The interleukin-6 (-174) G/C promoter polymorphism is associated with type-2 diabetes mellitus in Native Americans and Caucasians

Chronic low-grade activation of the immune system may play a role in the pathogenesis of type-2 diabetes mellitus (T2DM). Interleukin-6 (IL6), a powerful inducer of hepatic acute phase response, has been implicated in the etiology of insulin resistance and T2DM. Recently, an IL6 promoter polymorphism (G/C) at position -174 was found to be associated with measures of insulin sensitivity. Because we have previously found an association between high IL6 levels and insulin resistance in both Pima Indians - a population with high rates of insulin resistance and T2DM - and Caucasians, we aimed to assess whether the IL6 promoter polymorphism is associated with T2DM in these populations. We genotyped the IL6 (-174) G/C polymorphism using pyrosequencing in 463 Native Americans and by PCR-RFLP in 329 Spanish Caucasians. Among the Spanish Caucasian subjects, there was a significant difference in genotypic distribution between diabetic and non-diabetic subjects (P=0.028); the GG genotype was more common in diabetic (0.40) than in non-diabetic (0.29) subjects. The G allele was much more frequent in the Native American sample, and among a sample of 143 cases and 145 controls, the GG genotype was significantly more common in diabetic subjects (P=0.019). When this sample population was stratified according to ethnic heritage, all 211 subjects who were of full Pima Indian heritage had the GG genotype, whereas in the 77 American Indian subjects with non-Pima admixture, T2DM was associated with IL6 genotype (P=0.001). These findings are consistent with a role for genetic determinants of inflammation in the development of T2DM in both Native Americans and Caucasians.     

Association of humoral immunity to human Hsp60 with the IL-6 gene polymorphism C-174G in patients with type 2 diabetes and controls.

The relationship between humoral immunity to hsp60 and type 2 diabetes along with other relevant metabolic, inflammatory and immunogenetic variables was studied in 76 non-diabetic and 74 diabetic persons aged 55-74 years selected from the population-based KORA Survey 2000. Antibodies to human hsp60 were measured in serum samples by ELISA. Hsp60 antibodies were detected in all but two individuals in a considerable range of titres (22-1,856 AU/ml). There was no significant association to age and sex, or to key clinical or metabolic parameters (BMI, WHR, HbA1c, total cholesterol, LDL cholesterol, HDL cholesterol, systolic and diastolic blood pressure, albumin, uric acid) or immunological parameters (CRP, IL-6, sIL-6R, TNFalpha, sTNFalpha R60, sTNFalpha R80). Analysis of antibody-positive individuals revealed an association between hsp60 antibodies and diabetes at borderline significance (p = 0.047), which was lost when the two antibody-negative individuals were included. Genetic analyses indicated that this association was significant in carriers of the C allele of the IL-6 promoter region polymorphism at nucleotide -174 (p = 0.02), but not in GG genotype carriers. We conclude that humoral immunity to human hsp60 may be enhanced in those diabetic patients carrying the -174C allele of the IL-6 gene. This finding may contribute to an understanding of the relationship between the -174C allele and increased risk of atherosclerosis.     

Meta-analysis: Interleukin 6 gene -174G/C polymorphism associated with type 2 diabetes mellitus and interleukin 6 changes

The gene coding interleukin 6 (IL-6) is a promising candidate in predisposition to type 2 diabetes mellitus (T2DM). This study aimed to meta-analytically examine the association of IL-6 gene −174G/C polymorphism with T2DM and circulating IL-6 changes across −174G/C genotypes. Odds ratio (OR) and standard mean difference (SMD) with 95% confidence interval (CI) were calculated. Twenty-five articles were meta-analysed, with 20 articles for T2DM risk and 9 articles for circulating IL-6 changes. Overall, there was no detectable significance for the association between −174G/C polymorphism and T2DM, and this association was relatively obvious under dominant model (OR: 0.82, 95% CI: 0.56-1.21). Improved heterogeneity was seen in some subgroups, with statistical significance found in studies involving subjects of mixed races (OR: 0.63, 95% CI: 0.46-0.86). Begg's and filled funnel plots, along with Egger's tests revealed week evidence of publication bias. In genotype-phenotype analyses, carriers of −174CC and −174CG genotypes separately had 0.10 and 0.03 lower concentrations (pg/mL) of circulating IL-6 than −174GG carriers. Albeit no detectable significance for the association of −174G/C with T2DM, our findings provided suggestive evidence on a dose-dependent relation between −174G/C mutant alleles and circulating IL-6 concentrations, indicating possible implication of this polymorphism in the pathogenesis of T2DM.     

