Long-term repeatability of measures of early insulin secretion derived from an intravenous glucose tolerance test and conversion from impaired glucose tolerance to diabetes

Abstract

Aim. We assessed the long-term repeatability of the acute insulin response (AIR) and sensitivity index (S_I) derived from the frequently sampled intravenous glucose tolerance test (FSIGT).

Methods. An FSIGT was performed in 20 women who participated in a 6.5-month rye- and wheat-bread intervention trial, 70 men and women with impaired fasting glycaemia (IFG) or impaired glucose tolerance (IGT) who participated in the Genobin study, and 81 men and women with IGT who participated in the Finnish Diabetes Prevention Study (DPS).

Results. The correlation of AIR and S_I at base-line with respective values after the 6.5–8.5-month trials was 0.86–0.88 and 0.71–0.84, and before and after 4 years in the DPS substudy, 0.86 and 0.53. In multivariate analyses, AIR (relative risk for a 1-SD change, 0.67; 95% confidence intervals 0.46–0.97) predicted the conversion from IGT to diabetes in the DPS substudy.

Conclusion. AIR is highly repeatable even after 4 years of follow-up. The long-term repeatability of S_I is moderate. Our findings emphasize the importance of impaired early insulin secretion in the transition from IGT to diabetes, and the high degree of tracking of measures of early insulin secretion derived from the FSIGT.

• Impaired fasting glucose
• impaired glucose tolerance
• insulin secretion
• insulin sensitivity
• type 2 diabetes mellitus

Acknowledgements

This work was supported by grants from the Academy of Finland (40758 to M.U., 46558 to J.T., 209445 M.K. and 104943 to R.R.), the EVO-fund of the Kuopio University Hospital (no. 5106 to M.U.), the Finnish Diabetes Foundation, the Ministry of Education of Finland, the Diabetes Research foundation, and the Technology Development Center of Finland. Fazer Bakeries Ltd and Vaasan & Vaasan Oy provided breads for the rye-wheat intervention. We also thank the staff of the Department of Clinical Nutrition, University of Kuopio, for their skill in carrying out the intravenous glucose tolerance tests and other work in this study. None of the authors have competing interests related to this study.