Vitamin D3 restores altered cholinergic and insulin receptor expression in the cerebral cortex and muscarinic M3 receptor expression in pancreatic islets of streptozotocin induced diabetic rats

Nutritional therapy is a challenging but necessary dimension in the management of diabetes and neurodegenerative changes associated with it. The study evaluates the effect of vitamin D₃ in preventing the altered function of cholinergic, insulin receptors and GLUT3 in the cerebral cortex of diabetic rats. Muscarinic M3 acetylcholine receptors in pancreas control insulin secretion. Vitamin D₃ treatment in M3 receptor regulation in the pancreatic islets was also studied. Radioreceptor binding assays and gene expression was done in the cerebral cortex of male Wistar rats. Immunocytochemistry of muscarinic M3 receptor was studied in the pancreatic islets using specific antibodies. Y-maze was used to evaluate the exploratory and spatial memory. Diabetes induced a decrease in muscarinic M1, insulin and vitamin D receptor expression and an increase in muscarinic M3, α7 nicotinic acetylcholine receptor, acetylcholine esterase and GLUT3 expression. Vitamin D₃ and insulin treatment reversed diabetes-induced alterations to near control. Diabetic rats showed a decreased Y-maze performance while vitamin D₃ supplementation improved the behavioural deficit. In conclusion, vitamin D₃ shows a potential therapeutic effect in normalizing diabetes-induced alterations in cholinergic, insulin and vitamin D receptor and maintains a normal glucose transport and utilisation in the cortex. In addition vitamin D₃ modulated muscarinic M3 receptors activity in pancreas and plays a pivotal role in controlling insulin secretion. Hence our findings proved, vitamin D₃ supplementation as a potential nutritional therapy in ameliorating diabetes mediated cortical dysfunctions and suggest an interaction between vitamin D₃ and muscarinic M3 receptors in regulating insulin secretion from pancreas.     

Human CD8+ EMRA T cells display a senescence‐associated secretory phenotype regulated by p38 MAPK

Cellular senescence is accompanied by a senescence‐associated secretory phenotype (SASP). We show here that primary human senescent CD8⁺ T cells also display a SASP comprising chemokines, cytokines and extracellular matrix remodelling proteases that are unique to this subset and contribute to age‐associated inflammation. We found the CD8⁺ CD45RA⁺CD27^? EMRA subset to be the most heterogeneous, with a population aligning with the naïve T cells and another with a closer association to the effector memory subset. However, despite the differing processes that give rise to these senescent CD8⁺ T cells once generated, they both adopt a unique secretory profile with no commonality to any other subset, aligning more closely with senescence than quiescence. Furthermore, we also show that the SASP observed in senescent CD8⁺ T cells is governed by p38 MAPK signalling.     

Role of Vitamin D3 in Modulation of ΔNp63α Expression during UVB Induced Tumor Formation in SKH-1 Mice

ΔNp63α, a proto-oncogene, is up-regulated in non-melanoma skin cancers and directly regulates the expression of both Vitamin D receptor (VDR) and phosphatase and tensin homologue deleted on chromosome ten (PTEN). Since ΔNp63α has been shown to inhibit cell invasion via regulation of VDR, we wanted to determine whether dietary Vitamin D₃ protected against UVB induced tumor formation in SKH-1 mice, a model for squamous cell carcinoma development. We examined whether there was a correlation between dietary Vitamin D₃ and ΔNp63α, VDR or PTEN expression in vivo in SKH-1 mice chronically exposed to UVB radiation and fed chow containing increasing concentrations of dietary Vitamin D₃. Although we observed differential effects of the Vitamin D₃ diet on ΔNp63α and VDR expression in chronically irradiated normal mouse skin as well as UVB induced tumors, Vitamin D₃ had little effect on PTEN expression in vivo. While low-grade papillomas in mice exposed to UV and fed normal chow displayed increased levels of ΔNp63α, expression of both ΔNp63α and VDR was reduced in invasive tumors. Interestingly, in mice fed high Vitamin D₃ chow, elevated levels of ΔNp63α were observed in both local and invasive tumors but not in normal skin suggesting that oral supplementation with Vitamin D₃ may increase the proliferative potential of skin tumors by increasing ΔNp63α levels.     

