Changes of linoleic acid metabolism and cellular phospholipid fatty acid composition in LLC-PK cells cultured at low magnesium concentrations

An investigation of association between human milk mineral patterns and infant growth

Introduction

Human milk is widely acknowledged as the optimal food for infant aged 0 ~ 6 months. While there has been extensive documentation on the mineral and trace element composition of human milk, results on the relationship between mineral content and infant growth remain mixed. This cross-sectional study aims to explore human milk mineral patterns and to investigate associations between human milk mineral patterns, human milk metabolomic profile and infant growth.

Methods

A total of 200 breast milk samples from seven cities in China was included. Human milk mineral and trace elements was detected by inductively coupled plasma mass spectrometer (ICP-MS). K-means cluster analysis was utilized to derived human milk mineral patterns. Untargeted human milk metabolomic profiles was determined using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Differences of infant growth rate and metabolomic profiles were then compared across patterns identified.

Results

Three human milk mineral patterns were identified. Cluster I was characterized as the highest levels of potassium, magnesium and calcium, while the lowest levels of copper, zinc, manganese and selenium. Cluster II showed the most abundant sodium, iron, zinc, manganese and selenium. Cluster III had the lowest levels of sodium, potassium, magnesium, iron and calcium. Infants of cluster I showed significantly higher length-for-age z score (0.60 ± 2.03, p = 0.03). Compared with other clusters, samples of cluster I showed lower expression of metabolites of arachidonic acid (ARA) and nicotinate and nicotinamide metabolism pathway.

Discussion

A human milk mineral pattern was identified which is related to increased infant growth rate and altered metabolic signature. Future work is needed to understand these human milk patterns in terms of biologic mechanisms and generalization to other populations.

Molecular biochemical aspects of salt (sodium chloride) in inflammation and immune response with reference to hypertension and type 2 diabetes mellitus

Obesity, insulin resistance, type 2 diabetes mellitus (T2DM) and hypertension (HTN) are common that are associated with low-grade systemic inflammation. Diet, genetic factors, inflammation, and immunocytes and their cytokines play a role in their pathobiology. But the exact role of sodium, potassium, magnesium and other minerals, trace elements and vitamins in the pathogenesis of HTN and T2DM is not known. Recent studies showed that sodium and potassium can modulate oxidative stress, inflammation, alter the autonomic nervous system and induce dysfunction of the innate and adaptive immune responses in addition to their action on renin-angiotensin-aldosterone system. These actions of sodium, potassium and magnesium and other minerals, trace elements and vitamins are likely to be secondary to their action on pro-inflammatory cytokines IL-6, TNF-α and IL-17 and metabolism of essential fatty acids that may account for their involvement in the pathobiology of insulin resistance, T2DM, HTN and autoimmune diseases.

Magnesium protects against cisplatin-induced acute kidney injury without compromising cisplatin-mediated killing of an ovarian tumor xenograft in mice

Cisplatin, a commonly used chemotherapeutic for ovarian and other cancers, leads to hypomagnesemia in most patients and causes acute kidney injury (AKI) in 25-30% of patients. Previously, we showed that magnesium deficiency worsens cisplatin-induced AKI and magnesium replacement during cisplatin treatment protects against cisplatin-mediated AKI in non-tumor-bearing mice (Solanki MH, Chatterjee PK, Gupta M, Xue X, Plagov A, Metz MH, Mintz R, Singhal PC, Metz CN. Am J Physiol Renal Physiol 307: F369-F384, 2014). This study investigates the role of magnesium in cisplatin-induced AKI using a human ovarian tumor (A2780) xenograft model in mice and the effect of magnesium status on tumor growth and the chemotherapeutic efficacy of cisplatin in vivo. Tumor progression was unaffected by magnesium status in saline-treated mice. Cisplatin treatment reduced tumor growth in all mice, irrespective of magnesium status. In fact, cisplatin-treated magnesium-supplemented mice had reduced tumor growth after 3 wk compared with cisplatin-treated controls. While magnesium status did not interfere with tumor killing by cisplatin, it significantly affected renal function following cisplatin. Cisplatin-induced AKI was enhanced by magnesium deficiency, as evidenced by increased blood urea nitrogen, creatinine, and other markers of renal damage. This was accompanied by reduced renal mRNA expression of the cisplatin efflux transporter Abcc6. These effects were significantly reversed by magnesium replacement. On the contrary, magnesium status did not affect the mRNA expression of cisplatin uptake or efflux transporters by the tumors in vivo. Finally, magnesium deficiency enhanced platinum accumulation in the kidneys and renal epithelial cells, but not in the A2780 tumor cells. These findings demonstrate the renoprotective role of magnesium during cisplatin AKI, without compromising the chemotherapeutic efficacy of cisplatin in an ovarian tumor-bearing mouse model.

