cJun NH2-terminal kinase 1 (JNK1): roles in metabolic regulation of insulin resistance. Trends Biochem Sci. 2010;35:490-496. [PMID: 20452774 DOI: 10.1016/j.tibs.2010.04.004]

Methylophiopogonanone A alleviates diabetic cardiomyopathy via inhibiting JNK1 signaling

OBJECTIVE

Diabetic cardiomyopathy (DCM) is a common complication of type 2 diabetes mellitus (T2DM). The effects of methylophiopogonanone A (MO-A), a natural homoisoflavonoid with anti-inflammatory effects, on DCM and its underlying mechanisms were investigated in this study.

METHODS

The T2DM mouse model was induced by intraperitoneal injection of 30 mg/kg streptozotocin for 7 consecutive days and fed with a high-fat diet for 12 weeks. T2DM mice received MO-A (2.5, 5, or 10 mg/kg) treatment for two weeks. Cardiac function, hypertrophy, fibrosis, and inflammation were evaluated. The binding energy between MO-A and JNK1 was analyzed using molecular docking. The underlying mechanism was further investigated in high glucose (HG)-induced H9C2 cells. The cytotoxic effects, cardiomyocyte hypertrophy, fibrosis, inflammation, and relevant signaling proteins were assessed.

RESULTS

MO-A treatment alleviated cardiac function and histopathological changes in DCM mice. Moreover, MO-A treatment significantly decreased COLI, TGF-β1, MYH7, and ANP expression levels in DCM mice. Furthermore, TNF-α, IL-6, and IL-1β expression levels were notably downregulated after treatment with MO-A in DCM mice. Similar results were also observed in vitro. Mechanistically, MO-A targets JNK1 and downregulates its phosphorylation levels in DCM mice. The protective properties of MO-A were reversed by JNK1 overexpression in HG-induced H9C2 cells.

CONCLUSION

Our results revealed that MO-A could alleviate cardiac function, hypertrophy, fibrosis, and inflammation in DCM via inhibiting JNK1 signaling.

From lipids to glucose: Investigating the role of dyslipidemia in the risk of insulin resistance

Dyslipidemia is recognized as one of the most prevalent metabolic disorders and is frequently associated with other prevalent conditions, particularly diabetes mellitus. There appears to be a bidirectional connection between these two metabolic disorders. While considerable research has focused on how insulin resistance can lead to lipid abnormalities, the reverse relationship specifically, how dyslipidemia could assist in developing insulin resistance and diabetes mellitus has received relatively less attention. This review aims to comprehensively evaluate the mechanisms through which dyslipidemia can induce insulin resistance. Dyslipidemia is primarily classified into three main categories: hypercholesterolemia, hypertriglyceridemia, and low levels of HDL. These conditions may promote insulin resistance across multiple pathways, including the accumulation of lipid metabolites, dysfunction of pancreatic β-cells, increased reactive oxygen species, endoplasmic reticulum stress and inflammation, endothelial dysfunction, alterations in adiponectin levels, changes in bile acid composition and concentration, and dysbiosis of gut microbiota. However, further investigation is required to fully elucidate the cellular and molecular mechanisms underlying the relationship between lipid disorders and insulin resistance. Emphasizing such research could facilitate the development of therapeutic strategies targeting both conditions simultaneously.

Retinol-binding protein 4 in skeletal and cardiac muscle: molecular mechanisms, clinical implications, and future perspectives

Retinol-binding protein 4 (RBP4) has emerged as a critical adipokine involved in the pathophysiology of metabolic and cardiovascular diseases. Beyond its classical role in retinol transport, RBP4 influences insulin resistance, inflammation, lipid metabolism, mitochondrial function, and cellular apoptosis in both skeletal and cardiac muscles. Elevated levels of RBP4 are associated with obesity, type 2 mellitus diabetes, and cardiovascular diseases, making it a potential biomarker and therapeutic target. This comprehensive review elucidates the molecular mechanisms by which RBP4 affects skeletal and cardiac muscle physiology. We discuss its clinical implications as a biomarker for disease risk and progression, explore therapeutic strategies targeting RBP4, and highlight future research directions. Understanding the multifaceted roles of RBP4 could pave the way for novel interventions against metabolic and cardiovascular disorders.

Multi-tissue network analysis reveals the effect of JNK inhibition on dietary sucrose-induced metabolic dysfunction in rats

Excessive consumption of sucrose, in the form of sugar-sweetened beverages, has been implicated in the pathogenesis of metabolic dysfunction-associated fatty liver disease (MAFLD) and other related metabolic syndromes. The c-Jun N-terminal kinase (JNK) pathway plays a crucial role in response to dietary stressors, and it was demonstrated that the inhibition of the JNK pathway could potentially be used in the treatment of MAFLD. However, the intricate mechanisms underlying these interventions remain incompletely understood given their multifaceted effects across multiple tissues. In this study, we challenged rats with sucrose-sweetened water and investigated the potential effects of JNK inhibition by employing network analysis based on the transcriptome profiling obtained from hepatic and extrahepatic tissues, including visceral white adipose tissue, skeletal muscle, and brain. Our data demonstrate that JNK inhibition by JNK-IN-5A effectively reduces the circulating triglyceride accumulation and inflammation in rats subjected to sucrose consumption. Coexpression analysis and genome-scale metabolic modeling reveal that sucrose overconsumption primarily induces transcriptional dysfunction related to fatty acid and oxidative metabolism in the liver and adipose tissues, which are largely rectified after JNK inhibition at a clinically relevant dose. Skeletal muscle exhibited minimal transcriptional changes to sucrose overconsumption but underwent substantial metabolic adaptation following the JNK inhibition. Overall, our data provides novel insights into the molecular basis by which JNK inhibition exerts its metabolic effect in the metabolically active tissues. Furthermore, our findings underpin the critical role of extrahepatic metabolism in the development of diet-induced steatosis, offering valuable guidance for future studies focused on JNK-targeting for effective treatment of MAFLD.

Roux-en-Y gastric bypass improves liver and glucose homeostasis in Zucker diabetic fatty rats by upregulating hepatic trefoil factor family 3 and activating the phosphatidylinositol 3-kinase/protein kinase B pathway

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery is effective in ameliorating type 2 diabetes mellitus (T2DM); but its mechanism remains incompletely understood.

OBJECTIVES

This study aimed to investigate whether RYGB improves glucose metabolism by upregulating hepatic trefoil factor family 3 (TFF3) and thereby activating the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway.

SETTING

Affiliated Hospital of North Sichuan Medical college in Nanchong city, China.

METHODS

Zucker diabetic fatty (ZDF) rats underwent RYGB or sham surgery (SHAM), and Zucker lean (ZL) rats served as controls (CON). TFF3 expression and PI3K/Akt pathway activity were compared between groups using western blot, immunofluorescence, and RT-qPCR. Adeno-associated virus (AAV) was used to specifically overexpress and interfere with hepatic TFF3. Liver fibrosis and steatosis were assessed using Masson trichrome and Oil Red O staining. HepG2 cells overexpressing or knocking out TFF3 were constructed using lentiviral transfection and CRISPR/Cas9 technology. After verifying the activity of the PI3K/Akt pathway by western blot, rescue experiments were performed on HepG2 cell overexpressing and knocking out TFF3 using LY294002 and 740Y-P, respectively. The activities of gluconeogenic enzymes and glucose uptake capacity in different HepG2 cells were evaluated using qPCR and flow cytometry.

RESULTS

Compared with the SHAM group, the blood glucose, body weight, insulin resistance, and lipid metabolism of ZDF rats in the RYGB group were significantly improved. The expression of TFF3 and PI3K/Akt phosphorylation in the liver of the RYGB group were higher than those of the rats that had undergone SHAM. In addition, compared with the SHAM group, the liver fibrosis and fatty degeneration of RYGB rats were milder, and the activity of gluconeogenic enzymes was lower. After tail vein injection of AAV that specifically overexpresses liver TTF3 in rats in the SHAM group, rats' insulin resistance, glucose tolerance, gluconeogenic enzymes, and other glucose metabolism indicators improved. After tail vein injection of AAV that interferes with liver TFF3 in rats in the RYGB group, rats' glucose metabolism indicators deteriorated. In in vitro experiments, the PI3K/Akt activity of TFF3-knocked-out HepG2 cells was lower than that of other groups. Lower glucose concentration were observed in TFF3-overexpressing cell lines. After rescue experiments, differences were found. The glucose metabolism level of the TFF3-expressing HepG2 cell line was positively correlated with the activity of the PI3K/Akt pathway.

