非诺贝特对高胆固醇血症兔脂肪细胞摄取及降解氧化型低密度脂蛋白的影响

Effects of fenofibrate on uptake and degradationof oxidized low-density lipoprotein in adipocytes from rabbits with hypercholesterolemia

目的 观察兔脂肪细胞通过CD36摄取及降解氧化型低密度脂蛋白(OxLDL)的作用和非诺贝特对高胆固醇血症兔脂肪细胞OxLDL代谢的影响。方法 10只新西兰白兔给予高胆固醇饲料饲养8周后分为: (1)高胆固醇血症组:继续饲以高胆固醇饲料4周; (2)非诺贝特治疗组:在饲以高胆固醇饲料的基础上给予(30mg·kg-1·d-1 )非诺贝特4周。另选饲以普通饲料12周兔5只作为对照组。实验结束后,取皮下脂肪组织行脂肪细胞培养,放射配基法测定脂肪细胞对OxLDL的摄取及降解,RT PCR测定脂肪细胞CD36mRNA的表达。结果 喂饲胆固醇组血清总胆固醇、低密度脂蛋白胆固醇水平明显高于对照组(均P<0. 01),非诺贝特干预4周未对血脂产生影响,但能降低体重( -19%,P<0. 05 )。RT PCR示CD36在脂肪细胞分化过程中被诱导表达。放射配基实验发现兔脂肪细胞呈浓度依赖饱和型的摄取及降解OxLDL,细胞最大结合为2 065ng/mg细胞蛋白,解离常数(Kd)为4. 2mg/L;抗CD36抗体明显抑制脂肪细胞摄取(56% )及降解(54% )OxLDL;当125I OxLDL浓度为75mg/L时,对照组,高胆固醇组,非诺贝特治疗组脂肪细胞摄取125I OxLDL分别为3. 5, 2. 1, 2. 7μg/mg细胞蛋白, 降解125I OxLDL分别为2. 2, 1. 2,1. 7μg/mg细胞蛋白, 3组间差异有统计学意义(P<0. 05)。

Objective To observe the role of CD36 in uptake and degradation of oxidized low density lipoprotein (OxLDL) by adipocytes from rabbits with hyperdolestrolemia and the effect of fenofibrate on OxLDL uptake in these adipocytes. Methods After 10 New Zealand rabbits were fed with cholesterol-rich diet for 8 weeks, the animals were then divided into hypercholesterolemia group (continuously fed with cholesterol-rich diet for 4 weeks) and fenofibrate treatment group \[fed with cholesterol-rich diet and fenofibrate (30 mg·kg -1·d -1) for 4 weeks\]. Five rabbits were fed with ordinary diet for 12 week as controls.Subcutaneous adipose tissues were collected from rabbits for adipocytes culture. The uptake and degradation of OxLDL in adipocytes were assayed by radioligand method and CD36 mRNA expression wasevaluated by RT-PCR. Results Rabbits fed with cholesterol-rich diet showed higher serum levels of total cholesterol and LDL-cholesterol than those fed with ordinary diet (both P<0.01). Fenofibrate treatment did not change serum lipid levels, but did decrease the body weight by 19% (P<0.05). Cellular expression of CD36 was confirmed during differentiation of adipose cell by RT-PCR. In binding experiments at 4℃, 125I-OxLDL bound specifically and saturablely to adipocytes (Kd= 4.2 mg/L and maximal binding 2065 ng/mg cell protein). The anti-CD36 antibody inhibited the uptake and degradation of 125I-OxLDL in adipocytes by 56% and 54%, respectively. When 125I-OxLDL concentration was 75 mg/L, the specific uptake of 125I-OxLDL in adipocytes from control, high-cholesterol and fenofibrate-treated groups exhibited a dose-dependent saturation pattern with a plateau at 3.5, 2.1, 2.7 μg/mg cell protein and specific degradation of 125I-OxLDL was similarly increased with a plateau at 2.2, 1.2, 1.7 μg/mg cell protein in adipocytes from 3 groups, respectively, and significant differences existed among 3 groups (P<0.05). Conclusion CD36-mediated uptake and degradation of OxLDL by adipocytes are attenuated in case of hypercholesterolemia. Fenofibrate treatment improves the uptake and degradation of OxLDL in adipocytes from rabbits with hypercholesterolemia.