Hepatocyte nuclear factor-4alpha P2 promoter haplotypes are associated with type 2 diabetes in the Japanese population

Association Analysis of the HNF4A Common Genetic Variants with Type 2 Diabetes Mellitus Risk

Type 2 diabetes mellitus (T2DM) is a complex disease that involves a wide range of genetic and environmental factors. The hepatocyte nuclear factor (HNF4A) carries out hepatic gluconeogenesis regulation and insulin secretion crucially, and the corresponding gene was shown to be linked to T2DM in several studies. The aim of the present study was to evaluate the association between HNF4A genetic variants (rs1884613 and rs1884614) and T2DM risk in a group of Iranian patients. This case-control study included 100 patients with T2DM and 100 control subjects. Genotyping of two single nucleotide polymorphisms (SNPs) (rs1884613 and rs1884614) of HNF4A was performed using the sequencing method. There was no statistically significant difference for allele and genotype distribution of the HNF4A common variants (rs1884613 and rs1884614) between subjects with and without T2DM (P=0.9 and P=0.9, respectively). Regarding diabetic complications, although the presence of mentioned polymorphisms increased the odds of developing ophthalmic complications and reduction of the odds of renal complications among diabetic patients, the mentioned risk was non- significant and cannot be generalized to the whole population.  It seems that rs1884613 and rs1884614 polymorphisms are not associated with T2DM or its renal and ophthalmic complications. To investigate the precise influence of these polymorphisms, prospective cohorts with larger sample sizes are required.

HNF4A Haploinsufficiency in MODY1 Abrogates Liver and Pancreas Differentiation from Patient-Derived Induced Pluripotent Stem Cells

Maturity-onset diabetes of the young 1 (MODY1) is a monogenic diabetes condition caused by heterozygous HNF4A mutations. We investigate how HNF4A haploinsufficiency from a MODY1/HNF4A mutation influences the development of foregut-derived liver and pancreatic cells through differentiation of human induced pluripotent stem cells from a MODY1 family down the foregut lineage. In MODY1-derived hepatopancreatic progenitors, which expressed reduced HNF4A levels and mislocalized HNF4A, foregut genes were downregulated, whereas hindgut-specifying HOX genes were upregulated. MODY1-derived hepatocyte-like cells were found to exhibit altered morphology. Hepatic and β cell gene signatures were also perturbed in MODY1-derived hepatocyte-like and β-like cells, respectively. As mutant HNF4A (p.Ile271fs) did not undergo complete nonsense-mediated decay or exert dominant negativity, HNF4A-mediated loss of function is likely due to impaired transcriptional activation of target genes. Our results suggest that in MODY1, liver and pancreas development is perturbed early on, contributing to altered hepatic proteins and β cell defects in patients.

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HNF4A is downregulated and predominantly mislocalized in the cytoplasm in MODY1

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Foregut markers, pancreatic and hepatic genes, were downregulated in MODY1-HPPs

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A reciprocal upregulation of hindgut HOX genes was observed in MODY1-HPPs

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Mutant HNF4A resulted in loss of transcriptional activation of target genes

Association of HNF4α gene polymorphisms with susceptibility to type 2 diabetes

The present study aimed to explore the association between single nucleotide polymorphisms (SNPs) in the hepatocyte nuclear factor‑4α (HNF‑4α) gene and the incidence of type 2 diabetes in the Chinese Bai population in Dali city, China. The polymerase chain reaction‑restriction fragment length polymorphism method was used to analyze four SNPs (rs4810424, rs1884613, rs1884614 and rs2144908) in the HNF‑4α gene in 44 patients with type 2 diabetes and 87 healthy controls in Chinese Bai individuals. The haploid type was subsequently built to assess its association with the incidence of type 2 diabetes in the Bai population in Dali city. No significant differences were observed between the genotype and allele frequencies of the four SNPs in the HNF‑4α gene and type 2 diabetes mellitus (P>0.05). However, the frequency of haplotype, CCTA, built by rs4810424, rs1884613, rs1884614 and rs2144908 was significantly higher in the type 2 diabetes mellitus group compared with the control group (χ2=8.34, P=0.004). The four polymorphisms, rs4810424, rs1884613, rs1884614 and rs2144908, in the HNF‑4α gene were not the susceptible loci for type 2 diabetes in the Bai population of Dali city, however, the haplotype, CCTA, built from the four SNPs may increase the risk of type 2 diabetes in this population.