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.

Mercury exposure, nutritional deficiencies and metabolic disruptions may affect learning in children

Among dietary factors, learning and behavior are influenced not only by nutrients, but also by exposure to toxic food contaminants such as mercury that can disrupt metabolic processes and alter neuronal plasticity. Neurons lacking in plasticity are a factor in neurodevelopmental disorders such as autism and mental retardation. Essential nutrients help maintain normal neuronal plasticity. Nutritional deficiencies, including deficiencies in the long chain polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid, the amino acid methionine, and the trace minerals zinc and selenium, have been shown to influence neuronal function and produce defects in neuronal plasticity, as well as impact behavior in children with attention deficit hyperactivity disorder. Nutritional deficiencies and mercury exposure have been shown to alter neuronal function and increase oxidative stress among children with autism. These dietary factors may be directly related to the development of behavior disorders and learning disabilities. Mercury, either individually or in concert with other factors, may be harmful if ingested in above average amounts or by sensitive individuals. High fructose corn syrup has been shown to contain trace amounts of mercury as a result of some manufacturing processes, and its consumption can also lead to zinc loss. Consumption of certain artificial food color additives has also been shown to lead to zinc deficiency. Dietary zinc is essential for maintaining the metabolic processes required for mercury elimination. Since high fructose corn syrup and artificial food color additives are common ingredients in many foodstuffs, their consumption should be considered in those individuals with nutritional deficits such as zinc deficiency or who are allergic or sensitive to the effects of mercury or unable to effectively metabolize and eliminate it from the body.

Comparison of mechanism and functional effects of magnesium and statin pharmaceuticals

Since Mg(2+)-ATP is the controlling factor for the rate-limiting enzyme in the cholesterol biosynthesis sequence that is targeted by the statin pharmaceutical drugs, comparison of the effects of Mg(2+) on lipoproteins with those of the statin drugs is warranted. Formation of cholesterol in blood, as well as of cholesterol required in hormone synthesis, and membrane maintenance, is achieved in a series of enzymatic reactions that convert HMG-CoA to cholesterol. The rate-limiting reaction of this pathway is the enzymatic conversion of HMG CoA to mevalonate via HMG CoA. The statins and Mg inhibit that enzyme. Large trials have consistently shown that statins, taken by subjects with high LDL-cholesterol (LDL-C) values, lower its blood levels 35 to 65%. They also reduce the incidence of heart attacks, angina and other nonfatal cardiac events, as well as cardiac, stroke, and total mortality. These effects of statins derive less from their lowering of LDL-C than from their reduction of mevalonate formation which improves endothelial function, inhibits proliferation and migration of vascular smooth muscle cells and macrophages, promotes plaque stabilization and regression, and reduces inflammation, Mg has effects that parallel those of statins. For example, the enzyme that deactivates HMG-CoA Reductase requires Mg, making Mg a Reductase controller rather than inhibitor. Mg is also necessary for the activity of lecithin cholesterol acyl transferase (LCAT), which lowers LDL-C and triglyceride levels and raises HDL-C levels. Desaturase is another Mg-dependent enzyme involved in lipid metabolism which statins do not directly affect. Desaturase catalyzes the first step in conversion of essential fatty acids (omega-3 linoleic acid and omega-6 linolenic acid) into prostaglandins, important in cardiovascular and overall health. Mg at optimal cellular concentration is well accepted as a natural calcium channel blocker. More recent work shows that Mg also acts as a statin.

Erythrocyte plasma membrane perturbations in rats fed a cholesterol-rich diet: effect of drinking sulphurous mineral water

AIMS

The purpose of the present study was to evaluate the ability of calcic and magnesic-sulphate-sulphurous spring mineral water (SMW) to reduce total and erythrocyte plasma membrane cholesterol in rats fed a cholesterol-rich diet.

METHODS

By using different fluorescent probes, 1,6-diphenyl-1,3,5-hexatriene (DPH), 1-[4-(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH) and Laurdan, a possible correlation was evaluated between cholesterol content changes of the membranes and membrane fluidity.

RESULTS

The results clearly show that hydropinic treatment reduced cholesterol level. No significant change was observed in DPH and TMA-DPH anisotropy values. By using Laurdan, an increase was observed in generalized polarization (GP(340)) in both groups of rats (the one that drank tap water and the one that drank SMW) compared with the controls. The rate of haemolysis was reduced in those erythrocyte suspensions in which cholesterol was increased, even if the enzymatic activity of glutathione peroxidase and catalase decreased.