Effect of G(-174)C polymorphism in interleukin-6 gene on cardiovascular disease in type 2 diabetes patients

Interleukin-6 (IL-6) is an important pro-inflammatory cytokine of relevance to cardiovascular diseases. The aim of this case-control study was to evaluate the association between the G(-174)C functional polymorphism in the IL-6 gene and risk of cardiovascular disease (CVD) in type 2 diabetes patients. We examined 1090 patients with T2DM and 612 controls. All subjects were genotyped for the G(-174)C polymorphism by polymerase chain reaction (PCR) and restriction analysis. There were no significant differences in the distribution of genotypes and alleles between T2DM patients and healthy controls. Significantly higher C allele frequency was observed in CVD+ patients compared to CVD- subgroup (53% vs. 32%, p < 0.0001). The odds ratio for C allele was 2.4 (95% CI 1.99–2.9, p < 0.0001) and for CC genotype 4.55 (95% CI 3.12–6.63, p < 0.000). When the distribution of G(-174)C polymorphism was compared in subgroups with different clinical phenotypes of CVD, a significant association of CC genotype with myocardial infarction was observed. Forty eight percent of patients with MI had the CC genotype compared to 22% of patients without MI (p < 0.0001). In conclusion, type 2 diabetes patients carrying the C allele of the IL-6 G(-174)C polymorphism have a significantly increased risk of CVD.     

The K121Q polymorphism of the plasma cell glycoprotein-1 gene is not associated with diabetes mellitus type 2 in German Caucasians.

The K121Q polymorphism of the human plasma cell membrane glycoprotein 1 (PC-1) gene is known to be associated with diabetes mellitus type 2 in some populations studied, with contradictory results. The purpose of the present study was to examine a possible association between the presence of diabetes and the PC-1 K121Q polymorphism in a German Caucasian population. Associations between the polymorphism and various metabolic and anthropometric parameters were also examined. The presence of the K121Q variant was investigated using polymerase chain reaction restriction fragment-length polymorphism in 402 subjects with diabetes (231 men, 171 women, age 63+/-11 yrs, body mass index 28.7+/-5.1 kg/m2) and in 432 age- and sex-matched controls (247 men, 185 women, age 64+/-7 yrs, BMI 26.5+/-3.7 kg/m2). Ninety-seven subjects were carriers of the K121Q polymorphism in the control and 110 in the diabetic group (allelic frequency 11.9% and 14.7%, respectively, P=0.25). The polymorphism had no significant influence on the presence of atherosclerotic disease, body mass index, and blood pressure, both, in diabetics and in non-diabetic controls. Our data suggest that the K121Q polymorphism of the PC-1 gene is not associated with diabetes, obesity, hypertension or atherosclerosis in a German Caucasian population.     

The 223A>G polymorphism of the leptin receptor gene is associated with macroangiopathy in type 2 diabetes mellitus

To determine whether leptin receptor (LEPR) 223A>G polymorphism has an effect on the plasma leptin levels and the macroangiopathic complications in type 2 diabetes mellitus (T2DM). The genotypes and allelic frequencies of the LEPR 223A>G were examined with polymerase chain reaction and restriction fragment length polymorphism in 301 patients with T2DM and 172 unrelated healthy subjects. The plasma concentrations of leptin were determined in all subjects. The mean plasma leptin levels in the T2DM group were significantly higher than that of controls and the plasma levels of leptin were higher in diabetic patients with macroangiopathy than in patients without macroangiopathy (P < 0.05). The genotype (GG, AG and AA) distribution of 223A>G polymorphism was 58.3, 32.5, and 9.2% in diabetic patients with macroangiopathy, 75.3, 22.1, and 2.6% in patients without macroangiopathy, and 70.3, 27.5, 2.2% in controls respectively, a significant difference was found between diabetic patients with and without macroangiopathy (P < 0.05). The frequency of the allele A was higher in patients with macroangiopathy than in patients without macroangiopathy (25.6 vs. 16.3%; P < 0.05). Moreover, the plasma leptin levels were markedly higher in patients with AA genotype than those with AG or GG genotype in patients with macroangiopathy (P < 0.05). The LEPR 223A>G gene polymorphism associated with a predisposition to increased plasma leptin levels could constitute a useful predictive marker for diabetic macroangiopathy.     

