Inflammation correlates with markers of T-cell subsets including regulatory T cells in adipose tissue from obese patients.

Accumulation of cytotoxic and T-helper (T(h))1 cells together with a loss of regulatory T cells in gonadal adipose tissue was recently shown to contribute to obesity-induced adipose tissue inflammation and insulin resistance in mice. Human data on T-cell populations in obese adipose tissue and their potential functional relevance are very limited. We aimed to investigate abundance and proportion of T-lymphocyte sub-populations in human adipose tissue in obesity and potential correlations with anthropometric data, insulin resistance, and systemic and adipose tissue inflammation. Therefore, we analyzed expression of marker genes specific for pan-T cells and T-cell subsets in visceral and subcutaneous adipose tissue from highly obese patients (BMI >40 kg/m(2), n = 20) and lean to overweight control subjects matched for age and sex (BMI <30 kg/m(2); n = 20). All T-cell markers were significantly upregulated in obese adipose tissue and correlated with adipose tissue inflammation. Proportions of cytotoxic T cells and T(h)1 cells were unchanged, whereas those of regulatory T cells and T(h)2 were increased in visceral adipose tissue from obese compared to control subjects. Systemic and adipose tissue inflammation positively correlated with the visceral adipose abundance of cytotoxic T cells and T(h)1 cells but also regulatory T cells within the obese group. Therefore, this study confirms a potential role of T cells in human obesity-driven inflammation but does not support a loss of protective regulatory T cells to contribute to adipose tissue inflammation in obese patients as suggested by recent animal studies.