Hypoadiponectinemia is associated with progression toward type 2 diabetes and genetic variation in the ADIPOQ gene promoter

The Polymorphism rs17300539 in the Adiponectin Promoter Gene Is Related to Metabolic Syndrome, Insulin Resistance, and Adiponectin Levels in Caucasian Patients with Obesity

Background and Aims: The present study was designed to investigate SNP rs17300539 in the ADIPOQ gene and its relationships with obesity, metabolic syndrome (MS), and serum circulating adiponectin. Methods: The present design involved a Caucasian population of 329 subjects with obesity. Anthropometric and adiposity parameters, blood pressure, biochemical parameters, and the percentage of patients with metabolic syndrome were recorded. The ADIPOQ gene variant (rs17300539) genotype was evaluated. Results: The percentage of patients with different genotypes of the rs17300539 polymorphism in this sample was 86.0% (n = 283) (GG), 11.2% (n = 37) (GA), and 2.7% (n = 9) (AA). The allele frequency was G (0.76) and A (0.24). Applying the dominant genetic model (GG vs. GA + AA), we reported differences between genotype GG and genotype GA + AA for serum adiponectin levels (Delta: 7.5 ± 1.4 ng/mL; p = 0.03), triglycerides (Delta: 41.1 ± 3.4 mg/dL; p = 0.01), fastingcirculating insulin (Delta: 4.9 ± 1.1 mUI/L; p = 0.02), and insulin resistance as HOMA-IR (Delta: 1.4 ± 0.1 units; p = 0.02). The remaining biochemical parameters were not related to the genotype of obese patients. The percentages of individuals with MS (OR = 2.07, 95% CI = 1.3-3.88; p = 0.01), hypertriglyceridaemia (OR = 2.66, 95% CI = 1.43-5.01; p = 0.01), and hyperglycaemia (OR = 3.31, 95% CI = 1.26-8.69; p = 0.02) were higher in GG subjects than patients with A allele. Logistic regression analysis reported an important risk of the presence of metabolic syndrome in GG subjects (OR = 1.99, 95% CI = 1.21-4.11; p = 0.02) after adjusting for adiponectin, dietary energy intakes, gender, weight, and age. Conclusions: The GG genotype of rs17300539 is associated with hypertriglyceridaemia, insulin resistance, low adiponectin levels, and a high risk of metabolic syndrome and its components.

Association of metabolic syndrome components with circulating levels of cytokine clusters in young women

BACKGROUND

The purpose of this study was to investigate the relationship between circulating zinc α 2-glycoprotein (ZAG), irisin, betatrophin and adiponectin concentrations and metabolic syndrome (MetS) components and to analyze the effects of blood glucose and insulin on these cytokine concentrations in vivo.

METHODS

A total of 196 young women, including 78 healthy women and 118 women with MetS components, were recruited for this cross-sectional study. An oral glucose tolerance test and euglycemic-hyperinsulinemic clamp (EHC) were performed in healthy subjects and women with MetS components. An ELISA kit was used to measure serum ZAG, irisin, betatrophin, and adiponectin levels, and their relationship with the MetS components was analyzed.

RESULTS

In women with MetS components, circulating irisin and betatrophin levels were significantly higher than those in the healthy women ((207 (150-248) vs 178 (147-228); P < 0.05) for irisin; (0.51 (0.38-0.63) vs 0.38 (0.23-0.52); P < 0.001) for betatrophin), but circulating ZAG and adiponectin levels were significantly lower (39.8 (26.4-50.4) vs (46.7 (40.6-63.0); P < 0.001) for ZAG; (36.5 (22.0-47.6) vs 41.2 (35.7-54.7); P < 0.01) for adiponectin). FBG, WC, and triglyceride were significantly correlated with the circulating levels of these four cytokines (P < 0.001 or <0.05). All four cytokines were associated with MetS and its components. In response to increasing insulin levels, circulating ZAG concentrations were markedly increased in both healthy subjects and women with MetS components during the EHC. However, serum irisin, betatrophin, and adiponectin levels in both healthy subjects and women with MetS components were significantly reduced compared with baseline.

CONCLUSION

Serum ZAG, irisin, betatrophin and adiponectin were associated with MetS and might be biomarkers for screening MetS components.

A Metabolically Unhealthy Phenotype Is Associated with Genetic Variants and Lower Serum Adiponectin Levels

<b><i>Background:</i></b> Even though excessive adipose tissue is related to chronic metabolic disturbances, not all subjects with excess weight (EW) display metabolic alterations, and not all normal-weight (NW) subjects have a metabolically healthy (MH) phenotype, probably due to gene-environment interactions. The aim of this study was to investigate the interaction effects of <i>ADIPOQ</i> and <i>PPARG</i> genetic variants in NW and EW individuals with different metabolic phenotypes. <b><i>Methods:</i></b> Data on 345 adults from western Mexico were analyzed. The individuals were classified into NW and EW groups according to body mass index, and were categorized as MH or metabolically unhealthy (MUH), considering homeostatic model assessment insulin resistance (HOMA-IR) and National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) cut-off points for glucose, triglycerides, high-density lipoprotein cholesterol, and blood pressure. Subjects with ≤1 altered parameter were classified as MH. The single nucleotide polymorphisms (SNPs) –11377C&#x3e;G, –11391G&#x3e;A, +45T&#x3e;G, and +276G&#x3e;T for <i>ADIPOQ</i> and Pro12Ala for <i>PPARG</i> were analyzed by allelic discrimination. High-molecular-weight adiponectin isoform levels were measured by ELISA. <b><i>Results:</i></b> Lower serum adiponectin levels were associated with the MUH phenotype in EW subjects. NW subjects with the GG or TG genotype for the +45T&#x3e;G SNP had reduced odds of the MUH phenotype. Individuals who carried two copies of the GG haplotype at the –11391G&#x3e;A and –11377C&#x3e;G SNPs for <i>ADIPOQ</i> had lower serum adiponectin levels than those with zero copies. <b><i>Conclusion:</i></b> In this population, lower serum adiponectin levels were found in the EW-MUH phenotype, and no differences were observed between the NW-MH and the EW-MH phenotype. In addition, the +45T&#x3e;G SNP was associated with reduced odds of the MUH phenotype.

ADIPOQ -11377C>G Polymorphism Increases the Risk of Adipokine Abnormalities and Child Obesity Regardless of Dietary Intake

OBJECTIVE

The aim of the present study was to verify whether selected functional single nucleotide polymorphisms in LEP, LEPR, and ADIPOQ loci are associated with the development of obesity and serum levels of the respective adipokines in prepubertal white children with obesity.

METHODS

Frequencies of -2548G>A LEP (rs7799039), Q223R (rs1137101) and K656N (rs8129183) LEPR, and -11377C>G (rs266729) and -11426A>G (rs16861194) ADIPOQ polymorphisms were analyzed by restriction fragment length polymorphism in 101 obese (standard deviation score [SDS]-body mass index [BMI] >2) and 67 normal-weight (SDS-BMI <- 1 + 1 >) children. Serum adipokine concentrations were measured using the enzyme-linked immunosorbent assay method.

RESULTS

The GC/GG genotypes of -11377C>G ADIPOQ polymorphism were associated with a higher risk of obesity (P = 0.022, odds ratio 2.08 [95% confidence interval 1.11-3.90]). Individuals carrying the GG genotype had a higher leptin/total adiponectin ratio by 25% than CC homozygotes (P trend = 0.05). In the multivariate linear regression model, we found differences among particular genotypes of this polymorphism in concentrations of high molecular weight (HMW) adiponectin (P trend = 0.043) and HMW/total adiponectin ratio (P trend = 0.048), with the lowest values in GG homozygotes. Positive correlations between SDS-BMI and dietary reference intake percentage were observed in individuals homozygous for allele C (r = 0.403, P = 0.01) and CG heterozygotes (r = 0.428, P = 0.004). No significant correlations between both parameters were found in the GG homozygotes.

