Effect of endrin on the hepatic distribution of iron and calcium in female sprague-dawley rats

The distribution of iron and calcium in hepatic subcellular fractions of female rats treated with endrin (1, 2, 3, 4, 10, 10-hexachloro-6, 7-epoxy-1, 4, 4α, 5, 6, 7, 8, 8α-octahydroendo, endo-1, 4:5, 8-dimethanonaphthalene) was determined. Endrin in corn oil was administered orally to rats in single doses of 3, 4.5, or 6 mg/kg, and the animals were killed at 0, 12, 24, 48, or 72 hr posttreatment. Iron and calcium were determined by atomic absorption spectroscopy. The administration of endrin increased the iron content of mitochondria and decreased the iron content of microsomes and nuclei. Significant increases occurred in the calcium content of mitochondria, microsomes, and nuclei. Thus, the results indicate that with respect to the subcellular distribution of iron and calcium, endrin produces differential effects. Vitamin E succinate administration partially prevented the endrin-induced hepatic alterations in iron and calcium homeostasis. Endrin also produced dose- and time-dependent increases in the liver and spleen weight/body weight ratios, while decreasing the thymus weight/body weight ratios. The altered distribution of calcium and iron may contribute to the broad range of effects of endrin.     

Intake of vitamin D and risk of breast cancer--a meta-analysis

Vitamin D insufficiency has been shown to be associated with a number of conditions including diabetes, multiple sclerosis and the overall risk of cancer. We aimed at studying the association between vitamin D intake and risk of breast cancer in a meta-analysis. We searched Pubmed, Embase, and Web of Science using the MESH terms "vitamin D" and "breast cancer". A total of 1731 studies were identified, but only 6 studies contained original data on the association between intake of vitamin D and risk of breast cancer. Overall there was no association between amount of vitamin D and risk of breast cancer (RR=0.98, 95% CI: 0.93-1.03, test for heterogeneity p<0.01). However, most studies reported on very low intakes of vitamin D (typically in the range 100-400IU/day). Restricting the analyses to intakes >/=400IU/day yielded a more homogenous result with a trend towards less breast cancer with >/=400IU/day vs. the lowest intake (typically <50-150IU/day), RR=0.92, 95% CI: 0.87-0.97, p for heterogeneity 0.14. In conclusion there may be a trend towards fewer cases of breast cancer with higher intakes of vitamin D (>/=400IU/day). However, more research is needed, preferably in the form of randomized-controlled trials.     

Hypophosphatemia is responsible for skeletal muscle weakness of vitamin D deficiency

A deficiency of vitamin D results in muscle weakness as well as rickets in children and osteomalacia in the adult. To study the basis for this weakness, severe vitamin D deficiency was produced in rats as revealed by a low level or absence of 25-hydroxyvitamin D₃ in the serum. Vitamin D deficiency was achieved by feeding purified diets to weanlings for 16 weeks. Muscle force, peak contraction (P), time-to-half contraction (T_1/2), time-to-peak contraction (T_P), and time-to-half recovery (T_1/2r) were measured. A significant reduction in muscle force was found when vitamin D deficiency was accompanied by hypophosphatemia. Within 2 days of correcting the hypophosphatemia, muscle strength was normalized. When serum calcium and serum phosphorus were maintained in the normal range in vitamin D-deficient rats, muscle weakness did not develop. Further, hypocalcemia together with vitamin D deficiency did not produce muscle weakness. These results strongly suggest that muscle weakness noted in rachitic patients is the result of the hypophosphatemia of vitamin D deficiency.     

