ENPP1 K121Q Research Articles

An observational study of the risk of neonatal macrosomia, and early gestational diabetes associated with selected candidate genes for type 2 diabetes mellitus polymorphisms in women with gestational diabetes mellitus.

1) to analyse the prevalence of selected candidate genes for type 2 diabetes mellitus polymorphisms (IRS1 G972R; ENPP1 K121Q; ADRB3 W64R) among women with gestational diabetes; and 2) to investigate any association between variants of these genes and risk of neonatal macrosomia. We conducted a prospective observational study of a group of women (N = 140) in singleton pregnancies who delivered at term. Characteristics of the study group at enrolment: age: 32.0 ± 4.9 years; GA: 26.6 ± 7.5 weeks; HbA1c: 5.6 ± 0.6%; fasting blood glucose: 102.3 ± 16.3 mg/dL; insulin treatment (G2DM): 65.7%; chronic hypertension: 11.4%; gestational hypertension: 17.9%; preeclampsia: 1.4%; birth weight: 3590 ± 540 g; birth weight ≥ 4000 g (macrosomia): 18.6%; caesarean section: 44.3%; and female newborns: 57.1%. The maternal metabolic characteristics at the time of booking did not differ between polymorphisms. Macrosomia was insignificantly more frequent in females (22.5%) than in males (13.3%) (p = 0.193). Only maternal height and body weight at the time of booking significantly predicted birth weight (R = 0.27, p = 0.007; R = 0.25, p = 0.005, respectively). IRS1 G972R GR and ENPP1 K121Q KQ polymorphisms were associated with an insignificantly increased risk for macrosomia. Carriers of the heterozygotic variant of the IRS 1 gene were significantly more likely to be diagnosed with GDM/DiP in the first trimester: OR 5.2, 95% CI: 1.4; 19.2; p = 0.014. 1) having similar metabolic characteristics, carriers of specific variants of T2DM candidate genes might be at increased risk of delivery of macrosomic newborns; 2) any association between genetic variants and macrosomia in this population might be gender-specific; and 3) allelic variation in the IRS1 gene is associated with early GDM/DiP.

A multifactor dimensionality reduction model of gene polymorphisms and an environmental interaction analysis in type 2 diabetes mellitus study among Punjabi, a North India population

The effects of any single genetic variation for a common complex disease such as T2DM may be dependent on other genetic variations (gene-gene interactions) and environmental factors (gene-environment interactions). Multifactor Dimensionality Reduction (MDR) method helps in detection and characterization of susceptibility in common complex multifactor disorders like Type 2 Diabetes Mellitus (T2DM). The negligible studies are available with this model approach to detect the status of T2DM in north Indian population. Hence, the major objectives of the present study were to investigate the association of ENPP1 K121Q (rs1044498), TCF7L2 G > T (rs12255372) and GYS1 XbaI (A1 > A2) (rs8103451) gene variants with T2DM in the north Indian population; and to determine whether significant gene-gene and gene-environment (risk factors related to obesity and cardiovascular diseases) interactions exist between these selected genes in affecting type 2 diabetes mellitus using MDR analysis. A total of 500 participants consisting of 250 type 2 diabetes mellitus (T2DM) and 250 healthy subjects were recruited for this study. Genotyping was performed by PCR-RFLP method. Anthropometric and physiometric variables such as height, weight, waist circumference (WC), hip circumference (HC), SBP and DBP, were measured using standard protocol. The odds ratio and Hardy- Weinberg equilibrium deviation analyses were performed. The gene-gene and gene-environment interactions were performed by multifactor dimensionality reduction (MDR) analysis. In results it was observed that two genes ENPP1 and TCF7L2 are associated with T2DM. However, an insignificant association of the XbaI (A1 > A2) polymorphism in GYS1 gene with T2DM was demonstrated. The gene-gene interactions revealed that all the three SNPs have a synergistic effect with each other. The MDR method for gene-environment interactions showed all interaction models first to ninth order interactions for T2DM patients as significant for susceptibility of obesity. The results showed that both the genes ENPP1 and TCF7L2 interacting with WHR and WC increase the susceptibility of obesity many folds among T2DM patients and non-diabetic controls. In conclusion, it is suggested that pathogenesis of T2DM, obesity and hypertension involves interplay of a variety of susceptibility alleles and environment. The gene-gene and gene-environment interactions are not only possible, but, are probably ubiquitous in determining the susceptibility of complex human diseases. Further studies on epistatic interactions are warranted to elucidate their possible underlying role in pathogenesis of T2DM.

