Diabetes and Obesity Center, University of Louisville, Louisville, KY 40202, USA.
Christina Lee Brown Envirome Institute, University of Louisville, Louisville, KY 40202, USA.
Nutrients. 2020 Sep 23;12(10):2910. doi: 10.3390/nu12102910.
Type 2 diabetes (T2D), along with obesity, is one of the leading health problems in the world which causes other systemic diseases, such as cardiovascular diseases and kidney failure. Impairments in glycemic control and insulin resistance plays a pivotal role in the development of diabetes and its complications. Since skeletal muscle constitutes a significant tissue mass of the body, insulin resistance within the muscle is considered to initiate the onset of diet-induced metabolic syndrome. Insulin resistance is associated with impaired glucose uptake, resulting from defective post-receptor insulin responses, decreased glucose transport, impaired glucose phosphorylation, oxidation and glycogen synthesis in the muscle. Although defects in the insulin signaling pathway have been widely studied, the effects of cellular mechanisms activated during metabolic syndrome that cross-talk with insulin responses are not fully elucidated. Numerous reports suggest that pathways such as inflammation, lipid peroxidation products, acidosis and autophagy could cross-talk with insulin-signaling pathway and contribute to diminished insulin responses. Here, we review and discuss the literature about the defects in glycolytic pathway, shift in glucose utilization toward anaerobic glycolysis and change in intracellular pH [pH] within the skeletal muscle and their contribution towards insulin resistance. We will discuss whether the derangements in pathways, which maintain [pH] within the skeletal muscle, such as transporters (monocarboxylate transporters 1 and 4) and depletion of intracellular buffers, such as histidyl dipeptides, could lead to decrease in [pH] and the onset of insulin resistance. Further we will discuss, whether the changes in [pH] within the skeletal muscle of patients with T2D, could enhance the formation of protein aggregates and activate autophagy. Understanding the mechanisms by which changes in the glycolytic pathway and [pH] within the muscle, contribute to insulin resistance might help explain the onset of obesity-linked metabolic syndrome. Finally, we will conclude whether correcting the pathways which maintain [pH] within the skeletal muscle could, in turn, be effective to maintain or restore insulin responses during metabolic syndrome.
2 型糖尿病(T2D)与肥胖症一起,是世界上主要的健康问题之一,会导致其他系统性疾病,如心血管疾病和肾衰竭。血糖控制受损和胰岛素抵抗在糖尿病及其并发症的发展中起着关键作用。由于骨骼肌构成了身体的重要组织质量,因此肌肉内的胰岛素抵抗被认为是引发饮食引起的代谢综合征的开始。胰岛素抵抗与葡萄糖摄取受损有关,这是由于受体后胰岛素反应缺陷、葡萄糖转运减少、葡萄糖磷酸化、氧化和肌肉糖原合成受损所致。尽管胰岛素信号通路的缺陷已被广泛研究,但代谢综合征期间激活的与胰岛素反应相互作用的细胞机制的影响尚未完全阐明。许多报告表明,炎症、脂质过氧化产物、酸中毒和自噬等途径可能与胰岛素信号通路相互作用,并导致胰岛素反应减弱。在这里,我们回顾和讨论了关于糖酵解途径缺陷、葡萄糖利用向无氧糖酵解转移以及骨骼肌细胞内 pH 值 [pH]变化及其对胰岛素抵抗的贡献的文献。我们将讨论维持骨骼肌内 pH 值的途径(如单羧酸转运蛋白 1 和 4)和细胞内缓冲液(如组氨酸二肽)的消耗是否会导致 pH 值降低和胰岛素抵抗的发生。此外,我们将讨论 T2D 患者骨骼肌内 pH 值的变化是否会增强蛋白质聚集体的形成并激活自噬。了解糖酵解途径和肌肉内 pH 值变化导致胰岛素抵抗的机制,可能有助于解释肥胖相关代谢综合征的发生。最后,我们将得出结论,是否纠正维持骨骼肌内 pH 值的途径可以反过来有效地维持或恢复代谢综合征期间的胰岛素反应。