Genetic and functional evidence supporting SUMO4 as a type 1 diabetes susceptibility gene

SUMOylation in peripheral tissues under low perfusion-related pathological states

SUMOylation is described as a posttranslational protein modification (PTM) that is involved in the pathophysiological processes underlying several conditions related to ischemia- and reperfusion-induced damage. Increasing evidence suggests that, under low oxygen levels, SUMOylation might be part of an endogenous mechanism, which is triggered by injury to protect cells within the central nervous system. However, the role of ischemia-induced SUMOylation in the periphery is still unclear. This article summarizes the results of recent studies regarding SUMOylation profiles in several diseases characterized by impaired blood flow to the cardiorenal, gastrointestinal, and respiratory systems. Our review shows that although ischemic injury per se does not always increase SUMOylation levels, as seen in strokes, it seems that in most cases the positive modulation of protein SUMOylation after peripheral ischemia might be a protective mechanism. This complex relationship warrants further investigation, as the role of SUMOylation during hypoxic conditions differs from organ to organ and is still not fully elucidated.

Expatiating the molecular approaches of HMGB1 in diabetes mellitus: Highlighting signalling pathways via RAGE and TLRs

Diabetes mellitus (DM) has become one of the major healthcare challenges worldwide in the recent times and inflammation being one of its key pathogenic process/mechanism affect several body parts including the peripheral and central nervous system. High-mobility group box 1 (HMGB1) is one of the major non-histone proteins that plays a key role in triggering the inflammatory response. Upon its release into the extracellular milieu, HMGB1 acts as an "alarmin" for the immune system to initiate tissue repair as a component of the host defense system. Furthermore, HMGB1 along with its downstream receptors like Toll-like receptors (TLRs) and receptors for advanced glycation end products (RAGE) serve as the suitable target for DM. The forthcoming research in the field of diabetes would potentially focus on the development of alternative approaches to target the centre of inflammation that is primarily mediated by HMGB1 to improve diabetic-related complications. This review covers the therapeutic actions of HMGB1 protein, which acts by activating the RAGE and TLR molecules to constitute a functional tripod system, in turn activating NF-κB pathway that contributes to the production of mediators for pro-inflammatory cytokines associated with DM. The interaction between TLR2 and TLR4 with ligands present in the host and the activation of RAGE stimulates various immune and metabolic responses that contribute to diabetes. This review emphasizes to elucidate the role of HMGB1 in the initiation and progression of DM and control over the inflammatory tripod as a promising therapeutic approach in the management of DM.

Functions of nuclear receptors SUMOylation

The nuclear receptor superfamily is a family of ligand-activated transcription factors that play a key role in cell metabolism and human diseases. They can be modified after translation, such as acetylation, ubiquitination, phosphorylation and SUMOylation. Crosstalk between SUMO and ubiquitin, phosphorylation and acetylation regulates a variety of metabolic and physiological activities. Nuclear receptors play an important role in lipid metabolism, inflammation, bile acid homeostasis and autophagy. SUMOylation nuclear receptors can regulate their function and affect cell metabolism. It also provides a potential therapeutic target for atherosclerosis, tumor and other metabolic and inflammation-related diseases. This review focuses on the function of SUMOylation nuclear receptors.

Meta-analysis of the association between adiponectin SNP 45, SNP 276, and type 2 diabetes mellitus

Objective

The present study aimed to determine whether the polymorphisms at rs2241766 and rs1501299 on the ADIPOQ gene were related to the susceptibility of type 2 diabetes mellitus (T2DM).

Methods

Eight databases, PubMed, GWAS, Embase, Lochrane, Ebsco, CNKI (Chinese National Knowledge Infrastructure), VIP (Viper Database) and ChinaInfo were searched, and a meta-analysis of susceptibility was conducted between SNP45, SNP276 polymorphisms and T2DM. Furthermore, HWE test was conducted to assess the genetic balance of the study, evaluate the quality of Newcastle–Ottawa quality assessment scale (NOS), and establishing allelic, dominant, recessive, heterozygous, and homozygous gene models.

