Distinct cytoprotective roles of pyruvate and ATP by glucose metabolism on epithelial necroptosis and crypt proliferation in ischaemic gut.
Intestinal ischaemia causes epithelial death and crypt dysfunction, leading to barrier defects and gut bacteria-derived septic complications. Enteral glucose protects against ischaemic injury; however, the roles played by glucose metabolites such as pyruvate and ATP on epithelial death and crypt dysfunction remain elusive. A novel form of necrotic death that involves the assembly and phosphorylation of receptor interacting protein kinase 1/3 complex was found in ischaemic enterocytes. Pyruvate suppressed epithelial cell death in an ATP-independent manner and failed to maintain crypt function. Conversely, replenishment of ATP partly restored crypt proliferation but had no effect on epithelial necroptosis in ischaemic gut. Our data argue against the traditional view of ATP as the main cytoprotective factor by glucose metabolism, and indicate a novel anti-necroptotic role of glycolytic pyruvate under ischaemic stress.



Mesenteric ischaemia/reperfusion induces epithelial death in both forms of apoptosis and necrosis, leading to villus denudation and gut barrier damage. It remains unclear whether programmed cell necrosis [i.e. receptor-interacting protein kinase (RIP)-dependent necroptosis] is involved in ischaemic injury. Previous studies have demonstrated that enteral glucose uptake by sodium-glucose transporter 1 ameliorated ischaemia/reperfusion-induced epithelial injury, partly via anti-apoptotic signalling and maintenance of crypt proliferation. Glucose metabolism is generally assumed to be cytoprotective; however, the roles played by glucose metabolites (e.g. pyruvate and ATP) on epithelial cell death and crypt dysfunction remain elusive. The present study aimed to investigate the cytoprotective effects exerted by distinct glycolytic metabolites in ischaemic gut. Wistar rats subjected to mesenteric ischaemia were enterally instilled glucose, pyruvate or liposomal ATP. The results showed that intestinal ischaemia caused RIP1-dependent epithelial necroptosis and villus destruction accompanied by a reduction in crypt proliferation. Enteral glucose uptake decreased epithelial cell death and increased crypt proliferation, and ameliorated mucosal histological damage. Instillation of cell-permeable pyruvate suppressed epithelial cell death in an ATP-independent manner and improved the villus morphology but failed to maintain crypt function. Conversely, the administration of liposomal ATP partly restored crypt proliferation but did not reduce epithelial necroptosis and histopathological injury. Lastly, glucose and pyruvate attenuated mucosal-to-serosal macromolecular flux and prevented enteric bacterial translocation upon blood reperfusion. In conclusion, glucose metabolites protect against ischaemic injury through distinct modes and sites, including inhibition of epithelial necroptosis by pyruvate and the promotion of crypt proliferation by ATP.
Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan.
Ching-Ying
CY
Huang
Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan.
Wei-Ting
WT
Kuo
Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan.
Chung-Yen
CY
Huang
Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan.|Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
Tsung-Chun
TC
Lee
Department of Biochemical Science and Technology, National Taiwan University, Taipei, Taiwan.
Chin-Tin
CT
Chen
Graduate Institute of Anatomy and Cell Biology, National Taiwan University College of Medicine, Taipei, Taiwan.
Wei-Hao
WH
Peng
Graduate Institute of Anatomy and Cell Biology, National Taiwan University College of Medicine, Taipei, Taiwan.
Kuo-Shyan
KS
Lu
Department of Medical Imaging, E-Da Hospital, I-Shou University, Kaohsiung, Taiwan.|Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan.
Chung-Yi
CY
Yang
Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan.
Linda Chia-Hui
LC
Yu
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D020895:Enterocytes / Q000378:metabolism* / Q000473:pathology* / Q000648:ultrastructure; D005947:Glucose / Q000378:metabolism*; D007583:Jejunum / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D008099:Liver / Q000382:microbiology; D008297:Male; D046529:Microscopy, Electron, Transmission; D009336:Necrosis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D019289:Pyruvic Acid / Q000378:metabolism*; D017208:Rats, Wistar; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000378:metabolism; D015427:Reperfusion Injury / Q000378:metabolism* / Q000473:pathology*; D013154:Spleen / Q000382:microbiology
D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D017346:Protein Serine-Threonine Kinases; C586536:RIPK1 protein, rat; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C582791:Ripk3 protein, rat; D005947:Glucose