Pediatric obesity and vitamin D deficiency: a proteomic approach identifies multimeric adiponectin as a key link between these conditions

Association of selected adipokines with vitamin D deficiency in children with inflammatory bowel disease

BACKGROUND

Adipose tissue is significantly involved in inflammatory bowel disease (IBD). Vitamin D can affect both adipogenesis and inflammation. The aim of this study was to compare the production of selected adipokines, potentially involved in the pathogenesis of IBD - adiponectin, resistin, retinol binding protein 4 (RBP-4), adipocyte fatty acid binding protein and nesfatin-1 in children with IBD according to the presence of 25-hydroxyvitamin D (25(OH)D) deficiency.

METHODS

The study was conducted as a case-control study in pediatric patients with IBD and healthy children of the same sex and age. In addition to adipokines and 25(OH)D, anthropometric parameters, markers of inflammation and disease activity were assessed in all participants.

RESULTS

Children with IBD had significantly higher resistin levels regardless of 25(OH)D levels. IBD patients with 25(OH)D deficiency only had significantly lower RBP-4 compared to healthy controls and also compared to IBD patients without 25(OH)D deficiency. No other significant differences in adipokines were found in children with IBD with or without 25(OH)D deficiency. 25(OH)D levels in IBD patients corelated with RBP-4 only, and did not correlate with other adipokines.

CONCLUSIONS

Whether the lower RBP-4 levels in the 25(OH)D-deficient group of IBD patients directly reflect vitamin D deficiency remains uncertain. The production of other adipokines does not appear to be directly related to vitamin D deficiency.

From the Sun to the Cell: Examining Obesity through the Lens of Vitamin D and Inflammation

Obesity affects more than one billion people worldwide and often leads to cardiometabolic chronic comorbidities. It induces senescence-related alterations in adipose tissue, and senescence is closely linked to obesity. Fully elucidating the pathways through which vitamin D exerts anti-inflammatory effects may improve our understanding of local adipose tissue inflammation and the pathogenesis of metabolic disorders. In this narrative review, we compiled and analyzed the literature from diverse academic sources, focusing on recent developments to provide a comprehensive overview of the effect of vitamin D on inflammation associated with obesity and senescence. The article reveals that the activation of the NF-κB (nuclear factor kappa B subunit 1) and NLRP3 inflammasome (nucleotide-binding domain, leucine-rich-containing, pyrin domain-containing-3) pathways through the toll-like receptors, which increases oxidative stress and cytokine release, is a common mechanism underlying inflammation associated with obesity and senescence, and it discusses the potential beneficial effect of vitamin D in alleviating the development of subclinical inflammation. Investigating the main target cells and pathways of vitamin D action in adipose tissue could help uncover complex mechanisms of obesity and cellular senescence. This review summarizes significant findings related to opportunities for improving metabolic health.

Metabolic and Genetic Association of Vitamin D with Calcium Signaling and Insulin Resistance

Various evidences have unveiled the significance of Vitamin D in diverse processes which include its action in prevention of immune dysfunction, cancer and cardiometabolic disorders. Studies have confirmed the function of VD in controlling the expression of approximately nine hundred genes including gene expression of insulin. VD insufficiency may be linked with the pathogenesis of diseases that are associated with insulin resistance (IR) including diabetes as well as obesity. Thus, VD lowers IR-related disorders such as inflammation and oxidative stress. This review provides an insight regarding the molecular mechanism manifesting, how insufficiency of VD may be connected with the IR and diabetes. It also discusses the effect of VD in maintaining the Ca2+ levels in beta cells of the pancreas and in the tissues that are responsive to insulin.

Effect of Vitamin D3 on Chemerin and Adiponectin Levels in Uterus of Polycystic Ovary Syndrome Rats

BACKGROUND

Polycystic ovary syndrome (PCOS) is an endocrine disorder with disrupted uterus structure and function. A positive effect of vitamin D3 (VD3) in female reproduction was observed. Chemerin (RARRES2) and adiponectin (ADIPOQ) are the main adipokines whose levels are altered in PCOS patients. Therefore, the aim of this study was to investigate the impact of VD3 supplementation on RARRES2 and ADIPOQ levels in the uterus of PCOS rats.

METHODS

We analyzed the plasma levels and uterine transcript and protein expression of RARRES2 and ADIPOQ and their receptors (CCRL2, CMKLR1, GPR1, and ADIPOR1 and ADIPOR2, respectively) in rats with letrozole-induced PCOS.

RESULTS

In control animals, VD3 did not change plasma levels of both adipokines, while in PCOS rats supplemented with VD3, they returned to control levels. The expression of RARRES2 and all investigated receptors increased in the uterus of VD3-treated rats; however, the levels of Rarres2 and Gpr1 genes remained unchanged. VD3 supplementation decreased RARRES2, CMKLR1, and GPR1 but increased CCRL2 level to the control value. In the uterus of VD3-treated rats, the transcript and protein levels of ADIPOQ and both receptors ADIPOR1 increased. At the same time, VD3 supplementation induced an increase in Adipoq, Adipor1, and Adipor2 gene expression and restored protein levels to control level values.

CONCLUSIONS

our findings indicate a new mechanism of VD3 action in the uterine physiology of PCOS rats.

The Action of Vitamin D in Adipose Tissue: Is There the Link between Vitamin D Deficiency and Adipose Tissue-Related Metabolic Disorders?

Adipose tissue plays an important role in systemic metabolism via the secretion of adipocytokines and storing and releasing energy. In obesity, adipose tissue becomes dysfunctional and characterized by hypertrophied adipocytes, increased inflammation, hypoxia, and decreased angiogenesis. Although adipose tissue is one of the major stores of vitamin D, its deficiency is detective in obese subjects. In the presented review, we show how vitamin D regulates numerous processes in adipose tissue and how their dysregulation leads to metabolic disorders. The molecular response to vitamin D in adipose tissue affects not only energy metabolism and adipokine and anti-inflammatory cytokine production via the regulation of gene expression but also genes participating in antioxidant defense, adipocytes differentiation, and apoptosis. Thus, its deficiency disturbs adipocytokines secretion, metabolism, lipid storage, adipogenesis, thermogenesis, the regulation of inflammation, and oxidative stress balance. Restoring the proper functionality of adipose tissue in overweight or obese subjects is of particular importance in order to reduce the risk of developing obesity-related complications, such as cardiovascular diseases and diabetes. Taking into account the results of experimental studies, it seemed that vitamin D may be a remedy for adipose tissue dysfunction, but the results of the clinical trials are not consistent, as some of them show improvement and others no effect of this vitamin on metabolic and insulin resistance parameters. Therefore, further studies are required to evaluate the beneficial effects of vitamin D, especially in overweight and obese subjects, due to the presence of a volumetric dilution of this vitamin among them.

