Dietary magnesium affects susceptibility of lipoproteins and tissues to peroxidation in rats

The Roles of Platelet-Activating Factor and Magnesium in Pathophysiology of Hypertension, Atherogenesis, Cardiovascular Disease, Stroke and Aging

Hypertension and atherosclerosis are debilitating diseases that affect millions each year. Long-term consequences include but are not limited to stroke, myocardial infarction, and kidney failure. Platelet-activating factor (PAF) is a proinflammatory mediator synthesized from a subclass of phosphatidylcholines that increases platelet activation, leukocyte adhesion, infiltration of macrophages, and intracellular lipid accumulation, thereby contributing to atherosclerosis. Magnesium, a key micronutrient and free radical scavenger, is a water-soluble mineral that regulates peripheral vasodilation and calcium, phosphate, and hydroxyapatite homeostasis. Magnesium’s antihypertensive ability stems from its role as a natural calcium antagonist and promoter of vasodilatory mediators, such as nitric oxide. Platelet-activating factor and magnesium share an inverse relationship, and elevated magnesium levels have been shown to have protective effects against plaque formation as well as antihypertensive and antiarrhythmic effects, all of which allow for healthier aging. The purpose of this literature review is to investigate the role of platelet-activating factor and magnesium in the pathophysiology of hypertension, atherosclerosis, cardiovascular disease, stroke, and aging. Since the pathophysiology of the platelet-activating factor biomolecule is underexplored, further research studies are warranted in order to navigate the putative signaling pathways involved in the cardioprotective effects of dietary magnesium as a natural anti-PAF agent.

Magnesium, Little Known But Possibly Relevant: A Link between NASH and Related Comorbidities

Non-alcoholic steatohepatitis (NASH) is characterized by an abnormal hepatic lipid accumulation accompanied by a necro-inflammatory process and a fibrotic response. It comprises from 10% to 30% of cases of patients with non-alcoholic liver disease, which is a global health problem affecting around a quarter of the worldwide population. Nevertheless, the development of NASH is often surrounded by a pathological context with other comorbidities, such as cardiovascular diseases, obesity, insulin resistance or type 2 diabetes mellitus. Dietary imbalances are increasingly recognized as the root cause of these NASH-related comorbidities. In this context, a growing concern exists about whether magnesium consumption in the general population is sufficient. Hypomagnesemia is a hallmark of the aforementioned NASH comorbidities, and deficiencies in magnesium are also widely related to the triggering of complications that aggravate NASH or derived pathologies. Moreover, the supplementation of this cation has proved to reduce mortality from hepatic complications. In the present review, the role of magnesium in NASH and related comorbidities has been characterized, unraveling the relevance of maintaining the homeostasis of this cation for the correct functioning of the organism.

Magnesium Levels Modify the Effect of Lipid Parameters on Carotid Intima Media Thickness

Classical risk factors of atherosclerosis in the general population show paradoxical effects in chronic kidney disease (CKD) patients. Thus, low low-density lipoprotein (LDL) cholesterol levels have been associated with worse cardiovascular outcomes. Magnesium (Mg) is a divalent cation whose homeostasis is altered in CKD. Furthermore, Mg levels have been associated with cardiovascular health. The present study aims to understand the relationships of Mg and lipid parameters with atherosclerosis in CKD. In this analysis, 1754 participants from the Observatorio Nacional de Atherosclerosis en Nefrologia (NEFRONA) cohort were included. Carotid intima media thickness (cIMT) was determined in six arterial territories, and associated factors were investigated by linear regression. cIMT correlated positively with being male, Caucasian, a smoker, diabetic, hypertensive, dyslipidemic and with increased age, BMI, and triglyceride levels, and negatively with levels of HDL cholesterol. First-order interactions in linear regression analysis showed that Mg was an effect modifier on the influence of lipidic parameters. Thus, cIMT predicted values were higher when triglycerides or LDL levels were high and Mg levels were low. On the contrary, when Mg levels were high, this effect disappeared. In conclusion, Mg acts as an effect modifier between lipidic parameters and atherosclerotic cardiovascular disease. Therefore, Mg levels, together with lipidic parameters, should be taken into account when assessing atherosclerotic risk.

Prevention of Cardiovascular Disease: Screening for Magnesium Deficiency

Magnesium is an essential mineral naturally present in the human body, where it acts as cofactor in several enzymatic reactions. Magnesium is a key cardiovascular regulator, which maintains electrical, metabolic, and vascular homeostasis. Moreover, magnesium participates in inflammation and oxidative processes. In fact, magnesium deficiency is involved in the pathophysiology of arterial hypertension, diabetes mellitus, dyslipidemia, metabolic syndrome, endothelial dysfunction, coronary artery disease, cardiac arrhythmias, and sudden cardiac death. In consideration of the great public-health impact of cardiovascular disease, the recognition of the negative effects of magnesium deficiency suggests the possible role of hypomagnesaemia as cardiovascular risk factor and the use of serum magnesium level for the screening and prevention of cardiovascular risk factors and cardiovascular diseases. Moreover, it might help with the identification of new therapeutical strategies for the management of cardiovascular disease through magnesium supplementation.

Toxic Metal and Trace Element Concentrations in Blood and Outcome of In Vitro Fertilization in Women

The aim of this study was to investigate the association of trace element and toxic metal concentrations in blood and the outcome of in vitro fertilization (IVF). The study included 104 consecutive patients that underwent assisted reproductive technology (ART) procedures. The following parameters were determined: cadmium (Cd), mercury (Hg), arsenic (As), and lead (Pb); and copper (Cu), zinc (Zn), selenium (Se), and magnesium (Mg). Serum samples were obtained before commencing stimulation. Patients with smoking habit had significantly higher Pb concentrations (P = 0.022), as well as higher concentrations of As and Hg but not significantly. All subjects were divided into groups of pregnant and nonpregnant patients. Pregnant patients had lower mean values of Mg (P = 0.009), As (P < 0.05), and Pb (P = 0.034), compared to nonpregnant, and a significant correlation between pregnancy outcome and concentrations of Mg, Cd, and Pb was found. Women who had had delivered had lower Mg (P = 0.009) and Cd (P = 0.014) concentrations. There was a significant correlation of the negative outcome of IVF procedure with higher concentrations of Pb (P = 0.046) and Cd (P = 0.012). In conclusion, our results suggest that there is a difference in Mg, Pb, and Cd concentrations between pregnant and nonpregnant women. There was no association between toxic metals and number and quality of oocytes and embryos, while there was with fertilization rate. Concerning trace elements, we did not find the correlation of trace elements with oocyte number and quality, nor with a number of fertilized oocytes, except for Cu. Patients who were pregnant had lower concentrations of Mg.

Protective Effects of Different Kinds of Filtered Water on Hypertensive Mouse by Suppressing Oxidative Stress and Inflammation

Oxidative stress and inflammation play an important role in hypertensive animals and patients. Hydrogen plays a role of antioxidation and anti-inflammation. Calcium and magnesium play an important role in reducing hypertension and antioxidant. Filtered water contains abundant hydrogen and a large number of other essential elements of the human body. We investigated the protective effects of filtered water on hypertensive mice. To establish hypertension model, ICR mice were administered with N′-nitro-L-arginine methyl ester (L-NAME) hydrochloride 64 mg/kg per day for 1 month. The hypertensive mice were, respectively, administered with pure water, tap water, and filtered water for 2 months. Lipid peroxidation, antioxidant enzymatic activity, endothelin-1 (ET-1), angiotensin II (Ang II), and proinflammatory cytokines (TNF-α, IL-6, and IL-1β) were assessed. Expressions of phosphorylated NF-κB P65 in the kidney were analyzed by western blot. qRT-PCR analysis was adopted to determine the expression levels of the proinflammatory cytokines and NF-κB P65. The results demonstrated that filtered water can reduce the blood pressure. Filtered water treatment restored the activity of antioxidant enzymes, downregulated ET-1, and Ang II in the serum of mice. Filtered water treatment suppressed proinflammatory cytokines and decreased the mRNA expression of TNF-α, IL-6, IL-1β, and NF-κB P65. Consumption of filtered water inhibited the expression of NF-κB P65. This suggests that filtered water can reduce the blood pressure. The protection mechanisms include downregulating oxidative stress and inhibiting inflammation, which is partly due to the inhibition of the NF-κB signaling pathway.