Differencesin-Vitamin-D3-Dosing-Regimens in a Geriatric Community-Dwelling Population

ObjectiveThe adequate dose of vitamin D supple mentation for community-dwelling elderly people has not been thoroughly investigated. This study aims to determine the efficacy of a low-dose and a higher dose of vitamin D₃ in maintaining 25-hydroxyvitamin D [25(OH)D] levels at or above 30 ng/mL.MethodsThis was a single site, double-blind, ran domized exploratory clinical trial that enrolled adults 65 years of age and older. Within strata of baseline 25(OH) D levels (< 30 versus ≥ 30 ng/mL) subjects were random ized in a 1:2 ratio to receive either 400 or 2,000 IU vitamin D₃ daily for 6 months. The main outcome measures were changes in serum 25(OH)D levels according to baseline 25(OH)D levels and dose of vitamin D3.ResultsAt baseline, 41 of 105 participants (39%) had low 25(OH)D levels (< 30 ng/mL). After 6 months of vitamin D₃ supplementation, 21 of 32 participants (66%) receiving 400 IU and 14 of 59 participants (24%) receiving 2,000 IU of vitamin D₃ still had low 25(OH)D levels. Thelargest increases in serum 25(OH)D levels were observed in subjects with baseline levels < 30 ng/mL who received 2,000 IU of vitamin D daily.ConclusionRegardless of baseline 25(OH)D level, in persons 65 years of age and older, 6-month vitamin D₃ supplementation with 400 IU daily resulted in low 25(OH) D in most individuals, while 2,000 IU daily maintained 25(OH)D levels within an acceptable range in most people on this regimen. (Endocr Pract. 2012;18:847-854)     

Investigating Transdermal Delivery of Vitamin D3

Transdermal delivery of therapeutic amounts of vitamin D₃ is proposed to overcome its variable oral bioavailability, especially for people who suffer from fat malabsorption. The main challenge for this delivery route is to overcome the barrier properties of skin, especially for very lipophilic compounds such as vitamin D₃. In this study, the effect of different penetration enhancers, such as oleic acid, dodecylamine, ethanol, oleic acid in propylene glycol, isopropyl myristate, octyldodecanol, and oleyl alcohol in propylene glycol were evaluated in vitro for their effectiveness in delivering vitamin D₃ through polyamide filter, polydimethylsiloxane membrane, and porcine skin. A diffusion cell was used to study the transdermal permeability of vitamin D₃. Ointment formulations of vitamin D₃ were prepared containing the most widely used penetration enhancers, oleic acid, and dodecylamine. The ointment containing oleic acid as chemical penetration enhancer did not improve delivery compared to control. On the other hand, the formulation containing dodecylamine as a penetration enhancer did improve the transdermal delivery of vitamin D₃. However, statistical significance and an amount high enough for nutritional supplementation purposes were reached only when the skin was pretreated with 50% ethanol. In these conditions, the ointment delivered an amount of 760-ng vitamin D₃ per cm² of skin. The research shows promise that transdermal delivery could be an effective administration route for vitamin D₃ when ethanol and dodecylamine are used as penetration enhancers.KEY WORDS: dodecylamine, ethanol, penetration enhancer, transdermal delivery, vitamin D₃     

Effect of dietary cholecalciferol deficiency on plasma thyroid hormone concentrations in rainbow trout,Salmo gairdneri (Pisces,Salmonidae)

Synopsis Diets deficient in vitamin D effected a significant increase in plasma triiodothyronine (T3) concentration in raibow trout (Salmo gairdneri); different levels of dietary calcium exerted no effect on plasma T3 levels. These effects of vitamin D deficiency on plasma T3 levels appeared to be reversible, vitamin D supplementation after a period of vitamin D deficiency lowered T3 levels. Vitamin D3, vitamin D2 and the metabolites 25(OH)-D3 and 1, 25(OH)₂D3 were all effective in lowering plasma T3 levels; vitamin D3 appeared to be more effective than vitamin D₂. There appeared to be a correlation between weight gain and plasma T3 concentration in the groups fed different types and levels of vitamin D supplementation suggesting that the increased T3 levels may be a compensatory increase to the reduced weight gain of the vitamin D deficient fish. Plasma T4 levels were not affected by dietary vitamin D deficiency.     

Effectiveness of eight-week zinc supplementation on vitamin D3 status and leptin levels in a population of postmenopausal women: a double-blind randomized trial

