Cytidine-5'-diphosphocholine (Citicoline): a pilot study in patients with non-arteritic ischaemic optic neuropathy

The effect of citicoline oral solution on quality of life in patients with glaucoma: the results of an international, multicenter, randomized, placebo-controlled cross-over trial

PURPOSE

This study aims to evaluate whether the use of citicoline oral solution could improve quality of life in patients with chronic open-angle glaucoma (OAG).

DESIGN

Randomized, double-masked, placebo-controlled, cross-over study was used. Patients were randomized to one of the two sequences: either citicoline 500 mg/day oral solution-placebo or placebo-citicoline 500 mg/day oral solution. Switch of treatments was done after 3 months; patients were then followed for other 6 months. Follow-up included 3-month, 6-month, and 9-month visits.

OUTCOMES

The primary outcome was the mean change of "intra-patient" composite score of the Visual Function Questionnaire-25 (VFQ-25)^. after citicoline oral solution vs placebo at 6-month visit as compared with baseline.

METHODS

The trial was multicenter, conducted at 5 European Eye Clinics. OAG patients with bilateral visual field damage, a mean deviation (MD) ranging from - 5 to - 13 dB in the better eye, and controlled IOP were included. VFQ-25 and SF-36 questionnaires were administered at baseline and at 3-, 6-, and 9-month visits. A mixed effect model, with a random effect on the intercept, accounted for correlations among serial measurements on each subject.

RESULTS

The primary pre-specified outcome of the analysis reached statistical significance (p = 0.0413), showing greater improvement after citicoline oral solution. There was an increase in the composite score in both arms compared to baseline, but it was significant only for the placebo-citicoline arm (p = 0.0096, p = 0.0007, and p = 0.0006 for the three time-points compared to baseline). The effect of citicoline was stronger in patients with vision-related quality of life more affected by glaucoma at baseline.

CONCLUSIONS

This is the first placebo-controlled clinical study evaluating the effect of a medical treatment aiming at improving vision-related quality of life in glaucomatous patients.

Citicoline and Vitamin B12 Eye Drops in Type 1 Diabetes: Results of a 36-Month Pilot Study Evaluating Macular Electrophysiological Changes

Introduction

Our aim was to evaluate the effects of 36 months of treatment with citicoline and vitamin B₁₂ eye drops on macular function in patients with type 1 diabetes (DM1) with mild signs of non-proliferative diabetic retinopathy (NPDR).

Methods

A prospective, randomized, interventional, monocentric, double-masked study was conducted. Twenty patients with DM1 were enrolled and randomly divided into two groups: the DC group (10 patients; mean age ± standard deviation 46.86 ± 8.78 years) in which one eye of each patient was treated with citicoline and vitamin B₁₂ eye drops (OMK2^®, Omikron Italia srl, Italy, one drop thrice daily) for a period of 36 months; the DP group (10 patients; mean age ± standard deviation 47.89 ± 7.74 years) in which one eye of each patient was treated with placebo (eye drops containing hypromellose 0.3%, one drop thrice daily) for a period of 36 months. A total of 18 eyes (10 from the DP and 8 from the DC group, respectively) completed the study. In both groups, multifocal electroretinogram (mfERG) recordings were assessed at baseline and after 36 months. In mfERG analysis, the N1–P1 response amplitude density (RAD) evaluated in the 0–2.5° (ring 1), in the 2.5–5° (ring 2), in the 5–10° (ring 3), and in the 0–10° (ring 1 + ring 2 + ring 3) were considered.

Results

With respect to baseline, after 36 months of follow-up, the mfERG RADs recorded in R1, R2, R3, and R1 + R2 + R3 were significantly increased (i.e., R1 + R2 + R3 RAD from 21.552 ± 2.522 nV/degree² at baseline to 26.912 ± 2.850 nV/degree² at 36 months) in DC eyes, whereas in DP eyes they were significantly reduced (i.e., R1 + R2 + R3 RAD from 21.033 ± 3.574 nV/degree² at baseline to 16.151 ± 3.571 nV/degree² at 36 months).

Conclusions

This study indicates that patients with NPDR treated with citicoline and vitamin B₁₂ eye drops for a 36-month period achieved an improvement of the macular bioelectrical responses detectable by mfERG recordings. By contrast, during the same period of follow-up, patients with NPDR treated with placebo showed a worsening of the macular function.