CONCLUSIONS

Among the analyzed polymorphisms, only -11377C>G ADIPOQ single nucleotide polymorphism was associated with obesity during the prepubertal period. Adipokine abnormalities coexisting with the lack of relations between SDS-BMI and dietary intake may predict a higher risk of future obesity-related disorders in obese children carrying the GG genotype than in those with other genotypes.

Downregulation of adiponectin system in granulosa cells and low levels of HMW adiponectin in PCOS

PURPOSE

The purpose of the study was to investigate changes in adiponectin system expression in granulosa cells (GCs) and high molecular weight adiponectin levels in serum and follicular fluid (FF) of 40 women with polycystic ovary syndrome (PCOS) compared to those in 40 women with normal ovary function.

METHODS

Adiponectin (Adipo), adiponectin receptor 1 (AdipoR1), and adiponectin receptor 2 (AdipoR2) messenger RNA (mRNA) expression levels were measured using quantitative real-time polymerase chain reaction (qRT-PCR). High molecular weight (HMW) adiponectin protein concentration was evaluated by ELISA method. Data were analyzed using Student's t test and one-way ANOVA in SPSS 21 software. At oocyte retrieval, FF was aspirated and GCs were obtained from a pooled collection of FF per each patient.

RESULTS

PCR results showed expression of adiponectin, AdipoR1, AdipoR2, follicle-stimulating hormone receptor (FSHR), and luteinizing hormone receptor (LHR) in GCs. After controlling body mass index (BMI) values, qRT-PCR demonstrated a decreased expression of adiponectin system in GCs of PCOS patients compared to those in controls (p = 0.001). There was a strong positive correlation among AdipoR1 and AdipoR2 expression and also among FSH and LH receptor expression. (Both r = 0.8, p = 0.001). There were low levels of high molecular weight adiponectin in the serum of PCOS patients with controlled ovarian hyperstimulation (30.19 ± 4.3 ng/ml) compared to the controls (48.47 ± 5.9 ng/ml) and in the FF of PCOS patients with controlled ovarian hyperstimulation (7.86 ± 1.44 ng/ml) compared to the controls (14.22 ± 2.01 ng/ml; p = 0.02).

CONCLUSIONS

Lower expression of adiponectin and its receptors in GCs might be an important manifestation in gonadotropin-stimulated PCOS patients which could influence the physiologic adiponectin roles such as interaction with insulin and LH in induction of GC gene expression.

Pathway-Based Genome-wide Association Studies Reveal That the Rac1 Pathway Is Associated with Plasma Adiponectin Levels

Pathway-based analysis as an alternative and effective approach to identify disease-related genes or loci has been verified. To decipher the genetic background of plasma adiponectin levels, we performed genome wide pathway-based association studies in extremely obese individuals and normal-weight controls. The modified Gene Set Enrichment Algorithm (GSEA) was used to perform the pathway-based analyses (the GenGen Program) in 746 European American females, which were collected from our previous GWAS in extremely obese (BMI > 35 kg/m(2)) and never-overweight (BMI<25 kg/m(2)) controls. Rac1 cell motility signaling pathway was associated with plasma adiponectin after false-discovery rate (FDR) correction (empirical P < 0.001, FDR = 0.008, family-wise error rate = 0.008). Other several Rac1-centered pathways, such as cdc42racPathway (empirical P < 0.001), hsa00603 (empirical P = 0.003) were among the top associations. The RAC1 pathway association was replicated by the ICSNPathway method, yielded a FDR = 0.002. Quantitative pathway analyses yielded similar results (empirical P = 0.001) for the Rac1 pathway, although it failed to pass the multiple test correction (FDR = 0.11). We further replicated our pathway associations in the ADIPOGen Consortium data by the GSA-SNP method. Our results suggest that Rac1 and related cell motility pathways might be associated with plasma adiponectin levels and biological functions of adiponectin.

Adiponectin as a Protective Factor Against the Progression Toward Type 2 Diabetes Mellitus in Postmenopausal Women

Serum adiponectin levels have been suggested to be predictors of type 2 diabetes mellitus in diverse populations. However, the relationship between circulating adiponectin levels and the risk of development of type 2 diabetes in postmenopausal women has not been investigated.A total of 382 healthy postmenopausal women who participated in a prospective cohort study were followed for 5.8 years. Type 2 diabetes mellitus was defined according to the criteria set out by the American Diabetes Association. Adiponectin, osteoprotegerin (OPG), and high-sensitivity C-reactive protein (hs-CRP) levels were measured using ELISA.Of 195 women who did not have diabetes at baseline and who were reexamined in the second phase of the study for diabetic status, 35 subjects (17.9%) developed type 2 diabetes mellitus during the 5.8 years follow-up period. The women with type 2 diabetes had lower adiponectin levels than the healthy postmenopausal women. Multiple regression analysis showed that, after adjustments were made for age, cardiovascular risk factors, OPG, and hs-CRP levels, higher baseline adiponectin levels were associated with a lower relative risk (RR) of having type 2 (RR = 0.07, confidence interval [CI]: 0.01-0.66, P = 0.021).Higher baseline adiponectin levels functioned as a predictor of a lower risk of developing type 2 diabetes mellitus among postmenopausal women during a 5.8 years follow-up study. Therefore, it is suggested that elevated adiponectin levels may offer protection against the development of type 2 diabetes mellitus after the menopause.

Adiponectin as serum biomarker of insulin resistance in patients with polycystic ovarian syndrome

OBJECTIVE

To examine the role of adiponectin as a biomarker of insulin resistance in polycystic ovary syndrome (PCOS).

BACKGROUND

PCOS is associated with metabolic syndrome, which correlates to increased cardiovascular risk in these patients. Adiponectin is decreased in obese individuals.

METHODS

Ninety women with PCOS (45 with and 45 without metabolic syndrome) were enrolled in this study. Anthropometric variables, serum concentrations of fasting glucose, insulin, triglycerides, lipoproteins, cholesterol, testosterone and adiponectin were measured in all patients. Insulin sensitivity was examined in all patients. Numerical values were analyzed by t-tests and categorical data were analyzed by Chi-square test. Multiple regression analyses were performed to detect the factors that contributed to insulin resistance.

RESULTS

Metabolic syndrome predicted insulin resistance in PCOS patients. Serum adiponectin levels were suppressed in insulin resistant compared to insulin sensitive patients (10.7 ± 4.3 µg/mL, p < 0.001). Multiple linear regression analysis revealed for every 1 µg increase in adiponectin, insulin sensitivity index increases by 0.1 (p = 0.016). Serum testosterone failed to correlate with insulin sensitivity.

CONCLUSION

Serum adiponectin levels were suppressed in patients with both metabolic syndrome and insulin resistance. This protein could be used as a biomarker to distinguish the patients at a higher risk of diabetes and cardiovascular morbidity.

Adiponectin deletion impairs insulin signaling in insulin-sensitive but not insulin-resistant 3T3-L1 adipocytes

AIMS

Previous reports have demonstrated that the adipocyte-derived peptide adiponectin is closely associated with insulin resistance due to its insulin-sensitizing and anti-inflammatory properties in peripheral tissues; however the autocrine effects of adiponectin remain elusive. This study investigated regulatory effects of adiponectin on glucose transport and insulin signaling in insulin-sensitive or insulin-resistant 3T3-L1 adipocytes.

MAIN METHODS

3T3-L1 fibroblasts were transfected with non-target or adiponectin (ADN) siRNA and differentiated. Chronic treatment with insulin (24h, 100 nM) was employed to induce insulin resistance in differentiated adipocytes. Insulin-stimulated glucose transport was measured and protein and mRNA levels were assessed by Western blot and RT-PCR.

KEY FINDINGS

Prolonged incubation with insulin significantly reduced insulin-stimulated glucose uptake, suggesting the development of insulin resistance and adiponectin mRNA expression. In this insulin-resistant condition, adiponectin deletion did not alter insulin-stimulated glucose uptake. In insulin-sensitive adipocytes, adiponectin ablation reduced insulin-stimulated glucose uptake, expression of IRS-1 and GLUT4, and GLUT4 translocation to the membrane. Adiponectin knockdown did not affect the activation of AKT and p38MAPK (phosphorylation form/total form), but significantly decreased the activation of AMPK in insulin-responsive adipocytes.