Patients at risk for trace element deficiencies: Bariatric surgery

Obesity is a worldwide epidemic associated with diseases such as diabetes mellitus and cardiovascular disease. Current methods for weight loss are not very effective, particularly for those with morbid obesity. Surgical therapy may be recommended for those with a BMI ≥ 40 kg/m², or BMI ≥ 35 kg/m² with co-morbidities. This therapy can produce significant weight loss and improve/resolve co-morbidities including hypertension and hyperlipidemia. Yet successes may be tempered by adverse effects on trace element absorption and status. A PubMed literature search identified studies from January 1980 to February 2013 for inclusion in a meta-analysis. Publications that contained keywords ‘bariatric surgery or gastric bypass,’ ‘trace element or mineral or zinc or iron or copper or iodine or manganese’, and ‘absorption or status or rate or level’ were identified. Inclusion criteria were human markers that reflect changes in trace element status before and after bariatric surgery. The meta-analysis found a decrease in blood copper, zinc, hemoglobin, as well as an increase in iron, regardless of the type of surgery. The pooled effect sizes and 95% confidence intervals were 0.17 and −0.09 to 0.43 for plasma/serum iron (p = 0.20); −0.49 and −0.67 to −0.31 for blood hemoglobin (p = 0.00); −0.47 and −0.90 to −0.05 for plasma/serum copper (p = 0.03); −0.77 and −1.20 to −0.35 for plasma/serum zinc (p = 0.00). Differences in levels of these minerals pre- and post-surgery may have been influenced by the time period after surgery, a pre-existing deficiency, type and dose of vitamin–mineral supplements, and malabsorption due to elimination of parts of the gastrointestinal tract.     

Synthesis of VS-105: A novel and potent vitamin D receptor agonist with reduced hypercalcemic effects

We have synthesized a novel vitamin D receptor agonist VS-105 ((1R,3R)-5-((E)-2-((3αS,7αS)-1-((R)-1-((S)-3-hydroxy-2,3-dimethylbutoxy)ethyl)-7α-methyldihydro-1H-inden-4(2H,5H,6H,7H,7αH)-ylidene)ethylidene)-2-methylenecyclohexane-1,3-diol). Preparation of a-ring phenylphosphine oxide 11, followed by Wittig–Horner coupling of 11 with the protected 25-hydroxy Grundmann’s ketone 22 generated the precursor 12. Deprotection of the TBDMS groups of 12 produced the target compound VS-105. The biological profiles of VS-105 were evaluated using in vitro assays (VDR receptor binding, VDR reporter gene and HL-60 differentiation) in comparison to calcitriol (the endogenous hormone) or paricalcitol. Furthermore, the PTH suppressing potency and hypercalcemic side effects of VS-105 were evaluated in the 5/6 nephrectomized uremic rats in comparison to paricalcitol. Combining various changes at 20-epi, 22-oxa, 24-methyl, and 2-methylene yielded VS-105 that not only is highly potent in inducing functional responses in vitro, but also effectively suppresses PTH in a dose range that does not affect serum calcium in the 5/6 nephrectomized uremic rats.     

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 ≥ 30 kg/m² and hypovitaminosis D as 25(OH)D ≤ 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.     

Circulating vitamin D3 and 25-hydroxyvitamin D in humans: An important tool to define adequate nutritional vitamin D status

Circulating 25-hydroxyvitamin D [25(OH)D] is generally considered the means by which we define nutritional vitamin D status. There is much debate, however, with respect to what a healthy minimum level of circulation 25(OH)D should be. Recent data using various biomarkers such as intact parathyroid hormone (PTH), intestinal calcium absorption, and skeletal density measurements suggest this minimum level to be 80 nmol (32 ng/mL). Surprisingly, the relationship between circulating vitamin D₃ and its metabolic product—25(OH)D₃ has not been studied. We investigated this relationship in two separate populations: the first, individuals from Hawaii who received significant sun exposure; the second, subjects from a lactation study who received up to 6400 IU vitamin D₃/day for 6 months.

Results (1) the relationship between circulating vitamin D₃ and 25(OH)D in both groups was not linear, but appeared saturable and controlled; (2) optimal nutritional vitamin D status appeared to occur when molar ratios of circulating vitamin D₃ and 25(OH)D exceeded 0.3; at this point, the V_max of the 25-hydroxylase appeared to be achieved. This was achieved when circulating 25(OH)D exceeded 100 nmol.

