Genes, emotions and gut microbiota: The next frontier for the gastroenterologist

Table 1 Gene polymorphisms of the central energy balance and brain reward system

Gene	Locus	SNP (reference sequence)	Risk allele	Clinical implications	Ref.
Central nervous system genes related to hunger and satiety
LEP	7q31.3	-2548 G>A, (rs7799039)	G	Deficient anorectic signal	Mammès et al[84] Hoffstedt et al[85]
LEPR	1p31	668 A>G, Gln223Arg	G	Obesity, low satiety	Boumaiza et al[80] Dougkas et al[81]Mizuta et al[83]
		(rs1137101)
MC4R	18q22	-188 kb T>C, (rs17782313)	C	High energy intake	Loos et al[88]
				Low satiety	Acosta et al[90]
Brain reward system genes related to emotional disturbances
DRD2/ANKK1	11q23.2	2137 G>A, Glu713Lys	A	Addictions, impulsivity,	Blum et al[94]
		(rs1800497)		emotional disturbance
DAT 1/SLC6A3	5p15.3	G>A, (rs2550948)	A	Impulsivity,	Genro et al[96]
		G>A, (rs2652511)	A	increased food intake	Fontana et al[97]
		G>A, (rs1048953)	A
COMT	22q11.21	472 G>A, Val158Met	A (Met)	Impulsivity, cognitive function, anxiety, depression	Egan et al[101]
		(rs4680)			Gao et al[102]
BDNF	11p13	196 G>A, Val66Met	A (Met)	Learning, depression	Bonaccorso et al[104]
		(rs6265)

DRD2/ANKK1: Dopamine receptor 2/ankyrin repeat domain and containing kinase 1 or protein kinase 2 gene; DAT 1/SLC6A3: Dopamine transporter 1/solute carrier family 6 member 3 gene; COMT: Catechol-O-methyltransferase gene; BDNF: Brain-derived neurotrophic factor gene; LEP: Leptin gene; LEPR: Leptin receptor gene; MC4R: Melanocortin-4-receptor gene.