Heterozygous disruption of ALAS1 in mice causes an accelerated age-dependent reduction in free heme, but not total heme, in skeletal muscle and liver
Heterozygous disruption of ALAS1 in mice causes an accelerated age-dependent reduction in free heme, but not total heme, in skeletal muscle and liver
复制标题
小鼠中 ALAS1 的杂合破坏导致骨骼肌和肝脏中游离血红素加速减少，但不是总血红素随年龄增加
DOI：
10.1016/j.abb.2020.108721
复制
发表时间：
2021
影响因子：
3.9
通讯作者：
Nakajima Osamu
中科院分区：
文献类型：
--
作者：
van Wijk Koen;Akabane Takeru;Kimura Tomohiro;Saitoh Shinichi;Okano Satoshi;Kelly Vincent P.;Takagi Michiaki;Kodama Ken;Takahashi Kiwamu;Tanaka Tohru;Nakajima Motowo;Nakajima Osamu
5-氨基乙酰丙酸(ALA)是脊椎动物体内血红素生物合成的限速中间体，由线粒体ALA合成酶1(ALAS1)酶催化。此前，我们报道了在小鼠中普遍表达的ALAS1基因的敲除会扰乱正常的葡萄糖代谢，削弱线粒体功能，并导致动物超过20周时出现糖尿病前期的表型(Saitoh等人，2018年)。与我们的预期相反，ALAS1杂合子(A1+/-)小鼠的胞浆和线粒体血红素含量与WT动物相似。因此，我们推测，在A1+/-小鼠中，调节的“游离血红素”可能以一种年龄相关的方式减少，但不是总血红素。在这里，我们使用改进的丙酮提取方法检测WT和A1+/-小鼠骨骼肌和肝脏中的游离和总血红素，并通过比较8-12周和30-36周龄时的数量以及ALAS1的信使核糖核酸丰度来检验衰老对游离血红素的影响。我们发现A1+/-小鼠骨骼肌和肝脏中的游离血红素随着年龄的增长而减少，而WT小鼠的肝脏中只显示出轻微的减少。总血红素水平在年轻和老年WT和A1+/-小鼠之间没有显著差异，ALAS1mRNA水平显示出与游离血红素水平相似的随年龄的下降，表明ALAS1mRNA表达水平是游离血红素水平的主要决定因素。骨骼肌组织中的游离血红素库几乎是肝脏组织的两倍，这表明不同组织类型的血红素库是不同的。血红素加氧酶1(HO-1)mRNA的表达与游离血红素水平相似，与游离血红素含量成正比。综上所述，这项研究表明，不同组织的游离血红素池不同，ALAS1杂合小鼠的游离血红素水平随年龄的下降而加速，这可能是在这些动物中观察到的糖尿病前期表型和线粒体异常的原因。
5-Aminolevulinic acid (ALA) is the rate-limiting intermediate in heme biosynthesis in vertebrate species; a reaction catalyzed by the mitochondrial ALA synthase 1 (ALAS1) enzyme. Previously we reported that knockdown of the ubiquitously expressedALAS1gene in mice disrupts normal glucose metabolism, attenuates mitochondrial function and results in a prediabetic like phenotype when animals pass 20-weeks of age (Saitoh et al., 2018). Contrary to our expectations, the cytosolic and mitochondrial heme content ofALAS1heterozygous (A1+/-) mice were similar to WT animals. Therefore, we speculated that regulatory “free heme” may be reduced in an age dependent manner inA1+/- mice, but not total heme.Here, we examine free and total heme from the skeletal muscle and liver of WT andA1+/- mice using a modified acetone extraction method and examine the effects of aging on free heme by comparing the amounts at 8–12 weeks and 30–36 weeks of age, in addition to the mRNA abundance ofALAS1. We found an age-dependent reduction in free heme in the skeletal muscle and liver ofA1+/- mice, while WT mice showed only a slight decrease in the liver. Total heme levels showed no significant difference between young and aged WT andA1+/- mice.ALAS1mRNA levels showed an age-dependent reduction similar to that of free heme levels, indicating thatALAS1mRNA expression levels are a major determinant for free heme levels. The free heme pools in skeletal muscle tissue were almost 2-fold larger than that of liver tissue, suggesting that the heme pool varies across different tissue types. The expression ofheme oxygenase 1(HO-1) mRNA, which is expressed proportionally to the amount of free heme, were similar to those of free heme levels. Taken together, this study demonstrates that the free heme pool differs across tissues, and that an age-dependent reduction in free heme levels is accelerated in mice heterozygous forALAS1, which could account for the prediabetic phenotype and mitochondrial abnormality observed in these animals.