Association between -174 G/C promoter polymorphism of the interleukin-6 gene and progression of prostate cancer in North Indian population

The cellular alterations that give rise to cancer initiate changes in cytokine expression. Though IL-6 is known to play a major role in proliferation of tumor cells, IL-4 upregulates androgen receptors and prostate-specific antigen (PSA). The present study was undertaken to evaluate the association of IL-4 and IL-6 gene polymorphisms for the susceptibility to prostate cancer (PCa) risk. Our study included 200 controls and 200 histologically confirmed cases of PCa. Polymorphisms in IL-4 (intron 3, by VNTR analysis) and IL-6 (-174 G/C, by amplification refractory mutation system, i.e., ARMS-PCR) were genotyped in all the subjects. There was no significant association of IL-4 and IL-6 gene polymorphisms with the risk of PCa. Nevertheless, twofold risk with progression to bone metastasis (odds ratio = 2.09; 95% confidence interval = 1.16-3.75; p = 0.014) in PCa patients was observed. No association with other confounding factors such as PSA level, Gleason score, and lifestyle-associated risk factors like tobacco chewing and cigarette smoking was seen. Our study suggests that an IL-6 gene variant may be associated with prostate progression and bone metastasis.     

Calpain 10 SNP-44 gene polymorphism affects susceptibility to type 2 diabetes mellitus and diabetic-related conditions

The association of the gene encoding calpain 10 with type 2 diabetes mellitus (T2DM) has been reported. In this study we aimed to evaluate the association of SNP-19,-44, and -63 polymorphisms of calpain 10 with type 2 diabetes and diabetic-related conditions, such as diabetic retinopathy, nephropathy, and neuropathy in a Turkish population. The study group included 202 patients (133 female and 69 male) with T2DM, while the control group included 80 nondiabetic people (44 female and 36 male). Genotyping was done by the polymerase chain reaction and restriction fragment length polymorphism method. Calpain 10 SNP-44 TC genotype was found to be significantly frequent in type 2 diabetic patients with respect to the control group (p < 0.01). Body mass index (BMI) was found to be significantly high in TC genotype with type 2 diabetic patients (p < 0.05). SNP-44 T allele frequency was found to be lower in type 2 diabetic patients compared with the controls (p < 0.01). We conclude that the calpain 10 SNP-44 gene polymorphism may be accepted as a risk factor in the development of T2DM and elevated BMI in type 2 diabetic patients in a Turkish population.     

The interleukin-6 -174 promoter polymorphism is associated with extrapulmonary bacterial dissemination in Streptococcus pneumoniae infection

Interleukin-6 (IL-6) is required for the clearance of bacteria in pneumococcal pneumonia. The abundance of endogenous IL-6 production on infectious stimuli is associated with genotypic differences in the -174 promoter region of IL-6 (-174 G-->C), showing increased IL-6 levels in patients carrying the GG genotype. One hundred patients with culturally proven pneumococcal disease were analyzed for distribution of the G-/C-alleles in the IL-6 -174 promoter region in comparison to 50 age-matched controls. Extrapulmonary pneumococcal dissemination, including septic metastasis, endocardial and meningeal infection, was used as parameter for impaired clearance of the bacteria. No significant differences in the allele distribution were observed between patients and controls. Within the patient group, the interleukin-6 GG homozygous carriers were less likely to develop extrapulmonary pneumococcal infection (10.3% versus 30.9%; OR 0.26, 95% CI 0.07-0.94, p=0.04). The IL-6 GG genotype, encoding for enhanced IL-6 secretion on bacterial stimuli, reduces the risk of bacterial spread to extrapulmonary sites in pneumococcal infection, possibly due to a more effective clearance of the pathogen from the blood and the respiratory tract.     

