Magnesium deficiency enhances oxidative stress and collagen synthesis in vivo in the aorta of rats

Association of the oxidative balance score with obesity and body composition among young and middle-aged adults

Objective

The oxidative balance score (OBS) is important for determining the cause of obesity and its complications. We aimed to evaluate the association between OBS and obesity and other segmental body composition parameters among young and middle-aged U.S. adults.

Methods

9,998 participants from the National Health and Nutrition Examination Survey 2011-2018 were included. Lean mass percentage (LM%) and FM% were evaluated by dual-energy x-ray absorptiometry. Obesity was defined as body FM% ≥25% in men and ≥ 35% in women. The OBS was scored by 5 pro-oxidant and 21 antioxidant factors. Associations of quartiles of OBS with obesity risk were estimated using multivariable logistic regression models. Multivariable linear regression was conducted to estimate the association between OBS and segmental body composition measures including the arm LM%, leg LM%, torso LM%, whole LM%, arm FM%, leg FM%, torso FM% and total FM%.

Results

Compared to participants in the lowest quartile of OBS, those in the highest quartile of OBS were associated with a lower risk of BMI-defined obesity BMI-defined obesity [0.43 (0.36, 0.50)] and FM%-related obesity [0.43 (0.35, 0.52)]. Additionally, OBS was negatively associated with FM% of the limb and torso but positively associated with the percentage of lean mass (LM%) of the limb and trunk.

Conclusion

OBS was negatively associated with the risk of obesity and segmental FM%, but was positively associated with segmental LM% among US adults, indicating that adhering to an anti-oxidative diet and lifestyle management may be beneficial for preventing segmental obesity.

The Integral Role of Magnesium in Muscle Integrity and Aging: A Comprehensive Review

Aging is characterized by significant physiological changes, with the degree of decline varying significantly among individuals. The preservation of intrinsic capacity over the course of an individual's lifespan is fundamental for healthy aging. Locomotion, which entails the capacity for independent movement, is intricately connected with various dimensions of human life, including cognition, vitality, sensory perception, and psychological well-being. Notably, skeletal muscle functions as a pivotal nexus within this intricate framework. Any perturbation in its functionality can manifest as compromised physical performance and an elevated susceptibility to frailty. Magnesium is an essential mineral that plays a central role in approximately 800 biochemical reactions within the human body. Its distinctive physical and chemical attributes render it an indispensable stabilizing factor in the orchestration of diverse cellular reactions and organelle functions, thereby rendering it irreplaceable in processes directly impacting muscle health. This narrative review offers a comprehensive exploration of the pivotal role played by magnesium in maintaining skeletal muscle integrity, emphasizing the critical importance of maintaining optimal magnesium levels for promoting healthy aging.

The Benefits of Nanosized Magnesium Oxide in Fish Megalobrama amblycephala: Evidence in Growth Performance, Redox Defense, Glucose Metabolism, and Magnesium Homeostasis

This study evaluated the effects of dietary magnesium oxide nanoparticles (MgO NPs) on the growth, redox defense, glucose metabolism, and magnesium homeostasis in blunt snout bream. Fish (12.42 ± 0.33 g) were fed seven diets containing graded levels of MgO NPs (0, 60, 120, 240, 480, 960, and 1920 mg/kg) for 12 weeks. Whole-body Mg retention decreased significantly as the dietary Mg increased. As dietary MgO NPs levels reached 120 mg/kg, the growth performance and feed utilization remarkably improved. When added at 240 mg/kg, oxidative stress was significantly reduced evidenced by the increased Mn-sod transcription and the decreased CAT and GSH-Px activities and the MDA content. Meanwhile, it enhanced glucose transport, glycolysis, and glycogen synthesis, while inhibiting gluconeogenesis, as was characterized by the increased transcriptions of glut2, gk, and pk, and the decreased transcriptions of fbpase and g6pase. In addition, the supplementation of 120 mg/kg MgO NPs promoted Mg transport marked by a significant increase in the protein expressions of TRMP7, S41A3, and CNNM1. In conclusion, the moderate supplementation of MgO NPs improved the growth performance, reduced hepatic oxidative stress, and promoted glucose transport, glycolysis, glycogen synthesis, and magnesium homeostasis in fish while inhibiting glu.

