Short-term oral folic acid supplementation enhances endothelial function in patients with type 2 diabetes.
BACKGROUND
Endothelial dysfunction and arterial stiffening are commonly observed in type 2 diabetes. These abnormalities might be secondary to increased plasma concentrations of homocysteine. We sought to determine whether oral folic acid supplementation, by lowering homocysteine levels, enhanced endothelial function and reduced arterial stiffness in type 2 diabetes.


METHODS
Twenty-six type 2 diabetic patients (age 56.5 +/- 0.9 years, diabetes duration 5.5 +/- 0.6 years, means +/- SEM) with no history of cardiovascular disease received 5 mg/d of oral folic acid or placebo for 4 weeks in a double-blind, randomized controlled, parallel group trial. The following parameters were measured before and after treatment: 1) endothelial function (forearm arterial blood flow during local intra-arterial administration of endothelium-dependent [acetylcholine 1.5, 4.5, and 15 microg/min] and endothelium-independent [sodium nitroprusside 1, 2, and 4 microg/min] vasodilators); and 2) carotid-radial and carotid-femoral pulse wave velocity.


RESULTS
Folic acid reduced plasma homocysteine concentrations and enhanced endothelium-dependent vasodilatation during each acetylcholine infusion rate (mean and 95% confidence interval post versus pretreatment differences in forearm arterial blood flow ratio between the infused and control arm +0.19 (0.03-0.35), P < .01; +0.39 (0.02-0.81), P < .05; and +0.40 (0.09-0.89), P < .05, respectively). Endothelium-independent vasodilatation and pulse wave velocity were not affected. No significant changes in forearm arterial blood flow and pulse wave velocity were observed in the placebo group. Multiple regression analysis showed that changes in folic acid, but not homocysteine, concentrations independently described changes in maximal endothelium-dependent vasodilatation.


CONCLUSIONS
Short-term oral folic acid supplementation significantly enhances endothelial function in type 2 diabetic patients, independent of homocysteine lowering.
Mangoni
Arduino A
AA
Department of Clinical Pharmacology, Centre for Neuroscience, Flinders University, School of Medicine, Adelaide, Australia. arduino.mangoni@flinders.edu.au
Sherwood
Roy A
RA
Asonganyi
Belinda
B
Swift
Cameron G
CG
Thomas
Stephen
S
Jackson
Stephen H D
SH
D000109:Acetylcholine / Q000494:pharmacology; D000284:Administration, Oral; D001783:Blood Flow Velocity / Q000187:drug effects; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology*; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000503:physiopathology*; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000097:blood / Q000627:therapeutic use; D005542:Forearm / Q000098:blood supply; D006710:Homocysteine / Q000037:antagonists & inhibitors / Q000097:blood; D006801:Humans; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D011674:Pulse; D012039:Regional Blood Flow / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D006710:Homocysteine; D005492:Folic Acid; D000109:Acetylcholine