Oral vitamin D supplementation has a lower bioavailability and reduces hypersecretion of parathyroid hormone and insulin resistance in obese Chinese males

Pharmacokinetics of Oral Vitamin D in Children with Obesity and Asthma

BACKGROUND AND OBJECTIVE

Vitamin D insufficiency is common in several pediatric diseases including obesity and asthma. Little data exist describing the pharmacokinetics of oral vitamin D in children or the optimal dosing to achieve therapeutic 25(OH)D targets. Describe the pharmacokinetics of oral Vitamin D in children with asthma.

METHODS

This was a multi-center, randomized, open-label, oral supplementation study to describe the pharmacokinetics of vitamin D in children aged 6-17 years who have asthma and were overweight/obese. Participants had a serum 25(OH)D concentration between 10 and < 30 ng/mL at baseline. In Part 1 of the study, we assessed four 16-week dosing regimens for their ability to achieve 25(OH)D concentrations ≥ 40 ng/mL. Using serial serum 25(OH)D sampling over 28 weeks, we created a population pharmacokinetic model and performed dosing simulations to achieve 25(OH)D concentrations ≥ 40 ng/mL. In Part 2, the optimal regimen chosen from Part 1 was compared (2:1) to a standard-of-care control dose (600 international units [IU] daily) over 16 weeks. A final population pharmacokinetic model using both parts was developed to perform dosing simulations and determine important co-variates in the pharmacokinetics of vitamin D.

RESULTS

Based on empiric and simulation data, the daily dose of 8000 IU and a loading dose of 50,000 IU were chosen; this regimen raised 25(OH)D concentrations above 40 ng/mL in the majority of participants while avoiding concentrations > 100 ng/mL. A 50,000-IU loading dose led to faster achievement of 25(OH)D therapeutic concentrations (≥ 40 ng/mL). The estimated median (5th-95th percentiles) apparent clearance of vitamin D from the final population pharmacokinetic model was 0.181 (0.155-0.206) L/h. The body mass index z-score was a significant covariate on apparent clearance and was associated with a significantly decreased median half-life in 25(OH)D (body mass index z-score 1.00-1.99: 97.7 days, body mass index z-score 2.00-2.99: 65.9 days, body mass index z-score ≥ 3.00: 39.1 days, p < 0.001).

CONCLUSIONS

Obesity impacts vitamin D clearance and the half-life, but serum concentrations > 40 ng/mL can be reached in most children using a loading dose of 50,000 IU followed by a daily dose of 8000 IU.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier number NCT03686150.

Supplementation of hyaluronic acid injections with vitamin D improve knee function by attenuating synovial fluid oxidative stress in osteoarthritis patients with vitamin D insufficiency

Objectives

There is still controversy about the effect of vitamin D supplementation on osteoarthritis (OA). The purpose of this study was to investigate the effects of vitamin D supplementation with Hyaluronic acid (HA) injection on OA.

Methods

We investigated serum vitamin D levels and oxidative stress (OS) in synovial fluid from patients with OA who underwent total knee arthroplasty (grade IV, n = 24) and HA injection (grade II and III, n = 40). The effects of HA injection with or without oral vitamin D supplementation on synovial fluid OS and knee pain and function were then further investigated. Finally, patients underwent HA injection were divided into two groups according to vitamin D levels (vitamin D &lt; or &gt; 30 ng/ml), and the efficacy of the two groups were compared.

Results

The results showed that the levels of glutathione peroxidase (GSH-PX) (P &lt; 0.05) in the synovial fluid were lower in patients with stage IV OA than that in patients with stage II-III OA, while the levels of malondialdehyde (MDA) (P &lt; 0.05) and lactate dehydrogenase (LDH) (P &lt; 0.01) were significantly higher. Moreover, we found that age, BMI and vitamin D levels were significantly associated with the levels of oxidants and/or antioxidants in synovial fluid, and that vitamin D was significantly negatively correlated with BMI (R = −0.3527, p = 0.0043). Supplementation of HA injections with vitamin D significantly reduced the OS status in synovial fluid, attenuated knee pain and improved knee function in OA patients with vitamin D insufficiency.

Conclusion

We conclude that maintenance of vitamin D sufficiency may be beneficial for the treatment of OA by improving OS in synovial fluid.