Correlation of Serum Magnesium with Dyslipidemia in Maintenance Hemodialysis Patients

One of the factors involved in accelerated atherosclerosis in hemodialysis patients is dyslipidemia. In this study we considered factors involved in intensification of dyslipidemia in hemodialysis patients.This study was done on 36 maintenance hemodialysis patients. Serum lipoprotein (a), Triglyceride, Cholesterol, HDL-C,LDL-C and also serum Intact parathormone( iPTH), Calcium, Phosphorus, Magnesium were measured. In statistical analysis there was not any correlation between serum lipids and iPTH. There was not correlation between serum calcium with serum lipids (p>0.05). There was not correlation between CaxP product with serum lipids (p>0.05). There was a positive correlation between serum Magnesium and Lipoprotein(a) (P<0.05) and also positive correlation between serum magnesium with triglyceride level (P<0.05) was seen too. Magnesium doesn’t increase the lipoprotein synthesis. It may involve in the regulation of some enzymes responsible for lipoprotein synthesis. Correlation of serum magnesium with serum triglycerides can be due to changes in hepatic triglyceride metabolism. Lipoprotein(a) is a non traditional factor of premature atherosclerosis, its association with serum magnesium needs more attention in hemodialysis patients.

Evaluation of lipid peroxidation and antioxidant defense mechanisms in the bone of rats in conditions of separate and combined administration of vanadium (V) and magnesium (Mg)

The impact of vanadium (V) and magnesium (Mg) applied as sodium metavanadate (SMV, 0.125 mg V/ml) and magnesium sulfate (MS, 0.06 mg Mg/ml) on oxidative stress markers in bone of male Wistar rats was investigated. Some of them were also measured in the liver, e.g. l-ascorbic acid (hepatic L-AA). Additionally, relationships between selected indices determined in bone were examined. SMV alone (Group II) did not significantly alter the level of TBARS and the activity of SOD, compared with the control (Group I), but it slightly reduced the GR activity (by 13%) and the L-AA level (by 15.5%). It also markedly lowered the activity of CAT and GPx (by 34% and 29%), and to some degree elevated the activity of GST (by 16%) and the hepatic L-AA level (by 119%). MS alone (Group III) decreased the TBARS level (by 49%), slightly lowered the L-AA concentration (by 14%), and reduced the SOD, GPx, and GR activities (by 31%, 40%, and 28%), but did not change the activity of CAT, compared with the control. Additionally, it elevated the GST activity (by 56%) and the hepatic L-AA level (by 40%). In turn, the SMV + MS combination (Group IV) reduced the TBARS level (by 38%) and the SOD, CAT, GPx, and GR activities (by 61%, 58%, 72%, and 40%) but elevated the GST activity (by 66%), compared with the control. The activity of SOD and GPx in the rats in Group IV was also reduced, compared with Group II (by 61% and 61%) and Group III (by 44% and 54%). In turn, the activities of CAT and GR were decreased, compared with Group III (by 55%) and Group II (by 31%), and the L-AA level was lowered, in comparison with Groups II and III (by 53% and 54%). Further, the concentration of V in the bone of rats in Groups II and IV increased, whereas the concentration of Mg decreased, compared with Groups I and III, in which the V and Mg levels dropped and were not altered, respectively, compared with Group I. The total content of Fe in the bone of rats in Groups II and IV increased, compared with Group III, in which the total Fe content did not change, compared with Group I. In turn, the total bone Cu content significantly decreased in the rats in Groups III and IV, compared with Groups I and II, whereas the total Zn content and the Ca concentration did not change markedly. The results provided evidence that the concentration of V used as SMV did not enhance LPO in bone, whereas Mg, at the selected level, markedly reduced LPO in this tissue. On the other hand, both elements administered separately and in combination disrupted the antioxidant defense mechanisms and homeostasis of some metals in bone tissue, which consequently may have contributed to disturbances in the balance in the activities of osteoblastic and osteoclastic cells, and thereby negatively affected bone health.

Dietary Magnesium and Cardiovascular Disease: A Review with Emphasis in Epidemiological Studies

Magnesium (Mg) is an essential dietary element for humans involved in key biological processes. A growing body of evidence from epidemiological studies, randomized controlled trials (RCTs) and meta-analyses have indicated inverse associations between Mg intake and cardiovascular diseases (CVD). The present review aims to summarize recent scientific evidence on the topic, with a focus on data from epidemiological studies assessing the associations between Mg intake and major cardiovascular (CV) risk factors and CVD. We also aimed to review current literature on circulating Mg and CVD, as well as potential biological processes underlying these observations. We concluded that high Mg intake is associated with lower risk of major CV risk factors (mainly metabolic syndrome, diabetes and hypertension), stroke and total CVD. Higher levels of circulating Mg are associated with lower risk of CVD, mainly ischemic heart disease and coronary heart disease. Further, RCTs and prospective studies would help to clarify whether Mg intake and Mg circulating levels may also protect against other CVDs and CVD death.

Elucidating the role of the TRPM7 alpha-kinase: TRPM7 kinase inactivation leads to magnesium deprivation resistance phenotype in mice

TRPM7 is an unusual bi-functional protein containing an ion channel covalently linked to a protein kinase domain. TRPM7 is implicated in regulating cellular and systemic magnesium homeostasis. While the biophysical properties of TRPM7 ion channel and its function are relatively well characterized, the function of the TRPM7 enzymatically active kinase domain is not understood yet. To investigate the physiological role of TRPM7 kinase activity, we constructed mice carrying an inactive TRPM7 kinase. We found that these mice were resistant to dietary magnesium deprivation, surviving three times longer than wild type mice; also they displayed decreased chemically induced allergic reaction. Interestingly, mutant mice have lower magnesium bone content compared to wild type mice when fed regular diet; unlike wild type mice, mutant mice placed on magnesium-depleted diet did not alter their bone magnesium content. Furthermore, mouse embryonic fibroblasts isolated from TRPM7 kinase-dead animals exhibited increased resistance to magnesium deprivation and oxidative stress. Finally, electrophysiological data revealed that the activity of the kinase-dead TRPM7 channel was not significantly altered. Together, our results suggest that TRPM7 kinase is a sensor of magnesium status and provides coordination of cellular and systemic responses to magnesium deprivation.

The WOMED model of benign thyroid disease: Acquired magnesium deficiency due to physical and psychological stressors relates to dysfunction of oxidative phosphorylation

BACKGROUND

The aim of this study was to discern whether a relation between biochemical parameters, sonography and musculoskeletal data exists in cases of hyperthyroidism and whether they are modifiable through supplementation with selenomethionine and magnesium citrate as well as by acupuncture and manual medicine methods.

RESULTS

A direct correlation between whole blood selenium and serum magnesium was found in subjects without thyroid disease and in menopausal women while it was reversed in cases of thyroid diseases as well as in patients with depression, infection, and in infertile women. Vascularization indices were elevated in cases of newly diagnosed benign thyroid diseases. Musculoskeletal changes i.e. lateral tension and idiopathic moving toes, as well as situations of physical and psychological stress and minor trauma and infection led to an increase of vascularization. Magnesium levels correlated negatively with these two conditions. The supplementation brought a reduction of the vascularization indices and reduced the incidence of idiopathic moving toes. Treatment of lateral tension required manual medicine methods and acupuncture (gastrocnemius). A small subgroup of patients showed a further reduction of hyper-vascularization after receiving coenzyme Q10.