Association between the Oxidative Balance Score and Telomere Length from the National Health and Nutrition Examination Survey 1999-2002

Purpose. Leukocyte telomere length (LTL) is an important biomarker of aging. The oxidative balance score (OBS) is used to assess the oxidative stress-related exposures of diet and lifestyle. This study is aimed at exploring if the OBS was associated with LTL. Methods. 3220 adults were included in this study from the National Health and Nutrition Examination Survey (NHANES) 1999-2002. LTL was assayed from leukocyte DNA. Twenty dietary and lifestyle factors were selected to score the OBS. Survey-based multivariable linear regression was conducted to assess the association between the OBS and log-transformed LTL. Results. The association between the OBS and log-transformed LTL was positive in females but not males. For females, compared with the lowest OBS category as a reference, the multivariable-adjusted beta estimate (95% confidence interval, CI) for the highest OBS category was 0.0701 (0.0205–0.1197) ( $p$ for $\text{trend}<0.01$ ), and the multivariable-adjusted beta estimate (95% CI) of the continuous OBS was 0.0039 (0.0014–0.0065). There was also the gender difference in the correlations of the dietary OBS and the lifestyle OBS with log-transformed LTL. Conclusion. There was a positive association between the OBS and LTL in females. This result suggested that diet and lifestyle might affect LTL by regulating oxidative balance.

Magnesium intake and lung cancer risk: A systematic review and meta-analysis

Magnesium may reduce the risk of lung cancer by affecting cell proliferation, inflammation and by preserving lung function; however, the results of epidemiological studies on the potential benefits of magnesium in lung pathology are inconclusive. We conducted this meta-analysis to investigate the association between magnesium intake and the risk of lung cancer. A total of 5 studies were extracted from PubMed, SCOPUS, and the Cochrane Review (to May 2018). These studies involved 58,5821 participants with 8,977 lung cancer cases. The pooled relative risk (RR) indicated a significant association between lung cancer incidence and magnesium intake (RR = 0.88, 95% CI = 0.79 to 0.98; p = 0.018). To investigate the cause of heterogeneity of these studies (I² = 75.8%, p < 0.001), we performed a subgroup analysis which was affected by the mean dose of magnesium intake, where doses of magnesium intake lower than 300 mg/d significantly decreased lung cancer risk (RR = 0.83, 95% CI = 0.70 to 0.99; p = 0.034). Increasing magnesium intake doses to over 300 mg/d did not reduce the incidence of lung cancer (RR = 0.89, 95% CI = 0.78 to 1.01; p = 0.076). Our meta-analysis suggests that magnesium intake of less than 300 mg/d may have protective effects in lung cancer.

Dietary magnesium deficiency impaired intestinal structural integrity in grass carp (Ctenopharyngodon idella)

Grass carp (223.85–757.33 g) were fed diets supplemented with magnesium (73.54–1054.53 mg/kg) for 60 days to explore the impacts of magnesium deficiency on the growth and intestinal structural integrity of the fish. The results demonstrated that magnesium deficiency suppressed the growth and damaged the intestinal structural integrity of the fish. We first demonstrated that magnesium is partly involved in (1) attenuating antioxidant ability by suppressing Nrf2 signalling to decrease antioxidant enzyme mRNA levels and activities (except CuZnSOD mRNA levels and activities); (2) aggravating apoptosis by activating JNK (not p38MAPK) signalling to upregulate proapoptotic protein (Apaf-1, Bax and FasL) and caspase-2, -3, -7, -8 and -9 gene expression but downregulate antiapoptotic protein (Bcl-2, IAP and Mcl-1b) gene expression; (3) weakening the function of tight junctional complexes (TJs) by promoting myosin light chain kinase (MLCK) signalling to downregulate TJ gene expression [except claudin-7, ZO-2b and claudin-15 gene expression]. Additionally, based on percent weight gain (PWG), against reactive oxygen species (ROS), against caspase-9 and claudin-3c in grass carp, the optimal dietary magnesium levels were calculated to be 770.38, 839.86, 856.79 and 811.49 mg/kg, respectively.

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.

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.

Magnesium Counteracts Vascular Calcification: Passive Interference or Active Modulation?

