title: Restoration of Na+/H+ exchanger NHE3-containing macrocomplexes ameliorates diabetes-associated fluid loss.
abstract: Diarrhea is one of the troublesome complications of diabetes, and the underlying causes of this problem are complex. Here, we investigated whether altered electrolyte transport contributes to diabetic diarrhea. We found that the expression of Na+/H+ exchanger NHE3 and several scaffold proteins, including NHE3 regulatory factors (NHERFs), inositol trisphosphate (IP₃) receptor-binding protein released with IP₃ (IRBIT), and ezrin, was decreased in the intestinal brush border membrane (BBM) of mice with streptozotocin-induced diabetes. Treatment of diabetic mice with insulin restored intestinal NHE3 activity and fluid absorption. Molecular analysis revealed that NHE3, NHERF1, IRBIT, and ezrin form macrocomplexes, which are perturbed under diabetic conditions, and insulin administration reconstituted these macrocomplexes and restored NHE3 expression in the BBM. Silencing of NHERF1 or IRBIT prevented NHE3 trafficking to the BBM and insulin-dependent NHE3 activation. IRBIT facilitated the interaction of NHE3 with NHERF1 via protein kinase D2-dependent phosphorylation. Insulin stimulated ezrin phosphorylation, which enhanced the interaction of ezrin with NHERF1, IRBIT, and NHE3. Additionally, oral administration of lysophosphatidic acid (LPA) increased NHE3 activity and fluid absorption in diabetic mice via an insulin-independent pathway. Together, these findings indicate the importance of NHE3 in diabetic diarrhea and suggest LPA administration as a potential therapeutic strategy for management of diabetic diarrhea.
authors.forename: Peijian
authors.initials: P
authors.lastname: He
authors.forename: Luqing
authors.initials: L
authors.lastname: Zhao
authors.forename: Lixin
authors.initials: L
authors.lastname: Zhu
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Weinman
authors.forename: Roberto
authors.initials: R
authors.lastname: De Giorgio
authors.forename: Michael
authors.initials: M
authors.lastname: Koval
authors.forename: Shanthi
authors.initials: S
authors.lastname: Srinivasan
authors.forename: C Chris
authors.initials: CC
authors.lastname: Yun
mesh_terms: D043383:Adenosylhomocysteinase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D018938:Caco-2 Cells; D048909:Diabetes Complications / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D003921:Diabetes Mellitus, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D003967:Diarrhea / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000473:pathology; D037181:Lectins, C-Type / Q000235:genetics / Q000378:metabolism; D008246:Lysophospholipids; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008871:Microvilli / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
chemical_list: C470184:CLECL1 protein, human; D037181:Lectins, C-Type; D008246:Lysophospholipids; D008565:Membrane Proteins; D010750:Phosphoproteins; C000613385:SLC9A3 protein, human; C000613386:Slc9a3 protein, mouse; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D043383:Adenosylhomocysteinase; C510392:IRBIT protein, mouse; C032881:lysophosphatidic acid