SIGNIFICANCE

Adiponectin deficiency suppresses insulin-induced glucose uptake, insulin signaling, and the AMPK pathway only in insulin-responsive 3T3-L1 adipocytes.

Pleiotropy analysis of quantitative traits at gene level by multivariate functional linear models

In genetics, pleiotropy describes the genetic effect of a single gene on multiple phenotypic traits. A common approach is to analyze the phenotypic traits separately using univariate analyses and combine the test results through multiple comparisons. This approach may lead to low power. Multivariate functional linear models are developed to connect genetic variant data to multiple quantitative traits adjusting for covariates for a unified analysis. Three types of approximate F-distribution tests based on Pillai-Bartlett trace, Hotelling-Lawley trace, and Wilks's Lambda are introduced to test for association between multiple quantitative traits and multiple genetic variants in one genetic region. The approximate F-distribution tests provide much more significant results than those of F-tests of univariate analysis and optimal sequence kernel association test (SKAT-O). Extensive simulations were performed to evaluate the false positive rates and power performance of the proposed models and tests. We show that the approximate F-distribution tests control the type I error rates very well. Overall, simultaneous analysis of multiple traits can increase power performance compared to an individual test of each trait. The proposed methods were applied to analyze (1) four lipid traits in eight European cohorts, and (2) three biochemical traits in the Trinity Students Study. The approximate F-distribution tests provide much more significant results than those of F-tests of univariate analysis and SKAT-O for the three biochemical traits. The approximate F-distribution tests of the proposed functional linear models are more sensitive than those of the traditional multivariate linear models that in turn are more sensitive than SKAT-O in the univariate case. The analysis of the four lipid traits and the three biochemical traits detects more association than SKAT-O in the univariate case.

Adiponectin gene polymorphism rs2241766 T/G is associated with response to pioglitazone treatment in type 2 diabetic patients from southern China

INTRODUCTION

Insulin sensitizing drugs such as pioglitazone are not uniformly treatment effective among individual type 2 diabetic patients. Here, the relationship of pioglitazone efficacy to single nucleotide polymorphisms (SNP) of the adiponectin gene, a critical gene directly regulated by the drug, was examined in a cohort of Chinese Han type 2 diabetic patients.

METHODS

Eighty type 2 diabetic patients were treated with pioglitazone (15 mg/day) for 12 weeks without interruption of their current therapeutic regimen. Fasting plasma glucose, fasting insulin, homeostasis model assessment for insulin resistance (HOMA-IR), and glycated hemoglobin (HbA1c%) were collected both prior to and following pioglitazone treatment. Response to pioglitazone was defined as a decrease of at least 15% in HbA1c% levels. Three regions of the adiponectin gene containing SNPs (promoter, intron 2 and exon 2, and exon 3) were amplified and sequenced to determine genotype.

RESULTS

Serum adiponectin levels were significantly increased (p<0.001) whereas fasting plasma glucose, fasting insulin, HOMA-IR, and HbA1c% values were significantly decreased relative to baseline measurements (p<0.001). Response of patients with TG and TT genotypes at rs2241766 (exon2; 52.9% vs. 12.7%, respectively p = 0.001) was statistically significant relative to all other patients. Amongst rs2241766 TG and TT patients, the mean decrease in HbA1c% levels was greater where the genotype was TG (1.15±0.80 vs. 0.52±0.64, p = 0.001).

CONCLUSIONS

The adiponectin gene polymorphism rs2241766 T/G is associated with pioglitazone efficacy in type 2 diabetic patients, and status of the polymorphism may be an important clinical factor to consider prior to pioglitazone treatment.

Association study of ARL15 and CDH13 with T2DM in a Han Chinese population

Several studies indicate that plasma adiponectin levels are associated with the risk of type 2 diabetes mellitus (T2DM) or T2DM risk factors in diverse populations. In addition to the adiponectin gene, several other genes have been postulated to influence plasma adiponectin levels. In this study, we investigated two single nucleotide polymorphisms (SNPs), rs4311394 and rs4783244, located intronically in the ADP-ribosylation factor-like protein 15 (ARL15) and the T-cadherin (CDH13) genes, respectively. These SNPs were detected in a Han Chinese population using a TaqMan assay and evaluated for association with T2DM as well as with individual metabolic traits. Allele frequencies for rs4311394 were significantly different in T2DM and nondiabetes (NDM) groups (χ² = 4.49, P = 0.034). However, neither allele nor genotype frequencies for rs4783244 were associated with T2DM (χ² = 0.33, P = 0.56 and χ² = 2.35, P = 0.31 respectively). The SNPs did not exhibit significant association with individual metabolic traits in the T2DM and NDM groups. Our results indicated that the G allele of the rs4311394 might be a susceptibility factor for T2DM in the Han Chinese population (odds ratio: 1.20; 95% confidence interval: 1.01-1.41).

The role of adiponectin gene variants in glycemic control in patients with Type 2 diabetes

The aim of this study was to investigate the association between glycemic control in Type 2 diabetes mellitus patients and common genetic variants of ADIPQO gene. A total of 427 Type 2 diabetes patients were recruited in the study and divided into two groups: 172 patients with good glycemic control and 249 with poor glycemic control. Genotyping of C11377G, G276T and T45G ADIPQO SNPs were carried out using restriction fragment length polymorphisms-polymerase chain reaction. The results showed that C11377G ADIPQO SNP is strongly associated with glycemic control in Type 2 diabetes patients. Patients with the GG genotype at adiponectin C11377G had better glycemic control than those with CC or CG genotypes. However, other examined SNPs were not correlated with glycemic control in Type 2 diabetes patients. Other parameters that impacted glycemic control include duration of the disease (p < 0.01), use of insulin therapy (p < 0.01) and presence of neuropathy complications (p < 0.01). However, no contribution was observed for gender, statin use, lipid profile and other oral medications to glycemic control (p > 0.05). Glycemic control among Type 2 diabetes patients might be affected by variants in ADIPQO gene.

Assessment of small fiber neuropathy to predict future risk of type 2 diabetes

OBJECTIVE

Sudomotor dysfunction due to small fiber neuropathy can be observed very early in pre-diabetes. The aim of this study was to assess the predictive power of EZSCAN, a non invasive, quick and simple measurement of sudomotor function to identify glucose impairment.

RESEARCH DESIGN AND METHODS

The study was performed in 76 German subjects at risk of diabetes. Glucose metabolism was assessed by using, oral glucose tolerance test (OGTT) at baseline and after 2 year follow-up. Sudomotor function was evaluated by measuring hand and foot electrochemical sweat conductances to calculate a risk score.

RESULTS

At baseline, 38 patients had normal glucose tolerance (NGT), 34 had pre-diabetes (impaired fasting glucose, IFG and/or impaired glucose tolerance, IGT) and 4 had newly diagnosed type 2 diabetes. The AUC values for FPG, 2h-OGTT glucose, 1h-OGTT glucose, HbA1C and EZSCAN score to predict pre-diabetes were 0.50, 0.65, 0.64, 0.72 and 0.76, respectively. Subjects having a moderate or high EZSCAN score (>50) at baseline had a substantially increased risk for having IFG and/or IGT at follow-up visit presented by an odds ratio of 12.0 [1.4-100.5], the OR for having 1h-OGTT ≥ 8.6mmol/L at follow-up was 9.8 [1.0-92.8] and for having HbA1C ≥ 5.7% was 15.7 [1.9-131.5] compared to subjects with low EZSCAN risk.

CONCLUSIONS

This preliminary study, which must be confirmed in a larger population, shows that EZSCAN risk score is associated with diabetes progression which have implications for prevention and disease management.

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.

Factors related with adiponectinemia in obese and normal-weight women and with its variation in weight loss programs

OBJECTIVE

To assess different factors influencing adiponectinemia in obese and normal-weight women; to identify factors associated with the variation (Δ) in adiponectinemia in obese women following a 6-month weight loss program, according to surgical/non-surgical interventions.

