Elevations in serum brain-derived neurotrophic factor following occupational heat stress are not influenced by age or common chronic disease

ABSTRACT

With global warming, workers are increasingly exposed to strenuous occupations in hot environments. Given age- and disease-associated declines in thermoregulatory function, older workers are at an elevated risk of developing heat-related injuries. Brain-derived neurotrophic factor (BDNF) is thought to confer neuroprotection during acute exercise, however, the influence of environmental heat on BDNF responses during prolonged work remains unclear. Therefore, we evaluated serum BDNF concentrations before and after 180 min of moderate-intensity treadmill walking (200 W/m2) and after 60 min of post-exercise recovery in temperate (wet-bulb globe temperature (WBGT) 16°C) and hot (WBGT 32°C) environments in 13 healthy young men (mean [SD; 22 [3] years), 12 healthy older men (59 [4] years), 10 men with hypertension (HTN) (60 [4] years), and 9 men with type 2 diabetes (T2D) (60 [5] years). In the temperate condition, all but one participant (1 HTN) completed the 180 min of exercise. While exercise tolerance in the heat was lower in older men with HTN (117 min [45]) and T2D (123 min [42]) compared to healthy older men (159 min [31]) (both p ≤ 0.049), similar end-exercise rectal temperatures (38.9°C [0.4]) were observed across groups, paralleled by similar elevations in serum BDNF across groups at end-exercise (+1106 pg/mL [203]) and end-recovery (+938 pg/mL [146]; all p ≤ 0.01) in the heat. No changes in serum BDNF were observed in the temperate condition. Our findings indicate similar BDNF responses in individuals with HTN or T2D compared to their healthy counterparts, despite exhibiting reduced tolerance to heat.

KEYWORDS:

• Neurotrophin
• temperature
• physical activity
• aging
• hypertension
• diabetes

Abbreviations

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Acknowledgments

We thank all the individuals who dedicated their time to participate in this study. We also thank Dr. Martin Poirier, Brian Friesen, Dr. Joo-Young Lee, Dr. Sheila Dervis, Andrew D’Souza, Emma McCourt, Audrey Chamberlain, Andre Larocque-Graham, François Beaulieu, Maura Rutherford, Brodie Richards, Madison Schmidt, Serena Topshee, and Morgan McManus for their assistance with data collection, as well as Nick Koetje, Kristina-Marie Janetos, and Emily Tetzlaff for their assistance with blood analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

G.P.K. and S.R.N. conceptualized the research. J.J.M., K.E.K., and N.G. performed blood analysis. N.G. drafted the manuscript. All authors interpreted the results, revised, and approved the final version of the manuscript.

Data availability

Data are available from the corresponding author upon request.

Additional information

Funding

Project supported by the Ontario Ministry of Labor (16-R-036) and the Canadian Institutes of Health Research (funds held by G.P.K.).