Increased 24 h mean insulin-like growth factor binding protein-3 proteolytic activity in pubertal type 1 diabetic boys.
Hyperglycaemia and increased variability of blood glucose in pubertal children with type 1 diabetes may be related to increased growth hormone (GH) secretion and insulin resistance. The role of changes in insulin-like growth factor-I (IGF-I) bioavailability for the glycaemic control in these patients has not been completely elucidated. In particular, the possible role of increased IGF binding protein-3 (IGFBP-3) proteolysis reported in other insulin resistant states awaits further characterization. The aims of this study were to assess if hyperglycaemia in children with type 1 diabetes was associated with changes in free dissociable IGF-I (fdIGF-I) and IGF binding protein-3 protease activity (IGFBP-3-PA) and if increased insulin resistance during puberty was associated with changes in IGFBP-3-PA in healthy and diabetic children. In diabetic boys in the period of maximal linear growth (Tanner stage 3, n = 5), the mean level and the variability of IGFBP-3-PA, determined every second hour throughout 24 h, were significantly higher both compared to postpubertal diabetic boys (n = 6; P = 0.003 and P = 0.001, respectively), and to age matched healthy boys (n = 4; P = 0.006 and P < 0.001 respectively). This activation of IGFBP-3-PA was most prominent during the day time. The mean 24 h blood glucose level (determined hourly) was the only parameter studied that significantly predicted the changes in mean 24 h IGFBP-3-PA in the diabetes group. The mean 24 h concentrations of fdIGF-I were decreased in the diabetic boys compared to the healthy controls but statistical significance was only achieved in Tanner Stage 5 (p = 0.03). We speculate that the elevated levels of IGFBP-3-PA in Tanner 3 diabetic boys are related to deteriorated glucose homeostasis and that it may be a compensatory mechanism to attenuate the decrease in fdIGF-I in order to partly restore insulin sensitivity and glycemic control.
Zachrisson
I
I
Astrid Lindgren Children's Hospital, Karolinska Hospital and Institute, Stockholm, Sweden. ingmar.zachrisson@ks.se
Brismar
K
K
Carlsson-Skwirut
C
C
Dahlquist
G
G
Wallensteen
M
M
Bang
P
P
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D016022:Case-Control Studies; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D006801:Humans; D007328:Insulin / Q000627:therapeutic use; D007333:Insulin Resistance; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I