c-Jun N-terminal kinase pathways in diabetes

Molecular Aspects in the Development of Type 2 Diabetes and Possible Preventive and Complementary Therapies

The incidence of diabetes, including type 2 diabetes (T2DM), is increasing sharply worldwide. To reverse this, more effective approaches in prevention and treatment are needed. In our review, we sought to summarize normal insulin action and the pathways that primarily influence the development of T2DM. Normal insulin action involves mitogenic and metabolic pathways, as both are important in normal metabolic processes, regeneration, etc. However, through excess energy, both can be hyperactive or attenuated/inactive leading to disturbances in the cellular and systemic regulation with the consequence of cellular stress and systemic inflammation. In this review, we detailed the beneficial molecular changes caused by some important components of nutrition and by exercise, which act in the same molecular targets as the developed drugs, and can revert the damaged pathways. Moreover, these induce entire networks of regulatory mechanisms and proteins to restore unbalanced homeostasis, proving their effectiveness as preventive and complementary therapies. These are the main steps for success in prevention and treatment of developed diseases to rid the body of excess energy, both from stored fats and from overnutrition, while facilitating fat burning with adequate, regular exercise in healthy people, and together with necessary drug treatment as required in patients with insulin resistance and T2DM.

Bioinformatics analysis to disclose shared molecular mechanisms between type-2 diabetes and clear-cell renal-cell carcinoma, and therapeutic indications

Type 2 diabetes (T2D) and Clear-cell renal cell carcinoma (ccRCC) are both complicated diseases which incidence rates gradually increasing. Population based studies show that severity of ccRCC might be associated with T2D. However, so far, no researcher yet investigated about the molecular mechanisms of their association. This study explored T2D and ccRCC causing shared key genes (sKGs) from multiple transcriptomics profiles to investigate their common pathogenetic processes and associated drug molecules. We identified 259 shared differentially expressed genes (sDEGs) that can separate both T2D and ccRCC patients from control samples. Local correlation analysis based on the expressions of sDEGs indicated significant association between T2D and ccRCC. Then ten sDEGs (CDC42, SCARB1, GOT2, CXCL8, FN1, IL1B, JUN, TLR2, TLR4, and VIM) were selected as the sKGs through the protein-protein interaction (PPI) network analysis. These sKGs were found significantly associated with different CpG sites of DNA methylation that might be the cause of ccRCC. The sKGs-set enrichment analysis with Gene Ontology (GO) terms and KEGG pathways revealed some crucial shared molecular functions, biological process, cellular components and KEGG pathways that might be associated with development of both T2D and ccRCC. The regulatory network analysis of sKGs identified six post-transcriptional regulators (hsa-mir-93-5p, hsa-mir-203a-3p, hsa-mir-204-5p, hsa-mir-335-5p, hsa-mir-26b-5p, and hsa-mir-1-3p) and five transcriptional regulators (YY1, FOXL1, FOXC1, NR2F1 and GATA2) of sKGs. Finally, sKGs-guided top-ranked three repurposable drug molecules (Digoxin, Imatinib, and Dovitinib) were recommended as the common treatment for both T2D and ccRCC by molecular docking and ADME/T analysis. Therefore, the results of this study may be useful for diagnosis and therapies of ccRCC patients who are also suffering from T2D.

Betulinic acid improves TNF-α-induced insulin resistance by inhibiting negative regulator of insulin signalling and inflammation-activated protein kinase in 3T3-L1 adipocytes

CONTEXT

Obesity is related to insulin resistance, and adipose tissue-secreted TNF-α may play a role in inducing obesity. TNF-α activates inflammatory protein kinase and impairs insulin signalling.

OBJECTIVES

We investigated the effect of betulinic acid on insulin resistance caused by TNF-α treatment in 3T3-L1 adipocytes.

MATERIAL AND METHODS

3T3-L1 was exposed to TNF-α in the presence and absence of betulinic acid. Various parameters such as glucose uptake assay, cell viability, expression of proteins involved in insulin resistance were studied.

RESULTS

Betulinic acid increased glucose uptake in TNF-α pre-treated cells and inhibited the activation of PTP1B and JNK and reduced IκBα degradation. Tyrosine phosphorylation was increased, and serine phosphorylation was decreased in IRS-1.

DISCUSSION

Betulinic acid restored TNF-α impaired insulin signalling and increased PI3K activation and phosphorylation of Akt and increased plasma membrane expression of GLUT 4, which stimulated glucose uptake concentration-dependently.

CONCLUSION

These results suggest that betulinic acid is effective at improving TNF-α-induced insulin resistance in adipocytes via inhibiting the activation of negative regulator of insulin signalling and inflammation-activated protein kinase and may potentially improve insulin resistance.

Inflammation and immunological disarrays are associated with acute exercise in type 2 diabetes

Objective

Type 2 diabetes (T2D) is the most common metabolic disorder that is associated with insulin resistance. The aim of the present study is to discover details of the molecular mechanism of exercise on control or progress of diabetic condition in patients via network analysis.

Methods

Gene expression profiles of patients with T2D before and after doing exercise are retrieved from Gene Expression Omnibus (GEO) and are pre-evaluated by the GEO2R program. Data are studied based on expression values, regulatory relationships between the differentially expressed genes (DEGs), gene ontology analyses, and protein-protein interaction PPI network analysis.

Results

A number of 118 significant DEGs were identified and classified based on fold change (FC) values as most dysregulated genes and dysregulated individuals. Action map analysis revealed that 18 DEGs appeared as the critical genes. Gene ontology analysis showed that 24 DEGs are connected to at least four pathways. JUN, IL6, IL1B, PTGS2, FOS, MYC, ATF3, CXCL8, EGR1, EGR2, NR4A1, PLK3, TTN, and UCP3 were identified as central DEGs.

Conclusion

Finally; JUN, IL6, IL1B, PTGS2, FOS, ATF3, CXCL8, EGR1, and EGR2 were introduced as the critical targeted genes by exercise. Since the critical genes after exercise are upregulated and mostly are known as the risk factors of T2D, it can be concluded that unsuitable exercise can develop diabetic conditions in patients. Acute exercise-induced inflammation and immune disturbances seem to be associated with the development of T2D in patients.

To Explore the Putative Molecular Targets of Diabetic Nephropathy and their Inhibition Utilizing Potential Phytocompounds

BACKGROUND

This review critically addresses the putative molecular targets of Diabetic Nephropathy (DN) and screens effective phytocompounds that can be therapeutically beneficial, and highlights their mechanistic modalities of action.

INTRODUCTION

DN has become one of the most prevalent complications of clinical hyperglycemia, with individual-specific variations in the disease spectrum that leads to fatal consequences. Diverse etiologies involving oxidative and nitrosative stress, activation of polyol pathway, inflammasome formation, Extracellular Matrix (ECM) modifications, fibrosis, and change in dynamics of podocyte functional and mesangial cell proliferation adds up to the clinical complexity of DN. Current synthetic therapeutics lacks target-specific approach, and is associated with the development of inevitable residual toxicity and drug resistance. Phytocompounds provides a vast diversity of novel compounds that can become an alternative therapeutic approach to combat the DN.

METHODS

Relevant publications were searched and screened from research databases like GOOGLE SCHOLAR, PUBMED and SCISEARCH. Out of 4895 publications, the most relevant publications were selected and included in this article.

RESULT

This study critically reviews over 60 most promising phytochemical and provides with their molecular targets, that can be of pharmacological significance in context to current treatment and concomitant research in DN.

CONCLUSION

This review highlights those most promising phytocompounds that have the potential of becoming new safer naturally-sourced therapeutic candidates and demands further attention at clinical level.

