Ragnar Rylander

Renal Net Acid Excretion Capacity Is Comparable in Prepubescence, Adolescence, and Young Adulthood but Falls with Aging

OBJECTIVES: To evaluate whether renal net acid excretion capacity (NAEC) varies across different age groups and, specifically, whether it falls in elderly people.

Muscularity and adiposity in addition to net acid excretion as predictors of 24-h urinary pH in young adults and elderly

Objective:In patients with nephrolithiasis, an inverse relationship between 24-h urinary pH (24h-UpH) and body weight has been reported. Whether body composition indices and 24h-UpH are similarly associated in healthy subjects needs investigation.Design:Cross-sectional, retrospective analysis.Setting:Dortmund, Germany and Gothenburg, Sweden.Subjects:Healthy young adults (18–23 years; n=117) and elderly (55–75years; n=85) having a mean body mass index (BMI) of 22.80±3.4 and 25.3±3.9 kg/m2, respectively.Methods:Anthropometric data, 24h-UpH, and 24-h urinary excretion rates of net acid (NAE), creatinine, and urea were determined. After adjusting for urea (reflecting protein intake), renal creatinine output was used as a biochemical marker for muscularity. The BMI served as a marker of adiposity.Results:NAE, body weight, and BMI were significantly (P<0.05) higher, and height and creatinine significantly lower in the elderly, whereas body-surface area (BSA) was not different. Step-wise multiple regression analysis using BSA-corrected urinary variables revealed NAE as the primary predictor of 24h-UpH (with R 2 values of 0.64 and 0.68 in young adults and elderly, respectively, P<0.0001), followed by urea (P<0.0001), creatinine (P<0.05), and BMI (P<0.05 for the young adults and P=0.12 for the elderly). These associations were negative for NAE and BMI, and positive for urea and creatinine.Conclusions:Muscularity (i.e. creatinine adjusted for urea) and particularly in the group of young adults, adiposity (i.e. BMI) proved to be modest, but significant predictors of 24h-UpH. Future research should focus on more obese subjects in whom insulin resistance and particular kidney functions should also be examined to further substantiate the role of obesity in low-urine pH-associated conditions, for example, nephrolithiasis.

Acid-base conditions regulate calcium and magnesium homeostasis

BACKGROUND Previous experimental studies demonstrate that the acid-base balance influences mineral homeostasis by regulating the absorption of calcium and magnesium in the kidneys. No intervention studies are available on population samples. AIMS To study the urinary excretion of calcium and magnesium before and after an intervention with the aim of decreasing the acid load. METHODS Healthy subjects aged 50-75 years were recruited by advertising. Urinary calcium, magnesium and urea as well as blood pressure were measured before and after the intervention. This comprised taking tablets containing potassium hydrogen carbonate or potassium chloride (placebo) during 7-10 days. RESULTS There were significant relationships between the urinary excretion of urea and magnesium and calcium before the intervention. Comparing before and after intervention, the change in urinary excretion of urea was related to a change in urinary excretion of calcium and magnesium. There was a significant decrease in systolic as well as diastolic blood pressure both after administration of potassium hydrogen carbonate and citrate. CONCLUSION The results confirm previous studies showing a relation between acid conditions in the body and the excretion of calcium and add new data on magnesium. A blood pressure decrease after potassium has been found in previous studies. This suggests an alternative for the treatment of moderately increased levels of blood pressure that should be further explored.

