Evaluation of apolipoprotein A-II as a positional candidate gene for familial Type II diabetes, altered lipid concentrations, and insulin resistance

Serum biomarkers that predict lean mass loss over bed rest in older adults: An exploratory study

BACKGROUND

Lean mass (LM) loss during extended bed rest contributes to long term functional decline in older adults. Identifying blood biomarkers that predict a hospitalized individual's risk of losing LM could allow for timely intervention.

METHODS

LM from 19 healthy subjects (age 60-76 y, 4 males, 15 females), who were confined to 10 days of complete bed rest, was measured pre- and post-bed rest. One hundred eighty-seven biomarkers from pre-bed rest fasted serum samples were obtained from all evaluable subjects (n = 18), analyzed using multiplexed immunoassay array and pooled. Decision tree analysis was used to identify pre-bed rest markers that predict LM loss over bed rest.

RESULTS

Sixty-three markers were excluded due to being below assay detection limits. One pair of markers, Tissue inhibitor of metalloprotease-1 (TIMP1) and tenascin C (TNC), were found to correlate with percent change in total LM over bed rest: [R² = 0.71, all subjects; R² = 0.76, females]. Subjects with pre-bed rest TIMP1 ≥ 141 ng/ml had the highest loss of total LM over bed rest, whereas subjects with pre-bed rest TIMP1 < 141 and TNC ≥ 461 ng/ml maintained total LM over bed rest. An additional marker set was found to correlate with percent change in leg LM loss over bed rest: matrix metalloprotease-3 (MMP3) and apolipoprotein A2 (APOA2) [R² = 0.59, females]. Females with pre-bed rest MMP3 < 6.93 ng/ml had the highest loss of leg LM over bed rest. Whereas females with pre-bed rest MMP3 ≥ 6.93 and ApoA2 < 276 ng/ml, maintained leg lean mass at the end of bed rest.

CONCLUSIONS

Panels of blood biomarkers associated with the muscle extracellular matrix may predict the likelihood for LM loss over extended bed rest.

Association between the APOA2 promoter polymorphism and body weight in Mediterranean and Asian populations: replication of a gene-saturated fat interaction

OBJECTIVE

The APOA2 gene has been associated with obesity and insulin resistance (IR) in animal and human studies with controversial results. We have reported an APOA2-saturated fat interaction determining body mass index (BMI) and obesity in American populations. This work aims to extend our findings to European and Asian populations.

METHODS

Cross-sectional study in 4602 subjects from two independent populations: a high-cardiovascular risk Mediterranean population (n = 907 men and women; aged 67 ± 6 years) and a multiethnic Asian population (n = 2506 Chinese, n = 605 Malays and n = 494 Asian Indians; aged 39 ± 12 years) participating in a Singapore National Health Survey. Anthropometric, clinical, biochemical, lifestyle and dietary variables were determined. Homeostasis model assessment of insulin resistance was used in Asians. We analyzed gene-diet interactions between the APOA2 -265T>C polymorphism and saturated fat intake (<or ≥ 22 g per day) on anthropometric measures and IR.

RESULTS

Frequency of CC (homozygous for the minor allele) subjects differed among populations (1-15%). We confirmed a recessive effect of the APOA2 polymorphism and replicated the APOA2-saturated fat interaction on body weight. In Mediterranean individuals, the CC genotype was associated with a 6.8% greater BMI in those consuming a high (P = 0.018), but not a low (P = 0.316) saturated fat diet. Likewise, the CC genotype was significantly associated with higher obesity prevalence in Chinese and Asian Indians only, with a high-saturated fat intake (P = 0.036). We also found a significant APOA2-saturated fat interaction in determining IR in Chinese and Asian Indians (P = 0.026).

CONCLUSION

The influence of the APOA2 -265T>C polymorphism on body-weight-related measures was modulated by saturated fat in Mediterranean and Asian populations.

Impaired anti-inflammatory function of apolipoprotein A-II concentrations predicts metabolic syndrome and diabetes at 4 years follow-up in elderly Turks

BACKGROUND

We evaluated prospectively the predictive value of serum apolipoprotein (apo) A-II, the second major apolipoprotein of high-density lipoprotein (HDL), for cardiometabolic risk in Turkish adults showing abnormalities in other proteins that normally confer protection.

METHODS

Determinants of apoA-II and its associations with coronary heart disease (CHD), metabolic syndrome (MetS) and diabetes were investigated at 4 years follow-up in 193 elderly men and women.

