Proteomic Analysis of 3T3-L1 Adipocytes Treated with Insulin and TNF-α.

Hayley Chan,Aditya Vaidyam,Victoria Hedrick,Thomas G Sors,Ryan W Grant,Tiago Jose Paschoal Sobreira,Ketaki P Bhide,Uma K Aryal

doi:10.3390/proteomes7040035

Hayley Chan, Aditya Vaidyam + Show 6 more

Open Access

https://doi.org/10.3390/proteomes7040035

Copy DOI

Journal: Proteomes	Publication Date: Oct 20, 2019
Citations: 6	License type: CC BY 4.0

Affiliation: Purdue University West Lafayette

Abstract

Insulin resistance is an indication of early stage Type 2 diabetes (T2D). Insulin resistant adipose tissues contain higher levels of insulin than the physiological level, as well as higher amounts of intracellular tumor necrosis factor-α (TNF-α) and other cytokines. However, the mechanism of insulin resistance remains poorly understood. To better understand the roles played by insulin and TNF-α in insulin resistance, we performed proteomic analysis of differentiated 3T3-L1 adipocytes treated with insulin (Ins), TNF-α (TNF), and both (Ins + TNF). Out of the 693 proteins identified, the abundances of 78 proteins were significantly different (p < 0.05). Carnitine parmitoyltransferase-2 (CPT2), acetyl CoA carboxylase 1 (ACCAC-1), ethylmalonyl CoA decarboxylase (ECHD1), and methylmalonyl CoA isomerase (MCEE), enzymes required for fatty acid β-oxidation and respiratory electron transport, and β-glucuronidase, an enzyme responsible for the breakdown of complex carbohydrates, were down-regulated in all the treatment groups, compared to the control group. In contrast, superoxide dismutase 2 (SOD2), protein disulfide isomerase (PDI), and glutathione reductase, which are the proteins responsible for cytoskeletal structure, protein folding, degradation, and oxidative stress responses, were up-regulated. This suggests higher oxidative stress in cells treated with Ins, TNF, or both. We proposed a conceptual metabolic pathway impacted by the treatments and their possible link to insulin resistance or T2D.

Highlights

The alarmingly increasing frequency of obesity and non-insulin-dependent diabetes mellitus (T2D) in the United States poses a serious health crisis in the near future
Using a threshold of p value ≤ 0.05, we identified 78 proteins that were significantly different in of p value ≤ 0.05, we identified 78 proteins that were significantly different in cells treated with Ins only, cells treated with Ins only, TNF only, or both, compared to the control (Table 1)
We showed that the decreased expression of mitochondrial and cytosolic proteins involved in fatty acid beta-oxidation and carbohydrate metabolism, and increased abundances of proteins involved in folding, degradation, and stress responses

Summary

Introduction

The alarmingly increasing frequency of obesity and non-insulin-dependent (type II) diabetes mellitus (T2D) in the United States poses a serious health crisis in the near future. We need to better understand the molecular factors and cellular pathways that are responsible for insulin resistance. Insulin is a dipeptide hormone secreted by pancreatic islet β cells, which is essential. Proteomes 2019, 7, 35 for maintaining normal blood glucose levels [1]. Insulin resistance is defined as the inability of a cell to maintain glucose homeostasis, respond to the physiological level of insulin [2,3], and is a characteristic condition of the early state of T2D. Insulin lowers blood glucose levels by regulating glucose metabolism via glycolysis, gluconeogenesis, and glycogenesis pathways [4]. Glucose is converted into pyruvate or lactate via glycolysis by sequential glycolytic enzymes, including bifunctional 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 1

Methods

Findings

Discussion

Conclusion