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

A method for an unbiased estimate of cross-ancestry genetic correlation using individual-level data

Cross-ancestry genetic correlation is an important parameter to understand the genetic relationship between two ancestry groups. However, existing methods cannot properly account for ancestry-specific genetic architecture, which is diverse across ancestries, producing biased estimates of cross-ancestry genetic correlation. Here, we present a method to construct a genomic relationship matrix (GRM) that can correctly account for the relationship between ancestry-specific allele frequencies and ancestry-specific allelic effects. Through comprehensive simulations, we show that the proposed method outperforms existing methods in the estimations of SNP-based heritability and cross-ancestry genetic correlation. The proposed method is further applied to anthropometric and other complex traits from the UK Biobank data across ancestry groups. For obesity, the estimated genetic correlation between African and European ancestry cohorts is significantly different from unity, suggesting that obesity is genetically heterogenous between these two ancestries.

Waist-to-height ratio has a stronger association with cardiovascular risks than waist circumference, waist-hip ratio and body mass index in type 2 diabetes

AIMS

To compare the associations between four anthropometric indices including waist-to-height ratio (WHtR), waist circumference (WC), waist-hip-ratio (WHR) and body mass index (BMI) and cardio-cerebrovascular events (CCBVEs) in Chinese T2DM patients.

METHODS

The associations of four anthropometric measures with CCBVEs and metabolic syndrome (MetS) were compared by multiple regression model in 3108 T2DM patients. CCBVEs was defined as a history of myocardial infarction, angina, angioplasty, coronary artery bypass surgery, transient ischemic attack, ischemic or hemorrhagic stroke.

RESULTS

After controlling for age, sex and diabetes duration, the prevalence of CCBVEs and MetS significantly increased across the WHtR, WC, WHR and BMI quartiles in T2DM patients, respectively. However, when controlling for these four anthropometric measurements together, although four anthropometric measures were closely associated with MetS prevalence, only WHtR quartile was significantly associated with CCBVEs prevalence (6.5%, 13.8%, 16.9% and 21.3%, p < 0.001 for trend). After adjusting for multiple confounders including four anthropometric parameters, a regression analysis revealed that only WHtR was independently and positively associated with the presence of CCBVEs (p = 0.029).

CONCLUSIONS

Compared with WC, WHR and BMI, WHtR have a stronger association with CCBVEs in T2DM subjects. WHtR maybe a better indicator than other anthropometric measurements for evaluating cardiovascular risks in T2DM.

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.

Contribution of Different Phenotypes of Obesity to Metabolic Abnormalities from a Cross-Sectional Study in the Northwest China

BACKGROUND

This study has been conducted to explore the correlation between phenotypes of obesity and metabolic comorbidities.

METHODS

This cross-sectional study recruited 14,724 adults aged ≥18 years with a randomized stratified sampling strategy. Obesity was classified into four types according to body mass index (BMI) and waist-to-height ratio (WHtR): normal weight with central obesity (NWCO) and without (NW) CO, and obese or overweight with (OBCO) and without (OB) central obesity. Uric acid (UA), fasting blood glucose (FBG), and lipid profile were measured.

RESULTS

The prevalence of hyperuricemia in the 4 groups (NW, NWCO, OB and OBCO) was 3.7%, 5.6%, 8.7% and 12.4%, whilst the prevalence of hypertriglyceridemia was 13.4%, 27.4%, 30.3% and 43.7%, separately. The prevalence of hypo-high-density lipoprotein cholesterolemia (hypo-HDL emia) was 20.1%, 21.4%, 30.8% and 27.9%, while the prevalence of hyper-low-density lipoprotein cholesterolemia (hyper-LDL emia) was 9.8%, 24.4%, 12.3% and 27.9%. The prevalence of hypercholesterolemia was 11.2%, 23.5%, 14.7%, 28.5% and the prevalence of hyperglycemia was 9.7%, 22.6%, 18.5%, and 27.0%, respectively. The prevalence of hypertension was 6.9%, 13.1%, 14.7%, and 20.6%. For various metabolic abnormalities, OBCO have the highest risks compared with NW (hyperuricemia: adjusted OR (aOR)= 2.60; hypertriglyceridemia: aOR= 3.19; hypercholesterolemia: aOR= 1.48; hyper LDLemia: aOR= 2.21; hypo HDLemia: aOR= 1.42; hyperglycemia: aOR= 1.95; hypertension: aOR= 2.16). The risk of hyper LDLemia, hypercholesterolemia and hyperglycemia in the NWCO group was higher than that in the OB group (hyperLDLemia: aOR: 1.69 vs 0.97; hypercholesterolemia: aOR: 1.27 vs 1.24; hyperglycemia: aOR: 1.62 vs 1.28).