Association between Polymorphisms in Vitamin D Pathway-Related Genes, Vitamin D Status, Muscle Mass and Function: A Systematic Review

An association between vitamin D level and muscle-related traits has been frequently reported. Vitamin D level is dependent on various factors such as sunlight exposure and nutrition. But also on genetic factors. We, therefore, hypothesize that single nucleotide polymorphisms (SNPs) within the vitamin D pathway-related genes could contribute to muscle mass and function via an impact on vitamin D level. However, the integration of studies investigating these issues is still missing. Therefore, this review aimed to systematically identify and summarize the available evidence on the association between SNPs within vitamin D pathway-related genes and vitamin D status as well as various muscle traits in healthy adults. The review has been registered on PROSPERO and was conducted following PRISMA guidelines. In total, 77 studies investigating 497 SNPs in 13 different genes were included, with significant associations being reported for 59 different SNPs. Variations in GC, CYP2R1, VDR, and CYP24A1 genes were reported most frequently, whereby especially SNPs in the GC (rs2282679, rs4588, rs1155563, rs7041) and CYP2R1 genes (rs10741657, rs10766197, rs2060793) were confirmed to be associated with vitamin D level in more than 50% of the respective studies. Various muscle traits have been investigated only in relation to four different vitamin D receptor (VDR) polymorphisms (rs7975232, rs2228570, rs1544410, and rs731236). Interestingly, all of them showed only very low confirmation rates (6-17% of the studies). In conclusion, this systematic review presents one of the most comprehensive updates of the association of SNPs in vitamin D pathway-related genes with vitamin D status and muscle traits in healthy adults. It might be used for selecting candidate SNPs for further studies, but also for personalized strategies in identifying individuals at risk for vitamin D deficiency and eventually for determining a potential response to vitamin D supplementation.

Multiple micronutrient supplementation improves micronutrient status in primary school children in Hai Phong City, Vietnam: a randomised controlled trial

We aimed to determine the efficacy of multiple micronutrient supplementation on the biomarkers of iron, zinc, and vitamin A status across anthropometric status categories in Vietnamese school children. In this 22-week randomised controlled trial, 347 undernourished, normal weight, or overweight/obese children aged 6-9 years were allocated to receive every school day a multiple micronutrient supplement (10 mg iron, 10 mg zinc, 400 µg vitamin A) or a placebo. Haematological indices; circulating ferritin, zinc, and retinol (corrected for inflammation); and C-reactive protein were measured at baseline and 22 weeks. At week 22, linear mixed models showed that mean corpuscular volume increased by 0.3 fL, serum ferritin by 9.1 µg/L, plasma zinc by 0.9 µmol/L, and plasma retinol by 15%, and the prevalence of zinc deficiency decreased by 17.3% points in the intervention group compared to placebo. No intervention effects were found for other haematological indices, or the prevalence of anaemia. Multiple micronutrient supplementation for 22 weeks improved the biomarkers of zinc and vitamin A status and some biomarkers of iron status, and reduced the prevalence of zinc deficiency in Vietnamese school children.Trial registration: This trial was registered on 06/09/2016 at www.anzctr.org.au as ACTRN12616001245482.

Obesity and overweight decreases the effect of vitamin D supplementation in adults: systematic review and meta-analysis of randomized controlled trials

Overweight and obesity are associated with vitamin D deficiency (VitD), which are both important health problems. Reduced serum vitamin D levels has been registered in all phases of life and is commonly associated with the genesis of overweight and obesity. Thus, the objective of this review with meta-analysis was to investigate and evidence the efficacy of vitamin D supplementation in vitamin D. Interventional studies were searched for in 5 databases, without restriction of publication date or language. The absolute mean difference was used as a summary measure of the selected studies. A total of 2370 studies were identified, of which 18 descriptive articles were eligible - based on criteria and variables of selection and exclusion. Then the data were synthesized and submitted to meta-analysis. The results evidence that after supplementation individuals with obesity presented increased serum vitamin D 39.83 nmol/L (95% CI: 34.06-45.61) in relation to the control/placebo group. However, the obese state decreased serum vitamin D concentration by -38.17 nmol/L (95% CI: -59.90/-16.44) compared to the normal weight group. In addition, increasing the dose of VitD supplementation does not appear to contribute significantly to increased serum VitD levels. The study observed that obesity in adults reduced the effect of vitamin D supplementation. Therefore, research should be developed on the optimal dose of vitamin D supplementation for people with obesity.Systematic Review Registration: PROSPERO number CRD42018091.

