Takahide Nomura

Background: Tetrahydrobiopterin (BH4) is an essential cofactor of nitric oxide synthase, and GTP cyclohydrolase I (GCHI) is a rate-limiting enzyme in the biosynthesis of BH4. The expression of inducible nitric oxide synthase (NOS) was earlier demonstrated in the ventricles of patients with dilated cardiomyopathy (DCM) although that of GCHI was not clarified. The present study was designed to determine the GCHI mRNA expression as well as to confirm NOS mRNA expression in endomyocardial biopsy specimens from patients with DCM. Methods: Clinical details were assessed in 19 patients with DCM and in 9 control subjects. The real-time reverse transcription polymerase chain reaction (PCR) was performed on total RNA extracted from endomyocardial biopsy specimens. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA was quantified for use as an internal control. Results: iNOS/GAPDH for the DCM samples was 4.8-fold greater than that for the control ones (P < 0.01), whereas the GCHI/GAPDH for the DCM samples was reduced to 31.1% of the control (P < 0.05). Conclusions: The increased expression of NOS mRNA was confirmed in endomyocardial biopsy specimens from patients with DCM. The GCHI mRNA level was suppressed in these specimens. (C) 2004 Elsevier B.V. All rights reserved.

Although endothelial dysfunction deteriorates diabetic angiopathy, the mechanisms are obscure. We revealed that high glucose augmented eNOS through stimulation of eNOS mRNA in cultured BAECs. NO was decreased and O-2(-) was increased simultaneously. NOS inhibitor, inhibited O-2(-) release, so did NADPH oxidase inhibitor. The effects were synergistic. Both intracellular BH4 level and GTPCH1 activity were decreased by high glucose, in line with decrease of GTPCH1 mRNA. HMG-CoA, reductase inhibitor, atorvastatin increased GTPCH1 mRNA and activity, and BH4 level. Conclusively, high glucose leads to eNOS dysfunction by inhibiting BH4 synthesis and atorvastatin stimulate BH4 synthesis directly, and it may work as atherogenic process. (C) 2004 Elsevier Inc. All rights reserved.