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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.

ABSTRACTThe purpose of this study was to assess the heat strain experienced by children during unstructured physical activity outdoors in a temperate continental summer climate. Eighteen children (7 girls, 12.1 ± 1.7 years) performed up to 4 h of outdoor free-play (duration: 218 ± 33 min; air temperature of 24.5 ± 3.9°C and relative humidity of 66.2 ± 9.2%). Urine specific gravity (USG) was measured pre- and post-free-play, while body core temperature (Tco, ingestible pill) and heart rate (HR) were measured continuously. Physiological strain index (PSI) was calculated from Tcoand HR (scale: 0 (none) to 10 (very high)). Activity levels were categorized as rest, light, moderate, and vigorous based on the metabolic equivalent of task, estimated from video analysis. Most children were euhydrated pre (78%, USG ≤ 1.020), but not post-free-play (28%, USG ≤ 1.020). Mean and peak Tco, HR, and PSI responses were 37.8 ± 0.3°C and 38.4 ± 0.3°C, 133 ± 14 bpm and 180 ± 12 bpm, and 4.7 ± 1.1 (low) and 7.4 ± 1.0 (high), respectively. All children reached peak Tco≥38.0°C, with seven ≥38.5°C, and the highest at 38.9°C. The children spent 58 ± 15% of free-play engaged in moderate-to-vigorous intensity physical activity. During free-play, all of the children performed moderate-to-vigorous intensity physical activity, which was associated with pronounced elevations in heat strain.

Recently, a malfunction of the autophagic pathway has been implicated with impaired glucose metabolism and progression from prediabetes to type 2 diabetes. The aims of this study were to investigate the effect of exercise and rapamycin (RAPA) treatment on the autophagic process in peripheral blood mononuclear cells (PBMCs) from people with prediabetes compared with control subjects.