The brown adipose tissue glucagon receptor is functional but not essential for control of energy homeostasis in mice
Why this work is in the frame
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Bibliographic record
Abstract
Objective: Administration of glucagon (GCG) or GCG-containing co-agonists reduces body weight and increases energy expenditure. These actions appear to be transduced by multiple direct and indirect GCG receptor (GCGR)-dependent mechanisms. Although the canonical GCGR is expressed in brown adipose tissue (BAT) the importance of BAT GCGR activity for the physiological control of body weight, or the response to GCG agonism, has not been defined. Methods: We studied the mechanisms linking GCG action to acute increases in oxygen consumption using wildtype (WT), Ucp1 / and Fgf21 / mice. The importance of basal GCGR expression within the Myf5 domain for control of body weight, adiposity, glucose and lipid metabolism, food intake, and energy expenditure was examined in Gcgr BAT/ mice housed at room temperature or 4 C, fed a regular chow diet (RCD) or after a prolonged exposure to high fat diet (HFD). Results: Acute GCG administration induced lipolysis and increased the expression of thermogenic genes in BAT cells, whereas knockdown of Gcgr reduced expression of genes related to thermogenesis. GCG increased energy expenditure (measured by oxygen consumption) both in vivo in WT mice and ex vivo in BAT and liver explants. GCG also increased acute energy expenditure in Ucp1 / mice, but these actions were partially blunted in Ffg21 / mice. However, acute GCG administration also robustly increased oxygen consumption in Gcgr BAT/ mice. Moreover, body weight, glycemia, lipid metabolism, body temperature, food intake, activity, energy expenditure and adipose tissue gene expression profiles were normal in Gcgr BAT/ mice, either on RCD or HFD, whether studied at room temperature, or chronically housed at 4 C. Conclusions: Exogenous GCG increases oxygen consumption in mice, also evident both in liver and BAT explants ex vivo, through UCP1independent, FGF21-dependent pathways. Nevertheless, GCGR signaling within BAT is not physiologically essential for control of body weight, whole body energy expenditure, glucose homeostasis, or the adaptive metabolic response to cold or prolonged exposure to an energy dense diet.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it