Mechanisms Linking Vitamin D Deficiency to Impaired Metabolism: An Overview

Vitamin D deficiency is a common health problem worldwide. Despite its known skeletal effects, studies have begun to explore its extra-skeletal effects, that is, in preventing metabolic diseases such as obesity, hyperlipidemia, and diabetes mellitus. The mechanisms by which vitamin D deficiency led to these unfavorable metabolic consequences have been explored. Current evidence indicates that the deficiency of vitamin D could impair the pancreatic β-cell functions, thus compromising its insulin secretion. Besides, vitamin D deficiency could also exacerbate inflammation, oxidative stress, and apoptosis in the pancreas and many organs, which leads to insulin resistance. Together, these will contribute to impairment in glucose homeostasis. This review summarizes the reported metabolic effects of vitamin D, in order to identify its potential use to prevent and overcome metabolic diseases.

Can vitamin D be considered an adiponectin secretagogue? A systematic review and meta-analysis

There is some evidence for ameliorating effect of vitamin D on glycemic and lipidemic status which are likely to be mediated through other molecules including adiponectin. However, the overall results have been controversial. This study was conducted to evaluate the effect of vitamin D supplementation on serum adiponectin concentration. MEDLINE, PubMed, Embase, Cochrane Library, and Google Scholar were searched and 402 studies were found in a preliminary search. After screening of titles and abstracts nine studies were selected. Pooled data showed no significant effect on adiponectin concentrations (mean difference (MD) 0.37, 95 % CI: -0.1 to 0.87). However, there was a significant effect in a subgroup of participants who had diabetes (MD: 0.03, 95 % CI: 0.00 to 0.05, p = 0.029). The treatment effect on adiponectin concentrations was significant in those trials that used supplementation on a daily basis (MD: 0.03, 95 % CI: 0.00 to 0.05, p = 0.028) and vitamin D plus calcium (MD: 0.04, 95 % CI: 0.01 to 0.07, p = 0.014). The meta-regression revealed a significant association between BMI and age of participants at baseline and the treatment effect (B, -0.144, 95 % CI: -0.276 to -0.011, p = 0.033 and B, -0.043, 95 % CI: -0.075 to -0.012, p = 0.006). The results of this meta-analysis study indicates that vitamin D may be considered an adiponectin secretagogue in subjects with diabetes and this effect may be potentiated if vitamin D intake is on daily basis and in combination with calcium but can be weakened by increasing BMI.

Vitamin D status and healthy Egyptian adolescents: Where do we stand?

Vitamin D deficiency is a worldwide public health problem. Low vitamin D and its consequences among children and adolescents could be considered as one of the most important health-related problems. This study aimed to estimate the prevalence of vitamin D deficiency in healthy Egyptian adolescents and investigate factors associated with vitamin D status.A cross-sectional study was conducted on 572 school children (270 males and 302 females) aged 14 to 18 years, who were randomly selected from high schools in one governorate in Egypt. Data were collected through a self-administered questionnaire. Vitamin D level, serum calcium, phosphorus, alkaline phosphates were measured.Vitamin D deficiency was almost present in all the studied Egyptian healthy adolescents (99%), 94.8% had vitamin D deficiency and 4.2% had vitamin D insufficiency. Girls had a higher prevalence of vitamin D deficiency than boys. There was a significant association between lack of physical activity, sun exposure, and vitamin D deficiency.Vitamin D deficiency and insufficiency are highly prevalent. In sunny countries, the special pattern of conservative clothing and the lack of outdoor physical activity might be the underlying factors for the high prevalence in females. Vitamin D supplementation seems to be mandatory to halt the problem.

The Moderate Correlation Between 25(OH)D Serum and Saliva in Healthy People with Low Vitamin D Intake

Purpose

The routine examination of vitamin D levels is carried out by checking serum 25(OH)D levels, while serum 1.25(OH)D levels are less frequently utilized. The proposition that testing for salivary vitamin D can show a correlation with serum levels in healthy people is questionable, especially with low vitamin D intake. This study aimed to find the correlation between vitamin D levels, which were assessed as 25(OH)D and 1.25(OH)D in saliva, and serum 25(OH)D and 1.25(OH)D levels in people with low vitamin D intake.

Patients and Methods

This study is a cross-sectional study involving healthy men and women, aged 18–60 years, carried out from August to November, 2020, in North Sumatra Province, Indonesia. The parameters studied were the 25(OH)D and 1.25(OH)D levels in saliva and serum, and vitamin D intake. The statistical analysis used was the Spearman correlation test, performed to determine the correlation between each parameter.

Results

This study involved 56 study subjects, who were rural adults (male or female) with a 78.6% deficiency in 25(OH)D found by examining saliva, and a 76.8% deficiency found by examining the serum. All of the subjects were categorized as having low vitamin D intake (less than 15 micrograms per day). The analysis showed a moderate correlation between levels of saliva 25(OH)D and serum 25(OH)D (p = 0.424), and a weak correlation between levels of saliva 1.25(OH)D and serum 25(OH)D (p = 0.339).

Conclusion

In people with low vitamin D intake, there was a moderate correlation between serum 25(OH)D and saliva, but a weak correlation was found in the 1.25(OH)D assay. The use of saliva 25(OH)D levels to detect 25(OH)D in the circulation is a possible non-invasive alternative to serum testing.

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Molecular mechanisms from insulin-mimetic effect of vitamin D: treatment alternative in Type 2 diabetes mellitus

Diabetes mellitus is a complex and multifactorial disease with a global prevalence that exceeds 425 million people. Type 2 diabetes mellitus (T2DM) is characterized by a state of insulin resistance, which leads to metabolic alterations that aggravate the state of health of people. Vitamin D deficiency appears to play an important role in the triggering mechanisms of insulin resistance. In this review, an analysis is made of the biochemical mechanisms associated with the insulin-mimetic effect of vitamin D, its supplementation being a possible nutritional strategy for the T2DM treatment. The current scientific evidence is extensive regarding the dose of vitamin D used for an insulin-mimetic effect. However, clinical trials and systematic reviews show statistical differences on glucose, insulin, and glycated hemoglobin levels of patients with T2DM, associated with activation mechanisms of transcription factors related to genes of the glucide metabolism and the insulin receptor, and the regulation of intracellular Ca2+ insulin concentrations. Likewise, an indirect mechanism associated with antioxidant and anti-inflammatory effects has been shown that also leads to sensitivity to the insulin receptor. The use of a specific dose of vitamin D could be an effective alternative in the T2DM treatment, which would reduce the risk of complications derived from hyperglycemia.