The lack of association between interleukin-6 gene − 174 G/C polymorphism and the risk of type 1 diabetes mellitus: A meta-analysis of 18,152 subjects

Epidemiological studies have evaluated the association between interleukin-6 (IL-6) gene − 174 G/C polymorphism and type 1 diabetes mellitus (T1DM) risk, but results of different studies have been inconsistent. The present meta-analysis was therefore designed to clarify these controversies. PubMed, Embase and Web of Science were searched from the first available year to March 25, 2012, as well as hand searching of the references of identified articles were performed. All studies investigating the association between IL-6 gene − 174 G/C polymorphism and T1DM risk were included. Data analyses were carried out by Review Manager 5.1.2 and Stata 11.0. Seven studies were included in the final meta-analysis, covering a total of 9697 T1DM cases and 8455 controls. The results showed no evidence for significant association between IL-6 gene − 174 G/C polymorphism and T1DM risk (for C/C + C/G vs. G/G: OR = 1.30, 95% CI = 0.84–2.00, p = 0.24; for C/C vs. C/G + G/G: OR = 1.10, 95% CI = 0.75–1.60, p = 0.63; for C/C vs. G/G: OR = 1.34, 95% CI = 0.75–2.42, p = 0.33; for C allele vs. G allele: OR = 1.16, 95% CI = 0.88–1.53, p = 0.30). In addition, the similar results were obtained in the subgroup analysis based on ethnicity. In summary, the present meta-analysis suggests that IL-6 gene − 174 G/C polymorphism is not associated with T1DM risk. However, due to the small sample size in most of the included studies and the selection bias existed in some studies, the results should be interpreted with caution.     

Circulating C5L2 gene polymorphism is associated with type 2 diabetes mellitus in Saudi population

The aim of the present study was to examine the relationship between the novel single nucleotide polymorphism, 698C>T that causes an amino acid change from proline to leucine at codon 233 and type 2 diabetes mellitus (T2DM) in the Saudi population. From the general population in the Saudi Arabia a total of 551 samples were collected and categorized them as T2DM (n = 376) and healthy controls (n = 175). Five ml of the blood sample was collected and used for the Biochemical and Molecular analysis. With the help of serum sample lipid profile: Fasting blood sugar (FBS), Total Cholesterol (TC), Triglycerides (TG), High Density Lipoprotein Cholesterol (HDL-C), Low Density Lipoprotein Cholesterol (LDL-C) and VLDL were performed. PCR–RFLP was performed after separating the genomic DNA from the EDTA blood. The genotype distribution of C698T polymorphism was performed by the Chi square test with SPSS version 16.0 software for comparing T2DM subjects and healthy controls. In our study, genotypic distributions of C5L2 C698T polymorphism and allele frequency of patients and controls were found to be significant difference in the allele and the genotypic distribution. [For T Vs C; p = 0.01; Odds ratio = 3.594 (95 % CI; 1.256–10.28); and CT+TT Vs CC; p = 0.009; Odds ratio = 3.707 (95 % CI; 1.285–10.69)]. TT genotype was completely absent in both the cases and the controls. In conclusion, our study indicates that 698C>T polymorphism of C5L2 gene is associated with the T2DM in individuals of Saudi population which was found to be similar with other studies.     

Gliclazide mainly affects insulin secretion in second phase of type 2 diabetes mellitus.

We studied the effect of the acute administration of gliclazide at 160 mg on insulin release during hyperglycaemic clamps in 12 type 2 diabetes patients, age 50 +/- 9.0 years, diabetes duration 5.5 +/- 4.8 years, fasting blood glucose 9.6 +/- 2.1 mmol/L (means +/- SD). After a 210 min of hyperinsulinaemic euglycaemic clamp (blood glucose 4.6 +/- 0.14mmol/L), gliclazide or placebo (randomised, double-blind, cross-over) was administered; 60 minutes later, a hyperglycaemic clamp (4hr) at 8mmol/L was started. Plasma C-peptide levels increased significantly after the administration of gliclazide (increment 0.17 +/- 0.15 vs. 0.04 +/- 0.07 nmol/L, p = 0.024) before the clamp. After the start of the hyperglycaemic clamp, the areas under the curve (AUC) for insulin and C-peptide did not differ from 0-10 min (first phase) with gliclazide. However, second-phase insulin release (30-240 min) was markedly enhanced by gliclazide. AUC plasma insulin (30 to 240 min) was statistically significantly higher after gliclazide (12.3 +/- 13.9 vs. -0.56 +/- 9.4 nmol/L x 210 min, p = 0.022); similarly, AUC plasma C-peptide (30 to 240 min) was also higher: 128 +/- 62 vs. 63 +/- 50 nmol/L x 210 min, p = 0.002). In conclusion, in long-standing type 2 diabetes the acute administration of gliclazide significantly enhances second phase insulin release at a moderately elevated blood glucose level. In contrast to previous findings in mildly diabetic subjects, these 12 type 2 diabetes patients who had an inconsiderable first phase insulin release on the placebo day, only showed an insignificant increase in first phase with gliclazide.     

