Vitamine D : un acteur majeur en santé ?

Vitamin D status in preschool children in Algeria

It is well established today that an optimal vitamin D intake plays a crucial role in the constitution of optimal osseous mass during childhood, and hence in the prevention of the osteoporosis in adults. The prevalence of the vitamin D deficiency is increasing globally and Algeria is no exception in this regard. Our study is the first to be carried out with healthy children of preschool age in North Africa.

AIMS

The study aimed to evaluate the vitamin D status of a pediatric population, during all four seasons of the year, living in the north of Algeria, as well as to estimate the prevalence of vitamin D deficiency, identifying the potential risk factors.

MATERIAL AND METHODS

This was an analytic and cross-sectional study carried out between March 2014 and March 2016 with healthy preschool infants from an urban environment in the town of Hussein Dey. A total of 1016 infants aged 9-72 months were included during this period. The consensual threshold value was 20ng/mL.

RESULTS

The sex ratio was of 1.47 (535 boys/481 girls) and the average age of the children was 36.5±1.79 months. The daily average calcium ratio was 395±23 mg/with food contributions in vitamin D at an estimated average of 164 UI/day (4.1μg/day). The average concentration of the total 25-OHD for all four seasons of the year was 18.6±10.4ng/mL with an average rate of parathyroid hormone (PTH) of 30.9±14.6pg/mL. There was a highly significant inverse correlation between the serum level of vitamin D and PTH (r=-0.57; P=0.0001), the point of inflection was situated at 34.1ng/mL. The prevalence of vitamin D deficiency follows a seasonal variation that is statistically significant (P=0.0001), and the prevalence is higher during the autumn-winter period. The risk factors identified by multiple logistic regression were autumn-winter season (OR: 7; 95% CI: 3-11; P=0.001), age less than 24 months (OR: 3.8; 95% CI: 3.4-4.4; P=0.0001), high body mass index (OR: 2; 95% CI: 1.2-3.2; P=0.3), darker skin pigmentation (OR: 2.8; 95% CI: 2.2-5.2; P=0.001), duration of sunlight exposure less than 15min (OR: 6.1; 95% CI: 3.6-10.2; P=0.0001), low socioeconomic status (OR: 3.9; 95% CI: 1.5-4.3; P=0.01), calcium intake lower than 500 mg/day (OR: 2.5; 95% CI: 1.8-6; P=0.001), and a weekly dietary intake of vitamin D lower than 200 UI (OR: 2.6; 95% CI: 1.6-4.2; P=0.02).

DISCUSSION

No studies have been conducted in north Africa or Algeria concerning healthy preschool children; however, this population has a rapid growth rate and deserves special attention. The prevalence of vitamin D deficiency in the children of this study was higher than that reported in studies of children of the same age living in Europe or America, despite the fact that Algeria is closer to the equator (36° latitude north).

CONCLUSION

The changes experienced by Algerian society and the shorter exposure of the population to the sun call for more efforts regarding the detection and treatment of vitamin D deficiency, as well as an update of the vitamin D supplementation schedule.