Over the last decade, an increasing number of studies report a close relationship between serum magnesium concentration and cardiovascular disease risk in the general population. In end-stage renal disease, an association was found between serum magnesium and survival. Hypomagnesemia was identified as a strong predictor for cardiovascular disease in these patients. A substantial body of in vitro and in vivo studies has identified a protective role for magnesium in vascular calcification. However, the precise mechanisms and its contribution to cardiovascular protection remain unclear. There are currently 2 leading hypotheses: first, magnesium may bind phosphate and delay calcium phosphate crystal growth in the circulation, thereby passively interfering with calcium phosphate deposition in the vessel wall. Second, magnesium may regulate vascular smooth muscle cell transdifferentiation toward an osteogenic phenotype by active cellular modulation of factors associated with calcification. Here, the data supporting these major hypotheses are reviewed. The literature supports both a passive inorganic phosphate-buffering role reducing hydroxyapatite formation and an active cell-mediated role, directly targeting vascular smooth muscle transdifferentiation. However, current evidence relies on basic experimental designs that are often insufficient to delineate the underlying mechanisms. The field requires more advanced experimental design, including determination of intracellular magnesium concentrations and the identification of the molecular players that regulate magnesium concentrations in vascular smooth muscle cells.

Magnesium deficiency and oxidative stress: an update

Magnesium deficiency (MgD) has been shown to impact numerous biological processes at the cellular and molecular levels. In the present review, we discuss the relationship between MgD and oxidative stress (OS). MgD is accompanied by increased levels of OS markers such as lipid, protein and DNA oxidative modification products. Additionally, a relationship was detected between MgD and a weakened antioxidant defence. Different mechanisms associated with MgD are involved in the development and maintenance of OS. These mechanisms include systemic reactions such as inflammation and endothelial dysfunction, as well as changes at the cellular level, such as mitochondrial dysfunction and excessive fatty acid production.

The influence of oral magnesium sulfate on skin microvasculature blood flow in diabetic rats

Microvascular disease is a major feature of type1 diabetes and results from long-standing structural and functional changes especially in the skin microvasculature. Magnesium (Mg) deficiency has recently been proposed as a novel factor implicated in the pathogenesis of diabetes complications such as vascular disturbance, but its mechanism of action is not completely elucidated. The present study was designed to determine whether chronic magnesium sulfate administration could control streptozocin-induced diabetes and improve endothelium-dependent and endothelium-independent dilatation, and identify its probable mechanism in the skin microvasculature of diabetic rats. Fifty male Wistar rats (220 ± 10 g) were divided into two diabetic and one control groups. One subgroup of diabetic received magnesium sulfate (10 g/l) in their drinking water, while two other groups had only tap water. Laser Doppler flow meter with iontophoresis was used to measure the relative changes in skin blood flow. We used acetylcholine (Ach), sodium nitroprusside (SNP), and N (w)-nitro-L-arginine (LNNA; NO synthase inhibitor) with magnesium sulfate (0.1 M) in control and experimental animal by microsyringe pump microinjection. SNP- and Ach-induced cutaneous perfusion increased significantly by Mg treatment in the diabetic groups, and local microinjection of magnesium sulfate (0.1 M) increased cutaneous blood flow in all groups (p < 0.01). However, the administration of LNNA prior to magnesium sulfate attenuated (p < 0.05) but not abolished the increase in cutaneous blood flow in diabetic and normal rats. From the results of this study, it may be concluded that Mg could improve skin microvasculature of diabetic rats with potentiation of nitric oxide pathway.