Citicoline Modulates Glaucomatous Neurodegeneration Through Intraocular Pressure-Independent Control

Glaucoma is a neurodegenerative disease that causes progressive, irreversible vision loss. Currently, intraocular pressure (IOP) is the only modifiable risk factor for glaucoma. However, glaucomatous degeneration may continue despite adequate IOP control. Therefore, there exists a need for treatment that protects the visual system, independent of IOP. This study sought, first, to longitudinally examine the neurobehavioral effects of different magnitudes and durations of IOP elevation using multi-parametric magnetic resonance imaging (MRI), optokinetics and histology; and, second, to evaluate the effects of oral citicoline treatment as a neurotherapeutic in experimental glaucoma. Eighty-two adult Long Evans rats were divided into six groups: acute (mild or severe) IOP elevation, chronic (citicoline-treated or untreated) IOP elevation, and sham (acute or chronic) controls. We found that increasing magnitudes and durations of IOP elevation differentially altered structural and functional brain connectivity and visuomotor behavior, as indicated by decreases in fractional anisotropy in diffusion tensor MRI, magnetization transfer ratios in magnetization transfer MRI, T1-weighted MRI enhancement of anterograde manganese transport, resting-state functional connectivity, visual acuity, and neurofilament and myelin staining along the visual pathway. Furthermore, 3 weeks of oral citicoline treatment in the setting of chronic IOP elevation significantly reduced visual brain integrity loss and visual acuity decline without altering IOP. Such effects sustained after treatment was discontinued for another 3 weeks. These results not only illuminate the close interplay between eye, brain, and behavior in glaucomatous neurodegeneration, but also support a role for citicoline in protecting neural tissues and visual function in glaucoma beyond IOP control.

Citicoline in Ophthalmological Neurodegenerative Disease: A Comprehensive Review

Cytidine 5'-diphosphocholine has been widely studied in systemic neurodegenerative diseases, like Alzheimer's disease, Parkinson's disease, and brain ischemia. The rationale for the use of citicoline in ophthalmological neurodegenerative diseases, including glaucoma, anterior ischemic optic neuropathy, and diabetic retinopathy, is founded on its multifactorial mechanism of action and the involvement in several metabolic pathways, including phospholipid homeostasis, mitochondrial dynamics, as well as cholinergic and dopaminergic transmission, all being involved in the complexity of the visual transmission. This narrative review is aimed at reporting both pre-clinical data regarding the involvement of citicoline in such metabolic pathways (including new insights about its role in the intracellular proteostasis through an interaction with the proteasome) and its effects on clinical psychophysical, electrophysiological, and morphological outcomes following its use in ophthalmological neurodegenerative diseases (including the results of the most recent prospective randomized clinical trials).

[The role of citicoline in glaucoma]

Hintergrund

In den letzten Jahren wurde in vielen experimentellen und klinischen Studien gezeigt, dass bei der Glaukomerkrankung die neuronale Degeneration nicht nur auf der Höhe von Netzhaut und Sehnerv, sondern im Verlauf der gesamten Sehbahn und des Gehirns erfolgt.

Fragestellung

Dargestellt werden die neuroprotektive Wirkung und ihre Mechanismen von Citicolin bei der Glaukomerkrankung.

Material und Methode

Vor dem Hintergrund der Neuroanatomie, des Neuroimaging und der Pathogenese der Glaukomerkrankung wird die Relevanz erläutert. Die Daten der experimentellen und klinischen Studien werden dargelegt und ein Fazit für die klinische Anwendung gezogen.

Ergebnisse

Citicolin wirkt neuroprotektiv über glaukomrelevante Mechanismen. Die neuroprotektive Wirkung von Citicolin bei Offenwinkelglaukomen ist funktionell und morphologisch nachweisbar. Sie ist unabhängig vom Glaukomschaden und Augeninnendruck und tritt i. d. R. erst nach einem Jahr auf. Die Effekte von oralem Citicolin treten bei einer Tagesdosis von 500–1000 mg auf. Die Einnahme von Citicolin kann dauerhaft oder in Zyklen erfolgen. In den Studien traten bei der Einnahme von Citicolin keine Nebenwirkungen auf. Citicolin kann kognitive Leistungen und somit Therapieadhärenz sowie die Lebensqualität bei Glaukompatienten verbessern

Schlussfolgerung

Diese relativ alte nootrope Substanz, welche jetzt als Nahrungsergänzungsmittel vertrieben wird, scheint eine wertvolle Ergänzung zur konventionellen Therapie der Glaukomerkrankung und eine rationale Option zur Neuroprotektion und Prophylaxe zu sein.