Hypovitaminosis D in migrant children in Switzerland: a retrospective study

Cholecalciferol (vitamin D₃) is essentially known for its role in the phosphocalcic metabolism and its associated pathologies, such as rickets. In Switzerland, 35 to 50% of children are vitamin D deficient. Due to skin colour, poor nutrition, living conditions and cultural practices, migrant population is particularly at risk. Our aim is to attest the prevalence of hypovitaminosis D in children arriving in Switzerland. We retrospectively assessed 528 children's vitamin D status and parathyroid hormone, phosphate and calcium levels between 2015 and 2018 by electrochemiluminescence and spectrophotometry. Cholecalciferol was considered insufficient under 50 nmol/L and severely deficient below 25 nmol/L. Seventy-three percent of children showed hypovitaminosis D and 28% had a severe deficiency. Highest prevalence of deficiency was found in children from Eastern Mediterranean (80%) and African regions (75%). Severe deficiency was more prevalent in the South East Asian (39%) and Eastern Mediterranean regions (33%) and more frequent in females. Deficiency was more frequent and more severe in winter. Hypovitaminosis D increased with age. Two children presented with all three biological manifestations associated to severe hypovitaminosis D (hyperparathyroidism, hypocalcaemia and hypophosphatemia).Conclusion: A majority of migrant children presented with hypovitaminosis D. They should be supplemented to prevent complications. A strategy could be to supplement all children at arrival and during wintertime without regular vitamin D level checks. What is Known: Hypovitaminosis D is frequent in children and can lead to bone-related complications. Migrant children are particularly at risk of deficiency. What is New: Three-quarters of migrant children evaluated at our migrant clinic in Geneva's children hospital are deficient in vitamin D, one third severely. A strategy to correct the deficiency would be to supplement all migrant children at arrival and in winter.

Intermittent cholecalciferol supplementation in children and teenagers followed in pediatric nephrology: data from a prospective single-center single-arm open trial

Vitamin D deficiency is frequent in pediatric nephrology. The 2017 European guidelines recommend keeping 25OH vitamin D (25-D) levels within the 75-120 nmol/L range, ideally with daily supplementation. Intermittent supplementation with D3 has also been proposed. We aimed to assess the influence of our local protocol of intermittent vitamin D supplementation on the evolution of 25-D levels between baseline and 2 months. VITATOL is a prospective single-center study performed in our tertiary unit in children and teenagers followed for chronic kidney disease (CKD), kidney transplantation, or stable chronic nephrotic syndrome with 25-D levels below 75 nmol/L. Intermittent oral cholecalciferol (100,000 IU) was administered depending on baseline vitamin D levels and body weight. The primary outcome was the change in 25-D levels between baseline and 2 months. Secondary outcomes were the evolution of the main mineral biomarkers. Thirty-seven patients were included. Two months after beginning supplementation, corresponding to a median(min-max) of 46 (14-79) days after the last dose of vitamin D, 25-D levels increased from 50 to 76 nmol/L (p < 0.001), 18 patients having 25-D levels within the target range and 2 above. All patients displayed 25-D levels above 50 nmol/L. There were no significant changes in phosphate, PTH, alkaline phosphatase, and FGF23 levels before and after supplementation. Calcium levels increased from 2.39 to 2.44 mmol/L (p = 0.017), but no differences in calciuria and urinary calcium/creatinine ratio were observed.Conclusion: This vitamin D supplementation protocol using intermittent moderate doses of cholecalciferol seems efficient in 54% of cases, with neither significant overdose nor hypercalciuria. What is Known: • Vitamin D deficiency is frequent in pediatric nephrology. • The 2017 European guidelines recommend keeping 25OH vitamin D levels within the 75-120 nmol/L range ideally with daily supplementation, but intermittent supplementation with D3 has also been proposed. What is New: • We assessed the influence of a local protocol of intermittent vitamin D supplementation on the evolution of 25-D levels between baseline and 2 months in children and teenagers followed in pediatric nephrology. • The intermittent cholecalciferol supplementation protocol seems efficient in 54% of cases, with neither significant overdose nor hypercalciuria.

Cord-blood vitamin D level and night sleep duration in preschoolers in the EDEN mother-child birth cohort

OBJECTIVE

Deficiency in 25-hydroxyvitamin D (25OHD) has been associated with sleep disorders in adults. Only three cross-sectional studies were performed in children; which showed an association between 25OHD deficiency and both obstructive sleep apnea syndrome and primary snoring. No longitudinal study has been performed in children from the general population. We analyzed the association between cord-blood vitamin D levels at birth and night-sleep duration trajectories for children between 2 and 5-6 years old in a non-clinical cohort.

METHOD

We included 264 children from the French EDEN mother-child birth-cohort with cord-blood 25OHD level determined by radio-immunoassay at birth, and night-sleep trajectories for children between 2 and 5-6 years old obtained by the group-based trajectory modeling method. Associations between 25OHD and sleep trajectories were assessed by multinomial logistic regression adjusted for maternal and child characteristics.