Blood pressure in pregnancy and magnesium sensitive genes

OBJECTIVES High blood pressure during the last part of pregnancy is a risk indicator of pre-eclampsia and eclampsia which augment infant and maternal morbidity and mortality. Magnesium deficiency has been related to the risk of hypertension. A study was performed to assess the relation between pregnancy induced hypertension, excretion of urinary magnesium and expression of magnesium sensitive genes (MgSG). METHODS A cohort of healthy, nulliparous women with singleton pregnancies was recruited. Blood pressure was recorded throughout pregnancy. Urinary magnesium excretion and expression of MgSGs in leukocytes were determined. RESULTS The expression of the gene TRPM6 was higher among pregnant women compared to non-pregnant controls at week 12. All other genes had lower expressions in pregnant women. At week 37 the expressions of all genes were lower than at week 12. The expressions of SLC41A1, SLC41A3, and TRPM7 were related to the systolic and diastolic blood pressures. Furthermore, the expression of TRPM6 was related to the urinary excretion of magnesium and the change in diastolic blood pressure weeks 12-37 was inversely related to the change in magnesium excretion. CONCLUSIONS Systolic and diastolic blood pressure and the excretion of magnesium during pregnancy were related to the expression of different MgSGs. The results suggest that magnesium is involved in the regulation of blood pressure during pregnancy.

Magnesium in pregnancy blood pressure and pre-eclampsia – A review

Magnesium is an important cation present in more than 300 enzymes in the body. This review evaluates the information on magnesium and pregnancy. In normal pregnancies Mg responsive genes are upregulated, suggesting Mg deficiency. Blood pressure increase is related to the urinary excretion of Mg. In pregnancies complicated by preeclampsia the Mg homeostasis is different from normal pregnancies. Supplementation with Mg has shown beneficial effects on high blood pressure and infant conditions in some studies. Although several studies show important relationships between Mg homeostasis and pregnancy, particularly those with pre-eclampsia, further studies are needed to assess the relationship and formulate requirements for intervention programmes.

Pre-eclampsia during pregnancy and cardiovascular disease later in life: the case for a risk group

AbstractIntroductionWomen with pre-eclampsia (PE) have an increased risk of cardiovascular disease (CVD) later in life. This association might reflect an effect of pre-eclampsia on mechanisms inducing a higher risk of CVD or the presence of a group at risk.Materials and methodsThe possibility that women with a magnesium deficiency might constitute a risk group was examined using published evidence form investigations on PE and CVD.ResultsAvailable data strongly suggest that a magnesium deficiency is a major risk factor for both PE and for CVD disease later in life.ConclusionsMagnesium homeostasis studies in women with PE should be undertaken for validation purposes. The results suggest that women with PE should be given dietary counselling to decrease future risks of CVD.

O31. Magnesium homeostasis and gestational hypertension

Introduction Magnesium (Mg) is important for the normal functioning of muscles and blood vessels. A deficiency has been related to an increase in blood pressure and acute death in heart infarction and stroke. Objectives To review the literature regarding a relation between magnesium homeostasis and gestational hypertension (GH) during pregnancy. Methods A survey of published studies on the subject. Results Mg homeostasis is determined by intake through food and drinking water. A diet rich in proteins and poor in vegetables will increase the excretion of acids in the urine, resulting in a decrease of the normal reabsorption of Mg in the kidneys. Several population studies show that pregnant women often have a Mg intake below the recommended nutritional values. Pregnant women have also been found to have a higher expression of a gene regulating the uptake of Mg from the intestine, suggesting an increased demand for Mg during pregnancy. The incidence of pre-eclampsia (PE) is higher in developing countries, where the risk of nutritional insufficiencies including Mg is high. On the cellular level, results from studies of erythrocyte membranes, brain cells and cerebrospinal fluid suggest that women with PE have lower Mg values than women with normal pregnancies. Several studies show that Mg deficiency during pregnancy is been linked to high blood pressure and PE. Regarding intervention, Mg sulphate intravenously has long been used in the treatment of PE. Data from investigations in four different countries show that supplementation with Mg during pregnancy decreased the risk of GH. The expression of Mg responsive genes has been related to diastolic blood pressure and duration of delivery. Available data thus indicate that GH and PE are related to a lack of Mg. Conclusion From a public health point of view, further studies on Mg homeostasis in pregnancy and intervention in terms of supplementation have a high priority, with the ultimate aim to develop prevention programs.