Reduced glucose effectiveness associated with reduced insulin release: An artifact of the minimal-model method

Reduced glucose effectiveness associated with reduced insulin release: artifact of the minimal-model method. Am. J. Physiol. 271 (Endocrinol. Metab. 34): E485-E495, 1996.-We previously demonstrated that minimal model-derived estimates of glucose effectiveness (S-G), based on the frequently sampled intravenous glucose tolerance test (S-GFSIGT), were reduced in islet-transplanted or streptozotocin-treated dogs and in patients with insulin-dependent diabetes mellitus. To ascertain the validity of our observations, we compared S-GFSIGT With estimates based on a basal hormone replacement glucose clamp (S-GBRCLAMP) and a basal hormone replacement glucose tolerance test (S-GBRGTT) in normal control (CNTL, n = 12) and streptozotocin-treated dogs with normal fasting plasma glucose (STZ-Rx, n = 9). S-GFSIGT was reduced in STZ-Rx compared with CNTL (P < 0.05). However, neither S-GBRCLAMP nor S-GBRGTT was reduced in the STZ-Rx group (P > 0.05). Comparison of protocols for each subject indicated that S-GFSIGT was greater than either S-GBRCLAMP or S-GBRGTT in control (P < 0.002) but not in STZ-Rx dogs (P > 0.1). The relationship of S-GFSIGT to insulin secretory function suggests that our previous conclusion that S-GFSIGT was reduced in subjects with limited insulin release may be an artifact of the minimal-model method. Our results suggest that caution must be exercised in the interpretation of differences in minimal-model estimates of S-G between subject groups with significantly different levels of insulin secretory function.