Oral L-arginine administration attenuates postprandial endothelial dysfunction in young healthy males.
BACKGROUND
Endothelial dysfunction is considered the earliest stage of atherosclerosis. Postprandial phase is associated with a transient impairment of endothelial function concomitantly with the triglyceride-rich lipoprotein increase. This phenomenon may be explained by the oxidative burden induced by triglyceride-rich lipoproteins, reducing nitric oxide bioavailability.


OBJECTIVE
To investigate the effect of a diet enriched with L-arginine, the substrate for nitric oxide synthesis on endothelial function in healthy volunteers.


METHODS
Endothelial function (expressed as flow-mediated vasodilation (FMV) of the brachial artery), total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, LDL-size, Lp (a) and reduced glutathione (GSH) were evaluated in seven healthy males (mean age 23 +/- 3 years) without cardiovascular risk factors. Measurements were made at baseline and 2, 4 and 6 h after a standardized oral fat load. L-arginine (6 g daily) was administered for 10 days. On the 11th day the oral fat load and the parameters examined previously at entry were repeated.


RESULTS
After the first oral fat load, FMV significantly decreased at 2 and 4 h, and overlapped with the basal levels at 6 h. After L-arginine treatment, FMV significantly decreased at 2 h and normalized after 4 and 6 h. Triglycerides increased at 2 and 4 h and decreased after 6 h in both sets of observations relating to before and after L-arginine administration. GSH dropped 2 h after the fat load, both before and after L-arginine. Before L-arginine, FMV exhibited a significant correlation with triglycerides (r= -0.426, P= 0.024) and GSH (r=0.48; P=0.009). After L-arginine, FMV was related to GSH (r=0.39; P=0.03) but not to triglycerides (r= -0.12; P=0.52).


CONCLUSIONS
Postprandial endothelial impairment is partly abolished by L-arginine administration. These data, which require confirmation, suggest the importance of dietary choice for atherosclerosis prevention even in young healthy subjects.
Marchesi
S
S
Department of Internal Medicine, Angiology and Atherosclerosis, University of Perugia, Italy. simonamarchesi@yahoo.it
Lupattelli
G
G
Siepi
D
D
Roscini
A R
AR
Vaudo
G
G
Sinzinger
H
H
Mannarino
E
E
D000328:Adult; D001120:Arginine / Q000008:administration & dosage* / Q000097:blood; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology*; D002318:Cardiovascular Diseases / Q000517:prevention & control; D004041:Dietary Fats / Q000008:administration & dosage; D019587:Dietary Supplements; D004730:Endothelium, Vascular / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology*; D005215:Fasting; D005978:Glutathione / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D008055:Lipids / Q000097:blood; D008297:Male; D019518:Postprandial Period; D012307:Risk Factors; D013997:Time Factors; D014463:Ultrasonography; D014664:Vasodilation / Q000187:drug effects
D004041:Dietary Fats; D007328:Insulin; D008055:Lipids; D001120:Arginine; D005978:Glutathione