Title

The effects of psyllium and plant sterol therapy on clinical markers of cardiovascular disease and lipoprotein metabolism

Date of Completion

January 2007

Keywords

Health Sciences, Nutrition

Degree

Ph.D.

Abstract

LDL cholesterol (LDL-C), LDL subclasses and their composition have a strong association with the development of CHD. Dietary manipulation has been shown to modify plasma lipids and lipoprotein phenotypes. The present study was conducted to assess the combined effects of psyllium (PSY) and plant sterols (PS) provided via cookie on LDL-C and lipoprotein size and subfraction distribution, and to explore mechanisms underlying their effects. We conducted a randomized, double blind, crossover, placebo-controlled study in 33 healthy free-living individuals (11 males and 22 females), aged 35-65 y, with a BMI between 25 and 35 kg/m2 and initial plasma LDL-C concentrations between 2.6 and 4.1 mmol/L (100 and 160 mg/dL). The subjects were randomly assigned to receive treatment cookies (7.68 g/d PSY and 2.6 g/d PS) or placebo cookies (0 g PSY+0 g PS) for 4 wk. After a 3-wk washout period, subjects received the alternate cookies for an additional 4 wk. Plasma total cholesterol concentrations were significantly reduced for all subjects, from 5.65 ± 0.72 mmol/L after the placebo period to 5.28 ± 0.76 mmol/L after the PSY+PS cookie period (P < 0.05). ^ The reduction was primarily due to a decrease in LDL-C from 3.48 + 0.70 to 3.14 ± 0.78 mmol/L after PSY+PS cookie consumption (P < 0.05). Intake of the PSY+PS consumption decreased the number of intermediate density lipoprotein (IDL), LDL, and high density lipoprotein (HDL) particles (P < 0.05) and plasma apo B concentrations (P < 0.05). The decreases in LDL and HDL particles were in the small subfractions. PSY+PS decreased the concentration of cholesterol in LDL-1 and LDL-2 subfractions (P < 0.05). An increase in LDL peak and mean size (P < 0.05) and a decrease in the prevalence of LDL pattern B from 27% to 18% (P < 0.05) were also observed during the PSY+PS period. CETP activity decreased by 11% (P < 0.05). Notably, the abundance of the LDL receptor in circulating mononuclear cells as measured by real time PCR was increased by 26% (P < 0.05). These results indicate that the hypocholesterolemic action of PSY and PS can be explained by modifications in the intravascular processing of lipoproteins and by increasing LDL receptor-mediated uptake. ^