Hepatocyte nuclear factor 4 alpha polymorphisms and the metabolic syndrome in French-Canadian youth

Objectives

Hepatocyte nuclear factor 4 alpha (HNF4α) is a transcription factor involved in the regulation of serum glucose and lipid levels. Several HNF4A gene variants have been associated with the risk of developing type 2 diabetes mellitus. However, no study has yet explored its association with insulin resistance and the cardiometabolic risk in children. We aimed to investigate the relationship between HNF4A genetic variants and the presence of metabolic syndrome (MetS) and metabolic parameters in a pediatric population.

Design and Methods

Our study included 1,749 French-Canadians aged 9, 13 and 16 years and evaluated 24 HNF4A polymorphisms that were previously identified by sequencing.

Results

Analyses revealed that, after correction for multiple testing, one SNP (rs736824; P<0.022) and two haplotypes (P1 promoter haplotype rs6130608-rs2425637; P<0.032 and intronic haplotype rs736824-rs745975-rs3212183; P<0.025) were associated with the risk of MetS. Additionally, a significant association was found between rs3212172 and apolipoprotein B levels (coefficient: -0.14 ± 0.05; P<0.022). These polymorphisms are located in HNF4A P1 promoter or in intronic regions.

Conclusions

Our study demonstrates that HNF4α genetic variants are associated with the MetS and metabolic parameters in French Canadian children and adolescents. This study, the first exploring the relation between HNF4A genetic variants and MetS and metabolic variables in a pediatric cohort, suggests that HNF4α could represent an early marker for the risk of developing type 2 diabetes mellitus.

Prediabetes is associated with HNF-4 α P2 promoter polymorphism rs1884613: a case-control study in Han Chinese population and an updated meta-analysis

BACKGROUND

Controversy remains for the association between hepatocyte nuclear factor 4α (HNF-4α) P2 promoter polymorphism rs1884613 and type 2 diabetes (T2D). There was no association test of this polymorphism with prediabetes and T2D in the Chinese population. Moreover, an updated meta-analysis in various ethnic groups is needed to establish the contribution of rs1884613 to T2D risk.

METHODS

Using the Sequenom MassARRAY platform approach, we genotyped rs1884613 of HNF-4α in the P2 promoter region among 490 T2D patients, 471 individuals with prediabetes, and 575 healthy controls. All the individuals were recruited from 16 community health service centers in Nanshan district in Shenzhen province. Using STATA 11.0 software, meta-analysis was performed to summarize the overall contribution of rs1884613 to T2D risk.

RESULTS

Polymorphism rs1884613 was associated with genetic susceptibility to prediabetes in the whole samples (OR = 1.40, 95% CI = 1.16-1.68, P = 0.0001) and the female subgrouped samples (OR = 1.48, 95% CI = 1.14-1.92, P = 0.003) after adjusting for age and body mass index (BMI). In contrast, there was no association of rs1884613 with T2D in the whole samples and male in our case-control study and meta-analysis.

CONCLUSIONS

Our results suggest that rs1884613 contributes to susceptibility to prediabetes, whereas this polymorphism may not play an important role in the development of T2D.

Response to the dipeptidyl peptidase-4 inhibitors in Japanese patients with type 2 diabetes might be associated with a diplotype of two single nucleotide polymorphisms on the interleukin-6 promoter region under a certain level of physical activity

Aims/Introduction

Muscle-derived interleukin-6 (IL-6) has been reported to promote glucagon-like peptide-1 (GLP-1) secretion, and we explored the association of single nucleotide polymorphisms (SNPs) in the human IL-6 promoter region with the responsiveness to dipeptidyl peptidase-4 inhibitors (DPP-4Is), drugs that increase circulating GLP-1.

Materials and Methods

The present observational study enrolled Japanese patients with type 2 diabetes who took a DPP-4I over 3 months, and most of the clinical information was collected retrospectively. We defined non-responders as those having less than a 0.2% decrease of the glycated hemoglobin level at 3 or 4 months after starting DPP-4I treatment. Physical activity was retrospectively estimated by the Japanese short version of International Physical Activity Questionnaire.

