Vitamin D in Tear Fluid

Calcifediol and paricalcitol as adjunctive therapies for HSV-1 keratitis and corneal perforation: A case report

RATIONALE

Herpes simplex virus 1 establishes a latent infection in trigeminal ganglia. Reactivation causes cold sores, as well as viral keratitis. The purpose of this study was to report potential benefits of using active vitamin D receptor ligands (VDR-agonists) as adjunctive therapies for the treatment of infectious corneal perforations, and prevention of HSV recurrence.

PATIENT CONCERNS

A 57-year-old female with a past history of episodic, poorly-healing, corneal erosions, recurring orolabial herpetic lesions, as well as PCR-confirmed recurrences of herpes simplex keratitis presented with a burning sensation and slight pain in the right eye. Examination indicated HSV keratitis. Topical antibiotic and oral antiviral treatments were prescribed. Despite these standard-of-care treatments, a perforated corneal ulcer ensued.

DIAGNOSES

Corneal perforation associated with HSV-1 keratitis recurrence, later confirmed by PCR analysis of corneal scrapings.

INTERVENTIONS

Corneal perforation was treated with a human fibrin glue, fortified with multilayered amniotic membrane transplant, as well as a therapeutical contact lens. Following surgery, calcifediol and paricalcitol were started as oral adjunctive therapies in an attempt to boost tissue regeneration and innate-immunity within the slow-healing cornea. Anterior segment optical-coherence tomography was used to measure corneal thickness. Frequent follow-ups with various specialists allowed for comprehensive patient evaluation, and meticulous screening for any signs indicating potential HSV-1 recurrence.

OUTCOMES

Following calcifediol-paricalcitol therapy corneal thickening, and re-epithelization ensued. During combined calcifediol-paricalcitol therapy, the patient has had no recurrence of herpes simplex keratitis, or orolabial herpes lesions.

LESSONS

Corneal stabilization avoided a high-risk, full-thickness corneal transplantation, facilitating future cataract surgery, and allowing for some degree of visual recovery in this eye.

Analyzing Tear Fluid Composition by Synchronous Fluorescence for Diagnosing Dry Eye Disease and the Role of Phytotherapy Intervention

PURPOSE

Tear fluid gained attention as a representative biological fluid. Its simple and non-invasive collection methods as well as richness of candidate biomarkers made it a potential diagnostic tool for different diseases such as dry eye. Synchronous fluorescence spectroscopy is a highly sensitive analytical tool that results in narrowing and enhanced peak resolution, and has a potential role in disease diagnosis, biomarker identification, and therapeutic monitoring. We applied synchronous fluorescence spectroscopy to monitor variations of tear fluid composition during the development of dry eye disease and to evaluate the potential effects of phytotherapy.

METHODS

Dry eye model was induced in Chinchilla rabbits by instillation of 1% atropine sulfate ophthalmic solution. Then, the tear fluid was collected at 3, 7, and 14 days and subjected to synchronous fluorescence spectroscopy. Phytotherapy was achieved by topical instillation of 20 µl of water extracts of pomegranate peel or green tea powders.

RESULTS

The fluorescence results revealed changes in the structure of tear fluid over time and the eye is subjected to toxification due to oxidative stress. In addition, dry eye disease was found to affect the metabolic/energetic state of the eye. On the other hand, phytotherapy led to enhancement of the metabolic/biosynthesis state due to activation of flavin adenine dinucleotide-associated proteins.

CONCLUSION

There was change in the electrical conductivity of tear fluid proteins. In the case of dry eyes, they became electrical insulators, while in the case of treatment with extracts, their electrical conductivity properties improved. The effects of phytotherapy can be related to the high content of ellagic acid and anthocyanin of pomegranate extract, while in green tea, they are related to catechins and phenolic compounds.

Effects of Topical 1,25 and 24,25 Vitamin D on Diabetic, Vitamin D Deficient and Vitamin D Receptor Knockout Mouse Corneal Wound Healing

Delayed or prolonged corneal wound healing and non-healing corneas put patients at risk for ocular surface infections and subsequent stromal opacification, resulting in discomfort or visual loss. It is important to enhance corneal wound healing efficiency and quality. Vitamin D (Vit D) is both a hormone and a vitamin, and its insufficiency has been linked to immune disorders and diabetes. For this study, wound healing and recruitment of CD45+ cells into the wound area of normoglycemic and diabetic mice were examined following corneal epithelial debridement and treatment with 1,25-dihyroxyvitamin D (1,25 Vit D) or 24,25-dihydroxyvitamin D (24,25 Vit D). Treatment with topical 1,25-dihyroxyvitamin D (1,25 Vit D) resulted in significantly increased corneal wound healing rates of normoglycemic, diabetic and diabetic Vit D deficient mice. Furthermore, 24,25-dihydroxyvitamin D (24,25 Vit D) significantly increased corneal wound healing of diabetic Vit D deficient and Vit D receptor knockout (VDR KO) mice. In addition, CD45+ cell numbers were reduced in diabetic and VDR KO mouse corneas compared to normoglycemic mice, and 24,25 Vit D increased the recruitment of CD45+ cells to diabetic mouse corneas after epithelial debridement. CD45+ cells were found to infiltrate into the corneal basal epithelial layer after corneal epithelial debridement. Our data indicate that topical Vit D promotes corneal wound healing and further supports previous work that the Vit D corneal wound healing effect is not totally VDR-dependent.

