Targeted preventive measures and advanced approaches in personalised treatment of glaucoma neuropathy

New insight of metabolomics in ocular diseases in the context of 3P medicine

Metabolomics refers to the high-through untargeted or targeted screening of metabolites in biofluids, cells, and tissues. Metabolome reflects the functional states of cells and organs of an individual, influenced by genes, RNA, proteins, and environment. Metabolomic analyses help to understand the interaction between metabolism and phenotype and reveal biomarkers for diseases. Advanced ocular diseases can lead to vision loss and blindness, reducing patients' quality of life and aggravating socio-economic burden. Contextually, the transition from reactive medicine to the predictive, preventive, and personalized (PPPM / 3P) medicine is needed. Clinicians and researchers dedicate a lot of efforts to explore effective ways for disease prevention, biomarkers for disease prediction, and personalized treatments, by taking advantages of metabolomics. In this way, metabolomics has great clinical utility in the primary and secondary care. In this review, we summarized much progress achieved by applying metabolomics to ocular diseases and pointed out potential biomarkers and metabolic pathways involved to promote 3P medicine approach in healthcare.

Comparison of Different Nutritional and Lifestyle Factors between Glaucoma Patients and an Age-Matched Normal Population

PURPOSE

To compare nutritional and lifestyle factors between glaucoma patients and an age-matched control group.

METHODS

One hundred and ninety (190) glaucoma patients were enrolled in this study. The control group comprised 97 age-matched participants. Data on physical activity, nicotine smoking, and several nutritional habits like coffee and alcohol consumption as well as high-salt and high-protein intake were collected using a standardised questionnaire.

RESULTS

Age and gender were not statistically significantly different between the groups. There was a tendency for higher physical activity in the glaucoma group in comparison to the control group (47.3 vs. 35.4%; p = 0.056). Statistically significantly more glaucoma patients were nonsmokers (n = 169; 89.4%) compared to the control group (n = 64; 66.7%; p = 0.001). Glaucoma patients were also more often teetotal compared to the control group (21.6% compared to 14.4%; p < 0.001). Similarly, more glaucoma patients drank larger amounts of coffee in comparison to the control group (p = 0.001). One hundred and seventy-six (96.7%) glaucoma patients and 88 (90.7%) control subjects had high-protein intake (p = 0.035). High-salt intake was significantly lower in the glaucoma group (69.3 vs. 73.2%; p = 0.018). Of the 190 glaucoma patients, 81 had early visual field impairments (MD > - 6 dB) and 109 patients had moderate (MD between - 6 dB and - 12 dB) to severe (MD < - 12 dB) visual field defects. The severity of visual field defects, whether early, moderate, or severe, had no statistically significant impact on lifestyle parameters.

CONCLUSION

Contrary to our original hypothesis that glaucoma patients would tend to follow an unhealthier lifestyle than the control group, the opposite was seen. Presumably, the cause of this healthier lifestyle is the desire to contribute positively through the course of the disease.

What is glaucomatous optic neuropathy?

Glaucomatous optic neuropathy (GON) is the pathohistological feature of glaucoma in the optic nerve. The pathogenesis of GON has been hypothesized, to either originate from compromised mechanical conditions at the lamina cribrosa or as associated with pathological vascular involvement. From a historical perspective, glaucoma is the degeneration of retinal ganglion cells (RGC) due to the elevation of intraocular pressure (IOP). The consensus of glaucoma treatment is generally accepted as sufficient IOP reduction. Is there an additional option to treat GON from the perspective of the vascular theory? In this section, two distinguished leaders in glaucoma research advance their views and discuss the current opinions surrounding the two theories regarding the causes of GON in primary open angle glaucoma (POAG) and normal tension glaucoma (NTG).