Results

We studied 316 patients whose physical activity corresponding to the season of the DPP-4I administration was estimated. The non-responder rate was 29.7%. We analyzed rs1800796 and rs2097677, both are suggested to be functional in Japanese. Multivariate analysis for all patients showed that the adjusted odds ratio for the non-responder risk of the diplotype rs1800796 G/*–rs2097677 A/* against C/C-G/G (OR_G*A*) was 0.445 (P = 0.068). When patients were stratified by the International Physical Activity Questionnaire into low (n = 149) and moderate/high (n = 167) activity groups, however, OR_G*A* in each group was 1.58 (P = 0.615) and 0.153 (P = 0.003), respectively.

Conclusions

The diplotype rs1800796 G/*–rs2097677 A/* might contribute to responsiveness to DPP-4Is in Japanese patients with type 2 diabetes under a certain level of physical activity. However, further investigation is warranted to confirm this.

Association of the PPARG Pro12Ala polymorphism with type 2 diabetes and incident coronary heart disease in a Hong Kong Chinese population

AIMS

We examined the risk association between single nucleotide polymorphisms (SNPs) in eleven candidate genes with type 2 diabetes (T2D). T2D-associated polymorphisms were also examined for prediction of incident CHD.

METHODS

113 tagging SNPs were genotyped in stage 1 (467 T2D cases, 290 controls), and 15 SNPs were analyzed in the final cohort (1462 T2D cases, 600 controls). Three T2D-associated SNPs were further tested for prediction of CHD within a subset of 1417 T2D cases free of CHD at enrolment.

RESULTS

In the case-control analysis, PPARG rs1801282 (Pro12Ala) (OR=1.48 (1.02-2.16)), ADIPOQ rs1063539 (OR=1.17 (1.01-1.35)), and HNF4A rs1884614 (OR=1.16 (1.00-1.32) were associated with T2D (P(allelic)<0.05). Joint analysis of rs1801282-C, rs1063539-G, and rs1884614-T risk alleles showed an additive dosage effect (P for trend=0.001). Moreover, carriers with two PPARG rs1801282-C risk alleles were associated with an increased risk of incident CHD (HR=4.38 (1.03-18.57), P=0.045) in T2D patients in the prospective analysis.

CONCLUSIONS

Genetic variants of PPARG, ADIPOQ and HNF4A were individually and jointly associated with T2D in Hong Kong Chinese. The PPARG Pro12 risk allele contributed to increased risk for both T2D and CHD.

Variants in hepatocyte nuclear factor 4alpha gene promoter region and type 2 diabetes risk in Chinese

As a key regulator of insulin secretion and metabolism of glucose, cholesterol and fatty acid, hepatocyte nuclear factor 4alpha (HNF4A) was suggested as a candidate gene for type 2 diabetes (T2D); however, no association study between HNF4A and T2D in the Chinese population has been conducted before. To address this issue, we evaluated the impact of the HNF4A variants (rs1884614 and rs2425637) on T2D and metabolic traits in 1912 unrelated patients and 2041 control subjects in the Chinese Han population. Our results suggested that no individual single nucleotide polymorphisms of HNF4A was significantly associated with T2D at either allele or genotype level. However, rs2425637 in the promoter region of HNF4A was found to have an effect on total cholesterol and high-density lipoprotein before multiple testing correction. To summarize, our investigation did not confirm the effects of HNF4A variants (rs1884614 and rs2425637) on T2D risk, but found that the risk HNF4A contributed to T2D might be population specific.

Adiponectin and polycystic ovary syndrome

INTRODUCTION

Polycystic ovary syndrome (PCOS) has a prevalence of 5-8% in women of reproductive age. Women with PCOS have an increased risk of metabolic syndrome and associated comorbidities. Adiponectin is a circulating protein produced by adipocytes. Circulating levels of adiponectin are inversely related to adipocyte mass. Low levels occur with insulin resistance, type 2 diabetes, metabolic syndrome, and obesity-related cardiovascular disease. This article reviews the literature on the link between adiponectin and PCOS and the potential use of adiponectin as a biomarker for PCOS.

