Effects of low dietary magnesium intake on development of hypertension in stroke-prone spontaneously hypertensive rats: role of reactive oxygen species

Role of Nutrients in Pediatric Non-Dialysis Chronic Kidney Disease: From Pathogenesis to Correct Supplementation

Nutrition management is fundamental for children with chronic kidney disease (CKD). Fluid balance and low-protein and low-sodium diets are the more stressed fields from a nutritional point of view. At the same time, the role of micronutrients is often underestimated. Starting from the causes that could lead to potential micronutrient deficiencies in these patients, this review considers all micronutrients that could be administered in CKD to improve the prognosis of this disease.

Hypomagnesemia and Cardiovascular Risk in Type 2 Diabetes

Hypomagnesemia is tenfold more common in individuals with type 2 diabetes (T2D), compared to the healthy population. Factors that are involved in this high prevalence are low Mg2+ intake, gut microbiome composition, medication use and presumably genetics. Hypomagnesemia is associated with insulin resistance, which subsequently increases the risk to develop T2D or deteriorates glycaemic control in existing diabetes. Mg2+ supplementation decreases T2D associated features like dyslipidaemia and inflammation; which are important risk factors for cardiovascular disease (CVD). Epidemiological studies have shown an inverse association between serum Mg2+ and the risk to develop heart failure (HF), atrial fibrillation (AF) and microvascular disease in T2D. The potential protective effect of Mg2+ on HF and AF may be explained by reduced oxidative stress, fibrosis and electrical remodeling in the heart. In microvascular disease, Mg2+ reduces the detrimental effects of hyperglycemia and improves endothelial dysfunction. Though, clinical studies assessing the effect of long-term Mg2+ supplementation on CVD incidents are lacking and gaps remain on how Mg2+ may reduce CVD risk in T2D. Despite the high prevalence of hypomagnesemia in people with T2D, routine screening of Mg2+ deficiency to provide Mg2+ supplementation when needed is not implemented in clinical care as sufficient clinical evidence is lacking. In conclusion, hypomagnesemia is common in people with T2D and is both involved as cause, probably through molecular mechanisms leading to insulin resistance, and consequence and is prospectively associated with development of HF, AF and microvascular complications. Whether long-term supplementation of Mg2+ is beneficial, however, remains to be determined.

Association of Serum Magnesium with Oxidative Stress in the Pathogenesis of Diabetic Cataract

Magnesium deficiency enhances oxidative stress which contributes to early development of cataract formation, and also the progression in type 2 diabetes mellitus patients remains unclear. The present study was designed to evaluate the serum levels of magnesium, oxidative stress marker and antioxidant status and to find out if there is any association between them in the pathogenesis of diabetic cataract compared with non-diabetic senile cataract, diabetes without cataract and normal healthy subjects. This comparative study includes 90 type 2 diabetes mellitus patients with cataract, 90 non-diabetic senile cataract patients, 90 type 2 diabetes mellitus without cataract and 90 normal healthy individual subjects without cataract in the age group between 40 and 75 years of both genders. Serum magnesium was estimated by using a fully automated analyser. Serum malondialdehyde (MDA), an indicator of oxidative stress biomarker, was determined by spectrophotometry, and the antioxidant status such as serum reduced glutathione (GSH) and glutathione peroxidase-3(GPX-3) levels was estimated by ELISA method. The present study shows significantly decreased levels of magnesium, GSH, GPX-3 and increased level of MDA in type 2 diabetes mellitus patients with cataract when compared with non-diabetic senile cataract patients, type 2 DM without cataract and normal healthy individuals. A significant negative correlation of serum magnesium with MDA and positive correlation with GPX-3 were observed. The present findings indicate that hypomagnesaemia is a significant pathogenic factor which causes increased oxidative stress which may trigger earlier cataractogenesis in patients with type 2 diabetes mellitus.

The Role of Disturbed Mg Homeostasis in Chronic Kidney Disease Comorbidities

Some of the critical mechanisms that mediate chronic kidney disease (CKD) progression are associated with vascular calcifications, disbalance of mineral metabolism, increased oxidative and metabolic stress, inflammation, coagulation abnormalities, endothelial dysfunction, or accumulation of uremic toxins. Also, it is widely accepted that pathologies with a strong influence in CKD progression are diabetes, hypertension, and cardiovascular disease (CVD). A disbalance in magnesium (Mg) homeostasis, more specifically hypomagnesemia, is associated with the development and progression of the comorbidities mentioned above, and some mechanisms might explain why low serum Mg is associated with negative clinical outcomes such as major adverse cardiovascular and renal events. Furthermore, it is likely that hypomagnesemia causes the release of inflammatory cytokines and C-reactive protein and promotes insulin resistance. Animal models have shown that Mg supplementation reverses vascular calcifications; thus, clinicians have focused on the potential benefits that Mg supplementation may have in humans. Recent evidence suggests that Mg reduces coronary artery calcifications and facilitates peripheral vasodilation. Mg may reduce vascular calcification by direct inhibition of the Wnt/β-catenin signaling pathway. Furthermore, Mg deficiency worsens kidney injury induced by an increased tubular load of phosphate. One important consequence of excessive tubular load of phosphate is the reduction of renal tubule expression of α-Klotho in moderate CKD. Low Mg levels worsen the reduction of Klotho induced by the tubular load of phosphate. Evidence to support clinical translation is yet insufficient, and more clinical studies are required to claim enough evidence for decision-making in daily practice. Meanwhile, it seems reasonable to prevent and treat Mg deficiency. This review aims to summarize the current understanding of Mg homeostasis, the potential mechanisms that may mediate the effect of Mg deficiency on CKD progression, CVD, and mortality.

