CD4 and diabetes mellitus: Free short-chain fatty acids are a key and extensively studied class of molecules produced at the microbiota-diet interface.41 While primarily produced in the gut, these fatty acids can impact distant organs such as the liver, lungs, urogenital tract, and brain.42–44 They play a role in immune regulation, affecting T-cell functions, CD4+/CD8+ levels, and are implicated in health conditions like disrupted intestinal barrier function, and diseases, including autoimmune disorders, diabetes, and HIV.41,45,46