Effect of magnesium deficiency on post-heparin lipase activity and tissue lipoprotein lipase in the rat

Production, purification, and characterization of cold-active lipase from the psychrotroph Pseudomonas sp. A6

Cold-active lipases are presently employed extensively in the detergent, chemical intermediate, fine chemical, food, and pharmaceutical industries. Seven cold-adaptive bacteria were isolated from the Mediterranean Sea near Alexandria, Egypt, and tested for their ability to produce cold-active lipase, with the highest activity at 10 °C. The most potent isolate was Pseudomonas sp. A6. To determine the most important variables, the bacterium was exposed to a necessary medium component and environmental factor screening using a single factor-at-a-time approach, followed by a multifactorial Plackett-Burman design strategy. After purification and characterization, the optimal activity levels for the cold-active lipase were figured out. Inoculation of Pseudomonas A6 under near optimum conditions using medium consisting of (g/L) peptone 7.14; soybean oil 7.5% (v/v); K2HPO4, 0.4; MgSO4, 0.1; glucose 2; pH 8; and temperature 10 °C led to a maximum lipase activity anticipated to be 23.36 U/mL. Purified lipase showed the best activity and thermal stability at a pH of 8 and a temperature of 10 °C. The Pseudomonas A6 lipase tolerated the monovalent ions, while greater valence ions did not.

Magnesium intake is associated with the metabolically healthy obese phenotype

Although magnesium intake is inversely associated with the risk of metabolic abnormalities, whether magnesium intake plays a role on metabolically healthy obese (MHO) phenotype has not been explored. Therefore, the purpose of this study was to determine whether the magnesium intake is associated with the MHO phenotype. Apparently, healthy women and men aged 20-65 years with obesity were enrolled in a cross-sectional study. Subjects were allocated into MHO (n=124) and metabolically unhealthy obese (MUO) (n=123) groups. MHO phenotype was defined by abdominal obesity (waist circumference ≥90 cm in men and ≥80 cm in women) and none, or not more than one of the following risk factors: triglyceride levels ≥150 mg/dL; high-density lipoprotein cholesterol (HDL-C) levels <40 mg/dL in men and <50 mg/dL in women; fasting glucose ≥100 mg/dL; and systolic blood pressure ≥130 mm Hg and/or diastolic blood pressure ≥85 mm Hg. The MUO individuals were characterized by abdominal obesity and the presence of two or more of the aforementioned criteria. The proportion of individuals with high blood pressure (40.7% vs 5.6%, p<0.001), hyperglycemia (69.1% vs 16.9%, p<0.001), hypertriglyceridemia (84.6% vs 36.3%, p<0.001), and low HDL-C (51.2% vs 12.9%, p<0.001) was significantly higher in the MUO individuals as compared with individuals in the MHO group. The logistic regression analysis adjusted by sex and age showed that dietary magnesium intake is significantly associated with the MHO phenotype (OR=1.17; 95% CI 1.07 to 1.25, p=0.005). Our results show that magnesium intake is significantly associated with the MHO phenotype.

Magnesium intake is inversely associated with the risk of metabolic syndrome in the REasons for geographic and racial differences in stroke (REGARDS) cohort study

OBJECTIVE

To investigate the longitudinal association between magnesium (Mg) intake and the risk of metabolic syndrome (MetS).

METHODS

Poisson regression models with robust standard error estimation were used to examine the association between total Mg intake and the risk of MetS in 6802 participants aged ≥45 years at baseline in the REasons for Geographic And Racial Differences in Stroke (REGARDS) study. Dietary data were collected using the modified Block 98 food frequency questionnaire (FFQ) at baseline and incident MetS was diagnosed during follow-up if a participant had three or more of the five components of MetS based on the harmonized definition.

RESULTS

A total of 1470 participants developed MetS during an average follow-up of 10 years. Comparing the highest quintile of total Mg intake (>437.9 mg/day) to the lowest group (<223.5 mg/day), total Mg intake had a significant inverse association with the risk of MetS [relative risk (RR) = 0.79 (0.63, 0.98), P_trend = 0.043]. Dietary Mg intake was inversely associated with MetS [RR = 0.72 (0.56, 0.91), P_trend = 0.006]. Adjusting for baseline components of MetS attenuated the associations, but the linear trends remained.

