Activation and regulation of the pattern recognition receptors in obesity-induced adipose tissue inflammation and insulin resistance

Influence of Type 2 Diabetes and Adipose Tissue Dysfunction on Breast Cancer and Potential Benefits from Nutraceuticals Inducible in Microalgae

Breast cancer (BC) represents the most prevalent cancer in women at any age after puberty. From a pathogenetic prospective, despite a wide array of risk factors being identified thus far, poor metabolic health is emerging as a putative risk factor for BC. In particular, type 2 diabetes mellitus (T2DM) provides a perfect example bridging the gap between poor metabolic health and BC risk. Indeed, T2DM is preceded by a status of hyperinsulinemia and is characterised by hyperglycaemia, with both factors representing potential contributors to BC onset and progression. Additionally, the aberrant secretome of the dysfunctional, hypertrophic adipocytes, typical of obesity, characterised by pro-inflammatory mediators, is a shared pathogenetic factor between T2DM and BC. In this review, we provide an overview on the effects of hyperglycaemia and hyperinsulinemia, hallmarks of type 2 diabetes mellitus, on breast cancer risk, progression, treatment and prognosis. Furthermore, we dissect the role of the adipose-tissue-secreted adipokines as additional players in the pathogenesis of BC. Finally, we focus on microalgae as a novel superfood and a source of nutraceuticals able to mitigate BC risk by improving metabolic health and targeting cellular pathways, which are disrupted in the context of T2DM and obesity.

Excessive palmitic acid disturbs macrophage α-ketoglutarate/succinate metabolism and causes adipose tissue insulin resistance associated with gestational diabetes mellitus

Abnormal polarization of adipose tissue macrophages (ATMs) results in low-grade systemic inflammation and insulin resistance (IR), potentially contributing to the development of diabetes. However, the underlying mechanisms that regulate the polarization of ATMs associated with gestational diabetes mellitus (GDM) remain unclear. Thus, we aimed to determine the effects of abnormal fatty acids on macrophage polarization and development of insulin resistance in GDM. Levels of fatty acids and inflammation were assessed in the serum samples and adipose tissues of patients with GDM. An in vitro cell model treated with palmitic acid was established, and the mechanisms of palmitic acid in regulating macrophage polarization was clarified. The effects of excessive palmitic acid on the regulation of histone methylations and IR were also explored in the high-fat diet induced GDM mice model. We found that pregnancies with GDM were associated with increased levels of serum fatty acids, and inflammation and IR in adipose tissues. Increased palmitic acid could induce mitochondrial dysfunction and excessive ROS levels in macrophages, leading to abnormal cytoplasmic and nuclear metabolism of succinate and α-ketoglutarate (αKG). Specifically, a decreased nuclear αKG/succinate ratio could attenuate the enrichment of H3K27me3 at the promoters of pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α, leading to cytokine secretion. Importantly, GDM mice treated with GSK-J4, an inhibitor of histone lysine demethylase, were protected from abnormal pro-inflammatory macrophage polarization and excessive production of pro-inflammatory cytokines. Our findings highlight the importance of the metabolism of αKG and succinate as transcriptional modulators in regulating the polarization of ATMs and the insulin sensitivity of adipose tissue, ensuring a normal pregnancy. This novel insight sheds new light on gestational fatty acid metabolism and epigenetic alterations associated with GDM.

Therapeutic targeting of white adipose tissue metabolic dysfunction in obesity: mechanisms and opportunities

White adipose tissue is not only a highly heterogeneous organ containing various cells, such as adipocytes, adipose stem and progenitor cells, and immune cells, but also an endocrine organ that is highly important for regulating metabolic and immune homeostasis. In individuals with obesity, dynamic cellular changes in adipose tissue result in phenotypic switching and adipose tissue dysfunction, including pathological expansion, WAT fibrosis, immune cell infiltration, endoplasmic reticulum stress, and ectopic lipid accumulation, ultimately leading to chronic low-grade inflammation and insulin resistance. Recently, many distinct subpopulations of adipose tissue have been identified, providing new insights into the potential mechanisms of adipose dysfunction in individuals with obesity. Therefore, targeting white adipose tissue as a therapeutic agent for treating obesity and obesity-related metabolic diseases is of great scientific interest. Here, we provide an overview of white adipose tissue remodeling in individuals with obesity including cellular changes and discuss the underlying regulatory mechanisms of white adipose tissue metabolic dysfunction. Currently, various studies have uncovered promising targets and strategies for obesity treatment. We also outline the potential therapeutic signaling pathways of targeting adipose tissue and summarize existing therapeutic strategies for antiobesity treatment including pharmacological approaches, lifestyle interventions, and novel therapies.

White adipose tissue in metabolic associated fatty liver disease

BACKGROUND

Metabolic associated fatty liver disease (MAFLD) is a prevalent chronic liver condition globally, currently lacking universally recognized therapeutic drugs, thereby increasing the risk of cirrhosis and hepatocellular carcinoma. Research has reported an association between white adipose tissue and MAFLD.

SCOPE OF REVIEW

White adipose tissue (WAT) is involved in lipid metabolism and can contribute to the progression of MAFLD by mediating insulin resistance, inflammation, exosomes, autophagy, and other processes. This review aims to elucidate the mechanisms through which WAT plays a role in the development of MAFLD.

MAJOR CONCLUSIONS

WAT participates in the occurrence and progression of MAFLD by mediating insulin resistance, inflammation, autophagy, and exosome secretion. Fibrosis and restricted expansion of adipose tissue can lead to the release of more free fatty acids (FFA), exacerbating the progression of MAFLD. WAT-secreted TNF-α and IL-1β, through the promotion of JNK/JKK/p38MAPK expression, interfere with insulin receptor serine and tyrosine phosphorylation, worsening insulin resistance. Adiponectin, by inhibiting the TLR-4-NF-κB pathway and suppressing M2 to M1 transformation, further inhibits the secretion of IL-6, IL-1β, and TNF-α, improving insulin resistance in MAFLD patients. Various gene expressions within WAT, such as MBPAT7, Nrf2, and Ube4A, can ameliorate insulin resistance in MAFLD patients. Autophagy-related gene Atg7 promotes the expression of fibrosis-related genes, worsening MAFLD. Non-pharmacological treatments, including diabetes-related medications and exercise, can improve MAFLD.

Association between higher triglyceride glucose index and increased risk of osteoarthritis: data from NHANES 2015-2020

BACKGROUND

The relationship between the triglyceride glucose (TyG) index and osteoarthritis (OA) remains unclear. The objective of this study was to examine potential associations between an elevated TyG index and an increased risk of OA prevalence.

METHODS

3,921 participants with OA from the National Health and Nutrition Examination Survey (2015-2020) were included in this study. Participants were categorized into quartiles based on TyG index, which was determined using the formula: Ln [triglyceride (mg/dL) fasting blood glucose (mg/dL)/2]. Weighted multivariable regression, subgroup analyses, and threshold effect analyses were performed to calculate the independent association between TyG index and OA.

RESULTS

A total of 25,514 people were enrolled, with a mean TyG index of 8.48 ± 0.65. The results of multivariable logistic regression analysis after full adjustment showed a significant association between higher TyG index values and an increased risk of OA. Specifically, each incremental unit increase in the TyG index was associated with a 634% higher risk of OA [OR = 7.34; 95% CI: 2.25, 23.93; p = 0.0010]. Based on interaction tests, age, gender, BMI, and smoking status did not significantly affect the relationship between the TyG index and OA, while diabetes showed a stronger positive correlation between the TyG index and OA.

CONCLUSION

An increased risk of OA was associated with a higher TyG index. TyG could be a valuable predictor of OA and offer novel perspectives on the assessment and treatment of OA.