CONCLUSION

Hydropinic treatment with SMW is of interest from the biomedical point of view, because it could represent an alternative approach in interventions aimed at ameliorating biological injury deriving from hypercholesterolaemia.

Atorvastatin reduces the plasma lipids and oxidative stress but did not reverse the inhibition of prostacyclin generation by aortas in streptozotocin diabetic rats

The effect of atorvastatin (Lipitor) on diabetes-induced changes in plasma lipids, oxidative stress and the ability of aortic tissues to generate prostacyclin was studied in streptozotocin diabetic rats. In diabetic rats, plasma total cholesterol, triglycerides and serum glucose significantly increased compared to nondiabetic rats. Atorvastatin administration to diabetic rats did not affect hyperglycemia but significantly reduced plasma total cholesterol and triglycerides compared to diabetic rats. The oxidative stress markers urinary isoprostane, liver thiobarbituric acid reactive substances (TBARS) and plasma protein carbonyl content significantly increased in diabetic rats compared to nondiabetic rats. Atorvastatin admnistration to diabetic rats significantly reduced oxidative stress levels compared to diabetic rats, but urinary isoprostane and liver TBARS remained significantly higher than nondiabetic rats. Prostacyclin (PGI(2)) generation by aortic tissues significantly decreased in diabetic rats compared to nondiabetic rats. Atorvastatin administration to diabetic rats did not reverse that inhibition. These results were discussed in the light of the possible effects of hyperglycemia and statins on NAD(P)H-oxidase and cyclooxygenase-2 activities and the genetic difference between rats and other mammals regarding the level of vascular superoxide dismutase (SOD) activity.

Vitamin C or Vitamin B6 supplementation prevent the oxidative stress and decrease of prostacyclin generation in homocysteinemic rats

We hypothesize that homocysteinemia causes oxidative stress, decreases the aortic ability to generate prostacyclin and that antioxidants have a protective role. Four groups of eight rats each were fed for 8 weeks the control diet (group A), control diet with folic acid omitted and excess methionine (Me) added to drinking water (group B), diet B + 500 mg/kg of Vitamin C (group C) or diet B + 60 mg/kg Vitamin B6 (group D). The three groups of rats fed folic acid deficient (FD) diets (groups B, C and D) were homocysteinemic as indicated by the significant increase in their serum homocysteine (HC) concentration. Rats fed diet B had oxidative stress as indicated by an increase in serum thiobarbituric acid reactive substances (TBARS) and advanced oxidation protein products (AOPP) and urinary isoprostanes and had a decreased ability of their aortas to generate prostacyclin. Homocysteinemic rats fed a FD diet + Vitamin C (group C) or Vitamin B6 (group D) also had high levels of serum homocysteine but the oxidative stress markers and the ability of their aortas to generate prostacyclin returned to normal. This indicates that the homocysteinemic effect is through an oxidative mechanism and that Vitamin C as a free radical scavenger prevents these effects. Serum Vitamin C and liver glutathione concentrations significantly increased in rats fed excess Vitamin B6 compared to the control or FD rats. This may explain why Vitamin B6 has an antioxidative effect.

Magnesium chloride slows gastric emptying, but does not affect digestive functions

BACKGROUND

An inverse relationship has been established between serum magnesium and serum lipid levels. By means of breath tests, we tested the hypothesis that magnesium inhibits intraluminal lipid digestion and subsequently causes changes in lipid metabolism. We also investigated the influence of the administration of magnesium chloride on protein digestion and gastric emptying.

METHODS

Five healthy volunteers performed simultaneous breath tests for gastric emptying and intraluminal lipid digestion, and six others for gastric emptying and protein digestion. Each test was performed in basal conditions and after the intake of 800 mg of magnesium chloride dissolved in water. Breath samples were taken at regular time intervals and analysed for 13CO2 and 14CO2 enrichment in order to calculate gastric emptying and lipid and protein digestion rates.

RESULTS

The oral administration of a single dose of magnesium chloride resulted in a diminished rate of intraluminal lipid and protein digestion. The most pronounced effect of magnesium chloride, however, was a decreased gastric emptying rate of both test meals. After correction for gastric emptying, no differences were noted in intraluminal lipid or protein digestion. Therefore, the lower lipid levels noted after magnesium supplementation are unlikely to be the result of altered lipid assimilation.