We hypothesize that as humans live today, the 25-hydroxylase operates well below its V_max because of chronic substrate deficiency, namely vitamin D₃. When humans are sun (or dietary) replete, the vitamin D endocrine system will function in a fashion as do these other steroid synthetic pathways, not limited by substrate. Thus, the relationship between circulating vitamin D and 25(OH)D may represent what “normal” vitamin D status should be.     

Circulating vitamin D3 and 25-hydroxyvitamin D in humans: An important tool to define adequate nutritional vitamin D status

Circulating 25-hydroxyvitamin D [25(OH)D] is generally considered the means by which we define nutritional vitamin D status. There is much debate, however, with respect to what a healthy minimum level of circulation 25(OH)D should be. Recent data using various biomarkers such as intact parathyroid hormone (PTH), intestinal calcium absorption, and skeletal density measurements suggest this minimum level to be 80 nmol (32 ng/mL). Surprisingly, the relationship between circulating vitamin D₃ and its metabolic product—25(OH)D₃ has not been studied. We investigated this relationship in two separate populations: the first, individuals from Hawaii who received significant sun exposure; the second, subjects from a lactation study who received up to 6400 IU vitamin D₃/day for 6 months.Results (1) the relationship between circulating vitamin D₃ and 25(OH)D in both groups was not linear, but appeared saturable and controlled; (2) optimal nutritional vitamin D status appeared to occur when molar ratios of circulating vitamin D₃ and 25(OH)D exceeded 0.3; at this point, the V_max of the 25-hydroxylase appeared to be achieved. This was achieved when circulating 25(OH)D exceeded 100 nmol.We hypothesize that as humans live today, the 25-hydroxylase operates well below its V_max because of chronic substrate deficiency, namely vitamin D₃. When humans are sun (or dietary) replete, the vitamin D endocrine system will function in a fashion as do these other steroid synthetic pathways, not limited by substrate. Thus, the relationship between circulating vitamin D and 25(OH)D may represent what “normal” vitamin D status should be.     

A hetero-dimer model for concerted action of vitamin K carboxylase and vitamin K reductase in vitamin K cycle

Vitamin K carboxylase (VKC) is believed to convert vitamin K, in the vitamin K cycle, to an alkoxide-epoxide form which then reacts with CO₂ and glutamate to generate γ-carboxyglutamic acid (Gla). Subsequently, vitamin K epoxide reductase (VKOR) is thought to convert the alkoxide-epoxide to a hydroquinone form. By recycling vitamin K, the two integral-membrane proteins, VKC and VKOR, maintain vitamin K levels and sustain the blood coagulation cascade. Unfortunately, NMR or X-ray crystal structures of the two proteins have not been characterized. Thus, our understanding of the vitamin K cycle is only partial at the molecular level. In this study, based on prior biochemical experiments on VKC and VKOR, we propose a hetero-dimeric form of VKC and VKOR that may explain the efficient oxidation and reduction of vitamin K during the vitamin K cycle.     

Estrogen receptor alpha and vitamin D receptor gene polymorphisms and bone mineral density: association study of healthy pre- and postmenopausal Chinese women

In the present study, we tested the association between the estrogen receptor alpha (ER-alpha) and vitamin D receptor (VDR) genes with bone mineral density (BMD). A total of 649 healthy Chinese women, classified as pre-menopausal (N=388) and post-menopausal (N=261) groups, were genotyped at the ER-alpha PvuII, XbaI, and VDR ApaI sites. BMDs at the lumbar spine (L(1)-L(4)) and total hip were measured by dual-energy X-ray absorptiometry. For the VDR ApaI locus, AA carriers had lower spine BMD than Aa (p=0.02) and aa carriers (p<0.01) in the pre-menopausal group. For the ER-alpha gene, carriers of haplotype px had lower spine BMD than the non-carriers (p=0.03) in the pre-menopausal group. Furthermore, we observed significant interaction between the ER-alpha and VDR genes in the post-menopausal group: with AA genotype (or A allele) at the VDR ApaI locus, pX carriers had higher spine BMD than the non-carriers (p=0.02), and PX carriers had lower hip BMD than the non-carriers (p=0.04). Our data suggest that the ER-alpha and VDR genes may be associated with the BMD variation in Chinese women.     