Update on the Crosstalk Between Adipose Tissue and Mineral Balance in General Population and Chronic Kidney Disease

Adipose tissue is nowadays considered as a major endocrine organ, which apart from controlling lipid metabolism, displays a significant role in energy expenditure, food intake and in the regulation of various systemic physiological processes. Adipose derived pro-inflammatory cytokines and adipokines, particularly leptin and adiponectin, provide inter-communication of adipose tissue with various metabolic pathways, ultimately resulting in a complex network of interconnected organ systems. Recent clinical and experimental research has been focused on exploring the direct interaction between adipokine profile and elements of mineral metabolism, including parathormone (PTH), fibroblast growth factor-23 (FGF23) and calcitriol. The emerging crosstalk between adipose tissue and calcium and phosphorus homeostasis suggests that metabolic disorders from one system may directly affect the other and vice versa. It is current knowledge that fat metabolism disturbance, commonly encountered in obese individuals, influences the expression of calciotriopic hormones in general population, while various clinical trials attempting to successfully achieve body fat loss by modulating mineral profile have been published. In chronic kidney disease (CKD) state, there is an increasing evidence suggesting that mineral disorders, influence adipose tissue and linked endocrine function. On the contrary, the impact of disturbed fat metabolism on CKD related mineral disorders has been also evocated in clinical studies. Recognizing the pathogenetic mechanisms of communication between adipose tissue and mineral balance is critical for understanding the effects of metabolic perturbations from the one system to the other and for identifying possible therapeutic targets in case of disrupted homeostasis in one of the two connected systems. To that end, this review aims to enlighten the recent advances regarding the interplay between mineral metabolism, fat mass and adipokine profile, based on in vitro, in vivo and clinical studies, in general population and in the course of CKD.

Measurement of Serum Chemerin, Oxidized LDL, and Vitamin D Levels in Prader–Willi Syndrome: A Cross-Sectional Study in Pediatric Egyptian Patients

Prader–Willi syndrome (PWS) is the commonest genetic cause of obesity. Oxidative stress and chronic low-grade inflammation play a crucial role in the pathogenesis of obesity. Alterations of vitamin D (25-OHD) levels are commonly encountered with obesity. The aim of this study was to analyze serum chemerin, oxidized low-density lipoprotein (ox-LDL), and 25-OHD values in pediatric PWS patients in comparison with obese healthy children and nonobese control groups, highlighting possible correlations with body mass index (BMI) and obesity. Twenty-six PWS Egyptian patients and 26 obese healthy individuals referred to the outpatient clinic of the Clinical Genetics Department, National Research Centre, Cairo, Egypt, and 20 control patients with matching age and sex were enrolled in the study. Patients were clinically diagnosed and confirmed by routine cytogenetic and fluorescence in-situ hybridization analysis. Anthropometric measurements were performed, and BMI was calculated by weight/height2 (kg/m2), and BMI z score was also determined. Serum chemerin, ox-LDL, and vitamin D were determined by enzyme-linked immunosorbent assay. Chemerin levels, which reflected chronic inflammation, were significantly elevated as compared with obese and nonobese controls (p ≤ 0.0001). Concerning oxidative damage, children with PWS showed higher Ox-LDL levels compared with obese and nonobese controls (p < 0.0001). Vitamin D levels were significantly lower in PWS patients compared with obese and nonobese controls (p ≤ 0.0001). Our data showed that obesity in PWS is associated with oxidative stress and chronic low-grade inflammation. Ox-LDL is a good indicator of oxidative stress, and chemerin could be used as a biomarker for the chronic inflammatory state. Furthermore, vitamin D supplementation is recommended in PWS patients

The Molecular Mechanisms by Which Vitamin D Prevents Insulin Resistance and Associated Disorders

Numerous studies have shown that vitamin D deficiency is very common in modern societies and is perceived as an important risk factor in the development of insulin resistance and related diseases such as obesity and type 2 diabetes (T2DM). While it is generally accepted that vitamin D is a regulator of bone homeostasis, its ability to counteract insulin resistance is subject to debate. The goal of this communication is to review the molecular mechanism by which vitamin D reduces insulin resistance and related complications. The university library, PUBMED, and Google Scholar were searched to find relevant studies to be summarized in this review article. Insulin resistance is accompanied by chronic hyperglycaemia and inflammation. Recent studies have shown that vitamin D exhibits indirect antioxidative properties and participates in the maintenance of normal resting ROS level. Appealingly, vitamin D reduces inflammation and regulates Ca²⁺ level in many cell types. Therefore, the beneficial actions of vitamin D include diminished insulin resistance which is observed as an improvement of glucose and lipid metabolism in insulin-sensitive tissues.

Delta-like 1 (DLK1) is a possible mediator of vitamin D effects on bone and energy metabolism

Vitamin D effects on bone and mineral metabolism are well recognized, and its anti-inflammatory actions are gaining particular interest. Delta-like 1 (DLK1) is a protein, expressed by progenitor cells of different tissues, and increases the size of progenitor cell population during the inflammatory phase of tissue regeneration. DLK1 also plays a role in energy metabolism as it antagonizes insulin signaling in bone. In this one-year randomized clinical trial of overweight elderly individuals that received either 600 or 3750 IU daily cholecalciferol we assessed the effect of vitamin D supplementation on pre-specified secondary outcomes: DLK1, leptin, adiponectin, C-Reactive Protein (CRP) and Vascular Cell Adhesion Molecule (VCAM). We also examined correlations between DLK1 and bone (BMD, bone markers), fat (adipokines, body composition), insulin sensitivity and inflammatory markers. Multivariate analyses were conducted to further explore these associations. Overall, there was a significant increase in serum DLK1 and leptin and a decrease in VCAM, but no change in CRP, after 12 months of vitamin D supplementation. DLK1 was negatively correlated with BMD and positively correlated with bone markers, associations that persisted after adjusting for age, gender and BMI. DLK1 was also positively associated with indices of insulin resistance and negatively with indices of insulin sensitivity. Correlations between DLK1 and fat parameters, such as adipokines, and DXA derived fat mass were less consistent. There were no correlations between DLK1 and inflammatory markers. In conclusion, twelve months supplementation of vitamin D3 increased serum DLK1. DLK1 was negatively associated with indices of bone health and fuel metabolism, and with 1,25(OH)2D levels. Similar to the role of DLK1 in animal models, our findings support the hypothesis that DLK1 can be targeted to regulate bone and energy metabolism and develop drugs to improve BMD and insulin sensitivity. However, further studies are needed to explore the role of DLK1 and its relationship to vitamin D metabolites in vivo.