CONCLUSION

The findings from this study indicate that dietary Mg intake was inversely associated with the risk of MetS. We recommend further studies to explain the underlying mechanisms of action.

Magnesium, Oxidative Stress, Inflammation, and Cardiovascular Disease

Hypomagnesemia is commonly observed in heart failure, diabetes mellitus, hypertension, and cardiovascular diseases. Low serum magnesium (Mg) is a predictor for cardiovascular and all-cause mortality and treating Mg deficiency may help prevent cardiovascular disease. In this review, we discuss the possible mechanisms by which Mg deficiency plays detrimental roles in cardiovascular diseases and review the results of clinical trials of Mg supplementation for heart failure, arrhythmias and other cardiovascular diseases.

Are Circulating Mg2+ Levels Associated with Glucose Tolerance Profiles and Incident Type 2 Diabetes?

Magnesium (Mg²⁺) is an enzyme co-factor that plays a key role in many biochemical reactions, as well as in glucose metabolism. Clinical evidences have demonstrated that depletion of serum Mg²⁺ increases exponentially with the duration of type 2 diabetes mellitus (T2DM). Diabetes is associated with low Mg²⁺, and hypomagnesemia is associated with insulin resistance, inflammation, and increased risk for cardiovascular disease. In subjects at high risk of inflammation and insulin resistance, supplementation of Mg²⁺ alone ameliorates both phenotypes, slowing the development and progression of hepatic steatosis. We analyze the relationship between serum Mg²⁺ levels and the onset of T2DM in a large cohort of well-characterized adult white individuals participating in the CATAMERI study, who were reexamined after a mean follow-up of 5.6 ± 0.9 years. In our analysis we acquired a significant negative correlation between Mg²⁺ levels, fasting glucose, and 2h-post load glucose in subjects who underwent an OGTT. Moreover, Mg²⁺ levels correlated negatively with fasting insulin levels, and positively with the lipid profile. As for the detrimental effect of lower circulating Mg²⁺ levels, our data revealed a significant reduction of T2DM risk of about 20% for each 1 mg/dL increase of circulating Mg²⁺. The present results are consistent with the theory that Mg²⁺ supplementation could ameliorate insulin sensitivity reducing the risk to develop T2DM.

Magnesium deficiency prevents high-fat-diet-induced obesity in mice

AIMS/HYPOTHESIS

Hypomagnesaemia (blood Mg²⁺ <0.7 mmol/l) is a common phenomenon in individuals with type 2 diabetes. However, it remains unknown how a low blood Mg²⁺ concentration affects lipid and energy metabolism. Therefore, the importance of Mg²⁺ in obesity and type 2 diabetes has been largely neglected to date. This study aims to determine the effects of hypomagnesaemia on energy homeostasis and lipid metabolism.

METHODS

Mice (n = 12/group) were fed either a low-fat diet (LFD) or a high-fat diet (HFD) (10% or 60% of total energy) in combination with a normal- or low-Mg²⁺ content (0.21% or 0.03% wt/wt) for 17 weeks. Metabolic cages were used to investigate food intake, energy expenditure and respiration. Blood and tissues were taken to study metabolic parameters and mRNA expression profiles, respectively.

RESULTS

We show that low dietary Mg²⁺ intake ameliorates HFD-induced obesity in mice (47.00 ± 1.53 g vs 38.62 ± 1.51 g in mice given a normal Mg²⁺-HFD and low Mg²⁺-HFD, respectively, p < 0.05). Consequently, fasting serum glucose levels decreased and insulin sensitivity improved in low Mg²⁺-HFD-fed mice. Moreover, HFD-induced liver steatosis was absent in the low Mg²⁺ group. In hypomagnesaemic HFD-fed mice, mRNA expression of key lipolysis genes was increased in epididymal white adipose tissue (eWAT), corresponding to reduced lipid storage and high blood lipid levels. Low Mg²⁺-HFD-fed mice had increased brown adipose tissue (BAT) Ucp1 mRNA expression and a higher body temperature. No difference was observed in energy expenditure between the two HFD groups.

CONCLUSIONS/INTERPRETATION

Mg²⁺-deficiency abrogates HFD-induced obesity in mice through enhanced eWAT lipolysis and BAT activity.

