Association of TNF-.ALPHA. Gene Promoter C-857T Polymorphism with Higher Serum LDL Cholesterol Levels and Carotid Plaque Formation in Japanese Patients with Type 2 Diabetes

Vascular inflammation and low-density lipoproteins: is cholesterol the link? A lesson from the clinical trials

For long time, the role of LDL and inflammation in the pathogenesis of atherosclerosis have been studied independently from each other and only more recently a common platform has been suggested. Accumulation of excess cholesterol due to the presence of increased circulating LDL promotes endothelium dysfunction and activation, which is associated with increased production of pro-inflammatory cytokines, overexpression of adhesion molecules, chemokines and C-reactive protein (CRP), increased generation of reactive oxygen species and reduction of nitric oxide levels and bioavailability. All these processes favour the progressive infiltration of inflammatory cells within the arterial wall where cholesterol accumulates, both extracellularly and intracellularly, and promotes vascular inflammation. According to this, lipid-lowering therapies should improve inflammation and, indeed, statins decrease circulating inflammatory markers such as CRP and improve endothelial function and plaque burden. Pleiotropic activities have been proposed to explain this effect. However, mendelian randomization studies ruled out a direct role for CRP on coronary artery disease and studies with other lipid lowering drugs, such as ezetimibe showed that the beneficial effect of LDL-cholesterol-lowering therapies on systemic inflammatory status, as monitored by changes in CRP plasma levels, could be achieved, independently of the mechanism of action, only in patients presenting with baseline inflamed conditions. These observations strengthen the direct link between cholesterol and inflammation and indicate that decreasing LDL levels is one of the key goals for improving cardiovascular outcome.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

Genetic polymorphisms of cytokine genes in type 2 diabetes mellitus

Diabetes mellitus is a combined metabolic disorder which includes hyperglycemia, dyslipidemia, stroke and several other complications. Various groups all over the world are relentlessly working out the possible role of a vast number of genes associated with type 2 diabetes (T2DM). Inflammation is an important outcome of any kind of imbalance in the body and is therefore an indicator of several diseases, including T2DM. Various ethnic populations around the world show different levels of variations in single nucleotide polymorphisms (SNPs). The present review was undertaken to explore the association of cytokine gene polymorphisms with T2DM in populations of different ethnicities. This will lead to the understanding of the role of cytokine genes in T2DM risk and development. Association studies of genotypes of SNPs present in cytokine genes will help to identify risk haplotype(s) for disease susceptibility by developing prognostic markers and alter treatment strategies for T2DM and related complications. This will enable individuals at risk to take prior precautionary measures and avoid or delay the onset of the disease. Future challenges will be to understand the genotypic interactions between SNPs in one cytokine gene or several genes at different loci and study their association with T2DM.

Family association study between tumour necrosis factor a gene polymorphisms and polycystic ovary syndrome in Han Chinese

Polycystic ovary syndrome (PCOS) is a complex disease involving genetic and environmental components. Tumour necrosis factor a (TNFa) is a proinflammatory cytokine in the pathogenesis of PCOS. The genetic association between polymorphisms of TNFa gene and PCOS was investigated. A family based study was conducted with 216 family trios (648 participants) having a proband with PCOS. Transmission disequilibrium test (TDT) was used to analyse the association between two single nucleotide polymorphisms (SNP) (rs1799964, rs1799724) of TNFa gene and PCOS. Minor allele frequencies of the SNP were 0.178 (rs1799964) and 0.118 (rs1799724). The two SNP were in Hardy-Weinberg equilibrium; TDT was only conducted when one parent was heterozygous. Of 216 trios, 112 trios of rs1799964 and 76 trios of rs1799724 were tested. A significant difference in transmission was found for rs1799964 (transmitted: non-transmitted = 73 : 39; χ(2) = 10.321; P = 0.0013). rs1799724 showed no evidence of an association with PCOS; risk alleles were over transmitted (transmitted: non-transmitted = 43 : 33; χ(2) = 1.316). Transmission disequilibrium of the two SNP indicated that rs1799964 may participate in the pathogenesis of PCOS in Chinese women. These data provide a basis for further studies of TNFa in the cause of PCOS.

