The effect of magnesium and fluoride on nephrocalcinosis and aortic calcification in rats given high sucrose diets with added phospnates

Relationship between Serum Magnesium, Parathyroid Hormone, and Vascular Calcification in Patients on Dialysis: A Literature Review

Secondary hyperparathyroidism is present in most patients with end-stage renal disease and has been linked to uremic bone disease, vascular calcification, and mortality. Current literature suggests an association between hypomagnesemia and cardiovascular disease in the general population. We reviewed all published studies on the relationship between serum magnesium and parathyroid hormone and the relationship between serum Mg and vascular calcification in dialysis patients. Of these, 10 of 12 studies of patients on hemodialysis and 4 of 5 studies of patients on peritoneal dialysis showed a significant inverse relationship between serum Mg and serum intact parathyroid hormone. Hyperparathyroidism develops in peritoneal dialysis patients dialyzed with a solution containing normal calcium (1.25 mmol/L) and low Mg (0.25 mmol/L), even though serum calcium is maintained at a normal level. Four of the hemodialysis studies and one of the peritoneal dialysis studies indicated that there is an inverse relationship between serum Mg and vascular calcification in these patients. Potential benefits have been attributed to magnesium carbonate as a phosphate binder and it may possibly be an effective, less toxic, less expensive phosphate binder. We believe that the role of Mg in secondary hyperparathyroidism and vascular calcification merits further investigation.

Microvasculopathy and soft tissue calcification in mice are governed by fetuin-A, magnesium and pyrophosphate

Calcifications can disrupt organ function in the cardiovascular system and the kidney, and are particularly common in patients with chronic kidney disease (CKD). Fetuin-A deficient mice maintained against the genetic background DBA/2 exhibit particularly severe soft tissue calcifications, while fetuin-A deficient C57BL/6 mice remain healthy. We employed molecular genetic analysis to identify risk factors of calcification in fetuin-A deficient mice. We sought to identify pharmaceutical therapeutic targets that could be influenced by dietary of parenteral supplementation. We studied the progeny of an intercross of fetuin-A deficient DBA/2 and C57BL/6 mice to identify candidate risk genes involved in calcification. We determined that a hypomorphic mutation of the Abcc6 gene, a liver ATP transporter supplying systemic pyrophosphate, and failure to regulate the Trpm6 magnesium transporter in kidney were associated with severity of calcification. Calcification prone fetuin-A deficient mice were alternatively treated with parenteral administration of fetuin-A dietary magnesium supplementation, phosphate restriction, or by or parenteral pyrophosphate. All treatments markedly reduced soft tissue calcification, demonstrated by computed tomography, histology and tissue calcium measurement. We show that pathological ectopic calcification in fetuin-A deficient DBA/2 mice is caused by a compound deficiency of three major extracellular and systemic inhibitors of calcification, namely fetuin-A, magnesium, and pyrophosphate. All three of these are individually known to contribute to stabilize protein-mineral complexes and thus inhibit mineral precipitation from extracellular fluid. We show for the first time a compound triple deficiency that can be treated by simple dietary or parenteral supplementation. This is of special importance in patients with advanced CKD, who commonly exhibit reduced serum fetuin-A, magnesium and pyrophosphate levels.

Relationship between aortic mineral elements and osteodystrophy in mice with chronic kidney disease

In chronic kidney disease (CKD), osteodystrophy and arterial calcification often coexist. However, arterial alterations have not been addressed in CKD unaccompanied by evidence of calcification. We investigated the association of phosphate (P) and calcium (Ca) accumulation in calcification-free aortas with CKD-induced osteodystrophy. Aortic accumulation of magnesium (Mg), an inhibitor of calcification, was also examined. Male mice aged 26 weeks with CKD characterized by hyperparathyroidism and hyperphosphatemia (Nx, n = 8) and age-matched healthy male mice (shams, n = 8) were sampled for blood, and thoracic vertebrae and aortas were harvested. Bone structure and chemicals were analyzed by microcomputed tomography and infrared microspectroscopy, respectively, and aortic accumulation of P, Ca, and Mg was evaluated by plasma-atomic emission spectrometry. Volume fractions of cortical and trabecular bones were smaller in Nx than in sham animals (P < 0.05), attributed to cortical thinning and reduction in trabecular number, respectively. Bone chemicals were not different between the groups. No calcification was found in either group, but P, Ca, and Mg contents were higher in Nx than in shams (P < 0.05). The mass ratio of Ca/P was lower in Nx than in shams (P < 0.05), but that of Mg/Ca and Mg/P was not different between the groups. Aortic P and Ca contents were inversely correlated with the volume fraction of cortical bone (P < 0.05). In conclusion, the relationship of osteodystrophy with aortic P and Ca accumulation suggests the existence of a bone-vascular axis, even in calcification-free arteries in CKD. The preservation of ratios of Mg/Ca and Mg/P despite CKD development might contribute to calcification resistance.

