Nitrite plasma levels in type 1 and 2 diabetics with and without complications

The authors thought it interesting to examine the interrelationship between nitric oxide and diabetes mellitus by the determination of the nitrite plasma levels, stable end-products of nitric oxide, in various clinical patterns of diabetes mellitus.

Our series consisted of 161 female subjects (mean age 54 +/- 7 years, disease duration 5 +/- 3 months) subdivided into: a) 13 patients suffering from insulin-dependent diabetes (IDDM) without clinical and instrumental signs of micro- and macroangiopathy; b) 148 suffering from non insulin-dependent diabetes mellitus (NIDDM) of whom: 1) 52 without vascular complications (28 normal weight, BMI < 25, and 24 obese, BMI > 30); 2) 40 with clinical and instrumental signs of non hypertensive coronary heart disease (CHD); 3) 25 with CHD and hypertension (arterial blood pressure over 160/95 mmHg); 4) 31 with hypercholesterolemia (values over 250 mg/dl). All patients were examined in good glycometabolic conditions reached by oral hypoglycemiant (12 cases) or insulin (149 cases) treatment. As normal control 37 female subjects (mean age 48 +/- 7) without internistic diseases were considered. For each sample we determined the plasma levels of nitrites by the Gutman and Hollywood method.

Almost similar nitrite plasma levels in IDDM (17 +/- 0.5 mumol/L) and normal controls (17 +/- 0.2 mumol/L) were found; in non complicated non obese NIDDM a not significantly elevated value (21 +/- 0.8 mumol/L) as compared with the IDDM and control group was found; the obese NIDDM patients showed a value (18 +/- 0.4 mumol/L) not significantly different in comparison with the non obese NIDDM group. In the NIDDM group with non hypertensive CHD) the nitrite value was almost similar (20 +/- 0.5 mumol/L) to the corresponding group without vascular complications. In the patients with CHD and hypertension the nitrite level was superimposable (20 +/- 0.7 mumol/L) on the one recorded in NIDDM patients without vascular complications and in those with CHD without hypertension. In NIDDM patients with hypercholesterolemia the mean nitrite value was sharply elevated (24 +/- 0.8 mumol/L); the difference between this group and those of non hypercholesterolemic, non obese, obese and CHD (with or without hypertension) patients was significant (p < 0.05).

It is conceivable that diabetes mellitus per se causes a tendential not significant increase of NO production in comparison with normal controls; some factors such as blood pressure, overweight, disease duration, therapeutic treatment and coronary complications appear not to influence NO production. In hypercholesterolemic diabetic patients the nitrite enhanced level in plasma might mean a compensatory response to a continuous inactivation of NO involved in a protective competition towards damaging factors and chiefly against oxidised LDL.