Department of Cardiovascular Surgery, Affiliated Shanghai 1st People’s Hospital, Shanghai Jiaotong University, Shanghai 210008, People's Republic of China.
Lipids Health Dis. 2012 Dec 5;11:168. doi: 10.1186/1476-511X-11-168.
Administration of androgens decreases plasma concentrations of high-density lipid cholesterol (HDL-C). However, the mechanisms by which androgens mediate lipid metabolism remain unknown. This present study used HepG2 cell cultures and ovariectomized C57BL/6 J mice to determine whether apolipoprotein M (ApoM), a constituent of HDL, was affected by dihydrotestosterone (DHT).
HepG2 cells were cultured in the presence of either DHT, agonist of protein kinase C (PKC), phorbol-12-myristate-13-acetate (PMA), blocker of androgen receptor flutamide together with different concentrations of DHT, or DHT together with staurosporine at different concentrations for 24 hrs. Ovariectomized C57BL/6 J mice were treated with DHT or vehicle for 7d or 14d and the levels of plasma ApoM and livers ApoM mRNA were measured. The mRNA levels of ApoM, ApoAI were determined by real-time RT-PCR. ApoM and ApoAI were determined by western blotting analysis.
Addition of DHT to cell culture medium selectively down-regulated ApoM mRNA expression and ApoM secretion in a dose-dependent manner. At 10 nM DHT, the ApoM mRNA levels were about 20% lower than in untreated cells and about 40% lower at 1000 nM DHT than in the control cells. The secretion of ApoM into the medium was reduced to a similar extent. The inhibitory effect of DHT on ApoM secretion was not blocked by the classical androgen receptor blocker flutamide but by an antagonist of PKC, Staurosporine. Agonist of PKC, PMA, also reduced ApoM. At 0.5 μM PMA, the ApoM mRNA levels and the secretion of ApoM into the medium were about 30% lower than in the control cells. The mRNA expression levels and secretion of another HDL-associated apolipoprotein AI (ApoAI) were not affected by DHT. The levels of plasma ApoM and liver ApoM mRNA of DHT-treated C57BL/6 J mice were lower than those of vehicle-treated mice.
DHT directly and selectively down-regulated the level of ApoM mRNA and the secretion of ApoM by protein kinase C but independently of the classical androgen receptor.
雄激素的给药会降低高密度脂蛋白胆固醇（HDL-C）的血浆浓度。然而，雄激素介导脂代谢的机制尚不清楚。本研究使用 HepG2 细胞培养物和去卵巢 C57BL/6 J 小鼠来确定载脂蛋白 M（ApoM）是否受二氢睾酮（DHT）的影响，ApoM 是 HDL 的组成部分。
在存在 DHT、蛋白激酶 C（PKC）激动剂十四烷酰佛波醇-12-乙酸酯（PMA）、雄激素受体阻断剂氟他胺以及不同浓度 DHT 的情况下，将 HepG2 细胞培养 24 小时。或者，用不同浓度的 DHT 或 staurosporine 与 DHT 一起培养去卵巢 C57BL/6 J 小鼠 7 天或 14 天，测量血浆 ApoM 和肝脏 ApoM mRNA 的水平。通过实时 RT-PCR 确定 ApoM 和 ApoAI 的 mRNA 水平。通过 Western blot 分析测定 ApoM 和 ApoAI。
向细胞培养基中添加 DHT 可选择性地以剂量依赖性方式下调 ApoM mRNA 表达和 ApoM 分泌。在 10 nM DHT 时，ApoM mRNA 水平比未处理细胞低约 20%，在 1000 nM DHT 时比对照细胞低约 40%。ApoM 分泌到培养基中的量也相应减少。DHT 对 ApoM 分泌的抑制作用不能被经典的雄激素受体阻滞剂氟他胺阻断，但可被 PKC 拮抗剂 Staurosporine 阻断。PKC 激动剂 PMA 也降低了 ApoM。在 0.5 μM PMA 时，ApoM mRNA 水平和 ApoM 分泌到培养基中的水平比对照细胞低约 30%。另一种与 HDL 相关的载脂蛋白 AI（ApoAI）的 mRNA 表达水平和分泌不受 DHT 影响。DHT 处理的 C57BL/6 J 小鼠的血浆 ApoM 水平和肝脏 ApoM mRNA 水平低于载体处理的小鼠。
DHT 通过蛋白激酶 C 直接和选择性地下调 ApoM mRNA 水平和 ApoM 的分泌，而与经典的雄激素受体无关。