Effects of oral selenium and magnesium co-supplementation on lipid metabolism, antioxidative status, histopathological lesions, and related gene expression in rats fed a high-fat diet

Background

Supplementation with Selenium (Se) has been shown to lower blood cholesterol and increase tissue concentrations of the antioxidant glutathione (GSH); however, the effects of Se supplementation, in combination with supplemental magnesium, on high fat-induced hyperlipidemia have not been studied. This study was designed to elucidate the effects of oral selenium and magnesium co-supplementation on antihyperlipidemic and hepatoprotective, antioxidative activities, and related gene expression in a hyperlipidemic rat model.

Methods

Forty male Sprague Dawley rats were divided into 4 groups: one group served as control group (CT), provided control diet; The other groups were made hyperlipidemic with high-fat diet; specifically, a high-fat diet group (HF); low-dose selenium (0.05 mg/kg·bw) + low-dose magnesium (5.83 mg/kg·bw) supplement high-fat diet group (HF + LSe + LMg) and high-dose selenium (0.10 mg/kg·bw) + high-dose magnesium (58.33 mg/kg·bw) supplement high-fat diet group (HF + HSe + HMg). The first 4 weeks of the experiment was a hyperlipidemia inducing period using high-fat diet and the following 8 weeks involved in selenium and magnesium co-supplementation. On day 0, 20, 40 and 60 of the intervention, lipid profile was measured. At the end of the 12-week experiments, final blood and liver samples were collected for the measurements of lipid profile, antioxidative indexes, pathological examination, and liver lipid metabolism related gene expression.

Results

The elevated levels of serum and liver total cholesterol (TC) and serum LDL-C induced by feeding high-fat diets were significantly reduced by low-dose Se and Mg co-supplementation. Both doses of selenium and magnesium co-supplementation notably decreased the blood and liver TG levels, liver function indexes ALT and AST and the ratio of TC/HDL-C and TG/HDL-C. In contrast, Se and Mg supplementation showed a substantial increase in Se-dependent glutathione peroxidase (GSH-Px) and SOD activities and an significant reduce of level of MDA of hyperlipidemic rats. Oil Red O staining showed that selenium and magnesium co-supplementation significantly reduced hepatic intracellular triacylglycerol accumulation. H&E staining also showed that selenium and magnesium co-supplementation can attenuate liver steatosis. Selenium and magnesium co-supplementation remarkably inhibited the mRNA expression level of hepatic lipogenesis genes liver X receptor alpha (LXRα),SREBP-1c and FASN (fatty acid synthase), regulated the mRNA expression levels of liver enzymes related to cholesterol metabolism, including the down regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) and the upregulation of cholesterol 7α-hydroxylase (CYP7A1) and lecithin cholesterol acyltransferase (LCAT) in the liver of hyperlipidemia rats.

Conclusions

Oral selenium and magnesium co-supplementation inhibited an increase of lipid and liver profile and liver function index induced by a high-fat diet, and enhanced the activity of the antioxidant enzymes. Selenium combined with magnesium is a promising therapeutic strategy with lipid-lowering and antioxidative effects that protects the liver against hyperlipidemia.

Association of magnesium in serum and urine with carotid intima-media thickness and serum lipids in middle-aged and elderly Chinese: a community-based cross-sectional study

OBJECTIVE

Previous studies suggested that magnesium (Mg) might protect against atherosclerosis, but data were scarce in an Asian population. We examined the association of Mg levels in serum and urine with carotid intima-media thickness (cIMT) and serum lipids in Chinese adults.

METHODS

This community-based cross-sectional study recruited 2,837 participants aged 40-75 years in Guangzhou, China. General information, lifestyle factors, serum and urinary concentrations of Mg and cardiometabolic factors were determined. The cIMTs of the common carotid artery (CCA) and the carotid bifurcation (BIF) were measured ultrasonographically.

RESULTS

The mean (SD) concentration of serum Mg was 0.85 (0.07) mmol/L and median (IQR) for urinary Mg excretion was 2.29 (1.56-3.51) mmol/L. After adjustment for potential covariates, both serum and the urinary concentrations of Mg were inversely associated with CCA-IMT, but not with BIF-IMT. The regression coefficients (standard errors) were -100 (29) µm (total), -86 (34) µm (women) and -117 (52) µm (men) CCA-IMT per 1 mmol/L of serum Mg, and -41 (8) µm (total), -41 (10) µm (women) and -44 (15) µm (men) CCA-IMT per 1 unit of urinary Mg/creatinine (log mmol/mmol) (all p < 0.05), respectively. Higher serum Mg levels were associated with higher total cholesterol, HDLc, LDLc and triglyceride, but lower non-HDLc/HDLc in total population (all p < 0.05). Similar relationships of urinary Mg with lipoproteins were also found in total population (all p < 0.05).

