Evaluation of polymorphisms known to contribute to risk for diabetes in African and African-American populations

Genetic predisposition of LEPR (rs1137101) gene polymorphism related to type 2 diabetes mellitus - a meta-analysis

Background: Type 2 diabetes mellitus (T2DM) is a multifaceted disease appropriate to elevated blood glucose levels resulting from decreased insulin and beta-cell activity. Using a case-control methodology, researchers have examined the relationship between polymorphisms in LEPR and T2DM in a population from south India.Materials and Methods: We conducted a genetic analysis of 311 participants, and results were accomplished using a case-control study, a meta-analysis of previous studies on LEPR was conducted, and type 2 diabetes genotype distribution across various geographical regions Malaysians, Chinese Han, Kuwait, Iran, Mongolia, and Han Chinese, Greece, Saudi, India (North India, Punjabi), (South India, Tamilnadu). The study involved 254 prospective investigations, and nine association studies were preferred according to preset criteria. Studies were assessed for quality using the Hardy-Weinberg equilibrium (HWE) and the Newcastle-Ottawa Scale (NOS). An analysis of the genetic models was conducted to determine their relationship, statistical analysis was utilized to calculate odds ratios (ORs) and matching 95% confidence intervals (CIs).Results: The LEPR-rs1137101 polymorphism in the case-control study was associated with a significant increase in the risk of type 2 diabetes. A meta-analysis revealed a connection between LEPR gene polymorphism (rs1137101) and type 2 diabetes risk. Investigators might gain a more profound thought on the significance of the identified genetic variation and its impact on the chance of developing type 2 diabetes by verifying and strengthening previously reported findings. The model of fixed effects was chosen due to the low heterogeneity, and significant associations were observed in the allelic (OR = 0.79, 95% CI [0.70-0.87]), homozygote (OR = 0.58, 95% CI [0.46-0.72]), dominant (OR = 0.66, 95% CI [0.56-0.79]), and recessive (OR = 0.83, 95% CI [0.71-0.96]) genetic models. A Begg's funnel plot and Egger's test indicated no publication bias. These findings suggest that the rs1137101 variant in the LEPR gene has been linked to a higher risk of T2DM.Conclusions: A larger sample size, however, is required for further research, and consideration of potential confounding factors is needed to validate these associations. Understanding the implications of LEPR gene polymorphisms in T2DM susceptibility may contribute to personalized treatment strategies for patients with T2DM.

Clinical Study on the Relationship between the SNP rs8192675 (C/C) Site of SLC2A2 Gene and the Hypoglycemic Effect of Metformin in Type 2 Diabetes

This study investigates the correlation between the gene polymorphism of rs8192675 (C/C) locus of SLC2A2 in patients with type 2 diabetes (T2DM) and the efficacy of metformin. For this purpose, we have selected 110 T2DM patients (T2DM group) and 110 healthy people (control group) who were treated in our hospital from January 2019 to January 2020 as the research subjects. PCR-restriction fragment length polymorphism (PCR-RFLP) method detects the distribution frequency of gene polymorphism. The patients in the T2DM group were treated with metformin and followed up for 90 days to analyze the relationship between the efficacy of metformin and the SLC2A2 gene polymorphism. The genotypes of SLC2A2 rs8192675 in the control group and in the T2DM group conformed to the Hardy–Weinberg equilibrium law. Compared with the control group, the CT type and the CC type at rs8192675 in the T2DM group were significantly higher (P < 0.05). For rs8192675, there was no significant difference in TT, CT, CC FPG, 2hPBG, and HbA1c levels before treatment (P > 0.05); after metformin treatment, the reduction in FPG, 2hPBG, and HbA1c in CC patients was lower than that of TT and CT patients (P < 0.05). SLC2A2 gene polymorphism site rs8192675 CC type T2DM patients are sensitive to metformin and have a better hypoglycemic effect.

The role of Wnt pathway in obesity induced inflammation and diabetes: a review

Diabetes has become a major killer worldwide and at present, millions are affected by it. Being a chronic disease it increases the risk of other diseases ranging from pulmonary disorders to soft tissue infections. The loss of insulin-producing capacity of the pancreatic β-cells is the main reason for the development of the disease. Obesity is a major complication that can give rise to several other diseases such as cancer, diabetes, etc. Visceral adiposity is one of the major factors that play a role in the development of insulin resistance. Obesity causes a chronic low-grade inflammation in the tissues that further increases the chances of developing diabetes. Several pathways have been associated with the development of diabetes due to inflammation caused by obesity. The Wnt pathway is one such candidate pathway that is found to have a controlling effect on the development of insulin resistance. Moreover, the pathway has also been linked to obesity and inflammation. This review aims to find a connection between obesity, inflammation, and diabetes by taking the wnt pathway as the connecting link.

