Laboratory of Hepatic and Cardiovascular Diseases, Biochemistry and Molecular Biology Department, School of Pharmacy, Complutense University of Madrid, Madrid, Spain.
Liver Research Unit, Hospital Universitario Santa Cristina, Instituto de Investigación Sanitaria Princesa, Madrid, Spain.
Liver Int. 2023 Aug;43(8):1714-1728. doi: 10.1111/liv.15581. Epub 2023 Apr 14.
The molecular mechanisms driving non-alcoholic fatty liver disease (NAFLD) are poorly understood; however, microRNAs might play a key role in these processes. We hypothesize that let-7d-5p could contribute to the pathophysiology of NAFLD and serve as a potential diagnostic biomarker.
We evaluated let-7d-5p levels and its targets in liver biopsies from a cross-sectional study including patients with NAFLD and healthy donors, and from a mouse model of NAFLD. Moreover, the induction of let-7d-5p expression by fatty acids was evaluated in vitro. Further, we overexpressed let-7d-5p in vitro to corroborate the results observed in vivo. Circulating let-7d-5p and its potential as a NAFLD biomarker was determined in isolated extracellular vesicles from human plasma by RT-qPCR.
Our results demonstrate that hepatic let-7d-5p was significantly up-regulated in patients with steatosis, and this increase correlated with obesity and a decreased expression of AKT serine/threonine kinase (AKT), insulin-like growth factor 1 (IGF1), IGF-I receptor (IGF1R) and insulin receptor (INSR). These alterations were corroborated in a NAFLD mouse model. In vitro, fatty acids increased let-7d-5p expression, and its overexpression decreased AKT, IGF-IR and IR protein expression. Furthermore, let-7d-5p hindered AKT phosphorylation in vitro after insulin stimulation. Finally, circulating let-7d-5p significantly decreased in steatosis patients and receiver operating characteristic (ROC) analyses confirmed its utility as a diagnostic biomarker.
Our results highlight the emerging role of let-7d-5p as a potential therapeutic target for NAFLD since its overexpression impairs hepatic insulin signalling, and also, as a novel non-invasive biomarker for NAFLD diagnosis.
非酒精性脂肪性肝病 (NAFLD) 的分子机制尚不清楚；然而，microRNAs 可能在这些过程中发挥关键作用。我们假设 let-7d-5p 可能有助于 NAFLD 的病理生理学，并作为潜在的诊断生物标志物。
我们评估了来自包括 NAFLD 患者和健康供体的横断面研究以及 NAFLD 小鼠模型的肝活检中 let-7d-5p 的水平及其靶标。此外，还评估了脂肪酸对 let-7d-5p 表达的诱导作用。进一步，我们在体外过表达 let-7d-5p 以验证体内观察到的结果。通过 RT-qPCR 从人血浆中分离的细胞外囊泡中确定循环 let-7d-5p 及其作为 NAFLD 生物标志物的潜力。
我们的结果表明，脂肪变性患者肝组织中的 let-7d-5p 显着上调，这种增加与肥胖和 AKT 丝氨酸/苏氨酸激酶 (AKT)、胰岛素样生长因子 1 (IGF1)、IGF-I 受体 (IGF1R) 和胰岛素受体 (INSR) 的表达降低相关。这些改变在 NAFLD 小鼠模型中得到了证实。在体外，脂肪酸增加了 let-7d-5p 的表达，而过表达则降低了 AKT、IGF-IR 和 IR 蛋白的表达。此外，let-7d-5p 在胰岛素刺激后体外抑制 AKT 磷酸化。最后，脂肪变性患者的循环 let-7d-5p 显着降低，ROC 分析证实其可作为诊断生物标志物的用途。
我们的结果强调了 let-7d-5p 作为 NAFLD 潜在治疗靶点的新兴作用，因为其过表达会损害肝胰岛素信号，并且也是 NAFLD 诊断的新型非侵入性生物标志物。
