Tumor necrosis factor-alpha induces insulin resistance in endothelial cells via a p38 mitogen-activated protein kinase-dependent pathway

The multifaceted role of cytochrome P450-Derived arachidonic acid metabolites in diabetes and diabetic cardiomyopathy

Understanding lipid metabolism is a critical key to understanding the pathogenesis of Diabetes Mellitus (DM). It is known that 60-90% of DM patients are obese or used to be obese. The incidence of obesity is rising owing to the modern sedentary lifestyle that leads to insulin resistance and increased levels of free fatty acids, predisposing tissues to utilize more lipids with less glucose uptake. However, the exact mechanism is not yet fully elucidated. Diabetic cardiomyopathy seems to be associated with these alterations in lipid metabolism. Arachidonic acid (AA) is an important fatty acid that is metabolized to several bioactive compounds by cyclooxygenases, lipoxygenases, and the more recently discovered, cytochrome P450 (P450) enzymes. P450 metabolizes AA to either epoxy-AA (EETs) or hydroxy-AA (HETEs). Studies showed that EETs could have cardioprotective effects and beneficial effects in reversing abnormalities in glucose and insulin homeostasis. Conversely, HETEs, most importantly 12-HETE and 20-HETE, were found to interfere with normal glucose and insulin homeostasis and thus, might be involved in diabetic cardiomyopathy. In this review, we highlight the role of P450-derived AA metabolites in the context of DM and diabetic cardiomyopathy and their potential use as a target for developing new treatments for DM and diabetic cardiomyopathy.

A global analysis on the differential regulation of RNA binding proteins (RBPs) by TNF–α as potential modulators of metabolic syndromes

Metabolic syndrome (MetS) is associated with a group of conditions, which enhances the risk of diabetes, heart diseases and stroke in the affected individuals. Earlier reports from our lab have shown that Tumor necrosis factor-α (TNF-α) significantly modulates the expression of 56 genes at the alternative splicing level which are involved in various signaling and metabolic pathways (MetS genes) connected to MetS. These MetS genes were predicted to interact with various RNA-binding proteins (RBPs) when exposed to TNF-α, resulting changes in their alternative splicing patterns. Here we are presenting data of an RNA-Seq analysis, which identified 1218 unique, and significantly regulated genes by TNF-α, 15% of which are RBPs . Among the 1218 genes, 204 genes have been identified as MetS genes by the ingenuity pathway analysis, and 10% of the MetS genes are found as RBPs. Our results also show that TNF-α changes the phosphorylation status of certain RBPs such as SR proteins, crucial players in alternative splicing, possibly via changing the activation status of certain upstream signaling molecules which also act as upstream kinases for these proteins. Taken together, these findings suggest that TNF-α influences the regulation of the RBPs at the various levels for their expression, which may lead to the alteration of the splicing pattern of the MetS genes. MetS genes acting as RBPs and are modulated by TNF-α, predict the existence of highly interconnected mechanisms which require further analysis to understand their dual roles on the onset of these diseases.

Thrombin Signaling Contributes to High Glucose-Induced Injury of Human Brain Microvascular Endothelial Cells

BACKGROUND

Diabetes is one of the strongest disease-related risk factors for Alzheimer's disease (AD). In diabetics, hyperglycemia-induced microvascular complications are the major cause of end-organ injury, contributing to morbidity and mortality. Microvascular pathology is also an important and early feature of AD. The cerebral microvasculature may be a point of convergence of both diseases. Several lines of evidence also implicate thrombin in AD as well as in diabetes.

OBJECTIVE

Our objective was to investigate the role of thrombin in glucose-induced brain microvascular endothelial injury.

METHODS

Cultured Human brain microvascular endothelial cells (HBMVECs) were treated with 30 mM glucose±100 nM thrombin and±250 nM Dabigatran or inhibitors of PAR1, p38MAPK, MMP2, or MMP9. Cytotoxicity and thrombin activity assays on supernatants and western blotting for protein expression in lysates were performed.

RESULTS

reatment of HBMVECs with 30 mM glucose increased thrombin activity and expression of inflammatory proteins TNFα, IL-6, and MMPs 2 and 9; this elevation was reduced by the thrombin inhibitor dabigatran. Direct treatment of brain endothelial cells with thrombin upregulated p38MAPK and CREB, and induced TNFα, IL6, MMP2, and MMP9 as well as oxidative stress proteins NOX4 and iNOS. Inhibition of thrombin, thrombin receptor PAR1 or p38MAPK decrease expression of inflammatory and oxidative stress proteins, implying that thrombin may play a central role in glucose-induced endothelial injury.

CONCLUSION

Since preventing brain endothelial injury would preserve blood-brain barrier integrity, prevent neuroinflammation, and retain intact functioning of the neurovascular unit, inhibiting thrombin, or its downstream signaling effectors, could be a therapeutic strategy for mitigating diabetes-induced dementia.

Association between mesenteric panniculitis and non-neoplastic disorders

PURPOSE

To assess the relationship between MP and coexisting non-neoplastic disorders.

METHODS

Consecutive abdominal computed tomography (CT) scans of 4674 patients were evaluated retrospectively for CT features of MP between January 2017 and January 2018. Clinical findings of patients were analyzed. Four control patients were selected from our cohort for each MP patient such that they matched for age, gender and CT protocol. Statistical analysis was performed using a t, Mann-Whitney U, χ², or Fisher's test.

RESULTS

976 patients were excluded from the study due to the exclusion criteria and finally, 102/3698 patients were diagnosed with MP (mean age = 57.2 ± 12.5 years, 52% male). On CT, a hyperattenuated fatty mass (120/120), subcentimeter lymph nodes (117/120), congregation of mesenteric vessels (82/120) within the mass, a fat halo sign (28/120) and a pseudocapsule (88/120) were seen at the mesentery.The intra-observer agreement was almost perfect for the fatty mass and lymph nodes and moderate or substantial for other CT features (p < 0.001). The most prominent disorders were metabolic syndrome (MetS) and urogenital diseases in MP (45%, 37%, respectively) and control groups (31%, 26%, respectively). Between groups, no significant differences were found in the history of abdominal surgery, gastrointestinal and autoimmune diseases (p-value range 0.064-0.663); however, significant differences were found in the rates of vascular, urogenital diseases and MetS (p-value range 0.012-0.036).

CONCLUSION

MetS and urolithiasis were significantly more common in patients with MP than in those without MP. Therefore, there may be a clinically relevant association between these disorders. MetS may be a risk factor for MP and urolithiasis, and treatment of metabolic disorders should be undertaken to prevent these diseases.

Characterization and Exploration of Potential Neuroprotective Peptides in Walnut (Juglans regia) Protein Hydrolysate against Cholinergic System Damage and Oxidative Stress in Scopolamine-Induced Cognitive and Memory Impairment Mice and Zebrafish

The purpose of this study was to determine the neuroprotective effect and mechanism of walnut protein hydrolysates (WPH) against memory deficits induced by scopolamine in mice and further to validate the potent neuroprotective peptides identified by integrated approaches of in silico analysis and peptidomics in scopolamine-induced zebrafish. Results showed that a remarkable amelioration on behavioral performance was observed for oral administration of WPH, and disorders of cholinergic system and oxidative stress were normalized in the brains of mice also. Unfortunately, no obvious inflammatory response and anti-inflammatory effect were observed. Additionally, WPH significantly upregulated the expressions of antioxidant defense-related protein (Nrf2) and neurotrophic-related protein (BDNF and CREB). Furthermore, 20 peptides with relatively higher abundance and PeptideRanker scores were predicted by docking to AchE and Keap1. Among them, FY and SGFDAE with the highest binding affinities, -9.8 and -8.0 kcal/mol, were considered as the promising AchE and Keap1 inhibitors, respectively. They were further validated to have neuroprotective capacity in scopolamine-induced zebrafish, indicating that peptidomics and in silico prediction might be the effective approaches to screen neuroprotective peptides.