Current Understanding on Role of the Wnt Signaling Pathway Effector TCF7L2 in Glucose Homeostasis

The role of the Wnt signaling pathway in metabolic homeostasis has drawn our intensive attention, especially after the genome-wide association study discovery that certain polymorphisms of its key effector TCF7L2 are strongly associated with the susceptibility to type 2 diabetes. For a decade, great efforts have been made in determining the function of TCF7L2 in various metabolic organs, which have generated both considerable achievements and disputes. In this review, I will briefly introduce the canonical Wnt signaling pathway, focusing on its effector β-catenin/TCF, including emphasizing the bidirectional feature of TCFs and β-catenin post-translational modifications. I will then summarize the observations on the association between TCF7L2 polymorphisms and type 2 diabetes risk. The main content, however, is on the intensive functional exploration of the metabolic role of TCF7L2, including the disputes generated on determining its role in the pancreas and liver with various transgenic mouse lines. Finally, I will discuss those achievements and disputes and present my future perspectives.

Five linkage regions each harbor multiple type 2 diabetes genes in the African American subset of the GENNID Study

We previously localized type 2 diabetes (T2D)-susceptibility genes to five chromosomal regions through a genome-wide linkage scan of T2D and age of diagnosis (AOD) in the African American subset of the GENNID sample. To follow up these findings, we repeated the linkage and association analysis using genotypes on an additional 9203 fine-mapping single nucleotide polymorphisms (SNPs) selected to tag genes under the linkage peaks. In each of the five regions, we confirmed linkage and inferred the presence of ≥2 susceptibility genes. The evidence of multiple susceptibility genes consisted of: (1) multiple linkage peaks in four of the five regions; and (2) association of T2D and AOD with SNPs within ≥2 genes in every region. The associated genes included 3 previously reported to associate with T2D or related traits (GRB10, NEDD4L, LIPG) and 24 novel candidate genes, including genes in lipid metabolism (ACOXL) and cell-cell and cell-matrix adhesion (MAGI2, CLDN4, CTNNA2).

Wnt/β-catenin signaling may be involved with the maturation, but not the differentiation, of insulin-producing cells

Wnt/β-catenin signaling (WNT) has widespread roles during stem cell differentiation. Whether WNT suppresses or promotes insulin-producing cell (IPC) differentiation and function is still not known. In this study, we investigated the role of WNT signaling during human adipose-derived stem cell (hADSC) differentiation into IPCs. Western blot analysis revealed that several key components of WNT were dynamically regulated in a 12-day IPC differentiation assay. Specifically, protein levels of Wnt1, β-catenin, and GSK3β steadily increased from day 0 to day 9 and rapidly decreased by day 12 of differentiation. Similarly, endonuclear β-catenin levels peaked at day 9 and then, fell to pre-differentiation levels. The expression of two WNT pathway targets, TCF-1 and cyclin D1, closely followed the same pattern of regulation, confirming that WNT signaling was transiently activated during IPC differentiation. Interestingly, the inhibition of WNT signaling did not block IPC differentiation; instead, it resulted in the upregulation of IPC-specific markers, including PDX-1, insulin, IRS-1, and IRS-2. Notably, another IPC marker, glucokinase, remained downregulated since it is a direct target of WNT signaling. Next, we examined the effect of maintaining active WNT signaling from day 9 to day 12 of IPC differentiation. Differentiating cells were treated with Wnt1 on day 9, when WNT signaling is typically turned off, and subjected to gene expression analysis on day 12. Remarkably, Wnt1 treatment resulted in reduced expression of IPC-specific markers. Taken together, these data indicate that WNT may not be necessary for IPC differentiation but may be involved in IPC maturation.