ENPP1 K121Q Functional Variant Enhances Susceptibility to Insulin Resistance and Dyslipidemia with Metabolic Syndrome in Asian Indians

Background: Ectonucleotide pyrophosphatase/phosphodiesterase1 (ENPP1/PC-1) is a key modulator of the insulin signaling pathway, and its common variant, K121Q, increases the susceptibility to diabetes and cardiovascular diseases. Objectives: The main objective of the present study was to investigate the association of ENPP1 K121Q polymorphism with the pathophysiology of metabolic syndrome (MetS) in a north Indian population. Methods: A total of 567 participants (303 MetS subjects and 264 healthy controls) were examined for ENPP1 genotypes and various clinical parameters, including body mass index (BMI), waist circumference (WC), systolic and diastolic blood pressures (SBP/DBP), fasting blood glucose (FBG), cholesterol, triglycerides (TG), high-density lipoprotein, and insulin. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Statistical analysis of the data was done using SPSS. Results: Significant increases in BMI, WC, SBP, DBP, FBG, TG, low-density lipoprotein, insulin, and Homeostasis Model Assessment of insulin resistance (HOMA-IR) and of beta-cell function (HOMA-BF) were observed in MetS patients compared to healthy controls. Logistic regression analysis of data demonstrated a nonsignificant association of QQ and KQ+QQ genotypes with increased risk of MetS (OR [95% CI], 1.583 [0.455–5.507], p = 0.470 for QQ genotypes and 1.097 [0.784–1.540], p = 0.587 for KQ+QQ genotypes). Moreover, MetS subjects carrying Q alleles had significantly higher levels of TG, insulin, body fat percentage, and insulin resistance as evident by higher values of HOMA-IR. Conclusions: We conclude that ENPP1 K121Q functional variant enhances susceptibility to insulin resistance and dyslipidemia in MetS subjects of an Asian Indian population.

The ENPP1 K121Q polymorphism modulates developing of bone disorders in type 2 diabetes: A cross sectional study

BackgroundOsteoporosis and osteopenia are common diseases in every population. Type 2 diabetes mellitus (T2DM) can lead to the development of various complications, such as bone disorders especially among elderly individuals. Studies suggested that ectonucleotide pyrophosphatase/phosphodiesterase1 (ENPP1) is contributed in insulin resistance and also the inhibition of bone mineralization. In this study, association of K121Q (rs1044498) polymorphism of the ENPP1 gene with T2DM and bone disorders is evaluated. MethodsFour-hundred-and-ninety females who were classified based on bone mineral density (BMD) at lumbar spine and femur were included in this study. In addition, participants were classified according to their diabetes status. K121Q polymorphism was evaluated by the PCR-PFLF technique. One-way ANOVA was used for comparison of various analyzed factors in diseases subgroups and K121Q genotypes. Association of K121Q polymorphism with diabetes and bone disorders was evaluated by logistic regression. ResultsSignificant association was observed between K121Q polymorphism with osteoporosis and osteopenia (p=0.041, p=0.029, respectively), but a similar pattern was not observed in T2DM status (p=0.723). Moreover, in diabetic patients, K121Q polymorphism showed a better prediction potential for the development of bone disorders in comparison to non-diabetic subjects (p=0.018; OR=4.63, p=0.540; OR=1.31). There were no significant differences between K121Q genotypes with FBS, Ca, P, vitamin D, PTH and BMD status. ConclusionsThe present study implies that K121Q polymorphism of ENPP1 gene is able to modulate the development of bone disorders in T2DM. Therefore in diabetic patients screening of this polymorphism is suggested for the monitoring of these persons.

Association between the ENPP1 K121Q polymorphism and risk of diabetic kidney disease: a systematic review and meta-analysis.

