The absence of evidence for major effects of the frequent SNP +299G>A in the resistin gene on susceptibility to insulin resistance syndrome associated with Japanese type 2 diabetes

Polymorphisms of lipid metabolism enzyme-coding genes in patients with diabetic dyslipidemia

Objective:

The polymorphisms/mutations of genes encoding proteins and enzymes involved in lipoprotein metabolism play important roles in the development of diabetic dyslipidemia. The aim of our study was to investigate the effects of LPL (rs320), LIPC (rs2070895), SCARB1 (rs5888), LCAT (rs2292318), CETP (rs708272), ADIPOQ (rs1501299), RETN (rs3745367), PON1 (rs662), and MNSOD (rs4880) gene polymorphisms on lipid metabolism and diabetic dyslipidemia.

Methods:

This case-control study included 217 patients with diabetic dyslipidemia and 212 healthy age- and gender-matched individuals. Genomic DNA isolation was performed from blood samples, and genotype analysis was performed using melting curve analysis on a LightCycler^® 480 Instrument. The chi-square test was used to compare genotype distribution and allele frequencies between the groups.

Results:

Significant associations were observed between LPL (rs320) (p<0.001), LIPC (rs2070895) (p<0.001), SCARB1 (rs5888) (p<0.001), LCAT (rs2292318) (p<0.001), CETP (rs708272) (p<0.001), ADIPOQ (rs1501299) (p=0.01), RETN (rs3745367) (p<0.001), and MNSOD (rs4880) (p<0.001) polymorphisms and diabetic dyslipidemia. However, no association was observed between PON1 (rs662) polymorphisms and diabetic dyslipidemia (p=0.611).

Conclusion:

LPL (rs320), LIPC (rs2070895), SCARB1 (rs5888), LCAT (rs2292318), CETP (rs708272), ADIPOQ (rs1501299), RETN (rs3745367), and MNSOD (rs4880) polymorphisms play an important role in basic molecular metabolism in diabetic dyslipidemia. Therefore, these polymorphisms may be used as a predictive marker for diabetic dyslipidemia in high-risk patients. (Anatol J Cardiol 2017; 17: 313-21)

Resistin gene variations are associated with the metabolic syndrome in Japanese men

SUMMARY

OBJECTIVES

Metabolic syndrome is defined as a cluster of risk factors for cardiovascular disease and is intimately related to insulin resistance. Resistin, a hormone secreted by adipocytes, may play an important role in communication between adiposity and insulin resistance. We investigated whether variations in the resistin gene associated with metabolic syndrome in a Japanese population.

METHOD

We analyzed five SNPs, two of which were located in the promoter region (-420C > G, -358G > A), two in intron 2 (+157C > T, +299G > A), and one in the 3'-untranslated region (3'UTR) (+1263G > C) across the resistin gene in 2968 residents from an urban Japanese cohort. The associations of SNPs and haplotypes with metabolic syndrome were analyzed.

RESULTS

The GAC and CGC haplotypes (comprising -420C > G, -358G > A, and +157C > T) had opposite influences on metabolic syndrome susceptibility in men; the former was associated with an increased risk and the latter with a decreased risk. We also found that the -420G allele was significantly associated with an increased risk of metabolic syndrome and significantly correlated with high diastolic blood pressure, high HOMA-IR values, high serum triglyceride levels, low HDL-cholesterol levels and high serum levels of adiponectin.

CONCLUSION

We identified a risk-conferring SNP and haplotype of the resistin gene for metabolic syndrome in a Japanese population. Our data suggested that resistin gene is a susceptibility gene for metabolic syndrome in Japanese men.

Association of resistin gene polymorphisms with insulin resistance in Egyptian obese patients

BACKGROUND

Obesity associated insulin resistance is a major risk factor for type 2 diabetes mellitus. Resistin is recently reported to provide a link between obesity, insulin resistance and type 2 diabetes mellitus. We aimed to investigate the possible associations of resistin gene (RETN) polymorphisms with obesity, and to detect whether these polymorphisms are associated with glucose intolerance and type 2 diabetes mellitus in obese patients.

METHODS

One hundred and forty-five Egyptian obese patients with or without glucose intolerance and 155 unrelated healthy controls were enrolled in this study. Polymorphisms of RETN +299G>A and RETN -420 C>G gene were detected by polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP). Serum resistin was measured by ELISA.

RESULTS

RETN +299 AA and RETN -420 GG genotypes were significantly associated with obesity in Egyptian population. Moreover, the mutant alleles or genotypes of both examined polymorphisms were associated with impaired glucose tolerance and diabetes mellitus compared to normal glucose tolerant obese patients. Furthermore, our results revealed elevated waist/hip ratio, BMI, blood pressure, fasting blood glucose level, HOMA-IR, triglycerides, total cholesterol, resistin level, and decreased HDL cholesterol level in homozygote mutant genotypes carriers of both RETN polymorphisms among obese patients.

