Association of adiponectin gene polymorphisms with type 2 diabetes in an African American population enriched for nephropathy

Current Data and New Insights into the Genetic Factors of Atherogenic Dyslipidemia Associated with Metabolic Syndrome

Atherogenic dyslipidemia plays a critical role in the development of metabolic syndrome (MetS), being one of its major components, along with central obesity, insulin resistance, and hypertension. In recent years, the development of molecular genetics techniques and extended analysis at the genome or exome level has led to important progress in the identification of genetic factors (heritability) involved in lipid metabolism disorders associated with MetS. In this review, we have proposed to present the current knowledge related to the genetic etiology of atherogenic dyslipidemia, but also possible challenges for future studies. Data from the literature provided by candidate gene-based association studies or extended studies, such as genome-wide association studies (GWAS) and whole exome sequencing (WES,) have revealed that atherogenic dyslipidemia presents a marked genetic heterogeneity (monogenic or complex, multifactorial). Despite sustained efforts, many of the genetic factors still remain unidentified (missing heritability). In the future, the identification of new genes and the molecular mechanisms by which they intervene in lipid disorders will allow the development of innovative therapies that act on specific targets. In addition, the use of polygenic risk scores (PRS) or specific biomarkers to identify individuals at increased risk of atherogenic dyslipidemia and/or other components of MetS will allow effective preventive measures and personalized therapy.

Adiponectin gene polymorphisms associated with diabetes mellitus: A descriptive review

Diabetes is currently a growing concern of the age. Prevention and treatment of diabetes is a global health priority. Adiponectin is an adipocyte derived protein hormone that enhances insulin sensitivity and ameliorates diabetes by enhancing fatty acid oxidation and glucose uptake in skeletal muscle and reducing glucose production in the liver. Low serum adiponectin concentrations are associated with diabetes, central obesity, insulin resistance and metabolic syndrome. Adiponectin gene is located on chromosome 3q27, where a locus of susceptibility to diabetes was mapped. Several cross-sectional studies showed that single nucleotide polymorphisms (SNPs) in adiponectin gene (ADIPOQ) were associated with diabetes. SNPs in ADIPOQ help in assessing the association of common variants with levels of adiponectin and the risk of diabetes. Two common SNPs, rs2241766 and rs1501299, have been linked significantly to type 1 diabetes mellitus which endow the world with a block of haplotypes. Experimental evidences also suggest that rs1501299, rs2241766, rs266729, rs17366743, rs17300539, rs182052, rs822396, rs17846866, rs3774261 and rs822393 are significantly associated with type 2 diabetes mellitus which is the predominant form of the disease. In addition, rs2241766 and rs266729 are extensively associated with gestational diabetes, a condition that develops in women during pregnancy. Therefore not a particular single mutation but a number of SNPs in adiponectin gene could be a risk factor for developing diabetes among the individuals worldwide. This study firmly suggests that adiponectin plays a crucial role in the pathogenesis of type 1, type 2 and gestational diabetes mellitus.

No Association Between ADIPOQ or MTHFR Polymorphisms and Gestational Diabetes Mellitus in South African Women

PURPOSE

Gestational diabetes mellitus (GDM) is a growing public health concern. GDM affects approximately 14% of pregnancies globally, and without effective treatment, is associated with short- and long-term complications in mother and child. Lower serum adiponectin (ADIPOQ) concentrations and aberrant DNA methylation have been reported during GDM. The aim of this study was to investigate the association between the ADIPOQ -11377C>G and -11391G>A, and methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphisms and GDM in a population of black South African women.

MATERIALS AND METHODS

DNA was isolated from the peripheral blood of 447 pregnant women with (n=116) or without (n=331) GDM, where after ADIPOQ (rs266729 and rs17300539) and MTHFR (rs1801133) polymorphisms were genotyped using TaqMan Quantitative Real-Time PCR analysis.

RESULTS

Women with GDM had a higher body mass index (p=0.012), were more insulin resistant (p<0.001) and had lower adiponectin levels (p=0.013) compared to pregnant women with normoglycemia. Genotypic, dominant and recessive genetic models showed no association between ADIPOQ rs266729 and rs17300539 and MTHFR rs1801133 polymorphisms and GDM. Intriguingly, the risk G allele of ADIPOQ rs266729 was associated with higher fasting glucose and insulin concentrations, while the T allele in MTHFR rs1801133 was associated with higher fasting insulin concentrations only.

CONCLUSION

ADIPOQ rs266729 and rs17300539 and MTHFR rs1801133 polymorphisms are not associated with GDM in a population of black South African women. These findings suggest that these single nucleotide polymorphisms (SNPs) do not individually increase GDM risk in the African population. However, the role of these SNPs in possible gene-gene or gene-environment interactions remain to be established.

The Role Of Adiponectin, TNF-α And Glutathione In The Pathogenesis And Evolution Of Type 1 Diabetes

INTRODUCTION

Type 1 diabetes (T1DM) is a chronic autoimmune or idiopathic condition, featuring complex and unique interactions between proteins and enzyme systems. The purpose of the present study is to investigate the role of AdipoQ +276G>T, TNF-α-308G>A, GSTT1/GSTM1 polymorphic variants in the development of T1DM.