RESULTS

The trajectories short sleep (<10h30/night), medium-low sleep (10h30-11h00/night), medium-high sleep (≈11h30/night), long sleep (≥11h30/night) and changing sleep (decreased from ≥11h30 to 10h30-11h00/night) represented 5%, 46%, 37%, 4% and 8% of the children, respectively. The mean 25OHD level was 19 ng/ml (SD = 11, range 3-63). It was 12 (SD = 7), 20 (SD = 11), 19 (SD = 10), 14 (SD = 7) and 16 (SD = 8) ng/ml for children with short, medium-low, medium-high, long and changing sleep trajectories, respectively. On adjusted analysis, for each 1-ng/ml decrease in 25OHD level, the odds of belonging to the short sleep versus medium-high sleep trajectory was increased (odds ratio = 1.12, 95% confidence interval [1.01-1.25]). We found no other significant association between 25OHD level and other trajectories.

CONCLUSION

A low 25OHD level at birth may be associated with an increased probability of being a persistent short sleeper in preschool years. These results need confirmation.

[Vitamin D supplementation: not too much, not too little!]

Vitamin D deficiency is common in the general population and even more frequent in patients with chronic diseases. The prevention of rickets with native vitamin D supplementation is one of the oldest and most effective prophylactic measures ever reported in medicine, leading to an almost complete eradication of vitamin D-deficient rickets in developed countries. We report on two children with vitamin D abnormalities: the first, 10-year-old child developed rickets without any vitamin D supplementation despite different risk factors (autism, ethnicity, nutritional problems, chronic antiepileptic therapies). In contrast, the second, 8-month-old child received double doses of native vitamin D from birth for several months and was referred for acute and symptomatic hypercalcemia. As such, vitamin D supplementation must follow specific rules: neither too much nor too little! We also discuss the emergence of "new" genetic diseases such as mutations in the 24-hydroxylase (CYP24A1) gene inducing neonatal hypercalcemia and nephrocalcinosis: we believe that before prescribing conventional vitamin D supplementation as recommended by the national guidelines, pediatricians should quickly rule out a potential genetic abnormality in phosphate/calcium metabolism (namely a history of lithiasis or hypercalcemia) that would lead to further biological investigations.

[Vitamin D deficiency rickets complicating Dorfman-Chanarin syndrome]

Vitamin D deficiency rickets remains a public health issue in many parts of the world. In France, this diagnosis has almost disappeared since 1992 with routine vitamin D supplementation for children. Therefore, it is more difficult for doctors to identify risk factors and early signs of this disease. In this article, we report a rickets diagnosis acquired by vitamin D deficiency in a child who presented with the onset of a genu valgum and difficulty walking at the age of 9½ years. This patient was a Comorian child followed up from his birth for Dorfman-Chanarin syndrome. Dorfman-Chanarin syndrome is a rare disease, with about 80 cases reported in the literature. It belongs to the group of neutral lipid storage diseases (NLSD) characterized especially on the skin by ichthyosis. This child presented risk factors for vitamin D deficiency (dark skin color, prolonged and exclusive breastfeeding, premature end of supplementation, and particularly severe ichthyosis) that should have alerted us to the risk of vitamin D deficiency and the need for supplementation. This case highlights the importance of vitamin D, especially if there are risk factors such as ichthyosis, and the need to remain watchful in monitoring all chronic diseases.