CONCLUSION

Higher levels of serum and urinary Mg are associated with lower CCA-IMTs, and the role of Mg in lipid metabolism needs further investigation.

Endothelial cells and magnesium: implications in atherosclerosis

There is no doubt that the functional and structural integrity of the endothelium is critical in maintaining vascular homoeostasis and in preventing atherosclerosis. In the light of epidemiological and experimental studies, magnesium deficiency is emerging as an inducer of endothelial dysfunction. In particular, data on the effects of low extracellular magnesium on cultured endothelial cells reinforce the idea that correcting magnesium homoeostasis might be a helpful and inexpensive intervention to prevent and treat endothelial dysfunction and, consequently, atherosclerosis.

Magnesium intake and prevalence of metabolic syndrome in adults: Tehran Lipid and Glucose Study

Objective

We examined the association of metabolic syndrome (MetS) and its components with dietary intakes of Mg in Tehran adults.

Design

In a cross-sectional study, dietary intakes were assessed using a valid and reliable FFQ. MetS was defined according to the modified guidelines of the National Cholesterol Education Program Adult Treatment Panel III. Waist circumference (WC) was coded according to the newly introduced cut-off points for Iranian adults (≥95 cm for both genders).

Setting

Participants of the Tehran Lipid and Glucose Study (2006–2008).

Subjects

Adults (n2504; 1120 men and 1384 women) aged 18–74 years.

Results

The mean age of participants was 40·8 (sd14·6) years and 38·2 (sd13·5) years for men and women, respectively. The reported mean intake of Mg was 349 (sd109) mg/d. After adjustment for confounding factors, dietary Mg intake was inversely associated with fasting blood glucose (β= −0·08,P= 0·006), TAG (β= −0·058,P= 0·009) and WC (β= −0·013,P= 0·006); however, there were no associations between dietary Mg and diastolic blood pressure, systolic blood pressure or HDL cholesterol. An association was observed between MetSZ-score and Mg intake (crudeβ= −0·017,P= 0·001), independent of age, gender, smoking, physical activity and BMI; this association was attenuated following further adjustment for dietary factors and menopausal status (β= −0·034,P= 0·061).

Conclusions

Our findings suggest a significant inverse association between dietary Mg, MetS and its components.

Ethnic differences in dairy and related nutrient consumption among US adults and their association with obesity, central obesity, and the metabolic syndrome

BACKGROUND

Recent studies suggest dairy consumption and associated nutrients may be protective against some of the components of the metabolic syndrome (MetS).

OBJECTIVES

We examined the association between consumption of a variety of dairy products and their related nutrients with obesity, central obesity, and MetS, and attempted to explain some of the ethnic differences in metabolic outcomes through dairy consumption using national data.

DESIGN

Nationally representative indicators of obesity, central obesity, and MetS among US adults were constructed from National Health and Nutrition Examination Survey 1999-2004 data, including direct anthropometric assessments, blood pressure, and laboratory tests. Sample sizes ranged from 4519 for MetS to 14 618 for obesity. Associations between diet (assessed using 24-h recalls) and metabolic and other outcomes were tested using multivariate linear and logistic models and structural equation models.

RESULTS

We found a significant inverse association between intake of whole milk, yogurt, calcium, and magnesium and metabolic disorders. Odds ratios for one more daily serving of yogurt and 100 mg Mg for MetS were 0.40 (95% CI: 0.18, 0.89) and 0.83 (95% CI: 0.72, 0.96), respectively. The opposite was found for intakes of cheese, low-fat milk, and phosphorus. Using structural equation models, ethnic differences in some MetS outcomes, such as body mass index and systolic blood pressure, were partly explained by variations in dairy-related nutrients.

CONCLUSIONS

Various dairy products may have differential associations with metabolic disorders, including obesity. Ethnic differences in dairy consumption may explain in part the ethnic disparities in metabolic disorders in the US population.

