Association between -308G/A TNFA Polymorphism and Susceptibility to Type 2 Diabetes Mellitus: A Systematic Review

Comparative analysis of TNF-α (-308) gene polymorphism in Turkish patients with type 2 diabetes developing nephropathy and/or neuropathy

Type 2 diabetes (T2DM) is a group of chronic and systemic metabolic diseases. Nephropathy (NP) and neuropathy (NR) are two common complications that severely affect the quality of life of patients with T2DM. In this study, our aim was to investigate the association between TNF-alpha (-308) gene polymorphism and the risk of developing NP and NR in patients with T2DM We also aimed to determine the association between TNF-alpha (-308) gene polymorphism and several demographic characteristics and biochemical parameters of patients with T2DM developed NP and/or NR. First, blood samples of patients were collected, and DNA isolation was performed. Then, real-time PCR analysis was used for genotyping the TNF-α (-308) gene utilising fluorescently labelled probes. Patients' demographical data and biochemical parameters were also obtained. Our study did not detect any significant difference in the frequency of possessing the gene polymorphism (A allele) between the groups. Additionally, no significant difference was detected when the data on various biochemical parameters were evaluated in GG, GA, and AA genotypes.

Association of TNF-α 308G/A and LEPR Gln223Arg Polymorphisms with the Risk of Type 2 Diabetes Mellitus

The objective of the present study was to identify the association of the TNF-α- 308G/A and leptin receptor (LEPR) Gln223Arg polymorphisms with the risk of development of type 2 diabetes mellitus (T2DM). Methods: A total of 160 volunteers were studied: 108 with T2DM and 52 participants as control, who served as the control group. Polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) for the genomic region of TNF-α- 308G/A and LEPR Gln223Arg were carried out. Results: The frequency of LEPR Gln223Arg genotypes in T2DM and control groups showed significant differences in the distribution of genotypes (p < 0.05). The frequency also of TNF-α- 308G/A genotypes in T2DM and control subjects showed significant differences in the distribution of genotypes (p < 0.05). Conclusion: Our results indicate that there are significant differences in the distribution of genotypes and alleles between the individuals with T2DM and control subjects (p < 0.05).

Association of IL-10 (- 1082 A/G) and IL-6 (- 174 G/C) gene polymorphism with type 2 diabetes mellitus in Ethiopia population

BACKGROUND

Interleukin (IL)-6 and IL-10 are the most important cytokine with pro and anti-inflammatory activities, respectively. Dysregulation of IL-6 and IL-10 are associated with increased risk of developing Type 2 Diabetes Mellitus (T2DM). Despite this, a fundamental understanding of both cytokine gene polymorphisms with its expression is critical in understanding of cellular mechanism of insulin resistance as well as T2DM intervention. Therefore, this study aimed to assess IL-6 (- 174 G/C) and IL-10 (- 1082 A/G) gene polymorphism, and its association with T2DM, North West Ethiopia.

METHODS

A comparative cross-sectional study from January to May 2018 was conducted on study participants with T2DM and apparently healthy controls. Deoxyribonucleic acid (DNA) extraction and genotyping was carried out by using amplification refractory mutation system polymerase chain reaction to detect polymorphism of IL-6 and IL-10 gene at the position - 174 and - 1082, respectively. The logistic regression model was fitted to assess the association of between cytokine gene polymorphisms and T2DM. Odds ratio with 95% CI was determined to assess the presence and strength of association between the explanatory variables and outcome variable. A P-value < 0.05 was considered as statistically significant.

RESULT

Participants carrying the GG genotype of IL-6 (- 174) (OR (95% CI) = 4.61 (2.07-10.54) was a high likelihood of having T2DM compared to those carrying the CC and AA genotypes. AA and AG genotypes of IL-10 (- 1082) were at lower odd of developing T2DM compared to those carrying the GG genotype. In addition, individuals carrying the G allele of IL-6 (- 174) have 2.82-fold odds of developing T2DM compared to individuals carrying the C allele (OR (95% CI) =2.81 (1.78-4.50)).

CONCLUSION

Our study revealed that genetic polymorphisms of IL-6 (- 174) GG genotype is the potential host genetic risk factors to T2DM. While, IL-10 (- 1082) AA genotype is negatively associated with T2DM. Therefore, IL-6 (- 174) and IL-10 (- 1082) genetic variation may be considered as a biomarker for early screening and diagnosis of T2DM.