Genome-wide detection of allele specific copy number variation associated with insulin resistance in African Americans from the HyperGEN study

African Americans have been understudied in genome wide association studies of diabetes and related traits. In the current study, we examined the joint association of single nucleotide polymorphisms (SNPs) and copy number variants (CNVs) with fasting insulin and an index of insulin resistance (HOMA-IR) in the HyperGEN study, a family based study with proband ascertainment for hypertension. This analysis is restricted to 1,040 African Americans without diabetes. We generated allele specific CNV genotypes at 872,243 autosomal loci using Birdsuite, a freely available multi-stage program. Joint tests of association for SNPs and CNVs were performed using linear mixed models adjusting for covariates and familial relationships. Our results highlight SNPs associated with fasting insulin and HOMA-IR (rs6576507 and rs8026527, 3.7*10⁻⁷≤P≤1.1*10⁻⁵) near ATPase, class V, type 10A (ATP10A), and the L Type voltage dependent calcium channel (CACNA1D, rs1401492, P≤5.2*10⁻⁶). ATP10A belongs to a family of aminophospholipid-transporting ATPases and has been associated with type 2 diabetes in mice. CACNA1D has been linked to pancreatic beta cell generation in mice. The two most significant copy variable markers (rs10277702 and rs361367; P<2.0*10⁻⁴) were in the beta variable region of the T-cell receptor gene (TCRVB). Human and mouse TCR has been shown to mimic insulin and its receptor and could contribute to insulin resistance. Our findings differ from genome wide association studies of fasting insulin and other diabetes related traits in European populations, highlighting the continued need to investigate unique genetic influences for understudied populations such as African Americans.

Analysis of FTO gene variants with obesity and glucose homeostasis measures in the multiethnic Insulin Resistance Atherosclerosis Study cohort

OBJECTIVE

Previous studies have replicated the association of variants within FTO (fat mass- and obesity-associated) intron 1 with obesity and adiposity quantitative traits in populations of European ancestry. Non-European populations, however, have not been so intensively studied. The goal of this investigation was to examine the association of FTO single-nucleotide polymorphisms (SNPs), prominent in the literature in a multiethnic sample of non-Hispanic White American (n=458), Hispanic American (n=373) and African American (n=288) subjects from the Insulin Resistance Atherosclerosis Study (IRAS). This cohort provides the unique ability to evaluate how variation within FTO influences measures of adiposity and glucose homeostasis in three different ethnicities, which were ascertained and examined using a common protocol.

DESIGN

A total of 26 FTO SNPs were genotyped, including those consistently associated in the literature (rs9939609, rs8050136, rs1121980, rs1421085, rs17817449 and rs3751812), and tested for association with adiposity and glucose homeostasis traits.

RESULTS

For the adiposity phenotypes, these and other SNPs were associated with body mass index (BMI) in both non-Hispanic Whites (P-values ranging from 0.015 to 0.048) and Hispanic Americans (P-values ranging from 7.1 × 10(-6) to 0.027). In Hispanic Americans, four other SNPs (rs8047395, rs10852521, rs8057044 and rs8044769) still showed evidence of association after multiple comparisons adjustment (P-values ranging from 5.0 × 10(-5) to 5.2 × 10(-4)). The historically associated BMI SNPs were not associated in the African Americans, but rs1108102 was associated with BMI (P-value of 5.4 × 10(-4)) after accounting for multiple comparisons. For glucose homeostasis traits, associations were seen with acute insulin response in non-Hispanic Whites and African Americans. However, all associations with glucose homeostasis measures were no longer significant after adjusting for multiple comparisons.

CONCLUSION

These results replicate the association of FTO intron 1 variants with BMI in non-Hispanic Whites and Hispanic Americans but show little evidence of association in African Americans, suggesting that the effect of FTO variants on adiposity phenotypes shows genetic heterogeneity dependent on ethnicity.

Univariate and bivariate linkage analysis identifies pleiotropic loci underlying lipid levels and type 2 diabetes risk

Dyslipidemia frequently co-occurs with type 2 diabetes (T2D) and with obesity. To investigate whether the co-occurrence is due to pleiotropic genes, we performed univariate linkage analysis of lipid levels and bivariate linkage analysis of pairs of lipid levels and of lipid levels paired with T2D, body mass index (BMI), and waist-hip ratio (WHR) in the African American subset of the Genetics of NIDDM (GENNID) sample. We obtained significant evidence for a pleiotropic low density lipoprotein cholesterol (LDL-C)-T2D locus on chromosome 1 at 16-19 megabases (MB) (bivariate lod = 4.41), as well as a non-pleiotropic triglyceride (TG) locus on chromosome 20 at 28-34 MB (univariate lod = 3.57). In addition, near-significant evidence supported TG-T2D loci on chromosome 2 at 81-101 MB (bivariate lod = 4.23) and 232-239 MB (bivariate lod = 4.27) and on chromosome 7 at 147-151 MB (univariate lod = 3.08 for TG with P = 0.041 supporting pleiotropy with T2D), as well as an LDL-C-BMI locus on chromosome 3 at 137-147 MB (bivariate lod score = 4.25). These findings provide evidence that at least some of the co-occurrence of dyslipidemia with T2D and obesity is due to common underlying genes.