MATERIALS AND METHODS

The study is designed as a cross-sectional study, involving 72 diabetic cases and 90 controls. Genotyping was carried out according to specific protocols for the above-mentioned polymorphic variants.

RESULTS

The G allele of AdipoQ was associated with the development of type 1 diabetes (OR 0.577, CI95% 0.336-0.802, p=0.001), similar to the GG and GA genotypes (OR 0.405, CI95% 0.156-0.654, p=0.001 and OR 0.623, CI95% 0.401-0.855, p=0.004). The G allele of TNF-α was marginally associated with the development of type 1 diabetes (OR 0.789, CI95% 0.579-0.956, p=0.005). The presence of the T1 genotype was a strong predictor for type 1 diabetes (OR 3.4, CI95% 1.433-6.243, p<0.001).

CONCLUSION

The results of our study suggest that G alleles of AdipoQ and TNFα act as a protective factor in T1DM, while the T1 allele for GST could be considered a risk factor for the development of Type 1 diabetes in our study group.

Association Between Interleukin-10 Gene (-1082g/A) Polymorphism and Type 2 Diabetes, Diabetes-Related Traits, and Microvascular Complications in the Croatian Population

Interleukin (IL)-10 is an anti-inflammatory cytokine, and a decrease in its secretion is associated with obesity, metabolic syndrome and type 2 diabetes. However, it has not been established whether the intensity of the immune response during diabetes-associated chronic inflammation affects the development and/or progression of type 2 diabetes and its microvascular complications. The aim of this study was to investigate the role of single nucleotide polymorphism (SNP)-1082G/A for IL-10 gene in development of diabetes type 2 and its complications. DNA was extracted from blood cells of 240 overweight/obese subjects for IL-10 genotyping. Based on the presence of diabetes type 2, patients were divided in two groups: experimental group of 144 patients with diabetes type 2 and control group of 96 age- and gender-matched subjects without diabetes. Compared to control group, diabetic group had higher levels of leukocytes (p=0.012), fibrinogen (p=0.049) and plasminogen activator inhibitor-1 (PAI-1) (p=0.009), and lower levels of albumin (p=0.001). There were no differences in the frequency of SNP-1082G/A for IL-10 gene between the two groups (p=0.654). When considering diabetes related traits in all subjects in relation to specific genotype, a group with homozygous (AA) genotype had higher values of the mean fasting glucose (p<0.000001), HbA1c (p<0.000001) and HOMA-IR (p=0.003632), while the mean HOMA-B value (p=0.000178) was lower when compared to the groups with GG and GA genotypes. There was no difference in devel-opment of diabetic nephropathy, retinopathy and polyneuropathy between the IL-10 polymorphism genotypes. In conclusion, obese diabetes type 2 patients had an increased inflammation activity com-pared to obese non-diabetic individuals. There was no association of the investigated polymorphisms and development of type 2 diabetes and its microvascular complications. However, diabetes related traits clearly depended on the presence of specific IL-10 genotype.

Polymorphisms FTO rs9939609, PPARG rs1801282 and ADIPOQ rs4632532 and rs182052 but not lifestyle are associated with obesity related-traits in Mexican children

Concerning the genetic factors of obesity, no consistent association between populations has been reported, which may be due to the frequency of polymorphisms, the lifestyle of studied populations and its interaction with other factors. We studied a possible association of polymorphisms FTO rs9939609, PPARG rs1801282, and ADIPOQ rs4632532 and rs182052 with obesity phenotypes in 215 Mexican children. Glucose, triglycerides, cholesterol, HDL and LDL were measured. In addition, weight, height, waist circumference and triceps skin thickness were recorded. High-energy diets and sedentary behavior were evaluated with a validated questionnaire. In contrast with other reports, only FTO rs9939609 was associated with obesity related-traits, including BMI (p = 0.03), waist circumference (p = 0.02), triceps skinfold (p = 0.03) and waist/height ratio (p = 0.01), and also with cholesterol levels (p = 0.02) and LDL (p = 0.009). Lower levels of triglycerides (p=0.04) were related with presence of PPARG rs1801282, while ADIPOQ rs4632532 showed an effect on HDL (p = 0.03) levels. On the other hand, diet, physical activity and screen time were not related with obesity. In summary, only FTO rs9939609 was associated with obesity related-traits, while PPARG2 rs1801282 and ADIPOQ rs4632532 were involved in lipid metabolism.

Gender Differences in Adipocyte Metabolism and Liver Cancer Progression

Liver cancer is the third most common cancer type and the second leading cause of deaths in men. Large population studies have demonstrated remarkable gender disparities in the incidence and the cumulative risk of liver cancer. A number of emerging risk factors regarding metabolic alterations associated with obesity, diabetes and dyslipidemia have been ascribed to the progression of non-alcoholic fatty liver diseases (NAFLD) and ultimately liver cancer. The deregulation of fat metabolism derived from excessive insulin, glucose, and lipid promotes cancer-causing inflammatory signaling and oxidative stress, which eventually triggers the uncontrolled hepatocellular proliferation. This review presents the current standing on the gender differences in body fat compositions and their mechanistic linkage with the development of NAFLD-related liver cancer, with an emphasis on genetic, epigenetic and microRNA control. The potential roles of sex hormones in instructing adipocyte metabolic programs may help unravel the mechanisms underlying gender dimorphism in liver cancer and identify the metabolic targets for disease management.

