Nonenzymatic Glycation and Degree of Mineralization Are Higher in Bone From Fractured Patients With Type 1 Diabetes Mellitus.

Low-energy fractures are frequent complications in type 1 diabetes mellitus patients (T1DM). Modifications of bone intrinsic composition might be a potential cause of fragility observed in diabetic subjects. Advanced glycation end products (AGEs) were found in numerous connective tissues from T1DM patients.

Quantifying the vitamin D economy.

Vitamin D enters the body through multiple routes and in a variety of chemical forms. Utilization varies with input, demand, and genetics. Vitamin D and its metabolites are carried in the blood on a Gc protein that has three principal alleles with differing binding affinities and ethnic prevalences.

25-Hydroxyvitamin D response to graded vitamin D₃ supplementation among obese adults.

Context: Guidelines have suggested that obese adults need 2 to 3 times more vitamin D than lean adults to treat vitamin D deficiency, but few studies have evaluated the vitamin D dose response in obese subjects.

Objective: The purpose of this study was to characterize the pharmacokinetics of 25-hydroxyvitamin D [25(OH)D] response to 3 different doses of vitamin D₃ (cholecalciferol) in a group of obese subjects and to quantify the 25(OH)D dose-response relationship. DESIGN, SETTING, INTERVENTION, PATIENTS: This was a randomized, single-blind study of 3 doses of oral vitamin D₃ (1000, 5000, or 10,000 IU) given daily to 67 obese subjects for 21 weeks during the winter months.

Successful treatment of tumor-induced osteomalacia due to an intracranial tumor by fractionated stereotactic radiotherapy.

Context: Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome, characterized by tumor secretion of fibroblast growth factor-23 (FGF23) causing hypophosphatemia due to renal phosphate wasting. TIO is usually caused by small, benign, difficult-to-localize, mesenchymal tumors. Although surgery with wide excision of tumor borders is considered the "gold standard" for definitive therapy, it can be associated with considerable morbidity depending on the location.

All-source basal vitamin D inputs are greater than previously thought and cutaneous inputs are smaller.

The magnitude of vitamin D inputs in individuals not taking supplements is unknown; however, there is a great deal of information on quantitative response to varying supplement doses. We reanalyzed individual 25-hydroxyvitamin D [25(OH)D] concentration data from 8 studies involving cholecalciferol supplementation (total sample size = 3000). We extrapolated individual study dose-response curves to zero concentration values for serum 25(OH)D by using both linear and curvilinear approaches and measured seasonal oscillation in the serum 25(OH)D concentration.

Calcium absorption response to cholecalciferol supplementation in hemodialysis.

Background And Objectives: Recent understanding of extrarenal production of calcitriol has led to the use of more vitamin D supplementation in CKD populations. This paper reports the effect of cholecalciferol supplementation on calcium absorption.

Design, Setting, Participants, & Measurements: Paired calcium absorption tests were done before and after 12-13 weeks of 20,000 IU weekly cholecalciferol supplementation in 30 participants with stage 5 CKD on hemodialysis.

Pathophysiology of osteoporosis: new mechanistic insights.

Understanding of the pathophysiology of osteoporosis has evolved to include compromised bone strength and skeletal fragility caused by several factors: (1) defects in microarchitecture of trabeculae, (2) defective intrinsic material properties of bone tissue, (3) defective repair of microdamage from normal daily activities, and (4) excessive bone remodeling rates. These factors occur in the context of age-related bone loss. Clinical studies of estrogen deprivation, antiresorptives, mechanical loading, and disuse have helped further knowledge of the factors affecting bone quality and the mechanisms that underlie them.

25-Hydroxyvitamin D response to cholecalciferol supplementation in hemodialysis.

Background And Objectives: Recent understanding of extrarenal production of calcitriol has led to the exploration of native vitamin D treatment in dialysis patients. This paper reports the pharmacokinetics of 25-hydroxyvitamin D response to 10,333 IU cholecalciferol given weekly in subjects on chronic dialysis.

Design, Setting, Participants, & Measurements: This randomized, double-blind, placebo-controlled trial of 15 weeks of oral cholecalciferol in subjects with stage 5 CKD requiring maintenance hemodialysis was conducted from November of 2007 to March of 2010.

