Effects of dietary manganese deficiency on high density lipoprotein composition and metabolism in Sprague-Dawley rats

Abstract

Manganese (Mn) has been implicated in the development of atherosclorosis but its in vivo role in lipid and lipoprotein metabolism has been inconclusive to date. The objectives of this experiment were to study the effect of dietary Mn deificiency on high density lipoprotein (HDL) composition and structure. Weanling male Sprague-Dawley (SD) rats were fed either a Mn-deficient (MnD, 1.00 ppm) or a Mn-supplemented (MnS, 82.00 ppm) diet for 8 weeks. Very low density lipoproteins, low density lipoproteins and HDL, prestained with Sudan black, were separated by a discontinuous density gradient ultracentrifugation. High density lipoproteins were delipidated, apolipoproteins were separated by sodium dodecylsulfate polyacrylamide gel electrophoresis (5–20% gradient) and quantified by laser densitometry. Fluorescence spectroscopy was used to study changes in HDL structure with dietary Mn deficiency. Body weights, liver weights, liver Mn levels, total plasma protein, HDL cholesterol and HDL protein were significantly lower (P≤0.05) in the MnD rats. The molecular weight of apolipoprotein C-I was significantly less (P<-0.01), and the relative peak area of apolipoprotein E3 was less (P≤0.1) in the MnD rats. Fluorescence studies of apo-HDL showed 71% of tryptophan residues accessible to quenching by Mn +2 with a quenching constant of 1.03×10 5 M −1 for the MnD rats vs. 58% and 1.29×10 5 M −1 respectively, for the MnS rats. The data indicate that Mn is involved in HDL metabolism. Changes in HDL composition and surface charge may significantly affect cholesterol transport and metabolism in the SD rat.