Results

This meta-analysis included 53 articles, encompassing 9285 cases with rs2241766 and 14156 controls and 7747 cases with rs1501299 and 10607 controls. For the rs2241766 locus, a significant correlation was found in the three models by the subgroup analysis. Western Asians: dominant gene model (TT + TG vs. GG, P = 0.01); heterozygous gene model (TG vs. GG, P = 0.02); homozygous gene model (TT vs. GG, P = 0.01). South Asians: dominant gene model (TT + TG vs. GG, P = 0.004); heterozygous gene model (TG vs. GG, P = 0.009); homozygous gene model (TT vs. GG, P = 0.005). However, no statistically significant correlation was established among the five genetic models for rs1501299 locus.

Conclusion

The findings of the present study indicated that the T allele of rs2241766 polymorphism is the susceptibility locus of T2DM in the West Asian population, but has a protective effect in the South Asian population, albeit further studies are needed in other populations. Also, no association was found between the ADIPOQ rs1501299 polymorphism and T2DM.

Sumoylation of nucleoprotein (NP) mediated by activation of NADPH oxidase complex is a consequence of oxidative cellular stress during infection by Infectious salmon anemia (ISA) virus necessary to viral progeny

The study evaluated the effects of nucleoprotein viral and the infectious virus in SHK-1 cells. The results show a strong respiratory burst activation and the induction of p47phox, SOD, GLURED, and apoptotic genes. Additionally, the cells alter the profile of SUMOylated proteins by the effect of transfection and infection experiments. In silico analyses show a set of structural motifs in NP susceptible of post-translational modification by the SUMO protein. Interestingly, the inhibition of the NADPH oxidase complex blocked the production of reactive oxygen species and the high level of cellular ROS due to the nucleoprotein and the ISAv. At the same time, the blocking of the p38MAPK signaling pathway and the use of Aristotelia chilensis, decreased viral progeny production. These results suggest that the NP triggers a strong production of ROS and modifying the post-translational profile mediated by SUMO-2/3, a phenomenon that favors the production of new virions.

Association between rs3087243 and rs231775 polymorphism within the cytotoxic T-lymphocyte antigen 4 gene and Graves' disease: a case/control study combined with meta-analyses

We conducted a case/control study to assess the impact of SNP rs3087243 and rs231775 within the CTLA4 gene, on the susceptibility to Graves' disease (GD) in a Chinese Han dataset (271 cases and 298 controls). The frequency of G allele for rs3087243 and rs231775 was observed to be significantly higher in subjects with GD than in control subjects (p = 0.005 and p = 0.000, respectively). After logistic regression analysis, a significant association was detected between SNP rs3087243 and GD in the additive and recessive models. Similarly, association for the SNP rs231775 could also be detected in the additive model, dominant model and recessive model. A meta-analysis, including 27 published datasets along with the current dataset, was performed to further confirm the association. Consistent with our case/control results, rs3087243 and rs231775 showed a significant association with GD in all genetic models. Of note, ethnic stratification revealed that these two SNPs were associated with susceptibility to GD in populations of both Asian and European descent. In conclusion, our data support that the rs3087243 and rs231775 polymorphisms within the CTLA4 gene confer genetic susceptibility to GD.

The role of adipose-derived inflammatory cytokines in type 1 diabetes

Adipose tissue dysfunction correlates with the development of diabetes. Mice with an adipocyte-specific deletion of the SUMO-specific protease SENP1 develop symptoms of type-1 diabetes mellitus (T1DM). Peri-pancreatic adipocytes (PATs) exert both systemic and paracrine effects on pancreases function. Our recent studies report that PATs of SENP1-deficient mice have increased proinflammatory cytokine production compared with other adipose depots. Proinflammatory cytokines produced from PATs not only have direct cytotoxic effects on pancreatic islets, but also increase CCL5 expression in adjacent pancreatic islets, which induces persistent inflammation in pancreases by acquisition of Th1 and Th17 effector T cell subsets. Small ubiquitin-like modifier (SUMO) can post-translationally conjugate to cellular proteins (SUMOylation) and modulate their biological functions. Several components in SUMOylation associate with T1DM susceptibility. We find that SUMOylation of NF-κB essential molecule NEMO augments NF-κB activity, NF-κB-dependent cytokine production and pancreatic inflammation. NF-κB inhibitor should provide therapeutic approach to block PAT inflammation and ameliorate the T1DM phenotype. We further propose that adipocytes in PATs may play a primary role in establishing pancreatic immune regulation at onset of diabetes, providing new insights into the molecular pathogenesis of type 1 diabetes.