Analysis of interleukin-20 receptor complexes in trabecular meshwork cells and effects of cytokine signaling in anterior segment perfusion culture

Purpose

Inflammatory responses may be involved in the glaucomatous process. Our previous studies mapped a T104M mutation in interleukin-20 receptor beta (IL-20RB) in a family with primary open angle glaucoma (POAG). IL-20RB can heterodimerize with IL-20RA to propagate signals from IL-20 family cytokines, IL-19, IL-20, and IL-24 (the type I receptor complex), or it can heterodimerize with IL-22RA to propagate signals from IL-20 and IL-24 (type II receptor complex). In this study, we investigated IL-20 heterodimeric receptor complexes in the trabecular meshwork (TM) compared to dermal fibroblast cell cultures, and examined the phosphorylation of signal transducer and activator of transcription (STAT)-1, -3, and -5 following exposure to IL-20 family cytokines. Additionally, we determined the effects of IL-20 family cytokines on outflow rates in anterior segment perfusion culture, an in vitro model of intraocular pressure (IOP) regulation.

Methods

Primary human TM (HTM) cells were grown from dissected TM tissue, and IL-20 receptor expression was investigated with PCR. A Duolink assay was performed to investigate in situ IL-20 receptor protein interactions in HTM or dermal fibroblasts, and Imaris software was used to quantitate the association of the heterodimeric complexes. Phosphorylation of STAT-1, -3, and -5 were evaluated in HTM or dermal fibroblasts using Western immunoblotting after exposure to IL-10, IL-19, IL-20, IL-22, or IL-24. Anterior segment perfusion culture was performed in human cadaver and porcine eyes treated with IL-20, IL-19, or IL-24.

Results

All of the IL-20 receptors, IL-20RA, IL-20RB, and IL-22RA1 were expressed in HTM cells. Two isoforms of IL-20RA were expressed: The V1 variant, which is the longest, is the predominant isoform, while the V3 isoform, which lacks exon 3, was also expressed. The Duolink assay demonstrated that the type I (IL-20RA-IL-20RB) and type II (IL-22RA1-IL-20RB) receptors were expressed in HTM cells and dermal fibroblasts. However, in the HTM cells, the type I receptor was present at significantly higher levels, while the type II receptor was preferentially used in the dermal fibroblasts. The HTM cells and the dermal fibroblasts predominantly phosphorylate the Ser727 site in STAT-3. The dermal fibroblasts had higher induction of phosphorylated STAT-1 compared to the HTM cells, while neither cell type had phosphorylated STAT-5 in the cell lysates. The outflow rates in the human anterior segment cultures were increased 2.3-fold by IL-20. However, IL-19 and IL-24 showed differential responses. For IL-19 and IL-24, 50% of the eyes responded with a 1.7- or 1.5-fold increase, respectively, while the other half did not respond. Similarly, perfused porcine anterior segments showed "responders" and "non-responders": IL-20 responders (2.3-fold increase in outflow, n=12) and non-responders (n=11); IL-19 responders (2.1-fold increase, n=7) and non-responders (n=5); and IL-24 responders (1.8-fold increase, n=12) and non-responders (n=5).

Conclusions

Type I and type II IL-20 receptor complexes are expressed in human TM cells with predominant expression of the type I receptor (IL-20RA and IL-20RB), which propagates signals from all three IL-20 family cytokines. However, there was a variable response in the outflow rates following perfusion of cytokines in two different species. This may explain why some people are more susceptible to developing elevated IOP in response to inflammation.

Nutritional recommendations for individuals with Flammer syndrome

The Flammer syndrome (FS) describes the phenotype of people with a predisposition for an altered reaction of the blood vessels to stimuli like coldness or emotional stress. The question whether such people should be treated is often discussed. On the one hand, most of these subjects are healthy; on the other hand, FS seems to predispose to certain eye diseases such as normal tension glaucoma or retinitis pigmentosa or systemic diseases such as multiple sclerosis or tinnitus. A compromise between doing nothing and a drug treatment is the adaption of nutrition. But what do we mean by healthy food consumption for subjects with FS? The adaption of nutrition depends on the health condition. Whereas patients with e.g. a metabolic syndrome should reduce their calorie intake, this can be counterproductive for subjects with FS, as most subjects with FS have already a low body mass index (BMI) and the lower the BMI the stronger the FS symptoms. Accordingly, while fasting is healthy e.g. for subjects with metabolic syndrome, fasting can even dangerously aggravate the vascular dysregulation, as it has been nicely demonstrated by the loss of retinal vascular regulation during fasting. To give another example, while reducing salt intake is recommended for subjects with systemic hypertensions, such a salt restriction can aggravate systemic hypotension and thereby indirectly also the vascular regulation in subjects with FS. This clearly demonstrates that such a preventive adaption of nutrition needs to be personalized.