Intestinal protection by proanthocyanidins involves anti-oxidative and anti-inflammatory actions in association with an improvement of insulin sensitivity, lipid and glucose homeostasis

Recent advances have added another dimension to the complexity of cardiometabolic disorders (CMD) by directly implicating the gastrointestinal tract as a key player. In fact, multiple factors could interfere with intestinal homeostasis and elicit extra-intestinal CMD. As oxidative stress (OxS), inflammation, insulin resistance and lipid abnormalities are among the most disruptive events, the aim of the present study is to explore whether proanthocyanidins (PACs) exert protective effects against these disorders. To this end, fully differentiated intestinal Caco-2/15 cells were pre-incubated with PACs with and without the pro-oxidant and pro-inflammatory iron/ascorbate (Fe/Asc). PACs significantly reduce malondialdehyde, a biomarker of lipid peroxidation, and raise antioxidant SOD2 and GPx via the increase of NRF2/Keap1 ratio. Likewise, PACs decrease the inflammatory agents TNFα and COX2 through abrogation of NF-κB. Moreover, according to crucial biomarkers, PACs result in lipid homeostasis improvement as reflected by enhanced fatty acid β-oxidation, diminished lipogenesis, and lowered gluconeogenesis as a result of PPARα, γ and SREBP1c modulation. Since these metabolic routes are mainly regulated by insulin sensitivity, we have examined the insulin signaling pathway and found an upregulation of phosphoPI3K/Akt and downregulation of p38-MAPK expressions, indicating beneficial effects in response to PACs. Taken together, PACs display the potential to counterbalance OxS and inflammation in Fe/Asc-exposed intestinal cells, in association with an improvement of insulin sensitivity, which ameliorates lipid and glucose homeostasis.

Association of Gut Hormones and Microbiota with Vascular Dysfunction in Obesity

In the past few decades, obesity has reached pandemic proportions. Obesity is among the main risk factors for cardiovascular diseases, since chronic fat accumulation leads to dysfunction in vascular endothelium and to a precocious arterial stiffness. So far, not all the mechanisms linking adipose tissue and vascular reactivity have been explained. Recently, novel findings reported interesting pathological link between endothelial dysfunction with gut hormones and gut microbiota and energy homeostasis. These findings suggest an active role of gut secretome in regulating the mediators of vascular function, such as nitric oxide (NO) and endothelin-1 (ET-1) that need to be further investigated. Moreover, a central role of brain has been suggested as a main player in the regulation of the different factors and hormones beyond these complex mechanisms. The aim of the present review is to discuss the state of the art in this field, by focusing on the processes leading to endothelial dysfunction mediated by obesity and metabolic diseases, such as insulin resistance. The role of perivascular adipose tissue (PVAT), gut hormones, gut microbiota dysbiosis, and the CNS function in controlling satiety have been considered. Further understanding the crosstalk between these complex mechanisms will allow us to better design novel strategies for the prevention of obesity and its complications.

Cumulative inflammatory burden and obesity as determinants of insulin resistance in patients with established rheumatoid arthritis: cross-sectional study

OBJECTIVES

To describe the prevalence of insulin resistance (IR) in patients with established rheumatoid arthritis (RA) and to analyse the contribution of cumulative inflammatory burden and other factors to its development.

DESIGN

Observational cross-sectional study.

PARTICIPANTS

Patients with RA and controls matched for age, sex and Body Mass Index. We excluded patients with diabetes.

SETTINGS

Patients from an RA inception cohort at Hospital Regional Universitario de Málaga, Spain, were recruited between September 2016 and May 2018.

PRIMARY AND SECONDARY OUTCOME MEASURES

IR was evaluated using the homeostasis model assessment for IR and beta-cell function and the quantitative insulin sensitivity check index. Other variables included the cumulative 28-Joint Disease Activity Score (DAS28) with C reactive protein (CRP) body composition and cytokines. Two logistic regression models were constructed to identify factors associated with IR in patients with RA.

RESULTS

Eighty-nine patients with RA and 80 controls were included. The prevalence of IR was similar in both cases and controls. Inflammatory activity was controlled appropriately in patients during follow-up (mean DAS28 3.1 (0.8)). The presence of IR in patients with RA was associated with obesity (OR 6.01, 95% CI 1.9 to 8.7), higher cumulative DAS28-CRP values during follow-up (OR 2.8, 95% CI 1.3 to 6.0), and higher interleukin-1β levels (OR 1.6, 95% CI 1.1 to 2.4). The second model showed that the risk of IR increased by 10% for each kilogram of excess body fat.

CONCLUSION

In patients with well-controlled, established RA, IR is associated mainly with poorer control of inflammation from diagnosis and with obesity, specifically total fat mass.

Endothelial dysfunction due to selective insulin resistance in vascular endothelium: insights from mechanistic modeling

Previously, we have used mathematical modeling to gain mechanistic insights into insulin-stimulated glucose uptake. Phosphatidylinositol 3-kinase (PI3K)-dependent insulin signaling required for metabolic actions of insulin also regulates endothelium-dependent production of the vasodilator nitric oxide (NO). Vasodilation increases blood flow that augments direct metabolic actions of insulin in skeletal muscle. This is counterbalanced by mitogen-activated protein kinase (MAPK)-dependent insulin signaling in endothelium that promotes secretion of the vasoconstrictor endothelin-1 (ET-1). In the present study, we extended our model of metabolic insulin signaling into a dynamic model of insulin signaling in vascular endothelium that explicitly represents opposing PI3K/NO and MAPK/ET-1 pathways. Novel NO and ET-1 subsystems were developed using published and new experimental data to generate model structures/parameters. The signal-response relationships of our model with respect to insulin-stimulated NO production, ET-1 secretion, and resultant vascular tone, agree with published experimental data, independent of those used for model development. Simulations of pathological stimuli directly impairing only insulin-stimulated PI3K/Akt activity predict altered dynamics of NO and ET-1 consistent with endothelial dysfunction in insulin-resistant states. Indeed, modeling pathway-selective impairment of PI3K/Akt pathways consistent with insulin resistance caused by glucotoxicity, lipotoxicity, or inflammation predict diminished NO production and increased ET-1 secretion characteristic of diabetes and endothelial dysfunction. We conclude that our mathematical model of insulin signaling in vascular endothelium supports the hypothesis that pathway-selective insulin resistance accounts, in part, for relationships between insulin resistance and endothelial dysfunction. This may be relevant for developing novel approaches for the treatment of diabetes and its cardiovascular complications.

Mesalazine Activates Adenosine Monophosphate-activated Protein Kinase: Implication in the Anti-inflammatory Activity of this Anti-colitic Drug

OBJECTIVE

Mesalazine, 5-aminosalicylic acid (5-ASA), is an anti-inflammatory drug that is most widely used for the treatment of Inflammatory Bowel Disease (IBD). Despite extensive clinical use, the exact pharmacological mechanism underlying the anti-colitic effects of 5-ASA has not yet been elucidated. A potential molecular mechanism underlying 5-ASA-mediated anti-colitic activity was investigated.

METHODS

An anti-inflammatory pharmacology of 5-ASA was scrutinized in human colon carcinoma cells and murine macrophages and in a TNBS-induced rat colitis model.

RESULTS

5-ASA induced phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and its substrate acetyl-CoA carboxylase in cells. 5-ASA activation of AMPK occurred regardless of the presence of the pro-inflammatory mediators, Tumor Necrosis Factor Alpha (TNF-α) and lipopolysaccharide. 5-ASA inhibits TNF-α-dependent Nuclear Factor-Kappa B (NF-κB) activation, which was dampened by AMPK inhibition. Oral gavage of sulfasalazine (a colon-specific prodrug of 5- ASA) or rectal administration of 5-ASA ameliorated 2,4,6-trinitrobenzene sulfonic acid (TNBS)- induced rat colitis and activated AMPK in the inflamed colonic tissues while markedly diminishing the levels of NF-κB-regulated pro-inflammatory mediators cyclooxygenase-2, inducible nitric oxide synthase, and cytokine-induced neutrophil chemoattractant-3, elevated by the induction of inflammation. Rectal co-administration of 5-ASA and an AMPK inhibitor undermined 5-ASA-mediated activation of AMPK and its anti-colitic effects.

CONCLUSION

These findings suggest that the activation of AMPK is involved in 5-ASA-mediated anticolitic effects at least partly via interference with pro-inflammatory NF-κB signaling.

Glycomacropeptide Prevents Iron/Ascorbate-Induced Oxidative Stress, Inflammation and Insulin Sensitivity with an Impact on Lipoprotein Production in Intestinal Caco-2/15 Cells

Background. Metabolic Syndrome (MetS), a major worldwide concern for the public health system, refers to a cluster of key metabolic components, and represents a risk factor for diabetes and cardiovascular diseases. As oxidative stress (OxS) and inflammation are the major triggers of insulin sensitivity (IS), a cardinal MetS feature, the principal aim of the present work is to determine whether glycomacropeptide (GMP), a milk-derived bioactive peptide, exerts beneficial effects on their expression. Methods. Fully differentiated intestinal Caco-2/15 cells are used to evaluate the preventive action of 2 mg/mL GMP against OxS and inflammation induced by the mixture iron-ascorbate (Fe/Asc) (200 μM:2 mM). The potency of GMP of decreasing the production of lipoproteins, including chylomicrons (CM), very-low-density lipoproteins (VLDL) and low-density lipoproteins (LDL) is also assessed. Results. The administration of GMP significantly reduces malondialdehyde, a biomarker of lipid peroxidation, and raises superoxide dismutase 2 and glutathione peroxidase via the induction of the nuclear factor erythroid 2–related factor 2, a transcription factor, which orchestrates cellular antioxidant defenses. Similarly, GMP markedly lowers the inflammatory agents tumor necrosis factor-α and cyclooxygenase-2 via abrogation of the nuclear transcription factor-kB. Moreover, GMP-treated cells show a down-regulation of Fe/Asc-induced mitogen activated protein kinase pathway, suggesting greater IS. Finally, GMP decreases the production of CM, VLDL, and LDL. Conclusions. Our results highlight the effectiveness of GMP in attenuating OxS, inflammation and lipoprotein biogenesis, as well as improving IS, the key components of MetS. Further investigation is needed to elucidate the mechanisms mediating the preventive action of GMP.