Assessment of type 2 diabetes risk conferred by SNPs rs2241766 and rs1501299 in the ADIPOQ gene, a case/control study combined with meta-analyses

We conducted a case/control study to assess the impact of two SNPs, rs2241766 and rs1501299 within the ADIPOQ gene, on type 2 diabetes (T2D) susceptibility in a Chinese Han dataset (741 cases and 902 controls). SNP rs2241766 was found significantly associated with T2D risk in the additive model, dominant model and recessive model. A marginal association was detected for SNP rs1501299 in the additive model and recessive model after Bonferroni correction, and haplotype analysis provided additional evidence supporting the association between these two SNPs and T2D risk. A meta-analysis including 29 published datasets along with current dataset was next carried out to further confirm the association. In consistent with our case/control results, rs2241766 showed a significant association with T2D in the dominant model and additive model, and the association between rs1501299 and T2D was also characterized in the homozygote model, dominant model, recessive model, and additive model. Of note, the association became much stronger in East Asians after exclusion of ethnic stratification. Together, our data support that the rs2241766 and rs1501299 polymorphisms within the ADIPOQ gene confer genetic susceptibility for type 2 diabetes, especially in the Chinese Han population.

SENP2 regulated the stability of β-catenin through WWOX in hepatocellular carcinoma cell

SUMOylation and deSUMOylation are dynamic mechanisms regulating a spectrum of protein activities. The SUMO proteases (SENP) remove SUMO conjugate from proteins, and their expression is deregulated in cancers. SENP2 has been reported to play a critical role in the control of hepatocellular carcinoma (HCC) cell growth by modulating the stability of β-catenin. However, the underlying mechanism remains largely unknown. Here, we show that the WW domain-containing oxidoreductase (WWOX), a novel inhibitor of the Wnt/β-catenin pathway, is required for stabilization of β-catenin regulated by SENP2 in HCC cells. The transcriptional level of WWOX is tightly regulated by SENP2. Moreover, knockdown of WWOX by siRNA attuned SENP2-induced β-catenin degradation and decreased SENP2-mediated HCC cell proliferation arrest. Taken together, our data suggested that WWOX is a key downstream modulator of the SENP2 tumor suppressor function in HCC cell.

SUMO: a (oxidative) stressed protein

Redox species are produced during the physiological cellular metabolism of a normal tissue. In turn, their presence is also attributed to pathological conditions including neurodegenerative diseases. Many are the molecular changes that occur during the unbalance of the redox homeostasis. Interestingly, posttranslational protein modifications (PTMs) play a remarkable role. In fact, several target proteins are modified in their activation, localization, aggregation, and expression after the cellular stress. Among PTMs, protein SUMOylation represents a very important molecular modification pathway during "oxidative stress". It has been reported that this ubiquitin-like modification is a fine sensor for redox species. Indeed, SUMOylation pathway efficiency is affected by the exposure to oxidative species in a different manner depending on the concentration and time of application. Thus, we here report updated evidence that states the role of SUMOylation in several pathological conditions, and we also outline the key involvement of c-Jun N-terminal kinase and small ubiquitin modifier pathway cross talk.

Small ubiquitin-like modifier 4 M55V polymorphism is not associated with diabetic nephropathy in Iranian type 2 diabetes patients

INTRODUCTION:

We studied the impact of small ubiquitin-like modifier 4 (SUMO4) M55V polymorphism on susceptibility to diabetic nephropathy in Iranian type 2 diabetes patients.

MATERIALS AND METHODS:

The patient group consisted of 50 Iranian type 2 diabetes patients with nephropathy, and the control group consisted of 50 Iranian type 2 diabetes patients without nephropathy. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism method for the M55V.

RESULTS:

The frequency of SUMO4 AA, AG, and GG genotypes were 23%, 18%, and 9% in the patient group and 10%, 22%, and 18% in the control group. There was no significant difference in frequency of SUMO4 genotypes in patients compared to controls.

CONCLUSION:

These findings indicate that SUMO4 M55V polymorphism is not associated with diabetic nephropathy in Iranian type 2 diabetes patients.