Serum magnesium level and hematoma expansion in patients with intracerebral hemorrhage

Spontaneous intracerebral hemorrhage (ICH) is a devastating subtype of stroke that results in significant rates of mortality and morbidities. The initial hematoma volume, hematoma expansion (HE), blood pressure (BP), and coagulopathy are considered strong predictors of clinical outcomes and mortality. Low serum magnesium (Mg⁺⁺) levels have been shown to be associated with larger initial hematoma and greater HE. Coagulopathy, platelet dysfunction, high BP, and increased inflammatory response might form the mechanistic link between low serum Mg⁺⁺ levels, larger hematoma size and greater HE. However, randomized clinical trials administering intravenous Mg⁺⁺ have shown no benefit over placebo in ICH patients. The confounding effect of hypocalcemia and a delay in Mg⁺⁺ trafficking across the blood-brain barrier might explain the futile results for intravenous Mg⁺⁺ therapy. In the current review, we will discuss the evidence regarding the possible role of low serum Mg⁺⁺ level on HE in acute ICH.

Effects of dietary sodium selenite and organic selenium sources on immune and inflammatory responses and selenium deposition in growing pigs

The study was conducted to compare effects of different dietary Se sources (sodium selenite [NaSe], Se-enriched yeast [Se yeast] or L-selenomethionine [SeMet]) and one Se-deficient control diet on the expression of selected genes, hematological and clinical biochemical parameters, and muscle morphology in two parallel trials with finisher pigs. Se concentrations in blood plasma and tissues were also monitored. From the pigs in one of the parallel groups, muscle samples obtained from Musculus longissimus dorsi (LD) before and during the trial were examined. The pigs in the other parallel group were challenged once with lipopolysaccharide (LPS) intravenously. Transcriptional analyses of LD showed that selenogenes SelenoW and H were higher expressed in pigs fed Se-supplemented diets compared with control. Furthermore, the expression of interferon gamma and cyclooxygenase 2 was lower in the Se-supplemented pigs versus control. In whole blood samples prior to LPS, SelenoN, SelenoS and thioredoxin reductase 1 were higher expressed in pigs fed NaSe supplemented feed compared with the other groups, possibly indicating a higher level of oxidative stress. After LPS exposure glutathione peroxidase 1 and SelenoN were more reduced in pigs fed NaSe compared with pigs fed organic Se. Products of most above-mentioned genes are intertwined with the oxidant-antioxidant system. No significant effects of Se-source were found on hematologic parameters or microscopic anatomy. The Se-concentrations in various skeletal muscles and heart muscle were significantly different between the groups, with highest concentrations in pigs fed SeMet, followed by those fed Se yeast, NaSe, and control diet. Consistent with previous reports our results indicate that dietary Se at adequate levels can support the body's antioxidant system. Our results indicate that muscle fibers of pigs fed organic Se are less vulnerable to oxidative stress compared with the other groups.

Magnesium Replacement to Protect Cardiovascular and Kidney Damage? Lack of Prospective Clinical Trials

Patients with advanced chronic kidney disease exhibit an increase in cardiovascular mortality. Recent works have shown that low levels of magnesium are associated with increased cardiovascular and all-cause mortality in hemodialysis patients. Epidemiological studies suggest an influence of low levels of magnesium on the occurrence of cardiovascular disease, which is also observed in the normal population. Magnesium is involved in critical cellular events such as apoptosis and oxidative stress. It also participates in a number of enzymatic reactions. In animal models of uremia, dietary supplementation of magnesium reduces vascular calcifications and mortality; in vitro, an increase of magnesium concentration decreases osteogenic transdifferentiation of vascular smooth muscle cells. Therefore, it may be appropriate to evaluate whether magnesium replacement should be administered in an attempt to reduce vascular damage and mortality in the uremic population In the present manuscript, we will review the magnesium homeostasis, the involvement of magnesium in enzymatic reactions, apoptosis and oxidative stress and the clinical association between magnesium and cardiovascular disease in the general population and in the context of chronic kidney disease. We will also analyze the role of magnesium on kidney function. Finally, the experimental evidence of the beneficial effects of magnesium replacement in chronic kidney disease will be thoroughly described.

The Effect of Magnesium on Visual Evoked Potentials in L-NAME-Induced Hypertensive Rats

In the literature, although there are many studies regarding complications of hypertension, information concerning its influence on visual evoked potentials (VEPs) is limited. This study aims to clarify the possible therapeutic effects of the preferential magnesium (Mg) treatment on VEPs in an experimental hypertension model. Rats were divided into four groups as follows: control, Mg treated (Mg), N(omega)-nitro-L-arginine methyl ester (L-NAME) hypertension, and L-NAME hypertension + Mg treated (L-NAME + Mg). Hypertension was induced by L-NAME which was given to rats orally over 6 weeks (25 mg/kg/day in drinking water). A magnesium-enriched diet (0.8 g/kg) was given to treatment groups for 6 weeks. Systolic blood pressure (SBP) was determined by using the tail-cuff method. Flash VEPs were recorded. Our results revealed that the SBP was significantly increased in the L-NAME group compared to control. Magnesium treatment significantly attenuated SBP in the hypertensive rats compared to the L-NAME group. The mean latencies of P1, N1, P2, N2, and P3 components were significantly prolonged in hypertensive rats compared to control. Treatment with Mg provided a significant decrease in the latencies of P1, N1, P2, N2, and P3 potentials in the L-NAME + Mg group compared to the L-NAME group. Plasma Mg levels were increased in the L-NAME + Mg group compared to the L-NAME group. No change was detected in the Mg levels of the brains in all experimental groups. Magnesium treatment had no effect on the brain nitrate/nitrite and thiobarbituric acid-reactive substances (TBARS) levels in hypertensive rats compared to non-treated rats. There was a positive correlation between the brain TBARS levels and SBP of the rats. The present study suggests that Mg supplementation has the potential to prevent VEP changes in the L-NAME-induced hypertension model.

