Autophagy inhibition blunts PDGFRA adipose progenitors’ cell-autonomous fibrogenic response to high-fat diet

Adipose tissue (AT) fibrosis in obesity compromises adipocyte functions and responses to intervention-induced weight loss. It is driven by AT progenitors with dual fibro/adipogenic potential, but pro-fibrogenic pathways activated in obesity remain to be deciphered. To investigate the role of macroautophagy/autophagy in AT fibrogenesis, we used <i>Pdgfra-Cre^Ert2 </i> transgenic mice to create conditional deletion of <i>Atg7</i> alleles in AT progenitor cells (<i>atg7</i> cKO) and examined sex-dependent, depot-specific AT remodeling in high-fat diet (HFD)-fed mice. Mice with <i>atg7</i> cKO had markedly decreased extracellular matrix (ECM) gene expression in visceral, subcutaneous, and epicardial adipose depots compared to <i>Atg7^lox/lox </i> littermates. ECM gene program regulation by autophagy inhibition occurred independently of changes in the mass of fat tissues or adipocyte numbers of specific depots, and cultured preadipocytes treated with pharmacological or siRNA-mediated autophagy disruptors could mimic these effects. We found that autophagy inhibition promotes global cell-autonomous remodeling of the paracrine TGF-BMP family landscape, whereas ECM gene modulation was independent of the autophagic regulation of GTF2IRD1. The progenitor-specific mouse model of ATG7 inhibition confirms the requirement of autophagy for white/beige adipocyte turnover, and combined to <i>in vitro</i> experiments, reveal progenitor autophagy dependence for AT fibrogenic response to HFD, through the paracrine remodeling of TGF-BMP factors balance. <b>Abbreviations:</b> CQ: chloroquine; ECM: extracellular matrix; EpiAT: epididymal adipose tissue; GTF2IRD1: general transcription factor II I repeat domain-containing 1; HFD: high-fat diet; KO: knockout; OvAT: ovarian adipose tissue; PDGFR: platelet derived growth factor receptor; ScAT: subcutaneous adipose tissue; TGF-BMP: transforming growth factor-bone morphogenic protein

肥胖相关脂肪组织（Adipose Tissue, AT）纤维化会损害脂肪细胞功能，以及其对干预性减重的应答反应。该病变由兼具成纤维与成脂双重潜能的AT祖细胞介导，但肥胖状态下激活的促纤维化通路仍有待阐明。为探究巨自噬（macroautophagy）/自噬（autophagy）在AT纤维化发生中的作用，本研究使用<italic>Pdgfra-Cre^Ert2</italic>转基因小鼠，在AT祖细胞中条件性敲除<italic>Atg7</italic>等位基因（构建<italic>atg7</italic> cKO模型），并对高脂饮食（high-fat diet, HFD）喂养小鼠的性别依赖性、脂肪库特异性AT重塑进行了检测。与<italic>Atg7^lox/lox</italic>同窝对照小鼠相比，<italic>atg7</italic> cKO小鼠的内脏、皮下及心外膜脂肪库中细胞外基质（extracellular matrix, ECM）基因表达水平显著降低。自噬抑制对ECM基因程序的调控作用，并不依赖于特定脂肪库的脂肪组织重量或脂肪细胞数量的变化；而经药物或小干扰RNA（siRNA）介导的自噬抑制剂处理的体外培养前脂肪细胞，可模拟上述效应。本研究发现，自噬抑制可促进旁分泌型转化生长因子-骨形态发生蛋白（transforming growth factor-bone morphogenic protein, TGF-BMP）家族调控网络的全局性细胞自主性重塑，而ECM基因的调控并不依赖于GTF2IRD1的自噬调控。该AT祖细胞特异性ATG7抑制小鼠模型证实，自噬是白色/米色脂肪细胞更新所必需的；结合体外（in vitro）实验结果，本研究揭示了AT祖细胞的自噬依赖性，即高脂饮食诱导的AT纤维化应答依赖于祖细胞自噬，其机制通过重塑TGF-BMP家族因子的旁分泌平衡实现。**缩写说明：** CQ：氯喹（chloroquine）；ECM：细胞外基质（extracellular matrix）；EpiAT：附睾脂肪组织（epididymal adipose tissue）；GTF2IRD1：含通用转录因子II I重复结构域1（general transcription factor II I repeat domain-containing 1）；HFD：高脂饮食（high-fat diet）；KO：敲除（knockout）；OvAT：卵巢脂肪组织（ovarian adipose tissue）；PDGFR：血小板衍生生长因子受体（platelet derived growth factor receptor）；ScAT：皮下脂肪组织（subcutaneous adipose tissue）；TGF-BMP：转化生长因子-骨形态发生蛋白（transforming growth factor-bone morphogenic protein）