Visual Evoked Potentials in Joubert Syndrome: A Suggested Useful Method for Evaluating Future Approaches Targeted to Improve Visual Pathways' Function

Introduction

Joubert syndrome (JS) is a recessive disorder characterized by a congenital malformation of the mid-hindbrain and a large spectrum of clinical features including optic nerve morphologic abnormalities. The function of the visual pathways, including the optic nerve, can be objectively evaluated by visual evoked potential (VEP) recordings. Our work aims to employ VEP to evaluate the neural conduction along the visual pathways in JS patients with or without optic nerve morphologic abnormalities (ONMA).

Methods

In this observational and prospective study, 18 children with genetic diagnosis of JS (mean age 8.78 ± 5.87 years) and 17 healthy age-similar control subjects (control group, 9.05 ± 6.02 years) were enrolled.

Based on presence/absence of ONMA at fundus examination, JS patients were divided into two groups: the JS-A group (eight patients with ONMA) and JS-N group (ten patients without ONMA). Following the ISCEV standards, pattern VEPs were recorded in patients and controls in response to 60’ and 15’ checks to obtain a prevalent activation of large or small axons, respectively.

Results

Compared to controls, both the JS-A and JS-N groups showed significant abnormalities in 60’ and 15’ VEP implicit time and amplitude. Only in the JS-N group were values of 15’ VEP implicit significantly correlated with the corresponding values of visual acuity.

Conclusions

Our results suggest that a visual pathways dysfunction (of both large and small axons) detectable by VEP may occur in JS patients regardless of the presence of ONMA. Since clinical trials are envisaged in the near future to address JS-related ocular problems, our results might provide information about the potential usefulness of VEP recordings to assess the efficacy of treatments targeted to improve the visual pathways’ function.

Can Treatment With Citicoline Eyedrops Reduce Progression in Glaucoma? The Results of a Randomized Placebo-controlled Clinical Trial

Precis:

Citicoline eyedrops in patients with progressing glaucoma.

Purpose:

This study aimed to test whether the additional therapy with citicoline eyedrops to intraocular pressure (IOP)-lowering treatment could slow glaucoma progression in patients with worsening of damage and IOP 18 mm Hg or less.

Design:

This was a randomized, double-masked, placebo-controlled, multicenter 3-year study.

Outcomes:

The outcomes studied were difference in the visual field (mean deviation, MD, of 24-2; MD of 10-2) rates of progression and difference in retinal nerve fiber layer (RNFL) thickness change between the 2 study groups at 3 years.

Methods:

Patients with mild to moderate open-angle glaucoma (OAG) showing damage progression of at least −0.5 dB/y in the 2 years before enrollment despite IOP ≤18 mm Hg were randomized to receive citicoline eyedrops or placebo 3 times daily for 3 years. Patients were followed every 3 months and underwent a visual field examination with 24-2 and 10-2 strategies and RNFL assessment. Analysis of variance and linear models were used to test the differences between groups.

Results:

Eighty patients were randomized in the trial. The mean 3-year rates of progression were −1.03 (2.14) dB in the citicoline group and −1.92 (2.23) dB in the placebo group (P=0.07) for 24-2 MD and −0.41 (3.45) dB in the citicoline group and −2.22 (3.63) dB in the placebo group (P=0.02) for 10-2 MD. On average, patients receiving citicoline eyedrops lost 1.86 μm of RNFL in 3 years, versus 2.99 μm in the placebo group (P=0.02).

Conclusions:

Additional treatment with citicoline eyedrops to IOP-lowering treatment might reduce disease progression in patients with progressing glaucoma despite IOP ≤18 mm Hg.

Neuroprotective Effect of Citicoline Eye Drops on Corneal Sensitivity After LASIK

PURPOSE

To evaluate the accelerator role of a topically administered neuroprotective eye drop (citicoline) on the recovery of corneal sensitivity after laser in situ keratomileusis (LASIK).