METHODS

We studied 100 normal-weight women and 112 obese premenopausal women; none of them was on any medical treatment. Women were characterized for anthropometrics, daily macronutrient intake, smoking status, contraceptives use, adiponectin as well as IL-6 and TNF-α serum concentrations.

RESULTS

Adiponectinemia was lower in obese women (p < 0.001), revealing an inverse association with waist-to-hip ratio (p < 0.001; r = -0.335). Normal-weight women presented lower adiponectinemia among smokers (p = 0.041); body fat, waist-to-hip ratio, TNF-α levels, carbohydrate intake, and smoking all influence adiponectinemia (r(2) = 0.436). After weight loss interventions, a significant modification in macronutrient intake occurs followed by anthropometrics decrease (chiefly after bariatric procedures) and adiponectinemia increase (similar after surgical and non-surgical interventions). After bariatric intervention, Δ adiponectinemia was inversely correlated to Δ waist circumference and Δ carbohydrate intake (r(2) = 0.706).

CONCLUSION

Anthropometrics, diet, smoking, and TNF-α levels all influence adiponectinemia in normal-weight women, although explaining less than 50% of it. In obese women, anthropometrics modestly explain adiponectinemia. Opposite to non-surgical interventions, after bariatric surgery adiponectinemia increase is largely explained by diet composition and anthropometric changes.

Adiponectin trajectories before type 2 diabetes diagnosis: Whitehall II study

OBJECTIVE

The role of adiponectin in the natural history of diabetes is not well characterized. We set out to characterize prediagnosis trajectories of adiponectin in individuals who develop type 2 diabetes.

RESEARCH DESIGN AND METHODS

In a case-cohort study (335 incident diabetes case and 2,474 noncase subjects) nested in the Whitehall II study, serum adiponectin was measured up to three times per participant (1991-1993, 1997-1999, and 2003-2004). Multilevel models adjusted for age and ethnicity were fitted to assess 13-year trajectories of log-transformed adiponectin preceding diabetes diagnosis or a randomly selected time point during follow-up (year(0)) based on 755/5,095 (case/noncase) person-examinations.

RESULTS

Adiponectin levels were lower in diabetes case than in noncase subjects (median 7,141 [interquartile range 5,187-10,304] vs. 8,818 [6,535-12,369] ng/mL at baseline, P < 0.0001). Control subjects showed a modest decline in adiponectin throughout follow-up (0.3% per year, P < 0.0001) at higher levels in women than in men (difference at year(0): 5,358 ng/mL, P < 0.0001). Female case and early-onset case (age at diagnosis <52 years) subjects had a steeper decline than control subjects (slope difference -1.1% per year, P = 0.001 in females, -1.6% per year in early-onset case subjects, P = 0.034). In men, adiponectin slopes for case and noncase subjects were parallel. The slope differences by diabetes onset were largely attenuated after adjustment for changes in obesity, whereas the sex-specific slope differences were independent of obesity.

CONCLUSIONS

Lower adiponectin levels were observed already a decade before the diagnosis of diabetes. The marked sex difference in trajectories suggests that sex-specific mechanisms affect the association between adiponectin levels and diabetes development.

Common variants in genes encoding adiponectin (ADIPOQ) and its receptors (ADIPOR1/2), adiponectin concentrations, and diabetes incidence in the Diabetes Prevention Program

AIMS

Baseline adiponectin concentrations predict incident Type 2 diabetes mellitus in the Diabetes Prevention Program. We tested the hypothesis that common variants in the genes encoding adiponectin (ADIPOQ) and its receptors (ADIPOR1, ADIPOR2) would associate with circulating adiponectin concentrations and/or with diabetes incidence in the Diabetes Prevention Program population.

METHODS

Seventy-seven tagging single-nucleotide polymorphisms (SNPs) in ADIPOQ (24), ADIPOR1 (22) and ADIPOR2 (31) were genotyped. Associations of SNPs with baseline adiponectin concentrations were evaluated using linear modelling. Associations of SNPs with diabetes incidence were evaluated using Cox proportional hazards modelling.

RESULTS

Thirteen of 24 ADIPOQ SNPs were significantly associated with baseline adiponectin concentrations. Multivariable analysis including these 13 SNPs revealed strong independent contributions of rs17366568, rs1648707, rs17373414 and rs1403696 with adiponectin concentrations. However, no ADIPOQ SNPs were directly associated with diabetes incidence. Two ADIPOR1 SNPs (rs1342387 and rs12733285) were associated with ∼18% increased diabetes incidence for carriers of the minor allele without differences across treatment groups, and without any relationship with adiponectin concentrations.

CONCLUSIONS

  ADIPOQ SNPs are significantly associated with adiponectin concentrations in the Diabetes Prevention Program cohort. This observation extends prior observations from unselected populations of European descent into a broader multi-ethnic population, and confirms the relevance of these variants in an obese/dysglycaemic population. Despite the robust relationship between adiponectin concentrations and diabetes risk in this cohort, variants in ADIPOQ that relate to adiponectin concentrations do not relate to diabetes risk in this population. ADIPOR1 variants exerted significant effects on diabetes risk distinct from any effect of adiponectin concentrations.

The association studies of ADIPOQ with type 2 diabetes mellitus in Chinese populations

Adiponectin, which is secreted by the white adipose tissue, plays an important role in type 2 diabetes mellitus (T2DM) and its complications. Since 2002, many investigators explored the association between ADIPOQ single nucleotide polymorphisms and T2DM in different ethnic populations from different regions. In China, the results of numerous studies of the association between ADIPOQ and T2DM were not consistent, which may be caused by population-specific effects or environmental effects. This review describes the association between ADIPOQ and T2DM, the metabolic characteristics and the complications of T2DM in Chinese populations.

The metabochip, a custom genotyping array for genetic studies of metabolic, cardiovascular, and anthropometric traits

Genome-wide association studies have identified hundreds of loci for type 2 diabetes, coronary artery disease and myocardial infarction, as well as for related traits such as body mass index, glucose and insulin levels, lipid levels, and blood pressure. These studies also have pointed to thousands of loci with promising but not yet compelling association evidence. To establish association at additional loci and to characterize the genome-wide significant loci by fine-mapping, we designed the "Metabochip," a custom genotyping array that assays nearly 200,000 SNP markers. Here, we describe the Metabochip and its component SNP sets, evaluate its performance in capturing variation across the allele-frequency spectrum, describe solutions to methodological challenges commonly encountered in its analysis, and evaluate its performance as a platform for genotype imputation. The metabochip achieves dramatic cost efficiencies compared to designing single-trait follow-up reagents, and provides the opportunity to compare results across a range of related traits. The metabochip and similar custom genotyping arrays offer a powerful and cost-effective approach to follow-up large-scale genotyping and sequencing studies and advance our understanding of the genetic basis of complex human diseases and traits.

Genetic variants in the ADIPOQ gene and the risk of metabolic syndrome: a case-control study of a Chinese Han population

Our aim was to investigate whether the ADIPOQ gene polymorphisms are associated with the metabolic syndrome (MetS). Genotypes of MetS patients (n=1049) and normal controls (n= 1092) were analysed by TaqMan® assay, and serum adiponectin concentration was measured by ELISA. The variant genotypes rs266729CG; rs1063539GC, GC/CC; rs16861205AA and rs7649121AT, AT/TT (Adjusted P=0.037, 0.044, 0.025, 0.011, 0.019, 0.020, respectively) of the ADIPOQ gene were associated with MetS. Patients with rs266729CG, CG/GG genotypes (P=0.034, 0.035) and rs7649121AT, AT/TT genotypes (P=0.013, 0.022) had higher levels of serum adiponectin than those with the CC and AA genotypes respectively. Furthermore, the prevalence of haplotypes GGAAAATC and GGGTAACC was lower in cases (10.7% and 4.5%) than in controls (12.1% and 5.9%) [Adjusted ORs (95% CIs)=0.70 (0.54–0.91), 0.65 (0.46–0.92)]. The ADIPOQ gene variants associated with the risk of MetS in this study must be validated by further functional studies to reveal any potential effects on metabolism.