The potential association between the K121Q (A/C, rs1044498) polymorphism in the ectonucleotide pyrophosphatase/phosphodiesterase (ENPP1) gene and risk of diabetic kidney disease (DKD) has been investigated. Nevertheless, the effect of this variant on DKD risk is still under debate, and conflicting results have been reported. To this date, no meta-analysis has evaluated the association of the K121Q polymorphism with DKD. This paper describes the first meta-analysis conducted to evaluate whether the ENPP1K121Q polymorphism is associated with DKD. A literature search was conducted to identify all case-control or cross-sectional studies that evaluated associations between the ENPP1K121Q polymorphism and DKD. Pooled odds ratios (OR) and 95% confidence intervals (95% CI) were calculated for allele contrast, additive, dominant and recessive inheritance models. Seven studies were eligible for inclusion in the meta-analysis, providing data on 3571 type 1 or type 2 diabetic patients (1606 cases with DKD and 1965 diabetic controls without this complication). No significant heterogeneity was observed among the studies included in the meta-analysis when assuming different inheritance models (I² < 50% or P > 0.10 for the entire sample and after stratification by ethnicity). Meta-analysis results revealed significant associations between the K121Q polymorphism and risk of DKD in Asians and Europeans when assuming the different inheritance models analyzed. The most powerful association was observed for the additive model (OR = 1.74, 95% CI 1.27-2.38 for the total sample). In conclusion, the present meta-analysis detected a significant association between the ENPP1K121Q polymorphism and increased susceptibility of DKD in European and Asian populations.

Joint effect of insulin signaling genes on all-cause mortality

Objective: We have previously reported the combined effect of SNPs perturbing insulin signaling (ENPP1 K121Q, rs1044498; IRS1 G972R, rs1801278; TRIB3 Q84R, rs2295490) on insulin resistance (IR), type 2 diabetes (T2D) and cardiovascular events. We here investigated whether such a combined effect affects also all-cause mortality in a sample of 1851 Whites of European ancestry. Methods: We investigated a first sample of 721 patients, 232 deaths, 3389 person-years (py). Replication was assessed in two samples of patients with T2D: the Gargano Mortality Study (GMS) of 714 patients, 127 deaths, 5426 py and the Joslin Kidney Study (JKS) comprising 416 patients, 214 deaths, 5325 py. Results: In the first sample, individuals carrying 1 or ≥2 risk alleles had 33% (p = 0.06) and 51% (p = 0.02) increased risk of mortality, as compared with individuals with no risk alleles. A similar, though not significant, trend was obtained in the two replication samples only for subject carrying ≥ 2 risk alleles. In a pooled analysis, individuals carrying ≥2 risk alleles had higher mortality rate as compared to those carrying 0 risk alleles (HR = 1.34, 95%CI = 1.08–1.67; p = 0.008), and as compared to those carrying only one risk allele (HR = 1.41, 95%CI = 1.13–1.75; p = 0.002). This association was independent from several possible confounders including sex, age, BMI, hypertension and diabetes status. Conclusion: Our data suggest that variants affecting insulin signaling exert a joint effect on all-cause mortality and is consistent with a role of abnormal insulin signaling on mortality risk.

Role of the ENPP1 K121Q Polymorphism and Susceptibility to Type 2 Diabetes in North Indian Punjabi Population

In many worldwide populations, the K121Q variant of ENPP1 gene are associated with increased risk of type 2 diabetes mellitus (T2DM). The objective of the present study was to investigate the association of K121Q variant of ENPP1 gene with T2DM in North Indian Punjabi populations. A total of 500 participants consisting 250 T2DM patients and 250 healthy unrelated subjects were recruited for this study. The PCR-RFLP method was used for genotyping of K121Q polymorphism. The minor allele Q was found to be significantly associated with increased risk of T2DM (OR: 1.44, 95% CI: 1.06-1.94, p=0.015). A significant difference in QQ genotype was observed between T2DM patients and control groups (OR: 2.04, 95% CI: 1.04-3.98, p=0.033). It is also observed that co-dominant model would be best fit to predict the susceptible gene effect (OR: 1.36, 95% CI: 1.04-1.80, p=0.026). This study confirmed the association of ENPP1 polymorphism with increased risk of T2DM.

Association of Genetic Variants of MTHFR, ENPP1, and ADIPOQ with Myocardial Infarction in Egyptian Patients