Effects of an in vitro vitamin D treatment on the inflammatory responses in visceral adipose tissue from Ldlr-/- mice

BACKGROUND/OBJECTIVES

Atherosclerosis is associated with increased inflammation in the visceral adipose tissue (VAT). Vitamin D has been reported to modulate the inflammatory responses of stromal vascular cells (SVCs) and adipocytes in adipose tissue, but the role of vitamin D in atherosclerosis biology is unclear. This study examined the effects of in vitro 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) treatment on the inflammatory responses of SVCs and adipocytes from atherosclerotic mice.

MATERIALS/METHODS

C57BL/6J (B6) mice were divided randomly into 2 groups and fed a 10% kcal fat control diet (control group, CON) or 41% kcal fat, 0.21% cholesterol (high fat + cholesterol, HFC) diet (obese group, OB), and B6.129S7-Ldlrtm1Her/J (Ldlr-/-) mice were fed a HFC diet (obese with atherosclerosis group, OBA) for 16 weeks. SVCs and adipocytes isolated from VAT were pre-incubated with 1,25(OH)2D3 for 24 h and stimulated with lipopolysaccarides for the next 24 h. Proinflammatory cytokine production by adipocytes and SVCs, the immune cell population in SVCs, and the expression of the genes involved in the inflammatory signaling pathway in SVCs were determined.

RESULTS

The numbers of total macrophages and SVCs per mouse were higher in OB and OBA groups than the CON group. The in vitro 1,25(OH)2D3 treatment significantly reduced macrophages/SVCs (%) in the OBA group. Consistent with this change, the production of interleukin-6 and monocyte chemoattractant protein 1 (MCP-1) by SVCs from the OBA group was decreased by 1,25(OH)2D3 treatment. The 1,25(OH)2D3 treatment significantly reduced the toll-like receptor 4 and dual-specificity protein phosphatase 1 (also known as mitogen-activated protein kinase phosphatase 1) mRNA levels in SVCs and MCP-1 production by adipocytes from all 3 groups.

CONCLUSIONS

These findings suggest that vitamin D can attribute to the inhibition of the inflammatory response in VAT from atherosclerotic mice by reducing proinflammatory cytokine production.

The association between triglyceride glucose index and arthritis: a population-based study

OBJECTIVES

Insulin resistance is a well-established contributor to inflammation; however, the specific association between the triglyceride glucose (TyG) index, a biomarker reflecting insulin resistance, and arthritis remains unexplored. As a result, the main aim of this study was to examine the correlation between the TyG index and arthritis.

METHODS

This observational study used data from the National Health and Nutrition Examination Survey (NHANES), which was conducted between 2007 and 2018. To investigate the relationship between the TyG index and arthritis, various statistical analyses were employed, including weighted multivariable logistic regression analysis, subgroup analysis, curve fit analysis, and threshold effect analysis.

RESULTS

In total, 14,817 patients were enrolled in the trial, with 4,191 individuals (28.29%) diagnosed with arthritis. An increased risk of arthritis was found to be significantly correlated with higher TyG index values (odds ratio OR = 1.15, 95% confidence interval CI: 1.07-1.23), according to the results of multivariable logistic regression analysis after full adjustment. Subgroup analysis and interaction tests further indicated that the TyG index exhibited an additive effect when combined with other established risk factors, including age (OR = 1.29; 95% CI: 1.17-1.41), body mass index (BMI) (OR = 1.43; 95% CI: 1.24-1.69), and diabetes (OR = 1.20; 95% CI: 1.11-1.31). Additionally, curve fit analysis and threshold effect analysis demonstrated a nonlinear relationship with a breakpoint identified at 8.08 µmol/L.

CONCLUSION

The TyG index was positively correlated with arthritis in adults under 60 years of age in the United States who had normal weight and no diabetes. Further large-scale prospective studies are warranted for a comprehensive analysis of the role of the TyG index in arthritis.

Angiotensin II and dengue

Dengue is a disease caused by a flavivirus that is transmitted principally by the bite of an Aedes aegypti mosquito and represents a major public-health problem. Many studies have been carried out to identify soluble factors that are involved in the pathogenesis of this infection. Cytokines, soluble factors, and oxidative stress have been reported to be involved in the development of severe disease. Angiotensin II (Ang II) is a hormone with the ability to induce the production of cytokines and soluble factors related to the inflammatory processes and coagulation disorders observed in dengue. However, a direct involvement of Ang II in this disease has not been demonstrated. This review primarily summarizes the pathophysiology of dengue, the role of Ang II in various diseases, and reports that are highly suggestive of the involvement of this hormone in dengue.

Besides TLR2 and TLR4, NLRP3 is also involved in regulating Escherichia coli infection-induced inflammatory responses in mice

The host Toll-like Receptor-2 (TLR2) and Toll-like Receptor-4 (TLR4) play critical roles in defense against Escherichia coli (E. coli) infection is well-known. The NLR pyrin domain-containing 3 (NLRP3) inflammasome is also an important candidate during the host-recognized pathogen, while the roles of NLRP3 in the host inflammatory response to E. coli infection remains unclear. This study aimed to explore the roles of NLRP3 in regulating the inflammatory response in E. coli infection-induced mice. Our result indicated that compared to wild-type mice, the TLR2-deficient (TLR2^-/-), TLR4-deficient (TLR4^-/-), and NLRP3-deficient (NLRP3^-/-) mice had significant decrease in liver damage after stimulation with Lipopolysaccharide (LPS, 1 μg/mL), Braun lipoprotein (BLP, 1 μg/mL), or infected by WT E. coli (1 × 10⁷ CFU, MOI 5:1). Meanwhile, compared with wild-type mice, the TNF-α and IL-1β production in serum decreased in TLR2^-/-, TLR4^-/-, and NLRP3^-/- mice after LPS, BLP treatment, or WT E. coli infection. In macrophages from NLRP3^-/- mice showed significantly reduced secretion of TNF-α and IL-1β in response to stimulation with LPS, BLP, or WT E. coli infection compared with macrophages from wild-type mice. These results indicate that besides TLR2 and TLR4, NLRP3 also plays a critical role in host inflammatory responses to defense against E. coli infection, and might provide a therapeutic target in combating disease with bacterium infection.

Impact of myeloid differentiation protein 1 on cardiovascular disease

Cardiovascular disease remains the leading cause of disability and mortality worldwide and a significant global burden. Many lines of evidence suggest complex remodeling responses to cardiovascular disease, such as myocardial ischemia, hypertension and valve disease, which lead to poor clinical outcomes, including heart failure, arrhythmia and sudden cardiac death (SCD). The mechanisms underlying cardiac remodeling are closely related to reactive oxygen species (ROS) and inflammation. Myeloid differentiation protein 1 (MD1) is a secreted glycoprotein known as lymphocyte antigen 86. The complex of MD1 and radioprotective 105 (RP105) is an important regulator of inflammation and is involved in the modulation of vascular remodeling and atherosclerotic plaque development. A recent study suggested that the expression of MD1 in hypertrophic cardiomyopathy (HCM) patients is decreased compared with that in donor hearts. Therefore, MD1 may play an important role in the pathological processes of cardiovascular disease and have potential clinical value. Here, this review aims to discuss the current knowledge regarding the role of MD1 in the regulation of cardiac pathophysiology.

Obesity and Its Multiple Clinical Implications between Inflammatory States and Gut Microbiotic Alterations

Obesity is a chronic multifactorial disease that has become a serious health problem and is currently widespread over the world. It is, in fact, strongly associated with many other conditions, including insulin resistance, type 2 diabetes, cardiovascular and neurodegenerative diseases, the onset of different types of malignant tumors and alterations in reproductive function. According to the literature, obesity is characterized by a state of low-grade chronic inflammation, with a substantial increase in immune cells, specifically macrophage infiltrates in the adipose tissue which, in turn, secrete a succession of pro-inflammatory mediators. Furthermore, recent studies on microbiota have postulated new possible mechanisms of interaction between obesity and unbalanced nutrition with inflammation. This intestinal "superorganism" complex seems to influence not only the metabolic balance of the host but also the immune response, favoring a state of systemic inflammation and insulin resistance. This review summarizes the major evidence on the interactions between the gut microbiota, energetic metabolism and host immune system, all leading to a convergence of the fields of immunology, nutrients physiology and microbiota in the context of obesity and its possible clinical complications. Finally, possible therapeutic approaches aiming to rebalance the intestinal microbial ecosystem are evaluated to improve the alteration of inflammatory and metabolic states in obesity and related diseases.