Membrane polarization in non-neuronal cells as a potential mechanism of metabolic disruption by depolarizing insecticides

A significant rise in the incidence of obesity and type 2 diabetes has occurred worldwide in the last two decades. Concurrently, a growing body of evidence suggests a connection between exposure to environmental pollutants, particularly insecticides, and the development of obesity and type 2 diabetes. This review summarizes key evidence of (1) the presence of different types of neuronal receptors - target sites for neurotoxic insecticides - in non-neuronal cells, (2) the activation of these receptors in non-neuronal cells by membrane-depolarizing insecticides, and (3) changes in metabolic functions, including lipid and glucose accumulation, associated with changes in membrane potential. Based on these findings, we propose that changes in membrane potential (V_mem) by certain insecticides serve as a novel regulator of lipid and glucose metabolism in non-excitable cells associated with obesity and type 2 diabetes.

Phosphorylation of vaccinia-related kinase 1 at threonine 386 transduces glucose stress signal in human liver cells

Vaccinia-related kinase 1 (VRK1) is a chromatin-associated Ser-Thr kinase that regulates numerous downstream factors including DNA repair as well as stress factors c-Jun and p53. Both c-Jun and p53 are phosphorylated at Ser63 and Thr18, respectively, in response to low glucose (40 mg/dl of medium) but not high glucose (140 mg/dl of medium) in human hepatoma-derived Huh-7 cells. Here, we have determined the molecular mechanism by which VRK1 phosphorylates these residues in response to glucose in Huh-7 cells. Human VRK1 auto-phosphorylates Ser376 and Thr386 in in vitro kinase assays. In Huh-7 cells, this auto-phosphorylation activity is regulated by glucose signaling; Thr386 is auto-phosphorylated only in low glucose medium, while Ser376 is not phosphorylated in either medium. A correlation of this low glucose response phosphorylation of Thr386 with the phosphorylation of c-Jun and p53 suggests that VRK1 phosphorylated at Thr386 catalyzes this phosphorylation. In fact, VRK1 knockdown by siRNA decreases and over-expression of VRK1 T386D increases phosphorylated c-Jun and p53 in Huh-7 cells. Phosphorylation by VRK1 of c-Jun but not p53 is regulated by cadherin Plakophilin-2 (PKP2). The PKP2 is purified from whole extracts of Huh-7 cells cultured in low glucose medium and is characterized to bind a C-terminal peptide of the VRK1 molecules to regulate its substrate specificity toward c-Jun. siRNA knockdowns show that PKP2 transduces low glucose signaling to VRK1 only to phosphorylate c-Jun, establishing the low glucose-PKP2-VRK1-c-Jun pathway as a glucose stress signaling pathway.

In silico analysis of phytoconstituents from Tinospora cordifolia with targets related to diabetes and obesity

Traditionally, Tinospora cordifolia is commonly used in the treatment of diabetes and obesity; has been evaluated for their anti-diabetic and anti-obese potency in experimental animal models. However, the binding affinity of multiple bioactives with various proteins involved in the pathogenesis of diabetes and obesity has not been reported yet. Hence, the present study aimed to assess the binding affinity of multiple bioactives from T. cordifolia with various targets involved in the pathogenesis of diabetes and obesity. The ligands and targets were retrieved from the PubChem and Protein Data Bank respectively and docked using autodock4.0. Druglikeness and absorption, distribution, metabolism, excretion, and toxicity profile were predicted using Molsoft and admetSAR1 respectively. The multiple bioactives from T. cordifolia were identified to interact with multiple proteins involved in the pathogenesis of diabetes/obesity, i.e., isocolumbin (- 9 kcal/mol) with adiponectin (PDB: 4DOU), β-sitosterol (- 10.9 kcal/mol) with cholesteryl ester transfer protein (PDB: 2OBD), tinocordiside (- 6.9 kcal/mol) with lamin A/C (PDB: 3GEF), berberine (- 9.5 kcal/mol) with JNK1 (PDB:3ELJ), β-sitosterol & isocolumbin (- 10.1 kcal/mol) with peroxisome proliferator-activated receptor-γ (PDB:4CI5), berberine (- 7.5 kcal/mol) with suppressor of cytokine signaling 3 (PDB: 2BBU), isocolumbin (- 9.6 kcal/mol) with pancreatic α-amylase (PDB: 1B2Y), isocolumbin (- 9 kcal/mol) with α-glucosidase (PDB: 3TOP), and β-sitosterol (- 10.8 kcal/mol) with aldose reductase (PDB: 3RX2). Similarly, among the selected bioactives, tembetarine scored highest druglikeness score, i.e., 1.21. In contrast, isocolumbin scored lowest drug-likeness character i.e. - 0.52. The predicted result of phytochemicals from T. cordifolia for acute oral toxicity, rat acute toxicity, fish toxicity, drug-likeness score, and aqueous solubility showed the probability of lower side/adverse effects in human consumption. The study suggests processing for bioactives from T. cordifolia against diabetes and obesity via in-vitro and in-vivo approaches.

Sustained Stimulation of β2AR Inhibits Insulin Signaling in H9C2 Cardiomyoblast Cells Through the PKA-Dependent Signaling Pathway

INTRODUCTION

This study aimed to investigate the role of β2 adrenergic receptor (β2AR) in insulin signaling transduction in H9C2 cardiomyoblast cells to understand the formation of the β2AR-insulin receptor (IR) protein complex and its role in insulin-induced Glut4 expression.

METHODS

H9C2 cells were treated with various protein inhibitors (CGP, β1AR inhibitor CGP20712; ICI, β2AR inhibitor ICI 118,551; PKI, PKA inhibitor myristoylated PKI; PD 0325901, MEK inhibitor; SP600125, JNK inhibitor) with or without insulin or isoproterenol (ISO) before RNA-sequencing (RNA-Seq) and quantitative-PCR (Q-PCR). Yeast two-hybrid, co-immunoprecipitation and His-tag pull-down assay were carried out to investigate the formation of the β2AR-IR protein complex. The intracellular concentrations of cAMP in H9C2 cells were tested by high performance liquid chromatography (HPLC) and the phosphorylation of JNK was tested by Western blot.

RESULTS

Gene Ontology (GO) analysis revealed that the most significantly enriched processes in the domain of molecular function (MF) were catalytic activity and binding, whereas in the domain of biological processes (BP) were metabolic process and cellular process. Furthermore, the enriched processes in the domain of cellular components (CC) were cell and cell parts. The Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis showed that the most significant pathways that have been altered included the PI3K-Akt and MAPK signaling pathways. Q-PCR, which was performed to verify the gene expression levels exhibited consistent results. In evaluating the signaling pathways, the sustained stimulation of β2AR by ISO inhibited insulin signalling, and the effect was primarily through the cAMP-PKA-JNK pathway and MEK/JNK signaling pathway. Yeast two-hybrid, co-immunoprecipitation and His-tag pull-down assay revealed that β2AR, IR, insulin receptor substrate 1 (IRS1), Grb2-associated binding protein 1 (GAB1) and Grb2 existed in the same protein complex.

CONCLUSION

The sustained stimulation of β2AR might inhibit insulin signaling transduction through the cAMP-PKA-JNK and MEK/JNK pathways in H9C2 cells.