PARK7/DJ-1 dysregulation by oxidative stress leads to magnesium deficiency: implications in degenerative and chronic diseases

Disturbed magnesium (Mg(2+)) homoeostasis and increased levels of OS (oxidative stress) are associated with poor clinical outcomes in patients suffering from neurodegenerative, cardiovascular and metabolic diseases. Data from clinical and animal studies suggest that MD (Mg(2+) deficiency) is correlated with increased production of ROS (reactive oxygen species) in cells, but a straightforward causal relationship (including molecular mechanisms) between the two conditions is lacking. The multifactorial protein PARK7/DJ-1 is a major antioxidant protein, playing a key role in cellular redox homoeostasis, and is a positive regulator of AR (androgen receptor)-dependent transcription. SLC41A1 (solute carrier family 41 member 1), the gene encoding a ubiquitous cellular Mg(2+)E (Mg(2+)efflux) system, has been shown to be regulated by activated AR. We hypothesize that overexpression/up-regulation of PARK7/DJ-1, attributable to OS and related activation of AR, is an important event regulating the expression of SLC41A1 and consequently, modulating the Mg(2+)E capacity. This would involve changes in the transcriptional activity of PARK7/DJ-1, AR and SLC41A1, which may serve as biomarkers of intracellular MD and may have clinical relevance. Imipramine, in use as an antidepressant, has been shown to reduce the Mg(2+)E activity of SLC41A1 and OS. We therefore hypothesize further that administration of imipramine or related drugs will be beneficial in MD- and OS-associated diseases, especially when combined with Mg(2+) supplementation. If proved true, the OS-responsive functional axis, PARK7/DJ-1-AR-SLC41A1, may be a putative mechanism underlying intracellular MD secondary to OS caused by pro-oxidative stimuli, including extracellular MD. Furthermore, it will advance our understanding of the link between OS and MD.

Multiscale model of dynamic neuromodulation integrating neuropeptide-induced signaling pathway activity with membrane electrophysiology

We developed a multiscale model to bridge neuropeptide receptor-activated signaling pathway activity with membrane electrophysiology. Typically, the neuromodulation of biochemical signaling and biophysics have been investigated separately in modeling studies. We studied the effects of Angiotensin II (AngII) on neuronal excitability changes mediated by signaling dynamics and downstream phosphorylation of ion channels. Experiments have shown that AngII binding to the AngII receptor type-1 elicits baseline-dependent regulation of cytosolic Ca(2+) signaling. Our model simulations revealed a baseline Ca(2+)-dependent response to AngII receptor type-1 activation by AngII. Consistent with experimental observations, AngII evoked a rise in Ca(2+) when starting at a low baseline Ca(2+) level, and a decrease in Ca(2+) when starting at a higher baseline. Our analysis predicted that the kinetics of Ca(2+) transport into the endoplasmic reticulum play a critical role in shaping the Ca(2+) response. The Ca(2+) baseline also influenced the AngII-induced excitability changes such that lower Ca(2+) levels were associated with a larger firing rate increase. We examined the relative contributions of signaling kinases protein kinase C and Ca(2+)/Calmodulin-dependent protein kinase II to AngII-mediated excitability changes by simulating activity blockade individually and in combination. We found that protein kinase C selectively controlled firing rate adaptation whereas Ca(2+)/Calmodulin-dependent protein kinase II induced a delayed effect on the firing rate increase. We tested whether signaling kinetics were necessary for the dynamic effects of AngII on excitability by simulating three scenarios of AngII-mediated KDR channel phosphorylation: (1), an increased steady state; (2), a step-change increase; and (3), dynamic modulation. Our results revealed that the kinetics emerging from neuromodulatory activation of the signaling network were required to account for the dynamical changes in excitability. In summary, our integrated multiscale model provides, to our knowledge, a new approach for quantitative investigation of neuromodulatory effects on signaling and electrophysiology.

Intakes of magnesium, potassium, and calcium and the risk of stroke among men

BACKGROUND

Intakes of magnesium, potassium, and calcium have been inversely associated with the incidence of hypertension, a known risk factor for stroke. However, only a few studies have examined intakes of these cations in relation to risk of stroke.

AIM

The aim of this study was to investigate whether high intake of magnesium, potassium, and calcium is associated with reduced stroke risk among men.

METHODS

We prospectively examined the associations between intakes of magnesium, potassium, and calcium from diet and supplements, and the risk of incident stroke among 42 669 men in the Health Professionals Follow-up Study, aged 40 to 75 years and free of diagnosed cardiovascular disease and cancer at baseline in 1986. We calculated the hazard ratio of total, ischemic, and haemorrhagic strokes by quintiles of each cation intake, and of a combined dietary score of all three cations, using multivariate Cox proportional hazard models.

RESULTS

During 24 years of follow-up, 1547 total stroke events were documented. In multivariate analyses, the relative risks and 95% confidence intervals of total stroke for men in the highest vs. lowest quintile were 0·87 (95% confidence interval, 0·74-1·02; P, trend = 0·04) for dietary magnesium, 0·89 (95% confidence interval, 0·76-1·05; P, trend = 0·10) for dietary potassium, and 0·89 (95% confidence interval, 0·75-1·04; P, trend = 0·25) for dietary calcium intake. The relative risk of total stroke for men in the highest vs. lowest quintile was 0·74 (95% confidence interval, 0·59-0·93; P, trend = 0·003) for supplemental magnesium, 0·66 (95% confidence interval, 0·50-0·86; P, trend = 0·002) for supplemental potassium, and 1·01 (95% confidence interval, 0·84-1·20; P, trend = 0·83) for supplemental calcium intake. For total intake (dietary and supplemental), the relative risk of total stroke for men in the highest vs. lowest quintile was 0·83 (95% confidence interval, 0·70-0·99; P, trend = 0·04) for magnesium, 0·88 (95% confidence interval, 0·75-4; P, trend = 6) for potassium, and 3 (95% confidence interval, 79-09; P, trend = 84) for calcium. Men in the highest quintile for a combined dietary score of all three cations had a multivariate relative risk of 0·79 (95% confidence interval, 0·67-0·92; P, trend = 0·008) for total stroke, compared with those in the lowest.

CONCLUSIONS

A diet rich in magnesium, potassium, and calcium may contribute to reduced risk of stroke among men. Because of significant collinearity, the independent contribution of each cation is difficult to define.

Hypomagnesaemia in kidney transplantation

In the era of calcineurin inhibitors, hypomagnesaemia is a very common finding in kidney transplant recipients. Especially the first weeks after transplantation it is the rule rather than the exception. Hypomagnesaemia or low magnesium intake have been associated with a higher mortality or more cardiovascular events in the general population, but this association has never been explored in kidney transplant recipients, despite their increased cardiovascular risk. Kidney transplant recipients with pre- or post-transplant hypomagnesaemia seem to have an aberrant glucose metabolism and develop diabetes mellitus more frequently. Moreover, observations from alternate study populations, animal experiments or in vitro studies suggest a possible role of magnesium deficiency in graft dysfunction, bone metabolism and transplant immunology. Future observational and especially interventional studies should further define whether and to what extent we should make effort to correct this electrolyte disturbance in transplant recipients. Considering the mechanism of renal magnesium wasting, normalizing the serum magnesium concentration by oral supplementation alone might turn out to be cumbersome in kidney transplant recipients.

