# A185 A GUT MICROBIOME TRANSITION: THE JOURNEY FROM INDIA TO CANADA

## TL;DR

This study shows that Indian immigrants to Canada experience changes in their gut microbiome linked to dietary shifts, which may increase their risk of inflammatory bowel disease.

## Contribution

The study characterizes the gut microbiome of Indian populations and tracks its transformation due to immigration and dietary changes.

## Key findings

- Indian gut microbiomes are distinct from westernized cohorts, with higher stress tolerance and pathogenic potential.
- Indians in India have significantly higher Prevotella abundance and lower ultra-processed food intake compared to Indo-Canadians.
- Immigration to Canada is associated with reduced intake of key nutrients and a decline in Prevotella, linked to dietary changes.

## Abstract

Young Indian immigrants and Indo-Canadians face a significantly higher risk of inflammatory bowel disease (IBD) in westernized countries. While the etiology of IBD remains unclear, a gut microbiome that is no longer symbiotic with its host is a key player. However, Indians are underrepresented in microbiome research, therefore we cannot accurately assess the role of their gut microbiome in IBD. To understand why Indians are at a greater risk for IBD in Canada, we must first characterize their gut microbiome.

This study explores how immigration to Canada impacts the gut microbiome of Indian populations, potentially elevating their risk to IBD.

Stool samples from healthy volunteers (ages 17-53) were collected from Indians in India, Indo-Immigrants, Indo-Canadians, Euro-Canadians and Euro-Immigrants. DNA was extracted for 16S sequencing on the Illumina MiSeq platform and shotgun sequencing on the Illumina NovaSeq platform. Dietary data was processed in ESHA.

Weighted Unifrac revealed distinct clusters of Indian and Indo-Immigrant samples from the westernized cohorts. The most pronounced difference was between Indian and Euro-Canadians with a pseudo-F value of 49.18 (q = 0.00125). Indian versus Indo-Immigrants resulted in a pseudo-F value of 7.707 (q = 0.00125), and Indian versus Indo-Canadian had a pseudo-F value of 15.95 (q = 0.00125). BugBase estimated a significantly higher stress tolerance in the Indian gut, with Proteobacteria driving this phenotypic prediction. Compared to Euro-Canadians, a significantly higher pathogenic potential was predicted in Indians (pFDR= 1.04e-11) and Indo-Immigrants (pFDR= 1.41e-04), driven mainly from Proteobacteria and Bacteroidetes. Multiple comparisons with LDA revealed Prevotella was over 5 times more abundant in Indians residing in India. The gut microbiome in Indians were also enriched with taxa associated with a plant-based diet. Dietary data showed that 59% of Indians do not consume meat, and they also had the lowest consumption (12% caloric intake) of group 4 ultra-processed food (UPF), whereas the highest consumption of UPF was in Indo-Canadians (61% caloric intake) (pbonf ampersand:003C 0.0001). A frequent trend was observed in Indians living in Canada, which was a reduction in key nutrients including soluble fiber, zinc, iron, and folate, some of which are commonly found in plant-based foods.

Overall findings reveal that a loss of Prevotella abundance was observed in Indo-Immigrants and Indo-Canadians, which was associated with a reduction in key nutrients that are common to a plant-based diet, indicating a transition away from their traditional diet. Their dietary changes may be a driver to the displacement of Prevotella and other taxa commonly found in the Indian gut microbiome.

NSERC, Killam