Cardiovascular disease-risk factors in middle-aged osteopaenic women treated with calcium alone or combined to three nutrients essential to artery and bone collagen.

BACKGROUND: Recent research suggests that cardiovascular disease (CVD) and bone loss are functionally interwoven. This study examined the concomitant effects of a nutritional treatment of osteopaenia on CVD-risk factors. METHODS: A 1-year placebo-controlled trial was conducted on middle-aged women with normal (group A) or low (groups B and C) bone mineral density. Subjects (n = 20 per group) took daily either a placebo, calcium carbonate alone or combined to a vitamin (C and B(6))-proline capsule, respectively. Urinary pyridoxic acid (used to assess treatment compliance), plasma homocysteine, serum lipids and lipoproteins were measured before and after nutritional intervention. RESULTS: Groups were comparable at baseline in most parameters of interest. No changes occurred in groups A and B. The 4%, 7% and 25% reductions of total cholesterol, LDL and triglycerides, and 14% elevation of HDL were all significant in group C. A trend toward reduction was observed for homocysteine in this group. CONCLUSIONS: Vitamins C (500 mg) and B(6) (75 mg) combined with proline had consistent beneficial effects on CVD-risk factors, whereas calcium alone did not. This study also underlined the importance of considering vitamin B(6) status as a potential CVD risk factor.

Persistence of vitamin B12 insufficiency among elderly women after folic acid food fortification.

OBJECTIVE: To estimate the associated risk of folate and vitamin B12 (B12) insufficiency, as well as vitamin repletion, following folic acid food fortification. DESIGN: Retrospective cross-sectional study over a 5-year period. SETTING: Two large laboratory databases in the provinces of Ontario and British Columbia, Canada. PARTICIPANTS: Canadian women aged 65 years and over who underwent concomitant clinical testing of serum folate and B12 during the pre-fortification period of January 1996 to December 1997 in Ontario (n = 733) and British Columbia (n = 3839), and in the near-complete post-fortification period of January 1998 to December 2000 in Ontario (n = 4415) and British Columbia (n = 6677). MEASUREMENTS: Geometric mean concentrations of serum folate and B12 before and after folate fortification. Prevalence ratios (PR) were used to separately compare the post- and pre-fortification period rates of folate deficiency (below 6.0 nmol/L); B12 insufficiency (below 150 pmol/L); and B12 insufficiency in combination with supraphysiological concentrations of serum folate (above 45 nmol/L). RESULTS: The mean baseline folate and B12 concentrations were similar between provinces. Using the combined provincial data, the mean serum folate concentration increased by 64% after fortification, from 14.8 to 24.2 nmol/L (p < 0.001). The average B12 concentration increased from 280 to 300 pmol/L, which was more pronounced in BC (p < 0.001) than in Ontario (p = 0.16). The prevalence of folate deficiency declined from 6.3% to 0.88% after fortification (PR 0.14, 95% confidence interval [CI] 0.11-0.18), while the decline in B12 deficiency was less pronounced (PR 0.78, 95% CI 0.71-0.86). CONCLUSIONS: The prevalence of combined B12 insufficiency with supraphysiological concentrations of serum folate increased from 0.09% pre-fortification to 0.61% post (PR 7.0, 95% CI 2.6-19.2). The introduction of folic acid food fortification was associated with a substantial improvement in the folate status of Canadian women aged 65 years and older, paralleled by a large decline in the rate of folate deficiency. Improvement in the B12 status of these women was far less pronounced. Because the prevalence of combined B12 insufficiency and supraphysiological concentrations of serum folate may have increased with folic acid food fortification, consideration should be given to confirming this finding, and possibly, to the addition of B12 to folate fortified foods.

Declining rate of folate insufficiency among adults following increased folic acid food fortification in Canada.