The role of TNF-α G-308A promoter polymorphism in glycemic control in Type 2 diabetes patients

BACKGROUND

TNF-α polymorphisms were shown to be associated with insulin resistance and diabetes development and complications.

AIM

To investigate the association between glycemic control in Type 2 diabetes patients and TNF-α G-308A single nucleotide polymorphism (SNP).

METHODS

This was a cross-sectional observational study, where diabetes patients from both genders (170 male and 185 female) were enrolled in the study. Patients were divided into two groups: good glycemic control (n = 158) and poor glycemic control (n = 197). Genotyping of TNF-α G-308A SNP was carried out using restriction fragment length polymorphisms-polymerase chain reaction.

RESULTS

The results showed that TNF-α G-308A SNP is strongly associated with glycemic control in type 2 diabetes patients. Patients with the AA and AG genotypes had better glycemic control than those with GG genotype (P < 0.01). Other parameters that impacted glycemic control include duration of the disease (P < 0.01) and response to insulin therapy (P < 0.01). However, no contribution for gender or statins use to glycemic control was observed (P > 0.05).

CONCLUSION

TNF-α G-308A SNP might modulate glycemic control among type 2 diabetes patients.

Association of IL-6, TNF-α and IL-10 gene polymorphisms with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a metabolic pro-inflammatory disorder characterized by chronic hyperglycemia and increased levels of circulating cytokines suggesting a causal role of inflammation in its etiology. Polymorphism of cytokine genes including interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α) and interleukin-10 (IL-10) were studied in T2DM patients as well as in normal healthy controls. Genomic DNA was isolated from both T2DM patients and controls followed by quantification and genotyping by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using suitable primers. The genotypic, allelic and carriage rate frequency distribution in patients and controls were analyzed by SPSS (version 15.0). Odd ratios with 95 % confidence interval was determined to describe the strength of association by logistic regression model. Double and triple combinations of genotypes were analyzed by χ(2) test. Gene-gene interaction and linkage disequilibrium tests were performed using SHEsis software. Individually, IL-6, TNF-α and IL-10 did not show any association. In double combination, IL-6 -597 GA and TNF-α -308 GG genotypes increased the risk up to 21 times and in triple combination IL-6 -597 AA, TNF-α -308 GG and IL-10 -592 CA increased the risk of T2DM up to 314 times. In gene-gene interaction allele 'A' of all studied polymorphisms increased the risk of T2DM up to 1.41 times. Our results suggest that individuals having a haplotype combination of AA, GG and CA for IL-6, TNF-α and IL-10 gene polymorphisms will have higher susceptibility and be at greater risk of developing T2DM.

Different susceptibility to insulin resistance and fatty liver depending on the combination of TNF-α C-857T and adiponectin G+276T gene polymorphisms in Japanese subjects with type 2 diabetes

The C-857T promoter polymorphism of TNF-α gene is associated with obese type 2 diabetes, while the adiponectin G+276T gene polymorphism in intron 2 may influence the fat accumulation in the liver. In this study, we examined effects of these polymorphisms on clinical markers of insulin resistance and fatty liver (a liver/spleen CT ratio < 0.9). These polymorphisms were determined in 342 Japanese subjects with type 2 diabetes. The liver/spleen CT ratio was lower in the subjects with the adiponectin +276G/G genotype than that in the subjects with the +276T allele (P < 0.05), indicating that fat accumulation in the liver is associated with the +276G/G genotype. Multiple comparisons among the 4 combinations of each polymorphism of the TNF-α and adiponectin genes revealed a significant difference in the liver/spleen CT ratio (P < 0.05) among the 4 groups, indicating that the gene combinations influence the degree of fat accumulation in the liver. The subjects carrying the TNF-α -857T allele (C/T or T/T genotype) and the adiponectin +276G/G genotype had greater risks for fatty liver and insulin resistance that was evaluated by higher levels of fasting insulin and homeostasis model assessment of insulin resistance, as compared with the other groups. Therefore, Japanese subjects with the TNF-α -857T allele and the adiponectin +276G/G genotype may be more susceptible to insulin resistance and fatty liver. The present study provides the evidence for the interaction between TNF-α and adiponectin genes in the insulin resistance and fatty liver in Japanese subjects with type 2 diabetes.

