性别差异对磷脂转运蛋白基因敲除小鼠胆固醇逆转运效率的影响

Effect of gender difference on reverse cholesterol transport efficiency in PLTP-/- mice

摘要:

目的观察磷脂转运蛋白基因敲除（PLTP-/-）后雌雄小鼠血浆脂质水平的差异，比较PLTP-/-对雌雄小鼠胆固醇逆转运（RCT）效率的影响。方法选择8 周龄同窝出PLTP-/-小鼠雌雄各8 只，喂饲高脂饲料4 周后，酶法检测小鼠血浆中总胆固醇（TC）、三酰甘油（TG）、高密度脂蛋白胆固醇（HDL-Ch）和非高密度脂蛋白胆固醇（non-HDL-Ch）水平，Western blot检测血浆载脂蛋白A1（apoA1）表达，小鼠腹腔注射含3H-胆固醇的巨噬细胞，48 h 后，取小鼠血浆、肝脏、胆汁、小肠和粪便，利用液闪计数仪检测小鼠各组织中的放射活度，逆转录聚合酶链反应（RT-PCR）检测肝组织清道夫受体BI（SR-B1）、低密度脂蛋白受体（LDL-R）、三磷酸腺苷结 合转运蛋白G5/G8（ABCG5/G8）、肝X 受体α（LXRα）、胆固醇7α羟化酶（CYP7A1）、小肠ABCG5/G8 和肝x 受体α（LXRα）的基因表达。结果相比于雄性PLTP-/-小鼠，雌性PLTP-/-小鼠血浆中TC、TG、HDL-Ch和non-HDL-Ch 的表达无明显改变，但apoA1 水平，差异有统计学意义（P <0.05），雌性PLTP-/-小鼠升高；体内RCT 实验显示：与雄性PLTP-/-小鼠相比，雌性PLTP-/-小鼠血浆和小肠中放射活度无变化，肝脏、胆汁和粪便中放射活度，差异有统计学意义（P <0.05），雌性PLTP-/-小鼠升高；RT-PCR 显示：与雄性PLTP-/-小鼠相比，雌性PLTP-/-小鼠肝脏中RCT 相关因子LXRα、ABCG5/G8 及CYP7A1 表达，差异有统计学意义（P <0.05），雌性PLTP-/-小鼠升高，而SR-B1、LDL-R 表达无明显变化；小肠壁LXRα、ABCG5/G8表达未见明显变化。结论磷脂转运蛋白基因敲除后，雌性PLTP-/-小鼠的胆固醇逆转运效率较高于雄性PLTP-/-小鼠，肝脏中RCT 相关蛋白基因表达增加。

Abstract:

Objective To compare the effects of phospholipid transfer protein gene knockout (PLTP-/-) on reverse cholesterol transport effiency, and observe the changes of plasma lipids in male and female PLTP-/- mice. Methods In this study 8 male and 8 female 8-week littermate PLTP-/- mice were selected and fed with high-fat diet for 4 weeks. Then plasma lipids such as total cholesterol (TC), triglyceride (TG), high -density lipoprotein cholesterol(HDL-C) and non-high density cholesterol (non-HDL-C) were detected by an enzymatic method. The plasma level of apolipoprotein A1 (apoA1) was analyzed by Western blot. Then all mice were injected intraperitoneally with 3Hcholesterol labeled macrophages and the appearance of 3H-tracer in plasma, liver, bile, intestinal wall and feces over 48 h was determined by liquid scintillation counter. The mRNA expressions of scavenger receptor class B type 1(SR-B1), low density lipoprotein-receptor (LDL-R), ATP-binding cassette transporter G5/G8 (ABCG5/G8), liver X receptor α(LXRα) and cholesterol 7α-hydroxylase A1 (CYP7A1) in liver, and ABCG5/G8 and LXRαin intestinal wall were determined by RT-PCR. Results Compared with the male PLTP-/- mice, the expressions of TC, TG, HDL-C and non-HDL-C in the female PLTP-/- mice were not obvious changed, the expression of apoA1 was increased significantly (P < 0.05). The isotope tracing experiment showed 3H-cholesterol of plasma and intestine had no differences between the female and male mice; 3H-tracer of liver, bile and feces was increased significantly (P <0.05). Meanwhile, RT-PCR analysis showed the mRNA expressions of LXRα, ABCG5/G8 and CYP7A1 in the liver were up-regulated significantly in the female mice compared with the male mice (P < 0.05), while the mRNA expressions of SRB1 and LDL-R in the liver and LXRα and ABCG5/G8 in the intestinal wall were not different between the female and male mice (P > 0.05). Conclusions Reverse cholesterol transport efficiency is higher and the mRNA expressions of the genes related to reverse cholesterol transport in liver are also significantly higher in the female PLTP-/- mice than in the male PLTP-/- mice.