Association of ADIPOQ gene with type 2 diabetes and related phenotypes in African American men and women: the Jackson Heart Study

BACKGROUND

African Americans experience disproportionately higher prevalence of type 2 diabetes and related risk factors. Little research has been done on the association of ADIPOQ gene on type 2 diabetes, plasma adiponectin, blood glucose, HOMA-IR and body mass index (BMI) in African Americans. The objective of our research was to assess such associations with selected SNPs. The study included a sample of 3,020 men and women from the Jackson Heart Study who had ADIPOQ genotyping information. Unadjusted and adjusted regression models with covariates were used with type 2 diabetes and related phenotypes as the outcome stratified by sex.

RESULTS

There was no association between selected ADIPOQ SNPs with type 2 diabetes, blood glucose, or BMI in men or women. There was a significant association between variant rs16861205 and lower adiponectin in women with minor allele A in the fully adjusted model (β(SE) p = -.13(0.05), 0.003). There was also a significant association with variant rs7627128 and lower HOMA-IR among men with minor allele A in the fully adjusted model (β(SE) p = -0.74(0.20), 0.0002).

CONCLUSIONS

These findings represent new insights regarding the association of ADIPOQ gene and type 2 diabetes and related phenotypes in African American men and women.

Gender-specific associations between ADIPOQ gene polymorphisms and adiponectin levels and obesity in the Jackson Heart Study cohort

BACKGROUND

Despite the important role of adiponectin in regulating general metabolic homeostasis, analysis of genetic determinants of adiponectin and the related cardio-metabolic traits in African American population has been limited and inconsistent. Considering the high genetic admixture of African Americans and thus the important population stratification that may confound the genetic-trait associations, the objective of this work was to perform a comprehensive analysis of the associations between ADIPOQ variants and adiponectin levels and obesity phenotypes in a large African American population from the Jackson Heart Study (JHS) cohort.

METHODS

Genotype data was available for 2968 JHS participants (1131men; 1837women). Single Nucleotide Polymorphisms (SNPs) were selected by a Tag-SNP Approach and literature review. The genotype imputation was performed using IMPUTE2 software and reference phased data from the 1000G project. PLINK software was used for the genetic analysis. Plasma specimens were analyzed by ELISA for adiponectin levels. All analyses were controlled for population stratification assessed by Individual Proportions of European Ancestry (PEA) estimates calculated in HAPMIX using ancestry informative markers (AIMs).

RESULTS

We found a gender-dependent association of some ADIPOQ variants and adiponectin levels. In women four of the studied polymorphisms (rs6444174, rs16861205, rs1403697, rs7641507) were associated with adiponectin levels after Bonferroni correction and controlling for the percentage of PEA, age, annual household income and smoking. These results were consistent with the haplotype analysis. The association between the rs12495941 variant and obesity is modulated by the PEA, so that the relationship between the G allele and a higher incidence of obesity was present in those individuals within the lower PEA group. In addition we found an effect modification of obesity on the association between the ADIPOQ rs6444174 SNP and BMI so that the presence of the T allele was negatively and significantly associated with BMI only in participants with a normal weight.

CONCLUSIONS

In this large African American cohort, ADIPOQ variants were associated with adiponectin levels in a gender-dependent manner and the relationship of some of these variants with obesity and BMI was modulated by the PEA and obesity status respectively. This suggests that the effects of these polymorphisms on adiponectin and obesity phenotypes are subject to a strong interaction with genetic and environmental factors in African American population.

Renal Disease Risk Factors Among Risk Groups Comprised of African American Women With Type 2 Diabetes: A Secondary Analysis

PURPOSE

The purpose of this study was to explore and describe the prevalence of renal disease risk factors and the categorization of renal disease risk groups among African American women with type 2 diabetes mellitus (T2DM) who participated in a self-management and coping skills training intervention. We also explored and described the change in renal disease risk factors within and between risk groups, determining if participation in a culturally relevant coping skills training intervention decreased renal disease risk.

METHODS

This study was a secondary analysis of data from a longitudinal intervention study and included all 109 African American women with T2DM from the primary intervention study. This study examined the prevalence of 4 renal disease risk factors among the women at baseline via descriptive statistics, used cluster analysis to divide the women into risk groups and categorize the risk groups, and also measured the change in risk factors over time among risk groups via mixed modeling.

RESULTS

A majority of the women had a hemoglobin A1C ≥7% (62.39%) and were obese (75.93%). The high-risk cluster displayed clinically significant declines in mean systolic blood pressure, triglycerides, and A1C in both the control and intervention groups, and the intervention was more effective in reducing triglycerides and A1C levels among high-risk participants than low-risk. Overall, the control, high-risk group exhibited the largest declines in systolic blood pressure, triglycerides, and A1C.

CONCLUSIONS

This study displays the importance of acknowledging African American women with type 2 diabetes mellitus (T2DM) at high risk for renal disease in health care settings, which is often overlooked, and realizing that renal disease risk reduction is obtainable.

