Characterization of vitamin D production by human ocular barrier cells

Decreased choroidal vascularity index and subfoveal choroidal thickness in vitamin D insufficiency

BACKGROUND

To present the effects of vitamin D insufficiency on the choroidal vascularity index, central choroid and central macula.

METHODS

42 eyes of 42 patients with vitamin D insufficiency and 51 eyes of 51 age- and sex-matched healthy subjects were included in this retrospective, cross-sectional, and comparative study. The macular layer was examined using the retinal mapping mode of the spectral domain Optical coherence tomography (Optovue RTVue XR, Optovue Inc., Fremont, CA). Optical coherence tomography (OCT) images were taken in Enhanced Deep Imaging mode and transferred to Image J program. choroidal vascularity index (CVI) and subfoveal choroidal thickness (SFCT) measurements were evaluated.

RESULTS

The mean age of volunteers was 35.4 ± 7.2 years. There was a significant difference in CVI values 67.75±2.4 in the patients with vitamin D insufficiency and 69.22±1.75 in the control group. The SCFT of patients with vitamin D insufficiency and control group were 295.25±42.3 and 335.71±11.6 (p = 0.001, p<0.001 respectively).

CONCLUSION

OCT examination of patients with vitamin D insufficiency showed a decrease in CVI and SCFT values. These results are important in demonstrating the retinochoroidal effects of vitamin D insufficiency.

Real Life Impact of Dry Eye Disease

Dry Eye Disease (DED) is an increasingly common condition that affects between 5% and 50% of the global population. Even though DED is most frequently diagnosed in older people, it has also been diagnosed in young adults and adolescents more frequently in recent years (employees, gamers). People can experience different types of symptoms and find it challenging to read, watch TV, cook, climb stairs, and meet friends. Mild and severe dry eye can reduce quality of life similarly to mild psoriasis and moderate-to-severe angina. Furthermore, DED patients experience serious difficulties driving vehicles, especially at night, and show a decrease in work productivity, which, when combined with the relevant indirect cost that this condition produces, poses a serious challenge in our days. In addition, DED patients are more likely to develop depression and suicidal ideations and experience frequent sleep disorders. Finally, it is discussed how lifestyle changes, such as increased physical activity, blinking exercises, and a proper diet, have positive implications for the management of this condition. Our aim is to draw attention to the negative effects of dry eye in real life, which are unique to each patient, especially as they relate to the non-visual symptoms experienced by DED patients.

Challenges and Opportunities in P450 Research on the Eye

Of the 57 cytochrome P450 enzymes found in humans, at least 30 have ocular tissues as an expression site. Yet knowledge of the roles of these P450s in the eye is limited, in part because only very few P450 laboratories expanded their research interests to studies of the eye. Hence the goal of this review is to bring attention of the P450 community to the eye and encourage more ocular studies. This review is also intended to be educational for eye researchers and encourage their collaborations with P450 experts. The review starts with a description of the eye, a fascinating sensory organ, and is followed by sections on ocular P450 localizations, specifics of drug delivery to the eye, and individual P450s, which are grouped and presented based on their substrate preferences. In sections describing individual P450s, available eye-relevant information is summarized and concluded by the suggestions on the opportunities in ocular studies of the discussed enzymes. Potential challenges are addressed as well. The conclusion section outlines several practical suggestions on how to initiate eye-related research. SIGNIFICANCE STATEMENT: This review focuses on the cytochrome P450 enzymes in the eye to encourage their ocular investigations and collaborations between P450 and eye researchers.

What else can we do to prevent diabetic retinopathy?

The classical modifiable factors associated with the onset and progression of diabetic retinopathy are the suboptimal control of blood glucose levels and hypertension, as well as dyslipidaemia. However, there are other less recognised modifiable factors that can play a relevant role, such as the presence of obesity or the abnormal distribution of adipose tissue, and others related to lifestyle such as the type of diet, vitamin intake, exercise, smoking and sunlight exposure. In this article we revisit the prevention of diabetic retinopathy based on modulating the modifiable risk factors, as well as commenting on the potential impact of glucose-lowering drugs on the condition. The emerging concept that neurodegeneration is an early event in the development of diabetic retinopathy points to neuroprotection as a potential therapeutic strategy to prevent the advanced stages of the disease. In this regard, the better phenotyping of very early stages of diabetic retinopathy and the opportunity of arresting its progression using treatments targeting the neurovascular unit (NVU) are discussed.

Prevention and Treatment of Retinal Vein Occlusion: The Role of Diet-A Review

Retinal vein occlusion (RVO) is the second most common retinal disorder. In comparison to diabetic retinopathy or age-related macular degeneration, RVO is usually an unexpected event that carries a greater psychological impact. There is strong evidence to suggest that cardiovascular diseases are the most common risk factors in this pathology and it has long been known that a higher consumption of fish, nuts, fruits, and vegetables has a protective effect against these types of conditions. In the last several years, interest in plant-based diets has grown in both the general population and in the scientific community, to the point to which it has become one of the main dietary patterns adopted in Western countries. The aim of this review is to investigate the potential impact of macro- and micronutrients on retinal vein occlusion.

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.

A medication-wide association study to identify medications associated with incident clinically significant diabetic retinopathy

Background

Diabetic retinopathy, a common microvascular complication of diabetes mellitus, is one of the leading causes of vision loss worldwide. Although some oral drugs have been suggested to affect the risk of diabetic retinopathy, systematic evaluation about the associations between medications and diabetic retinopathy is still absent.

Objective

To comprehensively investigate associations of systemic medications with incident clinically significant diabetic retinopathy (CSDR).

Design

Population-based cohort study.

Methods

From 2006 to 2009, more than 26 000 participants residing in New South Wales were enrolled in the 45 and Up study. Diabetic participants with self-reported physician diagnosis or records of anti-diabetic medication prescriptions were finally included in the current analysis. CSDR was defined as diabetic retinopathy cases requiring retinal photocoagulation recorded in the Medicare Benefits Schedule database from 2006 to 2016. Prescriptions of systemic medication from 5 years to 30 days prior to CSDR were retrieved from the Pharmaceutical Benefits Scheme. The study participants were equally split into training and testing datasets. Logistic regression analyses were performed for the association between each of systemic medication and CSDR in the training dataset. After controlling the false discovery rate (FDR), significant associations were further validated in the testing dataset.

Results

The 10-year incidence of CSDR was 3.9% (n = 404). A total of 26 systemic medications were found to be positively associated with CSDR, among which 15 were validated by the testing dataset. Additional adjustments for pertinent comorbidities suggested that isosorbide mononitrate (ISMN) (OR: 1.87, 95%CI: 1.00-3.48), calcitriol (OR: 4.08, 95% CI: 2.02-8.24), three insulins and analogues (e.g., intermediate-acting human insulin, OR: 4.28, 95% CI: 1.69-10.8), five anti-hypertensive medications (e.g., furosemide, OR: 2.53, 95% CI: 1.77-3.61), fenofibrate (OR: 1.96, 95% CI: 1.36-2.82) and clopidogrel (OR: 1.72, 95% CI: 1.15-2.58) were independently associated with CSDR.

Conclusion

This study investigated the association of a full spectrum of systemic medications with incident CSDR. ISMN, calcitriol, clopidogrel, a few subtypes of insulin, anti-hypertensive and cholesterol-lowering medications were found to be associated with incident CSDR.

