A thickened heart loses fuel flexibility before it loses function
In short
The metabolic abnormalities of myocardial hypertrophy — loss of substrate flexibility, impaired fatty acid oxidation, increased glycolysis with anaplerotic rerouting, mitochondrial calcium and quality-control defects, NAD-sirtuin disruption, branched-chain amino acid accumulation, and ketone body adaptation — are now understood as early drivers rather than passive consequences of increased workload. They interact with growth signalling through AMPK, mTOR, YAP, and SIRT3/SIRT5/SIRT6, and this review argues that adaptive compensation and maladaptive remodelling separate at exactly this metabolic layer.
Myocardial hypertrophy starts as an adaptation to mechanical, neurohumoral, or metabolic stress. The problem is persistence: sustained hypertrophy raises the risk of heart failure, arrhythmia, and death. What this review reframes is the order of events. Metabolic remodelling is an early driver, not a passive consequence of the added workload.
A healthy heart has substrate flexibility. It burns mostly fatty acids and switches to glucose, lactate, or ketones as conditions demand. In hypertrophic myocardium, the switching itself is what breaks first.
What changes metabolically in a hypertrophic heart?
- Substrate inflexibility and impaired fatty acid oxidation — the default fuel stops being usable
- Increased glycolysis with anaplerotic rerouting — the shift is toward glucose, but it is not burned to completion
- Mitochondrial calcium and quality-control defects, redox stress, and ferroptosis
- NAD-sirtuin disruption, branched-chain amino acid accumulation, and ketone body adaptation
Every term here is one lifters already know
These abnormalities interact with AMPK, mTOR, PKA, YAP, STAT3, ERR, SIRT3/SIRT5/SIRT6 and inflammatory programmes. The axes discussed as growth signalling in skeletal muscle share their wiring with pathological remodelling in the heart. The same protein produces different outcomes in different tissue — the same problem covered in mTORC1 is not a volume knob.
Resistance training raising an NAD-related enzyme (resistance training raises an NAD enzyme) and the NAD-sirtuin disruption described here are two ends of one axis. But one end is healthy skeletal muscle and the other is diseased myocardium, and no human data connects them directly.
Can a blood test separate good from bad hypertrophy?
Metabolomics has moved from single metabolites toward integrated panels combining circulating acylcarnitines, amino acids, ketones, redox markers, and imaging-derived hypertrophy. Interpretation still depends heavily on aetiology, disease stage, sex, renal function, diabetes, and therapy, so it does not yet read off a single lab sheet.
Branched-chain amino acids accumulating in hypertrophic myocardium is not evidence that BCAA supplementation harms the heart. The review describes the metabolic state of diseased tissue; it does not address supplement intake in healthy people.
Where does this sit right now?
The review names its own remaining work: distinguishing adaptive compensation from maladaptive remodelling, validating tissue-to-plasma concordance, building longitudinal human cohorts, and harmonising multi-omics pipelines. It is equally direct that emerging therapies — NAD repletion, sirtuin activation, BCAA catabolism modulation, ferroptosis inhibition — require biomarker-guided trials first. This is a mechanistic map, not a clinical tool. Telling an athlete's heart from a pathological one still rests on the molecular programme difference and a physician's judgement.
Frequently asked questions
When do metabolic changes appear in cardiac hypertrophy?
This review treats metabolic remodelling as an early driver rather than a passive consequence of increased workload, meaning fuel metabolism begins shifting before the heart is visibly thickened.
What is substrate flexibility?
It is the heart's ability to switch fuels as conditions change — burning mostly fatty acids at rest and moving to glucose, lactate, or ketones when needed. Hypertrophic myocardium loses that switching capacity, with impaired fatty acid oxidation and increased glycolysis.
Should I stop taking BCAA supplements?
The review does not support that conclusion. Branched-chain amino acid accumulation in hypertrophic myocardium describes the metabolic state of diseased tissue, not the effect of supplementation in healthy people.
Can blood work reveal what kind of hypertrophy someone has?
Not yet. Metabolomics is moving toward panels combining circulating acylcarnitines, amino acids, ketones, redox markers, and imaging measures, but interpretation depends strongly on aetiology, stage, sex, renal function, diabetes, and therapy, so no standardised clinical assay exists.
What are the limits of this review?
It is a review, and it identifies missing longitudinal human metabolomic cohorts as a core gap, along with unvalidated tissue-to-plasma concordance, the unsolved problem of separating adaptive from maladaptive remodelling, and the absence of harmonised multi-omics pipelines.
Source: PubMed