ADIPOQ, ADIPOR1, and ADIPOR2 polymorphisms in relation to serum adiponectin levels and BMI in black and white women

Adiponectin is an adipose-secreted protein with influence on several physiologic pathways including those related to insulin sensitivity, inflammation, and atherogenesis. Adiponectin levels are highly heritable and several single-nucleotide polymorphisms (SNPs) in adiponectin-related genes (ADIPOQ, ADIPOR1, ADIPOR2) have been examined in relation to circulating adiponectin levels and obesity phenotypes, but despite differences in adiponectin levels and obesity prevalence by race, few studies have included black participants. Using cross-sectional interview data and blood samples collected from 990 black and 977 white women enrolled in the Southern Community Cohort Study (SCCS) from 2002 to 2006, we examined 25 SNPs in ADIPOQ, 19 in ADIPOR1, and 27 in ADIPOR2 in relation to serum adiponectin levels and BMI using race-stratified linear regression models adjusted for age and percentage African ancestry. SNP rs17366568 in ADIPOQ was significantly associated with serum adiponectin levels in white women only (adjusted mean adiponectin levels = 15.9 for G/G genotype, 13.7 for A/G, and 9.3 for A/A, P = 0.00036). No other SNPs were associated with adiponectin or BMI among blacks or whites. Because adiponectin levels as well as obesity are highly heritable and vary by race but associations with polymorphisms in the ADIPOQ, ADIPOR1, and ADIPOR2 genes have been few in this and other studies, future work including large populations from diverse racial groups is needed to detect additional genetic variants that influence adiponectin and BMI.

Role of glycated hemoglobin in the prediction of future risk of T2DM

AIM

The aim of this study was to assess the predictive power of glycated hemoglobin (HbA1c) for future type 2 diabetes risk.

RESEARCH DESIGN AND METHODS

Six hundred eighty-seven subjects who were free of type 2 diabetes mellitus (T2DM) participated in the study. Each subject received a 75-g oral glucose tolerance test at baseline and 624 received a repeat oral glucose tolerance test after 3.5 ± 0.1 yr of follow-up. Anthropometric measurements, lipid profile, and HbA1c were measured during the baseline visit. Logistic multivariate models were created with T2DM status at follow-up as the dependent variable and other parameters as the independent variables. The receiver-operating characteristic (ROC) was used to assess the predictive discrimination of the various models.

RESULTS

HbA1c was a significant predictor of future T2DM risk (area under the ROC curve = 0.73, P < 0.0001). A HbA1c cut point of 5.65% had the maximal sum of sensitivity and specificity. Although the area under the ROC curve of HbA1c was smaller than the area under the ROC curve of both the 1-h plasma glucose concentration and a multivariate logistic model (including anthropometric parameters, lipid profile, and fasting plasma glucose), the addition of HbA1c to both the 1-h plasma glucose and the multivariate logistic model significantly increased their predictive power.

CONCLUSION

Although HbA1c alone is a weaker predictor of future T2DM risk compared with the 1-h plasma glucose, it provides additive information about future T2DM risk when added to previously published prediction models.

Association of +45(T/G) and +276(G/T) polymorphisms in the adiponectin gene with coronary artery disease in a population of Iranian patients with type 2 diabetes

The relation of Two single nucleotide polymorphisms (SNPs) at the adiponectin locus (+45T/G and +276G/T) with coronary artery disease (CAD) is controversial. The aim of the present study was to evaluate the genetic influence of the adiponectin gene polymorphisms in the development of CAD among patients with Type 2 diabetes (T2D). The adiponectin genotypes were detected by polymerase chain reaction and restriction analysis (PCR-RFLP) in our patients. Two adiponectin gene (ADIPOQ) SNPs (i.e. SNPs +45T>G and +276G>T) were genotyped in 114 Type 2 diabetic subjects with CAD, and 127 Type 2 diabetic patients without CAD. Demographic and anthropometric data along with plasma biochemistry including lipids, glycemic indices, and adiponectin were collected. There was a significant difference in the distribution of genotypes of +45T/G and +276G/T between CAD and non-CAD individuals (P < 0.05). Based on our results SNP+276G>T is associated with decreased risk of CAD after adjustment for potential confounding factors [adjusted OR = 0.39 (95%CI: 0.22-0.68); P = 0.001]. Similar findings were not observed for the +45T>G SNP. Two haplotypes 45T-276T and 45G-276T were associated with a decreased risk of CAD [adjusted OR = 0.47 (95% CI: 0.32-0.94); P = 0.03 and adjusted OR = 0.33 (95% CI: 0.13-0.83); P = 0.02 respectively]. No significant difference was observed between HOMA-IR, BMI, waist circumference, history of hypertension, HbA1C, and lipid concentrations regarding the two SNPs. In conclusion, these findings suggest that T allele of +276G>T SNP is significantly associated with decreased risk of CAD in T2D Patients. Also Haplotype analysis showed that two haplotypes 45T-276T and 45G-276T were associated with a decreased risk of CAD.

Genetic effects of adiponectin on blood lipids and blood pressure

OBJECTIVE

Results from the published studies on the association of adiponectin gene (ADIPOQ) polymorphisms with blood lipids and blood pressure are conflicting. We investigated the association of three ADIPOQ polymorphisms, +45 T > G (rs2241766), +276 G > T (rs1501299) and -11377 C > G (rs266729), with these traits in this meta-analysis.

RESEARCH DESIGN AND METHODS

We included 35 studies in this meta-analysis. Dominant models were used for this meta-analysis.

RESULTS

We did not detect a significant association of the -11377 C > G polymorphism with blood lipids or blood pressure (P > 0·05). The association of the +45 T > G polymorphism with blood lipids and blood pressure was, similarly, not significant (P > 0·05). The meta-analysis suggested a significant overall association of the +276 G > T polymorphism with lower levels of total cholesterol: weighted mean difference (WMD) = -0·10, 95% confidence interval (CI, -0·17, -0·03), P = 0·005, P(heterogeneity)  = 0·04. This association was marginally significant in East Asians and East Asians with type 2 diabetes: WMD = -0·10, 95% CI (-0·20, 0·00), P = 0·05, P(heterogeneity)  = 0·002, and WMD = -0·09, 95% CI (-0·18, -0·00), P = 0·05, P(heterogeneity)  = 0·80, respectively. After exclusion of a study that was the source of heterogeneity, the association was significant in overall populations and marginally significant in East Asians: WMD= -0·06, 95% CI (-0·11, -0·01), P = 0·01, P(heterogeneity)  = 0·98, and WMD = -0·06, 95% CI (-0·12, 0·00), P = 0·07, P(heterogeneity)  = 0·83, respectively. However, none of these associations were significant after Bonferroni correction (significant threshold: P < 0·003).

CONCLUSIONS

Our meta-analysis does not suggest any association of the three ADIPOQ polymorphisms with blood lipids and blood pressure.

Relation of a common variant of the adiponectin gene to serum adiponectin concentration and metabolic traits in an aged Japanese population

Adiponectin is an adipocyte-derived protein that is down-regulated in obesity-linked disorders. Variants of the adiponectin gene (ADIPOQ) have been shown to affect adiponectin level. We have now examined the relation of polymorphisms of ADIPOQ to adiponectin concentration and to metabolic disorders in the Kita-Nagoya Genomic Epidemiology study, a population-based study of elderly Japanese. The genomic region including ADIPOQ was genotyped for 30 single nucleotide polymorphisms in 500 subjects of a screening population with the use of a fluorescence- or colorimetry-based allele-specific DNA primer-probe assay system. Four polymorphisms were then selected for genotyping in an additional 2797 subjects. Serum adiponectin level was negatively associated with metabolic abnormalities after adjustment for age and sex. The minor alleles of the rs1656930, Ile164Thr, and rs9882205 polymorphisms were associated with a low serum adiponectin level. Whereas the minor alleles of rs1656930 and rs9882205 were common (minor allele frequency of 6.2 and 38.5%, respectively), that of Ile164Thr was rare (0.9%). The minor allele of rs1656930 was positively associated with systolic blood pressure and the prevalence of hypertension. The association of rs1656930 with adiponectin level was replicated in an independent population. A subject with the 164Thr/Thr genotype had an extremely low serum adiponectin level (0.6 μg/ml) and the phenotype of metabolic syndrome. Our results suggest that a common variant of ADIPOQ, the minor allele of rs1656930, is associated with hypoadiponectinemia and hypertension. Screening for a common genetic background underlying low adiponectin levels might provide important information for assessment and management of metabolic disorders.