Inhibitory Effects of Walnut (Juglans regia) Peptides on Neuroinflammation and Oxidative Stress in Lipopolysaccharide-Induced Cognitive Impairment Mice

Increasing level of inflammation and oxidative stress could lead to memory impairment. The purpose of this study was to determine the neuroprotective effects of walnut peptides against memory deficits induced by lipopolysaccharide (LPS) in mice and further to explore the underlying anti-inflammatory mechanisms against LPS-elicited inflammation in BV-2 cells. Results showed that walnut protein hydrolysate (WPH) and its low-molecular-weight fraction (WPHL) could ameliorate the memory deficits induced by LPS via normalizing the inflammatory response and oxidative stress in brain, especially WPHL. Furthermore, 18 peptides with anti-inflammatory activities on LPS-activated BV-2 cells were identified from WPHL and it was found that Trp, Gly, and Leu residues in peptides might contribute to the anti-inflammation. Meanwhile, the strong anti-inflammatory effects of LPF, GVYY, and APTLW might be related to their hydrophobic and aromatic amino acid residues as well. LPF, GVYY, and APTLW could reduce the content of proinflammatory mediators and cytokines by downregulating related enzyme expressions and mRNA expressions. Additionally, ROS and mitochondria homeostasis might also contribute to their anti-inflammatory effects.

Evaluation of blood adiponectin levels as an index for subacute ruminal acidosis in cows: a preliminary study

The objective of this study was to evaluate blood levels of various hormones and compounds related to energy metabolism in cows with subacute ruminal acidosis (SARA). We investigated 11 lactating cows presumed to have SARA based on duration of ruminal pH <5.6 and reticulum pH <6.3 in 2015-2016. Kraft pulp (KP) was used to supplement feed of 7 of the cows studied in an effort to reduce SARA. We continuously monitored ruminal pH and measured blood concentrations of hormones and metabolites related to energy metabolism. Blood measurements included glucose (GLU), total cholesterol (TC), free fatty acid (FFA), insulin, adiponectin (ADN), malate dehydrogenase (MDH), and lactate dehydrogenase (LDH). Additionally, we analyzed milk data (milk yield, milk fat percentage, milk protein percentage, milk urea nitrogen, and protein fat ratio) and reproduction data. The results demonstrated that ADN levels at 4 weeks post-parturition correlated with the total amount of time that the ruminal or reticulum fluid pH was under the threshold during 1 week post-parturition, as well as the numbers of days the cows were diagnosed with SARA (SARA-positive days) up to 30 days post-parturition. SARA-positive days in 2016 were higher than those in 2015. In both years, numbers of SARA-positive days for cows supplemented with KP were lower than those for cows without KP. Increased ADN levels may be a compensatory reaction to frequent SARA which modulates the inflammatory response against high LPS levels and improves insulin resistance caused by LPS. ADN may serve as an estimative index for SARA.

Identification of Core Gene Biomarkers in Patients with Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) is a disorder of the myocardium in diabetic patients, which is one of the critical complications of diabetes giving rise to an increased mortality. However, the underlying mechanisms of DCM remain incompletely understood presently. This study was designed to screen the potential molecules and pathways implicated with DCM. GSE26887 involving 5 control individuals and 7 DCM patients was selected from the GEO database to identify the differentially expressed genes (DEGs). DAVID was applied to perform gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. A protein-protein interaction (PPI) network was also constructed to visualize the interactions among these DEGs. To further validate significant genes and pathways, quantitative real-time PCR (qPCR) and Western blot were performed. A total of 236 DEGs were captured, including 134 upregulated and 102 downregulated genes. GO, KEGG, and the PPI network disclosed that inflammation, immune disorders, metabolic disturbance, and mitochondrial dysfunction were significantly enriched in the development of DCM. Notably, IL6 was an upregulated hub gene with the highest connectivity degree, suggesting that it may interact with a great many molecules and pathways. Meanwhile, SOCS3 was also one of the top 15 hub genes in the PPI network. Herein, we detected the protein level of STAT3 and SOCS3 in a mouse model with DCM. Western blot results showed that the protein level of SOCS3 was significantly lower while phosphorylated-STAT3 (P-STAT3) was activated in mice with DCM. In vitro results also uncovered the similar alterations of SOCS3 and P-STAT3 in cardiomyocytes and cardiac fibroblasts induced by high glucose (HG). However, overexpression of SOCS3 could significantly reverse HG-induced cardiomyocyte hypertrophy and collagen synthesis of cardiac fibroblasts. Taken together, our analysis unveiled potential biomarkers and molecular mechanisms in DCM, which could be helpful to the diagnosis and treatment of DCM.

Increased endothelin-1-mediated vasoconstrictor tone in human obesity: effects of gut hormones

The heavy impact of obesity on the development and progression of cardiovascular disease has sparked sustained efforts to uncover the mechanisms linking excess adiposity to vascular dysfunction. Impaired vasodilator reactivity has been recognized as an early hemodynamic abnormality in obese patients, but also increased vasoconstrictor tone importantly contributes to their vascular damage. In particular, upregulation of the endothelin (ET)-1 system, consistently reported in these patients, might accelerate atherosclerosis and its complication, given the pro-inflammatory and mitogenic properties of ET-1. In recent years, a number of gut hormones, in addition to their role as modulators of food intake, energy balance, glucose and lipid metabolism, and insulin secretion and action, have demonstrated favorable vascular actions. They increase the bioavailability of vasodilator mediators like nitric oxide, but they have also been shown to inhibit the ET-1 system. These features make gut hormones promising tools for targeting both the metabolic and cardiovascular complications of obesity, a view supported by recent large-scale clinical trials indicating that novel drugs for type 2 diabetes with cardiovascular potential may translate into clinically significant advantages. Therefore, there is real hope that better understanding of the properties of gut-derived substances might provide more effective therapies for the obesity-related cardiometabolic syndrome.

Interaction of IL-6 and TNF-α contributes to endothelial dysfunction in type 2 diabetic mouse hearts

OBJECTIVES

Inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), are individually considered as important contributors to endothelial dysfunction in obesity and type 2 diabetes (T2D). However, their interactions in coronary arteriole endothelial dysfunction are uncertain. Therefore, this study aimed to determine the effects of TNF-α and IL-6 interactions on coronary endothelial dysfunction in experimental T2D.

METHODS

The studies used wild type (WT), diabetic mice (db/db), db/db null for TNF (dbTNF-/dbTNF-), and db/db mice treated with neutralizing antibody to IL-6 (anti-IL-6). Endothelium-dependent (acetylcholine [ACh], or luminal flow-induced shear stress) and endothelium-independent (sodium nitroprusside [SNP]) vasodilation of isolated and pressurized coronary arterioles were determined. Quantitative PCR, Western blot, and immunofluorescence staining were utilized for mechanistic studies.

RESULTS

Relative to WT, arteriolar dilation to both ACh and flow was attenuated in db/db mice and dbTNF-/dbTNF-. Treatment of dbTNF-/dbTNF- and db/db mice with anti-IL-6 improved arteriolar dilation compared to db/db mice. Immunofluorescence staining illustrated localization of IL-6 within the endothelial cells of coronary arterioles. In db/db mice, mRNA and protein expression of IL-6 and superoxide (O2-) production were higher, but reduced by anti-IL-6 treatment. Also, in db/db mice, mRNA and protein expression of TNF-α suppressed by the anti-IL-6 treatment and the reduced expression of mRNA and protein expression of IL-6 by the genetic deletion of TNF-α both supported a reciprocal regulation between TNF-α and IL-6. Superoxide dismutase 2 (SOD2) expression and phosphorylation of eNOS (p-eNOS/eNOS) were lower in db/db mice coronary arterioles and were restored in db/db+Anti-IL-6 and dbTNF-/dbTNF- mice.