Calcipotriol Attenuates Form Deprivation Myopia Through a Signaling Pathway Parallel to TGF-β2-Induced Increases in Collagen Expression

Purpose

To determine the role of calcipotriol, a vitamin D3 analogue, in myopia development and altering the expression of scleral α1 chain of type I collagen (Col1α1) in mice. We also aimed to identify if the signaling pathway mediating the above changes is different from the one involved in transforming growth factor β2 (TGF-β2)-mediated increases of COL1A1 in cultured human scleral fibroblasts (HSFs).

Methods

C57BL/6J mice were either intraperitoneally injected with calcipotriol and subjected to form deprivation (FD) or exposed to normal refractive development for 4 weeks. Scleral vitamin D receptor (Vdr) expression was knocked down using a Sub-Tenon's capsule injection of an adeno-associated virus-packaged short hairpin RNA (AAV8-shRNA). Refraction and biometric measurements evaluated myopia development. A combination of knockdown and induction strategies determined the relative contributions of the vitamin D3 and the TGF-β2 signaling pathways in modulating COL1A1 expression in HSFs.

Results

Calcipotriol injections suppressed FD-induced myopia (FDM), but it had no significant effect on normal refractive development. AAV8-shRNA injection reduced Vdr mRNA expression by 42% and shifted the refraction toward myopia (-3.15 ± 0.99D, means ± SEM) in normal eyes. In HSFs, VDR knockdown reduced calcipotriol-induced rises in COL1A1 expression, but it did not alter TGF-β2-induced increases in COL1A1 expression. Additionally, TGF-β2 augmented calcipotriol-induced rises in COL1A1 expression. TGF-β receptor (TGFBRI/II) knockdown blunted TGF-β2-induced increases in COL1A1 expression, whereas calcipotriol-induced increases in VDR and COL1A1 expression levels were unaltered.

Conclusions

Scleral vitamin D3 inhibits myopia development in mice, potentially by activating a VDR-dependent signaling pathway and increasing scleral COL1A1 expression levels.

Dry Eye Disease: What Is the Role of Vitamin D?

Dry eye disease (DED) is a multifactorial condition resulting from reduced tear secretion from the lacrimal glands, increased tear water evaporation or the production of poor-quality tears. Such tear instability can lead to inflammation and damage of the ocular surface, as well as to abnormal nociception. Historically, tear substitutes and corticosteroids have been the bastion of DED therapy, but a substantial number of patients still suffer from residual symptoms even after being treated with traditional treatments. Aiming to find safe and effective alternative therapies, recent efforts have been focused on the role of vitamin D in the cellular physiology of the eye. Possibly because of its positive effect in modulating the immune and inflammatory responses, the systemic supplementation of vitamin D seems, indeed, to be an effective therapeutic strategy, especially, but not only, for patients affected by DED that does not respond to conventional treatments. In this context, this review focuses on the literature reporting on the pathogenesis and treatment of DED, with a special emphasis on the recent investigations reporting on the potential role of the systemic administration of vitamin D as a therapeutic approach in the management of such condition.

Association of keratoconus with serum levels of 25-hydroxyvitamin D and antioxidant trace elements: A systematic review and meta-analysis

The aim of this systematic review and meta-analysis was to summarize and compare the available evidence on the level of vitamin D and antioxidant trace elements between the keratoconus (KC) patients and healthy controls. Seven case-control studies with 830 subjects were found eligible with a systematic search using PubMed, SCOPUS, Web of Science, and EMBASE till November 21, 2021. Data were synthesized with a DerSimonian and Laird random-effects method of meta-analysis. The mean serum vitamin D level was significantly lower in the patients with KC [standardized mean difference (SMD): -0.71; P < 0.001] as compared with the control group. The mean serum vitamin D level decreased more in the progressive patients (SMD: -0.80; P = 0.016) than in the stable patients (SMD: -0.66; P < 0.001) when compared with the control group. The mean serum zinc level was found significantly lower in the patients with KC compared with the control group (SMD: -1.98; P = 0.005). Pooled analysis based on the two studies showed significantly lower mean selenium levels in the KC patients (SMD: -0.34; P = 0.003). Regular evaluation of serum vitamin D, zinc, and selenium levels among the patients with KC at disease onset and future follow-ups could be promising in predicting the progressive disease and disease severity.

Conjunctival Histopathological Changes in Children With Vitamin D Deficiency

PURPOSE

The aim of this study was to investigate tear function-associated clinical findings and conjunctival histopathological changes in children with vitamin D (Vit-D) deficiency.

METHODS

This study used a prospective case-control design. Group 1 (n=38) comprised pediatric patients with Vit-D deficiency, and group 2 (n=45) was the control group. Tear break-up times (TBUTs), Schirmer-1 test measurements, ocular surface disease index (OSDI) scores, and conjunctival impression cytology (CIC) results of the groups were compared.

RESULTS

The participant demographic characteristics, including the mean age and the male-to-female ratio, were similar (P>0.05). The median TBUT and Schirmer-1 test measurement were 10 s (5-15) and 12 mm (6-19) in group 1 and 11 s (6-16) and 15 mm (8-21) in group 2 (P=0.004 and P=0.013, respectively). The median OSDI scores were 16 (10-20) in group 1 and 17 (10-21) in group 2 (P=0.092). According to the CIC, 25 samples in group 1 and 40 samples in group 2 were categorized as grade 0, 11 samples in group 1 and 5 samples in group 2 were categorized as grade 1, and 2 samples in group 1 and no sample in group 2 were categorized as grade 2 (P=0.027).

CONCLUSION

Significant conjunctival histopathological changes occur in children with Vit-D deficiency, and these changes have effects on some tear function-associated clinical findings including the Schirmer-1 test and TBUT measurements.

Vitamin D, the Vitamin D Receptor, Calcitriol Analogues and Their Link with Ocular Diseases

The global prevalence of eye diseases continues to grow, bringing with it a reduction in the activity levels and quality of life of patients, and partial or complete blindness if left untreated. As such, there is considerable interest in identifying more effective therapeutic options and preventive agents. One such agent is vitamin D, known to have a range of anti-cancer, anti-angiogenic, anti-inflammatory and anti-oxidative properties, and whose deficiency is linked to the pathogenesis of a range of cardiovascular, cancer, and inflammatory diseases. This review presents the current stage of knowledge concerning the link between vitamin D and its receptor and the occurrence of eye disease, as well as the influence of analogues of calcitriol, an active metabolite of vitamin D. Generally, patients affected by various ocular disorders have vitamin D deficiency. In addition, previous findings suggest that vitamin D modulates the course of eye diseases and may serve as a marker, and that its supplementation could mitigate some disorders. However, as these studies have some limitations, we recommend further randomized trials to clarify the link between vitamin D and its activity with eye disease.

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.

