Role of HDL in neutralizing the VLDL effect on endothelial dysfunction.

Microvascular research

PubMedID: 23778199

Zago V, Gorzalczany S, Lucero D, Taira C, Schreier L. Role of HDL in neutralizing the VLDL effect on endothelial dysfunction. Microvasc Res. 2013;89153-8.
OBJECTIVE
It has been reported that LDL inhibits endothelium-dependent relaxation (EDR) and that HDL can neutralize this effect. However, the atherogenic properties of VLDL have been so far difficult to demonstrate. Studies on VLDL are controversial, and nothing is known about the role of HDL on potential VLDL vascular actions. We examined the effect of human VLDLs on EDR, and the role of HDL in this system.

METHODS
VLDL (n=14) and LDL (n=6) were isolated from volunteer subjects. Normal HDL was obtained from one healthy donor. VLDL ability to inhibit ACh-induced vasorelaxation (10(-9)-10(-5)mM) on aortic rings previously precontracted by noradrenaline (10(-8)mM) was measured in the presence and absence of HDL.

RESULTS
ACh-induced maximal relaxation (R%) was mildly, but not significantly attenuated in the presence of VLDL (72±7%), while LDL caused a significant inhibition (60±10%, p<0.05) when compared to incubation in the absence of lipoproteins. VLDLs were subdivided into 2 groups depending on their cholesterol/triglyceride ratio: 0.18-0.22 (n=8) was considered typical and 0.10-0.15, rich in triglycerides (VLDLRT, n=6). Typical VLDL had no effect on EDR (p=0.38), however R% from VLDLRT was lower (54±7%, p<0.01) similar to the one obtained with LDL (p=0.32). HDL showed favorable effects on EDR inhibition induced by the presence of VLDLRT (p<0.05.).

CONCLUSION
Although typical VLDL did not cause endothelial dysfunction, triglyceride-enriched VLDL had inhibitory effect on EDR. It is proposed that alterations in VLDL composition would increase its atherogenic capacity. Moreover HDL appears to protect endothelium from VLDL action.