CONCLUSION

Resistin gene polymorphisms may play an important role in pathogenesis and susceptibility to obesity, impaired glucose tolerance, and type 2 diabetes mellitus in Egyptian population.

The Human Obesity Gene Map: The 2003 Update

This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome-wide scans and candidate regions in targeted studies. A total of 35 genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 272 studies reporting positive associations with 90 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, more than 430 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.

Association of variants in RETN with plasma resistin levels and diabetes-related traits in the Framingham Offspring Study

OBJECTIVE

The RETN gene encodes the adipokine resistin. Associations of RETN with plasma resistin levels, type 2 diabetes, and related metabolic traits have been inconsistent. Using comprehensive linkage disequilibrium mapping, we genotyped tag single nucleotide polymorphisms (SNPs) in RETN and tested associations with plasma resistin levels, risk of diabetes, and glycemic traits.

RESEARCH DESIGN AND METHODS

We examined 2,531 Framingham Offspring Study participants for resistin levels, glycemic phenotypes, and incident diabetes over 28 years of follow-up. We genotyped 21 tag SNPs that capture common (minor allele frequency >0.05) or previously reported SNPs at r2 > 0.8 across RETN and its flanking regions. We used sex- and age-adjusted linear mixed-effects models (with/without BMI adjustment) to test additive associations of SNPs with traits, adjusted Cox proportional hazards models accounting for relatedness for incident diabetes, and generated empirical P values (Pe) to control for type 1 error.

RESULTS

Four tag SNPs (rs1477341, rs4804765, rs1423096, and rs10401670) on the 3' side of RETN were strongly associated with resistin levels (all minor alleles associated with higher levels, Pe<0.05 after multiple testing correction). rs10401670 was also associated with fasting plasma glucose (Pe = 0.02, BMI adjusted) and mean glucose over follow-up (Pe = 0.01; BMI adjusted). No significant association was observed for adiposity traits. On meta-analysis, the previously reported association of SNP -420C/G (rs1862513) with resistin levels remained significant (P = 0.0009) but with high heterogeneity across studies (P < 0.0001).

CONCLUSIONS

SNPs in the 3' region of RETN are associated with resistin levels, and one of them is also associated with glucose levels, although replication is needed.

The +299(G>A) resistin gene polymorphism and susceptibility to type 2 diabetes in Thais

The prevalence of type 2 diabetes has been increased in Thais. Resistin is an adipokine that involve in glucose homeostasis and is a candidate gene for type 2 diabetes. We performed a case-control study in representative sample of 200 Thai volunteers, 105 controls and 95 type 2 diabetes subjects. The purposes of the present study were to investigate the association between two SNPs (single nucleotide polymorphisms) in the resistin gene, at positions +299(G>A) and -420(C>G), and biochemical parameters; to determine whether these polymorphisms are linked to increased risk of type 2 diabetes. At position +299(G>A) of the resistin gene, the resistin concentration among type 2 diabetes subjects was significantly higher in GA/AA genotypes (3.40 ng/ml) than the GG genotype (1.99 ng/ml). Resistin gene polymorphism at position +299(G>A) in type 2 diabetes patients was significantly more frequent than in the control group (p = 0.004). Polymorphism at position -420(C>G) showed no significant relationship with type 2 diabetes (p = 0.095). Logistic regression analysis was shown that +299(G>A) gene polymorphism was increased risk factors for type 2 diabetes (p = 0.013). In conclusion, these finding suggest that resistin gene polymorphism at position +299(G>A) has impact on the increased resistin concentrations and may influence susceptibility to type 2 diabetes in Thais.

Absence of evidence for an association between resistin gene variants and insulin resistance in an Asian population with low and high blood pressure

AIMS

Although the function of resistin in human biology is unclear, some evidence suggests resistin gene variants influence insulin resistance, and insulin resistance-related hypertension. We searched for associations between common resistin gene variants and factors related to insulin resistance in Asian individuals with high or low blood pressure (BP).

METHODS

Non-diabetic Chinese or Japanese sibling pairs were included if one had extreme hypertension and the other was either hypertensive or hypotensive. Four common, non-coding single nucleotide polymorphisms (SNPs) were identified by sequencing the resistin gene in 24 hypertensive probands. Generalized estimating equations (GEEs)-based regressions were then performed to test for SNP associations using the entire study population (n=1556).

RESULTS

Of 72 tests, only one was significant at the 0.05 level; 3.5 significant tests were expected by chance alone. High variability in insulin and triglyceride levels created wide confidence intervals, thus the negative results are not conclusive for these phenotypes. However, the large sample size resulted in narrow confidence intervals for BMI, fasting and 120min post-load glucose, and high and low density lipoprotein cholesterol (LDL-C).