CONCLUSIONS

We interpret the elevated thyroid vascularization and low magnesium levels as signs of an inflammatory process related to the musculoskeletal changes. Improvement of thyroid function and morphology can be achieved after correcting the influence of stressors together with the supplementation regime. We hypothesize that the central biochemical event in thyroid disease is that of an acquired, altered mitochondrial function due to deficiency of magnesium, selenium, and coenzyme Q10.

Magnesium protects against cisplatin-induced acute kidney injury by regulating platinum accumulation

Despite its success as a potent antineoplastic agent, ∼25% of patients receiving cisplatin experience acute kidney injury (AKI) and must discontinue therapy. Impaired magnesium homeostasis has been linked to cisplatin-mediated AKI, and because magnesium deficiency is widespread, we examined the effect of magnesium deficiency and replacement on cisplatin-induced AKI in physiologically relevant older female mice. Magnesium deficiency significantly increased cisplatin-associated weight loss and markers of renal damage (plasma blood urea nitrogen and creatinine), histological changes, inflammation, and renal cell apoptosis and modulated signaling pathways (e.g., ERK1/2, p53, and STAT3). Conversely, these damaging effects were reversed by magnesium. Magnesium deficiency alone significantly induced basal and cisplatin-mediated oxidative stress, whereas magnesium replacement attenuated these effects. Similar results were observed using cisplatin-treated LLC-PK1 renal epithelial cells exposed to various magnesium concentrations. Magnesium deficiency significantly amplified renal platinum accumulation, whereas magnesium replacement blocked the augmented platinum accumulation after magnesium deficiency. Increased renal platinum accumulation during magnesium deficiency was accompanied by reduced renal efflux transporter expression, which was reversed by magnesium replacement. These findings demonstrate the role of magnesium in regulating cisplatin-induced AKI by enhancing oxidative stress and thus promoting cisplatin-mediated damage. Additional in vitro experiments using ovarian, breast, and lung cancer cell lines showed that magnesium supplementation did not compromise cisplatin's chemotherapeutic efficacy. Finally, because no consistently successful therapy to prevent or treat cisplatin-mediated AKI is available for humans, these results support developing more conservative magnesium replacement guidelines for reducing cisplatin-induced AKI in cancer patients at risk for magnesium deficiency.

Dietary magnesium sulfate supplementation protects heat stress-induced oxidative damage by restoring the activities of anti-oxidative enzymes in broilers

The purpose of this study was to investigate the effect of dietary magnesium sulfate supplementation on heat stress-induced oxidative damage in broilers. One hundred twenty 14-day-old broilers were randomly assigned into four treatment groups with three replicates of ten birds each. The broilers were reared under normal ambient temperature (24 ± 1°C) fed with a basal (control) diet or reared under high ambient temperature (35 ± 1°C between 1000 and 1800 h, 8 h each day) fed with a basal diet supplemented with magnesium sulfate (0, 2.5 or 5.0 mg/kg of diet) from 14 to 42 days of age. Growth performance and oxidative damage were evaluated in each treatment group. Our results demonstrated that dietary magnesium sulfate supplementation significantly prevented heat stress-induced oxidative damage and improved growth performance in broilers compared with that of control. Mechanistically, this beneficial effect was mediated, at least partly, by restoring the activity of anti-oxidative enzymes. This finding suggests that magnesium sulfate supplementation might be a potential strategy to attenuate heat stress-induced detrimental effects in broilers raised in summer season or tropical areas.

Dietary magnesium intake and risk of stroke: a meta-analysis of prospective studies

BACKGROUND

Prospective studies of dietary magnesium intake in relation to risk of stroke have yielded inconsistent results.

OBJECTIVE

We conducted a dose-response meta-analysis to summarize the evidence regarding the association between magnesium intake and stroke risk.

DESIGN

Relevant studies were identified by searching PubMed and EMBASE from January 1966 through September 2011 and reviewing reference lists of retrieved articles. We included prospective studies that reported RRs with 95% CIs of stroke for ≥3 categories of magnesium intake. Results from individual studies were combined by using a random-effects model.

RESULTS

Seven prospective studies, with 6477 cases of stroke and 241,378 participants, were eligible for inclusion in the meta-analysis. We observed a modest but statistically significant inverse association between magnesium intake and risk of stroke. An intake increment of 100 mg Mg/d was associated with an 8% reduction in risk of total stroke (combined RR: 0.92; 95% CI: 0.88, 0.97), without heterogeneity among studies (P = 0.66, I(2) = 0%). Magnesium intake was inversely associated with risk of ischemic stroke (RR: 0.91; 95% CI: 0.87, 0.96) but not intracerebral hemorrhage (RR: 0.96; 95% CI: 0.84, 1.10) or subarachnoid hemorrhage (RR: 1.01; 95% CI: 0.90, 1.14).

CONCLUSION

Dietary magnesium intake is inversely associated with risk of stroke, specifically ischemic stroke.

Effects of crush and axotomy on oxidative stress and some trace element levels in phrenic nerve of rats

This study was designed to investigate the effect of crush and axotomy on oxidative stress and some trace element levels in phrenic nerve of rats. Eighteen male Wistar-albino rats were divided randomly into three groups, each consisting of 6 rats. The animals in the first group were not crushed or axotomized and served as control. Phrenic nerves of the animals in the second and third groups were crushed and axotomized, respectively. Animals in all groups were sacrificed one week after the crush or axotomy, and degenerated phrenic nerves were harvested for the determination of tissue oxidative stress and trace element levels. Lipid peroxidation product malondialdehyde and antioxidant glutathione levels increased in both crushed and axotomized phrenic nerves. The activities of antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase were lower in crushed and axotomized phrenic nerves than in controls. The levels of Fe, Pb, Mn, Cd and Co increased, and Mg and Cu levels decreased in crushed phrenic nerves. The levels of Fe and Mg decreased, Pb and Co levels increased in axotomized phrenic nerves. It was concluded that crushing or axotomizing the phrenic nerves may produce oxidative stress by increasing lipid peroxidation and decreasing antioxidant enzyme activities. It was also concluded that while crush to phrenic nerves causes accumulation of minerals, axotomizing phrenic nerves causes depletion of minerals in the tissues.

Nutritional deficiencies and phospholipid metabolism

Phospholipids are important components of the cell membranes of all living species. They contribute to the physicochemical properties of the membrane and thus influence the conformation and function of membrane-bound proteins, such as receptors, ion channels, and transporters and also influence cell function by serving as precursors for prostaglandins and other signaling molecules and modulating gene expression through the transcription activation. The components of the diet are determinant for cell functionality. In this review, the effects of macro and micronutrients deficiency on the quality, quantity and metabolism of different phospholipids and their distribution in cells of different organs is presented. Alterations in the amount of both saturated and polyunsaturated fatty acids, vitamins A, E and folate, and other micronutrients, such as zinc and magnesium, are discussed. In all cases we observe alterations in the pattern of phospholipids, the more affected ones being phosphatidylcholine, phosphatidylethanolamine and sphingomyelin. The deficiency of certain nutrients, such as essential fatty acids, fat-soluble vitamins and some metals may contribute to a variety of diseases that can be irreversible even after replacement with normal amount of the nutrients. Usually, the sequelae are more important when the deficiency is present at an early age.

Associations between blood metals and fecundity among women residing in New York State

Trace exposures to metals may affect female reproductive health. To assess the relation between trace concentrations of blood metals and female fecundity, 99 non-pregnant women discontinuing contraception for the purpose of becoming pregnant were prospectively followed. Participants completed a baseline interview and daily diaries until pregnant, or up to 12 menstrual cycles at risk for pregnancy; home pregnancy test kits were used. For 80 women, whole blood specimens were analyzed for arsenic, cadmium, lead, magnesium, nickel, selenium and zinc using inductively coupled plasma mass spectrometry (ICP-MS). Time to pregnancy was estimated using Cox proportional hazards models for discrete time. Metal concentrations were generally within population reference intervals. Adjusted models suggest a 51.5% increase in the probability for pregnancy per 3.60 μg/L increase in Mg (P=0.062), and a 27.7% decrease per 0.54 μg/L increase in Zn (P=0.114). Findings indicate that Mg and Zn may impact female fecundity, but in varying directions.