Evaluation of Iron in Serum and Urine and their Relation with Thyroid Function in Female Goitrous Patients

In many developing countries, women are at high risk of goiter and iron deficiency anemia (IDA). Iron deficiency adversely affects thyroid metabolism and may decrease the efficiency of thyroid hormones in areas of endemic goiter. The aim of the present study was to compare the level of iron (Fe) in biological samples (serum and urine) and serum thyroid hormones, thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxin (FT4) of goitrous female patients (GFPs; n = 69) with those of nongoitrous women as control subjects (n = 117), age range 21–45 years. The biological samples were analyzed for Fe concentration using flame atomic absorption spectrophotometer, prior to microwave-assisted wet acid digestion. The validity and accuracy of the method was checked by the certified sample and with those obtained by conventional wet acid digestion method on the same CRM and real samples. The overall recoveries of Fe in serum and urine were found in the range of 97.2–98.6% of certified values. The results of this study showed that the mean values of Fe in serum and urine samples of GFPs were significantly reduced as compared to control subjects (p = 0.002 and p = 0.015, respectively). The mean values of FT3 and FT4 were found to be lower in GFPs than in the age-matched healthy control women; in contrast, high mean values of TSH were detected in GFPs (p = 0.003). There was a positive correlation between serum Fe concentration and TSH (r = 0.85, p = 0.01), FT3 (r = 0.95, p = 0.003), and FT4 levels (r = 0.98, p = 0.007) in GFPs. It was observed that iron deficiency is prevalent in GFPs, so the need of Fe supplementation will be required to improve the efficacy of thyroid metabolism in goitrous women.     

Impact of iron and vitamin C-containing supplements on preterm human milk: in vitro

Stress due to reactive oxygen species (ROS) may lead to neonatal diseases, such as necrotizing enterocolitis and respiratory distress. Enteral supplements for premature infants (PREM) added to human milk (HM) to increase nutrient content may induce lipid oxidation due to free radical formation via Fenton chemistry. We hypothesized that ferrous iron and vitamin C-containing supplements added to HM in vitro cause oxidation of milk fats, affect intracellular redox balance, and induce DNA damage. Lipid peroxidation in HM was measured by FOX-2 and TBARS assays; fatty acid composition of supplemented HM was measured by gas chromatography. Two cell culture bioassays were used for assessing either intracellular oxidative stress or DNA damage: the former involved Caco-2BBe cells, a secondary differentiated cell line, and the latter utilized FHS-74 Int cells, a primary fetal small intestinal culture. Lipid oxidation products of HM increased after the addition of iron alone, iron and vitamin C, or iron and a vitamin C-containing supplement (Trivisol, TVS). A reduced content of mono and polyunsaturated fatty acids in HM was also observed. Iron, not iron+vitamin C, but iron+TVS induced significant intracellular oxidative stress in FHS-74 Int cells. In contrast, iron, either alone or in combination with TVS or vitamin C, increased DNA damage in Caco-2BBE cells. Iron supplementation may increase oxidative stress in PREM infants and should be given separately from vitamin C-containing supplements.     