CONCLUSION

The interactions between TNF-α and IL-6 exacerbate oxidative stress and reduce phosphorylation of eNOS, thereby contributing to coronary endothelial dysfunction in T2D mice.

Fructose induced neurogenic hypertension mediated by overactivation of p38 MAPK to impair insulin signaling transduction caused central insulin resistance

Type 2 diabetes are at a high risk of complications related to hypertension, and reports have indicated that insulin levels may be associated with blood pressure (BP). Fructose intake has recently been reported to promote insulin resistance and superoxide formation. The aim of this study is to investigate whether fructose intake can enhance superoxide generation and impair insulin signaling in the NTS and subsequently elevate BP in rats with fructose-induced hypertension. Treatment with fructose for 4 weeks increased the BP, serum fasting insulin, glucose, homeostatic model assessment-insulin resistance, and triglyceride levels and reduced the serum direct high-density lipoprotein level in the fructose group. The Tempol treatment recovered the fructose-induced decrease in nitric oxide production in the NTS. Immunoblotting and immunofluorescence analyses further showed that fructose increased the p38- and fructose-induced phosphorylation of insulin receptor substrate 1 (IRS1^S307) and suppressed Akt^S473 and neuronal nitric oxide synthase phosphorylation. Similarly, fructose was able to impair insulin sensitivity and increase insulin levels in the NTS. Fructose intake also increased the production of superoxide in the NTS. The results of this study suggest that fructose might induce central insulin resistance and elevate BP by enhancing superoxide production and activating p38 phosphorylation in the NTS.

PGBR extract ameliorates TNF-α induced insulin resistance in hepatocytes

Pre-germinated brown rice (PGBR) could ameliorate metabolic syndrome, however, not much research estimates the effect of PGBR extract on insulin resistance. The aim of this study is to examine the effects of PGBR extract in TNF-α induced insulin resistance. HepG2 cells, hepatocytes, were cultured in DMEM medium and added with 5 μM insulin or with insulin and 30 ng/ml TNF-α or with insulin, TNF-α and PGBR extract (50, 100, 300 μg/ml). The glucose levels of the medium were decreased by insulin, demonstrating insulin promoted glucose uptake into cell. However, TNF-α inhibited glucose uptake into cells treated with insulin. Moreover, insulin increased the protein expressions of AMP-activated protein kinase (AMPK), insulin receptor substrate-1 (IRS-1), phosphatidylinositol-3-kinase-α (PI3K-α), serine/threonine kinase PI3K-linked protein kinase B (Akt/PKB), glucose transporter-2 (GLUT-2), glucokinase (GCK), peroxisome proliferator activated receptor-α (PPAR-α) and PPAR-γ. TNF-α activated p65 and MAPKs (JNK1/2 and ERK1/2) which worsened the expressions of AMPK, IRS-1, PI3K-α, Akt/PKB, GLUT-2, GCK, glycogen synthase kinase-3 (GSK-3), PPAR-α and PPAR-γ. Once this relationship was established, we added PGBR extract to cell with insulin and TNF-α. We found glucose levels of medium were lowered and that the protein expressions of AMPK, IRS-1, PI3K-α, Akt/PKB, GLUT-2, GCK, GSK-3, PPAR-α, PPAR-γ and p65, JNK1/2 were also recovered. In conclusion, this study found that TNF-α inhibited insulin stimulated glucose uptake and aggravated related proteins expressions, suggesting that it might cause insulin resistance. PGBR extract was found to ameliorate this TNF-α induced insulin resistance, suggesting that it might be used in the future to help control insulin resistance.

Puerarin Improves Vascular Insulin Resistance and Cardiovascular Remodeling in Salt-Sensitive Hypertension

Puerarin is an isoflavonoid isolated from the Chinese herb, Kudzu roots (also known as Gegen), which has been widely used for the treatment of hypertensive diseases and diabetic mellitus in traditional Chinese medicine. Dahl salt-sensitive (DS) rat is a genetic model of salt-sensitive hypertension with cardiovascular injury and vascular insulin resistance. Here, we investigated whether puerarin improved vascular insulin resistance and attenuated cardiac and aortic remodeling in salt-sensitive hypertension. DS rats were given a normal (NS) or high salt diet (HS) for five weeks. An additional group of DS rats was pretreated with puerarin and NS for 10 days, then switched to HS plus puerarin for five weeks. HS for five weeks increased systolic blood pressure (SBP), cardiac hypertrophy and fibrosis, and aortic hypertrophy with increased the expression of phosphor-ERK1/2 in the aorta and heart; puerarin attenuated cardiac and aortic hypertrophy, cardiac fibrosis and phosphor-ERK1/2 with a mild reduction in SBP. Hypertensive rats also manifested impairment of acetylcholine- and insulin-mediated vasorelaxation and insulin-mediated Akt and eNOS phosphorylation associated with the activation of NF[Formula: see text]B/TNF[Formula: see text]/JNK pathway. Puerarin improved acetylcholine- and insulin-mediated vasorelaxation and insulin-stimulated Akt/NO signaling with the inhibition of the NF[Formula: see text]B inflammatory pathway. Our results demonstrated that in salt-sensitive hypertension, puerarin improved vascular insulin action with cardiovascular beneficial effects. Our results found that the underlying mechanisms may involve its inhibition of NF[Formula: see text]B/JNK and ERK1/2 pathway. These results suggest that puerarin could be used as a new antihypertensive agent to expand our armamentarium for the prevention and treatment of end-organ damage in individuals with hypertension and metabolic diseases.

Metabolic and Biochemical Stressors in Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) or diabetes-induced cardiac dysfunction is a direct consequence of uncontrolled metabolic syndrome and is widespread in US population and worldwide. Despite of the heterogeneous and distinct features of DCM, the clinical relevance of DCM is now becoming established. DCM progresses to pathological cardiac remodeling with the higher risk of heart attack and subsequent heart failure in diabetic patients. In this review, we emphasize lipid substrate quality and the phenotypic, metabolic, and biochemical stressors of DCM in the rodent and human pathophysiology. We discuss lipoxygenase signaling in the inflammatory pathway with multiple contributing and confounding factors leading to DCM. Additionally, emerging biochemical pathways are emphasized to make progress toward therapeutic advancement to treat DCM.

Hydroxycitric acid ameliorates high-fructose-induced redox imbalance and activation of stress sensitive kinases in male Wistar rats

BACKGROUND

Excess fructose consumption causes dyslipidemia, oxidative stress, and various complications. Hydroxycitric acid (HCA), one of the principal components of the fruit Garcinia cambogia, has been shown to possess antiobesity properties. The objective was to investigate the effects of HCA on redox imbalance and activation of stress sensitive kinases in high fructose-fed rats.

METHODS

Male Wistar rats (n=40) were randomly divided into four groups with 10 rats in each group. The rats were fed with either standard rodent diet or 60% fructose diet and administered with HCA at a dose of 400 mg/kg body wt/day for 10 weeks. Body weight was measured once a week, and food intake was noted daily. At the end of the study, lipid profile and oxidative stress parameters were estimated. Expressions of stress sensitive kinases were analyzed in liver homogenates.

RESULTS

Fructose-fed rats displayed elevated body weight, higher levels of plasma total cholesterol (TC), triacylglycerol (TAG), non-high-density lipoprotein cholesterol (non HDL-C), malondialdehyde (MDA), total oxidant status (TOS), oxidative stress index (OSI), lower levels of HDL-C, glutathione (GSH), glutathione peroxidase (GPx), and total antioxidant status (TAS). Fructose feeding caused higher phosphorylation of stress sensitive kinases ERK ½ and p38. Administration with HCA lowered body weight, food intake, TAG, non-HDL-C, MDA, TOS, and OSI and elevated GSH, GPx, and TAS levels. Reduced phosphorylation of ERK ½ and p38 mitogen-activated protein kinase (MAPK) was observed upon HCA treatment.

CONCLUSIONS

Thus, HCA improved fructose induced redox imbalance and activation of stress sensitive kinases through its hypolipidemic effects.

Resveratrol inhibits inflammation and ameliorates insulin resistant endothelial dysfunction via regulation of AMP-activated protein kinase and sirtuin 1 activities

BACKGROUND

Resveratrol is a phytoalexin with beneficial effects on human health. The aim of the present study was to investigate the effects of resveratrol on endothelial dysfunction involved in insulin signaling and inflammation.

METHODS

Endothelial cells were stimulated with palmitate (PA) to induce insulin resistance characterized by a loss of insulin-mediated nitric oxide (NO) production. Diabetes was induced in rats by fructose feeding. The effects of resveratrol and the mechanisms involved were investigated using an aortic relaxation assay and Western blot analysis.