Targeting NLRP3 inflammasome as a promising approach for treatment of diabetic nephropathy: Preclinical evidences with therapeutic approaches

Diabetes mellitus is an increasingly prevalent disease around the globe. The epidemic of diabetes mellitus and its complications pretenses the foremost health threat globally. Diabetic nephropathy is the notable complication in diabetes, leading to end-stage renal disease (ESRD) and premature death. Abundant experimental evidence indicates that oxidative stress and inflammation are the important mediators in diabetic kidney diseases and interlinked with various signal transduction molecular mechanisms. Inflammasomes are the critical components of innate immunity and are recognized as a critical mediator of inflammation and autoimmune disorders. NOD-like receptor protein 3 (NLRP3) inflammasome is the well-characterized protein and it exhibits the sterile inflammation through the regulation of pro-inflammatory cytokines interleukin (IL)-1β and IL-18 production in tissues. In recent years, the role of NLRP3 inflammasome in the pathophysiology of diabetic kidney diseases in both clinical and experimental studies has generated great interest. In the current review, we focused on and discussed the role of NLRP3 inflammasome in diabetic nephropathy. A literature review was performed using online databases namely, PubMed, Scopus, Google Scholar and Web of science to explore the possible pharmacological interventions that blunt the NLRP3 inflammasome-caspase-1-IL-1β/IL-18 axis and shown to have a beneficial effect in diabetic kidney diseases. This review describes the inhibition of NLRP3 inflammasome activation as a promising therapeutic target for drug discovery in future.

Kinome Profiling Reveals Abnormal Activity of Kinases in Skeletal Muscle From Adults With Obesity and Insulin Resistance

CONTEXT

Obesity-related insulin resistance (OIR) is one of the main contributors to type 2 diabetes and other metabolic diseases. Protein kinases are implicated in insulin signaling and glucose metabolism. Molecular mechanisms underlying OIR involving global kinase activities remain incompletely understood.

OBJECTIVE

To investigate abnormal kinase activity associated with OIR in human skeletal muscle.

DESIGN

Utilization of stable isotopic labeling-based quantitative proteomics combined with affinity-based active enzyme probes to profile in vivo kinase activity in skeletal muscle from lean control (Lean) and OIR participants.

PARTICIPANTS

A total of 16 nondiabetic adults, 8 Lean and 8 with OIR, underwent hyperinsulinemic-euglycemic clamp with muscle biopsy.

RESULTS

We identified the first active kinome, comprising 54 active protein kinases, in human skeletal muscle. The activities of 23 kinases were different in OIR muscle compared with Lean muscle (11 hyper- and 12 hypo-active), while their protein abundance was the same between the 2 groups. The activities of multiple kinases involved in adenosine monophosphate-activated protein kinase (AMPK) and p38 signaling were lower in OIR compared with Lean. On the contrary, multiple kinases in the c-Jun N-terminal kinase (JNK) signaling pathway exhibited higher activity in OIR vs Lean. The kinase-substrate-prediction based on experimental data further confirmed a potential downregulation of insulin signaling (eg, inhibited phosphorylation of insulin receptor substrate-1 and AKT1/2).

CONCLUSIONS

These findings provide a global view of the kinome activity in OIR and Lean muscle, pinpoint novel specific impairment in kinase activities in signaling pathways important for skeletal muscle insulin resistance, and may provide potential drug targets (ie, abnormal kinase activities) to prevent and/or reverse skeletal muscle insulin resistance in humans.

The Role of JNk Signaling Pathway in Obesity-Driven Insulin Resistance

Obesity is not only closely related to insulin resistance but is one of the main factors leading to the formation of Type 2 Diabetes (T2D) too. The c-Jun N-terminal kinase (JNK) family is a member of the mitogen-activated protein kinase (MAPK) superfamily. JNK is also one of the most investigated signal transducers in obesity and insulin resistance. JNK-centric JNK signaling pathway can be activated by growth factors, cytokines, stress responses, and other factors. Many researches have identified that the activated phosphorylation JNK negatively regulates insulin signaling pathway in insulin resistance which can be simultaneously regulated by multiple signaling pathways related to the JNK signaling pathway. In this review, we provide an overview of the composition of the JNK signaling pathway, its regulation of insulin signaling pathway, and the relationship between the JNK signaling pathway and other pathways in insulin resistance.

Cold-pressed Canola Oil Reduces Hepatic Steatosis by Modulating Oxidative Stress and Lipid Metabolism in KM Mice Compared with Refined Bleached Deodorized Canola Oil

The quality of canola oil is affected by different extraction methods. The effect of cold-pressed canola oil (CPCO) diet and traditional refined bleached deodorized canola oil (RBDCO) diet on lipid accumulation and hepatic steatosis in mice were investigated. The body weight, peroxisome proliferator-activated receptor-α concentration, serum lipid profile, insulin sensitivity, and oxidative stress were increased in mice fed with CPCO diet, which had higher unsaturated fatty acid, tocopherols, phytosterols, and phospholipids but lower saturated fatty acid than RBDCO, after 12 weeks,. Moreover, CPCO significantly increased tocopherols and phytosterols content in liver and reduced liver cholesterol contents and lipid vacuoles accumulation than RBDCO. Also, serum proinflammatory cytokines, 3-hydroxy-3-methylglutary coenzyme A reductase expression level, lipogenic enzymes, and transcriptional factors such as sterol regulatory element-binding proteins 1c, acetyl-CoA carboxylase, and fatty acid synthase in the liver were also markedly downregulated from CPCO diet mice. Overall, CPCO can reduce lipid accumulation and hepatic steatosis by regulating oxidative stress and lipid metabolism in Kun Ming mice compared with RBDCO. PRACTICAL APPLICATION: The results suggested that more bioactive components were contained in cold-pressed canola oil (CPCO) rather than refined bleached deodorized canola oil (RBDCO). CPCO could lower the risk of obesity and hyperlipidemia, reduce lipid accumulation, and prevent hepatic steatosis. It could be considered as a kind of better edible oil than RBDCO.

Effect of metformin and flutamide on insulin, lipogenic and androgen-estrogen signaling, and cardiometabolic risk in a PCOS-prone metabolic syndrome rodent model

Polycystic ovary syndrome (PCOS) is highly associated with cardiometabolic risk and the metabolic syndrome (MetS), predisposing women to increased risk of developing type 2 diabetes and cardiovascular disease. Metformin is commonly used to treat insulin resistance-glucose intolerance, and flutamide, an androgen receptor (AR) antagonist, is used to target hyperandrogenemia and dyslipidemia. Currently, the physiological mechanism of action of these treatments on androgen, lipidogenic, and insulin signaling pathways remains unclear in PCOS. The aim of this study was to investigate the effects and mechanisms of action of metformin and flutamide on plasma lipid-apolipoprotein (Apo)B-lipoprotein and insulin-glucose metabolism, and endocrine-reproductive indices in a PCOS-prone MetS rodent model. PCOS-prone rodents were treated with metformin (300 mg/kg body wt), flutamide (30 mg/kg body wt), or metformin + flutamide combination treatment for 6 wk. Metformin was shown to improve fasting insulin and HOMA-IR, whereas flutamide and combination treatment were shown to reduce plasma triglycerides, ApoB48, and ApoB100, and this was associated with decreased intestinal secretion of ApoB48/triglyceride. Flutamide and metformin were shown to reduce plasma androgen indices and to improve ovarian primary and preovulatory follicle frequency. Metformin treatment increased hepatic estrogen receptor (ER)α, and metformin-flutamide decreased intestinal AR and increased ERα mRNA expression. Metformin-flutamide treatment upregulated hepatic and intestinal insulin signaling, including insulin receptor, MAPK1, and AKT2. In conclusion, cardiometabolic risk factors, in particular ApoB-hypertriglyceridemia, are independently modulated via the AR, and understanding the contribution of AR and insulin-signaling pathways further may facilitate the development of targeted interventions in high-risk women with PCOS and MetS.