Opposing Actions of TLR2 and TLR4 in Adipocyte Differentiation and Mature-Onset Obesity

Understanding the signaling cascades that govern adipocyte metabolism and differentiation is necessary for the development of therapies for obesity. Toll-like receptors (TLRs) are key mediators in adipogenesis, but their specific role is not completely understood. In this study, siRNA knockdown of Tlr2 in 3T3-L1 cells allowed them to differentiate more efficiently into adipocytes, whereas the opposite was observed for the knockdown of Tlr4. At the same time, we show that TLR2 knock-out mice spontaneously developed mature-onset obesity and insulin resistance. Besides a higher incidence of hyperplasia and hypertrophy in white adipose tissue (WAT), we found a significantly increased number of adipocyte precursor cells in TLR2^-/- mice compared to TLR4^-/- mice. Interestingly, genetic inactivation of Tlr4 in TLR2^-/- mice reverted their increased adiposity, insulin resistance, and restored normal levels of adipocyte precursor cells. These findings provide evidence that TLR2 and TLR4 play opposing roles in WAT homeostasis and point to the existence of cross-regulation among TLR2 and TLR4 during adipocyte differentiation both in vitro and in vivo.

Angiotensin II and human obesity. A narrative review of the pathogenesis

Angiotensin II (Ang II) is a hormone and the main effector of the renin-angiotensin system (RAS). This peptide has crucial pathophysiologi-cal effects on hypertension, cardiac hypertrophy, endothelial proliferation, in-flammation and tissue remodelling through G protein-coupled receptors. The pro-inflammatory role of Ang II has been reported in various inflammatory pro-cesses. Obesity is linked to a chronic inflammatory process which in turn is the cause of some of its morbidities. Ang II is related to the comorbidities related to the comorbidities of obesity, which include alterations in the heart, kid-ney, hypertension and coagulation. In this regard, activation of AT1 receptors by Ang II can induce an inflammatory process mediated by the transcription factor NF-kB, triggering inflammation in various systems that are related to the comorbidities observed in obesity. The aim of this review was to highlight the pro-inflammatory effects of Ang II and the alterations induced by this hor-mone in various organs and systems in obesity. The search was done since 1990 through Medline, EMBASE and PubMed, using the keywords: angiotensin II; an-giotensin II, obesity; angiotensin II, kidney, obesity; angiotensin II, coagulation, obesity; angiotensin II, inflammation, obesity; angiotensin II, adipose tissue, obesity; angiotensin II, hypertension, obesity; angiotensin II, insulin resistance, obesity; angiotensin II, adiponectin, leptin, obesity; angiotensin II, COVID-19, obesity. Angiotensin II through its interaction with its AT1 receptor, can induce alterations in diverse systems that are related to the comorbidities observed in obesity. Therapeutic strategies to decrease the production and action of Ang II could improve the clinical conditions in individuals with obesity.

The regulation of efferocytosis signaling pathways and adipose tissue homeostasis in physiological conditions and obesity: Current understanding and treatment options

Obesity is associated with changes in the resolution of acute inflammation that contribute to the clinical complications. The exact mechanisms underlying unresolved inflammation in obesity are not fully understood. Adipocyte death leads to pro-inflammatory adipose tissue macrophages, stimulating additional adipocyte apoptosis. Thus, a complex and tightly regulated process to inhibit inflammation and maintain homeostasis after adipocyte apoptosis is needed to maintain health. In normal condition, a specialized phagocytic process (efferocytosis) performs this function, clearing necrotic and apoptotic cells (ACs) and controlling inflammation. For efficient and continued efferocytosis, phagocytes must internalize multiple ACs in physiological conditions and handle the excess metabolic burden in adipose tissue. In obesity, this control is lost and can be an important hallmark of the disease. In this regard, the deficiency of efferocytosis leads to delayed resolution of acute inflammation and can result in ongoing inflammation, immune system dysfunction, and insulin resistance in obesity. Hence, efficient clearance of ACs by M2 macrophages could limit long-term inflammation and ensue clinical complications, such as cardiovascular disease and diabetes. This review elaborates upon the molecular mechanisms to identify efferocytosis regulators in obesity, and the mechanisms that can improve efferocytosis and reduce obesity-related complications, such as the use of pharmacological agents and regular exercise.

Distinct responses between healthy and cirrhotic human livers upon lipopolysaccharide challenge: possible implications for acute-on-chronic liver failure

Patients with acute-on-chronic liver failure (ACLF) are at risk of developing acute hepatic decompensation and organ failures with an unraveled complex mechanism. An altered immune response toward insults in cirrhotic compared with healthy livers may contribute to the ACLF development. Therefore, we aim to investigate the differences in inflammatory responses between cirrhotic and healthy livers using human precision-cut liver slices (PCLSs) upon the lipopolysaccharide (LPS) challenge. PCLSs prepared from livers of patients with cirrhosis or healthy donors of liver transplantation were incubated ex vivo with or without LPS for up to 48 h. Viability test, qRT-PCR, and multiplex cytokine assay were performed. Regulation of the LPS receptors during incubation or with LPS challenge differed between healthy versus cirrhotic PCLSs. LPS upregulated TLR-2 in healthy PCLSs solely (P < 0.01). Culturing for 48 h induced a stronger inflammatory response in the cirrhotic than healthy PCLS. Upon LPS stimulation, cirrhotic PCLSs secreted more proinflammatory cytokines (IL-8, IL-6, TNF-α, eotaxin, and VEGF) significantly and less anti-inflammatory cytokine (IL-1ra) than those of healthy. In summary, cirrhotic PCLSs released more proinflammatory and less anti-inflammatory cytokines after LPS stimuli than healthy, leading to dysregulated inflammatory response. These events could possibly resemble the liver immune response in ACLF.NEW & NOTEWORTHY Precision-cut liver slices (PCLSs) model provides a unique platform to investigate the different immune responses of healthy versus cirrhotic livers in humans. Our data show that cirrhotic PCLSs exhibit excessive inflammatory response accompanied by a lower anti-inflammatory cytokine release in response to LPS; a better understanding of this alteration may guide the novel therapeutic approaches to mitigate the excessive inflammation during the onset of acute-on-chronic liver failure.

TLR2, TLR4, and NLRP3 mediated the balance between host immune-driven resistance and tolerance in Staphylococcus aureus-infected mice

Staphylococcus aureus (S. aureus) is a gram-positive pathogen that can cause infectious diseases in mammals. S. aureus-induced host innate immune responses have a relationship with Toll-like receptor 2 (TLR2), TLR4, and Nod-like receptor pyrin domain-containing protein 3 (NLRP3). However, the detailed roles of TLR2, TLR4, and NLRP3 in regulating the host inflammatory response to S. aureus infection remain unclear. Our data indicated that the S. aureus-induced mortality was aggravated by deficiency of TLR2, TLR4, and NLRP3 in mice. In the subsequent experiment, we found that during S. aureus infection, the roles of TLR2, TLR4, and NLRP3 seemed to be different at multiple timepoints. The deficiency of TLR2, TLR4, or NLRP3 attenuated the expression of High-mobility group box protein 1 (HMGB1) and Hyaluronic acid-binding protein 2 (HABP2), which is accompanied by decreased proinflammatory cytokine (TNF-α), chemokine (RANTES), and anti-inflammatory cytokine (IL-10) production in lungs and serum at 3 h and 6 h post-infection. However, with S. aureus infection prolonged (24 h post-infection), the trend was diametrically opposite. The results showed that deficiency of TLR2, TLR4, or NLRP3 aggravated HABP2 and HMGB1 expression, which is accompanied by enhanced proinflammatory cytokine (TNF-α), chemokine (RANTES), and anti-inflammatory cytokine (IL-10) production in lungs and serum. These results were consistent with the data observed in S. aureus-infected bone marrow-derived macrophages (BMDMs). All these results suggested that during S. aureus infection, TLR2, TLR4, and NLRP3 has time-dependent effect in regulating the balance between immune-driven resistance and tolerance.

