OBJECTIVE To explore the effects of nicotinic acid intervention on vascular endothelial dysfunction mediated by oxidized low density lipoprotein (ox-LDL)/lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) in diet-induced obese immature rats and its possible mechanism through detecting the expression levels of ox-LDL and LOX-1 in abdominal aorta. METHODS A model of diet-induced obese immature rats was established by high-fat diet. And 30 immature rats were divided randomly and equally into control (n = 10), high-fat (n = 10) and drug control (n = 10) groups. At the end of 12 weeks, the levels of serum total cholesterol (TC), triglyceride (TG), LDL and high-density lipoprotein (HDL) were examined. The levels of ox-LDL, soluble intercellular adhesion molecule-1 (sICAM-1), endothelin and nitric oxide (NO) were detected. The gene and protein expressions of LOX-1 and ICAM-1 in abdominal aorta were detected. And the location protein expressions of LOX-1 and ICAM-1 were examined. RESULTS High-fat diet induced hyperlipidemia and obesity in immature rats. The serum levels of TG, TC, LDL, ox-LDL and endothelin in high-fat and drug control groups were all higher than control group ((0.98 ± 0.12) and (0.69 ± 0.06) vs (0.49 ± 0.06) mmol/L, (2.11 ± 0.16) and (1.62 ± 0.12) vs (1.30 ± 0.12) mmol/L, (0.71 ± 0.04) and (0.50 ± 0.03) vs (0.30 ± 0.04) mmol/L, (44.2 ± 5.1) and (33.7 ± 2.1) vs (26.6 ± 2.9) µg/L, (187 ± 10) and (157 ± 6) vs (118 ± 7) pg/ml). The indices in high-fat group were higher than those in drug control group (all P < 0.01) . The levels of HDL and NO in high-fat and drug control groups were lower than those in control group (all P < 0.01); the levels of HDL and NO in high-fat group lower than those in drug control group (all P < 0.01). And the levels of LOX-1, ICAM-1 protein and mRNA in high-fat group were higher than those in drug control and control groups (all P < 0.01).ox-LDL was correlated positively with LOX-1, TC, TG, LDL, endothelin and ICAM-1 (r = 0.918, 0.867, 0.857, 0.834, 0.869, 0.644, all P < 0.01) , but negatively with NO and HDL (r = -0.823, -0.872, P < 0.01) . CONCLUSION Early treatment of nicotinic acid can protect endothelial function through inducing therapeutic effects on hyperlipidemia and antioxidation and down-regulating the expression level of ox-LDL/LOX-1 in vascular endothelium.