Vitamin D and acute and severe illness - a mechanistic and pharmacokinetic perspective

Parathyroidectomy reduces inflammatory cytokines and increases vitamin D metabolites in patients with primary hyperparathyroidism

CONTEXT

Primary hyperparathyroidism (PHPT) is accompanied by a decreased 25-hydroxyvitamin D (25OHD) and vitamin D binding protein (DBP). High parathyroid hormone (PTH) is associated with elevated interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1), yet the role of parathyroidectomy (PTX) on DBP and cytokines is not clear.

OBJECTIVE

To prospectively evaluate the effect of PTX on inflammatory profiles, total and free 25OHD, and DBP in patients with PHPT.

METHODS

Newly diagnosed patients with PHPT were recruited in the study (n=70). Twenty-eight patients returned after PTX, 3 months later. Biochemical markers were measured before and after PTX. A group of age and BMI-matched healthy subjects were included as controls (n=70).

RESULTS

Prior to PTX, patients had lower serum DBP (37.5±6.0 vs 41.5±6.1mg/dL, p<0.001) and total 25OHD (30.1±9.5 vs 33.3±7.9ng/mL, P<0.05), but similar free 25OHD when compared to controls. Serum IL-6, C-reactive protein (CRP), and MCP-1 were higher in PHPT patients (p<0.05), whereas interleukin-10 (IL-10) was similar to controls. PTX increased total and free 25OHD and DBP (p<0.001), and decreased serum IL-6 and MCP-1 (p<0.05), but not CRP and IL-10. Multiple regression analysis indicated that the preoperative PTH explained a significant portion of the variance of IL-6 and MCP-1 (p<0.05).

CONCLUSIONS

These findings suggest that PTH may upregulate the production of MCP-1 and IL-6 and downregulate circulating DBP in patients with PHPT, that are normalized by PTX. The exact effect of IL-6 and MCP-1 on DBP, vitamin D metabolites and the role on clinical outcomes in patients with PHPT is an area requiring further study.

Alterations in regulators of the renal-bone axis, inflammation and iron status in older people with early renal impairment and the effect of vitamin D supplementation

CONTEXT

Chronic kidney disease (CKD) leads to alterations in fibroblast growth factor 23 (FGF23) and the renal-bone axis. This may be partly driven by altered inflammation and iron status. Vitamin D supplementation may reduce inflammation.

OBJECTIVE AND METHODS

Older adults with early CKD (estimated glomerular filtration rate (eGFR) 30-60 ml/min/1.73 m2; CKDG3a/b; n = 35) or normal renal function (eGFR >90 ml/min/1.73 m2; CKDG1; n = 35) received 12,000, 24,000 or 48,000 IU D3/month for 1 year. Markers of the renal-bone axis, inflammation and iron status were investigated pre- and post-supplementation. Predictors of c-terminal and intact FGF23 (cFGF23; iFGF23) were identified by univariate and multivariate regression.

RESULTS

Pre-supplementation, comparing CKDG3a/b to CKDG1, plasma cFGF23, iFGF23, PTH, sclerostin and TNFα were significantly higher and Klotho, 1,25-dihydroxyvitamin D and iron were lower. Post-supplementation, only cFGF23, 25(OH)D and IL6 differed between groups. The response to supplementation differed between eGFR groups. Only in the CKDG1 group, phosphate decreased, cFGF23, iFGF23 and procollagen type I N-propeptide increased. In the CKDG3a/b group, TNFα significantly decreased, and iron increased. Plasma 25(OH)D and IL10 increased, and carboxy-terminal collagen crosslinks decreased in both groups. In univariate models cFGF23 and iFGF23 were predicted by eGFR and regulators of calcium and phosphate metabolism at both time points; IL6 predicted cFGF23 (post-supplementation) and iFGF23 (pre-supplementation) in univariate models. Hepcidin predicted post-supplementation cFGF23 in multivariate models with eGFR.

CONCLUSION

Alterations in regulators of the renal-bone axis, inflammation and iron status were found in early CKD. The response to vitamin D3 supplementation differed between eGFR groups. Plasma IL6 predicted both cFGF23 and iFGF23 and hepcidin predicted cFGF23.

Vitamin D Binding Protein and Postsurgical Outcomes and Tissue Injury Markers After Hip Fracture: A Prospective Study

CONTEXT

Hip fracture is a serious injury that can lead to increased morbidity and mortality. Vitamin D binding protein (DBP) is a potential prognostic indicator of outcomes since it is important for actin scavenging and inflammation after tissue injury.

OBJECTIVE

To determine whether circulating DBP is associated with mobility or mortality after hip fracture and its association with acute tissue injury markers.

METHODS

Post hoc analysis of a multisite North American prospective study of 260 patients with hip fracture; mobility assessed at 30 and 60 days and mortality at 60 days after repair surgery. Biochemical markers were measured before, and 2 to 4 days after surgery. Tissue injury markers were measured in 100 randomly selected patients and controls. The primary outcome was mobility and mortality by DBP tertiles. Secondary outcomes were assessment of pre- and postoperative biomarkers.

