ACUTE EXOGENOUS ELEVATION OF PLASMA-FREE FATTY-ACIDS DOES NOT INFLUENCE THE PLASMA MAGNESIUM CONCENTRATION

Objective: Plasma non-esterified (free) fatty acid concentrations rise as a consequence of stimulated endogenous lipolysis and are inversely related to the plasma magnesium concentration when plasma adrenaline concentration is increased. The aim of the study was to test whether h igh plasma non-esterified fatty acid concentration after infusion of n on-esterified fatty acids decreases plasma magnesium concentration. Me thods: Twelve healthy subjects received 500 ml Intralipid or saline in a randomised, cross-over, double-blind design. Infusion of Intralipid results in an isolated elevation of plasma non-esterified fatty acid concentration. Plasma magnesium concentration was determined at baseli ne and every 30 minutes; plasma nonesterified fatty acid and triglycer ide concentrations at baseline and after 120 minutes. Results: Initial plasma magnesium, non-esterified fatty acid, and triglyceride concent rations were similar in both groups. A significant increase in plasma nonesterified fatty acids (2.42 +/- 0.96 mmol/l vs 0.58 +/- 0.23 mmol/ l, p = 0.00013) and triglyceride (median and 95th percentile 5.36 (7.3 5) mmol/l vs 1.18 (1.92) mmol/l, p=0.003) concentrations was seen with Intralipid. Plasma magnesium concentration increased significantly af ter Intralipid (0.89 +/- 0.09 mmol/l vs 0.81 +/- 0.06 mmol/l, p = 0.00 7). No significant changes were seen with saline. A positive associati on was found between the change in plasma magnesium and triglyceride c oncentrations (r=0.85, p=0.001). Conclusion: Acute infusion of non-est erified fatty acids from an exogenous source does not: result in a fal l in plasma magnesium concentration, indicating that the circulating n on-esterified fatty acids play no part in a decrease in plasma magnesi um concentration. The high circulating non-esterified fatty acid level s and the fall in plasma magnesium concentration are both a consequenc e of intracellular lipolysis.