Serum Klotho Concentrations in Young and Older Men During Prolonged Exercise in Temperate and Hot Conditions

Abstract

Background: The protein klotho protects cellular function during various physiological stressors, such as exercise, however it is unknown how the age-related decline in klotho production affects responses during exercise, especially in the heat.

Objective: Our objective was to determine the effect of exercise in temperate and hot environmental conditions on serum klotho concentrations in young and older men.

Methods: 12 young (mean ± SD: 22 ± 3 years) and 12 older (59 ± 4 years) men performed 180 minutes of moderate-intensity treadmill walking (metabolic rate: 200 W/m²) in a temperate (wetbulb globe temperature [WBGT] 16°C, achieved with 21.9°C, 35% relative humidity [RH]) and hot (WBGT 32°C, achieved with 41.4°C, 35% RH) environment. Serum klotho was assessed before and after exercise, as well as 60-min post-exercise recovery in the respective environments.

Results: Absolute klotho concentrations were greater in young versus older men during all measured time points in the temperate (p = 0.032), but not the hot condition (p = 0.064). In the hot condition, the change in serum klotho from baseline was significantly higher after exercise in the heat (mean ± SEM: +251 ± 73 pg/mL) than the temperate (+75 ± 57 pg/mL) environment in both groups (p = 0.026). However, this elevation was not maintained during recovery.

Conclusion: We showed that prolonged exercise in a temperate environment does not elicit a klotho response in either group. In contrast, despite lower resting klotho levels, the older men showed a similar exercise-induced increase in serum klotho response as their younger counterparts.

Keywords: aging; exercise; heat stress; klotho; metabolic stress; serum.