PDF(Pubmed)
Abstract：
Glyoxalase I (GLO1) is the primary enzyme for detoxification of the reactive dicarbonyl methylglyoxal (MG). Loss of GLO1 promotes accumulation of MG resulting in a recapitulation of diabetic phenotypes. We previously demonstrated attenuated GLO1 protein in skeletal muscle from individuals with type 2 diabetes (T2D). However, whether GLO1 attenuation occurs prior to T2D and the mechanisms regulating GLO1 abundance in skeletal muscle are unknown. GLO1 expression and activity were determined in skeletal muscle tissue biopsies from 15 lean healthy individuals (LH, BMI: 22.4 ± 0.7) and 5 individuals with obesity (OB, BMI: 32.4 ± 1.3). GLO1 protein was attenuated by 26 ± 0.3 % in OB compared to LH skeletal muscle (p = 0.019). Similar reductions for GLO1 activity were observed (p = 0.102). NRF2 and Keap1 expression were equivocal between groups despite a 2-fold elevation in GLO1 transcripts in OB skeletal muscle (p = 0.008). GLO1 knock-down (KD) in human immortalized myotubes promoted downregulation of muscle contraction and organization proteins indicating the importance of GLO1 expression for skeletal muscle function. SIRT1 KD had no effect on GLO1 protein or activity whereas, SIRT2 KD attenuated GLO1 protein by 28 ± 0.29 % (p < 0.0001) and GLO1 activity by 42 ± 0.12 % (p = 0.0150). KD of NAMPT also resulted in attenuation of GLO1 protein (28 ± 0.069 %, p = 0.003), activity (67 ± 0.09 %, p = 0.011) and transcripts (50 ± 0.13 %, p = 0.049). Neither the provision of the NAD+ precursors NR nor NMN were able to prevent this attenuation in GLO1 protein. However, NR did augment GLO1 specific activity (p = 0.022 vs NAMPT KD). These perturbations did not alter GLO1 acetylation status. SIRT1, SIRT2 and NAMPT protein levels were all equivocal in skeletal muscle tissue biopsies from individuals with obesity and lean individuals. These data implicate NAD+-dependent regulation of GLO1 in skeletal muscle independent of altered GLO1 acetylation and provide rationale for exploring NR supplementation to rescue attenuated GLO1 abundance and activity in conditions such as obesity.
摘要：
乙二醛酶I（GLO1）是反应性二羰基甲基乙二醛（MG）解毒的主要酶。GLO1的缺失促进MG的积累,导致糖尿病表型的概述。我们先前证明了2型糖尿病（T2D）个体骨骼肌中GLO1蛋白的减弱。然而,GLO1是否在T2D之前发生衰减以及调节骨骼肌中GLO1丰度的机制尚不清楚.GLO1表达和活性在15个瘦健康个体的骨骼肌组织活检中测定(LH，BMI：22.4±0.7）和5名肥胖个体（OB，BMI：32.4±1.3）。与LH骨骼肌相比，OB中的GLO1蛋白减弱了26±0.3％（p=0.019）。观察到GLO1活性的类似降低(p=0.102)。尽管OB骨骼肌中的GLO1转录物升高了2倍，但NRF2和Keap1的表达在各组之间是模棱两可的（p=0.008）。人永生化肌管中的GLO1敲低（KD）促进肌肉收缩和组织蛋白的下调，表明GLO1表达对骨骼肌功能的重要性。SIRT1KD对GLO1蛋白或活性没有影响，SIRT2KD使GLO1蛋白减弱28±0.29%(p<0.0001),使GLO1活性减弱42±0.12%(p=0.0150)。NAMPT的KD也导致GLO1蛋白的衰减(28±0.069%,p=0.003),活性(67±0.09%，p=0.011)和转录物(50±0.13%，p=0.049)。NAD+前体NR和NMN的提供都不能阻止GLO1蛋白中的这种衰减。然而,NR确实增加了GLO1比活性(p=0.022vsNAMPTKD)。这些扰动没有改变GLO1乙酰化状态。在来自肥胖个体和瘦个体的骨骼肌组织活检中,SIRT1、SIRT2和NAMPT蛋白水平都是不明确的。这些数据暗示骨骼肌中GLO1的NAD依赖性调节与改变的GLO1乙酰化无关，并为探索NR补充以挽救诸如肥胖等病症中减弱的GLO1丰度和活性提供了理论基础。