Association of genetic variants with diabetic nephropathy

Diabetic nephropathy accounts for the most serious microvascular complication of diabetes mellitus. It is suggested that the prevalence of diabetic nephropathy will continue to increase in future posing a major challenge to the healthcare system resulting in increased morbidity and mortality. It occurs as a result of interaction between both genetic and environmental factors in individuals with both type 1 and type 2 diabetes. Genetic susceptibility has been proposed as an important factor for the development and progression of diabetic nephropathy, and various research efforts are being executed worldwide to identify the susceptibility gene for diabetic nephropathy. Numerous single nucleotide polymorphisms have been found in various genes giving rise to various gene variants which have been found to play a major role in genetic susceptibility to diabetic nephropathy. The risk of developing diabetic nephropathy is increased several times by inheriting risk alleles at susceptibility loci of various genes like ACE, IL, TNF-α, COL4A1, eNOS, SOD2, APOE, GLUT, etc. The identification of these genetic variants at a biomarker level could thus, allow the detection of those individuals at high risk for diabetic nephropathy which could thus help in the treatment, diagnosis and early prevention of the disease. The present review discusses about the various gene variants found till date to be associated with diabetic nephropathy.

Adiponectin gene (ADIPOQ) polymorphisms correlate with the progression of nephropathy in Taiwanese male patients with type 2 diabetes

AIMS

Polymorphisms of the ADIPOQ gene were associated with diabetic nephropathy (DN) in case-control studies predominantly among European populations. Gender may modify the ADIPOQ associated risk for DN. We investigated the association of 18 ADIPOQ polymorphisms with DN in a prospective Taiwanese cohort of type 2 diabetes (T2D) and explored whether gender plays a role in this genetic association.

METHODS

Selected single nucleotide polymorphisms (SNPs) of ADIPOQ were genotyped in 566 T2D patients with normoalbuminuria at baseline. DN was defined based on urinary albumin-to-creatinine ratio (ACR). The Cox proportional hazard model was used to explore the association of individual SNP to DN events under different genetic models over a 6-year follow-up period. Analyses were further stratified by gender.

RESULTS

In male patients, the adjusted hazard ratios under the recessive models were 1.81 for rs2241766 TT (vs. GT+GG, 95% CI=1.10-2.96, p=0.019) and 1.89 for rs1063537 CC (vs. CT+TT, 95% CI=1.15-3.11, p=0.013). In the Kaplan-Meier survival curve, males carrying rs2241766 TT (vs. GT+GG, p=0.050) and rs1063537 CC (vs. CT+TT, p=0.037) recessive homozygotes also had a reduced nephropathy-free survival rate. SNPs rs2241767 and rs2082940, both in strong correlation with tag SNP rs1063537 (r(2)≥ 0.96), were also associated with DN progression in males. In females, ADIPOQ polymorphisms were not associated with the progression of DN.

CONCLUSIONS

ADIPOQ genetic polymorphisms rs2241766 (+45T>G), rs1063537, rs2241767 and rs2082940 were correlated with the progression of DN in Taiwanese male patients with T2D. The role of gender in this ADIPOQ genetic association needs to be further investigated in other populations.

Transdisciplinary approach to restore pancreatic islet function

The focus of our research is on islet immunobiology. We are exploring novel strategies that could be of assistance in the treatment and prevention of type 1 diabetes, as well as in the restoration of metabolic control via transplantation of insulin producing cells (i.e., islet cells). The multiple facets of diabetes and β-cell replacement encompass different complementary disciplines, such as immunology, cell biology, pharmacology, and bioengineering, among others. Through their interaction and integration, a transdisciplinary dimension is needed in order to address and overcome all aspects of the complex puzzle toward a successful clinical translation of a biological cure for diabetes.

Adiponectin gene variants, adiponectin isoforms and cardiometabolic risk in type 2 diabetic patients

AIMS/INTRODUCTION

The aim of the present study was to examine the associations of rs2241766 (+45T>G), rs1501299 (+276G>T), rs17300539 (-11391G>A) and rs182052 (-10069G>A) in the adiponectin (Ad) gene with adiponectin concentrations, and concomitantly the association of these variants with cardiometabolic risk in type 2 diabetic patients of African ancestry.

MATERIALS AND METHODS

A cross-sectional study of 200 patients was carried out. Concentrations of total, high (HMW), middle (MMW) and low (LMW) molecular weight adiponectin isoforms were measured. The four polymorphisms were genotyped.

RESULTS

Decreased values were noted for total Ad in overweight, dyslipidemia and coronary artery disease (CAD), for HMW in overweight and dyslipidemia, for MMW in CAD, for LMW in dyslipidemia and CAD, for the percentage HMW/total in overweight, and for MMW:HMW ratio in patients without hypertriglyceridemic waist (HTGW). Significant associations were noted between total Ad, HMW, and HMW/total Ad and rs182052 under a dominant model (P = 0.04, P = 0.03 and P = 0.04, respectively), and between MMW and rs17300539 (P = 0.006). No significant difference in adiponectin concentrations was noted according to rs2241766 and rs1501299 genotypes. Patients carrying the rs2241766 G allele (TG+GG) had an increased risk of HTGW (odds ratio [OR] 3.1; P = 0.04) and of CAD (OR 3.3; P = 0.01). The odds of having low total adiponectin concentrations (<25th percentile: 3.49 ng/mL) for carrying the rs182052A allele (AA+GA) was: OR 0.40; P = 0.009. The single-nucleotide polymorphism associated with adiponectin levels was not concomitantly associated with cardiometabolic risk factors.