The discovery of the Flammer syndrome: a historical and personal perspective

This review describes the clinical and basic research that led to the description of Flammer syndrome. It is narrated from a personal perspective. This research was initiated by the observation of an increased long-term fluctuation of visual fields in a subgroup of glaucoma patients. As these patients had strikingly cold hands, peripheral blood flow was tested with a capillary microscopy, and vasospastic syndrome (VS) was diagnosed. Further studies on these patients revealed frequently weakened autoregulation of ocular blood flow and increased flow resistivity in retroocular vessels. Their retinal vessels were more rigid and irregular and responded less to flickering light. Holistic investigation demonstrated low blood pressure, silent myocardial ischaemia, altered beat-to-beat variation, altered gene expression in the lymphocytes, slightly increased plasma endothelin level and increased systemic oxidative stress. This combination of signs and symptoms was better described by the term primary vascular dysregulation (PVD) than by VS. Subsequent studies showed additional symptoms frequently related to PVD, such as low body mass index, cold extremities combined with slightly increased core temperature, prolonged sleep onset time, reduced feelings of thirst, increased sensitivity to smell and also for certain drugs and increased retinal venous pressure. To better characterise this entire syndrome, the term Flammer syndrome (FS) was introduced. Most subjects with FS were healthy. Nevertheless, FS seemed to increase the risk for certain eye diseases, particularly in younger patients. This included normal-tension glaucoma, anterior ischaemic optic neuropathy, retinal vein occlusions, Susac syndrome and central serous chorioretinopathy. Hereditary diseases, such as Leber’s optic neuropathy or retinitis pigmentosa, were also associated with FS, and FS symptoms and sings occurred more frequent in patients with multiple sclerosis or with acute hearing loss. Further research should lead to a more concise definition of FS, a precise diagnosis and tools for recognizing people at risk for associated diseases. This may ultimately lead to more efficient and more personalised treatment.

Anti-Inflammatory and Antioxidative Stress Effects of Oryzanol in Glaucomatous Rabbits

Purpose. γ-Oryzanol works by anti-inflammatory and radical scavenging activity as a neuroprotective, anticancer, antiulcer, and immunosuppressive agent. The present study was conducted to investigate effect of oryzanol in acute and chronic experimental glaucoma in rabbits. Methods. Effect of oryzanol was evaluated in 5% dextrose induced acute model of ocular hypertension in rabbit eye. Chronic model of glaucoma was induced with subconjunctival injection of 5% of 0.3 ml phenol. Treatment with oryzanol was given for next two weeks after induction of glaucoma. From anterior chamber of rabbit eye aqueous humor was collected to assess various oxidative stress parameters like malondialdehyde, superoxide dismutase, glutathione peroxidase, catalase, nitric oxide, and inflammatory parameters like TNF-α and IL-6. Structural damage in eye was examined by histopathological studies. Results. In acute model of ocular hypertension oryzanol did not alter raised intraocular pressure. In chronic model of glaucoma oryzanol exhibited significant reduction in oxidative stress followed by reduction in intraocular pressure. Oryzanol treatment reduced level of TNF-α and IL-6. Histopathological studies revealed decreased structural damage of trabecular meshwork, lamina cribrosa, and retina with oryzanol treatment. Conclusions. Oryzanol showed protective effect against glaucoma by its antioxidative stress and anti-inflammatory property. Treatment with oryzanol can reduce optic nerve damage.