METHODS

In this prospective, controlled study, 78 eyes of 78 patients (mean age: 26.8 ± 7.6 years) were enrolled in the study group and their eyes were treated with topical citicoline three times a day for 1 month postoperatively. Seventy-eight eyes of 78 patients (mean age: 26.1 ± 7.4 years) were randomly selected as the control group and their eyes were treated with lubricant hyaluronic acid (0.15%) eye drops three times a day for 1 month. Corneal sensitivity was assessed in both groups using a Cochet-Bonnet esthesiometer at baseline and 1, 2, 3, 4, 6, 8, and 12 weeks after the LASIK procedure.

RESULTS

Corneal sensitivity at 1, 2, 3, 4, and 6 weeks after LASIK was significantly better in the citicoline group than the control group (P < .05 for all). Differences between the groups at 8 and 12 weeks after LASIK were not significant (P > .05).

CONCLUSIONS

Topically administered citicoline eye drops had beneficial effects in the early recovery of corneal sensitivity during the first 6 weeks after LASIK, suggesting that citicoline may play a significant role in accelerating corneal reinnervation. [J Refract Surg. 2019;35(12):764-770.].

Effect of neuroprotective citicoline eye drops on macular microcirculation

BACKGROUND AND OBJECTIVE

To use optical coherence tomography (OCTA) examination of the retinal microvascular structures to evaluate the effect of neuroprotective eye drops (citicoline, OMK1^®) administered for laser in situ keratomileusis (LASIK) surgery.

PATIENTS AND METHODS

This prospective study included 45 patients treated with citicoline after LASIK and 48 patients not treated with citicoline after LASIK as a control group. In both groups, the foveal avascular zone (FAZ), retinal superficial vascular density (SVD), and deep vascular density (DVD) in the foveal and parafoveal areas were measured preoperatively and at 1 and 3 months postoperatively using OCTA.

RESULTS

No significant difference was detected between the groups in terms of preoperative SVD or DVD in the foveal and parafoveal zones and all quadrants (superior, inferior, temporal, and nasal) (P > 0.05). Similarly, no significant difference was detected between the citicoline group and control group in terms of SVD or DVD in the foveal and parafoveal zones at 1 and 3 months after LASIK (P > 0.05).

CONCLUSIONS

Despite their neuroprotective effect, topical citicoline drops had no significant effect on the superficial and deep microvascular structures of the retina or choriocapillaris.

Cytidine 5'-Diphosphocholine (Citicoline): Evidence for a Neuroprotective Role in Glaucoma

Glaucoma, a heterogeneous set of progressively degenerative optic neuropathies characterized by a loss of retinal ganglion cells (RGCs) and typical visual field deficits that can progress to blindness, is a neurodegenerative disease involving both ocular and visual brain structures. Although elevated intraocular pressure (IOP) remains the most important modifiable risk factor of primary open-angle glaucoma (POAG) and is the main therapeutic target in treating glaucoma, other factors that influence the disease course are involved and reaching the optimal IOP target does not stop the progression of glaucoma, as the visual field continues to narrow. In addition to a managed IOP, neuroprotection may be beneficial by slowing the progression of glaucoma and improving the visual defects. Citicoline (cytidine 5'-diphosphocholine) is a naturally occurring endogenous compound that has been investigated as a novel therapeutic agent for the management of glaucoma. Citicoline has demonstrated activity in a range of central neurodegenerative diseases, and experimental evidence suggests a it performs a neuromodulator and neuroprotective role on neuronal cells, including RGCs, associated with improvement in visual function, extension of the visual field and central benefits for the patient. This review aims to critically summarize the current evidence for the neuroprotective properties of citicoline in glaucoma.

Human vitreous concentrations of citicoline following topical application of citicoline 2% ophthalmic solution

PURPOSE

To evaluate the presence and concentration of citicoline and its metabolites (choline, cytidine and uridine) in the vitreous body in human eyes after topical application of an ophthalmic solution of citicoline 2%, in vivo.