BackgroundThe menopausal period is characterized by hormonal imbalance related to the alteration of parameters involved in lipid metabolism. In addition, menopause increases the risk of deficiencies of key vitamins and minerals such as vitamin D and zinc in such women. The present study investigates the influence of zinc supplementation on the status of vitamin D₃ and other lipid parameters in postmenopausal women.MethodsFifty-one healthy postmenopausal women aged 44–76 years from the province of Granada (Spain) were divided into two groups (placebo and zinc) of 25 and 26 women, respectively. The zinc group was supplemented with 50 mg/day of zinc for 8 weeks. Nutrient intake assessment was performed by means of a 24 -h reminder. Zinc was determined by flame atomic absorption spectrophotometry. Vitamin D was analyzed by liquid chromatography - tandem mass spectrometry. Leptin was determined by enzyme immunoassay.ResultsZinc supplementation improved the initial vitamin D₃ status of the postmenopausal population (p = 0.049). Plasma levels of 25−OH-D₃ increased significantly after Zn supplementation in women with lower age at menopause (p = 0.045). Both intake and plasma zinc levels were inversely correlated to serum leptin levels (p = 0.044 and p = 0.033, respectively), being significantly lower in lower age at menopause (p < 0.001).ConclusionZinc supplementation improved vitamin D₃ status and was associated to low leptin levels in the postmenopausal women of the study.     

Autophagy as a Mechanism of Radiation Sensitization in Breast Tumor Cells

Current studies to define the mechanism by which vitamin D₃ and analogs of vitamin D₃ enhance the response to ionizing radiation in breast tumor cells suggest that these effects are mediated, in large part, through the promotion of autophagic cell death. The residual surviving cell population remains in a senescent, growth arrested state, with minimal recovery of proliferative capacity. It is becoming evident that pathways other than or in addition to apoptosis, including senescence arrest, mitotic catastrophe and autophagy, contribute to loss of self-renewal capacity in tumor cells exposed to chemotherapeutic drugs and ionizing radiation. How and why the cell chooses a particular growth arrest and/or cell death pathway remains a puzzle to be solved.

Addendum to:

Potentiation of Radiation Sensitivity in Breast Tumor Cells by the Vitamin D₃ Analog, EB 1089 through Promotion of Autophagy and Interference with Proliferative Recovery

G. DeMasters, X. Di, R. Shiu, I. Newsham and D.A. Gewirtz

Mol Cancer Ther 2006; 5:2786-97     

Emerging role of NF-κB signaling in the induction of senescence-associated secretory phenotype (SASP)

The major hallmark of cellular senescence is an irreversible cell cycle arrest and thus it is a potent tumor suppressor mechanism. Genotoxic insults, e.g. oxidative stress, are important inducers of the senescent phenotype which is characterized by an accumulation of senescence-associated heterochromatic foci (SAHF) and DNA segments with chromatin alterations reinforcing senescence (DNA-SCARS). Interestingly, senescent cells secrete pro-inflammatory factors and thus the condition has been called the senescence-associated secretory phenotype (SASP). Emerging data has revealed that NF-κB signaling is the major signaling pathway which stimulates the appearance of SASP. It is known that DNA damage provokes NF-κB signaling via a variety of signaling complexes containing NEMO protein, an NF-κB essential modifier, as well as via the activation of signaling pathways of p38MAPK and RIG-1, retinoic acid inducible gene-1. Genomic instability evoked by cellular stress triggers epigenetic changes, e.g. release of HMGB1 proteins which are also potent enhancers of inflammatory responses. Moreover, environmental stress and chronic inflammation can stimulate p38MAPK and ceramide signaling and induce cellular senescence with pro-inflammatory responses. On the other hand, two cyclin-dependent kinase inhibitors, p16INK4a and p14ARF, are effective inhibitors of NF-κB signaling. We will review in detail the signaling pathways which activate NF-κB signaling and trigger SASP in senescent cells.     

Effect of vitamin D treatments on plasma metabolism and immune parameters of healthy dairy cows

The objective of this study was to investigate the possible beneficial effect of vitamin D repletion on certain immune parameters of vitamin D insufficient dairy cows. Twenty dairy cows in late lactation were treated daily with vitamin D in five different ways: sunlight exposure (SUN), D₂ supplementation combined with sunlight exposure (D2SUN), D₂ supplementation (D2), D₃ supplementation (D3), and D₂ and D₃ supplementation combined (D2D3). The cows had very low vitamin D levels at d 0 because of the vitamin D deprivation before the study. After 1 month of vitamin D repletion, all cows had plasma 25(OH)D levels within the normal range. Total 25(OH)D concentration was significantly higher in SUN, D2SUN and D2D3 than D2 or D3 at the end of the study. However, milk yield, as well as protein and fat content of the milk, was not influenced by vitamin D treatments. There was no difference obtained in the measured immune parameters: Leucocyte populations, somatic cell count, immunoglobulin concentrations in plasma and milk, and antigen-stimulated cytokine productions did not change in response to vitamin D repletion or difference in vitamin D sources, and no relations to plasma 25(OH)D levels were identified. Despite the fact that plasma 25(OH)D increased from a very low level to normal range, the present study did not show any effect of vitamin D repletion on the tested immune parameters of healthy dairy cows. Therefore, in this study, it was concluded that repletion to physiologically normal plasma 25-hydroxyvitamin D levels of vitamin D-depleted healthy dairy cows had no influence on immune parameters.     