RESULTS

In endothelial cells, 0.1-10 μmol/L resveratrol suppressed IκB kinase β (IKKβ)/nuclear factor-κB phosphorylation, as well as tumor necrosis factor-α and interleukin-6 production, and restored the insulin receptor substrate-1 (Irs-1)/Akt/endothelial NO synthase signaling pathway. Furthermore, resveratrol effectively inhibited the mitogenic actions of insulin by decreasing the secretion of endothelin-1 and plasminogen activator inhibitor-1. It also positively regulated AMP-activated kinase (AMPK) and sirtuin 1 (SIRT1) activation, which contributed to the inhibition of inflammation implicated in endothelial insulin resistance. Stimulation with PA and long term-fructose feeding impaired insulin-mediated vessel dilation in rat aorta, whereas pretreatment of aortic rings with resveratrol (0.1-10 μmol/L) or treatment of rats with 5 or 20 mg/kg resveratrol counteracted these changes.

CONCLUSION

The results indicate that resveratrol inhibits inflammation and facilitates insulin phosphatidylinositol 3-kinase signaling by beneficial modulation of IRS-1 function partly via regulation of AMPK and SIRT1 activity in the endothelium.

Thyroid Hormones, Oxidative Stress, and Inflammation

Inflammation and oxidative stress (OS) are closely related processes, as well exemplified in obesity and cardiovascular diseases. OS is also related to hormonal derangement in a reciprocal way. Among the various hormonal influences that operate on the antioxidant balance, thyroid hormones play particularly important roles, since both hyperthyroidism and hypothyroidism have been shown to be associated with OS in animals and humans. In this context, the nonthyroidal illness syndrome (NTIS) that typically manifests as reduced conversion of thyroxine (T₄) to triiodothyronine (T₃) in different acute and chronic systemic conditions is still a debated topic. The pathophysiological mechanisms of this syndrome are reviewed, together with the roles of deiodinases, the enzymes responsible for the conversion of T₄ to T₃, in both physiological and pathological situations. The presence of OS indexes in NTIS supports the hypothesis that it represents a condition of hypothyroidism at the tissue level and not only an adaptive mechanism to diseases.

Protective effect of apigenin on ischemia/reperfusion injury of the isolated rat heart

Apigenin (Api), a mainly bioactive component of Apium graveolens L. var. dulce DC. (a traditional Chinese medicinal herb), possesses a wide range of biological activities, including antioxidant effects. It also has been shown to associate with lower prevalence of cardiovascular diseases, but its mechanisms of action remain unclear. The aim of the present study is to investigate the role of Api in isolated rat heart model of ischemia/reperfusion (I/R). Langendorff-perfused isolated rat hearts were used in our study. Api was added to the perfusate before ischemia and during reperfusion in the isolated pulsed rat heart exposed to 30-min ischemia followed by 50-min reperfusion. The treatment with Api conferred a cardioprotective effect, and the treated hearts demonstrated an improved ischemic cardiac functional recovery, a decreased myocardial infarct size, a reduced activities of creatine kinase isoenzyme and lactate dehydrogenase in the coronary flow, a reduced number of apoptotic cardiomyocytes, a reduced activity of caspase-3, up-regulation of the anti-apoptotic protein Bcl-2 and down-regulation of the pro-apoptotic protein Bax. In addition, Api inhibited the phosphorylation of p38 MAPKS during I/R. In conclusion, these observations provide preliminary evidence that Api can protect cardiomyocytes from I-/R-induced injury, at least partially, through the inhibition of p38 MAPKS signaling pathway.

Association between Psoriasis Vulgaris and Coronary Heart Disease in a Hospital-Based Population in Japan

Background

Psoriasis vulgaris is a chronic inflammatory skin disease with an immune-genetic background. It has been reported as an independent risk factor for coronary heart disease (CHD) in the United States and Europe. The purpose of this study was to investigate the association between psoriasis and CHD in a hospital-based population in Japan.

Methods

For 113,065 in-hospital and clinic patients at our institution between January 1, 2011 and January 1, 2013, the diagnostic International Classification of Diseases (ICD)-10 codes for CHD, hypertension, dyslipidemia, diabetes, and psoriasis vulgaris were extracted using the medical accounting system and electronic medical record, and were analyzed.

Results

The prevalence of CHD (n = 5,167, 4.5%), hypertension (n = 16,476, 14.5%), dyslipidemia (n = 9,236, 8.1%), diabetes mellitus (n = 11,555, 10.2%), and psoriasis vulgaris (n = 1,197, 1.1%) were identified. The prevalence of CHD in patients with hypertension, dyslipidemia, diabetes, and psoriasis vulgaris were 21.3%, 22.2%, 21.1%, and 9.0%, respectively. In 1,197 psoriasis patients, those with CHD were older, more likely to be male, and had more number of the diseases surveyed by ICD-10 codes. Multivariate analysis showed that psoriasis vulgaris was an independent associated factor for CHD (adjusted odds ratio [OR]: 1.27; 95% confidence interval [CI]: 1.01–1.58; p = 0.0404) along with hypertension (adjusted OR: 7.78; 95% CI: 7.25–8.36; p < 0.0001), dyslipidemia (adjusted OR: 2.35; 95% CI: 2.19–2.52; p < 0.0001), and diabetes (adjusted OR: 2.86; 95% CI: 2.67–3.06; p < 0.0001).

Conclusion

Psoriasis vulgaris was independently associated with CHD in a hospital-based population in Japan.

Antioxidant Peptides Identified from Ovotransferrin by the ORAC Method Did Not Show Anti-Inflammatory and Antioxidant Activities in Endothelial Cells

Oxygen radical absorbance capacity (ORAC) is a widely used method of measuring antioxidant capacities of various antioxidant components. Surprisingly, 16 antioxidant peptides previously identified from egg protein ovotransferrin using the ORAC method did not show any anti-inflammatory and antioxidant activities in cells. After simulated gastro-intestinal digestion (GID), several peptide digests significantly reduced the expression of tumor necrosis factor-α (TNF-α)-induced pro-inflammatory intercellular cell adhesion molecule-1 (ICAM-1) by 65.7 ± 10.4% and vascular cell adhesion molecule-1 (VCAM-1) by 53.5 ± 9.6% to 61.0 ± 14.5%, but only GWNI reduced TNF-α-activated superoxide generation by 71.0 ± 12.9% when tested with dihydroethidium (DHE) assay. Mass spectrometer analysis identified two new peptides, GWN and GW, in the GWNI digest; however, only GW reduced TNF-α-induced VCAM-1 expression (64.3 ± 20.6%) significantly compared to the TNF-α treated cells. Our study suggested that ORAC lacked biological relevance in assessing bioactive peptides.

Cichoric Acid Reverses Insulin Resistance and Suppresses Inflammatory Responses in the Glucosamine-Induced HepG2 Cells

Cichoric acid, a caffeic acid derivative found in Echinacea purpurea, basil, and chicory, has been reported to have bioactive effects, such as anti-inflammatory, antioxidant, and preventing insulin resistance. In this study, to explore the effects of CA on regulating insulin resistance and chronic inflammatory responses, the insulin resistance model was constructed by glucosamine in HepG2 cells. CA stimulated glucosamine-mediated glucose uptake by stimulating translocation of the glucose transporter 2. Moreover, the production of reactive oxygen, the expression of COX-2 and iNOS, and the mRNA levels of TNF-α and IL-6 were attenuated. Furthermore, CA was verified to promote glucosamine-mediated glucose uptake and inhibited inflammation through PI3K/Akt, NF-κB, and MAPK signaling pathways in HepG2 cells. These results implied that CA could increase glucose uptake, improve insulin resistance, and attenuate glucosamine-induced inflammation, suggesting that CA is a potential natural nutraceutical with antidiabetic properties and anti-inflammatory effects.

Apigenin attenuates myocardial ischemia/reperfusion injury via the inactivation of p38 mitogen‑activated protein kinase

Apigenin (Api) is a plant monomer associated with reducing the risk of heart disease. However, the mechanism of action remains to be fully elucidated. In the present study, it was hypothesized that API has cardioprotective effects by attenuating myocardial ischemia/reperfusion (I/R) injury. Rats were randomly subjected to sham operation, myocardial I/R alone or I/R + Api. Cardiac function was measured, and infarct size was evaluated by triphenyltetrazolium chloride staining following reperfusion. The myocardial enzyme leakage was analyzed for lactate dehydrogenase (LDH) and creatine kinase (CK). The myocardium was also assessed for total superoxide dismutase (SOD) activity and malondialdehyde (MDA) content. The phosphorylation of p38 mitogen‑activated protein kinase (MAPK) was analyzed by western blotting. The present study reported for the first time, to the best of our knowledge, that I/R significantly increased infarct size, induced CK and LDH release, inhibited the activity of SOD and increased the levels of MDA, all of which were prevented by treatment with Api. In addition, I/R increased the phosphorylation of p38 MAPK, which was significantly decreased in the Api‑treated heart tissue samples following I/R, compared with the untreated heart tissue samples. In conclusion, the results of the present study demonstrated that Api inhibited the p38 MAPK signaling pathway to protect cardiomyocytes from I/R‑induced injury.