Vitamin D Receptor Polymorphisms Associated with Susceptibility to Obesity: A Meta-Analysis

BACKGROUND Obesity has become a global public health problem. Obesity increases the risk of several lethal diseases. This study aimed to assess whether the obesity susceptibility was associated with genetic variation in vitamin D receptor (VDR) gene by conducting a meta-analysis. MATERIAL AND METHODS PubMed, EMBASE and Cochrane Library databases were screened for all relevant articles published up to October 2018. The pooled odds ratios (OR) were calculated using STATA 13.0 software for 4 polymorphisms in the VDR gene (ApaI, BsmI, FokI and TaqI). RESULTS Seven case-control studies, including 1188 obese patients and 1657 healthy controls, were recruited. The pooled findings showed that there were no associations between obesity risk and the VDR polymorphisms in ApaI, BsmI and TaqI loci overall. However, VDR TaqI polymorphism was associated with the risk of obesity in Asian under homozygous [TT versus tt: odds ratio (OR)=0.26, 95% confidence interval (CI)=0.14-0.49; P<0.001], heterozygous (Tt versus tt: OR=0.34, 95% CI=0.18-0.64; P=0.001), and dominant (TT+Tt versus tt: OR=0.30, 95% CI=0.17-0.52; P<0.001) models; FokI variant was related with increased risk of obesity only under dominant model (FF+Ff versus ff: OR=1.54, 95% CI=1.15-2.06; P=0.004). CONCLUSIONS Our meta-analysis results suggest that the T allele of TaqI may have a protective effect, while the F allele of FokI is proposed as a risk factor related to obesity.

Vitamin D Improves Nitric Oxide-Dependent Vasodilation in Adipose Tissue Arterioles from Bariatric Surgery Patients

There is a high prevalence of vitamin-D deficiency in obese individuals that could be attributed to vitamin-D sequestration in the adipose tissue. Associations between vitamin-D deficiency and unfavorable cardiometabolic outcomes were reported. However, the pathophysiological mechanisms behind these associations are yet to be established. In our previous studies, we demonstrated microvascular dysfunction in obese adults that was associated with reduced nitric oxide (NO) production. Herein, we examined the role of vitamin D in mitigating microvascular function in morbidly obese adults before and after weight loss surgery. We obtained subcutaneous (SAT) and visceral adipose tissue (VAT) biopsies from bariatric patients at the time of surgery (n = 15) and gluteal SAT samples three months post-surgery (n = 8). Flow-induced dilation (FID) and acetylcholine-induced dilation (AChID) and NO production were measured in the AT-isolated arterioles ± NO synthase inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME), hydrogen peroxide (H2O2) inhibitor, polyethylene glycol-modified catalase (PEG-CAT), or 1,25-dihydroxyvitamin D. Vitamin D improved FID, AChID, and NO production in AT-isolated arterioles at time of surgery; these effects were abolished by L-NAME but not by PEG-CAT. Vitamin-D-mediated improvements were of a higher magnitude in VAT compared to SAT arterioles. After surgery, significant improvements in FID, AChID, NO production, and NO sensitivity were observed. Vitamin-D-induced changes were of a lower magnitude compared to those from the time of surgery. In conclusion, vitamin D improved NO-dependent arteriolar vasodilation in obese adults; this effect was more significant before surgery-induced weight loss.

The GC2 haplotype of the vitamin D binding protein is a risk factor for a low plasma 25-hydroxyvitamin D concentration in a Han Chinese population

Background

The GC haplotype of the vitamin D binding protein (encoded by the GC gene) might be a risk factor to the vitamin D (VD) nutritional status for many populations, while evidences from the Chinese Han population are sparse. We test the association between vitamin D binding protein genotypes and VD status as well as the metabolic parameters of glucose and lipids in a Han Chinese population.

Methods

In a cross-sectional study conducted at a health examination centre (registered in ClinicalTrials.gov as QLS2013), 2641 adults were included and grouped according to their plasma 25-hydroxyvitamin D (25OHD) concentrations as VD deficient (VDD), insufficient (VDI), or sufficient (VDS). The rs7041 and rs4588 genotypes were analysed with a molecular beacon-based qPCR method using blood samples.

Results

Plasma 25OHD concentrations were lower in the GC2/2, rs7041T/T, and rs4588A/A genotypes than the GC1f/1s, rs7041G/T, and rs4588C/C genotypes (P <  0.05). After adjusting for confounders, the GC2 haplotype increased the risk of low VD status (P <  0.05) in both genders. More genotypic models revealed the negative contributions of rs4588A than rs7041T to low VD status (P <  0.05). The combined rates of VDD and VDI were 80.2% in males and 86.1% in females. Compared with VDI, VDS, or both, VDD showed higher plasma concentrations of fasting blood glucose, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides in males (P <  0.05); however, no significant differences were found with regard to these parameters between the subgroups defined by the GC genotypes (P > 0.05).

Conclusions

In a Han Chinese population, the GC2 haplotype or more exactly rs4588A is a risk factor for low VD status but is not associated with glucose and lipid metabolic disorders, which are inversely correlated with the circulating 25OHD concentration in males.

