TAB3 involves in hepatic insulin resistance through activation of MAPK pathway

Inflammation in diabetes complications: molecular mechanisms and therapeutic interventions

At present, diabetes mellitus (DM) has been one of the most endangering healthy diseases. Current therapies contain controlling high blood sugar, reducing risk factors like obesity, hypertension, and so on; however, DM patients inevitably and eventually progress into different types of diabetes complications, resulting in poor quality of life. Unfortunately, the clear etiology and pathogenesis of diabetes complications have not been elucidated owing to intricate whole-body systems. The immune system was responsible to regulate homeostasis by triggering or resolving inflammatory response, indicating it may be necessary to diabetes complications. In fact, previous studies have been shown inflammation plays multifunctional roles in the pathogenesis of diabetes complications and is attracting attention to be the meaningful therapeutic strategy. To this end, this review systematically concluded the current studies over the relationships of susceptible diabetes complications (e.g., diabetic cardiomyopathy, diabetic retinopathy, diabetic peripheral neuropathy, and diabetic nephropathy) and inflammation, ranging from immune cell response, cytokines interaction to pathomechanism of organ injury. Besides, we also summarized various therapeutic strategies to improve diabetes complications by target inflammation from special remedies to conventional lifestyle changes. This review will offer a panoramic insight into the mechanisms of diabetes complications from an inflammatory perspective and also discuss contemporary clinical interventions.

A Bioinformatics Investigation into the Pharmacological Mechanisms of Sodium-Glucose Co-transporter 2 Inhibitors in Diabetes Mellitus and Heart Failure Based on Network Pharmacology

PURPOSE

Diabetes mellitus (DM) is a major risk factor for the development of heart failure (HF). Sodium-glucose co-transporter 2 (SGLT2) inhibitors have demonstrated consistent benefits in the reduction of hospitalization for HF in patients with DM. However, the pharmacological mechanism is not clear. To investigate the mechanisms of SGLT2 inhibitors in DM with HF, we performed target prediction and network analysis by a network pharmacology method.

METHODS

We selected targets of SGLT2 inhibitors and DM status with HF from databases and studies. The "Drug-Target" and "Drug-Target-Disease" networks were constructed using Cytoscape. Then the protein-protein interaction (PPI) was analyzed using the STRING database. Gene Ontology (GO) biological functions and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were performed to investigate using the Bioconductor tool for analysis.

RESULTS

There were 125 effective targets between SGLT2 inhibitors and DM status with HF. Through further screening, 33 core targets were obtained, including SRC, MAPK1, NARS, MAPK3 and EGFR. It was predicted that the Rap1 signaling pathway, MAPK signaling pathway, EGFR tyrosine kinase inhibitor resistance, AGE-RAGE signaling pathway in diabetic complications and other signaling pathways were involved in the treatment of DM with HF by SGLT2 inhibitors.

CONCLUSION

Our study elucidated the possible mechanisms of SGLT2 inhibitors from a systemic and holistic perspective based on pharmacological networks. The key targets and pathways will provide new insights for further research on the pharmacological mechanism of SGLT2 inhibitors in the treatment of DM with HF.

Potential type 2 diabetes mellitus drug HMPA promotes short-chain fatty acid production by improving carbon catabolite repression effect of gut microbiota

BACKGROUND AND PURPOSE

Gut microbiota plays an important role in type 2 diabetes mellitus (T2DM) progression. From our previous work N-(4-Hydroxyphenethyl)-3-mercapto-2-methylpropanamide (HMPA) is a potential T2DM drug. We evaluated the effect of HMPA on gut microbiota and studied the molecular mechanism underlying HMPA's regulation of gut microbiota.

EXPERIMENTAL APPROACH

The pseudo germ-free (PGF) T2DM model and faecal microbiota transplantation method were used to study whether gut microbiota mediates the actions of HMPA. The composition of gut microbiota was detected by using 16S rRNA sequence. Short-chain fatty acids (SCFAs) content was detected by gas chromatography. The HMPA probe was synthesised for finding and identifying the target protein of HMPA. The effect of HMPA on the utilisation of carbon sources in Bifidobacterium was evaluated.

KEY RESULTS

HMPA has a slight effect on the PGF T2DM model. The gut microbiota changed by HMPA can also alleviate the symptoms of T2DM. HMPA can regulate gut microbiota structure, increase SCFAs production and reduce nitrate content in the intestinal tissues. The thickness of the mucus on colon tissues increases after HMPA treatment. The target protein of HMPA in gut microbiota is the nitrogen metabolism global transcriptional regulator (GlnR). HMPA promotes the utilisation of less preferred carbon source in the gut microbiota and increases the fermentation product of SCFAs.