METHODS

Twenty-one subjects affected by epiretinal membrane with surgical indication for pars-plana vitrectomy underwent treatment with 1 drop 3 times/day of a solution of citicoline 2%, 0.2% high molecular weight hyaluronic acid and 0.01% benzalkonium chloride (OMK1, Omikron Italia s.r.l., Rome, Italy) 14 days before surgery and 2 hours prior to surgery. Five additional patients served as controls and received an OMK1 vehicle solution without citicoline. The vitreous samples were taken at the beginning of the pars-plana vitrectomy and analyzed for qualitative/quantitative determination of vitreous concentration of citicoline and its metabolites by means of high performance liquid chromatography.

RESULTS

The overall mean concentration of citicoline in patients treated with citicoline 2% solution was 406.72 ± 52.99 μg/mL, while the mean concentration of choline, cytidine and uridine was 180.88 ± 41.49 μg/mL, 44.45 ± 10.19 μg/mL and 330.41 ± 75.8 μg/mL, respectively. The concentration of citicoline in phakic eyes (n = 13, 366.61 ± 129.61 μg/mL) was lower compared to that found in pseudophakic eyes (n = 8, 435.89 ± 131.42 μg/mL) and the difference was not statistically significant. The concentration of citicoline in the control eyes was 45.66 ± 26.36 μg/mL, while the concentration of choline, cytidine and uridine were 17.21 ± 9.93 μg/mL, 6.24 ± 3.6 μg/mL and 172.80 ± 99.76 μg/mL, respectively.

CONCLUSION

Citicoline can reach the human vitreous in high concentration when administered in ophthalmic solution. This evidence contributes to the build-up of the pyramid of the evidences required for determining the role of citicoline administered in ophthalmic formulation in retinal and optic nerve neurodegenerative diseases.

Cholinergic nervous system and glaucoma: From basic science to clinical applications

The cholinergic system has a crucial role to play in visual function. Although cholinergic drugs have been a focus of attention as glaucoma medications for reducing eye pressure, little is known about the potential modality for neuronal survival and/or enhancement in visual impairments. Citicoline, a naturally occurring compound and FDA approved dietary supplement, is a nootropic agent that is recently demonstrated to be effective in ameliorating ischemic stroke, traumatic brain injury, Parkinson's disease, Alzheimer's disease, cerebrovascular diseases, memory disorders and attention-deficit/hyperactivity disorder in both humans and animal models. The mechanisms of its action appear to be multifarious including (i) preservation of cardiolipin, sphingomyelin, and arachidonic acid contents of phosphatidylcholine and phosphatidylethanolamine, (ii) restoration of phosphatidylcholine, (iii) stimulation of glutathione synthesis, (iv) lowering glutamate concentrations and preventing glutamate excitotoxicity, (v) rescuing mitochondrial function thereby preventing oxidative damage and onset of neuronal apoptosis, (vi) synthesis of myelin leading to improvement in neuronal membrane integrity, (vii) improving acetylcholine synthesis and thereby reducing the effects of mental stress and (viii) preventing endothelial dysfunction. Such effects have vouched for citicoline as a neuroprotective, neurorestorative and neuroregenerative agent. Retinal ganglion cells are neurons with long myelinated axons which provide a strong rationale for citicoline use in visual pathway disorders. Since glaucoma is a form of neurodegeneration involving retinal ganglion cells, citicoline may help ameliorate glaucomatous damages in multiple facets. Additionally, trans-synaptic degeneration has been identified in humans and experimental models of glaucoma suggesting the cholinergic system as a new brain target for glaucoma management and therapy.

Neuroenhancement and neuroprotection by oral solution citicoline in non-arteritic ischemic optic neuropathy as a model of neurodegeneration: A randomized pilot study

Purpose

To evaluate whether treatment with Citicoline in oral solution (OS-Citicoline) would increase visual function, retinal ganglion cells (RGCs) function, and neural conduction along visual pathways (neuroenhancement), and/or induce preservation of RGCs fibers’ loss (neuroprotection) in non-arteritic ischemic optic neuropathy (NAION), a human model of neurodegeneration.

Methods

Thirty-six patients with NAION and 20 age-matched controls were enrolled. Nineteen NAION patients received 500 mg/day of OS-Citicoline for a 6-month period followed by 3-month of wash-out (NC Group); 17 NAION patients were not treated (NN Group) from baseline to 9 months. In all subjects at baseline, and in NC and NN eyes at 6 and 9 months of follow-up, we assessed Visual Acuity (VA), Pattern Electroretinogram (PERG), Visual Evoked Potentials (VEP), retinal nerve fiber layer thickness (RNFL-T), and Humphrey 24–2 visual field mean deviation (HFA MD). Mean differences were statistically evaluated with ANOVA between Groups, and linear correlations were analysed with Pearson’s test.

