Mucosal-Associated Invariant T Cell Response To Acute Exercise In Overweight Older Women

Abstract

Mucosal Associated Invariant T (MAIT) cells have properties of both innate and adaptive immunity and are dysregulated in overweight/obese (OW) populations. MAIT cell proportion and number increase after acute exercise in healthy young men, but the effect of acute exercise on MAIT cells in OW women is unknown. PURPOSE: To investigate MAIT cell frequency and function after acute exercise, in OW, older women compared to lean controls. METHODS: Sedentary, OW women (n=15, 64 y ± 4, 32.9 kg/m2 ± 3.69, 21.7 ml/kg/min ± 3.40) completed 25 min of walking at 70-80% heart rate reserve and 2 sets of 8 resistance training exercises. Immune cells were isolated at rest, 0h and 1h post exercise. Cells were stimulated with PMA/ionomycin. Cell frequency and intracellular cytokine expression were determined using flow cytometry. A reference group of lean women (n=8, 64y ± 7, 21.5 kg/m2 ± 2.0, 29.8 (ml/kg/min) ± 5.06) provided a resting blood sample. RESULTS: Lymphocyte number increased at 0h by 44% ± 41 (p <0.001) before returning to resting levels at 1h. Compared to lean women, OW women had greater MAIT cell counts (OW 97 ± 99 cells/uL, Lean 27 ± 18, p=0.048) but lower MAIT cell frequencies at baseline (OW 0.4% ± 0.9, Lean 4.1 ± 2.1%, p<0.001). TNFα expression in stimulated MAIT cells was also lower in OW women (OW 79% ± 16%, Lean 98% ± 5% p<0.001). Following acute exercise, there was no change in MAIT cell frequency or absolute number in OW women. TNFα expression increased by 14% ± 34% (p=0.006) at 0h in the OW group. There were no differences in IFNγ expression between groups or with acute exercise. CONCLUSIONS: Obesity appears to attenuate the MAIT cell function and increase counts in OW women. Lower baseline TNFα expression suggests these cells have a reduced capacity to respond to stimulation with greater resting MAIT counts potentially being a compensatory response. Acute exercise did not alter MAIT cell counts or frequencies. However, TNFα expression increased with acute exercise, suggesting that exercise may increase MAIT cell sensitivity to mitogenic stimulation. This temporary increase in cell functionality may offset some of the detrimental effects of obesity on MAIT cells but the long-term training effects still need to be determined.