PROJECT SUMMARY / ABSTRACT
Systemic lipid homeostasis is controlled by the liver via complex but precisely regulated biochemical, signaling,
and cellular pathways. In obesity, hepatic lipid metabolism is altered, commonly leading to the pathogenic
accumulation of triacylglycerol and to a spectrum of liver disorders known as non-alcoholic fatty liver disease
(NAFLD). NAFLD is considered the hepatic manifestation of metabolic syndrome; as such, it often occurs in a
setting of insulin resistance and is associated with type 2 diabetes, dyslipidemia, and cardiovascular disease. It
is the most prevalent chronic liver disease worldwide, for which there is no approved pharmacotherapy. The
etiology of NAFLD is still unclear and advances in understanding the molecular mechanisms leading to hepatic
triacylglycerol accumulation are critical to the development of targeted therapies. Within the hepatocyte, free
fatty acid molecules experience one of several metabolic fates, including synthesis of complex lipids and
oxidation. An obligatory step in the metabolism of long-chain fatty acids is its activation by thioesterification to
CoA to form acyl-CoA. This reaction is catalyzed by the acyl-CoA synthetase (ACSL) enzymes. The specific
tissue distributions, subcellular locations, and substrate preferences suggest that individual ACSL isoforms have
distinct metabolic functions in partitioning acyl-CoAs into specific metabolic pathways. ACSL3 and ACSL5
isoforms are highly expressed in human and murine livers and studies in cell systems suggest that these
enzymes promote lipogenesis. However, to date, the metabolic roles of ACSL3 and ACSL5 in the liver in vivo
remain unresolved. We hypothesize that ACSL3 and ACSL5 function in the liver to direct acyl-CoA towards lipid
synthesis and away from oxidative pathways, thereby promoting hepatic triacylglycerol accumulation and VLDL
secretion. In Aim 1, we will use AAV-CRISPR/Cas9 technology to generate the first liver-specific knockout mice
for Acsl3 and Acsl5 to test the hypothesis that ACSL3 and ACSL5 activities in the liver contribute to the synthesis
of triacylglycerol, which in turn leads to hepatic steatosis and hypertriglyceridemia. In Aim 2, we will establish the
roles of ACSL3 and ACSL5 in human NAFLD pathogenesis by using AAV-CRISPR/Cas9 to achieve liver-specific
knockout of ACSL3 and ACSL5 in human liver chimeric mice. The proposed research delineates hepatocellular
basis contributing to the progression of metabolic diseases, which is clinically important as it provides new targets
for the management of obesity-related disorders such as NAFLD and dyslipidemia. In addition, this project
provides an intensive research career development training opportunity under the guidance of experienced
mentors in an outstanding scientific environment. This will allow me to consolidate and launch my independent
research program dedicated to the understanding of the molecular basis for human metabolic disorders. The
successful completion of these studies will: (i) provide me with knowledge and skills in liver-targeted genome
engineering and its application to clinically relevant human liver disorders; and (ii) inform an NIH R01 application
for the study of pathophysiological mechanisms that regulate hepatic lipid homeostasis.