Evaluation of Vitamin D binding protein and 25-hydroxy Vitamin D metabolites in COVID-19 patients

Objectives: The immunomodulatory roles of Vitamin D and Vitamin D binding protein (VDBP) are in interest with incidence or outcome of coronavirus disease-2019 (COVID-19). This study aimed to investigate the association between the severity of COVID-19 with VDBP, total 25-hydroxy Vitamin D (25(OH)D), and its metabolites free Vitamin D (VDfree) and bioavailable Vitamin D (VDbio). Methods: Study group consisted of 68 COVID-19 patients and 20 healthy subjects. Patients were subgrouped as asymptotic, mild/moderately pneumonia, or severe pneumonia. Plasma total 25(OH)D was quantitated by liquid chromatography with mass spectrometry and serum VDBP by a polyclonal sandwich enzyme immunoassay. In addition, routinely used laboratory parameters in follow-up were recorded. VDfree and VDbio were calculated using total 25(OH)D, VDBP, and albumin levels. Results: Plasma total 25(OH)D (13.3±5.7 vs. 30.3±13.3 ng/dL), VDfree (2.18 [1.52–3.44] vs. 4.34 [3.74–6.48] pg/mL), and VDbio (1.86 [1.09–2.81] vs. 4.28 [3.45–6.34] nmol/L) levels were lower in COVID-19 patients (p<0.001). Despite the insignificance of 25(OH)D and metabolites between COVID-19 severity subgroups, serum VDBP was highest in mild/ moderately pneumonia (601.8±278.6 ng/mL) and lowest in severe pneumonia (427.9±147.2 ng/mL) (p<0.001). In addition, VDBP was positively correlated with lymphocyte counts (B:87.9, r2=0.068, p=0.031) and negatively correlated with D-Dimer levels (B:−0.024, r2=0.081, p=0.032). Conclusion: COVID-19 patients have lower plasma 25(OH)D levels and lower 25(OH)D metabolites VDfree, VDbio which are physiologically active. In addition, serum VDBP concentrations significantly decrease in critically ill patients which needs further studies to be associated in the etiopathogenesis of the disease severity. [ FROM AUTHOR] Copyright of International Journal of Medical Biochemistry is the property of KARE Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)

Correlation of Plasma 25(OH)D3 and Vitamin D Binding Protein Levels with COVID-19 Severity and Outcome in Hospitalized Patients.

BACKGROUND: The Coronavirus Disease-19 (COVID-19) caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has been declared a worldwide pandemic. The severity of COVID-19 varies greatly across infected individuals. Possible factors may include plasma levels of 25(OH)D and vitamin D binding protein (DBP), as both are involved in the host immune response. Other possible nutrition-related factors include malnutrition and/or obesity which disrupt the optimal host immune response to infections. Current literature shows inconsistent evidence about the association of plasma 25(OH)D3 and DBP on infection severity and clinical outcomes. OBJECTIVES: This study aimed to measure plasma 25(OH)D3 and DBP in hospitalized COVID-19 cases and assess their correlation with infection severity, inflammatory markers, and clinical outcome. METHODS: 167 patients were included in this analytical cross-sectional study, of which 81 were critical and 86 were non-critical hospitalized COVID-19 patients. Plasma levels of 25(OH)D3, DBP, and the inflammatory cytokines, IL-6, IL-8, IL-10, and TNF-α were assessed using the Enzyme-linked Immunosorbent Assay (ELISA). Information regarding biochemical and anthropometrical indices, hospital length of stay (LoS), and illness outcome was obtained from the medical records. RESULTS: Plasma 25(OH)D3 level was found to be significantly lower in critical compared to non-critical patients (Median = 8.38 (IQR = 2.33) vs. 9.83 (IQR = 3.03) nmol/L, respectively; p < 0.001), and it positively correlated with hospital LoS. However, plasma 25(OH)D3 did not correlate with mortality or any of the inflammatory markers. DBP on the other hand correlated positively with mortality (rs = 0.188, p = 0.015) and hospital LoS (rs = 0.233, p = 0.002). DBP was significantly higher in critical than non-critical patients (Median = 1262.18 (IQR = 463.66) vs. 1153.35 (IQR = 418.46) ng/mL, respectively; p < 0.001). Furthermore, IL-6 and IL-8 were significantly higher in critical than non-critical patients. However, no differences were found in IL-10, TNF-α, IL-10/TNF-α, TNF-α/IL-10, IL-6/IL-10, or CRP between groups. CONCLUSION: The current study found that critical COVID-19 patients had lower 25(OH)D3 than non-critical patients, yet, levels were found to be suboptimal in both groups. Further, critical patients had higher DBP levels as compared to non-critical patients. This finding may encourage future research to unravel the effects of this understudied protein that appears to have significant associations with inflammation, even though the precise mechanism is unknown.