SENP1 deSUMOylates and regulates Pin1 protein activity and cellular function

The Pin1 prolyl isomerase regulates phosphorylation signaling by controlling protein conformation after phosphorylation, and its upregulation promotes oncogenesis via acting on numerous oncogenic molecules. SUMOylation and deSUMOylation are dynamic mechanisms regulating a spectrum of protein activities. The SUMO proteases (SENP) remove SUMO conjugate from proteins, and their expression is deregulated in cancers. However, nothing is known about the role of SUMOylation in regulating Pin1 function. Here, we show that Pin1 is SUMOylated on Lys6 in the WW domain and on Lys63 in the PPIase domain. Pin1 SUMOylation inhibits its protein activity and oncogenic function. We further identify that SENP1 binds to and deSUMOylates Pin1. Importantly, either overexpression of SENP1 or disruption of Pin1 SUMOylation promotes the ability of Pin1 to induce centrosome amplification and cell transformation. Moreover, SENP1 also increases Pin1 protein stability in cell cultures, and Pin1 levels are positively correlated with SENP1 levels in human breast cancer specimens. These results not only uncover Pin1 SUMOylation on Lys6/63 as a novel mechanism to inhibit its activity and function but also identify a critical role for SENP1-mediated deSUMOylation in promoting Pin1 function during tumorigenesis.

DNA methylation impairs TLR9 induced Foxp3 expression by attenuating IRF-7 binding activity in fulminant type 1 diabetes

Fulminant type 1 diabetes (FT1D) is an extremely aggressive disease characterized by the abrupt onset of insulin-deficient hyperglycemia. However, the precise mechanisms underlying disease etiology almost remain unclear. As mice deficient in regulatory T cells (Tregs) are prone to the development of an FT1D-like phenotype, we thus investigated whether FT1D patients manifest Treg deficiency and explored the related mechanisms. We first noted a significant reduction for Foxp3 and CTLA4 expression levels in PBMCs of FT1D patients. IRF-7 was found to selectively bind to the Foxp3 promoter, and by which it promotes Foxp3 transcription. Therefore, ectopic IRF-7 expression significantly promoted Foxp3 and CTLA4 expression in PBMCs, while knockdown of IRF-7 manifested opposite effect. Importantly, stimulation of PBMCs with CpG ODN, a ligand for TLR9, significantly induced Foxp3 expression, demonstrating that TLR9 signaling positively regulates Treg development. However, knockdown of IRF-7 expression almost completely diminished the enhancing effect of TLR9 signaling on Foxp3 expression, suggesting that IRF-7 is a downstream molecule of TLR9 signaling and is essential for TLR9 induced Treg generation. Of interestingly note, the Foxp3 promoter in FT1D patients was hypermethylated, indicating that DNA methylation could be a causative factor responsible for the reduced Foxp3 expression in FT1D patients. Indeed, our mechanistic studies revealed that DNA methylation blocked IRF-7 binding to the Foxp3 promoter. Together, our data support the notion that environmental insults in genetic predisposed subjects trigger Foxp3 promoter hypermethylation, which then prevents IRF-7 binding to the Foxp3 promoter and impairs Treg development/functionality contributing to the pathogenesis of FT1D.

Novel roles of SUMO in pancreatic β-cells: thinking outside the nucleus

The endocrine pancreas is critically important in the regulation of energy metabolism, with defective insulin secretion from pancreatic islet β-cells a major contributing factor to the development of type 2 diabetes. Small ubiquitin-like modifier (SUMO) proteins have been demonstrated to covalently modify a wide range of target proteins, mediating a broad range of cellular processes. While the effects of SUMOylation on β-cell gene transcription have been previously reviewed, recent reports indicate roles for SUMO outside of the nucleus. In this review we shall focus on the reported non-nuclear roles of SUMOylation in the regulation of β-cells, including SUMOylation as a novel signaling pathway in the acute regulation of insulin secretion.

No association of the SUMO4 polymorphism M55V variant in type 2 diabetes in Iranian subjects

INTRODUCTION

Diabetes mellitus incidence has an increasing rate and it's genetic aspect is an important approach as a risk factor and predictive value in this disorder. In some population, SUMO4, a regulator of NF-κB, gene polymorphism is associated with diabetes. A single-nucleotide polymorphism was detected in SUMO4; substituting a highly conserved methionine with a valine residue (M55V). We studied the association between M55V polymorphism in the SUMO4 gene insusceptibility of type 2 diabetes in patients with type 2 diabetes.