CONCLUSIONS

Adiponectin concentrations and ADIPOQ variants are implicated in the pathophysiological process leading to cardiovascular diseases, but the genetic effects seem to be independent of adiponectin concentrations in our Afro-Caribbean diabetic patients.

Adiponectin gene polymorphisms in Egyptian type 2 diabetes mellitus patients with and without diabetic nephropathy

Recently, several reports addressed the associations of adiponectin (ADIPOQ) gene polymorphisms with abnormal adiponectin serum levels, type 2 diabetes mellitus (T2DM), and diabetic nephropathy (DN); however, results are inconsistent. This study aimed to investigate the possible association of ADIPOQ gene polymorphisms with T2DM and/or DN and whether they affect serum adiponectin levels in Egyptian population. Two hundred and ninety-six T2DM patients (100 normoalbuminuric patients, 103 microalbuminuric patients, and 93 macroalbuminuric patients) and 209 controls were enrolled in the present study. Polymorphisms of +45, -11391, and +276 of the ADIPOQ gene were detected using polymerase chain reaction restriction fragment length polymorphism. Serum adiponectin was measured using ELISA. Our results revealed that ADIPOQ +45 TG and GG genotypes and G allele were significantly associated with T2DM, micro/macroalbuminuria, and decreased serum adiponectin level. ADIPOQ -11391 AA genotype frequency was significantly increased in T2DM group. Moreover, GA and AA genotypes and A allele of ADIPOQ -11391 were significantly associated with susceptibility to macroalbuminuria despite increased serum adiponectin concentrations. While, ADIPOQ +276 TT genotype and T allele were protective factors regarding the susceptibility to T2DM and micro/macroalbuminuria, and they were significantly associated with increased adiponectin levels. We observed also that the decrease of the serum Adiponectin level was accompanied by an insulin resistance, albuminuria, as well as an increase of serum creatinine. We concluded that ADIPOQ +45; ADIPOQ -11391 gene polymorphisms are associated with T2DM and/or DN in Egyptian population. While, ADIPOQ +276 gene polymorphism is a protective factor regarding T2DM and/or DN susceptibility.

Adiponectin gene polymorphisms and susceptibility to diabetic nephropathy: a meta-analysis

Adiponectin (ADIPOQ) plays an important role in the pathogenesis of diabetic nephropathy (DN) and previous studies regarding the association between ADIPOQ polymorphisms and DN risk reported conflicting results. To derive a more precise estimation of this association, we performed a meta-analysis to assess the association between four ADIPOQ polymorphisms [-11391G > A (rs17300539), -11377C > G (rs266729), +45T > G (rs2241766), and +276G > T (rs1501299)] and risk for DN. Odds ratios (ORs) with corresponding 95% confidence intervals (95% CIs) were pooled to assess the association between four aforementioned polymorphisms and susceptibility to DN. Based on the included criteria, we selected 13 articles, among which 7 studies (cases/controls: 2749/7585) for -11391G > A, 8 studies for -11377C > G (3074/3842), 9 studies for +45T > G (2654/7710), and 10 studies for +276G > T (2812/7821), respectively. Our meta-analysis indicated no evidence heterogeneity among the included studies; thus, the fixed-effects model was used. Overall, there was an association between ADIPOQ -11391A allele with increased DN risk (OR = 1.186, 95% CI: 1.051-1.338, p = 0.006). Subgroup by ethnicity suggested significant association between +45T > G polymorphism and DN risk among Caucasians (OR = 1.122, 95% CI: 1.007-1.250, p = 0.038). Sensitivity analysis suggested exclusion of any single study did not materially alter the overall pooled ORs above. Future studies are needed to validate these findings.

Mendelian randomization studies do not support a causal role for reduced circulating adiponectin levels in insulin resistance and type 2 diabetes

