Effect of Vitamin D Treatment on Dynamics of Stones Formation in the Urinary Tract and Bone Density in Children with Idiopathic Hypercalciuria

Decreased calcium permeability caused by biallelic TRPV5 mutation leads to autosomal recessive renal calcium-wasting hypercalciuria

Hypercalciuria is the most common metabolic risk factor in people with kidney stone disease. Its etiology is mostly multifactorial, although monogenetic causes of hypercalciuria have also been described. Despite the increased availability of genetic diagnostic tests, the vast majority of individuals with familial hypercalciuria remain unsolved. In this study, we investigated a consanguineous pedigree with idiopathic hypercalciuria. The proband additionally exhibited severe skeletal deformities and hyperparathyroidism. Whole-exome sequencing of the proband revealed a homozygous ultra-rare variant in TRPV5 (NM_019841.7:c.1792G>A; p.(Val598Met)), which encodes for a renal Ca2+-selective ion channel. The variant segregates with the three individuals with hypercalciuria. The skeletal phenotype unique to the proband was due to an additional pathogenic somatic mutation in GNAS (NM_000516.7:c.601C>T; p.(Arg201Cys)), which leads to polyostotic fibrous dysplasia. The variant in TRPV5 is located in the TRP helix, a characteristic amphipathic helix that is indispensable for the gating movements of TRP channels. Biochemical characterization of the TRPV5 p.(Val598Met) channel revealed a complete loss of Ca2+ transport capability. This defect is caused by reduced expression of the mutant channel, due to misfolding and preferential targeting to the proteasome for degradation. Based on these findings, we conclude that biallelic loss of TRPV5 function causes a novel form of monogenic autosomal recessive hypercalciuria, which we name renal Ca2+-wasting hypercalciuria (RCWH). The recessive inheritance pattern explains the rarity of RCWH and underscores the potential prevalence of RCWH in highly consanguineous populations, emphasizing the importance of exploration of this disorder within such communities.

Vitamin D Supplementation at a Dose of 10 µg/Day in Institutionalized Children with Severe Motor and Intellectual Disabilities

Vitamin D (VD) deficiency can lead to health-related consequences. This study determined the effects of VD administration in VD-deficient children with severe motor and intellectual disabilities (SMID). Twenty-eight subjects were included. Among them, 25 subjects with parental consent for VD administration were given 10 µg/day (400 IU/day) of VD in April 2021. Serum 25-hydroxyvitamin D [25(OH)D] levels were measured at least 30 days after the start of VD administration. The total VD intake, serum 25(OH)D levels, and ultraviolet (UV) exposure before the blood tests were investigated. The results showed that the median serum 25(OH)D levels were 8.7 ng/mL (4.3-17.2) and 24.0 ng/mL (7.8-39 ng/mL) from March to May in 2020 and 2021, respectively. Among the 25 subjects, 22 with UV exposure had >20 ng/mL serum 25(OH)D level, and 2 without UV exposure had <20 ng/mL serum 25(OH)D level. Three subjects who did not receive VD supplementation had <20 ng/mL serum 25(OH)D level. Taken together, VD supplementation (10 µg/day) is effective in children with SMID in institutional care. Moreover, it may be sufficient for children with UV exposure, but not for those without.

Vitamin D deficiency in children with severe disabilities under limited ultraviolet exposure

INTRODUCTION

Nutritional prevention of osteoporosis management is an important issue for children with severe disabilities. Due to the coronavirus disease 2019 (COVID-19) pandemic that started in 2020, children admitted to institutions had fewer opportunities for ultraviolet (UV) exposure owing to restrictions on attending school and going out. Hence, the vitamin D (VD) status of these children has been a cause of concern. This study aimed to assess the correlation between VD intake and VD status among children with severe disabilities who had limited UV exposure.