Genetics factors contributing to type 2 diabetes across ethnicities

Type 2 diabetes mellitus (T2DM) is among the many common diseases with a strong genetic component, but until recently, the variants causing this disease remained largely undiscovered. With the ability to interrogate most of the variation in the genome, the number of genetic variants has grown from 2 to 19 genes, many with multiple variants. An additional three genes are associated primarily with fasting glucose rather than T2DM. Despite the plethora of new markers, the individual effect is uniformly small, and the cumulative effect explains little of the genetic risk for T2DM. Furthermore, the success is largely restricted to European populations. Despite success in mapping genes in Asian populations, success in United States minorities, particularly African Americans, has been limited. The genetic findings highlight the role of the beta cell in diabetes pathogenesis, but much remains to be discovered before genetic prediction and individualized medicine can become a reality for this disease.

Genome-wide linkage and admixture mapping of type 2 diabetes in African American families from the American Diabetes Association GENNID (Genetics of NIDDM) Study Cohort

OBJECTIVE

We used a single nucleotide polymorphism (SNP) map in a large cohort of 580 African American families to identify regions linked to type 2 diabetes, age of type 2 diabetes diagnosis, and BMI.

RESEARCH DESIGN AND METHODS

After removing outliers and problematic samples, we conducted linkage analysis using 5,914 SNPs in 1,344 individuals from 530 families. Linkage analysis was conducted using variance components for type 2 diabetes, age of type 2 diabetes diagnosis, and BMI and nonparametric linkage analyses. Ordered subset analyses were conducted ranking on age of type 2 diabetes diagnosis, BMI, waist circumference, waist-to-hip ratio, and amount of European admixture. Admixture mapping was conducted using 4,486 markers not in linkage disequilibrium.

RESULTS

The strongest signal for type 2 diabetes (logarithm of odds [LOD] 4.53) was a broad peak on chromosome 2, with weaker linkage to age of type 2 diabetes diagnosis (LOD 1.82). Type 2 diabetes and age of type 2 diabetes diagnosis were linked to chromosome 13p (3-22 cM; LOD 2.42 and 2.46, respectively). Age of type 2 diabetes diagnosis was linked to 18p (66 cM; LOD 2.96). We replicated previous reports on chromosome 7p (79 cM; LOD 2.93). Ordered subset analysis did not overlap with linkage of unselected families. The best admixture score was on chromosome 12 (90 cM; P = 0.0003).

CONCLUSIONS

The linkage regions on chromosomes 7 (27-78 cM) and 18p overlap prior reports, whereas regions on 2p and 13p linkage are novel. Among potential candidate genes implicated are TCF7L1, VAMP5, VAMP8, CDK8, INSIG2, IPF1, PAX8, IL18R1, members of the IL1 and IL1 receptor families, and MAP4K4. These studies provide a complementary approach to genome-wide association scans to identify causative genes for African American diabetes.

Genome-wide linkage scan in Gullah-speaking African American families with type 2 diabetes: the Sea Islands Genetic African American Registry (Project SuGAR)

OBJECTIVE

The Gullah-speaking African American population from the Sea Islands of South Carolina is characterized by a low degree of European admixture and high rates of type 2 diabetes and diabetic complications. Affected relative pairs with type 2 diabetes were recruited through the Sea Islands Genetic African American Registry (Project SuGAR).

RESEARCH DESIGN AND METHODS

We conducted a genome-wide linkage scan, genotyping 5,974 single nucleotide polymorphisms in 471 affected subjects and 50 unaffected relatives from 197 pedigrees. Data were analyzed using a multipoint engine for rapid likelihood inference and ordered subsets analyses (OSAs) for age at type 2 diabetes diagnosis, waist circumference, waist-to-hip ratio, and BMI. We searched for heterogeneity and interactions using a conditional logistic regression likelihood approach.