Tea Polypeptide Ameliorates Diabetic Nephropathy through RAGE and NF-κB Signaling Pathway in Type 2 Diabetes Mice

Diabetic nephropathy (DN) is a major complication of type 2 diabetes (T2D), which is a key determinant of mortality in diabetic patients. Developing new therapeutic drugs which can not only control T2D but also prevent the development of DN is of great significance. We studied the therapeutic potential of Cuiyu tea polypeptides (TP), natural bioactive peptides isolated from a type of green tea, against DN and its underlying molecular mechanisms. TP (1000 mg/kg bw/day, p.o.) administration for 5 weeks significantly reduced the fasting blood glucose by 52.04 ± 9.23% in the high fat diet/streptozocin (HFD/STZ)-induced (30 mg/kg bw) diabetic mice. Compared to the model group, the serum insulin level of the TP group was decreased by 25.54 ± 6.06%, while at the same time, the HOMA-IR, HOMA-IS, and lipid levels showed different degrees of recovery ( p < 0.05). Moreover, in TP group mice the total urinary protein, creatinine, and urine nitrogen, all which can reflect the damage degree of the glomerular filtration function to a certain extent, dramatically declined by 34.51 ± 2.65%, 42.24 ± 15.24%, and 80.30 ± 6.01% compared to the model group, respectively. Mechanistically, TP stimulated the polyol PKCζ/JNK/NF-κB/TNF-α/iNOS and AGEs/RAGE/TGF-β1 pathways, upregulated the expression of podocin in the glomeruli, and decreased the release of pro-inflammatory cytokines. These results strongly indicate the therapeutic potential of TP against DN.

GNIP1 E3 ubiquitin ligase is a novel player in regulating glycogen metabolism in skeletal muscle

BACKGROUND

Glycogenin-interacting protein 1 (GNIP1) is a tripartite motif (TRIM) protein with E3 ubiquitin ligase activity that interacts with glycogenin. These data suggest that GNIP1 could play a major role in the control of glycogen metabolism. However, direct evidence based on functional analysis remains to be obtained.

OBJECTIVES

The aim of this study was 1) to define the expression pattern of glycogenin-interacting protein/Tripartite motif containing protein 7 (GNIP/TRIM7) isoforms in humans, 2) to test their ubiquitin E3 ligase activity, and 3) to analyze the functional effects of GNIP1 on muscle glucose/glycogen metabolism both in human cultured cells and in vivo in mice.

RESULTS

We show that GNIP1 was the most abundant GNIP/TRIM7 isoform in human skeletal muscle, whereas in cardiac muscle only TRIM7 was expressed. GNIP1 and TRIM7 had autoubiquitination activity in vitro and were localized in the Golgi apparatus and cytosol respectively in LHCN-M2 myoblasts. GNIP1 overexpression increased glucose uptake in LHCN-M2 myotubes. Overexpression of GNIP1 in mouse muscle in vivo increased glycogen content, glycogen synthase (GS) activity and phospho-GSK-3α/β (Ser21/9) and phospho-Akt (Ser473) content, whereas decreased GS phosphorylation in Ser640. These modifications led to decreased blood glucose levels, lactate levels and body weight, without changing whole-body insulin or glucose tolerance in mouse.

CONCLUSION

GNIP1 is an ubiquitin ligase with a markedly glycogenic effect in skeletal muscle.

Bioactive phytochemicals that regulate the cellular processes involved in diabetic nephropathy

BACKGROUND

Owing to the multiple causative factors, the current advances in medication for diabetic nephropathy (DN) do not appear to have improved therapies for patients. Furthermore, use of multiple synthetic medications has shown various adverse effects and ultimately leads to deterioration of the condition. Medicinal plants and their bioactive constituents are considered to be safer and more effective than synthetic medicines against various chronic diseases. Therefore, the use of natural products in the management of DN has been suggested. In this article, we review medicinal plants and their specific bioactive phytochemicals that regulate the various cellular processes involved in the initiation of DN. A wide range of literature on phytochemicals and medicinal plants that may ameliorate DN was explored from the online available English works in various electronic databases, including Embase, Google Scholar, PubMed, Scopus, and Science Direct.

RESULTS

Medicinal plants possess various bioactive constituents, which may slow or ameliorate the progression of DN and improve renal function through the targeting of multiple pathological causes via different pathways, including p38MAPK, JNK, ERK, TGF-β, RhoA, NF-κB, Wnt, JAK-STAT, AMPK, mTOR, Akt, and TXNIP. Depletion or inhibition of these accelerating factors may provide a significant treatment for DN.

CONCLUSION

Based on various experimental studies, traditional herbs and their bioactive constituents regulate the cellular processes involved in the initiation of DN owing to their significant pharmacological activities; however, the efficacy in animal models and humans has not yet been explored. Therefore, studies should be performed to evaluate the nephroprotective effects of medicinal plants in preclinical animal models and in humans.

Susceptible and Prognostic Genetic Factors Associated with Diabetic Peripheral Neuropathy: A Comprehensive Literature Review

Type 2 diabetes mellitus (T2D) is a disorder of glucose metabolism. It is a complex process involving the regulation of insulin secretion, insulin sensitivity, gluconeogenesis, and glucose uptake at the cellular level. Diabetic peripheral neuropathy (DPN) is one of the debilitating complications that is present in approximately 50% of diabetic patients. It is the primary cause of diabetes-related hospital admissions and nontraumatic foot amputations. The pathogenesis of diabetic neuropathy is a complex process that involves hyperglycemia-induced oxidative stress and altered polyol metabolism that changes the nerve microvasculature, altered growth factor support, and deregulated lipid metabolism. Recent literature has reported that there are several heterogeneous groups of susceptible genetic loci which clearly contribute to the development of DPN. Several studies have reported that some patients with prediabetes develop neuropathic complications, whereas others demonstrated little evidence of neuropathy even after long-standing diabetes. There is emerging evidence that genetic factors may contribute to the development of DPN. This paper aims to provide an up-to-date review of the susceptible and prognostic genetic factors associated with DPN. An extensive survey of the scientific literature published in PubMed using the search terms "Diabetic peripheral neuropathy/genetics" and "genome-wide association study" was carried out, and the most recent and relevant literature were included in this review.

Caffeic Acid Phenethyl Ester (Propolis Extract) Ameliorates Insulin Resistance by Inhibiting JNK and NF-κB Inflammatory Pathways in Diabetic Mice and HepG2 Cell Models

Caffeic acid phenethyl ester (CAPE), extracted from propolis, was evaluated for the ameliorative effects on insulin resistance and the mechanisms were identified, using non-insulin-dependent diabetes mellitus (NIDDM) model mice and insulin resistance (IR) model cells. After 5 weeks of CAPE supplementation, insulin sensitivity, hyperlipidemia, and peroxisome proliferator-activated receptor-α (PPAR-α) levels were improved in mice. Proinflammatory cytokines in serum and the expressions of tumor necrosis factor-alpha (TNF-α) mRNA in tissues were markedly downregulated from CAPE-treated mice. In vitro, CAPE supplement significantly improved glucose consumption, glucose uptake, glycogen content, and oxidative stress and decreased expression of glucose-6-phosphatase (G6Pase) mRNA in cells. Both in vivo and in vitro, CAPE enhanced p-Akt (Ser473) and p-insulin receptor substrate (IRS)-1 (Tyr612), but inhibited p-JNK (Thr183/Tyr185), p-NF-κB p65 (Ser536), and nuclear translocation of p-NF-κB p65 (Ser536). In summary, CAPE can ameliorate insulin resistance through modulation of JNK and NF-κB signaling pathway in mice and HepG2 cells.

