Full Project II: Novel Risk Factors and Disease Associations of Liver Cancer in Guam

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PROJECT SUMMARY/ABSTRACT The US territory of Guam has a staggeringly high burden of liver cancer with incidence and mortality more than twice that of overall rates in the United States (US) where rates have nearly tripled over the past three decades. Excess risk is most prominent among CHamorus who are the native people of Guam, comprising 42% of the population. Hepatocellular carcinoma (HCC), the primary form of liver cancer, develops entirely within the context of progressive chronic liver disease (CLD) characterized by advancing levels of fibrosis. Thus, there is an urgent need to understand the etiology of progressive CLD in CHamorus and to identify novel strategies and targets for prevention and early intervention. Our proposed research will address whether oral dysbiosis and sleep/circadian rhythm disturbance contribute to liver fibrosis through glucose and lipid dysmetabolism and the potential modifying effect of other exposures. We propose a case-control study of 300 liver fibrosis cases and 300 matched controls among CHamorus in Guam. Liver fibrosis, a well-established precursor of liver cancer, as well as liver steatosis as a secondary outcome, will be measured by transient elastrography (Fibroscan). The Specific Aims of Full Project II are to: 1) Evaluate the association of oral dysbiosis with liver fibrosis and steatosis. Oral dysbiosis will be defined as deleterious patterns of the oral microbiome and/or the presence of periodontal disease. We will perform bacterial 16S rRNA sequencing to measure oral bacterial diversity and composition. We will determine periodontal disease by clinical examination and self-report. The association between oral dysbiosis and liver fibrosis, with or without stratification by steatosis grades, will be evaluated; the potential modifying effects of other exposures (e.g., betel nut chewing, viral hepatitis, alcohol) and the mediating effects of glucose and lipid dysmetabolism will be assessed. We hypothesize that having moderate to severe liver fibrosis is associated with: 1a) reduced oral microbial diversity, enriched pathogenic and depleted commensal bacteria, and aberrations in insulin- signaling bacterial genes; 1b) the presence and severity of periodontal disease; and 1c) oral dysbiosis through and independently of glucose/lipid dysmetabolism. 2) Evaluate the associations of sleep (quantity and quality) and circulating Mrna expression levels of circadian clock genes with liver fibrosis and steatosis. We will determine sleep duration and quality using validated questionnaires and analyze the expression of the period (Per1, Per2, Per3) and cryptochrome (Cry2) genes in blood as a biomarker of circadian rhythm. We hypothesize that liver fibrosis is associated with: 2a) short sleep duration and sleep apnea; 2b) reduced expression of the clock genes; and 2c) sleep/circadian rhythm disturbances through and independently of glucose/lipid dysmetabolism.