Short-term magnesium deficiency upregulates sphingomyelin synthase and p53 in cardiovascular tissues and cells: relevance to the de novo synthesis of ceramide

The present study tested the hypotheses that 1) short-term dietary deficiency of magnesium (21 days) in rats would result in the upregulation of sphingomyelin synthase (SMS) and p53 in cardiac and vascular (aortic) smooth muscles, 2) low levels of Mg(2+) added to drinking water would either prevent or greatly reduce the upregulation of both SMS and p53, 3) exposure of primary cultured vascular smooth muscle cells (VSMCs) to low extracellular Mg(2+) concentration ([Mg(2)](o)) would lead to the de novo synthesis of ceramide, 4) inhibition of either SMS or p53 in primary culture VSMCs exposed to low [Mg(2+)](o) would lead to reductions in the levels of de novo ceramide synthesis, and 5) inhibition of sphingomyelin palmitoyl-CoA transferase (SPT) or ceramide synthase (CS) in primary cultured VSMCs exposed to low [Mg(2+)](o) would lead to a reduction in the levels of de novo ceramide synthesis. The data indicated that short-term magnesium deficiency (10% normal dietary intake) resulted in the upregulation of SMS and p53 in both ventricular and aortic smooth muscles; even very low levels of water-borne Mg(2+) (e.g., 15 mg·l(-1)·day(-1)) either prevented or ameliorated the upregulation in SMS and p53. Our experiments also showed that VSMCs exposed to low [Mg(2+)](o) resulted in the de novo synthesis of ceramide; the lower the [Mg(2+)](o), the greater the synthesis of ceramide. In addition, the data indicated that inhibition of either SMS, p53, SPT, or CS in VSMCs exposed to low [Mg(2+)](o) resulted in marked reductions in the de novo synthesis of ceramide.

Insinuation of exacerbated oxidative stress in sucrose-fed rats with a low dietary intake of magnesium: Evidence of oxidative damage to proteins

High sucrose diets and low magnesium intake have been independently implicated in induction of oxidative stress in animal models. The aim of this study was to investigate whether low dietary magnesium intake exacerbates the prooxidant effects of high sucrose feeding. Rats were fed control (C), high sucrose (HS); low magnesium (LM) and high sucrose low magnesium (HSLM) diets for 90 days and oxidative stress evaluated in terms of formation of TBARS, advanced oxidation protein products and protein carbonyls. HS and LM rats showed evidence of lipid peroxidation and protein oxidation in plasma and liver. Enhanced oxidative injury to lipids and proteins after HSLM feeding was indicated by increased carbonyl content (p <0.01) and significantly (p <0.005) higher levels of TBARS in plasma and hepatic tissue relative to both HS and LM groups. Altogether, these results illustrate the potential detrimental and cumulative effects of low magnesium intake combined with high sucrose consumption on oxidative stress variables.

Marginal zinc deficiency increases magnesium retention and impairs calcium utilization in rats

An experiment with rats was conducted to determine whether magnesium retention is increased and calcium utilization is altered by a marginal zinc deficiency and whether increased oxidative stress induced by a marginal copper deficiency exacerbated responses to a marginal zinc deficiency. Weanling rats were assigned to six groups of ten with dietary treatment variables of low zinc (5 mg/kg for 2 weeks and 8 mg/kg for 7 weeks), low copper (1.5 mg/kg), adequate zinc (15 mg/kg), and adequate copper (6 mg/kg). Two groups of rats were fed the adequate-zinc diet with low or adequate copper and pair-fed with corresponding rats fed the low-zinc diet. When compared to the pair-fed rats, marginal zinc deficiency significantly decreased the urinary excretion of magnesium and calcium, increased the concentrations of magnesium and calcium in the tibia, increased the concentration of magnesium in the kidney, and increased the urinary excretion of helical peptide (bone breakdown product). Marginal copper deficiency decreased extracellular superoxide dismutase and glutathione, which suggests increased oxidative stress. None of the variables responding to the marginal zinc deficiency were significantly altered by the marginal copper deficiency. The findings in the present experiment suggest that increased magnesium retention and impaired calcium utilization are indicators of marginal zinc deficiency.

Short-term magnesium deficiency results in decreased levels of serum sphingomyelin, lipid peroxidation, and apoptosis in cardiovascular tissues

The present study tested the hypothesis that short-term dietary deficiency of magnesium (Mg) (21 days) in rats would 1) result in decreased serum(s) [the present study tested the levels of Mg, sphingomyelin (SM), and phosphatidylcholine (PC)]; 2) promote DNA fragmentation, lipid peroxidation (LP), and activation of caspase-3 in cardiac (ventricular and atrial) and vascular(aortic) muscle; and 3) low levels of Mg(2+) added to drinking water would either prevent or greatly ameliorate these manifestations. The data indicate that short-term Mg deficiency (10% normal dietary intake) resulted in profound reductions in serum-ionized Mg and total Mg with an elevation in serum-ionized calcium (Ca(2+)), significant lowering of serum SM and serum PC, with concomitant LP, DNA fragmentation, and activation of caspase-3 in ventricular (right and left chambers), atrial (right and left chambers) and abdominal aortic smooth muscle. The greater the reduction in serum-ionized Mg, the greater the effects on DNA fragmentation, LP, and caspase-3 activity. The intake of water-borne Mg(2+) at all levels greatly attenuated or inhibited the reductions in serum SM and serum PC, activation of LP, DNA fragmentation, and the activation of caspase-3; even very low levels of Mg(2+) in drinking water (i.e., 15 parts.million(-1).day(-1)) were cardio- and vascular protective. In addition, we demonstrate that short-term dietary deficiency of Mg probably results in a downregulation of SM synthase and a decreased synthesis of PC.

Lipid metabolism and antioxidant status in sucrose vs. potato-fed rats

OBJECTIVE

Consumption of high levels of simple carbohydrates is associated with several metabolic disorders in humans and in laboratory animals, including symptoms of an early stage of metabolic syndrome (syndrome X). This disorder has several cardiovascular risk factors, such as hypertriglyceridemia, and is associated with an increase in oxidative stress. In contrast to sucrose, potato, a source of complex carbohydrates and antioxidant micronutrients, was thought to improve lipid metabolism and antioxidant protection.

METHODS

We investigated the effects of diets containing i) complex dietary carbohydrates and antioxidant micronutrients (potato Solanum tuberosum L.), ii) complex carbohydrates (starch) and iii) a simple carbohydrate (sucrose) on lipid metabolism and antioxidant status in rats.

RESULTS

An increase in short chain fatty acid (SCFA) pools was observed in the cecum of rats fed a potato-based diet, resulting from an increase in all SCFAs, especially propionate (+360%, P < 0.0001). Feeding rats a potato-based diet for 3 weeks led to a decrease in cholesterol (-37%, potato vs. control and -32%, potato vs. sucrose) and triglycerides (-31%, potato vs. control and -43%, potato vs. sucrose) concentrations in triglyceride-rich lipoproteins (TGRLP) fractions. The antioxidant status was decreased by sucrose consumption and improved by potato consumption.

CONCLUSIONS

Our present results suggest that consumption of complex carbohydrates (provided as cooked potatoes), in combination with different antioxidant micronutrients, may enhance the antioxidant defences and improve lipid metabolism, when compared with starch (complex carbohydrates) and to sucrose consumption (source of simple sugar). These effects limit oxidative stress and reduce the risk of developing the associated degenerative diseases, including cardiovascular disease, and could have potential in cardiovascular disease prevention.

