Effect of insulin sensitivity on pulsatile insulin secretion

Objective: The aim of the study was to determine whether derangements in in sulin pulsatility are related to the presence of insulin resistance or whet her these changes occur only in non-insulin-dependent diabetes mellitus (NI DDM). Design and methods: The study included 26 obese, 11 NIDDM and 10 central su bjects. The obese group was divided into a low insulin (plasma insulin <20 mU/l, OLI, 14 subjects) and a high insulin (OHI, 12 subjects) group. For pu lsatility analysis blood was sampled every 2 min for 90 min. Pulsatility an alysis was carried out using the PulsDetekt program. The insulin secretion randomness was quantified using interpulse interval deviation (IpID) and ap proximate entropy (ApEn). ApEn and ApEn normalized by S.D. of the individua l insulin time series (nApEn) were calculated. Lower values of ApEn and IpI D indicate more regular secretion. Homeostasis model assessment (HOMA) was used to quantify insulin sensitivity. Results: Insulin pulses were significantly less regular in the OHI and the NIDDM groups compared with the control and the OLI groups (control: ApEn 0. 54 +/- 0.16, nApEn 0.69 +/- 0.19, TpID 2.53 +/- 0.99; OLT: ApEn 0.64 +/- 0. 12, nApEn 0.79 +/- 0.15, IpID 7.92 +/- 1.09; OHI: ApEn 0.88 +/- 0.07, nApEn 0.92 +/- 0.07, IpID 3.95 +/- 0.84: NIDDM: ApEn 0.92 +/- 0.16, nApEn 0.99 /- 0.09, IpID 4.41 +/- 0.53; means +/- S.D.). There was no difference in th e pulse regularity between the OHI and the NIDDM groups. Conclusions: Decrease in insulin sensitivity was correlated with the reduct ion of insulin secretion regularity Therefore irregular insulin secretion i s related to a reduction in insulin sensitivity, and it is not unique to NI DDM.