High glucose-induced endothelial progenitor cell dysfunction

Vascular complications contribute significantly to morbidity and mortality of diabetes mellitus. The primary cause of vascular complications in diabetes mellitus is hyperglycaemia, associated with endothelial dysfunction and impaired neovascularization. Circulating endothelial progenitor cells was shown to play important roles in vascular repair and promoting neovascularization. In this review, we will demonstrate the individual effect of high glucose on endothelial progenitor cells. Endothelial progenitor cells isolated from healthy subjects exposed to high glucose conditions or endothelial progenitor cells isolated from diabetic patients exhibit reduced number of endothelial cell colony forming units, impaired abilities of differentiation, proliferation, adhesion and migration, tubulization, secretion, mobilization and homing, whereas enhanced senescence. Increased production of reactive oxygen species by the mitochondria seems to play a crucial role in high glucose-induced endothelial progenitor cells deficit. Later, we will review the agents that might be used to alleviate dysfunction of endothelial progenitor cells induced by high glucose. The conclusions are that the relationship between hyperglycaemia and endothelial progenitor cells dysfunction is only beginning to be recognized, and future studies should pay more attention to the haemodynamic environment of endothelial progenitor cells and ageing factors to discover novel treatment agents.

Roles of the NLRP3 inflammasome in the pathogenesis of diabetic nephropathy

Diabetic nephropathy (DN) is a serious complication of diabetes mellitus, and persistent inflammation in circulatory and renal tissues is an important pathophysiological basis for DN. The essence of the microinflammatory state is the innate immune response, which is central to the occurrence and development of DN. Members of the inflammasome family, including both "receptors" and "regulators", are key to the inflammatory immune response. Nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) and other inflammasome components are able to detect endogenous danger signals, resulting in activation of caspase-1 as well as interleukin (IL)-1β, IL-18 and other cytokines; these events stimulate the inflammatory cascade reaction, which is crucial for DN. Hyperglycaemia, hyperlipidaemia and hyperuricaemia can activate the NLRP3 inflammasome, which then mediates the occurrence and development of DN through the K⁺ channel model, the lysosomal damage model and the active oxygen cluster model. In this review, we survey the involvement of the NLRP3 inflammasome in various signalling pathways and highlight different aspects of their influence on DN. We also explore the important effects of the NLRP3 inflammasome on kidney function and structural changes that occur during DN development and progression. It is becoming more evident that NLRP3 inflammasome targeting has therapeutic potential for the treatment of DN.

Therapeutic effects of 1,25-dihydroxyvitamin D3 on diabetes-induced liver complications in a rat model

It has been suggested that 1,25-dihydroxyvitamin D3 (vitamin D) plays a protective role against inflammation and insulin resistance (IR) in type 2 diabetes mellitus (T2DM). The present study investigate the hypothesis that vitamin D may exert beneficial effects on the liver in a rat model of T2DM by regulating the expression of inflammation-related cytokines and ameliorating IR induced by inflammation. Normal control group rats were fed a basic diet (NC). Experimental rats received a high-fat diet for 8 weeks and were then injected with streptozotocin (STZ) to induce T2DM. Half of the T2DM model rats received vitamin D (0.03 µg/kg/day) for 8 weeks (vitamin D-treated group; VD; n=11), while the other (T2DM group; DM; n=10) and NC group received an equivalent quantity of peanut oil. Following sacrifice, fasting plasma glucose (FPG) and fasting insulin (FINS) were recorded and homeostasis model assessment of IR (HOMA-IR) was calculated. Liver histopathology was examined using hematoxylin and eosin staining. The levels of the inflammatory cytokines C-Jun N-terminal kinase, C-Jun, tumor necrosis factor-α and interleukin-1β were measured using immunohistology, quantitative polymerase chain reaction and western blot analyses. The results revealed that treatment with vitamin D markedly alleviated the pathological alterations of liver and reduced the expression of inflammatory cytokines at the protein and mRNA levels. Furthermore, decreased levels of FPG, HOMA-IR and increased FINS were detected. In conclusion, the results of the present study indicate that vitamin D has therapeutic effects on diabetes-induced liver complications in T2DM model rats, which may involve the modulation of the inflammatory response, attenuating the crosstalk' between inflammation and IR and ameliorating hyperglycemic state.

Role of Toll-like receptors in diabetic renal lesions in a miniature pig model

The mechanisms of diabetic renal injury remain unclear. Recent studies have shown that immunological and inflammatory elements play important roles in the initiation and development of diabetic nephropathy (DN). Toll-like receptors (TLRs) comprise a superfamily of innate immune system receptors. The roles and mechanisms of TLRs in the pathogenesis of diabetic renal lesions are mostly unknown. Compared with rodents, miniature pigs are more similar to humans with respect to metabolism, kidney structure, and immune system, and therefore represent an ideal large-animal model for DN mechanistic studies. A diabetes model was established by feeding miniature pigs with high-sugar and high-fat diets. Functional and pathological markers, expression and activation of endogenous TLR ligands [HSP70 (heat shock protein 70) and HMGB1], TLR1 to TLR11 and their downstream signaling pathway molecules (MyD88, IRAK-1, and IRF-3), nuclear factor κB (NF-κB) signaling pathway molecules (IKKβ, IκBα, and NF-κBp65), inflammatory cytokines [IL-6 (interleukin-6), MIP-2, MCP-1, CCL5, and VCAM-1 (vascular cell adhesion molecule-1)], and infiltration of inflammatory cells were systematically evaluated. The expression of HSP70 was significantly increased in diabetic pig kidneys. The expression of MyD88-dependent TLR2, TLR4, TLR5, TLR7, TLR8, and TLR11 and their downstream signaling molecules MyD88 and phospho-IRAK-1 (activated IRAK-1), as well as that of MyD88-independent TLR3 and TLR4 and their downstream signaling molecule phospho-IRF-3 (activated IRF-3), was significantly up-regulated. The expression and activation of NF-κB pathway molecules phospho-IKKβ, phospho-IκBα, NF-κBp65, and phospho-NF-κBp65 were significantly increased. Levels of IL-6, MIP-2, MCP-1, CCL5, VCAM-1, and macrophage marker CD68 were significantly increased in diabetic pig kidneys. These results suggested that the metabolic inflammation activated by TLRs might play an important role in diabetic renal injuries.

Research progress in signalling pathway in diabetic nephropathy

Diabetic nephropathy, a lethal diabetic complication, is a leading cause of end-stage renal disease, which is pathologically characterized by thickened tubular basal and glomerular membranes, accumulated extracellular matrix, and progressive mesangial hypertrophy. Growing evidence indicates that diabetic nephropathy is induced by multiple conditions, such as glucose metabolism disorder, oxidative stress, numerous inflammatory factors and cytokines, and haemodynamic changes that lead to the occurrence and development of diabetic nephropathy based on genetic susceptibility. A variety of abnormalities in the signalling pathway may interact to produce these pathologic processes. Research has aimed to highlight the signalling pathway mechanisms that lead to diabetic nephropathy so that preventative strategies and effective therapies might be developed. In this review, important pathways that appear to be involved in driving these processes are discussed.

[Implication of MAP kinases in obesity-induced inflammation and insulin resistance]

Insulin resistance is often associated with obesity and is a major risk factor for development of type 2 diabetes as well as cardiovascular and hepatic diseases. Insulin resistance may also increase the incidence or the aggressiveness of some cancers. Insulin resistance occurs owing to defects in insulin signaling in target tissues of this hormone. During the last ten years, it became evident that the chronic low-grade inflammatory state that develops during obesity plays an important role in insulin resistance development. Indeed, inflammatory cytokines activate several signaling pathways that impinge on the insulin signaling pathway. Among them, this review will focus on the implication of the MAP kinases JNK and ERK1/2 signaling in the development of insulin signaling alterations and will discuss the possibility to target these pathways in order to fight insulin resistance.