Environmental factors in multiple sclerosis

Although multiple sclerosis (MS) is recognized as a disorder involving the immune system, the interplay of environmental factors and individual genetic susceptibility seems to influence MS onset and clinical expression, as well as therapeutic responsiveness. Multiple human epidemiological and animal model studies have evaluated the effect of different environmental factors, such as viral infections, vitamin intake, sun exposure, or still dietary and life habits on MS prevalence. Previous Epstein-Barr virus infection, especially if this infection occurs in late childhood, and lack of vitamin D (VitD) currently appear to be the most robust environmental factors for the risk of MS, at least from an epidemiological standpoint. Ultraviolet radiation (UVR) activates VitD production but there are also some elements supporting the fact that insufficient UVR exposure during childhood may represent a VitD-independent risk factor of MS development, as well as negative effect on the clinical and radiological course of MS. Recently, there has been a growing interest in the gut-brain axis, a bidirectional neuro-hormonal communication system between the intestinal microbiota and the central nervous system (CNS). Indeed, components of the intestinal microbiota may be pro-inflammatory, promote the migration of immune cells into the CNS, and thus be a key parameter for the development of autoimmune disorders such as MS. Interestingly most environmental factors seem to play a role during childhood. Thus, if childhood is the most fragile period to develop MS later in life, preventive measures should be applied early in life. For example, adopting a diet enriched in VitD, playing outdoor and avoiding passive smoking would be extremely simple measures of primary prevention for public health strategies. However, these hypotheses need to be confirmed by prospective evaluations, which are obviously difficult to conduct. In addition, it remains to be determined whether and how VitD supplementation in adult life would be useful in alleviating the course of MS, once this disease has already started. A better knowledge of the influence of various environmental stimuli on MS risk and course would certainly allow the development of add-on therapies or measures in parallel to the immunotherapies currently used in MS.

Beyond mineral metabolism, is there an interplay between FGF23 and vitamin D in innate immunity?

Fibroblast growth factor 23 (FGF23) is an "endocrine" FGF acting in the kidney as a phosphaturic hormone and a suppressor of active vitamin D, through an inhibition of the 1α hydroxylase and a stimulation of the 24 hydroxylase. Beyond its well-known effects on the bone/kidney/parathyroid axis and its deregulation during chronic kidney disease (CKD), recent evidence has revealed its direct systemic effects on cardiovascular health. In the meantime, studies have highlighted the health implications for vitamin D inside and outside CKD that also extend beyond its classical actions on mineral homeostasis and bone metabolism: vitamin D has indeed been shown to exert pluripotent non-classical effects as a modulator of immune function in monocytes, mainly through the stimulation of the antimicrobial cathelicidin. The aim of this review is to provide new insights on the interplay between FGF23 and vitamin D in innate immunity in the context of CKD.

Postconcussion syndrome: a review of pathophysiology and potential nonpharmacological approaches to treatment

The incidence of all-cause concussions in the United States is estimated to range from 1.6 to 3.8 million annually, with the reported number of sport- or recreation-related concussions increasing dramatically, especially in youth sports.(1,2) Additionally, the use of roadside bombs in Iraq and Afghanistan has propelled the incidence of concussion and other traumatic brain injuries to the highest levels ever encountered by the US military. As a result, there has also been a marked increase in postconcussion syndrome (PCS) and the associated cognitive, emotional, and memory disabilities associated with the condition. Unfortunately, however, there have been no significant advancements in the understanding or treatment of PCS for decades. The current management of PCS mainly consists of rest, reduction of sensory inputs, and treating symptoms as needed. Recently, researchers investigating the underlying mechanisms of PCS have proposed that activation of the immune inflammatory response may be an underlying pathophysiology that occurs in those who experience prolonged symptoms after a concussion. This article reviews the literature and summarizes the immune inflammatory response known as immunoexcitotoxicity. This article also discusses the use of nonpharmacological agents for the management of PCS that directly address this underlying mechanism.