RESULTS

ApoA-II concentrations at baseline, in addition to being significantly related to HDL-cholesterol, were directly associated with complement C3 in multivariate linear regression analyses comprising nine variables. Following adjustment for gender, age and HDL-cholesterol (>30/>33 g/L, in men and women, respectively), low serum apoA-II concentrations predicted incident MetS [relative risk (RR) 3.5 (95% CI 1.4; 8.6)] and type 2 diabetes [RR 4.5 (95% CI 1.3; 15.6)] in both genders at an increment of 1 SD. Increased apoA-II values were not associated with prevalent or incident CHD, and tended to be marginally atheroprotective only in males.

CONCLUSIONS

Serum apoA-II concentrations confer risk for MetS and diabetes and exhibit evidence of anti-inflammatory properties among Turks. These findings support the effects seen for several other HDL protein constituents. This finding may explain the increased cardiometabolic risk among Turks.

Evaluating the association of common APOA2 variants with type 2 diabetes

Background

APOA2 is a positional and biological candidate gene for type 2 diabetes at the chromosome 1q21-q24 susceptibility locus. The aim of this study was to examine if HapMap phase II tag SNPs in APOA2 are associated with type 2 diabetes and quantitative traits in French Caucasian subjects.

Methods

We genotyped the three HapMap phase II tagging SNPs (rs6413453, rs5085 and rs5082) required to capture the common variation spanning the APOA2 locus in our type 2 diabetes case-control cohort comprising 3,093 French Caucasian subjects. The association between these variants and quantitative traits was also examined in the normoglycaemic adults of the control cohort. In addition, meta-analysis of publicly available whole genome association data was performed.

Results

None of the APOA2 tag SNPs were associated with type 2 diabetes in the French Caucasian case-control cohort (rs6413453, P = 0.619; rs5085, P = 0.245; rs5082, P = 0.591). However, rs5082 was marginally associated with total cholesterol levels (P = 0.026) and waist-to-hip ratio (P = 0.029). The meta-analysis of data from 12,387 subjects confirmed our finding that common variation at the APOA2 locus is not associated with type 2 diabetes.

Conclusion

The available data does not support a role for common variants in APOA2 on type 2 diabetes susceptibility or related quantitative traits in Northern Europeans.

Type 2 diabetes susceptibility genes on chromosome 1q21-24

Type 2 diabetes (T2D) has been linked to chromosome 1q21-24 in multiple samples, including a Utah family sample. Variants in 13 of the numerous candidate genes in the 1q region were tested for association with T2D in a Utah case-control sample. The most promising, 19 variants in 6 candidates, were genotyped on the Utah family sample. Herein, we tested the 19 variants individually and in pairs for an effect on T2D risk in family members using a logistic regression model that accounted for gender, age, and BMI and attributed residual genetic effects to a polygenic component. Seven variants increased risk significantly through 5 pairs of interactions. The significant variant pairs were apolipoprotein A-II (APOA2) rs6413453 interacting with calsequestrin 1 (CASQ1) rs617698, dual specificity phosphatase 12 (DUSP12) rs1503814, and retinoid X receptor gamma (RXRG) rs10918169, a poly-T insertion-deletion polymorphism in liver pyruvate kinase (PKLR) interacting with APOA2 rs12143180, and DUSP12 rs1027702 interacting with RXRG rs10918169. Genotypes of these 5 variant pairs accounted for 25.8% of the genetic variance in T2D in these pedigrees.

An apolipoprotein A-II polymorphism (-265T/C, rs5082) regulates postprandial response to a saturated fat overload in healthy men

Apolipoprotein (Apo) A-II is an apolipoprotein with an unknown role in lipid metabolism. It has been suggested that the presence of the less frequent allele of a single nucleotide polymorphism (Apo A-II -265T/C, rs5082) reduces the transcription rate of Apo A-II and enhances VLDL postprandial clearance in middle-aged men. To further investigate the role of Apo A-II -265T/C on lipid metabolism, we studied 88 normolipidemic young men. The participants were given a fatty meal containing 1 g fat and 7 mg cholesterol/kg weight and capsules containing 60,000 IU vitamin A (retinyl palmitate, 15.15 mg RE) per square meter body surface area. Postprandial lipemia was assessed during the 11 h following the meal. Total cholesterol (Chol) and triacylglycerols (TG) in plasma and TG-rich lipoproteins (TRL) (large TRL and small TRL) were measured, as well as HDL, Apo A-I, Apo B, Apo B-48, and Apo B-100. Postprandial responses were higher in the TT group than in carriers of the minor allele (CC/TC) for total TG in plasma (21.37% of change of area under curve, P = 0.014), large TRL-TG (24.75% change, P = 0.017) and small TRL-Chol (26.63% change, P = 0.003). Our work shows that carriers of the minor allele for Apo A-II -265T/C (CC/TC) have a lower postprandial response compared with TT homozygotes. This finding may partially explain the role of Apo A-II in lipid metabolism and can identify a population with a decreased risk of cardiovascular disease, as corresponds to the lower level of postprandial hypertriglyceridemia.

