Improvement of Pancreatic Islet Isolation Outcomes Using Glutamine Administration During Isolation or Culture after Isolation

Abstract

During procurement, isolation, and transplantation, islets are exposed to high levels of oxidative stress triggering a variety of signaling pathways that can lead to cell death. Oxidative stress during islet isolation induces a cascade of events injuring islets and hampering islet engraftment. Glutamine (GLN) is an important cellular fuel and an essential precursor for the antioxidant glutathione. Cell transplantation can make the culture condition after cell isolation. The aim of this study was to examine and compare the role of intraductal glutamine administration during isolation or culture after isolation in facilitating recovery of isolated rat islets from pancreases, to examine marginal islet syngenic transplantation outcomes after glutamine administration (culture). Islets were isolated in Lewis rats (n = 8). Pancreata in groups were procured immediately. Rat pancreas were treated with either a 5 mM solution of L-GLN or collagenase enzyme alone through the main pancreatic duct prior to pancreatectomy. Islet cells were cultured with L-GLN (10mM/L) supplementation for 24 hours or no receiving GLN. Islet yield, viability, in vitro function; markers of oxidative stress [Glutathione (GSH)] were assessed. Intraductal or cultured GLN treatment significantly improved islet yield [6845 ± 762 islets (IEQ) without glutamine vs. 8825 ± 933, 9461±1234 islets with glutamine, p < 0.05]. Glutamine also significantly improved islet viability (values were 72 ± 8% without glutamine vs. 94 ± 3%, 83±5 with glutamine, 24 hr after isolation p < 0.05). Similarly, glutathione levels were significantly elevated in both glutamine-treated groups. The basal Bcl-2 expression was markedly increased by glutamine treatment. The percentage of DM lewis rendered normoglycemic with glutamine cultured islets was higher than the controls (75% n = 8 vs. 50% n = 8; p < 0.05), and the time to reach normoglycemia was decreased in the glutamine cultured group (1.88 ± 0.4 vs. 3.3 ± 0.3 days; p < 0.05). We conclude that administration of glutamine reduces oxidative injury, improves islet yield and improve islet graft function after transplantation.