Association between the interleukin-6 promoter polymorphism -174G/C and serum lipoprotein(a) concentrations in humans

Background

Lipoprotein(a) [Lp(a)] is an independent risk factor for cardiovascular disease. The interleukin-6 (IL-6) receptor antagonist tocilizumab has been shown to lower serum Lp(a) concentrations. We investigated whether the IL-6 single nucleotide polymorphism −174G/C is associated with baseline serum Lp(a) concentrations.

Methodology/Principal Findings

We divided 2321 subjects from the Lipid Analytic Cologne (LIANCO) cohort into 2 groups, the ones with substantially elevated Lp(a), defined as concentrations ≥60 mg/dl (n = 510), and the ones with Lp(a) <60 mg/dl (n = 1811). The association with the genotypes GG (33.7%), GC (50.75%) and CC (15.55%) was investigated. The GC and the CC genotype were associated with a significantly increased odds ratio of having substantially elevated Lp(a) concentrations (OR = 1.3, 95% CI 1.04 to 1.63, P = 0.02 and OR = 1.44, 95% CI 1.06 to 1.93, P = 0.018). These associations remained significant after adjusting for age, sex, smoking behavior, body mass index, serum lipoproteins, hypertension and diabetes. Of these covariates, only LDL cholesterol was significantly and independently associated with elevated Lp(a) concentrations.

Conclusions/Significance

The IL-6 single nucleotide polymorphism −174G/C is associated with increased odds of having elevated Lp(a). Whether this association plays a role in the Lp(a)-lowering effects of IL-6 receptor antagonists remains to be established.     

IL-18 gene promoter polymorphism is involved in HIV-1 infection in a Brazilian pediatric population

In our study, we identified a polymorphism (C-607A) in the promoter region of the IL-18 gene that shows different frequencies between human immunodeficiency virus (HIV)-1-infected children and healthy controls in a pediatric Brazilian population. The presence of the −607 C allele correlates to HIV-1 infection and confers an increased risk of infection in subjects carrying the single nucleotide polymorphism.     

Association of the IL-6 -174G/C gene polymorphism with knee osteoarthritis in a Thai population

Osteoarthritis is a chronic progressive degenerative joint disease characterized by age-related regressive change in articular cartilage. A single nucleotide polymorphism has been described at position -174 of the interleukin-6 (IL-6) promoter region, leading to three possible genotypes, GG, GC, and CC. We investigated a possible association of the IL-6 -174G/C gene polymorphism with knee osteoarthritis in a Thai population. Genotype distributions and allelic frequencies of the IL-6 -174G/C polymorphism were investigated in 115 knee osteoarthritis patients and 100 healthy controls. Genotyping was performed using PCR-RFLP. The genotype distribution of IL-6 was 79 GG, 36 GC, 0 CC in knee osteoarthritis patients and 88 GG, 12 GC, 0 CC in controls. The frequency of the GC genotype in subjects with knee osteoarthritis was higher than in controls (P< 0.001). Logistic regression analysis showed that the GC genotype was independently associated with increased risk of knee osteoarthritis (odds ratio = 3.3, 95% confidence interval = 1.6-6.9, P = 0.001). These findings suggest that the -174G/C polymorphism of the IL-6 gene promoter plays a role in the pathogenesis of knee osteoarthritis.     