Characterization of Single-Nucleotide Polymorphisms in the Tumor Necrosis Factor α Promoter Region and in Lymphotoxin α in Squamous Intraepithelial Lesions, Precursors of Cervical Cancer

Development of cervical cancer is a long process of abnormal cancerous cell growth in the cervix and is primarily the result of infection with specific high-risk types of human papillomavirus (HPV). The cytokines tumor necrosis factor α (TNFα) and lymphotoxin α (LTA) have an important role in all stages of cervical cancer and have the ability to induce the regression or promote the development of human tumors. Biologically important single-nucleotide polymorphisms (SNPs) occur within the TNFα and LTA genes. Therefore, the purpose of this study was to investigate the SNPs in the TNFα promoter region (-163, -238, -244, -308, -376, -857, -863, and -1031) and in the first intron of LTA (+252) in women with precursor lesions of cervical cancer. Overall, we studied 396 women from Mexico City. A total of 191 patients with HPV infection and precursor cervical lesions were subdivided in two groups: those with low-grade squamous intraepithelial lesions (n = 132) and those with high-grade squamous intraepithelial lesions (n = 59). Women (n = 205) negative for HPV and without cervical lesions were also included in the study. DNA was extracted from peripheral white blood cells and from cervical samples, and detection of biallelic polymorphisms of TNFα and LTA was performed using the polymerase chain reaction-sequence-specific oligonucleotide probe and restriction fragment length polymorphism techniques, respectively. We demonstrated that risk is associated with the genotype G/A (odds ratio = 2.48) and that protection is associated with the genotype G/G of SNP TNFα -376 (odds ratio = 0.37).

Association of tumor necrosis factor-α (TNF-α) promoter polymorphisms with overweight/obesity in a Korean population

OBJECTIVE

Obesity is characterized by the activation of an inflammatory process leading to an increase in proinflammatory cytokines and adipokines. This study was designed to investigate the genetic association between tumor necrosis factor-α (TNF-α) polymorphisms and the risk of obesity in the Korean population.

METHODS

Three single nucleotide polymorphisms [G-238A (rs361525), C-857T (rs1799724), and C-863A (rs1800630)] in the promoter region of TNF-α gene were analyzed in 123 control [body mass index (BMI) between 18 and 23] and 208 overweight/obese (BMI ≥ 23) subjects.

RESULTS

The mean values of BMI in the control and overweight/obese groups were 21.1 ± 1.4 and 25.4 ± 1.8, respectively. Of the three SNPs, G-238A presented a significant association with overweight/obesity in the codominant model; the frequency of the G/G genotype in the overweight/obese group was 9.3% higher than that in the control group (P = 0.0046). When control and overweight/obesity subjects were combined together and analyzed, the level of high-density lipoprotein (HDL) was significantly higher in the C-857T C/C type SNP (P < 0.05).

CONCLUSIONS

The results of this study suggest that the G allele of G-238A in TNF-α gene may be a risk factor for overweight/obesity in the Korean population and that the C allele of C-857T may be an protective factor in relation to the HDL level in the general Korean population.