Risk of myocardial infarction in Finnish men in relation to fluoride, magnesium and calcium concentration in drinking water

To study the influence of drinking water composition on the risk of myocardial infarction, the following study was conducted: The cases (C), men 30-64 years of age, had been discharged with a first acute myocardial infarction (AMI) from Kotka Central Hospital. The hospital controls (HC), matched for age and type of community, were selected for each case among surgical patients. Population controls (PC), matched for age and municipality, were drawn for each case from the population register. Subjects submitted a sample of their drinking water and a filled-in questionnaire. After exclusions, a series of 50 C-HC and 50 C-PC pairs was finally constructed. The point estimate of relative risk (RR) for the association between low F (less than or equal to 0.1 ppm) and increased risk of AMI was 3.0 in the C-HC series. In the C-PC comparison, RR was 4.4 RR for low Mg (less than or equal to 1.2 ppm) was 2.0 in the C-HC comparison and 4.7 in the C-PC comparison. The results are consistent with the hypothesis that both a low F and a low Mg intake are conducive to atherosclerosis leading to AMI.

Non-dental tissue effects of fluoride

The anti-caries effects of water fluoridation are well-established. The non-dental tissue effects of fluoride in drinking water, either naturally occurring or as an additive, have been too poorly studied to permit definitive conclusions to be drawn. Claims have been made that fluoride results in an increased occurrence of malignancies, particularly osteogenic sarcoma. Experimental rat data have not resolved this issue, and epidemiologic studies are equally unclear. Initial claims that fluoride offers protection against atherosclerosis remain viable, but here too, much more directed research is needed. Early studies suggested that a water fluoride content greater than 1 ppm resulted in a lower prevalence of osteoporotic fractures. Recent epidemiologic data seriously question this conclusion and raise the possibility that even this relatively low level may increase the prevalence of osteoporotic hip fractures. Other elements, including calcium and magnesium, also vary in amount as water fluoride content varies, and it has proved difficult to distinguish the independent effects of the various nutrients in water from each other. Therapeutic use of fluoride has been largely restricted to studies of its effect on the osteoporotic study, this important issue remains unresolved. This review provides an overview of these issues, focusing on the uncertainties alluded to, and attempting to develop strategies for future research.

Dietary fluoride, unlike bromide or iodide, counteracts phosphorus-induced nephrocalcinosis in female rats

Supplemental dietary F has been shown to counteract P-induced nephrocalcinosis in female rats. In order to obtain information as to the specificity of this F effect, the effect of other halogens, namely Br and I, on P-induced nephrocalcinosis was studied in weanling female rats. Supplemental dietary Br (5.24 mmol/kg of diet) and I (1.43 mmol/kg of diet) did not influence P-induced nephrocalcinosis, whereas F at equimolar dietary concentrations had marked antinephrocalcinogenic activity. The halogens were added to the diets in the form of KBr, KI, and NaF; the diets were balanced for the kations with Cl salts. The addition of KI to the diet to a concentration of 5.24 mmol/kg caused pronounced growth retardation, decreased feed intake, hepatomegaly, and signs of lethargy. It is concluded that the protective effect of dietary F against P-induced nephrocalcinosis does not extend to other halogens.

Dietary fluoride prevents phosphorus-induced nephrocalcinosis in female rats

The effect of dietary fluoride (F) on nephrocalcinosis was studied in young, female rats. Nephrocalcinosis was induced by a diet rich in phosphorus (P). F in the diet effectively counteracted P-induced nephrocalcinosis in a dose-dependent fashion. The feeding of increasing amounts of F caused decreasing calcium (Ca) and F concentrations in kidney. This suggests that the amount of Ca in kidney determines F accumulation in this organ, rather than F intake. Increasing amounts of F in the diet caused increasing rates of urinary and fecal excretion and whole-body retention of F. Dietary F did not influence urinary and fecal excretion and plasma concentrations of Ca, magnesium (Mg), and P. The metabolic basis for the protective effect of F against the development of nephrocalcinosis remains to be established.

