Page 102 - October 2023

VETERINARY VIEWS
LEAKY GUT SYNDROME
Gastrointestinal disease in the horse takes many forms, ranging from inappetence to diarrhea to colic to
colitis or enteritis. It is sometimes difficult
to discern the chicken from the egg in these scenarios, i.e. whether an intestinal illness was precipitated by other internal events (hormonal, inflammatory, infectious, pharmaceutical) or
if a primary intestinal illness elicits secondary systemic inflammation.
The bottom line is that any condition that disrupts the intestinal lining leads to passage of substances and microorganisms across the intestinal barrier. A single layer of barrier cells,
by Nancy S. Loving, DVM
enterocytes, lines the equine intestinal tract to prevent undesirable substances – food antigens (proteins), bile, hydrolytic enzymes (enzymes that use water to break bonds), pathogens, and endotoxin – from accessing the bloodstream. In a healthy horse, the intestinal lining is renewed within a few days to a week’s time through proliferation of enterocytes.
Connecting each enterocyte is a tight junction, which is a protein complex that forms selective permeable seals to regulate passage,
or not, of substances from the intestine into the bloodstream. Disruption of tight junctions leads to development of leaky gut syndrome.
CAUSES OF INTESTINAL PERMEABILITY
The intestinal tract contributes as much as 70% to the body’s immune system. Normal secretion by the immune system of pro- inflammatory cytokines (signaling molecules that have effects on the immune system), such as interleukin (IL) and tumor necrosis factor (TNFα), provides a helpful physiological response to recover from infection or injury. When this response is overwhelming, such as occurs with a compromised intestinal barrier, excessive inflammation releases substances into the circulation that act systemically on other tissues throughout the body. While
The intestinal tract contributes as much as 70% to the body’s immune system.
100 SPEEDHORSE October 2023