MATERIALS AND METHODS

Participants were 50 patients with type 2 diabetes and 50 control Iranian subjects. Genotyping was done using polymorphism chain reaction (PCR) technique and subsequent cleavage by restriction endonuclease (RFLP) for the M55V SUMO4 gene variant.

RESULTS

The frequency of SUMO4 AA, AG and GG were 13%, 25% and 12% in control group and 20%, 22%, 18% in the type 2 diabetes patients respectively. The SUMO4 M55V variant was not associated with the susceptibility of type 2 diabetes.

CONCLUSION

The study indicates that the SUMO4 gene M55V variant was not associated with the susceptibility of the type 2 diabetes polymorphism.

Small ubiquitin-like modifier-4 Met55Val polymorphism is associated with glycemic control of Type 2 diabetes mellitus in Taiwan

AIM

The development of Type 2 diabetes mellitus (T2DM) has been recognized to be associated with a combination of pancreatic beta-cell dysfunction and insulin resistance. Nuclear factor-kappaB (NF-kappaB) has been recognized as one central mediator in the reaction of inflammation and proapoptotic event in beta-cells. A functional polymorphism at the codon 55 (methionine to valine; A163G) of the small ubiquitin- like modifier-4 (SUMO4) gene may result in higher NF-kappaB activity. This study investigates whether this SUMO4 Met55Val polymorphism also contributes to the development of T2DM.

MATERIALS AND METHODS

The study was performed using genomic DNA samples from 574 Type 2 diabetic patients and 323 healthy controls. The SUMO4 Met55Val polymorphism was genotyped using allele-specific real-time PCR.

RESULTS

The frequency of the G allele (encoding Val55) was significantly higher in Type 2 diabetic patients and Type 2 diabetic patients with the GG genotype had higher hemoglobin A1c level. Multivariate logistic regression analysis revealed the genotype of GG and GA was an independent risk factor contributing to the development of T2DM.

CONCLUSION

This study suggests that in Taiwan the SUMO4 Met 55Val polymorphism is associated with susceptibility to T2DM and Type 2 diabetic patients with GG genotype have worse glycemic control.

Characterization of a negative feedback network between SUMO4 expression and NFkappaB transcriptional activity

Previously, we have demonstrated evidence suggesting that SUMO4 negatively regulates NFkappaB transcriptional activity, probably through sumoylation of IkappaBalpha. Here, we present data indicating that SUMO4 possesses the capacity to conjugate to IkappaBalpha. Luciferase reporter assays in 3T3 cells deficient for IkappaBalpha further demonstrated that SUMO4 regulates NFkappaB signaling dependent on its sumoylation of IkappaBalpha. More importantly, a putative NFkappaB binding motif has been characterized within the SUMO4 promoter. Subsequent promoter reporter assays revealed that SUMO4 promoter with disrupted NFkappaB binding motif failed to response to NFkappaB specific IL-1beta stimulation. ChIP assays showed that NFkappaB binds to SUMO4 promoter and activates its transcription. Together, our data suggest that SUMO4 may act as a negative feedback regulator to prevent excessive activation of NFkappaB. Given the importance of NFkappaB signaling in immune response, SUMO4 could play a role to tightly control the potency of immune response to prevent autoimmunity.

Familial Graves' disease associated with type 1 diabetes

A 59-year-old woman was diagnosed as having Graves' disease and type 1 diabetes. DNA molecular HLA typing detected DRB1(*)0405 and DQB1(*)0401, as well as the haplotypes of DRB1(*)0901-DQB1(*)0303. We also performed polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to identify allele variations of other loci. The patient's son also manifested Graves' disease and type 1 diabetes, with both cases having strikingly homologous clinical features. Familial clustering of Graves' disease and type 1 diabetes, and their tendency to occur together along with a similar clinical course suggest that their etiology may involve shared genetic factors.

Repression of the SUMO-specific protease Senp1 induces p53-dependent premature senescence in normal human fibroblasts

The proliferative lifespan of normal somatic human cells in culture terminates in a permanent growth-arrested state known as replicative senescence. In this study, we show that RNA interference-mediated repression of the genes encoding the small ubiquitin-related modifier (SUMO)-specific proteases, Senp1, Senp2, and Senp7, induced low passage primary human fibroblasts to senesce rapidly. Following Senp1 repression, we observed a global increase in sumoylated proteins and in the number and size of nuclear SUMO-containing promyelocytic leukemia (PML) bodies. SUMO/PML bodies also increased during replicative senescence. p53 transcriptional activity was enhanced towards known p53 target genes following repression of Senp1, and inhibition of p53 function prevented senescence after Senp1 repression. These data indicate that Senp1 repression induces p53-mediated premature senescence and that SUMO proteases may thus be required for proliferation of normal human cells.

