SORT1 rs12740374 T allele lowers LDL cholesterol.

The association between the SORT1 rs12740374 T allele and reduced levels of low-density lipoprotein cholesterol (LDL-C) is a well-established finding in human genetics, supported by robust evidence from genome-wide association studies (GWAS) and detailed molecular mechanisms.

Clinical and genetic evidence

Extensive genetic research consistently identifies the rs12740374 variant at the 1p13 locus as a powerful predictor of circulating LDL cholesterol levels.

• Association strength: Large-scale GWAS have shown the T allele (the minor allele) to be one of the most significant common genetic variants affecting lipid levels. In studies of diverse populations, including American Indian and European-descent cohorts, this SNP has reached exceptional levels of statistical significance (e.g., p-values reaching $1 \times 10^{-102}$).
• Consistent effect: While the exact magnitude of effect varies slightly between individuals and populations, the directionality remains constant: the presence of the T allele correlates with significantly lower plasma LDL-C concentrations compared to the G allele.

Mechanistic explanations

The rs12740374 T allele functions as a regulatory switch that increases the production of the sortilin protein (encoded by SORT1) within the liver. This occurs through a dual-action pathway involving both reduced production and increased removal of lipoproteins.

• Altered hepatic secretion: The T allele creates a binding site for the transcription factor C/EBP$\alpha$, leading to increased SORT1 mRNA and protein expression in hepatocytes. Increased hepatic sortilin acts as a chaperone that redirects apolipoprotein B (ApoB)-containing particles—the precursors to LDL—toward lysosomal degradation via autophagy. This prevents the full assembly and secretion of very-low-density lipoproteins (VLDL) into the bloodstream.
• Enhanced LDL clearance: Sortilin also facilitates the direct clearance of LDL from the plasma. It functions as an alternative receptor, binding circulating LDL particles and internalizing them for degradation. Furthermore, sortilin interacts with PCSK9, a protein that normally degrades LDL receptors. By modulating PCSK9 trafficking, increased sortilin levels help maintain a higher density of LDL receptors on the surface of liver cells, further boosting the liver's ability to clear cholesterol from the blood.

Bottom line

The SORT1 rs12740374 T allele is definitively associated with lower LDL cholesterol. This effect is driven by increased hepatic sortilin expression, which simultaneously reduces the secretion of cholesterol precursors and enhances the clearance of circulating LDL particles.