CONCLUSION

Several factors associated with insulin resistance are not likely influenced by the resistin gene in non-diabetic Asian individuals with high and low blood pressure.

Analysis of genetic variations in the resistin gene shows no associations with obesity in women

Resistin is thought to be involved in the development of obesity and insulin resistance. Polymorphisms in the gene encoding resistin could contribute to this link, but different studies have yielded contradictory results. In this study, we investigated whether polymorphisms in resistin are involved in the development of obesity in a Belgian female population. We selected three single-nucleotide polymorphisms (SNPs; rs1862513, rs3745367, and rs3745369) and compared their genotype and allele frequencies between female obese patients (N = 541) and control individuals (N = 235). This analysis showed association with neither obesity for any of the variants nor with the haplotypes of these SNPs. Furthermore, we also investigated whether these variants have an influence on BMI. After Kruskal-Wallis analysis, we found that there was no difference in BMI between the genotypes for all variants. Together, these results suggest that these variants in resistin are not associated with obesity in the female population.

Association of Resistin Gene 3'-Untranslated Region EX4-44G-->A Polymorphism with Obesity- and Insulin-Related Phenotypes in Turkish Type 2 Diabetes Patients

Resistin, an adipocyte-secreted hormone, has been associated with obesity, insulin resistance and type 2 diabetes mellitus (T2DM) in some, but not all, rodent models. In humans, the exact function of resistin is unkown. Because 3'-untranslated region (3'-UTR) single nucleotide substitutions (SNPs) have been shown to affect gene expression, we examined the EX4-44G-->A SNP in the 3'-UTR of exon 3 within the resistin gene. The objective of this study was to investigate, for the first time in a Turkish study group, whether the 3'-UTR EX4-44G-->A variation in the resistin gene influences the development of T2DM, obesity and insulin-related phenotypes. We analyzed the genotype frequencies of the EX4-44G-->A polymorphism of the resistin gene in 116 type 2 diabetic and 102 normal subjects. Serum lipids, obesity-related and insulin-related phenotypes were analyzed. No significant difference for genotypic frequencies were observed for the BseRI restriction site in type 2 diabetic patients as compared to controls. Waist-to-hip ratio, BMI, body fat and apoAI levels were found to be affected by resistin genotype. In the control group, BMI (p < 0.01), HIS (p < 0.05) and BF (p < 0.05) levels were found to be elevated, whereas HOMA beta-cell index (p < 0.01) and apo AI (p < 0.05) levels were found to be decreased in GG genotype carriers. In the diabetic group, the GG genotype carriers were found to have higher BMI levels (p < 0.001), waist-to-hip ratio (p < 0.05), body fat (p < 0.01), HOMA (p < 0.001) and fasting insulin (p < 0.05), but lower HbA1c levels in comparison to GC + AA carriers. These data suggest that, in the Turkish study group, the EX4-44G-->A polymorphism of the resistin gene is associated with insulin and obesity-related phenotypes.

Further development of multiplex single nucleotide polymorphism typing method, the DigiTag2 assay

A number of single nucleotide polymorphisms (SNPs) are considered to be candidate susceptibility or resistance genetic factors for multifactorial disease. Genome-wide searches for disease susceptibility regions followed by high-resolution mapping of primary genes require cost-effective and highly reliable technology. To accomplish successful and low-cost typing for candidate SNPs, new technologies must be developed. We previously reported a multiplex SNP typing method, designated the DigiTag assay, that has the potential to analyze nearly any SNP with high accuracy and reproducibility. However, the DigiTag assay requires multiple washing steps in manipulation and uses genotyping probes modified with biotin for each target SNP. Here we describe the next version of the assay, DigiTag2, which works with simple protocols and uses unmodified genotyping probes. We investigated the feasibility of the DigiTag2 assay by genotyping 96 target SNPs spanning a 610-kb region of human chromosome 5. The DigiTag2 assay is suitable for genotyping an intermediate number of SNPs (tens to hundreds of sites) with a high conversion rate (>90%), high accuracy, and low cost.

Role of resistin in obesity, insulin resistance and Type II diabetes

Resistin is a member of a class of cysteine-rich proteins collectively termed resistin-like molecules. Resistin has been implicated in the pathogenesis of obesity-mediated insulin resistance and T2DM (Type II diabetes mellitus), at least in rodent models. In addition, resistin also appears to be a pro-inflammatory cytokine. Taken together, resistin, like many other adipocytokines, may possess a dual role in contributing to disease risk. However, to date there has been considerable controversy surrounding this 12.5 kDa polypeptide in understanding its physiological relevance in both human and rodent systems. Furthermore, this has led some to question whether resistin represents an important pathogenic factor in the aetiology of T2DM and cardiovascular disease. Although researchers still remain divided as to the role of resistin, this review will place available data on resistin in the context of our current knowledge of the pathogenesis of obesity-mediated diabetes, and discuss key controversies and developments.

