Effect of Insulin and Pioglitazone on Protein Phosphatase 2A Interaction Partners in Primary Human Skeletal Muscle Cells Derived from Obese Insulin-Resistant Participants

Abstract

Skeletal muscle insulin resistance is a major contributor to type-2 diabetes (T2D). Pioglitazone is a potent insulin sensitizer of peripheral tissues by targeting peroxisome proliferator-activated receptor gamma. Pioglitazone has been reported to protect skeletal muscle cells from lipotoxicity by promoting fatty acid mobilization and insulin signaling. However, it is unclear whether pioglitazone increases insulin sensitivity through changes in protein−protein interactions involving protein phosphatase 2A (PP2A). PP2A regulates various cell signaling pathways such as insulin signaling. Interaction of the catalytic subunit of PP2A (PP2Ac) with protein partners is required for PP2A specificity and activity. Little is known about PP2Ac partners in primary human skeletal muscle cells derived from lean insulin-sensitive (Lean) and obese insulin-resistant (OIR) participants. We utilized a proteomics method to identify PP2Ac interaction partners in skeletal muscle cells derived from Lean and OIR participants, with or without insulin and pioglitazone treatments. In this study, 216 PP2Ac interaction partners were identified. Furthermore, 26 PP2Ac partners exhibited significant differences in their interaction with PP2Ac upon insulin treatments between the two groups. Multiple pathways and molecular functions are significantly enriched for these 26 interaction partners, such as nonsense-mediated decay, metabolism of RNA, RNA binding, and protein binding. Interestingly, pioglitazone restored some of these abnormalities. These results provide differential PP2Ac complexes in Lean and OIR in response to insulin/pioglitazone, which may help understand molecular mechanisms underpinning insulin resistance and the insulin-sensitizing effects of pioglitazone treatments, providing multiple targets in various pathways to reverse insulin resistance and prevent and/or manage T2D with less drug side effects.

Dietary Methionine Restriction Improves Gastrocnemius Muscle Glucose Metabolism through Improved Insulin Secretion and H19/IRS-1/Akt Pathway in Middle-Aged Mice

“…56 Insulin resistance in skeletal muscle is characterized by decreased insulin-stimulated glucose uptake. 57 HFD can lead to insulin resistance in skeletal muscle. 58 It is caused by impaired insulin signaling and intracellular receptor defects, including impaired glucose transport, reduced glucose phosphorylation, glucose oxidation, and glycogen synthesis.…”

“…HFD can lead to insulin resistance in skeletal muscle . It is caused by impaired insulin signaling and intracellular receptor defects, including impaired glucose transport, reduced glucose phosphorylation, glucose oxidation, and glycogen synthesis. , In our experiment, the results in vitro showed that PA could reduce insulin-stimulated glucose uptake in C2C12 cells. In vivo , the HFD reduced the level of GSK3β phosphorylation, HK2 protein expression, and glycogen level in the gastrocnemius muscle of middle-aged mice.…”

“…Skeletal muscle is the regulator of glucose homeostasis, responsible for postprandial glucose uptake from the circulation . Insulin resistance in skeletal muscle is characterized by decreased insulin-stimulated glucose uptake . HFD can lead to insulin resistance in skeletal muscle .…”