Insulin treatment enhances expression of IGF-I in sural nerves of diabetic patients.
We studied the expression of insulin-like growth factor I (IGF-I) and its receptor in sural nerves from 8 diabetic patients divided into insulin-treated (IT) and non-insulin-treated (NIT) groups, compared with 5 patients with axonal neuropathies and 4 control patients (undergoing biopsies for diagnostic purposes). Insulin-like growth factor I mRNA levels did not differ in diabetic cases compared with control subjects. In sural nerves from IT patients and axonal neuropathies, IGF-I expression was higher than in NIT subjects and diagnostic controls. Changes in IGF-I receptor mRNA levels paralleled those of the ligand. Insulin-like growth factor I immunoreactivity was higher in nerves undergoing axonal degeneration and higher in IT than NIT diabetic patients and diagnostic controls. These findings suggest that insulin treatment increases IGF-I expression in diabetic nerves. Our data do not support the hypothesis of an absolute IGF-I deficiency in human diabetic neuropathy. A Schwann cell's incapacity to increase IGF-I expression after severe nerve damage, as happens in axonal neuropathies, may be a cofactor in the pathogenesis of diabetic neuropathy.
Grandis
M
M
Department of Neurological and Vision Sciences, University of Genoa, Via de Toni 5, 16132, Genoa, Italy. aschenone@neurologia.unige.it
Nobbio
L
L
Abbruzzese
M
M
Banchi
L
L
Minuto
F
F
Barreca
A
A
Garrone
S
S
Mancardi
G L
GL
Schenone
A
A
D000328:Adult; D000368:Aged; D003920:Diabetes Mellitus / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007328:Insulin / Q000627:therapeutic use*; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D008297:Male; D008875:Middle Aged; D016612:Paraffin Embedding; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013497:Sural Nerve / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology
D007328:Insulin; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1