The Role of the IL-20 Subfamily in Glaucoma

Glaucoma is a common disease that leads to loss of peripheral vision and, if left untreated, ultimately to blindness. While the exact cause(s) of glaucoma is still unknown, two leading risk factors are age and elevated intraocular pressure. Several studies suggest a possible link between glaucoma and inflammation in humans and animal models. In particular, our lab recently identified a T104M mutation in IL-20 receptor-B (IL-20RB) in primary open angle glaucoma patients from a large pedigree. Several of the interleukin- (IL-) 20 family of cytokines and receptors are expressed in ocular tissues including the trabecular meshwork, optic nerve head, and retinal ganglion cells. The DBA/2J mouse develops high intraocular pressures with age and has characteristic optic nerve defects that make it a useful glaucoma model. IL-24 expression is significantly upregulated in the retina of these mice, while IL-20RA expression in the optic nerve is downregulated following pressure-induced damage. The identification of a mutation in the IL-20RB gene in a glaucoma pedigree and changes in expression levels of IL-20 family members in the DBA/2J mouse suggest that disruption of normal IL-20 signaling in the eye may contribute to degenerative processes associated with glaucoma.

Neuroprotection in the treatment of glaucoma--A focus on connexin43 gap junction channel blockers

Glaucoma is a form of optic neuropathy and a common cause of blindness, affecting over 60 million people worldwide with an expected rise to 80 million by 2020. Successful treatment is challenging due to the various causes of glaucoma, undetectable symptoms at an early stage and inefficient delivery of drugs to the back of the eye. Conventional glaucoma treatments focus on the reduction of elevated intraocular pressure (IOP) using topical eye drops. However, their efficacy is limited to patients who suffer from high IOP glaucoma and do not address the underlying susceptibility of retinal ganglion cells (RGC) to degeneration. Glaucoma is known as a neurodegenerative disease which starts with RGC death and eventually results in damage of the optic nerve. Neuroprotective strategies therefore offer a novel treatment option for glaucoma by not only preventing neuronal loss but also disease progression. This review firstly gives an overview of the pathophysiology of glaucoma as well as current treatment options including conventional and novel delivery strategies. It then summarizes the rational for neuroprotection as a novel therapy for glaucomatous neuropathies and reviews current potential neuroprotective strategies to preserve RGC, with a focus on connexin43 (Cx43) gap junction channel blockers.

Cod liver oil: a potential protective supplement for human glaucoma

Glaucoma is one of the leading causes of visual impairment and blindness. Improved knowledge of the pathogenesis of this disease has allowed the exploration of new therapeutic methods. In general, elevated intraocular pressure (IOP), oxidative stress, and vascular insufficiency are accepted as the major risk factors for the progression of glaucoma. Many natural compounds have been found beneficial for glaucoma. Nutritional therapies are now emerging as potentially effective in glaucomatous therapy. One nutritional supplement with potential therapeutic value is cod liver oil, a dietary supplement that contains vitamin A and omega-3 polyunsaturated fatty acids (PUFAs). Vitamin A is important for preserving normal vision and it is a well-known antioxidant that prevents the oxidative damage that contributes to the etiology and progression of glaucoma. Vitamin A is also a crucial factor for maintaining the integrity of conjunctival and corneal ocular surfaces, and preventing the impairment of ocular epithelium caused by topical antiglaucomatous drugs. Omega-3 fatty acids are beneficial for glaucoma patients as they decrease IOP, increase ocular blood flow, and improve optic neuroprotective function. In this article, we propose that cod liver oil, as a combination of vitamin A and omega-3 fatty acids, should be beneficial for the treatment of glaucoma. However, further studies are needed to explore the relationship between cod liver oil and glaucoma.

Neurodegeneration: accelerated ageing or inadequate healthcare?

Current figures: About 300 million Diabetics frequently affected by Poly-Neuropathy as secondary complication, 18 million patients with Alzheimer’s disease also diagnosed as Diabetes Type 3, neurodegenerative eye diseases with leading causes of blindness—diabetic retinopathy and estimated 67 million glaucoma patients worldwide, millions of patients with Parkinson’s disease, Multiple Sclerosis, Epilepsy, Cerebral Palsy and Dementia in the elderly—altogether dramatically affect life quality, social and economical indexes of populations around the globe. Optimistic versus Pessimistic Prognosis depends much on diagnostic, preventive and treatment approaches which healthcare will preferably adopt in the near future. Without innovation in healthcare, neurodegenerative disorders can reach more than 30% of global disease burden till 2020. In contrast, effective utilisation of advanced early/predictive diagnostics, preventive and personalised medical approaches could enable a significant portion of population to reach the 100-year age limit remaining vibrant in excellent physical and mental health as actively contributing members of society.