Systemic vitamin intake impacting tissue proteomes

The kinetics and localization of the reactions of metabolism are coordinated by the enzymes that catalyze them. These enzymes are controlled via a myriad of mechanisms including inhibition/activation by metabolites, compartmentalization, thermodynamics, and nutrient sensing-based transcriptional or post-translational regulation; all of which are influenced as a network by the activities of metabolic enzymes and have downstream potential to exert direct or indirect control over protein abundances. Considering many of these enzymes are active only when one or more vitamin cofactors are present; the availability of vitamin cofactors likely yields a systems-influence over tissue proteomes. Furthermore, vitamins may influence protein abundances as nuclear receptor agonists, antioxidants, substrates for post-translational modifications, molecular signal transducers, and regulators of electrolyte homeostasis. Herein, studies of vitamin intake are explored for their contribution to unraveling vitamin influence over protein expression. As a body of work, these studies establish vitamin intake as a regulator of protein abundance; with the most powerful demonstrations reporting regulation of proteins directly related to the vitamin of interest. However, as a whole, the field has not kept pace with advances in proteomic platforms and analytical methodologies, and has not moved to validate mechanisms of regulation or potential for clinical application.

Changes of circulating neuregulin 4 and its relationship with 25-hydroxy vitamin D and other diabetic vascular complications in patients with diabetic peripheral neuropathy

BACKGROUND

Neuregulin 4 (Nrg4) is a novel neurotrophic adipokine associated with the development of diabetic peripheral neuropathy (DPN), however, the pathological mechanism remains poorly understood. The purpose of our study was to investigate the association of circulating Nrg4 with DPN and 25-hydroxy vitamin D [25(OH)D], a multifunctional secosteroid hormone that regulates other neurotrophic factors and adipokines gene expression, and other diabetic vascular complications.

METHODS

Circulating Nrg4 levels were measured with an ELISA kit in 164 newly diagnosed type 2 diabetes mellitus (nT2DM) patients. The relationship between circulating Nrg4 and DPN and other parameters was analyzed.

RESULTS

Circulating Nrg4 levels were significantly lower in nT2DM patients with DPN than those without, and subjects in the highest quartile of circulating Nrg4 had significantly lower vibration perception threshold (VPT), the prevalence of DPN, the proportion of persons with VPT > 25 V, and significantly higher circulating 25(OH)D (all P < 0.01). Moreover, circulating Nrg4 was positively and independently associated with 25(OH)D, and was negatively with VPT (P < 0.01 or P < 0.05), but showed no associations with the prevalence of peripheral arterial disease, diabetic nephropathy, and diabetic retinopathy (all P > 0.05). Additionally,the prevalence of DPN and risk of DPN development were progressively decreased with increasing circulating Nrg4 quartiles, independently of potential confounding factors.

CONCLUSIONS

These data demonstrate that decreased levels of circulating Nrg4 might lead to the development of DPN through its close interaction with circulating 25(OH)D not with other diabetic vascular complications. Further prospective studies are needed to identify our findings in these populations.

The relationship between vitamin D level and hepatosteatosis in obese children

OBJECTIVE:

The increasing incidence of obesity in children is a significant risk factor for nonalcoholic fatty liver disease and obesity-associated morbidity. In the present study, we aimed to explore the correlation between Vitamin D level and hepatosteatosis in obese children.

METHODS:

A total of 110 children aged 10–16 years who presented to pediatric endocrinology outpatient clinic for obesity were enrolled. The study was completed in a single season between September and November. Hepatosteatosis was diagnosed by ultrasonography. The patients were grouped into two groups: Group 1 comprised patients with hepatosteatosis and Group 2 consisted of patients without hepatosteatosis. 25 hydroxy (25-OH) Vitamin D levels were compared between patients with and without hepatosteatosis.

RESULTS:

No statistically significant difference was observed between 25-OH Vitamin D levels of patients with and without hepatosteatosis. When the effects of age and sex were kept constant, there was no significant correlation between Vitamin D level and aspartate aminotransferase, alanine aminotransferase, and body mass index values.

CONCLUSION:

Unlike the results of the previous studies, we were unable to detect any significant difference between Vitamin D levels of obese patients with and without hepatosteatosis. We think that obesity, rather than Vitamin D status, that is, in fact, independently associated with nonalcoholic fatty liver disease. Larger studies are needed to investigate the impact of Vitamin D in children with obesity with hepatosteatosis.

Plasma proteomics and the paediatric patient

INTRODUCTION

Plasma proteomics has been extensively utilized for studies that investigate various disease settings (e.g. cardiovascular disease), as well as to monitor the effect of pharmaceuticals on the plasma proteome (e.g. chemotherapy). However, plasma proteomic studies focusing on children represent a very small proportion of the plasma proteomic studies completed to date. Early disease detection and prevention is critical in pediatrics, as children must live with the disease outcomes for many years and often carry negative outcomes into adulthood. Pediatrics represents an area of plasma proteomics that is about to undergo a significant expansion. Areas covered: This review is based on a PubMed search focusing on five keywords that are plasma, biomarkers, pediatric, proteomics, and children. It is a comprehensive summary of plasma proteomic studies specific to the pediatric patient and discusses aspects such as the clinical setting, sample size, methodological approaches and outlines the significance of the findings. Expert commentary: Plasma proteomics is expanding significantly as a result of major advancements in proteomic technology. This is in synergy with the growing focus on true early disease detection and prevention in early life. We are about to see a new era of advanced medical science built from pediatric proteomics.

Analysis of Association between Vitamin D Deficiency and Insulin Resistance

Recent evidence revealed extra skeleton activity of vitamin D, including prevention from cardiometabolic diseases and cancer development as well as anti-inflammatory properties. It is worth noting that vitamin D deficiency is very common and may be associated with the pathogenesis of insulin-resistance-related diseases, including obesity and diabetes. This review aims to provide molecular mechanisms showing how vitamin D deficiency may be involved in the insulin resistance formation. The PUBMED database and published reference lists were searched to find studies published between 1980 and 2019. It was identified that molecular action of vitamin D is involved in maintaining the normal resting levels of ROS and Ca2+, not only in pancreatic β-cells, but also in insulin responsive tissues. Both genomic and non-genomic action of vitamin D is directed towards insulin signaling. Thereby, vitamin D reduces the extent of pathologies associated with insulin resistance such as oxidative stress and inflammation. More recently, it was also shown that vitamin D prevents epigenetic alterations associated with insulin resistance and diabetes. In conclusion, vitamin D deficiency is one of the factors accelerating insulin resistance formation. The results of basic and clinical research support beneficial action of vitamin D in the reduction of insulin resistance and related pathologies.

