Assessing the Induced Adipose Tissue Browning Effects of Hypoxic Swimming and Cold-Water Exposure in Healthy Human Participants Using Contrast-Enhanced Ultrasound (CEUS)

Abstract

Introduction:The prevalence of obesity in Canada has increased in recent years. Due to this, studies have been conducted on brown adipose tissue (BAT) as it consumes energy to regulate thermal homeostasis rather than storing it as fat. Particularly, studies have shown that exercise regimens combined with a cold-temperature setting elicit the most "browning" of white adipose tissue (WAT). Hypoxic exercise has been seen to prevent obesity and some metabolic disorders, but the browning of WAT via hypoxic exercise has yet to be studied. Thus, this study aims to determine the independent and synergistic effects of cold-water exposure and hypoxic exercise BAT activation and adipose tissue browning in healthy adult males. Methods: Moderately active healthy adult males will be randomized in three experimental groups (i.e., Cold-water exposure group (CG), Hypoxic exercise group (HG), and combined cold-water and hypoxic exercise group (HC)) and one control group. Familiarization sessions will be done prior to the three testing sessions. Cold conditions will be induced via exercise in 15 o C water. Hypoxic conditions will be induced via the endogenous-hypoxic breathing technique. Contrast-Enhanced Ultrasound (CEUS) scans of regions of interest (i.e., supraclavicular, axilla, anterior abdominal wall, and the inguinal fossa) will be obtained before and after familiarization and testing sessions and will be further utilized for analysis. Results: It is anticipated that all experimental groups will demonstrate BAT activation and adipose tissue browning as reflected by the Acoustic Intensity (AI) curve and color-flow doppler intensity. Particularly, more pronounced in the supraclavicular region for CG, inguinal fossa for HG, and both for HC. Discussion: This research protocol anticipates evidence that suggests independent cases of BAT activation and adipose tissue browning, reflected in the CG and HG. This protocol also anticipates synergistic effects of cold water and hypoxic exercise in inducing BAT activation and adipose tissue browning, reflected by HC. Conclusion: Thus, hypoxia and cold-water interventions may have potential clinical use for managing the rising cases of obesity. Future implications may include public health initiatives that inform the population on ways to mitigate the effects of obesity and provide a potential therapeutic avenue to treat the disease.