RESULTS

Among all patients (81 ± 9 years, BMI 25 ± 4 kg/m2; 72% female), the highest DBP tertile had greater mobility at 30 (OR: 2.66; 95% CI: 1.43, 4.92; P = .002) and 60 days (OR: 2.31; 95% CI: 1.17, 4.54; P = .014) and reduced mortality (OR: 0.18; 95% CI: 0.04, 0.86; P = .032) compared with the lowest DBP tertile (<28.0 mg/dL). Total 25-hydroxyvitamin-D did not differ between tertiles (22.0 ± 9.5 ng/mL). Circulating DBP and gelsolin were lower and interleukin-6, C-reactive protein, and F-actin were higher (P < .01) in patients vs controls, and worsened (P < .01) after surgery.

CONCLUSION

High circulating DBP concentrations are associated with better mobility and reduced mortality after hip fracture surgery. The role of DBP as an acute phase reactant to tissue injury and clinical outcomes should be addressed in future study.

Vitamin D status in hospitalized COVID‑19 patients is associated with disease severity and IL-5 production

BACKGROUND

There are many studies on the relationship between vitamin D and coronavirus disease 2019 (COVID-19), while the results are matters of debate and the mechanisms remain unknown. The present study was performed to assess the impact of serum 25-hydroxyvitamin D [25(OH)D] levels on the severity of disease in hospitalized COVID-19 patients and identify potential mechanisms of 25(OH)D alterations.

METHODS

A total of 399 hospitalized COVID-19 patients were recruited from three centers between December 19, 2022, and February 1, 2023. Medical history, laboratory examination, and radiologic data were retrospectively collected. The patients were divided into four groups based on disease severity. Serum 25(OH)D levels in the patients were determined by the electrochemiluminescence method and cytokines were detected by flow cytometry. The relationship between serum 25(OH)D status and the severity of COVID-19, and the correlation between 25(OH)D levels and cytokines in COVID-19 patients were assessed.

RESULTS

Levels of 25(OH)D were significantly lower in the deceased group than in the other three groups (P < 0.05), and lower in the critical group than in the general group (P < 0.05). There were no significant differences in the 25(OH)D levels between the general and severe groups (P > 0.05). The levels of 25(OH)D (odds ratio = 0.986, 95% confidence interval: 0.973-0.998, P = 0.024) and IL-5 (odds ratio = 1.239, 95% confidence interval: 1.104-1.391, P = 0.04) were independent risk factors for the severity of COVID-19 disease upon admission. Serum 25(OH)D levels were able to predict the mortality of patients with COVID-19, and the predictive value was even higher when combined with IL-5 levels and eosinophil (Eos) count. Circulating 25(OH)D status correlated negatively with the expression of IL-5 (r=-0.262, P < 0.001) and was positively linked with CD8+ T cell counts (r=-0.121, P < 0.05) in patients with COVID-19.

CONCLUSIONS

This study found that the serum 25(OH)D status combined with IL-5 levels and Eos counts could be identified as a predictive factor for recognizing the risk of COVID-19 mortality. The serum 25(OH)D status in COVID-19 patients correlated negatively with the expression of IL-5. The potential mechanism for this relationship is worth further exploration.

Towards harmonization of directly measured free 25-hydroxyvitamin D using an enzyme-linked immunosorbent assay

The majority of circulating 25-hydroxyvitamin D (25(OH)D) is protein bound and perhaps less available than the free fraction of 25(OH)D; therefore, researchers have proposed that the measurement of free 25(OH)D in human serum may be a better indicator of vitamin D health status than total 25(OH)D. The availability of a new enzyme-linked immunosorbent assay (ELISA) for the determination of free 25(OH)D provides a method for direct measurement of the low levels of non-protein bound 25(OH)D. As an initial step towards harmonization of measurements of free 25(OH)D, the ELISA was used to measure free 25(OH)D in three existing Standard Reference Materials (SRMs): SRM 972a Vitamin D Metabolites in Frozen Human Serum, SRM 2973 Vitamin D Metabolites in Frozen Human Serum (High Level), and SRM 1949 Frozen Prenatal Human Serum. Target values for free 25(OH)D in the nine SRM serum pools, obtained by combining the results from two laboratories, ranged from 3.76 ± 0.36 to 10.0 ± 0.58 pg/mL. Of particular significance is the assignment of free 25(OH)D target values to SRM 1949, which consists of four serum pools from non-pregnant female donors of reproductive age and pregnant women in each of the three trimesters and which also has values assigned for vitamin D binding protein, which increases during pregnancy. The availability of target values for free 25(OH)D in these SRMs will allow researchers to validate new analytical methods and to compare their results with other researchers as an initial step towards harmonization of measurements among different studies and laboratories.

Relationship between Vitamin D Status and Antibody Response to COVID-19 mRNA Vaccination in Healthy Adults

The immune response to vaccination with SARS-CoV-2 vaccines varies greatly from person to person. In addition to age, there is evidence that certain micronutrients influence the immune system, particularly vitamin D. Here, we analysed SARS-CoV-2 IgG and neutralisation potency along with 25-hydroxy-cholecalciferol [25(OH)D] concentrations in a cohort of healthy German adults from the time of vaccination over 24 weeks. Contrary to our expectations, no significant differences were found in the dynamic increase or decrease of SARS-CoV-2 IgG as a function of the 25(OH)D status. Furthermore, the response to the first or second vaccination, the maximum SARS-CoV-2 IgG concentrations achieved, and the decline in SARS-CoV-2 IgG concentrations over time were not related to 25(OH)D status. We conclude that the vaccination response, measured as SARS-CoV-2 IgG concentration, does not depend on 25(OH)D status in healthy adults with moderate vitamin D status.