Researchers explored the effect of antioxidants on blood lipid metabolism and the activity of lipoprotein lipase (LPL), an enzyme that breaks down fat, in rats fed a high-fat diet.
They also sought to determine whether the atherosclerotic index, a measurement of the risk of having a heart attack, is related to antioxidant levels and LPL activity.
The study authors randomly assigned 32 rats to one of four groups of 8 animals each. The control group consumed an ordinary diet. The other three experimental groups were fed with a high-fat diet alone consisting of 14.1 percent fat, a high-fat diet plus 0.1 percent lipoic acid, or a high-fat diet plus 0.1 percent N-acetyl cysteine.
After 4 weeks, the scientists measured serum levels of triglycerides, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol as well as activity of LPL, the enzyme that helps break down fat. The researchers also measured the animals’ antioxidant status.
The high-fat diet induced abnormal increases in lipid peroxidation, the process where fats become rancid. The high-fat diet also caused increases in serum concentrations of total cholesterol, triglycerides, and low-density lipoprotein cholesterol, and a decrease in the levels of the beneficial high-density lipoprotein cholesterol. Decreased activity of LPL, accompanied by a depressed antioxidant defense system, also was observed in the rats consuming a high-fat diet.
All of the damaging effects triggered by the high-fat diet were reduced in the NAC- and lipoic-acid-treated groups. In addition, the higher the antioxidant capacity of the animals, the lower the atherosclerotic index. Antioxidant levels also were correlated with an increase in LPL activity.
The researchers concluded, “Oxidative injury and lipid abnormalities were induced by a high-fat diet. Administration of lipoic acid and NAC can improve the antioxidant capacity and activity of LPL and reduce blood lipids significantly.”
Yang R, Le G, Li A, Zheng J, Shi Y. Effect of antioxidant capacity on blood lipid metabolism and lipoprotein lipase activity of rats fed a high-fat diet. Nutrition. 2006 November-December;22(11-12):1185-91.