Role of dietary magnesium in cardiovascular disease prevention, insulin sensitivity and diabetes

PURPOSE OF REVIEW

This review summarizes the evidence for benefits of magnesium on metabolic abnormalities, inflammatory parameters, and cardiovascular risk factors and related-potential mechanisms. Controversy due to contrasting results in the literature is also discussed.

RECENT FINDINGS

Increased dietary magnesium intake confers protection against the incidence of diabetes, metabolic syndrome, hypertension, and cardiovascular disease. It ameliorates insulin resistance, serum lipid profiles, and lowers inflammation, endothelial dysfunction, oxidative stress, and platelet aggregability. Magnesium acts as a mild calcium antagonist on vascular smooth muscle tone, and on postreceptor insulin signaling; it is critically involved in energy metabolism, fatty acid synthesis, glucose utilization, ATPase functions, release of neurotransmitters, and endothelial cell function and secretion. Prospective studies, however, have found only a modest effect for dietary magnesium on incident pathologies. Furthermore, magnesium supplementation on glucose metabolism, blood lipid levels, and ischemic heart disease has given inconsistent results.

SUMMARY

There is strong biological plausibility for the direct impact of magnesium intake on metabolic and cardiovascular risk factors, but in-vivo magnesium deficiency might play only a modest role. Reverse causality, the strong association between magnesium and other beneficial nutrients, or the possibility that people who choose magnesium-rich foods are more health-conscious may be confounding factors.

Magnesium intake and the metabolic syndrome: epidemiologic evidence to date

The importance of magnesium intake in relation to the metabolic syndrome has been increasingly recognized. Magnesium is an essential mineral, critical for a number of metabolic functions in the human body. The major dietary sources of magnesium intake include whole grains, legumes, nuts, and green leafy vegetables. Animal studies indicate a pivotal role of magnesium in glucose homeostasis and insulin secretion and action. Experimental and clinical studies suggest that magnesium intake may be inversely related to the risk of hypertension and type 2 diabetes mellitus, and may decrease blood triglyceride and increase high-density lipoprotein cholesterol levels. The purpose of this brief review is to summarize the epidemiologic data relating magnesium to the metabolic syndrome and to discuss the potential mechanisms.

Increased magnesium intake prevents hyperlipidemia and insulin resistance and reduces lipid peroxidation in fructose-fed rats

Studies have suggested that type 2 diabetes mellitus is associated with abnormal lipid metabolism, oxidative stress and insulin resistance. Increased magnesium intake may improve dyslipidemia, oxidative stress and insulin insensitivity in type 2 diabetes. Therefore, the present study investigated the influence of increasing dietary magnesium from 0.1% to 1.0% for 4 weeks on plasma lipids, lipid peroxidation, l-ascorbic acid and insulin sensitivity in male Wistar rats fed a high-fructose diet. The rats were divided into control (CR), fructose-fed (FRU-fed) and fructose-fed supplemented with magnesium (FRU-Mg-fed) groups (n=8 per group). Homeostasis model assessment for insulin resistance (HOMA-IR) and plasma thiobarbituric acid-reactive substances (TBARS) were used as indices of insulin sensitivity and lipid peroxidation, respectively. When compared with controls, the FRU-fed group had significantly higher values of HOMA-IR, fasting plasma glucose, insulin, triglyceride, total cholesterol/HDL-cholesterol ratio (atherogenic index), and TBARS. Their values in FRU-Mg-fed group were close to those of the controls. FRU-Mg-fed group had also significantly higher plasma magnesium and l-ascorbic acid levels, but significantly lower LDL-cholesterol levels than those in control and Fru-fed groups.

CONCLUSION

increased magnesium intake improved insulin sensitivity, hyperglycemia, hyperlipidemia and reduced lipid peroxidation in fructose-fed rats.

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.

Increase in serum magnesium level in haemodialysis patients receiving sevelamer hydrochloride

BACKGROUND

Clinical studies have shown that sevelamer hydrochloride improves lipid profiles and attenuates the progression of the cardiovascular calcifications in haemodialysis patients. It is known that both of these properties are associated with increased magnesium levels. The effect of sevelamer on serum magnesium level is not well documented. The aim of this study was to determine the effects of sevelamer treatment on serum magnesium in haemodialysis patients and to assess the association of magnesium levels with lipid profiles and intact parathyroid hormone (iPTH).

