Evidence that 1,25-dihydroxyvitamin D3 inhibits the hepatic production of 25-hydroxyvitamin D in man

Vitamin D3 exacerbates steatosis while calcipotriol inhibits inflammation in non-alcoholic fatty liver disease in Sod1 knockout mice: a comparative study of two forms of vitamin D

The role of vitamin D (VD) in non-alcoholic fatty liver disease (NAFLD) remains controversial, possibly due to the differential effects of various forms of VD. In our study, Sod1 gene knockout (SKO) mice were utilized as lean NAFLD models, which were administered 15 000 IU VD3 per kg diet, or intraperitoneally injected with the active VD analog calcipotriol for 12 weeks. We found that VD3 exacerbated hepatic steatosis in SKO mice, with an increase in the levels of Cd36, Fatp2, Dgat2, and CEBPA. However, calcipotriol exerted no significant effect on hepatic steatosis. Calcipotriol inhibited the expression of Il-1a, Il-1b, Il-6, Adgre1, and TNF, with a reduction of NFκB phosphorylation in SKO mice. No effect was observed by either VD3 or calcipotriol on hepatocyte injury and hepatic fibrosis. Co-immunofluorescence stains of CD68, a liver macrophage marker, and VDR showed that calcipotriol reduced CD68 positive cells, and increased the colocalization of VDR with CD68. However, VD3 elevated hepatocyte VDR expression, with no substantial effect on the colocalization of VDR with CD68. Finally, we found that VD3 increased the levels of serum 25(OH)D3 and 24,25(OH)2D3, whereas calcipotriol decreased both. Both VD3 and calcipotriol did not disturb serum calcium and phosphate levels. In summary, our study found that VD3 accentuated hepatic steatosis, while calcipotriol diminished inflammation levels in SKO mice, and the difference might stem from their distinct cellular selectivity in activating VDR. This study provides a reference for the application of VD in the treatment of lean NAFLD.

Dietary inflammatory index is associated with Vitamin D in CKD patients

OBJECTIVES

Multiple observational studies have shown that low serum level of 25-hydroxyvitamin D (25(OH)D) in patients with chronic kidney disease (CKD) have been associated with a faster progression of kidney disease and a higher risk of all-cause mortality. We aim to assess the association between dietary inflammatory index (DII) with Vitamin D in adults with CKD.

METHOD

The National Health and Nutrition Examination Survey appropriated participants from 2009 to 2018 were enrolled. The patients who were under the age of 18, pregnant, and having incomplete data were excluded. DII score were calculated based on a single 24-h dietary recall interview for each participant. Mutivariable regression analysis and subgroup analysis were utilized to determine the independent associations between vitamin D with DII in CKD patients.

RESULTS

In total, 4283 individuals were finally included. The results showed a negative association between DII scores and 25(OH)D with statistical significance (β =  - 1.83, 95% CI  - 2.31,  - 1.34, P < 0.001). In subgroup analysis stratified by gender, low eGFR, age and diabetes, the negative association between DII scores and 25(OH)D was still significant (all P for trend < 0.05). The results from interacion test indicated that the magnitude of the association was the same for the population with and without low eGFR (P for interacion = 0.464).

CONCLUSION

Higher consumption of pro-inflammatory diet correlates negatively with the 25(OH)D level in CKD patients with and without low eGFR. Anti-inflammatory diet management may reduce the reduction of vitamin D in CKD patients.

Evaluating the effect of body mass index and 25-hydroxy-vitamin D level on basal cell carcinoma using Mendelian randomization

Basal cell carcinoma (BCC) is the most common cancer with a rising incidence among white-skinned individuals. A number of epidemiological studies have suggested that obesity and serum 25-hydroxy-vitamin D (25(OH)D) levels may affect the arising of BCC. To address this, we selected 443 and 96 single nucleotide polymorphisms (SNPs) associated with body mass index (BMI) and serum level of 25(OH)D from large-scale genome-wide association studies (GWAS), respectively. The univariable and multivariable two-sample Mendelian randomization (MR) analyses were conducted with a series of sensitivity analyses to ensure the results were reliable and reproducible. The results of univariable two-sample MR analysis showed that higher BMI was related to lower risk for BCC (Odds ratio(OR) = 0.90; 95% confidence interval (CI),[0.81,0.99]; p = 0.02). In addition, this causal effect of BMI on BCC still remained (OR = 0.88; 95%CI,[- 0.22, - 0.03], p-value = 0.008) after adjusting for 25(OH)D level in the multivariable MR analysis. However, the results suggested that 25(OH)D level was not associated with BCC(OR = 1.02; 95%CI, [0.94,1.09], p-value = 0.67). In conclusion, similar to the conclusions of retrospective observational studies, the MR results indicate that high BMI is an independent protective factor for BCC. Meanwhile, vitamin D levels may not be causally associated with the risk of basal cell carcinoma and increasing vitamin D supplementation is unlikely to reduce the risk.

Modulation of cardiometabolic risk and CardioRenal syndrome by oral vitamin D3 supplementation in Black and White Southern Sahara residents with chronic kidney disease Stage 3: focus on racial and ethnic disparities

OBJECTIVES

Several studies have shown that cholecalciferol supplementation (25OHD-S) in chronic kidney disease (CKD) improves kidney injury by reducing fibrosis-related vascular calcification and declining apoptosis-linked nephron damage.

METHODS

The oral 25OHD-S was evaluated in 60,000 IU/month/36 weeks versus in 2000 IU/d/24 weeks in CKD Stage 3 with serum 25OHD level < 20 ng/mL. The study was undertaken on 156 black subjects and 150 white subjects Southern Sahara (SS). All biomarkers of cardiometabolic (CMet) and cardiorenal (CRenal) syndrome, Renin-angiotensin-aldosterone system (RAAS) profile, secondary hyperparathyroidism (SHPT), N-terminal pro B-type natriuretic peptide (NT-proBNP), Troponin T (cTnT) and atherogenicity risk were assessed by biochemical methods. Estimate glomerular filtration rate (eGFR) by chronic CKD-EPI equation formula. Total serum vitamin D by liquid chromatography-tandem mass spectrometry (MS).

RESULTS

Vitamin D deficiency alters in the same manner CMet, CRenal, and others biomarkers in both groups SS; however, these disorders are more acute in blacks compared to whites SS. Oral 25OHD-S a highlighted improvement of eGFR drop, SHPT decrease, decline proteinuria, and cardiac failure risk (NT-proBNP and cTnT) attenuation. Concomitantly, 25OHD-S normalizes Renin, Aldosterone, and Angiotensin System (RAAS) activity. Nevertheless, homocysteine and Lp (a) do not modulate by 25OHD-S.

CONCLUSIONS

The oral vitamin D3 supplementation, according the dose, and the treatment duration does not like in black-skinned people versus to white-skinned inhabitants, while the 02 groups are native to the same Saharan environment. It emerge that a high intermittent dose through an extensive supplementation (60,000 IU/36 weeks) was more effective in black subjects. At opposite, a lower dose during a short period supplementation is sufficient (2000 IU/24 weeks) in white subjects.

Oral Cholecalciferol Supplementation in Sahara Black People with Chronic Kidney Disease Modulates Cytokine Storm, Oxidative Stress Damage and Athero-Thromboembolic Risk

The 25-hydroxyvitamin D3 (25OHD3) deficiency in chronic kidney disease (CKD) is associated with immune system dysfunction (pro-inflammatory cytokines storm) through macrophages renal infiltration, oxidative stress (OxS) damage and athero-thromboembolic risk. Conversely, cholecalciferol supplementation (25OHD-S) prevents kidney fibrosis by inhibition of vascular calcification and nephrotic apoptosis (nephrons reduction). The objective of this study was to investigate the pleiotropic effects of 25OHD-S on immunomodulation, antioxidant status and in protecting against thromboembolic events in deficiency CKD Black and White individuals living in the Southern Sahara (SS). The oral 25OHD-S was evaluated in 60,000 IU/month/36 weeks versus in 2000 IU/day/24 weeks in Black (n = 156) and White (n = 150). Total serum vitamin D was determined by liquid chromatography-tandem mass spectrometry. All biomarkers of pro-inflammatory cytokines (PIC) were assessed by ELISA tests. OxS markers were assessed by Randox kits. Homocysteine and lipoproteine (a) were evaluated by biochemical methods as biomarkers of atherothromboembolic risk. All statistical analyses were performed with Student’s t-test and one-way ANOVA. The Pearson test was used to calculate the correlation coefficient. The means will be significantly different at a level of p value < 0.05. Multiple logistic regressions were performed using Epi-info and Statview software. Vitamin D deficiency alters the PIC profile, OxS damage and atherothrombogenic biomarkers in both SS groups in the same manner; however, these disorders are more acute in Black compared to White SS individuals. The results showed that the serum 25OHD3 concentrations became normal (>75 nmol/L or >30 ng/mL) in the two groups. We have shown that the dose and duration of 25OHD-S treatment are not similar in Black SS residents compared to White SS subjects, whilst the same inhabit the south Sahara environment. It appears that a high dose intermittent over a long period (D60: 36 weeks) was more efficient in Black people; while a lower dose for a short time is sufficient (D2: 24 weeks) in their White counterparts. The oral 25OHD-S attenuates PIC overproduction and OxS damage, but does not reduce athero-thromboembolic risk, particularly in Black SS residents.