Comparison of Q223R leptin receptor polymorphism to the leptin gene expression in Greek young volunteers

<abstract><sec> <title>Objective</title> <p>The objective of the present study was to identify the leptin gene expression and the leptin receptor polymorphisms in blood samples and to correlate gene expression values with anthropometric characteristics.</p> </sec><sec> <title>Methods</title> <p>Blood from 140 Greek young volunteers was subjected to polymerase chain reaction–restricted fragment length polymorphism (PCR–RFLP), for the genomic region of Q223R polymorphism at codon 223 in the leptin receptor gene (<italic>LEPR</italic>) coding region. RNA extraction, cDNA synthesis and Quantitative Real-Time PCR was performed for assessing the expression of the leptin gene (<italic>LEP</italic>).</p> </sec><sec> <title>Results</title> <p>Leptin gene was identified in all tested specimens and the gene was expressed in 88.9% of all volunteers with BMI &lt; 25. In addition, it was observed that gene expression is affected by various external factors, such as Body Mass Index (BMI), eating behavior, gender and age. It was also shown that as for the Q223R polymorphism (A to G) allele G occurs with a frequency of 100% in men with BMI &gt; 30 and 75.9% in men and 88.9% in women with BMI 25–30. Volunteers with BMI 25–30 who were homozygous on the G allele were 50% and 77.8% in men and women respectively. All subjects with a BMI &gt; 30 were homozygous on the G allele at 100%.</p> </sec><sec> <title>Conclusions</title> <p>In this small-scale study, results have shown that the leptin gene expression correlates with BMI and that the allele G in Q223R polymorphism is linked to overweight individuals.</p> </sec></abstract>

The Gene Polymorphisms (-308G/A) and the Tumor Necrosis Factor-alpha Levels in Type 2 Diabetic Patients with and Without Tuberculosis Infection

BACKGROUND

The gene polymorphism (-308G/A) and tumor necrosis factor-alpha (TNF-α) levels influence development of disease in type 2 diabetic patients and tuberculosis patients.

AIM

In this study, we analyze the association between the TNF-α polymorphisms (-308G/A) and the levels of TNF-α in type 2 diabetic patients with and without tuberculosis infection.

METHODS

This study was an analytic observational with cross sectional approach consisting 40 type 2 diabetic patients with tuberculosis infection, 40 type 2 diabetic patients without tuberculosis infection and 40 healthy control (HC) subjects. The TNF-α gene polymorphism (-308G/A) was analyzed with polymerase chain reaction-restriction fragment lengths polymorphisms (PCR-RFLP) method. The TNF-α levels were measured using an enzyme-linked immunosorbent assay. The association between gene polymorphism (-308G/A) in study groups was analyzed by Fisher's exact test, tumor necrosis factor-alpha (TNF-α) levels in study groups was carried out using the Kruskal-Wallis test. Hardy-Weinberg Equilibrium also determined genotype deviation and allele frequencies.

RESULTS

The GG and GA+AA genotypes frequency in both of patient groups and HC subjects were not differ significantly (95% and 5% vs 95% and 5% vs 92.5% and 7.5%; p > 0.05). The TNF-α levels (pg/ml) of type 2 diabetic without tuberculosis infection were higher than those of type 2 diabetic with tuberculosis infection and HC subjects (7.42 ± 0.78 vs 2.23 ± 0.51 vs 2.57 ± 0.63; p < 0.01). The TNF-α levels in the GA+AA genotypes were higher than the GG wild-type genotype (p > 0.05). There was no significant deviation of genotype frequency and allele from Hardy-Weinberg Equilibrium.

CONCLUSION

The gene polymorphism (-308G/A) had no association with type 2 diabetic patients with and without tuberculosis infection and the gene polymorphism (-308G/A) was not influence the TNF-α levels but there was a significant differentiation of TNF-α levels between the groups.

TNF-α (-308) Gene Polymorphism and Type 2 Diabetes Mellitus in Ethiopian Diabetes Patients

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a metabolic disorder resulting from insulin insufficiency or function. Predisposing factors for T2DM are mainly genetic and environmental. Genetic polymorphism of cytokines like tumor necrosis factor-alpha (TNF-α) is suggestive of interference with insulin-sensitive glucose uptake and induces insulin resistance that ultimately could lead to T2DM. In this study, we assessed the effect of TNF-α (-308) G/A gene polymorphism and its association with the development of T2DM in an Ethiopian population.

METHODS

An institutional-based cross-sectional study was conducted on study subjects with T2DM and non-diabetic healthy controls. DNA was extracted and genotyping was carried out by using amplification refractory mutation system polymerase chain reaction. A genetic-polymorphism on TNF-α (-308) G/A with T2DM was evaluated by logistic regression and Student's t-test. A P-value <0.05 was considered as statistically significant.

RESULTS

In the present study, we observed a significant association between T2DM and TNF-α (-308) gene polymorphism's GG genotype [χ2 test P = 0.005, OR (95% CI) =2.667 (1.309-5.45d8)]. In contrast, no statistically significant differences were observed in the frequencies of genotypes AA and AG (χ2 test P=0.132 and 0.067, respectively). Moreover, T2DM individuals had higher concentrations of lipid profiles for those carrying the TNF-α (-308) GG genotype as compared to the control group.

CONCLUSION

TNF-α (-308) genetic polymorphism may be implicated in the genetic susceptibility for, as well as the development of T2DM and lipid metabolism in the Ethiopian population. Therefore, a large-scale study and early screening of TNF-α (-308) genetic polymorphism may help in early management and control of diabetes and related outcomes.