Adiponectin is strongly inversely associated with insulin resistance and type 2 diabetes, but its causal role remains controversial. We used a Mendelian randomization approach to test the hypothesis that adiponectin causally influences insulin resistance and type 2 diabetes. We used genetic variants at the ADIPOQ gene as instruments to calculate a regression slope between adiponectin levels and metabolic traits (up to 31,000 individuals) and a combination of instrumental variables and summary statistics-based genetic risk scores to test the associations with gold-standard measures of insulin sensitivity (2,969 individuals) and type 2 diabetes (15,960 case subjects and 64,731 control subjects). In conventional regression analyses, a 1-SD decrease in adiponectin levels was correlated with a 0.31-SD (95% CI 0.26-0.35) increase in fasting insulin, a 0.34-SD (0.30-0.38) decrease in insulin sensitivity, and a type 2 diabetes odds ratio (OR) of 1.75 (1.47-2.13). The instrumental variable analysis revealed no evidence of a causal association between genetically lower circulating adiponectin and higher fasting insulin (0.02 SD; 95% CI -0.07 to 0.11; N = 29,771), nominal evidence of a causal relationship with lower insulin sensitivity (-0.20 SD; 95% CI -0.38 to -0.02; N = 1,860), and no evidence of a relationship with type 2 diabetes (OR 0.94; 95% CI 0.75-1.19; N = 2,777 case subjects and 13,011 control subjects). Using the ADIPOQ summary statistics genetic risk scores, we found no evidence of an association between adiponectin-lowering alleles and insulin sensitivity (effect per weighted adiponectin-lowering allele: -0.03 SD; 95% CI -0.07 to 0.01; N = 2,969) or type 2 diabetes (OR per weighted adiponectin-lowering allele: 0.99; 95% CI 0.95-1.04; 15,960 case subjects vs. 64,731 control subjects). These results do not provide any consistent evidence that interventions aimed at increasing adiponectin levels will improve insulin sensitivity or risk of type 2 diabetes.

Association of adiponectin promoter variants with traits and clusters of metabolic syndrome in Arabs: family-based study

Plasma levels of adiponectin are decreased in type 2 diabetes, obesity and hypertension. Our aim was to use a family-based analysis to identify the genetic variants of the adiponectin (ADIPOQ) gene that are associated with obesity, insulin resistance, dyslipidemia and hypertension, among Arabs. We screened 328 Arabs in one large extended family for single nucleotide polymorphisms (SNPs) in the promoter region of the ADIPOQ gene. Two common SNPs were detected: rs17300539 and rs266729. Evidences of association between traits related to the metabolic syndrome and the SNPs were studied by implementing quantitative genetic association analysis. Results showed that SNP rs266729 was significantly associated with body weight (p-value=0.001), waist circumference (p-value=0.037), BMI (p-value=0.015) and percentage of total body fat (p-value=0.003). Up to 4.1% of heritability of obesity traits was explained by the rs266729 locus. Further cross-sectional analysis showed that carriers of the G allele had significantly higher values of waist circumference, BMI and percentage of total body fat (p-values 0.014, 0.004 and 0.032, respectively). No association was detected between SNP rs266729 and other clusters of metabolic syndrome or their traits except for HOMA-IR and fasting plasma insulin levels, p-values 0.035 and 0.004, respectively. In contrast, both measured genotype and cross-sectional analysis failed to detect an association between the SNP rs17300539 with traits and clusters of metabolic syndrome. In conclusion, we showed family-based evidence of association of SNP rs266729 at ADIPOQ gene with traits defining obesity in Arab population. This is important for future prediction and prevention of obesity in population where obesity is in an increasing trend.

Variants of the adiponectin gene and diabetic microvascular complications in patients with type 2 diabetes

OBJECTIVE

The aim of this study was to examine the association between common polymorphisms of the adiponectin gene (ADIPOQ) and microvascular complications in patients with type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

Rs2241766 and rs1501299 of ADIPOQ were genotyped in 708 patients with T2DM. Fundus photography, nerve conducting velocity, and urine analysis were performed to check for the presence of microvascular complications including diabetic nephropathy, retinopathy and neuropathy.

RESULTS

The prevalence of diabetic nephropathy tended to be different according to rs2241766 genotype (p=0.057) and the GG genotype of rs2241766 was associated with diabetic nephropathy [urine albumin/creatinine ratio (UACR) greater than 30 mg/g] after adjusting for age, sex, body mass index, duration of diabetes, HDL-cholesterol, smoking status, and blood pressure (odds ratio=1.96; 95% confidence interval=1.01-3.82, p=0.049). Also, the G allele of rs2241766 demonstrated a trend to be associated with an increase in UACR (p=0.087). Rs2241766 genotype was not associated with diabetic retinopathy (p=0.955) and neuropathy (p=0.104) or any diabetic microvascular complications (p=0.104). There was no significant association between the rs1501299 genotype of ADIPOQ and the prevalence of diabetic retinopathy and neuropathy or any diabetic microvascular complications even after adjustment.

CONCLUSION

These data suggest that the GG genotype at rs2241766 is implicated in the pathogenesis of risk for diabetic nephropathy defined as UACR greater than 30 mg/day in patients with T2DM.

Association of Adiponectin Gene Polymorphism With Birth Weight in Korean Neonates

Adiponectin has been associated with insulin resistance and type 2 diabetes mellitus and possibly fetal growth. Our aim was to assess the association between the single nucleotide polymorphisms (SNPs) of the adiponectin gene (ADIPOQ) and the birth sizes. We investigated four SNPs of ADIPOQ (rs182052, rs2241766, rs1501299, and rs266729) and birth height and weight in 237 healthy full-term neonates. The neonates with the rs182052 G allele had a greater birth weight (p = .043 in the dominant model) and a higher ponderal index (p = .028 in the additive model). The rs2241766 G allele was associated with a greater birth weight (p = .016 in the recessive model). In a logistic regression analysis, the homozygotes for the rs182052 G allele and those for the rs2241766 G allele showed a significant association with a greater birth weight above 90 percentile (OR 2.75, 95% CI 1.13–6.70 and OR 5.15, 95% CI 1.66–15.99, respectively). In conclusion, we found an association between rs182052 and rs2241766 and birth weight and ponderal index among healthy neonates and suggested that adiponectin might have some roles in fetal growth.

