Author:
Sugahara Sho,Kume Shinji,Chin-Kanasaki Masami,Tomita Issei,Yasuda-Yamahara Mako,Yamahara Kosuke,Takeda Naoko,Osawa Norihisa,Yanagita Motoko,Araki Shin-ichi,Maegawa Hiroshi
Abstract
BackgroundEnergy metabolism in proximal tubular epithelial cells (PTECs) is unique, because ATP production largely depends on lipolysis in both the fed and fasting states. Furthermore, disruption of renal lipolysis is involved in the pathogenesis of diabetic tubulopathy. Emerging evidence suggests that protein O-GlcNAcylation, an intracellular nutrient-sensing system, may regulate a number of metabolic pathways according to changes in nutritional status. Although O-GlcNAcylation in PTECs has been demonstrated experimentally, its precise role in lipolysis in PTECs is unclear.MethodsTo investigate the mechanism of renal lipolysis in PTECs—specifically, the role played by protein O-GlcNAcylation—we generated mice with PTECs deficient in O-GlcNAc transferase (Ogt). We analyzed their renal phenotypes during ad libitum feeding, after prolonged fasting, and after mice were fed a high-fat diet for 16 weeks to induce obesity and diabetes.ResultsAlthough PTEC-specific Ogt-deficient mice lacked a marked renal phenotype during ad libitum feeding, after fasting 48 hours, they developed Fanconi syndrome–like abnormalities, PTEC apoptosis, and lower rates of renal lipolysis and ATP production. Proteomic analysis suggested that farnesoid X receptor–dependent upregulation of carboxylesterase-1 is involved in O-GlcNAcylation’s regulation of lipolysis in fasted PTECs. PTEC-specific Ogt-deficient mice with diabetes induced by a high-fat diet developed severe tubular cell damage and enhanced lipotoxicity.ConclusionsProtein O-GlcNAcylation is essential for renal lipolysis during prolonged fasting and offers PTECs significant protection against lipotoxicity in diabetes.
Publisher
American Society of Nephrology (ASN)
Subject
Nephrology,General Medicine
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