[Blood levels of true insulin and immunoreactive insulin in evaluating beta-cell function with arginine stimulation test].
To investigate the difference between serum true insulin (TI) and immunoreactive insulin (IRI) in evaluating islet beta-cell function and insulin resistance.



The arginine stimulation test was performed in 141 individuals, including 35 with normal glucose tolerance (NGT) and 106 with type 2 diabetes (T2DM). Plasma glucose (PG), TI, IRI and proinsulin (PI) levels were measured; the incremental value of TI/PG, (TI+PI)/PG and IRI/PG (delta TI/PG, delta(TI+PI)/PG and deltaIRI/PG) and the area under curve of TI/PG, (TI+PI)/PG and IRI/PG (AUC [TI/PG], AUC[(TI+PI)/PG] and AUC [IRI/PG]) after arginine stimulation were calculated to evaluate beta-cell function.



There were positive correlations of delta TI/PG with delta (TI+PI)/PG and delta IRI/PG in both NGT and T2DM patients (r=0.68 - 0.99, P<0.01). The similar correlations of AUC [TI/PG] with AUC [(TI+PI)/PG] and AUC [IRI/PG] were also shown (r=0.62 - 0.99, P<0.01). delta TI/PG was correlated with AUC [TI/PG] in two groups (NGT r=0.96, T2DM r=0.82, P<0.01). HOMA-IRTI, HOMA-IR(TI+PI) and HOMA-IRIRI in T2DM were higher than those in NGT (P<0.01). After arginine stimulation T2DM subjects mainly presented insulin resistance and decreased insulin secretion.



The determination of TI may be more accurate than IRI in evaluating beta-cell function and insulin resistance.
Ma
Xiao-jing
XJ
Department of Endocrinology and Metabolism, Shanghai Diabetes Institute, Sixth People's Hospital of Shanghai Jiaotong University, Shanghai 200233, China.
Jia
Wei-ping
WP
Zhou
Jian
J
Lu
Hui-juan
HJ
Lu
Jun-qian
JQ
Wu
Song-hua
SH
D000328:Adult; D000368:Aged; D001120:Arginine / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood* / Q000276:immunology; D007333:Insulin Resistance; D050417:Insulin-Secreting Cells / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011384:Proinsulin / Q000097:blood
D001786:Blood Glucose; D007328:Insulin; D011384:Proinsulin; D001120:Arginine