Extracellular high-mobility group box 1 acts as an innate immune mediator to enhance autoimmune progression and diabetes onset in NOD mice

OBJECTIVE

The implication of innate immunity in type 1 diabetes development has long been proposed. High-mobility group box 1 (HMGB1), an evolutionarily conserved chromosomal protein, was recently recognized to be a potent innate inflammatory mediator when released extracellularly. We sought to test the hypothesis that HMGB1 acts as an innate immune mediator implicated in type 1 diabetes pathogenesis.

RESEARCH DESIGN AND METHODS

Eight- and 12-week-old NOD mice were treated with an HMGB1 neutralizing antibody once a week until 25 weeks of age and monitored for insulitis progression and diabetes onset. The underlying mechanisms of HMGB1 regulation of autoimmune response were further explored.

RESULTS

During autoimmunity, HMGB1 can be passively released from damaged pancreatic beta-cells and actively secreted by islet infiltrated immune cells. Extracellular HMGB1 is potent in inducing NOD dendritic cell maturation and stimulating macrophage activation. Blockade of HMGB1 significantly inhibited insulitis progression and diabetes development in both 8- and 12-week-old NOD mice. HMGB1 antibody treatment decreased the number and maturation of pancreatic lymph node (PLN) CD11c(++)CD11b(+) dendritic cells, a subset of dendritic cells probably associated with autoantigen presentation to naïve T-cells, but increased the number for PLN CD4(+)Foxp3(+) regulatory T-cells. Blockade of HMGB1 also decreased splenic dendritic cell allo-stimulatory capability associated with increased tolergenic CD11c(+)CD8a(+) dendritic cells. Interestingly, the number of CD8(+)interferon-gamma(+) (Tc1) T-cells was increased in the PLNs and spleen after blockade of HMGB1, which could be associated with retarded migration of activated autoreactive T-cells into the pancreatic islets.

CONCLUSIONS

Extracellular HMGB1 functions as a potent innate immune mediator contributing to insulitis progression and diabetes onset.

SUMO4 and its role in type 1 diabetes pathogenesis

Susceptibility to type 1 diabetes (T1D) is determined by interactions of multiple genes with unknown environmental factors. Despite the characterization of over 20 susceptibility regions for T1D, identification of specific genes in these regions is still a formidable challenge. In 2004, we first reported the cloning of a novel, small ubiquitin-like modifier (SUMO) gene, SUMO4, in the IDDM5 interval on chromosome 6q25, and presented strong genetic and functional evidence suggesting that SUMO4 is a T1D susceptibility gene. Subsequent studies have consistently confirmed this association in multiple Asian populations despite controversial observations in Caucasians. In this review, we will update the genetic evidence supporting SUMO4 as a T1D susceptibility gene and discuss the possible explanations for the discrepant associations observed in Caucasians. We will then discuss the mechanisms through which SUMO4 contributes to the pathogenesis of T1D.

Genetic polymorphisms in susceptibility to Type 1 Diabetes

Type 1 Diabetes is a serious complex disease caused by several environmental and genetic factors. It is one of most common childhood diseases, requires life-long treatment, and is associated with increased mortality, mainly due to complications that occur later in life. More than three decades of genetic studies have identified several genetic disease variants and a longer list of putative associated genetic loci. These findings have greatly increased our understanding of the genetic background of T1D and have encouraged the development of genetic tools for mapping complex diseases. Here we review the wealth of data on T1D and discuss the major genetic polymorphisms involved in the disease. We place some putative genetic risk factors in perspective and look at those still to be detected.