Decision trees as a simple-to-use and reliable tool to identify individuals with impaired glucose metabolism or type 2 diabetes mellitus

OBJECTIVE

The prevalence of unknown impaired fasting glucose (IFG), impaired glucose tolerance (IGT), or type 2 diabetes mellitus (T2DM) is high. Numerous studies demonstrated that IFG, IGT, or T2DM are associated with increased cardiovascular risk, therefore an improved identification strategy would be desirable. The objective of this study was to create a simple and reliable tool to identify individuals with impaired glucose metabolism (IGM).

DESIGN AND METHODS

A cohort of 1737 individuals (1055 controls, 682 with previously unknown IGM) was screened by 75 g oral glucose tolerance test (OGTT). Supervised machine learning was used to automatically generate decision trees to identify individuals with IGM. To evaluate the accuracy of identification, a tenfold cross-validation was performed. Resulting trees were subsequently re-evaluated in a second, independent cohort of 1998 individuals (1253 controls, 745 unknown IGM).

RESULTS

A clinical decision tree included age and systolic blood pressure (sensitivity 89.3%, specificity 37.4%, and positive predictive value (PPV) 48.0%), while a tree based on clinical and laboratory data included fasting glucose and systolic blood pressure (sensitivity 89.7%, specificity 54.6%, and PPV 56.2%). The inclusion of additional parameters did not improve test quality. The external validation approach confirmed the presented decision trees.

CONCLUSION

We proposed a simple tool to identify individuals with existing IGM. From a practical perspective, fasting blood glucose and blood pressure measurements should be regularly measured in all individuals presenting in outpatient clinics. An OGTT appears to be useful only if the subjects are older than 48 years or show abnormalities in fasting glucose or blood pressure.

Association of adiponectin gene polymorphisms with the risk of ischemic stroke in a Chinese Han population

Adiponectin is inversely associated with the risk of ischemic stroke through its anti-inflammatory and anti-atherogenic effects. Genetic variations in the adiponectin gene (ADIPOQ) have been shown to be associated with the risk of ischemic stroke in Caucasians and Japanese populations. However, it was unknown whether variations in the ADIPOQ gene were associated with the risk of ischemic stroke in Chinese population. A case-control study was performed among 302 patients with ischemic stroke and 338 unrelated controls in a Chinese Han population. The single-nucleotide polymorphisms (SNPs) rs266729 (-11377C/G), rs2241766 (+45T/G), rs1501299 (+276G/T) in the ADIPOQ gene were genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The frequencies of GG genotype and G allele of rs266729 in the patients with ischemic stroke were significantly higher than those in the controls (P = 0.034, P = 0.010, respectively). In univariate logistic analysis, compared with CC genotype, GG genotype of rs266729 increased the risk of ischemic stroke (odds ratio (OR) = 2.062, 95% confidence interval (CI) = 1.145-3.715, P = 0.016). After adjustment for potential risk factors by the multivariate logistic analysis, rs266729 remained positive correlation with ischemic stroke (OR = 2.165; 95% CI = 1.116-4.197, P = 0.022). However, no significant association was observed among rs2241766, rs1501299 and ischemic stroke. In addition, no significant difference was found in haplotype frequencies between the patients with ischemic stroke and control subjects. The present study demonstrated that the promoter polymorphism rs266729 of the ADIPOQ gene was associated with an increased risk of ischemic stroke in the Chinese Han population.

Gestational diabetes mellitus screening based on the gene chip technique

AIM

The present study sought to validate the gene chip technique to screen for gestational diabetes mellitus (GDM).

METHODS

We selected 70 single-nucleotide polymorphisms (SNPs) associated with diabetes in previous studies, and SNP genotyping was performed in 130 cases (50 diabetes patients and 80 normal controls whose mean term of pregnancies are similarly 38-39 weeks). Relevant SNP patterns were established, and gene chips were designed after statistically analyzing the data. Peripheral blood samples were then collected from 24 healthy pregnant women and 24 pregnant women with GDM for gene chip analysis. The results of the gene chip method were also verified by DNA sequencing.

RESULTS

Four candidate SNPs (rs13266634, rs266729, rs3802177 and rs9300039) were obtained after genotyping. Primers were designed based on the four SNPs, and gene chips met the quality standard according to signal intensity. The genotypes of SNPs rs3802177, rs13266634 and rs266729 showed significant differences between healthy pregnant women and pregnant women with GDM, and these results were identical to those obtained with the DNA sequencing method.

CONCLUSIONS

We have demonstrated the feasibility of the gene chip technique in screening GDM and identified candidate loci with which to study this disease.

Adiponectin gene polymorphisms and their effect on the risk of myocardial infarction and type 2 diabetes: an association study in an Italian population

OBJECTIVE

While many studies have shown an association between the gene coding for adiponectin (ADIPOQ) and adiponectin levels, much more controversy surrounds its association with metabolic traits such as insulin resistance, obesity and type 2 diabetes. Furthermore, very few studies have looked into the relations between ADIPOQ variants and risk of cardiovascular disease. The present study assessed the influence of four common ADIPOQ Single Nucleotide Polymorphisms (SNPs), rs17300539 (-11391G→A), rs266729 (-11377C→G), rs2241766 (+45T→G) and rs1501299 (+276G→T) on the risk of myocardial infarction and type 2 diabetes.

METHODS

and

RESULTS

A large genetic association case-control study was conducted in 2008 Italians, including patients with myocardial infarction, type 2 diabetes, or both, and a reference group of healthy controls. Homozygotes TT for the rs1501299 (+276) had half the risk of either myocardial infarction alone or in association with type 2 diabetes when compared to the carriers of the G allele (OR = 0.58, p =0.01, and OR = 0.55, p =0.006 respectively). SNPs rs17300539 (-11391), rs266729 (-11377) and rs2241766 (+45) showed no significant association with any of the three case groups.

CONCLUSIONS

These results suggest that homozygotes TT for the adiponectin polymorphism rs1501299 (+276) are protected from the risk of myocardial infarction.

Gender differences in adiponectin and low-grade inflammation among individuals with normal glucose tolerance, prediabetes, and type 2 diabetes

BACKGROUND

Women with prediabetes and type 2 diabetes mellitus have a higher relative risk of cardiovascular disease than do men. The reason for this is unknown.

OBJECTIVE

We studied the gender differences in adiponectin and in low-grade inflammation, measured by high-sensitivity C-reactive protein (hs-CRP) and interleukin-1 receptor antagonist (IL-1RA), in individuals with normal glucose tolerance, prediabetes, and type 2 diabetes.

METHODS

In this population-based, cross-sectional study, all individuals born in 1942, 1947, 1952, 1957, and 1962 in Pieksämäki, East Finland, were recruited for participation. A 75-g oral glucose tolerance test and lipid panel were performed, and concentrations of adiponectin, hs-CRP, and IL-1RA were measured. The World Health Organization diagnostic criteria for diabetes and prediabetes (impaired fasting glucose and/or impaired glucose tolerance) were used. Statistical comparisons between men and women were performed by a bootstrap-type ANCOVA.