Association of serum apolipoprotein A-II concentration with combined hyperlipidemia and impaired glucose tolerance

We studied the relationship of serum apolipoprotein A-II concentration with biochemical parameters of lipid and carbohydrate metabolism, type of hyperlipidemia, and insulin sensitivity in male patients with hyperlipidemia. High concentration of apolipoprotein A-II was associated with increased indices of atherogenic lipoproteins and high-density lipoprotein-mediated reverse cholesterol transport, combined hyperlipidemia, and decreased insulin sensitivity calculated with consideration for glucose and insulin levels in glucose tolerance test and body weight.

The search for type 2 diabetes susceptibility loci: the chromosome 1q story

The unbiased approach of genome-wide linkage analysis has shown evidence for linkage of type 2 diabetes mellitus to the chromosome 1q21-25 region in at least eight independent studies. More than 26 candidate genes have already been evaluated, but to date none explain the evidence for linkage in this gene-dense region. Considerable data suggest that multiple genes account for this linkage result. The search for these genes is now the focus of an international consortium of groups reporting linkage of type 2 diabetes to this region of chromosome 1q21-q25.

Genome-wide linkage scan for loci influencing plasma triglycerides

BACKGROUND

Plasma triglyceride concentration is known to be a significant risk factor for cardiovascular disease (CVD). Previous studies have found that the level of triglycerides is strongly influenced by genetic factors.

METHODS

To identify quantitative trait loci influencing triglycerides, we conducted a genome-wide linkage scan on data from 485 Australian adult dizygotic twin pairs. Prior to linkage analysis, triglyceride values were adjusted for the effects of covariates including age, sex, time since last meal, time of blood collection (CT) and time to plasma separation.

RESULTS

The heritability estimate for ln(triglyceride) adjusted for all above fixed effects was 0.49. The highest multipoint LOD score observed was 2.94 (genome-wide p=0.049) on chromosome 7 (at 65 cM). This 7p region contains several candidate genes. Two other regions with suggestive multipoint LOD scores were also identified on chromosome 4 (LOD score=2.26 at 62 cM) and chromosome X (LOD score=2.01 at 81 cM).

CONCLUSIONS

The linkage peaks found represent newly identified regions for more detailed study, in particular the significant linkage observed on chromosome 7p13.

Vesicle-associated membrane protein 4, a positional candidate gene on 1q24-q25, is not associated with type 2 diabetes in the Old Order Amish

OBJECTIVE

The vesicle-associated membrane protein-4 (VAMP4) gene is an excellent type 2 diabetes (T2DM) positional candidate gene. It is located on chromosome 1q24-q25, a region of linkage to T2DM in the Amish and several other populations. VAMP4 is expressed in liver and skeletal muscle and participates in intracellular trafficking of secreted and membrane-associated proteins.

DESIGN AND METHODS

We sequenced VAMP4 in 20 Amish subjects. Polymorphisms in and around VAMP4 were genotyped in 65 Amish subjects with T2DM, 64 subjects with impaired glucose homeostasis (IGH), and 126 normal glucose tolerant controls, as well as in an expanded set of 749 participants of the Amish Family Diabetes Study for whom glucose and insulin levels during an oral glucose tolerance test (OGTT) and other quantitative traits related to diabetes were available. Case-control and quantitative trait association analyses were performed.