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.

Trabecular bone histomorphometry in humans with Type 1 Diabetes Mellitus.

Patients with Type 1 Diabetes Mellitus (DM) have markedly increased risk of fracture, but little is known about abnormalities in bone microarchitecture or remodeling properties that might give insight into the pathogenesis of skeletal fragility in these patients. We report here a case-control study comparing bone histomorphometric and micro-CT results from iliac biopsies in 18 otherwise healthy subjects with Type 1 Diabetes Mellitus with those from healthy age- and sex-matched non-diabetic control subjects. Five of the diabetics had histories of low-trauma fracture.

Vitamin D: the iceberg nutrient.

The understanding of vitamin D's role in human health has recently expanded. It is now recognized as more than a hormone activated in the kidney only for calcium homeostasis. It is metabolized and used by virtually every cell in the body.

Vitamin D(3) is more potent than vitamin D(2) in humans.

Background: Current unitage for the calciferols suggests that equimolar quantities of vitamins D(2) (D2) and D(3) (D3) are biologically equivalent. Published studies yield mixed results.

Objective: The aim of the study was to compare the potencies of D2 and D3.

Vitamin D3 distribution and status in the body.

Objective: To estimate the amount, type, and tissue distribution of vitamin D in the adult body under typical inputs.

Methods: Review and reanalysis of published measurements and analysis of tissue samples from growing pigs raised in confinement on diets providing about 2000 IU vitamin D/day. Cholecalciferol and 25-hydroxyvitamin D [25(OH)D] concentration measured by HPLC.

Do melanoidins induced by topical 9% dihydroxyacetone sunless tanning spray inhibit vitamin d production? A pilot study.

We report here preliminary pilot study data of the effect of sunless tanning spray with 9% [Correction added after online publication (August 24th, 2009): The concentration of Dihydroxyacetone used in the study was 9% and not 3% as previously stated] dihydroxyacetone (DHA) on 25-hydroxyvitamin D [25(OH)D] serum levels in subjects exposed to controlled amounts of UV-B radiation during April/May in Omaha, NE, 41 degrees N latitude. We found that DHA-induced melanoidins in skin act as a topical sunscreen attenuating the formation of 25(OH)D.

25-Hydroxylation of vitamin D3: relation to circulating vitamin D3 under various input conditions.

Background: Neither the efficiency of the 25-hydroxylation of vitamin D nor the steady state relation between vitamin D(3) and 25-hydroxyvitamin D [25(OH)D] has been studied in humans.

Objective: We aimed to examine the relation between serum vitamin D(3) and 25(OH)D in normal subjects after either oral administration of vitamin D(3) or ultraviolet-B radiation across a broad range of inputs.

Design: Values for serum vitamin D(3) and (OH)D(3) were aggregated from 6 studies--1 acute and 5 near-steady state--at various vitamin D(3) inputs.

Pharmacokinetics of a single, large dose of cholecalciferol.

Background: There is much interest in dosing vitamin D intermittently for patient convenience and long-term adherence.

Objective: The objective was to characterize the time course and response of 25-hydroxyvitamin D (calcidiol) to a large oral dose of cholecalciferol.

Design: One group (30 subjects) was supplemented with a single oral dose of 100,000 IU cholecalciferol.

Ultraviolet-B radiation increases serum 25-hydroxyvitamin D levels: the effect of UVB dose and skin color.

Background: Ultraviolet (UV)-B light increases vitamin D levels, but the dose response and the effect of skin pigmentation have not been well characterized.

Objective: We sought to define the relationship between UVB exposure and 25-hydroxyvitamin D (25-OH-D) concentrations as a function of skin pigmentation.

Methods: Seventy two participants with various skin tones had 90% of their skin exposed to UVB light (20-80 mJ/cm2) 3 times a week for 4 weeks.

Vitamin D2 is much less effective than vitamin D3 in humans.

Vitamins D(2) and D(3) are generally considered to be equivalent in humans. Nevertheless, physicians commonly report equivocal responses to seemingly large doses of the only high-dose calciferol (vitamin D(2)) available in the U.S.