Changes in Tear Meniscus Analysis of Children Who Have Type 1 Diabetes Mellitus, With and Without Vitamin D Deficiency

PURPOSE

The aim of this study was to quantitatively evaluate dry eye test parameters of pediatric patients with and without vitamin D deficiency (VDD) in type 1 diabetes mellitus.

METHODS

In this prospective cross-sectional study, the Ocular Surface Disease Index, Schirmer test, tear film breakup time, corneal staining score, and anterior segment optical coherence tomography were used to determine the dry eye test parameters of pediatric patients with type 1 diabetes mellitus (T1-DMPs) (group 1) and a healthy pediatric control group (group 2). Group 1 was divided into 2 subgroups based on their vitamin D status: group 1a, who had a VDD, and group 1b, who had vitamin D levels that were within the normal range.

RESULTS

This study compared 90 eyes of 90 pediatric T1-DMPs with 80 eyes of 80 healthy controls. The demographic characteristics of the groups were similar ( P > 0.05). The tear film breakup time, Schirmer test, corneal staining score, and values of the tear meniscus height and area were observed to have been lower in the patients in group 1a than the healthy pediatric control group, at P < 0.001. The same parameters were statistically significantly lower in the patients in group 1a when compared with group 1b ( P < 0.05 for both).

CONCLUSIONS

The tear measurements of the pediatric T1-DMPs were lower than those in the healthy pediatric control group. The accompanying VDD made this situation more pronounced.

Oral vitamin D3 supplementation for femtosecond LASIK-associated dry eye vitamin D for LASIK dry eye syndrome

PURPOSE

To assess the effect of oral vitamin D₃ supplementation in dry eye after femtosecond laser-assisted in situ keratomileusis (FS-LASIK).

SETTING

Liuzhou Worker's Hospital.

DESIGN

This prospective study included 90 patients selected between January and December in 2019, who underwent FS-LASIK operation in our hospital and had obvious symptoms indicating dry eyes 1 month after operation. The subjects were randomly divided into two groups: The experimental group (n = 45) received vitamin D3 2000 IU/D continuously for 12 weeks; the control group (n = 45) did not take vitamin D3 orally. Ocular surface disease index (OSDI), Tear breakup time (TBUT) and Schirmer's test I were evaluated premedication and 1,3,6 months after treatment. Serum vitamin D3 level and the mean concentration of cytokine IL-6, IL-17, IL-23 in t ears were also measured.

RESULTS

One month after treatment, the mean OSDI score of the experimental group (11.67 ± 8.53) was significantly lower than that of the control group (23.82 ± 13.22) (P = 0.007). TBUT (10.71 ± 1.02 s) and Schirmer I (9.36 ± 0.40 mm) of the experimental group were higher than those of the control group (7.49 ± 1.29 s and 7.51 ± 0.44 mm). The OSDI (10.25 ± 5.49) was significantly lower than those of the control group(20.22 ± 6.23) and TBUT (10.75 ± 1.09 s) and Schirmer I test value (11.34 ± 0.39 mm) of the experimental group were significantly higher than those of the control group (8.36 ± 1.23, 8.12 ± 0.50) at 3 months after treatment. There were significant differences in OSDI, TBUT (P < 0.05) and Schirmer I test value between the two groups at 6 months after treatment. Serum vitamin D₃ level was negatively correlated with OSDI score (r = - 0.90; P = 0.00) and positively correlated with Schirmer I test (r = 0.88; P = 0.00), TBUT score (r = 0.89; P = 0.00) and TMH (r = 0.80; P = 0.00). IL-17 level was shown to be significantly correlated with TBUT(r = - 0.25, P = 0.014) and Schirmer I test (r = - 0.21, P = 0.018). IL-6 level was significantly correlated with OSDI (R = 0.18, P = 0.020) and TBUT (R = 0.20, P = 0.019).

Sample preparation techniques for extraction of vitamin D metabolites from non-conventional biological sample matrices prior to LC-MS/MS analysis

The determination of vitamin D metabolites as status marker or for diagnostic purposes is almost entirely conducted from blood serum or plasma. Other biological matrices, however, have also interested researchers, for two main reasons: (1) alternative matrices may allow non-invasive sampling, permit easier sample transfer and require less demanding storage conditions; and (2) the levels of vitamin D metabolites in other body compartments may further aid the understanding of vitamin D metabolism and function. Thus, the development of reliable and efficient sample preparation protocols for sample matrices other than serum/plasma, which will remove potential interferences and selectively extract the targeted metabolites, is of great importance. This review summarizes sample preparation methods for measurement of vitamin D metabolites using liquid chromatography-(tandem)mass spectrometry in more than ten different human tissues, including hair, saliva, adipose tissue, brain and others.