CONCLUSION

Different phenotypes of obesity are significantly associated with metabolic abnormalities. NWCO is more closely associated with hypercholesterolemia, hyperglycemia and hyper LDLemia. General obesity and central obesity have a synergistic effect on the diseases.

Role of ceramide-to-dihydroceramide ratios for insulin resistance and non-alcoholic fatty liver disease in humans

INTRODUCTION

Sphingolipid accumulation has been linked to obesity, type 2 diabetes and non-alcoholic fatty liver disease (NAFLD). A recent study showed that depletion of dihydroceramide desaturase-1 (DES-1) in adipose and/or liver tissue decreases ceramide-to-dihydroceramide ratios (ceramide/dihydroceramide) in several tissues and improves the metabolic profile in mice. We tested the hypothesis that ceramide/dihydroceramide would also be elevated and relate positively to liver fat content and insulin resistance in humans.

RESEARCH DESIGN AND METHODS

Thus, we assessed total and specific ceramide/dihydroceramide in various biosamples of 7 lean and 21 obese volunteers without or with different NAFLD stages, who were eligible for abdominal or bariatric surgery, respectively. Biosamples were obtained from serum, liver, rectus abdominis muscle as well as subcutaneous abdominal and visceral adipose tissue during surgery.

RESULTS

Surprisingly, certain serum and liver ceramide/dihydroceramide ratios were reduced in both obesity and non-alcoholic steatohepatitis (NASH) and related inversely to liver fat content. Specifically, hepatic ceramide/dihydroceramide (species 16:0) related negatively to hepatic mitochondrial capacity and lipid peroxidation. In visceral adipose tissue, ceramide/dihydroceramide (species 16:0) associated positively with markers of inflammation.

CONCLUSION

These results failed to confirm the relationships of ceramide/dihydroceramide in humans with different degree of insulin resistance. However, the low hepatic ceramide/dihydroceramide favor a role for dihydroceramide accumulation in NASH, while a specific ceramide/dihydroceramide ratio in visceral adipose tissue suggests a role of ceramides in obesity-associated low-grade inflammation.

Estimating narrow-sense heritability using family data from admixed populations

Estimating total narrow-sense heritability in admixed populations remains an open question. In this work, we used extensive simulations to evaluate existing linear mixed-model frameworks for estimating total narrow-sense heritability in two population-based cohorts from Greenland, and compared the results with data from unadmixed individuals from Denmark. When our analysis focused on Greenlandic sib pairs, and under the assumption that shared environment among siblings has a negligible effect, the model with two relationship matrices, one capturing identity by descent and one capturing identity by state, returned heritability estimates close to the true simulated value, while using each of the two matrices alone led to downward biases. When phenotypes correlated with ancestry, heritability estimates were inflated. Based on these observations, we propose a PCA-based adjustment that recovers the true simulated heritability. We use this knowledge to estimate the heritability of ten quantitative traits from the two Greenlandic cohorts, and report differences such as lower heritability for height in Greenlanders compared with Europeans. In conclusion, narrow-sense heritability in admixed populations is best estimated when using a mixture of genetic relationship matrices on individuals with at least one first-degree relative included in the sample.

Waist circumference is associated with major adverse cardiovascular events in male but not female patients with type-2 diabetes mellitus

BACKGROUND

Although studies have shown that waist circumference (WC) is positively associated with an increased risk of cardiovascular diseases among the normal population, few studies have investigated WC in patients with type-2 diabetes mellitus (T2DM).

METHODS

This was a post hoc analysis of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study. The Cox proportional hazards models was used to investigate the relationship between WC and major adverse cardiovascular events (MACEs) in T2DM patients with cardiovascular disease (CVD) or high risk factors of CVD.

