Acute high-intensity interval exercise induces comparable levels of circulating cell-free DNA and Interleukin-6 in obese and normal-weight individuals

AIMS

Obesity is associated with lipid aggregation in adipocytes and macrophage infiltration, leading to increased oxidative stress and inflammation. Increased cell-free DNA (cfDNA) concentrations have been observed in clinical conditions of systemic inflammation. While the beneficial effects of regular physical activity on the release of circulating cfDNA still remain unknown, acute intense exercise has been shown to increase inflammatory cytokines and cfDNA concentrations in normal-weight individuals. Therefore, the primary purpose of this study was to examine the effect of acute high-intensity interval Exercise (HIIE) on plasma cfDNA and interleukin-6 (IL-6) responses in obese and normal-weight subjects.

MAIN METHODS

Fourteen male subjects (7 obese and 7 normal-weight) participated in an acute HIIE protocol (30 min, 4x4min @ 80% - 90% of VO_2max) on a treadmill. Between HIIE intervals, subjects performed 3 min of active recovery at 50-60% VO_2max. Blood samples were collected prior to, immediately following exercise, and one hour into recovery for measurements of plasma cfDNA and IL-6.

KEY FINDINGS

Our results demonstrated a significant elevation in plasma cfDNA immediately following acute HIIE in both obese and normal-weight subjects. A comparable elevation in the concentration of plasma IL-6 was also found between two groups in response to acute HIIE. Furthermore, the level of plasma cfDNA was not correlated with IL-6 either at baseline or in response to acute HIIE.

SIGNIFICANCE

These findings may support the utilization of HIIE as a time-efficient exercise protocol to understand the obesity-associated cfDNA and inflammatory responses.

Exercise reduced pentraxin 3 levels produced by endotoxin-stimulated human peripheral blood mononuclear cells in obese individuals

The purpose of this study was to determine whether obesity would reduce the capacity of peripheral blood mononuclear cells (PBMCs) to produce the anti-inflammatory protein pentraxin 3 (PTX3) in response to ex vivo stimulation with lipopolysaccharide (LPS), and if acute aerobic exercise would enhance this PTX3 production capacity. In addition, the inter-relationships of LPS-induced PTX3 with the inflammatory cytokines (interleukin 6 [IL-6], IL-10, and tumor necrosis factor alpha) were examined. Twenty-one healthy subjects (10 obese and 11 normal-weight) performed an acute bout of aerobic exercise at 75% VO_2max. The capacity of PBMCs to produce PTX3 ex vivo following LPS stimulation was the same in obese and normal-weight subjects at rest, and decreased equally in both subject groups following acute aerobic exercise. This is in contrast to plasma PTX3, which is lower in obese subjects at rest and increased equally in both obese and normal-weight subjects following exercise. In addition, ex vivo PTX3 production was positively associated with IL-6 and IL-10 in response to acute aerobic exercise ( r = 0.686, P = 0.020; r = 0.744, P = 0.009, respectively) in normal-weight, but not in obese individuals ( r = 0.429, P = 0.249; r = 0.453, P = 0.189, respectively). These findings indicate that concentrations of PTX3 observed in plasma are relatively independent of those produced by PBMCs ex vivo and the mechanisms associated with PTX3-mediated anti-inflammatory signaling may differ during obesity. Impact statement Our laboratory has previously demonstrated that obese individuals present with lower plasma concentrations of the anti-inflammatory protein pentraxin 3 (PTX3), whereas acute aerobic exercise increases plasma PTX3 levels similarly compared to normal-weight individuals. As a follow-up, the present study demonstrates that PBMCs isolated from obese and normal-weight individuals produce comparable amounts of PTX3 ex vivo in response to lipopolysaccharide (LPS). Furthermore, given that acute aerobic exercise reduced the ex vivo production of PTX3 in both groups, our results clearly indicate that plasma PTX3 levels are relatively independent of those produced by PBMCs ex vivo. In addition, our findings suggest that the mechanisms associated with PTX3-mediated production of the anti-inflammatory cytokine interleukin 10 may be impaired in obese individuals, and thus provides a key finding necessary for the elucidation of PTX3's role in the mediation of anti-inflammatory profiles and the subsequent amelioration of inflammatory disease during obesity.

Effects of Experience and Contextual Interference on Learning and Transfer by Boys and Girls

This study examined effects of experience and contextual interference reported earlier by Del Rey, Wughalter, and Whitehurst. Responses of children in Grades 1, 2, and 3 (40 boys and 40 girls) gave some support for the effects of experience on learning.

Contextual Interference and Experience in Acquisition and Transfer

This study was planned to pursue the effects of experience and contextual interference found earlier for a coincident-timing task. Male varsity football athletes and men with minimal experience in these tasks were selected as subjects. Battig's views of contextual interference were supported but no effects of experience level were found.