Fetuin B links vitamin D deficiency and pediatric obesity: Direct negative regulation by vitamin D

Vitamin D (VD) deficiency (VDD) correlates to obesity, with VD a recognized mediator of metabolic diseases. From a previous proteomic study identifying adiponectin as a link between VDD and pediatric obesity, herein we analysed another protein (SSP2301) increased with VDD. A focused 2D-electrophoretic analysis identified 4 corresponding plasma proteins, with one predicted to be fetuin B (FETUB). FETUB was studied due to its emerging role in metabolic diseases and cytogenetic location (3q27.3) with adiponectin. Results were confirmed in obese children, where plasma FETUB was higher with VDD. A direct effect by 1α,25-(OH)2D3 on hepatocellular FETUB synthesis was observed, with a time and dose dependent reduction. Further, we demonstrated the VD-receptor (VDR) is key, with FETUB "released" with VDR silencing. Finally, VD supplementation (6weeks) to juvenile mice fed a standard diet, reduced plasma FETUB. Only at 22weeks did liver FETUB correspond to plasma FETUB, highlighting the contribution of other VD-responsive tissues. Overall, FETUB is a key protein linking VDD to pediatric obesity. With an emerging role in metabolic diseases, we demonstrate that VD/VDR directly regulate FETUB.

Vitamin D status among adolescents in Kuwait: a cross-sectional study

OBJECTIVES

In Kuwait, as in many Arab states in the Gulf region, there are limited data on the prevalence of vitamin D deficiency among healthy adolescents. This study aimed to estimate the prevalence of vitamin D deficiency in a nationally representative sample of adolescents and investigate factors associated with vitamin D status.

METHODS

A cross-sectional study was conducted on 1416 adolescents aged 11-16 years, who were randomly selected from middle schools in all governorates of Kuwait. Data were collected from parents through self-administered questionnaire and from adolescents through face-to-face interview. Vitamin D was measured using liquid chromatography-tandem mass spectrometry. Logistic regression was used to investigate the independent factors associated with vitamin D status.

RESULTS

The prevalence of vitamin D deficiency was 81.21% (95% CI 71.61% to 90.81%), while severe deficiency was 39.48%. Only 3.60% of adolescents were vitamin D-sufficient. The prevalence of vitamin D deficiency was significantly higher among girls compared with boys (91.69% vs 70.32%; p<0.001). There was a significant inverse correlation between vitamin D and parathyroid hormone (Spearman correlation=-0.35; p<0.001). In the final model, gender, age, governorate, parental education, body mass index, vitamin D supplement and the number of times adolescents walk to schools per week were all significantly related to vitamin D deficiency.

CONCLUSION

High prevalence of vitamin D deficiency was noted among adolescents in Kuwait despite the abundant sunshine, which may reflect strong sun avoidance behaviour. Adequate outdoor daytime activities should be encouraged especially for girls. We call for locally tailored guidelines for vitamin D supplement in which girls should have a higher dose compared with boys.

25OH vitamin D levels in pediatric patients affected by Prader-Willi syndrome

PURPOSE

Obesity, insulin resistance, and puberty seem to influence and been inversely associated with 25-hydroxy vitamin D (25OHD) levels. To our knowledge, a study on 25OHD in children and adolescents with Prader-Willi syndrome (PWS), a genetic form of obesity, is not yet available.

OBJECTIVE

To analyze the 25OHD values in pediatric PWS subjects in comparison with a control group (CNT), highlighting the possible correlations with IR, BMD, body composition, pubertal stage, and GH therapy (GHT).

METHODS

Auxological and laboratory parameters, HOMA-IR, Vitamin D status, and bone density and body composition by DEXA scan were analyzed in 52 PWS and 110 controls (CNT), gender-, age-, and BMI-SD matched. None of them was on calcium or vitamin D. 20 PWS were on growth hormone (GH) therapy and 32 were previously treated.

RESULTS AND CONCLUSION

Altogether, PWS had similar values of 25OHD compared to CNT.16 PWS (30.7%) and 27 CNT (24.5%) had low 25OHD levels (< 20 ng/ml) (p = NS). 25OHD of PWS on GHT were comparable to those previously treated. In both groups, univariate analysis showed a negative correlation between 25OHD and fat mass% (FM%). GH therapy and pubertal stage were positively correlated with bone parameters analyzed by DXA. Multivariate regression confirmed only FM% as negative predictor of 25HOD in PWS patients, as previously described. GHT does not seem to influence 25OHD in PWS.

CONCLUSION

Our data showed that PWS had similar values of 25OHD compared to CNT. As already described, FM seems to be the only parameter influencing 25OHD levels. Finally, GHT does not seem to influence 25OHD metabolism in PWS.

The effect of vitamin D supplementation on insulin resistance, visceral fat and adiponectin in vitamin D deficient women with polycystic ovary syndrome: a randomized placebo-controlled trial

INTRODUCTION

Low plasma 25-hydroxy-vitamin D (25OHD) is associated with polycystic ovary syndrome (PCOS). Vitamin D deficiency may contribute to the development of insulin resistance, visceral fat and low level of adiponectin which are common feature in PCOS women. This study aimed to evaluate the effect of vitamin D supplementation on insulin resistance, visceral fat, and adiponectin in hypovitaminosis D women with polycystic ovary syndrome.

METHODS

In this randomized, placebo-controlled clinical trial, 44 PCOS women aged 20-38 years with plasma 25OHD <20 ng/mL were randomized in the intervention or placebo groups and followed for 8 weeks. Participants received 50,000 IU of oral vitamin D3 once weekly in the intervention group or placebo. The visceral adipose tissue, Insulin resistance (HOMA-IR), HOMA-B, QUICKI, and circulating adiponectin were compared before and after the intervention within groups using paired tests and the mean changes were analyzed between two groups by independent t-test.

RESULTS

Of 44 eligible participates, 36 patients (81.8%) completed the study. After 8 week intervention, vitamin D supplementation compared to the placebo group significantly decreased fasting plasma glucose (FPG) (7.67 ± 7.66 versus 1.71 ± 7.50 mg/dL, p = .001) and significantly increased homeostasis model of assessment-estimated B cell function (HOMA-B) (129.76 ± 121.02 versus 48.32 ± 128.35, p = .014), Adiponectin (5.17 ± 8.09 versus -5.29 ± 8.64 mg/dL, p = .001), and serum vitamin D level (28.24 ± 6.47 versus 3.55 ± 4.25 ng/mL, p = .001).

CONCLUSION

Vitamin D supplementation in vitamin D deficient women with PCOS, improved the FPG, HOMA-B, Adiponectin, and serum vitamin D level.

Adiponectin and vitamin D-binding protein are independently associated at birth in both mothers and neonates

CONTEXT

Adult body fat is associated with birth anthropometry, suggesting a role for metabolic regulators including vitamin D and the adipokines-adiponectin and irisin-which have been reported to interact but, as yet, data remain controversial.