Dietary magnesium and DNA repair capacity as risk factors for lung cancer

Magnesium (Mg) is required for maintenance of genomic stability; however, data on the relationship between dietary Mg intake and lung cancer are lacking. In an ongoing lung cancer case-control study, we identified 1139 cases and 1210 matched healthy controls with data on both diet and DNA repair capacity (DRC). Dietary intake was assessed using a modified Block-NCI food frequency questionnaire and DRC was measured using the host-cell reactivation assay to assess repair in lymphocyte cultures. After adjustment for potential confounding factors including DRC, the odds ratios (ORs) and 95% confidence intervals (CIs) for lung cancer with increasing quartiles of dietary Mg intake were 1.0, 0.83 (0.66-1.05), 0.64 (0.50-0.83) and 0.47 (0.36-0.61), respectively, for all subjects (P-trend < 0.0001). Similar results were observed by histology and clinical stage of lung cancer. Low dietary Mg intake was associated with poorer DRC and increased risk of lung cancer. In joint effects analyses, compared with those with high dietary Mg intake and proficient DRC, the OR (95% CI) for lung cancer in the presence of both low dietary Mg and suboptimal DRC was 2.36 (1.83-3.04). Similar results were observed for men and women. The effects were more pronounced among older subjects (>60 years), current or heavier smokers, drinkers, those with a family history of cancer in first-degree relatives, small cell lung cancer and late-stage disease. These intriguing results need to be confirmed in prospective studies.

Synthetic smooth muscle cell phenotype is associated with increased nicotinamide adenine dinucleotide phosphate oxidase activity: effect on collagen secretion

OBJECTIVE

Smooth muscle cells (SMCs) from prosthetic vascular grafts secrete higher levels of collagen than aortic SMCs under basal conditions and during incubation with oxidized low-density lipoprotein. We postulated that reactive oxygen species (ROS) contributed to the observed difference. The objective of this study was to assess the effect of ROS on collagen secretion by aortic and graft SMCs and explore the mechanism involved.

METHODS

SMCs isolated from canine aorta or Dacron thoracoabdominal grafts were incubated with 6-anilinoquinoline-5,8-quinone (LY83583), an agent that induces superoxide production. Type I collagen in the conditioned medium was measured by enzyme-linked immunosorbent assay, and superoxide anion production was measured by lucigenin assay.

RESULTS

LY83583 stimulated a rapid increase in collagen production by graft SMCs that paralleled the LY83583-induced increase in superoxide production. The increase in both collagen and superoxide was greater in graft SMCs than aortic SMCs. Collagen and superoxide production were inhibited by superoxide scavengers. Nicotinamide adenine dinucleotide phosphate (NADPH) induced significantly more superoxide production by graft SMCs than aortic SMCs, suggesting that the NADPH oxidase system was more active in graft SMCs. NADPH oxidase inhibitors blocked the superoxide and collagen production induced by LY83583.

CONCLUSION

In SMCs, the synthetic phenotype is associated with increased NADPH oxidase activity and elevated superoxide production in response to an oxidative stress. Superoxide, in turn, leads to increased collagen production.

CLINICAL RELEVANCE

The inflammatory process after prosthetic vascular graft implantation causes oxidative stress that can stimulate collagen production by graft SMCs, contributing to the progression of intimal hyperplasia. The exaggerated response of graft SMCs to oxidative stress offers a potential target for therapeutic interventions.

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.

Dietary magnesium intake can affect mechanical properties of rat carotid artery

The purpose of the present study was to determine the effects of Mg deficiency and supplementation on the mechanical properties of the rat common carotid artery. The internal diameter and intra-arterial pressure of carotid artery were measured continuously using an echo-tracking device. Systolic, diastolic and mean intra-arterial pressures were not significantly different in Mg-deficient, -supplemented or control rats. Histological examination showed a larger cross-sectional area, increased intima-media thickness and a greater media:lumen value in carotid artery of Mg-deficient rats, indicating that Mg deficiency may directly stimulate growth and/or proliferation of arterial wall components. In addition, we observed a negative linear relationship between intima-media thickness and plasma Mg concentration, suggesting that increased Mg intake may counteract arterial wall hypertrophy. Neither Mg deficiency nor supplementation modified the arterial distensibilityv.intra-arterial pressure curve or the Eincv.wall stress curve, indicating that dietary Mg intake did not modify wall stiffness in young rats. At mean intra-arterial pressure, the stress and Eincvalues were, however, significantly lower in Mg-deficient rats (P<0·05 in both cases); this finding could be related to the alteration in the geometry of the carotid artery. In conclusion, these findings suggest that Mg deficiency modifies the mechanical properties of the common carotid artery in young rats. Since Mg deficiency is considered a risk factor, these mechanical alterations could contribute to the development of atherosclerosis, hypertension and cardiovascular diseases.

