Department of Ophthalmology, Changzheng Hospital of Naval Medicine University, Shanghai, China.
Department of Ophthalmology, Changzheng Hospital of Naval Medicine University, Shanghai, China.
J Lipid Res. 2024 Sep;65(9):100606. doi: 10.1016/j.jlr.2024.100606. Epub 2024 Jul 26.
A high-fat diet (HFD) contributes to the pathogenesis of various inflammatory and metabolic diseases. Previous research confirms that under HFD conditions, the extraorbital lacrimal glands (ELGs) can be impaired, with significant infiltration of pro-inflammatory macrophages (Mps). However, the relationship between HFD and Mps polarization in the ELGs remains unexplored. We first identified and validated the differential expression of PPAR-γ in murine ELGs fed ND and HFD through RNA sequencing. Tear secretion was measured using the Schirmer test. Lipid droplet deposition within the ELGs was observed through Oil Red O staining and transmission electron microscopy. Mps phenotypes were determined through quantitative RT-PCR, immunofluorescence, and flow cytometric analysis. An in vitro high-fat culture system for Mps was established using palmitic acid (PA), with supernatants collected for co-culture with lacrimal gland acinar cells. Gene expression was determined through ELISA, immunofluorescence, immunohistochemistry, quantitative RT-PCR, and Western blot analysis. Pioglitazone reduced M1-predominant infiltration induced by HFD by increasing PPAR-γ levels in ELGs, thereby alleviating lipid deposition and enhancing tear secretion. In vitro tests indicated that PPAR-γ agonist shifted Mps from M1-predominant to M2-predominant phenotype in PA-induced Mps, reducing lipid synthesis in LGACs and promoting lipid catabolism, thus alleviating lipid metabolic disorders within ELGs. Conversely, the PPAR-γ antagonist induced opposite effects. In summary, the lacrimal gland is highly sensitive to high-fat and lipid metabolic disorders. Downregulation of PPAR-γ expression in ELGs induces Mps polarization toward predominantly M1 phenotype, leading to lipid metabolic disorder and inflammatory responses via the NF-κb/ERK/JNK/P38 pathway.
高脂肪饮食（HFD）是多种炎症和代谢性疾病发病机制的一个重要因素。先前的研究证实，在 HFD 条件下，眼外泪腺（ELG）会受到损伤，大量促炎巨噬细胞（Mps）浸润。然而，HFD 与 ELG 中 Mps 极化的关系尚未得到探索。我们首先通过 RNA 测序鉴定并验证了在 ND 和 HFD 喂养的小鼠 ELG 中 PPAR-γ 的差异表达。通过 Schirmer 测试测量泪液分泌。通过油红 O 染色和透射电子显微镜观察 ELG 内的脂滴沉积。通过定量 RT-PCR、免疫荧光和流式细胞术分析确定 Mps 表型。使用棕榈酸（PA）建立了 Mps 的体外高脂肪培养系统，并收集上清液与泪腺腺泡细胞共培养。通过 ELISA、免疫荧光、免疫组化、定量 RT-PCR 和 Western blot 分析确定基因表达。吡格列酮通过增加 ELG 中 PPAR-γ 的水平，减少由 HFD 引起的 M1 优势浸润，从而减轻脂滴沉积并增强泪液分泌，从而减轻 M1 优势浸润。体外试验表明，PPAR-γ 激动剂使 Mps 在 PA 诱导的 Mps 中从 M1 优势表型转变为 M2 优势表型，减少 LGAC 中的脂质合成并促进脂质代谢，从而减轻 ELG 中的脂质代谢紊乱。相反，PPAR-γ 拮抗剂则诱导相反的效果。总之，泪腺对高脂肪和脂质代谢紊乱非常敏感。ELG 中 PPAR-γ 表达的下调诱导 Mps 向主要为 M1 表型极化，通过 NF-κb/ERK/JNK/P38 途径导致脂质代谢紊乱和炎症反应。
