Low Vitamin D Level Is Associated with Acute Deep Venous Thrombosis in Patients with Traumatic Brain Injury

Is Circulating Vitamin D Status Associated with the Risk of Venous Thromboembolism? A Meta-Analysis of Observational Studies

BACKGROUND

Although vitamin D is antithrombotic, associations between serum vitamin D status and the risk of venous thromboembolism (VTE) remain inconsistent.

METHODS

We searched the EMBASE, MEDLINE, Cochrane Library, and Google Scholar databases from inception to June 2022 to identify observational studies examining associations between vitamin D status and VTE risk in adults. The primary outcome presented as odds ratio (OR) or hazard ratio (HR) was the association of vitamin D levels with the risk of VTE. Secondary outcomes included the impacts of vitamin D status (i.e., deficiency or insufficiency), study design, and the presence of neurological diseases on the associations.

RESULTS

Pooled evidence from a meta-analysis of sixteen observational studies, including 47648 individuals published from 2013 to 2021, revealed a negative relationship between vitamin D levels and the risk of VTE either based on OR (1.74, 95% confidence interval (CI): 1.37 to 2.20, p < 0.00001; I² = 31%, 14 studies, 16074 individuals) or HR (1.25, 95% CI: 1.07 to 1.46, p = 0.006; I² = 0%, 3 studies, 37,564 individuals). This association remained significant in subgroup analyses of the study design and in the presence of neurological diseases. Compared to individuals with normal vitamin D status, an increased risk of VTE was noted in those with vitamin D deficiency (OR = 2.03, 95% CI: 1.33 to 3.11) but not with vitamin D insufficiency.

CONCLUSIONS

This meta-analysis demonstrated a negative association between serum vitamin D status and the risk of VTE. Further studies are required to investigate the potential beneficial effect of vitamin D supplementation on the long-term risk of VTE.

Impact of vitamin D on the prognosis after spinal cord injury: A systematic review

Vitamin D (VitD) insufficiency is a worldwide health problem and affects billions of people. Spinal cord injury (SCI) patients seem more susceptible to developing suboptimal levels of VitD. However, the literature regarding its impact on the prognosis of SCI is limited. Thus, in this review, we systematically investigated the published studies via a combination of keywords associated with SCI and VitD in four medical databases (Medline, Embase, Scopus, and Web of Science). All included studies were analyzed, and selected clinical data on the prevalence of VitD insufficiency (serum 25-hydroxyvitamin D < 30 ng/ml) and deficiency (serum 25-hydroxyvitamin D < 20 ng/ml) were collected for further meta-analysis via random effects. Through literature review, a total of 35 studies were eligible and included. The meta-analysis of VitD status (13 studies, 1,962 patients) indicated high prevalence of insufficiency (81.6% [75.7, 87.5]) and deficiency (52.5% [38.1, 66.9]) after SCI. Besides, low levels of VitD were reported to be associated with a higher risk of skeletal diseases, venous thromboembolism, psychoneurological syndromes, and chest illness after injury. Existing literature suggested that supplemental therapy might act as an adjuvant treatment to facilitate post-injury rehabilitation. Non-human experimental studies highlighted the neuroprotective effect of VitD, which was associated with enhancing axonal and neuronal survival, suppressing neuroinflammation, and modulating autophagy. Therefore, the current evidence suggests that the prevalence of VitD insufficiency is high in the SCI population, and low-level VitD may impair functional restoration after SCI. VitD supplemental treatment may have potential benefits to accelerate rehabilitation in mechanistically related processes after SCI. However, due to the limitation of the available evidence, more well-designed randomized controlled trials and mechanism experimental research are still needed to validate its therapeutic effect, elucidate its neuroprotective mechanism, and develop novel treatments.

Vitamin D Protects against Traumatic Brain Injury via Modulating TLR4/MyD88/NF-κB Pathway-Mediated Microglial Polarization and Neuroinflammation

Vitamin D (VD) deficiency is associated with neuroinflammation and neurocognitive deficits in patients with traumatic brain injury (TBI). The present study was aimed at investigating the therapeutic effects of VD and the molecular mechanisms after TBI. After the intraperitoneal injection of VD (1 μg/kg), sensorimotor and cognitive function was assessed via a series of behavioral tests in TBI rats. Traumatic outcomes were investigated by brain edema, blood-brain barrier (BBB) disruption, and morphologic staining. In vitro, cellular viability and cytotoxicity in primary hippocampal neurons were detected via the MTT method and LDH release. Hippocampal oxidative stress-related enzymes and proinflammatory mediators and the serum concentration of VD were analyzed by ELISA. The expression of VDR, TLR4, MyD88, and NF-κB p65 was measured by Western blot. Furthermore, the levels of M1/M2 microglial markers were quantified using real-time PCR and Western blot. VD treatment significantly increased the serum level of VD and the hippocampal expression of VDR. VD not only effectively alleviated neurocognitive deficits, brain edema, and BBB disruption but also promoted hippocampal neuronal survival in vivo and in vitro. Moreover, VD therapy prevented excessive neuroinflammation and oxidative stress caused by TBI. Mechanically, the hippocampal expression of TLR4, MyD88, and nuclear NF-κB p65 was elevated in the TBI group but robustly restrained by VD treatment. Taken together, VD provides an important neuroprotection through modulating hippocampal microglial M2 polarization and neuroinflammation via the TLR4/MyD88/NF-κB pathway.