Twice single doses of 100,000 IU of vitamin D in winter is adequate and safe for prevention of vitamin D deficiency in healthy children from Ushuaia, Tierra Del Fuego, Argentina

In order to improve vitamin D status of children from Ushuaia (55°S), at the South of Argentina, double supplementation with 100.000 IU of vitamin D was administered at the beginning of winter (March 2004), and 3 months later during winter (June 2004). In 2004, serum 25-hydroxyvitamin D (25OHD) was measured before the first supplementation, a month after, and 3 months after receiving the second supplementation (March, April and September). We studied 18 healthy children from Ushuaia, age (mean ± S.D.) 7.3 ± 4.4 years old (range 1.2–14.6), seven girls and 11 boys. Before treatment, serum 25OHD was 29.3 ± 5.9 ng/ml. It increased significantly 1 month after the first supplementation (April): 35.3 ± 4.4 ng/ml (p < 0.001), and decreased significantly 3 months after the second supplementation: 22.4 ± 4.6 ng/ml (September (p < 0.001). No child was neither deficient (<10 ng/ml) nor insufficient (10–15 ng/ml) of vitamin D. On April, a month after the first supplementation, no children had vitamin D intoxication levels (>50 ng/ml). These results disclosed that to prevent vitamin D deficiency for children at zones of risk at the south of our country, double supplementation of 100,000 IU of vitamin D during autumn and winter, would be adequate and safe.     

Use of genetically modified mice to examine the skeletal anabolic activity of vitamin D

We employed genetically modified mice to examine the role of 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] on skeletal and calcium homeostasis. In mice expressing the null mutation for 25-hydroxyvitamin D 1 hydroxylase (1OHase^−/−), or the vitamin D receptor (VDR^−/−), 1,25(OH)₂D₃ and calcium were both required for optimal epiphyseal growth plate development, serum calcium and phosphorus alone were sufficient to mineralize skeletal tissue independent of 1,25(OH)₂D₃ and the VDR, and endogenous 1,25(OH)₂D₃ and the VDR were essential for baseline bone formation. In 2-week-old 1OHase^−/− mice and in 2-week-old mice homozygous for the PTH null mutation(PTH^−/−), PTH and 1,25(OH)₂D₃ were each found to exert independent and complementary effects on skeletal anabolism, with PTH predominantly affecting appositional trabecular bone growth and 1,25(OH)₂D₃ influencing both endochondral bone formation and appositional bone growth. Endogenous 1,25(OH)₂D₃ maintained serum calcium homeostasis predominantly by modifying intestinal and renal calcium transporters but not by producing net bone resorption. Administration of exogenous 1,25(OH)₂D₃ to double mutant PTH^−/−1OHase^−/− mice produced skeletal effects consistent with the actions of endogenous 1,25(OH)₂D₃. These studies reveal an important skeletal anabolic role for both endogenous and exogenous 1,25(OH)₂D₃ and point to a potential role for 1,25(OH)₂D₃ analogs in the treatment of disorders of bone loss.     

Estimation of the cutoff value of vitamin D: the Dong-gu study

Background

Vitamin D plays an essential role in bone health and growth, but the optimal serum 25-hydroxyvitamin D (25(OH)D) concentration is not known. This study was performed to investigate the optimal 25(OH)D concentration in regard to parathyroid hormone (PTH) concentration in the Korean general population aged 50 years or older.

Findings

The study population consisted of 8,857 subjects (3,545 men and 5,312 women) who participated in the baseline survey of the Dong-gu study, conducted in Korea between 2007 and 2010. Serum 25(OH)D and PTH concentrations were measured by chemiluminescent microparticle immunoassay. The optimal 25(OH)D concentration was estimated by using nonlinear regression model. Our data show that PTH concentration reached a theoretical plateau at 38.2 pg/ml and corresponding 25(OH)D concentration was 21.1 ng/ml in men and PTH concentration at 42.9 pg/ml and 25(OH)D concentration at 13.8 ng/ml in women.

Conclusions

These results indicate that, for Korean general population aged 50 years or older, the optimal 25(OH)D concentration is 21.1 ng/ml in men and 13.8 ng/ml in women.     

