视黄醇结合蛋白4在人皮下和网膜脂肪组织的差异表达及与肥胖和胰岛素抵抗的关系

目的 探讨视黄醇结合蛋白4(RBP4)在人皮下和网膜脂肪组织的差异表达,并分析其与肥胖及胰岛素抵抗的关系.方法 2009年1至4月在中山大学附属第三医院择期行腹部手术的正常糖调节患者41例,按体质指数(BMI)分为超重组(n=12)和正常体重组(n=29),采用酶联免疫吸附试验检测两组患者血清中RBP4水平,化学发光法检测两组患者空腹胰岛素(FINS)水平,葡萄糖氧化酶法检测患者空腹血糖(FPG)水平,计算稳态模型的胰岛素抵抗指数(HOMA-IR);分别在术中取其皮下和网膜脂肪组织,用半定量RT-PCR和Western印迹方法 检测脂肪组织中RBP4 mRNA和蛋白表达,并对两组患者皮下和网膜脂肪组织中RBP4 mRNA和蛋白表达水平与血清中RBP4水平、BMI、HOMA-IR行相关性分析.结果 (1)超重组患者血清RBP4、FINS及HOMA-IR均高于正常体重组RBP4:(39.61±1.57)mg/L比(33.40±1.28)mg/L,P＜0.01;FINS:(8.82±3.79)mU/L比(6.43±4.38)mU/L,P＜0.05;HOMA-IR:(1.91±0.85)比(1. 36±0.72),P＜0.05].(2)患者网膜脂肪组织RBP4 mRNA表达明显高于皮下脂肪组织(5.88±2.37)比(2.07±1.66),P＜0.01],网膜组织RBP4蛋白表达也高于皮下脂肪(0.76±0.18比0.15±0.07,P＜0.01).超重组网膜脂肪组织RBP4 mRNA和蛋白表达明显高于正常体重组mRNA:(7.52±0.58)比(4.37±0.45),P＜0.01;蛋白:(0.92±0.23)比(0.57±0.13),P＜0.05].皮下脂肪组织RBP4 mRNA和蛋白的表达在两组差异无统计学意义(P＞0.05).(3)血清RBP4水平与BMI、腰围/臀围、HOMA-IR、网膜脂肪组织mRNA表达呈正相关(P＜0.05).HOMA-IR与皮下脂肪组织RBP4 mRNA和蛋白表达水平呈负相关(r=-0.635,P＜0.05),与血清RBP4水平、网膜脂肪组织mRNA和蛋白表达水平呈正相关(r分别为0.391、0.473,P＜0.05).结论 RB阳在皮下和网膜脂肪组织中存在差异表达,RBP4在网膜脂肪组织的高表达及高血清水平可能参与肥胖和胰岛素抵抗的发生.

Depot-specific expression of retinol-binding protein 4 in human adipose tissue and their relationship with obesity and insulin resistance

Objective To explore the depot-specific mRNA and protein expression of retinolbinding protein 4 (RBP4) in human subcutaneous and omental adipose tissue and investigate their relationship with the serum RRP4 levels, obesity and insulin resistance. Methods A total of 41 subjects with normal glucose regulation were recruited. Among them, there were 29 cases with normal body mass index (BMI) and 12 cases with BMI ≥24 kg/m2. All were prepared to undergone a selective abdominal surgery. The levels of serum RBP4 and fasting insulin ( FINS ) were measured by ELISA ( enzyme-linked immunosorbent assay) and chemiluminescence ELISA kit respectively. Fasting plasma glucose (FPG) was tested by glucose oxidase and the home model insulin resistance index (HOMA-IR) calculated. Real-time PCR (RT-PCR) and Western blot were employed to assess the relative mRNA and protein expression of RBP4 in subcutaneous and omental adipose tissues. The mRNA and protein expression of RBP4 from different fat depots were compared and their correlations with BMI, the serum RBP4 concentrations and HOMA-IR analyzed. Results (1) The serum concentrations of RBP4, FINS and HOMA-IR were significantly higher in overweight and obesity group than those in the normal BMI group RBP4: (39. 61 ±1.57) mg/L vs (33.40 ± 1.28) mg/L, P ＜0. 01; FINS: (8. 82 ±3.79) mU/L vs (6. 43 ±4. 38) mU/L, P＜0. 05; HOMA-IR:1. 91 ±0. 85 vs 1.36 ±0. 72, P ＜0. 05]. (2) The expression levels of RBP4 mRNA and protein were significantly higher in omental adipose tissues than those in subcutaneous adipose tissue mRNA: (5. 88 ±2. 37)vs(2. 07 ± 1.66), P ＜0. 01; protein: (0. 76 ±0. 18 vs 0. 15 ±0. 07, P ＜0. 05]and these depots difference in both groups ( P ＜ 0. 05) . Moreover, the overweight patients had the higher expression levels of RBP4 mRNA and protein in omental adipose tissue than normal BMI group (mRNA:7.52±0.58 vs 4.37 ±0.45, P＜0. 01; protein: 0.92 ±0.23 vs 0.57 ±0.13, P ＜0.05). (3) The expressions of both RBP4 mRNA and protein in the omental adipose tissue were positively correlated with BMI, waist circumstance, serum concentrations of RBP4, FINS and HOMA-IR. The expression of was negatively correlated with HOMA-IR ( r = - 0. 635, P ＜ 0. 05 ) in subcutaneous adipose tissue. No correlations were found between the expressions of RBP4 mRNA and protein in subcutaneous adipose tissue with BMI, waist circumstance, serum RBP4 and FINS concentrations. Conclusions There is depot-specific expression of RBP4 in human subcutaneous and omental adipose tissues. A high expression of RBP4 in omental adipose tissue and an elevated level of serum RBP4 may contribute to the pathogenesis of obesity and IR.