Caveolin-1 phosphorylation regulates vascular endothelial insulin uptake and is impaired by insulin resistance in rats

AIMS/HYPOTHESIS

As insulin entry into muscle interstitium is rate-limiting for its overall peripheral action, defining the route and regulation of its entry is critical. Caveolin-1 is required for caveola formation in vascular endothelial cells (ECs) and for EC insulin uptake. Whether this requirement reflects simply the need for caveola availability or involves a more active role for caveolae/caveolin-1 is not known. Here, we examined the role of insulin-stimulated tyrosine 14 (Tyr(14))-caveolin-1 phosphorylation in mediating EC insulin uptake and the role of cellular Src-kinase (cSrc), TNF-α/IL-6 and high fat diet (HFD) in regulating this process.

METHODS

Freshly isolated ECs from normal or HFD-fed rats and/or cultured ECs were treated with FITC-labelled or regular insulin with or without a Src or phosphotidylinositol-3-kinase inhibitor, TNF-α or IL-6, or transfecting FLAG-tagged wild-type (WT) or mutant (Y14F) caveolin-1. Tyr(14)-caveolin-1/Tyr(416) cSrc phosphorylation and FITC-insulin uptake were quantified by immunostaining and/or western blots.

RESULTS

Insulin stimulated Tyr(14)-caveolin-1 phosphorylation during EC insulin uptake. Inhibiting cSrc, but not phosphotidylinositol-3-kinase, reduced insulin-stimulated caveolin-1 phosphorylation. Furthermore, inhibiting cSrc reduced FITC-insulin uptake by ∼50%. Overexpression of caveolin-1Y14F inhibited, while overexpression of WT caveolin-1 increased, FITC-insulin uptake. Exposure of ECs to TNF-α or IL-6, or to 1-week HFD feeding eliminated insulin-stimulated caveolin-1 phosphorylation and inhibited FITC-insulin uptake to a similar extent.

CONCLUSIONS/INTERPRETATION

Insulin stimulation of its own uptake requires caveolin-1 phosphorylation and Src-kinase activity. HFD in vivo and proinflammatory cytokines in vitro both inhibit this process.

Inhibition of endocytosis exacerbates TNF-α-induced endothelial dysfunction via enhanced JNK and p38 activation

Tumor necrosis factor-α (TNF-α) is a pro-inflammatory cytokine that causes endothelial dysfunction. Endocytosis of TNF-α receptors (TNFR) precedes endosomal reactive oxygen species (ROS) production, which is required for NF-κB activation in vascular smooth muscle cells. It is unknown how endocytosis of TNFRs impacts signaling in endothelial cells. We hypothesized that TNF-α-induced endothelial dysfunction is induced by both endosomal and cell surface events, including NF-κB and mitogen-activated protein kinases (MAPKs) activation, and endocytosis of the TNFR modifies signaling. Mesenteric artery segments from C57BL/6 mice were treated with TNF-α (10 ng/ml) for 22 h in tissue culture, with or without signaling inhibitors (dynasore for endocytosis, SP600125 for JNK, SB203580 for p38, U0126 for ERK), and vascular function was assessed. Endothelium-dependent relaxation to acetylcholine (ACh) was impaired by TNF-α, and dynasore exacerbated this, whereas JNK or p38 inhibition prevented these effects. In cultured endothelial cells from murine mesenteric arteries, dynasore potentiated JNK and p38 but not ERK phosphorylation and promoted cell death. NF-κB activation by TNF-α was decreased by dynasore. JNK inhibition dramatically increased both the magnitude and duration of TNF-α-induced NF-κB activation and potentiated intercellular adhesion molecule-1 (ICAM-1) activation. Dynasore still inhibited NF-κB activation in the presence of SP600125. Thus TNF-α-induced endothelial dysfunction is both JNK and p38 dependent. Endocytosis modulates the balance of NF-κB and MAPK signaling, and inhibition of NF-κB activation by JNK limits this pro-proliferative signal, which may contribute to endothelial cell death in response to TNF-α.

Angiotensin-(1-7) recruits muscle microvasculature and enhances insulin's metabolic action via mas receptor

Angiotensin-(1-7) [Ang-(1-7)], an endogenous ligand for the G protein-coupled receptor Mas, exerts both vasodilatory and insulin-sensitizing effects. In skeletal muscle, relaxation of precapillary arterioles recruits microvasculature and increases the endothelial surface area available for nutrient and hormone exchanges. To assess whether Ang-(1-7) recruits microvasculature and enhances insulin action in muscle, overnight-fasted adult rats received an intravenous infusion of Ang-(1-7) (0, 10, or 100 ng/kg per minute) for 150 minutes with or without a simultaneous infusion of the Mas inhibitor A-779 and a superimposition of a euglycemic insulin clamp (3 mU/kg per minute) from 30 to 150 minutes. Hind limb muscle microvascular blood volume, microvascular flow velocity, and microvascular blood flow were determined. Myographic changes in tension were measured on preconstricted distal saphenous artery. Ang-(1-7) dose-dependently relaxed the saphenous artery (P<0.05) ex vivo. This effect was potentiated by insulin (P<0.01) and abolished by either endothelium denudement or Mas inhibition. Systemic infusion of Ang-(1-7) rapidly increased muscle microvascular blood volume and microvascular blood flow (P<0.05, each) without altering microvascular flow velocity. Insulin infusion alone increased muscle microvascular blood volume by 60% to 70% (P<0.05). Adding insulin to the Ang-(1-7) infusion further increased muscle microvascular blood volume and microvascular blood flow (≈2.5 fold; P<0.01). These were associated with a significant increase in insulin-mediated glucose disposal and muscle protein kinase B and extracellular signal-regulated kinase 1/2 phosphorylation. A-779 pretreatment blunted the microvascular and insulin-sensitizing effects of Ang-(1-7). We conclude that Ang-(1-7) by activating Mas recruits muscle microvasculature and enhances the metabolic action of insulin. These effects may contribute to the cardiovascular protective responses associated with Mas activation and explain the insulin-sensitizing action of Ang-(1-7).

The levels of plasma growth arrest-specific protein 6 is associated with insulin sensitivity and inflammation in women

AIMS

Vitamin K-dependent growth arrest-specific protein 6 (Gas6) and its receptors of the TAM (TYRO-3/Axl/Mer) family are ubiquitously expressed in immune, cardiovascular, and reproductive systems. They play pivotal roles of regulating tissue homeostasis via anti-inflammatory effects. Recent studies show that the Gas6/TAM system is involved in glucose tolerance-related metabolic disorders. Our aim was to investigate the link between Gas6 protein, insulin sensitivity and inflammatory cytokines in men and women.

METHODS

A total of 278 adults (126 men and 152 women) were recruited in this study. Plasma Gas6 concentration and various biochemical, proinflammatory and endothelial markers were measured. Insulin sensitivity was estimated by homeostasis model assessment.

RESULTS

Waist, fasting and 2h post-load glucose, and glycated hemoglobin (HbA1C) were significantly lower in women than in men. Age, high-density lipoprotein cholesterol, and highly-sensitive C-reactive protein levels were significantly higher in women than in men. Plasma Gas6 levels were negatively correlated with waist (r = -0.187, P = 0.022), HOMA-IR (r = -0.171, P=0.035), interleukin 6 (r = -0.362, P < 0.001), and E-selectin (r = -0.216, P = 0.008), while they were positively correlated with insulin sensitivity (QUICKI) (r = 0.168, P = 0.039) in women, but not in men. Stepwise multiple regression analysis showed that TNF-α was independently correlated with plasma Gas6 levels in both the sexes (P < 0.001).

CONCLUSION

Plasma Gas6 is associated with obesity, insulin sensitivity, inflammation, and endothelial dysfunction in women and may be a general marker of inflammatory conditions in women.

