Impact of renal transplantation on glucose tolerance in Japanese recipients with impaired glucose tolerance.

AIMS: To investigate changes in glucose tolerance, insulin secretion and insulin sensitivity in Japanese recipients before and 1 year after renal transplantation.

METHODS: We conducted a study of Japanese recipients without diabetes who underwent renal transplantation at Hokkaido University Hospital. A 75-g oral glucose tolerance test was performed before and 1 year after renal transplantation in these recipients. Insulin sensitivity was estimated using the Matsuda index and homeostasis model assessment of insulin resistance (HOMA-IR). Insulin secretion was evaluated based on the insulin secretion sensitivity index-2 (ISSI-2).

RESULTS: Of the 62 renal transplant recipients, 31 were diagnosed as having impaired glucose tolerance before transplantation. Among these 31 recipients, after 1 year, four had developed new-onset diabetes after transplantation, and nine had impaired glucose tolerance. Unexpectedly, 18 changed from impaired to normal glucose tolerance. When these recipients with impaired glucose tolerance were classified into a non-amelioration group and an amelioration group, the ISSI-2 was significantly reduced, with no significant changes in the Matsuda index or HOMA-IR, in the non-amelioration group 1 year after renal transplantation. By contrast, ISSI-2 and Matsuda index values were significantly increased, with no significant changes in HOMA-IR values in the amelioration group.

CONCLUSIONS: More than half of Japanese renal transplant recipients with impaired glucose tolerance had normal glucose tolerance 1 year after renal transplantation. These results suggest that an increase in insulin secretion and whole insulin sensitivity was associated with improvement in glucose tolerance in these recipients.