OBJECTIVE: Canada introduced a mandatory folic acid food fortification program in November 1998. We investigated whether the rate of folate and vitamin B12 insufficiency among adults has changed since this mandatory fortification program was implemented. METHODS: We conducted a retrospective cross-sectional study using a large Ontario laboratory database. We included all individuals who underwent evaluation of their serum folate, red cell folate and serum vitamin B12 between April 1, 1997 to July 31, 1998 (Period A), August 1, 1998 to January 30, 1999 (Period B) and February 1, 1999 to March 31, 2000 (Period C). RESULTS: A total of 8,884 consecutive samples were analyzed during the period of study. Mean age was 57.4 years (SD 21.1), and 63.2% were female. The prevalence of serum folate insufficiency (below 3.4 nmol/L) fell from 0.52% in Period A to 0.22% in Period C [prevalence ratio (RR) 0.41, 95% confidence interval (CI) 0.18-0.93)]. The prevalence of red cell folate insufficiency (below 215 nmol/L) declined from 1.78% during Period A to 0.41% in Period C (RR 0.23, 95% CI 0.14-0.40). No significant difference was observed between periods in the prevalence of B12 insufficiency below 120 pmol/L (3.93% versus 3.11%, respectively; RR 0.79, 95% CI 0.62-1.01). CONCLUSIONS: There has been a significant decline in the prevalence of folate, but not vitamin B12 insufficiency, following Canadian folic acid food fortification. These changes may have important implications for the prevention and detection of folate and vitamin B12 insufficiency, including identifying the benefits of folic acid food fortification and the need to further consider fortification or supplementation with vitamin B12.

N-acetylcysteine neither lowers plasma homocysteine concentrations nor improves brachial artery endothelial function in cardiac transplant recipients.

BACKGROUND: N-acetylcysteine is a novel antioxidant that has been reported to reduce plasma homocysteine concentrations and improve endothelial function. Cardiac transplant recipients have a high incidence of coronary endothelial dysfunction and hyperhomocysteinemia, both of which may lead to the development of transplantation coronary artery disease. It was hypothesized that N-acetylcysteine would reduce plasma homocysteine concentrations and improve brachial endothelial function in cardiac transplant recipients. PATIENTS AND METHODS: A cohort of stable cardiac transplant recipients was recruited from the outpatient clinic at the Toronto General Hospital, Toronto, Ontario. Brachial artery endothelial functions were studied according to standard techniques to determine flow-mediated dilation of the brachial artery. Plasma homocysteine concentrations were assayed using high performance liquid chromatography with electrochemical detection and pulsed integrated amperometry. After baseline testing, patients were treated in an unblinded fashion with N-acetylcysteine 500 mg/day. After 10 weeks of therapy, patients returned for follow-up endothelial function and homocysteine testing. RESULTS: Thirty-one patients were initially enrolled. Two patients withdrew due to excessive gastrointestinal upset. Two patients did not return for follow-up testing. The remaining 27 patients tolerated the treatment well. At baseline, 85% of the patients had hyperhomocysteinemia (greater than 15 mol/L) with a mean plasma concentration of 18.6 4.7 mol/L. No changes in homocysteine concentrations were seen at follow-up. At baseline, the average flow-mediated dilation was only 4.7 6.3%. No changes were seen at follow-up. CONCLUSIONS: Hyperhomocysteinemia and brachial endothelial dysfunction are common in stable cardiac transplant recipients and are unaffected by supplementation with N-acetylcysteine.

Pyridoxine improves endothelial function in cardiac transplant recipients.

BACKGROUND: Endothelial dysfunction is common in cardiac transplant recipients and predicts the development of transplant coronary artery disease. Hyperhomocysteinemia is associated with endothelial dysfunction in the general population, is common in transplant recipients, and has been associated with transplant coronary artery disease. Thus therapy that decreases homocysteine concentrations might also improve endothelial function and decrease the risk of transplant coronary artery disease. Folate and pyridoxine are important cofactors in distinct aspects of homocysteine metabolism. The purpose of this study was to determine whether folate or pyridoxine supplementation improves endothelial function in cardiac transplant recipients. METHODS AND RESULTS: This was a double-blind, randomized, placebo-controlled trial. We assigned 31 transplant recipients to either pyridoxine (n = 11:100 mg/day), folate (n = 12:5 mg/day), or placebo (n = 8) for 10 weeks. Fasting and post-methionine-load (methionine 100 mg/kg orally) homocysteine concentrations were determined. Brachial artery flow-mediated dilatation was used as a measure of endothelial function. At follow-up, we noted no significant changes in homocysteine concentrations in any of the groups. However, pyridoxine supplementation was associated with a significant improvement in endothelial function (2.8 +/- 6.7 to 6.9 +/- 6.3, p = 0.05). No significant changes were seen in patients treated with folate or placebo. CONCLUSIONS: Pyridoxine, but not folate supplementation, significantly improves endothelial function in cardiac transplant recipients.

An Ontario-wide study of vitamin B12, serum folate, and red cell folate levels in relation to plasma homocysteine: is a preventable public health issue on the rise?.