Maternal hypomagnesemia causes placental abnormalities and fetal and postnatal mortality

INTRODUCTION

Magnesium (Mg(2+)) is essential for cellular growth and the maintenance of normal cellular processes. However, little is known about how maternal hypomagnesemia during pregnancy affects fetal growth and development. This study investigated the effects of maternal hypomagnesemia on the late gestation placenta and fetus, and postnatal outcomes until weaning.

METHODS

Female CD1 mice consumed a control (0.2% w/w Mg(2+)), moderately Mg(2+) deficient (MMD; 0.02% w/w Mg(2+)) or severely Mg(2+) deficient (SMD; 0.005% w/w Mg(2+)) diet for 4 weeks prior to mating and throughout pregnancy. Dams were killed at E18.5 for embryonic studies or allowed to litter naturally and the offspring studied up to postnatal day 21.

RESULTS

At E18.5, both Mg(2+) deficient diets decreased maternal plasma and bone Mg(2+) but only the SMD diet decreased fetal plasma Mg(2+). Maternal hypomagnesemia led to fetal loss and fetal growth restriction. Maternal Mg(2+) deficiency increased placental glycogen cell area and decreased spongiotrophoblast cell area while upregulating mRNA expression of the MagT1 Mg(2+) transporter in spongiotrophoblast cells. The SMD animals also displayed instances of gross placental abnormalities. After birth, pups in the SMD group had increased early postnatal mortality and failed to thrive. Pups in the MMD group underwent catch-up growth but remained shorter than controls at PN21 and were hypomagnesemic and hypoglycemic.

CONCLUSIONS

These changes suggest that maternal Mg(2+) deficiency during pregnancy impairs placental development and fetal growth, which may have long-term health consequences for offspring. Collectively, these results have important implications for women who are Mg(2+) deficient during pregnancy.

Pretreatment with magnesium ameliorates lipopolysaccharide-induced liver injury in mice

BACKGROUND

Lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacteria, is involved in the pathogenesis of sepsis. LPS administration induces systemic inflammation that mimics many of the initial clinical features of sepsis and has deleterious effects on several organs including the liver and eventually leading to septic shock and death. The present study aimed to investigate the protective effect of magnesium (Mg), a well known cofactor in many enzymatic reactions and a critical component of the antioxidant system, on hepatic damage associated with LPS-induced endotoxima in mice.

METHODS

Mg (20 and 40mg/kg, po) was administered for 7 consecutive days. Systemic inflammation was induced 1h after the last dose of Mg by a single dose of LPS (2mg/kg, ip) and 3h thereafter plasma was separated, animals were sacrificed and their livers were isolated.

RESULTS

LPS-treated mice suffered from hepatic dysfunction revealed by histological observation, elevation in plasma transaminases activities, C-reactive protein content and caspase-3, a critical marker of apoptosis. Liver inflammation was evident by elevation in liver cytokines contents (TNF-α and IL-10) and MPO activity. Additionally, oxidative stress was manifested by increased liver lipoperoxidation, glutathione depletion, elevated total nitrate/nitrite (NOx) content and glutathione peroxidase (GPx) activity. Pretreatment with Mg largely mitigated these alternations.

CONCLUSION

Pretreatment with Mg protects the liver from the acute injury which occurs shortly after septicemia.

Association between magnesium status, oxidative stress and inflammation in preeclampsia: A case-control study

BACKGROUND & AIMS

Preeclampsia is responsible for more than one-third of all maternal deaths in Brazil. The objectives of the present study were to evaluate magnesium status and its association with oxidative stress and inflammation in preeclamptic women, and to identify the predictor variables of the disorder.

METHODS

The study population consisted of 36 women divided into preeclamptic (n = 18) and control groups (n = 18). The preeclamptic group included women (≥20 weeks of pregnancy) with arterial pressure ≥ 140/90 mmHg and proteinuria >0.3 g/24 h, while the control group comprised pregnant women with no clinical/obstetric complications. Magnesium intake was assessed via a food frequency questionnaire validated for pregnant women in Brazil. Plasma, erythrocyte and urinary magnesium levels were determined by flame atomic absorption spectroscopy, while oxidative stress and inflammatory markers were assessed using standard protocols. Logistic regression analysis was used to identify the predictors of preeclampsia.

RESULTS

Preeclamptic and control groups were similar with respect to magnesium intake and urinary excretion, while plasma and erythrocyte magnesium concentrations were higher in the former group. Plasma magnesium was positively correlated with catalase and glutathione peroxidase activities and with concentrations of interleukin-6 and tumor necrosis factor alpha. Regression analysis showed that plasma magnesium and urinary 8-isoprostane were associated with preeclampsia.

CONCLUSION

Magnesium status appears to result from homeostatic imbalance and physiological alterations typical of preeclampsia. Increased plasma magnesium and decreased urinary 8-isoprostane were considered predictors of preeclampsia.

Additional antihypertensive effect of magnesium supplementation with an angiotensin II receptor blocker in hypomagnesemic rats

BACKGROUND/AIMS

Magnesium (Mg) is an essential element for vascular function and blood pressure regulation. Several studies have demonstrated that Mg concentration is inversely associated with blood pressure, and that Mg supplementation attenuates hypertension. The purpose of this study was to evaluate the effect of dietary Mg supplementation on the blood pressure effects of an angiotensin II receptor blocker (ARB) in hypomagnesemic rats.

METHODS

Fifty male Sprague-Dawley rats were randomly divided into Mg-deficient (n = 30), normal diet plus Mg (n = 10), and control groups (n = 10). Mg-free, high-Mg, and normal-Mg diets were respectively fed to the rats. After 14 weeks, 10 of the 30 Mg-deficient rats were treated with Mg, 10 Mg-deficient rats received an ARB, and 10 Mg-deficient rats received an ARB plus Mg for 4 weeks.

