Effects of trypsin inhibitor on plasma antioxidant activity and lipid levels in mice from sweet potato roots

BACKGROUND: Several inflammatory diseases are thought to be related to oxidative injury and reactive oxygen species have been proposed as important causative agents of heart disease and ageing. This study was designed to investigate the effects of sweet potato trypsin inhibitor (SPTI) on antioxidant enzymes, lipid peroxidation and lipid profiles in mice.RESULTS: Twenty mice were randomly divided into four groups and fed with TI (10, 50 and 100 mg kg⁻¹ BW) as treatment and with saline as a control in addition to regular diets. After 35 days, Trolox equivalent antioxidant capacity (TEAC), triglyceride (TG) and cholesterol levels in plasma and superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx), thiobarbituric acid reactive substances (TBARS) in liver were measured. Serum from the group that had received the the highest oral dose of SPTI (100 mg kg⁻¹ BW) had the highest total antioxidant activity (expressed as 3.59 ± 0.237 mmol L⁻¹ TEAC). The SOD, catalase and GPx activity of SPTI groups were significantly increased compared with the control group. Malondialdehyde (MDA) was significantly lower in all experimental groups compared with the control one. No significant differences in the concentration of low-density lipoprotein (LDL)-cholesterol was found, but high density lipoprotein (HDL)-cholesterol, triglyceride (TG) and total cholesterol tended to decrease.CONCLUSION: This study showed that the oral intake of SPTI in mice may trigger inflammatory responses which result in an increase in antioxidant enzyme activities, and a decrease in MDA, TG and total cholesterol, which are known risk factors of inflammatory and heart disease.