Genetic Variations of the Vitamin D Metabolic Pathway and COVID-19 Susceptibility and Severity: Current Understanding and Existing Evidence.

The immunomodulatory and metabolic effects of vitamin D receptor (VDR) activation have been considered beneficial in mitigating the susceptibility and severity of COVID-19 infection. Furthermore, vitamin D-binding protein (DBP) has pleiotropic effects on the immune system that may influence inflammation associated with COVID-19. Multiple observational studies have demonstrated an association between low levels of serum 25-hydroxyvitamin D and risk and the severity of COVID-19 infection. However, the impact of vitamin D supplementation as an adjunctive treatment for COVID-19 based on evidence from randomized clinical trials is unclear. Equally important is that certain variations of the genes involved in the vitamin D metabolic pathway have been shown to affect immune function and linked with various clinical outcomes, including cardio-metabolic disorders, autoimmune diseases, infections, and cancers. This indicates inter-individual difference in body response to vitamin D. There is also emerging evidence that common polymorphisms of these genes may influence the susceptibility and severity of COVID-19, although the confidence of these findings is limited by a small number of studies and participants. Further studies are needed to address the potential role of VDR activation and DBP in the pathophysiology of COVID-19 which take into account the genetic variations of vitamin D metabolic pathway.

Impaired Vitamin D Metabolism in Hospitalized COVID-19 Patients.

There is increasing data regarding the association between vitamin D and COVID-19. This study aimed to reveal the alterations of vitamin D metabolism in the setting of COVID-19. We examined 119 adult COVID-19 inpatients and 44 apparently healthy adult individuals with similar serum 25OH-D3 levels as a reference group. The assessment included serum biochemical parameters (total calcium, albumin, phosphorus, creatinine), parathyroid hormone (PTH), vitamin D-binding protein (DBP), vitamin D metabolites (25OH-D3, 25OH-D2, 1,25(OH)2D3, 3-epi-25OH-D3, 24,25(OH)2D3 and D3) and free 25OH-D. COVID-19 patients had in general very low vitamin D levels (median 25OH-D3 equals 10.8 ng/mL), accompanied by an increased production of the active vitamin D metabolite (1,25(OH)2D3), estimated as higher 1,25(OH)2D3 serum levels (61 [44; 81] vs. 40 [35; 50] pg/mL, p < 0.001) and lower 25OH-D3/1,25(OH)2D3 ratio (175 [112; 260] vs. 272 [200; 433], p < 0.001) which is presumably aimed at preventing hypocalcemia. Patients with COVID-19 also had elevated DBP (450 [386; 515] vs. 392 [311; 433] mg/L, p < 0.001) and low free 25OH-D levels (<LoB vs. 3.9 [3.2; 4.4] pg/mL, p < 0.001). Follow-up assessment of the COVID-19 inpatients showed recovery of the observed changes. Overall, hospitalized patients with an acute course of COVID-19 have not only very low levels of 25OH-D but also profound abnormalities in the metabolism of vitamin D regardless of the clinical course of the disease. These alterations might exacerbate existing vitamin D deficiency and its negative impact.

Vitamin D, vitamin D-binding protein, free vitamin D and COVID-19 mortality in hospitalized patients.

BACKGROUND: Vitamin D deficiency has been associated with worse coronavirus disease 2019 (COVID-19) outcomes, but circulating 25-hydroxyvitamin D [25(OH)D] is largely bound to vitamin D-binding protein (DBP) or albumin, both of which tend to fall in illness, making the 25(OH)D status hard to interpret. Because of this, measurements of unbound ("free") and albumin-bound ("bioavailable") 25(OH)D have been proposed. OBJECTIVES: We aimed to examine the relationship between vitamin D status and mortality from COVID-19. METHODS: In this observational study conducted in Liverpool, UK, hospitalized COVID-19 patients with surplus sera available for 25(OH)D analysis were studied. Clinical data, including age, ethnicity, and comorbidities, were extracted from case notes. Serum 25(OH)D, DBP, and albumin concentrations were measured. Free and bioavailable 25(OH)D were calculated. Relationships between total, free, and bioavailable 25(OH)D and 28-day mortality were analyzed by logistic regression. RESULTS: There were 472 patients with COVID-19 included, of whom 112 (23.7%) died within 28 days. Nonsurvivors were older (mean age, 73 years; range, 34-98 years) than survivors (mean age, 65 years; range, 19-95 years; P = 0.003) and were more likely to be male (67%; P = 0.02). The frequency of vitamin D deficiency [25(OH)D < 50 nmol/L] was similar between nonsurvivors (71/112; 63.4%) and survivors (204/360; 56.7%; P = 0.15) but, after adjustments for age, sex, and comorbidities, increased odds for mortality were present in those with severe deficiency [25(OH)D < 25 nmol/L: OR, 2.37; 95% CI, 1.17-4.78] or a high 25(OH)D (≥100 nmol/L; OR, 4.65; 95% CI, 1.51-14.34) compared with a 25(OH)D value of 50-74 nmol/L (reference). Serum DBP levels were not associated with mortality after adjustments for 25(OH)D, age, sex, and comorbidities. Neither free nor bioavailable 25(OH)D values were associated with mortality. CONCLUSIONS: Vitamin D deficiency, as commonly defined by serum 25(OH)D levels (<50 nmol/L), is not associated with increased mortality from COVID-19, but extremely low (<25 nmol/L) and high (>100 nmol/L) levels may be associated with mortality risks. Neither free nor bioavailable 25(OH)D values are associated with mortality risk. The study protocol was approved by the London-Surrey Research Ethics Committee (20/HRA/2282).

