Endocrine Abstracts

Background and aim: The role of derangements of nitric oxide (NO) metabolism in the pathogenesis of complications of type 1 diabetes mellitus (T1D) is not sufficiently clear. There is little data on simultaneous measurements of NO metabolites nitrite and nitrate (NO₂/NO₃) in urine and serum in T1D. Data about the measurement of NO production by electronparamagnetic spectroscopy (EPR) in whole blood in T1D were never published. To fill this gap we have characterised NO production and NO₂/NO₃ concentration in the biological fluids of patients with and without complications of T1D.

Methods: Two hundred and seventy-one patients with T1D duration > 1 year and 69 healthy volunteers were included. NO₂/NO₃ was measured by Griess reaction. Production of NO in whole blood was detected by EPR spectroscopy. Statistical analysis was performed by programme R.

Results: In T1D group vs control subjects, blood NO was higher, but serum NO₂/NO₃ was lower. There was a trend of higher serum NO₂/NO₃ in patients with diabetic nephropathy and chronic kidney disease (CKD), with concentrations reaching those of healthy subjects. Diabetic retinopathy, diabetic polyneuropathy, cardiovascular disease and arterial hypertension did not cause further changes in serum NO₂/NO₃ and whole blood NO as compared to the median value of T1D patients. Urine NO₂/NO₃ was lower in patients with microvascular T1D complications compared with milder phenotypes. In T1D, estimated glomerular filtration rate (eGFR) correlated with urine NO₂/NO₃ and whole blood NO.

Conclusions: Whole blood NO, serum NO₂/NO₃ and urine NO₂/NO₃ are affected differently by T1D and its complications. Decreased NO₂/NO₃ urine, but not in serum, is a marker of microvascular complications of T1D.