CONCLUSIONS

RYGB regulates the expression of TFF3 in the liver of ZDF rats, thereby activating the PI3K/Akt pathway and improving T2DM.

Exploring the Therapeutic Potential of Glycyrrhiza Compounds in Alzheimer's Disease: A Comprehensive Review

Alzheimer's disease (AD) is a progressive neurodegenerative disorder. Research shows that the development of AD is linked to neuroinflammation, endoplasmic reticulum stress, mitochondrial dysfunction, cell death, and abnormal cholinergic signaling. Glycyrrhiza compounds contain active ingredients and extracts that offer multiple benefits, including targeting various pathways, high efficacy with low toxicity, and long-lasting therapeutic effects. These benefits highlight the significant potential of Glycyrrhiza compounds for preventing and treating AD. This review summarizes recent advancements in Glycyrrhiza compounds for preventing and treating AD. It focuses on their inhibitory effects on key signaling pathways, such as Toll-like receptor 4 (TLR4), nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK), and cholinergic signaling. This study aims to establish a scientific framework for using Glycyrrhiza compounds in the clinical prevention and treatment of AD and to support the development of new therapeutic interventions.

Muscle cell palmitate-induced insulin resistance, JNK, IKK/NF-κB, and STAT3 activation are attenuated by carnosic and rosmarinic acid

The worldwide epidemic of obesity has drastically worsened with the increase in more sedentary lifestyles and increased consumption of fatty foods. Increased blood free fatty acids, often observed in obesity, lead to impaired insulin action, and promote the development of insulin resistance and type 2 diabetes mellitus. c-Jun N-terminal kinase (JNK), inhibitor of kappa B (IκB) kinase (IKK)-nuclear factor-kappa B (NF-κB), and signal transducer and activator of transcription 3 (STAT3) are known to be involved in skeletal muscle insulin resistance. We reported previously that carnosic acid (CA) and rosmarinic acid (RA) attenuated the palmitate-induced skeletal muscle insulin resistance, an effect that was associated with increased AMPK activation and reduced mammalian target of rapamycin-p70S6K signaling. In the present study, we examined the effects of CA and RA on JNK, IKK-NF-κB, and STAT3. Exposure of cells to palmitate increased the phosphorylation/activation of JNK, IKKα/β, IκBα, NF-κBp65, and STAT3. Importantly, CA and RA attenuated the deleterious effects of palmitate. Our data indicate that CA and RA have the potential to counteract the palmitate-induced skeletal muscle cell insulin resistance by modulating JNK, IKK-NF-κB, and STAT3 signaling.

Role of melatonin in mitigation of insulin resistance and ensuing diabetic cardiomyopathy

Addressing insulin resistance or hyperinsulinemia might offer a viable treatment approach to stop the onset of diabetic cardiomyopathy, as these conditions independently predispose to the development of the disease, which is initially characterized by diastolic abnormalities. The development of diabetic cardiomyopathy appears to be driven mainly by insulin resistance or impaired insulin signalling and/or hyperinsulinemia. Oxidative stress, hypertrophy, fibrosis, cardiac diastolic dysfunction, and, ultimately, systolic heart failure are the outcomes of these pathophysiological alterations. Melatonin is a ubiquitous indoleamine, a widely distributed compound secreted mainly by the pineal gland, and serves a variety of purposes in almost every living creature. Melatonin is found to play a leading role by improving myocardial cell metabolism, decreasing vascular endothelial cell death, reversing micro-circulation disorders, reducing myocardial fibrosis, decreasing oxidative and endoplasmic reticulum stress, regulating cell autophagy and apoptosis, and enhancing mitochondrial function. This review highlights a relationship between insulin resistance and associated cardiomyopathy. It explores the potential therapeutic strategies offered by the neurohormone melatonin, an important antioxidant that plays a leading role in maintaining glucose homeostasis by influencing the glucose transporters independently and through its receptors. The vast distribution of melatonin receptors in the body, including beta cells of pancreatic islets, asserts the role of this indole molecule in maintaining glucose homeostasis. Melatonin controls the production of GLUT4 and/or the phosphorylation process of the receptor for insulin and its intracellular substrates, activating the insulin-signalling pathway through its G-protein-coupled membrane receptors.

Update on JNK inhibitor patents: 2015 to present

INTRODUCTION

c-Jun N-terminal kinase (JNK) regulates various biological processes through the phosphorylation cascade and is closely associated with numerous diseases, including inflammation, cardiovascular diseases, and neurological disorders. Therefore, JNKs have emerged as potential targets for disease treatment.

AREAS COVERED

This review compiles the patents and literatures concerning JNK inhibitors through retrieving relevant information from the SciFinder, Google Patents databases, and PubMed from 2015 to the present. It summarizes the structure-activity relationship (SAR) and biological activity profiles of JNK inhibitors, offering valuable perspectives on their potential therapeutic applications.

EXPERT OPINION

The JNK kinase serves as a novel target for the treatment of neurodegenerative disorders, pulmonary fibrosis, and other illnesses. A variety of small-molecule inhibitors targeting JNKs have demonstrated promising therapeutic potential in preclinical studies, which act upon JNK kinases via distinct mechanisms, encompassing traditional ATP competitive inhibition, covalent inhibition, and bidentate inhibition. Among them, several JNK inhibitors from PregLem SA, Celegene SA, and Xigen SA have accomplished the early stage of clinical trials, and their results will guide the development and indications of future JNK inhibitors.

Deciphering the role of classical oestrogen receptor in insulin resistance and type 2 diabetes mellitus: From molecular mechanism to clinical evidence

The biological actions of oestrogen are mediated by the oestrogen receptor α or β (ERα or ERβ), which are members of a broad nuclear receptor superfamily. Numerous in vivo and in vitro studies have demonstrated that loss of circulating oestrogen modulated by classical ERα and ERβ led to rapid changes in pancreatic β-cell and islet function, GLUT4 expression, insulin sensitivity and glucose tolerance, dysfunctional lipid homeostasis, oxidative stress, and inflammatory cascades. Remarkably, 17β-oestradiol (E2) can completely reverse these effects. This review evaluates the current understanding of the protective role of classical ER in critical pathways and molecular mechanisms associated with insulin resistance and type 2 diabetes mellitus (T2DM). It also examines the effectiveness of menopausal hormone therapy (MHT) in reducing the risk of developing T2DM in menopausal women. Clinical trials have shown the protective effects of MHT on glucose metabolism, which may be useful to treat T2DM in perimenopausal women. However, there are concerns about E2's potential side effects of obesity and hyperlipidaemia in menopausal women. Further studies are warranted to gain understanding and find other oestrogen alternatives for treatment of insulin resistance and T2DM in postmenopausal women.

Role and mechanism of specialized pro-resolving mediators in obesity-associated insulin resistance

With the changing times, obesity has become a characteristic epidemic in the context of the current era. Insulin resistance (IR) is most commonly caused by obesity, and IR is a common basis of the pathogenesis of many diseases such as cardiovascular disease, nonalcoholic fatty liver disease, and type 2 diabetes, which seriously threaten human life, as well as health. A major pathogenetic mechanism of obesity-associated IR has been found to be chronic low-grade inflammation in adipose tissue. Specialized pro-resolving mediators (SPMs) are novel lipid mediators that both function as "stop signals" for inflammatory reaction and promote inflammation to subside. In this article, we summarize the pathogenesis of obesity-associated IR and its treatments and outline the classification and biosynthesis of SPMs and their mechanisms and roles in the treatment of obesity-associated IR in order to explore the potential of SPMs for treating metabolic diseases linked with obesity-associated IR.

Inflammation causes insulin resistance in mice via interferon regulatory factor 3 (IRF3)-mediated reduction in FAHFA levels

Obesity-induced inflammation causes metabolic dysfunction, but the mechanisms remain elusive. Here we show that the innate immune transcription factor interferon regulatory factor (IRF3) adversely affects glucose homeostasis through induction of the endogenous FAHFA hydrolase androgen induced gene 1 (AIG1) in adipocytes. Adipocyte-specific knockout of IRF3 protects male mice against high-fat diet-induced insulin resistance, whereas overexpression of IRF3 or AIG1 in adipocytes promotes insulin resistance on a high-fat diet. Furthermore, pharmacological inhibition of AIG1 reversed obesity-induced insulin resistance and restored glucose homeostasis in the setting of adipocyte IRF3 overexpression. We, therefore, identify the adipocyte IRF3/AIG1 axis as a crucial link between obesity-induced inflammation and insulin resistance and suggest an approach for limiting the metabolic dysfunction accompanying obesity.