Selenium and cardiovascular disease

For humans, ecological and epidemiological results are reported that show a relationship between the serum selenium concentration and cardiovascular disease in populations where low serum selenium concentrations are found, e.g., in Eastern Finland. From clinical studies done in Germany (FRG and GDR), Finland, and Sweden, subnormal serum selenium and partially whole blood selenium concentrations are reported in patients with acute myocardial infarction. For patients with coronary arteriosclerosis, subnormal serum selenium concentrations are reported from the USA and Germany and subnormal whole blood selenium concentrations from Germany. Subnormal serum and subnormal whole blood selenium concentrations of patients with cardiomyopathy are reported from non Keshan disease affected areas in Germany, France, and China. In selenium deficiency, an accumulation of lipid peroxides in the heart may occur, especially under ischemic conditions and if ischemic tissue is reperfused. Lipid peroxides in the heart may damage the cell membrane and may lead to an impaired calcium transport with an uncontrolled calcium accumulation in the cell. This may result in an activation of phospholipids, and, in consequence, to an enhanced formation of arachidonic acid. An increased concentration of lipid peroxides owing to selenium deficiency may shift the prostaglandin synthesis from prostacyclin to thromboxane, causing enhanced blood pressure and platelet aggregability. From animal experiments, it is known that selenium protects against cardiotoxic elements, cardiotoxic xenobiotics, and viral infections that affect the heart. Selenium deficiency may also be a secondary factor in the causation of hypertension and myocardial ischemia.

Effect of sport-drink with and without fluoride and magnesium supplements on rat performance

Young Osborne-Mendel rats were given different diets ad libitum for 6 weeks. Food was either a purified powder with sucrose (15%) or commercial pellets, and drink was either distilled water or a sugar-containing (6%) sport-drink with or without added fluoride (F), magnesium (Mg) or both. Despite differences in the energy density of the diets, daily intakes were the same in terms of metabolisable energy and resulted in equal weight gains for all groups. Interscapular brown fat hypertrophied in response to powdered food, while both sugar-containing food and sport-drink were effective in accumulating white fat. When exposed to cold air at -20 degrees C for 2-4 h, most of the rats were able to maintain normothermia. Only the rats fed pelleted food and given distilled water were less resistant to cold than the others. After exposure to cold, the reserves of muscle glycogen were least in those rats having the poorest performance in the cold. In contrast, the stores of liver glycogen, plasma glucose and adrenal ascorbic acid were associated with pelleted food, rather than with the exposure to cold or type of drink. It is concluded that the presence of purified, simple sugars, either in food or drink, is the most likely explanation of the results obtained. The F and Mg supplements to the sport-drink did not modify the parameters measured.

Determination of fluoride in urinary calculi using a quantitative microdiffusion method

A microdiffusion method for the separation of fluoride from other ions in urinary calculi has been developed, tested and assessed. The procedure involves digestion at 75 degrees C of samples with silicone-impregnated mixtures of nitric and perchloric acids in a specially designed diffusion cell and determination of the diffused fluoride with an ion-sensitive electrode. Several test samples were used to assess the recovery, accuracy and reproducibility of the procedure. Results for 20 stones of Indian origin are presented and discussed.

Metabolism of free fatty acids (FA) and triacylglycerol (TG) in acute and subacute fluoride intoxication of the rat

In rats acute intoxication with 100 mg sodium fluoride/kg body wt. orally has the following metabolic consequences. Oxygen consumption is reduced by about 30-50%. Plasma free FA decrease in fed as well as in starved rats. Hepatic FA synthesis is enhanced, but TG secretion to the blood is not altered. Intravenously injected Intralipid 20% is removed at a normal rate. In subacute intoxication (30 mg sodium fluoride/kg body wt given orally per day over 1 week) oxygen consumption is not affected. TG secretion and removal of Intralipid remain in the normal range whereas hepatic FA synthesis is increased as in acute intoxication. TG concentration in the liver, however, increases by about 30% after 1 week.

