Baseline and on-treatment characteristics, including age, obesity, calcium intake, and bone turnover markers, may predict the bone mineral density (BMD) response in women with postmenopausal osteoporosis (PMO) to 1 to 2 years of antiresorptive therapy and/or vitamin D supplementation. This study aimed to explore clinical characteristics associated with 12-month BMD improvement in Chinese women with postmenopausal osteoporosis (PMO).In this post hoc analysis of a previous phase 3 multicenter, randomized controlled trial, Chinese PMO women who were treated with once weekly alendronate 70 mg/vitamin D3 5600 IU (ALN/D5600) or once daily calcitriol 0.25 mcg, and had measurements of 1-year lumbar spine BMD (LS-BMD) and on-treatment bone turnover markers (BTMs) were included in the analysis.In Chinese PMO patients on ALN/D5600, 1-year LS-BMD change was negatively correlated with age (β = -0.00084, P < .01), dietary calcium (β = -0.0017, P = .07), and procollagen type 1 N-terminal propeptide (P1NP) change at month 6 (β = -0.000469, P = .0016), but positively with body mass index (BMI) (β = 0.00128, P = .08); baseline P1NP above the median was associated with a significantly greater BMD percentage change at the lumbar spine (P = .02) and the total hip (P = .0001). In the calcitriol group, a significant 1-year LS-BMD increase was associated with BMI (β = 0.0023, P = .02), baseline P1NP (β = 0.00035, P = .0067), history of prior vertebral fracture(s) (β = 0.034, P < .0001) and baseline serum 25(OH)D level (β = -0.00083, P = .02).The presented findings from Chinese postmenopausal osteoporotic women suggested clinically meaningful baseline and on-treatment characteristics predicting BMD improvement after 1 year of ALN/D5600 treatment, which differed from calcitriol treatment with baseline identifiable associations. The study remained exploratory and further accumulation of evidence is needed.

Calcitriol is the normal physiologically active form of vitamin D, 1,25-dihydroxyvitamin D. Limited data indicate that its use in nursing mothers in appropriately adjusted doses does not affect the breastfed infant. If calcitriol is required by the mother, it is not a reason to discontinue breastfeeding. Calcitriol and calcium dosage requirements are usually reduced during lactation in women with hypoparathyroidism.[1][2][3][4][5][6][7][8] The American Academy of Pediatrics recommends the administration of a minimum of 400 IU of vitamin D daily to all infants, children and adolescents.[9]

Vitamin D deficiency and up-regulated TNFα-related signals are reported to be involved in abnormalities including intestinal hyper-permeability, bacterial translocation, systemic/portal endotoxemia, intestinal/adipose tissue/hepatic inflammation, and hepatic steatosis in nonalcoholic steatohepatitis (NASH). This study aims to explore the molecular mechanisms and effects of chronic calcitriol [1,25-(OH)2D3, hormonal form of vitamin D] on gut-adipose tissue-liver axis abnormalities using a high-fat diet (HFD)-fed rat model of NASH. In HFD-fed obese rats on a 10-week calcitriol (0.3 μg/kg/TIW) or vehicle treatment (NASH-vit. D and NASH-V rats) reigme, various in vivo and in vitro experiments were undertaken. Through anti-TNFα-TNFR1-NFκB signaling effects, chronic calcitriol treatment significantly restored plasma calcitriol levels and significantly improved vitamin D receptor (VDR) expression in monocytes and the small intestine of NASH-vit. D rats. Significantly, plasma and portal endotoxin/TNFα levels, bacterial translocation to mesenteric lymph nodes, plasma DX-4000-FITC, fecal albumin-assessed intestinal hyper-permeability, over-expression of TNFα-related immune profiles in monocytes, inflammation of intestinal/mesenteric adipose tissue (MAT)/liver and hepatic steatosis were improved by chronic calcitriol treatment of NASH rats. Additionally, in vitro experiments with acute calcitriol co-incubation reversed NASH-V rat monocyte supernatant/TNFα-induced monolayer barrier dysfunction in caco-2 cells, cytokine release from MAT-derived adipocytes, and triglyceride synthesis by lean-V rat hepatocytes. Using in vivo and in vitro experiments, our study reported calcitriol signaling in the gut as well as in adipose tissue. Meanwhile, our study suggests that restoration of systemic and intestinal vitamin D deficiency using by chronic vitamin D treatment effectively reduces TNFα-mediated immunological abnormalities associated with the gut-adipose tissue-liver axis and hepatic steatosis in NASH rats.

The hormone fibroblast growth factor 23 (FGF23) is secreted from bone and is involved in phosphorus (P) metabolism. FGF23 mainly binds the FGF receptor, which interacts with αKlotho in the kidney or parathyroid and regulates Na-dependent phosphate co-transporter type IIa (NaPi-IIa) and type IIc (NaPi-IIc) expression, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) activity, and parathyroid hormone (PTH) secretion. In this study, we utilized hemi-nephrectomized rats fed a high-P diet (HP Nx), rats subjected to a partial nephrectomy (PN) and rats with doxorubicin-induced renal failure (DXR) as chronic kidney disease (CKD) animal models and analyzed the P metabolism and FGF23 expression in the kidneys in each CKD model. We cultured HK2 cells with a high level of P, 1,25(OH)2D3 or transforming growth factor-β1 (TGFβ1) to investigate the FGF23 expression mechanism. In both the HP Nx and PN rats, the blood FGF23 and PTH levels were increased. However, the 1,25(OH)2D3 level was increased in the HP Nx rats and decreased in the PN rats. In all three animal models, the mRNA expression of αKlotho, NaPi-IIa and NaPi-IIc was decreased, and the mRNA expression of TGFβ1, collagen1a1, osteopontin and FGF23 was elevated in the kidney. FGF23 protein and mRNA were expressed at high levels in the extended tubule epithelium, which was an osteopontin-positive region in the HP and PN rats. FGF23 and osteopontin mRNAs were expressed in HK2 cells incubated with TGFβ1; however, these levels were not altered in HK2 cells incubated with 1,25(OH)2D3 and high P levels in vitro. Altogether, FGF23 is expressed in the kidneys in CKD model rats. Following stimulation with TGFβ1, the injured renal tubular epithelial cells are strongly suspected to express both FGF23 and osteopontin. FGF23 produced in the kidney might contribute to P metabolism in subjects with CKD.

Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disease. Vitamin D has important roles both in the autoimmune response and in skeletal muscles. We investigated the levels of 1,25-dihydroxy vitamin D [1,25(OH)2D] and 25-hydroxy vitamin D [25(OH)D] in patients with MG and healthy subjects. MG patients were classified by disease stage, age of onset and treatment status whether or not to taking immunosuppressive agents. MG patients had lower plasma 25(OH)D levels (mean, 18.8 ± 8.4 ng/mL) than healthy controls (26.3 ± 6.1 ng/mL) (p < .05). 1,25(OH)2D levels showed slightly high in MG patients than healthy controls, but had no significant difference between two groups. In addition, no significant differences were observed between two groups divided by clinical characteristics. Serum 25(OH)D levels significantly lower in patients with MG compared with healthy controls. We recommend monitoring of vitamin D status in patients with MG to avoid direct negative effects on the muscles or autoimmune response.