Overexpression of p53 Improves Blood Glucose Control in an Insulin Resistant Diabetic Mouse Model

Metformin Decreases Insulin Resistance in Type 1 Diabetes Through Regulating p53 and RAP2A in vitro and in vivo

Purpose

Patients with type 1 diabetes (T1D) are associated with a high risk of multiple complications, so the development of T1D treatment is urgently needed. This study was set out to explore the molecular mechanism of metformin in the treatment of T1D insulin resistance.

Patients and Methods

Subcutaneous adipose tissues were collected from 68 T1D patients and 51 healthy controls. Insulin resistance model rats and cells were constructed and treated with metformin respectively. Western blot was used to detect p53 and RAP2A protein levels, and qPCR was utilized to measure p53 and RAP2A mRNA levels. SiRNA and RAP2A siRNA vectors were constructed to observe their effects on insulin resistance model cells.

Results

In T1D, p53 was up-regulated, while RAP2A was down-regulated. Metformin could effectively improve insulin resistance and inflammatory response while down-regulating p53 and up-regulating RAP2A. P53 induced insulin resistance and inflammatory response by inhibiting RAP2A and promoted apoptosis.

Conclusion

Metformin improves T1D insulin resistance and inflammatory response through p53/RAP2A pathway, and the regulation of p53/RAP2A pathway is conducive to improving the efficacy of metformin in the treatment of insulin resistance.

Hepatocyte p53 ablation induces metabolic dysregulation that is corrected by food restriction and vertical sleeve gastrectomy in mice

P53 has been implicated in the pathogenesis of obesity and diabetes; however, the mechanisms and tissue sites of action are incompletely defined. Therefore, we investigated the role of hepatocyte p53 in metabolic homeostasis using a hepatocyte-specific p53 knockout mouse model. To gain further mechanistic insight, we studied mice under two complementary conditions of restricted weight gain: vertical sleeve gastrectomy (VSG) or food restriction. VSG or sham surgery was performed in high-fat diet-fed male hepatocyte-specific p53 wild-type and knockout littermates. Sham-operated mice were fed ad libitum or food restricted to match their body weight to VSG-operated mice. Hepatocyte-specific p53 ablation in sham-operated ad libitum-fed mice impaired glucose homeostasis, increased body weight, and decreased energy expenditure without changing food intake. The metabolic deficits induced by hepatocyte-specific p53 ablation were corrected, in part by food restriction, and completely by VSG. Unlike food restriction, VSG corrected the effect of hepatocyte p53 ablation to lower energy expenditure, resulting in a greater improvement in glucose homeostasis compared with food restricted mice. These data reveal an important new role for hepatocyte p53 in the regulation of energy expenditure and body weight and suggest that VSG can improve alterations in energetics associated with p53 dysregulation.

Integrated Analysis of Multiple Microarray Studies to Identify Novel Gene Signatures in Non-alcoholic Fatty Liver Disease

Background: Non-alcoholic fatty liver disease (NAFLD) is a well-known cause of liver dysfunction and has become a common chronic liver disease in many countries. However, the intrinsic molecular mechanisms underlying the pathogenesis of NAFLD have not yet been fully elucidated. Methods: We obtained the gene expression datasets of NAFLD through the Gene Expression Omnibus (GEO) database. Subsequently, robust rank aggregation (RRA) method was used to identify differentially expressed genes (DEGs) between NAFLD patients and controls. Gene functional annotation and PPI network analysis were performed to explore the potential function of the DEGs. Finally, we used a sequencing dataset GSE126848 to validate our results. Results: In this study, GSE48452, GSE66676, GSE72756, GSE63067, GSE89632, and GSE107231 were included, including 125 NAFLD patients and 116 control patients. The RRA integrated analysis determined 96 significant DEGs (50 up-regulated and 46 down-regulated) and the most significant gene aberrantly expressed in NAFLD was ENO3 (P-value = 7.17E-05), followed by CYP7A1 (P-value = 9.04E-05), and P4HA1 (P-value = 1.67E-04). Carboxylic acid metabolic process (GO:0019752; P-value = 1.39E-03) was the most significantly enriched for biological process in GO (gene ontology) analysis. KEGG pathway enrichment analysis showed that steroid hormone biosynthesis (hsa00140; P-value = 6.68E-03) and PPAR signaling pathway (hsa03320; P-value = 9.95E-03) were significantly enriched. Based on the results of the PPI and the results of the RRA, we finally defined the four most critical genes as the hub genes, including ENO3, CYP7A1, P4HA1, and CYP1A1. Conclusions: Our integrated analysis identified novel gene signatures and will contribute to the understanding of comprehensive molecular changes in NAFLD.

Control of metabolism by p53 - Cancer and beyond

p53 is an important tumour suppressor gene, with loss of p53 contributing to the development of most human cancers. However, the activation of p53 in response to stress signals underpins a role for p53 in diverse aspects of health and disease. Activities of p53 that regulate metabolism can play a role in maintaining homeostasis and protecting cells from damage - so preventing disease development. By contrast, either loss or over-activation of p53 can contribute to numerous metabolic pathologies, including aging, obesity and diabetes.