RESULTS

Systolic blood pressure was significantly higher in the Mg-deficient rats than in the control rats at week 14. Hypomagnesemic rats exhibited decreased systolic blood pressure after treatment with Mg, and systolic blood pressure showed a greater decrease after ARB treatment. Treatment with the ARB/Mg combination resulted in the greatest decrease in systolic blood pressure. Mg deficiency did not affect the serum angiotensin II level, but did increase the serum aldosterone concentration. Concomitant Mg/ARB supplementation significantly decreased the elevated serum aldosterone level in hypomagnesemic rats. Kidney tissues of the hypomagnesemic rats revealed mild to moderate inflammatory infiltrates. Mg and/or ARB treatment did not reverse the inflammatory reaction in the kidneys of hypomagnesemic rats.

CONCLUSIONS

Concurrent dietary Mg supplementation can enhance ARB-induced blood pressure reduction in rats with hypomagnesemic hypertension.

Magnesium and vascular changes in hypertension

Many factors have been implicated in the pathogenesis of hypertension, including changes in intracellular concentrations of calcium, sodium, potassium, and magnesium. There is a significant inverse correlation between serum magnesium and incidence of cardiovascular diseases. Magnesium is a mineral with important functions in the body such as antiarrhythmic effect, actions in vascular tone, contractility, glucose metabolism, and insulin homeostasis. In addition, lower concentrations of magnesium are associated with oxidative stress, proinflammatory state, endothelial dysfunction, platelet aggregation, insulin resistance, and hyperglycemia. The conflicting results of studies evaluating the effects of magnesium supplements on blood pressure and other cardiovascular outcomes indicate that the action of magnesium in the vascular system is present but not yet established. Therefore, this mineral supplementation is not indicated as part of antihypertensive treatment, and further studies are needed to better clarify the role of magnesium in the prevention and treatment of cardiovascular diseases.

Thrombotic microangiopathy: a role for magnesium?

Despite advances in more recent years, the pathophysiology and especially treatment modalities of thrombotic microangiopathy (TMA) largely remain enigmatic. Disruption of endothelial homeostasis plays an essential role in TMA. Considering the proven causal association between magnesium and both endothelial function and platelet aggregability, we speculate that a magnesium deficit could influence the course of TMA and the related haemolytic uraemic syndrome and thrombotic thrombocytopenic purpura. A predisposition towards TMA is seen in many conditions with both extracellular and intracellular magnesium deficiency. We propose a rationale for magnesium supplementation in TMA, in analogy with its evidence-based therapeutic application in pre-eclampsia and suggest, based on theoretical grounds, that it might attenuate the development of TMA, minimise its severity and prevent its recurrence. This is based on several lines of evidence from both in vitro and in vivo data showing dose-dependent effects of magnesium supplementation on nitric oxide production, platelet aggregability and inflammation. Our hypothesis, which is further amenable to assessment in animal models before therapeutic applications in humans are implemented, could be explored both in vitro and in vivo to decipher the potential role of magnesium deficit in TMA and of the effects of its supplementation.

Transient receptor potential melastatin 7 (TRPM7) cation channels, magnesium and the vascular system in hypertension

Decreased Mg(2+) concentration has been implicated in altered vascular reactivity, endothelial dysfunction and structural remodeling, processes important in vascular changes and target organ damage associated with hypertension. Unlike our knowledge of other major cations, mechanisms regulating cellular Mg(2+) handling are poorly understood. Until recently little was known about protein transporters controlling transmembrane Mg(2+) influx. However, new research has uncovered a number of genes and proteins identified as transmembrane Mg(2+) transporters, particularly transient receptor potential melastatin (TRPM) cation channels, TRPM6 and TRPM7. Whereas TRPM6 is found primarily in epithelial cells, TRPM7 is ubiquitously expressed. Vascular TRPM7 has been implicated as a signaling kinase involved in vascular smooth muscle cell growth, apoptosis, adhesion, contraction, cytoskeletal organization and migration, and is modulated by vasoactive agents, pressure, stretch and osmotic changes. Emerging evidence suggests that vascular TRPM7 function might be altered in hypertension. The present review discusses the importance of Mg(2+) in vascular biology in hypertension and focuses on transport systems, mainly TRPM7, that might play a role in the control of vascular Mg(2+) homeostasis. Elucidation of the relationship between the complex systems responsible for regulation of Mg(2+) homeostasis, the role of TRPM7 in vascular signaling, and the cardiovascular impact will be important for understanding the clinical implications of hypomagnesemia in cardiovascular disease.

LIBS-based detection of antioxidant elements: a new strategy

The present study deals with the scientific evaluation of antioxidant potential of aqueous extract of Trichosanthes dioica fruits on diabetes-induced oxidative stress of diabetic rats. The most effective dose of mg/kg bw of fruit aqueous extract was given orally to diabetic rats for 30 days. Different oxidative stress parameters were analyzed in various tissues of control and treated diabetic rats. The observed elevated level of lipid peroxidation (LPO) comes down significantly (p < 0.05) and decreased activities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) got increased (p < 0.05) significantly of diabetic rats on extract treatment. Laser-Induced Breakdown Spectroscopy (LIBS) has been used as an analytical tool to detect major and minor elements like Mg, Fe, Na, K, Zn, Ca, H, O, C, and N present in the extract. The higher concentration of Ca(2+), Mg(2+), and Fe(2+), as reflected by their intensities are responsible for antioxidant potential of T. dioica.

