A new study published by the Journal of Clinical Investigation has revealed that chronic inflammation is caused by obesity and alters the immune system and the gut microbial environment. The changes to the immune system consist of alterations to the mucosal-associated invariant T (MAIT) cells. MAIT cells are an innate-like T cell population that recognizes bacterial ligands and is enriched in mucosal and inflamed tissues. Obesity is associated with low-grade inflammation in fat tissue and dysfunctional fat cells produce inflammatory molecules. The fat tissue accumulation of immune cells such as macrophages, lymphocytes, neutrophils, and mast cells is a contributing factor in obesity and obesity-induced type 2 diabetes (T2D).
In the fat tissue of lean people, the innate immune semi-invariant natural killer T (iNKT) cells are enriched in contrast to the fat tissue of obese patients. Mucosal-associated invariant T (MAIT) cells are a novel subset of innate-like immune cells found in peripheral blood, intestinal mucosa, and abundantly in human liver.
In obese people MATT cells are abundant in fat tissues and exhibit an inflammatory metabolic alteration. In healthy controls, the circulating MAIT cell population is reduced in individuals with Type 2 Diabetes and those that are severely obese.
Weight loss improves type 2 diabetes and lowers the inflammatory metabolic response. This diminished frequency is associated with increased production of IL-17 by circulating MAIT cells, and this Th17 shift was exacerbated in fat tissue from obese patients. Bariatric surgery restored circulating MAIT cell frequency and minimized functional alteration. This research study highlights the potential role of obesity in metabolic diseases.
Isabelle Magalhaes, Karine Pingris, Christine Poitou, Stéphanie Bessoles, Nicolas Venteclef, Badr Kiaf, Lucie Beaudoin, Jennifer Da Silva, Omran Allatif, Jamie Rossjohn, Lars Kjer-Nielsen, James McCluskey, Séverine Ledoux, Laurent Genser, Adriana Torcivia, Claire Soudais, Olivier Lantz, Christian Boitard, Judith Aron-Wisnewsky, Etienne Larger, Karine Clément, Agnès Lehuen. Mucosal-associated invariant T cell alterations in obese and type 2 diabetic patients. Journal of Clinical Investigation, 2015; DOI: 10.1172/JCI78941