High-Intensity Interval Training Improves Markers of Oxidative Metabolism in Skeletal Muscle of Individuals With Obesity and Insulin Resistance

Background: The excess body fat characteristic of obesity is related to various metabolic alterations, which includes insulin resistance (IR). Among the non-pharmacological measures used to improve insulin sensitivity are aerobic physical training, such as high-intensity interval training (HIIT). This study investigated the effects of 8 weeks of HIIT on blood and skeletal muscle markers related to IR and oxidative metabolism in physically inactive individuals with obesity and compared the changes between insulin resistant and non-insulin resistant phenotypes.Methods: Initially to investigate the effect of obesity and IR in the analyzed parameters, insulin-sensitive eutrophic volunteers (CON; n = 9) and obese non-insulin (OB; n = 9) and insulin-resistant (OBR; n = 8) were enrolled. Volunteers with obesity completed 8 weeks of HIIT in a cycle ergometer. Venous blood and vastus lateralis muscle samples were obtained before and after the HIIT. Body composition and peak oxygen consumption (VO2peak) were estimated before and after HIIT.Results: HIIT reduced IR assessed by the homeostatic model assessment of insulin resistance (HOMA-IR) in OBR (4.4 ± 1.4 versus 4.1 ± 2.2 μU L−2), but not in OB (HOMA-IR 1.8 ± 0.5 versus 2.3 ± 1.0 μU L−2) volunteers. HIIT increased VO2peak with no change in body fat in both groups. In skeletal muscle, HIIT increased the phosphorylation of IRS (Tyr612), Akt (Ser473), and increased protein content of β-HAD and COX-IV in both groups. There was a reduction in ERK1/2 phosphorylation in OBR after HIIT.Conclusion: Eight weeks of HIIT increased the content of proteins related to oxidative metabolism in skeletal muscle of individuals with obesity, independent of changes total body fat

Lymphocyte Redox Imbalance and Reduced Proliferation after a Single Session of High Intensity Interval Exercise

<div><p>This study investigated whether an acute session of high-intensity interval training (HIIT) is sufficient to alter lymphocyte function and redox status. Sixteen young healthy men underwent a HIIT session on a cycloergometer, consisting of eight bouts of 1 min at 90–100% of peak power, with 75 seconds of active recovery at 30 W between bouts. Venous blood was collected before, immediately after, and 30 minutes after the HIIT session. In response to <i>Staphylococcus aureus</i> superantigen B (SEB) stimulation, lymphocyte proliferation decreased and the IL-2 concentration increased after the HIIT session. However, the HIIT session had no effect on lymphocyte proliferation or IL-2 response to phytohemagglutinin stimulation. The HIIT session also induced lymphocyte redox imbalance, characterized by an increase in the concentration of thiobarbituric acid reactive substances and a decrease in the activity of the antioxidant enzyme catalase. Lymphocyte viability was not affected by the HIIT session. The frequencies of CD25⁺ and CD69⁺ T helper and B lymphocytes in response to superantigen stimulation were lower after exercise, suggesting that superantigen-induced lymphocyte activation was reduced by HIIT. However, HIIT also led to a reduction in the frequency of CD4⁺ and CD19⁺ cells, so the frequencies of CD25⁺ and CD69⁺ cells within the CD4 and CD19 cell populations were not affected by HIIT. These data indicate that the reduced lymphocyte proliferation observed after HIIT is not due to reduced early lymphocyte activation by superantigen. Our findings show that an acute HIIT session promotes lymphocyte redox imbalance and reduces lymphocyte proliferation in response to superantigenic, but not to mitogenic stimulation. This observation cannot be explained by alteration of the early lymphocyte activation response to superantigen. The manner in which lymphocyte function modulation by an acute HIIT session can affect individual immunity and susceptibility to infection is important and requires further investigation.</p></div

Physical and physiological characteristics of volunteers.

<p>Physical and physiological characteristics of volunteers.</p

HIIT effect on cytotoxic T CD8 cell activation by SEB.

<p><b>(A)</b> Frequency of CD8^highCD25⁺ lymphocytes. <b>(B)</b> Frequency of CD8^highCD69⁺ lymphocytes. Data shown as mean ± SE. pre-ex = before exercise, post-ex = immediately after exercise, 30 min post-ex = 30 min after exercise. N = 6.</p

Effect of the HIIT session on lymphocyte viability.

<p>Effect of the HIIT session on lymphocyte viability.</p

Modulation of lymphocyte redox status by HIIT.

<p><b>(A)</b> TBARS concentration. <b>(B)</b> GSH content. <b>(C)</b> CAT activity. <b>(D)</b> SOD activity. *P < 0.05, compared to pre-ex, one-way Anova, Tukey <i>post hoc</i>. pre-ex = before exercise, post-ex = immediately after exercise, 30 min post-ex = 30 min after exercise. N = 10.</p

HIIT effect on lymphocyte proliferative response.

<p><b>(A)</b> SEB-stimulated cells. <b>(B)</b> PHA-stimulated cells. Data shown as mean ± SE. ^#P < 0.05, compared to non-stimulated cells, in all moments. *P < 0.05, compared to pre-ex, Anova-two way, <i>Tukey post-hoc</i>. pre-ex = before exercise, post-ex = immediately after exercise, 30 min post-ex = 30 min after exercise. N = 10.</p

Analytic strategy used to evaluate lymphocyte GSH content by flow cytometry.

<p>Profile of size (FSC) and granularity (SSC) (A). Fluorescence intensity histograms of non-labeled (control) (B) and Thiol Tracker-labeled cells (C).</p

HIIT effect on TCD4 activation by SEB.

<p><b>(A)</b> Frequency of CD4⁺CD25⁺ lymphocytes. <b>(B)</b> Frequency of CD4⁺CD69⁺ lymphocytes. <b>(C)</b> Frequency of CD4⁺CD25⁺ cells within the T helper (CD4⁺) cell subpopulation. <b>(D)</b> Frequency of CD4⁺CD69⁺ cells within the T helper (CD4⁺) cell subpopulation. Data shown as mean ± SE. # P <0.05, compared to non-stimulated cells in all moments. *P < 0.05, compared to pre-ex. ^§P < 0.05, compared to post-ex. Two way Anova, Tukey <i>post-hoc</i>. pre-ex = before exercise, post-ex = immediately after exercise, 30 min post-ex = 30 min after exercise. N = 6.</p

Heart rate and perceived exertion during the HIIT sessions.

<p>Heart rate and perceived exertion during the HIIT sessions.</p