Circulatory 25(OH)D and 1,25(OH)2D as differential biomarkers between multiple system atrophy and Parkinson's disease patients

Background and purpose

There is sufficient evidence to support vitamin D's noncalcemic effects and the role of vitamin D deficiency in the development of a wide range of neurological disorders. This study aimed to evaluate whether serum 25(OH)D and 1,25(OH) 2 D could be used as biomarkers to differentiate between healthy subjects (HS), multiple system atrophy (MSA) and Parkinson's disease (PD) patients of both genders.

Methods

A total of 107 subjects were included in this study, divided into three groups: 1- HS (n = 61), 2- MSA patients (n = 19), and 3- PD patients (n = 27). The patients were assessed using UMSARS II, UPDRS III, H&Y, MMSE and MoCA rating scales. The levels of 25(OH)D and 1,25(OH) 2 D in serum were determined using the radioimmunoassay technique.

Results

The levels of 25(OH)D and 1,25(OH) 2 D in HS were 26.85 +/- 7.62 ng/mL and 53.63 +/- 13.66 pg/mL respectively. 25(OH)D levels were lower in both MSA and PD by 61% and 50%, respectively (P = 0.0001 vs. HS). 1,25(OH) 2 D levels were lower in MSA by 29%(P = 0.001 vs HS). There was a correlation between 25(OH)D and 1,25(OH) 2 D in MSA and PD, but not in HS. 1,25(OH) 2 D regressed with MMSE (β = 0.476, P = 0.04, R 2 = 0.226) in MSA, and with UPDRS III (β = -0.432, P = 0.024, R 2 = 0.187) and MoCA (β = 0.582, P = 0.005,R 2 = 0.279) in PD. 25(OH)D displayed considerable differentiative strength between HS and MSA (Wald = 17.123, OR = 0.586, P = 0.0001; AUC = 0.982, sensitivity and Youden index = 0.882, P = 0.0001) and PD (Wald = 18.552, OR = 0.700, P = 0.0001; AUC = 0.943, sensitivity = 0.889, YI = 0.791, P = 0.0001). 1,25(OH) 2 D distinguished MSA from PD (Wald 16.178, OR = 1.117, P = 0.0001; AUC = 0.868, sensitivity = 0.926, Youden index =0.632, P = 0.0001). H&Y exhibited the highest sensitivity, AUC, and significant distinguishing power between MSA and PD.

Conclusions

Serum 25(OH)D and 1,25(OH) 2 D could be useful biomarkers for MSA and PD. 25(OH)D and H&Y provided the highest sensitivity and group classification characteristics.

Weight Loss After RYGB Is Associated with an Increase in Serum Vitamin D in a Population with Low Prevalence of Hypovitaminosis D at Low Latitude

PURPOSE

In Brazil and worldwide, few studies have investigated vitamin D deficiency in patients with severe obesity who underwent bariatric surgery associated with latitude and level of solar radiation. The objective of this study was to investigate the prevalence of vitamin D deficiency and the predictive factors of serum level changes after 12 months of RYGB in a low latitude region.

MATERIALS AND METHODS

This study included 50 patients from a low-latitude city (10° 10' 8″ S) in the north of Brazil. We collected data before surgery and after 3 and 12 months of surgery. The level of vitamin D was classified as deficiency (< 20 ng/ml), insufficiency (20-30 ng/ml), and sufficiency (≥ 30 ng/ml).

RESULTS

The mean age of the patients was 38.7 ± 8.9 years, 69% were women, and percent excess weight loss (% EWL) was 83% after 1 year of surgery. The prevalence of vitamin D deficiency in the preoperative period was 14%, and after 3 and 12 months of surgery, it decreased to 4% and 6%, respectively. The variation in vitamin D after 12 months of surgery was positively associated with changes in BMI, body fat, and % EWL.

CONCLUSIONS

The prevalence of vitamin D deficiency is low in patients undergoing bariatric surgery in the northern region of Brazil, which is possibly related to low latitude. Weight loss was positively associated with an increase in serum vitamin D after surgery.

Sex Differences of Vitamin D Status across BMI Classes: An Observational Prospective Cohort Study

Growing evidence reported that vitamin D deficiency is a common finding in obesity. Vitamin D status also seems to be sex-related, although little is known regarding this association. Therefore, the aim of this study was to investigate the sex-related differences of serum 25OH vitamin D (25OHD) concentrations across body mass index (BMI) classes and, if there were any differences, whether they could be explained by sex-related differences in body composition. We enrolled 500 subjects (250 males, age 37.4 ± 11.8 years; 250 females, age 36.6 ± 11.8 years). Body composition was assessed by bioelectrical impedance analysis (BIA) phase-sensitive system. Serum 25OHD concentration was quantified by a direct, competitive chemiluminescence immunoassay. Vitamin D deficiency was defined as a serum 25OHD concentrations < 20 ng/mL (50 nmol/L). Stratifying the sample population according to sex and BMI categories, 25OHD concentrations were significantly higher in males compared to females in all BMI classes and decreased along with the increase of BMI values. Females with vitamin D deficiency had higher fat mass (FM) % compared to males with vitamin D deficiency. The 25OHD concentrations inversely correlated with FM % in both sexes. In a multiple regression analysis model, sex, FM %, and BMI were predictive factors of 25OHD concentration. In conclusion, our study suggests that 25OHD concentrations were lower in females than males across all BMI categories. Given the tight correlation between 25OHD concentrations and FM %, it can be hypothesized that the lower 25OHD concentrations in females than males can be explained by the fact that females have a higher amount of fat than males.

Mobilising vitamin D from adipose tissue: The potential impact of exercise

Vitamin D is lipophilic and accumulates substantially in adipose tissue. Even without supplementation, the amount of vitamin D in the adipose of a typical adult is equivalent to several months of the daily reference nutrient intake (RNI). Paradoxically, despite the large amounts of vitamin D located in adipose tissue, individuals with obesity are often vitamin D deficient according to consensus measures of vitamin D status (serum 25-hydroxyvitamin D concentrations). Thus, it appears that vitamin D can become 'trapped' in adipose tissue, potentially due to insufficient lipolytic stimulation and/or due to tissue dysfunction/adaptation resulting from adipose expansion. Emerging evidence suggests that exercise may mobilise vitamin D from adipose (even in the absence of weight loss). If exercise helps to mobilise vitamin D from adipose tissue, then this could have important ramifications for practitioners and policymakers regarding the management of low circulating levels of vitamin D, as well as chronically low levels of physical activity, obesity and associated health conditions. This perspective led us to design a study to examine the impact of exercise on vitamin D status, vitamin D turnover and adipose tissue vitamin D content (the VitaDEx project). The VitaDEx project will determine whether increasing physical activity (via exercise) represents a potentially useful strategy to mobilise vitamin D from adipose tissue.

Mineral bone disorders in chronic kidney disease

As the GFR loss aggravates, the disturbed mineral metabolism worsens the bone microstructure and remodelling - scenario, which is known as CKD-mineral bone disease (MBD). CKD-MBD is characterized by : (i) abnormal metabolism of calcium, phosphorus, parathyroid hormone (PTH), or vitamin D; (ii) abnormalities in bone turnover, mineralization, volume linear growth or strength; (iii) soft-tissue calcifications, either vascular or extra-osseous. Uremic vascular calcification and osteoporosis are the most common complications related to CKD-MBD. Disregulated bone turnover by uremic toxin or secondary hyperparathyroidism disturbed bone mineralization and makes it difficult for calcium and inorganic phosphate to enter into bone, resulting in increased serum calcium and inorganic phosphate. Vascular calcification worsens by hyperphosphatemia and systemic inflammation. Since vitamin D deficiency plays an important role in renal osteodystrophy, supplement of nutritional vitamin D is important in treating uremic osteoporosis and vascular calcification at the same time. Its pleotropic effect improves the bone remodeling initiated by osteoblast and alleviates the risk factors for vascular calcification with less hypercalcemia than vitamin D receptor analogs. Therefore, nutritional vitamin D should be considered in managing CKDMBD.

