine the genetic and environmental contributions of anthropometric traits to type 2 diabetes risk in the Sindhi families in central India.

Methods

We conducted a family study in Indian Sindhi families with at least one case of type 2 diabetes. Variance components methods were used to quantify the genetic association of 18 anthropometric traits with eight type 2 diabetes related traits. Univariate and bivariate polygenic models were used to determine the heritability, genetic and environmental correlation of anthropometric traits with type 2 diabetes related traits.

Results

We included 1,152 individuals from 112 phenotyped families. The ascertainment-bias corrected prevalence of type 2 diabetes was 35%. Waist circumference, hip circumference and the biceps, triceps, subscapular and medial calf skinfold thicknesses were polygenically and significantly associated with type 2 diabetes. The range of heritability of the anthropometric traits and type 2 diabetes related traits was 0.27–0.73 and 0.00–0.39, respectively. Heritability of type 2 diabetes as a discrete trait was 0.35. Heritability curves demonstrated a substantial local influence of type 2 diabetes related traits. Bivariate trait analyses showed that biceps and abdominal skinfold thickness and all waist-containing indexes were strongly genetically correlated with type 2 diabetes.

Conclusions

In this first study of Sindhi families, we found evidence for genetic and environmental concordance of anthropometric traits with type 2 diabetes. Future studies need to probe into the genetics of type 2 diabetes in this population.

Nasopharyngeal Epstein-Barr virus DNA loads in high-risk nasopharyngeal carcinoma families: Familial aggregation and host heritability

Nasopharyngeal carcinoma (NPC), the most common head and neck cancer, is characterized by distinct geographic distribution and familial aggregation. Multiple risk factors, including host genetics, environmental factor, and EBV infection, have been linked to the development of NPC, particularly in the familial clustering cases. However, the cause of NPC endemicity remains enigmatic due possibly to the complicated interplay between these risk factors. Recently, positive Epstein-Barr virus (EBV) DNA loads at nasopharyngeal (NP) cavity has been found to reflect NPC development and applied in NPC screening. To examine whether the increased NP EBV loads could aggregate in the families and be affected by host genetics and environmental factor, EBV loads were obtained by 510 NP brushing samples from eligible unaffected individuals, who have two or more relatives affected with NPC, in 116 high-risk NPC families. The correlation of relative pairs was estimated using S.A.G.E. (version 6.4, 2016), and host heritability of NP EBV loads was calculated with variance component models using SOLAR (version 8.4.2, 2019). In result, significant correlations of EBV loads were observed between parent-offspring pairs and sibling-sibling pairs (P < .001), but not in distant kin relationship pairs. Interestingly, after excluding the shared environmental factor within families, host genetics contributes significantly to NP EBV loads with a heritability of 56.41% (P = 1.00 × 10-7 ), and its effect was slightly elevated (68.86%, P = 3.40 × 10-6 ) in families with more NPC cases (≥3). These findings indicate that additional host-genetic variants involved in the EBV local NP mucosal behavior may be especially important for the development of NPC.

Heritability and genome-wide association analyses of fasting plasma glucose in Chinese adult twins

Background

Currently, diabetes has become one of the leading causes of death worldwide. Fasting plasma glucose (FPG) levels that are higher than optimal, even if below the diagnostic threshold of diabetes, can also lead to increased morbidity and mortality. Here we intend to study the magnitude of the genetic influence on FPG variation by conducting structural equation modelling analysis and to further identify specific genetic variants potentially related to FPG levels by performing a genome-wide association study (GWAS) in Chinese twins.

Results

The final sample included 382 twin pairs: 139 dizygotic (DZ) pairs and 243 monozygotic (MZ) pairs. The DZ twin correlation for the FPG level (r_DZ = 0.20, 95% CI: 0.04–0.36) was much lower than half that of the MZ twin correlation (r_MZ = 0.68, 95% CI: 0.62–0.74). For the variation in FPG level, the AE model was the better fitting model, with additive genetic parameters (A) accounting for 67.66% (95% CI: 60.50–73.62%) and unique environmental or residual parameters (E) accounting for 32.34% (95% CI: 26.38–39.55%), respectively. In the GWAS, although no genetic variants reached the genome-wide significance level (P < 5 × 10^− 8), 28 SNPs exceeded the level of a suggestive association (P < 1 × 10^− 5). One promising genetic region (2q33.1) around rs10931893 (P = 1.53 × 10^− 7) was found. After imputing untyped SNPs, we found that rs60106404 (P = 2.38 × 10^− 8) located at SPATS2L reached the genome-wide significance level, and 216 SNPs exceeded the level of a suggestive association. We found 1007 genes nominally associated with the FPG level (P < 0.05), including SPATS2L, KCNK5, ADCY5, PCSK1, PTPRA, and SLC26A11. Moreover, C1orf74 (P = 0.014) and SLC26A11 (P = 0.021) were differentially expressed between patients with impaired fasting glucose and healthy controls. Some important enriched biological pathways, such as β-alanine metabolism, regulation of insulin secretion, glucagon signaling in metabolic regulation, IL-1 receptor pathway, signaling by platelet derived growth factor, cysteine and methionine metabolism pathway, were identified.