CONCLUSION AND IMPLICATIONS

HMPA plays a hypoglycaemic role through the gut microbiota. HMPA improves the carbon catabolite repression effect of gut microbiota and increases SCFAs production by targeting GlnR. GlnR may be a target for gut microbiota regulation.

Salidroside from Rhodiola wallichiana var. cholaensis reverses insulin resistance and stimulates the GLP-1 secretion by alleviating ROS-mediated activation of MAPKs signaling pathway and mitigating apoptosis

The present study was aimed to investigate the mechanisms of salidroside (SAL) from Rhodiola wallichiana var. cholaensis on hypoglycemic and oxidative stress responses. The palmitate (PA)-induced GLUTag cells model and the glucosamine-induced insulin resistance model in HepG2 cells were built. SAL led to the up-regulation of the serum glucagon-like peptide 1 (GLP-1) level by facilitating the SCFAs production, the promotion of GLP-1 synthesis by improving p38 MAPK phosphorylation and regulating insulin resistance. Moreover, the production of reactive oxygen species (ROS) and the expression of MAPKs were down-regulated. Furthermore, SAL was found to be able to inhibit PA-induced apoptosis that down-regulates cleaved caspase-3 and Bax expressions, while up-regulating Bcl-2 expression and up-regulates the Bcl-2/Bax ratio in glucosamine induced insulin resistance model. Besides, SAL can also up-regulate the mTOR/p70S6k signaling pathway in the PA-induced GLUTag cells model. Our data demonstrated that SAL could reverse insulin resistance and stimulates the GLP-1 secretion by alleviating ROS-mediated activation of MAPKs signaling pathway and mitigating apoptosis. PRACTICAL APPLICATIONS: Our data showed that SAL could increase the GLP-1 level by stimulating the SCFAs production and p38 phosphorylation and facilitate the IR and GLP-1 synthesis by alleviating ROS-mediated activation of MAPKs signaling pathway and mitigating apoptosis. Furthermore, the SAL has also stimulated the mTOR/p70S6k signaling pathway in PA-induced GLUTag cells model. The results provided a possibility to employ SAL for diabetes treatment.

Weighted Gene Coexpression Network Analysis Identified MicroRNA Coexpression Modules and Related Pathways in Type 2 Diabetes Mellitus

Objective

Type 2 diabetes mellitus (T2DM) is a metabolic disease with high incidence, which has seriously affected human life and health. MicroRNA, a short-chain noncoding RNA, plays an important role in T2DM. Identification of meaningful microRNA modules and the role of microRNAs provide a basis for searching potential biomarkers of T2DM.

Materials and Methods

In this study, three newly diagnosed patients with T2DM and three controls were selected for Whole Peripheral Blood RNA Sequencing to establish a microRNA library. Weighted gene coexpression network analysis (WGCNA) was applied to construct coexpression modules and to detect the trait-related microRNA modules; then, KEGG enrichment analysis was performed to predict the biological function of the interest modules, and candidate hub microRNAs were screened out by the value of module membership (MM) and protein-protein interaction (PPI) network.

Result

Four microRNA modules (blue, brown, magenta, and turquoise) were highly associated with the T2DM; the number of miRNAs in these modules ranged from 41 to 469. The Fc gamma R-mediated phagocytosis pathway, Rap1 signaling pathway, MAPK signaling pathway, and Lysosome pathway were common pathways in three of the four modules. RPS27A, UBC, and RAC1 were the top three proteins in our study; their corresponding RNAs were miR-1271-5p, miR-130a-3p, miR-130b-3p, and miR-574-3p.

Conclusion

In summary, this study identified blood miRNAs in human T2DM using RNA sequencing. The findings may be the foundation for understanding the potential role of miRNAs in T2DM.