Diet induced obesity modifies vitamin D metabolism and adipose tissue storage in mice

Low circulating levels of total and free 25-hydroxyvitamin D (25(OH)D) indicative of vitamin D status have been associated with obesity in humans. Moreover, obesity is thought to play a causal role in the reduction of 25(OH)D levels, and several theories have been put forward to explain this relationship. Here we tested the hypothesis that obesity disrupts vitamin D homeostasis in key organs of vitamin D metabolism. Male C57BL6 mice were fed for 7 or 11 weeks on either a control diet (control, 10% energy from fat) or a high-fat diet (HF, 60% energy from fat) formulated to provide equivalent vitamin D3 intake in both groups. After 7 weeks, there was a transient increase of total 25(OH)D together with a significant decrease of plasma vitamin D3 that could be related to the induction of hepatic genes involved in 25-hydroxylation. After 11 weeks, there was no change in total 25(OH)D but a significant decrease of free 25(OH)D and plasma vitamin D3 levels. We also quantified an increase of 25(OH)D in adipose tissue that was inversely correlated to the free 25(OH)D. Interestingly, this accumulation of 25(OH)D in adipose tissue was highly correlated to the induction of Cyp2r1, which could actively participate in vitamin D3 trapping and subsequent conversion to 25(OH)D in adipose tissue. Taken together, our data strongly suggest that the enzymes involved in vitamin D metabolism, notably in adipose tissue, are transcriptionally modified under high-fat diet, thus contributing to the obesity-related reduction of free 25(OH)D.

No effects without causes: the Iron Dysregulation and Dormant Microbes hypothesis for chronic, inflammatory diseases

Since the successful conquest of many acute, communicable (infectious) diseases through the use of vaccines and antibiotics, the currently most prevalent diseases are chronic and progressive in nature, and are all accompanied by inflammation. These diseases include neurodegenerative (e.g. Alzheimer's, Parkinson's), vascular (e.g. atherosclerosis, pre-eclampsia, type 2 diabetes) and autoimmune (e.g. rheumatoid arthritis and multiple sclerosis) diseases that may appear to have little in common. In fact they all share significant features, in particular chronic inflammation and its attendant inflammatory cytokines. Such effects do not happen without underlying and initially 'external' causes, and it is of interest to seek these causes. Taking a systems approach, we argue that these causes include (i) stress-induced iron dysregulation, and (ii) its ability to awaken dormant, non-replicating microbes with which the host has become infected. Other external causes may be dietary. Such microbes are capable of shedding small, but functionally significant amounts of highly inflammagenic molecules such as lipopolysaccharide and lipoteichoic acid. Sequelae include significant coagulopathies, not least the recently discovered amyloidogenic clotting of blood, leading to cell death and the release of further inflammagens. The extensive evidence discussed here implies, as was found with ulcers, that almost all chronic, infectious diseases do in fact harbour a microbial component. What differs is simply the microbes and the anatomical location from and at which they exert damage. This analysis offers novel avenues for diagnosis and treatment.

Sunlight exposure is just one of the factors which influence vitamin D status

Studies on the determinants of vitamin D status have tended to concentrate on input - exposure to ultraviolet B radiation and the limited sources in food. Yet, vitamin D status, determined by circulating concentrations of 25-hydroxyvitamin D (25(OH)D), can vary quite markedly in groups of people with apparently similar inputs of vitamin D. There are small effects of polymorphisms in the genes for key proteins involved in vitamin D production and metabolism, including 7-dehydrocholesterol reductase, which converts 7-dehydrocholesterol, the precursor of vitamin D, to cholesterol, CYP2R1, the main 25-hydroxylase of vitamin D, GC, coding for the vitamin D binding protein which transports 25(OH)D and other metabolites in blood and CYP24A1, which 24-hydroxylates both 25(OH)D and the hormone, 1,25-dihydroxyvitamin D. 25(OH)D has a highly variable half-life in blood. There is evidence that the half-life of 25(OH)D is affected by calcium intake and some therapeutic agents. Fat tissue seems to serve as a sink for the parent vitamin D, which is released mainly when there are reductions in adiposity. Some evidence is presented to support the proposal that skeletal muscle provides a substantial site of sequestration of 25(OH)D, protecting this metabolite from degradation by the liver, which may help to explain why exercise, not just outdoors, is usually associated with better vitamin D status.

Dysregulated 1,25-dihydroxyvitamin D levels in high-fat diet-induced obesity can be restored by changing to a lower-fat diet in mice

Altered regulation of vitamin D metabolites, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D (1,25[OH]₂D), was observed in high-fat diet (HFD)-induced obesity. We hypothesized that these HFD-induced changes in vitamin D metabolism would be reversed by decreasing fat mass through dietary intervention. Four-week-old C57BL/6J mice were assigned to 1 of 3 experimental diet groups: (1) the LL group was fed a control diet for 31 weeks, (2) the HH group was fed an HFD for 31 weeks, and (3) the HL group was fed HFD for 15 weeks then switched to the control diet for the remaining 16 weeks. The fat mass of the HL group decreased by 15% from the 14th to the 30th week. Serum 1,25(OH)₂D level was significantly higher in the HH group than the LL group, whereas that of the HL group was intermediate to the 2 groups. Serum parathyroid hormone and renal 1-hydroxylase (Cyp27b1) mRNA levels, which are known to stimulate renal 1,25(OH)₂D production, were significantly higher in the HH group than the LL group. After losing fat mass, the HL group had significantly lower renal Cyp27b1 mRNA levels than the HH group. No differences were found in serum 25-hydroxyvitamin D levels and mRNA levels of hepatic 25-hydroxylases. In adipose tissue, mRNA levels of 25-hydroxylase and vitamin D receptor were elevated in parallel to the adiposity. In conclusion, serum 1,25(OH)₂D levels were closely associated with body adiposity, and reducing fat mass by changing to a lower-fat diet can reverse this obesity-associated increase in circulating 1,25(OH)₂D levels.

Serum vitamin D in patients with mild cognitive impairment and Alzheimer's disease

OBJECTIVES

To determine the relevance of Mini-Mental State Examination (MMSE), serum 25-hydroxyvitamin D (25(OH)D3), and 1,25(OH)2D3 concentrations to mild cognitive impairment (MCI) and various stages of Alzheimer's disease (AD).

MATERIALS AND METHODS

The study included 230 participants (>74 years) allocated to three main groups: 1-healthy subjects (HS, n = 61), 2-patients with MCI (n = 61), and 3- patients with Alzheimer's disease (AD) subdivided into three stages: mild (n = 41), moderate (n = 35), and severe AD (n = 32). The cognitive status was evaluated using MMSE. Serum 25 (OH)D3 (ng/ml) and 1,25(OH)2D3 concentrations (pg/ml) were determined by competitive radioimmunoassay.

RESULTS

MMSE scores and 25(OH)D3 were decreased in MCI and all stages of the AD in both genders. MMSE variability was due to gender in HS (11%) and to 25(OH)D3 in MCI (15%) and AD (26%). ROC analysis revealed an outstanding property of MMSE in diagnosis of MCI (AUC, 0.906; CI 95%, 0.847-0.965; sensitivity 82%; specificity, 98%) and AD (AUC, 0.997; CI 95%, 0.992-1; sensitivity, 100%; specificity, 98%). 25(OH)D3 exhibited good property in MCI (AUC, 0.765; CI 95%, 0.681-0.849; sensitivity, 90%; specificity, 54%) and an excellent property in diagnosis of AD (AUC, 0.843; CI 95%, 0.782-0.904; sensitivity, 97%; specificity, 79%). Logistic analyses revealed that, in MCI, MMSE could predict (or classify correctly) with 97.6% accuracy (Wald, 15.22, β, -0.162; SE, 0.554; OR = 0.115:0.039-0.341; p = .0001), whereas 25(OH)D3 with 80% accuracy (Wald, 41,013; β, -0.213; SE, 0.033; OR = 0.808: 0.757-863; p = .0001). 25(OH)D3 was the only significant predictor for the severe AD and contributed to MMSE variability. Age and gender were significant predictors only in the moderate AD. In patients with MCI, 25(OH)D3 and 1,25(OH)2D3 were correlated men, but in case of the AD, they were correlated in women.

CONCLUSIONS

MMSE and serum 25(OH)D3 concentrations could be useful biomarkers for prediction and diagnosis of MCI and various stages of the AD. The results support the utility of vitamin D supplementation in AD therapy regimen.

