A Gut-Eye Connection

Brijesh Takkar, Taraprasad Das, and colleagues from L V Prasad Eye Institute along with researchers across India identify changes in the gut microbiome of people with diabetic retinopathy laying the foundation for developing a non-invasive test to identify patients at risk and treat them with preventive therapy. 

India is home to the world’s second-largest diabetic population, with cases projected to rise by 75% over the next 25 years. One of the complications of diabetes is diabetic retinopathy (DR) — a condition in which high blood sugar damages the network of tiny blood vessels that supply the retina (the light-sensitive layer at the back of the eye).

At least 4% of people with diabetes develop sight-threatening complications due to DR. But it often takes five years or more for DR to surface clinically and even longer to reach treatable stages. The only proven strategy to curb DR is controlling blood sugar.

By then, exposure to years of changing glucose levels may already have left an imprint on retinal tissues — a phenomenon known as “metabolic memory” — allowing the damage to continue even after sugar levels are brought under control. Researchers are therefore looking at other biological processes that may influence DR progression.

One possibility lies inside the gut. The human gut is home to trillions of microorganisms including bacteria, fungi, viruses and archaea collectively known as the gut microbiome. This microbial ecosystem helps digest food, synthesize vitamins, regulate metabolism, and shape the immune system among other functions.

Scientists have linked imbalances in the gut microbiome to a range of conditions from obesity and diabetes to neurodegenerative and cardiovascular disease. Studies have shown that microbiota-induced changes can influence glucose metabolism and insulin resistance. Could it also predispose people with diabetes towards diabetic retinopathy? 

Preliminary results

In a new study published in Gut Pathogens, Brijesh Takkar and colleagues from the Diabetic Retinopathy Microbiome Study–India (DRMS-India) group explore this question. This ongoing study is a multicentre effort spanning 17 sites and over 500 persons across the country. The current paper presents results from the first 100 participants: 26 healthy controls, 33 people with diabetes alone, and 41 with diabetic retinopathy, all from India’s four geographic zones. 

The researchers analysed stool samples to examine whether gut microbial communities differed across the three groups. The large territorial extent of the study necessitated a standard operating clinical protocol (followed by the DRMS clinical group) and a laboratory protocol (followed at the National Institute of Biomedical Genomics). 

The findings showed that people with DR had the most diverse gut microbiomes i.e. they had higher number of microbial species than in healthy individuals or the diabetic group. The major microbial groups normally found in the human gut were present across all three cohorts, but the numbers differed.

For example, the bacterium Segatella copri was most abundant in healthy individuals and least in the DR group, indicating a disease-altered gut microbiome. The results represent trends from the first 100 participants. If these microbial patterns persist across the full cohort they could help identify which diabetic patients are at risk of DR using a simple stool sample.

‘Across diverse geographies and metabolic states, microbial patterns reveal a unique signature of diabetic retinopathy,’ notes Dr Taraprasad Das, Distinguished Ophthalmologist and Vice-Chair Emeritus at LVPEI.

‘Results from DRMS seem a powerful example of how our habits shape us in health and disease, and how traditional Indian science may have been right all along,’ notes Dr Brijesh Takkar, the first author on this paper and a consultant ophthalmologist at LVPEI. ‘Hopefully completed results will help Indians with better eye health. 

Citation 

Takkar B, Maddheshiya A, Adhikary P, Reddy VA, Majumder PP, Mukherjee S, Das T; the DRMS Group. Gut microbiome changes in people with diabetic retinopathy in India. DRMS-India report # 1: operational protocol and trends from first 100 participants. Gut Pathog. 2026 Mar 13;18(1):36. doi: 10.1186/s13099-026-00821-9. PMID: 41827072; PMCID: PMC13097751.