Organ‐Specific Dietary Fatty Acid Uptake in Cold‐Acclimated Humans
Bibliographic record
Abstract
In rodents, brown adipose tissue (BAT) plays an important role in producing heat to defend against the cold and in taking up and dissipating energy from dietary fat (Bartelt et al. Nat Med, 2011). Recent investigations have shown that BAT in humans can also contribute to cold‐induced thermogenesis, but its role in dietary fat metabolism remains unclear. Dietary fat may be responsible for the postprandial accretion of triglycerides in lean tissues in individuals with pre‐diabetes (Labbé SM et al. Diabetes, 2012; Kunach M et al. Diabetes 2015), which impairs insulin sensitivity. Thus, the contribution of BAT to postprandial thermogenesis and dietary fat metabolism warrants further clarification. We used our well‐established positron emission tomography (PET) method with oral administration of 18 F‐fluoro‐thiaheptadecanoic acid ( 18 FTHA) and i.v. 11 C‐acetate to determine the effect of BAT metabolic activation on organ‐specific dietary fatty acid uptake and partitioning in humans. Non‐cold acclimated healthy men took part in 2 metabolic studies before and after a 4‐week cold acclimation, previously shown to increase BAT oxidative capacity (Blondin et al. JCEM, 2014). A standard liquid meal containing the fatty acid PET tracer 18 FTHA was given at the beginning, while 11C‐acetate was given at time 60 min during a 4‐h acute cold exposure. Preliminary results show that fractional dietary fatty acid uptake was greater in BAT, compared to muscle or subcutaneous white adipose tissue (0.31±0.009 min −1 vs. 0.009±0.003 min −1 and 0.018±0.008 min −1 , respectively). However, increasing BAT oxidative capacity 2.9‐fold, through daily cold exposure over 4 weeks, did not increase BAT uptake of dietary fatty acids any further (0.31±0.009 min −1 vs. 0.021±0.006 min −1 ). Dietary fatty acid partitioning was significantly lower in BAT than in the liver and heart (0.37±0.12 SUV mean vs. 2.18±0.53 SUV mean and 1.01±0.30 SUV mean , respectively), but comparable to the levels seen in abdominal subcutaneous white adipose tissues (0.17.±0.05 SUV mean ) and skeletal muscles (0.17.±0.04 SUV mean ). These findings show that although cold‐stimulated BAT can contribute minimally to the clearance of dietary fatty acids in humans, dietary fatty acids are not the primary source of energy for the chronic cold acclimation‐induced increase in BAT oxidative metabolism. Support or Funding Information This research was supported by the Canadian Institutes of Health Research (OG‐3‐10‐2970‐AC) and the Natural Sciences and Engineering Research Council of Canada (RGPIN/326967‐2011).
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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) | 0.001 | 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 | 0.001 |
| 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".