Inhibition of AHCY impedes proliferation and differentiation of mouse and human adipocyte progenitor cells

S-adenosyl-homocysteine-hydrolase (AHCY) plays an important role in the methionine cycle regulating cellular methylation levels. AHCY has been reported to influence proliferation and differentiation processes in different cell types, e.g. in cancer cells and mouse embryonic stem cells. In the development of adipose tissue, both the proliferation and differentiation of adipocyte progenitor cells (APCs) are important processes, which in the context of obesity are often dysregulated. To assess whether AHCY might also be involved in cell proliferation and differentiation of APCs, we investigated the effect of reduced AHCY activity on human and mouse APCs <i>in vitro</i>. We show that the inhibition of AHCY using adenosine dialdehyde (AdOx) and the knockdown of AHCY using gene-specific siRNAs reduced APC proliferation and number. Inhibition of AHCY further reduced APC differentiation into mature adipocytes and the expression of adipogenic differentiation markers. Global DNA methylation profiling in human APCs revealed that inhibition of AHCY is associated with alterations in CpG methylation levels of genes involved in fat cell differentiation and pathways related to cellular growth. Our findings suggest that AHCY is necessary for the maintenance of APC proliferation and differentiation and inhibition of AHCY alters DNA methylation processes leading to a dysregulation of the expression of genes involved in the regulation of these processes.

S-腺苷同型半胱氨酸水解酶（S-adenosyl-homocysteine-hydrolase, AHCY）在调控细胞甲基化水平的甲硫氨酸循环中扮演关键角色。已有研究证实，AHCY可影响多种细胞类型的增殖与分化过程，例如癌细胞与小鼠胚胎干细胞。在脂肪组织发育进程中，脂肪细胞祖细胞（adipocyte progenitor cells, APCs）的增殖与分化均为核心环节；而在肥胖病理背景下，这些进程常出现调控异常。为探究AHCY是否同样参与APCs的细胞增殖与分化过程，我们针对人源及小鼠APCs开展<i>体外</i>实验，评估降低AHCY活性所产生的生物学效应。结果显示，采用腺苷二醛（adenosine dialdehyde, AdOx）抑制AHCY活性，或是通过基因特异性小干扰RNA（small interfering RNAs, siRNAs）敲低AHCY表达，均可削弱APCs的增殖能力并减少细胞数量。抑制AHCY活性还会阻碍APCs向成熟脂肪细胞的分化，并降低脂肪生成相关分化标志物的表达水平。对人源APCs开展的全基因组DNA甲基化谱分析显示，AHCY抑制作用与脂肪细胞分化相关基因以及细胞生长相关通路的CpG甲基化水平改变存在密切关联。本研究结果表明，AHCY对于维持APCs的增殖与分化能力不可或缺；抑制AHCY活性会改变DNA甲基化调控过程，进而导致调控上述进程的相关基因表达出现失调。