Evaluation of the frequency of RETN c.62G>A and RETN c.-180C>G polymorphisms in the resistin coding gene in girls with anorexia nervosa.

Introduction: Anorexia nervosa (AN) is a serious psychosomatic syndrome, classified as an eating disorder. AN patients strive to lose weight below the normal limits defined for a specific age and height, achieving their goal even at the expense of extreme emaciation. AN has a multifactorial aetiology. Genetic factors are believed to be significant in the predisposition to the development of AN. In girls suffering from AN significantly lower levels of resistin (RES) in blood serum are observed as compared to healthy girls. These differences may lead to a thesis that functional genetic polymorphisms in RES coding genes can be responsible for this phenomenon. In our pilot study we demonstrated significant differences in the distribution of genotypes in the locus RETN c.-180C>G of the RES gene in 67 girls with AN and 38 healthy girls. It seems reasonable to compare the frequency of polymorphisms of RETN c.62G>A and RETN c.-180C>G in the RES gene in girls with AN and in healthy subjects in a bigger cohort and to analyse correlations between individual variants of the polymorphisms referred to above and the RES levels in blood plasma.

Material And Methods: The study covered 308 girls with the restrictive form of AN (AN) and 164 healthy girls (C) (aged 11-19 years). The RES levels in blood serum were determined by means of the ELISA method on a Bio-Vendor machine from LLC (Asheville, North Carolina, USA). The DNA isolation was carried out by means of Genomic Mini AX BLOOD (SPIN). The PCR reaction was carried out on a ThermoCycle T100 thermocycler. 80-150 ng of the studied DNA and relevant F and R starters were added to the reaction mixture. The reaction products were subjected to digestion by restriction enzymes and separated on agarose gels (RFLP).

Results: The average RES level in blood serum in the AN group was significantly lower (p < 0.0001) than in the C group. The distribution of genotypes in the locus RETN c.62 of the RES gene was similar in both groups. A significant difference was demonstrated in the distribution of genotypes in the polymorphic site RETN c.-180 of the RES gene between AN and C (p = 0.0145) and in the distribution of the C and G alleles in the locus RETN c.-180 (p < 0.0001). The C allele occurred significantly more frequently than the G allele in the C group as compared to the AN group. In all the study subjects jointly (AN and C) a significant positive correlation between the blood RES levels on one hand and the body mass (r = 0.42; p < 0.0001) and BMI (r = 0.61; p< 0.0001) on the other was observed. There was no correlation between the concentration of RES in blood serum and the distribution of genotypes in the loci of the resistin gene referred to above.

Conclusions: The CG genotype in the locus RETN c.-180 C>G of the RES gene may constitute one of the factors predisposing to the development of AN in girls. The genotype in the loci RETN c.62 G>A and RETN c.-180 C>G of the resistin gene has no influence on the levels of this hormone in blood in AN patients.