Acylglycerol Recycling from Triacylglycerol to Phospholipid, Not Lipase Activity, Is Defective in Neutral Lipid Storage Disease Fibroblasts
Bibliographic record
Abstract
Neutral lipid storage disease (NLSD) is an autosomal recessive disorder in which excess triacylglycerol (TG) accumulates in most cells. Although it has been hypothesized that the TG accumulation is caused by a functional defect in cytosolic lipase activity, we were able to expose TG hydrolysis in NLSD cells by using triacsin C, an inhibitor of acyl-CoA synthetase that blocks the reincorporation of hydrolyzed fatty acids into glycerolipids. Our data suggest that TG lipolysis in NLSD cells is masked by rapid TG resynthesis, occurring because released acylglycerols cannot be used for phospholipid synthesis. In uptake studies, triacsin C blocked the incorporation of [3H]glycerol into glycerolipids, incorporation of [14C]oleate into TG, but not incorporation of [14C]oleate into phospholipid. Thus, the drug inhibited both de novo synthesis of glycerolipids via the glycerol-3-phosphate pathway and the synthesis of TG from diacylglycerol. The drug did not appear to block reacylation of lysophospholipids. Triacsin C caused a loss of about 60% of the TG mass from both NLSD and oleate-loaded control cells. Rates of TG lipolysis were similar in NLSD cells and oleate-loaded control cells labeled with [6-(7-nitro-2,1,3-benzoxadiazol-4-yl)-amino]hexanoic acid or labeled with [14C]oleate or [3H]glycerol and chased in the presence of triacsin C. During a 96-h chase, [14C]oleate reincorporation into the different phospholipid species increased only in control cells. Similar results were observed when NLSD, and control cells were chased after labeling with [3H]glycerol. These data strongly suggest that normal human fibroblasts mobilize stored TG for phospholipid synthesis and that recycling to PC occurs via a TG-derived mono- or diacylglycerol intermediate. Normal recycling to phosphatidylethanolamine may primarily involve TG-derived acyl groups rather than an acylglycerol precursor. NLSD cells appear to have a block in this recycling pathway with the result that both hydrolyzed fatty acids and the acylglycerol backbone are re-esterified to form TG. Because the NLSD phenotype includes ichthyosis, fatty liver, myopathy, cardiomyopathy, and mental retardation, the recycling pathway appears to be critical for the normal function of skin, liver, muscle, heart, and the central nervous system.
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How this classification was reachedexpand
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 | 0.001 |
| 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 | 0.001 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".