Magnesium and neoplasia: From carcinogenesis to tumor growth and progression or treatment

Magnesium is involved in a wide range of biochemical reactions that are crucial to cell proliferation, differentiation, angiogenesis, and apoptosis. Changes in magnesium availability have been shown to influence biological responses of immuno-inflammatory cells. Equally plausible seems to be an involvement of magnesium in the multistep and interconnected processes that lead to tumor formation and development; however, the "how" and "when" of such an involvement remain to be defined. Here, we reviewed in vitro and in vivo data that indicated a role for magnesium in many biological and clinical aspects of cancer (from neoplastic transformation to tumor growth and progression or pharmacologic treatment). In adopting this approach we went through a full circle from molecular aspects to observational or epidemiological studies that could reconcile in a unifying picture the otherwise fragmentary or puzzling data currently available on the role of magnesium in cancer.

Selected haematological and biochemical parameters of blood in rats after subchronic administration of vanadium and/or magnesium in drinking water

The purpose of these studies was to evaluate the effect of selected vanadium and magnesium doses on certain haematological and biochemical blood parameters in rats. Outbred 2-month-old, albino male Wistar rats received for a period of 6 weeks, as a sole drinking liquid, the following water solutions: group II, sodium metavanadate (SMV) at a concentration of 0.125 mg V/mL; group III, magnesium sulphate (MS) at a concentration of 0.06 mg Mg/mL; and group IV, SMV-MS solution at the same concentrations. The control group received at this time deionized water to drink. It was calculated that group II ingested with drinking water about 10.7 mg V/kg b. w./24 h, group III 6 mg Mg/kg b. w./24 h, and group IV about 9 mg V and 4.5 mg Mg/kg b. w./24 h. The exposure to vanadium alone (group II) led to a statistically significant decrease in body weight gain, food and fluid intakes. Moreover, in the same group of rats a statistically significant decrease in the RBC count, Hb concentration, MCV, and MCH values was demonstrated. Additionally, a statistically significant decrease in the plasma L-ascorbic acid concentration and a significant increase in MDA concentration in blood in this group were found. Instead, after the administration of magnesium alone (group III), a statistically significant decrease in the fluid intake and in the L-ascorbic acid concentration in plasma was noted. Furthermore, in the same group of rats a statistically significant increase in Hb level and in the plasma magnesium concentration was demonstrated. Two-way analysis of variance (ANOVA) did not reveal the interactions between V and Mg.

Cardiac fibrogenesis in magnesium deficiency: a role for circulating angiotensin II and aldosterone

Mechanisms underlying cardiac fibrogenesis in magnesium deficiency are unclear. It was reported earlier from this laboratory that serum from magnesium-deficient rats has a more pronounced stimulatory effect on cell proliferation, net collagen production, and superoxide generation in adult rat cardiac fibroblasts than serum from rats on the control diet. The profibrotic serum factors were, however, not identified. This study tested the hypothesis that circulating angiotensin II may modulate cardiac fibroblast activity in hypomagnesemic rats. Male Sprague-Dawley rats were pair-fed a magnesium-deficient (0.0008% Mg) or -sufficient (0.05%) diet for 6 days, and the effects of serum from these rats on [3H]thymidine and [3H]proline incorporation into cardiac fibroblasts from young adult rats were evaluated in the presence of losartan, an angiotensin II type 1 (AT1) receptor antagonist, and spironolactone, an aldosterone antagonist. Losartan and spironolactone markedly attenuated the stimulatory effects in vitro of serum from the magnesium-deficient and control groups, but the inhibitory effects were considerably higher in cells exposed to serum from magnesium-deficient animals. Circulating and cardiac tissue levels of angiotensin II were significantly elevated in magnesium-deficient animals (67.6% and 93.1%, respectively, vs. control). Plasma renin activity was 61.9% higher in magnesium-deficient rats, but serum angiotensin-converting enzyme activity was comparable in the two groups. Furthermore, preliminary experiments in vivo using enalapril supported a role for angiotensin II in magnesium deficiency. There was no significant difference between the groups in serum aldosterone levels. The findings suggest that circulating angiotensin II and aldosterone may stimulate fibroblast activity and contribute to a fibrogenic response in the heart in magnesium deficiency.