RESULTS

A total of 10,251 T2DM patients (6299 men [61.4%], 3952 women [38.6%]) were included in our analysis. The mean age was 64.0 ± 7.53 years. After a mean follow-up at 9.2 ± 2.4 years later, 1804 patients (event rate of 23 per 1000 person-years) had developed MACEs. MACEs rates in men and women were 18.0 and 26.0 events per 1000 person-years, respectively. After multivariable adjustment, each increase in WC of 1 SD increased the risk of MACEs (HR: 1.10, 95% CI 1.04-1.17; P < 0.01) in men, with a non-significant increase in MACEs (HR: 1.04, 95% CI 0.95-1.13; P = 0.40) in women. Compared with those in the first quartile of WC, male patients in the fourth quartile of WC had a hazard ratio (HR) of 1.24 (95% CI 1.05-1.46) for MACEs; female patients in the fourth quartile of WC had an HR of 1.22 (95% CI 0.96-1.56) for MACEs.

CONCLUSIONS

Higher WC is associated with increased risks of MACEs in male but not female T2DM patients. Trial registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000620).

Obesity, Hypertension, and Type-2 Diabetes Mellitus: The Interrelationships and the Determinants among Adults in Gaza City, Palestine

OBJECTIVES

To describe the distribution of social factors, lifestyle habits and anthropometric measurements according to hypertension and Type-2 diabetes.

METHODS

A cross-sectional study was conducted in Gaza City, Palestine that included 379 patients (20-60 years) who had hypertension and/or diabetes. Three groups of patients were involved; 106 hypertensive (HT), 109 diabetic (T2DM) and 164 hypertensive diabetics (HT + T2DM).

RESULTS

The HT + T2DM group were older and had a higher body mass index compared to HT and T2DM groups. There were 62.3% patients who were female, 49.2% were highly educated HT patients, and 49.3% patients had a low level of education and were HT + T2DM. There were 55.8% patients who lived in large families. Patients who were passive smokers or never smoked before were mostly HT + T2DM, while active smokers and past smokers had T2DM. There were 48.2% patients who were highly physically active who had HT, 40.9% whom were moderately active had T2DM, and 53.8% of patients who had a low level of activity were HT + T2DM. Multivariate linear regression showed that having a diseased mother, living in a large family, being a past or passive smoker, or never having smoked, having a low or moderate level of activity, and having HT or HT + T2DM, were significantly associated with an increased body mass index.

CONCLUSION

Parental health/disease conditions and environmental factors (social network and lifestyle habits) played the greatest role in the development of obesity and disease.

Opposite Genetic Effects of CMIP Polymorphisms on the Risk of Type 2 Diabetes and Obesity: A Family-Based Study in China

C-Maf Inducing Protein (CMIP) gene polymorphisms were reported to be associated with type 2 diabetes mellitus (T2DM). Whether the association between CMIP and T2DM is mediated via obesity-related phenotypes is still unclear. We analyzed the association of CMIP rs2925979 with T2DM and a comprehensive set of obesity-related phenotypes in 1576 families ascertained from a Chinese population. These families included a total of 3444 siblings (1582 with T2DM, 963 with prediabetes, and 899 with a normal glucose level). Using multi-level mixed effects regression models, we found that each copy of CMIP rs2925979_T allele was associated with a 29% higher risk of T2DM in females (p = 9.30 × 10^-4), while it was not significantly associated with T2DM in males (p = 0.705). Meanwhile, rs2925979_T allele was associated with lower levels of body mass index (BMI), waist circumference (WC), hip circumference (HC), percentage of body fat (PBF), PBF of arms, PBF of legs, and PBF of trunk in nondiabetes females (all p < 0.05). The opposite associations of rs2925979_T allele with T2DM and obesity-related phenotypes suggest that CMIP may exert independent pleiotropic effects on T2DM and obesity-related phenotypes in females.