Mechanism of Obesity-Related Lipotoxicity and Clinical Perspective

The link between cellular exposure to fatty acid species and toxicity phenotypes remains poorly understood. However, structural characterization and functional profiling of human plasma free fatty acids (FFAs) analysis has revealed that FFAs are located either in the toxic cluster or in the cluster that is transcriptionally responsive to lipotoxic stress and creates genetic risk factors. Genome-wide short hairpin RNA screen has identified more than 350 genes modulating lipotoxicity. Hypertrophic adipocytes in obese adipose are both unable to expand further to store excess lipids in the diet and are resistant to the antilipolytic action of insulin. In addition to lipolysis, the inability of packaging the excess lipids into lipid droplets causes circulating fatty acids to reach toxic levels in non-adipose tissues. Deleterious effects of accumulated lipid in non-adipose tissues are known as lipotoxicity. Although triglycerides serve a storage function for long-chain non-esterified fatty acid and their products such as ceramide and diacylglycerols (DAGs), overloading of palmitic acid fraction of saturated fatty acids (SFAs) raises ceramide levels. The excess DAG and ceramide load create harmful effects on multiple organs and systems, inducing chronic inflammation in obesity. Thus, lipotoxic inflammation results in β cells death and pancreatic islets dysfunction. Endoplasmic reticulum stress stimuli induce lipolysis by activating cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) and extracellular signal-regulated kinase (Erk) 1/2 signaling in adipocytes. However, palmitic acid-induced endoplasmic reticulum stress-c-Jun N-terminal kinase (JNK)-autophagy axis in hypertrophic adipocytes is a pro-survival mechanism against endoplasmic reticulum stress and cell death induced by SFAs. Endoplasmic reticulum-localized acyl-coenzyme A (CoA): glycerol-3-phosphate acyltransferase (GPAT) enzymes are mediators of lipotoxicity, and inhibiting these enzymes has therapeutic potential for lipotoxicity. Lipotoxicity increases the number of autophagosomes, which engulf palmitic acid, and thus suppress the autophagic turnover. Fatty acid desaturation promotes palmitate detoxification and storages into triglycerides. As therapeutic targets of glucolipotoxicity, in addition to caloric restriction and exercise, there are four different pharmacological approaches, which consist of metformin, glucagon-like peptide 1 (GLP-1) receptor agonists, peroxisome proliferator-activated receptor-gamma (PPARγ) ligands thiazolidinediones, and chaperones are still used in clinical practice. Furthermore, induction of the brown fat-like phenotype with the mixture of eicosapentanoic acid and docosahexaenoic acid appears as a potential therapeutic application for treatment of lipotoxicity.

Chicoric acid ameliorates LPS-induced inflammatory injury in bovine lamellar keratinocytes by modulating the TLR4/MAPK/NF-κB signaling pathway

Damage to lamellar keratinocytes, an essential cellular component of the epidermal layer of hoof tissue, can have a detrimental effect on hoof health and the overall production value of dairy cows. We isolated and cultured cow lamellar keratinocytes using the Dispase II and collagenase methods. We purified them by differential digestion and differential velocity adherent methods at each passaging and identified them by keratin 14 immunofluorescence. We established an in vitro model of inflammation in laminar keratinocytes using LPS and investigated whether chicoric acid protects against inflammatory responses by inhibiting the activation of the TLR4/MAPK/NF-κB signaling pathway. The results showed that cow lamellar keratinocytes were successfully isolated and cultured by Dispase II combined with the collagenase method. In the in vitro inflammation model established by LPS, the Chicoric acid decreased the concentration of inflammatory mediators (TNF-α, IL-1β, and IL-6), down-regulated the mRNA expression of TLR4 and MyD88 (P < 0.01), down-regulated the expression of TLR4, MyD88, p-ERK, p-p38, IKKβ, p-p65, p-p50 (P < 0.05), and increased the IκBα protein expression (P < 0.05). In conclusion, Chicoric acid successfully protected cow lamellar keratinocytes from LPS-induced inflammatory responses by modulating the TLR4/MAPK/NF-κB signaling pathway and downregulating inflammatory mediators.

Resveratrol as a potential protective compound against skeletal muscle insulin resistance

The increasing prevalence of type 2 diabetes has become a major global problem. Insulin resistance has a central role in pathophysiology of type 2 diabetes. Skeletal muscle is responsible for the disposal of most of the glucose under conditions of insulin stimulation, and insulin resistance in skeletal muscle causes dysregulation of glucose homeostasis in the whole body. Despite the current pharmaceutical and non-pharmacological treatment strategies to combat diabetes, there is still a need for new therapeutic agents due to the limitations of the therapeutic agents. Meanwhile, plant polyphenols have attracted the attention of researchers for their use in the treatment of diabetes and have gained popularity. Resveratrol, a stilbenoid polyphenol, exists in various plant sources, and a growing body of evidence suggests its beneficial properties, including antidiabetic activities. The present review aimed to provide a summary of the role of resveratrol in insulin resistance in skeletal muscle and its related mechanisms. To achieve the objectives, by searching the PubMed, Scopus and Web of Science databases, we have summarized the results of all cell culture, animal, and human studies that have investigated the effects of resveratrol in different models on insulin resistance in skeletal muscle.

Licochalcone A: A Potential Multitarget Drug for Alzheimer's Disease Treatment

Licochalcone A (Lico-A) is a flavonoid compound derived from the root of the Glycyrrhiza species, a plant commonly used in traditional Chinese medicine. While the Glycyrrhiza species has shown promise in treating various diseases such as cancer, obesity, and skin diseases due to its active compounds, the investigation of Licochalcone A's effects on the central nervous system and its potential application in Alzheimer's disease (AD) treatment have garnered significant interest. Studies have reported the neuroprotective effects of Lico-A, suggesting its potential as a multitarget compound. Lico-A acts as a PTP1B inhibitor, enhancing cognitive activity through the BDNF-TrkB pathway and exhibiting inhibitory effects on microglia activation, which enables mitigation of neuroinflammation. Moreover, Lico-A inhibits c-Jun N-terminal kinase 1, a key enzyme involved in tau phosphorylation, and modulates the brain insulin receptor, which plays a role in cognitive processes. Lico-A also acts as an acetylcholinesterase inhibitor, leading to increased levels of the neurotransmitter acetylcholine (Ach) in the brain. This mechanism enhances cognitive capacity in individuals with AD. Finally, Lico-A has shown the ability to reduce amyloid plaques, a hallmark of AD, and exhibits antioxidant properties by activating the nuclear factor erythroid 2-related factor 2 (Nrf2), a key regulator of antioxidant defense mechanisms. In the present review, we discuss the available findings analyzing the potential of Lico-A as a neuroprotective agent. Continued research on Lico-A holds promise for the development of novel treatments for cognitive disorders and neurodegenerative diseases, including AD. Further investigations into its multitarget action and elucidation of underlying mechanisms will contribute to our understanding of its therapeutic potential.

Causal relationship between insulin resistance and sarcopenia

Sarcopenia is a multifactorial disease characterized by reduced muscle mass and function, leading to disability, death, and other diseases. Recently, the prevalence of sarcopenia increased considerably, posing a serious threat to health worldwide. However, no clear international consensus has been reached regarding the etiology of sarcopenia. Several studies have shown that insulin resistance may be an important mechanism in the pathogenesis of induced muscle attenuation and that, conversely, sarcopenia can lead to insulin resistance. However, the causal relationship between the two is not clear. In this paper, the pathogenesis of sarcopenia is analyzed, the possible intrinsic causal relationship between sarcopenia and insulin resistance examined, and research progress expounded to provide a basis for the clinical diagnosis, treatment, and study of the mechanism of sarcopenia.