Association between ADIPOQ SNPs with plasma adiponectin and glucose homeostasis and adiposity phenotypes in the IRAS Family Study

CONTEXT

Adiponectin is an adipocytokine associated with a variety of metabolic traits. These associations in human studies, in conjunction with functional studies in model systems, have implicated adiponectin in multiple metabolic processes.

OBJECTIVE

We hypothesize that genetic variants associated with plasma adiponectin would also be associated with glucose homeostasis and adiposity phenotypes.

DESIGN AND SETTING

The Insulin Resistance Atherosclerosis Family Study was designed to identify the genetic and environmental basis of insulin resistance and adiposity in the Hispanic- (n=1,424) and African-American (n=604) population.

MAIN OUTCOME MEASURES

High quality metabolic phenotypes, e.g. insulin sensitivity (S(I)), acute insulin response (AIR), disposition index (DI), fasting glucose, body mass index (BMI), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and waist circumference, were explored.

RESULTS

Based on association analysis of more than 40 genetic polymorphisms in the adiponectin gene (ADIPOQ), we found no consistent association of ADIPOQ variants with plasma adiponectin levels and adiposity phenotypes. However, there were two promoter variants, rs17300539 and rs822387, associated with plasma adiponectin levels (P=0.0079 and 0.021, respectively) in the Hispanic-American cohort that were also associated with S(I) (P=0.0067 and 0.013, respectively). In contrast, there was only a single promoter SNP, rs17300539, associated with plasma adiponectin levels (P=0.0018) and fasting glucose (P=0.042) in the African-American cohort. Strikingly, high impact coding variants did not show evidence of association.

CONCLUSIONS

The lack of consistent patterns of association between variants, adiponectin levels, glucose homeostasis, and adiposity phenotypes suggests a reassessment of the influence of adiponectin in these pathways.

Association of 276G>T adiponectin gene polymorphism to plasma adiponectin and albuminuria in type 2 diabetic patients

PURPOSE

The 276G>T polymorphism of the adiponectin (ADIPOQ) gene has been correlated with plasma adiponectin, type 2 diabetes (T2D) and its complications. Studies of the role of 276G>T polymorphism in the prevalence of T2D kidney disease are few and contradictory; ethnic differences might play a role. We aimed to assess the relationship of this polymorphism with albuminuria in a cohort of Caucasian T2D patients.

METHODS

Consecutive T2D outclinic patients were screened and included upon informed consent; exclusion criteria were glomerular filtration rate (GFR)<30 ml/min, acute intercurrent illness and urinary tract infection. History, standard laboratory evaluation, total plasma adiponectin and genotyping for the 276 ADIPOQ locus were obtained.

RESULTS

One hundred and three T2D patients were included. Forty-three (41.7%) of them had GG genotype, 50 (48.5%) had GT and 10 (9.7%) had TT genotype. Plasma adiponectin was significantly higher in TT-allele carriers (19.03±3.46 μg/ml) than in GT (10.14±1.78 μg/ml) and GG carriers (8.71±1.60 μg/ml), P=0.003. Adiponectin was higher in albuminuric (13.97±2.07 μg/ml) than in normoalbuminuric patients (6.91±0.88 μg/ml), P=0.004. The prevalence of T allele was higher in normoalbuminuric patients [36 (69.2%) GT+TT carriers] than in albuminuric ones [24 (47.1%)], P=0.02. Logistic regression identified the following as predictors of albuminuria: GG genotype: P=0.003 (OR 4.2; CI 1.61-10.96); low GFR: P=0.003 (OR 0.97; CI 0.95-0.99); and high plasma adiponectin: P=0.012 (OR 1.07; CI 1.01-1.14).

CONCLUSIONS

Our data suggest that 276G>T polymorphism of the ADIPOQ gene is associated with plasma adiponectin levels. By influencing adiponectinemia, 276G>T polymorphism might predict the presence of albuminuria in Caucasian T2D patients.

The relationship of haplotype in lactotransferrin and its expression levels in Chinese Han ovarian cancer

Chromosomal DNA sequence polymorphisms may contribute to individuality, confer risk for diseases, and most commonly are used as genetic markers in association study. The iron-binding protein lactoferrin inhibits bacterial growth by sequestering essential iron and also exhibits antitumor, anti-inflammatory, and immunoregulatory activities. The gene coding for lactotransferrin (LTF) is polymorphic, with the occurrence of several common alleles in the general population. This genetically determined variation can affect LTF functions. In this study, we determined the distribution of LTF gene polymorphisms (rs1126477, rs1126478, rs2073495, and rs9110) in the Chinese Han population and investigated whether these polymorphisms were associated with increased risk of ovarian carcinoma in the Chinese. It was found that the rs1126477 was correlated significantly with ovarian cancer. The frequency of A allele of rs1126477 was significantly higher in 700 ovarian cancer patients compared with that in the control group of 700 cases (P< 0.01, χ(2)= 6.79). The frequency of AA genotype was significantly higher in ovarian cancer patients compared with that in the control group (P< 0.05, χ(2)= 6.49). AA genotype is the risk factor of ovarian cancer. The odds ratio (OR) was 2.24 and the 95% confidence interval (CI) was 1.08-4.59, respectively. The 'A-G-C-C' haplotype constructed with rs1126477, rs1126478, rs2073495, and rs9110 was the risk factor to be ovarian cancer. The expression of LTF gene was lower in individuals with 'A-G-C-C' haplotype compared with that in individuals without 'A-G-C-C' haplotype. These findings suggested that rs1126477 could play important roles in ovarian carcinoma physiological processes in the Chinese.