Pleiotropy of cardiometabolic syndrome with obesity-related anthropometric traits determined using empirically derived kinships from the Busselton Health Study

Over two billion adults are overweight or obese and therefore at an increased risk of cardiometabolic syndrome (CMS). Obesity-related anthropometric traits genetically correlated with CMS may provide insight into CMS aetiology. The aim of this study was to utilise an empirically derived genetic relatedness matrix to calculate heritabilities and genetic correlations between CMS and anthropometric traits to determine whether they share genetic risk factors (pleiotropy). We used genome-wide single nucleotide polymorphism (SNP) data on 4671 Busselton Health Study participants. Exploiting both known and unknown relatedness, empirical kinship probabilities were estimated using these SNP data. General linear mixed models implemented in SOLAR were used to estimate narrow-sense heritabilities (h ²) and genetic correlations (r _g) between 15 anthropometric and 9 CMS traits. Anthropometric traits were adjusted by body mass index (BMI) to determine whether the observed genetic correlation was independent of obesity. After adjustment for multiple testing, all CMS and anthropometric traits were significantly heritable (h ² range 0.18-0.57). We identified 50 significant genetic correlations (r _g range: - 0.37 to 0.75) between CMS and anthropometric traits. Five genetic correlations remained significant after adjustment for BMI [high density lipoprotein cholesterol (HDL-C) and waist-hip ratio; triglycerides and waist-hip ratio; triglycerides and waist-height ratio; non-HDL-C and waist-height ratio; insulin and iliac skinfold thickness]. This study provides evidence for the presence of potentially pleiotropic genes that affect both anthropometric and CMS traits, independently of obesity.

Diet quality and its relationship with central obesity among Mexican Americans: findings from National Health and Nutrition Examination Survey (NHANES) 1999-2012

OBJECTIVE

Using the Healthy Eating Index-2010 (HEI-2010), the present study aimed to examine diet quality and the impact of overall diet quality and its components on central obesity among Mexican-American men and women.

DESIGN

Cross-sectional data from NHANES 1999-2012 were used. The HEI-2010 data, including twelve components for a total score of 100, were collected with a 24 h recall interview. Central obesity was defined as a waist circumference of ≥88 cm for women and ≥102 cm for men. Weighted logistic regressions were performed to assess associations between HEI-2010 scores and central obesity.

SETTING

National Health and Nutrition Examination Survey (NHANES) 1999-2012.

SUBJECTS

A total of 6847 Mexican Americans aged ≥20 years with reliable dietary recall status and non-pregnancy status.

RESULTS

Higher HEI-2010 total score was associated with lower odds of central obesity in Mexican-American men (OR; 95 % CI=0·98; 0·98, 1·00). Among all Mexican Americans, one-unit higher score of total fruit and sodium (i.e. lower level of intake) was associated with 4 % (0·96; 0·93, 0·99) and 2 % (0·98; 0·96, 0·99) lower odds of central obesity, respectively. However, a higher total proteins score was associated with higher odds of central obesity (1·08; 1·00, 1·16). In gender-specific analyses, a higher whole fruit or sodium score was inversely associated with central obesity in men but not in women.

CONCLUSIONS

HEI-2010 scores of total fruit and sodium were inversely associated with central obesity among all Mexican Americans. However, total proteins score and central obesity was positively associated. In Mexican-American men, HEI-2010 total and whole fruit scores were inversely associated with central obesity.

Novel epigenetic determinants of type 2 diabetes in Mexican-American families

Although DNA methylation is now recognized as an important mediator of complex diseases, the extent to which the genetic basis of such diseases is accounted for by DNA methylation is unknown. In the setting of large, extended families representing a minority, high-risk population of the USA, we aimed to characterize the role of epigenome-wide DNA methylation in type 2 diabetes (T2D). Using Illumina HumanMethylation450 BeadChip arrays, we tested for association of DNA methylation at 446 356 sites with age, sex and phenotypic traits related to T2D in 850 pedigreed Mexican-American individuals. Robust statistical analyses showed that (i) 15% of the methylome is significantly heritable, with a median heritability of 0.14; (ii) DNA methylation at 14% of CpG sites is associated with nearby sequence variants; (iii) 22% and 3% of the autosomal CpG sites are associated with age and sex, respectively; (iv) 53 CpG sites were significantly associated with liability to T2D, fasting blood glucose and insulin resistance; (v) DNA methylation levels at five CpG sites, mapping to three well-characterized genes (TXNIP, ABCG1 and SAMD12) independently explained 7.8% of the heritability of T2D (vi) methylation at these five sites was unlikely to be influenced by neighboring DNA sequence variation. Our study has identified novel epigenetic indicators of T2D risk in Mexican Americans who have increased risk for this disease. These results provide new insights into potential treatment targets of T2D.