Conclusions

The FPG level is highly heritable in the Chinese population, and genetic variants are significantly involved in regulatory domains, functional genes and biological pathways that mediate FPG levels. This study provides important clues for further elucidating the molecular mechanism of glucose homeostasis and discovering new diagnostic biomarkers and therapeutic targets for diabetes.

The Extending Spectrum of NPC1-Related Human Disorders: From Niemann-Pick C1 Disease to Obesity

The Niemann-Pick type C1 (NPC1) protein regulates the transport of cholesterol and fatty acids from late endosomes/lysosomes and has a central role in maintaining lipid homeostasis. NPC1 loss-of-function mutations in humans cause NPC1 disease, a rare autosomal-recessive lipid-storage disorder characterized by progressive and lethal neurodegeneration, as well as liver and lung failure, due to cholesterol infiltration. In humans, genome-wide association studies and post-genome-wide association studies highlight the implication of common variants in NPC1 in adult-onset obesity, body fat mass, and type 2 diabetes. Heterozygous human carriers of rare loss-of-function coding variants in NPC1 display an increased risk of morbid adult obesity. These associations have been confirmed in mice models, showing an important interaction with high-fat diet. In this review, we describe the current state of knowledge for NPC1 variants in relationship to pleiotropic effects on metabolism. We provide evidence that NPC1 gene variations may predispose to common metabolic diseases by modulating steroid hormone synthesis and/or lipid homeostasis. We also propose several important directions of research to further define the complex roles of NPC1 in metabolism. This review emphasizes the contribution of NPC1 to obesity and its metabolic complications.

Genetics of HbA1c: a case study in clinical translation

Glycated hemoglobin (HbA1c) measures the amount of glucose in the blood in the previous 2-3 months and is used to test whether an individual has diabetes (HbA1c≥6.5%), or how well they are managing their diabetes. Genome-wide association studies have successfully identified multiple genomic loci influencing HbA1c, through both glycemic (factors that affect the amount blood glucose levels) and erythrocytic (factors that affect the red blood cell) pathways. Inaccuracies in HbA1c, due to non-glycemic variants, could lead to suboptimal care or adverse health consequences. A recently published example is the erythrocytic variant (rs1050828) in G6PD, which leads to the artificial lowering of HbA1c and missed diagnosis of diabetes using current thresholds. In this review we will discuss recent insights into the genetic etiology of HbA1c, and how these can translate to the clinic.

Distinct Predictors and Comorbidities in Early Onset Type 2 Diabetes Mellitus Among Asian Indians

BACKGROUND

The incidence of type 2 diabetes mellitus (T2DM) is increasing worldwide, and the age of disease onset is falling. Although there is rising prevalence of early onset T2DM in India, little is known about their clinical characteristics and cardiovascular risks profiles. The aim of this study was to address this knowledge gap by comparing the characteristics of early onset T2DM and usual onset T2DM patients from our clinic population in India.

METHODS

We studied the clinical and biochemical parameters of 98 consecutive early onset T2DM patients of age <45 and <5 years of disease duration and compared those parameters with 86 consecutive usual onset T2DM patients of age >50 years and similar disease duration.

RESULTS

There was a strong component of family history of T2DM in early onset T2DM patients; however, no difference was observed in body mass index or waist circumference between the groups. When compared with usual onset group, the early onset T2DM patients were more hypertriglycedemic, with higher total cholesterol, higher total cholesterol/high-density lipoprotein (HDL) ratio, higher low-density lipoprotein levels, and lower HDL cholesterol. Early onset T2DM patients showed significantly worse glycemic control and rapid decline in insulin secretion compared with usual onset T2DM patients.

