Center of Reproductive Medicine, Nanjing Jinling Hospital, Clinical School of Medical College, Nanjing University, Nanjing, 210002, Jiangsu, China.
Reprod Biol Endocrinol. 2018 Oct 17;16(1):98. doi: 10.1186/s12958-018-0416-0.
The Sertoli cell is the only somatic cell within the seminiferous tubules, and is vital for testis development and spermatogenesis. Rosiglitazone (RSG) is a member of the thiazolidinedione family and is a peroxisome proliferator-activated receptor-γ (PPARγ) agonist. It has been reported that RSG protects various types of cells from fatty acid-induced damage. However, whether RSG serves a protective role in Sertoli cells against palmitic acid (PA)-induced toxicity remains to be elucidated. Therefore, the aim of the present study was to investigate the effect of RSG on PA-induced cytotoxicity in Sertoli cells. MTT assay and Oil Red O staining revealed that RSG ameliorated the PA-induced decrease in TM4 cell viability, which was accompanied by an alleviation of PA-induced lipid accumulation in cells. In primary mouse Sertoli cells, RSG also showed similar protective effects against PA-induced lipotoxicity. Knockdown of PPARγ verified that RSG exerted its protective role in TM4 cells through a PPARγ-dependent pathway. To evaluate the mechanism underlying the protective role of RSG on PA-induced lipotoxicity, the present study analyzed the effects of RSG on PA uptake, and the expression of genes associated with both fatty acid oxidation and triglyceride synthesis. The results demonstrated that although RSG did not affect the endocytosis of PA, it significantly elevated the expression of carnitine palmitoyltransferase (CPT)-1A, a key enzyme involved in fatty acid oxidation, which indicated that the protective effect of RSG may have an important role in fatty acid oxidation. On the other hand, the expression of CPT1B was not affected by RSG. Moreover, the expression levels of diacylglycerol O-acyltransferase (DGAT)-1 and DGAT2, both of which encode enzymes catalyzing the synthesis of triglycerides, were not suppressed by RSG. The results indicated that RSG reduced PA-induced lipid accumulation by promoting fatty acid oxidation mediated by CPT1A. The effect of RSG in protecting cells from lipotoxicity was also found to be specific to Sertoli cells and hepatocytes, and not to other cell types that do not store excess lipid in large quantities, such as human umbilical vein endothelial cells. These findings provide insights into the cytoprotective effects of RSG on Sertoli cells and suggest that PPARγ activation may be a useful therapeutic method for the treatment of Sertoli cell dysfunction caused by dyslipidemia.
支持细胞是生精小管内唯一的体细胞，对睾丸发育和精子发生至关重要。罗格列酮（RSG）是噻唑烷二酮类的一员，是过氧化物酶体增殖物激活受体-γ（PPARγ）激动剂。据报道，RSG 可保护各种类型的细胞免受脂肪酸诱导的损伤。然而，RSG 是否在支持细胞中发挥保护作用以抵抗棕榈酸（PA）诱导的毒性仍有待阐明。因此，本研究旨在探讨 RSG 对 PA 诱导的支持细胞毒性的影响。MTT 检测和油红 O 染色显示，RSG 改善了 PA 诱导的 TM4 细胞活力下降，同时减轻了细胞内的 PA 诱导的脂质堆积。在原代小鼠支持细胞中，RSG 对 PA 诱导的脂毒性也表现出类似的保护作用。PPARγ 的敲低证实，RSG 通过 PPARγ 依赖性途径发挥其对 TM4 细胞的保护作用。为了评估 RSG 对 PA 诱导的脂毒性的保护作用机制，本研究分析了 RSG 对 PA 摄取以及与脂肪酸氧化和甘油三酯合成相关基因表达的影响。结果表明，尽管 RSG 不影响 PA 的内吞作用，但它显著上调了肉毒碱棕榈酰转移酶（CPT）-1A 的表达，CPT-1A 是参与脂肪酸氧化的关键酶，这表明 RSG 的保护作用可能在脂肪酸氧化中起重要作用。另一方面，RSG 对 CPT1B 的表达没有影响。此外，二酰基甘油 O-酰基转移酶（DGAT）-1 和 DGAT2 的表达水平不受 RSG 抑制，这两种酶均编码催化甘油三酯合成的酶。结果表明，RSG 通过促进 CPT1A 介导的脂肪酸氧化来减少 PA 诱导的脂质堆积。RSG 保护细胞免受脂毒性的作用也被发现仅针对支持细胞和肝细胞，而不是其他不大量储存多余脂质的细胞类型，如人脐静脉内皮细胞。这些发现为 RSG 对支持细胞的细胞保护作用提供了新的见解，并表明激活 PPARγ 可能是治疗脂代谢异常引起的支持细胞功能障碍的一种有用的治疗方法。