BACKGROUND: Plasma homocysteine has been reported to be useful in the evaluation of patients with suspected vitamin B12 or folate deficiency. In November 1998, Canada began its mandatory fortification of all flour, and some corn and rice products, with folic acid. We evaluated the status of folate and vitamin B12 in Ontario since this fortification program began, and also studied the role of plasma homocysteine in the assessment of vitamin B12 deficiency since that time. METHODS: A retrospective cross-sectional study design was performed using a community database of all Ontario samples analyzed by MDS Laboratories, a major provider of diagnostic laboratory services in Canada. All consecutive single-patient fasting samples for plasma homocysteine collected between January 1 and September 30, 1999 were included, as well as corresponding red cell folate and serum B12 concentrations. Data for serum folate were included when available. Descriptive statistics included the arithmetic and geometric means for each measure, as well as the lower and upper centile values. After excluding cases with a concomitant serum creatinine > 120 micromol/L or red cell folate < 215 nmol/L, we established the test properties of a plasma homocyteine level of 15 micromol/L or greater for the diagnosis of "low" (< 120 pmol/L) or "indeterminate" (i.e., between 120 and 150 pmol/L) serum vitamin B12 concentrations. RESULTS: The mean age of all subjects was 58.4 years (95% CI 57.4 to 59.4). Plasma homocysteine samples were obtained from 403 males (56.7%) and 308 females. The geometric mean homocysteine concentration for the entire population was 8.3 micromol/L, and was significantly higher among males (9.3 micromol/L) than females (8.3 micromol/L) (unpaired t-test: 2-p < 0.0001). The geometric mean serum folate concentration was significantly higher in females (35.8 nmol/L) than males (33.6 nmol/L) (2-p < 0.0001), as were the mean red cell folate levels (females 966.8 nmol/L, males 949.3 nmol/L; 2-p < 0.0001). Serum vitamin B12 concentrations were available for 692 subjects, with a geometric mean of 322.0 pmol/L. Again, mean vitamin B12 was higher in females (332.5 pmol/L) than males (314.3 pmol/L) (2-p < 0.0001). The fifth centile for vitamin B12 was 134.6 pmol/L. A plasma homocysteine concentration > 15 micromol/L did not discriminate between cobalamin concentrations below versus above 120 pmol/L (positive and negative predictive values 7.4% and 97.2%, respectively), nor did it discriminate "indeterminate" B12 levels between 120 and 150 pmol/L (positive and negative predictive values 6.3% and 94.0%, respectively). CONCLUSION: In a large select group of Ontarians, serum and red cell folate concentrations appear to be higher than expected, possibly due to a recent national folate fortification programme; cobalamin levels are no higher than expected. Given our inability to detect mild B12 deficiency using such indicators as plasma homocysteine, and considering the substantial growth in the elderly segment of the Canadian population, occult cobalamin deficiency could become a common disorder. Accordingly, we recommend either consideration of the addition of vitamin B12 to the current folate fortification programme, and/or the development of better methods for the detection of cobalamin deficiency.

Associations of the collagen type Ialpha1 Sp1 polymorphism with five-year rates of bone loss in older adults.

The collagen type Ialpha1 Sp1 (ColIA1) polymorphism has been associated with reduced bone mineral density (BMD) and increased prevalence of osteoporosis. This study examines associations of the ColIA1 genotype with BMD and 5-year rates of change in BMD in elderly men and women. The 243 subjects, aged 65 years and older, were participants in two consecutive studies lasting a total of 5-years. BMD of the total body, femoral neck, and lumbar spine were made by dual-energy X-ray absorptiometry (DXA). The distribution of the genotypes (155 in the SS genotype, 79 in Ss, and 9 in ss) was proportionately similar to those reported by others. Baseline BMD did not differ significantly at any skeletal site. Unadjusted 5-year percent changes in BMD differed significantly by genotype only at the total body (P = 0.009), where the change was -0.29+/-0.21 (SEM) in the SS genotype, -0.60+/-0.25 in the Ss genotype, and -3.01+/-0.72 in the ss genotype. This 9.4% increase in bone loss of the ss genotype relative to the SS genotype was reduced to an 8.9% increase after adjustment for sex, age, weight, and supplementation group. Results at the femoral neck were directionally similar, but not statistically significant. No effect of genotype on change in spine BMD was observed. In conclusion, bone loss from the total body was significantly greater in elderly men and women who were homozygous for the s allele compared with heterozygotes and SS homozygotes. This finding suggests a possible explanation for the association of the ColIA1 polymorphism with increased rates of osteoporotic fracture, but should be interpreted with caution because of the small number of subjects in the unfavorable ss genotype.

