PROJECT SUMMARY
Non-alcoholic fatty liver disease (NAFLD) affects >35% of older adults in the US. It is now the primary etiology
of chronic liver disease and liver cancer, and the driver of the recent upward trend in these lethal diseases. A
dysbiotic gut microbiome has been associated with NAFLD, but mostly in small-scale, cross-sectional or clinic-
based studies. Population-based longitudinal studies are needed to provide evidence for the temporal
relationship of the gut microbiome with the progression of NAFLD. In the cross-sectional Multiethnic Cohort
(MEC) Adiposity Phenotype Study (APS; P01 CA168530), we showed a significant difference in gut microbial
composition and inferred microbial function by NAFLD status, including enrichment of Fusobacterium and
endotoxin-producing bacteria and altered microbial pathways for bile acid and simple carbohydrate metabolism
in NAFLD. We now hypothesize that specific gut bacterial features (genera, metabolic pathways and blood
endotoxin biomarker lipopolysaccharide binding protein (LBP)) are associated with increase in liver fat and liver
fibrosis over time. We also hypothesize that several dietary factors are associated with NAFLD progression
and that fibrosis-promoting gut bacterial features mediate these associations. We propose a longitudinal
investigation by efficiently adding a ~10-year follow-up assessment among 300 of the MEC-APS participants,
aged 60-77 years at baseline and of three racial/ethnic groups (Japanese American, Native Hawaiian or
White), across a wide range of baseline liver fat. We will re-assess liver fat using MRI and measure liver
stiffness using MR elastography, gold-standard methods for non-invasive quantification of liver fat and liver
stiffness, respectively, and perform 16S rRNA gene sequencing (follow-up stool samples) and metagenomic
sequencing (baseline and follow-up stool samples). Specific Aims are to: 1) evaluate the change in specific gut
bacterial features (abundance of genera, metabolic pathways, and LBP) over time in relation to the change in
liver fat; 2) evaluate the change in gut bacterial features over time in relation to (2a) liver stiffness at follow-up
and (2b) change in a blood biomarker panel for liver fibrosis (Enhanced Liver Fibrosis (ELF) score), and (2c)
validate the top two bacterial features associated with liver stiffness using ddPCR; and 3) assess the
association of diet (3 dietary pattern scores for overall diet quality and 7 key components) with ELF-based
change in liver fibrosis and explore the mediation by fibrosis-promoting gut bacterial features from Aim 2,
stratified by liver fat level. Our results will identify gut microbial features associated with early NAFLD
progression, while specifically addressing the needs of understudied Asian Americans and Native Hawaiians
(NOT-HL-23-001), two high-risk populations for NAFLD and liver cancer. The strengths of the proposed
longitudinal design and rigorous imaging and laboratory methods will aid in understanding NAFLD progression
involving the gut microbiome. These findings may be used to inform novel targeted intervention strategies to
prevent NAFLD progression and, ultimately, reduce liver cancer burden in multiple racial/ethnic populations.