Cubilin, the intrinsic factor-vitamin B12 receptor

Cubilin (CUBN), the intrinsic factor-vitamin B12 receptor is a large endocytic protein involved in various physiological functions: vitamin B12 uptake in the gut; reabsorption of albumin and maturation of vitamin D in the kidney; nutrient delivery during embryonic development. Cubilin is an atypical receptor, peripherally associated to the plasma membrane. The transmembrane proteins amnionless (AMN) and Lrp2/Megalin are the currently known molecular partners contributing to plasma membrane transport and internalization of Cubilin. The role of Cubilin/Amn complex in the handling of vitamin B12 in health and disease has extensively been studied and so is the role of the Cubilin-Lrp2 tandem in renal pathophysiology. Accumulating evidence strongly supports a role of Cubilin in some developmental defects including impaired closure of the neural tube. Are these defects primarily caused by the dysfunction of a specific Cubilin ligand or are they secondary to impaired vitamin B12 or protein uptake? We will present the established Cubilin functions, discuss the developmental data and provide an overview of the emerging implications of Cubilin in the field of cardiovascular disease and cancer pathogenesis.

Effect of oral vitamin D supplementation on dry eye disease patients with vitamin D deficiency

CLINICAL RELEVANCE

Dry eye disease (DED) and vitamin D deficiency are both common clinical entities. Vitamin D has been reported to play a significant role in ocular surface homeostasis.

BACKGROUND

This study aimed to determine the therapeutic effect of oral vitamin D supplementation in dry eye disease patients with vitamin D deficiency.

METHODS

A randomized, controlled study was completed in 100 patients with dry eye disease and concurrent vitamin D deficiency (< 20 ng/ml). Participants were randomly allocated to 8 weeks of oral vitamin D supplementation with both groups receiving conventional dry eye treatment with artificial tears. Schirmer's, tear break-up time (TBUT) and osmolarity tests were measured before and after eight weeks of treatment.

RESULTS

The mean age of participants was 36.8 ± 8.56 years in the treatment group (n: 50) and 34.8 ± 10.13 year in the control group (n: 50). After eight weeks of treatment the mean differences in Schirmer's, TBUT and tear osmolarity were 2.38 ± 1.55 mm, 3.95 ± 1.48 s and -16.9 ± 6.28 mOsm/L, respectively in the treatment group, and 0.7 ± 0.86 mm, 0.92 ± 1.57s and -3.34 ± 2.0 mOsm/L respectively in the control group (p < 0.001 for all parameters). The treatment group demonstrated a more significant improvement than the control group in Schirmer<apos;>s, TBUT and osmolarity values (p < 0.001).

CONCLUSION

Vitamin D supplementation as an adjuvant to routine dry eye treatment improves ocular surface hemostasis parameters, results in better tear stability and a more improved tear osmolarity in patients with vitamin D deficiency.

Analysis of vitamin D metabolic markers by mass spectrometry: Recent progress regarding the "gold standard" method and integration into clinical practice

Liquid chromatography/tandem mass spectrometry is firmly established today as the gold standard technique for analysis of vitamin D, both for vitamin D status assessments as well as for measuring complex and intricate vitamin D metabolic fingerprints. While the actual mass spectrometry technology has seen only incremental performance increases in recent years, there have been major, very impactful changes in the front- and back-end of MS-based vitamin D assays; for example, the extension to new types of biological sample matrices analyzed for an increasing number of different vitamin D metabolites, novel sample preparation techniques, new powerful chemical derivatization reagents, as well the continued integration of high resolution mass spectrometers into clinical laboratories, replacing established triple-quadrupole instruments. At the same time, the sustainability of mass spectrometry operation in the vitamin D field is now firmly established through proven analytical harmonization and standardization programs. The present review summarizes the most important of these recent developments.

Tear fluid biomarkers in major depressive disorder: Potential of spectral methods in biomarker discovery

Spectroscopic methods represent a group of analytical methods that demonstrate high potential in providing clinically relevant diagnostic information, such as biochemical, functional or structural changes of macromolecular complexes that might occur due to pathological processes or therapeutic intervention. Although application of these methods in the field of psychiatric research is still relatively recent, the preliminary results show that they have the capacity to detect subtle neurobiological abnormalities in major depressive disorder (MDD). Methods of mass spectrometry (MALDI-TOF MS), zymography, synchronous fluorescence spectroscopy (SFS), circular dichroism (CD) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) were used to analyze the human tear fluid of subjects with MDD. Using MALDI-TOF MS, two diagnostically significant peaks (3747 and 16 411 m/z) were identified with an AUC value of 0.89 and 0.92 in tear fluid of subjects with MDD vs controls, respectively. We also identified various forms of matrix metalloproteinase 9 in subjects with MDD using zymography and synchronous fluorescence spectra (SFS) showed a significant increase in fluorescence intensity at 280 nm. CD spectra were redshifted in tear fluid of subjects with MDD vs healthy controls. FTIR spectroscopy showed changes in the positions of peaks for amide A, I, II in tear fluid of subjects with MDD vs controls. Moreover, atomic force microscopy (AFM) showed different pattern in the crystal structures of tear fluid components in subjects with MDD. SFS, CD, FTIR spectroscopy, AFM and MALDI-TOF MS confirmed, that the human tear fluid proteome could be helpful in discriminating between the group of subjects with MDD and healthy controls. These preliminary findings suggest that spectral methods could represent a useful tool in clinical psychiatry, especially in establishing differential diagnosis, monitoring illness progression and the effect of psychiatric treatment.

