Preliminary Observations on the use of Short‐term Ambient Cooling during a Day‐long Extreme Heat Exposure on Autophagy in Older Adults
Bibliographic record
Abstract
Aging is associated with impairments in autophagy, which is an integral cellular survival mechanism. Our ongoing work indicates that heat stress may worsen this age‐related impairment after a daylong (9‐hour) passive heat exposure (40°C) as assessed in peripheral blood mononuclear cells (PBMC). This was paralleled by a greater elevation in body core temperature in older compared to young adults, which together with diminished autophagy, may contribute to compromised health during extreme heat events (EHE). National and international health agencies widely recommend the use of short‐term ambient cooling (STAC; e.g., visiting a cooling center) to protect the health of vulnerable individuals during an EHE; however, its effects on body core temperature and autophagic function are currently unclear. We therefore sought to extend upon our previous work by assessing if STAC would mitigate rises in body core temperature, and thus, the heat‐related decline in autophagy in older adults during a simulated EHE. We evaluated the hypothesis that in parallel to a reduction in body core temperature, autophagy would be preserved in PBMCs from older adults exposed to STAC during the EHE when compared to those without access to a cool room. To assess this hypothesis, as part of a larger study evaluating thermal strain in older adults, autophagy was characterized in PBMCs of 7 older adults (mean [SD] 71 [5] years; 3 women) prior to and following a 9‐h heat exposure (40°C, ~15% relative humidity [RH]), with 2 h of exposure to a cool room (~23ºC; STAC) for hours 5 and 6. Responses were compared with 10 older adults (71 [3] years; 2 women) who had previously participated in a prolonged 9‐h exposure to an EHE (40°C, ~15% RH). Changes in autophagy were assessed via Western blot for autophagy‐related proteins p62 and microtubule associated protein 1 light chain 3 beta (LC3)‐II. All proteins were normalized to β‐actin and reported as fold changes relative to their respective baseline. Rectal temperature (T re ) was measured throughout and expressed as a change from baseline. Data were compared between‐groups using unpaired t‐tests (α=0.05). Following the first 4 h of heat exposure, T re did not differ between groups (both ~0.9 [0.3]°C; p>0.99), although following STAC (hour 6) T re was lower (by 0.8 [0.4]°C; p<0.001) than the non‐cooled group. Again, however, no significant difference between groups was observed at the end of the 9‐h exposure (both ~0.9 [0.2]°C; p>0.99). Despite this, p62 protein at end‐exposure (9 h) was lower in the STAC group when compared to the non‐cooled group (0.78 [0.51] vs. 2.57 [2.19]; p=0.03) and this was accompanied by a reduction in LC3‐II (0.72 [0.33] vs. 2.13 [1.83]; p=0.04). Given, LC3‐II and p62 undergo lysosomal degradation (indicative of normal autophagic function), our preliminary findings indicate STAC may reduce the time spent in a hyperthermic state, thereby preserving autophagy during a simulated EHE in older adults. Further work is required to evaluate if alternate cooling strategies (i.e., fan use) can preserve autophagic function in older adults during prolonged heat stress.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".