METHOD

Data-based studies on adiponectin and PCOS and adiponectin measurement were identified through the Medline (1950-2009) and ISI Web of Knowledge (1973-2009) databases.

RESULTS

Fifteen studies related to adiponectin and PCOS met inclusion criteria and were included in this review. These studies present evidence that adiponectin is linked to insulin resistance, insulin sensitivity, body mass index (BMI), and adiposity. In women with PCOS, lower levels, as opposed to higher levels, of adiponectin occur in the absence of adiposity.

CONCLUSION

The relationships between adiponectin and insulin resistance and sensitivity, metabolic syndrome, and BMI in women with PCOS suggest that adiponectin potentially could serve as a marker for disease risk and provide opportunity for earlier intervention if knowledge is successfully translated from laboratory to clinical practice. However, further study of the relationship between adiponectin and PCOS is required before there can be direct application to clinical practice.

Influence of hepatocyte nuclear factor 4alpha (HNF4alpha) gene variants on the risk of type 2 diabetes: a meta-analysis in 49,577 individuals

BACKGROUND

The nuclear receptor hepatocyte nuclear factor 4alpha (HNF4alpha) contributes to the regulation of a large fraction of liver and pancreatic islet transcriptomes.

AIM

To evaluate the influence of HNF4alpha polymorphisms across the entire locus on the occurrence of type 2 diabetes (T2D) by means of a meta-analysis.

METHODS

We evaluated haplotype block structure of HNF4alpha variants owing to linkage disequilibrium (LD). From 1455 reports, we evaluated 21 observational studies.

RESULTS

Six haplotype blocks of LD were constructed with SNPs with r(2)>0.8; there were also 14 unlinked SNPs. Overall, we included 22,920 cases and 26.657 controls. Among 17 heterogeneous studies (21,881 cases and 24,915 controls), including 3 SNPs of P2 promoter region in block 1, we observed a significant association with T2D in fixed (OR 0.94, 95%CI: 0.905-0.975, p=0.001) and random (OR 0.988, 95%CI: 0.880-0.948, p=0.000012) model. Three homogeneous studies were evaluated in block 2 (2684 cases and 2059 controls), and a significant association with T2D was also observed: OR: 1.121, 95%CI 1.013-1.241, p=0.027. Three additional variants were associated with T2D: two intronic SNPs (rs4810424: OR: 1.080, 95%CI: 1.010-1.154, p<0.03 and rs3212183: OR: 0.843, 95%CI: 0.774-0.918, p<0.00009) and one missense variant (rs1800961: OR: 0.770, 95%CI: 0.595-0.995, p<0.05, 6562 cases and 6723 controls).

CONCLUSIONS

In addition to HNF4alpha variants in the promoter region, other SNPs may be involved on the occurrence of T2D.

Pathomechanisms of type 2 diabetes genes

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

Interaction between HNF4A polymorphisms and physical activity in relation to type 2 diabetes-related traits: results from the Quebec Family Study

AIMS

To test for associations between type 2 diabetes mellitus (T2DM)-related traits and polymorphisms (SNPs) in the hepatocyte nuclear factor 4-alpha gene (HNF4A) in the Quebec Family Study cohort, and determine whether these associations are modulated by physical activity (PA).

METHODS

Two HNF4A SNPs (rs1885088 G>A; rs745975 C>T), previously reported to be associated with T2DM, were studied in 528 non-diabetic subjects who underwent a 75g oral glucose tolerance test (OGTT). Glucose, insulin and C-peptide plasma levels, measured in the fasting state and during the OGTT, were used in the analysis. The amount (hours per week) of PA was assessed by questionnaire.

RESULTS

The HNF4A rs1885088 SNP was not independently associated with T2DM-related traits, whereas the rs745975 was associated with fasting insulin, HOMA-IR and 2-h glucose levels (p<0.05 for all). Genotype by PA interactions were found for glucose homeostasis (p<0.0001) and insulin secretion (p<or=0.03). When subjects were stratified by PA level (according to the median value), we found that high level of PA (>2h/week) was associated with smaller glucose area under the curve (AUC) and 2-h glucose levels in rs1885088 A/A homozygotes and with lower fasting C-peptide and insulin AUC in rs745975 T/T homozygotes.

