Acylated and unacylated ghrelin levels in normal weight and obese children: influence of puberty and relationship with insulin, leptin and adiponectin levels.

Background. Ghrelin circulates in blood as acylated (AG) and unacylated (UAG) ghrelin. The physiological role of the two forms is poorly understood, in particular in childhood. Aim of the study was to evaluate the AG and UAG levels in obese and normal weight children prepubertal and pubertal and their relationship with insulin, leptin and adiponectin levels. Subjects and Methods. A population-based study in which AG, UAG, leptin, adiponectin, glucose, insulin, testosterone or estradiol levels, insulinemic indexes were evaluated in 82 normal weight (NW) and 58 obese (OB) children. Results. Both ghrelin forms in NW were higher (AG, p<0.02; UAG, p<0.0001) than in OB subjects, with the ratio of AG/UAG similar. While no differences were observed for gender, when evaluated for the puberty AG (p<0.01) and UAG (p<0.0001) levels were higher in prepubertal than pubertal NW and OB subjects. Adiponectin levels in NW were higher (p<0.001), while leptin and insulin levels were lower (p<0.0001) than OB.. NW showed HOMA and HOMAβ indices lower than OB (p<0,0001) with a QUICKI index higher (p<0.0001). AG and UAG levels correlated to each other (p<0.0001), each showing a negative correlation to age, height, weight and BMI. Both forms, but more strongly UAG, correlated with adiponectin, leptin, and insulin. Conclusions. OB children show lower levels of both AG and UAG when compared to NW subjects, with lower levels during puberty. These results demonstrate a peculiar strong relationship between UAG levels and metabolic parameters in the pediatric population, suggesting a role for UAG in metabolic functions.