Division of Cell Signalling and Immunology, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, UK.
Division of Cell Signalling and Immunology, Sir James Black Centre, School of Life Sciences, University of Dundee, Dundee, UK,
Cell Physiol Biochem. 2020 Oct 1;54(5):975-993. doi: 10.33594/000000282.
BACKGROUND/AIMS: Sustained increases in the circulating concentration of saturated fatty acids (SFAs, e.g. palmitate (PA), as seen during obesity, induces a chronic low grade inflammatory state that has been linked to metabolic dysfunction in tissues such as skeletal muscle that is characterized by disturbances in mitochondrial function and heightened production of reactive oxygen species (ROS). In contrast, monounsaturated (MUFAs, e.g. palmitoleate, PO; oleate, OL) and certain polyunsaturated (PUFAs, e.g. linoleate, LO) fatty acids have been shown to protect against some of the harmful metabolic effects induced by SFAs although it currently remains unknown whether this protection is associated with improved morphological and functional changes in mitochondrial biology and redox status in skeletal muscle cells. The aim of the present study was to investigate this issue.
Rat skeletal (L6) myotubes were subject to sustained 16h incubation with SFAs either alone or in combination with a MUFA (PO, OL) or PUFA (LO) prior to performing subcellular fractionation, immunoblotting, fixed/live cell imaging (for assessment of mitochondrial morphology and ROS) or analysis of real time mitochondrial respiration.
Incubation of L6 myotubes with PA or stearate (SFA, C18:0) but not laurate (a medium chain SFA, C12:0) induced a robust increase in proinflammatory NFkB signaling as judged by loss of IkBα and increased expression of IL-6. This heightened SFA-induced proinflammatory tone was associated with increased production of ROS (superoxide and hydrogen peroxide) and significant loss in proteins involved in mitochondrial biogenesis, respiration and morphology (i.e. PGC1α, SDHA, ANT1 and MFN2). Consistent with these changes, PA induced profound fragmentation of the mitochondrial network and a marked reduction in mitochondrial respiratory capacity. These changes were not evident in myotubes incubated with PO, OL or LO alone, and, strikingly, these MUFAs and PUFA not only negated the proinflammatory action of PA, but antagonised the biochemical, morphological and functional changes in mitochondrial biology and ROS production induced in myotubes by the sustained oversupply of PA.
Our findings indicate that PO, OL and LO exhibit anti-inflammatory and antioxidant characteristics and, significantly, they can ameliorate SFA-induced disturbances in mitochondrial form and function. These observations may have important nutritional implications in developing strategies that could potentially help limit obesity-induced metabolic dysfunction in tissues such as skeletal muscle.
背景/目的：循环中饱和脂肪酸（SFA，例如棕榈酸（PA））浓度持续升高，如肥胖时所见，会导致慢性低度炎症状态，与骨骼肌等组织的代谢功能障碍有关，其特征是线粒体功能障碍和活性氧（ROS）产生增加。相比之下，单不饱和脂肪酸（MUFAs，例如棕榈油酸（PO）；油酸（OL））和某些多不饱和脂肪酸（PUFAs，例如亚油酸（LO））已被证明可以预防 SFA 引起的一些有害代谢作用，尽管目前尚不清楚这种保护是否与骨骼肌细胞中线粒体生物学和氧化还原状态的形态和功能变化的改善有关。本研究旨在探讨这个问题。
在进行亚细胞分离、免疫印迹、固定/活细胞成像（评估线粒体形态和 ROS）或实时线粒体呼吸分析之前，大鼠骨骼肌（L6）肌管持续 16 小时用 SFA 单独或与 MUFAs（PO、OL）或 PUFAs（LO）组合孵育。
与月桂酸（中链 SFA，C12：0）相比，L6 肌管孵育 PA 或硬脂酸（SFA，C18：0）可诱导强烈的促炎 NFkB 信号，这可通过 IkBα 的丢失和 IL-6 的表达增加来判断。这种增强的 SFA 诱导的促炎音调与 ROS（超氧化物和过氧化氢）产生增加以及涉及线粒体生物发生、呼吸和形态的蛋白质显着丧失有关（即 PGC1α、SDHA、ANT1 和 MFN2）。与这些变化一致，PA 诱导线粒体网络的严重碎片化和线粒体呼吸能力的显着降低。在单独孵育 PO、OL 或 LO 的肌管中未观察到这些变化，并且这些 MUFAs 和 PUFAs 不仅消除了 PA 的促炎作用，而且拮抗了持续过度供应 PA 引起的肌管中线粒体生物学和 ROS 产生的生化、形态和功能变化。
我们的研究结果表明，PO、OL 和 LO 具有抗炎和抗氧化特性，重要的是，它们可以改善 SFA 诱导的线粒体形态和功能障碍。这些观察结果在开发可能有助于限制肥胖引起的代谢功能障碍的策略方面具有重要的营养意义，例如骨骼肌。