Vitamin D and Ocular Diseases: A Systematic Review

The contributory roles of vitamin D in ocular and visual health have long been discussed, with numerous studies pointing to the adverse effects of vitamin D deficiency. In this paper, we provide a systematic review of recent findings on the association between vitamin D and different ocular diseases, including myopia, age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), dry eye syndrome (DES), thyroid eye disease (TED), uveitis, retinoblastoma (RB), cataract, and others, from epidemiological, clinical and basic studies, and briefly discuss vitamin D metabolism in the eye. We searched two research databases for articles examining the association between vitamin D deficiency and different ocular diseases. One hundred and sixty-two studies were found. There is evidence on the association between vitamin D and myopia, AMD, DR, and DES. Overall, 17 out of 27 studies reported an association between vitamin D and AMD, while 48 out of 54 studies reported that vitamin D was associated with DR, and 25 out of 27 studies reported an association between vitamin D and DES. However, the available evidence for the association with other ocular diseases, such as glaucoma, TED, and RB, remains limited.

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.

Changes in the macular choroidal thickness of children who have type-1 diabetes mellitus, with and without vitamin D deficiency

PURPOSE

To assess the peripapillary retinal nerve fiber layer (RNFL) and macular choroidal thickness (CT) of children who have Type 1 diabetes mellitus (DM), both with and without vitamin D deficiency (VDD).

METHODS

The prospective, case-control study herein comprised that included 46 children with DM and VDD (Group 1), 42 children with DM and normal vitamin D levels (Group 2), and 73 healthy children (Control group). The peripapillary RNFL thickness and macular CT were measured at three different points (subfoveal, 1500 μm nasal, and 1500 μm temporal from the fovea) and compared.

RESULTS

The subfoveal, 1500 μm nasal, and 1500 μm temporal CT values were determined to be lower in the patients in Group 1 and Group 2 when compared to those in the Control group (P < 0.001). The same parameters were determined to be lower in the patients in Group 1 when compared to those in Group 2, although this difference was not found to be statistically significant (P > 0.05). In all of the quadrants, the RNFL thickness was determined to be similar between the groups, with P > 0.05 for all of the groups, except for the nasal quadrant (P = 0.031). In the correlation analysis of the patients in Group 1, it was revealed that a positive correlation existed between the CT and the vitamin D levels (P < 0.05).

CONCLUSION

The choroids of pediatric diabetic children were thinner when compared to those of healthy children. The alterations in these parameters were more prominent in subjects who were determined to have lower levels of vitamin D.

Evaluation of Retinal Structure in Pediatric Subjects With Vitamin D Deficiency

PURPOSE

To quantitatively evaluate the retinal structural parameters of pediatric patients who were determined to be deficient in vitamin D.

DESIGN

Prospective, cross-sectional study.

METHODS

Retinal structural parameters, including the peripapillary retinal nerve fiber layer (RNFL), central macula, retinal layer, and choroidal thicknesses, central retinal artery equivalent (CRAE), and central retinal vein equivalent (CRVE), in pediatric subjects with vitamin D deficiency (group 1) and those without (group 2) were compared.

RESULTS

Group 1 comprised 70 individuals, while group 2 comprised 80 individuals. The mean peripapillary RNFL (except for the nasal superior sector [P = .037]), central macula, and retinal layer thicknesses were also determined to be similar in both groups (P > .05 for both groups). The mean choroidal thickness was lower in the subfoveal (P = .006) and nasal 3000-µm-diameter areas (P = .004) in group 1. The mean CRAE was determined to be lower (P = .031) and the CRVE was higher in group 1 (P = .005); it was determined that there was a significant correlation between the vitamin D level and both the CRAE (r = 0.447, P < .001) and CRVE (r = -0.320, P = .013).

CONCLUSION

Choroidal thinning, a decrease in the CRAE, and increase in the CRVE were structural changes that occurred in the pediatric subjects who had vitamin D deficiency. The alterations in these parameters became more prominent in pediatric subjects who were determined to have lower vitamin D levels.

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.

Protective role of vitamin D against oxidative stress in diabetic retinopathy

Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus. There is much evidence showing that a high level of mitochondrial overproduction of reactive oxygen species in the diabetic retina contributes in modifying cellular signalling and leads to retinal cell damage and finally to the development of DR pathogenesis. In the last few decades, it has been reported that vitamin D is involved in DR pathogenesis. Vitamin D, traditionally known as an essential nutrient crucial in bone metabolism, has also been proven to be a very effective antioxidant. It has been demonstrated that it modulates the production of advanced glycosylated end products, as well as several pathways including protein kinase C, the polyol pathway leading to the reduction of free radical formation. It prevents the translocation of nuclear factor kappa B, preventing the inflammatory response, acting as an immunomodulator, and modulates autophagy and apoptosis. In this review, we explore the molecular mechanisms by which vitamin D protects the eye from oxidative stress, in order to evaluate whether vitamin D supplementation may be useful to mitigate the deleterious effects of free radicals in DR.

Effects of a New Combination of Natural Extracts on Glaucoma-Related Retinal Degeneration

BACKGROUND

Glaucoma is currently the leading cause of irreversible blindness; it is a neuropathy characterized by structural alterations of the optic nerve, leading to visual impairments. The aim of this work is to develop a new oral formulation able to counteract the early changes connected to glaucomatous degeneration. The composition is based on gastrodin and vitamin D3 combined with vitamin C, blackcurrant, and lycopene.

METHODS

Cells and tissues of the retina were used to study biological mechanisms involved in glaucoma, to slow down the progression of the disease. Experiments mimicking the conditions of glaucoma were carried out to examine the etiology of retinal degeneration.

RESULTS

Our results show a significant ability to restore glaucoma-induced damage, by counteracting ROS production and promoting cell survival by inhibiting apoptosis. These effects were confirmed by the intracellular mechanism that was activated following administration of the compound, either before or after the glaucoma induction. In particular, the main results were obtained as a preventive action of glaucoma, showing a beneficial action on all selected markers, both on cells and on eyecup preparations. It is therefore possible to hypothesize both the preventive and therapeutic use of this formulation, in the presence of risk factors, and due to its ability to inhibit the apoptotic cycle and to stimulate cell survival mechanisms, respectively.

CONCLUSION

This formulation has exhibited an active role in the prevention or restoration of glaucoma damage for the first time.

Synthetic high-density lipoprotein nanoparticles: Good things in small packages

Medicine has been a great beneficiary of the nanotechnology revolution. Nanotechnology involves the synthesis of functional materials with at least one size dimension between 1 and 100 nm. Advances in the field have enabled the synthesis of bio-nanoparticles that can interface with physiological systems to modulate fundamental cellular processes. One example of a diverse acting nanoparticle-based therapeutic is synthetic high-density lipoprotein (HDL) nanoparticles (NP), which have great potential for treating diseases of the ocular surface. Our group has developed a spherical HDL NP using a gold nanoparticle core. HDL NPs: (i) closely mimic the physical and chemical features of natural HDLs; (ii) contain apoA-I; (iii) bind with high-affinity to SR-B1, which is the major receptor through which HDL modulates cell cholesterol metabolism and controls the selective uptake of HDL cargo into cells; (iv) are non-toxic to cells and tissues; and (v) can be chemically engineered to display nearly any surface or core composition desired. With respect to the ocular surface, topical application of HDL NPs accelerates re-epithelization of the cornea following wounding, attenuates inflammation resulting from chemical burns and/or other stresses, and effectively delivers microRNAs with biological activity to corneal cells and tissues. HDL NPs will be the foundation of a new class of topical eye drops with great translational potential and exemplify the impact that nanoparticles can have in medicine.