CONCLUSION

Magnesium chloride slows gastric emptying but does not influence lipid digestion.

The central role of magnesium deficiency in Tourette's syndrome: causal relationships between magnesium deficiency, altered biochemical pathways and symptoms relating to Tourette's syndrome and several reported comorbid conditions

Prior studies have suggested a common etiology involved in Tourette's syndrome and several comorbid conditions and symptomatology. Reportedly, current medications used in Tourette's syndrome have intolerable side-effects or are ineffective for many patients. After thoroughly researching the literature, I hypothesize that magnesium deficiency may be the central precipitating event and common pathway for the subsequent biochemical effects on substance P, kynurenine, NMDA receptors, and vitamin B6 that may result in the symptomatology of Tourette's syndrome and several reported comorbid conditions. These comorbid conditions and symptomatology include allergy, asthma, autism, attention deficit hyperactivity disorder, obsessive compulsive disorder, coprolalia, copropraxia, anxiety, depression, restless leg syndrome, migraine, self-injurious behavior, autoimmunity, rage, bruxism, seizure, heart arrhythmia, heightened sensitivity to sensory stimuli, and an exaggerated startle response. Common possible environmental and genetic factors are discussed, as well as biochemical mechanisms. Clinical studies to determine the medical efficacy for a comprehensive magnesium treatment option for Tourette's syndrome need to be conducted to make this relatively safe, low side-effect treatment option available to doctors and their patients.

Oxidized low density lipoprotein inhibits prostacyclin generation by rat aorta in vitro: a key role of lysolecithin

The objective of this study was to examine the effect of oxLDL on prostacyclin (PGI2) generation by rat aortic segments and to see whether the lipid fraction of oxLDL or its components are responsible for that effect. We also tested if antioxidants have any protective role. LDL oxidized by copper was characterized by higher TBARS, conjugated diene, lysophosphatidylcholine (lyso PC), oxysterols and less polyunsaturated fatty acids (PUFA) than nLDL. Preincubation of aortas with oxLDL caused a significant inhibition of PGI2 generation compared to aortas preincubated with nLDL or buffer only. The percent inhibition was dependent on the concentration of oxLDL. Most of the inhibitory effect of oxLDL resided in its lipid moiety while the lipid fraction of nLDL, as well as native LDL had no effect. Preincubation of aortas with 10 microg/ml of 7-ketocholesterol the major oxysterol in oxLDL reduced the amount of PGI2 generated by aorta at all times tested; however that decrease did not reach a significant level. Aortas preincubated with 10 microg/ml of lyso PC showed a 21-36% inhibition of PGI2 generation which was comparable to the inhibition produced by preincubating the aortas with 50 microg protein/ml of oxLDL (containing about 7.5 microg lyso PC). This indicated that most of the inhibitory effect of oxLDL was due to its lyso PC. The small molecular weight fraction (< 10 kDa) with a high level of TBARS (TBARS solution) also significantly decreased the PGI2 generation by aorta. Addition of superoxide dismutase (SOD) + catalase or vitamin E simultaneously with oxLDL or TBARS solution in the preincubation medium did not reverse their inhibitory effects. This indicated that oxygen free radicals are not a contributing factor to the inhibitory effect of oxLDL but lyso PC and the lipid peroxides and probably other components already present within oxLDL are the important inhibitors.

The relationship of oxidized lipids to coronary artery stenosis

A total of 1200 patients with angina were cardiac catheterized establishing that 63% had 70-100% stenosis, 12% had 10-69% stenosis of one or more of their coronary arteries and 25% had microvascular angina listed as 0% stenosis. Prior to catheterization 10 ml of blood was drawn and the plasma subjected to analysis for the concentration of cholesterol, lipid peroxides (LPX), total antioxidant capacity (TAOC), fibrinogen (FB), ceruloplasmin (CP) and activation of polymorphonuclear leukocytes (PMNLs). Comparisons were made to non-smoking controls without angina. Significant differences in LPX were found between the patients with 0 and 10-69% stenosis (P<0.001), with 10-69 and 70-100% stenosis (P<0.001), and with 0 and 70-100% stenosis (P<0.001). Under 70 years of age there was a significant difference in LPX between patients with all levels of stenosis and age and sex matched controls (P<0.001). Differences in the mean plasma cholesterol concentration for different levels in the degree of stenosis were not significant, indicating that LPX provided consistent data on the severity of stenosis while the plasma cholesterol concentration did not. Compared with controls an increase in activation of PMNLs (P<0.01), an increase in concentration of both FB and CP (P<0.01) and a decrease in total antioxidant capacity were noted in the plasma of catheterized patients. In summary the concentration of oxidation products rather than the concentration of cholesterol in the plasma identified stenosis in cardiac catheterized patients.