Chemistry and antihypertensive effects of tempol and other nitroxides

Nitroxides can undergo one- or two-electron reduction reactions to hydroxylamines or oxammonium cations, respectively, which themselves are interconvertible, thereby providing redox metabolic actions. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (tempol) is the most extensively studied nitroxide. It is a cell membrane-permeable amphilite that dismutates superoxide catalytically, facilitates hydrogen peroxide metabolism by catalase-like actions, and limits formation of toxic hydroxyl radicals produced by Fenton reactions. It is broadly effective in detoxifying these reactive oxygen species in cell and animal studies. When administered intravenously to hypertensive rodent models, tempol caused rapid and reversible dose-dependent reductions in blood pressure in 22 of 26 studies. This was accompanied by vasodilation, increased nitric oxide activity, reduced sympathetic nervous system activity at central and peripheral sites, and enhanced potassium channel conductance in blood vessels and neurons. When administered orally or by infusion over days or weeks to hypertensive rodent models, it reduced blood pressure in 59 of 68 studies. This was accompanied by correction of salt sensitivity and endothelial dysfunction and reduced agonist-evoked oxidative stress and contractility of blood vessels, reduced renal vascular resistance, and increased renal tissue oxygen tension. Thus, tempol is broadly effective in reducing blood pressure, whether given by acute intravenous injection or by prolonged administration, in a wide range of rodent models of hypertension.

Dysregulation of vascular TRPM7 and annexin-1 is associated with endothelial dysfunction in inherited hypomagnesemia

Inadequate magnesium intake and hypomagnesemia may contribute to chronic diseases, such as hypertension. The novel magnesium transporter TRPM7 is a critical regulator of magnesium homeostasis in vascular cells, but its role in pathophysiology is unclear. In a model of hypomagnesemia, we examined microvascular structure and function, TRPM7 expression, and vascular inflammatory status using inbred mice selected for normal-high intracellular magnesium levels or low intracellular magnesium levels (MgLs). Blood pressure was significantly increased in MgLs compared with normal-high intracellular magnesium levels. Pressurized myography of mesenteric resistance arteries showed that MgLs had significantly impaired endothelial function together with decreased plasma nitrate levels and endothelial NO synthase expression when compared with normal-high intracellular magnesium levels. Significant differences in vascular structure were also evident in both mesenteric arteries and aortas from MgLs. Aortas from MgLs had increased medial cross-sectional areas, whereas mesenteric arteries from MgLs had increased lumen diameters with increased medial cross-sectional areas, indicating outward hypertrophic remodeling. Expression of the magnesium transporter TRPM7 was significantly elevated in the vasculature of MgLs, whereas expression of a TRPM7 downstream target, the anti-inflammatory molecule annexin-1, was reduced. MgLs had increased expression of vascular cell adhesion molecule-1 and plasminogen activator inhibitor-1, indicating vascular inflammation. Taken together, these data demonstrate that the inherited magnesium status of MgLs and normal-high intracellular magnesium levels mice affects magnesium transporter expression, endothelial function, vascular structure, and inflammation. Our findings suggest a potential regulatory role for TRPM7 signaling in the maintenance of vascular integrity. Alterations in magnesium status and/or TRPM7 signaling may contribute to vascular injury in conditions associated with hypomagnesemia.

Transient receptor potential melastatin 6 and 7 channels, magnesium transport, and vascular biology: implications in hypertension

Magnesium, an essential intracellular cation, is critically involved in many biochemical reactions involved in the regulation of vascular tone and integrity. Decreased magnesium concentration has been implicated in altered vascular reactivity, endothelial dysfunction, vascular inflammation, and structural remodeling, processes important in vascular changes and target organ damage associated with hypertension. Until recently, very little was known about mechanisms regulating cellular magnesium homeostasis, and processes controlling transmembrane magnesium transport had been demonstrated only at the functional level. Two cation channels of the transient receptor potential melastatin (TRPM) cation channel family have now been identified as magnesium transporters, TRPM6 and TRPM7. These unique proteins, termed chanzymes because they possess a channel and a kinase domain, are differentially expressed, with TRPM6 being found primarily in epithelial cells and TRPM7 occurring ubiquitously. Vascular TRPM7 is modulated by vasoactive agents, pressure, stretch, and osmotic changes and may be a novel mechanotransducer. In addition to its magnesium transporter function, TRPM7 has been implicated as a signaling kinase involved in vascular smooth muscle cell growth, apoptosis, adhesion, contraction, cytoskeletal organization, and migration, important processes involved in vascular remodeling associated with hypertension and other vascular diseases. Emerging evidence suggests that vascular TRPM7 function may be altered in hypertension. This review discusses the importance of magnesium in vascular biology and implications in hypertension and highlights the transport systems, particularly TRPM6 and TRPM7, which may play a role in the control of vascular magnesium homeostasis. Since the recent identification and characterization of Mg2+-selective transporters, there has been enormous interest in the field. However, there is still a paucity of information, and much research is needed to clarify the exact mechanisms of magnesium regulation in the cardiovascular system and the implications of aberrant transmembrane magnesium transport in the pathogenesis of hypertension and other vascular diseases.

Long-term moderate magnesium-deficient diet shows relationships between blood pressure, inflammation and oxidant stress defense in aging rats

Epidemiological and experimental studies have indicated a relationship among aging, dietary Mg, inflammatory stress, and cardiovascular disease. Our aim in the present study was to investigate possible links between dietary Mg, oxidant stress parameters, and inflammatory status with aging in rats. We designed a long-term study in which rats were fed for 22 months with moderately deficient (150 mg/kg), standard (800 mg/kg), or supplemented (3200 mg/kg) Mg diets. Comparisons were made with young rats fed with the same diets for 1 month. Compared to the standard and supplemented diets, the Mg-deficient diet significantly increased blood pressure, plasma interleukin-6, fibrinogen, and erythrocyte lysophosphatidylcholine, particularly in aging rats, it decreased plasma albumin. The impairment of redox status was indicated by increases in plasma thiobarbituric acid reactive substances and oxysterols and an increased blood susceptibility to in vitro free-radical-induced hemolysis. We concluded that Mg deficiency induced a chronic impairment of redox status associated with inflammation which could significantly contribute to increased oxidized lipids and promote hypertension and vascular disorders with aging. Extrapolating to the human situation and given that Mg deficiency has been reported to be surprisingly common, particularly in the elderly, Mg supplementation might be useful as an adjuvant therapy in preventing cardiovascular disease.