Effects of 1,25 Dihydroxyvitamin D3 on Human Retinal Pigment Epithelial Cell Lines

PURPOSE

To assess the effects of 1,25 dihydroxyvitamin D₃ (vitamin D₃) either alone or under oxidative damage on human retinal pigment epithelium cell lines.

METHODS

The human retinal pigment epithelial cell lines were pretreated with hydrogen peroxide with different concentrations (100-1000 μM) and durations (4, 12 and 24 h) to determine the appropriate dose. A group of cells were treated with vitamin D₃ alone, and another group of cells were co-treated with different concentrations of (10-100 nM) vitamin D₃ and hydrogen peroxide. Anti-cytotoxic, anti-apoptotic and anti-genotoxic effects of vitamin D₃ on the hydrogen peroxide treated cell line were evaluated. In addition, mitochondrial membrane potentials of treated cell lines were measured.

RESULTS

Vitamin D₃ showed statistically significant anti-cytotoxic effects and increased cell viability in all concentrations (p < 0.001). It has also significantly decreased the intracellular ROS generation at concentrations between 10-60 nM and increased intracellular reactive oxygen species in high doses over 90 nM (p < 0.01). When apoptosis was evaluated, vitamin D₃ caused statistically significant decrease in a dose-dependent manner (p < 0.001). In terms of DNA damage which was caused by oxidative stress, it was observed that vitamin D₃ significantly reduced the damage in a dose-dependent manner (p < 0.001). At the doses of 10-50 nM, vitamin D₃ significantly decreased the mitochondrial membrane potential (p < 0.01).

CONCLUSION

Our study suggests that 1,25 (OH)₂ D3 is capable for alleviating the oxidative damage in ARPE cell lines. With these results, vitamin D is thought to be a therapeutic alternative for the prevention of age-related macular degeneration. This warrants further investigations.

Ocular Findings Among Patients With Vitamin D Deficiency

Objective The aim of this study was to evaluate the ocular findings in patients with low vitamin D levels. Methods All patients who attended the Internal Medicine Clinic between March 2018 and February 2020 with vitamin low D levels but had been untreated for the same were included in our study. The exclusion criteria were as follows:history of intraocular surgery, trauma, steroid use, secondary glaucoma, and history of rheumatologic diseases. The patients were classified into three groups: group 1 had severe deficiency with vitamin D levels below 10 µg/L; group 2 had vitamin deficiency with levels of 10-20 µg/L; and group 3 had vitamin D insufficiency with levels of 20-30 µg/L. A comparison among groups was performed in terms of intraocular pressure (IOP), retinal nerve fiber layer (RNFL) thickness, central macular thickness (CMT), dry eyes, cataract, glaucoma, macular degeneration, and refractive error. The evaluation of statistical data was performed with the SPSS Statistics software version 22 (IBM, Armonk, NY). Results There were a total of 98 patients and 196 eyes, who were classified into three groups. There were 41 patients in group 1, 45 in group 2, and 12 in group 3. Groups were similar in terms of age (p=0.25) and gender (p=0.46). The average age among the cohort was 51 ± 13.08 years; 65 (66.3%) of the patients were female and 33 (33.7%) were male. There was no statistically significant difference in terms of IOP (p=0.55), dry eyes (p=0.35), cataract (p=0.22), glaucoma (p=0.50), macular degeneration (p=0.64), and refractive error (p=0.46) among the groups. There was a statistically significant difference in CMT between group 1 and other groups (p=0.002 and p=0.002, respectively). Also, there was a statistically significant difference in RNFL thickness between group 1 and group 2 (p=0.01). When compared in terms of quadrants, a significant difference was found only with regard to the nasal quadrant. Conclusion Based on our findings, lower levels of 25-hydroxyvitamin D might be related to thinning in CMT. Regarding RNFL thickness, while there was a significant difference between groups 1 and 2, there was no difference between groups 1 and 3, and hence the association between lower levels of 25-hydroxyvitamin D and thinning in RNFL thickness could not be clearly established. Hence, we have assumed that lower levels of 25-hydroxyvitamin D might cause thinning in the macula and nasal quadrant of RNFL, and vitamin D deficiency might affect the nasal quadrant of RNFL primarily. Further long-term studies with a larger number of patients might clarify the relationship between vitamin D deficiency and the thinning in CMT, RNFL quadrants, and RNFL thickness.

Anti-Inflammatory and Anti-Oxidative Synergistic Effect of Vitamin D and Nutritional Complex on Retinal Pigment Epithelial and Endothelial Cell Lines against Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a multifactorial disease of the retina featured by dysfunction of retinal pigmented epithelial (RPE) and loss of photoreceptor cells under oxidative stress and inflammatory conditions. Vitamin D and antioxidants have beneficial effects against retinal degenerative diseases, such as AMD. We investigated the impact of associating vitamin D (ND) with a nutritional antioxidant complex (Nutrof Total^®; N) on oxidative stress and inflammation-like induced conditions by H₂O₂ and LPS, respectively, in human retinal epithelial (ARPE-19) and human retinal endothelial (HREC) cells. Application of either N or ND treatments to H₂O₂-induced media in ARPE-19 cells counteracted late apoptosis, attenuated oxidative DNA damage, and increased cell proliferation. Significant reduction in the expression levels of MCP1, IL-8, and IL6 cytokines was observed following application of either N or ND treatments under LPS-induced conditions in ARPE-19 cells and in MCP-1 and IL12p70 cytokine levels in HREC cells. ND and not N revealed significant downregulation of IFNγ in ARPE-19 cells, and of IL-6 and IL-18 in HREC cells. In conclusion, adding vitamin D to Nutrof Total^® protects in a synergistic way against oxidative and inflammatory stress-induced conditions in retinal epithelial and endothelial cells.

Comparison of vitamin D levels between patients with pterygium and healthy subjects

PURPOSE

The purpose of this study was to compare vitamin D (VD) deficiency frequency among patients with pterygium to that of healthy subjects and to investigate the VD deficiency among patients with pterygium.

METHODS

One-hundred eight pterygium patients and 94 healthy subjects were included in the study. Blood samples were collected from groups during the same time interval and the samples were saved. Serum 25-hydroxyvitamin D (25(OH)D) and parathormone (PTH) levels were measured and analyzed.

RESULTS

The pterygium group consisted of 57 female and 51 male patients, while the control group consisted of 47 female and 47 male patients. The mean age, sex and mean BMI were similar in the two groups (p > 0.05). The percentage of time that individuals spent outdoors was higher in the pterygium group (p = 0.02). The percentage of VD deficiency was 83.3% in the pterygium group and 61.7% in the control group (p = 0.001). There was a positive correlation between VD and time spent outdoors (p < 0.05).

CONCLUSIONS

VD deficiency can play a role in pterygium etiopathogenesis. Wide population-based studies in different regions are needed to evaluate this result.

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.

Tear Fluid and Serum Vitamin D Concentrations in Unilateral Pterygium

SIGNIFICANCE

Vitamin D has antiangiogenic, anti-inflammatory, and antifibrotic properties, which may play an inhibitory role on pterygium formation. Vitamin D concentration was measured in few studies, and contradictory results have been reported. There is no study investigating tear fluid concentration of vitamin D in pterygium patients.

PURPOSE

This study evaluated tear fluid and serum vitamin D concentrations of pterygium patients in comparison with healthy controls.

