The Vitamin D Metabolite Ratio Is Associated With Volumetric Bone Density in Older Men.

CONTEXT: Serum 25-hydroxyvitamin D (25(OH)D) is the current marker of vitamin D adequacy, but its relationship with bone health has been inconsistent. The ratio of 24,25-dihydroxyvitamin D3 to 25(OH)D3 (vitamin D metabolite ratio or VMR) is a marker of vitamin D that has been associated with longitudinal changes in bone mineral density (BMD) and fracture risk. OBJECTIVE: High-resolution peripheral quantitative computed tomography (HR-pQCT) provides information on bone health beyond standard dual-energy x-ray absorptiometry, in that it measures volumetric BMD (vBMD) as well bone strength. The relationship of the VMR with vBMD and bone strength remains unknown. METHODS: We evaluated the associations of the VMR and 25(OH)D3 with vBMD and bone strength in the distal radius and tibia, assessed by HR-pQCT in 545 older men participating in the Osteoporotic Fractures in Men (MrOS) Study. Primary outcomes were vBMD and estimated failure load (EFL, a marker of bone strength) at the distal radius and tibia. RESULTS: The mean age was 84 ± 4 years, 88.3% were White, and 32% had an estimated glomerular filtration rate <60 mL/min/1.73 m2. In adjusted models, each twofold higher VMR was associated with a 9% (3%, 16%) higher total vBMD and a 13% (5%, 21%) higher EFL at the distal radius. Results were similar at the distal tibia. 25(OH)D3 concentrations were not associated with any of the studied outcomes. CONCLUSION: Among older men, a higher VMR was associated with greater vBMD and bone strength while 25(OH)D3 was not. The VMR may serve as a valuable marker of skeletal health in older men.

Development and Validation of Novel Free Vitamin D Equations: The Health Aging and Body Composition Study.

Vitamin D deficiency is prevalent in 25% of Americans. However, 25(OH)D may not be an accurate measure of vitamin D because the majority (85%-90%) of 25(OH)D is bound to vitamin D binding protein (VDBP), which varies by over 30% across individuals. Free 25(OH)D may be a better measure, but it is difficult to measure accurately and precisely. The existing free 25(OH)D estimating equation does not include VDBP phenotypes; therefore, new equations that include this variable may be more accurate. A total of 370 participants in the Health, Aging, and Body Composition Study, a cohort of healthy community-dwelling individuals aged 70-79 years old, underwent VDBP and vitamin D metabolite [25(OH)D, 24,25(OH)2D, 1,25(OH)2D, free 25(OH)D] measurements and were randomly allocated into equation development (two out of three) and internal validation (one out of three) groups. New equations were developed with multiple linear regression and were internally validated with Bland-Altman plots. The mean age was 75 ± 3 years, 53% were female, and the mean measured free 25(OH)D was 5.37 ± 1.81 pg/mL. Three equations were developed. The first equation included albumin, 25(OH)D3, 25(OH)D2, VDBP, 1,25(OH)2D3, and 24,25(OH)2D3. The second equation included all variables in Eq. (1) plus VDBP phenotypes. The third equation included albumin, 25(OH)D3, intact parathyroid hormone, and 1,25(OH)2D3. In internal validation, all three new equations predicted free 25(OH)D values within 30% and 15% of the measured free 25(OH)D concentrations in 76%-80% and 48%-52% of study participants, respectively. Equation (2) was the most precise, with a mean bias of 0.06 (95% limits of agreement -2.41 to 2.30) pg/mL. The existing equation estimated free 25(OH)D within 30% and 15% of measured free 25(OH)D in 43% and 22% of participants, respectively. Free 25(OH)D can be estimated with clinically available biomarkers as well as with more laboratory-intensive biomarkers with moderate precision. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

The Vitamin D Metabolite Ratio (VMR) is a Biomarker of Vitamin D Status That is Not Affected by Acute Changes in Vitamin D Binding Protein.

