NAFLD activity score criteria.

A family of Peptidyl-prolyl isomerases (PPIases), called Cyclophilins, localize to numerous intracellular and extracellular locations where they contribute to a variety of essential functions. We previously reported that non-immunosuppressive pan-cyclophilin inhibitor drugs like reconfilstat (CRV431) or NV556 decreased multiple aspects of non-alcoholic fatty liver disease (NAFLD) in mice under two different non-alcoholic steatohepatitis (NASH) mouse models. Both CRV431 and NV556 inhibit several cyclophilin isoforms, among which cyclophilin D (CypD) has not been previously investigated in this context. It is unknown whether it is necessary to simultaneously inhibit multiple cyclophilin family members to achieve therapeutic benefits or if loss-of-function of one is sufficient. Furthermore, narrowing down the isoform most responsible for a particular aspect of NAFLD/NASH, such as hepatocellular carcinoma (HCC), would allow for more precise future therapies. Features of human diabetes-linked NAFLD/NASH can be reliably replicated in mice by administering a single high dose of streptozotocin to disrupt pancreatic beta cells, in conjunction with a high sugar, high fat, high cholesterol western diet over the course of 30 weeks. Here we show that while both wild-type (WT) and Ppif-/- CypD KO mice develop multipe severe NASH disease features under this model, the formation of HCC nodules was significantly blunted only in the CypD KO mice. Furthermore, of differentially expressed transcripts in a qPCR panel of select HCC-related genes, nearly all were downregulated in the CypD KO background. Cyclophilin inhibition is a promising and novel avenue of treatment for diet-induced NAFLD/NASH. This study highlights the impact of CypD loss-of-function on the development of HCC, one of the most severe disease outcomes.一类名为亲环蛋白（Cyclophilins）的肽酰脯氨酰异构酶（Peptidyl-prolyl isomerases, PPIases）家族，定位于众多细胞内与细胞外位点，参与多种核心生理功能。我们此前的研究表明，诸如reconfilstat（CRV431）或NV556这类无免疫抑制性的广谱亲环蛋白抑制剂，可在两种不同的非酒精性脂肪性肝炎（non-alcoholic steatohepatitis, NASH）小鼠模型中，改善小鼠非酒精性脂肪性肝病（non-alcoholic fatty liver disease, NAFLD）的多项病理特征。CRV431与NV556均可抑制多种亲环蛋白亚型，其中亲环蛋白D（cyclophilin D, CypD）在此类研究中此前尚未被针对性探究。目前尚不明确，要实现治疗获益是否需要同时抑制多个亲环蛋白家族成员，亦或是仅敲除单个家族成员即可达到效果。此外，明确在NAFLD/NASH的特定病理进程（如肝细胞癌（hepatocellular carcinoma, HCC）发生）中起主要作用的亚型，将有助于开发更精准的未来治疗方案。通过单次高剂量注射链脲佐菌素以破坏胰岛β细胞，并联合高糖、高脂、高胆固醇的西式饮食喂养30周，可在小鼠中稳定复刻人类糖尿病相关NAFLD/NASH的病理特征。本研究显示，尽管野生型（wild-type, WT）与Ppif基因敲除的CypD敲除（Ppif-/- CypD KO）小鼠在该模型中均出现多项严重的NASH病理特征，但仅CypD敲除小鼠的肝细胞癌结节形成受到显著抑制。进一步的实时定量PCR（qPCR）靶向肝癌相关基因组合检测显示，在CypD敲除背景下，几乎所有差异表达的转录本均呈现下调趋势。亲环蛋白抑制是一条极具前景的饮食诱导型NAFLD/NASH治疗新途径。本研究阐明了CypD功能缺失对肝细胞癌发生的影响，而肝细胞癌是该疾病最严重的转归之一。