RESULTS

The eligible population included 1294 middle-aged individuals, and of these, 904 (406 men and 498 women) had complete data and were included in the analyses. Absolute adiponectin concentrations were significantly higher in women at all levels of glucose tolerance (normal, prediabetes, and type 2 diabetes), but the gender ratio (women to men) for adiponectin concentrations decreased linearly (P = 0.011) from normal glucose tolerance (1.61; 95% CI, 1.48-1.75) to prediabetes (1.57; 95% CI, 1.36-1.83) and diabetes (1.16; 95% CI, 0.87-1.53). Among participants with normal glucose tolerance, no significant difference was found between the sexes in hs-CRP or IL-1RA. Among patients with prediabetes or diabetes, women had significantly higher concentrations than did men for hs-CRP (for prediabetes, 2.0 vs 1.5 mg/L; ratio, 1.39; 95% CI, 1.04-1.85) and IL-1RA (for prediabetes, 255 vs 178 pg/mL; ratio, 1.43; 95% CI, 1.121.83). The gender ratios (women to men) increased linearly from normal glucose tolerance to prediabetes and type 2 diabetes for both hs-CRP (P = 0.019) and IL-1RA (P = 0.013).

CONCLUSIONS

Adiponectin concentrations in women decreased relatively more compared with men across individuals with normal glucose tolerance, prediabetes, and type 2 diabetes, whereas inflammatory markers increased relatively more in women. Higher inflammatory stress in women than in men with prediabetes and type 2 diabetes may explain their relatively higher cardiovascular disease risk.

Effect of short hairpin RNA-mediated adiponectin/Acrp30 down-regulation on insulin signaling and glucose uptake in the 3T3-L1 adipocytes

Adiponectin is a polypeptide hormone that is secreted by adipocytes with insulin-sensitizing and anti-inflammatory properties. The current study was to further investigate the role of adiponectin on glucose uptake and its underlying mechanism by down-regulation of adiponectin in 3T3-L1 adipocytes. Transfection of short hairpin RNA (shRNA)-vector significantly decreased adiponectin mRNA expression and its protein level in the cells. The down-regulation of adiponectin markedly reduced the cellular glucose uptake rate and increased intracellular triglyceride content. To study the mechanism of the physiologic action of adiponectin, several key regulatory factors in insulin signaling pathway were examined. The mRNA expression of insulin receptor substrate (IRS)-1 in both basal and insulin-stimulated states were down-regulated in the transfected cells (72% and 52% of controls, respectively), and the insulin-stimulated IRS-1 tyrosine phosphorylation was also significantly decreased. Adiponectin-deficient cells showed marked down-regulations of peroxisome proliferator-activated receptor alpha, glucose transporter (GLUT)-1, GLUT-4, hormone-sensitive lipase (HSL), and adipose triglyceride lipase. These results thus demonstrated that transfection of shRNA-vector effectively reduced the expression of adiponectin in 3T3-L1 adipocytes accompanied with a significant decrease in cellular glucose uptake rate and an increase in intracellular triglyceride content. Our data also suggested that adiponectin deficiency impair insulin action in vitro probably through the IRS-1 pathway, and increase intracellular fat accumulation partially through HSL down-regulation.

Low plasma adiponectin level, white blood cell count and Helicobacter pylori titre independently predict abnormal pancreatic beta-cell function

Adiponectin is an adipocytokine with insulin sensitizing effect while chronic inflammation damages pancreatic beta-cells leading to reduced insulin response. We aimed to prove the hypothesis that adiponectin levels and inflammatory markers (white blood cell counts [WCC], Helicobacter pylori [HP] titers, high sensitivity C-reactive protein [hs-CRP]) may interact to affect risk of diabetes. We studied 288 Chinese men (age-median: 41.0 years, IQR: 35.3-46.0 years) being recruited from the community in Hong Kong. The mean adiponectin level was 5.39+/-2.81 microg/ml and 40.9% (n=107) had low adiponectin level (<4 microg/ml). On multiple regression analysis, adiponectin was negatively associated with diabetes, HOMA insulin resistance top quartile, plasma glucose (PG) and 2h insulin; and positively associated with HOMA insulin sensitivity index. WCC was independently associated with PG and 15' insulin, and negatively associated with HOMA insulin sensitivity top quartile. HP titre was associated with 30' PG level and diabetes. hs-CRP did not enter the multivariable model. In conclusion, adiponectin, WCC and HP titer are independent predictors for hyperglycemia and reduced insulin sensitivity in Chinese men. These findings may explain the high risk for diabetes in Chinese population despite their relatively low adiposity.

APM1 gene variants -11377C/G and 4545G/C are associated respectively with obesity and with non-obesity in Chinese type 2 diabetes

In order to explore the different genetic backgrounds of non-obese and obese type 2 diabetes, we tried to genotype six SNPs (-11391G/A, -11377C/G, -10068G/A, G54V, Y111H and 4545G/C) in the adipose most abundant gene transcript-1 (APM1) gene in 338 type 2 diabetes (T2D) patients and 460 non-diabetic subjects by PCR-RFLP. Among these mutations, the 4545G/C mutation (rs1063539) contributed to the genetic risk of T2D in the non-obese group (OR=2.34, 95%CI: 1.31-4.21, P=0.004), and 57% of the risk is related to this polymorphism. On the contrary, -11377C/G (rs266729) was associated with type 2 diabetes in the obese group only (OR=2.45, 95%CI: 1.13-5.31, P=0.02), and 59% risk of diabesity could be attributed to that. All the associations above were adjusted for age and gender in unconditional logistic regression. Besides, the -11377G/4545C haplotype was merely related to obese diabetes (OR=2.12, 95%CI: 1.08-4.14, P=0.03). In addition, the obese diabetic group had significantly higher levels of triglyceride and insulin, better beta-cell function but lower glucose levels than the non-obese group (all P values <0.01). This study suggests that the genetic susceptibility is different between type 2 diabetes with and without obesity in Chinese Han population.

ADIPOQ polymorphisms, monounsaturated fatty acids, and obesity risk: the GOLDN study

Serum adiponectin levels have been positively associated with insulin sensitivity and are decreased in type 2 diabetes (T2D) and obesity. Genetic and environmental factors influence serum adiponectin and may contribute to risk of metabolic syndrome and T2D. Therefore, we investigated the effect of ADIPOQ single-nucleotide polymorphisms (SNPs), -11377C>G and -11391G>A, on metabolic-related traits, and their modulation by dietary fat in white Americans. Data were collected from 1,083 subjects participating in the Genetics of Lipid Lowering Drugs and Diet Network study. Mean serum adiponectin concentration was higher for carriers of the -11391A allele (P = 0.001) but lower for the -11377G allele carriers (P = 0.017). Moreover, we found a significant association with obesity traits for the -11391G>A SNP. Carriers of the -11391A allele had significantly lower weight (P = 0.029), BMI (P = 0.019), waist (P = 0.003), and hip circumferences (P = 0.004) compared to noncarriers. Interestingly, the associations of the -11391G>A with BMI and obesity risk were modified by monounsaturated fatty acids (MUFAs) intake (P-interaction = 0.021 and 0.034 for BMI and obesity risk, respectively). In subjects with MUFA intake above the median (> or =13% of energy intake), -11391A carriers had lower BMI (27.1 kg/m(2) for GA+AA vs. 29.1 kg/m(2) for GG, P = 0.002) and decreased obesity risk (odds ratio for -11391A = 0.52, 95% confidence interval (CI); 0.28-0.96; P = 0.031). However, we did not detect genotype-related differences for BMI or obesity in subjects with MUFA intake <13%. Our findings support a significant association between the -11391G>A SNPs and obesity-related traits and the potential to moderate such effects using dietary modification.

The Finnish Diabetes Risk Score is associated with insulin resistance and progression towards type 2 diabetes

OBJECTIVE

The Finnish Diabetes Risk Score (FINDRISC) questionnaire is a practical screening tool to estimate the diabetes risk and the probability of asymptomatic type 2 diabetes. In this study we evaluated the usefulness of the FINDRISC to predict insulin resistance in a population at increased diabetes risk.

