A groundbreaking study published in Nature Microbiology led by J. Oriol Sunyer professor of immunology and pathobiology at the School of Veterinary Medicine alongside researchers from Penn Vet and the University of New Mexico has identified secretory immunoglobulin M (sIgM) as a crucial contributor to gut health. While secretory immunoglobulin A (sIgA) has long been recognized for its role in maintaining intestinal bacterial balance the new findings suggest that sIgM may be equally if not more important in supporting gut function and overall health.

Secretory immunoglobulins found on the mucosal surfaces of various organs in vertebrates influence the colonization composition and metabolic activity of the gut microbiome. Traditionally sIgA in mammals and sIgT in fish have been seen as the primary antibodies maintaining microbiome stability. However Sunyer's team challenges this view by revealing that sIgM plays a fundamental role in regulating gut microbiota and metabolism.

The gut microbiome plays a vital role in key physiological functions such as digestion metabolite synthesis and the regulation of immune and neurological systems. In mammals secretory immunoglobulin A (sIgA) and in fish secretory immunoglobulin T (sIgT) coat a large portion of gut microbes an interaction essential for supporting beneficial bacterial colonization and maintaining microbial balance and metabolism. However emerging research indicates that secretory immunoglobulin M (sIgM) also coats a significant share of the gut microbiota in both fish and humans pointing to its potential role in sustaining microbiome homeostasis.

To investigate this Sunyer and his team conducted studies on rainbow trout a species whose sIgM coats gut bacteria similarly to that in humans. By selectively and temporarily depleting sIgM in these fish the researchers observed a marked disruption in the gut microbiome known as dysbiosis commonly associated with intestinal disorders and impaired physiological functions. The absence of sIgM also led to pronounced gut inflammation and tissue damage driven by shifts in microbial composition.

These harmful gut effects were linked to weight loss in the fish likely resulting from shifts in microbiome composition and the associated metabolic disruptions explains Sunyer. Additionally without sIgM bacteria were seen crossing from the gut lumen into the intestinal lining and even entering the bloodstream.

Source: https://penntoday.upenn.edu/news/new-penn-vet-study-uncovers-key-guardian-gut-health-and-metabolism