Department of Endocrinology, Shandong Provincial Hospital, Shandong University, Jinan, China.
Department of Obstetrics, Central Hospital Affiliated to Shandong First Medical University, Jinan, China.
Diabetes Metab J. 2024 Nov;48(6):1058-1072. doi: 10.4093/dmj.2023.0275. Epub 2024 Jul 29.
Diabetes mellitus (DM) is a chronic metabolic disease that poses serious threats to human physical and mental health worldwide. The PDZ domain-containing 8 (PDZD8) protein mediates mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) formation in mammals. We explored the role of PDZD8 in DM and investigated its potential mechanism of action.
High-fat diet (HFD)- and streptozotocin-induced mouse DM and palmitic acid (PA)-induced insulin 1 (INS-1) cell models were constructed. PDZD8 expression was detected using immunohistochemistry, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blotting. MAM formation, interactions between voltage-dependent anion-selective channel 1 (VDAC1) and inositol 1,4,5-triphosphate receptor type 1 (IP3R1), pancreatic β-cell apoptosis and proliferation were detected using transmission electron microscopy (TEM), proximity ligation assay (PLA), terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, immunofluorescence staining, and Western blotting. The mitochondrial membrane potential, cell apoptosis, cytotoxicity, and subcellular Ca2+ localization in INS-1 cells were detected using a JC-1 probe, flow cytometry, and an lactate dehydrogenase kit.
PDZD8 expression was up-regulated in the islets of HFD mice and PA-treated pancreatic β-cells. PDZD8 knockdown markedly shortened MAM perimeter, suppressed the expression of MAM-related proteins IP3R1, glucose-regulated protein 75 (GRP75), and VDAC1, inhibited the interaction between VDAC1 and IP3R1, alleviated mitochondrial dysfunction and ER stress, reduced the expression of ER stress-related proteins, and decreased apoptosis while increased proliferation of pancreatic β-cells. Additionally, PDZD8 knockdown alleviated Ca2+ flow into the mitochondria and decreased cyclophilin D (Cypd) expression. Cypd overexpression alleviated the promoting effect of PDZD8 knockdown on the apoptosis of β-cells.
PDZD8 knockdown inhibited pancreatic β-cell death in DM by alleviated ER-mitochondria contact and the flow of Ca2+ into the mitochondria.
糖尿病（DM）是一种慢性代谢性疾病，在全球范围内对人类身心健康构成严重威胁。富含 PDZ 结构域的 8 蛋白（PDZD8）在哺乳动物中介导线粒体相关内质网（ER）膜（MAM）的形成。我们探讨了 PDZD8 在 DM 中的作用，并研究了其潜在的作用机制。
构建高脂肪饮食（HFD）和链脲佐菌素诱导的小鼠 DM 及棕榈酸（PA）诱导的胰岛素 1（INS-1）细胞模型。采用免疫组织化学、实时定量聚合酶链反应（qRT-PCR）和 Western blot 检测 PDZD8 的表达。通过透射电子显微镜（TEM）、邻近连接分析（PLA）、末端脱氧核苷酸转移酶 dUTP 缺口末端标记（TUNEL）检测 MAM 形成、电压依赖性阴离子选择通道 1（VDAC1）与肌醇 1,4,5-三磷酸受体 1（IP3R1）的相互作用、胰岛β细胞凋亡和增殖，免疫荧光染色和 Western blot 检测。用 JC-1 探针、流式细胞术和乳酸脱氢酶试剂盒检测 INS-1 细胞线粒体膜电位、细胞凋亡、细胞毒性和细胞内 Ca2+定位。
PDZD8 在 HFD 小鼠胰岛和 PA 处理的胰岛β细胞中表达上调。PDZD8 敲低显著缩短 MAM 周长，抑制 MAM 相关蛋白 IP3R1、葡萄糖调节蛋白 75（GRP75）和 VDAC1 的表达，抑制 VDAC1 与 IP3R1 的相互作用，减轻线粒体功能障碍和内质网应激，降低内质网应激相关蛋白的表达，减少胰岛β细胞凋亡，增加增殖。此外，PDZD8 敲低减轻了 Ca2+流入线粒体和降低亲环素 D（Cypd）的表达。Cypd 过表达减轻了 PDZD8 敲低对β细胞凋亡的促进作用。
PDZD8 敲低通过减轻 ER-线粒体接触和 Ca2+流入线粒体来抑制 DM 中胰岛β细胞的死亡。
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