RESULTS

Linkage peaks on chromosome 14 at 123-124 cM were detected for type 2 diabetes (logarithm of odds [LOD] 2.10) and for the subset with later age at type 2 diabetes diagnosis (maximum LOD 4.05). Two linkage peaks on chromosome 7 were detected at 44-45 cM for type 2 diabetes (LOD 1.18) and at 78 cM for type 2 diabetes (LOD 1.64) and the subset with earlier age at type 2 diabetes diagnosis (maximum LOD 3.93). The chromosome 14 locus and a peak on 7p at 29.5 cM were identified as important in the multilocus model. Other regions that provided modest evidence for linkage included chromosome 1 at 167.5 cM (LOD 1.51) and chromosome 3 at 121.0 cM (LOD 1.61).

CONCLUSIONS

This study revealed a novel type 2 diabetes locus in an African American population on 14q that appears to reduce age of disease onset and confirmed two loci on chromosome 7.

A population-based analysis of the health experience of African Nova Scotians

BACKGROUND

People of African descent living in Britain and the United States have higher rates of morbidity from chronic disease than among the general population. We investigated whether the same applied to people of African descent living in a Canadian province.

METHODS

We used administrative data to calculate 10-year cumulative incidence rate ratios for the period 1996-2005 for treated circulatory disease, diabetes mellitus and psychiatric disorders in Preston (population 2425), a community of predominantly African Nova Scotians. We used data for the province of Nova Scotia as a whole as the population reference standard. We also calculated 10-year incidence rate ratios for visits to family physicians and specialists and for admissions to hospital. We compared these findings with those in 7 predominantly white communities in Nova Scotia with otherwise similar socio-economic characteristics.

RESULTS

In the province as a whole, we identified 787,787 incident cases for the 3 disease groups over the 10-year period. Incidence rate ratios for the community of interest relative to the provincial population were significantly elevated for the 3 diseases: circulatory disease (1.19, 95% CI 1.08-1.29), diabetes (1.43, 95% CI 1.21-1.64) and psychiatric disorders (1.13, 95% CI 1.06-1.20). Incidence rate ratios in the community of interest were also higher than those in the comparison communities. Visits to family physicians and specialists for circulatory disease and diabetes were similarly elevated, but the pattern was less clear for visits for psychiatric disorders and hospital admissions.

INTERPRETATION

African Nova Scotians had higher morbidity levels associated with treated disease, which could not be explained by socio-economic characteristics, recent immigration or language. Apart from psychiatric disorders, use of specialist services was consistent with morbidity. Further study is needed to investigate the relative contribution of genetic, biological, behavioural, psychosocial and environmental factors.

The WNT signalling pathway and diabetes mellitus

The WNT signalling pathway is involved in many physiological and pathophysiological activities. WNT ligands bind to Frizzled receptors and co-receptors (LDL receptor-related protein 5/6), triggering a cascade of signalling events. The major effector of the canonical WNT signalling pathway is the bipartite transcription factor beta-catenin/T cell transcription factor (beta-cat/TCF), formed by free beta-cat and one of the four TCFs. The WNT pathway is involved in lipid metabolism and glucose homeostasis, and mutations in LRP5 may lead to the development of diabetes and obesity. beta-Cat/TCF is also involved in the production of the incretin hormone glucagon-like peptide-1 in the intestinal endocrine L cells. More recently, genome-wide association studies have identified TCF7L2 as a diabetes susceptibility gene, and individuals carrying certain TCF7L2 single nucleotide polymorphisms could be more susceptible to the development of type 2 diabetes. Furthermore, beta-cat is able to interact with forkhead box transcription factor subgroup O (FOXO) proteins. Since FOXO and TCF proteins compete for a limited pool of beta-cat, enhanced FOXO activity during ageing and oxidative stress may attenuate WNT-mediated activities. These observations shed new light on the pathogenesis of type 2 diabetes as an age-dependent disease.

Exploration of the utility of ancestry informative markers for genetic association studies of African Americans with type 2 diabetes and end stage renal disease