Modified Signaling of Membrane Formyl Peptide Receptors in NADPH-Oxidase Regulation in Obesity-Resistant Mice

The signaling of membrane receptors is modified in obesity characterized by low-grade inflammation. The obesity-resistant state of organisms is poorly understood. We analyzed the generation of reactive oxygen species (ROS) initiated though membrane formyl peptide receptors (Fpr1, Fpr2) in bone-marrow granulocytes of obesity-resistant mice (ORM). A chemiluminescence assay was used to assess NADPH-oxidase-related intensity of ROS generation. ORM were chosen from animals that received high-fat diets and had metric body parameters as controls (standard diet). High spontaneous ROS production was observed in ORM cells. The EC50 for responses to bacterial or mitochondrial peptide N-formyl-MLF was higher in ORM with and without inflammation vs. the same control groups, indicating an insignificant role of high-affinity Fpr1. Increased responses to synthetic peptide WKYMVM (Fpr2 agonist) were observed in controls with acute inflammation, but they were similar in other groups. Fpr2 was possibly partially inactivated in ORM owing to the inflammatory state. Weakened Fpr1 and Fpr2 signaling via MAPKs was revealed in ORM using specific inhibitors for p38, ERK1/2, and JNK. P38 signaling via Fpr2 was lower in ORM with inflammation. Thus, a high-fat diet modified FPRs' role and suppressed MAPK signaling in NADPH-oxidase regulation in ORM. This result can be useful to understand the immunological features of obesity resistance.

P38γ modulates the lipid metabolism in non-alcoholic fatty liver disease by regulating the JAK-STAT signaling pathway

Non-alcoholic fatty liver disease (NAFLD) is a major health problem in Western countries and has become the most common cause of chronic liver disease. Although NAFLD is closely associated with obesity, inflammation, and insulin resistance, its pathogenesis remains unclear. The disease begins with excessive accumulation of triglycerides in the liver, which in turn leads to liver cell damage, steatosis, inflammation, and so on. P38γ is one of the four isoforms of P38 mitogen-activated protein kinases (P38 MAPKs) that contributes to inflammation in different diseases. In this research, we investigated the role of P38γ in NAFLD. In vivo, a NAFLD model was established by feeding C57BL/6J mice with a methionine- and choline-deficient (MCD) diet and adeno-associated virus (AAV9-shRNA-P38γ) was injected into C57BL/6J mice by tail vein for knockdown P38γ. The results indicated that the expression level of P38γ was upregulated in MCD-fed mice. Furthermore, the downregulation of P38γ significantly attenuated liver injury and lipid accumulation in mice. In vitro, mouse hepatocytes AML-12 were treated with free fatty acid (FFA). We found that P38γ was obviously increased in FFA-treated AML-12 cells, whereas knockdown of P38γ significantly suppressed lipid accumulation in FFA-treated AML-12 cells. Furthermore, P38γ regulated the Janus Kinase-Signal transducers and activators of transcription (JAK-STAT) signaling pathway. Inhibition of P38γ can inhibit the JAK-STAT signaling pathway, thereby inhibiting lipid accumulation in FFA-treated AML-12 cells. In conclusion, our results suggest that targeting P38γ contributes to the suppression of lipid accumulation in fatty liver disease.

Adipokines from white adipose tissue in regulation of whole body energy homeostasis

Diseases originating from altered energy homeostasis including obesity, and type 2 diabetes are rapidly increasing worldwide. Research in the last few decades on animal models and humans demonstrates that the white adipose tissue (WAT) is critical for energy balance and more than just an energy storage site. WAT orchestrates the whole-body metabolism through inter-organ crosstalk primarily mediated by cytokines named "Adipokines". The adipokines influence metabolism and fuel selection of the skeletal muscle and liver thereby fine-tuning the load on WAT itself in physiological conditions like starvation, exercise and cold. In addition, adipokine secretion is influenced by various pathological conditions like obesity, inflammation and diabetes. In this review, we have surveyed the current state of knowledge on important adipokines and their significance in regulating energy balance and metabolic diseases. Furthermore, we have summarized the interplay of pro-inflammatory and anti-inflammatory adipokines in the modulation of pathological conditions.

Phosphorylation of RXRα mediates the effect of JNK to suppress hepatic FGF21 expression and promote metabolic syndrome

The cJun NH₂-terminal kinase (JNK) signaling pathway in the liver promotes systemic changes in metabolism by regulating peroxisome proliferator-activated receptor α (PPARα)-dependent expression of the hepatokine fibroblast growth factor 21 (FGF21). Hepatocyte-specific gene ablation studies demonstrated that the Mapk9 gene (encoding JNK2) plays a key mechanistic role. Mutually exclusive inclusion of exons 7a and 7b yields expression of the isoforms JNK2α and JNK2β. Here we demonstrate that Fgf21 gene expression and metabolic regulation are primarily regulated by the JNK2α isoform. To identify relevant substrates of JNK2α, we performed a quantitative phosphoproteomic study of livers isolated from control mice, mice with JNK deficiency in hepatocytes, and mice that express only JNK2α or JNK2β in hepatocytes. We identified the JNK substrate retinoid X receptor α (RXRα) as a protein that exhibited JNK2α-promoted phosphorylation in vivo. RXRα functions as a heterodimeric partner of PPARα and may therefore mediate the effects of JNK2α signaling on Fgf21 expression. To test this hypothesis, we established mice with hepatocyte-specific expression of wild-type or mutated RXRα proteins. We found that the RXRα phosphorylation site Ser²⁶⁰ was required for suppression of Fgf21 gene expression. Collectively, these data establish a JNK-mediated signaling pathway that regulates hepatic Fgf21 expression.

Macrophages, Chronic Inflammation, and Insulin Resistance

The prevalence of obesity has reached alarming levels, which is considered a major risk factor for several metabolic diseases, including type 2 diabetes (T2D), non-alcoholic fatty liver, atherosclerosis, and ischemic cardiovascular disease. Obesity-induced chronic, low-grade inflammation may lead to insulin resistance, and it is well-recognized that macrophages play a major role in such inflammation. In the current review, the molecular mechanisms underlying macrophages, low-grade tissue inflammation, insulin resistance, and T2D are described. Also, the role of macrophages in obesity-induced insulin resistance is presented, and therapeutic drugs and recent advances targeting macrophages for the treatment of T2D are introduced.

Polystyrene microplastic exposure induces insulin resistance in mice via dysbacteriosis and pro-inflammation

Microplastics (MPs) as emerging contaminants have become a global environmental problem. However, studies on the effects of MPs on metabolic diseases remain limited. Here, we evaluated the effects of polystyrene (PS), one of the most prominent types of MPs, on insulin sensitivity in mice fed with normal chow diet (NCD) or high-fat diet (HFD), and explained the underlying mechanisms. Mice fed with NCD or HFD both showed insulin resistance (IR) after PS exposure accompanied by increased plasma lipopolysaccharide and pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin-1β. Exposure to PS also resulted in a significant decrease in the richness and diversity of gut microbiota, particularly an increase in the relative abundance of Gram-negative bacteria such as Prevotellaceae and Enterobacteriaceae. Additionally, PS with a small particle size (5 μm) accumulated in the liver, kidneys and blood vessels of mice. Further analyses showed inhibition of the insulin signaling pathway in the liver of PS exposed mice, such as inhibition of IRS1 and decreased expression of PI3K. Hence, the mechanism of PS exposure to induce IR in mice might be mediated through regulating gut microbiota and PS accumulation in tissues, stimulating inflammation and inhibiting the insulin signaling pathway. In conclusion, PS might be a potential environmental contaminant that causes metabolic diseases associated with IR.

Metabolic Impact of MKP-2 Upregulation in Obesity Promotes Insulin Resistance and Fatty Liver Disease

The mechanisms connecting obesity with type 2 diabetes, insulin resistance, nonalcoholic fatty liver disease, and cardiovascular diseases remain incompletely understood. The function of MAPK phosphatase-2 (MKP-2), a type 1 dual-specific phosphatase (DUSP) in whole-body metabolism, and how this contributes to the development of diet-induced obesity, type 2 diabetes (T2D), and insulin resistance is largely unknown. We investigated the physiological contribution of MKP-2 in whole-body metabolism and whether MKP-2 is altered in obesity and human fatty liver disease using MKP-2 knockout mice models and human liver tissue derived from fatty liver disease patients. We demonstrate that, for the first time, MKP-2 expression was upregulated in liver tissue in humans with obesity and fatty liver disease and in insulin-responsive tissues in mice with obesity. MKP-2-deficient mice have enhanced p38 MAPK, JNK, and ERK activities in insulin-responsive tissues compared with wild-type mice. MKP-2 deficiency in mice protects against diet-induced obesity and hepatic steatosis and was accompanied by improved glucose homeostasis and insulin sensitivity. Mkp-2^−/− mice are resistant to diet-induced obesity owing to reduced food intake and associated lower respiratory exchange ratio. This was associated with enhanced circulating insulin-like growth factor-1 (IGF-1) and stromal cell-derived factor 1 (SDF-1) levels in Mkp-2^−/− mice. PTEN, a negative regulator of Akt, was downregulated in livers of Mkp-2^−/− mice, resulting in enhanced Akt activity consistent with increased insulin sensitivity. These studies identify a novel role for MKP-2 in the regulation of systemic metabolism and pathophysiology of obesity-induced insulin resistance and fatty liver disease.

