The IGF-system is not affected by a twofold change in protein intake in patients with type 1 diabetes.
OBJECTIVE
In type 1 diabetes the circulating IGF-system is altered with low IGF-I and changes in levels of IGF-binding proteins (IGFBPs) which may be of importance for the development of diabetes complications. Our aim was to study if IGF-I, as supported by experimental data in animals, can be affected by dietary protein intake.


METHODS
Twelve patients with type 1 diabetes, age 37.5+/-10.0 years (mean+/-SD), diabetes duration 20.1+/-9.3 years and HbA1c 6.3+/-0.6% were allocated to isocaloric diets with either low normal protein content (LNP), (10 E%; 0.9 g protein/kg body weight) or high normal protein content (HNP) (20 E%; 1.8 g protein/kg body weight) in an open randomised cross-over study. Each diet was taken for 10 days with a wash-out period of 11 days in between. Circulating levels of total and free IGF-I and -II, IGFBP-1, -2 and -3 and GH-binding protein (GHBP) as well as ghrelin were measured with validated in-house immunoassays.


RESULTS
At day 10, urinary urea excretion was 320+/-75 mmol/24h during LNP diet compared with 654+/-159 mmol/24h during HNP diet (p<0.001). There were no changes in body weight or glycaemic control between the diets. Fasting levels of total IGF-I were 121+/-33 microg/L after LNP and 117+/-28 microg/L after HNP diet (ns) and the corresponding concentrations of IGFBP-1 were 142(141) and 132(157)mug/L [median (IQR)] (ns). There were no differences in plasma concentrations of total IGF-II, free IGF-I and -II, IGFBP-3, GHBP and ghrelin, whereas a small difference was found for IGFBP-2 (302+/-97 vs. 263+/-66 microg/L; LNP vs. HNP; p<0.04).


CONCLUSIONS
A twofold change of the dietary protein intake does not influence the altered circulating IGF-system in type 1 diabetes. In order to affect the IGF-system other interventions must be used.
Hedman
Christina A
CA
Division of Internal Medicine, Department of Medicine and Care, Diabetes Research Centre, Faculty of Health Sciences, SE-581 83 Linköping University, Linköping, Sweden. christina.hedman@lio.se
Frystyk
Jan
J
Fridell
Karin
K
Jönsson
Anna
A
Flyvbjerg
Allan
A
Lindström
Torbjörn
T
Arnqvist
Hans J
HJ
D000328:Adult; D001827:Body Height; D001835:Body Weight; D002352:Carrier Proteins / Q000097:blood; D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000628:therapy; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D054439:Ghrelin; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D036361:Peptide Hormones / Q000097:blood; D011257:Pregnancy Proteins / Q000097:blood; D011863:Radioimmunoassay
D002352:Carrier Proteins; D004044:Dietary Proteins; D054439:Ghrelin; C032231:IGFBP1 protein, human; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D036361:Peptide Hormones; D011257:Pregnancy Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; C051815:somatotropin-binding protein