Department of Surgery
Amino acid supplementation prevents islet cells death from nutrient deprivation during the peri-transplant period
Gaetano Faleo1, Holger Russ2, Vinh Nguyen1, Jonathan Freise1, Matthias Hebrok2, Qizhi Tang1,2.
1Department of Surgery, Transplantation Laboratory, UCSF, San Francisco, CA, United States; 2Diabetes Center, UCSF, San Francisco, CA, United States
Islet transplantation can confer insulin independence in more than half of the recipients at five years after transplantation, but often requires multiple donors per recipient because of peri-transplant loss of graft mass. One main reason for islet loss is disruption of native islet vascular system and the resulting ischemic injury. Much of the research in this area is focused on impact of hypoxia on islet death. However, ischemia also leads to nutrient deprivation and how low nutrient state affect islet health and function has not been well characterized.
To investigate the impact of nutrient deprivation on isolated islets independent of hypoxia, we established an in vitro culture system under atmospheric oxygen tension. We observed that culturing mouse islet at high density of 1000 islet per mL led to rapid decline of their function and viability in hours. This is mirrored by in vivo observation using bioluminescence imaging that high-density transplant exacerbate peri-transplant graft loss. Islets cultured at high density showed reduced mTOR activity reflected by their reduced phosphorylation of mTOR substrate protein S6. These islets also formed LC3+ autophagosomes consistent with cellular starvation. Supplementation of glucose was moderately effective in promoting islet survival in high-density cultures. By contrast, amino acid supplementation was more effective in preventing islet death. Interestingly, supplementation of a single amino acid like: alanine, tryptophan, glutamine, or leucine was sufficient in rescuing islets (Figure 1). Protection by amino acids was associated with restoration of S6 phosphorylation and the protective effect was abrogated in the presence of rapamycin, an inhibitor of mTOR, demonstrating that the mTOR pathway is necessary for amino acids to prevent islet death. Human embryonic stem cell (hESC)-derived islets are a promising renewable source of islets for transplantation. We found that hESC-derived islets were similarly impacted by nutrient deprivation in vitro and supplementation of single amino acids was able to prevent their death. Moreover, we observed that stem cells in a more advanced stage of differentiation die more in nutrient deprived cultures than their less differentiated counterpart.
These results demonstrate a previous unrecognized role of nutrient deprivation as an independent contributor of islet cell death in the peri-transplant period for both mouse and hESC-derived islets. The high responsiveness of islets to amino acid supplementation offers an interventional strategy to protect islets from nutrient deprivation and improve therapeutic efficacy of islet transplantation.
Larry H. Hillblom Foundation. American Diabetes Association.
15:30 - 17:00
|Islet Cell Transplantation - Miscellaneous||Amino acid supplementation prevents islet cells death from nutrient deprivation during the peri-transplant period||Room 111-112|