Modification of polycystic kidney disease and fatty acid status by soy protein diet

Modification of polycystic kidney disease and fatty acid status by soy protein diet.

BACKGROUND

Previous studies have demonstrated that soy protein can slow progression of renal injury in the Han:SPRD-cy rat. We undertook a study to establish whether this benefit was independent of any nutritional deprivation, and whether or not it was associated with changes in polyunsaturated fatty acid status that have been previously linked to the anti-inflammatory or antineoplastic potential of soy diets.

METHODS

Male Han:SPRD-cy rats were pair fed a 20% casein or 20% soy protein diet for six weeks from weaning. Tissue was harvested for analysis of cystic change, cell proliferation, macrophage infiltration, and fibrosis. Renal and hepatic tissues were also harvested for lipid analysis using gas chromatography.

RESULTS

Animals thrived on both diets. Soy protein feeding was associated with reduced cystic change (4.3 vs. 7.0 mL/kg, P < 0.0001), epithelial cell proliferation (15.7 vs. 21.0 cells/mm epithelium, P < 0.0001), macrophage infiltration (25.3 vs. 43.5 cells/high-power field, P < 0.0001), and fibrosis (0.6 vs. 1.07 mL/kg, P < 0.0001). The soy diet prevented a significant elevation in serum creatinine in diseased versus normal animals. Soy feeding was associated with higher renal and hepatic linoleic acid content and higher hepatic alpha-linolenic acid, but lower hepatic arachidonic acid content.

CONCLUSIONS

Isocaloric soy protein feeding ameliorates both epithelial and interstitial changes in the Han:SPRD-cy rat independent of a hypocholesterolemic effect. The histologic benefit is associated with changes in polyunsaturated fatty acid metabolism that may influence both inflammatory and proliferative pathways.

Effect of trans fatty acids on calcium influx into human arterial endothelial cells

BACKGROUND

A recent task force of The American Society for Clinical Nutrition and American Society for Nutritional Sciences recommended in a position paper on trans fatty acids that models be developed to assess the effects of changes in fat intake on disease risk.

OBJECTIVE

The objective was to investigate, using human arterial endothelial cells as a model, the influence of trans fatty acids and magnesium on cell membrane composition and on calcium influx into arterial cells, a hallmark of atherosclerosis.

DESIGN

Endothelial cells were cultured for 3 d in media with high (adequate) or low (inadequate) amounts of magnesium plus various concentrations of trans,trans linoelaidic; cis,cis linoleic; trans elaidic; oleic; or stearic acids. The cells were then harvested and the fatty acid composition and the amount of (45)Ca(2+) incorporated into the cell was determined.

RESULTS

The percentage of fatty acids incorporated into the endothelial cells was proportional to the amount added to the culture medium. Adequate magnesium was crucial in preventing calcium influx into endothelial cells. Without an adequate amount of magnesium in the culture medium, linoelaidic and elaidic acids, even at low concentrations, increased the incorporation of (45)Ca(2+) into the cells, whereas stearic acid and oleic acid did not (P < 0.05).

CONCLUSION

Our model indicated that a diet inadequate in magnesium combined with trans fat may increase the risk of calcification of endothelial cells.

Hydrogenated fat high in trans monoenes with an adequate level of linoleic acid has no effect on prostaglandin synthesis in rats

Our study was designed to determine whether hydrogenated fat high in trans monoenes concentration affected prostaglandin synthesis. Corn oil (CO), butter (B), hydrogenated vegetable oil (HF) and coating fat (CF) were used in this study. These fats were fed to rats for 10 wk at 10 g/100 g diet. The phospholipid (PL) fatty acid content of platelets, aorta and heart was determined by gas liquid chromatography, and the in vitro aorta production of prostacyclin (PGI2) from exogenous or endogenous arachidonic acid (AA) was measured using the radioimmuno-assay (RIA) method. Serum thromboxane B2 (TXB2) released by platelets as thromboxane A2 (TXA2) during incubation of whole blood was also measured by this method. In the group fed CF, AA was significantly lower in the PL of aorta, platelet and heart, and the ratio 20:3(n-9)/20:4(n-6) was greater than in the groups fed CO, B or HF, indicating that the group fed CF was essential fatty acid (EFA) deficient. Although AA was significantly lower in the aorta and platelet PL of the group fed HF compared to the group fed CO, that difference did not affect the amounts of PGI2 or TXB2 produced in these groups. The group fed CF had significantly less PGI2 and TXB2 released by aorta and platelets than the other groups. This was the result of the reduced level of AA and the presence of higher amounts of 20:3(n-9) acid in the PL, which might act as a competitive inhibitor for cyclooxygenase. The aortic production of PGI2 from exogenous AA did not differ among the groups indicating that prostaglandin synthetase was not affected by the dietary fat. We conclude that the consumption of hydrogenated fats high in trans 18:1 acids with adequate amount of linoleic acid had no effect on the amount of thromboxane or prostacyclin produced by platelet or aorta in vitro.