Primary infantile hypomagnesaemia: outcome after 21 years and treatment with continuous nocturnal nasogastric magnesium infusion.

UNLABELLED: Primary infantile hypomagnesaemia is an infrequent cause of neonatal hypocalcaemic seizures but one that responds well to magnesium supplementation. We describe a 22-year-old male, first reported at 4 months of age, who is currently free of neurological deficit but has suffered from intermittent hypomagnesaemic tetany and chronic diarrhoea due to large oral magnesium supplements. Hypothesizing that modest hypercalcaemia might prevent the tetany, we conducted a trial of 5 microg/day 1,25(OH)2D3 over 5 days. Despite the resultant increase in calcium, he developed tetany with the reduction of magnesium intake and decline of serum magnesium from 0.63 to 0.39 mmol/l (normal >0.65 mmol/l). After 1,25(OH)2D3 was stopped and the parenteral magnesium injections suspended, 33% of his usual oral supplement was given instead by continuous nasogastric infusion and serum magnesium rose to 0.60 mmol/l. This regimen was better tolerated because of decreased gastrointestinal side-effects and freedom from parenteral injections. We observed that 1,25(OH)2D3 supplements do not promote magnesium retention nor does the resultant hypercalcaemia prevent hypomagnesaemic tetany. CONCLUSION: Continuous nocturnal nasogastric infusion may be considered in lieu of parenteral therapy in primary infantile hypomagnesaemia.

Homocysteine: cholesterol of the 90s?

Homocysteine is a sulfur-containing amino acid generated through the demethylation of methionine. It is largely catabolized by trans-sulfuration to cysteine but it may also be remethylated to methionine. Dubbed 'the cholesterol of the 90s' by the lay press, homocysteine is thought to be thrombophilic and to damage the vascular endothelium. Total plasma homocysteine (tHcy) is now established as a clinical risk factor for coronary artery disease, as well as other arterial and venous occlusive disease in adult populations. Regulation of homocysteine is dependent on nutrient intake, especially folate, vitamins B6 and B12. It is also controlled by common genetic variations (polymorphisms) in how vitamins are utilized as cofactors in the reactions controlling homocysteine metabolism. Moreover, concentrations are age- and sex-dependent and are altered by renal function, hormonal status, drug intake and a variety of other common clinical factors. Considerable care must be taken in assaying tHcy. Plasma should be separated shortly after collection, to avoid artifactual increases due to synthesis by blood cells in vitro. Reference methods have not been validated and criteria for establishing reference ranges should take into account the variable prevalence of physiological hyperhomocysteinemia. Determination of tHcy should probably be limited to centres with relevant expertise and ability to maintain the high degree of precision required for reliable interpretation. Molecular testing for the genetic polymorphisms is still in the research phase but the ease and reliability of molecular diagnosis will speed its introduction into clinical laboratory practice--particularly in relation to diagnosis of thrombophilic disorders. Clinical research initiatives are being driven by the benefit that should be achieved by correction with vitamin supplements, particularly folate and B vitamins, but it must be recognized that prospective controlled studies to validate clinical benefit are only now being initiated. At the moment, it is safe to say that hyperhomocysteinemia is one of the few prevalent biochemical risk factors for thromboembolic disease that might be corrected by vitamin supplements. Such a possibility lies behind the growing momentum to recommend increased supplements of folate and B vitamins to at-risk population and patient groups today.

Homocysteine.

