OR22-07 Novel Variants in Protein Kinase a Signaling-Related Genes Identified in Obese Children with and Without NAFLD

Abstract

Context: Nonalcoholic fatty liver disease (NAFLD) is estimated to affect nearly 10% of Americans age 2-19 and about 38% of those affected are obesei. NAFLD is characterized by triglyceride accumulation in hepatocytes and can progress to nonalcoholic steatohepatitis, end stage liver disease and hepatocellular carcinoma. The underlying causes of NAFLD in youth are unclear although obesity, insulin resistance, type 2 diabetes mellitus and metabolic syndrome are risk factors. Genome-wide association studies and candidate gene studies have found several single nucleotide polymorphisms that affect susceptibility to and progression of NAFLD, but clinical translation for some of these genetics is lackingii. Study design: Because mouse models of dysregulated PKA signaling demonstrate the centrality of this pathway in hepatic lipid metabolism and glucose homeostasis, we hypothesized that defects in hepatic PKA signaling genes could affect susceptibility to or severity of NAFLD in children. We asked whether identified variants might be associated with differences in clinical markers in a cohort of obese pediatric patients (non-NAFLD, n=295; NAFLD, n=165) followed at Yale Medical School, where clinical data and genomic DNA were collected. Exon sequencing of 54 PKA-related candidate genes included those coding for PKA subunits, PDEs and other proteins integral to the hepatic PKA system. Variants were ranked by allele frequency and potential pathogenicity. Ongoing analyses aim to identify associations between single variants and potential additive effects with clinical parameters (anthropometric, liver function, glucose metabolism, plasma lipids). Results: Gene variants were identified in ABCA1, ADCY4, ADCY5, AKAP7, CREB3L1, CREB3L4, CREM, CYP27A1, DHCR7, ERN1, GYS2, IL6, IL10RB, MC2R, PDE1B, PDE2A, PDE3B, PDE4A, PDE7B, PDE10A, PDE11A, PPARGC1B, PRKAR2A, and PRKAR1B. Reported variants met criteria of high to moderate impact based on 9 in silico scores that predict pathogenicity. Allele frequency ranged from 2.5 to over 50 times higher in our cohort than the general population. One or more variant was identified in 34.9% of non-NAFLD and 19.4% of NAFLD patients (p=.0004). Conclusion: We report PKA-related gene variants among a cohort of pediatric obese patients that might serve as useful predictors of risk of NAFLD or obesity. Further analyses will help determine whether any of these variants may play a functional role in NAFLD. Endnotes i Schwimmer JB, Deutsch R, Kahen T, Lavine JE, Stanley C, Behling C. Pediatrics. 2006;118(4):1388. ii Vespasiani-Gentilucci U, Gallo P, Dell’Unto C et al. World J Gastroenterol. 2018;24(43):4835-4845.