Endocrinology, Diabetes, and Metabolism, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, Colorado, USA.
School of Biological and Population Health Sciences, Oregon State University, Corvallis, Oregon, USA.
JCI Insight. 2018 Feb 8;3(3). doi: 10.1172/jci.insight.96805.
Accumulation of diacylglycerol (DAG) and sphingolipids is thought to promote skeletal muscle insulin resistance by altering cellular signaling specific to their location. However,the subcellular localization of bioactive lipids in human skeletal muscle is largely unknown.
We evaluated subcellular localization of skeletal muscle DAGs and sphingolipids in lean individuals (n = 15), endurance-trained athletes (n = 16), and obese men and women with (n = 12) and without type 2 diabetes (n = 15). Muscle biopsies were fractionated into sarcolemmal, cytosolic, mitochondrial/ER, and nuclear compartments. Lipids were measured using liquid chromatography tandem mass spectrometry, and insulin sensitivity was measured using hyperinsulinemic-euglycemic clamp.
Sarcolemmal 1,2-DAGs were not significantly related to insulin sensitivity. Sarcolemmal ceramides were inversely related to insulin sensitivity, with a significant relationship found for the C18:0 species. Sarcolemmal sphingomyelins were also inversely related to insulin sensitivity, with the strongest relationships found for the C18:1, C18:0, and C18:2 species. In the mitochondrial/ER and nuclear fractions, 1,2-DAGs were positively related to, while ceramides were inversely related to, insulin sensitivity. Cytosolic lipids as well as 1,3-DAG, dihydroceramides, and glucosylceramides in any compartment were not related to insulin sensitivity. All sphingolipids but only specific DAGs administered to isolated mitochondria decreased mitochondrial state 3 respiration.
These data reveal previously unknown differences in subcellular localization of skeletal muscle DAGs and sphingolipids that relate to whole-body insulin sensitivity and mitochondrial function in humans. These data suggest that whole-cell concentrations of lipids obscure meaningful differences in compartmentalization and suggest that subcellular localization of lipids should be considered when developing therapeutic interventions to treat insulin resistance.
National Institutes of Health General Clinical Research Center (RR-00036), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (R01DK089170), NIDDK (T32 DK07658), and Colorado Nutrition Obesity Research Center (P30DK048520).
人们认为二酰基甘油 (DAG) 和神经酰胺的积累通过改变其特定位置的细胞信号转导来促进骨骼肌胰岛素抵抗。然而，人体骨骼肌中生物活性脂质的亚细胞定位在很大程度上是未知的。
我们评估了瘦个体（n = 15）、耐力训练运动员（n = 16）以及伴有（n = 12）和不伴有 2 型糖尿病的肥胖男性和女性（n = 15）骨骼肌中二酰基甘油和神经酰胺的亚细胞定位。肌肉活检被分成肌小节膜、胞浆、线粒体/内质网和核区室。使用液相色谱串联质谱法测量脂质，并用高胰岛素-正葡萄糖钳夹法测量胰岛素敏感性。
肌小节膜 1,2-DAG 与胰岛素敏感性无显著相关性。肌小节膜神经酰胺与胰岛素敏感性呈负相关，C18:0 种与胰岛素敏感性有显著关系。肌小节膜神经鞘磷脂也与胰岛素敏感性呈负相关，C18:1、C18:0 和 C18:2 种与胰岛素敏感性的关系最强。在线粒体/内质网和核区室中，1,2-DAG 与胰岛素敏感性呈正相关，而神经酰胺则与胰岛素敏感性呈负相关。任何区室中的胞质脂质以及 1,3-DAG、二氢神经酰胺和葡糖脑苷脂与胰岛素敏感性无关。所有神经酰胺，但只有特定的 DAG 被给予分离的线粒体，可降低线粒体状态 3 呼吸。
这些数据揭示了骨骼肌中二酰基甘油和神经酰胺亚细胞定位的先前未知差异，这些差异与人体的全身胰岛素敏感性和线粒体功能有关。这些数据表明，脂质的全细胞浓度掩盖了区室化的有意义差异，并表明在开发治疗胰岛素抵抗的治疗干预措施时应考虑脂质的亚细胞定位。
美国国立卫生研究院一般临床研究中心（RR-00036）、美国国立卫生研究院糖尿病、消化和肾脏疾病研究所（NIDDK）（R01DK089170）、NIDDK（T32 DK07658）和科罗拉多州营养肥胖研究中心（P30DK048520）。
