Post‐prandial exhaled 8‐isoprostane responses to meals of varying caloric and fat content in non‐asthmatic, insufficiently active men
Authors: Kurti Stephanie P , Emerson Sam R , Rosenkranz Sara K , Teeman Colby S , Emerson Emily M , Cull Brooke J , Smith Joshua R , Harms Craig A 
Published: November 2023

INTRODUCTION

Elevated levels of oxidative stress are associated with chronic diseases, such as asthma and cardiovascular disease. Even a single high‐fat meal (HFM) leads to an increase in triglycerides, inflammation, and oxidative stress. In particular, 8‐isoprostane, the gold standard for assessing oxidative stress, increases systemically (~48%) after a HFM in healthy men. However, no previous research has investigated whether airway oxidative stress increases after a HFM in non‐asthmatics. Therefore, our purpose was to compare 8‐isoprostane following two meals with differing levels of caloric and fat content in insufficiently active, non‐asthmatic men. We hypothesized that airway 8‐isoprostane would be significantly higher following a HFM as compared to a moderate‐fat meal (MFM).

METHODS

Eight non‐asthmatic men (age: 25.8 ± 6.9 years, ≤30 minutes of exercise per week) completed two trials in a randomized cross‐over design. Following a 10‐hour fast, subjects consumed either a HFM (17 kcal/kg body mass, 60% fat, 23% CHO) or a MFM (8.5 kcal/kg body mass, 30% fat, 52% CHO). Exhaled breath condensate was collected at baseline, 3 hours and 6 hours post‐HFM for assessment of free 8‐isoprostane in the airways. Venous blood samples were collected at baseline and every hour until 6 hours post‐HFM to assess triglyceride responses.

RESULTS

Fasting triglycerides (MFM: 104.4 ± 47.8 mg/dL, HFM: 121.6 ± 74.7 mg/dL, p=0.59) and 8‐isoprostane levels (MFM: 2.03 ± 0.63 pg/mL, HFM: 1.75 ± 0.39 pg/mL, p=0.30) were not significantly different between the two meal conditions. Triglycerides significantly increased in both meal conditions, and total area under the curve (AUC) for triglycerides was significantly greater following the HFM (1409.3 ± 815.0 mg/dL × 6 hours) compared to the MFM (819 ± 491.5 mg/dL × 6 hours; p=0.001). 8‐isoprostane decreased significantly in MFM from baseline to 3 hours (Δ= −0.44 pg/mL, p=0.03), but was not different from 3 to 6 hours (Δ= −0.09 pg/mL, p=0.73). 8‐isoprostane post‐HFM did not significantly change from baseline to 3 hours (Δ=0.01 pg/mL, p=0.94), but significantly decreased at 6 hours post‐HFM (Δ= −0.38 pg/mL, p=0.04). For 8‐isoprostane, there was no significant main effect for condition (p=0.25). However, there was a significant interaction effect as a quadratic function between time and condition (p=0.02), where 8‐isoprostane decreased initially post‐MFM, with no change from 3 to 6 hours. Conversely the HFM did not change initially, but decreased significantly from 3 hours to 6 hours post meal.

CONCLUSIONS

In insufficiently active, non‐asthmatic men, airway 8‐isoprostane responds differently to two meal conditions. However, our hypothesis that 8‐isoprostane would be significantly higher in the HFM compared with the MFM, was not supported. Additionally, the changes in 8‐isoprostane were not associated with the changes in triglycerides. Future research should focus on elucidating the mechanisms that explain the postprandial oxidative stress responses to varying meal types.