Trial registration

The study was retrospectively registered in January 2018 as NCT03406234 in the ClinicalTrials.gov online system.

Electronic supplementary material

The online version of this article (10.1186/s12986-019-0332-0) contains supplementary material, which is available to authorized users.

Is Hypovitaminosis D Related to Incidence of Type 2 Diabetes and High Fasting Glucose Level in Healthy Subjects: A Systematic Review and Meta-Analysis of Observational Studies

There is evidence that vitamin D status is associated with type 2 diabetes. Many observational studies have been performed investigating the relationship of vitamin D status and circulating biomarkers of glycemic regulation. To find out whether this association holds, we conducted a systematic review and meta-analysis of cross sectional and longitudinal studies. We searched Pubmed, Medline and Embase, all through June 2017. The studies were selected to determine the effect of vitamin D on the parameters of glucose metabolism in diabetic and non-diabetic subjects. Correlation coefficients from all studies were pooled in a random effects meta-analysis. The risk of bias was assessed using Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. We found significant inverse relationship of vitamin D status with glycemic level in both diabetic (r = -0.223, 95% CI = -0.184 to -0.261, p = 0.000) and non-diabetic (r = -0.073, 95% CI = -0.052 to -0.093, p = 0.000) subjects. This meta-analysis concludes that hypovitaminosis D is associated with increased risk of hyperglycemia both in diabetic and non-diabetic subjects. A future strategy for the prevention of impaired glycemic regulation could be individualized supplementation of vitamin D.

Sexual Dimorphism for the Association between Vitamin D and Insulin Resistance in Chinese People

BACKGROUND

The relationship between vitamin D and insulin resistance is still controversial. Many factors could influence this relationship. In addition, this relationship in different genders was still unclear.

METHODS

A total of 6597 subjects, including 2813 males and 3784 females, were analyzed. The serum levels of 25(OH)D, fasting blood glucose (FBG), fasting insulin, HbA1c, and other metabolic parameters were tested. The waist circumference (WC), weight, and height were also measured. Questionnaires regarding smoking and drinking were collected from these subjects.

RESULTS

Serum 25(OH)D was categorized into quartiles. Increasing 25(OH)D levels were associated with reduced trend of homeostasis model assessment of insulin resistance (HOMA-IR) in both males and females. Pearson's correlation indicated 25(OH)D level was inversely associated with the HOMA-IR for male subjects (r = -0.055, P = 0.028) but not for female subjects (r = -0.005, P = 0.798). Age, triglyceride (TG), and low-density lipoprotein (LDL) were associated with the vitamin D levels in males and females. In regression analysis, serum 25(OH)D concentration was significantly associated with HOMA-IR only in overweight males.

CONCLUSION

We found an inverse association between 25(OH)D and HOMA-IR in Chinese overweight males. Vitamin D supplementation might be beneficial in this population. However, further clinical trials are needed to confirm this association.

Change in serum 25-hydroxyvitamin D with antiretroviral treatment initiation and nutritional intervention in HIV-positive adults

Low vitamin D level in HIV-positive persons has been associated with disease progression. We compared the levels of serum 25-hydroxyvitamin D (25(OH)D) in HIV-positive and HIV-negative persons, and investigated the role of nutritional supplementation and antiretroviral treatment (ART) on serum 25(OH)D levels. A randomised nutritional supplementation trial was conducted at Jimma University Specialized Hospital, Ethiopia. The trial compared 200 g/d of lipid-based nutrient supplement (LNS) with no supplementation during the first 3 months of ART. The supplement provided twice the recommended daily allowance of vitamin D (10 μg/200 g). The level of serum 25(OH)D before nutritional intervention and ART initiation was compared with serum 25(OH)D of HIV-negative individuals. A total of 348 HIV-positive and 100 HIV-negative persons were recruited. The median baseline serum 25(OH)D level was higher in HIV-positive than in HIV-negative persons (42·5 v. 35·3 nmol/l, P17 kg/m2 were randomised to either LNS supplementation (n 189) or no supplementation (n 93) during the first 3 months of ART. The supplemented group had a 4·1 (95 % CI 1·7, 6·4) nmol/l increase in serum 25(OH)D, whereas the non-supplemented group had a 10·8 (95 % CI 7·8, 13·9) nmol/l decrease in serum 25(OH)D level after 3 months of ART. Nutritional supplementation that contained vitamin D prevented a reduction in serum 25(OH)D levels in HIV-positive persons initiating ART. Vitamin D replenishment may be needed to prevent reduction in serum 25(OH)D levels during ART.