Cholecalciferol Additively Reduces Serum Parathyroid Hormone Levels in Severe Secondary Hyperparathyroidism Treated with Calcitriol and Cinacalcet among Hemodialysis Patients

We evaluated the improvement of intact parathyroid hormone (iPTH) levels and bone parameters by supplementing nutritional vitamin D (cholecalciferol) to combined calcimimetic (cinacalcet) and active vitamin D analog (calcitriol) among severe secondary hyperparathyroidism (SHPT) hemodialysis (HD) patients. A randomized, controlled open-label study was undertaken in 60 HD patients with serum iPTH > 1000 pg/mL or persistently high iPTH ≥ 600 pg/mL even after >3 months of calcitriol (3 μg/week). The study group received oral cholecalciferol (5000 IU/ day) and the control group received a placebo. All patients received fixed dose cinacalcet (30 mg/day, orally) and calcitriol. Calcitriol was reduced if iPTH ≤ 300 pg/mL and cinacalcet was withdrawn if serum iPTH was persistently low (iPTH ≤ 300 pg/mL) for 4 weeks after the reduction of calcitriol. A significantly lower iPTH level was noted from the 20th week in the study group compared to the placebo group, and the target iPTH ≤ 300 pg/mL was achieved at the 24th week in the study group. Most patients achieved serum 25-(OH)D₃ ≥ 30 ng/mL in the study group. Nearly 40% of study patients gained >10% improvement in femoral neck (FN) bone mineral density (BMD). We conclude that cholecalciferol additively reduced serum iPTH levels, improved 25-(OH)D₃ levels and improved FN BMD when used together with cinacalcet/calcitriol in severe SHPT HD patients.

The impact of vitamin D status and parameters of calcium metabolism in patients with primary hyperparathyroidism

BACKGROUND

There is ample evidence associating vitamin D deficiency in primary hyperparathyroidism (PHP) patients with more severe disease manifestations and increased risk of postoperative hypocalcemia. Yet, there is limited data regarding the safety of vitamin D repletion in these patients.

AIM

To assess the safety of vitamin D repletion in PHP patients in a real-world setting.

DESIGN

We included patients with asymptomatic PHP and few symptomatic patients who declined surgery, followed in our clinic, and treated on a routine basis with 2000 IU/day of vitamin D3.

METHODS

Serum calcium (sCa), PTH, 25-hydroxyvitamin D, and 24 h urinary calcium (uCa) and creatinine collections were compared between the lowest and the highest vitamin D time points.

RESULTS

There were 40 patients of a mean age was 63 ± 10 years. 25(OH)D at lowest and highest vitamin D time points was 15.5 ± 6.2 ng/ml and 33.2 ± 8, respectively (P < 0.001). Serum calcium was not affected by the changes in vitamin D levels. In none of the patients did sCa exceed 11.5 mg/dL. uCa was 220 ± 110 mg/24 h at the lowest vitamin D time point and 260 ± 140 at the highest vitamin D time point (P = 0.14). uCa exceeded 400 mg/24 h in two vs. five patients (P = 0.23) at the lowest and highest vitamin D time points, respectively. PTH was not significantly different between the different vitamin D time points.

DISCUSSION/CONCLUSION

Vitamin D repletion in PHP seems safe. Considering the documented adverse influence of vitamin D deficiency in PHP, particularly on skeletal manifestations and on the postoperative course, vitamin D repletion is warranted.

Low vitamin D status and obesity: Role of nutritionist

Low vitamin D status and obesity have concomitantly reached epidemic levels worldwide. Up to now the direction of the association between low vitamin D status and obesity, the exact mechanisms responsible for this association and the clinical usefulness to increase vitamin D status for reducing adiposity still warrant further evaluation. The aim of the present review was to examine the current evidence linking low vitamin D status and obesity in relation to the role of the nutritionist. On the one side, considering obesity as a causal factor, low sun exposure in obese individuals due to their sedentary lifestyle and less outdoor activity, vitamin D sequestration in adipose tissue, and volumetric dilution of ingested or cutaneously synthesized vitamin D₃ in the large fat mass of obese patients, might represent some of the factors playing a major role in the pathogenesis of the low vitamin D status. On the other side, the expression of both vitamin D₃ receptors and enzymes responsible for vitamin D₃ metabolism in adipocytes depicted a role for the low vitamin D status per se in the development of obesity by modulating adipocyte differentiation and lipid metabolism. Nutritionists need to accurately address the aspects influencing the low vitamin D status in obesity and the vitamin D supplementation in obese individuals.

Cholecalciferol Additively Reduces Serum Parathyroid Hormone and Increases Vitamin D and Cathelicidin Levels in Paricalcitol-Treated Secondary Hyperparathyroid Hemodialysis Patients

Background: Active Vitamin D analogues are used clinically for prevention and treatment of secondary hyperparathyroidism (SHPT) in hemodialysis (HD) patients. Nutritional vitamin D supplementation is used for additional local parathyroid (PTH) suppression, with lower incidence of hypercalcemia and hyperphosphatemia. This study evaluates the possible beneficial effects of combined vitamin D treatment (paricalcitol and cholecalciferol). Methods: Sixty HD patients with serum parathyroid hormone (iPTH) >300 pg/mL were enrolled. All patients administered 2 mcg/day of paricalcitol and were randomly allocated into control group (placebo) or study group (cholecalciferol) for 16 weeks. Serum 25(OH)D₃, iPTH and human cathelicidin (hCAP-18) were measured at baseline and during follow-up. Results: iPTH levels decreased in the study group appropriately and were more significantly decreased at 16 weeks. Study group had significantly increased 25(OH)D₃ levels. In addition, the study group had significantly increased serum hCAP-18 levels compared with control group. Correlation analysis showed a significant correlation between the percentage increase in serum hCAP-18 and 25(OH)D₃ levels. Conclusions: Cholecalciferol, in combination with paricalcitol, additively lowers the iPTH levels in a significant number of patients after 16 weeks of supplementation. A dose of 5000 IU/week of cholecalciferol could maintain serum 25(OH)D₃ levels above 30 ng/dL as early as 8 weeks after beginning supplementation. Doubling of serum cathelicidin levels were noted after 16 weeks of cholecalciferol supplementation in 40% of study patients.

Vitamin D and body composition in the elderly

OBJECTIVE

To investigate the association between vitamin D status and body composition in the elderly.

METHODS

This study was embedded in the Rotterdam Study, a population-based prospective study in Rotterdam, the Netherlands, including subjects aged 55 years and older. Serum 25-hydroxyvitamin D (25(OH)D) was measured between 1997 and 1999. Total body fat, android fat, gynoid fat and lean mass were assessed using dual-energy X-ray absorptiometry (DXA) during a follow-up visit after a median time of 5 years (2002-2004). We calculated body fat percentage, lean mass percentage, and android/gynoid fat ratio. We had 2158 participants included in our analysis. We used multivariable linear regression models. Serum 25(OH)D was analyzed continuously and after categorization according to cut-offs.

RESULTS

Mean (±SD) serum 25(OH)D concentration of the study population was 52.6 ± 25.4 nmol/L. Compared to subjects with an adequate vitamin D status (25(OH)D ≥ 75 nmol/L), vitamin D deficient participants (25(OH)D < 50 nmol/L) had a higher body fat percentage (β = 1.29, 95% CI: 0.55, 2.04) whereas no association was found with lean mass (β = 0.01, 95%CI: -0.33, 0.35). Lower 25(OH)D was associated with higher total body fat percentage specifically in participants without cardio-metabolic disease. Each 10 unit increase in serum 25(OH)D was associated with 0.03 unit decrease in android fat (β = -0.03, 95%CI: -0.06, -0.01); after adjustment for BMI the association was no longer significant. Serum 25(OH)D was also associated with the android/gynoid fat ratio but this was also mainly explained by BMI.

CONCLUSION

Lower serum 25(OH)D concentrations were associated with a higher fat mass percentage. The association between serum 25(OH)D and differential fat distribution in the elderly was mainly explained by BMI and deserves further study.

Causes of Vitamin D Deficiency and Effect of Vitamin D Supplementation on Metabolic Complications in Obesity: a Review

Obese subjects are often characterized by low plasma 25-hydroxy-vitamin D (25OHD) levels. Many explanations for this association have been proposed. Low plasma 25OHD is associated with obesity-related comorbidities such as insulin resistance, type 2 diabetes mellitus, and low-grade inflammation. In this review, we discuss the proposed mechanisms for low 25OHD in obesity and explore the results of recent RCTs on vitamin D (VD) supplementation on obesity and its metabolic complications such as insulin resistance and type 2 diabetes. Although the results from these clinical randomized controlled trials vary, the general picture is that VD treatment of obese individuals does not seem to be an effective treatment of obesity-related metabolic complications.

