IMPAIRMENT OF GLUCOSE-INDUCED INSULIN-SECRETION IN HUMAN PANCREATIC-ISLETS TRANSPLANTED TO DIABETIC NUDE-MICE

Hyperglycemia-induced beta-cell dysfunction may be an important compon ent in the pathogenesis of non-insulin-dependent diabetes mellitus. Ho wever, most available data in this field were obtained from rodent isl ets, To investigate the relevance of this hypothesis for human beta-ce lls in vivo, human pancreatic islets were transplanted under the renal capsule of nude mice, Experimental groups were chosen so that grafted islets were exposed to either hyper- or normoglycemia or combinations of these for 4 or 6 wk, Grafts of normoglycemic recipients responded with an increased insulin release to a glucose stimulus during perfusi on, whereas grafts of hyperglycemic recipients failed to respond to gl ucose, The insulin content of the grafts in the latter groups was only 10% of those observed in controls. Recipients initially hyperglycemic (4 wk), followed by 2 wk of normoglycemia regained a normal graft ins ulin content, but a decreased insulin response to glucose remained. No ultrastructural signs of beta-cell damage were observed, with the exc eption of increased glycogen deposits in animals hyperglycemic at the time of killing. It is concluded that prolonged exposure to a diabetic environment induces a long-term secretory defect in human beta-cells, which is not dependent on the size of the islet insulin stores.