FFAR4 and hydrops fetalis: Furthermore, dietary supplementation with n-3 polyunsaturated fatty acids (PUFAs) can inhibit the cardiac fibrosis in HF by the interaction with nuclear factor erythropoietin 2 related factor 2 (Nrf2), G-protein coupled receptor (GPR), or free fatty acid receptor 4 (Ffar4) [54,55].