EFFECTS OF DIETARY MANGANESE DEFICIENCY ON HIGH-DENSITY-LIPOPROTEIN COMPOSITION AND METABOLISM IN SPRAGUE-DAWLEY RATS

Manganese (Mn) has been implicated in the development of atheroscleros is but its in vivo role in lipid and lipoprotein metabolism has been i nconclusive to date. The objectives of this experiment were to study t he effect of dietary Mn deficiency on high density lipoprotein (HDL) c omposition and structure. Weanling male Sprague-Dawley (SD) rats were fed either a Mn-deficient (MnD, 1.00 ppm) or a Mn-supplemented (MnS, 8 2.00 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 lip oproteins were delipidated, apolipoproteins were separated by sodium d odecylsulfate polyacrylamide gel electrophoresis (5-20% gradient) and quantified by laser densitometry. Fluorescence spectroscopy was used t o study changes in HDL structure with dietary Mn deficiency. Body weig hts, liver weights, liver Mn levels, total plasma protein, HDL cholest erol and HDL protein were significantly lower (P less-than-or-equal-to 0.05) in the MnD rats. The molecular weight of apolipoprotein C-1 was significantly less (P less-than-or-equal-to 0.01), and the relative p eak area of apolipoprotein E3 was less (P less-than-or-equal-to 0.1) i n the MnD rats. Fluorescence studies of apo-HDL showed 71% of tryptoph an residues accessible to quenching by Mn+2 with a quenching constant of 1.03 x 10(5) M-1 for the MnD rats vs. 58% and 1.29 x 10(5) M-1 resp ectively, for the MnS rats. The data indicate that Mn is involved in H DL metabolism. Changes in HDL composition and surface charge may signi ficantly affect cholesterol transport and metabolism in the SD rat.