OBJECTIVE

To study (i) the relationship between vitamin D, its binding protein (VDBP) and the adipokines, adiponectin, and irisin in mothers and neonates at birth and (ii) their effects on neonate anthropometric outcomes.

DESIGN

Cross-sectional study for healthy mothers with full-term and uncomplicated births.

SETTING

Primary care.

SUBJECTS

Seventy pairs of newly delivered neonates and their mothers.

MAIN OUTCOMES FEATURES

Biochemical markers from maternal and cord: VDBP, adiponectin, irisin, calcium, albumin, parathyroid hormone, 25OHD, 1,25(OH)₂D. Maternal demographic and social characteristics and neonate anthropometric parameters were recorded.

RESULTS

Maternal VDBP levels (364.1 ± 11.9 μg/ml) demonstrated a strong positive correlation with maternal adiponectin (4.4 ± 0.4 μg/ml) and irisin (308.8 ± 50.8 ng/ml) concentrations, which remained significant (p < 0.001 and p < 0.041, respectively) after adjustment with multiple parameters, including weeks of gestation, maternal age, and BMI. The finding of a strong association of VDBP (355.3 ± 29.2 μg/ml) and adiponectin (11.9 ± 2.0 μg/ml) but not irisin (174.4 ± 26.0 ng/ml) was also evident in neonates (p = 0.03 and p = 0.94, respectively). No association was observed in both maternal and neonatal vitamin D, adiponectin, and irisin.

CONCLUSIONS

The main findings of this study are (i) the perspective of a potential independent interaction of VDBP and adiponectin in both mothers and neonates and (ii) the lack of a causative model effect of both maternal/neonatal vitamin D status and adipokine profile on neonatal anthropometry at birth, as a surrogate marker of future metabolic health of the offspring.

Is There Any Relationship between Plasma 25-Hydroxyvitamin D₃, Adipokine Profiles and Excessive Body Weight in Type 2 Diabetic Patients?

A growing interest in the role of vitamin D in metabolic diseases led us to study the relationships between 25-hydroxyvitamin D₃ (25(OH)D₃) and the profiles of selected adipokines in type 2 diabetic (T2DM) patients. The study comprised 92 type 2 diabetics divided into quartiles regarding 25(OH)D₃ concentration. Each group was divided into male and female subgroups. All the studied patients had their anthropometric and biochemical parameters determined. Plasma 25-hydroxyvitamin D₃ concentration was determined by HPLC, while the selected adipokines (leptin, adiponectin, resistin and visfatin) by ELISA methods. The ratio of leptin to adiponectin (L/A) was calculated for all the patients. In 85.3% of diabetics a full (<20 ng/mL) or moderate (20-30 ng/mL) vitamin D deficit was found. Irrespective of sex, plasma leptin concentration decreased across increasing quartiles of 25(OH)D₃ level. In women, 25(OH)D₃ was negatively correlated with BMI, leptin level as well as L/A ratio, and positively with adiponectin concentration. In men, 25(OH)D₃ was positively correlated with HDL and negatively with systolic blood pressure (SBP), leptin level and L/A ratio. Considering all the patients, there ocurred a significant negative correlation between 25(OH)D₃ and SBP, BMI, WHR, TG, leptin and L/A ratio and positive ones between 25(OH)D₃ and both adiponectin and HDL. The results of the study support the existence of the relationship among vitamin D, obesity and leptin in type 2 diabetic patients.

Acute Vitamin D₃ Supplementation in Severe Obesity: Evaluation of Multimeric Adiponectin

Obesity predisposes to vitamin D deficiency (VDD) and glucose abnormalities. It is currently debated if vitamin D administration may improve glucose homeostasis by interacting with modulators of insulin sensitivity, such as adiponectin and its oligomers. In a 4-week inpatient study on a metabolic rehabilitation program, consisting of individualized caloric restriction and aerobic physical exercise in obese subjects with VDD, we assessed the acute effects of 600,000 IU cholecalciferol given per os VD group, 12 subjects; body mass index (BMI) 42.7 ± 1.3 kg/m²) or placebo per os (PL group, 12 subjects, BMI 39.8 ± 0.9 kg/m²) on high (HWM-A), medium (MMW-A), and low molecular weight adiponectin (LMW-A), as quantified by western immunoblot (WIB) and ELISA. During the 4-week study, dieting promoted a similar magnitude of weight loss in VD and PL groups. Compared to the PL group, cholecalciferol administration increased 25(OH)Vit D levels (p < 0.001) and promoted a significant increase of HMW-A expression analyzed by WIB (p = 0.02). In parallel, a significant decrease of leptin/HMW-A ratio (p < 0.05), a biomarker of metabolic homeostasis, was observed. During the study, changes of MMW-A and LMW-A occurred independently of cholecalciferol administration, and were likely explained by weight loss. At odds with these findings, the ELISA assessment of adiponectin oligomers showed no modifications in the VD group or PL group. Current findings suggest that acute cholecalciferol administration selectively modifies HMW-A and the leptin/HMW-A ratio.

Vitamin D deficiency and diabetes

Vitamin D deficiency has been linked to the onset of diabetes. This review summarizes the role of Vitamin D in maintaining the normal release of insulin by the pancreatic beta cells (β-cells). Diabetes is initiated by the onset of insulin resistance. The β-cells can overcome this resistance by releasing more insulin, thus preventing hyperglycaemia. However, as this hyperactivity increases, the β-cells experience excessive Ca2+ and reactive oxygen species (ROS) signalling that results in cell death and the onset of diabetes. Vitamin D deficiency contributes to both the initial insulin resistance and the subsequent onset of diabetes caused by β-cell death. Vitamin D acts to reduce inflammation, which is a major process in inducing insulin resistance. Vitamin D maintains the normal resting levels of both Ca2+ and ROS that are elevated in the β-cells during diabetes. Vitamin D also has a very significant role in maintaining the epigenome. Epigenetic alterations are a feature of diabetes by which many diabetes-related genes are inactivated by hypermethylation. Vitamin D acts to prevent such hypermethylation by increasing the expression of the DNA demethylases that prevent hypermethylation of multiple gene promoter regions of many diabetes-related genes. What is remarkable is just how many cellular processes are maintained by Vitamin D. When Vitamin D is deficient, many of these processes begin to decline and this sets the stage for the onset of diseases such as diabetes.