Native fluorescence of tear fluid as a tool for diagnostics of glaucoma

Glaucoma is one of the leading causes of irreversible vision loss worldwide. There is an enormous need for the detection of its early stages and also speeding up and simplifying regular examinations. Among the new diagnostic approaches, the use of tear fluid has been intensively investigated in recent years. For this purpose, we analyzed the tear fluid of patients with glaucoma and related diseases. To sensitively capture the subtle ocular abnormalities related to glaucoma and manifested in tear fluid, we used synchronous fluorescence spectroscopy. In this observational case-control study, we detected significant differences in the intensity of tear fluid fluorescence located at λ ex/Δλ = 280/70 nm between the groups of primary open-angle glaucoma (p < 0.01), suspected glaucoma (p < 0.0001), and ocular hypertension (p < 0.05), when compared to the healthy control group. The signal was not significantly higher in women than in men (p = 0.05), and no correlation was found with age (r = -0.05, p > 0.05), nor treatment (p > 0.05). Taken together, tear fluid fluorescence could serve as a discriminative parameter between patients with glaucoma, related diseases, and healthy control subjects and might contribute to the improvement of diagnostics of these diseases.

Effects of 1,25 and 24,25 Vitamin D on Corneal Fibroblast VDR and Vitamin D Metabolizing and Catabolizing Enzymes

Purpose: To investigate the effects of 1,25-Vit D3 and 24,25-Vit D3 on corneal fibroblast expression of the vitamin D-associated enzymes CYP27B1 and CYP24A1 and the roles of the vitamin D receptor (VDR) and protein disulfide isomerase, family A, member 3 (Pdia3) in these cells.Methods: CYP24A1, CYP27B1, VDR, and Pdia3 expression in corneas was detected using immunohistochemistry. Western blotting was used to measure protein expression in human and mouse fibroblasts, including VDR KO mouse cells, treated with 1,25-Vit D3 (20 nM) and 24,25-Vit D3 (100 nM). The Pdia3 inhibitor LOC14 was used to explore the role of Pdia3 as a Vit D3 receptor in these cells.Results: CYP24A1, CYP27B1, VDR, and Pdia3 were all expressed in mouse and human corneal fibroblasts. 1,25-Vit D3 significantly increased VDR expression in human and mouse fibroblasts. 1,25-Vit D3 and 24,25-VitD3 significantly increased CYP24A1 and CYP27B1 expression level in human, VDR WT mouse, and VDR KO mouse corneal fibroblasts. CYP24A1 and CYP27B1 expression was unchanged in VDR KO mouse fibroblasts treated with 1,25-Vit D3 or 24,25-Vit D3 plus LOC14. Human fibroblast VDR, CYP24A1, and CYP27B1 expression were unaffected by LOC14.Conclusions: Vitamin D metabolic enzymes, VDR, and Pdia3 are all expressed in mouse and human corneal fibroblasts. 1,25-Vit D3 modulates fibroblast vitamin D enzymes through both the VDR and Pdia3 pathways in a species-dependent manner. 24,25-Vit D3 can increase expression of fibroblast CYP24A1 and CYP27B1 in the absence of VDR and is likely involved in fibroblast regulation independent of 1,25-Vit D3 or VDR.

Association of vitamin D with incident glaucoma: findings from the Women's Health Initiative

The relationship between vitamin D and glaucoma is controversial. The objective of this study was to examine women from the Women's Health Initiative (WHI) to determine if there is an association between vitamin D and incident glaucoma in postmenopausal women. We examined the association between dietary vitamin D intake, vitamin D supplements and serum 25 hydroxyvitamin D (25(OH)D) levels and the risk of developing glaucoma. 143,389 postmenopausal women from the WHI including a subset with serum 25(OH) D measurements were examined to determine the association of dietary, supplemental and serum levels of vitamin D to the development of glaucoma. Dietary intakes of vitamin D, use of vitamin D supplements and serum levels of 25(OH) D were predictors examined for the main outcome of incident glaucoma. In multivariable models adjusted for demographic, clinical variables and medication use, dietary vitamin D, vitamin D supplements, total vitamin D intake (diet plus supplements) and serum 25 (OH) D measurements were not significantly associated with incident glaucoma. In the CaD placebo-controlled intervention clinical trial, there was also no association in the active intervention arm with glaucoma. We conclude that dietary vitamin D intake, supplements and serum levels are not significantly related to the risk of developing glaucoma in postmenopausal women.