Exons and functional regions of the human vitamin D receptor gene around and within the main 1a promoter are well conserved among mammals

The human vitamin D receptor (hVDR) gene encompasses eight exons (2–9) in the so-called coding region and six more exons (1a–1f) in the so-called regulatory region, which contains several reported promoters. Evolutionary comparison performed on the VDR promoter sequences of a dozen of mammalian species shows a very high conservation of numerous regions around and in the 1a promoter, including exons 1e, 1a and 1d, and the Sp1 site region. This suggests that the so-called 1a promoter is well conserved among mammals. Homology among mammals also concerns three functional SNP site regions of the hVDR 1a promoter, the 1e-G-1739A SNP region (a Cdx-2 binding site), and both 1a-G-1521C and 1a-A-1012G sites, the 1a-1012A being located within a GATA site. Interestingly, the 1521G and 1012A nucleotides are being evolutionary conserved, suggesting that the 1521C/1012G haplotype, which is found in human chromosomes (43% of Caucasians), is a human specificity.     

Progesterone and vitamin D: Improvement after traumatic brain injury in middle-aged rats

Progesterone (PROG) and vitamin D hormone (VDH) have both shown promise in treating traumatic brain injury (TBI). Both modulate apoptosis, inflammation, oxidative stress, and excitotoxicity. We investigated whether 21 days of VDH deficiency would alter cognitive behavior after TBI and whether combined PROG and VDH would improve behavioral and morphological outcomes more than either hormone alone in VDH-deficient middle-aged rats given bilateral contusions of the medial frontal cortex. PROG (16 mg/kg) and VDH (5 μg/kg) were injected intraperitoneally 1 h post-injury. Eight additional doses of PROG were injected subcutaneously over 7 days post-injury. VDH deficiency itself did not significantly reduce baseline behavioral functions or aggravate impaired cognitive outcomes. Combination therapy showed moderate improvement in preserving spatial and reference memory but was not significantly better than PROG monotherapy. However, combination therapy significantly reduced neuronal loss and the proliferation of reactive astrocytes, and showed better efficacy compared to VDH or PROG alone in preventing MAP-2 degradation. VDH + PROG combination therapy may attenuate some of the potential long-term, subtle, pathophysiological consequences of brain injury in older subjects.     

Synthesis and composition of vitamin D-3 metabolites in Solanum malacoxylon

The synthesis of vitamin D-3 hydroxylated metabolites in Solanum malacoxylon was investigated. When crude leaf homogenates and subcellular fractions were incubated with [³H]vitamin D-3 and [³H]25-hydroxy-vitamin D-3 under conditions described for animal vitamin D-3-25-hydroxylase and 25-hydroxy-vitamin D-3-1α-hydroxylase, respectively, labelled metabolites identified on the basis of their chromatographic properties as 25-hydroxy-vitamin D-3 and 1,25-dyhydroxy-vitamin D-3 were formed. Other unidentified product metabolites were also detected. Vitamin D-3-25-hydroxylase activity was localized in microsomes and 25-hydroxy-vitamin D-3-1α-hydroxylase in mitochondria and microsomes. Chromatography of sterols isolated from leaf extracts preincubated with β-glucosidase on Sephadex LH-20 columns permitted the isolation of three biologically active fractions with elution properties similar to vitamin D-3, 25-hydroxy-vitamin D-3 and 1,25-dihydroxy-vitamin D-3, respectively. Ultraviolet spectra characteristic of vitamin D-3 and its metabolites were obtained after purification of the fractions by TLC. Co-chromatography of individual fractions with authentic metabolites on TLC provided further evidence that the plant contains vitamin D-3, 25-hydroxy-vitamin D-3 and 1,25-dihydroxy-vitamin D-3 as glucoside derivatives. These results suggest that a similar pathway of vitamin D-3 hydroxylation as in animals may be operative in S. malacoxylon.