SAT-403 Palmitoleate Reverses Palmitate-Induced Autophagy

Autophagy is a well-known process that regulates cellular homeostasis by degrading malformed organelles and dysfunctional proteins. Normal autophagy is crucial to maintain the functionality of hypothalamic neurons, which are important in regulating energy balance. Fatty acids can be sensed by hypothalamic neurons and affect cell viability, inflammation and metabolic pathways. We recently found that the most prevalent dietary saturated fatty acid palmitate (PA) was able to induce hypothalamic autophagy by as yet undefined mechanisms. We are currently investigating if an unsaturated fatty acid palmitoleate (PO) has any effect on autophagy modulation. Given that unsaturated fatty acids protect other cells from palmitate-mediated dysfunction, we hypothesized that palmitoleate could protect neurons from palmitate-induced autophagy. We used the clonal, embryonic male, mHypoE-46, and adult-derived male, mHypoA-2/29, neuronal cell lines to evaluate autophagy modulation in response to palmitoleate (PO) treatment. Neurons were first treated with 25, 50 or 250 µM of PO alone. In the mHypoE-46 cells, the highest 250 µM concentration of PO was extremely toxic to the cells, as determined by cell death. In order to measure autophagy vacuoles (autophagosomes and autolysossomes) flow cytometry technique was performed. Partial data suggested that 25 and 50 µM PO was able to reduce overall autophagy. When we performed a co-treatment using PA (25 µM) and PO (25 µM), we observed that PA-mediated autophagy induction was blocked. In the mHypoA-2/29 cells, all concentrations of PO alone, including 250 µM, were able to reduce autophagy modulation, as detected by flow cytometry. We also tested the effect of a mixture of multiple saturated and unsaturated fatty acids (palmitate, stearic, oleic, linoleic and arachidonic) in the mHypoE-46 cells and found that this mixture did not affect autophagy. Thus, the saturated fatty acid PA increases autophagy, and we present evidence that an unsaturated fatty acid PO may rescue this induction, contributing to an overall protective response in neurons. We are now investigating the molecular mechanisms by which specific fatty acids control neuronal autophagy and predict that these will be unique to saturated versus unsaturated fatty acids. Understanding how fatty acids affect autophagy in neurons that control food intake could potentially represent a promising therapeutic target against obesity.