Molecular characterization and expression of TAK-binding proteins (TAB1-3) in Larimichthys crocea infected by Vibrio parahemolyticus and LPS

TAK1-binding proteins (TABs) are important immune protein involved in various intracellular signalling pathways. Here, TAB1-3 (lcTAB1-3) were characterized from Larimichthys crocea. The predicted 1524 bp coding sequence of lcTAB1 encoded a 507-residue protein, while lcTAB2 (2271 bp) and lcTAB3 (1836 bp) encoded 756 and 611 residue proteins, respectively. Their sequence shared conserved domain structures and functional sites with their orthologs from other species. The expression of lcTAB1-3 were detected in all tested tissues, which were upregulated in spleen, liver and kidney following Vibrio parahemolyticus infection. Immunofluorescence staining revealed that lcTAB1 were localized in cytoplasm, while lcTAB2 and lcTAB3 were in the endsome. Moreover, the NF-κB protein level was obviously upregulated after the co-overexpression of lcTAK1 and lcTABs, higher than that after the overexpression of lcTAK1 or lcTABs alone. Co-immunoprecipitation proved the direct interaction of lcTAB1/lcTAB2/lcTAB3 and lcTAK1. These findings indicated the roles of lcTABs in immune response of Larimichthys crocea.

Key genes and co-expression network analysis in the livers of type 2 diabetes patients

AIMS/INTRODUCTION

The incidence of type 2 diabetes is increasing worldwide. Hepatic insulin resistance and liver lipid accumulation contributes to type 2 diabetes development. The aim of the present study was to investigate the key gene pathways and co-expression networks in the livers of type 2 diabetes patients.

MATERIALS AND METHODS

Dataset GSE15653 containing nine healthy individuals and nine type 2 diabetes patients was downloaded from the National Center for Biotechnology Information Gene Expression Omnibus database. Differentially expressed genes were obtained from the livers of type 2 diabetes patients, annotated pathway enrichment and protein-protein interaction network analysis. Next, functional modules and transcription factor networks were constructed. Gene co-expression networks were analyzed by weighted correlation network analysis to identify key modules related to clinical traits, and the candidate key genes were validated in hepatic insulin resistance models in vitro.

RESULTS

A total of 778 differentially expressed genes were filtered in the livers of type 2 diabetes patients, pathway enrichment analysis identified ke y pathways, such as the mitogen-activated protein kinase signaling pathway, Hippo signaling pathway and hypoxia-inducible factor-1 signaling pathway, that were associated with type 2 diabetes. Several transcription factors of three functional modules identified from protein-protein interaction networks are likely to be implicated in type 2 diabetes. Furthermore, weighted correlation network analysis identified five modules that were shown to be highly correlated with type 2 diabetes and other clinical traits. Functional annotation showed that these modules were mainly enriched in pathways such as metabolic pathways, phosphoinositide 3-kinase-protein kinase B signaling pathway and natural killer cell-mediated cytotoxicity. UBE2M and GPER were upregulated in L02 and HepG2 models, whereas P2RY11 only upregulated in L02 model, and UBE2N only downregulated in HepG2 model at a significant level.

CONCLUSIONS

These results would offer new insights into hepatic insulin resistance, type 2 diabetes pathogenesis, development and drug discovery.

Clinopodium chinense Attenuates Palmitic Acid-Induced Vascular Endothelial Inflammation and Insulin Resistance through TLR4-Mediated NF- κ B and MAPK Pathways

Elevated palmitic acid (PA) levels are associated with the development of inflammation, insulin resistance (IR) and endothelial dysfunction. Clinopodium chinense (Benth.) O. Kuntze has been shown to lower blood glucose and attenuate high glucose-induced vascular endothelial cells injury. In the present study we investigated the effects of ethyl acetate extract of C. chinense (CCE) on PA-induced inflammation and IR in the vascular endothelium and its molecular mechanism. We found that CCE significantly inhibited PA-induced toll-like receptor 4 (TLR4) expression in human umbilical vein endothelial cells (HUVECs). Consequently, this led to the inhibition of the following downstream adapted proteins myeloid differentiation primary response gene 88, Toll/interleukin-1 receptor domain-containing adaptor-inducing interferon- β and TNF receptor-associated factor 6. Moreover, CCE inhibited the phosphorylation of Ikappa B kinase β , nuclear factor kappa-B (NF- κ B), c-Jun N-terminal kinase, extracellular regulated protein kinases, p38-mitogen-activated protein kinase (MAPK) and subsequently suppressed the release of tumor necrosis factor- α , interleukin-1 β (IL-1 β ) and IL-6. CCE also inhibited IRS-1 serine phosphorylation and ameliorated insulin-mediated tyrosine phosphorylation of IRS-1. Moreover, CCE restored serine/threonine kinase and endothelial nitric oxide synthase (eNOS) activation and thus increased insulin-mediated nitric oxide (NO) production in PA-treated HUVECs. This led to reverse insulin mediated endothelium-dependent relaxation, eNOS phosphorylation and NO production in PA-treated rat thoracic aortas. These results suggest that CCE can significantly inhibit the inflammatory response and alleviate impaired insulin signaling in the vascular endothelium by suppressing TLR4-mediated NF- κ B and MAPK pathways. Therefore, CCE can be considered as a potential therapeutic candidate for endothelial dysfunction associated with IR and diabetes.