CONCLUSIONS

Our results demonstrate that early onset T2DM in Asian Indians appears to be a disease phenotype with adverse risk factors having poor glycemic control and longer disease duration demanding strategies for novel clinical management.

WITHDRAWN: Impact of apolipoprotein E gene polymorphism and additional gene-obesity interaction on type 2 diabetes risk in a Chinese Han old population

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Sex Hormone-Binding Globulin in Children and Adolescents

Sex hormone-binding globulin (SHBG) is a circulating glycoprotein that transports testosterone and other steroids in the blood. Interest in SHBG has escalated in recent years because of its inverse association with obesity and insulin resistance, and because many studies have linked lower circulating levels of SHBG to metabolic syndrome, type 2 diabetes, nonalcoholic fatty liver disease, polycystic ovary syndrome, and early puberty. The purpose of this review is to summarize molecular, clinical, endocrine, and epidemiological findings to illustrate how measurement of plasma SHBG may be useful in clinical medicine in children.

Changes of Regulatory T Cells and of Proinflammatory and Immunosuppressive Cytokines in Patients with Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Objective. The aim of this study was to investigate the changes of regulatory T cells (Treg), interleukin-6 (IL-6), IL-10, transforming growth factor-β (TGF-β), and tumor necrosis factor-alpha (TNF-α) in patients with type 2 diabetes mellitus (T2DM). Methods. We performed a comprehensive search up to July 2016 for all clinical studies about the changes of Treg, IL-6, IL-10, IL-17, TGF-β, and TNF-α in T2DM patients versus healthy controls. Results. A total of 91 articles (5642 cases and 7378 controls) were included for this meta-analysis. Compared with the controls (all p < 0.001), the patients had increased serum levels of IL-6, TGF-β, and TNF-α but decreased the percentage of peripheral CD4⁺CD25⁺Foxp3⁺Treg and serum IL-10 level. Furthermore, the percentage of peripheral CD4⁺CD25⁺Foxp3⁺Treg (p < 0.001) and serum IL-10 level (p = 0.033) were significantly lower in the patients with complication and in the patients without complication, respectively. No significant changes about the percentage of CD4⁺CD25⁺Treg (p = 0.360) and serum IL-17 level (p = 0.459) were found in T2DM patients. Conclusions. T2DM patients have decreased the percentage of peripheral CD4⁺CD25⁺Foxp3⁺Treg and levels of serum IL-10 but elevated serum levels of IL-6, TGF-β, and TNF-α. Presence of diabetic complications further lowers the peripheral CD4⁺CD25⁺Foxp3⁺Treg number.

Paternal long-term exercise programs offspring for low energy expenditure and increased risk for obesity in mice

Obesity has more than doubled in children and tripled in adolescents in the past 30 yr. The association between metabolic disorders in offspring of obese mothers with diabetes has long been known; however, a growing body of research indicates that fathers play a significant role through presently unknown mechanisms. Recent observations have shown that changes in paternal diet may result in transgenerational inheritance of the insulin-resistant phenotype. Although diet-induced epigenetic reprogramming via paternal lineage has recently received much attention in the literature, the effect of paternal physical activity on offspring metabolism has not been adequately addressed. In the current study, we investigated the effects of long-term voluntary wheel-running in C57BL/6J male mice on their offspring's predisposition to insulin resistance. Our observations revealed that fathers subjected to wheel-running for 12 wk produced offspring that were more susceptible to the adverse effects of a high-fat diet, manifested in increased body weight and adiposity, impaired glucose tolerance, and elevated insulin levels. Long-term paternal exercise also altered expression of several metabolic genes, including Ogt, Oga, Pdk4, H19, Glut4, and Ptpn1, in offspring skeletal muscle. Finally, prolonged exercise affected gene methylation patterns and micro-RNA content in the sperm of fathers, providing a potential mechanism for the transgenerational inheritance. These findings suggest that paternal exercise produces offspring with a thrifty phenotype, potentially via miRNA-induced modification of sperm.

Diabetes in India: what is different?

PURPOSE OF REVIEW

The purpose of this study was to review the epidemiology and pathogenesis of diabetes in Asian Indians with a particular focus on 'Asian Indian type 2 diabetes phenotype'.

