Omega-3 Fatty Acids and Niacin Improve Lipid Profiles and Attenuate Vascular Oxidative Stress and Inflammation in Ovariectomized Rats Fed with Thermoxidized Oils

Background: Thermal oxidation of edible oils generates lipid oxidation products that contribute to dyslipidemia, oxidative stress, and vascular injury. Estrogen deficiency further increases susceptibility to cardiovascular dysfunction. This study evaluated the effects of omega-3 fatty acids (OFA) and niacin (NCN) on lipid abnormalities and vascular injury induced by thermoxidized oils in ovariectomized rats. Method: Forty-eight female Wistar rats were allocated to eight experimental groups. Ovariectomy was performed to model estrogen deficiency, after which animals received thermoxidized soybean oil (TSO) or thermoxidized palm oil (TPO) diets for 12 weeks with or without OFA or NCN treatment. Plasma lipid profiles, atherogenic indices, aortic oxidative-stress markers, TNF-α concentrations, nitrite concentrations, and histopathological changes were evaluated. Data were analyzed using a one-way analysis of variance followed by Bonferroni- or Tukey-adjusted multiple comparisons as appropriate. Results: Thermal processing altered the fatty acid composition and increased the free fatty acid content of both oils. Compared with sham rats, animals fed thermoxidized oil diets exhibited adverse lipid profiles, elevated aortic TBARS (expressed as MDA equivalents) and TNF-α concentrations, reduced nitrite concentrations, and histopathological alterations. OFA and NCN reduced total cholesterol, LDL-C, atherogenic indices, TBARS, and TNF-α concentrations while increasing HDL-C and catalase activity relative to the corresponding untreated oil-fed groups. Effects on glutathione and superoxide dismutase varied according to treatment and oil type. NCN increased aortic nitrite concentrations in both oil-fed groups, whereas OFA significantly increased nitrite only in the TPO group. Histological examination demonstrated less pronounced vascular alterations in treated animals than in untreated oil-fed controls. Conclusions: OFA and NCN improved lipid profiles and attenuated oxidative-stress and inflammatory responses in ovariectomized rats fed thermoxidized oils. These findings suggest that both interventions may mitigate biochemical and histopathological abnormalities associated with thermoxidized oil consumption under estrogen-deficient conditions. Further studies are required to define the underlying molecular mechanisms and determine the translational relevance of these findings.