Gastroenterology Research, Atlanta Veterans Administration Medical Center, Decatur, Georgia, United States.
Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States.
Am J Physiol Endocrinol Metab. 2023 Sep 1;325(3):E214-E226. doi: 10.1152/ajpendo.00145.2023. Epub 2023 Jul 19.
Gastrointestinal (GI) complications, including diarrhea, constipation, and gastroparesis, are common in patients with diabetes. Dysregulation of the Na/H exchanger NHE3 in the intestine is linked to diarrhea and constipation, and recent studies showed that NHE3 expression is reduced in type 1 diabetes and metformin causes diarrhea in the mouse model of type 2 diabetes (T2D) via inhibition of NHE3. In this study, we investigated whether NHE3 expression is altered in type 2 diabetic intestine and the underlying mechanism that dysregulates NHE3. NHE3 expression in the brush border membrane (BBM) of the intestine of diabetic mice and humans was decreased. Protein kinase C (PKC) activation is associated with pathologies of diabetes, and immunofluorescence (IF) analysis revealed increased BBM PKCα abundance. Inhibition of PKCα increased NHE3 BBM abundance and NHE3-mediated intestinal fluid absorption in mice. Previous studies have shown that (LA) stimulates intestinal ion transporters. LA increased NHE3 BBM expression and mitigated metformin-mediated inhibition of NHE3 in vitro and in vivo. To understand the underlying mechanism of LA-mediated stimulation of NHE3, we used Caco-2bbe cells overexpressing PKCα that mimic the elevated state of PKCα in T2D. LA diminished PKCα BBM expression, increased phosphorylation of ezrin, and the interaction of NHE3 with NHE regulatory factor 2 (NHERF2). In addition, inhibition of PKCι blocked phosphorylation of ezrin and activation of NHE3 by LA. These findings demonstrate that NHE3 is downregulated in T2D, and LA restores NHE3 expression via regulation of PKCα, PKCι, and ezrin. We used mouse models of type 2 diabetes (T2D) and human patient-derived samples to show that Na/H exchanger 3 (NHE3) expression is decreased in T2D. We show that protein kinase C-α (PKCα) is activated in diabetes and inhibition of PKCα increased NHE3 expression and mitigates diarrhea. We show that (LA) stimulates NHE3 via inhibition of PKCα and phosphorylation of ezrin.
胃肠道（GI）并发症，包括腹泻、便秘和胃轻瘫，在糖尿病患者中很常见。肠道中钠/氢交换器 NHE3 的失调与腹泻和便秘有关，最近的研究表明，1 型糖尿病中 NHE3 的表达减少，并且二甲双胍通过抑制 NHE3 在 2 型糖尿病（T2D）的小鼠模型中引起腹泻。在这项研究中，我们研究了 NHE3 的表达是否在 2 型糖尿病肠道中发生改变，以及调节 NHE3 的潜在机制。糖尿病小鼠和人类肠道刷状缘膜（BBM）中的 NHE3 表达减少。蛋白激酶 C（PKC）的激活与糖尿病的病理学有关，免疫荧光（IF）分析显示 BBM PKCα 丰度增加。PKCα 的抑制增加了 NHE3 BBM 的丰度，并增加了 小鼠的 NHE3 介导的肠道液体吸收。先前的研究表明， （LA）刺激肠道离子转运体。LA 增加了 NHE3 BBM 的表达，并减轻了体外和体内二甲双胍对 NHE3 的抑制。为了了解 LA 介导的 NHE3 刺激的潜在机制，我们使用了过表达 PKCα 的 Caco-2bbe 细胞，这些细胞模拟了 T2D 中 PKCα 的升高状态。LA 减少了 PKCα BBM 的表达，增加了 ezrin 的磷酸化，并增加了 NHE3 与 NHE 调节因子 2（NHERF2）的相互作用。此外，PKCι 的抑制阻断了 LA 对 ezrin 的磷酸化和对 NHE3 的激活。这些发现表明，NHE3 在 T2D 中下调，而 LA 通过调节 PKCα、PKCι 和 ezrin 来恢复 NHE3 的表达。我们使用 2 型糖尿病（T2D）的小鼠模型和人源性样本，证明 NHE3 在 T2D 中表达减少。我们表明，蛋白激酶 C-α（PKCα）在糖尿病中被激活，抑制 PKCα 增加了 NHE3 的表达并减轻了腹泻。我们表明，LA 通过抑制 PKCα 和 ezrin 的磷酸化来刺激 NHE3。