New type 2 diabetes risk genes provide new insights in insulin secretion mechanisms

Type 2 diabetes results from the inability of beta cells to increase insulin secretion sufficiently to compensate for insulin resistance. Insulin resistance is thought to result mainly from environmental factors, such as obesity. However, there is compelling evidence that the decline of both insulin sensitivity and insulin secretion have also a genetic component. Recent genome-wide association studies identified several novel risk genes for type 2 diabetes. The vast majority of these genes affect beta cell function by molecular mechanisms that remain unknown in detail. Nevertheless, we and others could show that a group of genes affect glucose-stimulated insulin secretion, a group incretin-stimulated insulin secretion (incretin sensitivity or secretion) and a group proinsulin-to-insulin conversion. The most important so far type 2 diabetes risk gene, TCF7L2, interferes with all three mechanisms. In addition to advancing knowledge in the pathophysiology of type 2 diabetes, the discovery of novel genetic determinants of diabetes susceptibility may help understanding of gene-environment, gene-therapy and gene-gene interactions. It was also hoped that it could make determination of the individual risk for type 2 diabetes feasible. However, the allelic relative risks of most genetic variants discovered so far are relatively low. Thus, at present, clinical criteria assess the risk for type 2 diabetes with greater sensitivity and specificity than the combination of all known genetic variants.

A validation study of type 2 diabetes-related variants of the TCF7L2, HHEX, KCNJ11, and ADIPOQ genes in one endogamous ethnic group of north India

The aim of this study was to validate the single nucleotide polymorphisms (SNPs) of four candidate genes (TCF7L2, HHEX, KCNJ11, and ADIPOQ) related to type 2 diabetes (T2D) in an endogamous population of north India; the Aggarwal population, having 18-clans. This endogamous population model was heavily supported by recent land mark work and we also verified the homogeneity of this population by clan-based stratification analysis. Two SNPs (rs4506565; rs7903146) in TCF7L2 were found to be significant (p-value = 0.00191; p-value = 0.00179, respectively), and odds ratios of 2.1 (dominant-model) and 2.0 (recessive-model) respectively, were obtained for this population. The TTT haplotype in the TCF7L2 gene was significantly associated with T2D. Waist-Hip ratio (WHR), systolic blood pressure (SBP), and age were significant covariates for increasing risk of T2D. Single-SNP, combined-SNPs and haplotype analysis provides clear evidence that the causal mutation is near to or within the significant haplotype (TTT) of the TCF7L2 gene. In spite of a culturally-learned sedentary lifestyle and fat-enriched dietary habits, WHR rather than body-mass-index emerged as a robust predictor of risk for T2D in this population.

Unravelling the genetic basis of renal diseases; from single gene to multifactorial disorders

Chronic kidney disease is common with up to 5% of the adult population reported to have an estimated glomerular filtration rate of < 60 ml/min/1.73 m(2). A large number of pathogenic mutations have been identified that are responsible for 'single gene' renal disorders, such as autosomal dominant polycystic kidney disease and X-linked Alport syndrome. These single gene disorders account for < 15% of the burden of end-stage renal disease that requires dialysis or kidney transplantation. It has proved more difficult to identify the genetic susceptibility underlying common, complex, multifactorial kidney conditions, such as diabetic nephropathy and hypertensive nephrosclerosis. This review describes success to date and explores strategies currently employed in defining the genetic basis for a number of renal disorders. The complementary use of linkage studies, candidate gene and genome-wide association analyses are described and a collation of renal genetic resources highlighted.

Pathomechanisms of type 2 diabetes genes

Type 2 diabetes mellitus is a complex metabolic disease that is caused by insulin resistance and beta-cell dysfunction. Furthermore, type 2 diabetes has an evident genetic component and represents a polygenic disease. During the last decade, considerable progress was made in the identification of type 2 diabetes risk genes. This was crucially influenced by the development of affordable high-density single nucleotide polymorphism (SNP) arrays that prompted several successful genome-wide association scans in large case-control cohorts. Subsequent to the identification of type 2 diabetes risk SNPs, cohorts thoroughly phenotyped for prediabetic traits with elaborate in vivo methods allowed an initial characterization of the pathomechanisms of these SNPs. Although the underlying molecular mechanisms are still incompletely understood, a surprising result of these pathomechanistic investigations was that most of the risk SNPs affect beta-cell function. This favors a beta-cell-centric view on the genetics of type 2 diabetes. The aim of this review is to summarize the current knowledge about the type 2 diabetes risk genes and their variants' pathomechanisms.