Exploring Metabolite Alteration from Age-Related Macular Degeneration with UHPLC-MS/MS

A research team used ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to study the alterations in metabolites of wet age-related macular degeneration (wAMD) using metabolomics in patients with wAMD. The team assessed the potential effects of anti-vascular endothelial growth factor (anti-VEGF) on these metabolites. A paper based on their work was published in Investigative Opthalmology & Visual Science (1).

A degenerative retinal condition impacting predominantly the elderly and stands as a principal cause of blindness among older people in industrialized nations (2), dry age-related macular degeneration (AMD) and wAMD constitute approximately 10% to 15% of all AMD cases and are marked by the abnormal proliferation of subretinal neovascularization (3). The newly formed blood vessels produced from this degeneration are prone to rupture, which can lead to retinal hemorrhage, fluid leakage, and scar formation; all of which can rapidly result in vision loss (4).

This study was a retrospective case-control analysis performed at Zhejiang Provincial People's Hospital (Zhejiang, China), with patients diagnosed with wAMD during outpatient visiting from March 2022 to October 2023 participating. These patients had exhibited a variety of symptoms, including sudden and severe vision loss, deep and/or superficial hemorrhages, subretinal neovascular membranes, drusen, or disciform scars in the macular area. Past ocular surgery, uveitis, glaucoma, or any other condition that may affect the retina were all considerations for a patient’s exclusion from the analysis. Aqueous humor samples (the clear liquid inside the front part of the eye which nourishes it and keeps it inflated [5] ) were collected from patients, positioned on ice to defrost until no ice remained. A mixture of50 µL of each sample and 150 µL of an internal standard extraction solution (20% acetonitrile, methanol) was formulated, transferred to tubes, incubated at −20°C for 30 min, and then subsequently centrifuged for 3 min (1).

Among the 1001 metabolites verified in the aqueous humor, 306 compounds separated patients with pre-wAMD from the control group, whereas 68 metabolites differentiated patients with post-wAMD from those with pre-wAMD. The enrichment in metabolic pathways was noted in adenosine triphosphate (ATP)-binding cassette (ABC) transporters (a transport system superfamily that is one of the largest and possibly one of the oldest gene families [6]), thiamine metabolism, glycerophospholipid metabolism, mammalian target of rapamycin signaling pathway and tyrosine metabolism, and so on. Machine learning and receiver operating characteristic curves analysis suggested that the metabolite δ-valerolactam could not only distinguish between patients with wAMD and the control group but differentiate between patients with post-wAMD and patients with pre-wAMD as well. Changes in another metabolite, acylcarnitine, were observed in anti-VEGF responders with wAMD. There were clear variations in the aqueous humor of patients with wAMD involving many metabolites that are associated with ABC transporters, glycerophospholipid metabolism, and the mammalian target of rapamycin signaling pathway. It is possible that δ-valerolactam can be applied as a biomarker in wAMD (1).

The authors of the study admit that their research possessed several limitations. Owing to the limited sample size, they refrained from performing a comprehensive study of AMD subtypes, like geographic atrophy and early AMD. Only patients with wAMD who consented to anti-VEGF medication had aqueous humor samples obtained for this research. The metabolic changes detected in aqueous humor may not accurately represent the true intraocular metabolism. The metabolites in the aqueous humor are dynamic and can be affected by several variables, including variations in the overall health status among the patients, testing techniques and circumstances. Consequently, larger longitudinal investigations with increased sample sizes are necessary to validate our findings and assess the progression of metabolites in relation to AMD advancement (1).

The risks of macular degeneration. ©Jack- stock.adobe.comNormal

References

1. Chen, Y.; Zhang, X.; Zhang, Y.; Zhang, S.; Huo, Y, Wu, Y.; Shen, L,; Mao, J.; Metabolomic Characteristics of Aqueous Humor in Wet Age-Related Macular Degeneration and the Impact of Anti-VEGF Treatment. Invest. Ophthalmol. Vis. Sci. 2025, 66 (2), 37.DOI: 10.1167/iovs.66.2.37

2. Klein, R.; Klein, B. E.; Knudtson, M. D.; Meuer, S. M.; Swift, M.; Gangnon, R. E. Fifteen-Year Cumulative Incidence of Age-Related Macular Degeneration: The Beaver Dam Eye Study. Ophthalmology 2007, 114 (2), 253-262. DOI: 10.1016/j.ophtha.2006.10.040

3. Wong, W. L.; Su, X.; Li, X.; Cheung, C. M.; Klein, R.; Cheng, C.Y.; Wong, T. Y. Global Prevalence of Age-Related Macular Degeneration and Disease Burden Projection for 2020 and 2040: A Systematic Review and Meta-Analysis. Lancet Glob. Health 2014, 2 (2), e106-116. DOI: 10.1016/S2214-109X(13)70145-1

4. Ferris, F. L. 3^rd; Fine, S. L,.; Hyman, L. Age-Related Macular Degeneration and Blindness Due to Neovascular Maculopathy. Arch. Ophthalmol. 1984, 102 (11), 1640-1642. DOI: 10.1001/archopht.1984.01040031330019

5. Aqueous Humor. American Academy of Opthalmology website. https://www.aao.org/eye-health/anatomy/aqueous-humor (accessed 2025-02-14)

6. ABC transportyer. Wiikipedia. https://en.wikipedia.org/wiki/ABC_transporter (accessed 2025-02-14)