Authors' reply: the biologic importance of the vitamin D binding protein polymorphism in pediatric COVID-19 patients.

What is Known? • Vitamin D has multiple roles in the immune system that can modulate the body reaction to an infection • Vitamin D binding protein (DBP) is the key transport protein which, along with albumin, binds over 99% of the circulating vitamin D metabolites What is New? • Lower 25 OH vitamin D levels were associated with higher inflammation markers, suggesting an important role of vitamin D in the clinical course of COVID-19 in children and adolescents probably by regulating the systemic inflammatory response • Further studies are warranted to investigate the possible causal association of DBP levels and polymorphism with vitamin D status (total and bioavailable vitamin D) in COVID-19 patients.

Genetic Polymorphisms in the Host and COVID-19 Infection.

The outbreak of the COVID-19 pandemic shows a marked geographical variation in its prevalence and mortality. The question arises if the host genetic variation may (partly) affect the prevalence and mortality of COVID-19. We postulated that the geographical variation of human polymorphisms might partly explain the variable prevalence of the infection. We investigated some candidate genes that have the potential to play a role in the immune defense against COVID-19: complement component 3 (C3), galactoside 2-alpha-L-fucosyltransferase 2 (FUT2), haptoglobin (Hp), vitamin D binding protein (DBP), human homeostatic iron regulator protein (HFE), cystic fibrosis transmembrane conductance regulator (CFTR), and angiotensin-converting enzyme 1 (ACE1). In a univariate approach, ACE1 D/I, C3, CFTR, and HFE polymorphisms correlated significantly with COVID-19 prevalence/mortality, whereas Hp and FUT2 polymorphism did not show any significant correlations. In a multivariate analysis, only ACE1 D/I and C3 polymorphisms were determinants for COVID-19 prevalence/mortality. The other polymorphisms (CFTR, DBP, FUT2, HFE, and Hp) did not correlate with COVID-19 prevalence/mortality. Whereas ACE1 D/I polymorphism shows functional links with ACE2 (which is the receptor for the virus) in COVID-19, C3 can act as a critical step in the virus-induced inflammation. Our findings plead against a bystander role of the polymorphisms as a marker for historical migrations, which comigrate with causal genes involved in COVID-19 infection. Further studies are required to assess the clinical outcome of COVID-19 in C3S and ACE1 D allele carriers and to study the role of C3 and ACE1 D/I polymorphisms in COVID-19 and their potential effects on treatment response.

The role of DBP gene polymorphisms in the prevalence of new coronavirus disease 2019 infection and mortality rate.

Since December 2019, coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2, has given rise to emerging respiratory infections with pandemic diffusion. The vitamin D binding protein (DBP) with emphasis on its regulation of total and free vitamin D metabolite levels participate in various clinical conditions. The main goal of this study was to evaluate if there was any association between the DBP gene polymorphism at rs7041 and rs4588 loci and the prevalence of COVID-19 and its mortality rates caused among populations of 10 countries including Turkey. Positive significant correlations were found between the prevalence (per million) and mortality rates (per million), and GT genotype (P < .05) while there was a negative significant correlation between prevalence (per million) and mortality rates (per million), and TT genotype at rs7041 locus among all populations (P < .05). However, no significant correlation was found at rs4588 locus. GT genotype was found to confer this susceptibility to the populations of Germany, Mexico, Italy, Czech, and Turkey. The variations in the prevalence of COVID-19 and its mortality rates among countries may be explained by Vitamin D metabolism differed by the DBP polymorphisms of rs7041 and rs4588.