Letters to the Editor

Abstract

The following is an abstract of the article discussed in the subsequent letter: Finegood, Diane T., and Dan Tzur. Reduced glucose effectiveness associated with reduced insulin release: an 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 (SG), based on the frequently sampled intravenous glucose tolerance test (SG FSIGT), 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 SG FSIGT with estimates based on a basal hormone replacement glucose clamp (SG BRCLAMP) and a basal hormone replacement glucose tolerance test (SG BRGTT) in normal control (CNTL, n = 12) and streptozotocin-treated dogs with normal fasting plasma glucose (STZ-Rx, n = 9). SG FSIGT was reduced in STZ-Rx compared with CNTL ( P < 0.05). However, neither SG BRCLAMP nor SG BRGTT was reduced in the STZ-Rx group ( P > 0.05). Comparison of protocols for each subject indicated that SG FSIGT was greater than either SG BRCLAMP or SG BRGTT in control ( P < 0.002) but not in STZ-Rx dogs ( P > 0.1). The relationship of SG FSIGT to insulin secretory function suggests that our previous conclusion that SG FSIGT 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 SG between subject groups with significantly different levels of insulin secretory function.