The study aimed to investigate the association between MTHFR C677T, ENPP1 K121Q, and ADIPOQ 45 T/G gene polymorphisms and incidence of myocardial infarction (MI) in Egyptian patients. The study included 60 unrelated patients suffering from their first MI and 60 unrelated controls. Patients were recruited from Kasr-El Eini hospital, Cairo University. The previously mentioned polymorphisms were determined in all participants by PCR-RFLP. There was no significant difference in the distribution of genotypes and alleles of MTHFR C677T between groups. In contrast, significant difference was found in the distributions of genotypes and alleles of ENPP1 K121Q and ADIPOQ 45 T/G between MI patients and controls (P = 0.01, P = 0.004, P = 0.009, P = 0.001, respectively). Univariate analysis revealed that 121Q ENPP1 and 45 G ADIPOQ alleles were associated with the increased risk of MI (OR = 3; 95 % CI = 1.45-6.2; P = 0.004 and OR = 5.8; 95 % CI = 1.92-17.54; P = 0.001, respectively). The mutant homozygous genotypes of MTHFR, ENPP1, and ADIPOQ were more prevalent in diabetic hypertensive MI patients than it was among non-diabetic normotensive MI patients. Regarding the coagulation profile, INR (P = 0.009) and PC % (P = 0.022) were significantly different among the three genotypes of MTHFR C677T. The 677 T, 121 Q, and 45G variants were associated with MI in Egyptian patients; however, more studies are needed to determine the possible protective effect for these polymorphisms in our population.

Joint Effect of Insulin Signaling Genes on Insulin Secretion and Glucose Homeostasis

Reduced insulin signaling in insulin secreting β-cells causes defective insulin secretion and hyperglycemia in mice. We investigated whether functional polymorphisms affecting insulin signaling (ie, ENPP1 K121Q, rs1044498; IRS1 G972R, rs1801278; and TRIB3 Q84R, rs2295490) exert a joint effect on insulin secretion and abnormal glucose homeostasis (AGH). Insulin secretion was evaluated by 1) the disposition index (DI) from an oral glucose tolerance test (OGTT) in 829 individuals; 2) insulin secretion stimulation index (SI) in islets from nondiabetic donors after glucose (n = 92) or glibenclamide (n = 89) stimulation. AGH (including impaired fasting glucose and/or impaired glucose tolerance or type 2 diabetes; T2D) was evaluated in case-control studies from the GENetics of Type 2 Diabetes in Italy and the United States (GENIUS T2D) Consortium (n = 6607). Genotype risk score, obtained by totaling individual weighted risk allele effects, was associated with the following: 1) DI (P = .005); 2) glucose and glibenclamide SI (P = .046 and P = .009); or 3) AGH (odds ratio 1.08, 95% confidence interval 1.03-1.13; P = .001). We observed an inverse relationship between genetic effect and age at AGH onset, as indicated by a linear correlation between AGH-genotype risk score odds ratios and age-at-diagnosis cutoffs (R(2) = 0.80, P < .001). Functional polymorphisms affecting insulin signaling exert a joint effect on both in vivo and in vitro insulin secretion as well as on early-onset AGH. Our data provide further evidence that abnormal insulin signaling reduces β-cell function and impairs glucose homeostasis.

Type 2 diabetes in a central Indian population: association with PPARG2 P121A allele but not ENPP1 K121Q

Type 2 diabetes in a central Indian population: association with PPARG2 P121A allele but not ENPP1 K121Q Arvind Kumar Tripathi,1 Smriti Shukla,1 Mrigendra Kumar Dwivedi,1 Jitendra Kumar Tripathi,1 Ugam Kumari Chauhan,1 Manoj Indurkar,2 Shivam Singh1 1Centre for Biotechnology Studies, Awdhesh Pratap Singh University, 2Department of Medicine, Shyam Shah Medical College, Rewa, India Background: It is known that genetic and environmental factors may influence susceptibility to type 2 diabetes and its complications. Objective: In the investigation reported here we selected the peroxisome proliferator-activated receptor (PPAR) G2 (rs1801282) and ENPP1, also called PC-1 (rs1044498) gene polymorphisms to determine whether there is a genetic association between these, obesity, and type 2 diabetes. We also examined and environmental factors influencing type 2 diabetes. Design and methods: The study was carried out on a central Indian population of 190 diabetics and 210 healthy controls. Anthropometric data were collected during sample collection. A genetic polymorphism study of PPARG2 and ENPP1 was undertaken using a polymerase chain reaction restriction fragment length polymorphism method and the observed genotype frequencies, allele frequencies, and carriage rates of the PPARG2 and ENPP1 polymorphisms were recorded. Results: The patterns of genotype and allele distribution in both groups suggested a significant association between PPARG2 Pro12Ala major allele A carriage (AA carriage) and type 2 diabetes. Further, the results also show the protective effect of the minor allele G. Overall, we found that the distribution of ENPP1 K121Q genotypes was not significantly different between healthy controls and diabetic patients. Thus, ENPP1 polymorphism was not found to be associated with type 2 diabetes in a central Indian population. Body mass index was also found to be significantly higher in female diabetic patient group than in female healthy controls (P = 0.0388), while there was no significant difference in body mass index for males in the case group compared with in the control group. Conclusion: Our study indicates that PPARG2 and obesity have a strong association with type 2 diabetes but ENPP1 polymorphism lacks any association. Keywords: obesity, BMI, polymorphism, restriction fragment length polymorphism, peroxisome proliferator-activated receptors