Low systemic vitamin D as a potential risk factor in primary open-angle glaucoma: a review of current evidence

Currently, intraocular pressure is the only modifiable risk factor for glaucoma; thus, identifying other modifiable determinants may have far-reaching outcomes. There has been increasing interest in vitamin D status and glaucoma pathogenesis as low vitamin D has been identified by some studies as an independent risk factor for glaucoma. Although the exact mechanism of vitamin D in glaucoma remains uncertain, there is sufficient evidence to continue research in this area. There is a potential physiological role for vitamin D as an anti-inflammatory agent in the oxidative stress-driven pathogenesis of primary open-angle glaucoma, and further studies are required to evaluate the temporal and causal relationship. Ocular vitamin D status in the tear, aqueous and vitreous fluid is a prospective gap in research.

Effects of Vitamin D Receptor Knockout and Vitamin D Deficiency on Corneal Epithelial Wound Healing and Nerve Density in Diabetic Mice

Diabetic keratopathy occurs in ∼70% of all people with diabetes. This study was designed to examine the effects of vitamin D receptor knockout (VDR-/-) and vitamin D deficiency (VDD) on corneal epithelial wound healing and nerve density in diabetic mice. Diabetes was induced using the low-dose streptozotocin method. Corneal epithelial wounds were created using an Algerbrush, and wound healing was monitored over time. Corneal nerve density was measured in unwounded mice. VDR-/- and VDD diabetic mice (diabetic for 8 and 20 weeks, respectively) had slower healing ratios than wild-type diabetic mice. VDR-/- and VDD diabetic mice also showed significantly decreased nerve density. Reduced wound healing ratios and nerve densities were not fully rescued by a supplemental diet rich in calcium, lactose, and phosphate. We conclude that VDR-/- and VDD significantly reduce both corneal epithelial wound healing and nerve density in diabetic mice. Because the supplemental diet did not rescue wound healing or nerve density, these effects are likely not specifically related to hypocalcemia. This work supports the hypothesis that low vitamin D levels can exacerbate preexisting ophthalmic conditions, such as diabetes.

Aqueous humor and serum 25-Hydroxyvitamin D levels in patients with cataracts

Background

Serum 25-hydroxyvitamin D (25 (OH) D) levels are associated with various pathologic ocular conditions. Few studies have assessed 25 (OH) D concentrations in non-serum specimens, and none to date has assessed 25 (OH) D concentrations in human aqueous humor and their association with ocular diseases. This study investigated the possible correlations between 25 (OH) D concentrations in aqueous humor and serum and whether vitamin D concentrations in aqueous humor were associated with cataract.

Methods

This study prospectively enrolled 136 patients, including 87 with senile cataract and 49 with diabetic cataract, who underwent cataract surgery from January to November 2017. 25 (OH) D was measured in aqueous humor and serum specimens collected from all patients, and their correlation was analyzed statistically. Clinical and laboratory data, including the results of ophthalmologic examinations, were compared in the two groups of cataract patients.

Results

No correlation was observed between 25 (OH) D concentrations in aqueous humor and serum (P = 0.381). 25 (OH) D concentrations in aqueous humor were significantly higher in patients with diabetic than senile cataract (P = 0.006). Multivariate logistic regression analysis showed that the adjusted odds ratio for diabetic cataract for the highest compared with the lowest quartile of 25 (OH) D concentration in aqueous humor was 4.36 ng/ml (95% confidence interval [CI]: 1.33–14.34 ng/ml; P = 0.015). Multivariate linear regression analysis showed that 25(OH) D concentration in aqueous humor was 2.68 ng/ml (95% CI: 0.34–5.01 ng/ml; P = 0.025) higher in patients with diabetic than senile cataract.

Conclusions

25(OH) D concentrations in aqueous humor and serum did not correlate with each other. Higher 25(OH) D level in aqueous humor was associated with diabetic cataract. These findings suggest that studies of vitamin D levels in patients with ocular conditions should include measurements of vitamin D levels in aqueous humor.

Vitamin D receptor and metabolite effects on corneal epithelial cell gap junction proteins

Vitamin D is a fat-soluble prohormone that can be activated both systemically and within individual tissues. Our lab has previously demonstrated that the corneal epithelium can activate vitamin D and that the vitamin D metabolites 1,25(OH)₂D3 and 24R,25(OH)₂D3 can affect corneal epithelial migration, proliferation, and tight and gap junction function. These vitamin D-derived metabolites signal through the vitamin D receptor (VDR). The purpose of this study was to specifically determine the effects of 1,25(OH)₂D3 and 24R,25(OH)₂D3 on corneal epithelial cell gap junction proteins. Connexin (Cx) 26, 30 and 43 protein expression was detected in a human corneal epithelial cell line (HCEC), wild type and vitamin D receptor knockout (VDR^-/-) mouse corneas, and cultured mouse primary epithelial cells (MPCEC). In vitro gap junction function was assessed using the scrape loading/dye transfer assay. HCEC and MPCEC were treated with 1,25(OH)₂D3 or 24R,25(OH)₂D3. Western blotting was used to detect gap junction proteins. Vitamin D3 effects on epithelial intracellular Ca⁺⁺ (Ca⁺⁺_i) were determined using the dye Cal-520. Cx26 and Cx43 protein levels were significantly increased in HCEC and MPCEC treated with both 1,25(OH)₂D3 and 24R,25(OH)₂D3. Cx30 and Cx43 protein levels were also significantly increased in VDR^-/- MPCEC. In vitro gap junction connectivity was significanlty enhanced in HCEC and MPCEC cultured with 24R,25(OH)₂D3 and 1,25(OH)₂D3. Ca⁺⁺_i was not affected by 1,25(OH)₂D3 or 24R,25(OH)₂D3 in HCEC or MPCEC. We conclude that both 1,25(OH)₂D3 and 24R,25(OH)₂D3 are positive regulators of connexin proteins and gap junction communication in the corneal epithelium. These vitamin D metabolites appear to signal through both VDR-dependent and -independent pathways. The effects of vitamin D on corneal epithelial gap junctions do not seem to be dependent on Ca⁺⁺_i.