METHODS

Thirty-five (21 male, 14 female) patients with unilateral pterygium and 25 (18 male, 7 female) healthy controls were included in this case-control study. After full ophthalmic examination, blood samples were taken, and basal tear fluid was collected using glass microcapillary tubes. Tear fluid and serum vitamin D concentrations were analyzed using enzyme-linked immunosorbent assay and analyzed statistically.

RESULTS

The mean ± standard deviation age of patients was 51.7 ± 16.7 years in the study group and 50.6 ± 18.7 years in the control group, respectively (P = .82). The mean tear fluid vitamin D concentration was statistically significantly higher than the mean serum concentration in the study groups (P < .0001). The mean tear fluid (P = .76) and serum vitamin D concentrations (P = .53) did not reveal statistically significant difference between patients and controls. There was no statistically significant difference for tear fluid vitamin D concentration between pterygium eyes and fellow eyes (P = .93). The difference in concentrations was compared within the pterygium subgroups, and it was found that the mean serum vitamin D concentration trended toward lower values as the stage of pterygium increased, and the mean tear fluid vitamin D concentration trended toward higher values as the stage of pterygium increased, although these differences were not statistically significant (all, P > .05).

CONCLUSIONS

Tear fluid and serum vitamin D concentrations do not seem to have a role in pterygium pathogenesis.

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.

Expression of vitamin D 1α-hydroxylase in human gingival fibroblasts in vivo

Background

Vitamin D 1α-hydroxylase CYP27B1 is the key factor in the vitamin D pathway. Previously, we analyzed the expression of CYP27B1 in human gingival fibroblasts in vitro. In the present study, we analyzed the gingival expression of CYP27B1 in vivo.

Methods

Forty-two patients with periodontitis Stage IV Grade C and 33 controls were recruited. All patients with periodontitis had unsalvageable teeth and part of the wall of the periodontal pocket was resected and obtained after tooth extraction. All controls needed crown-lengthening surgery, and samples of gingiva resected during surgery were also harvested. All the individuals' gingivae were used for immunohistochemistry and immunofluorescence. In addition, gingivae from seventeen subjects of the diseased group and twelve subjects of the control group were analyzed by real-time PCR.

Results

Expression of CYP27B1 was detected both in gingival epithelia and in gingival connective tissues, and the expression in connective tissues colocalized with vimentin, indicating that CYP27B1 protein is expressed in gingival fibroblasts. The expression of CYP27B1 mRNA in gingival connective tissues and the CYP27B1 staining scores in gingival fibroblasts in the diseased group were significantly higher than those in the control group.

Conclusions

Expression of CYP27B1 in human gingival tissues was detected, not only in the fibroblasts of gingival connective tissues, but also in the gingival epithelial cells, and might be positively correlated with periodontal inflammation.

A New Modified Experimental Meibomian Gland Injury Model: Partial Loss of Gland Due to Orifice Cauterization and the Alleviating Potential of 22-Oxacalcitriol

1α,-25-dihydroxy-22-oxacalcitriol (maxacalcitol) is a non-calcemic vitamin D3 analog clinically approved to treat psoriasis, and its role has been increasingly recognized in suppressing keratinocyte proliferation, mediating inflammation, and regulating the immune response. A large number of studies have suggested that vitamin D plays an important role in maintaining ocular surface health. However, its topical effects on the Meibomian gland (MG) has been insufficiently investigated. Here, we introduce an experimental MG orifice injury model, where the partial glandular loss occurred after electrical cauterization on a limited number of MG orifices, and investigate the efficacy and safety of maxacalcitol ointment in treating this MG orifice injury model. We confirm the alleviation of MG atrophy and ductal dilation by maxacalcitol ointment application. The recovery of injured MG visualizing as the residual MG area is significantly better in the maxacalcitol group (p = 0.020) compared with the Vaseline^® group, especially during the first two weeks. The cornea and other ocular tissues were not affected by maxacalcitol ointment application during our two-month observation period. Altogether, this work indicates that maxacalcitol has therapeutic potential in the amelioration of initial injury of MG orifices caused by electrocautery.

A Novel Integrated Active Herbal Formulation Ameliorates Dry Eye Syndrome by Inhibiting Inflammation and Oxidative Stress and Enhancing Glycosylated Phosphoproteins in Rats

Dry eye syndrome (DES) is a chronic condition of the eye with insufficient production of tears leading to inadequate lubrication of eyes. Symptoms of DES are associated with discomfort and redness of the eye, blurred vision, and tear film instability which leads to the damaged ocular surface. Inflammation and oxidative stress play a significant role in the pathogenesis of the disease. In this study, the protective effect of different doses (100 or 200 mg/kg) of a novel multi-component oral formulation of lutein/zeaxanthin, curcumin, and vitamin D3 (LCD) was evaluated using a rat model with benzalkonium chloride (BAC)-induced dry eye syndrome. The formulation was administered orally to rats for 4 weeks. We observed a significant improvement in tear volume, tear breakup time, tear film integrity, and reduction in overall inflammation in rats fed with the LCD at dose 200 mg/kg performing better than 100 mg/kg. Furthermore, the formulation helped in lowering oxidative stress by increasing antioxidant levels and restored protective tear protein levels including MUC1, MUC4, and MUC5AC with 200 mg of LCD having the most significant effect. The results strongly suggest that the combination of lutein/zeaxanthin, curcumin, and vitamin-D3 is effective in alleviating the symptoms of dry eye condition with a multi-modal mechanism of action.

Effect of Vitamin D Deficiency on Contrast Sensitivity Function

PURPOSE

The purpose of this study is to investigate the effects of vitamin D (vit D) deficiency on contrast sensitivity (CS) function and retinal layers.

MATERIALS AND METHODS

Group 1 consisted of 42 patients aged between 18 and 50 years with vit D deficiency and Group 2 consisted of sex- and age-matched 34 healthy subjects with normal vit D levels. Functional acuity contrast testing (FACT) was performed using the Optec 6500 vision testing system. The average retinal nerve fiber layer (RNFL) thickness and macular thickness (MT) obtained from nine macular areas in the Early Treatment Diabetic Retinopathy Study were evaluated using SD-OCT (RS-3000; Nidek Inc., Fremont, CA, USA) following a detailed ophthalmologic examination. Measurements were performed on both eyes.

RESULTS

A lower CS was found in Group 1 compared to Group 2 in all spatial frequencies. A statistically significant difference was observed between the groups in 6, 12 and 18 cpd spatial frequencies, respectively. (p = .004, p = .001, p = .042, respectively). There was no statistically significant difference between groups in terms of RNFL thicknesses (p = .200). There was an increase in MT in Group 1. However, this increase was statistically significant in the inferior inner area in the right eye, and in the inferior inner, temporal inner and outer macular areas in the left eye (p = .018, p = .003, p = .033, p = .040, respectively).

CONCLUSION

It was observed that vit D deficiency had negative effects on CS function and also caused thickness difference in certain segments of retinal layers.

Conjunctival impression cytology and tear-film changes in cases with vitamin D deficiency

PURPOSE

To evaluate conjunctival surface cells and tear-film functions in cases with vitamin D deficiency.

METHODS

Thirty-six patients with serum vitamin D deficiency and 27 control subjects with normal serum vitamin D levels were included in this prospective study. The tear break-up time (TBUT), Schirmer II test, and conjunctival impression cytology tests were performed to all participants.