Joint effect of insulin signaling genes on cardiovascular events and on whole body and endothelial insulin resistance

ObjectiveInsulin resistance (IR) and cardiovascular disease (CVD) share a common soil. We investigated the combined role of single nucleotide polymorphisms (SNPs) affecting insulin signaling (ENPP1 K121Q, rs1044498; IRS1 G972R, rs1801278; TRIB3 Q84R, rs2295490) on CVD, age at myocardial infarction (MI), in vivo insulin sensitivity and in vitro insulin-stimulated nitric oxide synthase (NOS) activity. Design and setting1. We first studied, incident cardiovascular events (a composite endpoint comprising myocardial infarction-MI, stroke and cardiovascular death) in 733 patients (2186 person-years, 175 events). 2. In a replication attempt, age at MI was tested in 331 individuals. 3. OGTT-derived insulin sensitivity index (ISI) was assessed in 829 individuals with fasting glucose <126 mg/dl. 4. NOS activity was measured in 40 strains of human vein endothelial cells (HUVECs). Results1. Risk variants jointly predicted cardiovascular events (HR = 1.181; p = 0.0009) and, when added to clinical risk factors, significantly improved survival C-statistics; they also allowed a significantly correct reclassification (by net reclassification index) in the whole sample (135/733 individuals) and, even more, in obese patients (116/204 individuals). 2. Risk variants were jointly associated with age at MI (p = 0.006). 3. A significant association was also observed with ISI (p = 0.02). 4. Finally, risk variants were jointly associated with insulin-stimulated NOS activity in HUVECs (p = 0.009). ConclusionsInsulin signaling genes variants jointly affect cardiovascular disease, very likely by promoting whole body and endothelium-specific insulin resistance. Further studies are needed to address whether their genotyping help identify very high-risk patients who need specific and/or more aggressive preventive strategies.

The ENPP1 Q121 Variant Predicts Major Cardiovascular Events in High-Risk Individuals

OBJECTIVEInsulin resistance (IR) and cardiovascular disease may share a common genetic background. We investigated the role of IR-associated ENPP1 K121Q polymorphism (rs1044498) on cardiovascular disease in high-risk individuals.RESEARCH DESIGN AND METHODSA prospective study (average follow-up, 37 months) was conducted for major cardiovascular events (myocardial infarction [MI], stroke, cardiovascular death) from the Gargano Heart Study (GHS; n = 330 with type 2 diabetes and coronary artery disease), the Tor Vergata Atherosclerosis Study (TVAS; n = 141 who had MI), and the Cardiovascular Risk Extended Evaluation in Dialysis (CREED) database (n = 266 with end-stage renal disease). Age at MI was investigated in cross-sectional studies of 339 type 2 diabetic patients (n = 169 from Italy, n = 170 from the U.S.).RESULTSIncidence of cardiovascular events per 100 person--years was 4.2 in GHS, 10.8 in TVAS, and 11.7 in CREED. Hazard ratios (HRs) for KQ+QQ versus individuals carrying the K121/K121 genotype (KK) individuals were 1.47 (95% CI 0.80–2.70) in GHS, 2.31 (95% CI 1.22–4.34) in TVAS, and 1.36 (95% CI 0.88–2.10) in CREED, and 1.56 (95% CI 1.15–2.12) in the three cohorts combined. In the 395 diabetic patients, the Q121 variant predicted cardiovascular events among obese but not among nonobese individuals (HR 5.94 vs. 0.62, P = 0.003 for interaction). A similar synergism was observed in cross-sectional studies, with age at MI being 3 years younger in Q121 carriers than in KK homozygotes among obese but not among nonobese patients (P = 0.035 for interaction).CONCLUSIONSThe ENPP1 K121Q polymorphism is an independent predictor of major cardiovascular events in high-risk individuals. In type 2 diabetes, this effect is exacerbated by obesity. Future larger studies are needed to confirm our finding.

