Review of eating disorders and oxytocin receptor polymorphisms.

Oxytocin, a nine amino acid peptide synthesised in the hypothalamus, has been widely recognised for its role in anxiolysis, bonding, sociality, and appetite. It binds to the oxytocin receptor (OXTR)—a G-protein coupled receptor—that is stimulated by the actions of oestrogen both peripherally and centrally. Studies have implicated OXTR genotypes in conferring either a risk or protective effect in autism, schizophrenia, and eating disorders (ED). There are numerous DNA variations of this receptor, with the most common DNA variation being in the form of the single nucleotide polymorphisms (SNPs). Two OXTR SNPs have been most studied in relation to ED: rs53576 and rs2254298. Each SNP has the same allelic variant that produces genotypes AA, AG, and GG. In this critical review we will evaluate the putative role of rs53576 and rs2254298 SNPs in ED. Additionally, this narrative review will consider the role of gene-environment interactions in the development of ED pathology. The OXTR SNPs rs53576 and rs2254298 show independent associations between the A allele and restrictive eating behaviours. Conversely, the G allele of the OXTR rs53576 SNP is associated with binging behaviours, findings that were also evident in neuroanatomy. One study found the A allele of both OXTR SNPs to confer risk for more severe ED symptomatology while the G allele conferred some protective effect. An interaction between poor maternal care and rs2254298 AG/AA genotype conferred increased risk for binge eating and purging in women. Individual OXTR SNP are unlikely in themselves to explain complex eating disorders but may affect the expression of and/or effectiveness of the OXTR. A growing body of G x E work is indicating that rs53576G homozygosity becomes disadvantageous for later mental health under early adverse conditions but further research to extend these findings to eating pathology is needed. The GWAS approach would benefit this area of knowledge. Oxytocin is a chemical made in the brain that affects human behaviour in areas from anxiety, bonding right through to appetite. Oxytocin works by binding to a specific cellular receptor. In humans, the genes that specify this receptor are found in slightly different versions that are inherited from each parent. Research has suggested that individuals who possess speicfic combinations of oxytocin receptor gene variants may be more susceptible to certain kinds of mental illness. This paper considers two different versions of the oxytocin receptor gene most studied in relation to eating disorders. The two different versions considered in this review do not seem to affect the structure of the oxytocin receptor itself. Together, research indicates that the presence or absence of a particular receptor gene variant in an individual might have some predictive capability in respect of potential susceptibility to eating disorders. However, further research is necessary as some of the findings are contradictory. In addition, environmental factors—such as poor maternal care early in life—have also been demonstrated to be important in determining whether an individual will develop an eating disorder. Research in this area would benefit from non-hypothesis driven studies.