The Impact of Obesity on the Regulation of Muscle Blood Flow during Exercise in Patients with Heart Failure with a Preserved Ejection Fraction

Obesity is now considered a primary comorbidity in heart failure with preserved ejection fraction (HFpEF) pathophysiology, mediated largely by systemic inflammation. While there is accumulating evidence for a disease-related dysregulation of blood flow during exercise in this patient group, the role of obesity in the hemodynamic response to exercise remain largely unknown. Small muscle mass handgrip (HG) exercise was utilized to evaluate exercising muscle blood flow in non-obese (BMI < 30 kg/m²,n=14) and obese (BMI > 30 kg/m²,n=40) patients with HFpEF. Heart rate (HR), stroke index (SI), cardiac index (CI), mean arterial pressure (MAP), forearm blood flow (FBF) and vascular conductance (FVC) were assessed during progressive intermittent HG exercise (15-30-45% maximal voluntary contraction, MVC). Blood biomarkers of inflammation (C-reactive protein (CRP) and Interleukin-6 (IL-6)) were also determined. Exercising FBF was reduced in obese patients with HFpEF at all work rates (15%: 304±42 vs. 229±15ml/min; 30%: 402±46 vs. 300±18ml/min; 45%: 484±55 vs. 380±23ml/min, non-obese vs. obese, p=0.025), and was negatively correlated with BMI (R=-.47, p<0.01). In contrast, no differences in central hemodynamics (HR, SI, CI, MAP) were found between groups. Proinflammatory biomarkers were markedly elevated in obese patients (CRP: 2133±418 vs. 4630±590ng/ml, p=0.02; IL-6: 2.9±0.3 vs. 5.2±0.7pg/ml, p = 0.04, non-obese vs. obese), and both biomarkers were positively correlated with BMI (CRP: R=0.40, p=0.03; IL-6: R=0.57, p<0.01). Together, these findings demonstrate the presence of obesity and an accompanying milieu of systemic inflammation as important factors in the dysregulation of exercising muscle blood flow in patients with HFpEF.

Title: p38δ Regulates IL6 Expression Modulating ERK Phosphorylation in Preadipocytes

IL6 is an essential cytokine in metabolism regulation and for intercommunication among different organs and tissues. IL6 produced by different tissues has different functions and therefore it is very important to understand the mechanism of its expression in adipose tissue. In this work we demonstrated that IL6 expression in mouse preadipocytes, like in human, is partially dependent on Wnt5a and JNK. Using mouse preadipocytes lacking each one of the p38 SAPK family members, we have shown that IL6 expression is also p38γ and p38δ dependent. In fact, the lack of some of these two kinases increases IL6 expression without altering that of Wnt5a. Moreover, we show that the absence of p38δ promotes greater ERK1/2 phosphorylation in a MEK1/2 independent manner, and that this increased ERK1/2 phosphorylation state is contributing to the higher IL6 expression in p38δ^−/- preadipocytes. These results suggest a new crosstalk between two MAPK signaling pathway, p38δ and ERK1/2, where p38δ modulates the phosphorylation state of ERK1/2.

Carnosic Acid Attenuates the Free Fatty Acid-Induced Insulin Resistance in Muscle Cells and Adipocytes

Elevated blood free fatty acids (FFAs), as seen in obesity, impair insulin action leading to insulin resistance and Type 2 diabetes mellitus. Several serine/threonine kinases including JNK, mTOR, and p70 S6K cause serine phosphorylation of the insulin receptor substrate (IRS) and have been implicated in insulin resistance. Activation of AMP-activated protein kinase (AMPK) increases glucose uptake, and in recent years, AMPK has been viewed as an important target to counteract insulin resistance. We reported previously that carnosic acid (CA) found in rosemary extract (RE) and RE increased glucose uptake and activated AMPK in muscle cells. In the present study, we examined the effects of CA on palmitate-induced insulin-resistant L6 myotubes and 3T3L1 adipocytes. Exposure of cells to palmitate reduced the insulin-stimulated glucose uptake, GLUT4 transporter levels on the plasma membrane, and Akt activation. Importantly, CA attenuated the deleterious effect of palmitate and restored the insulin-stimulated glucose uptake, the activation of Akt, and GLUT4 levels. Additionally, CA markedly attenuated the palmitate-induced phosphorylation/activation of JNK, mTOR, and p70S6K and activated AMPK. Our data indicate that CA has the potential to counteract the palmitate-induced muscle and fat cell insulin resistance.

Short-term high-fat diet favors the appearances of apoptosis and gliosis by activation of ERK1/2/p38MAPK pathways in brain

High-fat diet (HFD) has been associated with neuroinflammation and apoptosis in distinct brain regions. To explore the effect of short-term (7, 14 and 21 days) high-fat overfeeding on apoptosis, inflammatory signaling proteins, APP changes and glial cell activities in cerebral cortex and cerebellum. Mice were fed with HFD for different lengths (up to 21 days) and after each time body weights of mice was tested, then the apoptotic proteins, IL-1β, APP, BACE1and MAPKs, Akt and NF-κB signaling activity were evaluated by western blots. Results demonstrate that short period of high-fat overnutrition significantly promotes apoptosis, APP expression at day 21 of cerebral cortex and at day 7 of cerebellum compared to chow diet. In addition, increased GFAP+astrocytes, Iba-1+microglia and IL-1β 30 were observed in cerebral cortex after 21 days HFD, but no changes for 7 days overfeeding of cerebellum. Serendipitously, ERK1/2 pathway was activated both in cerebral cortex and cerebellum for different time course of HFD. Furthermore, increased phospho-p38 MAPK level was observed in cerebellum only. In consistent with in vivo results, SH-SY5Y cells treatment with cholesterol (50 μM, 100 μM) for 48 h culture in vitro demonstrated that pro-apoptotic proteins were enhanced as well. In brief, short-term HFD consumption increases sensitivity to apoptosis, APP and IL-1β production as well as gliosis in cerebral cortex and cerebellum, which may be related to enhancement of ERK1/2 and p38 MAPK activation.

Smoothelin-Like Protein 1 Regulates Development and Metabolic Transformation of Skeletal Muscle in Hyperthyroidism

Hyperthyroidism triggers a glycolytic shift in skeletal muscle (SKM) by altering the expression of metabolic proteins, which is often accompanied by peripheral insulin resistance. Our previous results show that smoothelin-like protein 1 (SMTNL1), a transcriptional co-regulator, promotes insulin sensitivity in SKM. Our aim was to elucidate the role of SMTNL1 in SKM under physiological and pathological 3,3',5-Triiodo-L-thyronine (T3) concentrations. Human hyper- and euthyroid SKM biopsies were used for microarray analysis and proteome profiler arrays. Expression of genes related to energy production, nucleic acid- and lipid metabolism was changed significantly in hyperthyroid samples. The phosphorylation levels and activity of AMPKα2 and JNK were increased by 15% and 23%, respectively, in the hyperthyroid samples compared to control. Moreover, SMTNL1 expression showed a 6-fold decrease in the hyperthyroid samples and in T3-treated C2C12 cells. Physiological and supraphysiological concentrations of T3 were applied on differentiated C2C12 cells upon SMTNL1 overexpression to assess the activity and expression level of the elements of thyroid hormone signaling, insulin signaling and glucose metabolism. Our results demonstrate that SMTNL1 selectively regulated TRα expression. Overexpression of SMTNL1 induced insulin sensitivity through the inhibition of JNK activity by 40% and hampered the non-genomic effects of T3 by decreasing the activity of ERK1/2 through PKCδ. SMTNL1 overexpression reduced IRS1 Ser307 and Ser612 phosphorylation by 52% and 53%, respectively, in hyperthyroid model to restore the normal responsiveness of glucose transport to insulin. SMTNL1 regulated glucose phosphorylation and balances glycolysis and glycogen synthesis via the downregulation of hexokinase II by 1.3-fold. Additionally, mitochondrial respiration and glycolysis were measured by SeaHorse analysis to determine cellular metabolic function/phenotype of our model system in real-time. T3 overload strongly increased the rate of acidification and a shift to glycolysis, while SMTNL1 overexpression antagonizes the T3 effects. These lines of evidence suggest that SMTNL1 potentially prevents hyperthyroidism-induced changes in SKM, and it holds great promise as a novel therapeutic target in insulin resistance.