Physiological functions of Vitamin D in adipose tissue

Adipose tissue has long been identified as the major site of vitamin D storage. Recent studies have demonstrated that VDR and vitamin D metabolizing enzymes are expressed in adipocytes. Furthermore, it has been shown that vitamin D regulates adipogenic gene expression as well as adipocyte apoptosis. Vitamin D is active in adipocytes at all levels. It interacts with membrane receptors, adaptor molecules, and nuclear coregulator proteins. Several functions of unliganded nVDR were discovered by studying human samples from patients having hereditary vitamin D resistant rickets, transgenic mice overexpressing the VDR and VDR knockout mice. Through its genomic action, vitamin D participates in the regulation of energy metabolism by controlling the expression of uncoupling proteins. In vitro, vitamin D stimulates lipogenesis and inhibits lipolysis by interacting with mVDR. mVDR is present in caveolae of the plasma membrane and is the same as the classic nVDR. In addition, vitamin D affects directly the expression of the appetite regulating hormone, leptin. Some researchers reported also that vitamin D regulates the expression of the insulin sensitizing hormone, adiponectin. Vitamin D reduced cytokine release and adipose tissue inflammation through the inhibition of NF-κB signaling. Scientific research investigating the role of adipose tissue resident immune cells in the pathogenesis of obesity-associated inflammation is scarce. Obesity is associated with vitamin D deficiency. However there is no scientific evidence to prove that vitamin D deficiency predispose to obesity. Vitamin D supplementation may prevent obesity but it does not lead to weight loss in obese subjects.

[Research advances in association between vitamin D and Kawasaki disease and related mechanisms of action]

Vitamin D is an important steroid hormone, which has a wide biological effect and is the protective factor against cardiovascular disease and other diseases. At present, the etiology and pathogenesis of Kawasaki disease (KD) remain unknown, but recent studies have shown that vitamin D insufficiency or deficiency is associated with KD. Vitamin D insufficiency or deficiency may affect KD via its influence on inflammatory response, adipokine, endothelial function, platelet function, and DNA methylation and increase the risk of coronary artery lesions. This article reviews the research advances in the association between vitamin D and KD and possible mechanisms of action.

[Research advances in association between vitamin D and Kawasaki disease and related mechanisms of action]

Vitamin D is an important steroid hormone, which has a wide biological effect and is the protective factor against cardiovascular disease and other diseases. At present, the etiology and pathogenesis of Kawasaki disease (KD) remain unknown, but recent studies have shown that vitamin D insufficiency or deficiency is associated with KD. Vitamin D insufficiency or deficiency may affect KD via its influence on inflammatory response, adipokine, endothelial function, platelet function, and DNA methylation and increase the risk of coronary artery lesions. This article reviews the research advances in the association between vitamin D and KD and possible mechanisms of action.

Predictors of Serum 25-Hydroxyvitamin D Concentrations among a Sample of Egyptian Schoolchildren

Objective. To assess the level of 25-hydroxyvitamin D status among a sample of Egyptian schoolchildren and to evaluate predictors of deficiency and insufficiency. Subjects and Methods. A cross-sectional study comprising 200 prepubescent schoolchildren aged from 9 to 11 years was performed. A questionnaire including frequency of midday sun exposure, milk intake, physical activity, and level of maternal education was taken. Body mass index (BMI) was calculated; serum 25-hydroxyvitamin D [25(OH)D], serum calcium, phosphorus, and parathyroid hormone were measured. Results. Vitamin D deficiency [serum 25(OH)D < 20 ng/mL] was detected in 11.5% of subjects while its insufficiency (serum 25(OH)D is between 20 and 29.9 ng/mL) was detected in 15%. Results revealed that obesity, low physical activity, low sun exposure, and low maternal education level are significant predictors of insufficiency, though female gender, low maternal education level, and low milk intake are significant predictors of deficiency. Lower serum phosphorus and higher serum parathyroid hormone were significantly associated with both deficiency and insufficiency (p < 0.05). Conclusion. Vitamin D deficiency and insufficiency are common among schoolchildren in Egypt. Food fortification, vitamin D supplementation, and increasing maternal awareness about the importance of physical activity and exposure of their children to ultraviolet light may help to overcome this problem.

Is there association between vitamin D levels, apelin 36, and visfatin in PCOS?

AIM

We aimed to evaluate vitamin D, apelin-36, and visfatin levels in patients with polycystic ovary syndrome (PCOS).

MATERIAL AND METHOD

The study was completed in six months, including a total of 110 patients who were admitted to the obstetrics and gynecology polyclinic. Patients with a diagnosis of PCOS were divided into two subgroups according to their vitamin D levels. Thirty-four patients had <10 ng/ml of vitamin D deficiency and 21 patients had 10-30 ng/ml of vitamin D insufficiency, with each being defined as a subgroup.

RESULTS

Average apelin-36 and visfatin levels in PCOS patients were 2.52 ± 0.68 nmol/L and 72.63 ± 22:31 ng/ml, in the control group they were 0.92 ± 0.33 nmol/L, 24.66 ± 6 ng/ml, respectively. The difference found in PCOS patients was statistically significant (p = 0.0001, p = 0.0001).

CONCLUSION

In conclusion, the present study shows that in PCOS patients with low levels of vitamin D, insulin resistance is greater and apelin-36 serum levels were significantly higher. Although there are different opinions in the literature on this subject, we believe that when vitamin D levels are brought to an optimal level in PCOS patient, it can prevent the negative effects of adipokines in the pathogenesis of PCOS.

A proteomic approach to obesity and type 2 diabetes

The incidence of obesity and type diabetes 2 has increased dramatically resulting in an increased interest in its biomedical relevance. However, the mechanisms that trigger the development of diabetes type 2 in obese patients remain largely unknown. Scientific, clinical and pharmaceutical communities are dedicating vast resources to unravel this issue by applying different omics tools. During the last decade, the advances in proteomic approaches and the Human Proteome Organization have opened and are opening a new door that may be helpful in the identification of patients at risk and to improve current therapies. Here, we briefly review some of the advances in our understanding of type 2 diabetes that have occurred through the application of proteomics. We also review, in detail, the current improvements in proteomic methodologies and new strategies that could be employed to further advance our understanding of this pathology. By applying these new proteomic advances, novel therapeutic and/or diagnostic protein targets will be discovered in the obesity/Type 2 diabetes area.

Comparing the effects of sun exposure and vitamin D supplementation on vitamin D insufficiency, and immune and cardio-metabolic function: the Sun Exposure and Vitamin D Supplementation (SEDS) Study

Background

Adults living in the sunny Australian climate are at high risk of skin cancer, but vitamin D deficiency (defined here as a serum 25-hydroxyvitamin D (25(OH)D) concentration of less than 50 nmol/L) is also common. Vitamin D deficiency may be a risk factor for a range of diseases. However, the optimal strategies to achieve and maintain vitamin D adequacy (sun exposure, vitamin D supplementation or both), and whether sun exposure itself has benefits over and above initiating synthesis of vitamin D, remain unclear.

