MAGNESIUM-DEFICIENCY MODULATES HEPATIC LIPOGENESIS AND APOLIPOPROTEINGENE-EXPRESSION IN THE RAT

The present study was performed to determine the effects of magnesium (Mg) deficiency upon plasma lipoproteins and hepatic apolipoprotein ge ne expression in the rat. The most obvious effect of Mg-deficiency on plasma lipids is a marked increase in post-prandial triacylglycerol co ncentration, This increased triglyceridemia persists in fasted rats. D ensity gradient ultracentrifugation analysis revealed marked alteratio ns in the distribution of plasma lipoproteins in Mg-deficient rats. An increase in triacylglycerol-rich lipoproteins (TGRLP) was associated with a significant increase in plasma apolipoprotein B (ape B) concent ration and was accompanied by selective accumulation of apo B-48, A de crease in high-density lipoproteins (HDL) was accompanied by a corresp onding decrease in plasma apo E concentration and a concordant decreas e in hepatic apo E mRNA abundance and biosynthesis. Hepatic apo B-100 synthesis was reduced by over 75% in Mg-deficient animals despite an i ncrease in hepatic apo B mRNA abundance. However, this change in hepat ic apo B gene expression was not associated with alterations in posttr anscriptional apo B mRNA editing. These changes in apolipoprotein gene expression were associated with increased hepatic lipogenesis, despit e the observation that net triacylglycerol secretion rates were not di fferent between Mg-deficient and control animals. Taken together, the data demonstrate a complex pattern of alterations in hepatic lipid met abolism and apolipoprotein gene expression in the Mg-deficient rat and suggest a defect in the catabolism rather than secretion of TGLRP as the major factor underlying the altered plasma lipoprotein profile.