Diverse transcriptional patterns of homoeologous recombinant transcripts in triploid fish (Cyprinidae)

Homoeologous recombination (HR), the exchange of homoeologous chromosomes, contributes to subgenome adaptation to diverse environments by producing various phenotypes. However, the potential relevance of HR and innate immunity is rarely described in triploid cyprinid fish species. In our study, two allotriploid genotypes (R₂C and RC₂), whose innate immunity was stronger than their inbred parents (Carassius auratus red var. and Cyprinus carpio L.), were obtained from backcrossing between male allotetraploids of C. auratus red var.×C. carpio L. and females of their two inbred parents, respectively. The work detected 140 HRs shared between the two triploids at the genomic level. Further, transcriptions of 54 homoeologous recombinant genes (HRGs) in R₂C and 65 HRGs in RC₂ were detected using both Illumina and PacBio data. Finally, by comparing expressed recombinant reads to total expressed reads in each of the genes, a range of 0.1%-10% was observed in most of the 99-193 HRGs, of which six recombinant genes were classified as "response to stimulus". These results not only provide a novel way to predict HRs in allopolyploids based on cross prediction at both genomic and transcriptional levels, but also insight into the potential relationship between HRs related to innate immunity and adaptation of the triploids and allotetraploids.

JNK downregulation improves olanzapine-induced insulin resistance by suppressing IRS1Ser307 phosphorylation and reducing inflammation

AIMS

c-jun N-terminal kinase (JNK) plays pivotal roles in many physiological processes, including inflammation and glucose metabolism. However, the effects of JNK on olanzapine-induced insulin resistance and the underlying mechanisms have not been fully elucidated. The aim of our study was to explore the role of JNK in olanzapine-induced insulin resistance and the underlying mechanisms.

METHODS

We studied glucose metabolism in olanzapine-treated female C57B/J mice and mice with adeno-associated virus (AAV)-mediated downregulation of JNK1 in epididymal white adipose tissue (eWAT). 3T3-L1 adipocytes were used to investigate the mechanism of JNK1 regulating insulin signaling after olanzapine treatment.

RESULTS

JNK was activated in eWAT after olanzapine treatment. JNK1 downregulation in eWAT ameliorated the insulin resistance and adipose tissue inflammation in olanzapine-treated mice. Furthermore, overexpression of JNK1 in adipocytes exacerbated the glucose disorder while JNK1 knockdown alleviated the impaired insulin signaling on olanzapine challenge, which was likely mediated by the reduced inflammation and insulin receptor substrate 1 (IRS1) phosphorylation. Moreover, the effect of JNK1 was attenuated by downregulation of IRS1 in adipocytes. Finally, the JNK1-IRS1 interaction and IRS1^S307 phosphorylation were required for JNK1-regulated olanzapine-induced insulin resistance in adipocytes.

CONCLUSIONS

Our results demonstrated that JNK1 activation by olanzapine induced insulin resistance by promoting IRS1^Ser307 phosphorylation and inflammation in eWAT. These results highlighted the importance of JNK1 in eWAT as a promising drug target for olanzapine-induced insulin resistance.

Hepatic steatosis integrated approach: nutritional guidelines and joined nutraceutical administration

BACKGROUND

The nonalcoholic fat liver disease (NAFLD) progresses in 30% of the patients to not alcoholic steatohepatitis (NASH) and subsequently in liver fibrosis and even primary cancer and death. Due to the complex physiopathology of the liver steatosis, NASH is an area orphan of specific drugs, but many authors suggest an integrated treatment based upon diet, lifestyle change, and pharmacology.

METHODS

Our clinical study selected from a wider patient cohort, 13 subjects, appealing to the Second Opinion Medical Consulting Network, for liver and nutritional problems. The diet was integrated with regular prescription of an herbal derivative based on Chrysanthellum americanum and Pistacia lentiscus L. extracts. Clinical data of the recruited patients including body weight, Body Mass Index, were recorded before and after treatment. Each patient underwent pre-post accurate clinical examination and lab exams. The liver stiffness and liver steatosis were evaluated by a trained hepatologist with FibroScan^®.

RESULTS

A significant reduction of anthropometric parameters was detected in all the patients at the end of the study; liver fibrosis and steatosis were instrumentally decreased in 8 subjects, but not significant changes in lab exams and no adverse effects were reported.

CONCLUSIONS

Chrysanthellum americanum and Pistacia lentiscus L. extracts were absolutely safe and effective and gave a substantial contribution to the life quality benefit, metabolic balance and gut function in patients with hepatic steatosis.

Hormonal Dysregulation and Unbalanced Specialized Pro-Resolving Mediator Biosynthesis Contribute toward Impaired B Cell Outcomes in Obesity

Diet-induced obesity is associated with impaired B-cell-driven humoral immunity, which coincides with chronic inflammation and has consequences for responses to infections and vaccinations. Key nutritional, cellular, and molecular mechanisms by which obesity may impair aspects of humoral immunity such as B cell development, class switch recombination, and formation of long-lived antibody secreting cells are reviewed. A key theme to emerge is the central role of white adipose tissue on the formation and function of pro-inflammatory B cell subsets that exacerbate insulin resistance. The underlying role of select hormones such as leptin is highlighted, which may be driving the formation of pro-inflammatory B cells in the absence of antigen stimulation. This review also extensively covers the regulatory role of lipid metabolites such as prostaglandins and specialized pro-resolving mediators (SPMs) that are synthesized from polyunsaturated fatty acids. Notably, SPM biosynthesis is impaired in obesity and contributes toward impaired antibody production. Future directions for research, including avenues for therapeutic intervention, are included.

A feed-forward regulatory loop in adipose tissue promotes signaling by the hepatokine FGF21

In this study, Han et al. demonstrate that JNK signaling in adipocytes causes an increased circulating concentration of the hepatokine fibroblast growth factor 21 (FGF21) that regulates systemic metabolism. This regulatory loop represents a novel signaling paradigm that connects autocrine and endocrine signaling modes of the same hormone in different tissues.

The cJun NH₂-terminal kinase (JNK) signaling pathway is activated by metabolic stress and promotes the development of metabolic syndrome, including hyperglycemia, hyperlipidemia, and insulin resistance. This integrated physiological response involves cross-talk between different organs. Here we demonstrate that JNK signaling in adipocytes causes an increased circulating concentration of the hepatokine fibroblast growth factor 21 (FGF21) that regulates systemic metabolism. The mechanism of organ crosstalk is mediated by a feed-forward regulatory loop caused by JNK-regulated FGF21 autocrine signaling in adipocytes that promotes increased expression of the adipokine adiponectin and subsequent hepatic expression of the hormone FGF21. The mechanism of organ cross-talk places circulating adiponectin downstream of autocrine FGF21 expressed by adipocytes and upstream of endocrine FGF21 expressed by hepatocytes. This regulatory loop represents a novel signaling paradigm that connects autocrine and endocrine signaling modes of the same hormone in different tissues.

JNK3 as Therapeutic Target and Biomarker in Neurodegenerative and Neurodevelopmental Brain Diseases

The c-Jun N-terminal kinase 3 (JNK3) is the JNK isoform mainly expressed in the brain. It is the most responsive to many stress stimuli in the central nervous system from ischemia to Aβ oligomers toxicity. JNK3 activity is spatial and temporal organized by its scaffold protein, in particular JIP-1 and β-arrestin-2, which play a crucial role in regulating different cellular functions in different cellular districts. Extensive evidence has highlighted the possibility of exploiting these adaptors to interfere with JNK3 signaling in order to block its action. JNK plays a key role in the first neurodegenerative event, the perturbation of physiological synapse structure and function, known as synaptic dysfunction. Importantly, this is a common mechanism in many different brain pathologies. Synaptic dysfunction and spine loss have been reported to be pharmacologically reversible, opening new therapeutic directions in brain diseases. Being JNK3-detectable at the peripheral level, it could be used as a disease biomarker with the ultimate aim of allowing an early diagnosis of neurodegenerative and neurodevelopment diseases in a still prodromal phase.

