The insulin secretion-sensitivity index-2 (ISSI-2) and the measurement of beta-cell function in women with gestational diabetes

Ravi Retnakaran
2010 Endocrine journal  
In their recent report on beta-cell dysfunction in Asian women with gestational diabetes (GDM) [1], Saisho and colleagues assess beta-cell function from the oral glucose tolerance test (OGTT) using a construct defined as the product of (i) insulin secretion, measured by the ratio of the area-under-the-insulincurve to the area-under-the-glucose curve (AUC ins/glu ), and (ii) insulin sensitivity, measured by the IS OGTT index of Matsuda and DeFronzo. They present a graphical representation of the
more » ... hyperbolic relationship between AUC ins/glu and IS OGTT , and describe the product of these two measures as the disposition index. There are several points that should be recognized with respect to this measure of beta-cell function. Firstly, it should be noted that a graphical presentation alone is not sufficient to establish a hyperbolic relationship between a measure of insulin secretion and a measure of insulin sensitivity. Instead, the confirmation of such a hyperbolic relationship requires its formal mathematical demonstration, as discussed in reference 18 from the report by Saisho et al. Indeed, the formal mathematical confirmation of a rectangular hyperbolic relationship between AUC ins/glu and IS OGTT was previously demonstrated in that reference [2] . Secondly, based on that demonstration, we introduced the product of AUC ins/glu and IS OGTT as a measure of beta-cell com-pensation that can be obtained from the OGTT and that is analogous to the disposition index derived from the intravenous glucose tolerance test (ivGTT). This product, which is called the Insulin Secretion-Sensitivity Index-2 (ISSI-2), has since been validated against the actual disposition index from the ivGTT [3] and used as an OGTT-based measure of beta-cell function in a series of publications, a few of which are cited here [3] [4] [5] . Finally, it should be recognized that ISSI-2 has previously been used to demonstrate beta-cell dysfunction in women with GDM, as compared to their peers, both during pregnancy [4] and in the first year postpartum [5]. These published data are thus supportive of the findings in Asian women reported by Saisho et al [1], albeit under the established name (ISSI-2) for the validated OGTT-based measure of beta-cell function used in the latter report. References 1. Saisho Y, Miyakoshi K, Tanaka M, Shimada A, Ikenoue S, Kadohira I, Yoshimura Y, Itoh H (2010) Beta cell dysfunction and its clinical significance in gestational diabetes. Endocr J: E-pub ahead of print Sep. 14; doi: 10.1507/endocrj.K10E-231. 2. Retnakaran R, Shen S, Hanley AJ, Vuksan V, Hamilton JK, Zinman B (2008) Hyperbolic relationship between insulin secretion and sensitivity on oral glucose tolerance test. Obesity 16(8):1901-1907. 3. Retnakaran R, Qi Y, Goran M, Hamilton J (2009) Evaluation of proposed oral disposition index measures in relation to the actual disposition index. Diabet Med 26: 1198-1203. 4. Retnakaran R, Qi Y, Sermer M, Connelly PW, Zinman B, Hanley AJ (2009) Comparison of National Diabetes Data Group and American Diabetes Association criteria for gestational diabetes in their identification of postpartum risk of glucose intolerance. Diabetes Res Clin Pract 85(1): 40-46. 5. Retnakaran R, Qi Y, Sermer M, Connelly PW, Hanley AJ, Zinman B (2010) Beta-cell function declines within the first year postpartum in women with recent glucose intolerance in pregnancy. Diabetes Care 33(8): 1798-1804.
doi:10.1507/endocrj.k10e-279 pmid:20972350 fatcat:rzxwhto57raeplb6ewgxwjmw5e