The Sun Exposure and Vitamin D Supplementation (SEDS) Study aims to compare the effectiveness of sun exposure and vitamin D supplementation for the management of vitamin D insufficiency, and to test whether these management strategies differentially affect markers of immune and cardio-metabolic function.

Methods/Design

The SEDS Study is a multi-centre, randomised controlled trial of two different daily doses of vitamin D supplementation, and placebo, in conjunction with guidance on two different patterns of sun exposure. Participants recruited from across Australia are aged 18–64 years and have a recent vitamin D test result showing a serum 25(OH)D level of 40–60 nmol/L.

Discussion

This paper discusses the rationale behind the study design, and considers the challenges but necessity of data collection within a non-institutionalised adult population, in order to address the study aims. We also discuss the challenges of participant recruitment and retention, ongoing engagement of referring medical practitioners and address issues of compliance and participant retention.

Trial registration

Australia New Zealand Clinical Trials Registry: ACTRN12613000290796 Registered 14 March 2013.

25-Hydroxy Vitamin D, Adiponectin Levels and Cardiometabolic Risk Factors in a Sample of Obese Children

BACKGROUND: Association between vitamin D, adiponectin and obesity is a matter of debate, as they play important role in linking obesity with different cardio metabolic risk factors.AIM: Evaluation of association between metabolic risk factors with both adiponectin and 25-Hydroxy vitamin D [25(OH) D] levels and that between adiponectin and [25(OH) D] among obese Egyptian children.SUBJECTS AND METHODS: This case-control cross sectional study consisted of 65 obese and 30 healthy children, aged 8-11 years. 25(OH) D, serum adiponectin, total cholesterol, triglycerides, high-density lipoprotein-cholesterol and low-density lipoprotein-cholesterol were measured.RESULTS: The mean 25(OH)D and adiponectin levels in the obese were lower than that in control group (𝑃<0.000). 25(OH)D were inversely correlated with body mass index, triglyceride, total cholesterol and LDL-cholesterol. While adiponectin level were inversely correlated with systolic and diastolic blood pressure, and positively correlated with high-density lipoprotein-cholesterol. However, there is no relation between 25(OH) D and adiponectin levels among obese children and total sample.CONCLUSION: Inspite of strong association between vitamin D and adiponectin levels with metabolic risk factors and obesity, there is no relation between 25(OH)D and adiponectin levels. In obese children, There are significant negative correlations between 25(OH)D with lipid profile, and between adiponectin levels with blood pressure.

Vitamin D insufficiency and insulin resistance in obese adolescents

Obese adolescents represent a particularly vulnerable group for vitamin D deficiency which appears to have negative consequences on insulin resistance and glucose homeostasis. Poor vitamin D status is also associated with future risk of type 2 diabetes and metabolic syndrome in the obese. The biological mechanisms by which vitamin D influences glycemic control in obesity are not well understood, but are thought to involve enhancement of peripheral/hepatic uptake of glucose, attenuation of inflammation and/or regulation of insulin synthesis/secretion by pancreatic β cells. Related to the latter, recent data suggest that the active form of vitamin, 1,25-dihydroxyvitamin D, does not impact insulin release in healthy pancreatic islets; instead they require an environmental stressor such as inflammation or vitamin D deficiency to see an effect. To date, a number of observational studies exploring the relationship between the vitamin D status of obese adolescents and markers of glucose homeostasis have been published. Most, although not all, show significant associations between circulating 25-hydroxyvitamn D concentrations and insulin sensitivity/resistance indices. In interpreting the collective findings of these reports, significant considerations surface including the effects of pubertal status, vitamin D status, influence of parathyroid hormone status and the presence of nonalcoholic fatty liver disease. The few published clinical trials using vitamin D supplementation to improve insulin resistance and impaired glucose tolerance in obese adolescents have yielded beneficial effects. However, there is a need for more randomized controlled trials. Future investigations should involve larger sample sizes of obese adolescents with documented vitamin D deficiency, and careful selection of the dose, dosing regimen and achievement of target 25-hydroxyvitamn D serum concentrations. These trials should also include clamp-derived measures of in vivo sensitivity and β-cell function to more fully characterize the effects of vitamin D replenishment on insulin resistance.

Prevalence of hypovitaminosis D and predictors of vitamin D status in Italian healthy adolescents

Background

Vitamin D plays an important role in health promotion during adolescence. Vitamin D deficiency and insufficiency are common in adolescents worldwide. Few data on vitamin D status and risk factors for hypovitaminosis D in Italian adolescents are currently available.

Methods

25-hydroxyvitamin D (25-OH-D) and parathyroid hormone (PTH) levels were evaluated in 427 Italian healthy adolescents (10.0-21.0 years). We used the following cut-off of 25-OH-D to define vitamin D status: deficiency < 50 nmol/L; insufficiency 50-75 nmol/L; sufficiency ≥ 75 nmol/L. Hypovitaminosis D was defined as 25-OH-D levels < 75.0 nmol/L and severe vitamin D deficiency as 25-OH-D levels < 25.0 nmol/L. We evaluated gender, residence, season of blood withdrawal, ethnicity, weight status, sun exposure, use of sunscreens, outdoor physical activity, and history of fractures as predictors of vitamin D status.

Results

Enrolled adolescents had a median serum 25-OH-D level of 50.0 nmol/L, range 8.1-174.7, with 82.2% having hypovitaminosis D. Vitamin D deficiency and insufficiency were detected in 49.9% and 32.3% of adolescents, respectively. Among those with deficiency, 38 subjects were severely deficient (38/427, 8.9% of the entire sample). Non-white adolescents had a higher prevalence of severe vitamin D deficiency than white subjects (6/17-35.3% vs 32/410-7.8% respectively, p = 0.002). Logistic regression showed increased risk of hypovitaminosis D as follows: blood withdrawal taken in winter-spring (Odds ratio (OR) 5.64) compared to summer-fall period; overweight-obese adolescents (OR 3.89) compared to subjects with normal body mass index (BMI); low sun exposure (OR 5.94) compared to moderate-good exposure and regular use of sunscreens (OR 5.89) compared to non regular use. Adolescents who performed < 3 hours/week of outdoor exercise had higher prevalence of hypovitaminosis D. Gender, residence, and history of fractures were not associated with vitamin D status. Serum 25-OH-D levels were inversely related to PTH (r = -0.387, p < 0.0001) and BMI-SDS (r = -0.141, p = 0.007). 44/427 (10.3%) adolescents showed secondary hyperparathyroidism.

Conclusions

Italian adolescents have high prevalence of vitamin D deficiency and insufficiency. Pediatricians should tackle predictors of vitamin D status, favoring a healthier lifestyle and promoting supplementation in the groups at higher risk of hypovitaminosis D.