Admixture and population stratification are major concerns in genetic association studies. We wished to evaluate the impact of admixture using empirically derived data from genetic association studies of African Americans (AA) with type 2 diabetes (T2DM) and end-stage renal disease (ESRD). Seventy ancestry informative markers (AIMs) were genotyped in 577 AA with T2DM-ESRD, 596 AA controls, 44 Yoruba Nigerian (YRI) and 39 European American (EA) controls. Genotypic data and association results for eight T2DM candidate gene studies in our AA population were included. Ancestral estimates were calculated using FRAPPE, ADMIXMAP and STRUCTURE for all AA samples, using varying numbers of AIMs (25, 50, and 70). Ancestry estimates varied significantly across all three programs with the highest estimates obtained using STRUCTURE, followed by ADMIXMAP; while FRAPPE estimates were the lowest. FRAPPE estimates were similar using varying numbers of AIMs, while STRUCTURE estimates using 25 AIMs differed from estimates using 50 and 70 AIMs. Female T2DM-ESRD cases showed higher mean African proportions as compared to female controls, male cases, and male controls. Age showed a weak but significant correlation with individual ancestral estimates in AA cases (r2 = 0.101; P = 0.019) and in the combined set (r2 = 0.131; P = 3.57 x 10(-5)). The absolute difference between frequencies in parental populations, absolute delta, was correlated with admixture impact for dominant, additive, and recessive genotypic models of association. This study presents exploratory analyses of the impact of admixture on studies of AA with T2DM-ESRD and supports the use of ancestral proportions as a means of reducing confounding effects due to admixture.

Association analysis in african americans of European-derived type 2 diabetes single nucleotide polymorphisms from whole-genome association studies

OBJECTIVE

Several whole-genome association studies have reported identification of type 2 diabetes susceptibility genes in various European-derived study populations. Little investigation of these loci has been reported in other ethnic groups, specifically African Americans. Striking differences exist between these populations, suggesting they may not share identical genetic risk factors. Our objective was to examine the influence of type 2 diabetes genes identified in whole-genome association studies in a large African American case-control population.

RESEARCH DESIGN AND METHODS

Single nucleotide polymorphisms (SNPs) in 12 loci (e.g., TCF7L2, IDE/KIF11/HHEX, SLC30A8, CDKAL1, PKN2, IGF2BP2, FLJ39370, and EXT2/ALX4) associated with type 2 diabetes in European-derived populations were genotyped in 993 African American type 2 diabetic and 1,054 African American control subjects. Additionally, 68 ancestry-informative markers were genotyped to account for the impact of admixture on association results.

RESULTS

Little evidence of association was observed between SNPs, with the exception of those in TCF7L2, and type 2 diabetes in African Americans. One TCF7L2 SNP (rs7903146) showed compelling evidence of association with type 2 diabetes (admixture-adjusted additive P [P(a)] = 1.59 x 10(-6)). Only the intragenic SNP on 11p12 (rs9300039, dominant P [P(d)] = 0.029) was also associated with type 2 diabetes after admixture adjustments. Interestingly, four of the SNPs are monomorphic in the Yoruba population of the HAPMAP project, with only the risk allele from the populations of European descent present.

CONCLUSIONS

Results suggest that these variants do not significantly contribute to interindividual susceptibility to type 2 diabetes in African Americans. Consequently, genes contributing to type 2 diabetes in African Americans may, in part, be different from those in European-derived study populations. High frequency of risk alleles in several of these genes may, however, contribute to the increased prevalence of type 2 diabetes in African Americans.

The Wnt signaling pathway effector TCF7L2 and type 2 diabetes mellitus

Since the relationship between TCF7L2 (also known as TCF-4) polymorphisms and type 2 diabetes mellitus was identified in 2006, extensive genome-wide association examinations in different ethnic groups have further confirmed this relationship. As a component of the bipartite transcription factor beta-catenin/TCF, TCF7L2 is important in conveying Wnt signaling during embryonic development and in regulating gene expression during adulthood. Although we still do not know mechanistically how the polymorphisms within the intron regions of TCF7L2 affect the risk of type 2 diabetes, this transcriptional regulator was shown to be involved in stimulating the proliferation of pancreatic beta-cells and the production of the incretin hormone glucagon-like peptide-1 in intestinal endocrine L cells. In this review, we introduce background knowledge of TCF7L2 as a component of the Wnt signaling pathway, summarize recent findings demonstrating the association between TCF7L2 polymorphisms and the risk of type 2 diabetes, outline experimental evidence of the potential function of TCF7L2 in pancreatic and intestinal endocrine cells, and present our perspective views.

Genetic polymorphisms of matrix metalloproteinases in lung, breast and colorectal cancer

The matrix metalloproteinases (MMPs) can degrade various components of the extracellular matrix and are implicated in the development and progression of cancer. There is evidence suggesting an association of MMP gene polymorphisms with cancer susceptibility and/or metastasis. This paper reviews the findings on several single nucleotide polymorphisms in the collagenase, stromelysin and gelatinase genes in lung cancer, breast cancer and colorectal cancer.