Common misconceptions about de novo lipogenesis
De novo lipogenesis is the cell's endogenous route to fatty acids, distinct from dietary fat intake. This page addresses common misconceptions about the pathway, its enzymes and the models in which it has been studied.
De novo lipogenesis (DNL) is the biochemical pathway by which cells synthesise fatty acids from non-lipid precursors, principally acetyl-CoA derived from carbohydrate and, to a lesser extent, amino acid carbon. It is distinct from the uptake and re-esterification of preformed dietary fatty acids, and the two routes are frequently conflated in popular discussion. The pathway is cytosolic in animals and is centred on the stepwise condensation of acetyl-CoA units into palmitate, catalysed by the multi-domain enzyme fatty acid synthase (FASN), with acetyl-CoA carboxylase (ACC) supplying the malonyl-CoA substrate. The evidence block for this page does not provide a sequence, formula or molecular weight for FASN, and none is asserted here.
The work summarised below centres on the lipogenic enzyme axis — ACC and FASN — and its relationship to hepatic and cardiac lipid handling, including the ceramide synthesis that can follow from sustained lipogenic flux [2].
Research Studies
FASN and ceramide accumulation in arrhythmogenic cardiomyopathy
In arrhythmogenic cardiomyopathy (ACM), a heritable disease caused by desmosomal gene mutations and characterised by progressive myocardial loss and fibrofatty replacement, FASN was reported to be upregulated in cardiomyocytes of ACM patients and of a corresponding model [2]. The same work reported that FASN-mediated de novo lipogenesis promoted ceramide accumulation and myocardial damage in that setting [2]. This is a disease-specific observation in a defined patient and model population, not a general statement about DNL in healthy tissue.
Hepatic steatosis and the definition of NAFLD
Non-alcoholic fatty liver disease (NAFLD) is defined as excessive accumulation of lipids within hepatocytes in the absence of significant alcohol consumption or other causes of chronic liver disease [1]. The minimum criterion for a histological diagnosis is stated in the source as greater than 5 percent, with the remainder of that figure truncated in the available evidence [1]. Affected patients typically present with hepatic steatosis on imaging and elevated liver enzymes alongside features of insulin resistance, including pre-diabetes, type 2 diabetes mellitus, arterial hypertension, dyslipidaemia and visceral obesity [1].
Population scale of NAFLD and why it matters for DNL claims
NAFLD is among the most common liver diseases, reported to affect 25 to 30 percent of the global population and nearly one third of the population in North America [1]. The size of that population is the reason hepatic DNL is so often discussed, and also the reason generalisations drawn from it should be read carefully: prevalence figures describe a disease population, not the behaviour of the pathway in any individual.
| Context | Population or model | Reported finding |
|---|---|---|
| Arrhythmogenic cardiomyopathy | ACM patients and a corresponding model | FASN upregulated in cardiomyocytes; DNL-linked ceramide accumulation and myocardial damage [2] |
| NAFLD | Global and North American populations | Prevalence 25–30% globally; nearly one third in North America [1] |
Insulin resistance as a clinical context, not a mechanism
Insulin resistance, pre-diabetes, type 2 diabetes, arterial hypertension, dyslipidaemia and visceral obesity are described as clinical features accompanying NAFLD presentation [1]. They are descriptors of the patient population. The evidence block does not establish that any one of them causes DNL flux, and no such causal claim is made here.
What the transcriptomic and lipidomic approach can and cannot show
The registered study underlying reference [1] is framed around diet impact on hepatic transcriptomics and lipidomics in pre-diabetes. Transcriptomic and lipidomic readouts describe gene expression and lipid species abundance in the sampled tissue. They do not, on their own, demonstrate flux through DNL, and the evidence block does not report flux measurements.
Animal and in vitro findings and their limits
The ACM findings in reference [2] derive from patient cardiomyocytes and a model system; the evidence block does not specify a human interventional design. Where a finding is animal-only or in vitro, it should be read as such. Extrapolation from a cardiomyopathy model to hepatic lipid handling, or from a disease cohort to healthy individuals, is not supported by the evidence given.
Why 'de novo' is not a synonym for 'dietary'
De novo lipogenesis refers specifically to synthesis from non-lipid precursors. Dietary fat enters lipid pools by absorption and re-esterification. The two are separate inputs, and the evidence block offers no basis for treating them as interchangeable when interpreting a lipidomic or transcriptomic result [1][2].
If you are reading this for personal health reasons
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Sources
- [1] Diet Impact on Hepatic Transcriptomics and Lipidomics in Pre-diabetes — ClinicalTrials.gov, public domain.
- [2] FASN-mediated de novo lipogenesis promotes ceramide accumulation and myocardial damage in arrhythmogenic cardiomyopathy — Europe PMC.