Determination of vitamin D in tears of healthy individuals by the electrochemiluminescence method

BACKGROUND

Vitamin D is a fat-soluble steroid hormone which can be converted into various forms and is of extreme physiological importance to our body. However, its functions and local metabolic pathways in some organs, such as the eye, have not yet been well studied. We aimed to verify the correlation between vitamin D levels in blood and tear fluid and the possibility of using tear fluid as a biological material for monitoring eye disorders in the future.

METHODS

The electrochemiluminescence method was used to examine blood and tear samples collected with Schirmer test strips from 21 individuals without ocular disease.

RESULTS

At the 95% confidence interval, mean tear fluid vitamin D = 37.8 ± 3.6 ng/mL, which is higher than the serum level, with a mean of 30.3 ± 7.7 ng/mL; Lin's concordance correlation coefficient = -0.018 (-0.174; 0.139), Pearson's coefficient = -0.070, and the Bland-Altman coefficient = -11.12 (-30.40; 8.16). Results were obtained using the program Stata version 11.0.

CONCLUSION

It is possible to determine vitamin D levels in tear fluid using the electrochemiluminescence method, and as the results do not correlate with blood, there is possibility of using tear fluid as a biological matrix for detection of vitamin D, which may increase the possibilities of new studies in eye disorders.

Noninvasive diagnostic methods for diabetes mellitus from tear fluid

Diabetes mellitus and prolonged hyperglycemia can cause diabetic retinopathy. Diabetic retinopathy arises from damage to retinal vessels and, in its final stages, causes blindness. The early stages are often asymptomatic and although regular screening of diabetic patients is recommended, the beginning of diabetic retinopathy is insufficiently detected. The diagnostic potential of fluorescence spectroscopy, infrared spectroscopy and atomic force microscopy as the untraditional methods for diabetes mellitus was investigated using tear fluid. In our pilot study the structural changes of tear fluid of patients with diabetes mellitus after insulin and oral antidiabetic drug treatment was compared with healthy subjects. The results of analysis, infrared spectroscopy and atomic force microscopy confirmed structural changes in tear fluid of patients in comparison with the tear fluid of healthy subjects. Using new experimental laboratory methods in future could contribute to an improvement in diagnosis of diabetes mellitus and other selected ocular diseases using tear fluid.

In our pilot study we assessed the diagnostic potential of FS, IRS and AFM for diabetes mellitus using tear fluid.

Cubilin, the Intrinsic Factor-Vitamin B12 Receptor in Development and Disease

Gp280/Intrinsic factor-vitamin B12 receptor/Cubilin (CUBN) is a large endocytic receptor serving multiple functions in vitamin B12 homeostasis, renal reabsorption of protein or toxic substances including albumin, vitamin D-binding protein or cadmium. Cubilin is a peripheral membrane protein consisting of 8 Epidermal Growth Factor (EGF)-like repeats and 27 CUB (defined as Complement C1r/C1s, Uegf, BMP1) domains. This structurally unique protein interacts with at least two molecular partners, Amnionless (AMN) and Lrp2/Megalin. AMN is involved in appropriate plasma membrane transport of Cubilin whereas Lrp2 is essential for efficient internalization of Cubilin and its ligands. Observations gleaned from animal models with Cubn deficiency or human diseases demonstrate the importance of this protein. In this review addressed to basic research and medical scientists, we summarize currently available data on Cubilin and its implication in renal and intestinal biology. We also discuss the role of Cubilin as a modulator of Fgf8 signaling during embryonic development and propose that the Cubilin-Fgf8 interaction may be relevant in human pathology, including in cancer progression, heart or neural tube defects. We finally provide experimental elements suggesting that some aspects of Cubilin physiology might be relevant in drug design.

Antioxidant effects of vitamin D on lacrimal glands against high dose radioiodine-associated damage in an animal model

PURPOSE

To evaluate antioxidant effects of active vitamin D (calcitriol) against high-dose radioiodine (RAI) therapy-associated damage of lacrimal gland.