BACKGROUND: 25-hydroxyvitamin D[25(OH)D] may be a poor marker of vitamin D status due to variability in levels of vitamin D binding protein (VDBP). The vitamin D metabolite ratio (VMR) is the ratio of 24,25-dihydroxyvitamin D[24,25(OH)2D3] to 25(OH)D3 and has been postulated to reflect vitamin D sufficiency independent of variability in VDBP. Therapeutic plasma exchange (TPE) is a procedure that removes plasma, including VDBP, and may lower bound vitamin D metabolite concentrations. Effects of TPE on the VMR are unknown. METHODS: We measured 25(OH)D, free 25(OH)D, 1,25-dihydroxyvitamin D[1,25(OH)2D], 24,25(OH)2D3, and VDBP in persons undergoing TPE, before and after treatment. We used paired t-tests to assess changes in these biomarkers during a TPE procedure. RESULTS: Study participants (n = 45) had a mean age of 55 ± 16 years; 67% were female; and 76% were white. Compared to pretreatment concentrations, TPE caused a significant decrease in total VDBP by 65% (95%CI 60,70%), as well as all the vitamin D metabolites-25(OH)D by 66% (60%,74%), free 25(OH)D by 31% (24%,39%), 24,25(OH)2D3 by 66% (55%,78%) and 1,25(OH)2D by 68% (60%,76%). In contrast, there was no significant change in the VMR before and after a single TPE treatment, with an observed mean 7% (-3%, 17%) change in VMR. CONCLUSIONS: Changes in VDBP concentration across TPE parallel changes in 25(OH)D, 1,25(OH)2D, and 24,25(OH)2D3, suggesting that concentrations of these metabolites reflect underlying VDBP concentrations. The VMR is stable across a TPE session despite a 65% reduction in VDBP. These findings suggest that the VMR is a marker of vitamin D status independent of VDBP levels.

Mandatory Research Biopsy Requirements Delay Initiation of Clinical Trials.

Background: There has been an increasing requirement for fresh tumor tissue to enroll in clinical trials in order to look for specific biomarkers. This has been shown to increase screening duration and increase screen failure rates. It was important to corroborate these results in other centers. Methods: This study is a non-randomized retrospective analysis of patients in one subset of patients seen by research nurses who operated in the standard head/neck and lung team not including patients in the phase 1 program. All patients were enrolled in clinical trials from January 16, 2013 to May 28, 2018 at USC Norris Comprehensive Cancer Institute in Los Angeles. Patients who were required to give fresh research biopsies prior to intervention were part of the research biopsy group. Results: In total, 76 patients were analyzed in this study. Thirty-three patients were in the research biopsygroup and 43 patients were in the no biopsy group. Trials that required a fresh biopsy had a longer median screening duration (30 vs. 14 days) than trials that did not require a biopsy (p < 0.0001). Conclusions: Our study shows that requiring biopsies prior to clinical trial treatment results in a statistically significant delay in treatment. The informed consent forms that were part of clinical trials involving mandatory research biopsies did not reflect this delay in treatment. However, these delays did not result in a statistically significant decrease in number of days on trial or days until progression of disease.

Tuberculosis following PD-1 blockade for cancer immunotherapy.

Because of the well-established therapeutic benefit of boosting antitumor responses through blockade of the T cell inhibitory receptor PD-1, it has been proposed that PD-1 blockade could also be useful in infectious disease settings, including Mycobacterium tuberculosis (Mtb) infection. However, in preclinical models, Mtb-infected PD-1-/- mice mount exaggerated TH1 responses that drive lethal immunopathology. Multiple cases of tuberculosis during PD-1 blockade have been observed in patients with cancer, but in humans little is understood about Mtb-specific immune responses during checkpoint blockade-associated tuberculosis. Here, we report two more cases. We describe a patient who succumbed to disseminated tuberculosis after PD-1 blockade for treatment of nasopharyngeal carcinoma, and we examine Mtb-specific immune responses in a patient with Merkel cell carcinoma who developed checkpoint blockade-associated tuberculosis and was successfully treated for the infection. After anti-PD-1 administration, interferon-γ-producing Mtb-specific CD4 T cells became more prevalent in the blood, and a tuberculoma developed a few months thereafter. Mtb-specific TH17 cells, CD8 T cells, regulatory T cells, and antibody abundance did not change before the appearance of the granuloma. These results are consistent with the murine model data and suggest that boosting TH1 function with PD-1 blockade may increase the risk or severity of tuberculosis in humans.