RESULTS

The mean serum vitamin D levels were 10.5 ± 5.0 µl in the study group and 33.9 ± 11.7 µl in the control group (p < 0.001). The median TBUT scores were 11 s and 17 s and the median Schirmer II values were 7.5 mm and 12 mm in the study and the control groups, respectively (p = 0.003, p = 0.049). According to the Nelson staging system, 69.4% of the patients in the study group had grade 2 or 3 impression cytology, whereas 18.5% of the participants in the control group had grade 2 or 3 impression cytology (p < 0.001).

CONCLUSION

Our study results showed that vitamin D deficiency may lead to dry eye causing conjunctival squamous metaplasia and loss of goblet cells on the ocular surface.

Intraocular calcidiol: Uncovering a role for vitamin D in the eye

Vitamin D has emerged as a potentially important molecule in ophthalmology. To date, all ophthalmic data pertaining to vitamin D has been restricted primarily to tear and serum analysis in human patients. Considering the isolated nature of the eye, we sought to determine the presence of intraocular vitamin D in ocular disease.

METHODS

25-Hydroxyvitamin D₃ (25(OH)D₃) concentrations were measured in the eye and blood of 120 participants undergoing ophthalmic procedures. Ocular localization of the 1,25-dihydroxyvitamin D₃-generating (CYP27B1) and deactivating (CYP24A1) hydroxylases was performed by immunohistochemistry. Gene expression of CYP27B1, CYP24A1 and VEGF-A was measured in eyes from patients with and without disease.

RESULTS

25(OH)D₃ was quantified in 112 ocular samples. In 40 cataract patient samples, the average 25(OH)D₃ concentration was 0.057 ng/mL, compared to 72 retinal disease patient samples, average of 0.502 ng/mL (p < 0.001). Intraocular 25(OH)D₃ did not correlate with serum levels of 25(OH)D₃. There was no difference between the level of 25(OH)D₃ measured in the aqueous and vitreous humour. The vitamin D-specific CYPs 27B1 and 24A1, strongly localized to complementary regions of the ciliary body, retinal pigment epithelium and neural retina. Gene expression analysis confirmed retinal CYP27B1 correlated strongly with VEGF-A in eyes from diabetic patients (r = 0.92, p < 0.001).

CONCLUSIONS

Our data confirms that vitamin D is present in the humours of the human eye and that local synthesis/degradation is possible via the ocular CYP27B1 and CYP24A1. This argues for a functional role for local vitamin D production and signaling in the eye and suggests that vitamin D may be an important intraocular mediator in disease pathogenesis.

Dysregulated Tear Fluid Nociception-Associated Factors, Corneal Dendritic Cell Density, and Vitamin D Levels in Evaporative Dry Eye

Purpose

The purpose of this study was to study the status and association among tear-soluble factors, corneal dendritic cell density, vitamin D, and signs and symptoms in dry eye disease (DED).

Methods

A total of 33 control subjects and 47 evaporative dry eye patients were included in the study. DED diagnosis and classification was based on the 2017 Report of the Tear Film & Ocular Surface Society International Dry Eye Workshop (TFOS DEWS II). DED workup, including tear film break-up time (TBUT), Schirmer's test I (STI), corneal and conjunctival staining, ocular surface disease index (OSDI) scoring, and in vivo confocal microscopy (to assess corneal dendritic cell density [cDCD] and subbasal nerve plexus [SBNP] features) was performed in the study subjects. Tear fluid using Schirmer's strip and serum were collected from the subjects. Multiplex ELISA or single analyte ELISA was performed to measure 34 tear-soluble factors levels including vitamin D.

Results

Significantly higher OSDI discomfort score, lower TBUT, and lower STI were observed in DED patients. cDCD was significantly higher in DED patients. No significant difference was observed in SBNP features. Tear fluid IL-1β, IL-17A, MMP9, MMP10, MMP9/TIMP ratio, and VEGF-B were significantly higher in DED patients. Significantly lower tear fluid IL-2, IP-10, NPY, VEGF-A, and vitamin D was observed in DED patients. These dysregulated tear factors showed significant associations with DED signs and symptoms.

Conclusions

Altered tear fluid soluble factors with potential to modulate nociception exhibited a distinct association with ocular surface discomfort status, TBUT, STI, and cDCD. This implies a functional relationship between the various tear-soluble factors and dry eye pathogenesis, indicating new molecular targets for designing targeted therapies.

Effects of vitamin D deficiency on intraocular pressure values obtained by ocular response analyzer

PURPOSE

To compare corneal biomechanical properties measured with ocular response analyzer (ORA) and intraocular pressure (IOP) measurements in patients with vitamin D deficiency and in healthy cases.

METHODS

One hundred and twenty eyes of 120 subjects (between the ages of 19 and 78) who applied to university's outpatient clinic were evaluated: 41 lacks of vitamin D (Group 1), 39 insufficient vitamin D (Group 2) and 40 controls (Group 3). Corneal hysteresis, corneal resistance factor, Goldmann-correlated IOP and corneal compensated IOP of patients were measured by ORA.

RESULTS

The mean ages were 48.9 ± 12.1, 52.8 ± 13.6 and 52.1 ± 13.9 in groups 1, 2 and 3, respectively (p = 0.370). Mean IOPcc values were 16.5 ± 3.6 (8.1-27.3), 16.7 ± 2.7 (12.0-22.7) and 16.3 ± 3.3 (10.8-27.4) mmHg (p = 0.889); mean IOPg values were 16.8 ± 5.0 (6.5-39.5), 16.3 ± 2.9 (10.3-23.0) and 15.9 ± 3.2 (10.0-26.0) mmHg (p = 0.539); mean CH values were 10.8 ± 1.9 (8.3-19.0), 11.4 ± 1.6 (6.9-14.0) and 11.2 ± 1.5 (7.5-13.2) (p = 0.257); mean CRF values were 10.5 ± 2.7 (7.4-25.0), 11.1 ± 1.5 (6.8-13.5) and 10.5 ± 1.2 (7.7-12.8) (p = 0.282) in groups 1, 2 and 3, respectively. There was no statistical difference between the groups in terms of IOPcc, IOPg CH and CRF. However, mean CH values were found less in the lack of vitamin D group.

CONCLUSION

The CH values were lower, and the IOPg values were higher in cases of vitamin D deficiency. Corneal biomechanical differences in patients with lack of vitamin D were not statistically significant.

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.

Vitamin D Attenuates Oxidative Damage and Inflammation in Retinal Pigment Epithelial Cells

Age-related macular degeneration (AMD), the most common visual disorder in elderly people, is characterized by the formation of deposits beneath the retinal pigment epithelium (RPE) and by dysfunction of RPE and photoreceptor cells. The biologically active form of vitamin D, 1,25-(OH)2D3 (VITD), is categorized as a multifunctional steroid hormone that modulates many transcriptional processes of different genes and is involved in a broad range of cellular functions. Epidemiological and genetic association studies demonstrate that VITD may have a protective role in AMD, while single nucleotide polymorphisms in the vitamin D metabolism gene (CYP24A1) increase the risk of AMD. However, the functional mechanisms of VITD in AMD are not fully understood. In the current study, we investigated the impact of VITD on H₂O₂-induced oxidative stress and inflammation in human RPE cells. We demonstrate that exposure to H₂O₂ caused significantly reduced cell viability, increased production of reactive oxygen species (ROS), lowered expression of antioxidant enzymes and enhanced inflammation. VITD exposure notably counteracted the above H₂O₂-induced effects. Our data suggest that VITD protects the RPE from oxidative damage and elucidate molecular mechanisms of VITD deficiency in the development of AMD.