An update on markers of carotid atherosclerosis in patients with Type 2 diabetes

Carotid atherosclerosis constitutes an important cause of ischemic brain attack and stroke, accounting for up to 40% of cases of ischemic cerebrovascular disease. Type 2 diabetes mellitus is an independent risk factor for stroke and its recurrence. Thus, identifying diabetic patients who are at high risk of developing stroke is of great clinical importance. Noninvasive measurements of surrogate markers of atherosclerosis, such as novel serum biomarkers, can be helpful in detecting subclinical carotid disease, especially among individuals at the highest cardio-/cerebro-vascular risk. Previous studies have proposed an expanding body of serum biomarkers, such as C-reactive protein, fibrinogen, adipokines, cytokines and growth factors, as novel indicators of carotid atherosclerosis development that predict carotid-related clinical outcomes. Furthermore, those biomarkers are expected to assess the efficacy of both pharmaceutical and interventional strategies. Accordingly, it is increasingly clear that measuring biomarkers may improve the definition of cerebrovascular risk profile in patients with Type 2 diabetes mellitus.

Association of longevity with IL-10 -1082 G/A and TNF-alpha-308 G/A polymorphisms

Cytokines are crucial for the regulation of inflammation development in humans. Many studies have shown that variations in cytokine genes might play a role in determining human longevity. This study examined the changes in the gene pool relevant to the -308 G/A polymorphism in the promoter region of the proinflammatory cytokine tumour necrosis factor (TNF)-alpha gene and the -1082 G/A polymorphism in the promoter region of anti-inflammatory cytokine interleukin (IL)-10 gene with aging and survival selection occurs in the Jordanian population. IL-10 -1028 G/A and TNF-alpha-308 G/A were genotyped in 119 randomly selected elderly subjects (41 women and 78 men) with a mean age of 90.2 years and young control subjects of 118 (46 women and 72 men) with a mean age of 31.9 years. No significant differences were found in the genotype and allele frequencies of TNF-alpha gene variants between the two groups (P > 0.05) while the IL-10 genotype and allele frequencies were significantly associated with longevity in men (P < 0.05) but not in women (P < 0.05). Thus, IL-10 -1028 G/A polymorphism seems to play a role in the pathway to longevity in Jordanian men.

Association of the TNF-{alpha}-C-857T polymorphism with resistance to the cholesterol-lowering effect of HMG-CoA reductase inhibitors in type 2 diabetic subjects

OBJECTIVE An association of the C-857T polymorphism of the tumor necrosis factor-alpha (TNF-alpha) gene promoter region with LDL cholesterol levels has been reported. This study was designed to evaluate the relationship between the TNF-alpha-C-857T polymorphism and LDL cholesterol levels according to statin treatment in subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS DNA was obtained from 322 Japanese subjects (160 male and 162 female) with type 2 diabetes, and TNF-alpha-C-857T polymorphisms were determined by direct sequencing. Serum LDL cholesterol was measured by a direct method. RESULTS Although serum LDL cholesterol levels were significantly higher in the T carriers (C/T + T/T) than in the non-T carriers (C/C) (3.14 +/- 0.86 vs. 2.89 +/- 0.75 mmol/l, P < 0.05), there was no difference in LDL cholesterol levels between the non-T carriers and the T carriers in statin-untreated subjects (2.87 +/- 0.73 vs. 2.89 +/- 0.76 mmol/l, NS), whereas in statin-treated subjects, LDL cholesterol levels were significantly higher in the T carriers than in the non-T carriers (3.43 +/- 0.89 vs. 2.90 +/- 0.78 mmol/l, P = 0.0007). There were no differences in HDL cholesterol and triglyceride levels between the non-T carriers and the T carriers in both statin-treated and -untreated subjects. The percent decrease in LDL cholesterol levels after administration of statins was significantly smaller in the T carriers compared with the non-T carriers (27.6 vs. 36.4%, P = 0.031). CONCLUSIONS The mutant allele of the C-857T promoter polymorphism of the TNF-alpha gene may predispose to resistance to the LDL cholesterol-lowering effect of statins and could be one of the markers used to predict the efficacy of statins.