Homocysteine is a sulfur-containing amino acid generated through the demethylation of methionine. It is largely catabolized by trans-sulfuration to cysteine, but it may also be remethylated to methionine. Regulation of homocysteine is dependent on nutrient intake, especially folate, vitamins B6 and B12. It is also controlled by individual genetic differences in how vitamins are utilized as cofactors in the reactions controlling homocysteine metabolism. In excess quantities, homocysteine is thought to be thrombophilic and to damage the vascular endothelium. Total plasma homocysteine (tHcy) is now established as a clinical risk factor for coronary artery disease, as well as other arterial and venous occlusive disease in adult populations. These effects are probably related to its role as a teratogen in the pathogenesis of neural tube defects--genetic variants causing hyperhomocysteinemia are associated with both neural tube defects in susceptible pregnancies and with risks for vaso-occlusive disease in later years. Considerable care must be taken in assaying tHcy. Plasma should be separated shortly after collection to avoid artifactual increases due to synthesis by blood cells in vitro. tHcy concentrations must be interpreted in light of the fact that serum albumin, urate, creatinine, and vitamin concentrations may be important analytical covariates. Moreover, concentrations are age- and sex-dependent and are altered by renal function, hormonal status, drug intake, and a variety of other common clinical factors. Why then is homocysteine now of such great clinical and scientific interest? If the homocysteine moiety itself is important in the pathogenesis of vaso-occlusive disease, then simple treatment of hyperhomocysteinemia with vitamins should lead to a significant reduction in disease risk. Such a possibility lies behind the growing momentum to recommend increased supplements of folate and B vitamins to at-risk populations and patient groups today.

Markedly reduced activity of mutant calcium-sensing receptor with an inserted Alu element from a kindred with familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism.

Missense mutations have been identified in the coding region of the extracellular calcium-sensing receptor (CASR) gene and cause human autosomal dominant hypo- and hypercalcemic disorders. The functional effects of several of these mutations have been characterized in either Xenopus laevis oocytes or in human embryonic kidney (HEK293) cells. All of the mutations that have been examined to date, however, cause single putative amino acid substitutions. In this report, we studied a mutant CASR with an Alu-repetitive element inserted at codon 876, which was identified in affected members of families with the hypercalcemic disorders, familial hypocalciuric hypercalcemia (FHH) and neonatal severe hyperparathyroidism (NSHPT), to understand how this insertion affects CASR function. After cloning of the Alu-repetitive element into the wild-type CASR cDNA, we transiently expressed the mutant receptor in HEK293 cells. Expression of mutant and wild-type receptors was assessed by Western analysis, and the effects of the mutation on extracellular calcium (Ca2+(o)) and gadolinium (Gd3+(o)) elicited increases in the cytosolic calcium concentration (Ca2+(i)) were examined in fura-2-loaded cells using dual wavelength fluorimetry. The insertion resulted in truncated receptor species that had molecular masses some 30 kD less than that of the wild-type CASR and exhibited no Ca2+(i) responses to either Ca2+(o) or Gd3+(o). A similar result was observed with a mutated CASR truncated at residue 876. However, the Alu mutant receptor had no impact on the function of the coexpressed wild-type receptor. Interestingly, the Alu mutant receptor demonstrated decreased cell surface expression relative to the wild-type receptor, whereas the CASR (A877stop) mutant exhibited increased cell surface expression. Thus, like the missense mutations that have been characterized to date in families with FHH, the Alu insertion in this family is a loss-of-function mutation that produces hypercalcemia by reducing the number of normally functional CASRs on the surface of parathyroid and kidney cells. In vitro transcription of exon 7 of the CASR containing the Alu sequence yielded the full-length mutant product and an additional shorter product that was truncated due to stalling of the polymerase at the poly(T) tract. In vitro translation of the mutant transcript yielded three truncated protein products representing termination in all three reading frames at stop codons within the Alu insertion. Thus sequences within the Alu contribute to slippage or frameshift mutagenesis during transcription and/or translation.

Contribution of sulfate and sulfoesters to total sulfur intake in infants fed human milk.

Colostrum (d 2-4) and mature human milk samples (d 23-30) collected from eight mothers giving birth at 31 +/- 7 wk of gestation were analyzed for total sulfur, free inorganic sulfate and acid labile sulfoesters. The data presented are representative of complete 24-h expressions. Total sulfur was measured using a wet digestion procedure in which all forms of sulfur were converted to inorganic sulfate. The sulfate was quantified by a radiometric barium precipitation assay. Total sulfur showed no marked diurnal variation, but the mean concentration in 19 colostrum samples (10.2 +/- 4.2 mmol/L) was significantly higher than in 14 mature milk samples (4.3 +/- 0.8 mmol/L) (P less than 0.001). The range of predicted 24-h intakes of sulfur by infants fed colostrum (0.78-3.22 mmol/kg body weight) was slightly higher than those fed mature milk (0.54-1.06 mmol/kg), but it was not significantly different. The combined fractions of free inorganic sulfate and acid-labile sulfoester fractions contribute less than 5% to the total sulfur content of either colostrum or mature milk. However, the physiological significance of these milk components remains to be determined.

