Effect of Micronutrient Supplementation on the Intestinal Microbiota in Patients With Age-related Macular Degeneration - The Gut-Retina-axis Study

Age-related macular degeneration (AMD) stands as the primary cause of visual impairment in the over-65-year-old population of industrialized countries, affecting approximately 170 million people worldwide . AMD is a multifactorial disease in the pathogenesis of which, that it's not yet fully understood, genetic and environmental factors are involved. Specifically, there are two main types of AMD, both culminating in central vision deficiency and potential blindness due to the death of photoreceptors. The first type of AMD type, known as dry AMD, is characterized by the accumulation of extracellular material (i.e. lipids, vitronectin, inflammatory or amyloid proteins) between the Bruch's membrane and the retinal pigment epithelium, leading to the formation of drusen. Drusen are small yellow or white spots on the retina that can gradually evolve either into retinal and pigment epithelium atrophy or, for approximately 20% of patients, progress into the second AMD type that is called wet AMD or neovascular AMD (nAMD). nAMD is distinguished by the development of new choroidal vessels, a condition that can result in permanent visual impairment. Presently, although therapeutic options for dry AMD are limited, nAMD is treated with intravitreal injections of anti-VEGF (vascular endothelial growth factor) drugs, which have proven effective in slowing angiogenic development and limiting the progression of nAMD. Moreover, recent investigations have implicated immune system alterations, oxidative stress, and overweight as critical factors in AMD pathogenesis. Particularly, many studies have recently highlighted the potential benefits of dietary supplementation with micronutrients having antioxidant and antiinflammatory effects in reducing the risk of AMD development. Notably, the AREDS2 study definitively demonstrated the efficacy of dietary supplementation with lutein and zeaxanthin in reducing the risk of progression of early-stage AMD. In detail, the administration of lutein and zeaxanthin, which can absorb blue light and neutralize free radicals and reactive oxygen species in the macula, has been associated with increased macular pigment optical density (MPOD), improved visual acuity and a reduced risk of retinal aging. Moreover, other micronutrients such as vitamins E and C can prevent the progression of maculopathy by providing protection against oxidative stress and maintaining GM homeostasis while oral zinc supplementation can reduce the complement-mediated inflammation in the retinal pigment epithelium, which plays a fundamental role in the etiology of AMD. Additionally, saffron (Crocus sativus), which contains active components such as crocin, safranal, crocetin, and picrocrocin, has demonstrated antioxidant and anti-inflammatory effects, leading to significant improvements in the retinal function of AMD patients. Furthermore, considering that the retina is an extension of the brain both anatomically and developmentally, the hypothesis of a gut-retina interplay has been recently proposed, paralleling the widely explored bidirectional communication between the gut and the brain. Objectives of the study To evaluate the GM composition and function of nAMD patients in comparison to healthy subjects and considering the dual potential of micronutrients to act through direct antioxidant mechanisms and modulation of the GM, the investigators assessed the impact of a novel micronutrient supplementation based on lutein, zeaxanthin and saffron on ophthalmological parameters and microbial features of nAMD patients.

Inclusion criteria

• Men and women >50 years of age.
• Willingness to cooperate during the study and ability to follow guidelines and to complete all clinical visits
• Ability to provide informed consent

Exclusion criteria

• Use of antibiotics or continued use of pre- or probiotics in the 2 months before enrolment
• Use of other treatments (medications or nutritional programs) that affect body weight, food intake, and/or energy expenditure
• Diagnosis of any ocular disease.