Results

At 6 months, significant differences between groups for all parameters were observed (ANOVA, p<0.01). In NC eyes, VA increased, PERG responses increased, VEP recordings improved and were significantly correlated with increases in HFA MD (p<0.01), and RNFL-T was unmodified or improved. In contrast, in NN eyes, VA, PERG, VEP responses, RNFL-T, and HFA MD were further worsened. Significant differences were still present at 9-month follow-up in the NN Group and after 3 months of OS-Citicoline wash-out in NC eyes.

Conclusions

OS-Citicoline treatment induced neuroenhancement (improvement in RGCs function and neural conduction along visual pathways related to improvement of visual field defects) and neuroprotection (unmodified or improved RNFL morphological condition) in a human model of NAION involving fast RGCs degeneration.

Trial registration

ClinicalTrials.gov NCT03758118.

The Effect of Citicoline Supplementation on Motor Speed and Attention in Adolescent Males

OBJECTIVE

This study assessed the effects of citicoline, a nutraceutical, on attention, psychomotor function, and impulsivity in healthy adolescent males.

METHOD

Seventy-five healthy adolescent males were randomly assigned to either the citicoline group ( n = 51 with 250 or 500 mg citicoline) or placebo ( n = 24). Participants completed the Ruff 2&7 Selective Attention Test, Finger Tap Test, and the Computerized Performance Test, Second Edition (CPT-II) at baseline and after 28 days of supplementation.

RESULTS

Individuals receiving citicoline exhibited improved attention ( p = 0.02) and increased psychomotor speed ( p = 0.03) compared with those receiving placebo. Higher weight-adjusted dose significantly predicted increased accuracy on an attention task ( p = 0.01), improved signal detectability on a computerized attention task ( p = 0.03), and decreased impulsivity ( p = 0.01).

DISCUSSION

Adolescent males receiving 28 days of Cognizin® citicoline showed improved attention and psychomotor speed and reduced impulsivity compared to adolescent males who received placebo.

Citicoline and Retinal Ganglion Cells: Effects on Morphology and Function

BACKGROUND

Retinal ganglion cells (RGCs) are the nervous retinal elements which connect the visual receptors to the brain forming the nervous visual system. Functional and/or morphological involvement of RGCs occurs in several ocular and neurological disorders and therefore these cells are targeted in neuroprotective strategies. Cytidine 5-diphosphocholine or Citicoline is an endogenous compound that acts in the biosynthesis of phospholipids of cell membranes and increases neurotransmitters' levels in the Central Nervous System. Experimental studies suggested the neuromodulator effect and the protective role of Citicoline on RGCs. This review aims to present evidence of the effects of Citicoline in experimental models of RGCs degeneration and in human neurodegenerative disorders involving RGCs.

METHODS

All published papers containing experimental or clinical studies about the effects of Citicoline on RGCs morphology and function were reviewed.

RESULTS

In rodent retinal cultures and animal models, Citicoline induces antiapoptotic effects, increases the dopamine retinal level, and counteracts retinal nerve fibers layer thinning. Human studies in neurodegenerative visual pathologies such as glaucoma or non-arteritic ischemic neuropathy showed a reduction of the RGCs impairment after Citicoline administration. By reducing the RGCs' dysfunction, a better neural conduction along the post-retinal visual pathways with an improvement of the visual field defects was observed.

CONCLUSION

Citicoline, with a solid history of experimental and clinical studies, could be considered a very promising molecule for neuroprotective strategies in those pathologies (i.e. Glaucoma) in which morpho-functional changes of RGCc occurs.

Citicoline - a neuroprotector with proven effects on glaucomatous disease

Citicoline is the generic name of cytidine-5’-diphosphocholine (CDP-choline), an endogenous compound that is able to increase the levels of neurotransmitters in the central nervous system by interacting with the synthesis of cellular membranes phospholipids, especially phosphatidylcholine. Exogenous Citicoline, administered by ingestion or injection, is hydrolyzed and dephosphorylated in order to form cytidine and choline, which resynthesize CDP-choline inside brain cells. It has proven neuroprotective effects in Alzheimer disease, stroke, and Parkinson’s disease, as well as in glaucoma and amblyopia. Citicoline acts as a neuroprotector for those patients with progressive glaucomatous disease in spite of well-controlled intraocular pressure. The purpose of this review was to outline the main features of Citicoline and the evidences of its effect in glaucoma.

