Effects of irbesartan on intracellular antioxidant enzyme expression and activity in adolescents and young adults with early diabetic angiopathy.
OBJECTIVE
Defective intracellular antioxidant enzyme production (IAP) has been demonstrated in adults with diabetic nephropathy. The objective of this study was to evaluate the effects of irbesartan, an angiotensin II receptor antagonist, on IAP in adolescents and young adults with type 1 diabetes and early signs of retinopathy and nephropathy.


METHODS
This prospective, matched case-control study was conducted between November 2001 and December 2002 among 14 type 1 diabetic patients with early signs of angiopathy (ages 14-21 years), 11 type 1 diabetic patients without angiopathy (ages 12-22 years), and 10 healthy volunteers (ages 16-22 years). Skin fibroblasts were obtained by skin biopsies from the anterior part of the forearm and cultured in Dulbecco's modified Eagle's medium. The activity and mRNA expression of CuZn superoxide dismutase (CuZnSOD), Mn superoxide dismutase (MnSOD), catalase (CAT), and glutathione peroxidase (GPX) were measured before and after 6 months of treatment with irbesartan (150 mg/day); on both occasions, antioxidant enzyme activity was evaluated at different glucose concentrations (5 and 22 mmol/l).


RESULTS
At a normal glucose concentration (5 mmol/l), the activity and mRNA expression of CuZnSOD (0.50 +/- 0.21 units/mg protein, 4.4 +/- 1.5 mRNA/glyceraldehyde-3-phosphate dehydrogenase), MnSOD (0.26 +/- 0.04 units/mg protein, 0.08 +/- 0.07 mRNA), CAT (0.32 +/- 0.08 units/mg protein, 4.8 +/- 1.3 mRNA), and GPX (0.53 +/- 0.09 units/mg protein, 2.2 +/- 0.9 mRNA) were not different among the three groups (only values of diabetic subjects with angiopathy are shown). At high glucose concentrations, the activity and mRNA expression of CuZnSOD increased similarly in all groups (diabetic subjects with angiopathy: 0.93 +/- 0.26 units/mg protein, 9.4 +/- 2.1 mRNA); that of CAT and GPX increased in only control subjects and diabetic subjects without angiopathy (diabetic subjects with angiopathy: 0.33 +/- 0.09 units/mg protein and 5.0 +/- 1.4 mRNA; 0.54 +/- 0.10 units/mg protein and 2.3 +/- 1.0 mRNA, respectively). MnSOD did not change in any group. Treatment with irbesartan in adolescents with diabetic angiopathy was able to restore CAT and GPX activity and mRNA expression after exposure to high glucose concentrations. Markers of oxidative stress (serum malondialdehyde, fluorescent products of lipid peroxidation, monocyte chemoattractant protein-1, and 8-isoprostanes prostaglandin F(2alpha)) were significantly reduced after treatment with irbesartan.


CONCLUSIONS
Adolescents and young adults with early signs of diabetic angiopathy have defective intracellular antioxidant enzyme production and activity. Treatment with irbesartan can substantially improve the activity and production of these enzymes in skin fibroblasts.
Department of Pediatrics, University of Chieti, Ospedale Policlinico, Via dei Vestini, 5, I-66100 Chieti, Italy. chiarelli@unich.it
Francesco
F
Chiarelli
Daniele
D
Di Marzio
Francesca
F
Santilli
Angelika
A
Mohn
Annalisa
A
Blasetti
Francesco
F
Cipollone
Andrea
A
Mezzetti
Alberto
A
Verrotti
D000293:Adolescent; D000328:Adult; D000419:Albuminuria; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001713:Biphenyl Compounds / Q000627:therapeutic use*; D001794:Blood Pressure; D016022:Case-Control Studies; D002374:Catalase / Q000235:genetics*; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology*; D003925:Diabetic Angiopathies / Q000188:drug therapy*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005919:Glomerular Filtration Rate; D005979:Glutathione Peroxidase / Q000235:genetics*; D006801:Humans; D000077405:Irbesartan; D015227:Lipid Peroxidation; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D013482:Superoxide Dismutase / Q000235:genetics*; D013777:Tetrazoles / Q000627:therapeutic use*
D000959:Antihypertensive Agents; D001713:Biphenyl Compounds; D012333:RNA, Messenger; D013777:Tetrazoles; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D000077405:Irbesartan