Forkhead box(O) in control of reactive oxygen species and genomic stability to ensure healthy lifespan

SIGNIFICANCE

Transcription factors of the Forkhead box O class (FOXOs) are associated with lifespan and play a role in age-related diseases. FOXOs, therefore, serve as a paradigm for developing an understanding as to how age-related diseases, such as cancer and diabetes interconnect with lifespan. Understanding the regulatory inputs on FOXO may reveal how changes in these regulatory signaling pathways affect disease and lifespan.

RECENT ADVANCES

Numerous regulators of FOXO have now been described and a clear and evolutionary conserved role has emerged for phosphoinositide-3 kinase/protein kinase B (also known as c-Akt or AKT) signaling and c-jun N-terminal kinase signaling. Analysis of FOXO function in the context of these signaling pathways has shown the importance of FOXO-mediated transcriptional regulation on cell cycle progression and other cell fates, such as cell metabolism, stress resistance, and apoptosis in mediating disease and lifespan.

CRITICAL ISSUES

Persistent DNA damage is also tightly linked to disease and aging; yet, data on a possible link between DNA damage and FOXO have been limited. Here, we discuss possible connections between FOXO and the DNA damage response in the context of the broader role of connecting lifespan and disease.

FUTURE DIRECTIONS

Understanding the role of lifespan in diseases onset may provide unique and generic possibilities to intervene in disease processes to ensure a healthy lifespan.

Skeletal myoblast transplantation on gene expression profiles of insulin signaling pathway and mitochondrial biogenesis and function in skeletal muscle

AIM

The study aims to investigate the gene expression profiling of insulin signaling pathway and mitochondrial biogenesis and function in the skeletal muscle of KK mice.

METHODS

KK mice were divided into the following groups: KK control group, basal medium (M199) only; KK fibroblast group, with human fibroblast transplantation; KK myoblast group, with human skeletal myoblast transplantation. C57BL mice received hSkM transplantation as a normal control. Cells were transplanted into mice hind limb skeletal muscle. All animals were treated with cyclosporine for 6 weeks only. The mice were sacrificed in a fasting state at 12 weeks after treatment. Hind limb skeletal muscle was harvested and used for study of gene expression profiling.

RESULTS

hSkMs survived extensively in mice skeletal muscle at 12 weeks after cell transplantation. Glucose tolerance test showed a significant decrease of blood glucose in the mice of KK myoblast group compared to the KK control and fibroblast groups. Transcriptional patterns of insulin signaling pathway showed alterations in KK myoblast as compared with KK control group (23 genes), KK fibroblast group (7 genes), and C57BL group (8 genes). Transcriptional patterns of mitochondrial biogenesis and function also had alterations in KK myoblast as compared with KK control group (27 genes), KK fibroblast group (9 genes), and C57BL group (6 genes).

CONCLUSIONS

These data demonstrated for the first time that hSKM transplantation resulted in a change of gene transcript in multiple genes involved in insulin signaling pathway and mitochondrial biogenesis and function.

Proteomic and bioinformatic analysis of membrane proteome in type 2 diabetic mouse liver

Type 2 diabetes mellitus (T2DM) is the most prevalent and serious metabolic disease affecting people worldwide. T2DM results from insulin resistance of the liver, muscle, and adipose tissue. In this study, we used proteomic and bioinformatic methodologies to identify novel hepatic membrane proteins that are related to the development of hepatic insulin resistance, steatosis, and T2DM. Using FT-ICR MS, we identified 95 significantly differentially expressed proteins in the membrane fraction of normal and T2DM db/db mouse liver. These proteins are primarily involved in energy metabolism pathways, molecular transport, and cellular signaling, and many of them have not previously been reported in diabetic studies. Bioinformatic analysis revealed that 16 proteins may be related to the regulation of insulin signaling in the liver. In addition, six proteins are associated with energy stress-induced, nine proteins with inflammatory stress-induced, and 14 proteins with endoplasmic reticulum stress-induced hepatic insulin resistance. Moreover, we identified 19 proteins that may regulate hepatic insulin resistance in a c-Jun amino-terminal kinase-dependent manner. In addition, three proteins, 14-3-3 protein beta (YWHAB), Slc2a4 (GLUT4), and Dlg4 (PSD-95), are discovered by comprehensive bioinformatic analysis, which have correlations with several proteins identified by proteomics approach. The newly identified proteins in T2DM should provide additional insight into the development and pathophysiology of hepatic steatosis and insulin resistance, and they may serve as useful diagnostic markers and/or therapeutic targets for these diseases.

A genome-wide siRNA screen to identify modulators of insulin sensitivity and gluconeogenesis

Background

Hepatic insulin resistance impairs insulin’s ability to suppress hepatic glucose production (HGP) and contributes to the development of type 2 diabetes (T2D). Although the interests to discover novel genes that modulate insulin sensitivity and HGP are high, it remains challenging to have a human cell based system to identify novel genes.

Methodology/Principal Findings

To identify genes that modulate hepatic insulin signaling and HGP, we generated a human cell line stably expressing beta-lactamase under the control of the human glucose-6-phosphatase (G6PC) promoter (AH-G6PC cells). Both beta-lactamase activity and endogenous G6PC mRNA were increased in AH-G6PC cells by a combination of dexamethasone and pCPT-cAMP, and reduced by insulin. A 4-gene High-Throughput-Genomics assay was developed to concomitantly measure G6PC and pyruvate-dehydrogenase-kinase-4 (PDK4) mRNA levels. Using this assay, we screened an siRNA library containing pooled siRNA targeting 6650 druggable genes and identified 614 hits that lowered G6PC expression without increasing PDK4 mRNA levels. Pathway analysis indicated that siRNA-mediated knockdown (KD) of genes known to positively or negatively affect insulin signaling increased or decreased G6PC mRNA expression, respectively, thus validating our screening platform. A subset of 270 primary screen hits was selected and 149 hits were confirmed by target gene KD by pooled siRNA and 7 single siRNA for each gene to reduce G6PC expression in 4-gene HTG assay. Subsequently, pooled siRNA KD of 113 genes decreased PEPCK and/or PGC1alpha mRNA expression thereby demonstrating their role in regulating key gluconeogenic genes in addition to G6PC. Last, KD of 61 of the above 113 genes potentiated insulin-stimulated Akt phosphorylation, suggesting that they suppress gluconeogenic gene by enhancing insulin signaling.

Conclusions/Significance

These results support the proposition that the proteins encoded by the genes identified in our cell-based druggable genome siRNA screen hold the potential to serve as novel pharmacological targets for the treatment of T2D.

NADPH oxidase-derived superoxide anion-induced apoptosis is mediated via the JNK-dependent activation of NF-κB in cardiomyocytes exposed to high glucose

Hyperglycemia-induced generation of reactive oxygen species (ROS) can lead to cardiomyocyte apoptosis and cardiac dysfunction. However, the mechanism by which high glucose causes cardiomyocyte apoptosis is not clear. In this study, we investigated the signaling pathways involved in NADPH oxidase-derived ROS-induced apoptosis in cardiomyocytes under hyperglycemic conditions. H9c2 cells were treated with 5.5 or 33 mM glucose for 36 h. We found that 33 mM glucose resulted in a time-dependent increase in ROS generation as well as a time-dependent increase in protein expression of p22(phox), p47(phox), gp91(phox), phosphorylated IκB, c-Jun N-terminal kinase (JNK) and p38, as well as the nuclear translocation of NF-kB. Treatment with apocynin or diphenylene iodonium (DPI), NADPH oxidase inhibitors, resulted in reduced expression of p22(phox), p47(phox), gp91(phox), phosphorylated IκB, c-Jun N-terminal kinase (JNK) and p38. In addition, treatment with JNK and NF-kB siRNAs blocked the activity of caspase-3. Furthermore, treatment with JNK, but not p38, siRNA inhibited the glucose-induced activation of NF-κB. Similar results were obtained in neonatal cardiomyocytes exposed to high glucose concentrations. Therefore, we propose that NADPH oxidase-derived ROS-induced apoptosis is mediated via the JNK-dependent activation of NF-κB in cardiomyocytes exposed to high glucose.