DESIGN

Data of 771 and 526 participants in a cross-sectional survey (1996) and a cohort study (1997-2000), respectively, were used for the analysis. Data on the FINDRISC and oral glucose tolerance test parameters were available from each participant. The predictive value of the FINDRISC was cross-sectionally evaluated using the area under the curve-receiver operating characteristics method and by correlation analyses. A validation of the cross-sectional results was performed on the prospective data from the cohort study.

RESULTS

The FINDRISC was significantly correlated with markers of insulin resistance. The receiver operating characteristics-area under the curve for the prediction of a homeostasis model assessment insulin resistance index of more than five was 0.78 in the cross-sectional survey and 0.74 at baseline of the cohort study. Moreover, the FINDRISC at baseline was significantly associated with disease evolution (P < 0.01), which was defined as the change of glucose tolerance during the 3 yr follow-up.

CONCLUSIONS

The results indicate that the FINDRISC can be applied to detect insulin resistance in a population at high risk for type 2 diabetes and predict future impairment of glucose tolerance.

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

OBJECTIVE

Polymorphisms in the adiponectin gene (ADIPOQ) have been associated with type 2 diabetes and diabetic nephropathy in type 1 diabetes, in mostly European-derived populations.

RESEARCH DESIGN AND METHODS

A comprehensive association analysis of 24 single-nucleotide polymorphisms (SNPs) in the adiponectin gene was performed for type 2 diabetes and diabetic nephropathy in African Americans.

RESULTS

The minor allele (A) in a single SNP in intron 1 (rs182052) was associated with diabetic nephropathy (P = 0.0015, odds ratio [OR] 1.37, CI 1.13-1.67, dominant model) in an African American sample of 851 case subjects with diabetic nephropathy and 871 nondiabetic control subjects in analyses incorporating adjustment for varying levels of racial admixture. This association remained significant after adjustment of the data for BMI, age, and sex (P = 0.0013-0.0004). We further tested this SNP for association with longstanding type 2 diabetes without nephropathy (n = 317), and evidence of association was also significant (P = 0.0054, OR 1.46, CI 1.12-1.91, dominant model) when compared with the same set of 871 nondiabetic control subjects. Combining the type 2 diabetes and diabetic nephropathy samples into a single group of case subjects (n = 1,168) resulted in the most significant evidence of association (P = 0.0003, OR 1.40, CI 1.17-1.67, dominant model). Association tests between age at onset of type 2 diabetes and the rs182052 genotypes also revealed significant association between the presence of the minor allele (A/A or A/G) and earlier onset of type 2 diabetes.

CONCLUSIONS

The SNP rs182052 in intron 1 of the adiponectin gene is associated with type 2 diabetes in African Americans.

An update on preventive and regenerative therapies in diabetes mellitus

Type 1A (immune-mediated) and type 2 diabetes mellitus are two of the most common severe chronic illnesses, affecting over 230 million people worldwide with an estimated global prevalence of 5.1%. Although type 1 and type 2 diabetes differ greatly in modes of pathogenesis, these illnesses share a common pathology and consequences characterized by loss of functional beta-cell mass and subsequent dysregulation of carbohydrate and lipid metabolism. Since therapy for diabetes and the associated complications poses enormous public health and economic burdens, novel preventive and regenerative therapies have emerged in the past decade with the aim to preserve beta-cell mass and delay the onset of diabetes. The goal of this review is to provide a comprehensive overview of current efforts in the fight against diabetes, and attempts to document all strategies that have emerged in clinical studies within the past 25 years. First, strategies to identify individuals at risk, ranging from whole-genome scans to autoantibody screening, will be discussed. Second, novel approaches to prevent or delay the onset of disease will be covered. Particular focus is given on emerging strategies for individuals at risk for type 1 diabetes that target T-cell regulation and induction of tolerance, while new pharmaceutical concepts in combination with lifestyle interventions are discussed within the scope of type 2 diabetes prevention. Lastly, important efforts to halt disease progression with emphasis on beta-cell regeneration are presented.

Low serum adiponectin level as a predictor of impaired glucose regulation and type 2 diabetes mellitus in a middle-aged Finnish population

Low levels of adiponectin are associated with obesity and type 2 diabetes mellitus (DM2). However, only few studies on this topic have used the most recent World Health Organization 1999 criteria, which include a definition of impaired glucose regulation (IGR). Our objective was to find out if a baseline low adiponectin level in initially normoglycemic subjects predicted IGR or DM2 during a mean follow-up period of 5.1 years. A population-based cohort study was carried out in Oulu, Northern Finland. Subjects born in 1935 and living in Oulu in 1990 were invited to participate in a follow-up study. At baseline, oral glucose tolerance tests and measurements of adiponectin, lipids, blood pressure, and body mass index were performed; and oral glucose tolerance tests were repeated at follow-up. Analyses were performed for 201 subjects who were normoglycemic at baseline. Low adiponectin level was defined as the lowest quartile of adiponectin levels. During the follow-up, 47 (23%) of the 201 subjects developed IGR or DM2. Impaired glucose regulation or DM2 developed in 15 of 41 (37%) subjects with low adiponectin level at baseline, whereas the corresponding proportion was 32 of 160 (20%) subjects with higher adiponectin levels (P = .025). In logistic regression analysis, the adjusted odds ratio for IGR or DM2 was 2.1 (95% confidence interval, 1.0-4.5) when adjustment was made for sex and body mass index. Low concentrations of adiponectin predicted subsequent development of IGR and DM2 in initially normoglycemic middle-aged Finnish subjects. Our findings support the hypothesis that adiponectin may play a role in the pathogenesis of abnormal glucose metabolism.

The genetics of gestational diabetes mellitus: evidence for relationship with type 2 diabetes mellitus

Gestational diabetes is a major public health problem because of its prevalence, its associated complications during pregnancy, and its increased risk for type 2 diabetes later in life. Insulin resistance is one of many physiological changes occurring during pregnancy, and when insulin resistance is accompanied by pancreatic beta-cell insufficiency, gestational diabetes may develop. Several lines of evidence suggest that gestational diabetes shares a common etiology with type 2 diabetes and support the hypothesis that gestational diabetes serves as a window to reveal a predisposition to type 2 diabetes. Pregnancy is an environmental stressor that may catalyze the progression to a diabetic state in genetically predisposed women; therefore, identification of these women during pregnancy could decrease the occurrence of type 2 diabetes through targeted prevention. This review presents an overview of the genetics of gestational diabetes, focusing on human association studies with candidate genes common to both type 2 diabetes and gestational diabetes.

Adiponectin gene ADIPOQ SNP associations with serum adiponectin in two female populations and effects of SNPs on promoter activity

Adiponectin is an insulin sensitiser in muscle and liver, and low serum levels characterise obesity and insulin resistance. Eight tagging single nucleotide polymorphisms (tSNPs) in the ADIPOQ gene and promoter were selected, and association with serum adiponectin was tested, in two independent samples of Caucasian women: the Chingford Study (n = 808, mean age 62.8 +/- 5.9 years) and Twins UK (n = 2,718, mean age 47.4 +/- 12.6 years). In the Chingford cohort, -11391 G/A, -10066 G/A (rs182052), -7734 C/A (rs16861209), +276 G/T (rs1501299) and +3228 C/T (rs1063537) were significantly associated with fasting serum adiponectin (Ps = 1.00 x 10(-4) to 1.40 x 10(-2)). Associations with all except +3228 C/T were replicated in the Twins UK cohort (Ps = 3.19 x 10(-9) to 6.00 x 10(-3)). In Chingford subjects, the 12 most common 8-SNP haplotypes (frequency 1.90%) explained 2.85% (p = 5.00 x 10(-2)) and in Twins UK subjects, the four most common 5-SNP haplotypes (frequency > 5.00%) explained 1.66% of the variance (p = 5.83 x 10(-7)). To investigate effects of -11391 G/A (rs17300539) and -11377 C/G (rs266729) on promoter activity, 1.2 kb of the ADIPOQ promoter region was cloned in a luciferase reporter plasmid, and the four haplotypes were transfected in differentiated 3T3-L1 adipocytes. No significant allelic effects on promoter activity were found.