Causal association between polyunsaturated fatty acids and acne: a two-sample Mendelian randomization study

BACKGROUND: Observational studies have demonstrated a close association between polyunsaturated fatty acids (PUFAs) and acne. However, the findings of clinical trials have been inconsistent, leaving the causal relationship between PUFAs and acne unclear. OBJECTIVES: To investigate the causal association between genetically proxied PUFAs and acne risk. METHODS: Mendelian randomization (MR) was performed using single nucleotide polymorphisms associated with PUFAs as instrumental variables. The causal associations between PUFAs and acne were estimated among 115 006 UK Biobank participants and 363 927 participants of Finnish descent. RESULTS: Genetically predicted docosahexaenoic acid (DHA) levels [β = -0.303, 95% confidence interval (CI) -0.480 to -0.126; P = 7.74 × 10-4] and its percentage to total fatty acids (β = -0.402, 95% CI -0.651 to -0.258; P = 5.91 × 10-6) showed a significant causal association with a decreased risk of acne. Conversely, genetically predicted percentages of linoleic acid (LA) in total fatty acids (β = 0.768, 95% CI 0.411-0.126; P = 2.87 × 10-4) and omega-6 : omega-3 ratio (β = 0.373, 95% CI 0.142-0.604; P = 4.48 × 10-3) were robustly associated with an increased risk of acne. These effects were attenuated after excluding a genetic variant of rs174528 located upstream of FADS1, highlighting the biologic link between FADS1 and delta-5 desaturase activity. Multivariable MR analysis indicated that PUFAs were causally associated with acne, independent of body mass index. CONCLUSIONS: Our study indicates that high DHA levels and their ratios to total fatty acids have causal protective effects against acne, while high LA levels and omega-6 : omega-3 ratio are associated with increased acne risk. This association was largely attributable to the influence of genetic variants related to FADS1.