No association of SUMO4 M55V with autoimmune diabetes in Asian-Indian patients

Autoimmune diabetes [type 1 diabetes mellitus (T1DM), latent autoimmune diabetes in adults (LADA) and part of malnutrition-related diabetes] has been shown to have genetic predisposition. Studies in IDDM 5 have lead to the discovery of a novel polymorphism 163 A-->G, of SUMO4 (small ubiquitin-related modifier) gene, associated with risk to T1DM in Asians, but not in Caucasians. We studied patients with T1DM (n = 134), patients with LADA (n = 101), patients with malnutrition-modulated diabetes mellitus (n = 66) and patients with fibrocalculous pancreatic diabetes (n = 43) and healthy controls subjects (n = 114) from Cuttack, India. Polymerase chain reaction-sequence-specific primer (PCR-SSP) was used to amplify the 163 A-->G sequences. Restriction fragment length polymorphism (RFLP) was performed using restriction enzyme Taq I (PCR-RFLP). Differences in the allelic frequencies of the A and the G alleles were tested statistically using Fisher's exact test or chi-squared test wherever appropriate. P-values were considered significant when equal to or less than 0.05. No significant association was detected between SUMO4 M55V and T1DM susceptibility in Asian-Indians. Comparison of the A and G alleles with HLA DR3-DR4 did not result in any significant P-values. No significant association was found between SUMO4 M55V and LADA or malnutrition-related diabetes mellitus (MRDM). Our results show that Asian-Indians with T1DM are different from other Asian populations. Asian-Indians show more similarity to Caucasians with respect to the association of SUMO4 M55V variant in T1DM. Association studies on Asian-Indian patients with LADA and MRDM showed no significant difference in the presence of the A and the G alleles when compared to healthy controls.

SUMO4 M55V polymorphism affects susceptibility to type I diabetes in HLA DR3- and DR4-positive Swedish patients

SUMO4 M55V, located in IDDM5, has been a focus for debate because of its association to type I diabetes (TIDM) in Asians but not in Caucasians. The current study aims to test the significance of M55V association to TIDM in a large cohort of Swedish Caucasians, and to test whether M55V is associated in those carrying human leukocyte antigen (HLA) class II molecules. A total of 673 TIDM patients and 535 age- and sex-matched healthy controls were included in the study. PCR-RFLP was performed to identify the genotype and allele variations. Our data suggest that SUMO4 M55V is not associated with susceptibility to TIDM by itself. When we stratified our patients and controls based on heterozygosity for HLA-DR3/DR4 and SUMO4 genotypes, we found that presence of SUMO4 GG increased further the relative risk conferred by HLA-DR3/DR4 to TIDM, whereas SUMO4 AA decreased the risk. From the current study, we conclude that SUMO4 M55V is associated with TIDM in association with high-risk HLA-DR3 and DR4, but not by itself.

Association of small ubiquitin-like modifier 4 (SUMO4) variant, located in IDDM5 locus, with type 2 diabetes in the Japanese population

CONTEXT

Despite distinct differences in the pathogenesis, epidemiological data have indicated familial clustering of type 1 and type 2 diabetes, suggesting a common genetic basis between these two types of diabetes. Few shared susceptibility genes, however, have been reported to date.

OBJECTIVE

Small ubiquitin-like modifier 4 (SUMO4) has been identified as a candidate gene for the IDDM5 locus and suggested to have possible involvement in immune responses, such as autoimmunity and inflammation. Recent reports demonstrated that a polymorphism with an amino acid substitution (Met55Val) in SUMO4 was associated with type 1 diabetes in Asian populations, although no association was reproduced in subjects of Caucasian descent. The present study aimed to clarify the contribution of SUMO4 to type 2 diabetes susceptibility in the Japanese population.

SUBJECTS

The 753 subjects included 355 cases and 398 control subjects.

METHODS

The SUMO4 Met55Val (rs237025) and 001Msp (rs577001) polymorphisms were genotyped.

RESULTS

Strong linkage disequilibrium (D': 1.0 in each pair of single-nucleotide polymorphisms) across the MAP3K7IP2/SUMO4 region was shown in the Japanese population. The frequency of genotypes with the G allele of the SUMO4 Met55Val polymorphism was significantly higher in patients with type 2 diabetes [odds ratio, 1.46; 95% confidence interval (CI), 1.08-1.93; P = 0.01, chi(2) test]. The association was concentrated in patients without insulin therapy (odds ratio, 1.56; 95% CI, 1.13-2.15; P = 0.0072), but not in those with insulin (odds ratio, 1.24; 95% CI, 0.81-1.89; not significant).

CONCLUSIONS

These data, together with previous reports, suggest the contribution of the SUMO4 Met55Val polymorphism to both type 1 and type 2 diabetes susceptibility in the Japanese population.