rs1799752 — ACE I/D (Alu insertion/deletion)

ACE I/D — The Causal Variant Behind the Endurance–Power Dial

The angiotensin-converting enzyme¹¹ angiotensin-converting enzyme
ACE cleaves angiotensin I into angiotensin II (a potent vasoconstrictor) and inactivates bradykinin (a vasodilator). It sits at the centre of the renin-angiotensin-aldosterone system (RAAS) governing blood pressure, fluid balance, and vascular tone gene contains one of the most studied variants in exercise genetics — and this entry covers the variant itself, not its proxy. rs1799752 is the actual 287-base-pair Alu repeat insertion/deletion in intron 16 of ACE; it is the causal variant that drives the differences in circulating and tissue ACE activity. The tag SNP rs4341 (already in the GeneOps database) is a C/G single-nucleotide variant in near-complete linkage disequilibrium with this locus and is used when direct structural genotyping is unavailable. Where a WGS-based genome file genotypes this structural variant directly, rs1799752 gives the most precise readout of ACE biology.

The I allele (insertion present) results in lower ACE activity; the D allele (deletion) results in higher activity. A substantial fraction of inter-individual variation in serum ACE levels is attributable to this single locus — making it the dominant genetic determinant of RAAS tone across the population.

The Mechanism

The Alu element in intron 16 is not just a neutral marker — it exerts a measurable effect on ACE gene expression at the mRNA level. A direct allele-specific quantification study²² direct allele-specific quantification study
Suehiro T et al. Increased amount of the angiotensin-converting enzyme (ACE) mRNA originating from the ACE allele with deletion. Hum Genet, 2004 in individuals heterozygous for the I/D measured mRNA from each allele separately. The D allele produced, on average, 1.79 times more ACE mRNA than the I allele in the same cell. This is mechanistically distinct from what a nearby tag SNP captures: the Alu element itself influences mRNA stability or splicing efficiency³³ mRNA stability or splicing efficiency
Intronic Alu elements are known to modulate alternative splicing and affect pre-mRNA folding, secondary structure, and interaction with RNA-binding proteins — any of these could reduce I-allele mRNA abundance or stability relative to D-allele mRNA, resulting in a constitutively lower transcriptional output from the I chromosome.

The functional consequence cascades downstream. DD homozygotes carry substantially more serum ACE activity than II homozygotes; ID heterozygotes are intermediate. Higher ACE activity means more angiotensin II⁴⁴ angiotensin II
Angiotensin II is a potent vasoconstrictor and anabolic signalling molecule; it promotes skeletal muscle protein synthesis and cardiac hypertrophy via AT1 receptors, and drives aldosterone secretion, sodium retention, and increased blood pressure and less bradykinin⁵⁵ bradykinin
Bradykinin is a vasodilator that activates nitric oxide synthase, promotes glucose uptake in working muscle via GLUT4 translocation, and improves metabolic efficiency during sustained aerobic effort; it is rapidly degraded by ACE. The II genotype does the reverse: lower ACE, prolonged bradykinin, more efficient aerobic muscle metabolism.

The Evidence

The 2024 updated meta-analysis of rs1799752 and public-health sports modalities — the most comprehensive analysis to date — examined 16 studies through June 2024 and found the II genotype associated with elite endurance athlete status⁶⁶ II genotype associated with elite endurance athlete status
Sommers L et al. Role of the ACE I/D Polymorphism in Selected Public Health-Associated Sporting Modalities: An Updated Systematic Review and Meta-Analysis. Int J Environ Res Public Health, 2024 at OR=1.54 (95% CI 1.24–1.91) versus controls and OR=1.56 (95% CI 1.07–2.28) versus power athletes. Sport-specific analysis revealed the strongest enrichment in triathlon (OR=2.69) and open-water swimming (OR=2.27), with running at OR=1.76.

The mechanistic underpinning for the endurance advantage was clarified by a training study of army recruits⁷⁷ training study of army recruits
Woods DR et al. Endurance enhancement related to the human ACE I-D polymorphism is not due to differences in the cardiorespiratory response to training. Eur J Appl Physiol, 2002 showing that II individuals gained significantly more efficiency — lower oxygen cost at a fixed workload — without a corresponding difference in peak VO2max. The advantage is therefore economic: doing the same aerobic work for less oxygen expenditure, not a larger aerobic ceiling.

For the D allele, evidence converges on strength adaptation and cardiovascular remodelling. DD individuals show larger strength gains per training cycle, greater left ventricular mass increases in response to endurance training, and higher enrichment among sprint and power athletes in multiple cohorts.

The pharmacogenomic dimension of rs1799752 is distinct from its athletic profile. A study of IgA nephropathy patients⁸⁸ study of IgA nephropathy patients
Teranishi J et al. ACE insertion/deletion polymorphism (rs1799752) modifies the renoprotective effect of renin-angiotensin system blockade. J Renin Angiotensin Aldosterone Syst, 2014 found that ACE inhibitors and ARBs significantly slowed disease progression in DD patients but had no measurable renoprotective effect in II patients. This genotype-dependent drug response reflects the underlying biology: DD individuals have more angiotensin II substrate for ACE inhibitors to suppress, whereas II individuals already have low baseline RAAS activity, leaving little room for further reduction.

Practical Implications

• II genotype: Lower ACE activity confers genuine aerobic efficiency advantages, particularly in sustained-output sports (running, triathlon, rowing, altitude events). Training response is likely to favour volume over intensity. ACE inhibitor or ARB therapy, if ever prescribed, may provide less renal protection than it would in DD individuals.
• DD genotype: Higher ACE activity supports strength adaptation and power-based athletics, but also elevates RAAS tone at rest. Cardiovascular monitoring matters regardless of fitness level. If prescribed ACE inhibitors or ARBs (for hypertension, heart failure, or renal protection), the drug acts on a more active target enzyme — these medications tend to be more effective and may produce larger blood pressure reductions.
• ID genotype: Intermediate ACE activity with genuine versatility across athletic modalities. No strong pull toward either endurance or power; training response will be shaped more by program design than genotype.

Relationship to rs4341

rs4341 (the C/G tag SNP, C=insertion, G=deletion) is in near-complete linkage disequilibrium with rs1799752 and can be used as a proxy when direct structural genotyping is unavailable — which is the case for all short-read consumer chip arrays (23andMe v3/v4/v5). When a genome file includes rs1799752 directly (WGS with structural variant calling), this entry provides the definitive interpretation. When only rs4341 is present, the rs4341 entry applies. The underlying biology is identical; the two entries differ only in the confidence of the genotype call and the mechanistic framing.

Interactions

The ACE I/D has been studied alongside ACTN3 R577X (rs1815739)⁹⁹ ACTN3 R577X (rs1815739) in multiple athlete cohorts. The compound combination of ACE II (insertion homozygote) with ACTN3 XX (both alpha-actinin-3 null) appears to compound endurance advantages; ACE DD with ACTN3 RR compounds power and sprint tendencies. These are the best-studied two-locus interactions in exercise genetics — observational, not interventional, but supported by coherent physiological logic.

ACE activity also interacts functionally with AGTR1 A1166C (rs5186)¹⁰¹⁰ AGTR1 A1166C (rs5186) — the angiotensin II type 1 receptor variant. DD individuals who also carry the AGTR1 C allele (more responsive AT1 receptor) may have amplified angiotensin II signalling through both higher ligand production and enhanced receptor sensitivity. This combination may be relevant to cardiovascular risk assessment.