ENPP1/PC-1 K121Q and Other Predictors of Posttransplant Diabetes

Diabetes mellitus is a major cause of morbidity and mortality among transplanted patients. This study evaluated the role of the ENPP1 K121Q polymorphism and other variables known to affect diabetes risk in 115 nondiabetic and unrelated patients who underwent kidney transplant at our institution and had consented for use of genetic material (30% whites, 48% blacks, and 22% Hispanics). Thirty-six of these patients (30%) developed posttransplant diabetes mellitus (PTDM) within 1 year of observation from transplant. Black race, ENPP1 K121Q polymorphism, age, body mass index (BMI), and immunosuppressive medications were found to have the strongest associations with PTDM in the logistic regression and receiver operator characteristic (ROC) analysis. However, because ENPP1 K121Q is more common in Hispanics and in blacks, who also have higher PTDM prevalence, the studied genetic polymorphism did not exert independent predictive effect, whereas ethnicity, specifically black versus non-black, was the most robust predictor of PTDM. The model with the largest ROC area under the curve (AUC) of 0.80 was comprised of black/non-black, age, BMI, and tacrolimus treatment as significant predictors. A reduced model containing only ethnicity (black/non-black) and age as predictors yielded similar results (ROC AUC 0.78). We conclude that black race and age are major and not modifiable risk factors for PTDM. The specific role of ENPP1 K121Q on ethnic susceptibility to PTDM deserves further investigation in larger cohorts of transplanted patients.

Association and meta-analysis of &lt;I&gt;ENPP1&lt;/I&gt; K121Q with type 2 diabetes in Han Chinese

Multiple meta-analyses in Europeans showed that ENPP1 K121Q polymorphism was associated with type 2 diabetes. However, no association in Japanese, Korean, and Chinese in Taiwan, and inconsistent results in mainland Chinese were reported. In this study, the single nucleotide polymorphism K121Q of the ENPP1gene was genotyped in 539 type 2 diabetes patients and 404 healthy controls. No difference was observed in the genotypic and alle-lic frequencies of ENPP1 K121Q between the cases and the controls. Logistic regression analysis with adjustment of sex, age, and BMI suggested that the XQ genotype was significantly associated with the risk of type 2 diabetes (OR=1.5, 95%CI: 1.39-1.62, P<0.001). Sub-group analysis by gender revealed that the association between ENPP1 K121Q and type 2 diabetes was observed only in women (Q: 12.4% vs. 6.1%, P=0.001; XQ: 23.7% vs. 11.7%, P=0.001). Our results suggest that the association of ENPP1 K121Q with type 2 diabetes in Hubei Han Chinese population is more evident in women. The first meta-analysis of 10 Chinese studies indicated that the Q allele increased the risk of type 2 diabetes (OR=1.42, P=0.042).

The ENPP1 K121Q polymorphism determines individual susceptibility to the insulin-sensitising effect of lifestyle intervention

The K121Q (rs1044498) single nucleotide polymorphism (SNP) in the ENPP1 gene has shown association with insulin resistance and type 2 diabetes in various ethnic populations. We hypothesised that K121Q may predict the success of lifestyle intervention in terms of improvement of insulin sensitivity. We genotyped 1,563 participants with an increased risk of type 2 diabetes for K121Q and performed correlational analyses with anthropometric data and variables of insulin sensitivity. For metabolic characterisation, all participants underwent an OGTT. A subgroup of 506 participants additionally underwent a euglycaemic-hyperinsulinaemic clamp. In 342 participants, metabolic traits and anthropometric data were re-evaluated after a 9 month lifestyle intervention. In the overall cohort, K121Q was not associated with measures of obesity, indices of glucose tolerance during OGTT and insulin sensitivity estimated from the OGTT or derived from a euglycaemic-hyperinsulinaemic clamp after appropriate adjustment. However, K121Q did significantly influence the change in insulin sensitivity during lifestyle intervention after appropriate adjustment (p (additive) = 0.0067, p (dominant) = 0.0027). Carriers of the minor allele had an impaired increase in OGTT-derived insulin sensitivity. A similar trend was obtained for clamp-derived insulin sensitivity, but did not reach significance. In our population of European ancestry, the ENPP1 SNP K121Q influenced the change in insulin sensitivity during lifestyle intervention. Thus, this SNP may determine susceptibility to environmental changes and could predict the success of lifestyle intervention.