Resistin gene 3'-untranslated region +62G-->A polymorphism is associated with hypertension but not diabetes mellitus type 2 in a German population

OBJECTIVES

Resistin, a peptide hormone produced by adipocytes, has been associated with diabetes mellitus type 2 (DM-2) in some rodent models. In humans the exact function of resistin remains unknown. Some, but not all studies have found associations between polymorphisms in the resistin gene with DM-2. Recently a 3'-untranslated region +62G-->A polymorphism of the resistin gene has been associated with decreased risk for DM-2 and for hypertension in diabetics in a Chinese population. Purpose of the present study was to examine for the first time in a German Caucasian population the possible association between this polymorphism and DM-2, hypertension, lipoprotein levels, resistin levels as well as atherosclerosis.

DESIGN, SETTING AND SUBJECTS

A total of 818 subjects participated in the study. The presence of the +62G-->A polymorphism of the resistin gene was investigated using polymerase chain reaction-restriction fragment length polymorphism in 384 subjects with DM-2 [224 men, 160 women, age 63.4 +/- 10.6 years, body mass index (BMI) 28.7 +/- 5.1 kg m(-2)] and in 434 nondiabetic age- and sex-matched control subjects (248 men, 186 women, age 64.4 +/- 6.5 years, BMI 26.5 +/- 3.7 kg m(-2)).

RESULTS

Thirty-four subjects were found to be carrying the +62G-->A polymorphism in the control and 24 in the diabetic group (allelic frequencies 4% and 3.2% respectively). Subjects with DM-2 were not found to have a different frequency of the genotypes (93.75% and 6.258%, for GG:GA/AA respectively) than the control subjects (92.2% and 7.8% for GG:GA/AA respectively) (OR 0.75, 95% CI 0.44-1.3, P = 0.31). In the total cohort, carriers of the A allele had a higher prevalence of hypertension (OR 1.82, 95% CI 1.03-3.21, P = 0.039). When analysed separately, the control group showed a strong association between the presence of the A allele and hypertension (OR 2.92, 95% CI 1.38-6.15, P = 0.005), whilst no such association could be established in the diabetic group (OR 1.05, 95% CI 0.43-2.54, P = 0.92). Multiple regression analysis confirmed that the presence of the A variant is associated with hypertension in control but not in diabetic subjects, independent of age and BMI. The polymorphism had no significant influence on the presence of atherosclerotic disease, BMI, and on triglyceride, HDL and LDL cholesterol levels, both, in the control and the diabetic groups. There was no difference in the serum resistin levels between the 62G-->A variant carriers and noncarriers.

CONCLUSIONS

In conclusion, the present data suggest that in a German Caucasian population the +62G-->A polymorphism of the resistin gene is associated with hypertension but not with DM-2.

Variation in the resistin gene is associated with obesity and insulin-related phenotypes in Finnish subjects

AIMS/HYPOTHESIS

Resistin is a peptide hormone produced by adipocytes that is present at high levels in sera of obese mice and may be involved in glucose homeostasis through regulation of insulin sensitivity. Several studies in humans have found associations between polymorphisms in the resistin gene and obesity, insulin sensitivity and blood pressure. An association between variation in the resistin gene and type 2 diabetes has been reported in some, but not all studies. The aim of this study was to analyse variants of the resistin gene for association with type 2 diabetes and related traits in a Finnish sample.

METHODS

In 781 cases with type 2 diabetes, 187 spouse controls and 222 elderly controls of Finnish origin, we genotyped four previously identified non-coding single-nucleotide polymorphisms (SNPs): -420C>G from the promoter region, +156C>T and +298G>A from intron 2, and +1084G>A from the 3' untranslated region. We then tested whether these SNPs were associated with type 2 diabetes and related traits.

RESULTS

The SNPs were not significantly associated with type 2 diabetes. However, SNPs -420C>G, +156C>T and +298G>A and the common haplotype for these three markers were associated with increased values of weight-related traits and diastolic blood pressure in cases, lower weight in elderly control subjects, and lower insulin sensitivity and greater acute insulin response in spouses. Furthermore, the +1084G allele was associated with lower HDL cholesterol in both cases and controls, higher systolic blood pressure and waist circumference in cases, and greater acute insulin response in spouse controls.

CONCLUSIONS/INTERPRETATION

Our results add to growing evidence that resistin is associated with variation in weight, fat distribution and insulin resistance.