Magnesium Deficiency Enhances Hydrogen Peroxide Production and Oxidative Damage in Chick Embryo Hepatocyte In Vitro

Magnesium deficiency and oxidative stress have been identified as correlative factors in many diseases. The origin of free radicals correlated with oxidative damage resulting from Mg-deficiency is unclear at the cellular level. To investigate whether hydrogen peroxide (H2O2) is associated in the oxidative stress induced by Mg-deficiency, the effect of Mg2+ deficiency (0, 0.4, 0.7 mM) on the metabolism of H2O2 was investigated in cultured chick embryo hepatocytes. After being cultured in the media with various concentrations of Mg2+ for 1, 2, 4, 6 and 10 days, parameters of H2O2 production, catalase activity, lipid peroxidation, intracellular total Mg and cell viability were analyzed. Results demonstrated that long-term incubation of chick embryo hepatocyte in extracellular Mg2+-deprivative and Mg2+-deficient (0.4 mM) states significantly enhanced the production of H2O2 (approximately twofold, respectively) and lipid peroxidation in the cell cultures, while decreasing the cell viability. Additionally, the reversing action of Mg2+ re-added to 1.0 mM and the partial reversing action of dimethylthiourea suggested that (i) [Mg2+]e deficiency induced the increase of H2O2 production, (ii) [Mg2+]e deficiency decreased catalase activity in chick embryo hepatocyte in vitro, subsequently causing oxidative stress and cell peroxidative damage.

Manganese depresses rat heart muscle respiration

It has previously been reported that moderately high dietary manganese (Mn) in combination with marginal magnesium (Mg) resulted in ultrastructural damage to heart mitochondria. Manganese may replace Mg in biological functions, including the role of enzyme cofactor. Manganese may accumulate and substitute for Mg during the condition of Mg-deficiency. The objective of the current study was to determine whether high Mn alters heart muscle respiration and Mg-enzyme activity as well as whole body Mn retention under marginal Mg. An additional objective was to determine whether high Mn results in increased oxidative stress. In experiment 1: forty-eight rats were fed a 2 x 3 factorial arrangement of Mn (10, 100, or 1000 mg/kg) and Mg (200 or 500 mg/kg). In experiment 2: thirty-two rats were fed one of four diets in a 2 x 2 factorial arrangement of Mn (10 or 250 mg/kg) and Mg (200 or 500 mg/kg). In experiment 3: thirty-two rats were fed one of four diets in a 2 x 2 factorial arrangement of Mn (10 or 650 mg/kg) and Mg (200 or 500 mg/kg). In experiment 2, high Mn and marginal Mg reduced (P<0.05) oxygen consumption of left ventricle muscle. Marginal Mg, but not Mn, reduced (P<0.05) activity of sarcoplasmic reticulum calcium-ATPase enzyme. Dietary Mg had no affect on (54)Mn kinetics, but high dietary Mn decreased (P<0.01) absorption, retention, and rate of excretion of (54)Mn. Neither cellular stress, measured by Comet assay, nor antioxidant activities were increased by high Mn. A strong interaction (P<0.001) between increasing Mn and adequate Mg on hematology was observed. These results confirm previous research in swine that high Mn alters myocardial integrity as well as function, but not as a result of altered calcium transport or oxidative stress.

Effects of administration of oral magnesium on plasma glucose and pathological changes in the aorta and pancreas of diabetic rats

1. Magnesium deficiency has recently been proposed as a novel factor implicated in the pathogenesis of the complications of diabetes. The purpose of the present study was to determine the relationship between oral Mg supplementation and changes in plasma glucose, calcium, haemoglobin, Ca/Mg ratio, blood pressure and the histology of the pancreas and vascular system in streptozotocin-induced diabetic rats. 2. Ten days after the induction of diabetes in male Wistar rats, half the diabetic animals were divided into six groups, receiving 0, 1, 3, 10, 30 or 50 g/L MgSO4 added into the drinking water for 8 weeks. Plasma glucose and Mg were measured at days 1, 2, 3, 5, 7, 14 and 21 to find the optimum dose of Mg and the time-course of its effect. In addition, histological observations were undertaken. Eight weeks later, all animals were decapitated, the pancreas and thoracic aorta were removed carefully and immersed immediately in 10% formaldehyde for histological study. 3. To evaluate the effects of Mg on plasma glucose, calcium, haemoglobin, Mg and blood pressure, another group of animals was divided into four experimental groups, as follows: (i) non-diabetic controls received tap water for 8 weeks; (ii) acute diabetics received tap water for 10 days; (iii) chronic diabetic controls received tap water for 8 weeks; and (iv) Mg-treated chronic diabetic rats received 10 g/L MgSO4 added into the drinking water 10 days after the induction of diabetes for 8 weeks. 4. Magnesium dose dependently affects plasma glucose levels. The peak effect was reached during the first 24 h following oral administration. Administration of 10 g/L MgSO4 results in the return of normal structure in the diabetic pancreas and aorta. Moreover, this concentration of MgSO4 causes glucose, haemoglobin, calcium, the Ca/Mg ratio and blood pressure to reach normal levels. Although the Mg level increases slightly following the administration of 10 g/L MgSO4 to diabetic rats, it never reaches control levels. 5. On the basis of the results of the present study, it may be concluded that chronic Mg administration may have beneficial effects on diabetes.