RECENT FINDINGS

The prevalence of diabetes is rapidly increasing among Asian Indians, particularly in the past two decades. The diabetes rates in urban India now exceed that seen in Indians migrated to developed nations. Urbanization, changes from traditional healthier diets to high-refined carbohydrate intake, and sedentary lifestyle have contributed to this steep increase in the prevalence of diabetes in India. Type 2 diabetes among Asian Indians is characterized by onset at a younger age, greater abdominal obesity despite relatively lower BMI, greater insulin resistance, and early decline in beta cell function. Asian Indians are also at a higher risk for premature coronary artery disease.

SUMMARY

The clinical profile of type 2 diabetes in Asian Indians differs from Caucasians with higher central obesity, increased inflammatory markers such as high sensitive C-reactive protein, greater insulin resistance, early loss of beta cell function, and a higher risk of coronary artery disease. Mechanistic studies are needed to characterize the pathophysiology of the Asian Indian phenotype.

Improving diabetes care in developing countries: the example of Pakistan

Pakistan is a developing country with limited recourses and diverse economic social patterns. Pakistan has high prevalence of diabetes and its complication, which is a huge challenge to the existing health care system. The major contributing risk factors are urbanization and change in lifestyle, maternal and fetal malnutrition and genetic factors. National action plans for control of diabetes have been made since 1995 but actions in this regard were not perfect. Training of primary care physicians and development of multidisciplinary diabetes care teams was initiated. Prioritization strategies were defined according to the International Diabetes Federation (IDF) guidance, mainly focusing on diabetic foot, diabetes education and children with diabetes. Researches for better understanding and management of diabetes in Pakistan were undertaken. Collaboration between various stakeholders was promoted at national and international level. In summary, public private relationships and development of multifaceted approaches is expected to improve the lives of millions of diabetics of Pakistan.

Common variants in BDNF, FAIM2, FTO, MC4R, NEGR1, and SH2B1 show association with obesity-related variables in Spanish Roma population

OBJECTIVES

The objective of this study is to investigate the association between previously GWAS identified genetic variants predisposing to obesity in Europeans and obesity-related phenotypes in Roma population.

METHODS

A total of 24 representative single nucleotide polymorphisms (SNPs) were genotyped in 372 individuals belonging to 50 extended families of Roma population. SNPs were tested for association with seven quantitative obesity-related phenotypes in the PLINK program.

RESULTS

Risk variants in NEGR1, FAIM2, FTO, and SH2B1 genes were associated with increased adiposity accumulation in Roma population with effect sizes between 0.21 and 0.34 Z-scores for each copy of the BMI increasing allele. Additionally, variants in BDNF and MC4R were significantly associated with adiposity distribution but not with overall fatness. No significant association was detected between obesity-related phenotypes and variants in the first intron of the FTO gene (e.g., rs9939609).

CONCLUSIONS

The results of this study suggest that SNPs in or near six genes (BDNF, FAIM2, FTO, MC4R, NEGR1, and SH2B1) are significantly associated with body fat accumulation and distribution in Roma people. However, the association observed among variants in the first intron of FTO and obesity in European derived populations is not evident in the analyzed Roma sample.

Influence of apolipoprotein E gene polymorphism on development of type 2 diabetes mellitus in Chinese Han population: a meta-analysis of 29 studies

OBJECTIVES

Published data regarding the association between apolipoprotein E (ApoE) gene polymorphism and type 2 diabetes mellitus (T2DM) risk in Chinese Han population were inconclusive. To derive a more precise estimation of the relationship between this variant and T2DM risk in Chinese Han population, we performed this meta-analysis.

DESIGN AND METHODS

A computerized literature search was conducted to identify the relevant studies from PubMed, EMbase, Web of Science, CBMdisc, CNKI, and Google Scholar. Additionally, hand searching of the references of identified articles was performed. All the statistical tests were performed using Stata 11.0.

RESULTS

A total of 29 articles with 4615 T2DM cases and 2867 controls were included in the present meta-analysis. The results showed evidence for significant association between ApoE gene polymorphism and T2DM risk (for ε2/ε3 vs. ε3/ε3: OR=1.37, 95% CI=1.12-1.68, P<0.01; for ε3/ε4 vs. ε3/ε3: OR=1.53, 95% CI=1.23-1.91, P<0.01; for ε4/ε4 vs. ε3/ε3: OR=1.86, 95% CI=1.22-2.84, P<0.01; for ε2 allele vs. ε3 allele: OR=1.28, 95% CI=1.08-1.52, P=0.01; for ε4 allele vs. ε3 allele: OR=1.43, 95% CI=1.22-1.68, P<0.01). In addition, significant association was also found between ApoE gene polymorphism and diabetic nephropathy (DN) risk.