Changes in linoleic acid metabolism and membrane fatty acids of LLC-PK cells in culture induced by 5 alpha-cholestane-3 beta,5,6 beta-triol

The aim of this study was to investigate the effect of the oxysterol 5 alpha-cholestane-3 beta,5,6 beta-triol (triol) on the metabolism of linoleic acid (18:2n-6) to arachidonic acid (20:4n-6) and on the cell membrane fatty acid composition. Porcine kidney cells were incubated in medium with or without 10 microgram(s)/mL of triol for 24 h, then incubated for 1, 6, or 12 h in a medium which contained 50 muM of either [14C] linoleic acid or unlabeled linoleic acid. The cellular uptake of [14C] linoleic acid was significantly higher in the triol-treated cells than in control cells. After 1- and 6-h incubations despite the increase of [14C] linoleic acid pool size in the triol-treated cells, neither total n-6 polyunsaturated fatty acids (PUFA) metabolites nor arachidonic acid were increased in the triol-treated cells as compared to the control cells, but trienoic acids accumulated to a greater extent in the triol-treated cells. Therefore, the ratios of n-6 PUFA metabolites vs. pool size of linoleic acid and of tetraenoic acids vs. dienoic acids were significantly decreased in triol-treated cells as compared to the control cells. The cellular fatty acid composition also showed that linoleic acid percentage was significantly increased while arachidonic acid percentage was significantly decreased in the triol-treated cells, and that the accumulation of trienoic acids (18:3n-6 + 20:3n-6) observed from the [14C] linoleic acid experiment was due solely to increased 20:3n-6 content. This latter finding indicates that a decrease of elongase activity by triol is unlikely. Our results also showed that the triol-treated cells had a lower level of free cholesterol but higher levels of phospholipid and triol in their membranes, suggesting that triol displaced free cholesterol from the cell membrane.

Magnesium deficiency and alcohol intake: mechanisms, clinical significance and possible relation to cancer development (a review)

A comprehensive and critical review of the evidence relating magnesium (Mg) deficiency to alcohol consumption reveals several important types of interactions. First, alcohol acts acutely as a Mg diuretic, causing a prompt, vigorous increase in the urinary excretion of this metal along with that of certain other electrolytes. Second, with chronic intake of alcohol and development of alcoholism, the body stores of Mg become depleted. During the late stages of alcoholism, the urinary excretion of Mg may become diminished as a physiological response to reduced intake and reduction of body stores. A number of aspects of the clinical syndrome of alcoholism contribute to and intensify that already existing reduction in body Mg stores. Third, a number of manifestations of alcoholism are believed due to effects of Mg deficiency, and some therapeutic benefit has been suggested from treatment of alcoholic patients with Mg. Finally, relatively little attention has been paid to the possible value of Mg administration as a preventive measure to forestall or minimize the deleterious effects of chronic use of alcohol or to prevent the development of cancer than can occur in this setting.

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.

The biosynthesis of polyunsaturated fatty acids by rat sertoli cells

1. The biosynthesis of polyunsaturated fatty acids (PUFA) of the n-6 and n-3 series was investigated in cultured Sertoli cells. 18:2n-6, 18:3n-6, 20:2n-6, 18:3n-3 and 20:3n-3 were added individually at a concentration of 20 mumol to culture media. 2. Maximum incorporation of 20- and 22-carbon PUFA into membrane lipids was observed after 72 hr of incubation with all the exogenous substrates used. 3. As reported in other cell systems, the delta 6 desaturation was the first rate-limiting step; the major factor regulating this activity was the concentration of linoleic acid or alpha-linolenic acid in the medium. 4. Our data show that the delta 5-desaturation represents a second regulatory step in PUFA biosynthesis. 5. The sum of n-6 and n-3 PUFA of the 22 carbon chain length constantly represented between 11 and 12% of total fatty acids, regardless of the exogenous substrate used. 6. Our kinetic studies of the incorporation of PUFA of the n-6 and n-3 series did not permit detection of a delta 8 desaturase activity.