Inorganic sulfate metabolism in the very low birthweight infant.

The effect of vitamin D supplementation on inorganic sulfate metabolism was examined in very low birth weight (less than 1,500 g) infants at biweekly intervals after birth until 6 weeks of postnatal age. Baseline serum sulfate concentrations were significantly higher in all infants (471 +/- 24 mumol/l, n = 80) than in adults (299 +/- 25 mumol/l, n = 17). In controls, the levels did not change significantly over the ensuing 6 weeks, although serum creatinine declined. Urinary sulfate excretion rose significantly to near adult levels by 2 weeks. Both urine and serum sulfate were correlated with weight gain but not with estimated glomerular filtration rate, suggesting that factors other than renal clearance have a preponderant influence on serum sulfate in these infants. At 6 weeks, the mean serum sulfate in the high-dose group (receiving 2,170 +/- 23 U/day of vitamin D, n = 41) was significantly higher than in controls (receiving 360 +/- 22 U/day, n = 40). In all infants, there was a significant correlation (r = 0.36, p less than 0.001) between serum sulfate and 25(OH)-vitamin D concentrations, but not other analytes or clinical variables, suggesting that vitamin D may be one of the factors modulating sulfate metabolism in the newborn period.

Effect of high-dose vitamin D supplementation on radiographically detectable bone disease of very low birth weight infants.

To test the hypothesis that high-dose vitamin D2 supplementation would result in a lower incidence of radiographically detectable bone disease, we randomly assigned 40 very low birth weight infants to a control group who received vitamin D2 in a dosage of 400 IU/day and 41 to an experimental group who received a dosage of 2000 IU/day. After 6 weeks, radiographs from all infants were scored blindly for degree of radiographic bone disease, and serum osteocalcin and 25-hydroxyvitamin D levels were measured. Mean vitamin D intake was 360 +/- 141 (SD) IU/day in the control group and 2170 +/- 144 (SD) IU/day in the experimental group. Median 6-week serum 25-hydroxyvitamin D levels were 24 ng/ml (range 3 to 60 ng/ml) in the control group and 68 ng/ml (range 9 to 150 ng/ml) in the experimental group (p less than 0.001). Overall, 20% of the infants had evidence of moderate radiographic bone disease and only 2% were severely affected. The radiographic bone score (median = 2.5) and serum osteocalcin concentration (mean = 21.7 +/- 8.7 ng/ml) in the control subjects did not differ significantly from those in the experimental group (median bone score = 2.0; mean osteocalcin level = 24.1 +/- 7.9 ng/ml). Although there may be a subset of very low birth weight infants who would benefit from high doses of vitamin D, we conclude that no generalized clinical improvement can be attributed to this regimen alone.

The comparative effects of feeding ammonium carbonate, ammonium sulfate, and ammonium chloride on urinary calcium excretion in the rat.

When either sulfate or chloride is added to the diet, the resulting acid load causes a rise in urinary calcium excretion. There is, however, the possibility that sulfate, which has been shown to complex renal tubular calcium, will further decrease renal calcium reabsorption and thus produce a greater calciuria than chloride. Because addition of a fixed cation (e.g., sodium) to the diet may also stimulate calciuresis, experiments were conducted using metabolizable ammonium to minimize cation effects. Ammonium salts of sulfate, chloride, and carbonate (control) were added to the diets of male rats at 0.3 mequiv./g weight of diet. Twenty-four hour excretion rates of calcium, sulfate, chloride, and net acid were measured at various intervals up to 1 month. As expected, the chloride and sulfate diets were both associated with significantly elevated urine calcium and net acid excretion as compared with controls. However, those fed sulfate exhibited significantly less calcium and acid excretion and absorbed a smaller proportion of the anion load than those given chloride. In a second experiment, the amounts of supplemental sulfate and chloride were adjusted so that total absorptions were similar. At 2 weeks, both calcium and acid excretions in the fixed anion groups were no longer significantly different. Thus, in chronic feeding trials, there appears to be no measurable difference in the calciuretic properties of sulfate and chloride anions.

Transient hyperphosphatasemia in a child with autosomal recessive vitamin D dependency.