Synthesis of vitamin D5: its biological activity relative to vitamins D3 and D2.

The chemical synthesis, spectral characterization, and biological activity of vitamin D₅ in vitamin D-deficient rats is reported. Vitamin D₅ is about 180-fold less active than vitamin D₃ in calcification of rachitic cartilage and about 100- to 200-fold less active in induction of bone-calcium mobilization. In stimulation of intestinal-calcium transport, vitamin D₅ is about 80-fold less active than vitamin D₃. Vitamins D₂ and D₃ appear to be equiactive in all three responses when low doses are administered.     

Dietary P regulates phosphate transporter expression,phosphatase activity,and effluent P partitioning in trout culture

Phosphate utilization by fish is an important issue because of its critical roles in fish growth and aquatic environmental pollution. High dietary phosphorus (P) levels typically decrease the efficiency of P utilization, thereby increasing the amount of P excreted as metabolic waste in effluents emanating from rainbow trout aquaculture. In mammals, vitamin D₃ is a known regulator of P utilization but in fish, its regulatory role is unclear. Moreover, the effects of dietary P and vitamin D₃ on expression of enzymatic and transport systems potentially involved in phosphate utilization are little known. We therefore monitored production of effluent P, levels of plasma vitamin D₃ metabolites, as well as expression of phosphatases and the sodium phosphate cotransporter (NaPi2) in trout fed semipu diets that varied in dietary P and vitamin D₃ levels. Mean soluble P concentrations varied markedly with dietary P but not with vitamin D₃, and constituted 40–70% of total effluent P production by trout. Particulate P concentrations accounted for 25–50% of effluent P production, but did not vary with dietary P or vitamin D₃. P in settleable wastes accounted for <10% of effluent P. The stronger effect of dietary P on effluent P levels is paralleled by its striking effects on phosphatases and NaPi2. The mRNA abundance of the intestinal and renal sodium phosphate transporters increased in fish fed low dietary P; vitamin D₃ had no effect. Low-P diets reduced plasma phosphate concentrations. Intracellular phytase activity increased but brushborder alkaline phosphatase activity decreased in the intestine, pyloric caeca, and gills of trout fed diets containing low dietary P. Vitamin D₃ had no effect on enzyme activities. Moreover, plasma concentrations of 25-hydroxyvitamin D₃ and of 1,25-dihydroxyvitamin D₃ were unaffected by dietary P and vitamin D₃ levels. The major regulator of P metabolism, and ultimately of levels of P in the effluent from trout culture, is dietary P.Communicated by: C.-H. Wang     

Vitamin D status and response to Vitamin D(3) in obese vs. non-obese African American children

Background: Serum 25‐hydroxyvitamin D (25(OH)D) is low in obese adults. Objective: To examine serum 25(OH)D in obese (BMI >95th percentile for age) vs. non‐obese (BMI = 5th–75th percentile for age) 6–10‐year‐old African American children and compare their differences in therapeutic response to vitamin D supplementation. Methods and Procedures: In an open label non‐randomized pre‐post comparison 21 obese (OB) and 20 non‐obese (non‐OB) subjects matched for age, sex, skin color, and pubertal maturation were treated with 400 IU of vitamin D₃ daily for 1 month. Serum 25(OH)D, 1,25‐dihydroxyvitamin D (1,25(OH)₂D), parathyroid hormone (PTH), leptin, and markers of bone turnover (serum bone‐specific alkaline phosphatase (BSAP), osteocalcin (OC), and urine n ‐telopeptide cross‐links of type 1 collagen (urine NTX)) were measured. Vitamin D deficiency was defined as serum 25(OH)D ≤20 ng/ml and insufficiency as 21–29 ng/ml respectively. Results: Vitamin D deficiency occurred in 12/21 (57%) OB vs. 8/20 (40%) non‐OB at baseline (P = 0.35) and persisted in 5/21 (24%) OB vs. 2/18 (11%) non‐OB (P = 0.42) after treatment. When the cohort was stratified by the baseline levels of 25(OH)D, there were differences in the response to treatment in the obese and non‐obese cohorts. Discussion: Vitamin D deficiency was common among OB and non‐OB preadolescent African American children, and 400 IU of vitamin D₃ (2× the recommended adequate intake) daily for 1 month was inadequate to raise their blood levels of 25(OH)D to ≥30 ng/ml.