Chronic Inflammation in Obesity and Cancer Cachexia

Chronic inflammation has long been linked to obesity and related conditions such as type 2 diabetes and metabolic syndrome. According to current research, the increased risk of cancer in people with certain metabolic diseases may be due to chronic inflammation. Adipocytokines, which are pro-inflammatory cytokines secreted in excess, are elevated in many chronic metabolic diseases. Cytokines and inflammatory mediators, which are not directly linked to DNA, are important in tumorigenesis. Cachexia, a type of metabolic syndrome linked to the disease, is associated with a dysregulation of metabolic pathways. Obesity and cachexia have distinct metabolic characteristics, such as insulin resistance, increased lipolysis, elevated free fatty acids (FFA), and ceramide levels, which are discussed in this section. The goal of this research project is to create a framework for bringing together our knowledge of inflammation-mediated insulin resistance.

Lipopolysaccharide and the gut microbiota: Considering structural variation

Systemic inflammation is associated with chronic disease and is purported to be a main pathogenic mechanism underlying metabolic conditions. Microbes harbored in the host gastrointestinal tract release signaling byproducts from their cell wall, such as lipopolysaccharides (LPS), which can act locally and, after crossing the gut barrier and entering circulation, also systemically. Defined as metabolic endotoxemia, elevated concentrations of LPS in circulation are associated with metabolic conditions and chronic disease. As such, measurement of LPS is highly prevalent in animal and human research investigating these states. Indeed, LPS can be a potent stimulant of host immunity but this response depends on the microbial species' origin, a parameter often overlooked in both preclinical and clinical investigations. Indeed, the lipid A portion of LPS is mutable and comprises the main virulence and endotoxic component, thus contributing to the structural and functional diversity among LPSs from microbial species. In this review, we discuss how such structural differences in LPS can induce differential immunological responses in the host.

The Action of Vitamin D in Adipose Tissue: Is There the Link between Vitamin D Deficiency and Adipose Tissue-Related Metabolic Disorders?

Adipose tissue plays an important role in systemic metabolism via the secretion of adipocytokines and storing and releasing energy. In obesity, adipose tissue becomes dysfunctional and characterized by hypertrophied adipocytes, increased inflammation, hypoxia, and decreased angiogenesis. Although adipose tissue is one of the major stores of vitamin D, its deficiency is detective in obese subjects. In the presented review, we show how vitamin D regulates numerous processes in adipose tissue and how their dysregulation leads to metabolic disorders. The molecular response to vitamin D in adipose tissue affects not only energy metabolism and adipokine and anti-inflammatory cytokine production via the regulation of gene expression but also genes participating in antioxidant defense, adipocytes differentiation, and apoptosis. Thus, its deficiency disturbs adipocytokines secretion, metabolism, lipid storage, adipogenesis, thermogenesis, the regulation of inflammation, and oxidative stress balance. Restoring the proper functionality of adipose tissue in overweight or obese subjects is of particular importance in order to reduce the risk of developing obesity-related complications, such as cardiovascular diseases and diabetes. Taking into account the results of experimental studies, it seemed that vitamin D may be a remedy for adipose tissue dysfunction, but the results of the clinical trials are not consistent, as some of them show improvement and others no effect of this vitamin on metabolic and insulin resistance parameters. Therefore, further studies are required to evaluate the beneficial effects of vitamin D, especially in overweight and obese subjects, due to the presence of a volumetric dilution of this vitamin among them.

Understanding diabetes-induced cardiomyopathy from the perspective of renin angiotensin aldosterone system

Experimental and clinical evidence suggests that diabetic subjects are predisposed to a distinct cardiovascular dysfunction, known as diabetic cardiomyopathy (DCM), which could be an autonomous disease independent of concomitant micro and macrovascular disorders. DCM is one of the prominent causes of global morbidity and mortality and is on a rising trend with the increase in the prevalence of diabetes mellitus (DM). DCM is characterized by an early left ventricle diastolic dysfunction associated with the slow progression of cardiomyocyte hypertrophy leading to heart failure, which still has no effective therapy. Although the well-known "Renin Angiotensin Aldosterone System (RAAS)" inhibition is considered a gold-standard treatment in heart failure, its role in DCM is still unclear. At the cellular level of DCM, RAAS induces various secondary mechanisms, adding complications to poor prognosis and treatment of DCM. This review highlights the importance of RAAS signaling and its major secondary mechanisms involving inflammation, oxidative stress, mitochondrial dysfunction, and autophagy, their role in establishing DCM. In addition, studies lacking in the specific area of DCM are also highlighted. Therefore, understanding the complex role of RAAS in DCM may lead to the identification of better prognosis and therapeutic strategies in treating DCM.

The Potential Role of RP105 in Regulation of Inflammation and Osteoclastogenesis During Inflammatory Diseases

Inflammatory diseases have a negative impact on bone homeostasis via exacerbated local and systemic inflammation. Bone resorbing osteoclasts are mainly derived from hematopoietic precursors and bone marrow monocytes. Induced osteoclastogenesis during inflammation, autoimmunity, metabolic diseases, and cancers is associated with bone loss and osteoporosis. Proinflammatory cytokines, pathogen-associated molecular patterns, or endogenous pathogenic factors induce osteoclastogenic differentiation by binding to the Toll-like receptor (TLR) family expressed on surface of osteoclast precursors. As a non-canonical member of the TLRs, radioprotective 105 kDa (RP105 or CD180) and its ligand, myeloid differentiation protein 1 (MD1), are involved in several bone metabolic disorders. Reports from literature had demonstrated RP105 as an important activator of B cells, bone marrow monocytes, and macrophages, which regulates inflammatory cytokines release from immune cells. Reports from literature had shown the association between RP105 and other TLRs, and the downstream signaling mechanisms of RP105 with different “signaling-competent” partners in immune cells during different disease conditions. This review is focused to summarize: (1) the role of RP105 on immune cells’ function and inflammation regulation (2) the potential regulatory roles of RP105 in different disease-mediated osteoclast activation and the underlying mechanisms, and (3) the different “signaling-competent” partners of RP105 that regulates osteoclastogenesis.

Age-dependent messenger RNA expression of toll-like receptor 4 and intercellular adhesion molecule-1 in peripheral blood mononuclear cells

BACKGROUND

Inflammation plays an important role in the ageing process in which monocytes/macrophages are important players. Intercellular adhesion molecule-1 (ICAM-1), tumour necrosis factor-α (TNF-α) and Toll-like receptor 4 (TLR4) are well-known inflammatory markers. This study aimed to investigate the relationship between age and the expression and correlation of ICAM-1, TNF-α and TLR4 mRNA in peripheral blood mononuclear cells (PBMCs).

METHODS

A total of 239 participants were recruited in a medical centre in Taiwan. The mRNA isolated from the PBMCs was used to determine the levels of ICAM-1, TNF-α and TLR4 mRNAs with real-time polymerase chain reaction (PCR). The propensity-matched analysis was also applied for subgroup analysis.

RESULTS

When compared 189 older adults (≧65 years) to 50 younger adults (<65 years), the ICAM-1, TNF-α and TLR4 mRNA levels in PBMCs were significantly higher in older adults (2.00 ± 0.72 vs 0.87 ± 0.34 for ICAM-1, 2.32 ± 0.69 vs 1.15 ± 0.44 for TNF-α and 1.56 ± 0.47 vs 1.05 ± 0.51 for TLR4, and all P < .0001). Also, both age and TLR4 were independent factors affecting mononuclear cell ICAM-1 in the multiple linear regression analysis (P < .0001).

