G. De Mattia

Reduction of oxidative stress by oral N-acetyl-L-cysteine treatment decreases plasma soluble vascular cell adhesion molecule-1 concentrations in non-obese, non-dyslipidaemic, normotensive, patients with non-insulin-dependent diabetes.

Summary To assess in vivo effects of antioxidants on vascular cell adhesion molecule (VCAM)-1 expression, circulating soluble VCAM-1 and intraerythrocytic reduced glutathione (GSH) and GSH disulphide (GSSG) concentrations were evaluated in non-insulin-dependent diabetic patients without complications (9 men, 6 women, 48 ± 6 years old) before and after 1 month of either oral N-acetyl-L-cysteine (1.200 mg/day) or placebo treatments, given in randomized, cross-over, double-blind fashion. Ten healthy subjects (7 men, 3 women, 52 ± 4 years old) served as control subjects. Baseline plasma VCAM-1 concentrations were higher (p = 0.007) in non-insulin-dependent diabetic patients (707.9 ± 52.5 ng/ml) than in control subjects (627.3 ± 84.6 ng/ml). Intraerythrocytic GSSG content was higher (non-insulin dependent diabetic patients: 0.618 ± 0.185 μmol/g Hb; control subjects: 0.352 ± 0.04 μmol/g Hb, p = 0.0002), whereas intraerythrocytic GSH concentrations were lower (p = 0.001) in non-insulin dependent diabetic patients (6.0 ± 0.7 μmol/g Hb) than in control subjects (7.1 ± 0.5 μmol/g Hb). The mean GSH:GSSG ratio was also lower (p = 0.0001) in the first (10.9 ± 4.5) than in the second group (20.2 ± 1.4). Circulating VCAM-1 and intraerythrocytic GSH concentrations were negatively correlated in non-insulin diabetic patients (r = 0.605, p = 0.01). Treatment with N-acetyl-L-cysteine decreased plasma VCAM-1 (p = 0.01) and intraerythrocytic GSSG (p = 0.006) but increased GSH concentrations (p = 0.04) and the GSH:GSSG ratio (p = 0.004) in non-insulin dependent diabetic patients. Our data indicate that the vascular endothelium is activated in non-insulin dependent diabetes. Antioxidant treatment counterbalanced such endothelial activation. Thus, antioxidant agents might protect against oxidant-related upregulation of endothelial adhesion molecules and slow down the progression of vascular damage in non-insulin dependent diabetes. [Diabetologia (1998) 41: 1392–1396]

Influence of reduced glutathione infusion on glucose metabolism in patients with non—insulin-dependent diabetes mellitus

To evaluate the relationship between oxidative stress and glucose metabolism, insulin sensitivity and intraerythrocytic reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio were measured in 10 non-insulin-dependent diabetes mellitus (NIDDM) patients and 10 healthy subjects before and after the intravenous administration of GSH. In particular, after baseline insulin sensitivity was assessed by a 2-hour euglycemic hyperinsulinemic clamp, either glutathione (1.35 g x m2 x min(-1)) or placebo (saline) were infused over a period of 1 hour. The same protocol was repeated at a 1-week interval, in cross-over, according to a randomized, single-blind design. In healthy subjects, baseline intraerythrocytic GSH/GSSG ratio (P < .0005) and total glucose uptake (P < .005) were significantly higher than in NIDDM patients. In the same subjects, GSH infusion significantly increased total glucose uptake (from 37.1 +/- 6.7 micromol kg(-1) x min(-1) to 39.5 +/- 7.7 micromol x kg(-1) x min(-1), P < .05), whereas saline infusion was completely ineffective. In addition, the mean intraerythrocytic GSH/GSSG ratio significantly increased after GSH infusion (from 21.0 +/- 0.9 to 24.7 +/- 1.3, P < .05). Similar findings were found in diabetic patients, in whom GSH infusion significantly increased both total glucose uptake (from 25.3 +/- 9.0 micromol x kg(-1) x min(-1) to 31.4 +/- 10.0 micromol x kg(-1) x min(-1), P < .001) and intraerythrocytic GSH/GSSG ratio (from 14.8 +/- 4.1 to 21.7 +/- 6.7, P < .01). Pooling diabetic patients and controls, significant correlations were found between intraerythrocytic GSH/GSSG ratio and total glucose uptake (r = .425, P < .05), as well as between increments of the same variables after GSH infusion (r = .518, P < .05). In conclusion, our data support the hypothesis that abnormal intracellular GSH redox status plays an important role in reducing insulin sensitivity in NIDDM patients. Accordingly, intravenous GSH infusion significantly increased both intraerythrocytic GSH/GSSG ratio and total glucose uptake in the same patients.