METHODS

Phosphate binders were discontinued during a two week washout period. Forty-seven patients, whose serum phosphate was greater than 6.0 mg/dl at the end of washout, received sevelamer hydrochloride for eight weeks. The patients were then washed off sevelamer for another two weeks.

RESULTS

Mean serum phosphorus concentration declined from 7.5 +/- 1.3 to 6.4 +/- 1.2 mg/dl (P < 0.001), mean serum magnesium levels increased from 2.75 +/- 0.35 to 2.90 +/- 0.41 mg/dl (P < 0.001) and median serum iPTH levels decreased from 297 to 213 pg/ml (P=0.001) during the eight weeks of sevelamer treatment. After the two week post-treatment washout phosphorus levels increased to 7.3 +/- 1.3 mg/dl (P < 0.001), magnesium levels were reduced to 2.77 +/- 0.39 mg/dl (P < 0.001) and iPTH levels increased to 240 pg/ml (P=0.012). No change was observed in serum calcium levels during the sevelamer treatment period and the subsequent washout period. The mean decline in total and low density lipoprotein (LDL) cholesterol during sevelamer treatment was 16.3 and 28.3 (P < 0.001), respectively. The mean increase in high density lipoprotein (HDL) cholesterol and in apolipoprotein A1 was 2.9 +/- 5.8 mg/dl (P=0.004) and 6.8 +/- 11.1 mg/dl (P=0.001), respectively. Multivariate analysis showed that the rise in serum magnesium concentration significantly correlated with reductions in iPTH levels (r=-0.40, P=0.016), but did not have any significant correlation with the changes in lipid profiles.

CONCLUSIONS

Our findings indicate that patients on haemodialysis receiving sevelamer have a significant increase in serum magnesium concentrations. This increase in serum magnesium is associated with reduction in iPTH levels. The changes in lipid profiles of these patients however are not related to changes in serum magnesium levels.

Magnesium Intake and Incidence of Metabolic Syndrome Among Young Adults

Background— Studies suggest that magnesium intake may be inversely related to risk of hypertension and type 2 diabetes mellitus and that higher intake of magnesium may decrease blood triglycerides and increase high-density lipoprotein (HDL) cholesterol levels. However, the longitudinal association of magnesium intake and incidence of metabolic syndrome has not been investigated.

Methods and Results— We prospectively examined the relations between magnesium intake and incident metabolic syndrome and its components among 4637 Americans, aged 18 to 30 years, who were free from metabolic syndrome and diabetes at baseline. Metabolic syndrome was diagnosed according to the National Cholesterol Education Program/Adult Treatment Panel III definition. Diet was assessed by an interviewer-administered quantitative food frequency questionnaire, and magnesium intake was derived from the nutrient database developed by the Minnesota Nutrition Coordinating Center. During the 15 years of follow-up, 608 incident cases of the metabolic syndrome were identified. Magnesium intake was inversely associated with incidence of metabolic syndrome after adjustment for major lifestyle and dietary variables and baseline status of each component of the metabolic syndrome. Compared with those in the lowest quartile of magnesium intake, multivariable-adjusted hazard ratio of metabolic syndrome for participants in the highest quartile was 0.69 (95% confidence interval [CI], 0.52 to 0.91; P for trend <0.01). The inverse associations were not materially modified by gender and race. Magnesium intake was also inversely related to individual component of the metabolic syndrome and fasting insulin levels.

Conclusions— Our findings suggest that young adults with higher magnesium intake have lower risk of development of metabolic syndrome.

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.

Magnesium repletion therapy improved lipid metabolism in hypomagnesemic renal transplant recipients: a pilot study

BACKGROUND

Hypomagnesemia has been associated with hypertension, abnormal glucose and lipid metabolism, and accelerated atherosclerosis in nontransplant patients.

METHODS

In this prospective short-term pilot study, 14 hypomagnesemic renal transplant recipients with stable renal function were evaluated monthly over a 6-month interval. The first 3 months was the baseline observation period. During the second 3 months, MgO2 was administered to normalize the serum Mg level. Glucose tolerance, lipid levels, blood pressure, weight, and routine chemistries were assessed before and after Mg replacement. All others medications were held constant during the 6-month study.