Effect of bee venom on IL-6, COX-2 and VEGF levels in polycystic ovarian syndrome induced in Wistar rats by estradiol valerate

BACKGROUND

Polycystic ovarian syndrome (PCOS) is a low-grade inflammatory disease characterized by hyperandrogenemia, hirsutism, chronic anovulation and vascular disorder. Interleukin-6 (IL-6), cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF) are triggered by inflammatory stimuli and lead to angiogenesis and pathogenesis of the ovary. Honeybee venom (HBV) contains an array of biologically active components possessing various pharmaceutical properties. This study was designed to assess the possibility of HBV application as an anti-inflammatory therapeutic agent to suppress levels of the main inflammatory mediators IL-6, COX-2 and VEGF.To induce PCOS, 1 mg of estradiol valerate (EV) per 100 g of body weight was subcutaneously (SC) injected into eight-week-old rats. After 60 days, 0.5 mg/kg of HBV was administered Intraperitoneal (IP) for 14 consecutive days, and the results of PCOS treatment were investigated. Rats were then anesthetized with CO2, and the ovaries were surgically removed. Serum IL-6 was detected by the ELISA kit. Immunoexpression of COX-2 and VEGF were examined in three groups: EV-induced PCOS, HBV-treated PCOS and control animals.

RESULTS

Thickness of theca layer, number and diameter of cysts and levels of IL-6 significantly decreased in HBV group relative to PCOS group. The immunohistochemical analysis showed an increase in COX-2 and VEGF expression in PCOS group whereas HBV-treated rats presented weak and irregular immunostaining.

CONCLUSIONS

Our results suggest that the beneficial effect of HBV may be mediated through its inhibitory effect on serum IL-6 level and ovarian COX-2 and VEGF expression.

MicroRNA-494, upregulated by tumor necrosis factor-α, desensitizes insulin effect in C2C12 muscle cells

Chronic inflammation is fundamental for the induction of insulin resistance in the muscle tissue of vertebrates. Although several miRNAs are thought to be involved in the development of insulin resistance, the role of miRNAs in the association between inflammation and insulin resistance in muscle tissue is poorly understood. Herein, we investigated the aberrant expression of miRNAs by conducting miRNA microarray analysis of TNF-α-treated mouse C₂C₁₂ myotubes. We identified two miRNAs that were upregulated and six that were downregulated by a >1.5-fold change compared to normal cells. Among the findings, qRT-PCR analysis confirmed that miR-494 is consistently upregulated by TNF-α-induced inflammation. Overexpression of miR-494 in CHO_IR/IRS1 and C₂C₁₂ myoblasts suppressed insulin action by down-regulating phosphorylations of GSK-3α/β, AS160 and p70S6K, downstream of Akt. Moreover, overexpression of miR-494 did not regulate TNF-α-mediated inflammation . Among genes bearing the seed site for miR-494, RT-PCR analysis showed that the expression of Stxbp5, an inhibitor of glucose transport, was downregulated following miR-494 inhibition. In contrast, the expression of PTEN decreased in the cells analyzed, thus showing that both positive and negative regulators of insulin action may be simultaneously controlled by miR-494. To investigate the overall effect of miR-494 on insulin signaling, we performed a PCR array analysis containing 84 genes related to the insulin signaling pathway, and we observed that 25% of genes were downregulated (P<0.05) and 11% were upregulated (P<0.05). These results confirm that miR-494 might contribute to insulin sensitivity by positive and negative regulation of the expression of diverse genes. Of note, PCR array data showed downregulation of Slc2A4, a coding gene for Glut4. Altogether, the present study concludes that the upregulation of miR-494 expression by TNF-α-mediated inflammation exacerbates insulin resistance. Therefore, we suggest that miR-494 could prove an important target for the diagnosis and therapy of inflammation-mediated insulin resistance in muscle.

Nitric oxide directly promotes vascular endothelial insulin transport

Insulin resistance strongly associates with decreased nitric oxide (NO) bioavailability and endothelial dysfunction. In the vasculature, NO mediates multiple processes that affect insulin delivery, including dilating both resistance and terminal arterioles in skeletal muscle in vivo. However, whether NO directly regulates vascular endothelial cell (EC) insulin uptake and its transendothelial transport (TET) is unknown. We report in this article that L-N(G)-nitro-L-arginine methyl ester (L-NAME) pretreatment blocked, whereas L-arginine and sodium nitroprusside (SNP) each enhanced, EC uptake of fluorescein isothiocyanate (FITC)-labeled insulin. SNP also partly or fully reversed the inhibition of EC insulin uptake caused by L-NAME, wortmannin, the Src inhibitor PP1, and tumor necrosis factor-α. In addition, SNP promoted [(125)I]Tyr(A14)insulin TET by ~40%. Treatment with insulin with and without SNP did not affect EC cyclic guanosine monophosphate (cGMP) levels, and the cGMP analog 8-bromo-cGMP did not affect FITC-insulin uptake. In contrast, treatment with insulin and SNP significantly increased EC protein S-nitrosylation, the colocalization of S-nitrosothiol (S-NO) and protein-tyrosine phosphatase 1B (PTP1B), and Akt phosphorylation at Ser(473) and inhibited PTP1B activity. Moreover, a high-fat diet significantly inhibited EC insulin-stimulated Akt phosphorylation and FITC-insulin uptake that was partially reversed by SNP in rats. Finally, inhibition of S-nitrosylation by knockdown of thioredoxin-interacting protein completely eliminated SNP-enhanced FITC-insulin uptake. We conclude that NO directly promotes EC insulin transport by enhancing protein S-nitrosylation. NO also inhibits PTP1B activity, thereby enhancing insulin signaling.

Modulation of Rho-Rock signaling pathway protects oligodendrocytes against cytokine toxicity via PPAR-α-dependent mechanism

We earlier documented that lovastatin (LOV)-mediated inhibition of small Rho GTPases activity protects vulnerable oligodendrocytes (OLs) in mixed glial cell cultures stimulated with Th1 cytokines and in a murine model of multiple sclerosis (MS). However, the precise mechanism of OL protection remains unclear. We here employed genetic and biochemical approaches to elucidate the underlying mechanism that protects LOV treated OLs from Th1 (tumor necrosis factor-α) and Th17 (interleukin-17) cytokines toxicity in in vitro. Cytokines enhanced the reactive oxygen species (ROS) generation and mitochondrial membrane depolarization with corresponding lowering of glutathione (reduced) level in OLs and that were reverted by LOV. In addition, the expression of ROS detoxifying enzymes (catalase and superoxide-dismutase 2) and the transactivation of peroxisome proliferators-activated receptor (PPAR)-α/-β/-γ including PPAR-γ coactivator-1α were enhanced by LOV in similarly treated OLs. Interestingly, LOV-mediated inhibition of small Rho GTPases, i.e., RhoA and cdc42, and Rho-associated kinase (ROCK) activity enhanced the levels of PPAR ligands in OLs via extracellular signal regulated kinase (1/2)/p38 mitogen-activated protein kinase/cytoplasmic phospholipase 2/cyclooxygenase-2 signaling cascade activation. Small hairpin RNA transfection-based studies established that LOV mainly enhances PPAR-α and less so of PPAR-β and PPAR-γ transactivation that enhances ROS detoxifying defense in OLs. In support of this, the observed LOV-mediated protection was lacking in PPAR-α-deficient OLs exposed to cytokines. Collectively, these data provide unprecedented evidence that LOV-mediated inhibition of the Rho-ROCK signaling pathway boosts ROS detoxifying defense in OLs via PPAR-α-dependent mechanism that has implication in neurodegenerative disorders including MS.

Ranolazine recruits muscle microvasculature and enhances insulin action in rats

Ranolazine, an anti-anginal compound, has been shown to significantly improve glycaemic control in large-scale clinical trials, and short-term ranolazine treatment is associated with an improvement in myocardial blood flow. As microvascular perfusion plays critical roles in insulin delivery and action, we aimed to determine if ranolazine could improve muscle microvascular blood flow, thereby increasing muscle insulin delivery and glucose use. Overnight-fasted, anaesthetized Sprague-Dawley rats were used to determine the effects of ranolazine on microvascular recruitment using contrast-enhanced ultrasound, insulin action with euglycaemic hyperinsulinaemic clamp, and muscle insulin uptake using (125)I-insulin. Ranolazine's effects on endothelial nitric oxide synthase (eNOS) phosphorylation, cAMP generation and endothelial insulin uptake were determined in cultured endothelial cells. Ranolazine-induced myographical changes in tension were determined in isolated distal saphenous artery. Ranolazine at therapeutically effective dose significantly recruited muscle microvasculature by increasing muscle microvascular blood volume (∼2-fold, P < 0.05) and increased insulin-mediated whole body glucose disposal (∼30%, P = 0.02). These were associated with an increased insulin delivery into the muscle (P < 0.04). In cultured endothelial cells, ranolazine increased eNOS phosphorylation and cAMP production without affecting endothelial insulin uptake. In ex vivo studies, ranolazine exerted a potent vasodilatatory effect on phenylephrine pre-constricted arterial rings, which was partially abolished by endothelium denudement. In conclusion, ranolazine treatment vasodilatates pre-capillary arterioles and increases microvascular perfusion, which are partially mediated by endothelium, leading to expanded microvascular endothelial surface area available for nutrient and hormone exchanges and resulting in increased muscle delivery and action of insulin. Whether these actions contribute to improved glycaemic control in patients with insulin resistance warrants further investigation.

