1-磷酸鞘氨醇对2型糖尿病小鼠胰岛β细胞损伤的保护作用

Protective effects of sphingosine-1-phosphate on islet β-cell proliferation and less cell apoptosis in type 2 diabetic mice

目的研究1-磷酸鞘氨醇(S1P)对2型糖尿病(T2DM)小鼠胰岛β细胞的促进增殖、抑制凋亡情况和对血糖的影响,以及S1P受体S1PR1-3在T2DM小鼠胰腺中的表达定位,探讨S1P对糖尿病胰岛β细胞损伤的保护作用。方法雄性C57BL/6J小鼠,高脂饮食联合小剂量链脲佐菌素(STZ)制备T2DM小鼠模型,随机分为S1P高剂量组(S1PH)、S1P低剂量组(S1PL)、糖尿病对照组(DC)及正常对照组(NC),每日予S1PH组和S1PL组S1P溶液100μg/kg及20μg/kg腹腔注射,DC组及NC组予同体积溶剂替代。给药3周后行葡萄糖耐量试验(IPGTT),胰腺组织HE及TUNEL染色,免疫组化检测胰岛中胰岛素、Ki67及S1PR1-3蛋白的表达。结果 S1P给药3周后,S1PL组及S1PH组空腹血糖及IPGTT 2h血糖较DC组轻度下降。胰岛组织HE染色及胰岛素免疫组化染色示S1PL组及S1PH组较DC组胰岛病变减轻。Ki67免疫组化染色示S1PL组及S1PH组胰岛β细胞增殖率较DC组明显升高(P<0.05);TUNEL染色示S1PL组及S1PH组胰岛β细胞凋亡率较DC组明显降低(P<0.05)。胰岛组织免疫组化示S1P受体S1PR1-3均表达于小鼠胰岛β细胞中,在胰腺组织外分泌部表达甚微或不表达。其中S1PL组、S1PH组和DC组S1PR1及S1PR2的表达均较NC组明显增多,各组间S1PR3表达差异无统计学意义。结论 S1P与其受体S1PR1及S1PR2结合能够显著改善T2DM小鼠胰岛β细胞形态,促进小鼠胰岛β细胞增殖、抑制凋亡,提示S1P对T2DM胰岛β细胞损伤有保护作用。S1P/S1PR信号通路在T2DM中发挥着重要作用,有可能成为未来药物治疗的新靶点。

Objective To explore the potential protective effects of sphingosine-1-phosphate(S1P)on pancreatic isletβ-cell proliferation and less cell apoptosis in type 2 diabetic mice and to detect the localization and expression of S1P receptors in the islets of type 2 diabetic mice.Methods Mice with type 2 diabetes induced by high-fat diet with low-dose streptozotocin were randomly divided into 4 groups:high-dose S1P administration group(S1PH),low-dose S1P administration group(S1PL),diabetic model control group(DC),and normal control group(NC).Exogenous S1P was intraperitoneally injected daily at a dose of 100μg/kg for S1PH group and 20μg/kg for S1PL group for 3 weeks.The potential protective effects of S1P onβ-cell proliferation and apoptosis were determined.Intraperitoneal glucose tolerance test(IPGTT)and homeostasis model assessment(HOMA)index were assessed to test the effects of S1P on islet function.Expressions of insulin,Ki67,S1P receptor isoforms(S1PR1,S1PR2 and S1PR3)proteins in pancreatic islets were tested by immunohistochemical staining.Results Three weeks after S1P administration,fasting blood glucose and 2-hour glucose after injection during IPGTT in the two S1P administration groups were decreased slightly compared to DC group.β-cell proliferation rate was higher and the apoptosis rate was lower in S1PH and S1PL groups than in DC group(P<0.05).S1P receptors S1PR1,S1PR2 and S1PR3 were positively stained in the islet cell cytoplasm and membrane.S1PR1 and S1PR2 proteins were significantly expressed in S1PH and S1PL groups and DC diabetic groups compared with NC group(P<0.01),while S1PR3 expression did not significantly differ among these groups.Conclusion Extracellular S1P promotesβ-cell proliferation and suppresses cell apoptosis via S1P receptor isoforms S1PR1 and S1PR2 in diabetic mice.Therefore,S1P/S1PR signaling can be considered as a potential therapeutic target for the treatment of diabetes for its important role in T2DM.