Intracellular free magnesium in hypertension: relation to peripheral insulin resistance

In order to study the importance of altered intracellular ion metabolism in hypertension, we used P nuclear magnetic resonance (NMR) spectroscopy to measure intracellular free magnesium levels in normotensive (n = 19), essential hypertensive (n = 17) and diet-controlled diabetic (n = 6) subjects given a standard 100-g oral glucose load. The intracellular Mg level was significantly lower in hypertensives compared with normotensives (183 ± 7 versus 232 ± 10 μmol/l, P < 0.001), and for all subjects was closely linked to both systolic (r = −0.84, P < 0.001) and diastolic (r = −0.76, P < 0.001) pressure. Hypertensives also showed a significantly greater insulinaemic response to glucose loading (P < 0.001), and intracellular Mg was also closely and inversely linked to the integrated insulin response (r = −0.78, P < 0.001). Despite the absence of hyperinsulinaemia, diabetics had the lowest intracellular Mg levels (156 ± 8 μmol/l).Thus, suppressed intracellular Mg is linked to hypertension and to decreased tissue insulin sensitivity, and is not consequent to the hyperinsulinaemia itself. We suggest that intracellular Mg may provide a common pathophysiological basis for understanding the clinical association of hypertension and diabetes mellitus.