CONCLUSIONS

The results of this meta-analysis suggest that the ApoE ε2 and ε4 alleles may be associated with increased risks of T2DM and DN in Chinese Han population. Additional well-designed genome-wide association studies are required to confirm these results.

Genotype by energy expenditure interaction and body composition traits: The Portuguese Healthy Family Study

Background and Aims. Energy expenditure has been negatively correlated with fat accumulation. However, this association is highly variable. In the present study we applied a genotype by environment interaction method to examine the presence of Genotype x by Total Daily Energy Expenditure and Genotype x by Daily Energy Expenditure interactions in the expression of different body composition traits. Methods and Results. A total of 958 subjects from 294 families of The Portuguese Healthy Family Study were included in the analysis. TDEE and DEE were assessed using a physical activity recall. Body fat percentages were measured with a bioelectrical impedance scale. GxTDEE and GxDEE examinations were performed using SOLAR 4.0 software. All BC traits were significantly heritable, with heritabilities ranging from 21% to 34%. The GxTDEE and GxDEE interaction models fitted the data better than the polygenic model for all traits. For all traits, a significant GxTDEE and GxDEE interaction was due to variance heterogeneity among distinct levels of TDEE and DEE. For WC, GxTDEE was also significant due to the genetic correlation function. Conclusions. TDEE and DEE are environmental constraints associated with the expression of individuals' BC genotypes, leading to variability in the phenotypic expression of BC traits.

Association of the C242T polymorphism in the NAD(P)H oxidase P22 phox gene with type 2 diabetes mellitus risk: a meta-analysis

OBJECTIVES

A number of epidemiological studies have explored the association between NAD(P)H oxidase P22 phox gene C242T (rs4673) polymorphism and susceptibility to type 2 diabetes mellitus (T2DM), but the results are still debatable. Therefore, we conducted a meta-analysis to assess the potential association between the NAD(P)H oxidase P22 phox gene C242T polymorphism and T2DM risk.

METHODS

Electronic literature searches of the PubMed, Embase, Web of Science, CBMdisc, CNKI and Google Scholar were performed up to June 15, 2013. Additionally, hand searching of the references of identified articles was performed. Data analyses were carried out by Stata 11.0.

RESULTS

Seven studies were included in the final meta-analysis, covering a total of 1661 T2DM cases and 1265 controls. The results showed evidence for significant association between the NAD(P)H oxidase P22 phox gene C242T polymorphism and T2DM risk (for T/T vs. T/C: OR=1.61, 95% CI=1.14-2.26, p=0.007; for T/T vs. T/C+C/C: OR=1.50, 95% CI=1.10-2.05, p=0.009). In the subgroup analysis, there was also evidence for significant association between the NAD(P)H oxidase P22 phox gene C242T polymorphism and T2DM risk, either for Asians (T/T vs. T/C+C/C: OR=1.74, 95% CI=1.15-2.64, p=0.009) or for non-Asians (for T allele vs C allele: OR=1.30, 95% CI=1.04-1.61, p=0.02).

CONCLUSIONS

The present meta-analysis indicates that the NAD(P)H oxidase P22 phox gene 242 T allele might be associated with an increased T2DM risk.

Waist circumference is genetically correlated with incident Type 2 diabetes in Mexican-American families

AIMS

We aimed to determine the genetic and environmental correlation between various anthropometric indexes and incident Type 2 diabetes with a focus on waist circumference.

METHODS

We used the data on extended Mexican-American families (808 subjects, 7617.92 person-years follow-up) from the San Antonio Family Heart Study and estimated the genetic and environmental correlations of 16 anthropometric indexes with the genetic liability of incident Type 2 diabetes. We performed bivariate trait analyses using the solar software package.

RESULTS

All 16 anthropometric indexes were significantly heritable (range of heritabilities 0.24-0.99). Thirteen indexes were found to have significant environmental correlation with the liability of incident Type 2 diabetes. In contrast, only anthropometric indexes consisting of waist circumference (waist circumference, waist-hip ratio and waist-height ratio) were significantly genetically correlated (genetic correlation coefficients: 0.45, 0.55 and 0.44, respectively) with the liability of incident Type 2 diabetes. We did not observe such a correlation for BMI.