Zinc in a combination with magnesium helps reducing negative effects of heat stress in quails

The objective of this study was to investigate whether zinc (Zn) along with magnesium (Mg) is effective in alleviating the negative effects of heat stress in Japanese quails. One hundred and twenty 10-day-old healthy Japanese quails were randomly assigned to four treatment groups, three replicates of ten birds each. The birds were fed either a basal diet or the basal diet supplemented with either 30 mg of Zn/kg of diet, 600 mg of Mg/kg of diet, or 30 mg of Zn + 600 mg of Mg/kg of diet. The birds were kept under a high temperature (35 degrees C) for 8 h/day. Feed consumption was greatest with the combination of Zn and Mg supplementation (P < 0.01). Hot and chilled dressing percentages were greater (P < 0.05) with Zn- and Mg-supplemented diets. Concentrations of plasma malondialdehyde were lower (P < 0.01) with both Zn and Mg supplementations. Mg concentrations in the serum remained similar with either Zn or Mg supplements in the diet (P > 0.05). Serum glucose concentrations were lowest in birds fed the basal diet. Supplementing a combination of Zn and Mg may offer a potential protective management practice in preventing heat stress-related depression in performance of quails.

Preferential response of glutathione-related enzymes to folate-dependent changes in the redox state of rat liver

BACKGROUND

Oxidative stress likely constitutes an important contributing factor in the onset of degenerative diseases associated with folate deficiency. Direct, as well as homocysteine-linked, antioxidant properties of folate could explain its preventive effect on these pathologies.

AIM OF THE STUDY

Our study aimed at determining the changes in the redox status of adult rats as a function of folate intake.

METHODS

Adult male rats were pair-fed for 4 weeks with a semi-synthetic diet containing 0, 0.5, 1.5, 8 or 20 mg of folic acid/kg. Folate and homocysteine concentrations, redox status markers and antioxidant enzyme activities were measured in the plasma and/or liver of the rats. A principal component analysis of the overall data was performed to draw a general scheme of the changes observed between the conditions.

RESULTS

Folate deficiency caused increased homocysteinemia and features of oxidative stress including reduced plasma antioxidant capacity together with increased lipid peroxidation in liver and heart. This was associated with an increase in the specific activity of several enzymes involved in liver glutathione metabolism (glutathione peroxidase, glutathione reductase and glutathione S-transferase), suggesting an adaptive tissue response to the oxidative stress induced by folate deficiency. In contrast, no such variation was observed for hepatic superoxide dismutase and catalase.

CONCLUSION

Despite no changes in hepatic levels of total glutathione, our findings indicate that glutathione-dependent antioxidant pathways could be particularly involved in the compensatory mechanism committed by liver to counteract the oxidative stress induced by folate deficiency. They also suggest that folate supplementation may not be associated with a better antioxidant protection of rats.

Accelerated thymus involution in magnesium-deficient rats is related to enhanced apoptosis and sensitivity to oxidative stress

Experimental Mg deficiency leads to alterations in the immune response. Reduction of thymus weight and histological changes were previously observed in Mg-deficient rats after several weeks on a deficient diet, suggesting that functions of this immune organ may be affected by Mg deficiency. More recently, changes in the immune system during early Mg deficiency were shown. Thus, in the present study we examined modifications in the thymus during the early stages of Mg deficiency in weanling rats. From our results, it appears that Mg deficiency accelerates thymus involution. The assessment of apoptosis (enumeration of apoptotic cells on the basis of morphological criteria and intranucleosomal degradation of genomic DNA) showed greater values in thymuses from Mg-deficient rats as compared with controls. This was observed very early, since a significant difference was shown on the second day of deficiency, before reduced weight of thymus, which was recorded in the later period. These results indicate the relationship of accelerated thymus involution with an active process of cell death. Mg deficiency led to histological changes in the thymus. In the early stage of deficiency (second day) the presence of inflammatory cells was shown, suggesting that the inflammatory process was already occurring in the tissue studied. Later (eighth day) an increased proportion of epithelial reticular cells in the cortex was shown, indicating a remodelling process occurring in this period. Enhanced susceptibility to peroxidation also occurred very early during Mg deficiency. It may be hypothesized that disturbances in Mg status of short duration could have cellular effects with various deleterious consequences.

Time-course of the change in blood pressure level in magnesium-deficient Wistar rats

To investigate the relationships between maternal, umbilical cord and piglet fatty acid status, multiparous sows (six per diet) were fed on diets containing supplements (30 g/kg) of either soyabean oil or tuna oil for the last 21 d of pregnancy. The proportions of most fatty acids differed between diets: in particular, the tuna-oil-containing diet supplied more 22:6n-3 and less 18:2n-6 fatty acids than the soyabean-oil-containing diet. Maternal plasma fatty acid concentrations (mg/l) were greater than those in umbilical plasma and 20:4n-6 and 22:6n-3 fatty acids were present in higher proportions (g/100 g fatty acids) in umbilical than maternal plasma. Feeding tuna oil increased the proportionate amounts (g/100 g fatty acids) of total n-3 fatty acids (particularly 22:6n-3) in umbilical cord, plasma and piglet tissues compared with feeding soyabean oil: in contrast, the proportion of 20:4n-6 was decreased by feeding tuna oil. Changes in piglet fatty acid proportions as a result of oil feeding were not influenced by piglet weight. While proportions of the long-chain n-3 and n-6 polyunsaturated fatty acids in piglet liver, spleen and reproductive tract (ovaries plus uterus of the female, testes of the male) correlated well with those of umbilical plasma, those in brain and retina were poorly correlated. Therefore umbilical plasma cannot be used to predict the fatty acid status of piglet brain.

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.

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.

Entire potato consumption improves lipid metabolism and antioxidant status in cholesterol-fed rat

BACKGROUND

Vegetables and fruits are rich sources of a variety of nutrients, including vitamins (E and C), trace minerals, and dietary fibers, and many other classes of biologically active compounds such as carotenoids and polyphenols, which are often assumed to protect against degenerative pathologies such as cardiovascular diseases. Although potato is considered as a starchy food, it is also included in the category of vegetables by its micronutrient content.

AIM OF THE STUDY

In the present study, we investigated in the rat the effect of a potato-enriched diet on lipid metabolism and antioxidant protection.

RESULTS

Feeding rats a potato-enriched diet for 3 weeks led to a significant decrease in cholesterol and triglyceride levels in plasma (respectively, -30%, P<0.0001 and -36%, P<0.05) and cholesterol level in liver (-42%, P<0.0001). Antioxidant status was also improved by potato consumption. TBARS levels in heart were decreased and vitamin E/triglycerides ratio in plasma was improved.

CONCLUSIONS

Our present results suggest that consumption of cooked potatoes (consumed with skin) may enhance antioxidant defense and improve the lipid metabolism. These effects could be interesting for prevention of cardiovascular disease.

Health effect of vegetable-based diet: lettuce consumption improves cholesterol metabolism and antioxidant status in the rat

BACKGROUND & AIMS

It is often assumed that fruits and vegetables contribute to protect against degenerative pathologies such as cardiovascular diseases. Besides epidemiological observations, scientific evidences for their mechanism of action are scarce. In the present study, we investigated the mean term and post-prandial effects of lettuce ingestion on lipid metabolism and antioxidant protection in the rat.

RESULTS

Feeding rats a 20% lettuce diet for 3 weeks resulted in a decrease cholesterol LDL/HDL ratio and a marked decrease of liver cholesterol levels (-41%). Concurrently, fecal total steroid excretion increased (+44%) and apparent absorption of dietary cholesterol was significantly depressed (-37%) by the lettuce diet. Lettuce diet also displayed an improvement of vitamin E/TG ratio in plasma and limited lipid peroxidation in heart as evidenced by TBARS. In post-prandial experiment, lettuce intake significantly increased both ascorbic acid and alpha-tocopherol plasma levels which contribute to improve plasma antioxidant capacity within 2 h of consumption. Other lipid-soluble antioxidants (lutein and vitamin E) may also improve the plasma antioxidant capacity.