RESULTS

We found three common non-coding intragenic polymorphisms: a 23bp insertion/deletion (I/D) in the 5' untranslated region (UTR) in exon 1 at position 73127, and G35319T and C335296T single nucleotide polymorphisms (SNPs) in the 3' UTR (NCBI Accession No. Z98751). The two 3' UTR SNPs were in complete linkage disequilibrium (LD) and both were in strong LD with the exon 1 I/D polymorphism (|D'|=0.82). Similarly, three extragenic flanking SNPs (rs978985, rs203255, and rs1023479) showed moderate LD with the neighboring intragenic SNPs (|D'|=0.23-0.69). None of the SNPs individually nor any of the 2-, 3-, 4-, or 5-polymorphism haplotypes were associated with T2DM or IGH. The exon 1 I/D polymorphism was not associated with significant differences in mean fasting or stimulated glucose or insulin levels during an OGTT or other diabetes-related quantitative traits in the expanded set of 749 subjects.

CONCLUSION

Variation in VAMP4 does not significantly influence risk of T2DM or IGH in the Amish.

Comparison of Gene Expression in Intra-Abdominal and Subcutaneous Fat: A Study of Men with Morbid Obesity and Nonobese Men Using Microarray and Proteomics

Extent of intra-abdominal fat had significant linear relations with six metabolic coronary risk factors: systolic and diastolic blood pressure, fasting blood concentrations of glucose, high density lipoprotein (HDL) cholesterol, triglyceride, and plasminogen activator inhibitor-1. Tumor necrosis factor-alpha and adiponectin can be biological mediators from the intra-abdominal fat to the metabolic coronary risk factors. Complementarily, we describe a new study that will analyze the gene expression in intra-abdominal and subcutaneous fat on mRNA and protein level using high throughput methods. The study will elucidate further whether intra-abdominal obesity is the common denominator for the different components of the metabolic syndrome.

Does the aspartic acid to asparagine substitution at position 76 in the pancreas duodenum homeobox gene (PDX1) cause late-onset type 2 diabetes?

OBJECTIVE

Considerable data support an inherited defect in insulin secretion as one component of type 2 diabetes. Coding variants of the pancreas duodenum homeobox gene (PDX1) were proposed to predispose late-onset type 2 diabetes and to decrease transactivation in vitro. We tested the hypothesis that the Asp76Asn (D76N) variant that was identified in several populations predisposed type 2 diabetes and reduced insulin secretion.

RESEARCH DESIGN AND METHODS

We performed a case-control study in 191 control subjects and 190 individuals with type 2 diabetes, all of European descent, then characterized the D76N variant in 704 members of 68 families. We compared the phenotypic characteristics of those with and without the variant by diagnostic status and determined the insulin secretory response to intravenous glucose and tolbutamide among nondiabetic family members.

RESULTS

D76N was not associated with type 2 diabetes, either in our population or when all reported studies in Caucasians were combined. D76N did not segregate with diabetes among the families examined. Among D76N carriers, nondiabetic individuals had a lower waist-to-hip ratio and a trend to lower BMI than their diabetic counterparts. Diabetic carriers of D76N were significantly leaner by BMI (P = 0.012) and tended to be younger than diabetic individuals with the D/D genotype. However, insulin secretion in response to oral and intravenous glucose challenge and to intravenous tolbutamide was not reduced in D76N carriers.

CONCLUSIONS

The D76N variant of PDX1 does not significantly alter insulin secretion or act as a high-risk susceptibility allele for late-onset type 2 diabetes as proposed previously, although we cannot exclude a minor role in increasing risk of diabetes.

Apolipoprotein A-II, genetic variation on chromosome 1q21-q24, and disease susceptibility

PURPOSE OF REVIEW

Apolipoprotein (apo) A-II is the second most abundant HDL apolipoprotein; however its function remains largely unknown. Owing to the lack of consequences of apoA-II deficiency in humans, it has long been considered an apolipoprotein of minor importance. Overexpression of apoA-II in transgenic mice, however, causes combined hyperlipidemia and, in some cases, insulin resistance. This, and the location of the apoA-II gene in chromosome 1q23, a hot region in the search for genes associated with familial combined hyperlipidemia, insulin resistance and type 2 diabetes mellitus, has greatly increased interest in this protein.

RECENT FINDINGS

ApoA-II is biochemically and genetically linked to familial combined hyperlipidemia. Given that the chromosome 1q21-q24 region is associated with insulin resistance or type 2 diabetes, this region is a now a focus of interest in the study of these complex, often overlapping diseases. However, no polymorphisms that increase apoA-II levels have been identified to date in humans. Other nonstructural loci may regulate apoA-II plasma concentration. Further, plasma apoA-II concentration is increased by saturated fat intake. Several reports have added to our understanding of the relationship between apoA-II mutations and amyloidosis both in humans and mice.