Effect of adipose tissue volume loss on circulating 25-hydroxyvitamin D levels: results from a 1-year lifestyle intervention in viscerally obese men

BACKGROUND/OBJECTIVES

Although weight loss has been associated with changes in circulating 25-hydroxyvitamin D (25(OH)D) levels, the quantification of the increase in 25(OH)D levels as a function of adipose tissue volume loss precisely assessed by imaging has not been reported before. The objective of this substudy was to describe the effects of a 1-year lifestyle intervention on plasma 25(OH)D levels. The relationships between changes in 25(OH)D levels and changes in adiposity volume (total and by adipose tissue compartment) were studied.

SUBJECTS/METHODS

This intervention study was performed between 2004 and 2006 and participants were recruited from the general community. Sedentary, abdominally obese and dyslipidemic men (n=103) were involved in a 1-year lifestyle modification program. Subjects were individually counseled by a kinesiologist and a nutritionist once every 2 weeks during the first 4 months with subsequent monthly visits in order to elicit a 500-kcal daily energy deficit and to increase physical activity/exercise habits. Body weight, body composition and fat distribution were assessed by dual-energy X-ray absorptiometry and computed tomography, whereas the 25(OH)D levels were measured with an automated assay.

RESULTS

The 1-year intervention resulted in a 26% increase in circulating 25(OH)D (from 48±2 nmol l(-1) or 19±0.8 ng ml(-1) (±s.e.m.) to 58±2 nmol l(-1) or 23±0.8 ng ml(-1), P<0.0001) along with a 26% decrease in visceral adiposity volume (from 1947±458 to 1459±532 cm3). One-year increases in 25(OH)D levels correlated inversely with changes in all adiposity indices, especially Δvisceral (r=-0.36, P<0.0005) and Δtotal abdominal (r=-0.37, P<0.0005) adipose tissue volumes.

CONCLUSIONS

These results indicate that there is a linear increase in circulating 25(OH)D levels as a function of adiposity volume loss, and therefore suggest a role of adiposity reduction in the management of obesity-associated vitamin D insufficiency.

High fat diet-Induced obesity alters vitamin D metabolizing enzyme expression in mice

Low serum 25(OH)D concentrations have been reported in obese humans. Inadequate sun exposure and impaired hepatic 25-hydroxylation have been suggested as possible reasons for obesity-associated vitamin D deficiency; however, the underlying mechanism has not been elucidated. We investigated the effects of high fat diet-induced obesity on vitamin D status and vitamin D metabolizing enzyme expression. Male C57BL mice (4 weeks old) were fed control diet containing 10% energy from fat (control group) or high fat diet containing 45% energy from fat (obese group) for 18 weeks. There were no differences in serum 25(OH)D concentrations between two groups, while serum 1,25(OH)2 D concentrations were significantly higher in obese mice. Hepatic mRNA levels of 25-hydroxylases (Cyp2r1, Cyp27a1, and Cyp2j3) were lower in the obese group (31, 30, and 48% lower, respectively). Renal 1α-hydroxylase (Cyp27b1) mRNA levels were higher and 24-hydroxylase (Cyp24) mRNA levels were lower in the obese group. Serum 1,25(OH)2 D concentrations correlated positively with renal Cyp27b1 expression levels and negatively with renal Cyp24 expression levels. Serum PTH concentrations were higher in obese mice. In visceral adipose tissue, Cyp27a1, Cyp2j3, and vitamin D receptor mRNA levels were higher in obese mice. Overall, vitamin D metabolizing enzyme expression was influenced by high fat diet-induced obesity, which might partly explain the mechanisms of the altered vitamin D endocrine system associated with obesity. Higher serum PTH and 1,25(OH)2 D concentrations in obese mice suggest abnormal regulation of serum 1,25(OH)2 D concentrations due to hyperparathyroidism, which might have contributed to lower hepatic 25-hydroxylase mRNA levels.

Inflammation and vitamin D: the infection connection

INTRODUCTION

Inflammation is believed to be a contributing factor to many chronic diseases. The influence of vitamin D deficiency on inflammation is being explored but studies have not demonstrated a causative effect.

METHODS

Low serum 25(OH)D is also found in healthy persons exposed to adequate sunlight. Despite increased vitamin D supplementation inflammatory diseases are increasing. The current method of determining vitamin D status may be at fault. The level of 25(OH)D does not always reflect the level of 1,25(OH)2D. Assessment of both metabolites often reveals elevated 1,25(OH)2D, indicating abnormal vitamin D endocrine function.

FINDINGS

This article reviews vitamin D's influence on the immune system, examines the myths regarding vitamin D photosynthesis, discusses ways to accurately assess vitamin D status, describes the risks of supplementation, explains the effect of persistent infection on vitamin D metabolism and presents a novel immunotherapy which provides evidence of an infection connection to inflammation.

CONCLUSION

Some authorities now believe that low 25(OH)D is a consequence of chronic inflammation rather than the cause. Research points to a bacterial etiology pathogenesis for an inflammatory disease process which results in high 1,25(OH)2D and low 25(OH)D. Immunotherapy, directed at eradicating persistent intracellular pathogens, corrects dysregulated vitamin D metabolism and resolves inflammatory symptoms.

Vascular calcification and renal bone disorders

At the early stage of chronic kidney disease (CKD), the systemic mineral metabolism and bone composition start to change. This alteration is known as chronic kidney disease-mineral bone disorder (CKD-MBD). It is well known that the bone turnover disorder is the most common complication of CKD-MBD. Besides, CKD patients usually suffer from vascular calcification (VC), which is highly associated with mortality. Many factors regulate the VC mechanism, which include imbalances in serum calcium and phosphate, systemic inflammation, RANK/RANKL/OPG triad, aldosterone, microRNAs, osteogenic transdifferentiation, and effects of vitamins. These factors have roles in both promoting and inhibiting VC. Patients with CKD usually have bone turnover problems. Patients with high bone turnover have increase of calcium and phosphate release from the bone. By contrast, when bone turnover is low, serum calcium and phosphate levels are frequently maintained at high levels because the reservoir functions of bone decrease. Both of these conditions will increase the possibility of VC. In addition, the calcified vessel may secrete FGF23 and Wnt inhibitors such as sclerostin, DKK-1, and secreted frizzled-related protein to prevent further VC. However, all of them may fight back the inhibition of bone formation resulting in fragile bone. There are several ways to treat VC depending on the bone turnover status of the individual. The main goals of therapy are to maintain normal bone turnover and protect against VC.

Vitamin D insufficiency is associated with abdominal obesity in urban Asian Indians without diabetes in North India

OBJECTIVE

We evaluated the associations of serum 25-hydroxyvitamin D [25(OH) D] levels with clinical, biochemical, and anthropometric profiles and total abdominal adipose tissue (TAAT), subcutaneous abdominal adipose tissue (SCAT), and intraabdominal adipose tissue (IAAT) depots in Asian Indians without diabetes residing in north India.

SUBJECTS AND METHODS

In this cross-sectional study (n=137; 74 males and 63 females; 18-60 years of age), anthropometric (body mass index, waist and hip circumferences, and skinfold thickness at four sites) and biochemical (fasting plasma glucose, lipid profile, and fasting insulin levels) assessments were done. Measurement of percentage body fat was done by dual energy x-ray absorptiometry, and areas of TAAT, SCAT and IAAT were measured at the L2-L3 intervertebral level by single-slice magnetic resonance imaging. Levels of 25(OH) D were measured by radioimmunoassay. Correlation analysis was used to assess relationships among clinical, biochemical, and anthropometric profiles, areas of TAAT, SCAT, and IAAT, and 25(OH) D levels.

RESULTS

The mean concentration of 25(OH) D was 40.5 ± 8.6 ng/mL. Overall, 6.6% had vitamin D deficiency (<10 ng/mL), 87.6% had insufficiency (<30 ng/mL), and 5.8% had a sufficient level (>30 ng/mL). Levels of 25(OH) D did not correlate with demographic, biochemical, and anthropometric profiles or with abdominal fat depots (TAAT, SCAT, and IAAT). In the correlation regression model, 25(OH) D was associated with TAAT in obese subjects.

CONCLUSIONS

In obese urban Asian Indians without diabetes, higher values of total abdominal fat at the L2-L3 intervertebral level were associated with low 25(OH) D levels.

