Metabolic Signalling Peptides and Their Relation to Clinical and Demographic Characteristics in Acute and Recovered Females with Anorexia Nervosa

<b>Background/Objectives</b>: Recent research has established that metabolic factors may increase the vulnerability to develop anorexia nervosa (AN). The aim of this study was to explore the serum concentrations of leptin, insulin-like growth factor-1 (IGF-1), insulin and insulin receptor substrate (IRS-1) as possible state or trait biomarkers for AN in the acute and recovery (recAN) phases. Our secondary aim was to test associations between the tested markers and demographic and clinical characteristics. <b>Methods</b>: This cross-sectional study included data from 56 participants with AN, 24 recAN participants and 51 healthy controls (HCs). Enzyme-linked immunosorbent assays (ELISAs) were used to quantify serum concentrations of leptin, IGF-1, insulin and IRS-1. An analysis of covariance (ANCOVA) and linear regression models were utilised to test our results. <b>Results</b>: There were significant differences with a large effect size between the groups for serum leptin (<i>p</i> < 0.001; <i>d</i> = 0.80), whereby people with AN had lower leptin than those with recAN (<i>p</i> = 0.023; <i>d</i> = 0.35) and HCs (<i>p</i> < 0.001; <i>d</i> = 0.74). The between-group comparison of IGF-1 did not reach significance, although the effect size was moderate (<i>d</i> = 0.6) and was driven by lower levels of IGF-1 in people with acute AN compared to HCs (<i>p</i> = 0.036; <i>d</i> = 0.53). Serum insulin and IRS-1 did not differ between groups. <b>Conclusions</b>: Low leptin levels seen in individuals with AN may be due to starvation leading to fatty tissue depletion. Understanding the regulation of IGF-1 and insulin signalling over the course of the disorder requires further investigation.