SUMMARY

An increased plasma concentration of apoA-II might contribute to familial combined hyperlipidemia or type 2 diabetes mellitus expression, which emphasizes the need to understand its function and metabolism. Genetic studies in well characterized patients and genomic and proteomic approaches in cell and mouse models may help to achieve this understanding.

In vitro transcriptional induction of the human apolipoprotein A-II gene by glucose

Type 2 diabetic patients present high triglyceride and low HDL levels, significant determinants for the risk of atherosclerosis. Transgenic mice overproducing human apolipoprotein (apo)A-II, one of the two major apos of HDLs, display the same lipid disorders. Here, we investigated the possible regulation of apoA-II gene expression by glucose. In primary rat hepatocytes and in HepG2 cells, the transcription of the human apoA-II gene was upregulated by glucose. This response was mediated by a hormone-responsive element within the enhancer of the apoA-II promoter and was dependent on hepatocyte nuclear factor-4alpha. Accordingly, in transgenic mice, the human apoA-II gene is stimulated by a high-carbohydrate diet after fasting and at weaning. By contrast, the apoA-II mRNA level is not modified in streptozotocin-induced diabetic rats. In transgenic mice overexpressing the human apoA-II gene, plasma human apoA-II concentration was positively correlated with blood glucose levels. These mice displayed a marked delay in plasma glucose tolerance as compared with control mice. We hypothesize that the following pathogenic pathway might occur in the course of type 2 diabetes: increased apoA-II level causes a rise in plasma triglyceride level and glucose intolerance, resulting in hyperglycemia, which in turn might further increase apoA-II gene transcription.

Linkage and association mapping of a chromosome 1q21-q24 type 2 diabetes susceptibility locus in northern European Caucasians

We have identified a region on chromosome 1q21-q24 that was significantly linked to type 2 diabetes in multiplex families of Northern European ancestry and also in Pima Indians, Amish families, and families from France and England. We sought to narrow and map this locus using a combination of linkage and association approaches by typing microsatellite markers at 1.2 and 0.5 cM densities, respectively, over a region of 37 cM (23.5 Mb). We tested linkage by parametric and nonparametric approaches and association using both case-control and family-based methods. In the 40 multiplex families that provided the previous evidence for linkage, the highest parametric, recessive logarithm of odds (LOD) score was 5.29 at marker D1S484 (168.5 cM, 157.5 Mb) without heterogeneity. Nonparametric linkage (NPL) statistics (P = 0.00009), SimWalk2 Statistic A (P = 0.0002), and sib-pair analyses (maximum likelihood score = 6.07) all mapped to the same location. The one LOD CI was narrowed to 156.8-158.9 Mb. Under recessive, two-point linkage analysis, adjacent markers D1S2675 (171.5 cM, 158.9 Mb) and D1S1679 (172 cM, 159.1 Mb) showed LOD scores >3.0. Nonparametric analyses revealed a second linkage peak at 180 cM near marker D1S1158 (163.3 Mb, NPL score 3.88, P = 0.0001), which was also supported by case-control (marker D1S194, 178 cM, 162.1 Mb; P = 0.003) and family-based (marker ATA38A05, 179 cM, 162.5 Mb; P = 0.002) association studies. We propose that the replicated linkage findings actually encompass at least two closely spaced regions, with a second susceptibility region located telomeric at 162.5-164.7 Mb.

Uncoupling protein-2 polymorphisms in type 2 diabetes, obesity, and insulin secretion

The onset of type 2 diabetes (T2DM) is preceded by obesity, insulin resistance, and impaired beta-cell function. Uncoupling protein-2 (UCP2) is a widely expressed inner mitochondrial membrane protein. Common polymorphisms of the UCP2 gene have been implicated in diabetes, in obesity, and with changes in UCP2 mRNA levels. We tested the hypothesis that common UCP2 variants influence T2DM susceptibility in four parallel studies of separate populations. We typed the -866 promoter (G/A) variant, a nonsynonymous (Ala55Val or A55V) single-nucleotide polymorphism in exon 4, and a 45-nt insertion in the 3'-untranslated (3'UTR) region. Study populations included a case-control population study, a family-based association study, and a metabolic study of individuals who had been characterized for insulin sensitivity and secretion. To evaluate UCP2 mRNA levels, we examined a fourth population of subjects, who had undergone subcutaneous fat biopsy. All three variants showed a trend to an association with T2DM (P = 0.05 to 0.07) in the population but not the family-based association study. The 3' insertion/deletion (3'UTR I/D) variant was associated with body mass index (BMI, P = 0.035) among nondiabetic family members. Haplotype combinations were significantly associated with BMI (P = 0.028), triglyceride levels (P = 0.026), and fasting insulin (P = 0.029); highest values for the three traits were observed in individuals with the heterozygous combination GVI/AVD. In the metabolic study, all three variants were associated with an index of beta-cell compensation for insulin sensitivity (disposition index), particularly in interaction with family membership (P < 0.000001). Individuals homozygous for the -866 A allele had decreased adipose mRNA levels relative to GG homozygous individuals (P = 0.009), but the 3'UTR I/D variant had no impact on mRNA levels. We confirm modest effects of UCP2 variants on BMI and T2DM and show significant effects on insulin secretion in interaction with family-specific factors. However, the associated allele and the effects on gene expression are opposite to those reported previously.