CONCLUSION

The mRNA levels of ICAM-1 and TLR4 in PBMCs are higher in older adults than those in younger adults. TLR4 is an independent factor affecting ICAM-1 expression in PBMCs, especially in older adults. This may suggest that ICAM-1 and TLR4 in PBMCs are potential biomarkers and their relationship may shed some light on the ageing process.

The potential roles of chitosan oligosaccharide in prevention of kidney injury in obese and diabetic conditions

Obesity is closely associated with insulin resistance (IR). The most likely links between the two are obesity-mediated systemic low-grade chronic inflammation, endoplasmic reticulum stress and mitochondrial dysfunction, which are all known to contribute to the development of type 2 diabetes (T2DM) and eventually diabetic nephropathy (DN). Chitosan oligosaccharide (COS) is an oligomer of chitosan prepared by the deacetylation of chitin commonly found in exoskeletons of crustaceans such as shrimp and crab as well as the cell walls of fungi. COS has various biological effects including lipid lowering, anti-inflammation, anti-diabetes, and anti-oxidant effects. Therefore, COS is a potential new therapeutic agent for treatment of the obesity-induced DN condition. It is an abundant natural polymer and therefore freely available. This review includes information regarding the relationship between obesity, IR, T2DM, and DN as well as the potential usefulness of COS in controlling lipid and cholesterol metabolism, T2DM and kidney injury models in both in vivo and in vitro studies. However, evidence is limited regarding the effect of COS on the DN model. Further studies, especially in obesity-induced DN, are needed to support the mechanisms proposed in this review.

The Role of Vitamin D in Adipose Tissue Biology: Adipocyte Differentiation, Energy Metabolism, and Inflammation

Adipose tissue is composed of diverse cell types and plays a major role in energy homeostasis and inflammation at the local and systemic levels. Adipose tissue serves as the main site for vitamin D storage and is among the most important extraskeletal targets of vitamin D which can modulate multiple aspects of adipose tissue biology. Vitamin D may exert inhibitory or stimulatory effects on adipocyte differentiation depending on cell type, stage of differentiation, and the treatment time point. Moreover, vitamin D controls energy metabolism in adipose tissue by affecting fatty acid oxidation, expression of uncoupling proteins, insulin resistance, and adipokine production. Adipose tissue inflammation can have a significant impact on the metabolic disorders often associated with obesity, and vitamin D can modulate the inflammatory response of immune cells and adipocytes within the adipose tissue. This review discusses the role of adipose tissue in vitamin D metabolism, as well as the regulatory role of vitamin D in adipocyte differentiation, adipose tissue energy metabolism, and inflammation, thereby providing insights into the importance of vitamin D in adipose tissue biology.

Maintaining Digestive Health in Diabetes: The Role of the Gut Microbiome and the Challenge of Functional Foods

Over the last decades, the incidence of diabetes has increased in developed countries and beyond the genetic impact, environmental factors, which can trigger the activation of the gut immune system, seem to affect the induction of the disease process. Since the composition of the gut microbiome might disturb the normal interaction with the immune system and contribute to altered immune responses, the restoration of normal microbiota composition constitutes a new target for the prevention and treatment of diabetes. Thus, the interaction of gut microbiome and diabetes, focusing on mechanisms connecting gut microbiota with the occurrence of the disorder, is discussed in the present review. Finally, the challenge of functional food diet on maintaining intestinal health and microbial flora diversity and functionality, as a potential tool for the onset inhibition and management of the disease, is highlighted by reporting key animal studies and clinical trials. Early onset of the disease in the oral cavity is an important factor for the incorporation of a functional food diet in daily routine.

Helicobacter pylori CagA Interacts with SHP-1 to Suppress the Immune Response by Targeting TRAF6 for K63-Linked Ubiquitination

Helicobacter pylori is the major etiological agent for most gastric cancer. CagA has been reported to be an important virulence factor of H. pylori, but its effect on the immune response is not yet clear. In this study, wild-type C57BL/6 mice and Ptpn6^me-v/me-v mice were randomly assigned for infection with H. pylori We demonstrated that CagA suppressed H. pylori-stimulated expression of proinflammatory cytokines in vivo. Besides, we infected mouse peritoneal macrophages RAW264.7 and AGS with H. pylori Our results showed that CagA suppressed expression of proinflammatory cytokines through inhibiting the MAPKs and NF-κB pathways activation in vitro. Mechanistically, we found that CagA interacted with the host cellular tyrosine phosphatase SHP-1, which facilitated the recruitment of SHP-1 to TRAF6 and inhibited the K63-linked ubiquitination of TRAF6, which obstructed the transmission of signal downstream. Taken together, these findings reveal a previously unknown mechanism by which CagA negatively regulates the posttranslational modification of TRAF6 in innate antibacterial immune response and provide molecular basis for new therapeutics to treat microbial infection.

Adipose tissue and insulin resistance in obese

Currently, obesity has become a global health issue and is referred to as an epidemic. Dysfunctional obese adipose tissue plays a pivotal role in the development of insulin resistance. However, the mechanism of how dysfunctional obese-adipose tissue develops insulin-resistant circumstances remains poorly understood. Therefore, this review attempts to highlight the potential mechanisms behind obesity-associated insulin resistance. Multiple risk factors are directly or indirectly associated with the increased risk of obesity; among them, environmental factors, genetics, aging, gut microbiota, and diets are prominent. Once an individual becomes obese, adipocytes increase in their size; therefore, adipose tissues become larger and dysfunctional, recruit macrophages, and then these polarize to pro-inflammatory states. Enlarged adipose tissues release excess free fatty acids (FFAs), reactive oxygen species (ROS), and pro-inflammatory cytokines. Excess systemic FFAs and dietary lipids enter inside the cells of non-adipose organs such as the liver, muscle, and pancreas, and are deposited as ectopic fat, generating lipotoxicity. Toxic lipids dysregulate cellular organelles, e.g., mitochondria, endoplasmic reticulum, and lysosomes. Dysregulated organelles release excess ROS and pro-inflammation, resulting in systemic inflammation. Long term low-grade systemic inflammation prevents insulin from its action in the insulin signaling pathway, disrupts glucose homeostasis, and results in systemic dysregulation. Overall, long-term obesity and overnutrition develop into insulin resistance and chronic low-grade systemic inflammation through lipotoxicity, creating the circumstances to develop clinical conditions. This review also shows that the liver is the most sensitive organ undergoing insulin impairment faster than other organs, and thus, hepatic insulin resistance is the primary event that leads to the subsequent development of peripheral tissue insulin resistance.

Gut Microbiota as a Trigger for Metabolic Inflammation in Obesity and Type 2 Diabetes

The gut microbiota has been linked to the development of obesity and type 2 diabetes (T2D). The underlying mechanisms as to how intestinal microbiota may contribute to T2D are only partly understood. It becomes progressively clear that T2D is characterized by a chronic state of low-grade inflammation, which has been linked to the development of insulin resistance. Here, we review the current evidence that intestinal microbiota, and the metabolites they produce, could drive the development of insulin resistance in obesity and T2D, possibly by initiating an inflammatory response. First, we will summarize major findings about immunological and gut microbial changes in these metabolic diseases. Next, we will give a detailed view on how gut microbial changes have been implicated in low-grade inflammation. Lastly, we will critically discuss clinical studies that focus on the interaction between gut microbiota and the immune system in metabolic disease. Overall, there is strong evidence that the tripartite interaction between gut microbiota, host immune system and metabolism is a critical partaker in the pathophysiology of obesity and T2D.

Consumption of a high energy density diet triggers microbiota dysbiosis, hepatic lipidosis, and microglia activation in the nucleus of the solitary tract in rats

Introduction

Obesity is a multifactorial chronic inflammatory disease. Consumption of high energy density (HED) diets is associated with hyperphagia, increased body weight and body fat accumulation, and obesity. Our lab has previously shown that short-term (4 weeks) consumption of a HED diet triggers gut microbiota dysbiosis, gut inflammation, and reorganization of the gut-brain vagal communication.