Innate Immune Signaling and Its Role in Metabolic and Cardiovascular Diseases

The innate immune system is an evolutionarily conserved system that senses and defends against infection and irritation. Innate immune signaling is a complex cascade that quickly recognizes infectious threats through multiple germline-encoded cell surface or cytoplasmic receptors and transmits signals for the deployment of proper countermeasures through adaptors, kinases, and transcription factors, resulting in the production of cytokines. As the first response of the innate immune system to pathogenic signals, inflammatory responses must be rapid and specific to establish a physical barrier against the spread of infection and must subsequently be terminated once the pathogens have been cleared. Long-lasting and low-grade chronic inflammation is a distinguishing feature of type 2 diabetes and cardiovascular diseases, which are currently major public health problems. Cardiometabolic stress-induced inflammatory responses activate innate immune signaling, which directly contributes to the development of cardiometabolic diseases. Additionally, although the innate immune elements are highly conserved in higher-order jawed vertebrates, lower-grade jawless vertebrates lack several transcription factors and inflammatory cytokine genes downstream of the Toll-like receptors (TLRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) pathways, suggesting that innate immune signaling components may additionally function in an immune-independent way. Notably, recent studies from our group and others have revealed that innate immune signaling can function as a vital regulator of cardiometabolic homeostasis independent of its immune function. Therefore, further investigation of innate immune signaling in cardiometabolic systems may facilitate the discovery of new strategies to manage the initiation and progression of cardiometabolic disorders, leading to better treatments for these diseases. In this review, we summarize the current progress in innate immune signaling studies and the regulatory function of innate immunity in cardiometabolic diseases. Notably, we highlight the immune-independent effects of innate immune signaling components on the development of cardiometabolic disorders.

Egr2 enhances insulin resistance via JAK2/STAT3/SOCS-1 pathway in HepG2 cells treated with palmitate

Insulin resistance is generally responsible for the pathogenesis of type 2 diabetes mellitus (T2DM). Early growth response proteins-2 (Egr2) has been reported to be able to increase the expression of the suppressors of cytokine signaling-1 (SOCS-1), and impair insulin signaling pathway through suppression of insulin receptor substrates (IRS), including IRS-1 and IRS-2. However, whether Egr2 is directly involved in the development of insulin resistance, and how its potential contributions to insulin resistance still remain unknown. Here, our present investigation found that the expression levels of Egr2 were up-regulated when insulin resistance occurs, and knockdown of Egr2 abolished the effect of insulin resistance in HepG2 cells induced with palmitate (PA). Importantly, inhibition of Egr2 decreased the expression of SOCS-1 as well as reduced phosphorylation of JAK2 and STAT3. And, our data indicated that silencing of Egr2 accelerated hepatic glucose uptake and reversed the impaired lipid metabolism upon insulin resistance. In summary, the present study confirms that Egr2 could deteriorate insulin resistance via the pathway of JAK2/STAT3/SOCS-1 and may shed light on resolving insulin resistance and further the pathogenesis of T2DM.

miR199a-5p inhibits hepatic insulin sensitivity via suppression of ATG14-mediated autophagy

MicroRNAs (miRNAs) are known to contribute to many metabolic diseases, including diabetes. In this study, we investigated the role of miR199a-5p in the regulation of hepatic insulin sensitivity. Ad-anti-miR199a-5p adenoviruses were injected into male C57BL/6J WT mice fed a high-fat diet to inhibit miR199a-5p expression before the glucose levels and insulin resistance were assessed. Similarly, Ad-miR199a-5p adenoviruses were injected into male C57BL/6J WT mice to cause the overexpression of miR199a-5p. To investigate the roles of autophagy-related protein 14 (ATG14) and miR199a-5p in the regulation of insulin sensitivity, we injected Ad-miR199a-5p with or without Ad-ATG14 viruses into WT C57BL/6J mice before performing functional assays. Moreover, we infected HepG2 cells or primary hepatocytes with Ad-anti-miR199a-5p or Ad-miR199a-5p viruses to determine the effect of miR199a-5p on insulin resistance in vitro. Finally, we explored the clinical relevance of miR199a-5p by examining the expression level of miR199a-5p in liver samples derived from diabetes patients. We first demonstrated that knocking down miR199a-5p led to decreased glucose tolerance and clearance in vivo, whereas the overexpression of miR199a-5p had the opposite effect. We further identified ATG14 as the target of miR199a-5p, and ATG14 partially rescued miR199a-5p-potentiated glucose and insulin tolerance. In addition, transmission electron microscopy data and western blot data regarding ATG14, LC3 and BECLIN1 illustrated that miR199a-5p regulates autophagy via ATG14. Knocking down miR199a-5p in primary hepatocytes and HepG2 cells suppressed the insulin-stimulated phosphorylation of insulin receptor β, glycogen synthase kinase 3β and protein kinase B, whereas the overexpression of miR199a-5p further potentiated their phosphorylation. Finally, we detected upregulated miR199a-5p levels, which were correlated with reduced ATG14 mRNA levels and downregulated autophagy in liver samples obtained from diabetes patients. Our study uncovered a novel biological role of miR199a-5p in the regulation of hepatic insulin sensitivity via ATG14-mediated autophagy.

