Genome-wide association and transcriptome analysis suggests total serum ghrelin to be linked with GFRAL

Abstract

Objective Ghrelin is an orexigenic peptide hormone involved in the regulation of energy homeostasis, food intake and glucose metabolism. Serum levels increase anticipating a meal and fall afterwards. Underlying genetic mechanisms of the ghrelin secretion are unknown. Methods Total serum ghrelin was measured in 1501 subjects selected from the population-based LIFE-ADULT-sample after an overnight fast. A genome-wide association study (GWAS) was performed. Gene-based expression association analyses (transcriptome-wide association study (TWAS)) are statistical tests associating genetically predicted expression to a certain trait and were done using MetaXcan. Results In the GWAS, three loci reached genome-wide significance: the WW-domain containing the oxidoreductase-gene (WWOX; P = 1.80E-10) on chromosome 16q23.3-24.1 (SNP: rs76823993); the contactin-associated protein-like 2 gene (CNTNAP2; P = 9.0E-9) on chromosome 7q35-q36 (SNP: rs192092592) and the ghrelin And obestatin prepropeptide gene (GHRL; P = 2.72E-8) on chromosome 3p25.3 (SNP: rs143729751). In the TWAS, the three genes where the expression was strongest associated with serum ghrelin levels was the ribosomal protein L36 (RPL36; P = 1.3E-06, FDR = 0.011, positively correlated), AP1B1 (P = 1.1E-5, FDR = 0.048, negatively correlated) and the GDNF family receptor alpha like (GFRAL), receptor of the anorexigenic growth differentiation factor-15 (GDF15), (P = 1.8E-05, FDR = 0.15, also negatively correlated). Conclusions The three genome-wide significant genetic loci from the GWA and the genes identified in the TWA are functionally plausible and should initiate further research.