Reginato Andressa, Siqueira Beatriz Piatezzi, Miyamoto Josiane Érica, Portovedo Mariana, Costa Suleyma de Oliveira, de Fante Thaís, Rodrigues Hosana Gomes, Ignácio-Souza Letícia Martins, Torsoni Márcio Alberto, Torsoni Adriana Souza, Le Stunff Hervé, Belsham Denise D, Milanski Marciane
Faculty of Applied Science, University of Campinas, Campinas, Brazil.
Obesity and Comorbidities Research Center, University of Campinas, UNICAMP, Campinas, Brazil.
J Neuroendocrinol. 2020 Oct;32(10):e12900. doi: 10.1111/jne.12900.
High-fat diet (HFD) feeding is deleterious to hypothalamic tissue, leading to inflammation and lipotoxicity, as well as contributing to central insulin resistance. Autophagy is a process that restores cellular homeostasis by degrading malfunctioning organelles and proteins. Chronic HFD-feeding down-regulates hypothalamic autophagy. However, the effects of short-term HFD-feeding and the saturated fatty acid palmitate (PA) on hypothalamic autophagy and in neurones that express neuropeptide Y (NPY) and agouti-related peptide remains unknown. Therefore, we assessed hypothalamic autophagy after 1 and 3 days of HFD-feeding. We also injected PA i.c.v and analysed the modulation of autophagy in hypothalamic tissue. Both interventions resulted in changes in autophagy-related gene profiles without significant differences in protein content of p62 and LC3B-II, markers of the autophagy pathway. When we assessed native NPY neurones in brain slices from PA-treated animals, we observed increased levels of Atg7 and LC3B protein in response to PA treatment, indicating the induction of autophagy. We then tested the direct effects of fatty acids using the immortalised hypothalamic NPY-expressing neuronal cell model mHypoE-46. We found that PA, but not palmitoleate (PO) (a monounsaturated fatty acid), was able to induce autophagy. Co-treatment with PA and PO was able to block the PA-mediated induction of autophagy, as assessed by flow cytometry. When the de novo ceramide synthesis pathway was blocked with myriocin pre-treatment, we observed a decrease in PA-mediated induction of autophagy, although there was no change with the toll-like receptor 4 inhibitor, TAK-242. Taken together, these findings provide evidence that saturated and unsaturated fatty acids can differentially regulate hypothalamic autophagy and that ceramide synthesis may be an important mediator of those effects. Understanding the mechanisms by which dietary fats affect autophagy in neurones involved in the control of energy homeostasis will provide potential new pathways for targeting and containing the obesity epidemic.
高脂饮食（HFD）喂养对下丘脑组织有害，会导致炎症和脂毒性，还会导致中枢胰岛素抵抗。自噬是一个通过降解功能失调的细胞器和蛋白质来恢复细胞内稳态的过程。长期高脂饮食喂养会下调下丘脑自噬。然而，短期高脂饮食喂养和饱和脂肪酸棕榈酸（PA）对下丘脑自噬以及对表达神经肽Y（NPY）和刺鼠相关肽的神经元的影响仍不清楚。因此，我们评估了高脂饮食喂养1天和3天后的下丘脑自噬情况。我们还通过脑室内注射PA，并分析下丘脑组织中自噬的调节情况。两种干预措施均导致自噬相关基因谱发生变化，但自噬途径标志物p62和LC3B-II的蛋白质含量无显著差异。当我们评估PA处理动物脑片中的天然NPY神经元时，我们观察到Atg7和LC3B蛋白水平因PA处理而升高，表明自噬被诱导。然后，我们使用永生化的表达下丘脑NPY的神经元细胞模型mHypoE-46测试了脂肪酸的直接作用。我们发现PA能够诱导自噬，而棕榈油酸（PO，一种单不饱和脂肪酸）则不能。通过流式细胞术评估，PA和PO共同处理能够阻断PA介导的自噬诱导。当用myriocin预处理阻断从头合成神经酰胺的途径时，我们观察到PA介导的自噬诱导作用减弱，尽管Toll样受体4抑制剂TAK-242处理后没有变化。综上所述，这些发现提供了证据，表明饱和脂肪酸和不饱和脂肪酸可以不同地调节下丘脑自噬，并且神经酰胺合成可能是这些作用的重要介质。了解膳食脂肪影响参与能量稳态控制的神经元自噬的机制，将为针对和控制肥胖流行提供潜在的新途径。
