肥胖促进骨关节炎(OA)的发展。它也是公认的肥胖导致过度的脂质沉积在非脂肪组织,经常引起脂毒性。这项研究的目的是研究肥胖情况下小鼠软骨中各种脂质水平的变化,并确定软骨细胞从头脂肪生成是否改变。我们使用油红O来确定高脂饮食(HFD)或低脂饮食(LFD)的小鼠软骨中脂质滴的积累。我们进一步使用基于质谱的脂质组学分析来量化不同脂质种类的水平。参与脂肪酸(FA)摄取的基因的表达,合成,伸长率,使用定量聚合酶链反应检查去饱和。为了进一步研究潜在的机制,我们在高糖和高胰岛素条件下培养原代小鼠软骨细胞,以模拟与肥胖相关的局部微环境,随后检测细胞脂滴的丰度.乙酰辅酶A羧化酶(ACC)抑制剂,将ND-630加入到培养基中,以检查抑制从头脂肪生成对软骨细胞中脂质积累的影响。与接受LFD的小鼠相比,HFD组显示更多的软骨细胞具有可见的细胞内脂滴。在HFD组中还检测到显著较高量的总FA。六个显著上调的FA中有五个是ω-6FA,而两个显著下调的FAs是ω-3FAs。因此,HFD组显示出显著较高的ω-6/ω-3FA比率。还发现醚连接的磷脂酰胆碱在HFD组中较高。脂肪酸去饱和酶(Fad1-3),脂肪酸结合蛋白4(Fabp4),和脂肪酸合酶(Fasn)转录本在治疗组之间没有发现差异,并且脂肪酸延伸酶(Elovl1-7)转录本在软骨中检测不到。神经酰胺合酶2(Cers-2),在这些研究中发现的唯一被改变的转录本,在HFD组中显著上调。体外,软骨细胞在高葡萄糖下培养时上调从头脂肪生成,高胰岛素条件,这个观察结果与ACC的激活有关,通过添加ND-630而减弱。这项研究提供了第一个证据,表明肥胖软骨中脂质沉积增加,这与ACC介导的从头脂肪生成的上调有关。我们的观察结果支持了ACC抑制改善软骨细胞中的脂质积累,因此表明ACC可能有针对性地治疗肥胖相关的OA。
Obesity promotes the development of osteoarthritis (OA). It is also well-established that obesity leads to excessive lipid deposition in nonadipose tissues, which often induces lipotoxicity. The objective of this study was to investigate changes in the levels of various lipids in mouse cartilage in the context of obesity and determine if chondrocyte de novo lipogenesis is altered. We used Oil Red O to determine the accumulation of lipid droplets in cartilage from mice fed high-fat diet (HFD) or low-fat diet (LFD). We further used mass spectrometry-based lipidomic analyses to quantify levels of different lipid species. Expression of genes involving in fatty acid (FA) uptake, synthesis, elongation, and desaturation were examined using quantitative polymerase chain reaction. To further study the potential mechanisms, we cultured primary mouse chondrocytes under high-glucose and high-insulin conditions to mimic the local microenvironment associated with obesity and subsequently examined the abundance of cellular lipid droplets. The acetyl-CoA carboxylase (ACC) inhibitor, ND-630, was added to the culture medium to examine the effect of inhibiting de novo lipogenesis on lipid accumulation in chondrocytes. When compared to the mice receiving LFD, the HFD group displayed more chondrocytes with visible intracellular lipid droplets. Significantly higher amounts of total FAs were also detected in the HFD group. Five out of six significantly upregulated FAs were ω-6 FAs, while the two significantly downregulated FAs were ω-3 FAs. Consequently, the HFD group displayed a significantly higher ω-6/ω-3 FA ratio. Ether linked phosphatidylcholine was also found to be higher in the HFD group. Fatty acid desaturase (Fad1-3), fatty acid-binding protein 4 (Fabp4), and fatty acid synthase (Fasn) transcripts were not found to be different between the treatment groups and fatty acid elongase (Elovl1-7) transcripts were undetectable in cartilage. Ceramide synthase 2 (Cers-2), the only transcript found to be changed in these studies, was significantly upregulated in the HFD group. In vitro, chondrocytes upregulated de novo lipogenesis when cultured under high-glucose, high-insulin conditions, and this observation was associated with the activation of ACC, which was attenuated by the addition of ND-630. This study provides the first evidence that lipid deposition is increased in cartilage with obesity and that this is associated with the upregulation of ACC-mediated de novo lipogenesis. This was supported by our observation that ACC inhibition ameliorated lipid accumulation in chondrocytes, thereby suggesting that ACC could potentially be targeted to treat obesity-associated OA.