Cardiolipins and biomembrane function

Evidence is discussed for roles of cardiolipins in oxidative phosphorylation mechanisms that regulate State 4 respiration by returning ejected protons across and over bacterial and mitochondrial membrane phospholipids, and that regulate State 3 respiration through the relative contributions of proteins that transport protons, electrons and/or metabolites. The barrier properties of phospholipid bilayers support and regulate the slow proton leak that is the basis for State 4 respiration. Proton permeability is in the range 10(-3)-10(-4) cm s-1 in mitochondria and in protein-free membranes formed from extracted mitochondrial phospholipids or from stable synthetic phosphatidylcholines or phosphatidylethanolamines. The roles of cardiolipins in proton conductance in model phospholipid membrane systems need to be assessed in view of new findings by Hübner et al. [313]: saturated cardiolipins form bilayers whilst natural highly unsaturated cardiolipins form nonlamellar phases. Mitochondrial cardiolipins apparently participate in bilayers formed by phosphatidylcholines and phosphatidylethanolamines. It is not yet clear if cardiolipins themselves conduct protons back across the membrane according to their degree of fatty acyl saturation, and/or modulate proton conductance by phosphatidylcholines and phosphatidylethanolamines. Mitochondrial cardiolipins, especially those with high 18:2 acyl contents, strongly bind many carrier and enzyme proteins that are involved in oxidative phosphorylation, some of which contribute to regulation of State 3 respiration. The role of cardiolipins in biomembrane protein function has been examined by measuring retained phospholipids and phospholipid binding in purified proteins, and by reconstituting delipidated proteins. The reconstitution criterion for the significance of cardiolipin-protein interactions has been catalytical activity; proton-pumping and multiprotein interactions have yet to be correlated. Some proteins, e.g., cytochrome c oxidase are catalytically active when dimyristoylphosphatidylcholine replaces retained cardiolipins. Cardiolipin-protein interactions orient membrane proteins, matrix proteins, and on the outerface receptors, enzymes, and some leader peptides for import; activate enzymes or keep them inactive unless the inner membrane is disrupted; and modulate formation of nonbilayer HII-phases. The capacity of the proton-exchanging uncoupling protein to accelerate thermogenic respiration in brown adipose tissue mitochondria of cold-adapted animals is not apparently affected by the increased cardiolipin unsaturation; this protein seems to take over the protonophoric role of cardiolipins in other mitochondria. Many in vivo influences that affect proton leakage and carrier rates selectively alter cardiolipins in amount per mitochondrial phospholipids, in fatty acyl composition and perhaps in sidedness; other mitochondrial membrane phospholipids respond less or not at all.(ABSTRACT TRUNCATED AT 400 WORDS)

Does dietary magnesium modulate blood lipids?

In a randomized, single-blind, controlled study (400 patients aged 25-63 yr; 374 males, 26 females), 206 subjects were administered a magnesium-rich diet, and 194 subjects their usual diet, for 6 wk. Age, sex, body weight, hypertension, hyperlipidemia, smoking, obesity, diuretic therapy, and diabetes were comparable between the two groups, as were laboratory data at entry to the study. Intervention-group A received a significantly higher amount of dietary magnesium and potassium compared to group B, which received its usual diet. After 6 wk, there was a significant fall in total serum cholesterol (228.5 +/- 46.2 mg/dL), LDL cholesterol 146.5 +/- 75.5 mg/dL), and triglyceride (143.8 +/- 40.5 mg/dL) in group A compared to serum cholesterol (242.5 +/- 58.2 mg/dL), LDL cholesterol (157.0 +/- 78.4 mg/dL), and triglyceride (156.5 +/- 60.0 mg/dL) at entry to study, but no such changes in group-B subjects. HDL cholesterol showed a marginal mean decrease of 0.8 mg/dL in group B and a 2.5 mg/dL increase in group A. The changes in blood lipids were consistent with an increased intake of magnesium and with a rise in serum levels. Although a general blood-lipid-reducing effect of such a diet cannot be excluded, it is possible that dietary magnesium may have contributed to the reduction of total serum cholesterol, LDL cholesterol, and triglyceride, and the marginal rise in HDL cholesterol. More studies with longer follow-up periods are needed to confirm this observation.