Molecular screening and association studies of retinoid-related orphan receptor gamma (RORC): a positional and functional candidate for type 2 diabetes

The retinoid-related orphan receptor gamma (RORC) is a member of the nuclear hormone superfamily which maps to the 1q21-q23 region. Linkage of type 2 diabetes (T2DM) to this region is well replicated. Several factors argue that RORC is a strong candidate for T2DM susceptibility within this region. RORC may form heterodimers with peroxisome-proliferator activated receptor gamma, it is expressed at high levels in skeletal muscle, and expression is induced in adipocytes during differentiation. To test the hypothesis that sequence variation in RORC is a risk factor for T2DM, we screened approximately 21kb of DNA for sequence variation, including 11 exons of the RORC gene, a region 1-kb upstream (5' flanking region), intronic regions flanking the exons, and the entire 3' untranslated region (UTR). Screening was performed using single strand conformation polymorphism (SSCP) analysis in Caucasian individuals of northern European ancestry and in African American individuals. We detected 11 single nucleotide polymorphisms (SNPs), ranging from the promoter region to intron 10. We also confirmed 2 SNPs from public databases that were in regions not included in our screening. Only 1 SNP was nonsynonymous, resulting in Ala to Gly at residue 464 (exon 10). All other SNPs were noncoding. One SNP (intron 3) was unique to Caucasians, and three SNPs (Ala464Gly, intron 2, intron 6) were specific to African American subjects. We typed 7 SNPs spanning the gene from the promoter to 3' UTR in unrelated cases with T2DM and controls of Northern European ancestry. We also tested linkage of a microsatellite within the RORC gene. Modest evidence for linkage (LOD=1.47) was seen on two-point analysis, but no linkage to the RORC region was found on multipoint analysis. However, transmission of the microsatellite alleles from parents to affected offspring showed a trend to deviate from the expected 50% (p=0.078). No association of any other SNP with T2DM was found, but the Ala454Gly variant was 3-fold more common among African American patients with diabetes than in controls. SNPs 1, 2 and 4 were in strong linkage disequilibrium (D>0.85) and may constitute a haplotype block. Our data suggest that RORC cannot explain the linkage of T2DM in this region. The role of the unusual Ala454Gly variant will require a much larger study size to evaluate.

Liver pyruvate kinase polymorphisms are associated with type 2 diabetes in northern European Caucasians

Pyruvate kinase is a key glycolytic enzyme. Isoforms that are expressed in the red cell, liver, pancreatic beta-cells, small intestine, and proximal renal tubule are encoded by the 12 exons of the PKLR gene, which maps to chromosome 1q23. We hypothesized that common variants of the PKLR gene could account for the linkage of diabetes to this region. We screened the promoter regions, exons and surrounding introns, and the 3' untranslated region for mutations. We identified five single-nucleotide polymorphisms (SNPs), and only one (V506I, exon 11) altered the coding sequence. We tested the five SNPs, a poly-T insertion-deletion polymorphism, and an ATT triplet repeat in 131 unrelated diabetic patients and 118 nondiabetic control subjects. The V506I variant was rare and not associated with type 2 diabetes. The four SNPs and the insertion-deletion polymorphism were associated with diabetes, with a 10% difference between individuals with diabetes and nondiabetic individuals (P = 0.001-0.011, relative risk for minor allele 1.85). The same trend was found for the ATT repeat (P = 0.029). Common variants in the PKLR are associated with increased risk of type 2 diabetes, but because of strong linkage disequilibrium between variants, the actual susceptibility allele may be in a different gene.