BACKGROUND Interleukin-6 (IL-6) gene regulates IL-6 levels, interplay of which has been found to influence pathophysiology of osteoarthritis (OA). Polymorphism within promoter region of IL-6 gene and its association with plasma levels of pro-inflammatory cytokines; IL-6, interleukin 1-beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) remained to be investigated in Punjab region of India, where OA is highly prevalent. METHODS Six single nucleotide polymorphisms (SNPs) in the promoter region of IL-6 gene; rs1800795 (-174G/C), rs1800796 (-572G/C), rs1800797 (-597G/A), rs2069827 (-1363G/T), rs12700386 (-2954G/C) and rs10499563 (-6331G/T) were investigated by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 279 confirmed osteoarthritis patients and 287 controls. Plasma levels of pro-inflammatory cytokines; IL-6, IL-1β and TNF-α were measured by sandwich Enzyme Linked Immunosorbent Assay (ELISA). RESULTS Allele frequency spectrum after adjusting the effect of systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TC), low density lipoprotein (LDL), triglycerides (TG) and body mass index (BMI) revealed that major allele G of rs1800795 and T of rs10499563 were significantly associated with increased risk of OA (P < 0.01) in all the three genetic models; co-dominant (OR 4.08 & 4.12, P < 0.001), recessive (OR 3.00 & 2.51, P < 0.001) and dominant (OR 2.56 & 3.09, P < 0.05). Major allele G of rs1800796 and rs1800797 was observed to enhance OA risk in recessive mode (OR 1.75, P < 0.001 & 1.62, P = 0.01 respectively). Disease risk analysis after adjusting the effect of confounders exposed a susceptibility haplotype GGGGCT, which increased the OA risk by 2.27 times (OR 2.27, 95%CI: 1.26-4.10, P = 0.009) and a protective haplotype CGAGGC which significantly reduced the OA risk (OR 0.47, 95%CI 0.27-0.92, P = 0.031). Both of these haplotypes manifested in the recessive mode of inheritance. Subjects who had one copy of the susceptibility haplotype had lower values of IL-6 (3.6 pg/ml) and IL-1β levels (3.2 pg/ml) than those who had 2 copies of it (4.4 pg/ml & 4.2 pg/ml respectively). IL-6 and IL-1β levels were observed to be negatively associated with protective haplotype CGAGGC (P < 0.05). Carriers of 1 copy of this haplotype showed decreased IL-1β levels than those who had none (1.00 pg/ml vs. 1.3 pg/ml respectively) which further decreased to 0.9 pg/ml in those subjects who carried two copies of protective haplotype. CONCLUSION The present study discovered susceptibility (GGGGCT) and protective (CGAGGC) haplotypes within promoter region of IL-6 gene which influenced the plasma levels of IL-6 and IL-1β for the risk of osteoarthritis in the population of Punjab, India.

中文翻译：

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IL-6 基因启动子多态性影响促炎细胞因子对骨关节炎风险的影响

背景白细胞介素6 (IL-6) 基因调节IL-6 水平，已发现其相互作用影响骨关节炎(OA) 的病理生理学。IL-6基因启动子区多态性及其与血浆促炎细胞因子水平的关系；IL-6、白细胞介素 1-β (IL-1β) 和肿瘤坏死因子-α (TNF-α) 在印度旁遮普地区仍有待研究，那里的 OA 非常普遍。方法 IL-6基因启动子区6个单核苷酸多态性（SNPs）；rs1800795 (-174G/C), rs1800796 (-572G/C), rs1800797 (-597G/A), rs2069827 (-1363G/T), rs12700386 (-2954G/C) (-2954G/C), rs12700386 (-2954G/C) (-2954G/C) rs3/C 调查了rs12700386 (-2954G/C) (-63T)在 279 名确诊的骨关节炎患者和 287 名对照者中使用聚合酶链反应限制性片段长度多态性 (PCR-RFLP)。促炎细胞因子的血浆水平; IL-6，IL-1β 和 TNF-α 通过夹心酶联免疫吸附试验 (ELISA) 进行测量。结果调整收缩压（SBP）、舒张压（DBP）、总胆固醇（TC）、低密度脂蛋白（LDL）、甘油三酯（TG）和体重指数（BMI）影响后的等位基因频谱显示，主要在所有三个遗传模型中，rs1800795 的等位基因 G 和 rs10499563 的 T 与 OA 风险增加显着相关（P < 0.01）；共显性 (OR 4.08 & 4.12, P < 0.001)、隐性 (OR 3.00 & 2.51, P < 0.001) 和显性 (OR 2.56 & 3.09, P < 0.05)。rs1800796 和 rs1800797 的主要等位基因 G 被观察到在隐性模式下增加 OA 风险（OR 1.75，P < 0.001 和 1.62，分别为 P = 0.01）。调整混杂因素影响后的疾病风险分析暴露了易感性单倍型 GGGGCT，使 OA 风险增加了 2.27 倍（OR 2.27，95%CI：1.26-4.10，P = 0.009）和保护性单倍型 CGAGGC，其显着降低了 OA 风险（OR 0.47，95% CI 0.27-0.92，P = 0.031）。这两种单倍型都以隐性遗传模式表现出来。具有 1 个易感性单倍型拷贝的受试者的 IL-6 (3.6 pg/ml) 和 IL-1β 水平 (3.2 pg/ml) 值低于具有 2 个拷贝 (4.4 pg/ml & 4.2 pg/ml) 的受试者毫升）。观察到 IL-6 和 IL-1β 水平与保护性单倍型 CGAGGC 呈负相关（P < 0.05）。这种单倍型的 1 个拷贝的载体显示出 IL-1β 水平比没有的那些降低（分别为 1.00 pg/ml 和 1.3 pg/ml），并进一步降至 0。在携带两个保护性单倍型拷贝的那些受试者中为 9 pg/ml。结论 本研究在 IL-6 基因的启动子区域内发现了易感性 (GGGGCT) 和保护性 (CGAGGC) 单倍型，这些单倍型影响了印度旁遮普邦人群中 IL-6 和 IL-1β 的血浆水平，从而导致骨关节炎的风险。