Gut microbiota alterations linked to diabetic retinopathy in meta-analysis
A meta-analysis in BMC Ophthalmology found distinct gut microbiome compositional and functional alterations in diabetic retinopathy. The review identified depleted SCFA-producing bacteria, enriched pro-inflammatory bacteria, and dysregulated metabolic pathways.
Imbalances in gut bacteria might contribute to the development of diabetic retinopathy (DR), opening the door for new treatments focused on the gut-eye axis, a meta-analysis published in BMC Ophthalmology suggests. The review analyzed data from 18 observational and genetic studies totaling 268 DR patients, 269 diabetic patients without retinopathy, and 99 healthy individuals. According to investigators, distinct compositional and functional alterations were identified in the gut bacteria of patients with DR compared to those with diabetes but no retinopathy and healthy controls.
While the meta-analysis of alpha diversity indices across 8 studies showed no significant differences between groups, consistent beta diversity shifts were observed, indicating structurally distinct microbial communities in the DR patient. Key differences in the DR groups included an altered Firmicutes/Bacteroidetes ratio, with several studies reporting higher populations of Bacteroidetes.
In addition, anti-inflammatory short-chain fatty acid (SCFA)-producing bacteria such as Faecalibacterium, Roseburia, Blautia, and Butyricicoccus were found to be depleted, while pro-inflammatory bacteria, such as Escherichia-Shigella, Pseudomonas, and Enterobacter were enriched, according to the investigators. They note that functional analyses based on microbial composition and direct fecal metabolomic analysis revealed dysregulated pathways, particularly in amino acids such as arginine, proline and lysine, as well as in lipid metabolism.
The observational studies were primarily conducted in China and India, while the genetic data came largely from those of European ancestry. The researchers acknowledge several limitations to their review, including high heterogeneity across studies, variations in sequencing methods, and a demographic bias toward Asian populations in the observational studies. In addition, the randomized genetic studies relied predominantly on European ancestry data, limiting generalizability.
The researchers recommend that future research focus on large-scale, longitudinal, and multi-ethnic studies with standardized sequencing protocols to validate findings, clarify causal relationships, and guide clinical translation. They add that diet, probiotics or fecal transplantation may offer novel strategies to complement conventional treatment of patients with DR.