Objetives

The aim of this study was to investigate the effect of long-term (6 months) consumption of HED diet on body composition, gut microbiome, hepatocellular lipidosis, microglia activation in the nucleus of the solitary tract, and systemic inflammation.

Methods

Male Sprague–Dawley rats were fed a low energy density (LED) diet for 2 weeks and then switched to a HED diet for 26 weeks. Twenty-four-hour food intake, body weight, and body composition were measured twice a week. Blood serum and fecal samples were collected at baseline, 1, 4, 8, and 26 weeks after introduction of the HED diet. Serum samples were used to measure insulin, leptin, and inflammatory cytokines using Enzyme-linked Immunosorbent Assay. Fecal samples were assessed for 16 S rRNA genome sequencing.

Results

HED diet induced microbiota dysbiosis within a week of introducing the diet. In addition, there was significant microglia activation in the intermediate NTS and marked hepatic lipidosis after 4 weeks of HED diet. We further observed changes in the serum cytokine profile after 26 weeks of HED feeding.

Conclusions

These data suggest that microbiota dysbiosis is the first response of the organism to HED diets, followed by increased liver fat accumulation, microglia activation in the brain, and circulating levels of inflammatory markers. To our knowledge, this is the first study to present longitudinal and cross-sectional results on effect of long-term consumption of HED diets on all these parameters in a single cohort of animals.

Biochemical and Molecular Mechanisms of Glucose Uptake Stimulated by Physical Exercise in Insulin Resistance State: Role of Inflammation

Obesity associated with systemic inflammation induces insulin resistance (IR), with consequent chronic hyperglycemia. A series of reactions are involved in this process, including increased release of proinflammatory cytokines, and activation of c-Jun N-terminal kinase (JNK), nuclear factor-kappa B (NF-κB) and toll-like receptor 4 (TLR4) receptors. Among the therapeutic tools available nowadays, physical exercise (PE) has a known hypoglycemic effect explained by complex molecular mechanisms, including an increase in insulin receptor phosphorylation, in AMP-activated protein kinase (AMPK) activity, in the Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) pathway, with subsequent activation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), Rac1, TBC1 domain family member 1 and 4 (TBC1D1 and TBC1D4), in addition to a variety of signaling molecules, such as GTPases, Rab and soluble N-ethylmaleimide-sensitive factor attached protein receptor (SNARE) proteins. These pathways promote greater translocation of GLUT4 and consequent glucose uptake by the skeletal muscle. Phosphoinositide-dependent kinase (PDK), atypical protein kinase C (aPKC) and some of its isoforms, such as PKC-iota/lambda also seem to play a fundamental role in the transport of glucose. In this sense, the association between autophagy and exercise has also demonstrated a relevant role in the uptake of muscle glucose. Insulin, in turn, uses a phosphoinositide 3-kinase (PI3K)-dependent mechanism, while exercise signal may be triggered by the release of calcium from the sarcoplasmic reticulum. The objective of this review is to describe the main molecular mechanisms of IR and the relationship between PE and glucose uptake.

Altered mitochondrial metabolism in the insulin-resistant heart

Obesity-induced insulin resistance and type 2 diabetes mellitus can ultimately result in various complications, including diabetic cardiomyopathy. In this case, cardiac dysfunction is characterized by metabolic disturbances such as impaired glucose oxidation and an increased reliance on fatty acid (FA) oxidation. Mitochondrial dysfunction has often been associated with the altered metabolic function in the diabetic heart, and may result from FA-induced lipotoxicity and uncoupling of oxidative phosphorylation. In this review, we address the metabolic changes in the diabetic heart, focusing on the loss of metabolic flexibility and cardiac mitochondrial function. We consider the alterations observed in mitochondrial substrate utilization, bioenergetics and dynamics, and highlight new areas of research which may improve our understanding of the cause and effect of cardiac mitochondrial dysfunction in diabetes. Finally, we explore how lifestyle (nutrition and exercise) and pharmacological interventions can prevent and treat metabolic and mitochondrial dysfunction in diabetes.

Effects of 1,25-dihydroxyvitamin D3 on the Inflammatory Responses of Stromal Vascular Cells and Adipocytes from Lean and Obese Mice

Vitamin D status has been implicated in obesity and adipose tissue inflammation. In the present study, we explored the effects of dietary vitamin D supplementation on adipose tissue inflammation and immune cell population, and the effects of in vitro 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) treatment on pro-inflammatory cytokine production by stromal vascular cells (SVCs) and adipocytes in lean and high-fat diet-induced obese mice. The results show that epididymal fat Mcp-1 and Rantes mRNA levels, which were higher in obese mice compared with lean mice, were significantly down-regulated by vitamin D supplementation. While obese mice had higher numbers of macrophages and natural killer (NK) cells within adipose tissue, these remained unaltered by vitamin D supplementation. In accordance with these in vivo findings, the in vitro 1,25(OH)2D3 treatment decreased IL-6, MCP-1, and IL-1β production by SVCs from obese mice, but not by adipocytes. In addition, 1,25(OH)2D3 treatment significantly decreased Tlr2 expression and increased mRNA levels of Iκba and Dusp1 in SVCs. These findings suggest that vitamin D supplementation attenuates inflammatory response in adipose tissue, especially in SVCs, possibly through inhibiting NF-κB and MAPK signaling pathways in SVCs but not by the inhibition of macrophage infiltration.

Shared pathways for neuroprogression and somatoprogression in neuropsychiatric disorders

Activated immune-inflammatory, oxidative and nitrosative stress (IO&NS) pathways and consequent mitochondrial aberrations are involved in the pathophysiology of psychiatric disorders including major depression, bipolar disorder and schizophrenia. They offer independent and shared contributions to pathways underpinning medical comorbidities including insulin resistance, metabolic syndrome, obesity and cardiovascular disease - herein conceptualized as somatoprogression. This narrative review of human studies aims to summarize relationships between IO&NS pathways, neuroprogression and somatoprogression. Activated IO&NS pathways, implicated in the neuroprogression of psychiatric disorders, affect the pathogenesis of comorbidities including insulin resistance, dyslipidaemia, obesity and hypertension, and by inference, metabolic syndrome. These conditions activate IO&NS pathways, exacerbating neuroprogression in psychiatric disorders. The processes whereby proinflammatory cytokines, nitrosative and endoplasmic reticulum stress, NADPH oxidase isoforms, PPARγ inactivation, SIRT1 deficiency and intracellular signalling pathways impact lipid metabolism and storage are considered. Through associations between body mass index, chronic neuroinflammation and FTO expression, activation of IO&NS pathways arising from somatoprogression may contribute to neuroprogression. Early evidence highlights the potential of adjuvants targeting IO&NS pathways for treating somatoprogression and neuroprogression.

Socioeconomic Deprivation, Adverse Childhood Experiences and Medical Disorders in Adulthood: Mechanisms and Associations

Severe socioeconomic deprivation (SED) and adverse childhood experiences (ACE) are significantly associated with the development in adulthood of (i) enhanced inflammatory status and/or hypothalamic-pituitary-adrenal (HPA) axis dysfunction and (ii) neurological, neuroprogressive, inflammatory and autoimmune diseases. The mechanisms by which these associations take place are detailed. The two sets of consequences are themselves strongly associated, with the first set likely contributing to the second. Mechanisms enabling bidirectional communication between the immune system and the brain are described, including complex signalling pathways facilitated by factors at the level of immune cells. Also detailed are mechanisms underpinning the association between SED, ACE and the genesis of peripheral inflammation, including epigenetic changes to immune system-related gene expression. The duration and magnitude of inflammatory responses can be influenced by genetic factors, including single nucleotide polymorphisms, and by epigenetic factors, whereby pro-inflammatory cytokines, reactive oxygen species, reactive nitrogen species and nuclear factor-κB affect gene DNA methylation and histone acetylation and also induce several microRNAs including miR-155, miR-181b-1 and miR-146a. Adult HPA axis activity is regulated by (i) genetic factors, such as glucocorticoid receptor polymorphisms; (ii) epigenetic factors affecting glucocorticoid receptor function or expression, including the methylation status of alternative promoter regions of NR3C1 and the methylation of FKBP5 and HSD11β2; (iii) chronic inflammation and chronic nitrosative and oxidative stress. Finally, it is shown how severe psychological stress adversely affects mitochondrial structure and functioning and is associated with changes in brain mitochondrial DNA copy number and transcription; mitochondria can act as couriers of childhood stress into adulthood.