MATERIALS AND METHODS

This research included patients admitted to Iwate Prefectural Rehabilitation and Nursery Center for Disabled Children. Serum 25-hydroxyvitamin D [25(OH)D] levels were assessed during school/outing restriction periods and after restriction removal and the introduction of sunbathing periods. The trends in 25(OH)D levels and oral VD intake before the two measurements were analyzed.

RESULTS

Although 17 of 32 patients had VD intake above the recommended level of Dietary Reference Intakes for Japanese during the first measurement, 31 patients had VD deficiency. The 25(OH)D levels of 13 patients without UV exposure before the first evaluation and those with UV exposure before the second evaluation were 2.03 times higher, despite of constant VD intakes. In contrast, there were no remarkable changes in both VD intakes and 25(OH)D levels in five patients without UV exposure before both assessments.

CONCLUSION

Japanese children with severe disabilities who consume the recommended oral VD intake but who have limited UV exposure can still present VD deficiency.

Preconception vitamin D intake and obstetric outcomes in women using assisted reproductive technology: the Japan Environment and Children’s Study

Background

In reproductive medicine, vitamin D (VitD) is of particular interest because its deficiency has been linked to various infertility issues. Thus, preconception care, including appropriate VitD supplementation, is essential, especially in women using assisted reproductive technology (ART). Despite the therapeutic benefits of VitD, adverse events due to a high daily intake may influence obstetric outcomes. However, the effects of either low or high preconception VitD intake on obstetric outcomes, including the outcomes in women who used ART, remain unclear. Therefore, the aim of this study was to examine the association between pre-pregnancy daily VitD intake and obstetric outcomes in Japanese women, including those who conceived through ART.

Methods

Data were obtained from the Japan Environment and Children’s study database comprising 92,571 women recruited between January 2011 and March 2014 in Japan. Participants were categorized into five quintiles according to pre-pregnancy VitD intake (Q1 and Q5 had the lowest and highest VitD intake, respectively) and stratified according to the use of ART. Multiple logistic regression was performed to identify the effects of pre-pregnancy VitD intake on preterm birth (PTB), low-birth weight infant (LBW), and small for gestational age (SGA).

Results

Using Q3 (middle VitD intake) as a reference, our analysis revealed that Q5 (highest VitD intake) showed an increased risk of LBW < 1500 g (adjusted odds ratio [aOR]: 1.09, 95% confidence interval [CI]: 1.00–1.18) and SGA (aOR: 1.26, 95% CI: 1.14–1.39) among women who conceived without ART. Among women who conceived with ART, we found that Q5 (highest VitD intake) showed an increased risk of PTB at < 37 weeks (aOR: 2.05, 95% CI: 1.27–3.31).

Conclusion

The present study revealed that higher VitD intake before pregnancy may affect perinatal outcomes, particularly in women using ART. Our findings may facilitate personalized preconceptional counseling regarding VitD intake based on the method of conception, especially among women using ART.

Beyond kidney stones: Why pediatricians should worry about hypercalciuria

The incidence of urolithiasis (UL) is increasing, and it has become more common in children and adolescents over the past few decades. Hypercalciuria is the leading metabolic risk factor of pediatric UL, and it has high morbidity, with or without lithiasis as hematuria and impairment of bone mass. The reduction in bone mineral density has already been described in pediatric idiopathic hypercalciuria (IH), and the precise mechanisms of bone loss or failure to achieve adequate bone mass gain remain unknown. A current understanding is that hypercalciuria throughout life can be considered a risk of change in bone structure and low bone mass throughout life. However, it is still not entirely known whether hypercalciuria throughout life can compromise the quality of the mass. The peak bone mass is achieved by late adolescence, peaking at the end of the second decade of life. This accumulation should occur without interference in order to achieve the peak of optimal bone mass. The bone mass acquired during childhood and adolescence is a major determinant of adult bone health, and its accumulation should occur without interference. This raises the critical question of whether adult osteoporosis and the risk of fractures are initiated during childhood. Pediatricians should be aware of this pediatric problem and investigate their patients. They should have the knowledge and ability to diagnose and initially manage patients with IH, with or without UL.

