Published in the journal Nutrients, the study by authors in Florence, Italy, evaluated gut microbiota composition in nAMD patients versus healthy controls and examined the effects of micronutrient supplementation with lutein, zeaxanthin, and saffron on vision and microbial features.
The gut-retina axis, the bidirectional communication and functional connection between the gut microbiome and the retina of the eye, has gained attention in recent research, suggesting that the health of the gut microbiome can influence retinal health and potentially play a role in eye diseases.
The gut-retina axis
Age-related macular degeneration (AMD) primarily causes visual impairment among individuals over 65, affecting 170 million people globally.
In nAMD, abnormal blood vessels grow through Bruch’s membrane, driven by mechanisms like oxidized low-density lipoproteins (LDL) accumulation, which disrupts the retinal pigment epithelium’s ability to process photoreceptor outer segments, leading to toxic compound buildup.
Typical treatments for nAMD aim to inhibit abnormal blood vessel growth, however, while early laser photocoagulation can limit progression, it has reportedly been found to cause vision loss.
Recent research has linked AMD to an altered immune system, oxidative stress, and obesity, which highlights the potential of dietary supplements in prevention and management.
One study found that lutein and zeaxanthin reduce early-stage AMD progression by absorbing blue light, neutralizing reactive oxygen species, and increasing macular pigment optical density.
As vitamins E and C protect against oxidative stress, and zinc reduces complement-mediated inflammation, the researchers suggest these micronutrients may offer protective effects. Saffron may also enhance retinal function through its antioxidant and anti-inflammatory properties.
Study details
The researchers recruited 30 nAMD patients, who were randomized to receive daily micronutrient supplementation alongside anti-VEGF (vascular endothelial growth factor) therapy, or anti-VEGF treatment alone, over a six-month period, with comparisons made to a healthy control (HC) group (N = 15).
The micronutrient supplement contained 10 mg lutein, 2 mg zeaxanthin, 80 mg vitamin C, 12 mg vitamin E, 10 mg zinc, and 20 mg saffron.
Ophthalmological assessments, biochemical measurements, and stool samples were obtained before and after treatment.
Gut microbiota characterization was performed using 16S rRNA sequencing, and short-chain fatty acids (SCFAs), medium-chain fatty acids (MCFAs), and long-chain fatty acids (LCFAs) were analyzed.
Results showed reduced gut bacterial diversity in nAMD patients compared to healthy controls (HC). Key bacterial taxa, including Bacteroidota, Bacteroidales, and Prevotellaceae, were less abundant in nAMD patients, while pro-inflammatory bacteria like Lactobacillales and Escherichia-Shigella were enriched.
SCFA-producing genera, such as Lachnospira and Faecalibacterium, were also reduced, correlating with decreased SCFA levels and increased inflammatory metabolites in nAMD patients.
The researchers concluded that micronutrient supplementation including lutein, zeaxanthin, and saffron improved patients’visual acuity and reduced inflammatory markers, but that “further studies are warranted to more thoroughly define the relationship between the gut microbiota and retinal health.”
Source: Nutrients 2024, 16(22), 3971; https://doi.org/10.3390/nu16223971
“Beneficial Effects of Micronutrient Supplementation in Restoring the Altered Microbiota and Gut–Retina Axis in Patients with Neovascular Age-Related Macular Degeneration—A Randomized Clinical Trial.”
Authors: Baldi, S. et al.