Prostaglandin E2 Regulates Activation of Mouse Peritoneal Macrophages by Staphylococcus aureus through Toll-Like Receptor 2, Toll-Like Receptor 4, and NLRP3 Inflammasome Signaling

Prostaglandin E2 (PGE2), an essential endogenous lipid mediator for normal physiological functions, can also act as an inflammatory mediator in pathological conditions. We determined whether Staphylococcus aureus lipoproteins are essential for inducing PGE2 secretion by immune cells and whether pattern recognition receptors mediate this process. PGE2 levels secreted by mouse peritoneal macrophages infected with the S. aureus isogenic mutant, lgt::ermB (Δlgt; deficient in lipoprotein maturation), decreased compared with those from macrophages infected with wild-type (WT) S. aureus. Experiments using toll-like receptors 2 (TLR2)-deficient, TLR4-deficient, and NLRP3-deficient mice indicated that these 3 proteins are involved in macrophage PGE2 secretion in response to S. aureus, and lipoproteins were essential for S. aureus invasion and survival within macrophages. Inhibition of endogenous PGE2 synthesis had no effect on bacterial invasion. Exogenous PGE2 inhibited phagocytosis in the WT S. aureus and its isogenic mutant but increased intracellular killing accompanied by enhanced IL-1β secretion. Our data demonstrate that S. aureus can induce macrophage TLR/mitogen-activated protein kinase/NF-κB signaling and that PGE2 treatment upregulates NLRP3/caspase-1 signaling activation. Thus, macrophage PGE2 secretion after S. aureus infection depends on bacterial lipoprotein maturation and macrophage receptors TLR2, TLR4, and NLRP3. Moreover, exogenous PGE2 regulates S. aureus-induced macrophage activation through TLRs and NLRP3 inflammasome signaling.

Omega-3 Polyunsaturated Fatty Acids Inhibit IL-17A Secretion through Decreased ICAM-1 Expression in T Cells Co-Cultured with Adipose-Derived Stem Cells Harvested from Adipose Tissues of Obese Subjects

SCOPE

Obese adipose tissue (AT) is infiltrated by inflammatory immune cells including IL-17A-producing-T (Th17) cells. It has been previously demonstrated that adipose-derived stem cells from obese (ob-ASCs), but not lean AT promote Th17 cells. Because n-3 PUFAs are known to inhibit obese AT inflammation, it is tested here whether they could inhibit ob-ASC-mediated IL-17A secretion.

METHODS AND RESULTS

The n-3 PUFA precursor, alpha-linolenic acid (ALA), or its derivatives, eicosapentaenoic, or docosahexaenoic acid, is added to co-cultures of human ob-ASCs and mononuclear cells (MNCs). All three inhibited IL-17A, but not IL-1β, IL-6, nor TNFα  secretion. As a control, palmitic acid (PA), a saturated fatty acid, did not inhibit IL-17A secretion. ALA also inhibited IL-17A secretion mediated by adipocytes differentiated from ob-ASCs. Toll-like-receptor 4 is shown to be involved in ob-ASC-mediated-IL-17A secretion, and to be inhibited by ALA, together with Cyclo-Oxygenase-2 and Signal-Transducer-and-Activator-of-transcription-3. In addition, ALA down-regulated Intercellular-Adhesion-Molecule-1 (ICAM-1) expression in both monocytes and ASCs, which resulted in decreased interactions between ob-ASCs and MNCs, and inhibition of IL-17A secretion.

CONCLUSION

It is demonstrated herein that ALA inhibits Th17 cell promotion, through decreased ICAM-1expression in both ob-ASCs and monocytes. This novel mechanism may contribute to explain the beneficial effects of n-3 PUFA in IL-17A-related inflammatory pathologies.

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

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

Pattern recognition receptors as potential therapeutic targets in metabolic syndrome: From bench to bedside

Pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) and NOD-like receptors (NLRs) play crucial roles in the underlying mechanisms of metabolic syndrome (MetS). Mainly, these receptors have been suggested to participate in the pathophysiological processes involved in the complications associated with this condition. Therefore, to evolve therapeutic strategies targeting PRRs might be an imperative approach to avoid the development of further complications in human subjects. In this work, we discuss the understanding regarding the roles of PRRs in the pathways of MetS to further describe potential advancements made to target these receptors within this pathology.

Cardiolipotoxicity, Inflammation, and Arrhythmias: Role for Interleukin-6 Molecular Mechanisms

Fatty acid infiltration of the myocardium, acquired in metabolic disorders (obesity, type-2 diabetes, insulin resistance, and hyperglycemia) is critically associated with the development of lipotoxic cardiomyopathy. According to a recent Presidential Advisory from the American Heart Association published in 2017, the current average dietary intake of saturated free-fatty acid (SFFA) in the US is 11–12%, which is significantly above the recommended <10%. Increased levels of circulating SFFAs (or lipotoxicity) may represent an unappreciated link that underlies increased vulnerability to cardiac dysfunction. Thus, an important objective is to identify novel targets that will inform pharmacological and genetic interventions for cardiomyopathies acquired through excessive consumption of diets rich in SFFAs. However, the molecular mechanisms involved are poorly understood. The increasing epidemic of metabolic disorders strongly implies an undeniable and critical need to further investigate SFFA mechanisms. A rapidly emerging and promising target for modulation by lipotoxicity is cytokine secretion and activation of pro-inflammatory signaling pathways. This objective can be advanced through fundamental mechanisms of cardiac electrical remodeling. In this review, we discuss cardiac ion channel modulation by SFFAs. We further highlight the contribution of downstream signaling pathways involving toll-like receptors and pathological increases in pro-inflammatory cytokines. Our expectation is that if we understand pathological remodeling of major cardiac ion channels from a perspective of lipotoxicity and inflammation, we may be able to develop safer and more effective therapies that will be beneficial to patients.

Right ventricular dysfunction and remodeling in diabetic cardiomyopathy

The increasing prevalence of diabetic cardiomyopathy (DCM) is an important threat to health worldwide. While left ventricular (LV) dysfunction in DCM is well recognized, the accurate detection, diagnosis, and treatment of changes in right ventricular (RV) structure and function have not been well characterized. The pathophysiology of RV dysfunction in DCM may share features with LV diastolic and systolic dysfunction, including pathways related to insulin resistance and oxidant injury, although the RV has a unique cellular origin and composition and unique biomechanical properties and is coupled to the lower-impedance pulmonary vascular bed. In this review, we discuss potential mechanisms responsible for RV dysfunction in DCM and review the imaging approaches useful for early detection, protection, and intervention strategies. Additional data are required from animal models and clinical trials to better identify the onset and features of altered RV and pulmonary vascular structure and function during the onset and progression of DCM and to determine the efficacy of early detection and treatment of RV dysfunction on clinical symptoms and outcomes.

Regulation of Metabolic Disease-Associated Inflammation by Nutrient Sensors

Visceral obesity is frequently associated with the development of type 2 diabetes (T2D), a highly prevalent chronic disease that features insulin resistance and pancreatic β-cell dysfunction as important hallmarks. Recent evidence indicates that the chronic, low-grade inflammation commonly associated with visceral obesity plays a major role connecting the excessive visceral fat deposition with the development of insulin resistance and pancreatic β-cell dysfunction. Herein, we review the mechanisms by which nutrients modulate obesity-associated inflammation.