CONCLUSION

Lettuce consumption increases the total cholesterol end-products excretion and improves antioxidant status due to the richness in antioxidants (vitamins C, E and carotenoids). In our model, lettuce clearly shows a beneficial effect on lipid metabolism and on tissue oxidation. Therefore regular consumption of lettuce should contribute to improve protection against cardiovascular diseases.

Low Serum Magnesium Predicts Neurological Events in Patients With Advanced Atherosclerosis

Background and Purpose— Magnesium (Mg) deficiency is thought to be a risk factor for cerebrovascular atherosclerosis and complications. We investigated the prognostic impact of Mg serum levels with respect to the occurrence of neurological events in patients with advanced atherosclerosis.

Methods— We prospectively studied 323 patients with symptomatic peripheral artery disease and intermittent claudication (197 men; median age, 68 years). Serum Mg was determined, and patients were followed for a median of 20 months (interquartile range, 12 to 25 months) for the occurrence of neurological events, defined as ischemic stroke and/or carotid revascularization (carotid endarterectomy or carotid stenting). Multivariate Cox proportional hazards analysis was applied to assess the association of serum Mg (in tertiles) and neurological events.

Results— Neurological events occurred in 35 patients (11%) (15 patients with stroke, 13 with carotid revascularization, and 7 with stroke and subsequent revascularization). Compared with patients in the highest tertile of Mg serum levels (>0.84 mmol/L), patients with Mg serum values <0.76 mmol/L (lowest tertile) exhibited a 3.29-fold increased adjusted risk (95% CI, 1.34 to 7.90; P=0.009) for neurological events, but patients with Mg serum values of 0.76 mmol/L to 0.84 mmol/L (middle tertile) had no increased risk (adjusted hazard ratio, 1.10; 95% CI, 0.35 to 3.33; P=0.88). Mg serum levels were not associated with all-cause mortality (P=0.87) or coronary events (P=0.67) during follow-up.

Conclusions— Low Mg serum levels indicate an increased risk for neurological events in patients with symptomatic peripheral artery disease, favoring Mg substitution therapy in those patients with advanced atherosclerosis.

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.

Magnesium deficiency induces apoptosis in primary cultures of rat hepatocytes

The effects of extracellular magnesium (Mg) concentration on the rate of apoptosis in rat hepatocytes in primary culture were examined. After overnight attachment, incubations were conducted for up to 72 h in serum-free media containing low (0-0.4 mmol/L), physiological (0.8 mmol/L) or high (2 and 5.6 mmol/L) Mg concentrations. At 72 h, we observed numerous rounded hepatocytes on top of a shrunken cell monolayer at extracellular Mg concentrations < 0.8 mmol/L. These morphological features were associated with Mg-dependent differences in the total protein levels. The various Mg concentrations did not affect DNA synthesis; however, at a concentration < 0.8 mmol/L, the susceptibility of cultured rat hepatocytes to oxidative stress was increased as shown by the reduced glutathione concentration (10.6 +/- 2.8 vs. 37.3 +/- 4.1 nmol/mg protein with 0 and 0.8 mmol/L, respectively; P < 0.05) and increased lipid peroxidation (0.36 +/- 0.03 vs. 0.21 +/- 0.01 nmol malondialdehyde/mg protein with 0 and 0.8 mmol/L, respectively; P < 0.05). Fluorescence microscopy after Hoechst dye staining revealed numerous apoptotic figures in Mg-free monolayers compared with 0.8 and 5.6 mmol/L Mg conditions. These observations were confirmed quantitatively by flow-cytometric analysis after propidium iodide staining. The proportion of subdiploid cells decreased with increasing Mg concentration; for example, it was greater at 72 h in Mg-free cultures (76%) than in cultures containing 0.8 mmol/L or 5.6 mmol/L Mg (28%; P < 0.05). Caspase-3 was highly activated in Mg-free cultures after 48 h of treatment compared with 0.8 and 5.6 mmol/L conditions (P < 0.05). Overall, these results show that extracellular Mg deficiency has a negative effect on the survival of cultured rat hepatocytes by inducing apoptosis; however, supplementation of extracellular Mg did not reduce the spontaneous apoptosis that occurred over time in rat hepatocyte cultures.

Biochemical changes induced by hypomagnesaemia in lactating cows and ewes

Severe hypomagnesaemia was induced in lactating cows and lactating sheep by feeding them magnesium-deficient diets for 17 and 14 days, respectively. Hypomagnesaemia in cows was associated with abnormally high rates of change in the numbers of leucocytes, neutrophils, monocytes and platelets. There were increases in the concentration of iron in the liver of the hypomagnesaemic ewes and in the heart of the hypomagnesaemic cows, which were not associated with a haemolytic process. The percentage of some of the peroxidisable fatty acids was lower in the heart tissue of hypomagnesaemic cows, but the reduction was not associated with significant lipid peroxidation.

Increased phagocytosis and production of reactive oxygen species by neutrophils during magnesium deficiency in rats and inhibition by high magnesium concentration

Recent studies underline the importance of the immunoinflammatory processes in the pathology of Mg deficiency. Neutrophils possess a superoxide anion-generating NADPH oxidase and its inappropriate activation may result in tissue damage. The aim of the present study was to assess the effect of experimental Mg deficiency in the rat on polymorphonuclear leucocytes (PMN) activity and the role of increasing extracellular Mg. Weaning male Wistar rats were fed either a Mg-deficient or a control diet for 8 d. In Mg-deficient rats, the characteristic inflammatory response was accompanied by a marked increase in the number of PMN. Higher plasma interleukin 6 and NO concentrations and increased lipid peroxidation in the heart were found in Mg-deficient rats as compared with control rats. As shown by chemiluminescence studies, basal neutrophil activity from Mg-deficient rats was significantly elevated when compared with neutrophils from control rats. Moreover, the chemiluminescence of PMN from Mg-deficient rats was significantly higher than that of control rats following phorbol myristate acetate or opsonized zymosan activation. PMN from Mg-deficient rats also showed an increased activity of phagocytosis in comparison with neutrophils from control animals. Increasing extracellular Mg concentration in the incubating medium of PMN (0.8 v. 8.0 mM) decreased the chemiluminescence activity of PMN from control rats following opsonized zymosan activation. Chemiluminescence activities of PMN from Mg-deficient rats following phorbol myristate acetate or opsonized zymosan challenge were also decreased by high extracellular Mg concentration. From this work, it appears that PMN activation is an early consequence of Mg deficiency and that high extracellular Mg concentration inhibits free radicals generation.

Magnesium deprivation decreases cellular reduced glutathione and causes oxidative neuronal death in murine cortical cultures

The vulnerability of cultured cortical neurons to oxidative injury is an inverse function of the extracellular Mg2+ concentration. In order to test the hypothesis that depolarization-enhanced release of reduced glutathione (GSH) contributes to this phenomenon, we assessed the effect of Mg2+ deprivation on cellular and medium glutathione levels. Incubation of mixed neuronal and glial cultures in Mg2+-free medium resulted in a decline in cellular total glutathione (GSx) within 8 h, without change in oxidized glutathione (GSSG); no effect was seen in pure glial cultures. This decrease in cellular GSx was associated with a progressive increase in GSx but not GSSG in the culture medium. Cellular GSH loss was not attenuated by concomitant treatment with antioxidants (ascorbate, Trolox, or deferoxamine), but was prevented by the NMDA receptor antagonist MK-801. Mg2+ deprivation for over 24 h produced neuronal but not glial death, with release of about 40% of neuronal lactate dehydrogenase by 48-60 h. Most of this cytotoxicity was prevented by treatment with either antioxidants or MK-801. These results suggest that Mg2+ deprivation causes release of neuronal reduced glutathione via a mechanism involving excessive NMDA receptor activation. If prolonged, cellular GSH depletion ensues, leading to oxidative neuronal death.