Vitamin D and obesity

Obesity is a significant health problem world-wide, particularly in developed nations. Vitamin D deficiency is pandemic, and has been implicated in a wide variety of disease states. This paper seeks to examine the consistently reported relationship between obesity and low vitamin D concentrations, with reference to the possible underlying mechanisms. The possibility that vitamin D may assist in preventing or treating obesity is also examined, and recommendations for future research are made. There is a clear need for adequately-powered, prospective interventions which include baseline measurement of 25D concentrations and involve adequate doses of supplemental vitamin D. Until such studies have been reported, the role of vitamin D supplementation in obesity prevention remains uncertain.

The role of vitamin D in Alzheimer's disease: possible genetic and cell signaling mechanisms

Alzheimer's disease (AD) is the most common form of dementia in the elderly individuals and is associated with progressive memory loss and cognitive dysfunction. A significant association between AD and low levels of vitamin D has been demonstrated. Furthermore, vitamin D supplements appear to have a beneficial clinical effect on AD by regulating micro-RNA, enhancing toll-like receptors, modulating vascular endothelial factor expression, modulating angiogenin, and advanced glycation end products. Vitamin D also exerts its effects on AD by regulating calcium-sensing receptor expression, enhancing amyloid-β peptides clearance, interleukin 10, downregulating matrix metalloproteinases, upregulating heme oxygenase 1, and suppressing the reduced form of nicotinamide adenine dinucleotide phosphate expression. In conclusion, vitamin D may play a beneficial role in AD. Calcitriol is the best vitamin D supplement for AD, because it is the active form of the vitamin D3 metabolite and modulates inflammatory cytokine expression. Therefore, further investigation of the role of calcitriol in AD is needed.

Low 25-Hydroxyvitamin D Does Not Affect Insulin Sensitivity in Obesity after Bariatric Surgery

OBJECTIVE

A positive correlation between levels of 25-hydroxyvitamin D [25(OH)D] and insulin sensitivity has been shown in healthy subjects. We aimed to test the hypothesis that concentration of 25(OH)D influences insulin sensitivity in obesity before and after weight loss.

RESEARCH METHODS AND PROCEDURES

We investigated the relation between serum 25(OH)D and insulin sensitivity (estimated by euglycemic-hyperinsulinemic clamp) in 116 obese women (BMI > or = 40 kg/m2) evaluated before and 5 and 10 years after biliopancreatic diversion (BPD). Body composition was estimated by the isotope dilution method.

RESULTS

Prevalence of hypovitaminosis D was 76% in the obese status and 91% and 89% at 5 and 10 years after BPD, respectively, despite ergocalciferol supplementation. 25(OH)D concentration decreased from 39.2 +/- 22.3 in obesity (p = 0.0001) to 27.4 +/- 16.4 and 25.1 +/- 13.9 nM 5 and 10 years after BPD, respectively. Whole-body glucose uptake increased from 24.27 +/- 4.44 at the baseline to 57.29 +/- 11.56 and 57.71 +/- 8.41 mumol/kg(fat free mass) per minute 5 and 10 years after BPD, respectively (p = 0.0001). Predictor of 25(OH)D was fat mass (R2 = 0.26, p = 0.0001 in obesity; R2 = 0.20, p = 0.02 after BPD). Parathormone correlated with fat mass (R2 = 0.19; p = 0.0001) and BMI (R2 = 0.053; p = 0.01) and inversely with M value (R2 = 0.16; p = 0.0001), but only in obese subjects.

DISCUSSION

A high prevalence of hypovitaminosis D was observed in morbid obesity both before and after BPD. Low 25(OH)D did not necessarily imply increased insulin resistance after BPD, a condition where, probably, more powerful determinants of insulin sensitivity overcome the low circulating 25(OH)D levels. However, the present data cannot exclude some kind of influence of vitamin D status on glucose and insulin metabolism.

Volumetric dilution, rather than sequestration best explains the low vitamin D status of obesity

Vitamin D status is known to be poor in obese individuals; there is no consensus as to the reason. Cross-sectional study of the relation between serum 25-hydroxyvitamin D (25(OH)D) concentration and body size in the baseline data from unsupplemented adults entering two study cohorts in our research unit, N = 686. Regression analyses of body size variables against serum 25(OH)D concentration, using both linear and hyperbolic models. The fit to a hyperbolic model of 25(OH)D against body weight completely removed the obesity-related component of inter-individual variability in serum 25(OH)D concentration. The hyperbolic fit using total body weight was significantly better than any linear model, and specifically better than any using BMI. Dilution of ingested or cutaneously synthesized vitamin D in the large fat mass of obese patients fully explains their typically low vitamin D status. There is no evidence for sequestration of supplemental or endogenous cholecalciferol. Vitamin D replacement therapy needs to be adjusted for body size if desired serum 25(OH)D concentrations are to be achieved.

Baseline characteristics of subjects enrolled in the Evaluation of Cinacalcet HCl Therapy to Lower Cardiovascular Events (EVOLVE) trial

BACKGROUND

Secondary hyperparathyroidism (sHPT) and other abnormalities associated with chronic kidney disease-mineral bone disorder can contribute to dystrophic (including vascular) calcification. Dietary modification and variety of medications can be used to attenuate the severity of sHPT. However, it is unknown whether any of these approaches can reduce the high risks of death and cardiovascular disease in patients with end-stage renal disease.

METHODS

The Evaluation of Cinacalcet HCl Therapy to Lower Cardiovascular Events (EVOLVE) trial was designed to test the hypothesis that treatment with the calcimimetic agent cinacalcet compared with placebo (on a background of conventional therapy including phosphate binders +/- vitamin D sterols) reduces time to death or non-fatal cardiovascular events (specifically myocardial infarction, unstable angina, heart failure and peripheral arterial disease events) among patients on hemodialysis with sHPT. This report describes baseline characteristics of enrolled subjects with a focus on regional variation.

RESULTS

There were 3883 subjects randomized from 22 countries, including the USA, Canada, Australia, three Latin American nations, Russia and 15 European nations. The burden of overt cardiovascular disease at baseline was high (e.g. myocardial infarction 12.4%, heart failure 23.3%). The median plasma parathyroid hormone concentration at baseline was 692 pg/mL (10%, 90% range, 363-1694 pg/mL). At baseline, 87.2% of subjects were prescribed phosphate binders and 57.5% were prescribed activated vitamin D derivatives. Demographic data, comorbid conditions and baseline laboratory data varied significantly across regions.

CONCLUSIONS

EVOLVE enrolled 3883 subjects on hemodialysis with moderate to severe sHPT. Inclusion of subjects from multiple global regions with varying degrees of disease severity will enhance the external validity of the trial results.

Suboptimal maternal vitamin D status and low education level as determinants of small-for-gestational-age birth weight

PURPOSE

This study aimed firstly to investigate the contribution of maternal 25(OH) vitamin D to the association of maternal education and small-for-gestational-age birth weight (SGA) and secondly to examine whether the contribution of 25(OH) vitamin D differs by overweight, season, and maternal smoking.

METHODS

Logistic regression analysis was carried out in this study, using data of 2,274 pregnant women of Dutch ethnicity from the ABCD study, a population-based cohort study in the Netherlands. Maternal 25(OH) vitamin D was measured in early pregnancy. Stratified analyses were conducted for overweight, season of blood sampling, and smoking.

RESULTS

Low-educated women had lower 25(OH) vitamin D levels compared to high-educated women, and women in the lowest 25(OH) vitamin D quartile had a higher risk of SGA offspring. In addition, low-educated women had a higher risk of SGA offspring (OR 1.95 [95% CI: 1.20-3.14]). This association decreased with 7% after adjustment for 25(OH) vitamin D (OR 1.88 [95% CI 1.16-3.04]). In stratified analyses, adjustment for 25(OH) vitamin D resulted in a decrease in OR of about 17% in overweight women and about 15% in women who conceived in wintertime.

CONCLUSIONS

25(OH) vitamin D appears to be a modifiable contributor to the association between low maternal education and SGA offspring, particularly in overweight women and women who conceived in the winter period. In those women, increasing the intake of vitamin D, either through dietary adaptation or through supplementation in order to achieve the recommendation, could be beneficial.

The beneficial role of vitamin D in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia in the elderly individuals and is associated with progressive neurodegeneration of the human neocortex. Patients with AD have a high prevalence of vitamin D deficiency, which is also associated with low mood and impaired cognitive performance in older people. Genetic studies have provided the opportunity to determine which proteins link vitamin D to AD pathology (ie, the major histocompatibility complex class II molecules, vitamin D receptor, renin-angiotensin system, apolipoprotein E, liver X receptor, Sp1 promoter gene, and the poly(ADP-ribose) polymerase-1 gene). Vitamin D also exerts its effect on AD through nongenomic factors, that is, L-type voltage-sensitive calcium channels, nerve growth factor, the prostaglandins, cyclooxygenase 2, reactive oxygen species, and nitric oxide synthase. In conclusion, vitamin D clearly has a beneficial role in AD and improves cognitive function in some patients with AD. Calcitriol, 1 α,25-dihydroxyvitamin D3, is best used for AD because of its active form of vitamin D(3) metabolite and its receptor in the central nervous system.