Globular adiponectin enhances muscle insulin action via microvascular recruitment and increased insulin delivery

RATIONALE

Adiponectin enhances insulin action and induces nitric oxide-dependent vasodilatation. Insulin delivery to muscle microcirculation and transendothelial transport are 2 discrete steps that limit insulin's action. We have shown that expansion of muscle microvascular surface area increases muscle insulin delivery and action.

OBJECTIVE

To examine whether adiponectin modulates muscle microvascular recruitment thus insulin delivery and action in vivo.

METHODS AND RESULTS

Overnight fasted adult male rats were studied. We determined the effects of adiponectin on muscle microvascular recruitment, using contrast-enhanced ultrasound, on insulin-mediated microvascular recruitment and whole-body glucose disposal, using contrast-enhanced ultrasound and insulin clamp, and on muscle insulin clearance and uptake with (125)I-insulin. Globular adiponectin potently increased muscle microvascular blood volume without altering microvascular blood flow velocity, leading to a significantly increased microvascular blood flow. This was paralleled by a ≈30% to 40% increase in muscle insulin uptake and clearance, and ≈30% increase in insulin-stimulated whole-body glucose disposal. Inhibition of endothelial nitric oxide synthase abolished globular adiponectin-mediated muscle microvascular recruitment and insulin uptake. In cultured endothelial cells, globular adiponectin dose-dependently increased endothelial nitric oxide synthase phosphorylation but had no effect on endothelial cell internalization of insulin.

CONCLUSIONS

Globular adiponectin increases muscle insulin uptake by recruiting muscle microvasculature, which contributes to its insulin-sensitizing action.

Endothelial dysfunction in (pre)diabetes: characteristics, causative mechanisms and pathogenic role in type 2 diabetes

Endothelial dysfunction associated with diabetes and cardiovascular disease is characterized by changes in vasoregulation, enhanced generation of reactive oxygen intermediates, inflammatory activation, and altered barrier function. These endothelial alterations contribute to excess cardiovascular disease in diabetes, but may also play a role in the pathogenesis of diabetes, especially type 2. The mechanisms underlying endothelial dysfunction in diabetes differ between type 1 (T1D) and type 2 diabetes (T2D): hyperglycemia contributes to endothelial dysfunction in all individuals with diabetes, whereas the causative mechanisms in T2D also include impaired insulin signaling in endothelial cells, dyslipidemia and altered secretion of bioactive substances (adipokines) by adipose tissue. The close association of so-called perivascular adipose tissue with arteries and arterioles facilitates the exposure of vascular endothelium to adipokines, particularly if inflammation activates the adipose tissue. Glucose and adipokines activate specific intracellular signaling pathways in endothelium, which in concert result in endothelial dysfunction in diabetes. Here, we review the characteristics of endothelial dysfunction in diabetes, the causative mechanisms involved and the role of endothelial dysfunction(s) in the pathogenesis of T2D. Finally, we will discuss the therapeutic potential of endothelial dysfunction in T2D.

Microvascular dysfunction: an emerging pathway in the pathogenesis of obesity-related insulin resistance

The prevalence of type 2 diabetes mellitus (T2DM) and its major risk factor, obesity, has reached epidemic proportions in Western society. How obesity leads to insulin resistance and subsequent T2DM is incompletely understood. It has been established that insulin can redirect blood flow in skeletal muscle from non-nutritive to nutritive capillary networks, without increasing total blood flow. This results in a net increase of the overall number of perfused nutritive capillary networks and thereby increases insulin-mediated glucose uptake by skeletal muscle. This process, referred to as functional (nutritive) capillary recruitment, has been shown to be endothelium-dependent and to require activation of the phosphatidylinositol-kinase (PI3K) pathway in the endothelial cell. Several studies have demonstrated that these processes are impaired in states of microvascular dysfunction. In obesity, changes in several adipokines are likely candidates to influence insulin signaling pathways in endothelial cells, thereby causing microvascular dysfunction. Microvascular dysfunction, in turn, impairs the timely access of glucose and insulin to their target tissues, and may therefore be an additional cause of insulin resistance. Thus, microvascular dysfunction may be a key feature in the development of obesity-related insulin resistance. In the present review, we will discuss the evidence for this emerging role for the microcirculation as a possible link between obesity and insulin resistance.

Effect of gelam honey on the oxidative stress-induced signaling pathways in pancreatic hamster cells

Background. Oxidative stress induced by reactive oxygen and nitrogen species is critically involved in the impairment of β -cell function during the development of diabetes. Methods. HIT-T15 cells were cultured in 5% CO2 and then preincubated with Gelam honey extracts (20, 40, 60, and 80 µg/mL) as well as quercetin (20, 40, 60, and 80 µM), prior to stimulation by 20 and 50 mM of glucose. Cell lysate was collected to determine the effect of honey extracts and quercetin on the stress activated NF- κ B, MAPK pathways, and the Akt (ser473) activated insulin signaling pathway. Results. HIT-T15 cells cultured under hyperglycemic conditions demonstrated insulin resistance with a significant increase in the levels of MAPK, NF- κ B, and IRS-1 serine phosphorylation (ser307); however, Akt expression and insulin contents are significantly decreased. Pretreatment with quercetin and Gelam honey extract improved insulin resistance and insulin content by reducing the expression of MAPK, NF- κ B, and IRS-1 serine phosphorylation (ser307) and increasing the expression of Akt significantly. Conclusion. Gelam honey-induced differential expression of MAPK, NF- κ B, IRS-1 (ser307), and Akt in HIT-T15 cells shows that Gelam honey exerts protective effects against diabetes- and hyperglycemia-induced oxidative stress by improving insulin content and insulin resistance.

Tumor necrosis factor-induced cerebral insulin resistance in Alzheimer's disease links numerous treatment rationales

The evident limitations of the amyloid theory of the pathogenesis of Alzheimer's disease are increasingly putting alternatives in the spotlight. We argue here that a number of independently developing approaches to therapy-including specific and nonspecific anti-tumor necrosis factor (TNF) agents, apolipoprotein E mimetics, leptin, intranasal insulin, the glucagon-like peptide-1 mimetics and glycogen synthase kinase-3 (GSK-3) antagonists-are all part of an interlocking chain of events. All these approaches inform us that inflammation and thence cerebral insulin resistance constitute the pathway on which to focus for a successful clinical outcome in treating this disease. The key link in this chain presently absent is a recognition by Alzheimer's research community of the long-neglected history of TNF induction of insulin resistance. When this is incorporated into the bigger picture, it becomes evident that the interventions we discuss are not competing alternatives but equally valid approaches to correcting different parts of the same pathway to Alzheimer's disease. These treatments can be expected to be at least additive, and conceivably synergistic, in effect. Thus the inflammation, insulin resistance, GSK-3, and mitochondrial dysfunction hypotheses are not opposing ideas but stages of the same fundamental, overarching, pathway of Alzheimer's disease pathogenesis. The insight this provides into progenitor cells, including those involved in adult neurogenesis, is a key part of this approach. This pathway also has therapeutic implications for other circumstances in which brain TNF is pathologically increased, such as stroke, traumatic brain injury, and the infectious disease encephalopathies.

Tat-Mediated p66shc Transduction Decreased Phosphorylation of Endothelial Nitric Oxide Synthase in Endothelial Cells

We evaluated the role of Tat-mediated p66shc transduction on the activation of endothelial nitric oxide synthase in cultured mouse endothelial cells. To construct the Tat-p66shc fusion protein, human full length p66shc cDNA was fused with the Tat-protein transduction domain. Transduction of TAT-p66shc showed a concentration- and time-dependent manner in endothelial cells. Tat-mediated p66shc transduction showed increased hydrogen peroxide and superoxide production, compared with Tat-p66shc (S/A), serine 36 residue mutant of p66shc. Tat-mediated p66shc transduction decreased endothelial nitric oxide synthase phosphorylation in endothelial cells. Furthermore, Tat-mediated p66shc transduction augmented TNF-α-induced p38 MAPK phosphorylation in endothelial cells. These results suggest that Tat-mediated p66shc transduction efficiently inhibited endothelial nitric oxide synthase phosphorylation in endothelial cells.