Inflammatory response following acute magnesium deficiency in the rat

The importance of inflammatory processes in the pathology of Mg deficiency has been recently reconsidered but the sequence of events leading to the inflammatory response remains unclear. Thus, the purpose of the present study was to characterize more precisely the acute phase response following Mg deficiency in the rat. Weaning male Wistar rats were pair-fed either a Mg-deficient or a control diet for either 4 or 8 days. The characteristic allergy-like crisis of Mg-deficient rats was accompanied by a blood leukocyte response and changes in leukocytes subpopulations. A significant increase in interleukin-6 (IL-6) plasma level was observed in Mg-deficient rats compared to rats fed a control diet. The inflammatory process was accompanied by an increase in plasma levels of acute phase proteins. The concentrations of alpha2-macroglobulin and alpha1-acid glycoprotein in the plasma of Mg-deficient rats were higher than in control rats. This was accompanied in the liver by an increase in the level of mRNA coding for these proteins. Moreover, Mg-deficient rats showed a significant increase in plasma fibrinogen and a significant decrease in albumin concentrations. Macrophages found in greater number in the peritoneal cavity of Mg-deficient rats were activated endogenously and appeared to be primed for superoxide production following phorbol myristate acetate stimulation. A high plasma level of IL-6 could be detected as early as day 4 for the Mg-deficient diet. Substance P does not appear to be the initiator of inflammation since IL-6 increase was observed without plasma elevation of this neuropeptide. The fact that the inflammatory response was an early consequence of Mg deficiency suggests that reduced extracellular Mg might be responsible for the activated state of immune cells.

Magnesium status and parameters of the oxidant-antioxidant balance in patients with chronic fatigue: effects of supplementation with magnesium

OBJECTIVE

Magnesium deficiency and oxidative stress have both been identified as pathogenic factors in aging and in several age-related diseases. The link between these two factors is unclear in humans although, in experimental animals, severe Mg deficiency has been shown to lead to increased oxidative stress.

METHODS

The relationship between Mg body stores, dietary intakes and supplements on the one hand and parameters of the oxidant-antioxidant balance on the other was investigated in human subjects.

RESULTS

The study population consisted of 93 patients with unexplained chronic fatigue (median age 38 years, 25% male, 16% smokers and 54% with Chronic Fatigue Syndrome (CFS). Mg deficient patients (47%) had lower total antioxidant capacity in plasma (p=0.007) which was related to serum albumin. Mg deficient patients whose Mg body stores did not improve after oral supplementation with Mg (10 mg/kg/day) had persistently lower blood glutathione levels (p=0.003). In vitro production of thiobarbituric acid reactive substances (TBARS) by non-HDL lipoproteins incubated with copper was related to serum cholesterol (p<0.001) but not to Mg or antioxidants and did not improve after Mg supplementation. In contrast, velocity of formation of fluorescent products of peroxidation (slope) correlated with serum vitamin E (p<0.001), which was, in turn, related to Mg dietary intakes. Both slope and serum vitamin E improved after Mg supplementation (p<0.001).

CONCLUSIONS

These results show that the lower antioxidant capacity found in moderate Mg deficiency was not due to a deficit in Mg dietary intakes and was not accompanied by increased lipid susceptibility to in vitro peroxidation. Nevertheless, Mg supplementation was followed by an improvement in Mg body stores, in serum vitamin E and its interrelated stage of lipid peroxidation.

Association of alcohol in brain injury, headaches, and stroke with brain-tissue and serum levels of ionized magnesium: a review of recent findings and mechanisms of action

Although there is general agreement that chronic ingestion of alcohol poses great risks for normal cardiovascular functions and peripheral-vascular homeostasis, a direct cause and effect between the real phenomena of alcohol-induced headache and risk of brain injury and stroke is not appreciated. "Binge drinking" of alcohol is associated with an ever-growing number of strokes and sudden death. It is becoming clear that alcohol ingestion can result in profoundly different actions on the cerebral circulation (e.g., vasodilation, vasoconstriction-spasm, vessel rupture), depending upon dose and physiologic state of host. Using rats, it has been demonstrated that acute, high doses of ethanol can result in stroke-like events concomitant with alterations in brain bioenergetics. We review recent in vivo findings obtained with 31P-NMR spectroscopy, optical reflectance spectroscopy, and direct in vivo microcirculatory studies on the intact brain. Alcohol-induced hemorrhagic stroke is preceded by a rapid fall in brain intracellular free magnesium ions ([Mg2+]i) followed by cerebrovasospasm and reductions in phosphocreatine (PCr)/ATP ratio, intracellular pH, and the cytosolic phosphorylation potential (CPP) with concomitant rises in deoxyhemoglobin (DH), mitochondrial reduced cytochrome oxidase aa3 (rCOaa3), blood volume, and intracellular inorganic phosphate (Pi). Using osmotic mini-pumps implanted in the third cerebral ventricle, containing 30% ethanol, it was found that brain [Mg2+]i is reduced 30% after 14 days; brain PCr fell 15%, whereas the CPP fell 40%. Such animals became susceptible to stroke from nonlethal doses of ethanol. Human subjects with mild head injury have been found to exhibit early deficits in serum ionized Mg (IMg2+); the greater the degree of early head injury (30 min-8 h), the greater and more profound the deficit in serum IMg2+ and the greater the ionized Ca (ICa2+) to IMg2+ ratio. Patients with histories of alcohol abuse or ingestion of alcohol prior to head injury exhibited greater deficits in IMg2+ (and higher ICa2+/IMg2+ ratios) and, unlike the subjects without alcohol, did not leave the hospital for at least several days. Women, for some unknown reason, exhibit a much higher incidence of morbidity and mortality from subarachnoid hemorrhage (SAH) than men. Data on 105 men and women with different types of stroke indicate that, on the average, a 20% deficit in serum IMg2+ is seen; total Mg (TMg) or blood pH is usually near normal. Women with SAH, however, exhibit much lower IMg2+ and higher ICa2+/IMg2+ ratios; the presence of ethanol in the blood is associated with even more depression in IMg2+ in SAH in women. It is possible that prior alcohol ingestion is, in large measure, responsible for a great deal of this unexplained higher incidence of SAH in women. It has recently been reported that the cyclical changes in estrogenic hormones appear to control the serum IMg2+ level in young women. A surge in estrogenic levels prior to SAH could thus precipitate, in part, the SAH. In other human studies, it has been shown that migraines and headache, dizziness, and hangover, which accompany ethanol ingestion, are associated with rapid deficits in serum IMg2+ but not in TMg. The former, and the alcohol-associated headache, can be ameliorated with IV administration of MgSO4. Premenstrual tension-headache (PTH) and its exacerbation by alcohol in women is also accompanied by deficits in IMg2+, and elevation in serum ICa2+/IMg2+; IV MgSO4 corrects the PTH and the serum deficit in IMg2+. Animal experiments show that IV Mg2+ can prevent alcohol-induced hemorrhagic stroke and the subsequent fall in brain [Mg2+]i, [PCr], pHi, and CPP. Other recent data indicate that alcohol-induced cellular loss of [Mg2+]i is associated with cellular Ca2+ overload and generation of oxygen-derived free radicals; chronic pretreatment with vitamin E prevents alcohol-induced vascular injury and pathology in the brain. (ABSTRACT TRUNCATED)

Magnesium modulates contractile responses of rat aorta to thiocyanate: A possible relationship to smoking-induced atherosclerosis

