The pecan nut (Carya illinoinensis) and its oil and polyphenolic fractions differentially modulate lipid metabolism and the antioxidant enzyme activities in rats fed high-fat diets

•Pecan nut, as part of a high fat diet, prevented hyperleptinemia, fat accumulation and liver lipid peroxidation.•Pecan nut stimulated hepatic expression of LDL receptor and SREBP 1c mRNA.•Pecan polyphenols stimulated hepatic expression of LXR alpha mRNA.•Stronger effects were produced by the whole pecan and not by the isolated oil or polyphenol fractions. Tree nuts such as pecans (Carya illinoinensis) contain mostly oil but are also a source of polyphenols. Nut consumption has been linked to a reduction in serum lipid levels and oxidative stress. These effects have been attributed to the oil while overlooking the potential contribution of the polyphenols. Because the evidence regarding each fraction’s bioactivity is scarce, we administered high-fat (HF) diets to male Wistar rats, supplementing them with pecan oil (HF+PO), pecan polyphenols (HF+PP) or whole pecans (HF+WP), and analysed the effects of each fraction. The HF diet increased the serum leptin and total cholesterol (TC) with respect to the control levels. The HF+WP diet prevented hyperleptinemia and decreased the TC compared with the control. The HF+WP diet upregulated the hepatic expression of apolipoprotein B and LDL receptor mRNAs with respect to the HF levels. The HF+PO diet reduced the level of triacylglycerols compared with the control. The HF+PP diet stimulated the hepatic expression of liver X receptor alpha mRNA. The HF+WP diet increased the activities of hepatic catalase, glutathione peroxidase and glutathione S transferase compared with the control, and decreased the degree of lipid peroxidation compared with the HF diet. The most bioactive diet was the WP diet.