JNK-mediated disruption of bile acid homeostasis promotes intrahepatic cholangiocarcinoma

Metabolic stress causes activation of the cJun NH2-terminal kinase (JNK) signal transduction pathway. It is established that one consequence of JNK activation is the development of insulin resistance and hepatic steatosis through inhibition of the transcription factor PPARα. Indeed, JNK1/2 deficiency in hepatocytes protects against the development of steatosis, suggesting that JNK inhibition represents a possible treatment for this disease. However, the long-term consequences of JNK inhibition have not been evaluated. Here we demonstrate that hepatic JNK controls bile acid production. We found that hepatic JNK deficiency alters cholesterol metabolism and bile acid synthesis, conjugation, and transport, resulting in cholestasis, increased cholangiocyte proliferation, and intrahepatic cholangiocarcinoma. Gene ablation studies confirmed that PPARα mediated these effects of JNK in hepatocytes. This analysis highlights potential consequences of long-term use of JNK inhibitors for the treatment of metabolic syndrome.

Differential DNA methylation analysis across the promoter regions using methylated DNA immunoprecipitation sequencing profiling of porcine loin muscle

Background and Aim:

Pork leanness and marbling are among the essential traits of consumer preference. To acquire knowledge about universal epigenetic regulations for improving breed selection, a meta-analysis of methylated DNA immunoprecipitation sequencing (MeDIP-seq) profiling data of mixed loin muscle types was performed in this study.

Materials and Methods:

MeDIP-seq profiling datasets of longissimus dorsi muscle and psoas major muscles from male and female pigs of Landrace and Tibetan breeds were preprocessed and aligned to the porcine genome. Analysis of differential methylated DNA regions (DMRs) between the breeds was performed by focusing on transcription start sites (TSSs) of known genes (−20,000-3000 bases from TSS). All associated genes were further reviewed for their functions and predicted for transcription factors (TF) possibly associated with their TSSs.

Results:

When the methylation levels of DMRs in TSS regions of Landrace breed were compared to those of Tibetan breed, 10 DMRs were hypomethylated (Landrace < Tibetan), and 19 DMRs were hypermethylated (Landrace > Tibetan), accordingly (p≤0.001). According to the reviews about gene functions, all associated genes were pieces of evidence for their roles in a variety of muscle and lipid metabolisms. Prediction of the binding TFs revealed the six most abundant binding TFs to such DMRs-associated TSS (p≤0.0001) as follows: ZNF384, Foxd3, IRF1, KLF9, EWSR1-FLI1, HES5, and TFAP2A.

Conclusion:

Common DMRs-associated TSS between the lean-type and the marbled-type loin muscles were identified in this study. Interestingly, the genes associated with such regions were strongly evidenced for their possible roles on the muscle trait characteristics by which further novel research topics could be focused on them in the future.

Resveratrol alleviates obesity-induced skeletal muscle inflammation via decreasing M1 macrophage polarization and increasing the regulatory T cell population

Resveratrol was reported to inhibit inflammatory responses; however, the role of this polyphenol in obesity-induced skeletal muscle inflammation remains unknown. Mice fed a high fat diet (HFD) were treated with resveratrol for 16 weeks. Resveratrol treatment decreased macrophage infiltration into skeletal muscle of HFD-fed mice. Resveratrol also led to the polarization of macrophages to the M2 direction, as well as decreasing the expression of a number of M1 pro-inflammatory cytokines [tumor necrosis factor α (TNF-α), interleukin 1 β (IL-1β) and interleukin 6 (IL-6)]. In addition, increased infiltration of regulatory T cells (Treg cells) was found following resveratrol treatment in skeletal muscle of mice. Decreased intramyocellular lipid deposition was associated with reduced expression levels of toll-like receptors 2 (TLR2) and TLR4 in resveratrol treated mice. We also found that diminished inflammation in skeletal muscle following resveratrol treatment was accompanied by increasing phosphorylation of 5'-adenosine monophosphate-activated protein kinase (AMPK) and decreasing phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK). Taken together, these findings suggest that resveratrol ameliorates inflammation in skeletal muscle of HFD-induced model of obesity. Therefore, resveratrol might represent a potential treatment for attenuation of inflammation in skeletal muscle tissue.

Catestatin improves insulin sensitivity by attenuating endoplasmic reticulum stress: In vivo and in silico validation

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An endogenous peptide catestatin alleviates obesity-induced ER stress.

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Alleviation of ER stress by catestatin improves insulin sensitivity.

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PID controller based model of ER stress is supported by experimental findings.

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It predicts AKT phosphorylation achieves insulin sensitivity overcoming ER stress.

Obesity is characterized by a state of chronic, unresolved inflammation in insulin-targeted tissues. Obesity-induced inflammation causes accumulation of proinflammatory macrophages in adipose tissue and liver. Proinflammatory cytokines released from tissue macrophages inhibits insulin sensitivity. Obesity also leads to inflammation-induced endoplasmic reticulum (ER) stress and insulin resistance. In this scenario, based on the data (specifically patterns) generated by our in vivo experiments on both diet-induced obese (DIO) and normal chow diet (NCD) mice, we developed an in silico state space model to integrate ER stress and insulin signaling pathways. Computational results successfully followed the experimental results for both DIO and NCD conditions. Chromogranin A (CgA) peptide catestatin (CST: hCgA352-372) improves obesity-induced hepatic insulin resistance by reducing inflammation and inhibiting proinflammatory macrophage infiltration. We reasoned that the anti-inflammatory effects of CST would alleviate ER stress. CST decreased obesity-induced ER dilation in hepatocytes and macrophages. On application of Proportional-Integral-Derivative (PID) controllers on the in silico model, we checked whether the reduction of phosphorylated PERK resulting in attenuation of ER stress, resembling CST effect, could enhance insulin sensitivity. The simulation results clearly pointed out that CST not only decreased ER stress but also enhanced insulin sensitivity in mammalian cells. In vivo experiment validated the simulation results by depicting that CST caused decrease in phosphorylation of UPR signaling molecules and increased phosphorylation of insulin signaling molecules. Besides simulation results predicted that enhancement of AKT phosphorylation helps in both overcoming ER stress and achieving insulin sensitivity. These effects of CST were verified in hepatocyte culture model.

Sarcopenic Obesity, Insulin Resistance, and Their Implications in Cardiovascular and Metabolic Consequences

The prevalence of sarcopenic obesity is increasing worldwide, particularly amongst aging populations. Insulin resistance is the core mechanism of sarcopenic obesity and is also associated with variable cardiometabolic diseases such as cardiovascular disease, type 2 diabetes mellitus, and non-alcoholic fatty liver disease. Fat accumulation in muscle tissue promotes a proinflammatory cascade and oxidative stress, leading to mitochondrial dysfunction, impaired insulin signaling, and muscle atrophy. To compound the problem, decreased muscle mass aggravates insulin resistance. In addition, the crosstalk between myokines and adipokines leads to negative feedback, which in turn aggravates sarcopenic obesity and insulin resistance. In this review, we focus on the molecular mechanisms linking sarcopenic obesity and insulin resistance with various biological pathways. We also discuss the impact and mechanism of sarcopenic obesity and insulin resistance on cardiometabolic disease.

Improving Obesity and Insulin Resistance by Targeting Skeletal Muscle MKP-1

Obesity has reached a global epidemic and it predisposes to the development of insulin resistance, type 2 diabetes and related metabolic diseases. Current interventions against obesity and/or type 2 diabetes such as calorie restriction, exercise, genetic manipulations or established pharmacological treatments have not been successful for many patients with obesity and/or type 2 diabetes. There is an urgent need for new strategies to treat insulin resistance, T2D and obesity. Increased activity of stress-responsive pathways has been linked to the pathogenesis of insulin resistance in obesity. In this commentary, we argue that chronic upregulation of MKP-1 in skeletal muscle is part of a stress response that contributes to the development of insulin resistance, T2D and obesity. Therefore, inhibition of MKP-1 in skeletal muscle is a potential strategy for the treatment of T2D and obesity. We highlight therapeutic strategies for potential targeting of MKP-1 in skeletal muscle for the treatment of metabolic diseases as well as other diseases of skeletal muscle.