Implication of inflammatory signaling pathways in obesity-induced insulin resistance

Obesity is characterized by the development of a low-grade chronic inflammatory state in different metabolic tissues including adipose tissue and liver. This inflammation develops in response to an excess of nutrient flux and is now recognized as an important link between obesity and insulin resistance. Several dietary factors like saturated fatty acids and glucose as well as changes in gut microbiota have been proposed as triggers of this metabolic inflammation through the activation of pattern-recognition receptors (PRRs), including Toll-like receptors (TLR), inflammasome, and nucleotide oligomerization domain (NOD). The consequences are the production of pro-inflammatory cytokines and the recruitment of immune cells such as macrophages and T lymphocytes in metabolic tissues. Inflammatory cytokines activate several kinases like IKKβ, mTOR/S6 kinase, and MAP kinases as well as SOCS proteins that interfere with insulin signaling and action in adipocytes and hepatocytes. In this review, we summarize recent studies demonstrating that PRRs and stress kinases are important integrators of metabolic and inflammatory stress signals in metabolic tissues leading to peripheral and central insulin resistance and metabolic dysfunction. We discuss recent data obtained with genetically modified mice and pharmacological approaches suggesting that these inflammatory pathways are potential novel pharmacological targets for the management of obesity-associated insulin resistance.

MAPK/ERK signaling regulates insulin sensitivity to control glucose metabolism in Drosophila

The insulin/IGF-activated AKT signaling pathway plays a crucial role in regulating tissue growth and metabolism in multicellular animals. Although core components of the pathway are well defined, less is known about mechanisms that adjust the sensitivity of the pathway to extracellular stimuli. In humans, disturbance in insulin sensitivity leads to impaired clearance of glucose from the blood stream, which is a hallmark of diabetes. Here we present the results of a genetic screen in Drosophila designed to identify regulators of insulin sensitivity in vivo. Components of the MAPK/ERK pathway were identified as modifiers of cellular insulin responsiveness. Insulin resistance was due to downregulation of insulin-like receptor gene expression following persistent MAPK/ERK inhibition. The MAPK/ERK pathway acts via the ETS-1 transcription factor Pointed. This mechanism permits physiological adjustment of insulin sensitivity and subsequent maintenance of circulating glucose at appropriate levels.

Insulin signaling is an important and conserved physiological regulator of growth, metabolism, and longevity in multicellular animals. Disturbance in insulin signaling is common in human metabolic disorders. For example insulin resistance is a hallmark of diabetes and metabolic syndrome. While the core components of the insulin signaling pathway have been well established, the mechanisms that adjust the insulin responsiveness are only known to a limited extent. Here we present results from a genetic screen in Drosophila that was designed to identify regulators of cellular insulin sensitivity in an in vivo context. Surprisingly, we discovered cross-talk between the epidermal growth factor receptor (EGFR)–activated MAPK/ERK and insulin signaling pathways. This regulatory mechanism, which involves transcriptional control of insulin-like receptor gene, is utilized in vivo to maintain circulating glucose at appropriate levels. We provide evidence for a regulatory feed-forward mechanism that allows for dynamic transient responsiveness as well as more stable, long-lasting modulation of insulin responsiveness by growth factor receptor signaling. The combination of these mechanisms may contribute to robustness, allowing metabolism to be appropriately responsive to physiological inputs while mitigating the effects of biological noise.

The identification of gene expression profiles associated with progression of human diabetic neuropathy

Diabetic neuropathy is a common complication of diabetes. While multiple pathways are implicated in the pathophysiology of diabetic neuropathy, there are no specific treatments and no means to predict diabetic neuropathy onset or progression. Here, we identify gene expression signatures related to diabetic neuropathy and develop computational classification models of diabetic neuropathy progression. Microarray experiments were performed on 50 samples of human sural nerves collected during a 52-week clinical trial. A series of bioinformatics analyses identified differentially expressed genes and their networks and biological pathways potentially responsible for the progression of diabetic neuropathy. We identified 532 differentially expressed genes between patient samples with progressing or non-progressing diabetic neuropathy, and found these were functionally enriched in pathways involving inflammatory responses and lipid metabolism. A literature-derived co-citation network of the differentially expressed genes revealed gene subnetworks centred on apolipoprotein E, jun, leptin, serpin peptidase inhibitor E type 1 and peroxisome proliferator-activated receptor gamma. The differentially expressed genes were used to classify a test set of patients with regard to diabetic neuropathy progression. Ridge regression models containing 14 differentially expressed genes correctly classified the progression status of 92% of patients (P < 0.001). To our knowledge, this is the first study to identify transcriptional changes associated with diabetic neuropathy progression in human sural nerve biopsies and describe their potential utility in classifying diabetic neuropathy. Our results identifying the unique gene signature of patients with progressive diabetic neuropathy will facilitate the development of new mechanism-based diagnostics and therapies.

Obesity and susceptibility to autoimmune diseases

For decades, obesity has been considered to be the result of the complex interaction between genes and the environment and its pathogenesis is still unresolved. The discovery of hormones and neural mediators responsible for the control of food intake and metabolism at the hypothalamic level has provided fundamental insights into the complicated pathways that control food intake. However, the molecular basis for the association between obesity and low-degree chronic inflammation is still unknown. More recently, the discovery of leptin, one of the most abundant adipocyte-derived hormones, has suggested that nutritional status, through leptin secretion, can control immune self-tolerance modulating Treg suppressive function and responsiveness. Furthermore, recent experimental evidence has shown the presence of an abundant adipose tissue-resident Treg population responsible for the control of metabolic parameters and glucose homeostasis. Better knowledge of the intricate network of interactions among leptin-related energy regulation, Treg activities and obesity could lead to valuable strategies for therapeutic intervention in obesity and obesity-associated insulin resistance.

Measuring the constitutive activation of c-Jun N-terminal kinase isoforms

The c-Jun N-terminal kinases (JNK) are important regulators of cell growth, proliferation, and apoptosis. JNKs are typically activated by a sequence of events that include phosphorylation of its T-P-Y motif by an upstream kinase, followed by homodimerization and translocation to the nucleus. Constitutive activation of JNK has been found in a variety of cancers including non-small cell lung carcinomas, gliomas, and mantle cell lymphoma. In vitro studies show that constitutive activation of JNK induces a transformed phenotype in fibroblasts and enhances tumorigenicity in a variety of cell lines. Interestingly, a subset of JNK isoforms was recently found to autoactivate rendering the proteins constitutively active. These constitutively active JNK proteins were found to play a pivotal role in activating transcription factors that increase cellular growth and tumor formation in mice. In this chapter, we describe techniques and methods that have been successfully used to study the three components of JNK activation. Use of these techniques may lead to a better understanding of the components of JNK pathways and how JNK is activated in cancer cells.