CONCLUSION

These results indicate that the associations of HNF4A rs1885088 with glucose tolerance and rs745975 with insulin secretion are modulated by PA. Our finding therefore suggests that the effect of HNF4A polymorphisms on the risk of T2DM is influenced by PA.

A common P2 promoter polymorphism of the hepatocyte nuclear factor-4alpha gene is associated with insulin secretion in non-obese Japanese with type 2 diabetes

AIMS

Heterozygous mutations of the hepatocyte nuclear factor (HNF)-4alpha gene cause a particular form of maturity-onset diabetes of the young (MODY1). Recent genetic studies have shown that single nucleotide polymorphisms (SNPs) of the beta-cell type P2 promoter of the HNF-4alpha gene are associated with type 2 diabetes in some populations. In the Japanese population, a haplotype consisting of two SNPs (rs1884614 and rs2144908) in the P2 promoter region is reported to show a significant association with type 2 diabetes.

METHODS

Both rs1884614 and rs2144908 were genotyped in 349 type 2 diabetic patients and 203 non-diabetic controls. The relation of these SNPs to clinical characteristics was also examined in the diabetic subjects.

RESULTS

There were no differences in the genotype distribution of the two SNPs between the control and diabetic subjects, and the haplotype distribution was also similar in the two groups. However, the rs1884614 T/T genotype was significantly associated with a smaller area under the plasma insulin curve (AUC) during the OGTT in non-obese (BMI <25 kg/m(2)) patients (p=0.0272; adjusted for age and sex).

CONCLUSIONS

SNP rs1884614 in the P2 promoter region of the HNF-4alpha gene may influence insulin secretion in non-obese Japanese subjects with type 2 diabetes.

Population-specific risk of type 2 diabetes conferred by HNF4A P2 promoter variants: a lesson for replication studies

OBJECTIVE

Single nucleotide polymorphisms (SNPs) in the P2 promoter region of HNF4A were originally shown to be associated with predisposition for type 2 diabetes in Finnish, Ashkenazi, and, more recently, Scandinavian populations, but they generated conflicting results in additional populations. We aimed to investigate whether data from a large-scale mapping approach would replicate this association in novel Ashkenazi samples and in U.K. populations and whether these data would allow us to refine the association signal.

RESEARCH DESIGN AND METHODS

Using a dense linkage disequilibrium map of 20q, we selected SNPs from a 10-Mb interval centered on HNF4A. In a staged approach, we first typed 4,608 SNPs in case-control populations from four U.K. populations and an Ashkenazi population (n = 2,516). In phase 2, a subset of 763 SNPs was genotyped in 2,513 additional samples from the same populations.

RESULTS

Combined analysis of both phases demonstrated association between HNF4A P2 SNPs (rs1884613 and rs2144908) and type 2 diabetes in the Ashkenazim (n = 991; P < 1.6 x 10(-6)). Importantly, these associations are significant in a subset of Ashkenazi samples (n = 531) not previously tested for association with P2 SNPs (odds ratio [OR] approximately 1.7; P < 0.002), thus providing replication within the Ashkenazim. In the U.K. populations, this association was not significant (n = 4,022; P > 0.5), and the estimate for the OR was much smaller (OR 1.04; [95%CI 0.91-1.19]).

CONCLUSIONS

These data indicate that the risk conferred by HNF4A P2 is significantly different between U.K. and Ashkenazi populations (P < 0.00007), suggesting that the underlying causal variant remains unidentified. Interactions with other genetic or environmental factors may also contribute to this difference in risk between populations.

Studies in 3,523 Norwegians and meta-analysis in 11,571 subjects indicate that variants in the hepatocyte nuclear factor 4 alpha (HNF4A) P2 region are associated with type 2 diabetes in Scandinavians

OBJECTIVE

Recent publications have found an association between common variants near the hepatocyte nuclear factor 4 alpha (HNF4A) P2 promoter and type 2 diabetes in some populations but not in others, and the role for HNF4A in type 2 diabetes has remained unclear. In an attempt to address these inconsistencies, we investigated HNF4A single nucleotide polymorphisms (SNPs) in a large population-based sample and included a meta-analysis of published studies.