Role of c-Jun N-Terminal Kinases (JNKs) in Epilepsy and Metabolic Cognitive Impairment

Previous studies have reported that the regulatory function of the different c-Jun N-terminal kinases isoforms (JNK1, JNK2, and JNK3) play an essential role in neurological disorders, such as epilepsy and metabolic-cognitive alterations. Accordingly, JNKs have emerged as suitable therapeutic strategies. In fact, it has been demonstrated that some unspecific JNK inhibitors exert antidiabetic and neuroprotective effects, albeit they usually show high toxicity or lack therapeutic value. In this sense, natural specific JNK inhibitors, such as Licochalcone A, are promising candidates. Nonetheless, research on the understanding of the role of each of the JNKs remains mandatory in order to progress on the identification of new selective JNK isoform inhibitors. In the present review, a summary on the current gathered data on the role of JNKs in pathology is presented, as well as a discussion on their potential role in pathologies like epilepsy and metabolic-cognitive injury. Moreover, data on the effects of synthetic small molecule inhibitors that modulate JNK-dependent pathways in the brain and peripheral tissues is reviewed.

Fibroblast Growth Factor-1 Improves Insulin Resistance via Repression of JNK-Mediated Inflammation

Insulin resistance is associated with a greatly increased risk of type 2 diabetes. Administration of fibroblast growth factor-1 (FGF-1) resulted in a marked improvement in insulin sensitivity. However, the underlying molecular mechanism whereby FGF-1 represses insulin resistance remains largely unknown. Here, we sought to delineate the role of FGF-1 in insulin resistance with respect to its anti-inflammatory capability. In this study, we found that FGF-1 had positive effects on glucose intolerance, hepatic lipid accumulation, and insulin resistance, while it markedly repressed cytokine secretion (TNF-α and IL-6) in serum and reduced liver inflammation in diet-induced obesity (DIO) mice. Further, FGF-1 treatment significantly represses TNF-α-induced insulin resistance in vitro and in vivo. These results indicate that FGF-1 likely ameliorates insulin resistance via a mechanism that is independent of its glucose-lowering activity. Subsequent experiments demonstrated that FGF-1 ameliorated insulin resistance, and inflammation was accompanied by decreased c-Jun N-terminal kinase (JNK) signaling. In addition, it is likely that FGF-1 impedes JNK phosphorylation via blocking the transforming growth factor-β activated kinase 1 (TAK1) and TAK1 binding protein 1 (TAB1) interaction. These findings reveal that FGF-1 regulates insulin sensitivity and may represent an attractive therapeutic target for preventing the development of insulin resistance.

Neural JNK3 regulates blood flow recovery after hindlimb ischemia in mice via an Egr1/Creb1 axis

Diseases related to impaired blood flow such as peripheral artery disease (PAD) impact nearly 10 million people in the United States alone, yet patients with clinical manifestations of PAD (e.g., claudication and limb ischemia) have limited treatment options. In ischemic tissues, stress kinases such as c-Jun N-terminal kinases (JNKs), are activated. Here, we show that inhibition of the JNK3 (Mapk10) in the neural compartment strikingly potentiates blood flow recovery from mouse hindlimb ischemia. JNK3 deficiency leads to upregulation of growth factors such as Vegfa, Pdgfb, Pgf, Hbegf and Tgfb3 in ischemic muscle by activation of the transcription factors Egr1/Creb1. JNK3 acts through Forkhead box O3 (Foxo3a) to suppress the activity of Egr1/Creb1 transcription regulators in vitro. In JNK3-deficient cells, Foxo3a is suppressed which leads to Egr1/Creb1 activation and upregulation of downstream growth factors. Collectively, these data suggest that the JNK3-Foxo3a-Egr1/Creb1 axis coordinates the vascular remodeling response in peripheral ischemia.

Stress kinases are activated in peripheral ischemic tissues in the presence of vascular diseases. Here the authors show that inhibition of the neural JNK3 kinase improves recovery from hind limb ischemia in animals through activation of the transcription factors Egr1/Creb1 and upregulation of growth factors.

The Involvement of Peripheral and Brain Insulin Resistance in Late Onset Alzheimer's Dementia

Nowadays, Alzheimer's disease (AD) is a severe sociological and clinical problem. Since it was first described, there has been a constant increase in its incidence and, for now, there are no effective treatments since current approved medications have only shown short-term symptomatic benefits. Therefore, it is imperative to increase efforts in the search for molecules and non-pharmacological strategies that are capable of slowing or stopping the progress of the disease and, ideally, to reverse it. The amyloid cascade hypothesis based on the fundamental role of amyloid has been the central hypothesis in the last 30 years. However, since amyloid-directed treatments have shown no relevant beneficial results other theories have been postulated to explain the origin of the pathology. The brain is a highly metabolically active energy-consuming tissue in the human body. It has an almost complete dependence on the metabolism of glucose and uses most of its energy for synaptic transmission. Thus, alterations on the utilization or availability of glucose may be cause for the appearance of neurodegenerative pathologies like AD. In this review article, the hypothesis known as Type 3 Diabetes (T3D) will be evaluated by summarizing some of the data that has been reported in recent years. According to published research, the adherence over time to low saturated fatty acids diets in the context of the Mediterranean diet would reduce the inflammatory levels in brain, with a decrease in the pro-inflammatory glial activation and mitochondrial oxidative stress. In this situation, the insulin receptor pathway would be able to fine tune the mitochondrial biogenesis in neuronal cells, regulation the adenosine triphosphate/adenosine diphosphate intracellular balance, and becoming a key factor involved in the preservation of the synaptic connexions and neuronal plasticity. In addition, new targets and strategies for the treatment of AD will be considered in this review for their potential as new pharmacological or non-pharmacological approaches.

JNK and cardiometabolic dysfunction

Cardiometabolic syndrome (CMS) describes the cluster of metabolic and cardiovascular diseases that are generally characterized by impaired glucose tolerance, intra-abdominal adiposity, dyslipidemia, and hypertension. CMS currently affects more than 25% of the world’s population and the rates of diseases are rapidly rising. These CMS conditions represent critical risk factors for cardiovascular diseases including atherosclerosis, heart failure, myocardial infarction, and peripheral artery disease (PAD). Therefore, it is imperative to elucidate the underlying signaling involved in disease onset and progression. The c-Jun N-terminal Kinases (JNKs) are a family of stress signaling kinases that have been recently indicated in CMS. The purpose of this review is to examine the in vivo implications of JNK as a potential therapeutic target for CMS. As the constellation of diseases associated with CMS are complex and involve multiple tissues and environmental triggers, carefully examining what is known about the JNK pathway will be important for specificity in treatment strategies.

NOD1: An Interface Between Innate Immunity and Insulin Resistance

Insulin resistance is driven, in part, by activation of the innate immune system. We have discussed the evidence linking nucleotide-binding oligomerization domain (NOD)1, an intracellular pattern recognition receptor, to the onset and progression of obesity-induced insulin resistance. On a molecular level, crosstalk between downstream NOD1 effectors and the insulin receptor pathway inhibits insulin signaling, potentially through reduced insulin receptor substrate action. In vivo studies have demonstrated that NOD1 activation induces peripheral, hepatic, and whole-body insulin resistance. Also, NOD1-deficient models are protected from high-fat diet (HFD)-induced insulin resistance. Moreover, hematopoietic NOD1 deficiency prevented HFD-induced changes in proinflammatory macrophage polarization status, thus protecting against the development of metabolic inflammation and insulin resistance. Serum from HFD-fed mice activated NOD1 signaling ex vivo; however, the molecular identity of the activating factors remains unclear. Many have proposed that an HFD changes the gut permeability, resulting in increased translocation of bacterial fragments and increased circulating NOD1 ligands. In contrast, others have suggested that NOD1 ligands are endogenous and potentially lipid-derived metabolites produced during states of nutrient overload. Nevertheless, that NOD1 contributes to the development of insulin resistance, and that NOD1-based therapy might provide benefit, is an exciting advancement in metabolic research.