Inhibition of GCN5 decreases skeletal muscle fat metabolism during high fat diet feeding
Bibliographic record
Abstract
Abstract Introduction GCN5 ( Kat2a ) is a lysine acetyl transferase capable of acetylating and inhibiting PGC-1α activity. As such, it is described as a negative regulator of PGC-1α and subsequently restricts mitochondrial content. However, elimination of GCN5 in skeletal muscle does not increase mitochondrial content or alter lipid metabolism under normal metabolic conditions. GCN5 levels increase with high-fat diet (HFD) feeding in rodents. Additionally, the GCN5 homolog, PCAF, has previously been shown to also acetylate and inhibit PGC-1α and therefore may possibly compensate for loss of GCN5. Objective The objective of this study was to examine if with HFD feeding that elimination of GCN5 ( Kat2a gene) from skeletal muscle would elicit improvements in mitochondrial and metabolic markers. Methods Skeletal muscle specific GCN5 knockouts ( Gcn5 skm-/- ) were fed an HFD. Body composition, cardio-metabolic and physical fitness outcomes were monitored. Additionally, cultured myotubes were treated with a pan-GCN5/PCAF inhibitor and examined for changes in mitochondrial markers. Results Elimination of skeletal muscle GCN5 did not alter body composition, tissue masses, energy intake, or energy expenditure measurements of mice fed an HFD. Furthermore, whole body glucose homeostasis and cardiac measurements were not altered. There were few differences in lipid metabolism genes, relatively more glucose oxidation versus Gcn5 skm+/+ (wildtype) mice, and a reduction in Pdk4 expression. Exercise capacity and mitochondrial content levels were not altered in Gcn5 skm-/- mice. Further, elimination of GCN5 in skeletal muscle increased Kat2b (PCAF) mRNA expression; however, inhibition of GCN5/PCAF bromodomains in cultured myotubes did not increase oxidative metabolism genes and decreased expression of some mitochondrial genes and Pdk4 mRNA. Conclusions Neither elimination of GCN5, nor simultaneous inhibition of GCN5 and its homolog PCAF improved skeletal muscle mitochondrial content under normal or HFD-fed conditions. Despite this, GCN5 may play a role in regulating macronutrient preference by regulating Pdk4 content. Thus, HFD/macronutrient excess revealed novel roles of GCN5 in skeletal muscle. Highlights – Skeletal muscle specific elimination of Gcn5/Kat2a decreases fat oxidation without 1) preventing high-fat diet induced weight gain, 2) improving whole body glucose handling, or 3) improving skeletal muscle mitochondrial content. – Inhibition of the GCN5 and PCAF bromodomains and Gcn5 ablation decreases expression of Pdk4 . – Expression of Kat2b increases with Gcn5 elimination in skeletal muscle. – Inhibition of the GCN5 and PCAF bromodomains do not result in increased skeletal muscle mitochondrial content.
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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) | 0.002 | 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".