Safety of megadose of vitamin D in patients with nephrolithiasis

OBJECTIVE

This article describes two patients with renal lithiasis who received a megadose of 25-hydroxy vitamin D (25[OH]D) and had a good outcome.

METHODS

The first case reports a 74-year-old man with a long-term history of renal lithiasis and about four episodes of renal crisis. He was treated once with extracorporeal shock wave lithotripsy. He also had a history of dyslipidemia, myocardial infarction, and stroke. Laboratory tests demonstrated 25(OH)D of 28 ng/mL (normal range (nr): >30 ng/mL), normal lipid levels, creatinine of 1.1 mg/dL, and homocysteine of 26.6 mcmol/L (nr: 5-15 mcmol/L); parathyroid hormone (PTH) was high at 67.3 pg/mL (nr: 10-65 pg/mL), serum total calcium was 8.6 mg/dL, 24-h urinary calcium was 139 mg/d (normal range 100-300 mg/d), and urinary sediment was normal. He received 50 000 IU per week of vitamin D for 3 mo, and 25(OH)D increased to 36.6 ng/mL. Urinary calcium was 142 mg/d, PTH was 46.7 pg/mL, and serum calcium was 9.6 mg/dL. No renal crisis was perceived. He asked for an alternative form of medication since he usually would forget to take drugs. Vitamin D in a single dose of 600 000 IU intramuscular was prescribed. He was asked to increase water intake to 2 to 3 L/d. After 3 mo his 25(OH)D was 75.0 ng/mL, serum calcium was 9.2 mg/dL, urinary calcium was 148 mg/d, and PTH was 38.7 pg/mL. He had no episodes of lithiasis renal crisis. Folic acid and methylcobalamin were added, and homocysteine normalized. At follow-up 3 y later, the patient was asymptomatic, cardiologic evaluation was stable without any other renal lithiasis crises, 25(OH)D continued to be normal at 62 ng/mL, and he received a megadose of vitamin D every 6 mo. Renal ultrasound revealed only microlithiasis. The second case reports a 52-year-old man with a long-term history of renal lithiasis experienced since he was 30 y old, with three renal crisis episodes. He was treated with an extracorporeal shock wave three times. Laboratory tests demonstrated 25(OH)D 18 ng/mL, normal biochemistry, total serum calcium of 10.2 mg/dL, 24-h urinary calcium of 154 mg/d, and normal urinary sediment. He received 50 000 IU per week of 25(OH)D for 3 mo, and 25(OH)D increased to 40.3 ng/mL. Urinary calcium was 167 mg/d, PTH was 35.3 pg/mL, and serum calcium was 10.1 mg/dL. No renal crisis was perceived. He asked for an alternative form of medication, and vitamin D in a single dose of 600 000 IU intramuscular was prescribed. He was asked to increase water intake to 2 to 3 L/d. After 3 mo, his 25(OH)D was 82.0 ng/mL, serum calcium was 9.6 mg/dL, urinary calcium was 175 mg/d, and PTH was 35.3 pg/mL. The renal ultrasound was unchanged. He had no episodes of lithiasis renal crisis. At follow-up 4 y later, the patient was asymptomatic without any other renal lithiasis crises, a renal ultrasound revealed a reduction of calculi size to microlithiasis, 25(OH)D continues normal, and he received a megadose of this vitamin every 4 mo.

CONCLUSION

To the best of our knowledge, this is the first description of a megadose of vitamin D used in patients with nephrolithiasis. Furthermore, this shows the safety of this strategy in patients without hypercalciuria.

Vitamin D in 2020: An Old Pro-Hormone with Potential Effects beyond Mineral Metabolism

Vitamin D is not a vitamin but a pro-hormone. [...].