RESULTS

Serum Mg levels increased to normal range after MgO2 therapy, which was well tolerated. There were significant decreases in total cholesterol, low density lipoprotein, and total cholesterol/high density lipoprotein ratio after 3 months of MgO2 therapy. Only three patients had abnormal baseline glucose tolerance tests. All three patients showed improved glucose tolerance after MgO2, but this was not statistically significant.

CONCLUSIONS

Mg repletion may be an important ancillary therapy in hypomagnesemic renal transplant patients with hyperlipidemia.

Influence of magnesium deficiency on concentration of calcium in soft tissue of uremic rats

The influence of magnesium (Mg) deficiency on the concentration of calcium (Ca) in the aorta, heart, and kidney was evaluated in uremic rats. A total of 32 rats were randomly assigned to two groups: one group made uremic by the 5/6 nephrectomy method, and the other serving as sham-operated controls. Both groups were randomly assigned to two subgroups: one group given a Mg-deficient diet and the other fed a Mg-supplemented diet. After 12 weeks on the regimen, all animals were sacrificed. In Mg-supplemented uremic rats, the concentration of Ca in the aorta was higher than in Mg-supplemented control rats. The concentration of Ca in the aorta was further increased in Mg-deficient uremic rats. The concentrations of Ca in the heart and the kidney were also increased in Mg-deficient uremic rats, as compared with Mg-supplemented uremic rats. The concentration of Mg was decreased in the aorta and increased in the kidney of Mg-deficient rats. There was no significant influence of Mg deficiency on the concentration of phosphate in tissue. Results suggest that Mg deficiency in uremia may increase aortic calcification.

Magnesium deficiency modulates hepatic lipogenesis and apolipoprotein gene expression in the rat

The present study was performed to determine the effects of magnesium (Mg) deficiency upon plasma lipoproteins and hepatic apolipoprotein gene expression in the rat. The most obvious effect of Mg-deficiency on plasma lipids is a marked increase in post-prandial triacylglycerol concentration. This increased triglyceridemia persists in fasted rats. Density gradient ultracentrifugation analysis revealed marked alterations in the distribution of plasma lipoproteins in Mg-deficient rats. An increase in triacylglycerol-rich lipoproteins (TGRLP) was associated with a significant increase in plasma apolipoprotein B (apo B) concentration and was accompanied by selective accumulation of apo B-48. A decrease in high-density lipoproteins (HDL) was accompanied by a corresponding decrease in plasma apo E concentration and a concordant decrease in hepatic apo E mRNA abundance and biosynthesis. Hepatic apo B-100 synthesis was reduced by over 75% in Mg-deficient animals despite an increase in hepatic apo B mRNA abundance. However, this change in hepatic apo B gene expression was not associated with alterations in posttranscriptional apo B mRNA editing. These changes in apolipoprotein gene expression were associated with increased hepatic lipogenesis, despite the observation that net triacylglycerol secretion rates were not different between Mg-deficient and control animals. Taken together, the data demonstrate a complex pattern of alterations in hepatic lipid metabolism and apolipoprotein gene expression in the Mg-deficient rat and suggest a defect in the catabolism rather than secretion of TGLRP as the major factor underlying the altered plasma lipoprotein profile.

Oxidative modification of triglyceride-rich lipoproteins in hypertriglyceridemic rats following magnesium deficiency

Hypertriglyceridemia observed in magnesium (Mg)-deficient rats was associated with a significant increase in the very low-density lipoprotein (VLDL) plus low-density lipoprotein (LDL) fractions. The results from in vitro copper-induced lipid peroxidation, expressed in terms of conjugated dienes and thiobarbituric acid reactive substances content, showed that VLDL + LDL particles from Mg-deficient rats were more susceptible to oxidative damage than lipoproteins from control rats. These results suggest that the mechanism responsible for the atherogenicity and tissue damage characteristic of Mg deficiency may be mediated by an increased susceptibility of triglyceride-rich lipoproteins to peroxidation in hypertriglyceridemic animals.

