Figure 2: Intravenous ghrelin administration alters the circulating metabolite profile.

Serum metabolite profiles were analyzed from repeated serum samples collected during each of the four sessions (see Figure 1). When comparing area under the curve values using linear mixed-effect models, significant differences between ghrelin and placebo infusions were seen in both the intravenous (IV) alcohol self-administration (ASA) experiment and the IV alcohol clamp (AC) experiment in levels of cortisol (FRD corrected q-value = 0.0003, and <0.0001, respectively), corticosterone (q = 0.0202, and <0.0001, respectively), and glycochenodeoxycholic acid (q = 0.0375, and 0.0013, respectively). Furthermore, during the IV-ASA experiment, significant differences between ghrelin and placebo infusions were seen also in the levels of cortisone (q = 0.0352), fatty acids (FA) 18:1 (q = 0.0406) and FA 18:3 (q = 0.0320), and hippuric acid (q = 0.0112). However, these metabolites were not significantly altered in the IV-AC experiment (cortisone q = 0.5237, FA 18:1 q = 0.9698, FA 18:3 q = 0.9843, and hippuric acid q = 0.9886). Moreover, in the IV-AC experiment, significant differences between the ghrelin and placebo infusions were seen in levels of glycocholic acid (q < 0.0001), and phenylalanine (q = 0.0458). However, these metabolites were not significantly altered in the IV-ASA experiment (glycocholic acid q = 0.3197, and phenylalanine q = 0.9259). Mean ion abundance and standard error of mean are shown for each measurement point. Abbreviations: BrAC=Breath Alcohol Concentration; infusion=continuous infusion of ghrelin or placebo; IV=Intravenous; IV-ASA=IV Alcohol Self-Administration; IV-A=IV Alcohol Clamp; LD=Loading Dose.