An athlete's enlarged heart and a diseased one differ at the RNA level
In short
A heart enlarged by training and a heart enlarged by disease look similar but run different molecular programmes. The cardiac lncRNAs CPhar, lncExACT1, and Mhrt779 discriminate physiological from pathological hypertrophy, and some of them encode an antihypertrophic 'memory' that persists after the stimulus ends. In skeletal muscle, CYTOR and TUG1 modulate fast-twitch myogenesis, mitochondrial function, and fibre-type specification. These lncRNA programmes are highly specific to exercise modality, tissue, and cell type — part of why the same training produces different adaptation in different people.
The pathways explaining training adaptation looked settled long ago. AMPK-PGC-1α, Ca²⁺/calcineurin, mTORC1 — endurance, fibre type, protein synthesis, one axis each. What this review argues is that there is another regulatory layer sitting on top: RNA that never becomes protein, the long non-coding RNAs.
The sharpest finding is cardiac. CPhar, lncExACT1, and Mhrt779 discriminate physiological from pathological hypertrophy. A heart thickened by training and a heart thickened by hypertension or valve disease both read as thickened myocardium on an echo — but in the expression pattern of these RNAs they are already different states.
What does 'antihypertrophic memory' mean?
Some of these lncRNAs are reported to encode antihypertrophic memory: a trace that persists after the stimulus is gone, leaving the heart less inclined toward pathological growth. It points at exercise leaving behind not only a load response in the moment, but a state that changes how the tissue responds later.
Which lncRNAs act in skeletal muscle?
- CYTOR, TUG1 — exercise-induced, modulating fast-twitch myogenesis, mitochondrial function, and fibre-type specification
- Endothelial NEAT1 — integrates aerobic training with m⁶A-modulated pyroptosis and works in an atheroprotective direction
- MALAT1 — mediates neuroprotection after exercise preconditioning in ischaemia/reperfusion models
Is this why the same programme works differently on different people?
Partly. Omics and network analyses found lncRNA programmes to be highly modality-, tissue-, and cell-type-specific. Aerobic and resistance training flip different switches, and inside one body muscle, heart, and vessels each run their own programme. It is one more reason variance in training response does not reduce to effort or willpower.
Will a blood test show your adaptation?
Candidate stage only. Circulating MALAT1 and HOTTIP are supported by emerging clinical data as candidate biomarkers of vascular function and training adaptation. If that holds, something currently inferred only from performance — is this programme actually producing adaptation — becomes visible in a blood draw. But candidate is the operative word; there is no standardised assay.
Does any of this change training today?
No. The review is explicit about its own ceiling: mechanistic evidence is limited to a small number of flagship lncRNAs, and non-muscle tissues and inter-organ communication remain underexplored. Pulling a training prescription out of this runs far ahead of the evidence.
What it does change is the interpretive frame. An enlarged heart is not good or bad on the basis of size. When a heavy lifter gets a left-ventricular wall-thickness finding at a check-up, the number is not the answer — which programme produced that growth is, and that judgement still belongs to a physician.
This is a review, and much of the mechanistic evidence it cites comes from animal models and cell work. What has been confirmed in humans is expression patterns at the omics level and a few circulating biomarker candidates.
On the hypertrophy signalling side, see mTORC1 is not a volume knob.
Frequently asked questions
How do you tell athletic heart enlargement from pathological hypertrophy?
The cardiac lncRNAs CPhar, lncExACT1, and Mhrt779 discriminate the two at the molecular level. Both present as thickened myocardium, but the expression programmes differ, and some of these lncRNAs encode an antihypertrophic memory that persists after the stimulus ends.
What do lncRNAs do in training adaptation?
They form an additional regulatory layer operating above classical pathways such as AMPK-PGC-1α, Ca²⁺/calcineurin, and mTORC1. In skeletal muscle CYTOR and TUG1 modulate fast-twitch myogenesis, mitochondrial function, and fibre-type specification, while endothelial NEAT1 links aerobic training to atheroprotection.
Does this explain why the same programme gives different results?
In part. Omics and network analyses found lncRNA programmes to be highly specific to exercise modality, tissue, and cell type. Aerobic and resistance training activate different programmes, and within one person muscle, heart, and vasculature each run their own.
Can a blood test measure training adaptation?
Not yet in practice. Circulating MALAT1 and HOTTIP have emerging clinical support as candidate biomarkers of vascular function and training adaptation, but they are not standardised clinical assays.
Should this research change how you train?
No. Mechanistic evidence is confined to a small number of flagship lncRNAs, and non-muscle tissues and inter-organ communication remain largely unexplored. Deriving a training prescription at this stage runs ahead of the evidence.
Source: PubMed