A comprehensive bioinformatics analysis on multiple Gene Expression Omnibus datasets of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Fatty liver disease is one of the leading causes of chronic damage in western countries. Approximately 25% of adults in the United States have fatty livers in the absence of excessive alcohol consumption, a condition termed nonalcoholic fatty liver disease (NAFLD). Little is known about the prevalence and genetic background of NAFLD or the factors that determine its development. In this study, we used the Gene-Cloud of Biotechnology Information bioinformatics platform to carry out a comprehensive bioinformatics analysis identifying differentially expressed genes (DEGs), key biological processes and intersecting pathways. We imported 3 Gene Expression Omnibus datasets (GSE31803, GSE49541, and GSE63067). Then, we assessed the expression of the DEGs in clinical samples. We found that CD24 was the only gene co-expressed in all 3 datasets. "Glycolysis/gluconeogenesis", "p53 signaling pathway" and "glycine, serine and threonine metabolism" were 3 common pathways related to the fatty liver process. In NAFLD tissues, CD24, COL1A1, LUM, THBS2 and EPHA3 were upregulated, and PZP was downregulated. CD24 is a core gene among these DEGs and have not yet been studied of its impact on NAFLD. Co-expressed genes, common biological processes and intersecting pathways identified in the study might play an important role in NAFLD progression. Further studies are needed to elucidate the mechanism of these potential genes and pathways in NAFLD.

p53 as a Dichotomous Regulator of Liver Disease: The Dose Makes the Medicine

Lifestyle-related disorders, such as the metabolic syndrome, have become a primary risk factor for the development of liver pathologies that can progress from hepatic steatosis, hepatic insulin resistance, steatohepatitis, fibrosis and cirrhosis, to the most severe condition of hepatocellular carcinoma (HCC). While the prevalence of liver pathologies is steadily increasing in modern societies, there are currently no approved drugs other than chemotherapeutic intervention in late stage HCC. Hence, there is a pressing need to identify and investigate causative molecular pathways that can yield new therapeutic avenues. The transcription factor p53 is well established as a tumor suppressor and has recently been described as a central metabolic player both in physiological and pathological settings. Given that liver is a dynamic tissue with direct exposition to ingested nutrients, hepatic p53, by integrating cellular stress response, metabolism and cell cycle regulation, has emerged as an important regulator of liver homeostasis and dysfunction. The underlying evidence is reviewed herein, with a focus on clinical data and animal studies that highlight a direct influence of p53 activity on different stages of liver diseases. Based on current literature showing that activation of p53 signaling can either attenuate or fuel liver disease, we herein discuss the hypothesis that, while hyper-activation or loss of function can cause disease, moderate induction of hepatic p53 within physiological margins could be beneficial in the prevention and treatment of liver pathologies. Hence, stimuli that lead to a moderate and temporary p53 activation could present new therapeutic approaches through several entry points in the cascade from hepatic steatosis to HCC.

P53 modulates hepatic insulin sensitivity through NF-κB and p38/ERK MAPK pathways

Besides its well-established oncosuppressor activity, the role of p53 in regulating metabolic pathways has been recently identified. Nevertheless, the function of p53 with respect to insulin resistance appears highly controversial. To address this issue, we investigated the expression of p53 in experimental model of insulin resistance. Then we used activator (nutlin-3α) and inhibitor (pifithrin-α, PFT-α) of p53 in HepG2 cell. Here we showed that p53 protein level was decreased in the hepatic tissue of high-fat diet-induced insulin resistance mice, genetically diabetic ob/ob mice and palmitate (PA) treated HepG2 cells. And high expression of phosphor-p38, ERK1/2 and nuclear factor kappa B (NF-κB) p65 accompanied with low expression of p53. But activation of p53 with nutlin-3α prevented PA-induced reduction of glucose consumption and suppression of insulin signaling pathways. At the same time, nutlin-3α downregulated the activation of NF-κB, p38 and ERK1/2 pathways upon stimulation with PA. In contrast, inhibition of p53 with PFT-α decreased glucose consumption and suppressed insulin signaling pathway. Furthermore, PFT-α activated NF-κB, p38 and ERK1/2 pathways in HepG2 cells. Overall, these results suggest that p53 is involved in improving insulin sensitivity of hepatic cells via inhibition of mitogen-activated protein kinases (MAPKs) and NF-κB pathways.

Is p53 Involved in Tissue-Specific Insulin Resistance Formation?

p53 constitutes an extremely versatile molecule, primarily involved in sensing the variety of cellular stresses. Functional p53 utilizes a plethora of mechanisms to protect cell from deleterious repercussions of genotoxic insults, where senescence deserves special attention. While the impressive amount of p53 roles has been perceived solely by the prism of antioncogenic effect, its presence seems to be vastly connected with metabolic abnormalities underlain by cellular aging, obesity, and inflammation. p53 has been found to regulate multiple biochemical processes such as glycolysis, oxidative phosphorylation, lipolysis, lipogenesis, β-oxidation, gluconeogenesis, and glycogen synthesis. Notably, p53-mediated metabolic effects are totally up to results of insulin action. Accumulating amount of data identifies p53 to be a factor activated upon hyperglycemia or excessive calorie intake, thus contributing to low-grade chronic inflammation and systemic insulin resistance. Prominent signs of its actions have been observed in muscles, liver, pancreas, and adipose tissue being associated with attenuation of insulin signalling. p53 is of crucial importance for the regulation of white and brown adipogenesis simultaneously being a repressor for preadipocyte differentiation. This review provides a profound insight into p53-dependent metabolic actions directed towards promotion of insulin resistance as well as presenting experimental data regarding obesity-induced p53-mediated metabolic abnormalities.