When a unit of insulin is not a unit: Detemir dosing and insulin cost in type 2 diabetes mellitus

Background: Increasing acceptance of basal-bolus insulin therapy for the control of diabetes mellitus (DM) has led to newer formulations of basal insulin analogues. The newest one is detemir.Objectives: Clinical evidence suggests that patients with type 2 DM require higher doses of detemir than other basal insulins to achieve equivalent glycemic control. This study examines evidence for greater dosing requirements and the implications of higher doses on the cost of insulin treatment.Methods: We performed a MEDLINE search for randomized, prospective studies comparing detemir with other basal insulins in patients with type 2 DM that were published in English between January 2000 and November 2008. The mean daily doses of basal and bolus insulin and the mean total daily insulin doses were determined. Overall weighted mean doses of the insulins were used to estimate the mean total daily insulin doses required for a 100-kg patient, and published 2008 US retail prices were used to estimate the retail costs of basal-bolus and basal-only insulin regimens.Results: Seven trials involving 3311 patients were identified in the literature search. The mean total daily insulin dose was 0.80 unit/kg for detemir-based regimens and 0.58 unit/kg for comparison regimens. For basal-bolus regimens, the estimated retail cost of the mean total daily insulin dose was $11.24 for detemir-based regimens compared with $8.99 for glargine-based regimens and $6.41 for neutral protamine Hagedorn (NPH)-based insulins. For basal-only regimens, the estimated retail cost of the mean total daily insulin dose was $8.23 for detemir compared with $5.19 for glargine and $2.35 for NPH.Conclusions: It is important for health care providers and patients to know that patients with type 2 DM may require substantially higher doses of detemir than other basal insulins. This should be considered when titrating the dose as well as in cost-benefit analyses of detemir versus other insulins.     

Interleukin-6 -174 promoter polymorphism does not influence IL-6 production after LPS and IL-1 beta stimulation in human umbilical cord vein endothelial cells

The IL-6 is a typical pleiotropic cytokine, which regulates T cell response, B cell differentiation and immunoglobulin production. Endothelial cells can produce large amounts of IL-6. SNP at position -174 (G/C) in the IL-6 promoter region was found to be associated with a series of complex diseases. In this study we analyzed whether IL-6 -174 G/C polymorphism has any effect on IL-6 production of in vitro cultured HUVECs. Thirty-three fresh umbilical cords were recruited from healthy pregnancies. The endothelial cells isolated from human umbilical cords were genotyped for IL-6 -174 SNP. C allele frequency was 0.379. The IL-6 production of each primary HUVEC line was measured after IL-1beta or LPS treatment by ELISA. Serial dilutions of the stimulating agents were applied and maximum amount of produced IL-6 (R(max)) and stimulator concentrations at half-maximal IL-6 response (MR(50)) were calculated for each of the cell lines. IL-6 production was not associated with IL-6 -174 SNP genotypes or with presence of C allele. Our results showed that IL-6 production of HUVEC after proinflammatory stimulation was not influenced by IL-6 -174 SNP. Further functional studies are required to compare differences and similarities in IL-6 -174 SNP dependent expression of IL-6 among various cell types.     

Influence of the interleukin-6 -174 G/C gene polymorphism on exercise training-induced changes in glucose tolerance indexes.

A polymorphism in the IL-6 gene, a G-to-C substitution 176 bp upstream of the ATG translation initiation site, has been associated with diabetes prevalence and insulin resistance. Interventions including exercise training are frequently used to modify cardiovascular disease risk factors. Consequently, this project examined associations between the IL-6 -174 genotype and oral glucose tolerance test outcomes in 50- to 75-yr-old sedentary men and postmenopausal women before and after aerobic exercise training. Among the 87 individuals who started the study, 56 were retested after 6 mo of aerobic exercise training. Subject characteristics at baseline did not differ between the IL-6 genotype groups with the exception of fasting glucose, which was higher (P = 0.02, covariates age, gender, and ethnicity) in the CC genotype group. The training-induced change in glucose area under the curve during the oral glucose tolerance test varied between the IL-6 -174 genotype groups (P = 0.05, covariates age, gender, ethnicity, baseline glucose area under the curve, and percent body fat change) with a significant decrease occurring only in the GG genotype group. Insulin outcomes did not differ among the groups at baseline or after training. Training-induced changes in weight, percent body fat, maximal oxygen consumption, fasting glucose, and an insulin sensitivity index also changed similarly among the genotype groups. In conclusion, fasting glucose and the extent to which glucose tolerance changes with exercise training may be influenced by the IL-6 -174 gene polymorphism.