Oxidized LDL and small LDL particle size are independently predictive of a selective defect in microcirculatory endothelial function in type 2 diabetes.
OBJECTIVE
To explore the associations of LDL (low-density lipoprotein) particle size and oxidized LDL with endothelium-dependent function of the forearm microcirculation in diabetes.


METHODS
Endothelium-dependent function was examined in 43 middle-aged men and women with type 2 diabetes and 10 age-matched controls. All received aspirin to inhibit endothelial cyclo-oxygenase. Forearm blood flow (FBF) was measured using venous occlusion plethysmography with separate administration of acetylcholine (ACh) and bradykinin (BK) into the brachial artery. Endothelium-independent function was assessed using sodium nitroprusside (SNP). N(G)-monomethyl-L-arginine (L-NMMA) was co-infused with ACh (ACh + L-NMMA) and BK (BK + L-NMMA) to assess non-NO-mediated contributions to endothelium-dependent function.


RESULTS
Subjects with diabetes had impaired endothelium-dependent and endothelium-independent function compared with controls (p < 0.01 for ACh, BK and SNP). In multivariate regression analysis, LDL size (r = 0.41 and p = 0.007), oxidized LDL (r = -0.41 and p = 0.007) and duration of diabetes (r = -0.37 and p = 0.02) predicted FBF response to ACh independently of age, gender and systolic blood pressure. There were no associations between LDL size, oxidized LDL, duration of diabetes and FBF response to BK, SNP, ACh + L-NMMA or BK + L-NMMA.


CONCLUSIONS
In type 2 diabetes, small dense LDL particles, duration of diabetes and oxidized LDL may independently contribute to endothelial dysfunction of the microcirculation. These disturbances may occur via a selective defect, because ACh and BK activate endothelial NO synthase via different G-protein signal transduction pathways.
Woodman
R J
RJ
School of Medicine and Pharmacology, The University of Western Australia and West Australian Heart Research Institute, Perth, Australia.
Watts
G F
GF
Playford
D A
DA
Best
J D
JD
Chan
D C
DC
D000109:Acetylcholine; D000368:Aged; D000886:Anthropometry; D001920:Bradykinin; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D003925:Diabetic Angiopathies / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005260:Female; D005542:Forearm / Q000098:blood supply; D006801:Humans; D008077:Lipoproteins, LDL / Q000737:chemistry / Q000502:physiology*; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D009599:Nitroprusside; D010316:Particle Size; D010991:Plethysmography; D015398:Signal Transduction; D013997:Time Factors; D014665:Vasodilator Agents
D008077:Lipoproteins, LDL; D014665:Vasodilator Agents; C099252:oxidized low density lipoprotein; D009599:Nitroprusside; D000109:Acetylcholine; D001920:Bradykinin