Effect of stable glutamine compounds on porcine islet culture.
Brandhorst H., Duan Y., Iken M., Bretzel RG., Brandhorst D.
BACKGROUND: Pig islets are characterized by significant fragility, preventing successful islet culture prior to xenotransplantation. To improve outcome after culture, we compared the effects of glutamine supplementation on survival and viability of isolated pig islets during culture. METHODS: Pig islets were suspended in CMRL 1066 supplemented either with 2.5 mmol/L N-acetyl-L-alanyl-L-glutamine (NALG), a stable compound of L-glutamine, or with 2.5 or 5.0 mmol/L of free L-glutamine (L-Glu). After 24 hours of preincubation, islets were stressed for additional 48 hours with H2O2, DETA, or a cytokine mix. RESULTS: Twenty-four-hour survival of unstressed controls precultured with 2.5 mmol/L NALG was significantly decreased compared with islets pretreated with 2.5 or 5.0 mmol/L L-Glu (P < .01). Fresh islets, viability decreased significantly after NALG preincubation, but was maintained after preincubation in 2.5 or 5.0 mmol/L L-Glu (not significant vs fresh; P < .05 vs NALG). Compared with NALG pretreatment L-Glu did not significantly ameliorate the relative survival (related to cultured controls) of islets during proinflammatory treatment. Nevertheless, the beneficial effect of L-Glu preculture on absolute survival (related to freshly isolated islets) of stressed islets was still present in contrast to NALG pretreatment (P < .01). Viability of stressed islets was significantly protected by L-Glu but not by NALG. CONCLUSIONS: Pig islet culture is significantly improved if L-glutamine is administered in an unbound form compared with the stable compound NALG. Stress resistance of pig islets seems to be increased by free L-glutamine as well.