Double blind trial of nicotinamide in recent-onset IDDM (the IMDIAB III study)

SummaryNicotinamide has been recently introduced, in addition to intensive insulin therapy for patients with recent-onset insulin-dependent diabetes mellitus (IDDM) to protect beta cells from end-stage destruction. However, available data are conflicting. A double blind trial in 56 newly-diagnosed IDDM patients receiving nicotinamide for 12 months at a dose of 25 mg/kg body weight or placebo was designed in order to determine whether this treatment could improve the integrated parameters of metabolic control (insulin dose, glycated haemoglobin and C-peptide secretion) in the year after diagnosis. In addition to nicotinamide or placebo, patients received three to four insulin injections daily to optimize blood glucose levels. Patients treated with nicotinamide or placebo received similar doses of insulin during follow-up and 1 year after diagnosis with comparable glycated haemoglobin levels (6.7±1.8 % nicotinamide vs 7.1±0.6 % placebo). Basal and glucagon stimulated C-peptide secretion detectable at diagnosis were similarly preserved in the course of 12 months follow-up both in nicotinamide and placebo treated patients. No adverse effects were observed in patients receiving nicotinamide. When age at diagnosis was taken into account, nicotinamide treated older patients ( > 15 years of age) showed significantly higher stimulated C-peptide secretion than placebo treated patients (p < 0.02). These results suggest that nicotinamide can preserve and improve stimulated beta-cell function only in patients diagnosed after puberty. We conclude that in these patients nicotinamide can be added to insulin at the time of disease diagnosis to maintain and possibly improve residual beta-cell function. However, further studies on patients diagnosed after puberty are needed to confirm whether nicotinamide can be considered an additional tool to insulin in early-onset IDDM.

Gliclazide improves anti‐oxidant status and nitric oxide‐mediated vasodilation in Type 2 diabetes

Aims To evaluate the effects of gliclazide on oxidative status and vascular response to systemic administration of L‐arginine, the natural precursor of nitric oxide (NO), in Type 2 diabetic patients.

Endogenous Insulin Modulates Circulating Endothelin-1 Concentrations in Humans

OBJECTIVE To assess the effect of oral glucose loading on plasma endothelin-1 (ET-1) levels in humans. RESEARCH DESIGN AND METHODS A total of 75 g D-glucose was given orally to 14 nonobese nondiabetic essential hypertensive subjects (eight men and six women, mean age 43.1 ± 3.0 years) and eight normotensive subjects (four men and four women, mean age 45.2 ± 4.1 years). Blood samples for plasma ET-1 measurement were drawn every 30 min for 2 h and then at 180 and 240 min. RESULTS After glucose load, insulin increased more significantly in hypertensive subjects than in normotensive subjects at times 60 (P = 0.004) and 90 (P = 0.001) min. Glucose loading was followed by a mild but significant increase in circulating ET-1 levels in both groups (hypertensive subjects, from 0.87 ± 0.25 pg/ml at time 0 to 1.64 ± 0.33 pg/ml at 120 min and 1.74 ± 0.38 pg/ml at 180 min, P < 0.05; normotensive subjects, from 0.82 ± 0.38 pg/ml at time 0 to 1.42 ± 0.18 pg/ml at 180 min, P < 0.05). Whereas baseline ET-1 levels were similar between the two groups, postload ET-1 levels were higher in hypertensive subjects than in normotensive subjects (P = 0.003 at 120 min; P = 0.04 at 180 min). CONCLUSIONS This study indicates that significant changes in circulating ET-1 levels occur after oral glucose loading, probably due to a glucose-induced increment in endogenous insulin concentration.