Genetic Ancestry, Skin Reflectance and Pigmentation Genotypes in Association with Serum Vitamin D Metabolite Balance

BACKGROUND

Lower serum vitamin D (25(OH)D) among individuals with African ancestry is attributed primarily to skin pigmentation. However, the influence of genetic polymorphisms controlling for skin melanin content has not been investigated. Therefore, we investigated differences in non-summer serum vitamin D metabolites according to self-reported race, genetic ancestry, skin reflectance and key pigmentation genes (SLC45A2 and SLC24A5).

MATERIALS AND METHODS

Healthy individuals reporting at least half African American or half European American heritage were frequency matched to one another on age (+/- 2 years) and sex. 176 autosomal ancestry informative markers were used to estimate genetic ancestry. Melanin index was measured by reflectance spectrometry. Serum vitamin D metabolites (25(OH)D₃, 25(OH)D ₂ and 24,25(OH)₂D₃) were determined by high performance liquid chromatography (HPLC) tandem mass spectrometry. Percent 24,25(OH)₂D₃ was calculated as a percent of the parent metabolite (25(OH)D₃). Stepwise and backward selection regression models were used to identify leading covariates.

RESULTS

Fifty African Americans and 50 European Americans participated in the study. Compared with SLC24A5 111^Thr homozygotes, individuals with the SLC24A5 111^Thr/Ala and 111^Ala/Ala genotypes had respectively lower levels of 25(OH)D₃ (23.0 and 23.8 nmol/L lower, p-dominant=0.007), and percent 24,25(OH)₂D₃ (4.1 and 5.2 percent lower, p-dominant=0.003), controlling for tanning bed use, vitamin D/fish oil supplement intake, race/ethnicity, and genetic ancestry. Results were similar with melanin index adjustment, and were not confounded by glucocorticoid, oral contraceptive, or statin use.

CONCLUSIONS

The SLC24A5 111^Ala allele was associated with lower serum vitamin 25(OH)D₃ and lower percent 24,25(OH)₂D₃, independently from melanin index and West African genetic ancestry.

Effect of adiposity on vitamin D status and the 25-hydroxycholecalciferol response to supplementation in healthy young and older Irish adults

There is increasing epidemiological evidence linking sub-optimal vitamin D status with overweight and obesity. Although increasing BMI and adiposity have also been negatively associated with the change in vitamin D status following supplementation, results have been equivocal. The aim of this randomised, placebo-controlled study was to investigate the associations between anthropometric measures of adiposity and the wintertime serum 25-hydroxycholecalciferol (25(OH)D) response to 15 μg cholecalciferol per d in healthy young and older Irish adults. A total of 110 young adults (20-40 years) and 102 older adults ( ≥ 64 years) completed the 22-week intervention with >85 % compliance. The change in 25(OH)D from baseline was calculated. Anthropometric measures of adiposity taken at baseline included height, weight and waist circumference (WC), along with skinfold thickness measurements to estimate fat mass (FM). FM was subsequently expressed as FM (kg), FM (%), FM index (FMI (FM kg/height m2)) and as a percentage ratio to fat-free mass (FFM). In older adults, vitamin D status was inversely associated with BMI (kg/m2), WC (cm), FM (kg and %), FMI (kg/m2) and FM:FFM (%) at baseline (r - 0·33, - 0·36, - 0·33, - 0·30, - 0·33 and - 0·27, respectively, all P values < 0·01). BMI in older adults was also negatively associated with the change in 25(OH)D following supplementation (β - 1·27, CI - 2·37, - 0·16, P = 0·026); however, no such associations were apparent in younger adults. Results suggest that adiposity may need to be taken into account when determining an adequate wintertime dietary vitamin D intake for healthy older adults residing at higher latitudes.

Not a simple fat-soluble vitamin: Changes in serum 25-(OH)D levels are predicted by adiposity and adipocytokines in older adults

OBJECTIVE

To determine the associations between body adiposity and change in serum 25-(OH)D levels over 2.6 years, and if these associations are mediated by metabolic and inflammatory factors in older adults.

METHODS

This is a longitudinal study of 859 randomly selected subjects (mean 62 years, range 51-80, 49% women). Serum 25-hydroxyvitamin D [25-(OH)D] was assessed by radioimmunoassay at baseline and 2.6 years later. Baseline serum level of leptin was assessed by radioimmunoassay and interleukin (IL)-6 by a chemiluminescent immunoassay in the first 183 subjects.

RESULTS

In multivariable analyses, body mass index, trunk fat percentage and waist-to-hip ratio were significant predictors of increased incident vitamin D deficiency [a 25-(OH)D < 50 nmol L⁻¹ at follow-up when ≥50 nmol L⁻¹ at baseline] and decreased recovery of vitamin D deficiency [a 25-(OH)D ≥ 50 nmol L⁻¹ at follow-up when < 50 nmol L⁻¹ at baseline]. Change in 25-(OH)D levels per annum was also independently predicted by baseline leptin (β: -0.09/unit, 95% CI: -0.17, -0.03), IL-6 (β: -0.68/quartile, 95% CI: -1.35, -0.02) and total cholesterol/high-density lipoprotein (HDL) ratio (β: -0.51, 95% CI: -0.88, -0.14). The associations between body adiposity measures and change in 25-(OH)D completely disappeared after adjustment for leptin, diminished after adjustment for IL-6, but remained unchanged after adjustment for total cholesterol/HDL ratio. All associations were independent of season and sun exposure.

CONCLUSIONS

Body fat is not simply a passive reservoir for 25-(OH)D. In addition to season and sun exposure, 25-(OH)D levels appear to be determined by metabolic and, to a lesser extent, inflammatory factors, and these appear to mediate the effects of adiposity on change in 25-(OH)D.

Reversing bacteria-induced vitamin D receptor dysfunction is key to autoimmune disease

Vitamin D research is discussed in light of the hypothesis that the lower average levels of vitamin D frequently observed in autoimmune disease are not a sign of deficiency. Instead, it is proposed that the lower levels result from chronic infection with intracellular bacteria that dysregulate vitamin D metabolism by causing vitamin D receptor (VDR) dysfunction within phagocytes. The VDR dysfunction causes a decline in innate immune function that causes susceptibility to additional infections that contribute to disease progression. Evidence has been accumulating that indicates that a number of autoimmune diseases can be reversed by gradually restoring VDR function with the VDR agonist olmesartan and subinhibitory dosages of certain bacteriostatic antibiotics. Diseases showing favorable responses to treatment so far include systemic lupus erythematosis, rheumatoid arthritis, scleroderma, sarcoidosis, Sjogren's syndrome, autoimmune thyroid disease, psoriasis, ankylosing spondylitis, Reiter's syndrome, type I and II diabetes mellitus, and uveitis. Disease reversal using this approach requires limitation of vitamin D in order to avoid contributing to dysfunction of nuclear receptors and subsequent negative consequences for immune and endocrine function. Immunopathological reactions accompanying bacterial cell death require a gradual elimination of pathogens over several years. Practical and theoretical implications are discussed, along with the compatibility of this model with current research.

Vitamin D in overweight/obese women and its relationship with dietetic and anthropometric variables

Overweight/obese persons usually have an inadequate vitamin D status, a situation commonly made worse by an inadequate intake of this vitamin. For this reason, the aim of this study was to analyze dietetic and anthropometric differences in a group of young, overweight/obese Spanish women with respect to their vitamin D status. The study subjects were 66 white Spanish women (aged 20-35 years) with a BMI of 24-35 kg/m(2). Dietetic, anthropometric, and biochemical data were collected. Women were divided into two groups depending on their serum vitamin D concentrations: LD (women with <90 nmol/l 25(OH)D) and HD (women with >or=90 nmol/l 25(OH)D). The intakes of vitamin D, calcium, and supplements were similar in both groups. The body weight, BMI, and waist circumference of the HD subjects were smaller than those recorded for the LD subjects (68.6 +/- 4.2 kg, 26.0 +/- 1.3 kg/m(2), and 79.4 +/- 3.4 cm compared to 76.2 +/- 9.8, 28.6 +/- 3.2 kg/m(2), and 86.2 +/- 9.3 cm, respectively; P < 0.05). The hip circumference and the waist/hip ratio were similar in both groups. A BMI of <27.7 kg/m(2) (P50) was associated with serum vitamin D concentrations of >or=90 nmol/l (odds ratio = 0.1313; confidence interval: 0.0149-1.1599; P < 0.05). Overweight/obese women are at higher risk of vitamin D deficiency, largely due to excess adiposity rather than inadequate intake.