Neuroprotection in Glaucoma: Old and New Promising Treatments

Glaucoma is a major global cause of blindness, but the molecular mechanisms responsible for the neurodegenerative damage are not clear. Undoubtedly, the high intraocular pressure (IOP) and the secondary ischemic and mechanical damage of the optic nerve have a crucial role in retinal ganglion cell (RGC) death. Several studies specifically analyzed the events that lead to nerve fiber layer thinning, showing the importance of both intra- and extracellular factors. In parallel, many neuroprotective substances have been tested for their efficacy and safety in hindering the negative effects that lead to RGC death. New formulations of these compounds, also suitable for chronic oral administration, are likely to be used in clinical practice in the future along with conventional therapies, in order to control the progression of the visual impairment due to primary open-angle glaucoma (POAG). This review illustrates some of these old and new promising agents for the adjuvant treatment of POAG, with particular emphasis on forskolin and melatonin.

Molecular structure and differential function of choline kinases CHKα and CHKβ in musculoskeletal system and cancer

Choline, a hydrophilic cation, has versatile physiological roles throughout the body, including cholinergic neurotransmission, memory consolidation and membrane biosynthesis and metabolism. Choline kinases possess enzyme activity that catalyses the conversion of choline to phosphocholine, which is further converted to cytidine diphosphate-coline (CDP-choline) in the biosynthesis of phosphatidylcholine (PC). PC is a major constituent of the phospholipid bilayer which constitutes the eukaryotic cell membrane, and regulates cell signal transduction. Choline Kinase consists of three isoforms, CHKα1, CHKα2 and CHKβ, encoded by two separate genes (CHKA(Human)/Chka(Mouse) and CHKB(Human)/Chkb(Mouse)). Both isoforms have similar structures and enzyme activity, but display some distinct molecular structural domains and differential tissue expression patterns. Whilst Choline Kinase was discovered in early 1950, its pivotal role in the development of muscular dystrophy, bone deformities, and cancer has only recently been identified. CHKα has been proposed as a cancer biomarker and its inhibition as an anti-cancer therapy. In contrast, restoration of CHKβ deficiency through CDP-choline supplements like citicoline may be beneficial for the treatment of muscular dystrophy, bone metabolic diseases, and cognitive conditions. The molecular structure and expression pattern of Choline Kinase, the differential roles of Choline Kinase isoforms and their potential as novel therapeutic targets for muscular dystrophy, bone deformities, cognitive conditions and cancer are discussed.

Cytidine 5'-Diphosphocholine (Citicoline) in Glaucoma: Rationale of Its Use, Current Evidence and Future Perspectives

Cytidine 5'-diphosphocholine or citicoline is an endogenous compound that acts in the biosynthetic pathway of phospholipids of cell membranes, particularly phosphatidylcholine, and it is able to increase neurotrasmitters levels in the central nervous system. Citicoline has shown positive effects in Parkinson's disease and Alzheimer's disease, as well as in amblyopia. Glaucoma is a neurodegenerative disease currently considered a disease involving ocular and visual brain structures. Neuroprotection has been proposed as a valid therapeutic option for those patients progressing despite a well-controlled intraocular pressure, the main risk factor for the progression of the disease. The aim of this review is to critically summarize the current evidence about the effect of citicoline in glaucoma.

Levodopa as a possible treatment of visual loss in nonarteritic anterior ischemic optic neuropathy

PURPOSE

To determine the clinical effectiveness and potential neuroprotection of levodopa in improving visual acuity, visual field, and retinal nerve fiber layer (RNFL) thickness in eyes affected by NAION.

METHOD

Retrospective cohort study involving 59 eyes of 59 participants with NAION who were evaluated within 15 days of NAION onset. Participants received 25 mg carbidopa/100 mg levodopa three times daily with meals for 12 weeks (levodopa group) or were untreated (control group). Best-corrected visual acuity converted to logMAR, mean deviation (MD) threshold sensitivity on automated perimetry, and mean RNFL thickness on optical coherence tomography (OCT) were assessed. The primary outcome was the categorization of eyes into improved visual acuity (by 0.3 logMAR difference), worsened visual acuity (by 0.3 logMAR difference), or no change in visual acuity. The proportions in each category were compared between the levodopa and control groups.