CONCLUSIONS

Waist circumference as a predictor of future Type 2 diabetes is supported by the finding that they share common genetic influences.

Evaluation of Body Mass Index (BMI) Percentile cut-off Levels with Reference to Insulin Resistance: A Comparative Study on South Indian Obese and Non-Obese Adolescents

OBJECTIVES

To investigate the relationship of Body Mass Index (BMI) percentile cut off with Homeostasis Model Assessment-Insulin Resistance (HOMA-IR), a surrogate marker for insulin resistance in obese, overweight and non-obese adolescents.

STUDY DESIGN

A cross-sectional analysis of 120 adolescents (divided into sixty overweight/obese and an equal number of non-obese) was performed on nondiabetic, nonpregnant (11 to 18 year old school going) adolescents in south Indian (Puducherry) population. The main outcome measure of insulin resistance was calculated as HOMA-IR (greater than 3.16). Obesity was defined as per the BMI criteria, BMI greater than or equal to 95(th) percentile,overweight greater than or equal to 85(th) percentile and non-obese less than 84.9(th) percentile. All adolescents were subjected to analysis of anthropometric parameters that included weight, height and BMI (body mass index). Biochemical parameters, namely venous plasma glucose (fasting) and venous plasma insulin (fasting) were included for insulin resistance calculation by HOMA-IR.

RESULTS

Having a BMI of greater than or equal to 85(th) percentilewas associated with high HOMA-IR levels. As the BMI percentile increased, HOMA-IR levels also increased. Prevalence of insulin resistance for a BMI percentile of less than 84.9 was nil. Prevalence of insulin resistance for a BMI percentile of 85-94.9 was 26%.Prevalence of insulin resistance for BMI of greater than or equal to 95(th) percentile was 64%.

CONCLUSION

Insulin resistance is highly prevalent in obese and overweight adolescents as compared to that in non-obese adolescents. The onset of Impaired Fasting Glucose (IFG) is associated with the development of severe hyper-insulinaemia in obese adolescents and early primordial and primary prevention can thus alleviate the burden of future cardiometabolic disorders.

Sex hormone-binding globulin and the risk for metabolic syndrome in children of South Asian Indian origin

OBJECTIVE

To determine whether the plasma level of sex hormone-binding globulin (SHBG) identifies South Asian Indian children at risk for metabolic syndrome.

METHODS

Adults and their children aged 5 to 9 years were recruited at the annual health fair at the Hindu temple serving the South Asian Indian community in Louisville, Kentucky. Anthropometric data were collected in adults and children, and blood pressure, lipid, and glucose levels were measured in adults. SHBG levels were measured in children using a fingerstick blood sample. In adults, metabolic syndrome was diagnosed according to the International Diabetes Federation criteria. Twelve months later, follow-up anthropometric data were obtained for a portion of the children.

RESULTS

The study included 30 sets of parents and 30 children. The prevalence of metabolic syndrome among 310 adults attending the health fair was 42% in men and 39% in women. Children with 1 parent with metabolic syndrome had 24% lower SHBG levels that increased to 55% if both parents had metabolic syndrome. SHBG levels were inversely related to waist circumference and to body mass index percentile. Both SHBG and waist circumference predicted weight gain over 1 year in children. CONCLUSIONS Low SHBG levels were found in South Asian Indian children whose parents had attributes of metabolic syndrome. The dose dependency of SHBG is consistent with inheritance of a genetic trait, and if the results are applicable to other racial/ethnic groups, SHBG may be a useful marker to identify at-risk children for early intervention.

Association between the interleukin-6 gene -572 C/G polymorphism and the risk of type 2 diabetes mellitus: a meta-analysis of 11,681 subjects

The association between the interleukin-6 (IL-6) gene -572 C/G (rs1800796) polymorphism and type 2 diabetes mellitus (T2DM) risk remains controversial. Thus, we performed this meta-analysis by searching PubMed, Embase, Web of Science, CBMdisc and CNKI databases until January 30, 2012. In addition, hand searching of the references of identified articles was performed. A total of 10 case-control studies including 11,681 subjects were selected to evaluate the possible association. Our results showed evidence for significant association between the IL-6 gene -572 C/G polymorphism and T2DM risk (for G allele vs. C allele: odds ratio [OR] = 1.29, 95% confidence interval [CI] = 1.09-1.52, P = 0.002, P = 0.008 after Bonferroni testing; for G/G vs. C/C: OR = 1.89, 95% CI = 1.51-2.37, P < 0.00001, P < 0.00004 after Bonferroni testing; for GG vs. G/C + C/C: OR = 1.75, 95% CI = 1.20-2.56, P = 0.004, P = 0.016 after Bonferroni testing; for G/G + G/C vs. C/C: OR = 1.32, 95% CI = 1.11-1.57, P = 0.001, P = 0.004 after Bonferroni testing). In addition, similar results were obtained in the subgroup analysis based on ethnicity. In summary, the present meta-analysis suggests a significant association between the IL-6 gene -572 G allele and increased risk of T2DM.

