Heart disease is the leading cause of mortality in the United States in both men and women. Obesity is
rapidly growing epidemic and a major risk factor for the development of cardiomyopathies and heart failure. The
pathology of obesity-related cardiomyopathies is associated with abnormal cardiac accumulation of fat and
lipotoxic metabolites. Preventing such lipotoxic effects is a potential avenue for therapeutic intervention in heart
disease and heart failure. However, the molecular mechanisms of cardiac lipotoxicity remain elusive.
In this proposal, we seek to address these gaps in knowledge by leveraging our established, robust
Drosophila heart models of ceramide- and high-fat-diet (HFD)-induced lipotoxic cardiomyopathy (LCM), which
exhibit LCM-like pathology observed in mammalian LCM, including compromised contractility and elevated
accumulation of both triglyceride fat and sphingolipid ceramide with either diet. Drosophila is an extremely
versatile genetic model system with highly conserved metabolic pathways and cardiac physiology, well suited to
address fundamental mechanisms of LCM. Nevertheless, we will validate our findings in Drosophila in human
cardiomyocytes that are derived from induced pluripotent stem cell (hiPSC-CMs) to gain further human relevant
insights into the mechanisms of LCM (in collaboration with co-Investigator Dr. Alexandre Colas – see letter).
In ceramide-protein trap experiments we identified 3 enriched ontologies of putative ceramide interacting
proteins (180 putative overlapping mouse-human CIPs): (1) sarcomeric regulatory proteins (40 CIPs), including
the myosin chaperone Uncoordinated-45b (Unc45b), (2) metabolic regulatory proteins (33 CIPs), including fatty
acid synthase FASN, and (3) apoptosis & DNA damage response (DDR) proteins (21 CIPs). Indeed, found that
cardiac Unc45 overexpression or FASN RNAi knockdown in the fly heart prevents ceramide-induced LCM. LCM-
inducing and subthreshold-sensitizing ceramide and high fat treatments will be used to interrogate the above
CIPs in participating in LCM. This will be the first step in determining in detail the mechanisms how ceramide
interacts with these 3 classes of proteins and how that disrupts or protects cardiac function and homeostasis.
The goal is to construct and test a myofibrillar maintenance/lipogenesis/ apoptosis-centric regulatory network
weighted with novel CIPs, which we will experimentally evaluate further in our LCM models.