Study on the insulin resistance and β-cell function in individuals with normal and those with abnormal glucose metabolism

Objective: To study the insulin resistance and β-cell function in individuals with normal glucose tolerance (NGT) and those with glucose metabolism dysfunction. Methods: Insulin resistance and β-cell function were studied with oral glucose tolerance test and the following parameters: 2h insulin/2h plasma glucose (2hIns/2hPG), insulin resistance index (IRI), insulin sensitivity index (ISI) and 30 min net increment of insulin/30min net increment of glucose (AI30/AG30) were examined in 44 individuals with NGT, 45 subjects with impaired glucose tolerance (IGT), 66 recently diagnosed diabetics and 175 well-established diabetics. Results: The insulin resistance index (IRI) increased progressively from that in NGT individuals to that in recently diabetics (20 ± 1. 5→3.1 ± 1.6→4.1 ± 1.8), while the 2hIns/2hPG, ΔI30/ΔG30 and ISI decreased progressively with significant differences between those in successive groups (P<0.01). In well-establised diabetics, the IRI kept stable but the ΔI30/ΔG30 and ISI kept decreasing (values in patients with disease history less than 3 yrs vs those in patients with disease over 3yrs: 2.9 ± 3.2 vs 2.4 + 2.3, 30.2 + 1.1 vs 23.4 ± 2.3, P<0.01). In multiple regression display, Sex, 2hIns/2hPG and ΔI30/ΔG30 were significantly correlated with ISI (F =96.3, 58.4 and 47.5 respectively). For principal component analysis display, the cumulative contribution rate of four parameters (2hIns/2hPG, ISI, ΔI30/ΔG30 and 2h C-peptide) exceeded 85% (86.5%). Conclusion: As the dysfunction of glucose metabolism proceeded from IGT to well established diabetes, the IR increased first with decrease of β-cell secretion followed. The parameters 2hIns/2hPG, ISI, 2h C-peptide ΔI30/ΔG30 were especially useful for the investigation . (authors)