Short-term high-intensity interval and moderate-intensity continuous training reduce leukocyte TLR4 in inactive adults at elevated risk of type 2 diabetes

Abstract

Exercise can have anti-inflammatory effects in obesity, but the optimal type and intensity of exercise are not clear. This study compared short-term high-intensity interval training (HIIT) with moderate-intensity continuous training (MICT) in terms of improvement in cardiorespiratory fitness, markers of inflammation, and glucose control in previously inactive adults at elevated risk of developing type 2 diabetes. Thirty-nine inactive, overweight/obese adults (32 women) were randomly assigned to 10 sessions over 2 wk of progressive HIIT (n = 20, four to ten 1-min sessions at ∼90% peak heart rate, 1-min rest periods) or MICT (n = 19, 20-50 min at ∼65% peak heart rate). Before and 3 days after training, participants performed a peak O2 uptake test, and fasting blood samples were obtained. Both HIIT (1.8 ± 0.4 vs. 1.9 ± 0.4 l/min, pre vs. post) and MICT (1.8 ± 0.5 vs. 1.9 ± 0.5 l/min, pre vs. post) improved peak O2 uptake (P < 0.001) and lowered plasma fructosamine (P < 0.05). Toll-like receptor (TLR) 4 (TLR4) expression was reduced on lymphocytes and monocytes after both HIIT and MICT (P < 0.05) and on neutrophils after MICT (P < 0.01). TLR2 on lymphocytes was reduced after HIIT and MICT (P < 0.05). Plasma inflammatory cytokines were unchanged after training in both groups, but MICT led to a reduction in fasting plasma glucose (P < 0.05, 5.9 ± 1.0 vs. 5.6 ± 1.0 mmol/l, pre vs. post). Ten days of either HIIT or MICT can improve cardiorespiratory fitness and glucose control and lead to reductions in TLR2 and TLR4 expression. MICT, which involved a longer duration of exercise, may be superior for reducing fasting glucose.

Keywords: aerobic exercise; chronic inflammation; glucose control; high-intensity interval training; prediabetes.

Fig. 1.

Flow cytometry gating strategy used to quantify toll-like receptors (TLRs) on immune cell subtypes. Flow cytometry plots show gating cells with CD45⁺ trigger (P1; A), identification of monocyte (P3), lymphocyte (P4), and neutrophil (P2) populations based on scatter (B), gate for CD45⁺/CD14⁺ monocytes (P5; C), and histogram of TLR4 expression on CD14⁺ monocytes (P6) with corresponding fluorescence-minus-one (FMO) control (D).

Fig. 2.

A 2-wk period of both high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) increases cardiorespiratory fitness [i.e., peak O₂ uptake (V̇o_2peak)]. A: individual changes. B: group change from pretraining. Main effect of time was significant (P < 0.05). *Significant increase from pretraining within group (P < 0.05).

Fig. 3.

A 2-wk period of both HIIT and MICT leads to reductions in immune cell TLR expression. TLR4 was measured on lymphocytes (A), CD14⁺ monocytes (B), CD15⁺ neutrophils (C), and TLR2 measured on lymphocytes (D) by flow cytometry before and after training. MFI, median fluorescence intensity. Main effects of time were significant for all (P < 0.05), with a significant group × time interaction for CD15⁺ neutrophils (P = 0.018). *Significant difference from pretraining within group. There were no significant changes in TLR2 on CD14⁺ monocytes or CD15⁺ neutrophils (data not shown).