Liver protein profiles in insulin receptor-knockout mice reveal novel molecules involved in the diabetes pathophysiology

Abstract

It is under a complex control by substrates such as hormones, nutrients, and neuronal impulses. Insulin promotes glycogen synthesis, lipogenesis, and lipoprotein synthesis and inhibits gluconeogenesis, glycogenolysis, and VLDL secretion by modifying the expression and enzymatic activity of specific molecules. To understand the pathophysiological mechanisms leading to metabolic liver disease, we analyzed liver protein patterns expressed in a mouse model of diabetes by proteomic approaches. We used insulin receptor-knockout (IR Ϫ/Ϫ ) and heterozygous (IR ϩ/Ϫ ) mice as a murine model of liver metabolic dysfunction associated with diabetic ketoacidosis and insulin resistance. We evaluated liver fatty acid levels by microscopic examination and protein expression profiles by orthogonal experimental strategies using protein 2-DE MALDI-TOF/TOF and peptic nLC-MS/MS shotgun profiling. Identified proteins were then loaded into Ingenuity Pathways Analysis to find possible molecular networks. Twenty-eight proteins identified by 2-DE analysis and 24 identified by nLC-MS/MS shotgun were differentially expressed among the three genotypes. Bioinformatic analysis revealed a central role of high-mobility group box 1/2 and huntigtin never reported before in association with metabolic and related liver disease. A different modulation of these proteins in both blood and hepatic tissue further suggests their role in these processes. These results provide new insight into pathophysiology of insulin resistance and hepatic steatosis and could be useful in identifying novel biomarkers to predict risk for diabetes and its complications. insulin resistance; huntigtin; high-mobility group-B1; proteomics TYPE 2 DIABETES (T2D) is a complex metabolic disorder characterized by increased levels of insulin resistance and impaired ␤-cell function with reduced insulin secretion (35). In T2D, modification of hepatic metabolism is associated with glucose and lipid overproduction, leading to overt hyperglycemia and diabetic dyslipidemia. Glucose overproduction is a physiological response in T2D, whereas the overproduction of lipids linked with insulin resistance remains a phenomenon to clarify since insulin increases abundance of lipogenic enzymes and insulin resistance diminishes lipogenesis (31, 41). Furthermore, insulin resistance and T2D are linked with hepatic steatosis, which is an exacerbation of liver dysfunction generated by accumulation of lipids, mainly triglycerides (23).Several etiological mechanisms have been proposed to explain the pathological link between insulin resistance, T2D, and liver disease, including inflammation and oxidative stress (36). Recently, novel anti-inflammatory proteins called chaperones and Toll-like receptors (TLRs) have been suggested to play a significant role in this pathological process (27). However, to date, the molecular mechanisms linking the impairment in glucose homeostasis with liver disease are not fully understood.Therefore, elucidation of molecular alterations, which regulate metabolic liver dysfunct...

Insulin and Exendin-4 Reduced Mutated Huntingtin Accumulation in Neuronal Cells

“…However, whether the dysfunction in the pathways regulating glycemic homeostasis triggers brain proteinaceous accumulation or vice versa is still not clear. What is known so far is that HTT is involved in both HD and T2DM (Capuani et al, 2015) and that this implication is further validated by present results.…”

“…By using a proteomic approach in a diabetic mouse model, we demonstrated a novel central role of huntingtin protein (HTT) in metabolism and in glucose homeostasis (Capuani et al, 2015). An expansion of the CAG (polyQ) repeats in the gene encoded for HTT caused HD, which is an orphan autosomal dominant disease leading to neuronal death (apoptosis), dementia, and movement disorders (Jimenez-Sanchez et al, 2017).…”

Screening for insulin-independent pathways that modulate glucose homeostasis identifies androgen receptor antagonists

“…To further explore the nature of the metabolic defects in zebrafish ins mutants, we probed the proteome of 108 hpf ins mutants compared to their WT siblings and assessed this dataset relative to seven other proteomes from diabetic tissues of rodent or human origin (Hwang et al, 2010; Mullen and Ohlendieck, 2010; Giebelstein et al, 2012; Valle et al, 2012); S.-J. Kim et al, 2014a; Capuani et al, 2015; Braga et al, 2016; Zabielski et al, 2016). Strikingly, pathways like gluconeogenesis, mitochondrial dysfunction, sirtuin signaling, and oxidative phosphorylation, which were affected in diabetic conditions across these studies, were similarly disrupted in zebrafish ins mutants (Figure 1F and supplementary file 1).…”

Proteomics reveals different pathological processes of adipose tissue, liver, and skeletal muscle under insulin resistance

“…Soltis et al (2017) identified 362 significant differential proteins in the liver of mice fed with high-fat diet, and upregulated proteins played a part in fatty acid β-oxidation, fatty acid transport, and carbohydrate biosynthesis, the downregulated proteins were participated in cholesterol biosynthesis and urea cycle. Capuani et al (2015) thought that the differential proteins in the liver of insulin receptor-knockout mice were mainly involved in glycolipid metabolism and oxidative stress processes. Holper, Nolte, Bober, Braun, and Kruger (2015) found 407 significant regulatory proteins, which involved in fatty acid metabolism, PPAR signaling, and the degradation of branched chain amino acids (BCAAs).…”