RESEARCH DESIGN AND METHODS

We genotyped 12 SNPs in the HNF4A region in a Norwegian population-based sample of 1,644 individuals with type 2 diabetes and 1,879 control subjects (the Nord-Trøndelag Health Study [HUNT] 2). We combined our data with all previously published case/control studies and performed a meta-analysis.

RESULTS

Consistent with initial studies, we found a trend toward association for the SNPs rs1884613 (odds ratio [OR] 1.17 [95% CI 1.03-1.35]) and rs2144908 (1.21 [1.05-1.38]) in the P2 region and for rs4812831 (1.21 [1.02-1.44]), located 34 kb downstream of the P2 promoter. Meta-analysis, comprising 12,292 type 2 diabetic case and 15,519 control subjects, revealed a nonsignificant OR of 1.05 (95% CI 0.98-1.12) but with significant heterogeneity between the populations. We therefore performed a subanalysis including only the data for subjects from Scandinavia. Among the 4,000 case and 7,571 control Scandinavian subjects, a pooled OR of 1.14 (1.06-1.23), P = 0.0004, was found for the SNP rs1884613.

CONCLUSIONS

Our results suggest that variation in the HNF4A region is associated with type 2 diabetes in Scandinavians, highlighting the importance of exploring small genetic effects in large, homogenous populations.

HNF4A genetic variants: role in diabetes

PURPOSE OF REVIEW

Variants in the hepatocyte nuclear factor 4alpha (HNF4A) gene play a role in the development of diabetes mellitus. Although genetic variation in and around HNF4A regulatory regions has received considerable attention, the significance of these variants in the common type 2 diabetes varies in the literature. This review will provide a general overview of recent genetic studies involving the evaluation of HNF4A as a contributor to the risk and pathophysiology of diabetes mellitus and related risk factors.

RECENT FINDINGS

These studies report newly identified variants, evaluate previously reported polymorphisms that were associated with type 2 diabetes in several distinct populations with maturity-onset diabetes of the young, type 2 diabetes, gestational diabetes, and diabetes related risk factors, and propose a role for HNF4A in insulin secretion via the potassium ATP channel.

SUMMARY

HNF4A variants identified so far appear to modestly contribute to predisposition for type 2 diabetes. Continued identification and especially functional characterization of variants, however, will be critical in future studies to enhance our understanding of the metabolic impact of this gene.

Genes, diet and type 2 diabetes mellitus: a review

Diabetes mellitus is widely recognized as one of the leading causes of death and disability. While insulin insensitivity is an early phenomenon partly related to obesity, pancreatic beta-cell function declines gradually over time even before the onset of clinical hyperglycemia. Several mechanisms have been proposed to be responsible for insulin resistance, including increased non-esterified fatty acids, inflammatory cytokines, adipokines, and mitochondrial dysfunction, as well as glucotoxicity, lipotoxicity, and amyloid formation for beta-cell dysfunction. Moreover, the disease has a strong genetic component, although only a handful of genes have been identified so far. Diabetic management includes diet, exercise and combinations of antihyperglycemic drug treatment with lipid-lowering, antihypertensive, and antiplatelet therapy. Since many persons with type 2 diabetes are insulin resistant and overweight, nutrition therapy often begins with lifestyle strategies to reduce energy intake and increase energy expenditure through physical activity. These strategies should be implemented as soon as diabetes or impaired glucose homoeostasis (pre-diabetes) is diagnosed.

Search of type 2 diabetes susceptibility gene on chromosome 20q

Significant evidence of linkage to type 2 diabetes (T2D) has been shown in a relatively broad region on chromosome 20q, where the hepatocyte nuclear factor-4alpha (HNF4A) has been noted as a positional candidate. To systematically evaluate genetic susceptibility to T2D in the relevant region, we examined the disease association by using 1145 SNPs in two-step screening in the Japanese population. The marker screening enabled us to identify significant disease association in the lipopolysaccharide binding protein (LBP) but not in the HNF4A locus. In a 17.7-Mb interval screened, the strongest association was identified for a SNP, rs2232592, located in the intron of LBP, with an estimated odds ratio of 1.73 (95% CI 1.30-2.31) (P=0.0002) in the whole study panel involving 675 case and 474 control subjects. Our data suggest that the LBP gene may confer genetic susceptibility to T2D and this warrants further replication study.