Role of magnesium in hypertension

Magnesium affects blood pressure by modulating vascular tone and reactivity. It acts as a calcium channel antagonist, it stimulates production of vasodilator prostacyclins and nitric oxide and it alters vascular responses to vasoactive agonists. Magnesium deficiency has been implicated in the pathogenesis of hypertension with epidemiological and experimental studies demonstrating an inverse correlation between blood pressure and serum magnesium levels. Magnesium also influences glucose and insulin homeostasis, and hypomagnesemia is associated with metabolic syndrome. Although most epidemiological and experimental studies support a role for low magnesium in the pathophysiology of hypertension, data from clinical studies have been less convincing. Furthermore, the therapeutic value of magnesium in the management of hypertension is unclear. The present review addresses the role of magnesium in the regulation of vascular function and blood pressure and discusses the implications of magnesium deficiency in experimental and clinical hypertension, in metabolic syndrome and in pre-eclampsia.

Lipoic acid supplementation prevents cyclosporine-induced hypertension and nephrotoxicity in spontaneously hypertensive rats

BACKGROUND

Cyclosporine (CsA) has significantly improved long-term survival after organ transplantations. Hypertension and nephrotoxicity are common side effects during CsA treatment and are aggravated by high salt intake.

OBJECTIVE

To examine whether lipoic acid (LA), a natural antioxidant that scavenges reactive oxygen species and regenerates/recycles endogenous antioxidants, could prevent CsA-induced hypertension and nephrotoxicity.

METHODS

Six-week-old spontaneously hypertensive rats (SHR) on a high-sodium diet (NaCl 6%) received CsA [5 mg/kg subcutaneously (s.c.)] alone or in combination with LA (0.5% w/w) for 6 weeks. Blood pressure, arterial functions, and tissue morphology were determined. Immunohistochemistry, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and high-pressure liquid chromatography were used for kidney and heart samples.

RESULTS

CsA induced severe hypertension, cardiac hypertrophy, endothelial dysfunction, and pronounced albuminuria. Histologically, the kidneys showed severe thickening of the media of the afferent arteries with fibrinoid necrosis, perivascular monocyte/macrophage infiltration and nitrotyrosine overexpression. CsA induced the expression of fibrogenic connective tissue growth factor both in the heart and kidneys. The detrimental effects of CsA were associated with upregulation of myocardial atrial natriuretic peptide (ANP) mRNA expression, paradoxical activation of the renin-angiotensin system (RAS), induction of renal reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, and overexpression of oxidative stress-induced transcription factor NRF2. LA lowered blood pressure, ameliorated cardiac hypertrophy and endothelial dysfunction, and totally normalized albuminuria. In LA-treated rats, renal and cardiac morphologies were indistinguishable from those of SHR controls. CsA-induced myocardial ANP and connective tissue growth factor (CTGF) mRNA overexpression, RAS activation, NADPH oxidase induction, and NRF2 overexpression were prevented by LA. LA induced the mRNA expression of gamma-glutamylcysteine ligase, the rate-limiting enzyme in glutathione synthesis, and markedly increased hepatic cysteine and glutathione concentrations.

CONCLUSIONS

Our findings suggest a salutary role for lipoic acid supplementation in the prevention of CsA-induced hypertension and nephrotoxicity, and underscore the importance of increased oxidative stress in the pathogenesis of CsA toxicity.

Magnesium and the inflammatory response: potential physiopathological implications

The purpose of this review is to summarize experimental findings showing that magnesium modulates cellular events involved in inflammation. Experimental magnesium deficiency in the rat induces after a few days a clinical inflammatory syndrome characterized by leukocyte and macrophage activation, release of inflammatory cytokines and acute phase proteins, excessive production of free radicals. Increase in extracellular magnesium concentration, decreases inflammatory response while reduction in the extracellular magnesium results in cell activation. Because magnesium acts as a natural calcium antagonist, the molecular basis for inflammatory response is probably the result of modulation of intracellular calcium concentration. The priming of phagocytic cells, the opening calcium channel and activation of N-methyl-d-aspartate (NMDA) receptors, the activation of nuclear factor-kappa B (NFkappaB) have been considered as potential mechanisms. Moreover, magnesium deficiency induces a systemic stress response by activation of neuro endocrinological pathways. As nervous and immune systems interact bidirectionally, the roles of neuromediators have also been considered. Magnesium deficiency contributes to an exaggerated response to immune stress and oxidative stress is the consequence of the inflammatory response. Inflammation contributes to the pro-atherogenic changes in lipoprotein metabolism, endothelial dysfunction, thrombosis, hypertension and explains the aggravating effect of magnesium deficiency on the development of metabolic syndrome. Further studies are still needed to assess more accurately the role of magnesium in immune response in humans, but these experimental findings in animal models suggest that inflammation is the missing link to explain the role of magnesium in many pathological conditions.

Magnesium supplementation prevents angiotensin II-induced myocardial damage and CTGF overexpression

OBJECTIVES AND DESIGN

Magnesium deficiency promotes vasoconstriction and myocardial damage. Recent studies provide evidence that Ang II mobilizes intracellular Mg through AT1 receptor-mediated pathways. We tested the hypothesis of whether magnesium supplementation prevents Ang II-induced myocardial damage and induction of the profibrotic connective tissue growth factor (CTGF).

METHODS

Four-week-old double transgenic rats harboring human renin and angiotensinogen genes (dTGR) were given dietary magnesium supplementation (0.6%) for 3 weeks. Control dTGR and normotensive Sprague-Dawley (SD) rats received normal diet (Mg 0.2%). Histopathological, immunohistochemical and mRNA analysis were used to detect the treatment-related effects of dietary magnesium in dTGR.

RESULTS

Magnesium (Mg) supplementation decreased blood pressure, ameliorated cardiac hypertrophy, protected against the development of Ang II-induced myocardial damage and increased serum ionized Mg2+ concentration (all variables P < 0.05). There was no difference in serum ionized Mg2+ concentration between dTGR and SD rats. Myocardial connective tissue growth factor (CTGF) mRNA and protein expressions were increased by 300% in dTGR (P < 0.05), especially in areas with myocardial infarctions and vascular inflammation. Magnesium supplementation prevented Ang II-induced myocardial CTGF overexpression (P < 0.05). Magnesium supplementation also improved the therapeutic effects of the calcineurin inhibitor tacrolimus, which produced marked hypomagnesemia when given as monotherapy.

CONCLUSION

Our findings suggest a salutary effect for magnesium supplementation in the treatment of Ang II-induced myocardial complications.