Ethanol-induced HO-1 and NQO1 are differentially regulated by HIF-1alpha and Nrf2 to attenuate inflammatory cytokine expression

Oxidative stress plays an important role in alcohol-induced inflammation and liver injury. Relatively less is known about how Kupffer cells respond to oxidative stress-induced expression of heme oxygenase-1 (HO-1) and NAD(P)H:quinone oxidoreductase (NQO1) to blunt inflammation and liver injury. We showed that Kupffer cells from ethanol-fed rats and ethanol-treated rat Kupffer cells and THP-1 cells displayed increased mRNA expression of HO-1, NQO1, and hypoxia-inducible factor-1α (HIF-1α). Our studies showed that silencing with HIF-1α and JNK-1 siRNAs attenuated ethanol-mediated mRNA expression of HO-1, but not NQO1, whereas Nrf2 siRNA attenuated the mRNA expression of both HO-1 and NQO1. Additionally, JunD but not JunB formed an activator protein-1 (AP-1) oligomeric complex to augment HO-1 promoter activity. Ethanol-induced HO-1 transcription involved antioxidant response elements, hypoxia-response elements, and an AP-1 binding motif in its promoter, as demonstrated by mutation analysis of the promoter, EMSA, and ChIP. Furthermore, livers of ethanol-fed c-Jun(fl/fl) mice showed reduced levels of mRNA for HO-1 but not of NQO1 compared with ethanol-fed control rats, supporting the role of c-Jun or the AP-1 transcriptional complex in ethanol-induced HO-1 expression. Additionally, attenuation of HO-1 levels in ethanol-fed c-Jun(fl/fl) mice led to increased proinflammatory cytokine expression in the liver. These results for the first time show that ethanol regulates HO-1 and NQO1 transcription by different signaling pathways. Additionally, up-regulation of HO-1 protects the liver from excessive formation of inflammatory cytokines. These studies provide novel therapeutic targets to ameliorate alcohol induced inflammation and liver injury.

ERK-1 MAP kinase prevents TNF-induced apoptosis through bad phosphorylation and inhibition of Bax translocation in HeLa Cells

Extracellular signal-regulated kinase (ERK) 1/2 signaling is involved in tumor cell survival through the regulation of Bcl-2 family members. To explore this further and to demonstrate the central role of the mitochondria in the ERK1/2 pathway we used the HeLa cellular model where apoptosis was induced by tumor necrosis factor (TNF) and cycloheximide (CHX). We show that HeLa cells overexpressing ERK-1 displayed resistance to TNF and CHX. HeLa cells overexpressing a kinase-deficient form of ERK-1 (K71R) were more sensitive to TNF and CHX. In the ERK-1 cells, Bad was phosphorylated during TNF + CHX treatment. In the HeLa wt cells and in the K71R clones TNF and CHX decreased Bad phosphorylation. ERK-1 cells treated with TNF and CHX did not release cytochrome c from the mitochondria. By contrast, HeLa wt and K71R clones released cytochrome c. Bax did not translocate to the mitochondria in ERK-1 cells treated with TNF + CHX. Conversely, HeLa wt and K71R clones accumulated Bax in the mitochondria. In the HeLa wt cells and in both ERK-1 transfectants Bid was cleaved and accumulated in the mitochondria. The caspase-8 inhibitor IETD-FMK and the mitochondrial membrane permeabilization inhibitor bongkrekic acid (BK), partially prevented cell death by TNF + CHX. Anisomycin, a c-Jun N-terminal kinases activator, increased TNF-killing. The ERK-1 cells were resistant to TNF and anisomycin, whereas K71R clones resulted more sensitive. Our study demonstrates that in HeLa cells the ERK-1 kinase prevents TNF + CHX apoptosis by regulating the intrinsic mitochondrial pathway through different mechanisms. Inhibition of the intrinsic pathway is sufficient to almost completely prevent cell death.

Regulatory T cells in obesity: the leptin connection

Studies to understand the pathogenesis of obesity have revealed mediators that are responsible for the control of food intake and metabolism at the hypothalamic level. However, molecular insight explaining the link between obesity and low-degree chronic inflammation remains elusive. The adipocyte-derived hormone leptin, and thereby the nutritional status, could control immune self-tolerance by affecting regulatory T (Treg) cell responsiveness and function. Furthermore, resident Treg cells, which are capable of modulating metabolism and glucose homeostasis, are abundant in adipose tissue. Here, we provide an update on recent findings relating Treg cells to obesity and discuss how the intricate network of interactions among leptin, Treg cells and adipose tissue might provide new strategies for therapeutic interventions.

Endoplasmic reticulum stress induced by surfactant protein C BRICHOS mutants promotes proinflammatory signaling by epithelial cells

Chronic interstitial lung disease in both adults and children is associated with mutations of the surfactant protein C (SP-C) proprotein. Among these, mutations within the distal COOH propeptide, known as the BRICHOS domain, are associated with a severe disease phenotype. We showed that prolonged expression of the BRICHOS mutants, SP-C(Δexon4) and SP-C(L188Q), destabilizes endoplasmic reticulum (ER) quality-control mechanisms (the unfolded protein response, or UPR), resulting in the induction of ER stress signaling, an inhibition of the ubiquitin/proteasome system, and the activation of apoptotic pathways. Based on recent observations that the UPR and ER stress can be linked to the induction of proinflammatory signaling, we hypothesized that the epithelial cell dysfunction mediated by SP-C BRICHOS mutants would activate proinflammatory signaling pathways. In a test of this hypothesis, A549 and human embryonic kidney epithelial (HEK293) cells, transiently transfected with either SP-C(Δexon4) or SP-C(L188Q) mutants, each promoted the upregulation of multiple UPR response genes, including homocysteine-inducible, endoplasmic reticulum stress-inducible, ubiquitin-like domain member 1 (HERPUD1) and GRP78. Commensurate with these results, increases in IL-8 secretion occurred and were accompanied by the activation of c-Jun N-terminal kinase (JNK)/activating protein-1 signaling. The stimulation of IL-8 cytokine release was completely attenuated by treatment with the JNK-specific inhibitor, SP600125. In addition, SP-C(Δexon4), but not SP-C(L188Q), activated NFκB. The treatment of SP-C(Δexon4) transfected cells with 4-phenylbutyric acid, a small molecule chaperone known to improve protein folding, blocked the activation of NFκB, but not the release of IL-8. Taken together, the results support the role of JNK signaling in mediating SP-C BRICHOS-induced cytokine release, and provide a link between SP-C BRICHOS mutants and proinflammatory cytokine signaling.

Role of muscle c-Jun NH2-terminal kinase 1 in obesity-induced insulin resistance

Obesity caused by feeding of a high-fat diet (HFD) is associated with an increased activation of c-Jun NH(2)-terminal kinase 1 (JNK1). Activated JNK1 is implicated in the mechanism of obesity-induced insulin resistance and the development of metabolic syndrome and type 2 diabetes. Significantly, Jnk1(-)(/)(-) mice are protected against HFD-induced obesity and insulin resistance. Here we show that an ablation of the Jnk1 gene in skeletal muscle does not influence HFD-induced obesity. However, muscle-specific JNK1-deficient (M(KO)) mice exhibit improved insulin sensitivity compared with control wild-type (M(WT)) mice. Thus, insulin-stimulated AKT activation is suppressed in muscle, liver, and adipose tissue of HFD-fed M(WT) mice but is suppressed only in the liver and adipose tissue of M(KO) mice. These data demonstrate that JNK1 in muscle contributes to peripheral insulin resistance in response to diet-induced obesity.

Cell Defence and Survival

Central to immune defence mechanisms is the role of transcription factor nuclear factor kappa B (NF-kB). This is a complex biochemical topic with ever more controls revealed. NF-kB determines the production of proinflammatory cytokines and chemokines. Pharmacologists step in with possible means of control. Other systems involved in defence include the cyclooxygenase 2 (Cox-2) enzyme and perioxisome proliferator-activated receptors. Insulin receptor activation needs to be seen in context. The mTOR system directs uptake of nutrients by cells. mTOR is suppressed by rapamycin, whose usage is now quite considerable in the control of transplant rejection.