Triglyceride-derived fatty acids reduce autophagy in a model of retinal angiomatous proliferation
Emilie Heckel, Gael Cagnone, Tapan Agnihotri, Bertan Cakir, Ashim Das, Jin Sung Kim, Nicholas Kim, Geneviève Lavoie, Anu Situ, Sheetal Pundir, Ye Sun, Florian Wünnemann, Kerry A. Pierce, Courtney Dennis, Grant A. Mitchell, Sylvain Chemtob, Flavio A. Rezende, Gregor Andelfinger, Clary B. Clish, Philippe P. Roux, Przemyslaw Sapieha, Lois E.H. Smith, Jean-Sébastien Joyal
Emilie Heckel, Gael Cagnone, Tapan Agnihotri, Bertan Cakir, Ashim Das, Jin Sung Kim, Nicholas Kim, Geneviève Lavoie, Anu Situ, Sheetal Pundir, Ye Sun, Florian Wünnemann, Kerry A. Pierce, Courtney Dennis, Grant A. Mitchell, Sylvain Chemtob, Flavio A. Rezende, Gregor Andelfinger, Clary B. Clish, Philippe P. Roux, Przemyslaw Sapieha, Lois E.H. Smith, Jean-Sébastien Joyal
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Research Article Ophthalmology Vascular biology

Triglyceride-derived fatty acids reduce autophagy in a model of retinal angiomatous proliferation

Abstract

Dyslipidemia and autophagy have been implicated in the pathogenesis of blinding neovascular age-related macular degeneration (NV-AMD). VLDL receptor (VLDLR), expressed in photoreceptors with a high metabolic rate, facilitates the uptake of triglyceride-derived fatty acids. Since fatty acid uptake is reduced in Vldlr–/– tissues, more remain in circulation, and the retina is fuel deficient, driving the formation in mice of neovascular lesions reminiscent of retinal angiomatous proliferation (RAP), a subtype of NV-AMD. Nutrient scarcity and energy failure are classically mitigated by increasing autophagy. We found that excess circulating lipids restrained retinal autophagy, which contributed to pathological angiogenesis in the Vldlr–/– RAP model. Triglyceride-derived fatty acid sensed by free fatty acid receptor 1 (FFAR1) restricted autophagy and oxidative metabolism in photoreceptors. FFAR1 suppressed transcription factor EB (TFEB), a master regulator of autophagy and lipid metabolism. Reduced TFEB, in turn, decreased sirtuin-3 expression and mitochondrial respiration. Metabolomic signatures of mouse RAP-like retinas were consistent with a role in promoting angiogenesis. This signature was also found in human NV-AMD vitreous. Restoring photoreceptor autophagy in Vldlr–/– retinas, either pharmacologically or by deleting Ffar1, enhanced metabolic efficiency and suppressed pathological angiogenesis. Dysregulated autophagy by circulating lipids might therefore contribute to the energy failure of photoreceptors driving neovascular eye diseases, and FFAR1 may be a target for intervention.

Authors

Emilie Heckel, Gael Cagnone, Tapan Agnihotri, Bertan Cakir, Ashim Das, Jin Sung Kim, Nicholas Kim, Geneviève Lavoie, Anu Situ, Sheetal Pundir, Ye Sun, Florian Wünnemann, Kerry A. Pierce, Courtney Dennis, Grant A. Mitchell, Sylvain Chemtob, Flavio A. Rezende, Gregor Andelfinger, Clary B. Clish, Philippe P. Roux, Przemyslaw Sapieha, Lois E.H. Smith, Jean-Sébastien Joyal

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Figure 5

Human and mouse with RAP phenotypes share a common metabolite signature.

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Human and mouse with RAP phenotypes share a common metabolite signature....
(A) Metabolomics pathway enrichment analysis of differentially regulated metabolites from mouse Vldlr–/– retinas (n = 15) and human RAP vitreous (n = 9) compared with their respective control (WT, n = 12; and macular hole, n = 4). Ac, acetyl; ET, electron transport. (B) Heatmap of TCA cycle metabolites (A) of Vldlr–/– retinas and human RAP and CNV vitreous relative to their respective controls. n = 4 (control), 6 (CNV), and 9 (RAP) human vitreous; 12 (WT) and 15 (Vldlr–/–) retinas. (C) Schematic representation of TCA cycle perturbation hypothesized to contribute to pathological angiogenesis in RAP. IDH2 enzymatic activity is governed by SIRT3. Lower α-KG levels stabilize HIF1α and stimulate VEGFA secretion, increasing vascular supply. (D) Sirt1 and mitochondrial sirtuin (Sirt3, Sirt4, and Sirt5) mRNA retinal expression at P16. n = 12 retinas per group. (E and F) SIRT3 protein expression (E, n = 6 retinas) measured in whole retinas, and (F) mRNA expression in photoreceptors obtained by laser capture microdissection (LCM) of RAP-like lesions (white circles) and adjacent regions (blue circles) of WT and Vldlr–/– retinas by qRT-PCR (n = 6 retinas per group) at P16. Retinal flat mounts were sectioned across the photoreceptor outer nuclear layer (ONL; below the dotted line, left). INL, inner nuclear layer. (G) Normalized enrichment scores (NESs) for the GO_Positive Regulation of Mitochondrial ATP Synthesis Coupled Electron Transport gene set from GSEA of differentially expressed genes between Vldlr–/– and WT across retinal cell types in Vldlr–/– retinas relative to WT. RGCs, retinal ganglion cells; ECs, endothelial cells. n = 3801 WT and 5642 Vldlr–/– cells pooled from 3 retinas per group. Data are represented as mean ± SEM. *P < 0.05, **P < 0.01. One-way ANOVA with Tukey’s multiple-comparison test and 2-tailed Student’s t test. See also Supplemental Figure 5.