Oral magnesium administration prevents vascular complications in STZ-diabetic rats

Vascular disease is one of the complicating features of diabetes mellitus. Magnesium deficiency has recently been proposed as a novel factor implicated in the pathogenesis of diabetes complications. Several studies have indicated that hypertension in diabetic patients is an independent altered reaction of blood vessels to neurotransmitters and circulating hormones. Since magnesium has been proposed to decrease vascular sensitivity to vasoconstrictor agents, the present study was designed to determine whether chronic magnesium sulfate administration could prevent vascular complications of STZ-induced diabetes in rats. The animals were divided into six groups: two groups served as controls and received tap water for 8 weeks, while in the other four groups, made diabetic with a single IV injection of 40 mg/kg STZ, two groups treated with magnesium sulfate (10 g/L) added to the drinking water, and the other two groups received tap water only. After 8 weeks, in 3 groups (control, diabetic and Mg-treated), left common carotid artery was cannulated for continuous recording of blood pressure. All animals in these groups were decapitated and blood samples were drawn for glucose, Ca and Mg measurements. In the 3 remaining groups (again divided into control, diabetic and Mg-treated), the mesenteric vascular bed was perfused according to the McGregor method, and descending thoracic aortas were used for measurement of elasticity. In diabetic rats, plasma glucose was significantly increased and plasma magnesium was significantly decreased compared to controls and Mg-treated animals. Although plasma magnesium of Mg-treated animals increased significantly, it failed to reach to the magnesium level of the control group. Ca/Mg ratio was also increased compared to the control and Mg-treated animals. Mean arterial blood pressure in diabetics was significantly higher than control and Mg-treated rats. Similarly, there was a significant difference in mean arterial blood pressure of Mg-treated rats compared to control animals. Baseline perfusion pressure of diabetic group was significantly higher than control and Mg-treated groups with intact and denuded endothelium. Magnesium sulfate treatment decreased mean perfusion pressure of mesenteric vascular bed in intact and denuded endothelium in comparison with non-treated diabetic rats. There was a significant increase in passive tension in the aorta of diabetic rats compared to control and Mg-treated rats. However, there was no significant difference between Mg-treated and control rats. From the results of this study it may be concluded that magnesium could control STZ-induced diabetes and prevent its vascular complications.

Relaxatory effect of magnesium on mesenteric vascular beds differs from normal and streptozotocin induced diabetic rats

Magnesium deficiency has recently been proposed as a novel factor implicated in the pathogenesis of diabetes complications. Previous studies have shown that magnesium decreases basal tone in normal isolated aortic rings and reduces phenylephrine-induced contraction. The mechanism of this magnesium action is not very well known. The present study was designed to determine the role of endothelium and nitric oxide in magnesium sulfate-induced vasorelaxation in diabetic rat vessels. Diabetes was induced by a single tail injection of streptozotocin. Eight weeks later, superior mesenteric arteries of control and diabetic animals were isolated and perfused according to the McGregor method. Prepared vascular beds were constricted with phenylephrine to induce 70-75% of maximal constriction. Magnesium sulfate at concentrations of 0.001 M to 0.1 M was added into the medium and perfusion pressure was then recorded. Mesenteric bed baseline perfusion pressure in intact and denuded endothelium of diabetic groups was higher than controls. In all groups, relaxant response to magnesium in mesenteric bed was attenuated after endothelium removal, but a relaxatory effect appears at high concentration. In the presence of N (omega)-nitro-L-arginine methyl ester (L-NAME), magnesium-induced relaxation was significantly suppressed in intact mesenteric bed of control animals but in diabetics, the relaxant response was slightly inhibited. From the results of this study, it can be concluded that magnesium-induced endothelium dependent and endothelium independent vasorelaxation are mediated by nitric oxide in control rats while in diabetic animals other mechanisms may be involved.

