Circulating LEAP-2 Levels in Adult Growth Hormone Deficiency and Their Relationship With IGF-1

Liver enriched antimicrobial peptide-2 (LEAP-2) is an endogenous antagonist of ghrelin, which acts as an allosteric modulator of growth hormone secretagogue receptors. It is expressed predominantly in liver, followed by kidney, jejunum, duodenum and stomach. Its expression in conditions of metabolic impairment, obesity for instance, may be upregulated, usually pairing with a concomitant reduction in ghrelin secretion. Weight gain and hyperglycaemia seem to be the main trigger factors for LEAP-2 production. Adult growth hormone deficiency (aGHD) is known as a pathological condition characterized by metabolic impairment (insulin resistance, weight gain, increased fat mass, decreased lean mass). To the best of our knowledge, no study in literature deals with the problem of circulating LEAP-2 levels in GHD. Therefore, the primary endpoint of this cross-sectional observational study was to evaluate circulating LEAP-2 levels in GHD in comparison to healthy controls whether the secondary endpoint was to evaluate any possible correlation with IGF-1 and metabolic parameters in such condition. 30 patients were included in the study. Group A included adult GHD: 15 patients, 7 females and 8 males, mean±standard error of the mean (SEM) age 54.6±3.51 years, BMI 29,95±1.63 kg/m2). The etiologies of GHD were empty sella (n=6), idiopathic (n=6), post-surgical hypopituitarism (n=2), pineal cyst (n=1). Group B was formed by controls: 15 patients, 11 females and 4 males, mean±SEM age 40.33±2.61 years, BMI 24.19±1.33 kg/m2. They were evaluated for: serum glucose and insulin, HOMA-index, QUICKI-index, Total/LDL/HDL cholesterol, triglycerides, IGF-1 and LEAP-2 (measured using Human LEAP-2 ELISA kit, Phoenix Pharmaceuticals Inc, according to manufacturer’s instructions). Circulating LEAP-2 is significantly higher in GHD than in control group (26.98±3.12 vs 18.7±1.9 ng/ml, p=0.03). LEAP-2 levels in our cohort was not influenced by BMI, while a significant direct correlation between LEAP-2 and age was detected in aGHD group. A strong significative inverse correlation between LEAP-2 and IGF-1 was evidenced in aGHD (r2=0.5). Finally, in this group, LEAP-2 inversely correlates with total cholesterol (r2=0.45). As expected circulating LEAP-2 levels, in a condition of metabolic impairment such as GHD, were higher than controls even if no correlation with BMI was evidenced in our cohort. The inverse correlation between LEAP-2 and IGF-1 in GHD patients may suggest a body adjustment in a worse clinical condition. LEAP-2 may act as a brake for ghrelin production, thus preventing further weight gain and fat mass increase, although losing its secretagogue effect.