Abstract
We studied the correlation between insulin resistance, measured by the steady state plasma glucose (SSPG), and either fasting plasma insulin (F-IRI) alone or combined with fasting plasma glucose (FPG) levels, examining the precise limits of these two indices.
We found a strong correlation between SSPG and F-IRI, F-IRI×FPG/405 (homeostatic model assessment of insulin resistance: HOMA-R) among the 63 cases with type 2 diabetes who were examined at Oita Prefectural Hospital using SSPG (vs F-IRI, r=0.286, p<0.05, vs HOMA-R, r=0.393, p<0.005). Although we found that F-IRI and HOMA-R had no correlation between pretreatment SSPG and F-IRI in subjects whose glucose toxicity was reduced through insulin or α-glucosidase inhibitor, we did find a correlation with HOMA-R (r=0.426, p<0.05). Following the reduction of glucose toxicity, we detected a correlation between both indices (vs F-IRI, r=0.524, p<0.01, vs HOMA-R, r=0.670, p<0.001). We then split subjects into 2 groups based on insulin secretory ability through glucagon tolerance testing and compared them. We found that while the group still retaining insulin secretory ability had a higher correlation (vs F-IRI, ρ=0.421, p<0.05, vs HOMA-R, ρ=0.584, p<0.005), no correlation was seen in the group with reduced insulin secretory ability. Although both F-IRI and HOMA-R are convenient indices of insulin resistance, HOMA-R appears to be the more reliable indicator, and the reliability of both indices is reduced among patients with reduced insulin secretion.