Influence of 26-hydroxycholesterol on the composition and function of gel-filtered platelets

The influence of 26-hydroxycholesterol (26-OH-CHOL) on the structure and function of gel-filtered rat platelets, as a model membrane, was studied in vitro. Its influence on structure was determined by a fatty acid and a phospholipid analysis of the platelet lipids and on function by the cytoplasmic calcium concentration of the platelets exposed to increasing concentrations of 26-OH-CHOL for various periods of time. The intracellular free calcium (Ca2+)i of the gel-filtered rat platelets was monitored by a fluorescent probe (quin 2) after incubation in a 37 degrees C water bath with 1 mM Ca2+ and 20 microM quin 2/AM. The presence of 26-OH-CHOL in the incubation media changed both the phospholipid composition and the mixed fatty acid composition in the membrane and increased the intracellular free Ca2+ level of the platelets. As the incubation of platelets with cholesterol (CHOL) or esterified 26-OH-CHOL did not increase intracellular Ca2+ levels, these results indicate that the hydrophilic free 26-hydroxy group in 26-OH-CHOL may have influenced the enzymes catalyzing the synthesis of the phospholipid in the platelet membrane so as to allow it to become more and more "leaky" to Ca2+. Such a fundamental change in membrane structure and function may be responsible for the development of atherosclerosis in the intimal layer of the coronary arteries.

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

Previous studies have provided evidence that Mg deficiency affects lipid metabolism. The present experiments were designed to assess whether the hypertriglyceridemia associated with Mg deficiency was related to alterations in post-heparin lipase activity (PHLA). Mg-deficient and control diets were pair-fed to weanling Wistar rats for eight days and plasma lipoproteins were separated into various density classes by sequential preparative ultracentrifugation. Triglycerides were significantly increased in chylomicrons and in the very low density lipoprotein, low density lipoprotein and high density lipoprotein (HDL) fractions. Cholesterol and phospholipid levels were significantly lower in the HDL fraction. PHLA in deficient rat was substantially lower than in control rats. The inverse correlation between plasma triglyceride concentration and PHLA strongly suggests that hypertriglyceridemia is the result of defective lipolysis of plasma triglycerides in Mg-deficient rats. Further examination of the PHLA was carried out by salt-mediated inhibition of lipoprotein lipase (LPL) and by heparin sepharose affinity chromatography and purified rat LPL antiserum. The results indicate that hepatic lipase is significantly decreased in Mg-deficient rats but the low PHLA is due mainly to a decline in LPL. However, total LPL activity, that is, both the intracellular and the extracellular pools of LPL in adipose tissue, heart and diaphragm, were unaffected by Mg deficiency. The results suggest that the decrease of LPL activity in the plasma of Mg-deficient rats may be due to a selective decrease in the heparin-releasable pool of enzyme.

Effects of a dietary magnesium deficiency and excess vitamin D3 on swine coronary arteries

The effect of a moderate magnesium (Mg) deficiency on coronary arteries of 61 swine, fed various levels of vitamin D3, was studied by light and electron microscopy. The effect of subnormal Mg intake on vitamin D3-induced intimal lesions of the arteries showed a trend towards increased damage. The degree of cell degeneration and intimal thickening, which was induced by high vitamin D intakes, was as great in swine whose diet was low in Mg and moderately high in vitamin D as it was in those on twice as much vitamin D. Also, the degree of arterial calcification was intensified by inadequate Mg intake at the two higher vitamin D intakes. Present findings indicate that suboptimal dietary Mg, in combination with an excess of vitamin D, has an additive effect in the initiation of ultrastructural changes in the coronary arteries. Extension of the study is indicated to ascertain the extent to which further reduction of Mg intake can potentiate vitamin-D-induced coronary lesions.

Changes in phospholipid composition and calcium flux in LLC-PK cells cultured at low magnesium concentrations

Monolayers of porcine kidney cells (LLC-PK) were grown in a series of Nu-Serum-supplemented media containing different Mg(2+) concentrations (480, 250, 25, 6.3 or 2.6 microM) to study the effect of Mg(2+) depletion on cellular phospholipid changes and the consequent effect on the membrane permeability to Ca(2+). Cells grown on 6.3 or 2.6 microM Mg(2+) showed a decrease in PE, PS, Sph, PI and an increase of PC. These changes were attributed mainly to the decreased rate of Sph synthesis through the transfer of phosphocholine from PC to ceramide, or due to the increase of PE N-methylation as found in Mg(2+)-deficient cells. The (45)Ca uptake was increased in cells grown on 25.0 microM Mg(2+), while it was decreased in cells grown on 6.3 or 2.6 microM Mg(2+). These changes in Ca(2+) uptake were related to changes of cellular phospholipids and fatty acids which affect adenylate cyclase activity in the membrane, as well as the membrane fluidity.