Does the GG genotype at PCSK9 rs11591147 mean you do not carry the LDL‑lowering T allele?

The rs11591147 polymorphism in the PCSK9 gene is one of the most well-characterized genetic markers influencing cholesterol metabolism. Scientific evidence strongly supports the claim that the T allele (representing the p.Arg46Leu or R46L missense mutation) is a loss-of-function variant that naturally lowers LDL cholesterol levels.

Clinical and effectiveness evidence

The presence of the T allele at rs11591147 is associated with significant reductions in serum low-density lipoprotein cholesterol (LDL-C) and a decreased risk of cardiovascular disease.

• LDL reduction: In American Indian cohorts, carriers of the T allele demonstrated mean LDL-C levels of 76.9 mg/dL compared to 107.4 mg/dL in those with the GG genotype ($p = 1.4 \times 10^{-5}$).
• Cardiovascular protection: Large-scale studies, including those in Danish populations, show that T-allele carriers experience a 12% to 20% reduction in the risk of coronary heart disease and aortic valve stenosis compared to GG non-carriers.
• Effect of GG genotype: The GG genotype represents the "wild-type" or ancestral state. Individuals with this genotype do not possess the R46L variant and typically have LDL-C levels approximately 24 mg/dL higher than carriers of the protective T allele.

Mechanistic explanations

PCSK9 (Proprotein Convertase Subtilisin/Kexin type 9) plays a central role in cholesterol regulation by binding to LDL receptors (LDLR) on the surface of liver cells and targeting them for degradation.

• Loss-of-function (LOF): The T allele (R46L) impairs the function of the PCSK9 protein, likely by disrupting its secretion, trafficking, or its binding affinity for the LDLR EGF-A domain.
• Increased receptor density: Because the R46L mutation reduces PCSK9's ability to degrade receptors, carriers have a higher density of LDLRs available on their liver cells to clear LDL-C from the bloodstream.
• Wild-type function: In individuals with the GG genotype, PCSK9 functions normally, leading to the standard turnover of LDLRs and higher circulating levels of LDL-C compared to those with the variant.

Bottom line

The claim is fully supported: the rs11591147 T allele is a loss-of-function variant that provides a natural LDL-lowering effect. Carrying the GG genotype means you do not have this specific genetic advantage, resulting in standard PCSK9 activity and higher baseline LDL cholesterol.