Effects of magnesium sulfate on lipid peroxidation and blood pressure regulators in preeclampsia

OBJECTIVES

To investigate the status of lipid peroxidation and serum levels of several vasoactive substances in preeclamptic (PE) pregnant women before and during treatment with magnesium sulfate (MgSO(4)).

DESIGN AND METHODS

The study population included 16 PE women. Circulating levels of malondialdehyde (MDA), endothelin 1 (ET-1), nitric oxide (NO) metabolites, and calcitonin gene-related peptide (CGRP) were measured before (at admission) and during MgSO(4) treatment (at delivery and 24 h postpartum).

RESULTS

At admission systolic and diastolic blood pressures were 157 +/- 3 mm Hg and 106 +/- 2 mm Hg, respectively, and decreased significantly during treatment at delivery and 24 h postpartum (P < 0.0001). Before treatment, serum MDA concentrations were 0.383 +/- 0.037 micromol/L, and decreased significantly during MgSO(4) administration at delivery and 24 h postpartum (P < 0.0001). In contrast, serum ET-1 levels at 24 h postpartum were significantly higher as compared with those observed before treatment (79 +/- 3 versus 65 +/- 2 pg/mL, P = 0.002). Serum NO metabolite concentrations were 26 +/- 3 micromol/L, and no significant changes were observed during treatment. Serum levels of CGRP were 50 +/- 3 pg/mL at admission, and increased significantly at partum (P < 0.001). Serum ET-1 correlated negatively with NO metabolites before treatment (r = -0.69, P = 0.002), but not during treatment. In contrast, ET-1 correlated positively with serum CGRP levels during treatment (r = 0.73, P = 0.002 and r = 0.71, P = 0.002, at delivery and 24 h postpartum, respectively), but not before treatment.

CONCLUSIONS

This study demonstrates that MgSO(4) administration to PE pregnant women induced significant changes in lipid peroxidation, production of ET-1 and CGRP.

Cellular-free magnesium depletion in brain and muscle of normal and preeclamptic pregnancy: a nuclear magnetic resonance spectroscopic study

Preeclampsia is a pregnancy disorder of unknown origin, characterized by vasospasm, elevated blood pressure, and increased neuromuscular irritability, features common to syndromes of magnesium deficiency. Evidence of serum and ionized magnesium metabolism disturbances have been observed in women with preeclampsia. This and the therapeutic utility of magnesium in preeclampsia led us to investigate the extent to which an endogenous tissue magnesium deficiency might be present in and contribute to its pathophysiology. We used (31)P nuclear magnetic resonance spectroscopy to noninvasively measure in situ intracellular-free magnesium levels in brain and skeletal muscle of fasting nonpregnant women (n=12), and of third trimester women with uncomplicated pregnancies (n=11) and preeclampsia (n=7). Compared with nonpregnant controls (brain 519+/-59 micromol/L; muscle 604+/-34 micromol/L), brain and skeletal muscle intracellular magnesium levels were significantly lower in both normal pregnant (brain 342+/-23 micromol/L; muscle 482+/-40 micromol/L; P=0.05 for both tissues) and preeclamptic women (brain 229+/-17 micromol/L; muscle 433+/-46 micromol/L; P=0.05 for both tissues). Brain intracellular magnesium was further reduced in preeclamptics compared with normal pregnant subjects (P=0.05). For all pregnant subjects, blood pressure was significantly and inversely related to the concomitantly measured intracellular magnesium level in brain (systolic, r=-0.59, P=0.01; diastolic, r=-0.52, P=0.02) but not in muscle. Cellular magnesium depletion is characteristic of normal pregnancy and may be one factor contributing to the pathophysiology of preeclampsia. Furthermore, the influence of central nervous system factors on blood pressure may be mediated, at least in part, by ambient intracellular magnesium levels.

Effect of diets with different magnesium content in ischemic stroke rats

Rats fed with low (0.015%), normal (0.08%) or high (0.32%) magnesium (Mg) diet for 5-6 weeks were subjected to photothrombosis-induced infarction. As compared to normal diet, Mg deprivation increased by 45% infarct volume at 24 h after photothrombosis but did not modify the lesion at 4 h after photothrombosis. Mg supplementation did not protect from infarction whatever the time point examined. No differences in pre-ischemic systolic blood pressure and glycemia as well as in post-ischemic kaliemia, calcemia and plasma antioxidant activity were observed between groups. However, plasma total Mg level correlated with plasma antioxidant activity at 4 h after photothrombosis. These results demonstrate that brains from Mg deficient rats are more susceptible to permanent focal ischemia than rats fed with normal or high Mg diet.

Enhancement of endotoxin-induced vascular hyporeactivity to phenylephrine in the thoracic aortas of Mg-deficient rats ex vivo

Since endotoxin lethality is enhanced by Mg deficiency in animals, we determined whether endotoxin-induced vascular hyporeactivity to phenylephrine (PE) is enhanced in Mg-deficient rats. Normal and Mg-deficient adult male Wistar rats were injected with Escherichia coli 011: B4 lipopolysaccharide (1 or 5 mg/kg, i.p.). Six h later, rings prepared from their thoracic aortas showed severe hyporeactivity to PE. This was more pronounced in the Mg-deficient rats, and was reversed by in vitro treatment with a highly selective inducible nitric oxide (NO) synthase inhibitor, 1400 W, or a highly selective soluble guanylyl cyclase inhibitor, ODQ. However, reversal required high doses of both inhibitors in Mg-deficient rats. Endotoxemia for 6 h was associated with elevated serum interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha levels, and strong TNF receptor mRNA expression in the abdominal aortas, which were significantly greater in the Mg-deficient rats. Treatment of the thoracic aortas, isolated from control and Mg-deficient rats before endotoxic challenge, with IL-1beta or TNF-alpha for 6 h in vitro caused hyporeactivity to PE, but its severity did not differ significantly between the two groups. These results suggest that high serum IL-1beta and TNF-alpha levels, and increased TNF receptor production in the vascular tissue, contribute to vascular hyporeactivity to PE in endotoxemia, and to its enhancement in Mg-deficient rats, via NO/cGMP signaling.