Identification of Surrogate Biomarkers for the Prediction of Patients at Risk of Low Macular Pigment in Type 2 Diabetes

Purpose: This cross-sectional study compared macular pigment (MP) levels among persons with Type 2 diabetes relative to healthy controls. Additionally, a range of behavioral, anthropometric, clinical and serum measures were explored as possible predictors of low MP optical density (MPOD) in diabetes.Methods: Two health status groups; Group 1: Type 2 diabetes (n = 188), and Group 2: Healthy controls (n = 2,594) completed a full MP assessment using customized heterochromatic flicker photometry, as part of The Irish Longitudinal Study on Aging (TILDA). Clinical [blood pressure; cataract status; MPOD] and anthropometric [waist (cm); weight (kg); hip (cm)] measurements were taken, and a blood sample drawn for analysis of serum biomarkers [lipoproteins; inflammatory markers (C reactive protein and vitamin-D)].Results: One-way ANOVA revealed lower MPOD in subjects with Type 2 diabetes relative to controls (p = .047). Amongst participants with diabetes, those with low serum vitamin D (≤50 nmol/L) had significantly lower mean MPOD compared to those with sufficient serum vitamin D levels >50 nmol/L (0.173(0.148) vs. 0.226(0.145); p = .006). Concomitantly, MP was significantly lower in diabetes participants with raised serum triglyceride (TG) to high density lipoprotein (HDL) ratio (TG/HDL); values >1.74 mmol/L (0.172 (0.140) vs 0.215 (0.152); p = .039). Body mass index, waist-to-height ratio and waist circumference, were all significantly negatively correlated with MPOD (Pearson's correlation, p < .05 for all). Significant correlates of MPOD in the multivariate regression model included smoking, cataract, and vitamin D, which collectively contributed 18.5% of the overall variability in MPOD status amongst participants with Type 2 diabetes.Conclusions: This study provides additional evidence that low MP may indeed be a feature of Type 2 diabetes, and further identifies smoking, cataract and vitamin D status as plausible predictors of low MPOD amongst persons with Type 2 diabetes.

Vitamin D receptors (VDR), hydroxylases CYP27B1 and CYP24A1 and retinoid-related orphan receptors (ROR) level in human uveal tract and ocular melanoma with different melanization levels

In recent years, a significant number of studies have investigated the preventive role of vitamin D in a number of different neoplasms. In this study, we analyze various components of the vitamin D signaling pathways in the human uveal tract and uveal melanoma, including analysis of the expression of vitamin D receptors (VDR), the activating and inactivating hydroxylases, respectively, CYP27B1 and CYP24A1, and the retinoic acid-related orphan receptors (ROR) α (RORα) and γ (RORγ) in these tissues. We further analyzed the expression of VDR, CYP27B1, CYP24A1, and ROR in relation to melanin levels, clinical stage and prognosis. Our study indicated that the uveal melanoma melanin level inversely correlated with VDR expression. We further showed that vitamin D is metabolized in uveal melanoma. This is significant because until now there has been no paper published, that would describe presence of VDR, hydroxylases CYP27B1 and CYP24A1, and RORα and RORγ in the human uveal tract and uveal melanomas. The outcomes of our research can contribute to the development of new diagnostic and therapeutic methods in uveal tract disorders, especially in uveal melanoma. The presented associations between vitamin D signaling elements and uveal melanoma in comparison to uveal tract encourage future clinical research with larger patients’ population.

Low serum 25-hydroxyvitamin D is associated with increased bladder cancer risk: A systematic review and evidence of a potential mechanism

The development of some cancers is associated with vitamin D deficiency. We suggest that reduced conversion of 25-hydroxyvitamin D (25(OH)D) to 1,25-dihydroxyvitamin D (1,25(OH)₂D) and the resulting modification of tissue specific immune responses may be key. Non-muscle-invasive bladder cancer is highly immunoresponsive and stimulation of an inflammatory response by intravesical bacillus Calmette-Guerin (BCG) treatment prevents recurrence. To assess the relationship between serum 25(OH)D and bladder cancer risk we conducted a systematic review. To test our hypothesis, the synthesis of 1,25(OH)₂D by human bladder epithelial cell lines (T24/83 and RT4) was examined. Studies were identified from Medline, Web of Science, Embase and Cochrane library (limited to English language, humans and 1990-2018). After removal of duplicates, title and abstract review 6 full papers were appraised. Low vitamin D levels were associated with bladder cancer risk in 5/6 of the studies. Both cell lines express the vitamin D receptor, 25-hydroxyvitamin D 1α-hydroxylase (1α-OHase) and 24-hydroxylase (24-OHase) mRNA, which was induced by 1,25(OH)₂D. 24-OHase mRNA was also increased by 25(OH)D indicating 1α-OHase activity. Both cell types expressed TLR1,2,4 and the TLR partners MyD88 and CD14mRNA. Cathelicidin mRNA was undetectable in both cell lines but was induced by 1,25(OH)₂D and 25(OH)D in RT4 cells. The systematic review demonstrated that bladder cancer risk correlates with serum 25(OH)D levels. In addition, we have shown that transitional epithelial cells express functional vitamin D signaling and can synthesize sufficient 1,25(OH)₂D to stimulate a local immune response. We suggest that in order to maintain optimal immune surveillance within the bladder adequate levels of serum 25(OH)D are required for direct synthesis of 1,25(OH)₂D by bladder epithelial cells.

Megalin mediates 25-hydroxyvitamin D3 actions in human mesenchymal stem cells

Osteoblast differentiation of human mesenchymal stem cells (hMSCs) is stimulated by 1α,25-dihydroxycholecalciferol [1α,25(OH)₂D₃] and 25-hydroxycholecalciferol [25(OH)D₃]; the latter's effects require intracellular hydroxylation to 1α,25(OH)₂D₃. Thus, hMSCs are both a source of and target for 1α,25(OH)₂D₃. Megalin is a transmembrane receptor for serum d-binding protein (DBP) in kidney cells and is required for uptake of the 25(OH)D₃-DBP complex. We tested the hypothesis that megalin is required for D actions in hMSCs with cells from surgically discarded marrow for RT-PCR, for effects of 25(OH)D₃ and 1α,25(OH)₂D₃, for 1α,25(OH)₂D₃ biosynthesis, for osteoblastogenesis, and for small interfering RNA for megalin (si-Meg) and control (si-Ctr). In hMSCs with high constitutive megalin expression, both 1α,25(OH)₂D₃ and 25(OH)D₃ stimulated osteoblastogenesis (P < 0.05), but only 1α,25(OH)₂D₃ did so in hMSCs with lower megalin (lo-Meg, P < 0.001) or in si-Meg cells (P < 0.05). In addition, 1α,25(OH)₂D₃ biosynthesis was significantly lower in lo-Meg (46%, P = 0.034) and in si-Meg (23%, P < 0.001) than each control. Leptin significantly stimulated megalin expression 2.1-fold in lo-Meg cells (P < 0.01). These studies show that megalin is expressed in hMSCs and is required for the biosynthesis of 1α,25(OH)₂D₃ and for the 25(OH)D₃/DBP complex to stimulate vitamin D receptor targets and osteoblastogenesis.-Gao, Y., Zhou, S., Luu, S., Glowacki, J. Megalin mediates 25-hydroxyvitamin D₃ actions in human mesenchymal stem cells.