RESULTS

Among participants with 20/60 or worse initial visual acuity, levodopa-treated participants had significant improvement (P < 0.0001) in the mean change from initial to final logMAR visual acuity of -0.74 ± 0.56 (95 % CI, -0.98 to -0.50), while the mean change for the control group at -0.37 ± 1.09 (95 % confidence interval estimate, -1.00 to +0.26) was not significant (P = 0.23). A significant difference between groups was observed (P = 0.0086) such that 19/23 (83 %) in the levodopa group improved and none got worse, as compared with 6/14 (43 %) in the control group improving while four (29 %) worsened. The change in visual field MD and RNFL thickness on OCT showed no significant difference at P = 0.23 and P = 0.75 respectively. No levodopa-treated participant had any adverse event from the levodopa.

CONCLUSIONS

Treatment within 15 days of onset of NAION with levodopa improved central visual acuity by an average of 6 lines on Snellen acuity chart. Levodopa may promote neuroprotection of the maculopapular retinal ganglion cell fibers in NAION.

Treatment with citicoline eye drops enhances retinal function and neural conduction along the visual pathways in open angle glaucoma

PURPOSE

To evaluate the retinal function and the neural conduction along the visual pathways after treatment with citicoline eye drops in patients with open angle glaucoma (OAG).

METHODS

Fifty-six OAG patients (mean age 52.4 ± 4.72 years, IOP <18 mmHg with beta-blocker monotherapy only) were enrolled. Of these, 47 eyes completed the study: 24 OAG eyes were treated with topical citicoline (OMK1®, Omikron Italia, 3 drops/day) (GC eyes) over a 4-month period (month 4) followed by a 2-month period of citicoline wash-out (month 6), and another 23 OAG eyes were only treated with beta-blocker monotherapy (GP eyes). In GC and GP eyes, pattern electroretinogram (PERG) and visual evoked potentials (VEP) were assessed at baseline and at months 4 and 6 in both groups.

RESULTS

At baseline, similar (ANOVA, p > 0.01) PERG and VEP values in GC and GP eyes were observed. After treatment with topical citicoline, a significant (p < 0.01) increase of PERG P50-N95 and VEP N75-P100 amplitudes, and a significant (p < 0.01) shortening of VEP P100 implicit times were found. In GC eyes, the shortening of VEP P100 implicit times was correlated significantly (p < 0.01) with the increase of PERG P50-N95 amplitudes. After a 2-month period of topical Citicoline wash-out, PERG and VEP values were similar (p > 0.01) to baseline ones. GP eyes showed not significant changes of PERG and VEP values during the entire follow-up.

CONCLUSIONS

Topical treatment with citicoline in OAG eyes induces an enhancement of the retinal bioelectrical responses (increase of PERG amplitude) with a consequent improvement of the bioelectrical activity of the visual cortex (shortening and increase of VEP implicit time and amplitude, respectively).

Citicoline oral solution in glaucoma: is there a role in slowing disease progression?

PURPOSE

To assess the effect of citicoline on visual field rates of progression in patients with progressing glaucoma.

PATIENTS AND METHODS

Forty-one patients with a diagnosis of progressing glaucoma received citicoline in oral solution for 2 years. Included were patients with a disease progression of at least -1 dB/year (at MD, mean deviation) for at least 3 years before entering the study despite controlled intraocular pressure (IOP). Patients were followed with 4 visual field examinations per year for 2 years.

RESULTS

At baseline, the mean rate of progression was -1.1 (±0.7) dB/year despite the fact that the IOP had been below 18 mm Hg for at least 3 years. At study inclusion, the mean IOP was 15.5 (±2.6) mm Hg and the mean MD was -9.2 (±6.7) dB in the worst eye. Starting from the first cycle of treatment with citicoline, the mean rate of progression significantly changed to -0.15 (±0.3) dB/year at the end of the study (p = 0.01).

CONCLUSIONS

This study seems to indicate that supplementation with citicoline might significantly slow down glaucomatous rates of progression.