Tissue-Specific Phenotype and Activation of iNKT Cells in Morbidly Obese Subjects: Interaction with Adipocytes and Effect of Bariatric Surgery

Background The immune response of visceral adipose tissue (VAT) in obesity, in particular the role of invariant natural killer T (iNKT) cells, has not yet been fully elucidated. Objective To characterize iNKT cells and its activation status in VAT and peripheral blood mononuclear cells (PBMC) in morbidly obese subjects (MO), and to analyze their association with metabolic parameters. Subjects and Methods Twenty non-obese and 20 MO subjects underwent Roux-en-Y gastric bypass (RYGB) and were studied before and 6 months after RYGB. VAT and PBMC were obtained. Results A decrease in VAT iNKT cells from MO was found, however, not in PBMC. Visceral adipocytes from MO presented increased CD1d expression (p = 0.032). MO presented an increase in early activated CD69+ iNKT cells in PBMC before RYGB (p < 0.001), but not after RYGB nor in VAT, and an increase in later activated CD25+ iNKT in VAT (p = 0.046), without differences in PBMC. The co-expression of early and later markers (CD69+CD25+) in iNKT cells was increased in MO in VAT (p = 0.050) and PBMC (p = 0.006), decreasing after RYGB (p = 0.050). CD69+ iNKT and CD69+CD25+ iNKT cells in PBMC after RYGB correlated negatively with glucose, insulin, and insulin resistance levels. Conclusions There is a tissue-specific phenotype and activation of iNKT cells in VAT in morbid obesity, which could be involved in VAT immunometabolism dysregulation. Also, the increase in CD1d expression could be to offset the lack of VAT iNKT cells.