Acute high-intensity interval exercise reduces human monocyte Toll-like receptor 2 expression in type 2 diabetes

Abstract

Type 2 diabetes (T2D) is characterized by chronic low-grade inflammation that contributes to disease pathophysiology. Exercise has anti-inflammatory effects, but the impact of high-intensity interval training (HIIT) is not known. The purpose of this study was to determine the impact of a single session of HIIT on cellular, molecular, and circulating markers of inflammation in individuals with T2D. Participants with T2D (n = 10) and healthy age-matched controls (HC; n = 9) completed an acute bout of HIIT (7 × 1 min at ~85% maximal aerobic power output, separated by 1 min of recovery) on a cycle ergometer with blood samples obtained before (Pre), immediately after (Post), and at 1 h of recovery (1-h Post). Inflammatory markers on leukocytes were measured by flow cytometry, and TNF-α was assessed in both LPS-stimulated whole blood cultures and plasma. A single session of HIIT had an overall anti-inflammatory effect, as evidenced by 1) significantly lower levels of Toll-like receptor (TLR) 2 surface protein expression on both classical and CD16+ monocytes assessed at Post and 1-h Post compared with Pre (P < 0.05 for all); 2) significantly lower LPS-stimulated TNF-α release in whole blood cultures at 1-h Post (P < 0.05 vs. Pre); and 3) significantly lower levels of plasma TNF-α at 1-h Post (P < 0.05 vs. Pre). There were no differences between T2D and HC, except for a larger decrease in plasma TNF-α in HC vs. T2D (group × time interaction, P < 0.05). One session of low-volume HIIT has immunomodulatory effects and provides potential anti-inflammatory benefits to people with, and without, T2D.

Keywords: CD14+ monocyte; inflammation; innate immunity; leukocyte; tumor necrosis factor-α.

Fig. 1.

Gating strategy for analysis of surface Toll-like receptor (TLR) 2 and TLR4 on monocytes and neutrophils. Cells that stained positive for propidium idodide were first excluded from analysis. Cells are first gated on expression of CD14+/CD16− (classical monocytes), CD14−/CD16+ (CD16+ neutrophils), or both CD14+/CD16+ (CD16+ monocytes) (A). Cell type is then confirmed via characteristic forward and side-scatter profile for classical monocytes, CD16+ monocytes, and neutrophils (B, C, and D, respectively). Cell surface TLR2 and TLR4 expression were then measured on each cell type (i.e., classical monocytes, CD16+ monocytes, and CD16+ neutrophils), Fluorescence minus one controls are displayed in gray (E and F). MFI, median fluorescence intensity; SSC-H, side scatter height; FSC-H, forward scatter height.

Fig. 2.

Toll-like receptor 2 expression on CD14+/CD16− classic monocytes, CD16+ monocytes, and CD16+ neutrophils in response to an acute bout of high-intensity interval training (HIIT). Blood samples were obtained before (Pre), immediately after (Post), and 1 h after (1-h Post) a single session of HIIT involving 7 × 1-min at 85% peak power output and TLR2 MFI was measured by flow cytometry on CD14+/CD16− monocytes (A), CD16+ monocytes (B), and CD16+ neutrophils (C). Group means are denoted by dotted (Healthy Controls) or solid (Type 2 Diabetes) horizontal lines. Repeated-measures ANOVA revealed a significant main effect of time for classical monocytes and CD16+ monocytes (all P < 0.05). *P < 0.05 vs. Pre [Fisher least significant difference (LSD) post hoc]. †A main effect of group was also detected for CD16+ neutrophils (P < 0.05).

Fig. 3.

TLR4 expression on CD14+/CD16− classic monocytes, CD16+ monocytes, and CD16+ neutrophils in response to an acute bout of HIIT. Blood samples were obtained before (Pre), immediately after (Post), and 1 h after (1-H Post) a single session of HIIT involving 7 × 1 min at 85% peak power output and TLR4 MFI was measured by flow cytometry on CD14+/CD16− monocytes (A), CD16+ monocytes (B), and CD16+ neutrophils (C). Group means are denoted by dotted (Healthy Controls) or solid (Type 2 Diabetes) horizontal lines. †Repeated-measures ANOVA revealed a significant main effect of group for CD16+ monocytes and CD16+ neutrophils (both P < 0.05).

Fig. 4.

Whole blood culture TNF-α concentration from 4-h supernatants stimulated with 10 ng/ml LPS in response to an acute bout of HIIT. Blood samples were obtained before (Pre), immediately after (Post), and 1 h after (1-H Post) a single session of HIIT involving 7 × 1-min at 85% peak power output and absolute TNF-α (A) and leukocyte concentration corrected TNF-α (B) secretion in whole blood cultured in the presence of 10 ng/ml LPS was measured. Supernatants were collected after 4 h in culture, and TNF-α was measured by Magpix ELISA. Group means are denoted by dotted (Healthy Controls) or solid (Type 2 Diabetes) horizontal lines. Repeated-measures ANOVA revealed a significant main effect of time for absolute TNF-α concentration (P < 0.05) and a significant main effect of group for leukocyte-corrected TNF-α concentration (†P < 0.05). *P < 0.05 vs. Pre (Fisher LSD post hoc). #P < 0.05 vs. Post (Fisher LSD post hoc).

Fig. 5.

Circulating plasma TNF-α concentration in response to an acute bout of HIIT. Blood samples were obtained before (Pre), immediately after (Post), and 1 h after (1-H Post) a single session of HIIT involving 7 × 1-min at 85% peak power output and TNF-α in plasma samples was measured by Magpix ELISA. Groups means are denoted by dotted (Healthy Controls) or solid (Type 2 Diabetes) horizontal lines. Repeated-measures ANOVA revealed a significant group × time interaction for TNF-α concentration (P < 0.05). ‡P < 0.05 vs. Pre within each group (Fisher LSD post hoc).