The case of a 4.5-year-old girl with autosomal recessive vitamin D dependency is described. Although she had been effectively treated since one month postpartum with 1 alpha-hydroxycholecalciferol [1 alpha(OH)D3, alfacalcidol], her mean alkaline phosphatase (EC 3.1.3.1) activity in serum increased to 3680 U/L from a stable value [335 (SD 50) U/L; n = 12] within three weeks, then returned to baseline over the ensuing four months. Transient hyperphosphatasemia was diagnosed. Extensive investigation of an isolated episodic increase in alkaline phosphatase activity is as superfluous in the child with adequately treated metabolic bone disease as it is in other healthy and asymptomatic children.

The comparative toxicity of vitamin D metabolites in the weanling mouse.

The potential toxicity of vitamin D, alpha-calcidol [1 alpha(OH)D3], and calcitriol [1,25(OH)2D3] was studied by administration of these compounds at three different doses to weanling C57BL/6J mice over a 4-week period. Drug effects on calcium were monitored by serum calcium and urine calcium/creatinine ratio determinations. Tests of renal function included serum creatinine, 24-h urine volume, urinary protein, and glucose excretion, and histological evaluation of renal tissue. At 2 weeks, serum calcium was significantly elevated in animals receiving the higher doses of alpha-calcidol (2.78 +/- 0.25 at 50 ng/kg and 3.45 +/- 0.13 at 250 ng/kg body wt vs 2.14 +/- 0.06 mmol/l in controls, respectively). A similar effect was seen in the urinary calcium/creatinine ratio but serum creatinine remained unchanged. By 4 weeks, all animals receiving alpha-calcidol had significantly higher serum calcium and urinary calcium/creatinine ratios than other groups. Severe nephrocalcinosis was observed in the high-dose alpha-calcidol group only. We conclude that alpha-calcidol is more toxic than calcitriol in the mouse and suggest that the degree of toxicity is correlated to the degree of hypercalcemia and to the vitamin D metabolite used.

Serum osteocalcin in the treatment of inherited rickets with 1,25-dihydroxyvitamin D3.

Osteocalcin is a vitamin K-dependent protein, synthesized in bone, which can be detected in serum. We have measured circulating osteocalcin levels in 10 patients with x-linked hypophosphatemia (XLH) and in 6 patients with autosomal recessive vitamin D dependence (ARVDD) who started 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] therapy. Patients with XLH were studied before and after 7-12 months of therapy that included 1,25-(OH)2D3 (10-72 ng/kg x day) and oral phosphate. Serum osteocalcin rose from 28 +/- 12 to 52 +/- 12 ng/ml (mean +/- SE; P less than 0.01) in concert with improvements in biochemical status and bone mineralization. Vitamin D therapy was withdrawn for 2 weeks from patients with ARVDD. The vitamin D-deplete status was evidenced by low 1,25-(OH)2D3 levels (12 +/- 2 pg/ml; n = 6). After 1 week of therapy with 1,25-(OH)2D3, serum calcium rose from 9.03 +/- 0.21 to 9.67 +/- 0.25 mg/dl (P less than 0.002), while serum phosphorus and alkaline phosphatase remained unchanged. Serum osteocalcin rose from 35 +/- 7 to 83 +/- 32 ng/ml (P less than 0.05). At 3 weeks, serum calcium remained elevated (9.63 +/- 0.18 ng/dl) over control levels (P less than 0.01); phosphorus and alkaline phosphatase were still unchanged. Serum osteocalcin rose to 114 +/- 42 ng/ml, significantly greater than values at 1 week (P less than 0.05). Thus, serum osteocalcin increases after 1,25-(OH)2D3 therapy in both ARVDD and XLH.

Autosomal hypophosphataemic bone disease responds to 1,25-(OH)2D3.

We diagnosed non X-linked hypophosphataemic bone disease in a 38-month-old girl. Findings included: genu varum, shortened stature, fasting hypophosphataemia (2.3-2.5 mg/100 ml; 0.74-0.81 mmol/l), diminished theoretical renal threshold for phosphate (TmP/GFR), and osteomalacia without rickets. One patient (the father) had fasting hypophosphataemia (2.3-2.7 mg/100 ml; 0.74-0.87 mmol/l) and low TmP/GFR without osteomalacia or shortened stature. Treatment of the girl with 1,25-(OH)2D3 (1 microgram a day) raised the level of serum phosphorus, improved tubular reabsorption of phosphate, and healed the bone deformity; this combination of responses is not present in X-linked hypophosphataemia. There was no correction of hypophosphataemia or TmP/GFR with 1,25-(OH)2D3 treatment (1-3 micrograms a day) in the father.