Insights on pathogenesis of type 2 diabetes from MODY genetics

Maturity-onset diabetes of the young (MODY) is a type of non-insulin-dependent diabetes mellitus caused by rare autosomal-dominant mutations. MODY genes play key biochemical roles in the pancreatic beta cell; therefore, common variants of MODY genes are excellent candidate genes for type 2 diabetes. We review recent studies that suggest that common MODY gene variation contributes modestly to the heritability of type 2 diabetes.

P2 promoter variants of the hepatocyte nuclear factor 4alpha gene are associated with type 2 diabetes in Mexican Americans

Common and rare variants of the hepatocyte nuclear factor 4alpha (HNF4A) gene have been associated with type 2 diabetes and related traits in several populations suggesting the involvement of this transcription factor in diabetes pathogenesis. Single nucleotide polymorphisms (SNPs) within a large haplotype block surrounding the alternate P2 promoter, located approximately 45 kb upstream from the coding region, have been investigated in several populations of varying ethnicity with inconsistent results. Additionally, SNPs located within the P1 promoter and coding region have also been inconsistently associated with type 2 diabetes. Characterization of variation across this gene region in Mexican-American populations has not been reported. We therefore examined polymorphisms across the HNF4A gene in a cohort of Mexican-American pedigrees and assessed their association with type 2 diabetes. We observed evidence for association of SNPs in the P2 promoter region with type 2 diabetes (P = 0.003) and its age at diagnosis (P = 0.003). The risk allele frequency (53%) was intermediate to that reported in Caucasian populations (20-27%) and Pima Indians (83%). No other SNPs were associated with either trait. These results support the possibility that a variant in the P2 promoter region of HNF4A, or variants in linkage disequilibrium within this region, contributes to susceptibility to type 2 diabetes in many ethnic populations including Mexican Americans.

Alternate mRNA processing of the hepatocyte nuclear factor genes and its role in monogenic diabetes

Variation in mRNA processing has the capacity to exert fine control over gene expression in most cell types. The hepatic nuclear factor genes, like approximately 74% of the genome, produce multiple transcripts. Hepatic nuclear factor isoforms exhibit both spatial and temporal variation in expression. In this review, the known isoforms of the hepatocyte nuclear factor-1α, hepatocyte nuclear factor-1β and hepatocyte nuclear factor-4α genes are described and their properties are compared. Finally, data are discussed regarding the influence of hepatocyte nuclear factor-1α alternate mRNA processing on the clinical phenotype of maturity-onset diabetes of the young.

Phenotypic screening of hepatocyte nuclear factor (HNF) 4-gamma receptor knockout mice

Using the mouse as a model organism in pharmaceutical research presents unique advantages as its physiology in many ways resembles the human physiology, it also has a relatively short generation time, low breeding and maintenance costs, and is available in a wide variety of inbred strains. The ability to genetically modify mouse embryonic stem cells to generate mouse models that better mimic human disease is another advantage. In the present study, a comprehensive phenotypic screening protocol is applied to elucidate the phenotype of a novel mouse knockout model of hepatocyte nuclear factor (HNF) 4-gamma. HNF4-gamma is expressed in the kidneys, gut, pancreas, and testis. The first level of the screen is aimed at general health, morphologic appearance, normal cage behaviour, and gross neurological functions. The second level of the screen looks at metabolic characteristics and lung function. The third level of the screen investigates behaviour more in-depth and the fourth level consists of a thorough pathological characterisation, blood chemistry, haematology, and bone marrow analysis. When compared with littermate wild-type mice (HNF4-gamma(+/+)), the HNF4-gamma knockout (HNF4-gamma(-/-)) mice had lowered energy expenditure and locomotor activity during night time that resulted in a higher body weight despite having reduced intake of food and water. HNF4-gamma(-/-) mice were less inclined to build nest and were found to spend more time in a passive state during the forced swim test.