The consequences of chronic kidney disease on bone metabolism and growth in children

Growth retardation, decreased final height and renal osteodystrophy (ROD) are common complications of childhood chronic kidney disease (CKD), resulting from a combination of abnormalities in the growth hormone (GH) axis, vitamin D deficiency, hyperparathyroidism, hypogonadism, inadequate nutrition, cachexia and drug toxicity. The impact of CKD-associated bone and mineral disorders (CKD-MBD) may be immediate (serum phosphate/calcium disequilibrium) or delayed (poor growth, ROD, fractures, vascular calcifications, increased morbidity and mortality). In 2012, the clinical management of CKD-MBD in children needs to focus on three main objectives: (i) to provide an optimal growth in order to maximize the final height with an early management with recombinant GH therapy when required, (ii) to equilibrate calcium/phosphate metabolism so as to obtain acceptable bone quality and cardiovascular status and (iii) to correct all metabolic and clinical abnormalities that can worsen bone disease, growth and cardiovascular disease, i.e. metabolic acidosis, anaemia, malnutrition and 25(OH)vitamin D deficiency. The aim of this review is to provide an overview of the mineral, bone and vascular abnormalities associated with CKD in children in terms of pathophysiology, diagnosis and clinical management.

Vitamin D: still a topical matter in children and adolescents. A position paper by the Committee on Nutrition of the French Society of Paediatrics

The aims of the present position paper by the Committee on Nutrition of the French Society of Paediatrics were to summarize the recently published data on vitamin D in infants, children and adolescents, i.e., on metabolism, physiological effects, and requirements and to make recommendations on supplementation after careful review of the evidence. Scientific evidence indicates that calcium and vitamin D play key roles in bone health. The current evidence, limited to observational studies, however, does not support other benefits for vitamin D. More targeted research should continue, especially interventional studies. In the absence of any underlying risk of vitamin D deficiency, the recommendations are as follows: pregnant women: a single dose of 80,000 to 100,000 IU at the beginning of the 7th month of pregnancy; breastfed infants: 1000 to 1200 IU/day; children less than 18 months of age, receiving milk supplemented with vitamin D: an additional daily dose of 600 to 800 IU; children less than 18 months of age receiving milk not supplemented with vitamin D: daily dose of 1000 to 1200 IU; children from 18 months to 5 years of age: 2 doses of 80,000 to 100,000 IU every winter (November and February). In the presence of an underlying risk of vitamin D deficiency (dark skin; lack of exposure of the skin to ultraviolet B [UVB] radiation from sunshine in summer; skin disease responsible for decreased exposure of the skin to UVB radiation from sunshine in summer; wearing skin-covering clothes in summer; intestinal malabsorption or maldigestion; cholestasis; renal insufficiency; nephrotic syndrome; drugs [rifampicin; antiepileptic treatment: phenobarbital, phenytoin]; obesity; vegan diet), it may be justified to start vitamin D supplementation in winter in children 5 to 10 years of age as well as to maintain supplementation of vitamin D every 3 months all year long in children 1 to 10 years of age and in adolescents. In some pathological conditions, doses of vitamin D can be increased. If necessary, the determination of 25(OH) vitamin D serum concentration will help determine the level of vitamin D supplementation.

[FGF23 and Klotho: the new cornerstones of phosphate/calcium metabolism]

Since its first description as a phosphaturic agent in the early 2000s, fibroblast growth factor 23 (FGF23) has rapidly become the third key player of phosphate/calcium metabolism after PTH and vitamin D. FGF23 is a protein synthesized by osteocytes that acts mainly as a phosphaturic factor and a suppressor of 1α hydroxylase activity in the kidney. It inhibits the expression of type IIa and IIc sodium-phosphate cotransporters on the apical membrane of proximal tubular cells, thus leading to inhibition of phosphate reabsorption. Moreover, it also inhibits 1α hydroxylase activity. These two renal pathways account together for the hypophosphatemic effect of FGF23, but FGF23 has also been recently described as an inhibiting factor for PTH synthesis. Its exact role in bone remains to be defined. A transmembrane protein, Klotho, is an essential cofactor for FGF23 biological activity, but it can also act by itself for calcium and PTH regulation. This paper gives an overview of these recent data of phosphate/calcium physiology, as well as a description of clinical conditions associated with FGF23 deregulation (genetic diseases and chronic kidney disease). As a conclusion, future therapeutic consequences of the FGF23/Klotho axis are discussed.