MATERIALS AND METHODS

Wistar albino rats were used and divided into three groups randomly (n = 12/group). The first group was appointed as the negative control group and received no RAI or medication. The second group was appointed as the positive control group that only received 3 mCi/kg (111 MBq/kg) RAI via gastric gavage and the last group was the treatment group that received 3 mCi/kg RAI via same method and calcitriol (200 ng/kg/day) via intraperitoneal administration. Seven days after RAI administration, bilateral intraorbital (IG), extraorbital (EG) and Harderian (HG) glands were removed for the evaluations of histopathologic, tissue cytokine, total oxidant status (TOS) and total antioxidant status (TAS).

RESULTS

RAI led to significant increase in tissue TOS, TNF-α, IL-6 levels and significant decrease in IL-10 and TAS levels (p < 0.05 for each). Addition of adjunctive calcitriol reversed all these parameters significantly (p < 0.05 for each).The following histopathologic parameters were seen more frequently in positive control group than the other groups: Abnormal lobular pattern, perivascular infiltration, periductal infiltration, lipofuscin-like accumulation, acinar atrophy, periductal and periacinar fibrosis in all lacrimal gland types (p < 0.05), acinar fibrosis in EG (p = 0.049), periductal fibrosis in EG and HG (p = 0.049 and 0.038, respectively), abnormal cell outlines in EG and HG (p = 0.020 and 0.011, respectively) and variation in cell size in the IG and the HG (p = 0.003 and 0.049 respectively).

CONCLUSIONS

RAI caused significant oxidative stress and inflammation in lacrimal glands. Vitamin D demonstrated potent anti-inflammatory, antioxidant and radio-protective effects on lacrimal glands in histopathologic, tissue cytokine and oxidant/antioxidant level evaluations.

Vitamin D and regulation of vascular cell function

Vitamin D deficiency is linked to pathogenesis of many diseases including cardiovascular, cancer, and various eye diseases. In recent years, important roles for vitamin D in regulation of immune function, inflammation, angiogenesis, and aging have been demonstrated. Thus, vitamin D and its analogs have been evaluated for the treatment of various types of cancer and chronic diseases. We have previously shown that the active form of vitamin D [1,25(OH)₂D₃] is a potent inhibitor of angiogenesis. This activity is consistent with the important role proposed for vitamin D and its analogs in the mitigation of tumor growth through inhibition of angiogenesis. Here, we review the important nutritional value of vitamin D and the abnormalities linked to its deficiency. We will explore its potential role as a regulator of angiogenesis and vascular cell function and the role vitamin D receptor (VDR) expression plays in these activities during vascular development and neovascularization. Our studies have established an important role for 1,25(OH)₂D₃ and VDR in the regulation of perivascular supporting cell function. In addition, the interaction of 1,25(OH)₂D₃ and VDR is essential for these activities and inhibition of neovascularization. Delineating the signaling pathways involved and identification of genes that are the target of 1,25(OH)₂D₃ regulation in vascular cells will allow us to identify novel pathways that are targets for regulation of vascular function and angiogenesis.

Effects of 1,25 and 24,25 Vitamin D on Corneal Epithelial Proliferation, Migration and Vitamin D Metabolizing and Catabolizing Enzymes

This study investigated the effects of 1,25(OH)₂D3 and 24R,25(OH)₂D3 on corneal epithelial cell proliferation, migration, and on the vitamin D activating enzyme CYP27B1 (produces 1,25(OH)₂D3) and inactivating enzyme CYP24A1 (produces 24R,25(OH)₂D3). The role of the vitamin D receptor (VDR) was also examined. In VDR wildtype mouse corneal epithelial cells (WT), 1,25(OH)₂D3 increased CYP24A1 protein expression and decreased CYP27B1 expression. In VDR knockout mouse epithelial cells (KO), 1,25(OH)₂D3 increased CYP24A1 and CYP27B1 protein expression. 1,25(OH)₂D3 did not affect WT cell proliferation, but did stimulate VDR KO cell proliferation. In a human corneal epithelial cell line (HCEC), 1,25(OH)₂D3 increased CYP24A1 mRNA and protein expression. 1,25(OH)₂D3 increased CYP27B1 mRNA levels in HCEC, but had no effect on CYP27B1 protein levels. 1,25(OH)₂D3 inhibited HCEC proliferation and stimulated cell migration in primary human epithelial cells. 24,25(OH)₂D3, on the other hand, increased both CYP24A1 and CYP27B1 protein expression in WT and VDR KO cells, and stimulated cell proliferation in both WT and KO cells. In HCEC, 24,25(OH)₂D3 increased CYP24A1 and CYP27B1 mRNA and protein expression, and stimulated cell migration. In human primary corneal epithelial cells, 24,25(OH)₂D3 stimulated migration. We conclude that 24R,25(OH)₂D3 is likely involved in corneal epithelial cell regulation independent of 1,25(OH)₂D3 or VDR.

Vitamin D Replacement Improves Tear Osmolarity in Patients with Vitamin D Deficiency

BACKGROUND

Vitamin D deficiency is a common health problem worldwide. Many parts of the human eye, including the epithelium of the cornea, lens, ciliary body, and retinal pigment epithelium, as well as the corneal endothelium, ganglion cell layer, and retinal photoreceptors, contain vitamin D receptor (VDR). Dry eye is also a common health problem. An adequate tear film is required for maintaining health and function of the eye. Tear hyperosmolarity is considered to be the cause of ocular surface inflammation, symptoms, and tissue damage. It is well-documented that vitamin D has an anti-inflammatory action. We aimed to investigate the effect of vitamin D replacement on tear osmolarity in patients with vitamin D deficiency.