Effect of aldose reductase inhibition on glutathione redox status in erythrocytes of diabetic patients

Diabetic patients undergo a chronic oxidative stress. This phenomenon is demonstrated by low levels of reduced glutathione (GSH) levels. The NADPH used by glutathione reductase for the reduction of oxidized glutathione (GSSG) to GSH is also used by aldose reductase for the reduction of glucose to sorbitol through the polyol pathway. The competition for NADPH could be responsible for the decreased glutathione levels found in non-insulin-dependent diabetic patients. For this purpose, we investigated the effect of polyol pathway inhibition on the glutathione redox status in these patients. We measured GSH and GSSG levels in erythrocytes of non-insulin-dependent diabetic patients (n = 15) before and after 1 week of treatment with placebo, followed by 1 week of treatment with an aldose reductase inhibitor (tolrestat 200 mg/dl). We found lower GSH levels (7.7 +/- 1.4 mumol/g hemoglobin [Hb]), higher GSSG levels (0.35 +/- 0.09 mumol/g Hb), and lower GSH/GSSG ratios (23.9 +/- 7.7) in diabetics compared with controls (n = 15; 9.8 +/- 0.8 mumol/g Hb, P < .001; 0.17 +/- 0.02, P < .001; and 58.3 +/- 9.1, P < .001, respectively). We did not demonstrate any statistical difference after 1 week of treatment with placebo. In contrast, the treatment with tolrestat induced a significant increase in GSH (8.9 +/- 0.7 mumol/g Hb, P < .01), a decrease in GSSG (0.25 +/- 0.06 mumol/g Hb, P < .02), and an increase in the GSH/GSSG ratio (37.3 +/- 8.4, P < .01). These data strongly support the hypothesis that the polyol pathway plays an important role in the impairment of the glutathione redox status in diabetic patients.

Effects of insulin on in vitro vascular cell adhesion molecule-1 expression and in vivo soluble VCAM-1 release

Aims/hypothesis. To evaluate the effects of insulin on vascular cell adhesion molecule-1 expression by cultured human vascular endothelial cells and soluble vascular cell adhesion molecule-1 release in vivo. Methods. Human vascular endothelial cells derived from umbilical cord veins were incubated with either insulin (from 10–6 to 10–9 mol/l) or tumour necrosis factor-α (5 ng/ml) for 6 to 24 h. Plasma soluble vascular cell adhesion molecule-1 concentrations were evaluated in 12 non-insulin-dependent diabetic patients (8 men, 4 women, mean age 47.1 ± 7.7 years) and 12 healthy volunteers matched for age, sex and weight (7 men, 5 women, mean age 42.2 ± 7.2 years) before and after a 2-h euglycaemic hyperinsulinaemic clamp. Results. Transcriptional activities of nuclear factor-ϰB luciferase and vascular adhesion molecule-1 luciferase statistically significantly increased after incubation with tumour necrosis factor-α. By contrast, a slight increment of nuclear factor-ϰB luciferase (mean: 1.8 ± 0.3 fold) but not of vascular cell adhesion molecule-1 luciferase transcriptional activities were detected in cells stimulated with insulin. Soluble vascular cell adhesion molecule-1 concentrations in cell supernatants increased after tumour necrosis factor-α but not insulin stimulation. In vivo, baseline plasma soluble vascular cell adhesion molecule-1 concentrations were higher (p = 0.03) in non-insulin-dependent patients (708.7 ± 97.4 μg/l) than controls (632.1 ± 65.2 μg/l) but were not related to fasting insulin concentrations and did not change during insulin infusion. Conclusion/interpretation. The increased concentrations of circulating soluble vascular cell adhesion molecule-1 indicates that the vascular endothelium is activated in non-insulin dependent diabetic patients. Our in vitro and in vivo findings show that vascular cell adhesion molecule-1 activation cannot be due to hyperinsulinaemia. [Diabetologia (1999) 42: 1235–1239]