Insulin resistance enhances the mitogen-activated protein kinase signaling pathway in ovarian granulosa cells

The ovary is the main regulator of female fertility. Granulosa cell dysfunction may be involved in various reproductive endocrine disorders. Here we investigated the effect of insulin resistance on the metabolism and function of ovarian granulosa cells, and dissected the functional status of the mitogen-activated protein kinase signaling pathway in these cells. Our data showed that dexamethasone-induced insulin resistance in mouse granulosa cells reduced insulin sensitivity, accompanied with an increase in phosphorylation of p44/42 mitogen-activated protein kinase. Furthermore, up-regulation of cytochrome P450 subfamily 17 and testosterone and down-regulation of progesterone were observed in insulin-resistant mouse granulosa cells. Inhibition of p44/42 mitogen-activated protein kinase after induction of insulin resistance in mouse granulosa cells decreased phosphorylation of p44/42 mitogen-activated protein kinase, downregulated cytochrome P450 subfamily 17 and lowered progesterone production. This insulin resistance cell model can successfully demonstrate certain mechanisms such as hyperandrogenism, which may inspire a new strategy for treating reproductive endocrine disorders by regulating cell signaling pathways.

CtBP2 ameliorates palmitate-induced insulin resistance in HepG2 cells through ROS mediated JNK pathway

Oxidative stress plays a significant role in the development of hepatic insulin resistance, but the underlying molecular mechanisms remain poorly understood. In this study, we discovered that C-terminal-binding protein 2 (CtBP2) level was decreased in insulin resistance. Taking into account the relationship between CtBP family protein (ANGUSTIFOLIA) and reactive oxygen species (ROS) accumulation, we conjectured CtBP2 was involved in insulin resistance through ROS induced stress. In order to verify this hypothesis, we over-expressed CtBP2 in palmitate (PA) treated HepG2 cells. Here, we found that over-expression of CtBP2 ameliorated insulin sensitivity by increasing phosphorylation of glycogen synthase kinase 3β (GSK3β) and protein kinase B (AKT). These data suggest that CtBP2 plays a critical role in the development of insulin resistance. Moreover, CtBP2 reversed the effects of PA on ROS level, lipid accumulation, hepatic glucose uptake and gluconeogenesis. We also found that over-expression of CtBP2 could suppress PA induced c-jun NH2 terminal kinase (JNK) activation. Furthermore, JNK inhibitor SP600125 was shown to promote the effect of CtBP2 on insulin signaling. Thus, we demonstrated that CtBP2 ameliorated PA-induced insulin resistance via ROS-dependent JNK pathway.

The Role of p38 MAPK in the Development of Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) is a major complication of diabetes that contributes to an increase in mortality. A number of mechanisms potentially explain the development of DCM including oxidative stress, inflammation and extracellular fibrosis. Mitogen-activated protein kinase (MAPK)-mediated signaling pathways are common among these pathogenic responses. Among the diverse array of kinases, extensive attention has been given to p38 MAPK due to its capacity for promoting or inhibiting the translation of target genes. Growing evidence has indicated that p38 MAPK is aberrantly expressed in the cardiovascular system, including the heart, under both experimental and clinical diabetic conditions and, furthermore, inhibition of p38 MAPK activation in transgenic animal model or with its pharmacologic inhibitor significantly prevents the development of DCM, implicating p38 MAPK as a novel diagnostic indicator and therapeutic target for DCM. This review summarizes our current knowledge base to provide an overview of the impact of p38 MAPK signaling in diabetes-induced cardiac remodeling and dysfunction.