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Although hydrogen peroxide (H(2)O(2)) induces proliferation of vascular smooth muscle cells, its role in endothelial cell proliferation is unclear. Our aim was to study the role of hydrogen peroxide in endothelial cell proliferation by overexpressing catalase. Human aortic endothelial cells were transduced with adenoviral vectors encoding beta-galactosidase (Adbetagal) or catalase (AdCat) or were exposed to diluent alone (control). Transgene expression was demonstrated by beta-galactosidase staining, Western analysis, and significantly increased enzyme activity in AdCat-transduced cells. Overexpression of catalase decreased DNA synthesis in AdCat compared with control and Adbetagal-transduced cells (536.8 +/- 31 vs. 1,875.1 +/- 132.9 vs. 1,347.5 +/- 93.7 dpm/well, respectively; P < 0.05 vs. control and Adbetagal). Six days after transduction with AdCat (multiplicity of infection = 50), cell numbers were significantly reduced (AdCat: 38 +/- 1.8% of cell counts in control, P < 0.05; and 45 +/- 2% of cell count in Adbetagal, P < 0.05). Incubation with aminotriazole 10 mmol/l, an inhibitor of catalase, prevented this effect. The number of apoptotic cells was increased one- and threefold 2 and 4 days, respectively, after transduction with AdCat. Exogenous administration of low concentrations of H(2)O(2) (50 microM) significantly increased cell proliferation, whereas it was inhibited by higher concentrations. These results suggest that H(2)O(2) is an important modulator of endothelial cell proliferation.

To evaluate the role of blood cells in interorgan amino acid transport and in the estimates of regional protein turnover, we studied the effects of plasma vs. whole blood sampling on regional leucine kinetics in postabsorptive humans. Studies were carried out by combining the arteriovenous difference technique with the measurement of [14C]- and [15N]leucine isotope exchange across the human kidney, the splanchnic area, and the leg. In the kidney, whole blood-derived rates of leucine-carbon appearance, disappearance, and net balance (NB) were greater (by 3-15 times; P < 0.035) than those calculated in plasma. In addition, the net leucine-carbon (i.e., protein) balance across the kidney was negative in whole blood (-5.6 +/- 1.3 micromol/min x 1.73 m2, P < 0.01 vs. 0) but neutral in plasma [-0.24 +/- 1.33, P = not significant from 0; P < 0.01 vs. whole blood]. A net leucine transport out of renal cells was shown in blood but not in plasma. In contrast, rates of leucine-carbon appearance, disappearance, NB, and net transport, in both the splanchnic area and the leg, were similar in whole blood and plasma. These data suggest that blood cells play a key role in leucine transport out of the kidney and, consequently, in the leucine-derived estimates of renal protein degradation and NB, which is at variance with what is observed across the splanchnic organs or the leg. These data also emphasize the need for complete whole blood arteriovenous measurements to accurately estimate protein turnover across the kidney.

Background: Alcohol may impair protein turnover and insulin sensitivity in vivo., Objective: The acute effects of moderate wine intake on amino acid kinetics and on the fractional synthetic rate (FSR) of albumin and fibrinogen in patients with type 1 diabetes were studied., Design: Six patients with type 1 diabetes ingested an elementary mixed meal (46 kJ/kg) over 4 h, first without and 3 mo later with approximately 300 mL red wine. Postprandial glucose concentrations were maintained at <10 mmol/L., Results: Postprandially, the FSR of fibrinogen was approximately 30% greater (21.5 +/- 6.6% compared with 14.1 +/- 3.6% of pool/d; P < 0.01) and glucagon concentrations were approximately 40% greater (103 +/- 20 compared with 61 +/- 13 ng/L; P < 0.015) with wine than without wine. However, the FSR of albumin and the rates of appearance of total and endogenous phenylalanine and leucine were not significantly different between treatments. First-pass splanchnic uptake (in micromol*kg(-1)*min(-1)) of dietary phenylalanine (0.22 +/- 0.02 compared with 0.19 +/- 0.02) and leucine (0.25 +/- 0.04 compared with 0.14 +/- 0.02) were greater with wine (P < 0.05), whereas dietary phenylalanine oxidation was lower with wine, by approximately 25% (0.10 +/- 0.02 compared with 0.14 +/- 0.01 micromol.kg(-1).min(-1); P < 0.05). Selected amino acid concentrations were significantly lower but glutamate concentrations were significantly higher with wine., Conclusions: In insulin-infused patients with type 1 diabetes, moderate wine intake with a meal resulted in 1) a higher fibrinogen FSR, glucagon concentration, and first-pass splanchnic uptake of leucine and phenylalanine; 2) lower dietary phenylalanine oxidation; 3) selective changes in plasma amino acid concentrations; 4) and no impairment in endogenous proteolysis and albumin synthesis.