Search

Chronic Mg 2+ deficiency is the underlying cause of a broad range of health dysfunctions. As 25% of body Mg 2+ is located in the skeletal muscle, Mg 2+ transport and homeostasis systems (MgTHs) in the muscle are critical for whole-body Mg 2+ homeostasis. In the present study, we assessed whether Mg 2+ deficiency alters muscle fiber characteristics and major pathways regulating muscle physiology. C57BL/6J mice received either a control, mildly, or severely Mg 2+ -deficient diet (0.1%; 0.01%; and 0.003% Mg 2+ wt/wt, respectively) for 14 days. Mg 2+ deficiency slightly decreased body weight gain and muscle Mg 2+ concentrations but was not associated with detectable variations in gastrocnemius muscle weight, fiber morphometry, and capillarization. Nonetheless, muscles exhibited decreased expression of several MgTHs ( MagT1 , CNNM2 , CNNM4 , and TRPM6 ). Moreover, TaqMan low-density array (TLDA) analyses further revealed that, before the emergence of major muscle dysfunctions, even a mild Mg 2+ deficiency was sufficient to alter the expression of genes critical for muscle physiology, including energy metabolism, muscle regeneration, proteostasis, mitochondrial dynamics, and excitation-contraction coupling.

The importance of Mg for the immune function is well recognized; however, there is no information available about the effect of Mg intake on the modulation of local immune response in the intestine. Thus, in the present study the hypothesis that short periods of Mg deprivation can affect intestinal mucosa and local immune response was tested. For this purpose, OF1 female mice were fed a semipurified diet (1000 mg Mg/kg diet). For 3 d before immunization and 1 d after, half of the animals were fed a Mg-deficient diet (30 mg Mg/kg diet), three immunizations per os were performed every 3 weeks with Escherichia coli producing the CS31A capsule-like protein (1010 or bacteria per animal). Mice were killed 10 d after the last immunization. The level of specific anti CS31A immunoglobulin (Ig) G and IgA in the serum and secretory IgA in the intestinal secretions and faeces were measured by ELISA. The results indicated that administration of a high dose of immunogen with a low-Mg diet led to lower specific IgA levels in the intestinal mucus and serum. Administration of a low dose of immunogen with a low-Mg diet led to lower IgA and IgG levels in the serum and secretory IgA coproantibodies. To assess alterations of intestinal mucosa caused by a low-Mg diet for a short period, histological and scanning electron microscopy analyses were performed on samples from mice (not submitted to the vaccination protocol) after 3 d on the Mg-deficient diet. These analyses showed several alterations, suggesting perturbations in the growth of the intestinal mucosa. These changes were accompanied by modifications in the expression of several genes involved in cell growth and stress response. From this present work, it may be concluded that short periods of Mg deprivation can affect the intestinal mucosa and local immune response of the intestine.

Magnesium deficiency in experimental animals leads to inflammation, exacerbated immune stress response and a decrease of specific immune response. It also results in a significant increase in free radical species and subsequent tissue injury. An accelerated thymus involution was observed in Mg-deficient rats in relation to enhanced apoptosis and enhanced susceptibility to oxidative stress. To examine the stress-inducing effects of low Mg status on thymocytes, cDNA arrays were used to evaluate changes in gene expression in weaning rats submitted to Mg deficiency of short duration (2 days). Several genes exhibited changes in their expression caused by Mg deficiency before any perceptible modification in cell integrity and functions. The up-regulated genes included cytochrome c oxidase, glutathione transferase, CuZn superoxide dismutase, genes associated with the stress response (HSP70 and HSP84) and a gene involved in DNA synthesis and repair (GADD45). The down-regulated genes included Na/P cotransporter 1. These findings are consistent with altered cell growth, modifications of ion fluxes and oxidative stress described during Mg deficiency. The observation of induction of genes involved in protection and repair in cells from Mg-deficient animals provides additional evidence of the role of oxidative stress in the pathobiology of this deficiency.