Association of the ENPP1 K121Q polymorphism with type 2 diabetes and obesity in the Moroccan population

Aim The ectonucleotide pyrophosphatase/phosphodiesterase 1 enzyme ( ENPP1), which downregulates insulin signaling by inhibiting insulin-receptor tyrosine kinase activity, is encoded by the ENPP1 gene. A common functional ENPP1 K121Q polymorphism has been suggested to contribute to insulin resistance, obesity and type 2 diabetes (T2D) in various ethnic groups. For this reason, we assessed the association between the ENPP1 K121Q polymorphism in T2D and obesity phenotypes in the Moroccan population. Methods Using LightCycler ® technology, we genotyped the ENPP1 K121Q polymorphism in 503 subjects with T2D and 412 normoglycaemic individuals. Results There was no evidence of an association between ENPP1 K121Q and T2D in either an additive ( P = 0.99) or recessive mode of inheritance ( P = 0.47). However, the Q121 variant was significantly more frequent in obese than in non-obese subjects after adjusting for age, gender and T2D status. We observed genetic heterogeneity between obese and non-obese T2D patients ( P = 0.02). The K121Q polymorphism was associated with T2D in the presence of obesity in both additive (1.55 [95% CI 1.16–2.07]; P = 0.003) and recessive (2.31 [95% CI 1.34–3.97]; P = 0.002) modes of inheritance. Conclusion Although there was no evidence of an association between the ENPP1 K121Q variant and the general phenotype of T2D, we did find an association with adult obesity and T2D. The Q121 allele frequency in Morocco is 37.3%, placing it between European Caucasians (15%) and Black Africans (79%). This study is the first to report an association between K121Q and metabolic diseases in the Moroccan population.

Role of the ENPP1 K121Q polymorphism in glucose homeostasis.

OBJECTIVE— To study the role of the ENPP1 Q121 variant on glucose homeostasis in whites from Italy.RESEARCH DESIGN AND METHODS— We conducted case-control studies in 764 adults (from two independent samples of 289 nonobese and 485 obese individuals) and 240 overweight/obese children undergoing oral glucose tolerance testing (OGTT). Early-phase insulin secretion and insulin sensitivity (the insulinogenic index and the insulin sensitivity index) and their interplay (the disposition index) were calculated.RESULTS— In adult subjects, glucose profiles during OGTT were significantly (P = 2 × 10−2) different across K121Q genotype groups and higher in QQ than KK individuals (P = 5 × 10−2). The insulinogenic index was significantly reduced in QQ (18.5 ± 3.4) compared with both KK (31.6 ± 1.0; P = 2.2 × 10−7) and KQ (30.5 ± 1.5; P = 3.2 × 10−6) individuals. KQ individuals also showed a reduced insulin sensitivity index compared with KK subjects (P = 3.6 × 10−2). The disposition index was lower in QQ carriers than in KQ and KK individuals (P = 8 × 10−3 and 4 × 10−4, respectively) and lower in KQ than in KK individuals (P = 3 × 10−2). Data obtained in overweight/obese children were very similar to those observed in adults, with QQ individuals showing (compared with KQ and KK subjects) a reduced insulinogenic index (P = 7 × 10−3 and 2 × 10−2, respectively) and disposition index (P = 2 × 10−2 and 7 × 10−3, respectively).CONCLUSIONS— Homozygous carriers of the ENPP1 Q121 variant are characterized by an altered glucose homeostasis. Reduced early-phase insulin secretion and inefficient interplay between insulin secretion and sensitivity, which occur at early ages, are major determinants of this defect.

Further Evidence For the Role of ENPP1 in Obesity: Association With Morbid Obesity in Finns

The aim of this study was to investigate a series of single-nucleotide polymorphisms (SNPs) in the genes MC2R, MC3R, MC4R, MC5R, POMC, and ENPP1 for association with obesity. Twenty-five SNPs (2-7 SNPs/gene) were genotyped in 246 Finns with extreme obesity (BMI > or = 40 kg/m2) and in 481 lean subjects (BMI 20-25 kg/m2). Of the obese subjects, 23% had concomitant type 2 diabetes. SNPs and SNP haplotypes were tested for association with obesity and type 2 diabetes. Allele frequencies differed between obese and lean subjects for two SNPs in the ENPP1 gene, rs1800949 (P = 0.006) and rs943003 (P = 0.0009). These SNPs are part of a haplotype (rs1800949 C-rs943003 A), which was observed more frequently in lean subjects compared to obese subjects (P = 0.0007). Weaker associations were detected between the SNPs rs1541276 in the MC5R, rs1926065 in the MC3R genes and obesity (P = 0.04 and P = 0.03, respectively), and between SNPs rs2236700 in the MC5R, rs2118404 in the POMC, rs943003 in the ENPP1 genes and type 2 diabetes (P = 0.03, P = 0.02 and P = 0.02, respectively); these associations did not, however, remain significant after correction for multiple testing. In conclusion, a previously unexplored ENPP1 haplotype composed of SNPs rs1800949 and rs943003 showed suggestive evidence for association with adult-onset morbid obesity in Finns. In this study, we did not find association between the frequently studied ENPP1 K121Q variant, nor SNPs in the MCR or POMC genes and obesity or type 2 diabetes.

