Table 4.

Genetic abnormalities involved in the onset and/or outcomes of CD.

Genetic Abnormality	Mechanism of Action	Effects
Polymorphisms of the human receptor of vitamin D	The vitamin D receptor form is different from the classical one [121,122,123]	Polymorphism increasing susceptibility to IBD [121,122,123]
PPAR-γ variant Pro12Ala	Regulation of the immune response [134,135]	Variant protecting from CD [134,135]
miR-595 and miR-1246	Small non-coding RNA molecule promote RNA silencing and post-transcriptional regulation of gene expression [139,140,141]	High levels of circulating miR-595 and miR-1246 are associated with a more aggressive form of the disease [141]
Polymorphisms of the gene BCMO1 (R267S: rs12934922 or A379V: rs7501331)	The conversion from beta-carotene to retinol does not occur [136,137,138]	Limited vitamin A production [136,137,138]
FFAR2, FADS1, FADS2, PPARA, PPARG, XRCC1, SCD1 gene mutations	Act on serum levels of LC-PUFA-omega-3 and omega-6 fatty acids [138]	Affect metabolic pathways and inflammation; increase cancer risk [138]
FUT2 gene loss of function	FUT2 function is lost [150]	Significant reduction of Bifidobacterium bifidum, B. adolescentis, and B. catenulatum/pseudocatenulatum colonization [150]

Abbreviations: IBD, Inflammatory Bowel Disease; PPAR-γ Peroxisome proliferator-activated receptor gamma; miR-595, MicroRNA 595; miR-1246, MicroRNA 1246; BCMO1, β,β-carotene-15,15’-monooxygenase 1; FFAR2, Free Fatty Acid Receptor 2; FADS1, Fatty Acid Desaturase 1; FADS2, Fatty Acid Desaturase 2; PPARA, Peroxisome Proliferator Activated Receptor Alpha; PPARG, Peroxisome Proliferator-Activated Receptor Gamma; XRCC1, X-ray Repair Cross Complementing 1; SCD1, Stearoyl-CoA Desaturase-1; LC-PUFA-omega-3 and omega-6, Long Chain Polyunsaturated Fatty Acids-omega-3 and omega-6; FUT2, Fucosyltransferase 2.