METHODS

A total of 44 patients (38 females, six males, mean age:43.5 ± 12.8 years) with vitamin D deficiency currently managed by the Endocrinology and Metabolism Department of Diskapi Training and Research Hospital in Turkey were enrolled in the study. Patients were given 50,000 units of 25(OH)D₃ intramuscularly, once weekly, over a period of eight weeks. All of the patients underwent tear function osmolarity (TFO) measurement initially and eight weeks after vitamin D replacement. Demographic, anthropometric, and biochemistry data of patients were recorded.

RESULTS

The mean TFO was significantly decreased (313.7 ± 17.3 mOsm/L; 302.7 ± 14.2 mOsm/L, p<0.001) at the end of the second month; 25(OH)D₃ concentrations increased from 8.3 ± 3.5 ng/mL to 68.8 ± 22.3 ng/mL (p<0.001). The mean levels of hsCRP, FPG, P were 2.5 ± 2.5 mg/L, 5.09 ± 0.48 mmol/L, 1.06 ± 0.16 mmol/L initially, and 3.8 ± 5.9 mg/L, 5.11 ± 0.68 mg/dL, 1.09 ± 0.16 mmol/L after vitamin D replacement, respectively (p>0.05). The mean Ca level was 2.37 ± 0.07 mmol/L initially and 2.35 ± 0.07 mmol/L after vitamin D replacement (p<0.05). The change of TFO was negatively correlated with the variation of 25(OH)D₃ before and after replacement in patients with dry eye disease (r=-0.390, p=0.049).

CONCLUSIONS

As a consequence of the presence of VDR and 1α-hydroxylase in different parts of the eye, vitamin D replacement improves tear hyperosmolarity that is considered to be induced by ocular surface inflammation.

Correlation of vitamin D levels with tear film stability and secretion in patients with dry eye syndrome

PURPOSE

To investigate tear film stability and secretion according to serum 25-hydroxyvitamin D3 [25(OH)D] levels in dry eye patients.

METHODS

In this retrospective observational study, the medical charts of 92 patients who visited the Department of Ophthalmology at Hallym University Kangnam Sacred Heart Hospital from April to August 2015 were reviewed. Serum 25(OH)D levels were measured. Subjects were divided into three groups according to serum 25(OH)D levels: sufficient, inadequate or deficient group. Eye discomfort was measured by ocular surface disease index (OSDI). Tear break-up time (TBUT), fluorescein staining score and Schirmer's tear secretion test were measured.

RESULTS

The mean age was 53.38 ± 13.69 years. Mean serum 25(OH)D level was 14.41 ± 5.98 ng/ml. Tear break-up time (TBUT) and tear secretion were positively correlated with serum 25(OH)D levels (r = 0.389, p = 0.001; and r = 0.428, p < 0.001, Pearson correlation test). Tear break-up time (TBUT) and tear secretion were shorter in the vitamin D-deficient group compared to the sufficient group (p = 0.022 and p = 0.004). Fluorescein staining scores and OSDI scores were not different between the three groups.

CONCLUSION

Tear break-up time (TBUT) and secretion were correlated with serum vitamin D levels. Vitamin D status may be an important factor for dry eye syndrome.

A new sensitive LC/MS/MS analysis of vitamin D metabolites using a click derivatization reagent, 2-nitrosopyridine

There is an increased demand for comprehensive analysis of vitamin D metabolites. This is a major challenge, especially for 1α,25-dihydroxyvitamin D [1α,25(OH)2VitD], because it is biologically active at picomolar concentrations. 4-Phenyl-1,2,4-triazoline-3,5-dione (PTAD) was a revolutionary reagent in dramatically increasing sensitivity of all diene metabolites and allowing the routine analysis of the bioactive, but minor, vitamin D metabolites. A second generation of reagents used large fixed charge groups that increased sensitivity at the cost of a deterioration in chromatographic separation of the vitamin D derivatives. This precludes a survey of numerous vitamin D metabolites without redesigning the chromatographic system used. 2-Nitrosopyridine (PyrNO) demonstrates that one can improve ionization and gain higher sensitivity over PTAD. The resulting vitamin D derivatives facilitate high-resolution chromatographic separation of the major metabolites. Additionally, a liquid-liquid extraction followed by solid-phase extraction (LLE-SPE) was developed to selectively extract 1α,25(OH)2VitD, while reducing 2- to 4-fold ion suppression compared with SPE alone. LLE-SPE followed by PyrNO derivatization and LC/MS/MS analysis is a promising new method for quantifying vitamin D metabolites in a smaller sample volume (100 µL of serum) than previously reported methods. The PyrNO derivatization method is based on the Diels-Alder reaction and thus is generally applicable to a variety diene analytes.