Leptin and membrane fluidity of erythrocytes in essential hypertension: an electron paramagnetic resonance investigation

Abstract

There has been an indication that leptin, the product of the human obesity gene, actively participates not only in metabolic regulation but also in the control of blood pressure. Recently, it has been proposed that abnormalities in the physical property of cell membranes may underlie the defects that are strongly linked to hypertension, stroke, and other cardiovascular diseases. We have shown previously that leptin significantly increased the membrane fluidity and improved the microviscosity of erythrocytes in humans through the nitric oxide-dependent mechanism. In the present study, we examined the effects of leptin on membrane fluidity of erythrocytes in subjects with essential hypertension by means of an electron paramagnetic resonance (EPR) and spin-labeling method. The values of the order parameter (S) and the peak height ratio (ho/h-1) obtained from the EPR spectra of erythrocytes were significantly greater in patients with essential hypertension (HT) than in age-matched normotensive subjects (NT) (S: HT 0.719 ± 0.002, n = 16, NT 0.713 ± 0.001, n = 29, P < .05; ho/h-1: HT 5.17 ± 0.02, n = 16, NT 5.05 ± 0.02, n = 29, P < .05). The finding indicated that the erythrocyte membrane fluidity was lower in patients with HT than in NT. Leptin decreased S and ho/h-1 in a dose-dependent manner in both NTs and HTs. The effect of leptin on the membrane fluidity was significantly more pronounced in HTs than in NTs (percent change in S: leptin 10 −8 g/mL, HT −3.4% ± 0.2%, n = 16, NT −2.3% ± 0.1%, n = 29, P < .05; leptin 10 −7 g/mL, HT −4.3% ± 0.3%, n = 16, NT −3.3% ± 0.1%, n = 29, P < .05). The results of the present study showed that leptin might have a crucial role in the regulation of the rheologic behavior of erythrocytes and the microcirculation in hypertension.