A comparison of oxidized LDL-induced collagen secretion by graft and aortic SMCs: role of PDGF

Smooth muscle cells (SMCs) from prosthetic vascular grafts constitutively secrete higher levels of collagen than aortic SMCs. Lipid oxidation products accumulate in grafts, and we postulated that they stimulate SMC production of collagen. The effect of oxidized low-density lipoprotein (oxLDL) on type I collagen secretion by aortic and graft SMCs was compared. SMCs isolated from the canine thoracic aorta or Dacron thoracoabdominal grafts (n = 10) were incubated with native LDL or oxLDL (0-400 microg cholesterol/ml) for 72 h. Type I collagen in the conditioned medium was measured by ELISA. OxLDL increased collagen production by graft SMCs from 4.1 +/- 0.3 to 11.0 +/- 0.4 ng/microg DNA and by aortic SMCs from 2.3 +/- 0.1 to 3.5 +/- 0.2 ng/microg DNA. Native LDL had little effect. LY-83583, a superoxide generator, stimulated a dramatic increase in collagen secretion by graft SMCs and a smaller but significant elevation by aortic SMCs. OxLDL has been shown to increase PDGF production by graft SMCs, and PDGF can stimulate collagen production. Anti-PDGF antibody inhibited the increase in collagen production by graft SMCs that was stimulated by oxLDL, implicating PDGF as one mechanism of oxLDL-induced collagen production. Lipid oxidation products that accumulate in prosthetic vascular grafts can cause an oxidative stress that stimulates PDGF production by graft SMCs that in turn stimulates collagen production, contributing to the progression of intimal hyperplasia.

Superoxide-mediated activation of cardiac fibroblasts by serum factors in hypomagnesemia

Magnesium deficiency is known to produce myocardial fibrosis in different animal models, but the underlying mechanisms are unclear. However, circulating levels of pro-oxidant and mitogenic factors are reported to be elevated in a rodent model of acute magnesium deficiency, suggesting a role for humoral factors in the pathogenesis of the cardiovascular lesions. Probing the mechanism of cardiac fibrogenesis in magnesium deficiency, the present study furnished evidence that serum from magnesium-deficient rats has a more marked effect than serum from magnesium-sufficient rats on mitogenesis, net collagen production, and superoxide generation in cardiac fibroblasts from young adult rats. The enhanced mitogenic response was abolished by superoxide dismutase and N-acetyl cysteine, showing that it is mediated by superoxide anion. Further, a modest inhibitory effect of the neurokinin-1 receptor antagonist, spantide, suggested that factors acting via neurokinin-1 receptors may partly modulate cardiac fibroblast function in magnesium deficiency. The findings are consistent with the postulation that serum factors may activate cardiac fibroblasts via a superoxide-mediated mechanism and contribute to the fibrogenic response in the heart in magnesium deficiency.

Model of cardiovascular injury in magnesium deficiency

Magnesium deficiency is known to produce cardiovascular lesions. It is, however, not clear as to what constitutes magnesium deficiency - reduced serum levels, reduced tissue levels or reduced intracellular levels of the ionic form of the element. This article cites evidence in support of a hypothesis that a fall in serum magnesium levels may trigger a temporal sequence of events involving vasoconstriction, hemodynamic alterations and vascular endothelial injury to produce pro-inflammatory, pro-oxidant and pro-fibrogenic effects, resulting in initial perivascular myocardial fibrosis which, in turn, would cause myocardial damage and replacement fibrosis. Further, angiotensin II may be the prime mover of the pathogenetic cascade in magnesium deficiency. Importantly, such a mechanism of cardiovascular injury would be independent of a reduction in myocardial or vascular tissue levels of magnesium.