African walnut (Tetracarpidium conophorum) modulates hepatic lipid accumulation in obesity via reciprocal actions on HMG-CoA reductase and paraoxonase.

Obesity is characterized by increased body fat and involves an imbalance between synthesis and degradation of lipids.To investigate the effect of African walnuts (Tetracarpidium conophorum) on storage lipids and the regulatory enzymes of hepatic lipid metabolism in obese rats.The nuts were extracted in ethanol (WE) and further separated to obtain the ethyl-acetate fraction (ET) and the residue (RES). These were administered orally to 3 groups of monosodium glutamate-obese rats (n = 6), respectively, for 6 weeks. Other groups in the study were the normal (NC), obese control (OC) and standard control (SC) which received orlistat. Hepatic total lipids, total phospholipids, triacylglycerol (TG), total cholesterol (TCHOL), 3-hydroxyl-3-methylglutaryl-CoA (HMG-CoA) reductase and paraoxonase were studied.Total lipids, TG and TCHOL which increased in OC compared to NC group, were decreased. HMG-CoA reductase activity decreased in the 3 study groups relative to OC. Paraoxonase activity which decreased in OC, was up-regulated, while the magnitude of hepatic cholesterol decreased from 94.32 % in OC to 52.19, 65.43 and 47.04 % with WE, ET and RES, respectively. Flavonoids, alkaloids, glycosides, tannins and saponins were detected in the nut. GC-MS analysis revealed 16, 18 and 10 volatile components in WE, ET and RES, respectively. Unsaturated fatty acids (linolenic acids: 33.33, 47.95 and 50.93 %, and α-linolenic acids: 25, 19.66 and 26.63 %) in WE, ET and RES, respectively, being most abundant, and likely responsible for the observed activity.African walnuts can prevent hepatic lipid accumulation through reciprocal actions on HMG-CoA reductase and paraoxonase in obesity.