Background: Post-transplant diabetes mellitus is a known complication of steroid therapy in renal transplant recipients. Both insulin resistance and insulin deficiency have been shown to be necessary for development of post-transplant diabetes mellitus. It is not known whether recipients with impaired glucose tolerance have similar degree of insulin resistance or deficient insulin response as recipients with post-transplant diabetes mellitus.
Method: To address this question, we used an oral glucose tolerance test to categorize 46 renal transplant recipients on triple immunosuppressive medication to groups with normal glucose tolerance, impaired glucose tolerance or post-transplant diabetes mellitus. Insulin sensitivity was measured using a hyperinsulinaemic euglycaemic clamp. Insulin response was calculated from the increase in serum insulin concentration during the oral glucose tolerance test.
Results: Twenty-five were categorized to normal glucose tolerance, 15 to impaired glucose tolerance and six to post-transplant diabetes mellitus. There were no statistically significant differences between the groups regarding prednisolone dose, azathioprine dose, use of beta-blocker, age, gender, weight, waist-hip ratio, body mass index, donor source, smoking habits, or first-degree relatives with histories of diabetes mellitus. The impaired glucose tolerance and post-transplant diabetes mellitus groups showed a significant reduction in insulin-stimulated glucose disposal rate (mg/kg.min) compared to the normal glucose tolerance group (4.6 +/- 1.6 and 3.4 +/- 1.3 respectively vs 7.1 +/- 2.4, P < 0.05). The insulin response (picomol/l) was not different between the normal glucose tolerance and impaired glucose tolerance groups but was significantly reduced in the post-transplant diabetes mellitus group (448 +/- 310 and 450 +/- 291 respectively vs 170 +/- 128, P < 0.05).
Conclusion: Insulin resistance is a common denominator of post-transplant diabetes mellitus and impaired glucose tolerance in renal transplant recipients.