Role of insulin-like growth factor (IGF)-1 in the modulation of renal haemodynamics in Type I diabetic patients.
OBJECTIVE
We investigated in normotensive Type I (insulin-dependent) diabetic patients with normoalbuminuria the role of growth hormone-induced IGF-1 in the modulation of renal haemodynamics.


METHODS
We measured glomerular filtration (GFR) and renal plasma flow (RPF) at baseline and at 24 h after injection of different doses of growth hormone (0.1, 0.2, 0.4 U x kg(-1) x body weight(-1) in six patients with normal GFR under a euglycaemic clamp. We also examined a 24 h profile of plasma growth hormone and IGF-1 during usual insulin therapy in two other groups each with seven patients with a lower (from 93 to 114 ml x min(-1) x (1.73 m2)(-1) and higher (from 121 to 146 ml min(-1) x (1.73 m2)(-1) GFR.


RESULTS
Plasma growth hormone concentrations peaked 2 h after its injection and plasma concentrations of IGF-1 peaked about 24 h after the growth hormone injection. There was a significant increase in GFR and RPF 24 h after the highest dose of the growth hormone injection (corresponding to the highest IGF-1 concentration), from baseline values of 115 +/- 24 and 536 +/- 141 ml x min(-1) x (1.73 m2)(-1) to 160 +/- 33 and 657 +/- 137 ml x min(-1) x (1.73 m2)(-1), respectively (p < 0.01 for GFR and p < 0.05 for RPF). No differences were observed in the 24 h profile of growth hormone and IGF-1 plasma concentrations between the two groups; growth hormone and IGF-1 concentrations were lower than those obtained after the injection of 0.4 U x kg(-1) x body weight(-1) of growth hormone.


CONCLUSIONS
These results show that pharmacological growth hormone-induced IGF-1 concentrations are required to modify renal haemodynamics in Type I diabetic patients and suggest that, under the "physiological" conditions of diabetes, IGF-1 has no role as a mediator of glomerular hyperfiltration.
Bacci
S
S
Division and Research Unit of Endocrinology, Scientific Institute Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy.
De Cosmo
S
S
Garruba
M
M
Placentino
G
G
Liuzzi
A
A
Barbano
F
F
Di Giorgio
A
A
Trischitta
V
V
Viberti
G C
GC
D000328:Adult; D001794:Blood Pressure; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D019382:Human Growth Hormone / Q000097:blood / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000627:therapeutic use; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*
D007328:Insulin; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I