The genetic susceptibility to type 2 diabetes may be modulated by obesity status: implications for association studies

BackgroundConsidering that a portion of the heterogeneity amongst previous replication studies may be due to a variable proportion of obese subjects in case-control designs, we assessed the association of genetic variants with type 2 diabetes (T2D) in large groups of obese and non-obese subjects.MethodsWe genotyped RETN, KCNJ11, HNF4A, HNF1A, GCK, SLC30A8, ENPP1, ADIPOQ, PPARG, and TCF7L2 polymorphisms in 1,283 normoglycemic (NG) and 1,581 T2D obese individuals as well as in 3,189 NG and 1,244 T2D non-obese subjects of European descent, allowing us to examine T2D risk over a wide range of BMI.ResultsAmongst non-obese individuals, we observed significant T2D associations with HNF1A I27L [odds ratio (OR) = 1.14, P = 0.04], GCK -30G>A (OR = 1.23, P = 0.01), SLC30A8 R325W (OR = 0.87, P = 0.04), and TCF7L2 rs7903146 (OR = 1.89, P = 4.5 × 10-23), and non-significant associations with PPARG Pro12Ala (OR = 0.85, P = 0.14), ADIPOQ -11,377C>G (OR = 1.00, P = 0.97) and ENPP1 K121Q (OR = 0.99, P = 0.94). In obese subjects, associations with T2D were detected with PPARG Pro12Ala (OR = 0.73, P = 0.004), ADIPOQ -11,377C>G (OR = 1.26, P = 0.02), ENPP1 K121Q (OR = 1.30, P = 0.003) and TCF7L2 rs7903146 (OR = 1.30, P = 1.1 × 10-4), and non-significant associations with HNF1A I27L (OR = 0.96, P = 0.53), GCK -30G>A (OR = 1.15, P = 0.12) and SLC30A8 R325W (OR = 0.95, P = 0.44). However, a genotypic heterogeneity was only found for TCF7L2 rs7903146 (P = 3.2 × 10-5) and ENPP1 K121Q (P = 0.02). No association with T2D was found for KCNJ11, RETN, and HNF4A polymorphisms in non-obese or in obese individuals.ConclusionGenetic variants modulating insulin action may have an increased effect on T2D susceptibility in the presence of obesity, whereas genetic variants acting on insulin secretion may have a greater impact on T2D susceptibility in non-obese individuals.

The K121Q Polymorphism in ENPP1 (PC-1) Is Not Associated with Type 2 Diabetes or Obesity in Korean Male Workers

Type 2 diabetes is characterized by insulin resistance, and ENPP1 plays an important role in insulin resistance. We investigated the association of the ENPP1 K121Q polymorphism with both diabetes and obesity (body mass index [BMI]) in Korean male workers. The study design was case-control. Subjects were 1,945 male workers (type 2 diabetes, 195; non-diabetes, 1,750) of nuclear power plants who received examinations from March to October in 2004. We collected venous blood samples under fasting (≥8 hr) conditions, calculated BMI by height and weight, and assessed relevant biochemical factors. The results of this study demonstrated that the ENPP1 121Q genotype (KQ+QQ types) was not associated with type 2 diabetes (odds ratios [OR], 0.854; 95% confidence interval [CI], 0.571-1.278) or obesity (OR, 0.933; 95% CI, 0.731-1.190). In addition, the frequency of the Q allele was not related to type 2 diabetes (OR, 0.911; 95% CI, 0.630-1.319) or obesity (OR, 0.962; 95% CI, 0.767-1.205). We concluded that the ENPP1 121Q allele is not a critical determinant for either diabetes or obesity in Korean males. The discordance between the results of this study and those derived from studies of Dominican, South Asian, Caucasian, Finnish, and French populations might be due to differences in genetic backgrounds between these populations.