High Cholesterol Feeding May Induce Tubular Dysfunction Resulting in Hypomagnesemia

Abstract

Background/Aims: Hypomagnesemia may induce hypercholesterolemia, but the contrary has not been described yet. Thus, magnesium homeostasis was evaluated in rats fed a cholesterol-enriched diet for 8 days. This study has a relevant clinical application if hypomagnesemia, due to hypercholesterolemia, is confirmed in patients with long-term hypercholesterolemia. Methods: Both hypercholesterolemic (HC) and normocholesterolemic rats (NC) were divided into sets of experiments to measure hemodynamic parameters, physiological data, maximum capacity to dilute urine (C_H_₂_O), variations (Δ) in [Ca²⁺]_i and the expression of transporter proteins. Results: HC developed hypomagnesemia and showed high magnesuria in the absence of hemodynamic abnormalities. However, the urinary sodium excretion and C_H_₂_O in HC was similar to NC. On the other hand, the responses to angiotensin II by measuring Δ [Ca²⁺]_i were higher in the thick ascending limb of Henle’s loop (TAL) of HC than NC. Moreover, high expression of the cotransporter NKCC2 was found in renal outer medulla fractions of HC. Taken together, the hypothesis of impairment in TAL was excluded. Actually, the expression of the epithelial Mg²⁺ channel in renal cortical membrane fractions was reduced in HC. Conclusion: Impairment in distal convoluted tubule induced by hypercholesterolemia explains high magnesuria and hypomagnesemia observed in HC.