Ezetimibe Promotes Brush Border Membrane-to-Lumen Cholesterol Efflux in the Small Intestine.
Ezetimibe Promotes Brush Border Membrane-to-Lumen Cholesterol Efflux in the Small Intestine.
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DOI：
10.1371/journal.pone.0152207
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Murakoshi T
中科院分区：
文献类型：
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作者：
Nakano T;Inoue I;Takenaka Y;Ono H;Katayama S;Awata T;Murakoshi T
依折麦布抑制Niemann-Pick C1-like 1（NPC 1 L1），这是一种肠细胞的顶膜胆固醇转运蛋白，从而减少肠道胆固醇吸收。这种治疗还通过未确定的机制增加肝外胆固醇逆向转运。为了探索这一点，我们采用了跨肠胆固醇流出（TICE）测定，该测定直接检测插管空肠段中循环至肠腔的3 H-胆固醇转运，并发现TICE增加了45%。为了检查这种外排的增加是否发生在肠刷状缘膜（BBM）水平，我们进行了管腔灌注试验，类似于TICE，但空肠壁用口服给予的3 H-胆固醇标记，并测定了依折麦布使BBM至管腔胆固醇外排增加3.5倍。这种增加的流出可能最终促进循环至管腔胆固醇转运;从而增加TICE。接下来，我们想知道如何抑制NPC 1 L1（一种内流转运蛋白）导致外排增加。当我们在小鼠中追踪经口给予的3 H-胆固醇时，我们发现管腔至BBM的3 H-胆固醇转运迅速，对依折麦布治疗的敏感性较低。外排和部分胆固醇吸收的比较显示出负相关，表明外排作为胆固醇吸收效率的相反调节因子，并抵消自然发生的胆固醇快速流入BBM。这表明依折麦布刺激的外排增加在降低胆固醇吸收方面至关重要。在具有内源性ATP结合盒G5/G8异二聚体（肠细胞的主要固醇外排转运蛋白）的小鼠中，依折麦布诱导的胆固醇外排增加约为敲除小鼠的2.5倍，表明异二聚体在对NPC 1 L1抑制的反应中赋予额外的快速BBM至管腔胆固醇外排。所观察到的肠道胆固醇通量的框架可以提供调节通量以有效地处置内源性胆固醇用于治疗目的的方法。
Ezetimibe inhibits Niemann-Pick C1-like 1 (NPC1L1), an apical membrane cholesterol transporter of enterocytes, thereby reduces intestinal cholesterol absorption. This treatment also increases extrahepatic reverse cholesterol transport via an undefined mechanism. To explore this, we employed a trans-intestinal cholesterol efflux (TICE) assay, which directly detects circulation-to-intestinal lumen 3H-cholesterol transit in a cannulated jejunal segment, and found an increase of TICE by 45%. To examine whether such increase in efflux occurs at the intestinal brush border membrane(BBM)-level, we performed luminal perfusion assays, similar to TICE but the jejunal wall was labelled with orally-given 3H-cholesterol, and determined elevated BBM-to-lumen cholesterol efflux by 3.5-fold with ezetimibe. Such increased efflux probably promotes circulation-to-lumen cholesterol transit eventually; thus increases TICE. Next, we wondered how inhibition of NPC1L1, an influx transporter, resulted in increased efflux. When we traced orally-given 3H-cholesterol in mice, we found that lumen-to-BBM 3H-cholesterol transit was rapid and less sensitive to ezetimibe treatment. Comparison of the efflux and fractional cholesterol absorption revealed an inverse correlation, indicating the efflux as an opposite-regulatory factor for cholesterol absorption efficiency and counteracting to the naturally-occurring rapid cholesterol influx to the BBM. These suggest that the ezetimibe-stimulated increased efflux is crucial in reducing cholesterol absorption. Ezetimibe-induced increase in cholesterol efflux was approximately 2.5-fold greater in mice having endogenous ATP-binding cassette G5/G8 heterodimer, the major sterol efflux transporter of enterocytes, than the knockout counterparts, suggesting that the heterodimer confers additional rapid BBM-to-lumen cholesterol efflux in response to NPC1L1 inhibition. The observed framework for intestinal cholesterol fluxes may provide ways to modulate the flux to dispose of endogenous cholesterol efficiently for therapeutic purposes.