The regulatory effects of haw pectin pentaoligosaccharide (HPPS) on fatty acid oxidation-related enzyme activities and mRNA levels were investigated in the liver of high fat diet induced hyperlipidemic mice. Results showed that HPPS (150 mg/kg for 10 weeks) significantly suppresses weight gain (32.3 +/- 0.26 and 21.1 +/- 0.14 g for high-fat diet and HPPS groups, respectively), decreases serum triacylglycerol levels (1.64 +/- 0.09 and 0.91 +/- 0.02 mmol/L, respectively), and increases lipid excretion in feces (55.7 +/- 0.38 and 106.4 +/- 0.57 mg/g for total lipid, respectively), compared to high-fat diet as control. HPPS significantly increased the hepatic fatty acid oxidation-related enzyme activities of acyl-CoA oiddase, carnitine palmitoyltransferase I, 3-ketoacyl-CoA thiolase, and 2,4-dienoyl-00A reductase by 53.8, 74.2, 47.1, and 24.2%, respectively. Meanwhile, the corresponding mRNAs were up-regulated by 89.6, 85.8, 82.9, and 30.9%, respectively. Moreover, HPPS was able to up-regulate the gene and protein expressions of peroxisome proliferator-activated receptor a. Results suggest that continuous HPPS ingestion may be used as dietary therapy to prevent obesity and cardiovascular diseases.