Effect of a sport drink mixture with and without addition of fluoride and magnesium on plaque formation, dental caries and general health of rats

A sport drink mixture (pH 3.2) containing 6% sucrose was given to Osborne-Mendel rats for 42 days. In some experimental groups the drink was supplemented with 15 ppm F, 38.5 ppm Mg or both F and Mg. The rats were fed a slightly cariogenic powdered diet containing 15% sucrose. Sport drink mixture increased significantly the accumulation of plaque but, compared with a group that drank distilled water, did not affect caries. Addition of fluoride to the sport drink mixture, alone or with magnesium, significantly reduced caries and tended to decrease plaque; addition of magnesium had no clear effect on plaque or caries. In spite of the fact that the rats had a sport drink mixture as the only drink for 6 wk, there were no untoward effects on growth, in histological studies of the inner organs, or in Ca, Mg, Na and K contents of kidney, heart and aorta.

Caries prevention in rats by fluoride varnish treatment combined with addition of fluoride to dietary sugar

Osborne-Mendel rats were fed a cariogenic diet containing 43% sucrose for 48 days. The control group received no additional treatment. The teeth of the second group received topical treatment with a sodium fluoride varnish which was applied twice onto newly-erupted molars. The third group received topical treatment with the sodium fluoride varnish combined with a NaF + Mg addition to the diet. In both treatment groups, caries was significantly reduced as compared with caries in the control group. Combined treatment was significantly more effective than was the varnish alone. In spite of the high fluoride concentration in the varnish, no changes in the oral mucosa were found at the end of the study.

Arrestment of caries in rats by adding fluoride and magnesium to the diet

90 weanling Osborne-Mendel rats were divided into six groups of 15 animals each. Half of them received a modified MIT 200 control diet in which one third of the sucrose of the original formula was replaced by high-extraction wheat fluor, magnesium content reduced to 360 parts/10(6) and phosphorus content increased NaH2PO4 . 2H2O to 0.49%. For the experimental diet, an additive containing 75 parts/10(6) fluoride as (NaF) and 50 parts/10(6) magnesium (as MgO) was mixed into the above composition. Each diet was given to three experimental or three control groups for 25, 40, or 55 d. Caries involving dentin-enamel junction was significantly reduced through the F+Mg addition by 37%, 51%, and 61% on the 25th, 40th, and 55th day, respectively. Caries involving dentin was significantly reduced by 58%, 68%, and 70%, respectively. Caries arrestment was observable in both the control rats and rats fed the F rMg additive but in the latter animals the reduction meant an arrestment at a lower level than in controls. This arrestment resembles an early caries arrestment obtained recently in a clinical trial by fluoridation of dietary sugar products. The growth of the animals was only temporarily retarded by the additives.

The influence of dietary carbohydrate and fat on kidney calcification and the urinary excretion of N-acetyl-beta-glucosaminidase (EC 3.2.1.30)

1. Male Sprague-Dawley rats were fed on diets containing either sucrose or starch as the carbohydrate component. In one experiment, the diets also contained 200 g either butter or polyunsaturated margarine/kg; in a second experiment, the diets contained less fat in the form of 20 g maize oil/kg.

2. Over a period of 11 months assays were made in the urine of several ions and of the activity of the enzymeN-acetyl-β-glucosaminidase (β-2-acetamido-2-deoxy-β-D glucoside acetamidodeoxygluco-hydrolase;EC3.2.1.30); at 13 months, examination was made of some of the abdominal viscera, especially of the kidneys.

3. In rats fed on the higher amount of fat, dietary sucrose produced a higher activity of the enzyme than did dietary starch, and a greater excretion of inorganic phosphate.

4. With both the higher and lower amounts of dietary fat, sucrose led to an increase in the weight of the liver and of the kidneys, and an increase in the concentration of calcium and of phosphate in kidney tissue. With the higher amount of fat, sucrose also produced an increase in the concentration of magnesium in the kidney. There was no difference in the concentration of any of the ions assayed in the plasma or, apart from inorganic phosphate, in the urine.

5. The kidneys of the sucrose-fed rats showed nephrocalcinosis, mostly in the cortico-medullary region, and basophilic deposits in the tubules. Attention is drawn to this unusual occurrence of nephrocalcinosis in male rats.