Alrial Natriuretic Factor in Hypertensive and Normotensive Diabetic Patients

OBJECTIVE To evaluate plasma amai natriuretic factor (ANF) behavior in hypertensive patients with either insulin-dependent (type I) or non-insulin-dependent (type II) diabetes. RESEARCH DESIGN AND METHODS Plasma ANF levels were measured in euglycemic normotensive patients (n = 18) and hypertensive patients (n = 18), in diabetic normotensive patients (type I diabetes, n = 12; type II diabetes, n = 12), and in diabetic hypertensive patients (type I diabetes, n = 12; type II diabetes, n = 22). In all groups, plasma ANF levels were determined at the end of a normal NaCl diet period (120 mmol NaCl per day for 10 days) in both the supine and the upright positions. RESULTS Plasma ANF levels were significantly higher (P < 0.05) in hypertensive euglycemic patients (supine vs. upright: 13.4 ± 6.7 vs. 8.5 ± 4.3 fmol/ml) than in normotensive type I diabetic patients (supine vs. upright: 8.6 ± 2.2 vs. 5.9 ± 2.9 fmol/ml) but not in euglycemic normotensive subjects (supine vs. upright: 11.4 ± 5.1 vs. 7.6 ± 5.8 fmol/ml) and normotensive type II diabetic patients (supine vs. upright: 10.1 ±4.1 vs. 7.9 ±4.1 fmol/ml). Moreover, in the normotensive groups plasma ANF levels did not significantly differ among euglycemic type I and type II diabetic patients. However, the highest levels of plasma ANF were observed in hypertensive type II diabetic patients (supine vs. upright: 16.9 ± 7.4 fmol/ml [P < 0.01 vs. euglycemic normotensive subjects, P < 0.0001 vs. normotensive type I diabetic patients, P < 0.01 vs. hypertensive type I diabetic patients and normotensive type II diabetic patients] vs. 11.6 ± 2.9 fmol/ml [P < 0.005 vs. normotensive type I diabetic patients, P < 0.01 vs. hypertensive type I diabetic patients]). On the contrary, plasma ANF levels were higher (P < 0.05) in hypertensive type I diabetic patients (supine vs. upright: 10.8 ±1.9 vs. 6.4 ± 2.2 fmol/ml) compared with normotensive type I diabetic patients, but not with any other patient group. A significant correlation between supine ANF and insulin levels was found in both type II diabetic (r = 0.457; P < 0.05) and nondiabetic hypertensive patients (r = 0.716; P < 0.0001). CONCLUSIONS These findings indicate that circulating ANF levels are markedly elevated in type II diabetic patients affected by essential hypertension. On the contrary, plasma ANF levels are in the range of normality in normotensive type I and type II diabetic patients.

Circulating catecholamines and metabolic effects of captopril in NIDDM patients

OBJECTIVE To evaluate the effects of captopril on circulating catecholamine levels in NIDDM patients and the possible relationship between captopril-related changes in circulating catecholamine levels and insulin sensitivity. RESEARCH DESIGN AND METHODS Fourteen nonobese normotensive NIDDM men (aged 44.5 ± 5.1 years) underwent a 2-h euglycemic-hyperinsulinemic clamp (40 mU·m−2 · min−1). Baseline evaluation of insulin sensitivity was followed by the random assignment of each patient to either captopril or placebo treatment, according to a crossover double-blind design. Euglycemic-hyperinsulinemic clamp studies were then repeated for all patients after both placebo and captopril treatments. Plasma norepinephrine (NE) and epinephrine (E) levels were assessed before, during, and after each clamp. RESULTS Resulting data showed that plasma catecholamine levels increased during baseline euglycemic-hyperinsulinemic clamp (NE: +23.6% time 0 vs. time 120 min, P < 0.05; E: +24.8% time 0 vs. time 120 min, P < 0.05). Captopril treatment significantly increased total glucose uptake (from 19.0 ± 9.0 to 26.8 ± 10.1 mmol·kg−1 · min−1, P < 0.05) and reduced baseline plasma NE (P < 0.001) and E (P < 0.05) levels. However, the magnitude of the NE (+25.7% time 0 vs. time 120 min, P < 0.001) and E (+27.2% time 0 vs. time 120 min, P < 0.05) increments during euglycemic hyperinsulinemia were not affected by the drug. Percentage changes in the ratio of total body glucose uptake to circulating insulin levels and corresponding decrements of baseline plasma E levels after captopril therapy were negatively correlated (r = −0.57, P < 0.05). CONCLUSIONS The reduction of circulating catecholamines could contribute, at least in part, to the captopril-related amelioration of insulin sensitivity.

The effects of gliclazide on platelet function in patients with diabetes mellitus

Eighteen diabetic patients with abnormal platelet function were treated for 1 month with gliclazide (80 to 160 mg/day). Platelet aggregation, circulating beta-thromboglobulin levels and platelet malondialdehyde concentrations were significantly reduced after 30 (but not 15) days of treatment. Although fasting and post-prandial glycaemia significantly improved in these patients, similar changes in platelet function were noted in 5 other patients in whom glycaemia did not change. Gliclazide therapy, therefore, brought about an improvement in platelet function and a reduction activation in the thromboxane metabolic pathway, possibly by a direct on the platelets.