Plasma concentrations of 25-hydroxycholecalciferol in 22 captive tortoises (Testudo species)

The plasma concentration of 25-hydroxycholecalciferol was measured in 13 adult Hermann's tortoises (Testudo hermanni), seven adult spur-thighed tortoises (Testudo graeca) and two adult marginated tortoises (Testudo marginata) during 2004. They were healthy, of both sexes, and kept in captivity under natural unfiltered sunlight in southern England with no dietary sources of cholecalciferol. Blood samples were taken in March, June and August, and the concentration of 25-hydroxycholecalciferol did not vary significantly with the seasons. However, the concentrations in the female tortoises were always significantly lower than in the males.

Correction of preoperative vitamin D deficiency after Roux-en-Y gastric bypass surgery

BACKGROUND

To evaluate the adequacy of supplementation to correct preoperative vitamin D deficiency in adult patients during the year after Roux-en-Y gastric bypass (RYGB) surgery.

METHODS

The medical records were reviewed and the preoperative and 12-month postoperative serum 25-hydroxyvitamin D [25(OH)D] levels were compared in patients who underwent RYGB from 2002 to 2004. The serum 25(OH)D levels were defined as being optimal (> or = 80 nmol/L), suboptimal (50-79 nmol/L), or deficient (<50 nmol/L). Patients with deficient 25(OH)D levels were prescribed 50,000 IU ergocalciferol weekly. The remaining patients averaged 710 IU supplemental vitamin D intake daily.

RESULTS

The mean patient age was 43.8 +/- 10.7 years, and the mean preoperative body mass index was 51.8 +/- 9.8 kg/m2. Of the 95 patients with baseline and 12-month 25(OH)D levels, 89% were women. The mean preoperative 25(OH)D level was 49.7 +/- 26.5 nmol/L; 34% had suboptimal 25(OH)D levels and 54% had deficient levels before surgery. Twelve months after surgery, those receiving 50,000 IU weekly (n = 40) had a mean 25(OH)D level of 69.2 +/- 22.2 nmol/L; 63% had suboptimal and 8% deficient levels. Those taking 710 IU daily (n = 55) had a mean 25(OH)D level of 85.5 +/- 33.0 nmol/L; 44% had suboptimal and 6% deficient levels.

CONCLUSION

Vitamin D deficiency is prevalent in RYGB patients before surgery. The vitamin D status improved markedly after RYGB surgery with either 710 IU vitamin D daily or 50,000 IU weekly. Current supplementation practices do not appear to optimize the serum 25(OH)D levels and need to be more closely examined.

Outdoor exercise reduces the risk of hypovitaminosis D in the obese

Obesity is associated with lower levels of serum 25-hydroxyvitamin D (25(OH)D). Obese individuals might need higher doses of vitamin D supplementation than the general population. In this cross-sectional study, associations between 25(OH)D serum levels, body mass index (BMI), and outdoor exercise were assessed in a population of 291 ambulatory patients attending the Osteoporosis Center at the University of Miami, mean age 62+/-13.48 years. Obesity was defined as BMI> or =30 kg/m(2) and hypovitaminosis D as 25(OH)D< or =30 ng/ml. Overall, prevalence of obesity was 14.1% and of hypovitaminosis D was 42.4%. Among Hispanics, there was a significantly higher prevalence of hypovitaminosis D in obese (63.2%) compared to non-obese individuals (35.8%). Outdoor exercise had a significant effect on the prevalence of hypovitaminosis D in Hispanics, with a lower prevalence in those performing outdoor exercise (24.1%) compared to those who did not (47.9%). After adjusting for age, gender, and ethnicity, those reporting outdoor exercise were 47% less likely to have hypovitaminosis D, while those with obesity had more than twice the risk. Since outdoor exercise may protect overweight individuals from hypovitaminosis D, prevention programs involving higher doses of vitamin D and/or outdoor exercise may result in additional metabolic and functional benefits in this population.

Isolation and properties of the CYP2D25 promoter: Transcriptional regulation by vitamin D3 metabolites

Previous studies have suggested that hepatic production of 25-hydroxyvitamin D3 may be suppressed by 1alpha,25-dihydroxyvitamin D3. However, the molecular details of these observations have not been clarified. In the current study, the 5'-flanking DNA sequence of CYP2D25, a porcine microsomal vitamin D 25-hydroxylase, was isolated and analyzed. The CYP2D25 promoter contains a putative vitamin D response element (VDRE). The promoter activity was markedly suppressed by 1alpha,25-dihydroxyvitamin D3 and 25-hydroxyvitamin D3 in presence of vitamin D receptor (VDR). The data suggest that VDR-mediated inhibition of 25-hydroxylase(s) by vitamin D3 metabolites at the transcriptional level may play an important role in the regulation of 25-hydroxyvitamin D3 production in liver and other tissues.

Body fat and cholecalciferol supplementation in elderly homebound individuals

Vitamin D deficiency, observed mainly in the geriatric population, is responsible for loss of bone mass and increased risk of bone fractures. Currently, recommended doses of cholecalciferol are advised, but since there are few studies evaluating the factors that influence the serum levels of 25-hydroxyvitamin D (25(OH)D) following supplementation, we analyzed the relationship between the increase in serum 25(OH)D after supplementation and body fat. We studied a group of 42 homebound elderly subjects over 65 years old (31 women) in order to assess whether there is a need for adjustment of the doses of cholecalciferol administered to this group according to their adipose mass. Baseline measurements of 25(OH)D, intact parathyroid hormone and bone remodeling markers (osteocalcin and carboxy-terminal fraction of type 1 collagen) were performed. Percent body fat was measured by dual-energy X-ray absorptiometry. The patients were divided into three groups according to their percent body fat index and were treated with cholecalciferol, 7,000 IU a week, for 12 weeks. The increases in serum levels of 25(OH)D were similar for all groups, averaging 7.46 ng/mL (P < 0.05). It is noteworthy that this increase only shifted these patients from the insufficiency category to hypovitaminosis. Peak levels of 25(OH)D were attained after only 6 weeks of treatment. This study demonstrated that adipose tissue mass does not influence the elevation of 25(OH)D levels following vitamin D supplementation, suggesting that there is no need to adjust vitamin D dose according to body fat in elderly homebound individuals.

Teenage girls and elderly women living in northern Europe have low winter vitamin D status

OBJECTIVE

To determine the vitamin D status (serum 25-hydroxyvitamin D; S-25OHD) in adolescent girls and elderly community-dwelling women living in four countries of northern Europe and to explain differences in S-25OHD concentrations between and within the countries.

DESIGN

A cross-sectional observational study conducted in a standardised way during February-March. S-25OHD was analysed by high-performance liquid chromatography. Vitamin D and calcium intake was calculated using a standardised food composition database.

SETTING

Denmark, Finland, Ireland, and Poland.

SUBJECTS

A total of 199 girls (mean (s.d.) age 12.6 (0.5) y) and 221 women (mean (s.d.) age 71.8 (1.4) y).

RESULTS

The median (inter quartiles) concentration of S-25OHD was 29.4 (20.3, 38.3) nmol/l for the girls and 40.7 (28.0, 54.2) nmol/l for the women. S-25OHD below 25 nmol/l was found in 37% of the girls and 17% of the women, and S-25OHD below 50 nmol/l was found in 92% of the girls and 37% of the women. Positive significant determinants for S-25OHD in girls were use of vitamin D supplements, and in women sun habits, dietary vitamin D intake, use of vitamin D and calcium supplements. Body mass index and smoking were negative determinants in women. For women predictors could explain the differences between countries (P(country) = 0.09, R(2) = 0.39), but for girls the difference remained significant even after including predictors (P(country) = 0.03, R(2) = 0.15).

CONCLUSION

Vitamin D status is low in northern Europe during winter. More than one-third of the adolescent girls have vitamin D status below 25 nmol/l and almost all are below 50 nmol/l. Two-thirds of the elderly community-dwelling women have vitamin D status below 50 nmol/l. Use of vitamin D supplements is a significant positive determinant for S-25OHD for both girls and women (P = 0.001).

SPONSORSHIP

The European Fifth Framework Programme (Contract No. QLK1-CT-2000-00623).