Low fasting and insulin-mediated intracellular magnesium accumulation in hypertensive patients with left ventricular hypertrophy: role of insulin resistance.

Twenty-five hypertensive patients (13 males/12 females) with left ventricular hypertrophy (LVH) and 12 hypertensive patients (6 males/6 females) without LVH were studied. Both groups were matched for age, sex, body mass index, percentage body fat, arterial BP and known duration of hypertension. After a seven day wash-out period from antihypertensive treatment each subject underwent: (1) an oral glucose tolerance test, (2) an euglycemic hyperinsulinaemic glucose clamp (insulin infusion rate 7.1 pM/kg per min), (3) an echocardiographic determination of left ventricular mass index, and (4) 24h ECG Holter monitoring. All tests were performed in random order and on different days. All investigators were unaware of the patient groups. Hypertensive patients with LVH had lower fasting intracellular (erythrocyte) magnesium concentrations (1.85 +/- 0.06 vs. 2.07 +/- 0.04 mM; P < 0.001) but higher fasting plasma insulin concentrations (86 +/- 4 vs. 59 +/- 5 pM; P < 0.001) Glucose clamp study demonstrated a lower insulin-mediated glucose disposal (24.8 +/- 0.4 vs. 30.1 +/- 0.3 microM/kg of lean body mass per min; P < 0.05) and a net change in intracellular magnesium accumulation (17.9 +/- 1.3 vs. 27.3 +/- 1.8%, P < 0.01) in response to insulin infusion in hypertensive patients with LVH than in those without LVH. After adjustment for fasting plasma insulin levels and insulin-mediated glucose uptake, fasting and insulin-mediated erythrocyte magnesium accumulation were no longer different between the two groups. In conclusion, hypertensive patients with LVH compared with those without LVH have a lower intracellular magnesium content due a higher degree of insulin resistance.