Is FADS1 rs174547 associated with delta-5 desaturase activity and long-chain polyunsaturated fatty acid levels?

The FADS1 gene is a critical regulator of lipid metabolism, with its variations driving distinct differences in systemic fatty acid composition. Extensive genetic and clinical evidence validates the link between the FADS1 rs174547 polymorphism, enzymatic activity, and circulating lipid profiles.

Impact on delta-5 desaturase activity

• The rs174547 polymorphism is a major determinant of delta-5 desaturase (D5D) activity. Carriers of the minor C-allele experience a pronounced, dose-dependent reduction in D5D activity compared to major-allele (T) homozygotes, reflecting a standardized mean difference (SMD) of approximately -1.55. This impairment is clinically demonstrated by a significant decrease in the product-to-precursor AA:DGLA ratio in blood lipids.

Modulation of circulating LCPUFA levels

• Genotypic variations at rs174547 directly shape circulating long-chain polyunsaturated fatty acid (LCPUFA) concentrations. Individuals with the major TT genotype ("high converters") exhibit elevated levels of arachidonic acid (AA) and eicosapentaenoic acid (EPA). Conversely, TC and CC carriers have significantly lower circulating AA and EPA, alongside an accumulation of upstream precursors like linoleic acid and alpha-linolenic acid.

Molecular mechanism

• The FADS1-encoded D5D enzyme catalyzes the rate-limiting conversion of dihomo-gamma-linolenic acid (DGLA) to AA, and eicosatetraenoic acid to EPA. The rs174547 variant alters FADS1 expression, directly regulating this enzymatic bottleneck and dictating the efficiency of systemic LCPUFA biosynthesis.

Bottom line

• The FADS1 rs174547 polymorphism is a highly validated genetic modifier of PUFA metabolism; the minor C-allele significantly impairs D5D activity, resulting in lower circulating levels of crucial downstream LCPUFAs like AA and EPA.