Association among obesity-related anthropometric phenotypes: analyzing genetic and environmental contribution

Obesity has become a public-health and policy problem in many parts of the world. Epidemiological and population studies in this field are usually based on different anthropometric measures; however, common genetic and environmental factors between these phenotypes have been scarcely studied. The objective of this article is to assess the strength of these factors on the covariation among a large set of obesity-related traits. The subject group consisted of 533 nuclear families living in the Greater Bilbao (Spain), and included 1,702 individuals aged 2-61 years. Detailed anthropometric measurements (stature, breadths, circumferences and skinfolds) were carried out in each subject. Bivariate quantitative genetic analyses were performed using a variance-components procedure implemented in the software SOLAR. The results revealed that the majority of these traits is affected by common genetic and environmental factors. All correlations were significantly different from 1 and varied from non-significant to very high (>0.90, P < 0.0001), with clearly lower pleiotropic effects among pairs including fat-distribution traits. Despite the strong common genetic effects detected among phenotypes determining the amount of body fat and mass, there is a residual genetic influence on the local fatness measures that cannot be explained exclusively by the genetic influence on overall fatness. Moreover, the observed relationships confirm a partially different genetic control of truncal and peripheral fat. In conclusion, our findings highlight the relevance of considering different types of traits in the prevention and treatment of obesity, as well as in the search for genes involved in its development.

Shared genetic variance between the features of the metabolic syndrome: heritability studies

Heritability estimates of MetS range from approximately 10%-30%. The genetic variation that is shared among MetS features can be calculated by genetic correlation coefficients. The objective of this paper is to identify MetS feature as well as MetS related features which have much genetic variation in common, by reviewing the literature regarding genetic correlation coefficients. Identification of features, that have much genetic variation in common, may eventually facilitate the search for pleitropic genetic variants that may explain the clustering of MetS features. A PubMed search with the search terms "(metabolic syndrome OR insulin resistance syndrome) and (heritability OR genetic correlation OR pleiotropy)" was performed. Studies published before 7th July 2011, which presented genetic correlation coefficients between the different MetS features and genetic correlation coefficients of MetS and its features with adipose tissue-, pro-inflammatory and pro-thrombotic biomarkers were included. Nine twin and 19 family studies were included in the review. Genetic correlations varied, but were strongest between waist circumference and HOMA-IR (r(2): 0.36 to 0.79, median: 0.50), HDL cholesterol and triglycerides (r(2): -0.05 to -0.59, median -0.45), adiponectin and MetS (r(2): -0.32 to -0.43; median -0.38), adiponectin and insulin (r(2): -0.10 to -0.60; median -0.30) and between adiponectin and HDL-cholesterol (r(2): -0.22 to -0.51, median -0.29). In conclusion, heritability studies suggest that genetic pleiotropy exist especially between certain MetS features, as well as between MetS and adiponectin. Further research on actual genetic variants responsible for the genetic pleiotropy of these combinations will provide more insight into the etiology of MetS.

Dissecting prenatal, postnatal, and inherited effects: ART and design

With the failure of common variants alone to explain the bulk of trait heritability, it becomes more important to understand the contribution of maternally inherited effects, prenatal effects, and postnatal environmental effects. These effects can be disentangled by studying families containing children conceived by assisted reproductive technologies (ART). We propose and develop a model that is an extension of the variance component model commonly used in pedigree analysis. Our model is flexible enough to allow any number of family members and degrees of relationship; thus, researchers can use both small and extended families simultaneously. Simulations demonstrate that our method has appropriate statistical properties and is robust to model misspecification and accurate in the presence of missing data. Most importantly, our method is able to disentangle maternally inherited effects from prenatal effects, which are confounded in traditional family studies. Our analyses also provide guidance to researchers designing studies that will use ART families to clarify genetic and environmental factors underlying traits.