Acute hyperglycemia does not alter central respiratory CO <sub>2</sub> chemoreflex responsiveness
Bibliographic record
Abstract
The control of breathing is modulated by two distinct but interacting respiratory chemoreceptor compartments: peripheral chemoreceptors (PCRs; carotid bodies) and central chemoreceptors (CCRs; brainstem). The PCRs respond to variety of chemostimuli, including arterial oxygen, arterial carbon dioxide, glucose, insulin and temperature, and are now thought to act as metabolic sensors. However, CCRs have only been characterized as carbon dioxide/acid sensors (PCO 2 /[H + ]). PCRs respond to chemostimulation faster than CCRs, which may mask CCR responses to stimuli like acute hyperglycemia. The aim of this study was to characterize the relationship between alterations in blood glucose concentration and central respiratory chemoreflex responsiveness via hyperoxic rebreathing in healthy humans. We hypothesized that experimentally‐induced relative hyperglycemia following an oral glucose tolerance test (OGTT; 75g, 300 ml) would (a) increase the rate of CO 2 accumulation during rebreathing and (b) augment central respiratory chemoreflex responsiveness due to a synergistic effect of hyperglycemia on the CO 2 sensitivity of CCR neurons. In 10 healthy participants, we measured minute ventilation (V I ; L/min; pneumotachometer) and end‐tidal carbon dioxide (P ET CO 2 ; Torr; gas analyzer). We used the modified hyperoxic rebreathing test to isolate CCRs and quantify the central chemoreflex responsiveness to increases in metabolically‐derived CO 2 . Blood glucose levels were higher 30‐min following the OGTT beverage (i.e., glucose‐loaded) compared to fasted (7.8±1.1 vs. 4.7±0.4 mmol/L; P<0.0001). During rebreathing, the rate of end‐tidal (P ET )CO 2 accumulation was greater in the glucose loaded trial compared to the fasted trial (0.086±0.007 vs. 0.07±0.008 vs. Torr/sec; P=0.0002). These findings confirm the hyperglycemic stimulation between trials. However, the central respiratory chemoreflex responsiveness during rebreathing was not different between glucose loaded and fasted trials (2.3±1.4 vs. 2.5±1.8 vs. L/min/Torr CO 2 ; P=0.59). These preliminary findings suggest that relative hyperglycemia does not affect the central respiratory chemoreflex responsive to hyperoxic rebreathing. The CCRs may be a more specialized respiratory chemoreceptor, with a phenotype to detect only metabolically‐derived accumulations in CO 2 . Support or Funding Information NSERC Discovery and MRU Faculty of Science and Technology This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".