Magnesium and the Insulin Resistance Syndrome

Sammanfattning: Insulin resistance, defined as a state of reduced insulin-mediated glucose uptake in peripheral tissues, and disorders such as obesity, hypertension, and dyslipidemia, have been found to be associated in the conglomerate of the insulin resistance syndrome. Some antihypertensive drugs have been shown to decrease insulin sensitivity further. In the studies described in this thesis relations between the magnesium status and some aspects of the insulin resistance syndrome were investigated. In a cross-sectional study serum Mg was found to be directly related to insulin sensitivity and lipoprotein lipase activity, and inversely to fasting glucose concentration. During treatment with angiotensin-converting enzyme inhibitors, ACEi, in patients with essential hypertension, an increase in serum Mg in relation to serum Ca was found to be correlated to improved insulin sensitivity and decreased serum lipid concentrations. In trials with ACEi or bendrofluazide treatment, a reduced Ca/Mg ratio in skeletal muscle was associated with the blood pressure response. A change in Mg concentration in skeletal muscle was inversely correlated to the change in serum glucose, but was not correlated to the insulin sensitivity per se. Atherogenic lipid fractions were more closely related to the plasma ionized Mg concentration than to circulating total Mg levels. Intra-arterial Mg infusion improved endothelium-dependent vasodilation, EDV, in healthy normotensive subjects. In summary, magnesium improves endothelium-dependent vasodilation and lipoprotein lipase activity, which might help to explain the inverse correlations between circulating Mg concentrations and some lipid and glucometabolic variables.The Mg content in skeletal muscle is related to blood pressure response and serum glucose levels during antihypertensive treatment with ACEi or bendrofluazide.