Thiocyanate anions (SCN-) as the end products of tobacco smoke and found in the blood of cigarette smokers have been implicated in atherogenesis and heart diseases. Magnesium deficiency has also been implicated in the etiology of atherogenesis. The contractile responses of rat aorta to SCN- and the modulation of extracellular magnesium ions ([Mg2+]o) on the effect of SCN- were, therefore, studied in isolated rat aortic rings. SCN- exposure at a range of concentrations (from 10(-5) to 5 x 10(-2) M) induces contractile responses of isolated rat aortic rings with and without endothelium in a concentration-dependent manner. Significant differences in responsiveness to SCN- were found in rat aortic ring segments with and without endothelial cells. Preincubation of these vessels with low [Mg2+]o markedly shifted the contractile concentration-effect curves to the left, and the contractile effects of SCN- in rat aortic rings were potentiated. In contrast to lowering [Mg2+]o, increasing [Mg2+]o to 2.4 mM was found to dramatically attenuate the contractile responses to SCN-. In the absence of extracellular Ca2+ ([Ca2+]o), SCN--induced contractions were, however, almost abolished after exposure to Mg2+-free medium. In order to investigate the mechanisms of [Mg2+]o modulation of SCN--induced contractile response of rat aorta, changes in intracellular Ca2+ ([Ca2+]i) were measured in cultured primary smooth muscle cells isolated from rat aorta. The resting level of [Ca2+]i in the rat aortic smooth muscle cells was 80.6 +/- 6.6 nM. Exposure of these cells to SCN- (5 x 10(-5) to 5 x 10(-3) M) produced rises in [Ca2+]i in a concentration-dependent manner. Preincubation of these cells with low [Mg2+]o (0 or 0.3 mM, the lowest physiological range) for 24 h significantly potentiated increments in [Ca2+]i induced by SCN-. These rises in [Ca2+]i induced by SCN- were completely inhibited by pretreating the cells with 2.4 mM [Mg2+]o for 24 h. These results support a hypothesis whereby cigarette smoking or exposure to smoking can induce cardiovascular diseases, at least partly, probably by causing spasm and thickening of arterial blood vessels as a consequence of large rises in [Ca2+]i in vascular smooth muscle cells. The chronic presence of or exposure to both thiocyanate and low Mg2+ in the blood of smokers can result in rapid flux of Ca2+ into vascular smooth muscle cells, thus accelerating or initiating atherosclerotic processes in smokers.

Enhanced tumor necrosis factor-alpha production following endotoxin challenge in rats is an early event during magnesium deficiency

Magnesium (Mg) plays an essential role in fundamental cellular reactions and the importance of the immuno-inflammatory processes in the pathology of Mg deficiency has been recently reconsidered. The purpose of the present study was to assess the effect of different stages of Mg deficiency on endotoxin response and tumor necrosis factor-alpha (TNF alpha) production. Weaning male Wistar rats were pair fed either a Mg-deficient or a control diet. At day 7, lipopolysaccharide (LPS) induced no lethal effects in control rats but resulted in 70% mortality in Mg-deficient rats within 3 h. The vulnerability of Mg-deficient rats to LPS was associated with higher TNF alpha plasma values. Mg-deficient animals that received magnesium supplementation before endotoxin challenge had significantly increased survival. At day 2, control and Mg-deficient rats were also subjected to endotoxin challenge with or without magnesium pre-treatment. A significant increase in TNF alpha plasma level was observed in Mg-deficient rats compared to rats fed the control diet. Mg-deficient rats that received magnesium replacement therapy before endotoxin challenge had significantly lower TNF alpha plasma values than those receiving saline before endotoxin. Thus, the results of this experiment suggest that the activated or primed state of immune cells is an early event occurring in Mg deficiency.

Effect of dietary phytate on magnesium bioavailability and liver oxidant status in growing rats

Male albino rats (initial average weight 60 g) were fed semi-synthetic diets based on casein, corn starch and sunflower oil over 21 days. All diets were supplemented with 300 mg magnesium from MgSO4x7H2O and 0,7.5 and 15 g phytic acid (PA) from sodium phytate per kg. The addition of PA to the diets resulted in a dose-dependent decrease of apparent Mg absorption and Mg concentration in the plasma and femur. Impaired Mg bioavailability due to 15 g PA/kg diet was accompanied by an increase of hepatic thiobarbituric acid reactive substances and protein carbonyls as well as by a moderate decline in liver reduced glutathione (GSH) levels. The liver homogenates of rats receiving the diets with 7.5 and 15 g PA/kg, respectively, were much more susceptible to iron-induced lipid peroxidation than those of the controls. Hepatic antioxidative enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx), glucose-6-phosphate dehydrogenase (G6PDH)], alpha-tocopherol concentration and phenyl-N-tert-butylnitrone (PBN) adducts using electron spin resonance spectroscopy remained unchanged by the different dietary treatments. Under the conditions of a marginal dietary Mg supply, phytate had pro-oxidative rather than antioxidative effects in the case of liver metabolism.

Intake of potassium, magnesium, calcium, and fiber and risk of stroke among US men

BACKGROUND

Animal experiments and epidemiological studies have suggested that high potassium intake may reduce the risk of stroke, but the evidence is inconclusive, and the role of other nutrients in potassium-rich foods remains unknown.

METHODS AND RESULTS

We examined the association of potassium and related nutrients with risk of stroke among 43 738 US men, 40 to 75 years old, without diagnosed cardiovascular diseases or diabetes, who completed a semiquantitative food frequency questionnaire in 1986. During 8 years of follow-up, 328 strokes (210 ischemic, 70 hemorrhagic, 48 unspecified) were documented. The multivariate relative risk of stroke of any type for men in the top fifth of potassium intake (median intake, 4.3 g/d) versus those in the bottom (median, 2.4 g/d) was 0.62 (95% CI, 0.43, 0.88; P for trend=0.007). Results for ischemic stroke alone were similar. Intakes of cereal fiber and magnesium, but not of calcium, were also inversely associated with risk of total stroke. These inverse associations were all stronger in hypertensive than normotensive men and were not materially altered by adjustment for blood pressure levels. Use of potassium supplements was also inversely related to risk of stroke, particularly among men taking diuretics (relative risk, 0.36; 95% CI, 0.18, 0.72).

CONCLUSIONS

Although these data do not prove a causal relationship, they are consistent with the hypothesis that diets rich in potassium, magnesium, and cereal fiber reduce the risk of stroke, particularly among hypertensive men. Potassium supplements may also be beneficial, but because of potential risks, use should be carefully monitored and restricted to men taking potassium-losing diuretics.

Study of magnesium bioavailability using stable isotopes and the inductively-coupled plasma mass spectrometry technique in the rat: single and double labelling approaches

The present work aimed to investigate the feasibility of using stable isotopes and inductively-coupled plasma mass spectrometry (ICP/MS) to study Mg absorption in rats. Male Wistar rats, aged 7 weeks and weighing 180 g, were used. They were fed on a semi-purified diet containing 1070 mg Mg/kg, and had free access to feed and distilled water. In the first experiment, after a 16 d adaptation period, two doses of enriched 25Mg (6 and 12 mg) were administered by oral intubation, faeces and urine were collected daily and blood was sampled. Isotope ratios were determined by ICP/MS. 'True' absorption values, using the faecal isotope data, were 0.63 and 0.56 in rats receiving 6 and 12 mg 25Mg respectively, while apparent absorption was 0.50 for two successive periods of metabolic balance studies. Moreover, the oral isotope administration resulted in a measurable isotopic enrichment in plasma within hours which was still detectable on the third day following the isotope administration. In the second experiment, investigating the double labelling technique, similar rats were dosed simultaneously with 5 mg 26Mg orally (premixed with diet) and 0.29 mg 25Mg intravenously. The calculated Mg true absorption values were very similar when calculated from blood or urine data (0.38) but were lower than that obtained from faecal data (0.50). The possible causes of such an unexpected difference and limits of the double labelling technique for Mg absorption are discussed here. Together these results indicate that although 25Mg and 26Mg isotopes have high natural abundance, the described methodology permits meaningful investigations of Mg bioavailability and metabolism.