Early exposure to distinct sources of lipids affects differently the development and hepatic inflammatory profiles of 21-day-old rat offspring

Introduction

Maternal diet composition of fatty acids during pregnancy and lactation seems to modify the fetal programming, epigenetic pattern and offspring phenotype.

Aim

Herein, we investigated the effects of maternal consumption of normal-fat diets with distinct lipid sources during pregnancy and lactation on the somatic development and proinflammatory status of 21-day-old rat offspring.

Materials and Methods

On the first day of pregnancy, female Wistar rats were divided into four groups as follows: soybean oil (M-SO), lard (M-L), hydrogenated vegetable fat (M-HVF) and fish oil (M-FO). Diets were maintained during pregnancy and lactation. Male offspring constituted the SO, L, HVF and FO groups. Pups were weighed and measured weekly. Lipopolysaccharide serum concentration was determined. Tumor necrosis factor alpha, interleukin (IL)-6 and IL-10 in the liver were evaluated by enzyme-linked immunosorbent assay. Liver gene expressions were determined by real-time polymerase chain reaction. Protein expressions in the liver were analyzed by Western blotting.

Results

We observed an increase in body weight and adiposity in L and HVF groups. Moreover, HVF group showed an increase in the toll-like receptor 4 mRNA levels, IL10Rα and phosphorylated form of IκB kinase (IKK; p-IKKα+β) protein expression. The FO group presented a decrease in body weight, relative weight of retroperitoneal adipose tissue, ADIPOR2 gene expression, lipopolysaccharide and p-IKKα+β and phosphorylated form of nuclear transcription factor kappa B (NFκB) p50 (p-NFκB p50) protein expression.

Conclusion

Summarily, whereas maternal intake of normal-fat diets based on L and HVF appear to affect the somatic development negatively, only early exposure to HVF impairs the pups’ proinflammatory status. In contrast, maternal diets based on FO during pregnancy and lactation have been more beneficial to the adiposity and toll-like receptor 4 signaling pathway of the 21-day-old rat offspring, particularly when compared to L or HVF diets.

Integrated Immunomodulatory Mechanisms through which Long-Chain n-3 Polyunsaturated Fatty Acids Attenuate Obese Adipose Tissue Dysfunction

Obesity is a global health concern with rising prevalence that increases the risk of developing other chronic diseases. A causal link connecting overnutrition, the development of obesity and obesity-associated co-morbidities is visceral adipose tissue (AT) dysfunction, characterized by changes in the cellularity of various immune cell populations, altered production of inflammatory adipokines that sustain a chronic state of low-grade inflammation and, ultimately, dysregulated AT metabolic function. Therefore, dietary intervention strategies aimed to halt the progression of obese AT dysfunction through any of the aforementioned processes represent an important active area of research. In this connection, fish oil-derived dietary long-chain n-3 polyunsaturated fatty acids (PUFA) in the form of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been demonstrated to attenuate obese AT dysfunction through multiple mechanisms, ultimately affecting AT immune cellularity and function, adipokine production, and metabolic signaling pathways, all of which will be discussed herein.

Inflammation and metabolic cardiomyopathy

Excessive feeding is associated with an increase in the incidence of chronic metabolic diseases, such as obesity, insulin resistance, and type 2 diabetes. Metabolic disturbance induces chronic low-grade inflammation in metabolically-important organs, such as the liver and adipose tissue. Many of the inflammatory signalling pathways are directly triggered by nutrients. The pro-inflammatory mediators in adipocytes and macrophages infiltrating adipose tissue promote both local and systemic pro-inflammatory status. Metabolic cardiomyopathy is a chronic metabolic disease characterized by structural and functional alterations and interstitial fibrosis without coronary artery disease or hypertension. In the early stage of metabolic cardiomyopathy, metabolic disturbance is not accompanied by substantial changes in myocardial structure and cardiac function. However, metabolic disturbance induces subcellular low-grade inflammation in the heart, and in turn, subcellular component abnormalities, such as oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress, and impaired calcium handling, leading to impaired myocardial relaxation. In the advanced stage, the vicious cycle of subcellular component abnormalities, inflammatory cell infiltration, and neurohumoral activation induces cardiomyocyte injury and death, and cardiac fibrosis, resulting in impairment of both diastolic and systolic functions. This review discusses some recent advances in understanding involvement of inflammation in metabolic cardiomyopathy.

Polyinosinic-polycytidylic acid inhibits the differentiation of mouse preadipocytes through pattern recognition receptor-mediated secretion of tumor necrosis factor-α

Viral infections can disturb the functions of adipose tissues and thus result in metabolic diseases. Polyinosinic-polycytidylic acid (poly(I:C)), a synthetic analog of viral double-stranded RNA, induces innate antiviral responses by mimicking viral infection through the activation of pattern recognition receptors (PRRs) such as Toll-like receptor 3 (TLR3), retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5). Poly(I:C) also inhibits the differentiation of mouse preadipocytes but the mechanism underlying this process remains unclear. In this study, poly(I:C) inhibited preadipocyte differentiation in a dose-dependent manner, but not in a time-dependent manner. Endogenously transfected poly(I:C) severely impaired the adipogenesis of preadipocytes compared with exogenously added poly(I:C). Low concentration of tumor necrosis factor-α (TNF-α) could effectively inhibit the preadipocyte differentiation. The effect of exogenously added poly(I:C) on inhibition of differentiation was significantly diminished in the preadipocytes of TLR3 knockout mice. By contrast, endogenously transfected poly(I:C) still inhibited the differentiation of TLR3-deficient preadipocytes. Hence, MDA5/RIG-I signaling was involved in the poly(I:C)-induced inhibition of preadipocyte differentiation. The effect of poly(I:C) stimulation, either through endogenous transfection or exogenous addition, on inhibition of differentiation was significantly diminished in the preadipocytes of TNF-α knockout mice. These results confirmed the evidence that poly(I:C) inhibited the differentiation of mouse preadipocytes through PRR-mediated secretion of TNF-α.

Adipocytes as a Link Between Gut Microbiota-Derived Flagellin and Hepatocyte Fat Accumulation

While the role of both elevated levels of circulating bacterial cell wall components and adipose tissue in hepatic fat accumulation has been recognized, it has not been considered that the bacterial components-recognizing adipose tissue receptors contribute to the hepatic fat content. In this study we found that the expression of adipose tissue bacterial flagellin (FLG)-recognizing Toll-like receptor (TLR) 5 associated with liver fat content (r = 0.699, p = 0.003) and insulin sensitivity (r = -0.529, p = 0.016) in humans (n = 23). No such associations were found for lipopolysaccharides (LPS)-recognizing TLR4. To study the underlying molecular mechanisms of these associations, human HepG2 hepatoma cells were exposed in vitro to the conditioned culture media derived from FLG or LPS-challenged human adipocytes. The adipocyte-mediated effects were also compared to the effects of direct HepG2 exposure to FLG and LPS. We found that the media derived from FLG-treated adipocytes stimulated fat accumulation in HepG2 cells, whereas either media derived from LPS-treated adipocytes or direct FLG or LPS exposure did not. This is likely due to that FLG-treatment of adipocytes increased lipolysis and secretion of glycerol, which is known to serve a substrate for triglyceride synthesis in hepatocytes. Similarly, only FLG-media significantly decreased insulin signaling-related Akt phosphorylation, IRS1 expression and mitochondrial respiratory chain ATP5A. In conclusion, our results suggest that the FLG-induced TLR5 activation in adipocytes increases glycerol secretion from adipocytes and decreases insulin signaling and mitochondrial functions, and increases fat accumulation in hepatocytes. These mechanisms could, at least partly, explain the adipose tissue TLR5 expression associated with liver fat content in humans.