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.

Association of FokI, TaqI, BsmI and ApaI polymorphisms with diabetic retinopathy: a pooled analysis of case-control studies

Background

To assess synthetically the association between polymorphisms in the vitamin D receptor (VDR) gene (FokI, BsmI, ApaI, and TaqI) and diabetic retinopathy (DR).

Methods

Pubmed, Embase, ISI Web of Science, Google-scholar and CBMDisc, CNKI and Chongqing VIP databases were searched. A meta-analysis was performed.

Results

Six studies with 636 cases and 1,035 controls were included in this meta-analysis. The outcomes showed that the FokI polymorphism (F allele) of VDR gene had no statistical protective relationship with DR in overall studies. Interestingly, stratification analysis showed that the FokI polymorphism (Fallele) was significantly associated with decreased DR risk in the Chinese population, among included studies without publication bias, during a comparison analysis between normal subjects and DR patients, and among articles published after 2010. However, the TaqI, BsmI and ApaI polymorphisms of VDR gene had no significant association with the risk of DR.

Conclusion

This meta-analysis of case-control studies revealed that the VDR-FokI polymorphism (F allele) decreased the risk of DR in Chinese people, among included studies without publication bias, during a comparison analysis between normal subjects and DR patients, and among articles published after 2010. Further rigorous and prospective studies with large sample size are needed to confirm our findings.

Association between pterygium, sun exposure, and serum 25-hydroxyvitamin in a nationally representative sample of Korean adults

Purpose

Ultraviolet-B (UVB) light exposure is the major risk factor for developing a pterygium, and serum 25-hydroxyvitamin D (25(OH)D) level is an objective measure of UVB light exposure. In this study, we investigated the association between pterygium, sun exposure, and serum 25(OH)D.

Methods

This population-based, cross-sectional study comprised 12,258 adults (aged ≥19 years) participating in the fifth annual Korea National Health and Nutrition Examination Survey from 2010 to 2012. The enrolled subjects underwent interviews, clinical examinations, and laboratory investigations. The serum 25(OH)D levels were measured, and pterygium was examined by using a slit lamp. We used three adjusted logistic regression models and selected covariates as potential confounders.

Results

The overall prevalence of pterygium was 7.09, and 53.1% of these subjects were women. The prevalence of pterygium was higher in elderly subjects and those who lived at low latitudes. In multivariate analysis with adjustment for confounding factors, subjects with a serum 25(OH)D level > 30 ng/mL, 25–30 ng/mL, and 15–20 ng/mL had an odds ratio (OR) (95% confidence interval [CI]) of 1.565 (1.035–2.366), 1.545 (1.086–2.198), 1.8 (1.358–2.386), and 1.535 (1.216–1.938), respectively, compared to those with a serum 25(OH)D level < 15 ng/mL. Subjects with a daily sun exposure > 5 h had an OR (95% CI) of 1.761 (1.395–2.223) compared to subjects with a daily sun exposure < 2 h.

Conclusion

The present study provides epidemiological evidence of an association of daily sun exposure and serum 25(OH)D levels with pterygium in a representative Korean population.

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.

Corneal endothelial changes in patients with vitamin D deficiency

Purpose:

The purpose of this study is to evaluate the effect of vitamin D deficiency on corneal endothelial layer using specular microscopy.

Methods:

Fifty-eight eyes of 58 patients whose vitamin D level was below 15 ng/ml and who had no ocular pathology were included in the study (Group 1). Forty eyes of 40 age-and sex-matched subjects were enrolled as control group (Group 2). Corneal endothelial cell density (CD), coefficient of variation (CV), hexagonal cell ratio (HEX), and central corneal thickness (CCT) were measured using specular microscopy (Konan Medical Inc., Nishinomiya, Japan). The obtained data were compared between the groups.

Results:

There was no significant difference between the groups in terms of age and gender (P = 0.344, P = 0.399, respectively). The mean CD value was 2772.79 ± 202.21 cells/mm² in Group 1 and 2954.97 ± 116.89 cells/mm² in Group 2 (P = 0.001). The mean CV value was 30.31 ± 3.65 in Group 1 and 28.20 ± 2.71 in Group 2 (P = 0.003). The mean HEX value was 46.56 ± 6.32 in Group 1 and 51.07 ± 5.28 in Group 2 (P = 0.001). The mean CCT value was 555.87 ± 36.90 μ in group 1 and 549.0 ± 37.39 μ in Group 2 (P = 0.96).

Conclusion:

Vitamin D deficiency may affect the corneal endothelial layer. Patients with vitamin D deficiency should be evaluated for endothelial parameters in particular before an intraocular surgery. Further studies are needed to confirm our results.

Pseudoexfoliative glaucoma and molecular genetic characteristics of vitamin D metabolism

Purpose. To study the possible association of 25-hydroxyvitamin D level, and vitamin D receptor (VDR) gene polymorphisms (BsmI, ApaI, TaqI, FokI) with pseudoexfoliative glaucoma (PEG) clinical manifestations. Methods. We examined 160 subjects (72 males (45%), and 88 females (55%)) aged from 55 to 75 years, residents of St. Petersburg and Leningrad region. 122 patients with PEG were enrolled in the main study group, the control group comprised 38 subjects without PEG, primary open angle glaucoma (POUG) and pseudoexfoliation syndrome (PES). 25(OH)D serum levels were assessed by chemiluminescent immunoassay (CLIA) method. Detection of VDR gene allele polymorphisms (ApaI, BsmI, FokI, and TaqI) was carried out using polymerase chain reaction – restriction fragment length polymorphism (PCR-RFLP) technique. Results. Patients with PEG had lower 25(OH)D serum levels compared to patients in the control group (39.3 ± 1.2 and 52.7 ± 2.1 nMol/l, respectively, p < 0.01). The prevalence of vitamin D deficiency was found to be higher among PEG patients than among healthy subjects (86.4% and 59.5%, respectively, p < 0.01). The prevalence of b allele (p < 0.001) and bb genotype (p < 0.001) (BsmI polymorphism), as well as of f allele and ff genotype (p < 0.05) (FokI polymorphism) in PEG patients were higher compared to healthy subjects. We found that the Fallele carriers (FokI polymorphism) had greater corneal thickness than the ff genotype carriers (547.3 ± 4.1 μm and 502.1 ± 25.8 μm, respectively, p < 0.01). It was revealed, that bb genotype, Bb genotype (BsmI polymorphism), and ff genotype (FokI polymorphism) were associated with the increased risk of PEG (OR = 8.2, CI 95%: 3.4-19.9; OR = 3.9, CI 95%: 1.7-9.0; OR = 2.3, CI 95%: 1.2-4.5, respectively). Conclusions. Results of this study for the first time ever showed the association between BsmI and FokI VDR gene polymorphisms and pseudoexfoliative glaucoma.