Plasma lipid physical properties in swine fed margarine or butter in relation to dietary magnesium intake

Plasma lipids obtained from swine which had been fed butter or margarine at two dietary magnesium (Mg) levels indicated that the level of dietary Mg was more significant to plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) levels than was the presence of butter or margarine. At 270 mg Mg/kg, which is considered adequate for swine, there was a significant difference in the plasma TC between swine fed margarine and those fed butterfat (105 and 126 mg %, respectively). Plasma LDL-C was higher in swine fed butter than in those fed margarine (88 and 71 mg %, respectively). In swine fed an additional 247 mg Mg/kg, however, there was no significant difference in plasma TC between those fed margarine or butter. Although at 247 mg Mg/kg, however, there was no significant difference in plasma TC between those fed margarine or butter. Although at 247 mg Mg/kg plasma LDL-C was higher in swine fed margarine and HDL-C was higher in those fed butter, there were no significant differences in the order parameters of LDL and HDL. Studies in which the influences of dietary fats on plasma cholesterol were first noted were carried out on liquid diets deficient in Mg. Mg, a cofactor in the enzymes involved in desaturation of saturated fatty acids, is also necessary in desaturation of linoleic to arachidonic acid.

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

Magnesium (Mg)-deficient and control diets were pair-fed to weanling Wistar rats for 8 days. Plasma lipoproteins were separated into various density classes by sequential preparative ultracentrifugation. The extent of lipid peroxidation was measured in terms of thiobarbituric acid reactive substances in lipoproteins and tissue homogenates before or after iron-induced lipid peroxidation. Hyperlipemia in Mg-deficient rats was accompanied by increased oxidation of very-low-density lipoproteins and low-density lipoproteins. Moreover, very-low-density lipoproteins and high-density lipoproteins from Mg-deficient rats were more susceptible to oxidative damage following iron incubation. Mg deficiency increased lipid peroxidation in liver, heart and skeletal muscles. Their homogenates were more susceptible to in vitro peroxidation. Mg deficiency has been discussed as a possible contributory factor in the development of cardiovascular disease and was associated with tissue damage and membrane alteration. These results demonstrate for the first time that Mg affects the susceptibility of lipoproteins to peroxidation and suggest that the mechanism responsible for the pathological consequences of Mg deficiency may be mediated by lipid peroxidation products.

Magnesium deficiency affects malaria susceptibility in mice

One hundred twenty mice were fed control and magnesium-(Mg) deficient diets containing 960 and 50 mg Mg/kg, respectively. After 12 days, mice were inoculated with several strains of Plasmodium (P). Parasitemias and survivals were monitored for 20 days after infection. The Mg-deficient diet protected mice against the nonlethal parasite P. chabaudi as shown by decreased parasitemia. All control mice infected with P. vinckei died from the infection. Mg-deficient mice had a much lower parasitemia and recovered from the infection. In mice infected with the lethal strain P. berghei, the parasitemia showed a biphasic response. In control mice, the first phase resulted in the death of 40% of the animals. After a spontaneous reduction of parasitemia, the surviving animals showed a second increase in parasitemia, which resulted in the death of the remaining animals. In the deficient group, all the animals survived the first phase of infection. By contrast, the evolution of the second phase was similar to that observed in controls. Examination of blood smears showed that the second phase corresponded to an invasion of young reticulocytes by the parasite. The results suggest that the protective effect of Mg deficiency is related to the decrease in erythrocyte Mg and to the prooxidative effect of this mineral deficiency in mature erythrocytes.

Erythrocytes from magnesium-deficient hamsters display an enhanced susceptibility to oxidative stress

Previous studies in our laboratory have indicated a role for free radical participation in magnesium deficiency cardiomyopathy. We have demonstrated the ability of various antioxidant drugs and nutrients to protect against magnesium deficiency-induced myocardial injury. In this study, we have examined erythrocytes from normal and magnesium-deficient animals and compared their susceptibility to an in vitro oxidative stress. Syrian male hamsters were placed on either magnesium-deficient or magnesium-supplemented diets. Animals from each group also received vitamin E in doses of 10 and 25 mg as subcutaneous implants. Erythrocytes obtained after 14 days on the diet were exposed to an exogenous hydroxyl (.OH) radical generating system (dihydroxyfumarate not equal to Fe3+ ADP) at 37 degrees C for 20 min. Erythrocyte crenation was observed and quantified by scanning electron microscopy. Lipid peroxidation, hemolysis (%), and intracellular glutathione levels were determined. In addition, serum lipid changes and membrane phospholipids were characterized. Our data demonstrate that erythrocytes from magnesium-deficient animals are more susceptible to free radical injury, supporting our hypothesis that magnesium deficiency reduces the threshold antioxidant capacity.