Hyperglycemia in diabetes mellitus (DM) patients is a causative factor for amyloidogenesis and induces neuropathological changes, such as impaired neuronal integrity, neurodegeneration, and cognitive impairment. Regulation of mitochondrial calcium influx from the endoplasmic reticulum (ER) is considered a promising strategy for the prevention of mitochondrial ROS (mtROS) accumulation that occurs in the Alzheimer’s disease (AD)-associated pathogenesis in DM patients. Among the metabolites of ellagitannins that are produced in the gut microbiome, urolithin A has received an increasing amount of attention as a novel candidate with anti-oxidative and neuroprotective effects in AD. Here, we investigated the effect of urolithin A on high glucose-induced amyloidogenesis caused by mitochondrial calcium dysregulation and mtROS accumulation resulting in neuronal degeneration. We also identified the mechanism related to mitochondria-associated ER membrane (MAM) formation. We found that urolithin A-lowered mitochondrial calcium influx significantly alleviated high glucose-induced mtROS accumulation and expression of amyloid beta (Aβ)-producing enzymes, such as amyloid precursor protein (APP) and β-secretase-1 (BACE1), as well as Aβ production. Urolithin A injections in a streptozotocin (STZ)-induced diabetic mouse model alleviated APP and BACE1 expressions, Tau phosphorylation, Aβ deposition, and cognitive impairment. In addition, high glucose stimulated MAM formation and transglutaminase type 2 (TGM2) expression. We first discovered that urolithin A significantly reduced high glucose-induced TGM2 expression. In addition, disruption of the AIP–AhR complex was involved in urolithin A-mediated suppression of high glucose-induced TGM2 expression. Markedly, TGM2 silencing inhibited inositol 1, 4, 5-trisphosphate receptor type 1 (IP3R1)–voltage-dependent anion-selective channel protein 1 (VDAC1) interactions and prevented high glucose-induced mitochondrial calcium influx and mtROS accumulation. We also found that urolithin A or TGM2 silencing prevented Aβ-induced mitochondrial calcium influx, mtROS accumulation, Tau phosphorylation, and cell death in neuronal cells. In conclusion, we suggest that urolithin A is a promising candidate for the development of therapies to prevent DM-associated AD pathogenesis by reducing TGM2-dependent MAM formation and maintaining mitochondrial calcium and ROS homeostasis.

糖尿病 (DM) 患者的高血糖是淀粉样变性的致病因素，并诱导神经病理学变化，例如神经元完整性受损、神经变性和认知障碍。调节来自内质网 (ER) 的线粒体钙流入被认为是预防 DM 患者阿尔茨海默病 (AD) 相关发病机制中发生的线粒体 ROS (mtROS) 积累的有希望的策略。在肠道微生物群中产生的鞣花单宁代谢物中，尿石素 A 作为一种在 AD 中具有抗氧化和神经保护作用的新型候选物，受到越来越多的关注。这里，我们研究了尿石素 A 对由线粒体钙失调和 mtROS 积累导致神经元变性引起的高葡萄糖诱导的淀粉样变性的影响。我们还确定了与线粒体相关内质网膜 (MAM) 形成相关的机制。我们发现尿石素 A 降低线粒体钙内流显着减轻了高糖诱导的 mtROS 积累和淀粉样 β (Aβ) 产生酶的表达，如淀粉样前体蛋白 (APP) 和 β-分泌酶-1 (BACE1)，以及作为 Aβ 的产生。在链脲佐菌素 (STZ) 诱导的糖尿病小鼠模型中注射尿石素 A 减轻了 APP 和 BACE1 表达、Tau 磷酸化、Aβ 沉积和认知障碍。此外，高葡萄糖刺激 MAM 形成和转谷氨酰胺酶 2 (TGM2) 表达。我们首先发现尿石素 A 显着降低了高葡萄糖诱导的 TGM2 表达。此外，AIP-AhR 复合物的破坏参与了尿石素 A 介导的对高葡萄糖诱导的 TGM2 表达的抑制。明显地，TGM2沉默抑制了肌醇 1, 4, 5-三磷酸受体 1 (IP3R1) - 电压依赖性阴离子选择性通道蛋白 1 (VDAC1) 的相互作用，并阻止了高葡萄糖诱导的线粒体钙内流和 mtROS 积累。我们还发现尿石素 A 或TGM2沉默阻止了 Aβ 诱导的线粒体钙流入、mtROS 积累、Tau 磷酸化和神经元细胞中的细胞死亡。总之，我们认为尿石素 A 是一种有希望的候选药物，可通过减少 TGM2 依赖性 MAM 形成和维持线粒体钙和 ROS 稳态来开发预防 DM 相关 AD 发病机制的疗法。